Posts Tagged ‘smallpox’

An ACTUAL killer virus that could rise from the grave

1 May, 2014
Section through Variola virus.  Copyright Russell Kightley Media

Section through Variola virus. Copyright Russell Kightley Media

Having poo-pooed the possibility of killer viruses roaring out of the tundra to kill as all – see here – I find myself having to reconsider my words.  Just slightly, mind, but a reconsideration nonetheless.

This is because of an excellent post in Nature News recently, entitled “Infectious diseases: Smallpox watch“, by Sara Reardon.  This has raised quite a stir in the Twittersphere, as people speculate on just how likely this is, but I think the article itself does a very good job of discussing the possibility that smallpox could come back from the grave(s).

I have discussed smallpox a number of times in this blog, with one of the most read posts being this one by my PhD student (and now postdoc) Alta van Zyl.  I recall a while back a discussion around just how likely it was that people working on expanding what was the Rietfontein Infectious Diseases Hospital (now Sizwe Hospital)’s premises in Johannesburg, would find live smallpox in coffins of people who died of it at the old Hospital and were buried nearby.

The verdict then was “No” – Johannesburg is too hot, and the was seen to be NO chance of the virus surviving the rapid putrefaction that occurs in these parts.

Sara Reardon’s essay, however, raises the real, if rather remote, prospect of there being live smallpox in mummified corpses which have either dried out at low temperatures, or been frozen soon after death, in permafrost.  She says that

“A more likely source of infectious virus would be frozen bodies. Influenza viruses seem to be able to survive freezing in lakes and may thereby infect migrating birds…”

Now the good thing is that people have actually gone out looking for live virus in just such potential sources, and found nothing except fragments of DNA.

However, she also says:

“Another concern is that smallpox could escape from a secret cache. Few biosecurity specialists believe that the two stocks kept at the CDC and VECTOR are the only ones in existence. For instance, variola could very well be in the freezer of someone who defected from the Soviet Union…”

Now, the old Soviet Union had an active programme on weaponising smallpox, with some sources claiming than “several tonnes” of material were eventually made.  There is even evidence that smallpox escaped from a facility in Aralsk, Kazakhstan, in 1971.   What is not so clear is where any of this material is NOW, and in what state it is.

Time to work on the emergency-response smallpox vaccines and strategies, folks – even if you use the potential threat of monkeypox as the reason!

 

 

A life in Virology

15 February, 2012

With a group of my UCT Medical School colleagues, I have been attending reasonably regular informal talks by Professor Keith Dumbell, formerly of St Mary’s Hospital, London, the University of Liverpool, and UCT.

Keith is a poxvirus expert, and was involved in the eradication of smallpox. He has also lived through several eras of modern virology, starting in 1945 in the pre-DNA and electron microscope days, through the advent of tissue culturing viruses, to the application of recombinant DNA techniques to viruses – and has a treasure trove of fascinating stories he is sharing with us.

Mostly about viruses, but occasionally about the characters involved as well. And the fact that any virologist worth their salt in the 1950s had to have skills in cutting sections, culturing viruses in eggs, centrifugation techniques, and keeping a veritable zoo of small animals.

I hope to get his permission to release a DVD of his reminiscences some day.

A Short History of the Discovery of Viruses – Part 1

6 February, 2012

The following text may or may not appear in a book of some kind in the future.  However, I thought I may as well share it – both for general education purposes, as well as for comment.  Enjoy!

A Short History of the Discovery of Viruses

While people were aware of diseases of both humans and animals now known to be caused by viruses many hundreds of years ago, the concept of a virus as a distinct entity dates back only to the very late 1800s.  Although the term had been used for many years previously to describe disease agents, the word “virus” comes from a Latin word simply meaning “slimy fluid”.  This discovery, along with many that followed later, was made possible by the development of new technology.  Though this simple invention essentially enabled the establishment of a whole new science – virology – the continued development of the discipline required a string of technical developments, which I will highlight throughout this piece.

The Magic Filter

The invention that allowed viruses to be discovered at all was the Chamberland-Pasteur filter.  This was developed in 1884 in Paris by Charles Chamberland, who worked with Louis Pasteur.  It consisted of unglazed porcelain “candles”, with pore sizes of 0.1 – 1 micron (100 – 1000 nm), which could be used to completely remove all bacteria or other cells known at the time from a liquid suspension.

