Western blot analysis of the antibody response of patients with AIDS and toxoplasma encephalitis: antigenic diversity among Toxoplasma strains.

We used immunoblotting to ascertain if toxoplasma encephalitis in disease caused by the human immunodeficiency virus (HIV) could be diagnosed by the appearance of characteristic antibodies recognizing specific Toxoplasma antigens. The profile of antibodies to Toxoplasma was examined in human serum and cerebrospinal fluid from patients with chronic and acute toxoplasmosis with or without HIV infection. Many Toxoplasma antigens were recognized by all sera; the majority were presumably surface proteins, as determined by 125I labeling. All sera recognized antigens at 38, 35, 28, and 26 kilodaltons. No specific antibody or pattern of antibodies distinguished between groups of patients. A 120-kilodalton antigen recognized by sera from Atlanta was not, however, seen in most sera from New York. Study of the recognition of the antigens of different strains of Toxoplasma gondii (RH, C56, T100) by the same human sera demonstrated strain-specific antigenic differences. These strain variations may account for the antibody diversity among the patients studied.