One dose of a porcine circovirus 2 subunit vaccine induces humoral and cell-mediated immunity and protects against porcine circovirus-associated disease under field conditions

Abstract

This study investigated the efficacy of a one-dose porcine circovirus 2 (PCV2) subunit vaccine based on the PCV2 Cap protein expressed in a baculovirus system on two different farms at which a history of porcine circovirus-associated disease (PCVD) was present. Morbidity, mortality, average daily weight gain, carcass weight, PCV2 load in serum and vaccine immunogenicity were assessed. Serology to porcine reproductive and respiratory syndrome virus (PRRSV) and Mycoplasma hyopneumoniae was performed. A double-blind, randomised, and controlled field trial was performed distributing 818 piglets between two treatment groups. At inclusion (weaning at 21±3 days of age), 408 animals (group B) received a 2-mL intramuscular dose of Porcilis PCV® (vaccinated group). Controls (group A, 410 pigs) received 2mL of the adjuvant Diluvac Forte® intramuscularly. Weights were recorded at inclusion and at 12 and 26 weeks of age, and the average daily weight gain (ADWG) was calculated. The carcass weights of the pigs from farm 2 were recorded at slaughter (274 days old). All dead animals (died or culled) underwent autopsy to classify them as PMWS-affected or not. At each farm, blood samples were taken from 22 pigs/group for serologic studies. A beneficial effect was found after vaccination with a single dose of a PCV2 Cap vaccine against PCVD. The vaccination reduced the mortality rate and morbidity, reduced PCV2 viremia and viral load, improved productive performances (e.g. ADWG: +70g/day between 12 and 26 weeks of age when viremia and the specific disease occurred) as well as carcass weight at slaughter age (+4.5kg). These effects were associated with virologic and clinical protection from the immunogenicity of the vaccine measured as activation of both a humoral and a cellular immune response.