Tobacco mosaic virus particles: courtesy Linda Stannard

As the first in what was to be an interesting succession of events, Adolph Mayer from Germany, working in Holland in 1886, showed that the “mosaic disease” of tobacco could be transmitted to other plants by rubbing a liquid extract, filtered through paper, from an infected plant onto the leaves of a healthy plant.  However, he came to the conclusion it must be a bacterial disease.

The first use of porcelain filters to characterize what we now know to be a virus was reported by Dmitri Ivanowski in St Petersburg in Russia, in 1892.  He had used a filter candle on an infectious extract of tobacco plants with mosaic disease, and shown that it remained infectious: however, he concluded the agent was either a toxin or bacterial in nature.

The Dutch scientist Martinus van Beijerinck in 1898 described how he did similar experiments with bacteria-free extracts, but made the conceptual leap and described the agent of mosaic disease of tobacco as a “contagium vivum fluidum”, or living contagious fluid. The extract was completely sterile, could be kept for years, but remained infectious.  The term virus was later used to describe such fluids, also called “filterable agents”, which were thought to contain no particles.  The virus causing mosaic disease is now known as Tobacco mosaic virus (TMV).

Foot and mouth disease virus particles: courtesy Russell Kightley Media

The second virus discovered was what is now known as Foot and mouth disease virus (FMDV) of farm and other animals, in 1899 by the German scientists Friedrich Loeffler and Paul Frosch.  Again, their “sterile” filtered liquid proved infectious in calves, providing the first proof of viruses infecting animals.  In fact, some believe that the true discoverers of viruses were these two scientists, as they concluded the infectious agent was a tiny particle, and was not liquid.

In the same year – 1898 – G Sanarelli, working in Uruguay, described the smallpox virus relative and tumour-causing myxoma virus of rabbits as a virus – but on the basis of sterilisation by centrifugation rather than filtration.

The first human virus described was the agent which causes yellow fever: this was discovered and reported in 1901 by the US Army physician Walter Reed, after pioneering work in Cuba by Carlos Finlay proving that mosquitoes transmitted the deadly disease.  The agent became the subject of intense study because, in the recent Spanish-American war in Cuba, about 13 times as many soldiers died of yellow fever as died from wounds.  The subsequent eradication of mosquitoes in Panama is probably what allowed the completion of the Panama Canal – stalled because of the death rate among workers from the deadly disease.

The paper describing rinderpest as a virus disease

A finding that was later to have great importance in veterinary virology was the discovery by Maurice Nicolle and Adil Mustafa (also known as Adil-Bey), in Turkey in 1902, that rinderpest or cattle plague was caused by a virus.  This had been for several centuries the worst animal disease known worldwide in terms of mortality: for example, an epizootic or animal epidemic in Africa in the 1890s that had started in what is now Ethiopia in 1887 from cattle imported from Asia, had spread throughout the continent by 1897, and killed 80-90% of the cattle and a large proportion of susceptible wild animals in southern Africa.  Many thousands of people died of starvation as a result.  The virus is, incidentally, only the second to have ever been eradicatednearly 100 years after its discovery.

Viruses and Vaccines

Sir Arnold Theiler, a Swiss-born veterinarian working in South Africa, had developed a crude vaccine against rinderpest by 1897, without knowledge of the nature of the agent: this consisted of blood from an infected animal, injected with serum from one that had recovered.  This risky mixture worked well enough, however, to eradicate the disease in the region.  He went on to do the same thing successfully for African horsesickness virus and others in an institute (Onderstepoort Veterinary Institute) that still works on the virus.

The description in Annales de l’Institut Pasteur by Remlinger and Riffat-Bay in 1903 of the agent of rabies as a “filterable virus was the culmination of many years of distinguished work in France on the virus, started by Louis Pasteur himself. While Remlinger credited Pasteur with having the notion in 1881 that rabies virus was an ultramicroscopic particle, the fact is that Pasteur and Emile Roux had also, in 1885, effectively made a vaccine against rabies by use of dried infected rabbit spinal cords, without any knowledge of what the agent was.

