NAPRRS: PCV3 immune response

Porcine circovirus type 3 (PCV3) was first identified in the United States in 2016 and has been associated with reproductive failure and multisystemic inflammation. PCV3 is a circular, single stranded DNA virus of approximately 2000 bp with two major identified structural proteins, the capsid (Cap) and replicase (Rep).

Information regarding PCV3’s humoral response is scarce. The Cap and Rep humoral response was evaluated following experimental PCV3 infection and transfer of maternal antibodies in piglets from naturally infected sows by IFA and ELISA. The results of the study by M. Kroeger and colleagues at Iowa State University and South Dakota State University were presented at the 2024 North American PRRS Symposium.

Eighteen, 5-week-old CD/CD pigs were randomly assigned to 4 treatment groups: PCV3, PCV3+KLH (keyhole limpet haemocyanin), negative control, and KLH control. PCV3 and PCV3+KLH groups were intramuscularly and intranasally inoculated with 2 mL of PCV3 tissue homogenate on days 0 and 7. PCV3+KLH and KLH control groups were administered 1 mL of KLH in the hip and shoulder on days 3 and 7. Serum was collected weekly until day 42 post inoculation (dpi). Piglet serum from three PCV3 seropositive sows was collected weekly until 9 weeks post farrowing.

Experimentally infected pigs developed Cap IgG antibodies at 14 dpi, reaching significantly higher levels between 28-42 dpi. Rep IgG antibodies were detectable at 28 dpi with significantly higher levels between 35-42 dpi. Antibody titers detected by IFA against the Cap were 16-fold higher than the Rep.