Archive for the ‘Evolution’ Category

20 years on, and here we are with Ebola, again

25 August, 2014

Browsing through my own web pages in an effort to clean up dead-end links, and cull tired material, I discovered that my link to an essay I wrote 19 years ago was still live – and as it referred to something written in and put up on our nascent Web server in 1994, means it has a 20-year anniversary round about now.

My essay is

The Student, the Web and the Ebola Connection

or:

Dr Jacobson, are you going to Kikwit?”

…and it is a record of events that resulted in 1994 from (a) an Honours student essay being written on “Emerging Viruses”, and (b) me playing around with the then-very-new WWW server that UCT has enabled – but didn’t tell anyone about, because they didn’t want anyone to use it until they had sorted out policies.  Oh, and (c) – the Kikwit Ebola outbreak in 1995.

I wrote in 1995:

“The whole phenomenon has been an object exercise in the power of the Web as a tool for the wide dissemination of information: we reached not only professional virologists, but also health-care professionals, and – most importantly – the lay public on a large scale”

And of course, this is even more true now – which is why, following the benign guidance of The Guru Cann, I maintain ViroBlogy and Virology News, and heartily recommend a Web presence to anyone who feels they need to disseminate information on topics of specialist and generalist interest to the world at large.

Of course, nearly all the links out of that essay are now dead – including to the original essay, that for a while there in 1995 was the ONLY detailed information on Ebola available on the Web.  So here is Alison Jacobson’s original essay, in full, revealed by going to my teaching material and checking out essays from 1997 and thereabouts:

EMERGING AND RE-EMERGING VIRUSES: AN ESSAY

Of course, I also maintained a daily update on the Kikwit outbreak, and then a couple of the next ones, before the Web caught up with me and it became easier to just trawl it for news via Google and its predecessors.  It still makes interesting reading, though, to go through some of what was posted from the disease frontlines back in the 1990s – and to remember that I had the TIME to do that kind of thing!

Where we are now

Well, here we are with what is the worst outbreak of Ebola in history, and here am I – again – trying to keep up with it.  This time, by the very excellent medium of the Web news aggregator Scoop.it, where I have established Virology News as a means of quickly and easily getting news out to the public.  Again, following the very excellent example of TGC, but also Chris Upton, who babied me along by letting me co-curate his Virology and Bioinformatics site.

Of course, there is a new angle to this outbreak – and that has been the compassionate use of a plant-made monoclonal antibody cocktail (ZMapp), hitherto only tested preclinically in a primate model.  Fortuitously, this all happened while I was finishing off a review on plant-made viral vaccines, so I reported on it – with references – here on ViroBlogy.

I was also able to report on it in my Plant Molecular Farming news site, with some authoritative statements from pioneers of the technology: Charles Arntzen from the Arizona Biodesign Institute sent through a link for an interview he did, and CNN covered it quite well too.  Charlie also sent through a set of links in an email that he was happy to share:

“The original story

There is a lot of interest from the press in “why tobacco” and “how does it work”?

The other focus is on the politics of scale up of the drug — it seems that criticism of the US is mounting in some sectors of Africa, and elsewhere.   I talked to a Spanish Language radio news station this morning, and the main questions related to “why is this a Secret Drug; are you trying to hide the secret from the world?”    “Is Reynolds tobacco trying to stop the supply of this drug to Africans?”    One guy asked if it was true that the Ebola Virus had been created in a test tube.

It seems that the press is largely to blame for using terms like Secret Drug.   It appears that they are also trying to mount political pressure to make a lot more of the drug to help Africans.   [This was] a nice job answering some of this….”

And at time of writing, the outbreak was still raging, had spread to Nigeria, and airlines were banning travel to half of West Africa – and alarmist tourist firms were advising people not to come to South and East Africa, as well.  The WHO has also said the impact is probably much greater than reported.

And Alison Jacobson is alive and well, and NOT working in virology any more.  Sadly!

What Would Happen if You Got Ebola?

13 August, 2014

A secondary infection in the U.S. is highly unlikely. But here’s how the healthcare system would respond if there was one.

Source: www.theatlantic.com

Goes without saying that this would happen in a lot of other places, too.  Including our very own South Africa – where it HAS happened, with Marburg, Ebola and Lujo viruses.  Written about right here on ViroBlogy.

See on Scoop.itVirology News

Plant-made antibodies used as therapy for Ebola in humans: post-exposure prophylaxis goes green!