Title of the paper describing rabies virus isolation

The viral nature of many disease agents started to be made evident around this time, as more researchers started investigating known diseases.  In 1906, Adelchi Negri – who had previously discovered the Negri bodies in cells infected with rabies virus – showed that vaccinia virus, the vaccine for the dreaded smallpox caused by variola virus, was filterable.  This was the final step in a long series of discoveries around smallpox, that started with Edward Jenner’s use of what was supposedly cowpox, but may have been horsepox virus to protect people from the disease in 1796.

Viruses, Humans and Cancer

In 1908, Oluf Bang and Vilhelm Ellerman in Denmark were the first to associate a virus with leukaemia: they successfully used a cell-free filtrate from chickens with avian leukosis to transmit the disease to healthy chickens.

An Egyptian stele thought to represent a polio victim (1403–1365 BC). Note the characteristic withering of one leg.

An important development in human virology 1908 was the finding by Karl Landsteiner and Erwin Popper in Germany that poliomyelitis or infantile paralysis in humans was caused by a virus: they proved this by injecting a cell-free extract of a suspension of spinal cord from a child who had died of the disease, into monkeys, and showing that they developed symptoms of the disease.

The first solid tumour-causing virus, or virus associated with cancer, was found by Peyton Rous in the USA in 1911.  He showed that chicken sarcomas, or solid connective tissue tumours, could be transmitted by grafting, but also that a filterable or cell-free agent extracted from a sarcoma was infectious.  The virus was named for him as Rous sarcoma virus, and is now known to be a “retrovirus”, in the same virus family as HIV.

Eaters of Bacteria: The Phages

Bacteriophages bursting from a bacterium

Two independent investigations led to the important discovery of viruses that infect bacteria: in 1915, Frederick Twort in the UK accidentally found a filterable agent that caused the bacteria he was growing to lyse, or burst open.  While he was not sure whether or not it was a virus, Félix d’Hérelle in Paris published in 1917 that he had discovered a virus that lysed a bacterial agent he was culturing that caused dysentery, or diarrhoea.  He named the virus “bacteriophage”, or eater of bacteria, derived from the Greek term “phagein”, meaning to eat.

The discovery of bacteriophages was a landmark in the history of virology, as it meant that for the first time it was relatively easy to work with viruses: many kinds of bacteria could be grown in solid or liquid culture quite easily, and the life cycle of the viruses could be studied in detail.

The 1896 paper from Annales de l'Institut Pasteur

Interestingly, and as reported in ViroBlogy previously, “…the first discovery of phages was probably described by a gentleman named M. Hankin, in 1896 in Annales de l’Institut Pasteur: he 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.”

The Spanish Flu

Influenza A viruses in waterbirds - Russell Kightley Media

Possibly the worst human plague the world has ever seen swept across the planet between 1918 and 1922: this was known as the Spanish Flu, from where it was first properly reported, and it went on to kill more than 50 million people all over the world.  We now know it to have been H1N1 influenza type A: modern reconstruction of the virus from archived tissue samples and frozen bodies found in permafrost has shown it probably jumped directly into humans from birds.

Most medical authorities at the time thought the disease was caused by bacteria – however, MJ Dujarric de la Rivière, and Charles Nicolle – brother of Maurice – and Charles  Lebailly in France, separately proposed in 1918 that the causative agent was a virus, based on properties of infectious extracts from diseased patients.  Specifically, Nicolle and Lebailly found that the infectious agent was filterable, not present in the blood of an infected monkey, and caused disease in human volunteers.  However, many scientists still doubted that influenza was a viral disease – and most people seem to accept that the virus was only discovered in the 1930s.

Conclusions from the Nicolle and Lebailly paper

Translation of this passage (courtesy of Mrs Francoise Williamson):

“Conclusions.

