Posts Tagged ‘DNA vaccine’

Virology Africa 2011: viruses at the V&A Waterfront 2

19 December, 2011

We thank Russell Kightley for permission to use the images

Marshall Bloom (Rocky Mountain Laboratories, NIAID) opened the plenary session on Thursday the 1st of December, with a talk on probing the pathogen-vector-host interface of tickborne flaviruses.   Although thoroughly infected with a rhinovirus, he held our attention most ably while reminding us that while many flaviviruses are tick borne, the hard and soft body ticks that vector them are very phylogenetically different – as different as they are from spiders – meaning that if similar flaviruses replicated in them, these viruses may have much wider host range than we know.

He pointed out that while about 95% of the virus life cycle takes place in a tick, transmission to a vertebrate means suddenly adapting to a very different host.  Infection in ticks is persistent, as befits their vector role – but vertebrate infection generally is not.  It was interesting, as a sometime plant virologist, to hear that they look for dsRNA as a marker for replication, and do Ab staining for it: the technique was invented with plant viruses, and very few other virologists seem to appreciate that dsRNA can be quite easily isolated and detected.

They compared Vero and tick cells for virus replication, and saw significant differences: while tick cells could go out to 60+ days and look fine, Vero cells were severely affected at much shorter times post infection.  There was also 100-fold less virus in tick cells, and prominent tubular structures in old infected tick cells.  He noted that ticks evade host defences quite efficiently: eg they suppress host clotting during feeding, and there is huge gene activation in the tick during feeding.  In another study to envy, they are doing array work on ticks to see what is regulated and how.

 Linda Dixon (Institute for Animal Health, Pirbright, UK) recounted her lab’s work on African swine fever (ASFV), a poxvirus-like large DNA virus.  The virus is endemic to much of Africa, and keeps escaping – and there is no effective  vaccine to prevent spread, so regulation is by slaughter.  There are 3 types of isolate, with the most highly pathogenic causing up to 10% fatality and a haemorrhagic syndrome.  She described how in 2007 the virus had spread from Africa to Georgia, then in 2009 to southern Russia and all way to the far north, in wild boar.

There are more than 50 proteins in the dsDNA-containing virion; two infectious forms similar to the poxviruses with multilayer membranes and capsid layers can form, and neutralising Ab play no part in protection as a result.  They studied the interaction of viruses with cells and the immune system, and compared the genomes of pathogenic and non-pathogenic strains, in order to understand how to develop an effective vaccine.

The biggest differences were large deletions in non-virulent isolates, including genes coding for  proteins responsible for binding to RBC, and various immune evasion multicopy genes.  They planned to target regions to delete to make an attenuated virus for vaccine.  They had found non-essential genes involved in immune evasion, and ones that lower virulence, and had been systematically cutting them out.  She noted that pigs can be protected if they survive natural infection and if vaccinated with TC-attenuated virus, and can be protected by passive transfer of Abs from immune pigs – which indicated that an effective live vaccine was very possible.

Subunit vaccines were being investigated, and they had found partial protection with baculovirus-expressed proteins.  They were doing genome-wide screens for protective Ag, and were pooling Ags expressed from predicted ORFs in immunization trials – up to 47 Ags without reduction in specific  T cell responses.

Discovery One

My former labmate Dion du Plessis (Onderstepoort Veterinary Institute, OVI) made a welcome return to Cape Town, with a talk entitled “2011: A Phage Odyssey”.  He explained the title by noting the distinct resemblance of P1 coliphage to the Discovery One spacecraft dreamed up by Arthur C Clarke and Stanley Kubrick – and then went on to exuberantly and idiosyncratically recount a brief history of bacteriophages and their use in biotechnology since their discovery.  A revelation from his talk was that the first discovery of phages was probably described by a gentleman named Hankin, in 1896 in Annales de l’Institut Pasteur: he

The 1896 paper from Annales de l'Institut Pasteur

showed that river water downstream of cholera-infested towns on the Jumma river in India contained no viable Cholera vibrio – and that this was a reliable property of the water.  We were also introduced to the concept of turtles as undertakers in the Ganges….

He took us through the achievements of the Phage Group of Max Delbruck and others – where science was apparently fun, but also resulted in the establishment of modern molecular biology – through to the use of phages as exquisitely sensitive indicators immunochemistry studies in the 1960s.

All too soon we got to the modern uses of phages, with 3 types of gene library – random peptide, fragmented gene, and antibody V regions – being used to make recombinant phage tail proteins to be used for “panning” and enrichment purposes, in order to select either specific antibodies or antigens.  Dion manages a research programme at OVI aimed at developing a new generation of veterinary vaccines – and has for some years now been making significant progress in generating reagents from a chicken IgY single-chain Fv phage display library.

Carolyn Williamson (IIDMM, UCT) gave us an update on CTL epitopes associated with control of HIV-1 subtype C infections.  She said that it was now known that genome-wide association studies (GWAS) gives you certain HLAs which are associated with low viral load, and others with high – meaning that to some extent at least, control of infection was down to genetic luck.  She noted that they and others had shown that CTL escape was quick: this generally happened in less than 5 weeks in acute phase infections.

They had looked for evidence of a fitness cost of CTL escape – and shown that it exists.  She noted that this meant that even if one has “bad” HLA genes, if one was infected with a virus with fitness cost mutations from another, that one could still control infection.

It had been shown that “controllers” mainly have viruses with attenuating mutations, or have escapes in the p24 region – and it was a possible vaccine strategy to include these mutated epitopes in vaccines to help people with infections control their infections.

An interesting topic she broached was that of dual infections – there was the possibility of modelling if infection with two different viruses results in increased Ab neutralisation breadth, and if one would get different results if infections were staggered, possibly with increased nAb evolution if isolates were divergent.  She noted it was possible to track recombination events with dual virus infections too.

It was interesting that, as far as Ab responses went, there were independent responses to 2 variants and one could get a boost in Ab titres to the superinfecting virus, but not a boost to Abs reacting with the originally-infecting virus

Carolyn was of the opinion that HIV vaccines needed to include CTL epitopes where escape is associated with fitness cost.  She also reiterated that superinfection indicated that one can boost novel responses, which I take to mean that therapeutic applications are possible.