5 August, 2014
Ebola virus budding from an infected cell.  Courtesy of Russell Kightley Media

Ebola virus budding from an infected cell.
Courtesy of Russell Kightley Media

Yes, I know you fans of ViroBlogy like Ebola – and just coincidentally, I was desperately trying to finish a review* on “Plant-based vaccines against viruses” against a backdrop of an out-of-control Ebola epidemic in West Africa, when three different people emailed me different links to news of use of a plant-made monoclonal antibody cocktail.  I immediately included it in my review – and I am publishing an excerpt here, for informations’ sake.  Enjoy!

Plantibodies against Ebola

The production of anti-Ebola virus antibodies has recently been explored in plants: this could yet become an important part of the arsenal to prevent disease in healthcare workers, given that at the time of writing an uncontrolled Ebola haemorrhagic fever outbreak was still raging in West Africa, and the use of experimental solutions was being suggested (Senthilingam, 2014). For example, use of a high-yielding geminivirus-based transient expression system in N benthamiana that is particularly suited to simultaneous expression of several proteins allowed expression of a MAb (6DB) known to protect animals from Ebola virus infection, at levels of 0.5 g/kg biomass (Chen et al., 2011). The same group also used the same vector system (described in detail here (Rybicki and Martin, 2014)) in lettuce to produce potentially therapeutic MAbs against both Ebola and West Nile viruses (Lai et al., 2012).

A more comprehensive investigation was reported recently, of both plant production of Mabs and post-exposure prophylaxis of Ebola virus infection in rhesus macaques (Olinger et al., 2012). Three Ebola-specific mouse-human chimaeric MAbs (h-13F6, c13C6, and c6D8; the latter two both neutralising) were produced in whole N benthamiana plants via agroinfilration of magnICON TMV-derived viral vectors. A mixture of the three MAbs – called MB-003 – given as a single dose of 16.7 mg/kg per Mab 1 hour post-infection followed by doses on days 4 and 8, protected 3 of 3 macaques from lethal challenge with 1 000 pfu of Ebola virus. The researchers subsequently showed significant protection with MB-003 treatment given 24 or 48 hours post-infection, with four of six monkeys testing surviving, compared to none in two controls. All surviving animals treated with MB-003 experienced insignificant if any viraemia, and negligible clinical symptoms compared to the control animals. A significant finding was that the plant-produced MAbs were three times as potent as the CHO cell-produced equivalents – a clear case of plant production leading to “biobetters”. A follow-up of this work investigated efficacy of treatment with MB-003 after confirmation of infection in rhesus macaques, “according to a diagnostic protocol for U.S. Food and Drug Administration Emergency Use Authorization” (Pettitt et al., 2013). In this experiment 43% of treated animals survived, whereas all controls tested here and previously with the same challenge protocol died from the infection.

In news from just prior to submission of this article, a report quoted as coming from the National Institute of Allergy and Infectious Diseases states that two US healthcare workers who contracted Ebola in Liberia were treated with a cocktail of anti-Ebola Mabs called ZMapp – described as a successor to MB-003 – developed by Mapp Pharmaceutical of San Diego, and manufactured by Kentucky BioProcessing (Langreth et al., 2014). Despite being given up to nine days post-infection in one case, it appears to have been effective (Wilson and Dellorto, 2014).

A novel application of the same technology was also used to produce an Ebola immune complex (EIC) in N benthamiana, consisting of the Ebola envelope glycoprotein GP1 fused to the C-terminus of the heavy chain of the humanised 6D8 MAb, which binds a linear epitope on GP1. Geminivirus vector-mediated co-expression of the GP1-HC fusion and the 6D8 light chain produced assembled immunoglobulin, which was purified by protein G affinity chromatography. The resultant molecules bound the complement factor C1q, indicating immune complex formation. Subcutaneous immunisation of mice with purified EIC elicited high level anti-GP1 antibody production, comparable to use of GP1 VLPs (Phoolcharoen et al., 2011). This is the first published account of an Ebola virus candidate vaccine to be produced in plants.

References

Chen, Q., He, J., Phoolcharoen, W., Mason, H.S., 2011. Geminiviral vectors based on bean yellow dwarf virus for production of vaccine antigens and monoclonal antibodies in plants. Human vaccines 7, 331-338.

Lai, H., He, J., Engle, M., Diamond, M.S., Chen, Q., 2012. Robust production of virus-like particles and monoclonal antibodies with geminiviral replicon vectors in lettuce. Plant biotechnology journal 10, 95-104.

Langreth, R., Chen, C., Nash, J., Lauerman, J., 2014. Ebola Drug Made From Tobacco Plant Saves U.S. Aid Workers. Bloomberg.com.

