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Coxsackie NY and the virus named after it

10 August 2009 by Vincent Racaniello

coxsackie-nyRecently while driving north on the New York State Thruway I passed the exit for the town of Coxsackie, NY (population 8,884). I grabbed my camera and photographed the exit sign, and reminded myself to write about the virus named after this small town.

In the summer of 1947 there were several small outbreaks of poliomyelitis in upstate New York. Gilbert Dalldorf, the director of the Wadsworth Laboratory in Albany, NY, and his associate Grace M. Sickles investigated this outbreak. In particular they sought polioviruses that could replicate in mice. This search was motivated by the fact that research on poliovirus required the use of monkeys which were extremely expensive. Dalldorf had attended the Fourth International Congress for Microbiology in 1947 where he heard that very young mice – suckling mice – could readily be infected with Theiler’s virus.

Dalldorf and Sickles made fecal suspensions from two children suspected of having poliomyelitis, and inoculated these into adult and suckling mice. Only the suckling mice (1 – 7 days old) developed paralysis; animals more than one week old were resistant to infection. The damage responsible for limb paralysis was widespread lesions in skeletal muscles, not in the central nervous system as occurs with poliovirus. Further study revealed that the viruses could be distinguished serologically from poliovirus.

Not only had Dalldorf and Sickles identified the first members of a very large group of human viruses, but they also introduced and popularized a new and inexpensive animal into the virology laboratory – the suckling mouse. In 1949 Dalldorf suggested that the new viruses be called Coxsackie viruses, because the first recognized human cases were residents of that New York village. This unique name is of native North American origin.

Over ten years later the importance of this work was recognized by Dr. Max Finland of Boston City Hospital:

The isolation by Dalldorf and Sickles of viruses which produced paralysis with destructive lesions of muscle in sucking mice and hamsters, from the stools of two children with signs of paralytic poliomyelitis was an achievement that may rank in importance with Landsteiner and Popper’s production of human poliomyelitis in monkeys.

In subsequent years many different Coxsackieviruses were isolated that cause a variety of clinical syndromes. Today at least 30 serotypes of Coxsackieviruses are classified in the enterovirus genus of the Picornaviridae. The viruses are classified into groups A or B depending upon the pathological effect in suckling mice.

Not every locale is pleased to have a virus named after it. In May 1993, an outbreak of an unexplained pulmonary illness occurred in the southwestern United States, in an area shared by Arizona, New Mexico, Colorado and Utah called “The Four Corners.” Muerto Canyon was proposed as the name for the etiologic agent of the disease, because the virus was first isolated from a rodent near the canyon. However after residents objected, the name Sin nombre virus was given to the agent of hantavirus pulmonary syndrome.

Dalldorf G, & Sickles GM (1948). An Unidentified, Filtrable Agent Isolated From the Feces of Children With Paralysis. Science (New York, N.Y.), 108 (2794), 61-62 PMID: 17777513

Filed Under: Basic virology, Information Tagged With: Coxsackie, coxsackievirus, Gilbert Dalldorf, Grace Sickles, myositis, paralysis, picornavirus, poliomyelitis, suckling mice, viral, virology, virus

A viral protease interferes with interferon

15 June 2009 by Vincent Racaniello

Viruses are known to evade the early, or innate, host defenses by interfering with the sensing of infection, production of IFN, and synthesis and activity of ISGs. Today we’ll examine the evidence that the function of one or more ISGs is blocked in poliovirus-infected cells.

When IFN is added to the medium of cultured cells, hundreds of ISGs are produced, establishing an antiviral state. Many viruses are unable to replicate in cells treated in this way. An example is the inhibition of replication of encephalomyocarditis virus (EMCV), a picornavirus, by IFN shown in this figure:

emcv-ifn

In this experiment, IFN was added to the medium of HeLa cells for 16 hours, and then the cells were infected with EMCV. At the indicated times after infection, the medium was removed, and EMCV titer was determined by plaque assay. In mock-treated cells, EMCV produces about 100 plaque-forming units (pfu) per cell*, while IFN treatment of cells blocks virus production.

If the same experiment is done using poliovirus, the outcome is quite different. As shown in the figure below, poliovirus replication is reduced by IFN treatment of cells, but a good amount of virus is nevertheless produced.

polio-ifn

This result suggests that the genome of poliovirus encodes one or more proteins that antagonize the activity of ISGs. Likely candidates for the ISG-busting activity are the two proteases encoded in the viral genome. These proteases, called 2Apro and 3Cpro, process the viral protein and also are known to inactivate cellular proteins. Consistent with this idea, poliovirus with a one amino acid change in 2Apro was found to be completely sensitive to IFN.

This observation indicates that 2Apro blocks the antiviral activity of one or more ISGs.