Ulrich Desselberger (University of Cambridge) is a long-time expert on rotaviruses and the vaccines against them, and it was a pleasure to finally hear him speak – and that he was mentoring young people in South Africa.  He said that more than a third of children admitted to hospital worldwide were because of rotavirus infections, meaning that the viruses were still a major cause of death and morbidity – and they were ubiquitous.

He reviewed the molecular biology and replication cycle of rotaviruses in order to illustrate where they could be targeted for prevention of infection or therapy, and noted that drugs that interfere with lipid droplet homeostasis interfere with rotavirus replication because 2 viral proteins associated proteins of lipid droplets.

He stated that there were lots of recent whole-genome sequences – we already there were many types, based on the 2 virion surface proteins; we  now know that other genes are also highly variable.  As far as correlates of immunity were concerned, VP7 & 4 were responsible for eliciting neutralising Ab.  Additionally, protective efficacy of VP6 due to elicitation of non-neutralising Ab had been shown in mice – but not in piglets, and not convincingly in humans.  Abs to VP2, and NSP2 and 4 were also partially protective in humans.  It was interesting that protection was not always correlated with high titre nAb responses.

He noted that in clinical disease primary infections partially protected against subsequent infections which are normally milder; subsequently no disease was seen even when infection occurred.  Cross-protection occurred at least partially after initial infection, and this got better after more exposure.  There was evidence one could get intracellular neutralisation by transcytosed Ab, and especially to VP6.  Ab in the gut lumen was a good indication of protection.

As far as the live modern vaccines were concerned, Merck’s Rotateq elicited type-specific nAb, with 9% of recipients shedding live virus.  GSK’s Rotarix gets elicits cross-reactive nAb and one gets 50% of recipients shedding virus.

While the vaccines seemed safe, he noted that where vaccines had been introduced, efficacy ranged from 90% in the USA and Europe, down to as low as 48% in Bangladesh, Malawi and SA, due to type mismatch, and that efficacy was correlated inversely with disease incidence and child mortality generally.  He mentioned that there had been much VLP work, but that none of the candidates was near licensure.

Johan Burger (Stellenbosch University) spoke on one of the more important non-human virus problems in our immediate environment – specifically, those affecting wine grape production in our local area.  He opened by stating that SA now produced 3.7% of the world’s wine, making grapes a nationally and especially locally important crop.  Leafroll disease was a major worldwide problem – as well as being the reason for the wonderful autumn reddening seen in grapevines, it also significantly limited production in affected vineyards.  His laboratory has done a lot of work in both characterising viruses in grapevine, and trying to engineer resistance to them.  Lately they were also investigating the use of engineered miRNAs as a response to and means of controlling, virus infection.

His group has for a couple of years been involved in “metaviromic” or high-throughput sequencing studies of grapevines, with some significant success in revealing unsuspected infections.  In this connection, he and Don Cowan pointed out that they had lots of data that they ignore – but which we should keep and study, as a resource for other studies not yet thought of.

As far as Johan’s work went, novel viruses kept popping up, including grapevine virus E (GVE), which hitherto had only been found in Japan.  They were presently looking at Shiraz disease, which was unique to SA, and was still not understood.  This was infectious, typified by a lack of lignification which led to rubbery vines, and kills plants in 5 years.  It also limits the production of the eponymous grapes – a crime when SA shirazes seem to be doing so well!

Veterinary Virology and Vaccines parallel session.

I again dodged the clinical / HIV session because of my personal biases, and was again treated to a smorgasbord of delight: everyone spoke well, and to time, and I was really gratified to see so many keen, smart young folk coming through in South African virology.  It was also very interesting to see highly topical subjects like Rift Valley fever and rare bunyavirus outbreaks being thoroughly covered, so I will concentrate on these.

P Jansen van Veeren (NICD, Johaanesburg) was again a speaker, this time representing his absent boss, Janusz Paweska.  He gave an account of the 2010 Rift Valley fever outbreak in SA, and epidemiological findings in humans – something of keen interest to me.  He said there had been some forecasting success for outbreaks in East Africa; however, there were long gaps between outbreaks, which were generally linked to abnormal rainfall and movement of mosquito and animal hosts.  RVFV isolates differed in pathogenicity but were structurally and serologically indistinguishable – because virulence was due to the NSs protein, and not a virion component.  He recounted how artificial flooding of a dambo in Kenya resulted in a population boom in the floodwater Aedes mosquitoes responsible for inititating an outbreak, and then of the Culex which maintained the epidemic.  He said there was a strong correlation between viral load and disease severity.

In terms of South African epidemiology, there had been smaller outbreaks from 2008 round the Kruger National Park (NE SA), then in the Northern Cape and KZN in 2009.  People had been infected from autopsy of animals, and handling butchered animal parts.  The 2010 outbreak started in the central Free State after an unusually wet period, and had then spread to all provinces except Limpopo and KZN.  In-house serological methods at the NICD were validated in-house too: these were HAI screening and IgM and IgG ELISAs and a virus neutralisation test.  They had got 1600+ samples of human serum, and confirmed 242 cases of disease and 26 deaths for 2010.

He noted that with winter rains there was a continuous outbreak in the Western Cape, and in 2011 the epidemic had started again in the Eastern and Western Cape Provinces, but has since tailed off.  Some 82% of human cases were people who occupationally handled dead animals, although there was some possibility of transmission by mosquitoes.

In human cases there was viraemia from 2-7 days, with IgM present transiently from 3 days at low level.  They had sequenced partial GP2 after PCR from 47 isolates, and showed some recombination occurring.  The 2010 isolates were very closely related to each other, and to a 2004 Namibian isolate.  There had been no isolation from mosquitoes yet.

Two talks on FMDV followed: Belinda Blignaut (OVI and Univ Pretoria) spoke on indirect assessment of vaccine matching by serology, and Rahana Dwarka (OVI) on a FMDV outbreak in KZN Province in 2011.  Belinda’s report detailed how 6 of 7 serotypes of FMDV occur in SA, with SAT-1 and -2 and O the most common – and that vaccines needed to be matched to emerging strains.  This was done by indirect vaccine matching tests such as serological r-value, determined by the ratio of the reciprocal serum titre to the heterologous virus against that to the homologous virus.  They had put 4 different viruses into cattle and got sera to test a range of 26 newly isolated viruses.  While they had not got sequence from the test panel viruses, indications were that topotype 3 viruses are antigenically more disparate and that a vaccine consisting of topotype 1 or 2 antigens may not be effective in the control of FMD.

