Immunohistochemical, Immunofluorescent, and Molecular Investigation of Canine Distemper Virus, Nectin 4, and CD150 Receptors in Naturally Infected Dogs with Canine Distemper Virus.

Canine distemper virus uses CD150 and Nectin-4 receptors to infect cells. In the central nervous system, astrocytes, the main canine distemper virus target, reportedly lack these receptors, suggesting alternative entry pathways. This study investigated canine distemper virus distribution and receptor usage in naturally infected dogs' organs and tissues using immunohistochemistry and immunofluorescence. Tissue samples from 34 dogs (including the central nervous system, internal organs, footpads, and planum nasale) were examined for CDV, CD150, Nectin-4, and GFAP; diagnosis was confirmed by immunochromatographic assay and RT-PCR. Thirty-two dogs were canine distemper virus positive. Triple immunofluorescence staining showed epithelial cells were CDV/Nectin-4 positive, lymphocytes and macrophages were CDV/CD150 positive, while astrocytes were CDV-positive but negative for both receptors. Double immunofluorescence for CDV and GFAP in the CNS confirmed astrocyte infection. These findings indicate that CDV enters lymphocytes/macrophages via CD150 and epithelial cells via Nectin-4, whereas astrocytes likely use alternative entry pathways outside the classical receptor framework.