High levels of maternally derived antibodies do not significantly interfere with the development of humoral and cell-mediated responses to Porcine circovirus 2 after intradermal vaccination

Abstract

Background: Vaccination of pigs against PCV2 is usually performed around weaning when animals still have maternally derived antibodies (MDA). The present study aimed to assess the possible interference of MDA in the development of the PCV2-specific immune response after vaccination of commercial weaners. For this purpose, a PRRS-negative 600-sow farrow-to-finish farm was selected. Half of the sows were vaccinated and revaccinated with Porcilis® PCV ID against PCV2 7 and 3 weeks before farrowing. After farrowing, piglets were tested by AlphaLisa to select 72 animals with high and low levels of MDA. Groups were further subdivided and vaccinated intradermally with Porcilis® PCV ID at 21 or 28 days of age. Unvaccinated controls were also included. Animals were followed afterward for 42 days to examine the development of PCV2-specific antibodies and interferon-γ secreting cells (IFN-γ SC).

Results: The average titres of antibodies of the groups vaccinated in the presence of low or high MDA levels were similar at 28 and 42 days post-vaccination while in the controls the titres declined throughout the observation period. Results of vaccinating at 21 or 28 days of age were equivalent with regard to antibody development. Regarding the IFN-γ SC, vaccinated animals produced significant frequencies of IFN-γ SC by day 28. Again, no differences were observed between the groups with high or low antibody levels.

Conclusion: High levels of MDA did not interfere with the development of humoral and cell-mediated responses to Porcine circovirus 2 after intradermal vaccination at 21 or 28 days of age.

Keywords: Immune response; Interference; Maternally derived antibodies; Porcine circovirus 2.

Fig. 1

Distribution of anti-PCV2 antibody titres at 7 days of age using the PCV2 AlphaLISA. The graph shows the individual values for each serum and the median of the 161 piglets examined (horizontal bar). Animals in the high antibody level subgroup (offspring of vaccinated sows) were located above the median and animals in the low antibody subgroup (offspring of non-vaccinated sows) were located below the median

Fig. 2

Average and standard deviation of the anti-PCV2 antibody titres as determined by AlphaLisa at different time points after vaccination. High 21, Low 21 = animals with high or low levels of antibodies vaccinated at 21 days of age; High 28, Low 28 = animals with low levels of anti-PCV2 antibodies vaccinated at 28 days of age, C-high = Controls selected with high levels of antibodies; C-Low: controls selected with low levels of antibodies. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001; ns = non-significant differences

Fig. 3

Levels of PCV2-specific IFN-γ secreting cells as determined by ELISPOT. Frequencies of PCV2-specific IFN-γ secreting cells at different timepoints after vaccination (mean and standard deviation). *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001; ns = non-significant differences

Fig. 4

Individual responses of PCV2-specific IFN-γ secreting cells as determined by ELISPOT. The graphs show the frequencies of PCV2-specific IFN-γ producing cells only for the vaccinated groups