1⁰ The bronchial  expectoration of people suffering from flu, collected during the acute period, is virulent.
2⁰   The monkey (M. cynomolgus)  is sensitive to the virus  by sub-conjunctival and nasal inoculation.
3⁰   The flu agent is a filterable organism.  The inoculation  of the filtrate has indeed reproduced the illness in two of the people injected subcutaneously;  on the other hand when given intravenously it  appears to be ineffective. (two failures out of two tries).
4⁰ It is possible that the influenza virus does not occur in the patient’s blood.  The blood of a monkey with influenza, inoculated subcutaneously, did not infect man;  the negative blood result of subject 2 at D, is however, not convincing, the blood route seeming to be ineffective for  the flu virus transmission.”

Other agents of other diseases were found to be “filterable viruses” in the 1920s, including yellow fever virus by Adrian Stokes in 1927, in Ghana.  Indeed, the US bacteriologist and virologist Thomas Rivers in 1926 counted some sixty-five disease agents that had been identified as viruses.

Mouse Brains and Viruses

Another in a chain of related discoveries was the one by Howard Andervost, at Harvard University in 1929, who showed that human herpes simplex virus could be cultured by injection into the brains of live mice.

This led to the demonstration in 1930 by the South African-born Max Theiler – son of Sir Arnold – also at Harvard, that yellow fever virus could be similarly cultured: this allowed much easier handling of the virus, which until then had to be injected into monkeys in order to multiply it in their livers.  In addition, it allowed the development of attenuated or weakened strains of virus, by him and in parallel by a French laboratory, by serial passage or repeated transmission of the virus between mice.  It also allowed the successful animal testing of vaccine candidates, and of protective antisera, for which Theiler was awarded the Nobel Prize in 1951.  

Until 2008, this was the first and only recognition of virus vaccine work by the Nobel Foundation.

A consequence of this work was the landmark in medical virology that was the development of human vaccines against yellow fever virus, by Wilbur Sawyer in the USA in 1931: this followed on Theiler’s mouse work in using brain-cultured virus plus human immune serum from recovered patients to immunize humans – very similar to Theiler Senior’s strategy with rinderpest, more than thirty years later.

Copyright Edward P Rybicki and Russell Kightley, February 2012, except where otherwise noted.

Monkeypox vaccine?? We don’t need no monkeypox vaccine….

22 December, 2011

An in-press article in Vaccine that was tweeted by MicrobeTweets (well worth signing up to, BTW) has the intriguing title “Whither monkeypox vaccination?”

Now, some background to this: monkeypox virus is a rather nasty relative of smallpox (family Poxviridae; subfamily Chordopoxvirinae, genus Orthopoxvirus), meaning it is a large dsDNA virus (170-250 kb) with a complex structure.  The virus is endemic in remote forest areas in central Africa – principally in the Democratic Republic of the Congo – and naturally infects a number of animal species, including giant pouched rats (Cricetomys sp.), dormice (Graphiurus sp.) and African squirrels (Heliosciurus, Funisciurus), as well as laboratory monkeys, which is how it was isolated and got its name.

Monkeypox gets transmitted to humans by contact with infected animals: this includes by simple handling, as well as by exposure to meat and blood of butchered animals.  It causes a disease in humans that is very similar in appearance to smallpox, with a case fatality rate of 1-10%, but is apparently far less easily transmitted person-to-person.  It caused only sporadic and limited outbreaks in Africa and was of limited interest until an outbreak in the USA in 2003, which was linked to young prairie dogs kept in a pet store in close proximity to an infected Gambian pouched rat (Cricetomys gambianus) recently imported from West Africa. Seventy-three people were reportedly infected, among whom there were no fatalities.  The CDC recommends vaccination of people exposed to human or suspected animal cases with smallpox vaccine, as this protects animals from experimental lethal monkeypox challenge.

The Vaccine paper makes the point that the potential for monkeypox virus (MPX) to fill the disease niche recently vacated by smallpox was evaluated in the 1970s – and discounted, largely because human-to-human spread was inefficient enough for outbreaks not be self-sustaining – thus, although smallpox vaccine protected against MPX, the WHO thought there was insufficient justification to continue vaccination.

Now, however, the incidence of the virus in humans

“…appears to have markedly increased. In addition to diminished vaccine-induced orthopoxvirus immunity, there have been profound social and demographic changes that have increased human MPX exposures and the likelihood of severe disease. Recurrent civil war and subsequent economic decline have forced rural residents to flee deep into the rain forests for extended periods of time, disrupted traditional village life and increased dependence on hunting for sustenance, thus increasing exposure to animal reservoirs of MPX.”

