Different kinetics of humoral response against individual antigens in the ovine model of Toxoplasma gondii infection and its pathological association

Abstract

Background: Toxoplasma gondii is a globally distributed protozoan parasite withmajor implications for human and animal health. In sheep, infection can causereproductive failure and represents an important source of zoonotic transmissionthrough contaminated meat. While cell-mediated immunity is the mainprotective mechanism, the contribution of humoral responses, particularlyagainst individual recombinant antigens (rAGs), remains poorly characterized inovine toxoplasmosis.Methods: We analyzed the humoral response of lambs experimentally infectedwith two reference strains of T. gondii (RH and Me49) using different inoculationdoses. Recombinant antigens rGra4Gra7, rGra8, rRop2, rCST9, and rBCLA weretested by IgG-ELISA to evaluate their kinetics during infection. Histopathologicalanalyses of brain tissues were performed to assess lesion severity and cystpresence. Additionally, sera from naturally infected sheep were evaluated totest diagnostic performance.Results: An early IgG response against rGra4Gra7 and rGra8 was detected,consistent with markers of acute infections. Anti-rBCLA, rRop2, and rCST9 IgGresponses were associated with the chronic phase and correlated with cystburden. Notably, stronger anti-rGra4Gra7 IgG responses tended to associatewith lower lesion scores, suggesting a potential protective role. In naturallyinfected sheep, IgG-ELISA against rGra4Gra7 and rGra8 demonstrated thehighest diagnostic performance, outperforming total lysate antigen (TLA)-based assays.Conclusion: Our findings highlight distinct kinetics of specific antibodyresponses against selected T. gondii antigens in sheep, suggesting their valueas markers of infection stage and pathology. rGra4Gra7 and rGra8 appearparticularly promising both as diagnostic candidates and for exploringmechanisms of humoral modulation in ovine toxoplasmosis.