Olinger, G.G., Jr., Pettitt, J., Kim, D., Working, C., Bohorov, O., Bratcher, B., Hiatt, E., Hume, S.D., Johnson, A.K., Morton, J., Pauly, M., Whaley, K.J., Lear, C.M., Biggins, J.E., Scully, C., Hensley, L., Zeitlin, L., 2012. Delayed treatment of Ebola virus infection with plant-derived monoclonal antibodies provides protection in rhesus macaques. Proceedings of the National Academy of Sciences of the United States of America 109, 18030-18035.

Pettitt, J., Zeitlin, L., Kim do, H., Working, C., Johnson, J.C., Bohorov, O., Bratcher, B., Hiatt, E., Hume, S.D., Johnson, A.K., Morton, J., Pauly, M.H., Whaley, K.J., Ingram, M.F., Zovanyi, A., Heinrich, M., Piper, A., Zelko, J., Olinger, G.G., 2013. Therapeutic intervention of Ebola virus infection in rhesus macaques with the MB-003 monoclonal antibody cocktail. Science translational medicine 5, 199ra113.

Phoolcharoen, W., Bhoo, S.H., Lai, H., Ma, J., Arntzen, C.J., Chen, Q., Mason, H.S., 2011. Expression of an immunogenic Ebola immune complex in Nicotiana benthamiana. Plant biotechnology journal 9, 807-816.

Rybicki, E.P., Martin, D.P., 2014. Virus-Derived ssDNA Vectors for the Expression of Foreign Proteins in Plants. Current topics in microbiology and immunology 375, 19-45.

Senthilingam, M., 2014. Ebola outbreak: Is it time to test experimental vaccines? CNN.

Wilson, J., Dellorto, D., 2014. 9 questions about this new Ebola drug. CNN.

* = which, despite their having commissioned from me, the good folk at “Viruses” an unnamed journal decided “…may not have substantial differences with the reviews you published recently” – and rejected.  I shall have revenge.  Oh, yes…B-)

“Controversial scientist recreates H1N1 flu that killed 500K people” – NOT

2 July, 2014

Dr Yoshihiro Kawaoka, professor of virology at University of Wisconsin at Madison, has tweaked the 2009 strain of pandemic influenza to make it resistant the human immune system’s antibodies.

Source: www.dailymail.co.uk

Trust the Dimwitted Mail to misstate what happened – which is that Yoshihiro Kawaoka selected the H1N1pdm 2009 flu virus in culture till he came up with antibody-binding escape mutants.

What he said:

‘Through selection of immune escape viruses in the laboratory under appropriate containment conditions, we were able to identify the key regions [that] would enable 2009 H1N1 viruses to escape immunity,’

Now recall that the H1N1pdm 2009 virus is NOT a particularly nasty variant; that it has NOT been proved the escape mutants will infect vaccinated people at all – and that all the work was done "a state-of-the-art laboratory at the Institute for Influenza Virus Research in Madison", so the odds that it will get out are VERY low.

But papers have been sold, and the scare is in.

A new virus from the Namib – and a guilty secret revealed

26 June, 2014

I have to confess to a guilty secret: there is a pleasure-inducing activity I have been indulging in for a week at a time these past three years.

And not alone….

This consists of going to the Gobabeb Research & Training Centre in the Namib Desert as part of an international “scientific expedition” aimed at investigating microbial soil biodiversity in the sandy and stony desert round Gobabeb.  These were started by Professor Don Cowan when he was at the University of the Western Cape, and have fortunately continued now that he has moved to a new Institute at the University of Pretoria.

Typical quartz-associated hypolith

Typical quartz-associated hypolith

I put the scientific expedition in quotes because anything that much fun shouldn’t be called scientific, but hey, it’s already resulted in one major paper on hypolith-associated viruses that I’m a minor author on, another co-authored opinion piece in the South African Journal of Science on biodiversity assessment that got the cover, as well as me being invited to be part of the Gobabeb station’s Microbiology & Fungi research “Theme Group“.

Moreover, I am now on the Board of the Institute for Microbial Biotechnology and Metagenomics at UWC on the strength of working with Marla Trindade and Lonnie van Zyl and others on scraping bits of green stuff off rocks and then watching them ultrafilter washings of it – so I suppose that we really did do some science, even if it was sinfully enjoyable. In any case, something that happened last year took me back to my roots – as well as possibly getting me some street (or gully) cred with the biodiversity crowd.

