Evolutionary dynamics of porcine parvovirus type 1 reveal antigenic divergence with implications for vaccine coverage

Porcine parvovirus type 1 (PPV1) is globally recognized as the etiological agent responsible for one of the main causes of reproductive failure in swine herds, known by the acronym SMEDI. Although it has been identified since the mid-1960s, PPV1 continues to be isolated worldwide, leading to significant financial losses. Vaccination remains the primary preventive measure against the virus. However, the emergence of new variants globally raises concerns regarding the efficacy of currently available vaccines. This study analyzed 200 complete VP2 gene sequences (1963-2021) using phylogenetics, protein modeling, epitope prediction, and molecular docking simulations. Phylogenetic analysis revealed a total of five lineages. Two of these lineages did not contain vaccine reference variants. One lineage was predominantly composed of European strains, whereas another showed a mixed Eurasian distribution. Predictions and simulations identified structural differences at several protein positions among the five phylogenetic groups and the three reference vaccine strains (NADL-2, 27a, and PPV014), including regions overlapping predicted epitopes and sites under positive selection. These findings indicate antigenic divergence between circulating and vaccine reference strains and should be interpreted as computational, hypothesis-generating evidence that requires experimental validation by cross-neutralization and challenge studies.