Resposta imune humoral em ovinos de diferentes raças e Haplótipos da β-globina infectados com Haemonchus contortus

Abstract

Haemonchus contortus infection is one of the main challenges in sheep farming. Altered susceptibility to this infection can be attributed to factors such as breed, age, physiological and/or nutritional state and genetic alterations. Santa Ines sheep are highly resistant, while White Dorper and Texel sheep are more susceptible. Among the intra-breed variations, there was a significant effect of the polymorphism of ovine β-globin on resistance to the parasite. The presence he βA allele, related to the compensatory increase in hemoglobin affinity for oxygen in response to parasitic anemia, is also associated with a more robust immune response and higher levels of plasma anti-H. contortus IgM. As a gastrointestinal nematode, H. contortus interacts directly with the mucosa of the digestive tract, making the local immune response essential in fighting infection. However, few studies have evaluated this response. The aim of this study was to develop and apply a method for quantifying the local humoral response (nasal and oral secretions) in comparison to the systemic response. The target antigen was the 24 kDa excretory-secretory protein (ES24) of H. contortus. White Dorper, Texel and Santa Inês lambs of different β-globin haplotypes were experimentally infected. Nasal and oral swabs and plasma samples were collected weekly (D0 to D28) to quantify anti-ES24 antibodies of the IgG, IgM and IgA isotypes. Higher immunoglobulin titers were detected in nasal secretions compared to oral secretions. Santa Ines lambs showed higher levels of all isotypes in the nasal mucosa compared to other breeds, with no significant differences in plasma and oral mucosa. In Santa Ines lambs, the β-globin polymorphism influenced the immune response.Hb_AA animals showed higher systemic titers of anti-ES24 IgM and higher globular volume values, while nasal IgA showed trends towards lower levels compared to Hb-AB and Hb-BB. These findings corroborate previous studies associating the IgM isotype with greater resistance to hemonchosis. The quantification of antibodies in the mucosa appears to be a promising tool for assessing infection and host protection, contributing to immunoprophylactic management strategies for hemonchosis.