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.