The EMCV genome encodes a 2A protein that does not have the ability to cleave other proteins. This observation may explain the exquisite sensitivity of EMCV to IFN. Can poliovirus 2Apro turn EMCV into an IFN-resistant virus? To test this hypothesis, the gene encoding 2A was inserted into the genome of EMCV. The resulting virus, EMCV-2A, was able to replicate in cells treated with IFN.

Which ISGs are targeted by poliovirus 2Apro? That is not an easy question to answer, as there are nearly 1000 known ISGs. We’re working on it.

(*The plaque assay is one of several methods for determining virus titer. We’ll discuss this assay in an upcoming post).

Morrison, J., & Racaniello, V. (2009). Proteinase 2Apro Is Essential for Enterovirus Replication in Type I Interferon-Treated Cells Journal of Virology, 83 (9), 4412-4422 DOI: 10.1128/JVI.02177-08

Filed Under: Information Tagged With: EMCV, IFN, interferon, ISG, picornavirus, poliovirus, viral, virology, virus

Cosavirus – a new human picornavirus

3 February 2009 by Vincent Racaniello

phil_235_loresThe WHO strategy to eradicate poliomyelitis depends upon immunization of every child under 5 years of age, and nationwide AFP (acute flaccid paralysis) surveillance to identify cases of poliomyelitis. A laboratory network then determines whether AFP is caused by poliovirus. Recently a new member of the picornavirus family was identified in children with non-poliovirus AFP. This virus has been named cosavirus (common stool-associated  picornavirus).

In one study, a combination of mass sequencing, RT-PCR,  and RACE was used to obtain the viral sequence from a stool sample from an Australian child with acute diarrhea. In the second study, stool samples from South Asian children with AFP were partially purified to obtain particle-protected RNA, which was then amplified by randomized oligonucleotides. In both cases a novel picornavirus was identified which is most closely related to cardioviruses and Senecaviruses. However, the viral genome sequences are sufficiently diverged to warrant placing them in a new genus, Cosavirus.

Perhaps the most interesting aspect of this work is the observation that in Pakistan and Afghanistan, cosavirus sequences were detected in over 40% of stool samples from healthy children as well as from children with AFP. In contrast, only 1 of 1000 stool samples from Edinburgh, UK was positive for the virus.

An important question which must be resolved is whether cosavirus can cause AFP. It is possible that many cosavirus infections are asymptomatic, as is the case with poliovirus infection, where only 1 infection in 100 leads to paralysis. Does replication of cosavirus in the intestine interfere with the poliovirus vaccine strains, possibly explaining immunization failures in India? It will also be interesting to study the replication of this virus in cell cultures and in laboratory animals. The viral genome has some unusual features, including two 2A proteins, one of which is not related to any other picornavirus 2A, and a long 5′-noncoding region. Such studies are so far hindered by the fact that no laboratory has yet reported propagation of cosavirus in cultured cells.

Holtz, L., Finkbeiner, S., Kirkwood, C., & Wang, D. (2008). Identification of a novel picornavirus related to cosaviruses in a child with acute diarrhea Virology Journal, 5 (1) DOI: 10.1186/1743-422X-5-159

Kapoor A, Victoria J, Simmonds P, Slikas E, Chieochansin T, Naeem A, Shaukat S, Sharif S, Alam MM, Angez M, Wang C, Shafer RW, Zaidi S, & Delwart E (2008). A highly prevalent and genetically diversified Picornaviridae genus in South Asian children. Proceedings of the National Academy of Sciences of the United States of America, 105 (51), 20482-7 PMID: 19033469

Filed Under: Information Tagged With: acute flaccid paralysis, cosavirus, enterovirus, picornavirus

Hantavirus protein replaces eIF4F

22 January 2009 by Vincent Racaniello

eif4fThe cellular translation machinery is frequently modified in virus-infected cells. Antiviral defense systems or stress responses may be initiated to inhibit protein synthesis and restrict virus replication. On the other hand, many viral genomes encode proteins that modify the cellular translation apparatus to favor the production of viral proteins over those of the cell. One such well-studied modification is the cleavage of the cellular translation protein eIF4G (see illustration) in cells infected by picornaviruses. The consequence of this modification is that capped cellular mRNAs cannot be translated. As the viral genomes are translated by internal ribosome entry, viral protein synthesis is not affected by cleavage of eIF4G.

