Characterization of Toxoplasma gondii antigens that react with human immunoglobulin M and immunoglobulin G antibodies

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Abstract
Studies were performed to define the nature of the T. gondii antigens that are recognized by human IgM and IgG antibodies. Both IgM and IgG antibodies were found to be directed mainly against T. gondii membrane antigens in sera obtained from patients with acute toxoplasmosis. Treatment of the membrane preparation with DNase, RNase, or lipase had no apparent effect on the reactivity of the membrane antigens with IgM and IgG antibodies. Lipids isolated from tachyzoites were not recognized by either IgM or IgG antibodies. Exposure of T. gondii membranes to heat, proteolysis, or oxidation with sodium periodate decreased the reactivity of the membrane preparations with both IgM and IgG antibodies. A preparation of T. gondii proteins and polysaccharides were recognized by both Ig classes. T. gondii polysaccharides reacted with human IgG antibodies produced during both the acute and chronic phases of the infection. After infection with T. gondii, IgM and IgG antibodies are elicited in response to both protein and carbohydrate constituents of the invading parasite.