SERUM ANTIBODY REACTIVITY TO RECOMBINANT MIG AND WHOLE-CELL ANTIGENS IN MYCOBACTERIUM-AVIUM INFECTION

Mycobacterium avium is a significant opportunistic pathogen in immunoc ompromised patients. Moreover, the prevalence of infections in patient s without known predisposing conditions has also been increasing in re cent years. Patients would greatly benefit from early diagnosis of dis seminated infection. Serodiagnostic tests have already been promising in tuberculosis and immunocompetent patients but studies in HIV-infect ed patients and humoral response to M. avium antigens resulted in conf licting data. We have evaluated the use of the phagocytosis-induced MI G protein of M. avium as a diagnostic antigen. Serum antibody levels o f M. avium-infected, HN-negative patients were significantly elevated for the recombinant of MIG (p < 0.001) and also for M. avium whole-cel l antigens (p < 0.025) as compared to controls. In contrast, HIV-infec ted patients with disseminated M. avium infection demonstrated also el evated levels of antibody for the whole-cell antigen (p < 0.00001) but a decreased reactivity for the MIG antigen (p < 0.007). The recombina nt antigen proved to have no cross-reactivity with M. tuberculosis ant igens as antibody levels were decreased in tuberculosis patients Ip < 0.001). Therefore, a simultaneous serological test using recombinant M IG and the whole cell antigens might be helpful in the sometimes probl ematic diagnosis of M. avium infections in patients without predisposi ng conditions.