A new MIC1-MAG1 recombinant chimeric antigen can be used instead of the Toxoplasma gondii lysate antigen in serodiagnosis of human toxoplasmosis

Abstract

This study presents an evaluation of the MIC1 (microneme protein 1)-MAG1 (matrix antigen 1) Toxoplasma gondii recombinant chimeric antigen for the serodiagnosis of human toxoplasmosis for the first time. The recombinant MIC1-MAG1 antigen was obtained as a fusion protein containing His tags at the N- and C-terminal ends using an Escherichia coli expression system. After purification by metal affinity chromatography, the chimeric protein was tested for usefulness in an enzyme-linked immunosorbent assay (ELISA) for the detection of anti-T. gondii immunoglobulin G (IgG). One hundred ten sera from patients at different stages of infection and 40 sera from seronegative patients were examined. The results obtained for the MIC1-MAG1 chimeric antigen were compared with those of IgG ELISAs using a Toxoplasma lysate antigen (TLA), a combination of recombinant antigens (rMIC1ex2-rMAG1) and single recombinant proteins (rMIC1ex2 and rMAG1). The sensitivity of the IgG ELISA calculated from all of the positive serum samples was similar for the MIC1-MAG1 chimeric antigen (90.8%) and the TLA (91.8%), whereas the sensitivities of the other antigenic samples used were definitely lower, at 69.1% for the mixture of antigens, 75.5% for the rMIC1ex2, and 60% for rMAG1. This study demonstrates that the MIC1-MAG1 recombinant chimeric antigen can be used instead of the TLA in the serodiagnosis of human toxoplasmosis.

Fig 1

Representative results of Western blotting analyses. Lanes M, molecular mass markers (Fermentas, Vilnius, Lithuania). Purified rMIC1ex2 (lane 1), rMAG1 (lane 2), and chimeric antigen MIC1-MAG1 (lane 3) were tested with serum samples from a T. gondii-infected individual (A) and a healthy patient (B).

Fig 2

Immunoreactivities of the MIC1-MAG1 chimeric protein (A), the mixture of antigens (B), and the TLA (C) with sera from the patient group in the chronic phase of toxoplasmosis, divided according to IgG titers as follows: □, >300 IU/ml; ○, 51 to 300 IU/ml; ▵, ≤50 IU/ml. Absorbance was measured at 492 nm. The horizontal lines represent the cutoff values.