A recent report in The EMBO Journal has revealed a novel modification of the cellular translation apparatus in cells infected with Sin Nombre virus, a hantavirus.The authors show that the viral nucleocapsid (N) protein binds with high affinity to the cap structure on cellular mRNAs. The N protein can also bind the 43S preinitiation complex (which consists of the 40S ribosomal subunit, several initiation proteins, and the met-tRNAi). Finally, N protein has RNA helicase activity, which facilitates ribosome movement through areas of RNA secondary structure. This viral protein therefore functionally replaces  all three components of eIF4F: eIF4E (the cap-binding protein), eIF4G (the scaffolding protein which connects the ribosome to the mRNA), and eIF4A, an RNA helicase. It does so even though it has no amino acid similarity to the proteins of eIF4F. Furthermore, the N protein was previously shown to be involved in viral RNA replication and encapsidation. The multifunctional nature of the N protein should come as no surprise: the hantavirus genome encodes only four proteins. Each must therefore fulfill multiple functions in the replication cycle.

Why would the hantavirus genome encode a protein that replaces eIF4F? One of the earliest cellular responses to virus infection is inhibition of translation;the goal is to restrict viral spread. The properties of the N protein could enable unabated viral translation in the face of such a cellular defense. Furthermore, many viral genomes encode proteins that inhibit viral translation. No such activity has been described in cells infected with hantaviruses. Nevertheless, the N protein could permit translation of viral mRNAs when that of cellular mRNAs is inhibited.

The participation of the hantavirus N proteins in multiple events in the cell identify it as an excellent target for therapeutic intervention.

Mohammad A Mir, Antonito T Panganiban (2008). A protein that replaces the entire cellular eIF4F complex The EMBO Journal, 27 (23), 3129-3139 DOI: 10.1038/emboj.2008.228

Filed Under: Information Tagged With: eIF4G, hantavirus, IRES, picornavirus, translation

Europic 2008

28 May 2008 by Vincent Racaniello

Since Monday I have been in Sitges, Spain for Europic 2008. This is a scientific meeting on picornaviruses held every other year in a European country. The picornaviruses are a family of non-enveloped, positive-strand RNA viruses, and includes poliovirus, rhinovirus, and foot-and-mouth disease virus.

I have been attending Europic meetings since 1983, when it was held in Urbino, Italy. Not only is the science excellent and focussed, but the venues are fabulous. Sitges is a lovely town on the coast of the Mediterranean. While the sessions leave little time for seeing the town, it is nice to be in a different place, with old buildings, culture, and a history.

We have already held sessions on virus entry into cells, epidemiology, surveillance, and evolution. I learned yesterday that virus classification is now entirely based on sequence comparisons, with little concern for the biology of the virus. For example, the rhinovirus and enterovirus genera will be combined into one genus called enterovirus. While this change reflects the sequence relationships among the viruses, it will surely be hard to explain why respiratory viruses (rhinoviruses) are classified in a genus whose name implies replication in the enteric tract (enterovirus). The proposed changes in classification can be viewed here.

Another interesting topic was serotyping. Many years ago, new viruses were classified according to an immunological definition: If antiserum against one virus did not neutralize the infectivity of a related virus, they were said to be different serotypes. Modern sequence analyses now indicate that different serotypes are often highly related. Therefore the use of an antigenic classification is somewhat outdated. Sequence analysis will now be used to define serotype, and the different viruses will now be called types, rather than serotypes.

These changes reflect the growing influence of genomics on virology.

Filed Under: Events, Information Tagged With: classification, picornavirus, serotype, viral, virology, virus, viruses

Enterovirus 71 Outbreak in Asia

15 May 2008 by Vincent Racaniello

enterovirus 71There is an ongoing outbreak of enterovirus 71 (EV71) in a broad region of Asia, including China, Vietnam, Mongolia, Taiwan, and Singapore. There have been 3606 cases in China, including 36 deaths.

Infection with EV71 is common in Asia, where it causes hand-foot-and-mouth disease in children, a febrile syndrome accompanied by flat or raised red spots in the tongue, gums, inside of cheeks, palms, soles of feet, and buttocks. Neurological complications of EV71 infection include aseptic meningitis, encephalitis, and poliomyelitis-like polyneuritis. The high fatality rate of the current outbreak is unusual, but not unprecedented. A study of the Taiwan epidemic of 1998 revealed an unusual neurologic manifestation, brainstem encephalitis, which was also observed in Malaysia in 1997 but not in earlier epidemics. The changes in EV71 disease might be a consequence of the emergence of a more virulent viral strain.

EV 71 is a member of the family Picornaviridae, which also contains the well-known pathogen poliovirus. The virus was first isolated in 1969 from a case of fatal human encephalitis in California. EV71 is distributed worldwide and is spread by fecal-oral and possibly by respiratory droplet transmission.

In some locations EV71 is emerging as the most significant neurotropic enterovirus. It has been suggested that the incidence of EV71 might increase after the eradication of poliovirus, in which case there will be increased efforts to develop vaccines and antivirals against this agent.

Filed Under: Basic virology, Events, Information Tagged With: enterovirus 71, ev71, outbreak, picornavirus, viral, virology, virus

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