In introducing Rahana’s talk, the chair (Livio Heath, OVI) mentioned that there had been 5 different major animal pathogens causing outbreaks in SA over the last 3 years – and that they had to produce reagents and validate tests for ASFV, classical swine fever (CSF) and FMDV, etc, with each outbreak.  Rahana described how they had neutralisation assays and blocking and competition ELISA for FMDV, as well as a big database of isolates from buffalo in KZN – so they were well-placed to type viruses found in cattle in the region.

C van Eeden (Univ Pretoria) had an intriguing account of their investigation of the occurrence of an orthobunyavirus causing neurological symptoms in horses and wildlife.  Horses seem to be particularly vulnerable to many of the viruses involved in such disease, and so are a useful sentinel species.  Shuni virus was first isolated from Culicoides midges and sheep and a child in Nigeria in the 1960s.  SA workers subsequently found it in some livestock and Culex mosquitoes and in horses.  The virus was shown to be a neurologic disease agent in horses and wildlife – then disappeared for some 30 years, much like Ebola.  There is apparently a new research unit at UP with a BSL3 lab, so they are well equipped to do tests with the virus.

Ms van Eeden noted that the incidence of encephalitic disease in humans and animal in SA is underreported, and the causes are mainly unknown – a revelation to me!  Horses are susceptible to many of the agents, and are useful sentinels – workers have identified flavi- and alphaviruses in some outbreaks, but many are not IDed.  They had done cell culture and EM on samples from an ataxic horse: they got a bunyavirus-like virus by EM, and did bunya-specific PCR, and got Shuni virus back.  Sequence relationships showed no linkage to type of animal or date, in subsequent samplings from horses, crocodiles,  a rhino and a warthog, and from blood, brain and spinal cord.  All positive wildlife were sampled in Limpopo Province; horses only from most other provinces.

She noted that latest cases were neurological, whereas previously these were mainly febrile.  The virus accounted for 10% all neurological cases, with a 50% fatality rate.  She noted further that vets often work without masks or gloves, and so had no protection from exposure in such cases….  There was no idea on what the vector was, but they would like to test mosquitoes, etc.  Ulrich Desselberger suggested  rodents may be a reservoir, but they don’t know if this is true.

Stephanie van Niekerk (Univ Pretoria) investigated alphaviruses as neurological disease agents in African wildlife.  The most common alphaviruses in SA are Sindbis and Middelburg viruses.  Old World alphaviruses are usually not too bad, and cause arthritic and febrile symptoms, while New World cause severe neurological diseases.  Sindbis was been found in SA outbreaks in 1974.  However, Stephanie noted that a severe neurological type had appeared since 2008 in horses.  Accordingly, they looked at unexplained cases in wildlife in the period 2009-2011: brain and spinal cord samples were investigated for all cases.  They found alphavirus in a number of rhinos, buffalo, warthog, crocodiles and jackal – and all except for one rhino were Middelburg virus.  They want to isolate viruses in cell culture, and increase the size of regions used for cDNA PCR.  Stephanie said the opinion was that the values of the animal involved justifies the development of vaccines.

 

Virology Africa 2011: viruses at the V&A Waterfront 1

12 December, 2011

We thank Russell Kightley for permission to use the images

Anna-Lise Williamson and I again hosted the Virology Africa Conference (only the second since 2005!), at the University of Cape Town‘s Graduate School of Business in the Victoria & Alfred Waterfront in Cape Town.  While this was a local meeting, with just 147 attendees, we had a very international flavour in the plenaries: of 18 invited talks, 9 were by foreign guests.  Plenaries spanned the full spectrum of virology, ranging from discovery virology to human papillomaviruses to HIV vaccines to tick-borne viruses to bacteriophages found in soil to phages used as display vectors, and to viromes of whole vineyards.  There were a further 52 contributed talks and 41 posters, covering topics from human and animal clinical studies, to engineering plants for resistance to viruses.

A special 1-day workshop on “Human Papillomaviruses – Vaccines and Cervical Cancer Screening” preceded the main event: this was sponsored by Merck Sharp & Dohme, Roche and Aspen Pharmacare, and had around 90 attendees.  Anna-Lise Williamson (NHLS & IIDMM, UCT) opened the workshop with a talk entitled “INTRODUCTION TO HPV IN SOUTH AFRICA – SCREENING FOR CERVICAL CANCER AND VACCINES”, and set  the stage for Jennifer Moodley (Community Health Dept, UCT) to cover health system issues around the prevention of cervical cancer in SA, and the newly-minted Dr Zizipho Mbulawa (Medical Virology, UCT) to speak on the the impact of HIV infection on the natural history of HPV.  This last issue is especially interesting, given that HIV-infected women may have multiple (>10) HPV types and progress faster to cervical malignancies, and HPV infection is a risk factor for acquisition of HIV.  The Roche-sponsored guest, Peter JF Snijders (VU University Medical Center, Amsterdam), gave an excellent description of novel cervical screening options using primary HPV testing, to be followed by two accounts of cytological screening in public and private healthcare systems in SA, by Irene le Roux (National Health Laboratory Service) and Judy Whittaker (Pathcare), respectively.  Ulf Gyllensten (University of Uppsala, Sweden) described the Swedish experience with self-sampling and repeat screening for the prevention of cervical cancer, especially in groups that are not reached by standard screening modalities.  Hennie Botha and Haynes van der Merwe (both University of Stellenbosch) closed out the session with talks on the effect of the HIV pandemic on cervical cancer screening, and a project aimed at piloting adolescent female vaccination against HPV infection in Cape Town.

The next part of the Workshop overlapped with the Conference opening, with a Keynote address by Margaret Stanley (Cambridge University) on how HPV evades host defences (sponsored by MSD), and another by Hugues Bogaert (HB Consult, Gent, Belgium)) on comparisons of the cross-protection by the two HPV vaccines currently registered worldwide (sponsored by Aspen Pharmacare). Margaret Stanley’s talk was a masterclass on HPV immunology: the concept that such a seemingly simple virus (only 8 kb of dsDNA) could interact with cells in such a complex way, was a surprise for all not acquainted with the viruses.  Bogaert’s talk was interesting in view of the fact that the GSK offering, which has only only two HPV types, raises far higher titre antibody responses than the MSD vaccine with four HPV types, AND seems to elicit better cross-protective antibodies: this should help inform choice of product from the individual point of view.  However, the fact that MSD seems able to respond better to national healthcare system tenders in terms of price per dose is also a major factor in the adoption stakes.

