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Working Group One: Influenza Virulence and Antigenic Change Research Recommendations

John R. LaMontagne Memorial Symposium on Pandemic Influenza Research April 4-5, 2005 Institute of Medicine. Working Group One: Influenza Virulence and Antigenic Change Research Recommendations. Defining the loci for pathogenicity (Combined Q1 and in part Q4)

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Working Group One: Influenza Virulence and Antigenic Change Research Recommendations

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  1. John R. LaMontagne Memorial Symposiumon Pandemic Influenza ResearchApril 4-5, 2005Institute of Medicine Working Group One: Influenza Virulence and Antigenic Change Research Recommendations

  2. Defining the loci for pathogenicity (Combined Q1 and in part Q4) Known: HA cleavage site, NA binding plaminogen, CHO-sites around cleavage site, NS1 mutations affecting cytokine production, mutations that affect replication (e.g. cold-adapted virus, PB2 627 mutation: mice but not ferrets). Suitable animal model: currently mice/ferrets/chickens Non-human primates questionable. Major questions about use of inbred mice: lacking Mx gene (anti-viral state) Ferrets: no adaptation required for human viruses. Problems with ferret model: need to use one agreed upon strain of ferret, Few immunological reagents, how to do cytokine response, a ferret DNA sequence genome project would help. To do: Determine genes needed for both transmission and pathogenicity (reverse genetics reassortments). Study genetic basis that underlies transmission, virulence and pathogenicity. Increase number of ferrets. Need lg. breeding colony of ferrets. Ferret reagents. Test hamsters and pigs. Need containment facilities.

  3. Q2. Do incremental changes in genome lead to pandemics?. From 1997 to 2005 H5N1 virus gained ability to kill ducks and it transferred and kills cats. Need series of viruses where a change in virulence/pathogenicity has occurred. Need sequences of all of these genomes of all of these viruses and posted to public database. Need reverse genetics working for each of these viruses. Need appropriate animal model systems. Show mutations are sufficient and necessary for property being examined.

  4. Q3. Studies needed to track the rate of antigenic change in avian and human Strains and to predict the changes that occur. Note: Only 3 HA subtypes caused major disease in humans H1, H2 and H3. Note: 1918 “W”-shaped death rate. Presumably prior H1 exposure for older population (H3 and H1 thought to circulate before 1918 - not H5/H7/H9). Note: Viral archeology - difficult. No preservation of tissues before 1900. Continue predictions of changes and effect on antigenic epitopes: e.g. Simon Levin’s PNAS paper on prediction of HA sequence clusters and antigenic evolution. Continue surveillance. Continue nucleotide sequencing of viral genomes. Ideally need better immunological markers - HAI tests are insensitive and do not work on H5

  5. Q4 in part: Studies needed to determine pandemic risk associate with antigenic characteristics. Determine the extent of antigenic variation to give a pandemic strain. Need both human and animal studies. Does pre-existing antibody to one sub-type have an effect on infection with another sub-type? Look at ability of viruses of different sub-types to infect animal(s) (ferret?) that already has antibody levels to common human viruses (H1N1, H2N2, H3N2). Question 5: NEW Are there human genetic changes that increase/decrease susceptibility to influenza virus infection. Coupling to Cancer Genome Project?

  6. Priorities • Determine sequences of human, animal and avian isolates within an epidemiological framework. • Need for clinical data from human cases. • Determine the genes and their function for transmission and pathogenicity in ferrets using qualified reagents.

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