Immunization with thiol-binding proteins from Haemonchus contortus adult worms partially protects goats against infection during prepatency

Abstract

To contribute of the knowledge of the immune mechanisms underlying the response to the immunization of goats with thiol-binding proteins fractions (PBS-TSBP) from Haemonchus contortus (H. contortus) adult worms, this study analyzed the degree of protection and the immune responses developed against the parasite after vaccination with this antigenic complex during the time-elapsing between challenge with L3 of the parasite and the development of adult worms, evidenced by the appearance of first faecal eggs (prepatent period or prepatency). Goat kids immunized with PBS-TBSP generated an immune response during the prepatency which translates into a reduction in the number of worms, as well as a lower reduction on packed cell volume and plasma protein levels in relation to the non-vaccinated animals. As previously described in other studies carried out after the prepatent period, this protection was associated with a systemic humoral response. At the local level, a specific humoral response was also observed, together with an immune-inflammatory infiltrate in the gastric mucosa of MCH-II+cells and CD4+ lymphocytes, whose number was associated with a reduction in the number of worms and an increase in plasma proteins. A high peripheral eosinophilia was detected, but no corresponding increased infiltration of the gastric mucosa by eosinophils or globular leukocytes was observed. In agreement with previous data on the immunolocalization of the antigens used here, the results obtained contribute to the idea that these may be excretion/secretion (E/S) products necessary for parasite survival, whose inactivation during the larval and/or pre-adult stages may have contributed to immunoprotection.