Influence of porcine circovirus type 2 (PCV2) maternal antibodies on efficacy of PCV2 vaccination to protect pigs from experimental infection with PCV2

Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, Fort Dodge Animal Health, Inc., Fort Dodge, Iowa, and Department of Biomedical Sciences and Pathobiology, Center for Molecular Medicine and Infectious Diseases, College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

^* To whom correspondence should be addressed. Email: tanjaopr{at}iastate.edu.

	Abstract

Due to the ubiquitous nature of porcine circovirus type 2 (PCV2) in the pig population and the increasing use of PCV2 vaccines in the breeding herds, the majority of dams have been exposed to field PCV2 or PCV2 vaccines, resulting in piglets with varying levels of passively-acquired PCV2 maternal antibodies. The objective of the current research was to investigate the influence of passively-acquired anti-PCV2-antibodies on PCV2-vaccine efficacy. Sixty, 26-day-old pigs were divided into four groups: vaccinated pigs with no maternal PCV2 antibodies at the time of vaccination (VAC-NEG; n=9), vaccinated pigs with maternal PCV2 antibodies at the time of vaccination (VAC-POS; n=21), non-vaccinated pigs with no maternal antibodies at time of challenge (NVAC-CNEG; n=15) and non-vaccinated pigs with maternal antibodies at time of challenge (NVAC-CPOS; n=15). Vaccination and challenge were performed on trial day 0 and 28 respectively according to group designation. The pigs were monitored for clinical signs of disease daily, weighed weekly, and blood was collected weekly. All pigs were necropsied on trial day 49 and tissues were evaluated for macroscopic and microscopic lesions. Serum was evaluated using PCV2-IgG and PCV2-IgM ELISAs, quantitative PCV2 PCR, and a serum PCV2 neutralizing antibody test. In comparison to NVAC-CPOS pigs, VAC-POS animals had significantly (P < 0.01) less severe microscopic PCV2-associated lymphoid lesions and significantly (P < 0.04) reduced PCV2 genomic copies in serum following PCV2 challenge. These results indicate that vaccination with Suvaxyn® PCV2 One Dose^TM reduces viremia and prevents microscopic lesions associated with PCV2 in the presence of maternal antibodies.