Genetic and antigenic analysis of type of foot-and-mouth disease viruses isolated in India during 1987-1996

Twenty-three foot-and-mouth disease virus (FMDV) type PI field isolates, re covered from different outbreaks during 1987-1996 in India, were subjected to antigenic and genetic analysis. The isolates showed a close antigenic re lationship to the current vaccine strain (MD 17/77) in micro-neutralization test conducted using a vaccine strain (IND 17/77) antiserum and a peptide (aa 136-151 of VP1 protein of the A22/Azerbaijan/65 strain) antiserum. Howe ver, the isolates revealed minor antigenic differences in their reactivity with three neutralizing monoclonal antibodies (MAbs) recognizing trypsin-se nsitive conformation-independent epitopes of tile vaccine virus strains. Ph ylogenetic relationship between the isolates was carried out employing a pa rt of the 1D gene (168 nucleotides at the 3 ' -end). Additional seven type A Indian field isolates reported earlier were included in the analysis. The percent similarity among the Indian isolates varied from 82.7% to 99.4% at nucleotide level, and from 83.9% to 100% at amino acid level. These observ ations clearly demonstrate genetic heterogeneity of the field isolates. The current vaccine strain MD 17/77 showed divergence of 9.7% at nucleotide le vel and 5.6% at amino acid level from the A22 Iraq 24/64 isolate. The field strains were divergent from the vaccine strain IND 17/77 by 5.6%-14.6% and 3.7%-13.7 % at nucleotide and amino acid level, respectively. In the phylo genetic tree, the isolates were distributed into 21 genetic groups. The clu stering pattern of the isolates in the phylogenetic tree revealed Ilo speci fic distribution pattern of the foot-and-mouth disease (FMD) outbreaks in r elation to their geographical locations, caused by unrestricted animal move ment and endemic nature of the disease.