Novel Gene Mutations in Tunisian Isolate of Avian H9N2 Influenza Virus

Abstract

A new strain of H9N2 avian influenza virus (AIV) was isolated from suspected broiler flocks and characterized using RT-PCR and sequencing techniques which have shown new interesting mutations as compared to previously characterized Tunisian strains of major clinical importance. Reverse transcription-PCR, nucleotide sequencing, and GenBank BLAST database analyses of external and internal genes of the virus demonstrated that the new isolate, designated A/CK/TUN/145/12, has the 333PSRSSR*GLF341 motif at the cleavage site of its hemagglutinin (HA), different from that described in the older Tunisian strains, which possess the motif 333PARSSR*GLF34, and others reported strains in the world. The presence of Leu at position 234 in the amino acid sequence of HA indicated the virus binding preference to the human cellular receptor α-2,6 sialic acid. Besides, such HA amino acid sequence showed two new mutations D280N and Y144S. The hemadsorption (HB) site of its neuraminidase (NA) did show three new mutations H441N, N342D and S331N in comparison to older Tunisian strains. Such mutations were reported for the highly pathogenic H5N2 subtype in Nigeria. Phylogenetic data allowed classification of the new Tunisian isolate in a new genetic group including the old Tunisian isolates.