Introduction: Porcine cytomegalovirus (PCMV), an enveloped DNA virus in the Herpesviridae family (subfamily Betaherpesvirinae), has not been reported to infect humans but raises concerns about transmission via xenotransplantation. In non-human primate studies, PCMV infection has influenced xenotransplantation outcomes. Active viremia typically occurs in pigs between 20 and 90 days of age, after which the virus establishes latency. During latency, viral DNA is no longer shed in nasal secretions, though anti-PCMV antibodies remain detectable. Additionally, latent PCMV can reactivate in peripheral blood mononuclear cell (PBMC) cultures following allogenic stimulation or organ transplant into a immunosuppressed recipient. Current diagnostic options for PCMV are limited. Veterinary diagnostic laboratories (VDLs) offer PCR assays to detect DNA in viremic animals, but PCR cannot identify latent PCMV infection. While serological assays are needed to detect latent infections, these are not currently offered by VDLs. To address this gap, we developed a high-throughput PCMV serology western blot assay to detect anti-PCMV antibodies.
Methods: A portion of the PCMV glycoprotein B was synthesized with a His-tag in E. coli for western blot application using an automated capillary system (Bio-Techne). Serum and nasal secretion samples were collected between May and December 2024 from 78 pigs of varying ages housed in a biosecure facility (without barrier controls for pathogen transmission). All nasal secretion samples were tested for PCMV via PCR and serum samples for anti-PCMV antibodies via the serology western blot assay.
Results: The western blot assay detected anti-PCMV antibodies in serum samples from pigs at various stages: newborn (~14 days) with maternal antibodies, juvenile (~70 days) in the acute infection phase (PCR positive), and adult (~323 days) in the latent infection phase (PCR negative). Surveillance of 78 pigs in the biosecure facility revealed that 96% of serum samples tested positive for anti-PCMV antibodies, while 97% of PCR samples were negative, indicating successful detection of a latent infection stage.
Conclusion: The PCMV serology western blot assay effectively detects anti-PCMV antibodies at different infection stages in pigs.