Preservation of monocyte effector functions against Mycobacterium avium-M. intracellulare in patients with AIDS

Mycobacterium avium-M. intracellulare is a frequent cause of late disseminated infection in patients with AIDS. The ability of human peripheral blood monocytes to phagocytose and kill M. avium was examined in an in vitro model. Monocytes were obtained from 13 healthy volunteers and 11 patients with AIDS, three of whom had documented disseminated M. avium infection. Monocytes were precultured for 2 days before infection with two AIDS-associated and two non-AIDS-associated strains of M. avium. Uptake of M. avium as measured by counting intracellular acid-fast bacilli did not differ among healthy subjects, patients with AIDS, or patients with AIDS and previously documented disseminated M. avium infection. Intracellular growth of M. avium was examined by a CFU assay of cell lysates from M. avium-infected monocytes after 0, 4, and 7 days of culture. Intracellular growth inhibition of M. avium at 7 days after infection was comparable between patients with AIDS and healthy donors for all M. avium strains tested. The effects of the addition of recombinant gamma interferon on M. avium uptake and intracellular growth in monocytes also were studied. Pretreatment of monocytes with gamma interferon prior to infection suppressed monocyte phagocytosis of M. avium. Continuously coculturing of monocytes with gamma interferon after infection augmented killing of M. avium among both patients with AIDS and healthy controls for three of the four strains of M. avium tested. The magnitude of this effect, however, was variable from donor to donor and strain to strain. No significant differences were noted between the growth-inhibiting abilities of gamma-interferon-treated monocytes obtained from healthy volunteers and those obtained from patients with AIDS.