The heavily gullied area near Homeb

The heavily gullied area near Homeb

Basically, there we were in the Welwitschia-rich gullies near Homeb, 11 km from Gobabeb, visiting said plants.  There had been some rain 3 weeks previously, apparently, and there was an amazing eruption of foliage from some kind of bulb, every plant the same age and every one frantically flowering for all they were worth.  This alone was noteworthy, as the gullies were completely devoid of any trace of such plants the previous year. As we were wandering about, looking at Welwitschias, one Olivier Zablocki from the Univ Pretoria team – who had just done a MSc in plant virology with Gerhard Pietersen at UP – said something along the lines of “I wonder if there are any viruses infecting these plants?”.

welwitschia 2012

Welwitschia down in the gully

“What, like that one?” I said, having just fortuitously noticed a plant with tell-tale streaks on its leaves.  Of course, I seem to have lost my photos – temporarily, I hope! – after a Mac Mini OSX update disaster, but Olivier was kind enough to provide the necessary:

diseased albuca

Streaky Albuca. Note how quickly the fruit has formed, just a couple of days after flowering.

This sparked a flurry of activity, with people being called to observe the plant, and going out and looking for more.

Which were not found: not one other plant, of the hundreds we saw there and nearer Homeb, had any streaks at all.  What is more, they were growing all up and down some of the more inhospitable gravelly and rocky slopes I have ever seen, meaning they had to be seriously drought-tolerant, given the unlikelihood of them ever being exposed to much water.  This meant they must be ephemeral, or putting out foliage and flowers only after rain – and I have never seen anything flower as fast; three days later they were already fruiting.

albuca 2013

Albuca growing in the gully

We made the collective decision that this was sufficiently scientifically interesting to warrant its collection, and the plant was carefully dug up – with difficulty; the onion-like bulb was deep and seriously embedded among rocks – and carefully transported back to Gobabeb, hopefully for identification and then packaging to be taken back to Pretoria.

healthy albuca

Healthy Albuca growing in gravel

And yes, we did have a permit!

Meaning the foliage could go back to Pretoria, and there be subjected by Olivier to electron microscopy, and then RNA isolation and cDNA synthesis.  And lo, it came to pass – that a new potyvirus was discovered.  Kudos, Olivier and the Cowan lab!  The ms is submitted, and we wait only for…well, acceptance would be nice, but the proof is in the sequence.  And the pictures – murky EMs done by Olivier from precious tissue extracts, to boot.

Transmission EM from diseased Albuca extract

Transmission EM from diseased Albuca extract

And it took an old plant virologist to find it.  Life in the greying dog yet!

Giant Zombie Killer Virus Rises From Its 30 000 Year Grave To Kill Us All! Or Not?

27 March, 2014

I am not a fan of “Science By Hype”, which I think I have made abundantly clear via Virology News and elsewhere. Thus, I pour scorn on the “We found a structure which will lead to an AIDS vaccine”, and “We found an antibody that will cure AIDS” type of articles, WHILE at the same time, appreciating the ACTUAL science behind the hype.

If there is any, of course.

Which is why I am torn, on the subject of a giant DNA virus purportedly found in 30 000 year-old Siberian permafrost. I am also a fan of zombies, hence the title. But seriously, now: here we are, with news media and semi- and fully-serious science mags all hailing the description in PNAS, no less, of “Pithovirus sibericum“.  A giant virus, wakened from a 30 000 year sleep in Siberian permafrost, by the kiss of an amoeba. OK, by infecting an amoeba, but you see where I’m going here. Pithovirus_sibericum__Researchers_Resurrect_30_000-Year-Old_Giant_Virus___Biology___Sci-News_com So here we are, with an article from Sci.news.com, trumpeting the discovery.  And there’s more:

“The findings have important implications in terms of public health risks related to the exploitation of mining and energy resources in circumpolar regions, which may arise as a result of global warming. “The re-emergence of viruses considered to be eradicated, such as smallpox, whose replication process is similar to Pithovirus, is no longer the domain of science fiction. The probability of this type of scenario needs to be estimated realistically.””

Yeah.  Rii-ii-ght.  Giant viruses are going to erupt from the permafrost and kill us all!  Really??

No.

Curtis Suttle, he of oceanic metaviromes fame, is quoted as saying the following, in Ed Yong’s Nature blog:

“…people already inhale thousands of viruses every day, and swallow billions whenever they swim in the sea. The idea that melting ice would release harmful viruses, and that those viruses would circulate extensively enough to affect human health, “stretches scientific rationality to the breaking point”, he says. “I would be much more concerned about the hundreds of millions of people who will be displaced by rising sea levels.””

Amen!  In other words, just because there ARE revivable viruses in permafrost – itself no new thing, BTW – does NOT mean they will harm humans. Think about this a moment: something locked away under the surface of the ground for 30 000+ years has to SURVIVE, first; second, it has to INFECT humans if it is to cause any harm. And what evidence do we have that anything found in Siberian permafrost can do that?

