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A commercial vaccine based on PCV2a and an experimental vaccine based on a variant mPCV2b are both effective in protecting pigs against challenge with a 2013 U.S. variant mPCV2b strain

Opriessnig, Tanja, Gerber, Priscilla F., Xiao, Chao-Ting, Mogler, Mark, Halbur, Patrick G.
Vaccine 2014 v.32 no.2 pp. 230-237
DNA, Porcine circovirus, Porcine reproductive and respiratory syndrome virus, antigens, models, swine, vaccination, vaccines, viremia, United States
During 2012 and 2013, an apparent increase in porcine circovirus associated disease occurred in the USA. A variant PCV2b strain designated mPCV2b was recovered from many of these cases. This raised concerns of a decrease in efficacy of commercially available PCV2 vaccines. The objective of this study was to compare the ability of a commercial PCV2a-based vaccine and an experimental mPCV2b-based vaccine to control mPCV2b-associated disease, lesions, and viremia in a challenge model. Twenty-six caesarian-derived, colostrum-deprived pigs were randomly assigned to one of four groups: (1) vaccinated with a commercial PCV2a-based vaccine and challenged (PCV2a-VAC; n=7), (2) vaccinated with an experimental mPCV2b-based vaccine and challenged (mPCV2b; n=7), (3) sham-vaccinated with saline and challenged (positive controls; n=7), and (4) sham-vaccinated with saline without challenge (negative controls; n=5). Vaccination was done on D0 and D14, challenge was done on D28 using a tissue homogenate containing PRRSV and mPCV2b and the experiment was terminated on D49. Among the challenged pigs, 47.6% (10/21) developed severe clinical disease and either died or had to be humanely euthanized between D39 and D48 (11–20 days after challenge). PCV2 viremia was almost completely absent in the vaccinated groups regardless of vaccine type except for two PCV2a-vaccinated pigs which had detectable PCV2 DNA levels on individual days after challenge. Microscopic lesions typical of PCV2 infection were limited to the positive control group which developed mild-to-severe lesions associated with low-to-abundant PCV2 antigen. Under the conditions of this study, PCV2 vaccines regardless of PCV2 type were effective against mPCV2b challenge.