Harnessing Toxoplasma gondii microneme proteins for serodiagnosis and vaccine development: a review

Toxoplasma gondii (T. gondii), an obligate intracellular apicomplexan parasite, infects virtually all warm-blooded animals through a sophisticated sequential invasion mechanism involving coordinated secretion from specialized apical organelles. Among these secretory proteins, microneme proteins (MICs) serve as central molecular effectors orchestrating host-parasite interactions. This review comprehensively examines the structural organization, regulatory mechanisms, and diverse functions of MICs in T. gondii pathogenesis, and evaluates their translational potential for diagnostics and vaccine development.

Key MIC adhesin complexes - including the lectin-based MIC1/4/6 complex and the transmembrane MIC2-M2AP complex - mediate glycan recognition, host cell attachment, moving junction formation, and gliding motility. Beyond invasion, MICs function as immunomodulators engaging Toll-like receptors (TLR2, TLR4, TLR11) to elicit pro-inflammatory responses while activating EGFR-Akt signaling to inhibit autophagy. The translational potential is substantial: MIC-based antigens enable sensitive serodiagnosis, differentiating acute from chronic infections. In contrast, MIC-based vaccines across multiple platforms demonstrate considerable protective efficacy in preclinical experimental models. Notably, the MIC1-3 knockout strain confers protection in sheep that is comparable to that of commercial vaccines; however, it is important to note that most supporting evidence remains at the preclinical stage and clinical validation in human populations is still required.

MICs represent promising targets that bridge fundamental parasitology and clinical applications. Integration of MIC biology with translational strategies provides foundations for developing next-generation diagnostics and vaccines against toxoplasmosis.