None.  None whatsoever.

Think again: how many humans, and how many mammals with virus that could infect humans, were there around on the Siberian plains 30 000 years ago?

Precious few.

And what likelihood is there that any viruses that COULD infect humans, got preserved? Vanishingly small. So what COULD get released from said permafrost, as it melts with inexorable global warming? Well, phages: lots and lots of phages.

Then some plant viruses, maybe: there have been previous reports of Tomato mosaic virus found in 1999 in glacial ice from Greenland, that was between 500 – 140 000 years old – that was also supposed to be a threat, as it escaped from melting icecaps.

To tomatoes, possibly.  If they grew in seawater.

But there’s more: here we have “New Deadly Flu Viruses Reemerge from Melting Ice“, from 2006.  Here we have

“An international team [that] found flu viruses in the ice of Siberian lakes, fact that warns about the possibility that global warming may release germs locked in glaciers for decades or even centuries.”

Yah. Right.  But at the same time, considerably more worthy of alarm than Pandoraviruses. Because what our worthy French colleagues did NOT do, in their report in PNAS, was see what ELSE was in their permafrost samples. Seriously: they trawled melting ice from a core sample with amoebae ONLY.

This is the equivalent of the 2nd year prac I used to do, when we made students screen water obtained from the environment with E coli to see if they could amplify coliphages out of it.  Why did they not do a metagenomic sequence trawl, after filtering out bits of mammoth crap and cockroaches and bits of twigs??  What did they MISS?  HBVs that infected Denisovans?  And are we SURE that the virus came from that long ago?  Has the ice really remained frozen all that time – and is there not the possibility that water didn’t percolate down through cracks and pores in the permafrost, carrying the virus with it, from a more clement environment on the surface??

OK, OK, so it’s a great find, and reasonably worthy of SOME hype.  BUT: it is NOT a harbinger of doom, because most viruses will NOT survive 30 000 years worth of entombment in ice, and in any case, would NOT infect humans even if they did. AND I hate the name: “Pithovirus sibericum“?  Really??  Viruses are not named like that!  Except by French folk who find these strange “amphora-shaped” viruses, apparently.

Antivaxer HPV nonsense!

14 March, 2014

Fair Lady magazine just published a short but very useful article on HPV vaccines, with question-and-answer format commentary from a number of local experts on safety and such.

Then some loony takes them on in this piece.

My comment to that:

OK: this is a sadly under-informed and over-complicated response to a very good, simple article, with expert comments that are no way out of line with what is known to be the case about these vaccines.

Please allow me to correct a few things: in the first place, you say “Several ingredients in the two HPV vaccines are known to be a problem. One is the use of the microbe Saccharomyces cerevisiae, common yeast, as the medium in which the Gardasil antigen is developed. S. cerevisiae is known to trigger autoimmune response, as discussed recently in Yeast in Vaccines Tied to Autoimmune Diseases. Cervarix, though, was produced with a different medium, Trichoplusiani.”

Yeast is known to trigger autoimmune responses? Really? Then what about all those millions of people who have received Hepatitis B virus vaccine, also made in yeast? There is NO documented correlation with vaccination with yeast-made products and autoimmunity. NONE.

Then, Cervarix is “made in a different medium” – you obviously mean cell type, because Trichoplusia ni [note!] is a species of insect, from which the tissue-cultured cells used to make the HPV vaccine are derived. And? You have no problem with that? You shouldn’t.

Further: “The two vaccines, Gardasil and Cervarix, are distinctly different in another way. Gardasil contains a single adjuvant… while Cervarix utilizes a combination …These differences, since they involve the hyper-activation of the immune system and a known trigger for autoimmune disorders in only one of the vaccines, suggest that a recent study’s finding that there are no adverse effects whatsoever in either vaccine beggar belief.”

So you have a problem with the finding that there are no adverse effects BECAUSE the adjuvant regime is different? Not because of the evidence? Sorry, that isn’t very good science!

And it gets better: “Most significantly, in every clinical trial evaluating safety for both Gardasil and Cervarix, the so-called placebo groups were given injections that included an active aluminum adjuvant!
Though this is a common practice in vaccine trials, it is obviously a blatant means of biasing the results.”

So – a perfectly acceptable placebo arm in a clinical trial, with adjuvant given so that any difference would not be due to just this, means the studies are meaningless? Really?? What about the UNvaccinated groups these were compared to? ALL vaccines are associated with SOME events – and I note that YOUR piece above contains the sentence “The high proportion of adverse events reported is mainly due to the design of the study, since women were requested to report all events occurring after the vaccination; however the majority of events were mild and transient”.

