Local and systemic immune mediators of Morada Nova lambs with divergent Haemonchus contortus resistance phenotypes

Abstract

Haemonchus contortus, the most pathogenic sheep parasite, is the major limiting factor for sheep farming in tropical countries, including in Brazilian territory. 1-4 As chemical control is the main tool for combating this parasite, the widespread multiple resistance of H. contortus to anthelmintics highlights the urgent need for alternative control measures, such as the selective breeding for parasite resistance or development of immune-related therapeutics. 5-8 Therefore, better understanding of the immuno-genetic mechanisms underlying this resistance is required. Immunity against helminths depends on cellular adaptive responses, through participation of T-helper lymphocytes (Th, CD4+), which are functionally grouped into two subpopulations: Th1,

Enhanced mucosal response in sheep harbouringβAbeta‐globin against haemonchosis

“…Th2 response induces IgE synthesis and increased numbers of mucosal eosinophils and mast cells, which release proteins responsible for helminth clearance, especially against larval forms, through specific IgE recognition by high‐affinity receptors ( FcεRI ) in an antibody‐mediated cytotoxicity 52,53 . In this context, higher expression of the FcεRI ‐encoding gene ( MS4A2 ) was associated with resistance against nematode infections in sheep 16,19,43 . Our findings corroborate with these previous studies associating parasite resistance and increased eosinophilia accompanied by IgE and Th2 responses, 16 since higher levels of IgE receptor ( MS4A2 ) and IL4 transcripts were also found in Hb‐AA compared to Hb‐BB group.…”

“…52,53 In this context, higher expression of the FcεRI-encoding gene (MS4A2) was associated with resistance against nematode infections in sheep. 16,19,43 Our findings corroborate with these previous studies associating parasite resistance and increased eosinophilia accompanied by IgE and Th2 responses, 16 since higher levels of IgE receptor (MS4A2) and IL4 transcripts were also found in Hb-AA compared to Hb-BB group.…”

“…The multiple correspondence analysis has associated Hb‐BB with lower grades of eosinophils, lymphocytes and total microscopic lesions, compared to those observed for Hb‐AA haplotype. In a previous study, Morada Nova lambs experimentally infected with H. contortus , phenotypically classified as resistant also presented significantly higher counts of eosinophils in the fundic region of the abomasum 43 . Eosinophils and mast cells are the main cellular populations involved in the defence against nematodes 16 .…”

“…as resistant also presented significantly higher counts of eosinophils in the fundic region of the abomasum. 43 Eosinophils and mast cells are the main cellular populations involved in the defence against nematodes. 16 Therefore, increased response mediated by eosinophils in the abomasum of sheep harbouring the Hb-AA β-globin haplotype, may be important for the effective control of parasitic infection.…”