The Conference proper started with a final address by Barry Schoub, long-time but now retired Director of the National Institute of Virology / National Institute of Communicable Diseases in Johannesburg, and also long-time CEO of the Poliomyelitis Research Foundation (PRF): this is possibly the premier funding agency for anything to do with viruses in South Africa, and a major sponsor of the Conference.  He spoke on the history of the PRF, and how it had managed to shepherd an initial endowment of around 1 million pounds in the 1950s, to over ZAR100 million today – AND to dispense many millions in research project and bursary funding in South Africa over several decades.

The first session segued into a welcoming cocktail reception and registration at the Two Oceans Aquarium in the V&A Waterfront: this HAS to be one of the only social events for an academic conference where the biggest sharks are the ones in the tank, and not in the guest list!  I think people were suitably blown away – as always, in the aquarium – and the tone was set for the rest of the meeting.  The wine and food were good, too.

The first morning session of the conference featured virus hunting and HIV vaccines, as well as plant-made vaccines and more HPV.  W Ian Lipkin (Columbia University, USA) opened with “Microbe Hunting” – which lived up to its title very adequately, with discussion of a plethora of infectious agents.  As well as of the methods newly used to discover them, which include high-throughput sequencing, protein arrays, very smart new variants on PCR….  I could see people drooling in the audience; the shop window was tempting enough to make one jump ship to work with him without a second thought.  He said that probably 99% of vertebrate viruses remain to be discovered, and that advances in DNA sequencing technology were a major determinant in the rapidly-increasing pace of discovery.  He made the point that while the emphasis in the lab had shifted from wet lab people to bioinformatics, he thought it would move back again as techniques get easier and more automated – meaning (to me) that there is no substitute for people who understand the actual biological problems.  It was interesting that, while telling us of his work on the recently-released blockbuster “Contagion” – where “the virus is the star!” – he showed a slide with a computer in the background running a recombination detection package called RDP, which was designed in South Africa.  It can also be seen in the trailer, apparently.  Darren Martin will not be looking for royalties or screen credits, however.

Don Cowan (University of the Western Cape) continued the discovery theme, albeit with bacteriophages as the target rather than vertebrate viruses.  It is worth emphasising that phages probably represent the biggest source of genetic diversity on this planet – and given how even the most extreme of microbes have several kinds of viruses, as Don pointed out, it is possible that this extends to neighbouring planets too [my speculation - Ed].  He occupies an interesting niche – much like the microbes he hunts – in that he specialises in both hot and cold terrestrial desert environments, which are drastically understudied in comparison to marine habitats.  He made the interesting point that metagenome sequencing studies such as his own generate data that is in danger of being discarded without reuse, given that folk tend to take what they are interested out of it and neglect the rest.

Anna-Lise Williamson (NHLS, IIDMM, UCT) then described the now-defunct SA AIDS Vaccine Initiative vaccine development project at UCT.  It is rather sobering to revisit a project that used to employ some 45 people, and had everything from Salmonella, BCG, MVA, DNA and insect cell and plant-made subunit HIV vaccines in the pipeline – and now employs just 5, to service the two vaccines that made it into into clinical trial.  The BCG-based vaccines continued to be funded by the NIH, however, and the SA National Research Foundation funds novel vaccine approaches.  Despite all the funding woes, the first clinical trial is complete with moderate immunogenicity and no significant side effects, and two more are planned: these are an extension of the first – HVTN073/SAAVI102 – with a Novartis-made subtype C gp140 subunit boost, and the other is HVTN086/SAAVI103, which compprises different commbinations of DNA, MVA and gp140 vaccines.

It was clear from the talk that if South Africa wants to support local vaccine development, the government needs to support appropriate management structures to enable this – and above all, to provide funding.  However, all is not lost, as much of the remaining expertise in several of the laboratories that were involved in the HIV vaccine programme can now involve themselves in animal vaccine projects.

Plant-made HPV16 VLPs

Ed Rybicki made it an organisational one-two with an after-tea plenary on why production of viral vaccines in plants is a viable rapid-response option for emerging or re-emerging diseases or bioterror threats.  The talk briefly covered the more than 20 year history of plant-made vaccines, highlighting important technological advances and proofs of concept and efficacy, and concentrated on the use of transient expression for the rapid, high-level expression of subunit vaccines.  Important breakthoughs that were highlighted included the development of the Icon Genetics TMV-based vectors, Medicago Inc and Fraunhofer USA’s recent successes with H5N1 and H1N1 HA protein production in plants – and the Rybicki group’s successes with expression of HPV L1-based and E7 vaccine candidates.  The talk emphasised how the technology was inherently more easily scalable, and quicker to respond to demand, than conventional approaches to vaccine manufacture – and how it could profitably be applied to “orphan vaccines” such as for Lassa fever.

Ulf Gyllensten had another innings in the main conference, with a report on a study of a possible linkage of gene to disease in HPV infections – which could explain why some people clear infections, and why some have persistent infections.  They used the Swedish cancer registry (a comprehensive record since the end of the 1950s) to calculate familial relative risk of cancer of the cervix (CC): relative risk was  2x for a full sister, the same for a mother-daughter pair and the risk for a half sister was 50% higher while risk was not linked to non-biological siblings or parents, meaning the link was not environmental.  A preliminary study found HLA alleles associated with CC, and increased carriage of genes was linked to increased  viral load.   A subsequent genome wide association study using an Omni Express Bead Chip detecting700K+ SNPs yielded one area of major interest, on Chr 6 – this is a HLA locus.  They got 3 independent signals in the HLA region and can now potentially link HPV type and host genotype for a prediction of disease outcome.  Again, the kinds of technology available could only be wished for here; so too the registry and survey options.

Molecular and General Virology contributed talks parallel session

I attended this because of my continued fascination with veterinary and plant viruses – and because Anna-Lise was covering the Clinical and Molecular session – and was not disappointed: talks were of a very high standard, and the postgraduate students especially all gave very good accounts of themselves.

Melanie Platz (Univ Koblenz-Landau, Germany) kicked off with a description of a fascinating interface between mathematics and virology for early warning, spatial awareness and other applications.  She gave an example using a visual representation of risk using GIS for Chikungunya virus, based on South African humidity and temperature data going back nearly 100 years: this had a 3D plot model, into which one could plug data to get predictions of mosquito likelihood.  They could generate risk maps from the data, to both inform public and policy / planning.  They had a GUI for mobile devices for public information, including estimates of risk and what to do about it, including routes of escape.