You then quote – at excruciating length – a number of articles purportedly supporting your case, that can be summarised as showing that “HPV vaccination does not have a therapeutic effect in young women with pre-existing human papillomavirus infection”.

Yes? And? The two licenced HPV vaccines are PROPHYLACTIC, and were never intended to be therapeutic! It is unfortunate that the vaccines do not in fact lessen ESTABLISHED infections; however, there is plentiful evidence that they PREVENT INFECTIONS FROM BEING ESTABLISHED.

You are being alarmist and spreading falsehoods from a very shaky evidential base. You should stop doing that, or risk being shown up as being an antivax crank.

VIGS in fungi – using TMV?!

5 March, 2014

See on Scoop.itVirology News

RNA interference (RNAi) is a powerful approach for elucidating gene functions in a variety of organisms, including phytopathogenic fungi. In such fungi, RNAi has been induced by expressing hairpin RNAs delivered through plasmids, sequences integrated in fungal or plant genomes, or by RNAi generated in planta by a plant virus infection. All these approaches have some drawbacks ranging from instability of hairpin constructs in fungal cells to difficulties in preparing and handling transgenic plants to silence homologous sequences in fungi grown on these plants.

Here we show that RNAi can be expressed in the phytopathogenic fungus Colletotrichum acutatum (strain C71) by virus-induced gene silencing (VIGS) without a plant intermediate, but by using the direct infection of a recombinant virus vector based on the plant virus, tobacco mosaic virus (TMV). We provide evidence that a wild-type isolate of TMV is able to enter C71 cells grown in liquid medium, replicate, and persist therein. With a similar approach, a recombinant TMV vector carrying a gene for the ectopic expression of the green fluorescent protein (GFP) induced the stable silencing of the GFP in the C. acutatumtransformant line 10 expressing GFP derived from C71.

The TMV-based vector also enabled C. acutatum to transiently express exogenous GFP up to six subcultures and for at least 2 mo after infection, without the need to develop transformation technology. With these characteristics, we anticipate this approach will find wider application as a tool in functional genomics of filamentous fungi.

TMV graphic from Russell Kightley Media

Ed Rybicki‘s insight:

This is a nice paper for two main reasons: one, they were able to get VIGS – virus-induced gene silencing – working in a non-model fungus; two, they did it with TMV.

TMV! A plant virus in good standing, not previously shown to infect fungi productively, even if it has been studied in yeast as far as replication requirements go.

This is very interesting, not the least because it opens up the possibility that TMV NATURALLY infects some soil / leaf surface fungi.

Which could open up some investigation of just how the virus gets around, because it has always been touted as being only “mechanically” transmissible – even though we and others have shown it CAN be transmitted by aphids (reasonably inefficiently).

Mind you, Barbara von Wechmar and others in our lab showed in the 1980s that wheat stem and leaf rust fungi could transmit Brome mosaic virus and that Puccinia sorghi could transmit a potyvirus; they just did not have the techniques to look at whether or not it replicated too.

As far as my last post here is concerned, I think there is going to be a LOT of stuff coming out in the next few years on how “plant” and “insect” and “fungal” viruses are in fact considerably more promiscuous in choice of host(s) than we have hitherto been aware.

Now, just to prove what Barbara always said, that Tobacco necrosis virus is also a bacteriophage….

Thanks to Gary Foster (@Prof_GD_Foster) for pointing this out!

See on m.pnas.org

TRSV or not TRSV, that is the question. In bees, obviously.

25 February, 2014

I promised some time ago now to blog on the exciting topic of whether or not a plant virus is infecting honeybees – and here it is!  I was also contacted by the legendary Dr Adrian Gibbs about this paper, because he has read this blog, so I am including a commentary from him as well.

A little while ago, Ji Lian Li and co-workers published a paper entitled “Systemic Spread and Propagation of a Plant-Pathogenic Virus in European Honeybees, Apis mellifera” in ASM’s Open Access journal mBio.  They stated that:

“Pathogen host shifts represent a major source of new infectious diseases. Here we provide evidence that a pollen-borne plant virus, tobacco ringspot virus (TRSV), also replicates in honeybees and that the virus systemically invades and replicates in different body parts. In addition, the virus was detected inside the body of parasitic Varroa mites, which consume bee hemolymph, suggesting that Varroa mites may play a role in facilitating the spread of the virus in bee colonies. This study represents the first evidence that honeybees exposed to virus-contaminated pollen could also be infected and raises awareness of potential risks of new viral disease emergence due to host shift events. About 5% of known plant viruses are pollen transmitted, and these are potential sources of future host-jumping viruses. The findings from this study showcase the need for increased surveillance for potential host-jumping events as an integrated part of insect pollinator management programs”.

