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Helminth parasites are highly prevalent in swine production, causing chronic infections and considerable morbidity due to growth retardation. Moreover, helminths actively modulate host immune responses to other pathogens and/or vaccines. Here, we investigated the modulatory effects of Ascaris suum adult body fluid (ABF) and Trichuris suis Soluble Products (TsSP) on the cytokine response in porcine peripheral blood mononuclear cells (PBMCs) and the intestinal epithelial cell line IPEC-J2. In PBMCs, TsSP induced the secretion of IL-6, IL-10 and IL-1β, but not TNF-α. Moreover, TsSP significantly enhanced the production of bacterial lipopolysaccharide (LPS)-induced IL-6 and IL-10 but suppressed the production of LPS-induced TNF-α. ABF did not induce cytokine secretion from PBMC, but suppressed LPS-induced secretion of TNF-α and IL-6. ABF did not have any effect on cytokine production in IPEC-J2 cells. In contrast, TsSP selectively induced the secretion of IL-6, and enhanced the IL-6 response induced by LPS. The IL-6 response appeared to be a conserved response to T. suis products, as significant secretion was also observed in alveolar macrophages. Thus, T. suis products have diverse modulatory effects on cytokine secretion in vitro, with IL-6 production a consistent feature of the innate host response., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Naïve CD4+ T cells may differentiate into a number of subsets including T helper 1 (Th1) Th2, Th3, Th17 and T regulatory (Treg) cells depending on the type of antigen they encounter. These CD4+ families have been defined based on the array of cytokines they produce and the effects they have on adaptive immune responses. CD4+ subsets are cross regulatory and at times cooperative. The study of these adaptive immune modulators has revealed the important role that cytokines play in mounting effective as well as detrimental immune responses to pathogens. Examining the cytokine responses of lymphocytes in culture can provide important understanding of how immune responses to pathogens are orchestrated. For this purpose the in vitro cytokine production of peripheral blood mononuclear cells (PBMC) from healthy dogs was examined in response to stimulation with antigens from a common canine virus (canine distemper virus, CDV), a commensal skin yeast of dogs (Malassezia pachydermatis) and a common canine helminth (Toxocara canis (T. canis)). Cell culture supernatants were removed from antigen stimulated and unstimulated control PBMC after 4, 24, 48 and 72 h and the concentration of Th1 type cytokines (IL-2, IFN-gamma, TNF-alpha) and Th2 type cytokines (IL-4, IL-5, IL-10) was determined using sandwich ELISA assays. CDV induced low levels of cytokine production initially with a predominance of IL-10 at 24h and a balanced response at 48 h of incubation. Malassezia antigen stimulated an early type 2 cytokine response with dramatic production of IL-4 at 24h of incubation compared to the other stimulants examined. By 48 h of incubation, however, the cytokine mix in response to Malassezia had also moved toward a Th1 type response. T. canis induced early production of Th2 type cytokines with IL-5 predominating; however, with longer incubation (48-72 h) there was a switch to a balanced Th1/Th2 response. In conclusion, the cytokines produced in vitro by canine PBMC in response to prototypical Th1 and Th2 type pathogens were not clearly polarized and shifted over time. While the in vitro study of PBMC cytokine responses cannot be directly extrapolated to in vivo responses to the same antigens, the results do highlight the dynamic and fluctuating nature of cytokine production., (Copyright 2009 Elsevier B.V. All rights reserved.)

While the response to Leishmania spp. is well characterized in mice and humans, much less is known concerning the canine immune response, particularly soon after exposure to the parasite. Early events are considered to be a determinant of infection outcome. To investigate the dog's early immune response to L. chagasi, an in vitro priming system (PIV) using dog naïve PBMC was established. Until now, dog PIV immune response to L. chagasi has not been assessed. We co-cultivated PBMC primarily stimulated with L. chagasi in vitro with autologous infected macrophages and found that IFN-gamma mRNA is up-regulated in these cells compared to control unstimulated cells. IL-4 and IL-10 mRNA expression by L. chagasi-stimulated PBMC was similar to control unstimulated PBMC when incubated with infected macrophages. Surprisingly, correlation studies showed that a lower IFN-gamma/IL-4 expression ratio correlated with a lower percentage of infection. We propose that the direct correlation between IFN-gamma/IL-4 ratio and parasite load is dependent on the higher correlation of both IFN-gamma and IL-4 expression with lower parasite infection. This PIV system was shown to be useful in evaluating the dog immune response to L. chagasi, and results indicate that a balance between IFN-gamma and IL-4 is associated with control of parasite infection in vitro.