Cover Illustration: J Virol, October 2011, volume 85, issue 20

This was followed by one of my co-supervised PhD students, Aderito Monjane – who recently got the cover of Journal of Virology with his paper on modelling maize streak virus (MSV) movement and evolution, so I will not detail more here.  However, even as a co-supervisor I was blown away by the fact that he was able to show animations of MSV spread – at  30 km/yr, across the whole of sub-Saharan Africa.

Christine Rey of Wits University provided another state-of-the-art geminivirus talk, with an account of the use of siRNAs and derivatives for silencing cassava-infecting geminiviruses.  They were using genomic miRNA precursors as templates to make artificial miRNAs containing viral sequences, meaning they got no interference with nuclear processing and there was less chance of recombination with other viruses, a high target specificity, and the transgenes would not be direct targets of virus-coded suppressors.  They could also use multiple miRNAs to avoid mutational escape.  The concept was successful in tobacco, and they had got transformation going well for cassava, so hopes were high for success there.

Dionne Shepherd (UCT) spoke on our laboratory’s 15+ year work on engineered resistance in maize to MSV.  She pointed out that the virus threatens the livelihood of 200 million+ subsistence farmers in Africa, and is thought to be the biggest disease concern in maize – which is still the biggest edible crop in Africa.  Most of the work has been described elsewhere with another journal cover; however, new siRNA-based constructs still under investigation were even more effective than the previous dominant negative mutant-based protection: the latter gave 50-fold reduction in virus replication, but silencing allowed > 200-fold suppression of replication.

2-colour surface rendition of HcRNAV

Arvind Varsani – a former UCT vaccinology PhD who is now a structural biology and virology lecturer at Univ Christchurch (NZ) – described what is probably the first 3D structure of a virus to come out of Africa.  This was of a 30 nm isometric ssRNA virus – Heterocapsa circularisquama RNA virus (HcRNAV) – infecting a dinoflagellate, which is one of the most noxious red tide bloom agents and is a major factor in killing farmed oysters.  The virus apparently controls the diatom populations.  There are two distinct strains of virus, and specificity of infection is due to the entry process, as biolistic bombardment obviates the block.  The single capsid protein probably has the classic jelly-roll β-barrel fold, but they observe a new packing arrangement that is only distantly related to the other ssRNA (+) virus capsids known.  They will go on to look at structural differences between strains that change cell entry properties.

FF Maree from the Onderstepoort Veterinary Institute and the Univ Pretoria spoke on structural design of FMDV to improve vaccine strains: they wished to engineer viruses by inserting the cell culture adapted HSPG-binding signature sequence and to mutate capsid residues to increase the heat stability of SAT-2 subtype virus vaccines.  If they put the signature sequence in a SAT1 virus, they found it could infect CHO cells – which do not express any of 4 integrins that FMDV binds to, but are far better for large-scale production of the virus than the BHK cells used till now.  It was also possible to increase hydrophobic interactions in the capsid by modeling: eg a VP2 Ser to Tyr replacement gave a considerably better thermal inactivation profile to the virus.

Daria Rutkowska (Univ Pretoria) detailed how African horsesickness orbivirus (AHSV) VP7 protein had significant potential as a scaffold that could act as a vaccine carrier.  The native protein formed as trimers assembled in a VP3+VP7 “core” particle; however, the VP7 when expressed alone could form soluble trimmers – and the “top” domain hydrophilic loop can tolerate large inserts.  The group had very promising FMDV P1 peptide responses from engineered VP7 constructs, including protection of experimental animals.

P Jansen van Veeren of the National Institute of Communicable Disease in Johannesburg finished off the session, with a description of the cellular pathology caused by Rift Valley fever bunyavirus (RVFV) in mice in acute infections.  The virus seems to have been of particular international interest recently as a potential bioterror agent; however, global warming is also responsible for its mosquito vector spreading outside of its natural base in Africa to the Arabian peninsula, and there are fears of the virus getting into Europe soon.  While there are vaccines against the virus, including a live attenuated version, none are licenced for human use.  It was interesting to hear that the viral NP appears to be the main immunogen, as there are massive amounts of NP produced in infection, and huge responses to it in infected animals – and NP immunisation protects mice.  There is a good Ab response but it is not neutralising, while NP is released independently of other proteins from infected cells.  The liver is the major target of virus infection, with a bias to apoptosis of hepatocytes and severe inflammatory responses.  Viral load is linked to these effects and is much lower in vaccinees.  Immunisation reduces liver replication markedly; that in the spleen less so.  A screen of cytokines and other gene responses showed a big down-regulation of many genes in non-vaccinated mice to do with cytokines, and down-regulation of B and T cells and NK cells.  He thinks recombinant vaccine candidates should have both the surface glycoproteins and the NP in order to be effective – and that there is a major need for proper reagents for big animal studies.

HIV Vaccines From Bangkok – 4, and final….

22 September, 2011

Thursday morning started with three parallel oral sessions – and I chose Symposium 07, Characterization of Breakthrough Viruses.  The second talk – by Morgane Rolland, in the US Military HIV Research Program – detailed a study of the sieve analysis of breakthrough viruses in the RV144 Thai trial.  They wished to see whether or not the vaccine could block infection of specific variants, and thought they might see that viruses in vaccinees were evolutionarily distant from the insert in the vaccine, relative to the placebo arm.

HIV and its life cycle

The saw no differences in virus diversity over 10 sequences per person, in 121 people,  71 of whom were in the placebo arm.  They did note, however, that linked transmissions showed less diversity in the env gene than normal – 1 vs 10%.  Over 75% of cases had a single founder virus, in both placebo and vaccine arms.  There was no significant divergence from the vaccine sequence in either group in anything but the Pro aa sequence – with some non-significant evidence for Env variation.

When they looked for Env sites under selection in gp120, they saw 4 in the placebo group at positions 181, 208, 327 and 359 – with less variation in vaccine than placebo recipients.  Rolland speculated that this could be to do with entry being more restrictive in vaccinees?  4 different sites in the vaccine group were under selection: they found that for MHC I epitopes there was a greater distance for vaccine than placebo groups, with a result that was not significant for MHC II epitopes.

