A8 The epidemiology and evolution of influenza A/H1N1 and A/H3N2 virus from 2010 to 2015, in Ho Chi Minh City, Vietnam

Abstract

Influenza A viruses are highly infectious pathogens that constantly circulate in many animal hosts including humans, birds,pigs, horses and dogs. Infections with influenza viruses resultin protective immunity mediated by antibodies against the viralsurface glycoproteins hemagglutinin (HA) and neuraminidase(NA). However, human and some avian influenza viruses havecontinuously undergone antigenic evolution to evade pre-existing host immunity, a phenomenon known as antigenic drift(accumulation of point mutations in HA and NA antigens).Antigenic drift explains the occurrence of repeated seasonalinfluenza epidemics in humans. In order to determine the virus'attack rate, cross-sectional seroprevalence studies are necessary. Typically, these seroprevalence studies of influenzaviruses rely on HI (Hemagglutinin Inhibition assay) or MN(microneutralization test) to measure antibody titers in serumsamples; these tests can have low sensitivity and they normallyoffer binary results (past infection, or not). Here, we conducted aseroprevalance study of influenza virus A/H1N1 and A/H3N2 inHo Chi Minh City population between 2010 and 2015 using anovel protein microarray to measure the continuous-scale antibody titers against these subtypes in 5000 serum samples. Ourplatform is high-throughput, reproducible and can providemore informative antibody titers than previous assays. We alsoperform whole-genome sequencing of 190 influenza strains toinvestigate the antigenic changes of these subtypes over thestudy period. Tracking the antigenic changes of the viruses couple with a measurement of antibiotic response against theseviruses in a population is an ideal data set to understand theevolution and immuno-epidemiology of these important pathogens and to provide timely and accurate data for the selectionof vaccine strains.