Canine parvovirus type 2c in Vietnam continues to produce distinct descendants with new mutations restricted to Vietnamese variants.

Viral protein 2 (VP2) of canine parvovirus (CPV) exhibits a high degree of genetic and antigenic diversity. We analyzed 88 Vietnamese CPV-VP2 sequences (1755 bp), 34 from this study and 54 from previous studies, and discovered a new sublineage, "new var.", within the lineage CPV-2c-"new", characterized by the mutation 5G/447M, which is restricted to the Vietnamese isolates. These new mutants appear to have emerged in recent years, accounting for 65.5% of the total. With strong nodal support (98%), the distinct Vietnamese 2c-"new-var." sublineage (5G/426E/447M) was found to be separate from the 2c-"new" sublineage (5G/426E/447I) within the 2c-(Asia)/Asia-2c lineage. Amino acid changes in epitopes of VP2 might have led to the generation of subvariants and affected the antigenicity, immunogenicity, or virulence of the virus, resulting in vaccine failure worldwide.