Whole-genome sequence analysis of canine parvovirus reveals replacement with a novel CPV-2c strain throughout India.

Canine parvovirus (CPV) infection causes severe gastroenteritis in canines, with high mortality in puppies. This virus evolved from feline panleukopenia virus by altering its transferrin receptor (TfR), followed by the emergence of CPV-2 variants in subsequent years with altered immunodominant amino acid residues in the VP2 protein. While previous studies have focused on the VP2 gene, there have been fewer studies on non-structural protein (NS1 and NS2) genes. In the present study, CPV genome sequences from clinical samples collected from canines throughout India in 2023, previous Indian CPV isolates from 2009-2019, and the current Indian CPV vaccine strain were compared. The study showed that the CPV-2c (N426E) variant had almost completely replaced the previously dominant CPV-2a variant (N426) in India. The Q370R mutation of VP2 was the most common change in the recent CPV-2c strain (CPV-2c 370Arg variant). Phylogenetic analysis showed the existence of three clades among the recent CPV-2c strains, and sequence analysis identified several new sites of positive selection in the VP1 (N-terminus), VP2, NS1, and NS2 protein-encoding genes in recent CPV strains, indicating the emergence of new CPV-2c variants with varied antigenic and replication properties. The predominant 'CPV-2c 370Arg variants' were grouped with the Chinese and Nigerian CPV-2c strains but were separate from the CPV vaccine strain and earlier isolates from our repository. VP2 epitope analysis predicted nine amino acid variations (including two new variations) in four potential linear B-cell epitopes in the CPV-2c 370Arg variants that might make vaccine failure more likely. This pan-Indian study lays the foundation for further research concerning the dynamics of virus evolution and understanding genetic mutations.