Kinetic analysis of the humoral immune response against 3 Toxoplasma gondii-recombinant proteins in infants with suspected congenital toxoplasmosis

The reactivity values of Toxoplasma gondii ROP2, GRA4, and GRA7 recombinant antigens (rAgs) were analyzed by immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) in 23 congenitally infected (I) and 36 noninfected (NI) infants. The reactivity values observed from the serum samples of I versus NI infants for each recombinant protein were 91% versus 67% for rROP2 (P = .05), 86% versus 29% for rGRA4 (P < .001), and 56% versus 11% for rGRA7 (P = .003). The follow-up showed that serum samples from NI infants became negative for specific IgG at 5.8 months (95% confidence interval [CI], 4.9–6.7) using a commercial assay; meanwhile, by specific recombinant protein ELISA, the samples became negative at 3.7 months with rROP2 (95% CI, 2.8–4.6), at 1.3 months with rGRA4 (95% CI, 0.8–1.8), and at 0.9 months with rGRA7 (95% CI, 0.5–1.3). Kinetic analysis also showed that serum samples from group I presented different IgG-profiles among rAgs. The rROP2 IgG profile was similar to that of the commercial assay, whereas rGRA4 and rGRA7 profiles showed a gradual decrease along the period of the study. The potential of the utility of rAgs to develop a diagnostic system that discriminates congenitally I infants from NI is discussed.