Analysis of IgG subclasses (IgG1 and IgG3) to recombinant SAG2A protein from Toxoplasma gondii in sequential serum samples from patients with toxoplasmosis

► We evaluated antibody kinetics to rSAG2A and STAg in patients with toxoplasmosis. ► The follow-up of IgG and IgG1 showed a similar increasing profile for both antigens. ► IgG3 levels to SAG2A were higher from 0 to 6 months of infection. ► IgG3/IgG1 ratio to SAG2A was higher than STAg in the first 3 months of infection. ► Association IgG3/IgG1 > 1.0 to SAG2A with IgM+ or IgA+ can indicate early acute phase.