There was a trend toward longer Env V2 loop sequences in vaccinees at later times, and a reduced number of cysteines in Env among vaccinees – this was seen also in the VAX004 trial.

Phil Berman – formerly of VaxGen, which made the gp120 for RV144 and earlier trials – mentioned that there was lower variance in Env than in the unsuccessful VAX 003 trial.  Jerome Kim noted that men seroconverting had a much higher incidence of HCV infection – which could be associated with undeclared IV drug use.

Katharine Barr of Univ Alabama spoke next, on the increased incidence of multiple variant transmission of HIV in VAX003 injection drug users.  She noted that this efficacy trial was of gp120 in IV drug users, while VAX004  was in MSM and high-risk women: they speculated that differences if any could be due to transmission route – as in, IV route vs sexual.  She further noted that in RV144, the best (non-significant) effect was in low-risk heterosexuals.

Something that was a little disturbing to me, given HIV transmission in our part of the world is overwhelmingly by heterosexual sex, was that the IV route is responsible for 10% of world infections.  They had looked at transmitted founder viruses – the ones going in and replicating in recipients.  They predicted that consensus of a low diversity lineage is the sequence of the founder virus – and that several founders would give multiple low variance lineages.

She noted that 80% of heterosexual infections are established by single viruses, so there exists a window of opportunity of viral vulnerability when vaccine-induced immunity could block infection.  However, with MSM, the multiple infection goes up to 40%; while injection drug users (IDUs) are less studied, multiplicity goes up  60% in one study and 31% in another….

Looking at Vax003 results, they had asked how high a barrier there had been for placebo infections, and whether in vaccinees there were more or fewer founder viruses?  While they had found that there was an 44% incidence of multiple variant transmission in the  placebo arm, and  22% in the vaccinees, this was unfortunately not significant, given the low numbers.  There was a median of 1.8 viruses per transmission vs 1.3, but this too was not significant.  However, it could mean there is a higher bar for vaccine protection among IDUs, which has important implications for which groups to use in vaccine trials.

Katherine incidentally gave the best answer yet heard to a long and detailed question: “I think that’s a really good question but I have zero data to address it…” = I don’t know.

Which prompted thoughts of new conference drinking games: take a shot every time you hear a speaker say “I would like to thank the organisers for inviting me…”, or “Our hypothesis [generally pronounced hy-PAH-the-sis] was…”, or a question which starts with either “…really good talk / great data” or “So – ummmm – when you/we did…”.

Paul Edlefsen (Fred Hutchinson Cancer Res Ctr) described a sieve analysis of RV144 [and started: “So...umm...” = another shot!].  He repeated the finding that observed correlates of risk generated two hypotheses; namely, that high IgG response to Env protected from HIV infection while a high IgA response interfered with protection.  Additionally, analysis of the antibody response using scaffold V region showed that a high V2 response correlated with a lower infection rate.  He noted that the STEP trial results showed a distinct difference in Gag between vaccine and placebo groups.  He noted further that were only 110 usable subjects in RV144, so they could only detect large sieve effects in their study of CTL and Ab epitope responses.

MUCH MIND-NUMBINGLY BORING STATISTICAL METHODOLOGY FOLLOWED…sorry, Paul!

There were 2 sites of evidence for sieving – aa positions 169 and 181 in the Env V2 loop, in the middle of a region identified by Ab binding array data.  There was also some evidence of covariation among pairs of aa residues in the V2 loop for vaccinees only.

After a long and complicated structural question, he gave the second-best answer of the conference: “I could say that I do, or that I don’t – but I have so little expertise in this area…(laughter)”.  And after long rambling statement: – “I’m sorry, was there a question in there?”

Brandon Keele (National Cancer Inst, MD) described work on NHPs which they had extended to studying human transmission of HIV, on transmitted/founder viruses.  NHP studies show multiple founders because doses are high generally, in order to get 100% infection rates.  One study using very low dose multiple intrarectal exposures to see if one can immunise macaques showed that one virus could do it.  Animals followed up from early times stayed with one evolving variant.

He noted that the consensus sequences in humans posited to have had one transmitted variant are average in  neutralisation susceptibility.  These viruses are all functional in vitro and in vivo and one can get full length viral clones ex NHPs which recap original founder viral load and pathogenicity.  All such viruses use the CCR5 coreceptor.  All HIV clones replicate in CD4 T-cells but not in  macrophages.  The transmission signature is to increase Env processing and infectivity.

They now mix cloned viruses with tags so can follow them in NHP challenge experiments, as most challenge studies have used virus with <1% diversity, which represents a clone in any one epitope – which he felt to be non-reflective of the real world .

The closing plenary session was opened by IAVI‘s Wayne Koff, who remarked that he had heard someone say “The  airport….”, in answer to the session name “Where do we go next?”….

Jeffrey Boyington (Vaccine Res Ctr) described some very impressive work on using structure of Env for rational immunogen design, specifically to target the CD4 binding site as a good target for broadly neutralising Ab.  They used crytallographic data to make proteins best mimicking the struc and then used them as immunogens.  They had used stabilised resurfaced gp120 with mutations around the binding site and isolated dozens of Abs with them from several infected subjects.  Part of the process involved stabilising flexible regions by bolstering cysteine content, removing glycans from the site of interest and adding them to immunodominant sites, and using Chikungunya virus VLPs to multimerise spike proteins for maximal immunogenicity.  Boyington noted that there were 80 native trimers on the surface of the VLPs, and that one can put the Outer Domain of gp120 on the tip of each monomer.  They get good Ab back for gp120 and get CD4 binding site Ab in rabbits.  In rhesus monkeys primed with gp140 trimers they got good boosting and better Abs to the CD4 BS.

Altogether a very impressive account – and one which advances to possibility of other opportunities for the design of other good broad-binding vaccine epitopes.

Rick King of IAVI followed, with an account of the current status and future directions of vector-based HIV vaccines.  He stated that most HIV vaccines now involve vectors – so there is a wealth of data that can be efficacious, so how to use it?  He thinks that we want the next generation of vectored vaccines to block infection and control virus load – meaning a combination of Ab and cellular responses.He noted that in NHPs, SIV protection is possible, and that it requires Env in the vaccine – and that the mechanism of protection is under intense investigation right now.

