ABSTRACT
Besides humans, H3 subtypes of influenza A viruses (IAVs) can infect various animal hosts, including avian, swine, equine, canine, and sea mammal species. These H3 viruses are both antigenically and genetically diverse. Here, we characterized the antigenic diversity of contemporary H3 avian IAVs recovered from migratory birds in North America. Hemagglutination inhibition (HI) assays were performed on 37 H3 isolates of avian IAVs recovered from 2007 to 2011 using generated reference chicken sera. These isolates were recovered from samples taken in the Atlantic, Mississippi, Central, and Pacific waterfowl migration flyways. Antisera to all the tested H3 isolates cross-reacted with each other and, to a lesser extent, with those to H3 canine and H3 equine IAVs. Antigenic cartography showed that the largest antigenic distance among the 37 avian IAVs is about four units, and each unit corresponds to a 2 log 2 difference in the HI titer. However, none of the tested H3 IAVs cross-reacted with ferret sera derived from contemporary swine and human IAVs. Our results showed that the H3 avian IAVs we tested lacked significant antigenic diversity, and these viruses were antigenically different from those circulating in swine and human populations. This suggests that H3 avian IAVs in North American waterfowl are antigenically relatively stable.
Subject(s)
Antigenic Variation , Influenza A virus/genetics , Influenza A virus/immunology , Influenza in Birds/virology , Orthomyxoviridae Infections/veterinary , Animals , Animals, Wild/virology , Anseriformes/classification , Anseriformes/virology , Chick Embryo , Chickens , Hemagglutination Inhibition Tests , Humans , Influenza A virus/classification , Influenza A virus/isolation & purification , Influenza, Human/virology , North America , Orthomyxoviridae Infections/virology , Phylogeny , Poultry Diseases/virology , Swine , Swine Diseases/virologyABSTRACT
To determine whether, and to what extent, influenza A subtype H3 viruses were present in feral swine in the United States, we conducted serologic and virologic surveillance during October 2011-September 2012. These animals were periodically exposed to and infected with A(H3N2) viruses, suggesting they may threaten human and animal health.