So, in other words, people are getting a whole lot more exposure to sick animals.  Increasingly, by eating them.  The paper goes on to say:

“Although orthopoxviruses are relatively genetically stable MPX has diverged into two clades with different levels of virulence. As incidence rises, each new MPX infection provides an opportunity for viral evolution or adaptation that may result in a more virulent or contagious variant capable of sustained person-to-person transmission. These new circumstances merit a re-evaluation of the need for immunizing against MPX”.

So – that should be relatively simple, surely?  I mean, South Africa alone has millions of doses of smallpox vaccine safely frozen away from the 1970s?  Not so fast….

“However, in an era where the threat of smallpox is not imminent and there are conditions such as AIDS, tissue transplantation, and therapies for cancer and autoimmunity that cause immunodeficiency, the adverse events associated with live vaccinia are no longer considered acceptable for the general population.”

The paper goes on to mention how all sorts of supposedly safe new smallpox vaccines have been deposited into biodefence stockpiles, based on animal testing.

And there it is again – that word “biodefence”, in the context of human vaccines – implying that there is a “biothreat” to counter.  Specifically, in this case, the spectre of weaponised smallpox.

The authors go on to make reasonable statements about surveilling for monkeypox in central Africa, and vaccinating people at risk, and say that treatment options should also be investigated given that clinical diagnosis is relatively easy.

They also close with this:

“If immunization studies in developing countries are contemplated to support the licensure of orthopoxvirus vaccines for industrialized countries or for military purposes, then provisions from those countries or organizations should be secured to distribute successful products in endemic regions where the products were tested.” [my emphases]

I should hope so.  I should really, really hope so – because then one country’s biodefence interests could end up benefitting quite a few others, who are the ones who really need the product.  Now, while you’re busy with that, what about vaccines for Rift Valley fever, Crimean-Congo haemorrhagic fever and Chikungunya – which are actually far more serious a problem, in a much bigger geographical area?

 

Should remaining stockpiles of smallpox virus be destroyed?

19 April, 2011

Our Department has a journal club every Friday, when research folk (staff and students) get together to hear a postgrad student present an interesting new paper.  Last Friday Alta Hattingh from my lab gave a thought-provoking and insightful presentation on whether or not smallpox virus should be destroyed – so I asked her to turn it into a blog post.

Should remaining stockpiles of smallpox virus (Variola) be destroyed? 

Raymond S. Weinstein

Emerging Infectious Diseases (2011), Vol 17(4): 681 – 683

Smallpox is believed to have emerged in the Middle East approximately 6000 to 10 000 years ago and is one of the greatest killers in all of human history, causing the death of up to 500 million people in the 20th century alone.  Smallpox is the first virus to ever be studied in detail and it is also the first virus for which a vaccine was developed.  Smallpox was beaten by the Jenner vaccine (first proposed in 1796) and the disease was declared eradicated in 1980 in one of the greatest public health achievements in human history.

The last officially acknowledged stocks of variola are held by the United States at the Centres for Disease Control and Prevention (consisting of 450 isolates) and in Russia at the State Research Centre of Virology and Biotechnology (various sources place the number of specimens at ~150 samples, consisting of 120 strains).  This includes strains that were collected during the Cold War as potential for biological weapons due to their increased virulence. Then, there is also the added possibility that stolen smallpox cultures are in the hands of terrorists organizations.

In 2011 the World Health Organisation (WHO) plans to announce its recommendation for the destruction of all known remaining stockpiles of smallpox virus.  They have wanted to destroy the virus ever since 1980 when the Secretary of Health and Human Services, Louis Sullivan, promised destruction of US stockpiles within 3 years. This never happened in the US or Russia and no official recommendation for destruction have been recommended by the World Health Assembly.  In 2007 the final deadline for a decision was postponed until 2011 as no consensus could be reached among the executive board of the WHO.

The only real benefit that could be gained from destroying all known remaining stockpiles of smallpox virus in the world would be the prevention of causing a lethal epidemic due to theft or accidental release of the virus.  However, according to Weinstein destruction would only provide an illusion of safety and that the drawbacks of eliminating variola from existence are many.

