Avian influenza A viruses (IAVs) are able to overcome the interspecies barrier and adapt to the new non-avian host. The process of adaptation requires the adaptive changes of IAV genome resulting in amino acid substitutions. The aim of this work was the description of amino acid substitutions in avian influenza A viruses (IAVs) occurring during their adaptation to equine host. Today, viruses of the equine influenza H3N8 subtype, first isolated in 1963, represent a single genetic lineage of IAV causing a respiratory disease in horses. We compared the amino acid sequences of the conserved proteins PB2, PB1, PA, NP, M1, M2, NS1 and NEP of equine influenza H3N8 subtype IAV with sequences of avian viruses, both available in the NCBI's Influenza Virus Resource Database. The amino acid substitutions persisting in equine IAV isolates and occurring in avian IAV at f both hosts.
Keywords: equine influenza virus; equine H3N8 virus lineage; adaptation to host; amino acid substitution; host-specific marker..