In vivo depletion of T-cells and cytokines during primary exposure of sheep to parasites

Gene characterization and expression of the γδ T cell co-receptor WC1 in sheep

Sheep are known to express the hybrid co-receptor/pattern recognition receptor WC1 on their γδ T cells but details of the ovine WC1 multigenic array and gene expression were unknown. Annotation of the sheep genome assembly (Oar_rambouillet_v1.0) yielded 15 complete and 42 partial WC1 genes predicted to code for six different protein structures. RT-PCR amplification of the most distal scavenger receptor cysteine rich (SRCR) domain known as a1, which serves as the gene signature, from genomic and cDNA templates verified the majority of annotated genes. As for cattle and goats, sheep a1 domain sequences included WC1.1 and WC1.2 types. A unique ovine gene, WC1-16, had multiple SRCR a-pattern domains in tandem similar to one found in goats. Intracytoplasmic domains of WC1 transcripts had splice variants that may affect signal transduction. The larger number of WC1 genes in sheep and differences in structures and splice variants relative to cattle could have implications in expression patterns and engagement of γδ T cells by pathogens or vaccine constructs.

Goat γδ T cells

Goats are important food animals and are disseminated globally because of their high adaptability to varying environmental conditions and feeding regimes that provide them with a comparative advantage. Productivity is impacted by infectious diseases; this then contributes to societal poverty, food insecurity, and international trade restrictions. Since γδ T cells have been shown to have vital roles in immune responses in other mammals we reviewed the literature regarding what is known about their functions, distribution in tissues and organs and their responses to a variety of infections in goats. It has been shown that caprine γδ T cells produce interferon-γ and IL-17, are found in a variety of lymphoid and nonlymphoid tissues and constitute a significant population of blood mononuclear cells. Their representation in tissues and their functional responses may be altered concomitant with infection. This review summarizes caprine γδ T cell responses to Brucella melitensis, Fasciola hepatica, Mycobacterium avium paratuberculosis, caprine arthritis encephalitis virus (CAEV), and Schistosoma bovis in infected or vaccinated goats. Caprine γδ T cells have also been evaluated in goats infected with M. caprae, Ehrilichia ruminantium, Haemonchus contortus and peste des petits ruminants (PPR) virus but found to have an unknown or limited response or role in either protective immunity or immunopathogenesis in those cases.

Immunomodulatory effects of adult Haemonchus contortus excretory/secretory products on human monocyte-derived dendritic cells

The levels of expression of surface molecules and release of cytokines and chemokines of human monocyte-derived dendritic cells were determined after their exposure to adult H. contortus excretory/secretory (ES) products or a combination of ES products and bacterial lipopolysaccharide (LPS). Worm products provoked a weak response and only partial maturation of the dendritic cells, consistent with the hyporesponsiveness and more tolerogenic immune environment present in parasitized animals and humans. Co-stimulation with LPS demonstrated that H. contortus secretions, like those of other helminths, contain immunomodulators capable of reducing some aspects of the strong T(H)1/T(H)2 response evoked by bacterial LPS. There were significant reductions in the release of some cytokine/chemokines by LPS-stimulated mdDCs and a trend (although not significant at P < 0.05) for reduced expression levels of CD40, CD80 and HLA-DR. A prominent feature was the variability in responses of dendritic cells from the four donors, even on different days in repeat experiments, suggesting that generalized conclusions may be difficult to make, except in genetically related animals. Such observations may therefore be applicable only to restricted populations. In addition, previous exposure to parasites in a target population for immunomodulatory therapy may be an important factor in assessing the likelihood of adverse reactions or failures in the treatment to worm therapy.

Experimental infection by Haemonchus contortus in lambs: influence of disease on purine levels in serum

The aim of this study was to evaluate the purine levels of lambs experimentally infected with Haemonchus contortus. A total of 12 healthy lambs were divided into two groups, composed of 6 animals each: Group A represented the healthy animals (uninfected), while in Group B the animals were infected with 15 000 larvae of H. contortus. Blood was drawn on days 15, 45 and 75 post-infection (PI) in order to perform the purine analysis (ATP, ADP, AMP, adenosine, inosine, hypoxanthine, xanthine and uric acid) by high pressure liquid chromatography (HPLC) in serum. On day 15 PI a significant (P<0·05) increase in the levels of ATP and inosine was observed in the infected animals, unlike the levels of ADP, adenosine, xanthine and uric acid which were reduced. On day 45 PI a significant (P<0·05) increase in the ATP and xanthine levels in infected animals was observed, contrasting with reduced levels of ADP and uric acid. Finally, on day 75 PI an increase occurred in the levels of ATP, adenosine and hypoxanthine in infected lambs, concomitant with a reduction in the levels of ADP and uric acid (P<0·05). These changes in purine levels may influence the inflammatory process and the pathological events.

Gastrointestinal nematode infection in sheep--a review of the alternatives to anthelmintics in parasite control

Efforts to curb production losses caused by nematode parasitism in sheep have led to the development of a number of control methods to complement or replace anthelmintics. The need for alternative control measures stems from the emergence of anthelmintic-resistant parasitic nematodes with reports of multi-class resistance to these drugs now emerging. A number of these control methods such as predacious microfungi, protein supplementation, plant extracts in feed and vaccines have demonstrated potential to control infection but require development and examination under natural conditions. Breeding for natural resistance to nematode infection has already shown success in controlling the disease under natural conditions. Selection for resistance is currently based on fecal egg count measurements but identification of genetic indicators of resistance will provide a more efficient method of selection. Current quantitative trait loci for nematode resistance include the MHC genes, interferon gamma gene, IgE gene and microsatellites on chromosome 1, 5 and 6. This paper reviews the current alternatives to anthelmintics to control infection, with an emphasis on breeding for host resistance and identification of genetic indicators of resistance.