Immunochemical Identification and Detection of a 36‐KDa Toxoplasma gondii Circulating Antigen in Sera of Infected Women for Laboratory Diagnosis of Toxoplasmosis

Abstract

The detection of Toxoplasma gondii circulating antigens has been indicated to be a reliable diagnostic approach of active human toxoplasmosis. However, few reports have appeared in the literature regarding the diagnostic potential of T. gondii circulating antigens. Here, a specific antibody and western blot analyses were used to demonstrate the presence of a highly reactive antigen of 36‐kDa, not only in the extract of T. gondii tachyzoites, but also in selected sera of women with confirmed laboratory and clinical signs of recent toxoplasmosis. The 36‐kDa Toxoplasma antigen was purified from T. gondii tachyzoites and human serum using electroelution from preparative polyacrylamide gels. The purified polypeptides showed a single peak at 10.9 min when analyzed by capillary zone electrophoresis. Based on the above encouraging results, we have developed an ELISA format for the detection of target Toxoplasma antigen (TAg‐ELISA) in human serum samples. The TAg‐ELISA detected the target antigen in 88% sera of acutely infected women and showed high degree of specificity (91%) among sera from non‐infected women. In conclusion, the detection of 36‐kDa Toxoplasma circulating antigen in human sera appears to be a promising alternative approach for laboratory diagnosis of active T. gondii infection.

Keywords:

• Toxoplasma gondii
• 36‐kDa antigen
• Serum
• Western blot
• ELISA

Acknowledgments

The authors would like to thank A. T. Kombar, M. M. El‐Bakry, and R. E. Gamal‐Eldeen at the Biotechnology Research Center, New Damietta for their kind help.