Molecular analysis of the full-length VP2 gene of Brazilian strains of canine parvovirus 2 shows genetic and structural variability between wild and vaccine strains

Canine parvovirus 2 (CPV-2), a highly contagious virus, affects dogs worldwide. Infected animals present severe and acute gastroenteritis which may culminate in death. CPV-2 VP2 protein is responsible for important biological functions related to virus-host interactions. Herein we obtained VP2 full-length gene sequences from Brazilian dogs with bloody diarrhea (n=15) and vaccine strains (n=7) produced by seven different laboratories and marketed in Brazil. All wild sequences and one vaccine strain were classified as CPV-2b and six vaccines were the classic CVP-2. Mutations in VP2 protein from vaccine and wild strains obtained in Brazil and worldwide were analyzed (n=906). Amino acid sequences from vaccine strains remarkably diverge from each other, even that classic CPV-2. Phylogenetic analysis based on VP2 gene and conducted with sequences displaying mutations in epitope regions previously described shows that vaccine strains are distantly related from the wide range of wild CPV-2. The impact of amino acid mutations over VP2 protein structure shows that vaccine and wild strains obtained in this study diverge in loop 3, an epitope region that plays a role in the CPV-2 host range. This is the first analysis of CPV-2 VP2 from commercial vaccine strains in Brazil and wild ones from Minas Gerais State, Brazil, and the first detailed attempt to vaccinal VP2 molecular and structural analyses.