The immunoreactivity of haemagglutinin (HA) polypeptides of equine influenza virus was compared among the strains isolated in Poland, using H3 monoclonal antibody. A stronger signal in immunoblot reaction was observed for A/equi/Pulawy/2008 HA polypeptides compared to A/equi/Pulawy/2006, despite the fact that both strains are phylogenetically closely related and belong to Florida clade 2 of American lineage. The strongest signal, observed in the case of A/equi/Pulawy/2008, seemed to be connected with the presence of G135, 1213, E379, and/or V530 instead of R135, M213, G379, and 1530 present in A/equi/Pulawy/2006 HA sequence. This implies that point mutations within amino acid sequences of HA polypeptides of equine influenza virus may change their immunoreactivity even when they are not located within five basic antigenic sites.
The aim of the study was to monitor genetic diversity and antigenic changes in the genome of influenza A(H1N1)pdm09 viral isolates detected during the post-pandemic period in Poland. Clinical specimens obtained from three suspected cases of influenza were analysed by sequencing. Among the differences identified in amino acids sequences, nine substitutions were located within the antigenic HA1 sites and in five residues forming receptor-binding pocket. The HA(D222G) mutation was shown in the isolate Swine/Poland/134312/12 obtained from a mild case of the disease. It must be emphasized that, in general, clinically mild cases are caused by the viruses in which that specific mutation, i.e. haemagglutinin (D222G), does not occur.