Abstract
Maternal-derived immunity is a critical component for the survival and success of offspring in pigs to protect from circulating pathogens such as Type 2 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV-2). The purpose of this study is to investigate the transfer of anti-PRRSV immunity to piglets from gilts that received modified-live virus (MLV) alone (treatment (TRT) 0), or in combination with one of two autogenous inactivated vaccines (AIVs, TRT 1+2). Piglets from these gilts were challenged with the autogenous PRRSV-2 strain at two weeks of age and their adaptive immune response (IR) was evaluated until 4 weeks post inoculation (wpi). The systemic humoral and cellular IR was analyzed in the pre-farrow gilts, and in piglets, pre-inoculation, and at 2 and 4 wpi. Both AIVs partially protected the piglets with reduced lung pathology and increased weight gain; TRT 1 also lowered piglet viremia, best explained by the AIV-induced production of neutralizing antibodies in gilts and their transfer to the piglets. In piglets, pre-inoculation, the main systemic IFN-γ producers were CD21α+ B cells. From 0 to 4 wpi, the role of these B cells declined and CD4 T cells became the primary systemic IFN-γ producers. In the lungs, CD8 T cells were the primary and CD4 T cells were the secondary IFN-γ producers, including a novel subset of porcine CD8α−CCR7− CD4 T cells, potentially terminally differentiated CD4 TEMRA cells. In summary, this study demonstrates that maternal AIV vaccination can improve protection of pre-weaning piglets against PRRSV-2; it shows the importance of transferring neutralizing antibodies to piglets, and it introduces two novel immune cell subsets in pigs—IFN-γ producing CD21α+ B cells and CD8α−CCR7− CD4 T cells.
Highlights
Maternal-derived immunity (MDI) in mammals is an awe-inspiring symphony (“harmonious complexity”—[1])
While lung pathology is generally resolved in PRRSV infection and was similar between groups at 4 wpi (d.n.s.), both maternal autogenous inactivated vaccines (AIVs) vaccinations, so TRT 1+2, significantly reduced the lung pathology at 2 wpi: both decreased the percentage levels of macroscopic lesions and/or interstitial pneumonia (Figure 2C,D)
While lung pathology is generally resolved in PRRSV infection and was similar between groups at 4 wpi (d.n.s.), both maternal AIV vaccinations, so TRT 1+2, significantly reduced the lung pathology at 2 wpi: both decreased the percentage levels of tion can significantly reduce viremia and lung pathology, they show that maternal AIV vaccination against PRRSV-2 can boost the immunity of 2-week old piglets
Summary
Maternal-derived immunity (MDI) in mammals is an awe-inspiring symphony (“harmonious complexity”—[1]). While immunoglobulins can be received from different sows (= cross-fostering), only biological mothers can successfully transfer immune cells to their offspring [5], and the quantity of colostrum intake in piglets significantly decreases mortality and improves performance [6]. These immune cells include B cells [7], as well as different T-cell subsets—CD4, CD8 and mainly T-cell receptor (TCR)-γδ T cells [8]. Immune cell subsets and antibodies are transferred to the offspring to protect them against various pathogens [4,5]
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