Antibodies to 68, 52, and 48 kd proteins of Mycobacterium avium in serum samples from patients with Mycobacterium avium infection

Mycobacterium avium complex (MAC) is responsible for the highest incidence of disseminated bacterial infection in patients with AIDS. Disease caused by this organism was originally thought to be rare in nonimmunocompromised individuals, but it is now being encountered more frequently. Relatively little is known about the components that play a role in the immunopathology of infection caused by MAC. To identify the immunoreactive antigens of this organism that are important targets of the humoral immune response in MAC infection, serum samples from MAC-infected and non-MAC-infected patients were analyzed by Western Blot analysis with sonic extracts of M. avium (MA) as the antigen. The MAC-infected population included patients who were HIV-negative as well as patients with AIDS, and the non-MAC-infected population included non-AIDS, HIV-positive patients and normal, purified protein derivative-negative individuals. The immunodominant antigens recognized by the MAC-infected patients were the 68, 52, and 48 kd proteins of MA. These antigens were also recognized by a few of the non-MAC-infected patients. However, significant differences were observed between the number of MAC-infected and non-MAC-infected patients reacting with these antigens. Sixty-nine percent of the MAC-infected patient serum samples were found to react with the 68 kd antigen, whereas only 24% of the serum samples from patients without MAC infection recognized this antigen (p < 0.001). Of the MAC-infected serum samples, 53.1% were found to react with the 52 kd antigen, whereas only 22% of the non-MAC-infected patient serum samples reacted with this antigen (p = 0.008). In the case of the 48 kd antigen, 53.1% of the MAC-infected patient serum samples were found to react with this antigen, compared with 18% in the non-MAC-infected group (p = 0.002). Similar immunodominant bands were also detected by Western blot analysis of sonic extracts of patients or water isolates of MA with MAC-infected patient serum, suggesting a broad distribution of these antigens within the species. MA antigens described in the present study may serve as targets of the humoral response in individuals infected with MAC.