He further noted that in a DNA prime MVA boost vaccine regime, protection is associated with the avidity of the Abs.  Thus, a major goal is to improve the response to Env, by identifying the nature of the protective response, and enhancing and using native Envs to do it.  He stated in this context that there were only two vaccine regimens using native spike protein – and that one of them is the SA AIDS Vaccine Initiative (SAAVI) vaccine.

It was possible to engineer Env to bind a broader array of broadly neutralising Ab and to incorporate it into vesicular stomatitis virus (VSV) instead of the native G protein spike, or into canine distemper virus (CDV, a measles relative), which replicates in lymphoid tissue.  One could also bias processing of Env in CDV to get better cleavage and presentation.  The rCDV could be put into ferrets and shown to replicate.

He said that while the RV144 vaccine did not control viral load, vaccines can control SIV replication, so we need to have those components in HIV vaccines.  For instance, recombinant live cytomegalovirus (CMV) expressing the whole proteome of SIV could control the virus, this was associated with CD8 effector memory T-cells.

He thought we need to capitalise on information on mechanisms of control, and to increase immunity by use of replicating vectors and heterologous prime/boost combos, and deal with diversity by broadening the response.  The reason for replicating vectors was because live attenuated virus works for SIV – preventing infection and controlling replication.  Possibilities were vaccinia, measles, VSV, Sendai, CMV, AdV, CDV and VSV-HIV chimaeras.  As for diversity, one could increase the number of epitopes by using mosaics, and direct responses using conserved epitopes, as Tomas Hanke has demonstrated in IAVI-funded trials using chimpanzee Ad as prime then MVA as a boost with his HIVCONS Ag.

Finally, there was what I consider to have been the best talk of the conference – simply because it was much wider in scope than the rest: Steven Reed of the Infectious Disease Res Inst, Seattle, described new generation adjuvants for use with HIV.  He started by noting that adjuvants were necessary for lots of things; eg: for T-cell vaccines for TB and leishmania; for Ab response-broadening (Cervarix, HPV vaccine); Ag dose sparing (eg flu); to combat immune sensescence, and for vaccine therapy.

They had focused on a toll-like receptor (TLR4) agonist as an adjuvant, following work that showed that the well-known MPL was a TLR4 agonist ,and vaccines including TLR agonists had been used unknowingly since 1885.

He thinks the ideal adjuvant should have no effect on lymphocytes, no systemic effects, no non-specific B or T cell responses, should elicit potent long-lived responses, should redirect ongoing immune responses, and should be safe and effective in all age groups.  They had accordingly designed GLA – based on lipid A – to bind TLR4: this was purely synthetic, and induces Th1 CD4 helper cells and a broad humoral immunity.  They used a hexaacyl chain length that was preferred by human TLR4, which is restricted to macrophages and dendritic cells, has transient local effects, and reduces inflammation so as to get better central memory.

They can also formulate it differently for different vaccines and can get very different effects thereby.  For example, emulsion alone stimulates Th2 responses while GLA stimulates Th1 even in combo with an emulsion, which helps in leishmania and TB vaccines.

He noted that alum-based adjuvant stimulated mainly a Th2 response, while adding GLA gives a Th1 response with the same antigen.  They get good Ab diversity with GLA and expansion of it with the malaria vaccine – and Ab diversity leads to better neutralisation (eg transl med 2011).

GLA increases and broadens the haemagglutination-inhibtion (HAI) Ab response to the influenza vaccine Fluzone, which contains lots of inactivated virions.  He noted one gets a better protective response against “drifted” viruses – which have evolved away from the vaccine strains – with GLA.  Baculovirus-made H5N1 vaccine requires 30x less vaccine to get the same response with GLA.

It is also possible to get mucosal immunity by IM vaccination with HIV gp140, according to Robin Shattock’s results.

Reed noted that intradermal adjuvants are very rare – and that this looks good with flu vaccines delivered this way.  They were in the process of optimising the adjuvant formulation for intradermal delivery to increase vaccine potency, get mucosal immunity, and CD8+ T-cell responses.  Dermal dendritic cells have a wider range of TLRs than Langerhans cells – so Sanofi target them with ID delivery, and GLA works well to amplify the response.  It was impressive that they could protect ferrets with a single ID vaccine shot of flu vaccine.  It was also interesting that they are working with Medicago Inc., who have one of the most successful plant-produced influenza virus vaccine candidates, presently in human trial.

Thereafter, closing remarks from the conference organiser were as one would expect; people were honoured for their present and long-term contributions – notably Jose Esparza – and the venue of the next conference was announced to be Boston, with Dan Barouch as Organising Chair.

It was a good conference, with all of the high-intensity interactions and presentations one would expect from such a loaded topic.  However, it possibly suffered from over-emphasis of the “RV144 results” – which weren’t that impressive, in my opinion – as part of an effort to keep up perceived momentum from announcement of the RV144 success (small as it was) from the previous meeting.  For me, the highlights were the envelope antigen design talks, and what I managed to catch of the actual virology, and especially analysis of diversity by massively parallel sequencing.

We still don’t have an effective HIV vaccine – but we’re getting closer. 

Re-engineering AAV

8 February, 2010

Adeno-associated virus (AAV) virion. Copyright Russell Kightley Media

Tweaking virus vectors used for gene therapy to change their receptor specificity is not necessarily new – but it has seldom been done (at least, to my mind) as elegantly as is reported in January’s Nature Biotechnology.  Asokan et al. report on

Reengineering a receptor footprint of adeno-associated virus enables selective and systemic gene transfer to muscle
Nature Biotechnology 28, 79 – 82 (2010)
Published online: 27 December 2009 | doi:10.1038/nbt.1599

From the abstract:

We generated a panel of synthetic AAV2 vectors by replacing a hexapeptide sequence in a previously identified heparan sulfate receptor footprint with corresponding residues from other AAV strains. This approach yielded several chimeric capsids displaying systemic tropism after intravenous administration in mice. Of particular interest, an AAV2/AAV8 chimera designated AAV2i8 displayed an altered antigenic profile, readily traversed the blood vasculature, and selectively transduced cardiac and whole-body skeletal muscle tissues with high efficiency. Unlike other AAV serotypes, which are preferentially sequestered in the liver, AAV2i8 showed markedly reduced hepatic tropism.

What impressed me most about the paper was the excellent modelling graphics: the authors were able to show, in simple 3-D atomic models, just how their mutations had changed the surface archotecture of the virus in question.  The whole-animal imaging was also very useful in showing very simply how effective their different constructs were.

