GILTS AND SOWS PCV2 RE-VACCINATION AT MATING INCREASES THE HOMOGENEITY AND THE TITRES OF ANTIBODIES AT FARROWING AND THE PASSIVE TRANSFER TO THE PIGLTES, BUT DOES NOT AFFECT THE FREQUENCY OF IFN-GAMMA SECRETING CELLS

The study aims at evaluating the effect of repeated PCV2 vaccinations (one dose of a commercial PCV2a-based subunit vaccine containing the Cap protein expressed in a baculovirus system) in gilts/sows on the variability of the antibody titres and the frequency of IFN- secreting cells (SC). At the start/enrolment, 46 gilts were considered at first mating, bled and vaccinated. At first, second and third farrowing the dams were bled and re-vaccinated at the subsequent mating after weaning piglets. At 4 weeks of age the matching piglets were also bled in order to evaluate the level of passively acquired antibodies. Serology was performed by using a commercial ELISA antibody test and the frequencies of IFN- SC were also enumerated. The evaluation of the variability of the antibody titres and the IFN- SC was assessed by measuring the coefficient of variation (CV). The standard formulation of the CV, the ratio of the standard deviation to the mean. The higher the CV, the greater the dispersion is in the variable. The results obtained in the dams showed that at the sampling before the first vaccination (mating of the gilts) the CV of the antibody titers was high (47.5) and their level very low (0.6±0.27). At first farrowing, the level of antibodies was significantly increased (1.5±0.33) and the CV was substantially reduced (21%). At the second and third farrowing either the level of antibodies and the CV was not significantly modified as compared to the previous sampling time. The frequency of IFN- SC significantly increased (p<0.01) and was more homogeneous compared to the first and the second sampling, but in the subsequent time points, a high inter-individual variability was observed. It is worth mentioning that no PCR positive samples to PCV2 were detected in sows at any sampling sustaining that the field virus infection had little or no effect on the observed variations. In piglets, the antibody titers were slightly increased from the first to the third farrowing. Conversely, the CV did not significantly vary in association to the increased parity of the re-vaccinated dams. In conclusion, the re-vaccination of sows at each mating increases the antibody titers and their homogeneity at the subsequent farrowing and slightly increases the level of antibody transferred via the colostrum to the newborn piglets.