Canine visceral leishmaniasis (CVL) is caused by Leishmania infantum, an intracellular protozoan parasite that causes a severe infectious disease. To evaluate the gene expression profile associated to CVL in vivo, we have measured monthly by real-time PCR over one year the IL-4, IL-10, IL-12, IL-13, IFN-gamma, TGF-beta and TNF-alpha mRNA levels in peripheral blood mononuclear cells in 6 experimentally infected dogs that exhibited different progressions of the illness. While in two dogs no parasite, or a very low number of parasites, was detected and the two dogs did not show any clinico-pathological abnormalities at the end of the study (L dogs), for the remaining dogs high parasite loads were detected and they developed clinical leishmaniasis (H dogs). The L dogs have null expression of both IL-4 and IL-13 for the first 4 months after the infection, whereas an early IL-4 and IL-13 expression occurs in this period of infection in most of the dogs that developed clinical leishmaniasis (H dogs). Furthermore, a higher IFN-gamma expression was associated with the increase of parasite load and clinical status in these dogs. Moreover, the high variability of expression at the pre-infection stage causes us to reject the possibility that the basal levels of these cytokines indicate the prognosis of the subsequent response against infection.

Interleukin 4 (IL-4) is expected to play a dominant role in the development of T helper (Th) 2 cells. Th2 immune responses with expression of relatively large amounts of interleukin 4 (IL-4) but little interferon gamma (IFN-gamma) are characteristic for chronic helminth infections. But no information is available about IL4 expression during early Fasciola hepatica (F. hepatica) infections in cattle. Therefore, we investigated F. hepatica specific IL-4 and IFN-gamma mRNA expression in peripheral blood mononuclear cells (PBMCs) from calves experimentally infected with F. hepatica. Cells were collected prior to infection and on post-inoculation days (PIDs) 10, 28 and 70. Interestingly, PBMCs responded to stimulation with F. hepatica secretory-excretory products (FhSEP) already on PID 10 and expressed high amounts of IL-4 but not of IFN-gamma mRNA suggesting that F. hepatica induced a Th2 biased early immune response which was not restricted to the site of infection. Later in infection IL-4 mRNA expression decreased whereas IFN-gamma mRNA expression increased slightly. Isolated lymph node cells (LNCs) stimulated with FhSEP and, even more importantly, non-stimulated LN tissue samples indicated highly polarized Th2 type immune responses in the draining (hepatic) lymph node, but not in the retropharyngeal lymph node. During preliminary experiments, two splice variants of bovine IL-4 mRNA, boIL-4delta2 and boIL-4delta3, were detected. Since a human IL-4delta2 was assumed to act as competitive inhibitor of IL-4, it was important to know whether expression of these splice variants of bovine IL-4 have a regulatory function during an immune response to infection with F. hepatica. Indeed, IL-4 splice variants could be detected in a number of samples, but quantitative analysis did not yield any clue to their function. Therefore, the significance of bovine IL-4 splice variants remains to be determined.

Theileria annulata infection is controlled by MHC class I restricted cytotoxic T cell killing of infected cells. The long term persistence of parasite suggests that it employs a mechanism to avoid immune surveillance. In this paper we describe the modification of BoLA class I antigens on the surface of Theileria annulata transformed lymphoblastoid cells. The extent of modification is different between individuals varying from extensive to undetectable.

Complement fixing antibodies were measured in sera from animals immunised with either Theileria annulata sporozoites or autologous or allogeneic schizont-infected mononuclear cells using a complement-mediated micro-cytotoxicity test. The test demonstrated the presence of anti-lymphocyte antibodies in allogeneic cell-immunised animals, which were not detectable in autologous cell- or sporozoite-immunised animals; also that these antibodies were directed to T. annulata-infected and (MHC) class I antigens. Their potential importance in repeated immunisations is discussed.

Infection and transformation of cells of the bovine immune system by Theileria annulata and T. parva were compared. Preliminary experiments with mammary gland macrophages indicated that they were permissive to infection by T. annulata but only to a limited extent by T. parva. Further experiments involved several purified subpopulations of bovine cells including bovine monocytes, T cells and MHC class II positive and negative populations. These subpopulations were incubated with T. annulata or T. parva sporozoites in limiting dilution cultures. T. annulata preferentially infected macrophage type cells and also MHC class II positive cells, whereas the frequency of MHC class II negative cells infected by this parasite was negligible. T cells also showed a very low level of infection. In complete contrast, T. parva preferentially infected T cells and did not infect cells phenotypically defined as monocytes at all. These results suggested that class II expression was necessary for T. annulata infection and not necessary for, though not a barrier to T. parva infection. T. annulata infected cell lines all expressed class II molecules to varying degrees. Other available phenotypic markers were only expressed at very low levels or no longer expressed. The immunological significance of the different cell preferences and phenotypes of infected cell lines of T. annulata and T. parva is discussed.