Helminth antigen-induced innate immune response in porcine peripheral blood mononuclear cells

Abstract

Helminths are among the gastrointestinal parasites that are responsible for substantial loss of productivity in swine and other livestock industry. Despite indoor intensive rearing with routine anthelmintics, helminth infections in pigs are still not well managed. Elucidating mechanisms of host innate responses to helminth infection and their genetic correlation is important to improve the pig breeding strategies through selecting animals with better immunocompetence. This dissertation aims to investigate the innate immune responses to two helminth antigens from each of Trichinella spiralis derived tyvelose (TY) and Ascaris suum derived haemoglobin (AsHb) using the in vitro peripheral blood mononuclear cells (PBMCs) model. To achieve the objectives, PBMCs from German Landrace (LR) and Pietrain (Pi) pigs were in vitro stimulated with tyvelose and AsHb with or without mitogenic co-stimulation, and cells were harvested 24, 48 and 72 h post stimulation. The cell viability and proliferation and phagocytosis were evaluated followed by relative expression analysis of cytokines mRNA (IFN-γ, IL-2, IL-6, IL-10 and TGF-β1) using qRT-PCR. Results showed that TY-specific proliferation of PBMCs was transient and temporally associated with the duration and concentration of treatments. The highest viability of TY treated PBMCs were found at 24 h time point compared to the 48 h and 72 h. The cytokine responses were dominated by up regulation of IL-10 and IL-6, but also IL-2 with rapid resolution or appearance from time to time. The resulting host immunity revealed the dominance of Th1/Th2 as evident from the elevated level of IL-10 and IL-6. The variation in the expression levels of IL-10, IL-2, TGF-β1, IL-6 and IFN-γ in PBMCs obtained from LR and Pi pigs was significant, but not consistent across the course of the experiment and the state of mitogen-activation. TY induced cytokine expression dynamics and kinetics were different in PBMCs of LR and of Pi pigs. AsHb induced phenotypic variation in cell viability between breeds was observed after 72 h of cultivation only in the co-stimulated group. Significantly higher phagocytosis was observed in phagocytes of LR origin compared to that of Pi. In naïve PBMCs treated with AsHb, a significant breed effect was noticeable in case of IL-10, IL-6 and TGF-β1 expression, although the interrelationship between these regulatory cytokines was not always synchronous. In AsHb sensitized and costimulated PBMCs, the cytokine expression was rather skewed and only at 24 h of culture, a significant effect of both, breed and AsHb, was noted. In conclusion, the systemic immune response to TY and AsHb was characterized by a dominance of mixed Th1/Th2/regulatory immune response; LR pigs showed relatively early and stronger response compared to the PBMCs of Pi pigs. This indicated a breed variation in the innate immune-responsiveness to T. spiralis and A. suum between LR and Pi pigs.