Early and accurate diagnosis of congenital toxoplasmosis

OBJECTIVE: Early diagnosis of congenital toxoplasma infection is difficult to establish using serological methods. We explored specific T cell immunity to Toxoplasma gondii antigens to identify more accurate diagnostic tests for an early diagnosis of toxoplasma infection in newborns at risk for congenital toxoplasmosis. STUDY DESIGN: T lymphocyte proliferation, interferon (IFN)-gamma production and lymphocyte activation antigens expression were evaluated in 23 infected and 65 uninfected neonates at different times, in the first year of life. RESULTS: The immunologic tests accurately discriminated when tested <or=90 and >90 days of age, respectively and were significantly lower in uninfected than in infected infants: activation antigen CD25, P < 0.001 and P < 0.00001; activation antigen histocompatibility leukocyte antigen (HLA)-DR, P < 0.01 and P < 0.00001; T cell proliferation, P < 0.0001 and P < 0.00001; IFN-gamma production, P < 0.001 and P < 0.00001. Evaluation of the specific T cell response allowed identification at 3 months of age or younger, 2 of 23 infected neonates, who had negative serologic tests. Moreover specific T lymphocyte activity increased with age even in neonates undergoing therapy, suggesting that medical treatment does not affect lymphocyte response. CONCLUSIONS: Evaluation of T cell immunity is important for an early and accurate diagnosis of congenital toxoplasmosis.