This paper has caused all sorts of excitement, as well as coming to some possibly misleading conclusions, and leading to quite a lot of uninformed speculation – so I think it is as well to explore quite carefully what they did.

Adrian first:

“This paper reports that tobacco ringspot nepovirus, a well-known virus of plants, replicates in honeybees.  TRSV, first identified nearly a century ago in the USA, has a wide range of plant hosts, and is spread in pollen and seed, and also by many unrelated vectors, not only root-feeding nematodes, like other nepoviruses, but also insects and mites.

This report tells us that TRSV virions have been isolated from bees, and that their gene sequences are closely similar to those of TRSV.  Convincingly, biochemical tests showed that there were replication intermediates of the TRSV genome in the bees, so the virus had not merely contaminated the bees when they fed on the honey and pollen of infected plants, but had seemingly multiplied in them.

However, there are several gaps in this story.  Surprisingly, it seems that no tests were done to show whether the virus isolated from bees infected known plant hosts of TRSV; perhaps this crucial evidence will be in the sequel.  Furthermore, the reported sequences of the virus represented only around 20% of the RNA1 of typical nepoviruses, and around 50% of their RNA2, so there is still the possibility of further genetic surprises when the genome sequence is completed.

Although TRSV is a well-known and long studied virus with many distinct symptom variants, there are relatively few of its gene sequences in Genbank.  When these are compared with those of the ‘bee TRSV’ it is obvious that more sequences will be required to sort out exactly where this virus clusters; differences in the homology patterns of the RNAs 1 and 2 suggest that recombination or reassortment is active among nepoviruses.

The gene sequencing revolution is, to paraphrase Pliny the Elder, revealing that in virology the only certainty is that nothing is certain.”

Me next:

I have the same reservations as Adrian: the TRSV sequence isolated from bees and from Varroa mites is only partial (~30%); thus, it is by no means certain that the whole genome is colinear with genomes of established TRSVs or of other nepoviruses, although they assume that it is – with some justification, possibly, as sequence identities of up to 96% were found in Genbank for the putative CP fragment sequence.  They could isolate particles: why, then, in this metagenomic and NGS age, could they not sequence the whole thing??

nepo fig1

Another reservation I have concerns their methodology.  First, while I was impressed that they did strand-specific PCR to show  both the presence of viral (+ strand) and of replicative form (- strand) RNA in bee and mite tissue (see their Figure above), and did in situ hybridisation to show (-) strand presence in mites, they did not do something very simple that could have shown the same thing, AND given them genome-length +/- strand RNA to play with.

I refer, of course, to dsRNA isolation, which is a very easy and extremely clean technique that can be used to get full-length dsRNAs for many (+) strand RNA viruses from plant or insect tissues.  Moreover, the simple fact of isolating dsRNA forms for a single-strand RNA virus is indicative that replication is occurring – and was used by our group as long ago as 1988 (C Williamson, PhD Thesis, UCT) to isolate full-length ~10 kb dsRNA for two aphid picorna-like viruses.

Scan 04 Jan 2014, 16.31-page8

This means they could have had clear and simple evidence via dsRNA extraction of ALL of the coinfecting viruses present – without all of the expense of total cDNA sequencing.  And sampled more hives….

Second, I have to echo Adrian: “…no tests were done to show whether the virus isolated from bees infected known plant hosts of TRSV”.  Why ever not?  I am afraid that if I were a referee, I would have insisted on this: they did enough other work, after all, that this would not exactly have been an onerous requirement!

And here’s another thing: the authors say, in their Discussion,

“The finding from this study illustrates the complexity of relationships between plant pathogens and the pollinating insects and emphasizes the need for surveillance for potential host-jumping events as an integrated part of insect pollinator conservation.”

Ummmm…no, it doesn’t.  This is overstating the significance of their results by an order of magnitude at least.  They have simply illustrated that ONE species of honeybee may be infectable by ONE species of plant virus, and that this is ASSOCIATED with “weak” colonies.  Moreover, while the presence of TRSV was apparently associated with four weak colonies (out of only ten surveyed), it is quite possible that this is simply the emergence of a commensal-type infection against a background of known bee viruses, and in particular Israeli acute paralysis virus which was found in the same colonies (and blogged on here).  The authors also seem to take it as a given that the “emergence” of TRSV into bees is a recent jump – when it may not be recent at all.  Their statement in the abstract that

“The tree topology indicated that the TRSVs from arthropod hosts shared a common ancestor with those from plant hosts and subsequently evolved as a distinct lineage after transkingdom host alteration”

is pretty much unsubstantiated, in the absence of any investigation of the lineage in plants or in other bee colonies.  Further, they say that

“This study represents a unique example of viruses with host ranges spanning both the plant and animal kingdoms. “

Ummmmm….it doesn’t really do that, either: there are a LOT of arboviruses, with quite a few of them infecting insects and plants.  Here, for example, is an illustration from my teaching material of why it is that I think that viruses of insects and plants are an underappreciated evolutionary link for later evolution of viruses that got into mammals.

