The Development of TIM-Barrel Based Multi-Epitope Protein for Toxoplasma gondii Serological Detection in Cats.

Toxoplasma gondii, a pathogen of significant concern in animal production, companion animal health, and public health, particularly affects immunocompromised individuals and pregnant women. Current diagnostic techniques employ both direct and indirect methods, with serological assays widely used for detecting T. gondii infections in humans and animals. In this study, the TIM-barrel structure of Br2 β-glucosidase was engineered to create 10 chimeric multi-epitope proteins for T. gondii serological detection. Indirect ELISA screening identified three promising candidate proteins, V4Z, SFF, and S7V-V4Z-SFF, with sensitivities ranging from 71-86% and specificities ranging from 68-76%. Among these, ELISA-V4Z achieved the highest concordance with the reference IFAT method (Kappa = 0.58, 95% CI = 0.32-0.84) and demonstrated a moderate positive predictive value (PPV, 67%) and strong negative predictive value (NPV, 90%). These results suggest that the V4Z chimeric protein demonstrated the strongest performance among the tested candidates for T. gondii detection, exhibiting the highest sensitivity and specificity along with moderate agreement with the reference IFAT. However, its overall diagnostic performance remains limited. These findings highlight the need for further refinement and validation to enhance its diagnostic potential and assess its applicability for broader serological testing.