Genetic and antigenic characterization of Indian foot-and-mouth disease virus serotype O isolates collected during the period 2001 to 2012.

The phylogenetic analysis of VP1 sequences of the 39 type O foot and mouth virus (FMDV) isolates collected from different regions of India during the year of 2001-12 revealed that all isolates belonged to the Middle East - South Asia (ME-SA) topotype. Based on the amount of divergence among the isolates, the viruses were further classified into three distinct lineages namely Ind 2001, PanAsia and PanAsia-2 as well as a minor, unnamed group. Ind 2001 lineage viruses accounted for most of the current type O outbreaks. At the nucleotide level these isolates showed a divergence of 2% to 14% with an average sequence variation of ~9.9%. The serological spectrum of the current vaccine strain was studied by using bovine vaccinate serum (BVS) raised against O/IND/R2/75. All the current field isolates (n=24) were homologous ('r' value 0.4 to 1.0) to the vaccine strain. Examination of the amino acid sequences for selection pressure revealed the positive selection at amino acid sites 13 and 45.