Heat shock protein 70 (hsp70) as a major target of the antibody response in patients with pulmonary cryptococcosis

Cryptococcus neoformans causes infection in individuals with defective T cell function, such as AIDS, as well as without underlying disease. It has been suggested that humoral as well as cellular immunity might play an important role in the immune response to C. neoformans infection. We have recently shown, using immunoblotting, that the 70-kD hsp family of C. neoformans was the major target molecule of the humoral response in murine pulmonary cryptococcosis. In this study we also used immunoblotting to define the antibody responses in the sera of 24 patients with pulmonary cryptococcosis: 21 proven and three suspected diagnoses. Anti-C. neoformans hsp70 antibody was detected in 16 of 24 (66.7%) patients with pulmonary cryptococcosis. Fourteen of 17 (82.3%) patients with high antigen titres (> or = 1:8) and two of seven (28.6%) patients with low titres (< or = 1:4) had detectable levels of anti-hsp70 antibody. Sera from patients positive for anti-hsp70 antibody showed high titres in the Eiken latex agglutination test for the detection of serum cryptococcal antigen. Our results indicate that the 70-kD hsp family from C. neoformans appears to be a major target molecule of the humoral response, not only in murine pulmonary cryptococcosis, but also in human patients with pulmonary cryptococcosis.