(a) Three-dimensional structural model of the AAV2 capsid highlighting the 585–590 region containing basic residues implicated in heparan sulfate binding. Inset shows VP3 trimer, with residues 585-RGNRQA-590 located on the innermost surface loop highlighted in red. VP3 monomers are colored salmon, blue, and gray. Images were rendered using Pymol. (c) Representative live animal bioluminescent images of luciferase transgene expression profiles in BALB/c mice (n = 3) injected intravenously (tail vein) with AAV2, AAV8, AAV2i8 and structurally related AAV2i mutants (dose 1 × 1011 vg in 200 μl PBS) packaging the CBA (chicken beta actin)-Luc cassette. All AAV2i mutants show a systemic transduction profile similar to that of AAV8, with AAV2i8 showing enhanced transduction efficiency. Bioluminescence scale ranges from 0–3 × 106 relative light units (photons/sec/cm2). Residues within 585–590 region in each AAV2i mutant is indicated below corresponding mouse image data. (d) Comparison of AAV2, AAV2i8 and AAV8 capsid surface residues based on schematic “Roadmap” projections. A section of the asymmetric unit surface residues on the capsid crystal structures of AAV2 and AAV8, as well as a model of AAV2i8, are shown. Close-up views of the heparan sulfate binding region and residues 585–590 reveal a chimeric footprint on the AAV2i8 capsid surface. Red, acidic residues; blue, basic residues; yellow, polar residues; green, hydrophobic residues. Each residue is shown with a black boundary and labeled with VP1 numbering based on the AAV2 capsid protein sequence.

Adapted by permission from Macmillan Publishers Ltd: Nature Biotechnology 28, 79 – 82 copyright (2010)

Changing the tissue specificity of a well-characterised and often-used vector virus such as AAV in this way is an extremely useful thing to have done: it probably lowers the potential toxicity of the vector – by avoiding the liver – while preserving useful features such as the higher-level expression afforded by use of AAV2.

West Nile virus vaccine: almost a replicant

2 June, 2008

West Nile virus - a member of the family Flaviviridae - has insidiously spread halfway around the world from its origins in Africa, in just a few years.  It invaded the east coast of the USA, probably from the Middle East,  via either infected birds, mosquitoes, humans, or another vertebrate host in around 1999; since then it has spread all the way across the continent to the west coast, and has become truly endemic. 

Virions have a regular icosahedral-type structure, despite being enveloped, as a result of a structured nucleocapsid and a highly-structured array of envelope glycoprotein.  They contain a positive strand RNA genome of ~11 kb with a single long open reading frame that is translated as a polyprotein of about 3400 amino acids, which is then processed into individual regulatory and structural proteins.

The virus subtype spreading in North America – lineage 1 – causes encephalitis in humans, unlike the enzootic variant circulating in birds and animals in Africa.  It also cause severe mortality – near 100% in experimentally infected animals – among American Crows and other corvids: a feature of the spread of the disease has been dead crows found in and around towns in the USA.  A feature of lineage 1 viruses is their infection of horses and other equines as well – with up to one in three clinically-infected horses dying.  The human impact, however, is seen as a major problem: systemic febrile illness develops in ~20% of those infected with WNV, while severe neurologic illness developes in <1% of persons infected – with mortality rates of 5 -14% among persons with neurologic symptoms in recent US, Romanian, Russian, and Israeli outbreaks.

There has been a concentrated effort to develop a human vaccine or vaccines since the onset of the US epidemic – horse vaccines are already commercially available – and our knowledge of the virus has benefitted greatly as a result.  This includes a detailed structure for the virus, obtained by cryoelectron microscopy image reconstruction.

http://www.purdue.edu/uns/html4ever/031009.Kuhn.westnile.html

Purdue team solves structure of West Nile virus via kwout

 Now a team led by Alexander Khromykh from Brisbane in Queensland, Australia, writing in the May issue of Nature Biotechnology, have described a novel “single-round infectious particle” DNA vaccine against WNV which significantly increases protection in mice to lethal challenge with the live virus.   In the words of the authors:

“We augment the protective capacity of a capsid-deleted flavivirus DNA vaccine by co-expressing the capsid protein from a separate promoter. In transfected cells, the capsid-deleted RNA transcript is replicated and translated to produce secreted virus-like particles lacking the nucleocapsid. This RNA is also packaged with the help of co-expressed capsid protein to form secreted single-round infectious particles (SRIPs) that deliver the RNA into neighboring cells. In SRIP-infected cells, the RNA is replicated again and produces additional virus-like particles, but in the absence of capsid RNA no SRIPs are formed and no further spread occurs. Compared with an otherwise identical construct that does not encode capsid, our vaccine offers better protection to mice after lethal West Nile virus infection. It also elicits virus-neutralizing antibodies in horses. This approach may enable vaccination against pathogenic flaviviruses other than West Nile virus.”

Adapted by permission from Macmillan Publishers Ltd: Nature Biotechnology 26, 571 – 577, 20 April 2008 doi:10.1038/nbt1400 Single-round infectious particles enhance immunogenicity of a DNA vaccine against West Nile virus, David C Chang et al., copyright 2008

This is a very clever use of fundamental knowledge of virus structure and assembly: the virus envelope proteins – E and prM – can form budded particles if expressed in isolation; if expressed with the capsid protein, the particles encapsidate RNA with the appropriate encapsidation signal to form virions.  The DNA vaccine encodes a transcriptional unit corresponding to a viral genome which lacks only the capsid protein gene, as well as a separate capsid gene under back-to-back cytomegalovirus (CMV) promoters.  Thus, cells transfected with the DNA vaccine can produce both virus-like prM and E protein and membrane particles (VLPs), or pseudovirions which in addition contain a capsid and the engineered (=lacking capsid protein gene) genome.  While both are highly immunogenic, the pseudovirions can additionally infect other cells to release replicative genomic RNA, which can produce VLPs but not pseudovirions, as the capsid protein-encoding RNA is not encapsidated.  Thus, initial transfection leads to release of particles which allow a single subsequent round of VLP production, but no further spread of the replicative RNA.

A very clever trick – and worthy of being repeated for a number of related pathogenic flaviruses, including dengue and yellow fever viruses.

Even if the particles can’t pass the Voight-Kampff test…B-)



Follow

Get every new post delivered to your Inbox.

Join 594 other followers