Junctional adhesion molecule-1 (JAM-1) restricts canine parvovirus type 2 replication in vitrovia impairing viral attachment and modulating innate immune responses.

Canine parvovirus type 2 (CPV-2) is a highly contagious pathogen that causes severe hemorrhagic enteritis in dogs and other carnivores. Junctional adhesion molecule-1 (JAM-1), a transmembrane tight junction (TJ)-associated biological macromolecule belonging to the immunoglobulin superfamily, plays essential roles in epithelial barrier maintenance and host-pathogen interactions. However, the involvement of JAM-1 during CPV-2 replication remains unclear. In this study, we investigated the dynamic regulation of TJ proteins and the antiviral role of JAM-1 during in vitro co-culture with CPV-2. CPV-2 treatment induced a biphasic regulation of TJ-associated proteins, characterized by an early decrease (6-12 h post co-culture) followed by a later increase (48-72 h post co-culture). During the early stage, the expression of claudin-4 (CLDN4), occludin (OCLN), and JAM-1 decreased to 68%, 51%, and 66% of control levels, respectively. At later time points, CLDN1, CLDN4, OCLN, and JAM-1 were increased by 1.53-, 2.23-, 2.08-, and 2.01-fold, respectively. Co-immunoprecipitation (Co-IP) and glutathione-S-transferase (GST) pull-down assays demonstrated interactions between the CPV-2 VP2 capsid protein and several TJ proteins (TJs), including CLDN1, OCLN, and JAM-1. Functional analyses showed that JAM-1 overexpression markedly reduced VP2 protein levels and viral DNA abundance in vitro, whereas siRNA-mediated JAM-1 knockdown enhanced CPV-2 replication. Mechanistically, JAM-1 overexpression was associated with reduced viral attachment and the modulation of innate immune factors. Collectively, these findings identify JAM-1 as a key biological macromolecule involved in restricting CPV-2 replication in vitro and provide new insights into host factors mediating CPV-2-host interactions.