Mycobacterium avium complex (MAC) is a group of genetically related bacterium belonging to the genus Mycobacterium. It includes Mycobacterium avium and Mycobacterium intracellular Mycobacterium avium complex include ubiquitous atypical bacterium found in the environment which can infect patients with HIV and low CD4 cell count (below 100/microliter); mode of infection is usually inhalation or ingestion.
There are currently no vaccines in use against MAC. However, there is increasing interest to develop a vaccine against tuberculosis, which may provide immunity against MAC. Researchers have determined that a PE protein expressed by MAC is an effective T-cell immunogen in the mouse model. While these studies are promising, it has already been established that HIV infected patients have variable response rates to vaccines and loss of immunity as T-cell counts decline. This makes it unclear how effective a vaccine with activity against MAC would be for the severely immune compromised HIV infected population at greatest risk for developing disseminated MAC.