Diagnosis of human toxoplasmosis by using the recombinant truncated surface antigen 1 of Toxoplasma gondii

The goal of the present study is to develop an enzyme-linked immunosorbent assay (ELISA) using a truncated surface antigen 1 (SAG1) gene of Toxoplasma gondii for the diagnosis of human toxoplasmosis. The truncated SAG1 gene was highly expressed in Escherichia coli. An ELISA kit based on the purified recombinant truncated SAG1 (rtSAG1) was developed, which was used to detect antibodies against T. gondii in human sera. The results showed that the infection of T. gondii could be detected sensitively and specifically by this serologic method. The positive concordance between rtSAG1-ELISA and Western blot, the gold standard, was 93.9% (31/33). However, the positive concordance between the commercial available ELISA Kit 1 (Haitai, Zhuhai, China) and ELISA Kit 2 (DiaSorin ETI-TOXOK-M reverse Plus, Italy) with Western blot was 79.5% (31/39) and 91.2% (31/34), respectively. Comparatively, the positive concordance of ELISA Kit 1 and 2 with Western blot was lower than rtSAG1-ELISA, in particular, the ELISA Kit 1 (P < 0.01), which indicated that the rtSAG1 protein could be used as the diagnostic antigen for human toxoplasmosis.