In this paper Weinstein mentions the possible reasons behind the hesitance to destroy smallpox.  The prolonged existence of smallpox along with the important clinical implications of its high infectivity and mortality rates suggests that the human immune system evolved under the disease’s evolutionary influence.  In the last decade research has been done which suggests that variola (and vaccinia) have the ability to alter the host immune response by targeting various components of the immune system.  We are only beginning to understand the complex pathophysiology and virulence mechanisms of the smallpox virus.  An example of the importance of smallpox in human evolution is the CC-chemokine receptor null mutation (CCR5Δ32), which first appeared in Europe ~3500 years ago one person and today it can be found in ~10% of all those from northern European decent.  The mutation prevents expression of the CCR5 receptor on the surface of many immune cells and provides resistance to smallpox.  This same mutation also confers nearly complete immunity to HIV. In a recent study done by Weinstein and co-workers (2010) it was postulated that exposure to vaccinia and variola may have previously inhibited successful spread of HIV, suggesting that we swopped out one major disease for another. By eliminating the variola stockpiles from existence on-going research in this direction might be hampered and the possibility future studies employing intact virus will be rendered impossible.

Finally, we are capable of creating a highly virulent smallpox-like virus from scratch or a closely related poxvirus through genetic manipulation.  This renders moot any argument for the destruction of remaining stockpiles of smallpox in the belief that it would be for the benefit of protecting mankind.

In an editorial of the Vaccine journal, the editors make a compelling case in favour for the destruction of remaining stockpiles of smallpox virus.    To follow is their take on the situation:

Why not destroy the remaining smallpox virus stocks?

Editorial (by J. Michael Lane and Gregory A. Poland)

Vaccine (2011), Vol 29:  2823 – 2824

The Advisory Committee on Variola Virus Research (created in 1998 as part of the WHO) concluded that live variola is no longer necessary except to continue attempts to create an animal model which might mimic human smallpox and assist in the licensure of new generation vaccines and antivirals.

The editors feel that scientific recommendation for keeping smallpox stocks need to be scrutinized and that a number of political and ethical issues need to be addressed.  Below are comments by editors on these issues:

Scientific issues:

The smallpox virus is no longer needed to elucidate its genome, 49 strains have been sequenced and published, the editors feel that there is no need to sequence additional strains.  The smallpox virus can be destroyed as it is possible to reconstruct it from published sequences or to insert the genes of interest into readily available strains of vaccinia or monkeypox.  Refinements regarding diagnostics can be made by using other orthopoxviruses or parts of the smallpox strains already sequenced; vaccines have been produced that are far less reactogenic than the first and second generation of vaccinia vaccines and they are very effective against other orthopoxviruses.  Finally, the development of an animal model is difficult to perfect as variola is host-specific, thus there are no guarantees that a model will be found that mimics the pathophysiology of smallpox in humans.

Political/ethical issues:

The US is a supporter of the WHO and the UN and failure to comply with the request of the World Health Assembly jeopardizes the US’s potential to work with the UN to further their foreign policy and population health goals.  Biological weapons have been banned from the US military arsenal and there is no way they would use a biological weapons such as smallpox whether it be in offense or defence.  The editors reckon that the risk of a biological warfare attack using smallpox is highly unlikely as terrorists who have the knowledge and sophistication to grow and prepare smallpox for dispersal would realize that they could cause harm to their own countries.  Apart from that, Western nations have the facilities to isolate and vaccinate against smallpox in a timely manner.

According to the editors there is no ethical way to justify maintaining an eradicated virus.  Even though the possibility of accidental release is very small, it is an unacceptable risk.  Maintenance of the smallpox virus stocks is expensive and time consuming, it also burdens the CDC without scientific merit and their resources are better used to protect the public from infectious diseases.

In conclusion the editors maintain that the remaining smallpox stocks should be destroyed and the world should make possession of the virus an “international crime against humanity”.

We are presented with two very different views with regards to whether or not smallpox virus stocks should be destroyed forever.  The WHO meets again this year to decide the final fate of smallpox. Will the board reach consensus or will the smallpox virus yet again receive a stay of execution? 


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