Transkingdom viruses

I note that bunyaviruses, rhabdoviruses, reoviruses and (not shown) picorna-like viruses appear linked by the fact that insects have possibly the most diverse representatives of these families, which may indicate that these originated in insects.  Which were the first complex animals to crawl out of the oceans, to join…plants on dry land?  Which explains how plants link up with the far more closely related (in evolutionary terms) insects and vertebrates: plants and insects were alone together for a long, long time before things with spines lurched up out of the water to join them.  So were their viruses.

I also said the following in the material there:

“A complicating factor in the picture of viruses co-evolving with their hosts over millennia is the fact that viruses apparently can – and obviously do – make big jumps in hosts every now and then.  It seems obvious, for example, that arthropods are almost certainly the original source for a number of virus families infecting insects and mammals – such as the Flaviviridae – and probably also of viruses infecting insects and other animals and plants – such as the Rhabdoviridae and Reoviridae – as well (see also here).  For example, picornaviruses of mammals are very similar structurally and genetically to a large number of small RNA viruses of insects and to at least two plant viruses, and – as the insect viruses are more diverse than the mammalian viruses – probably had their origin in some insect that adapted to feed on mammals (or plants) at some distant point in evolutionary time.”

Now quite a lot of interest has been shown in this paper in the blogosphere, and there have been quite a few conclusions drawn from the results that I think are largely unsubstantiated.  For example, this Sci Am blog claims

“When HIV jumped from chimpanzees to humans sometime in the early 1900s, it crossed a gulf spanning several million years of evolution. But tobacco ringspot virus, scientists announced last week, has made a jump that defies credulity. It has crossed a yawning chasm ~1.6 billion years wide.”

Again, ummmm…in light of the discussion above, not necessarily!  I am of the opinion that picorna-like viruses were shared between insects and plants, and then between insects and animals, hundreds of millions of years ago.  And TRSV is a nepovirus – and nepoviruses look like nothing more or less than a picornavirus with a divided genome.

I think TRSV represents something coming back into insects.  And I think we will probably find a lot more of them.

Bats and SARS-CoV: deja vu all over again

1 November, 2013

In 2008, I wrote a blog piece entitled “Who do you bind to, my lovely?”, about a couple of papers on SARS-CoV – the coronavirus that causes severe acute respiratory syndrome.  I closed that piece with the following:

“Adding fuel to the speculative fire is another paper in the same issue: this reports that there is evidence of a recombinant origin for SL-CoVs, and there is probably “…an uncharacterized SLCoV lineage that is phylogenetically closer to S[ARS]CoVs than any of the currently sampled bat SLCoVs.”

So let’s all just wait for the next one, shall we?”

…in connection with the fact that horseshoe bat coronaviruses were VERY similar to SARS-CoV, but bound to different receptors.  And we had to wait five years, but heeeeeere we are… these folk may well have found the missing virus(es) that are directly transmissible from bats to humans:

Isolation and characterization of a bat SARS-like coronavirus that uses the ACE2 receptor

 Xing-Yi Ge et al.

Nature (2013) doi:10.1038/nature12711

Here we report whole-genome sequences of two novel bat coronaviruses from Chinese horseshoe bats (family: Rhinolophidae) in Yunnan, China: RsSHC014 and Rs3367. These viruses are far [! - my comment; the last ones were pretty close...] more closely related to SARS-CoV than any previously identified bat coronaviruses, particularly in the receptor binding domain of the spike protein. Most importantly, we report the first recorded isolation of a live SL-CoV (bat SL-CoV-WIV1) from bat faecal samples in Vero E6 cells, which has typical coronavirus morphology, 99.9% sequence identity to Rs3367 and uses ACE2 from humans, civets and Chinese horseshoe bats for cell entry. Preliminary in vitro testing indicates that WIV1 also has a broad species tropism. Our results provide the strongest evidence to date that Chinese horseshoe bats are natural reservoirs of SARS-CoV, and that intermediate hosts may not be necessary for direct human infection by some bat SL-CoVs. They also highlight the importance of pathogen-discovery programs targeting high-risk wildlife groups in emerging disease hotspots as a strategy for pandemic preparedness.

So – I told you so…B-)

 


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