• safety and efficacy of a prime-boost immunization strategy for the prevention of HIV-associated dTB and pTB [ Time Frame: every six months ] [ Designated as safety issue: Yes ]
  

• Risk factors for HIV-associated dTB and relative contributions of primary infection, reinfection, and reactivation in its pathogenesis [ Time Frame: every six months ] [ Designated as safety issue: No ]
  

Disseminated infection with Mycobacterium tuberculosis (dMTB) has been documented in 10% to 25% of patients with HIV infection in Africa. Unlike pulmonary tuberculosis (pMTB), most cases of dMTB are not recognized and death ensues rapidly. Therefore, dMTB may be a more important cause of HIV-associated mortality than pMTB in developing countries. Mycobacterium vaccae (MV) is an investigational vaccine prepared by heat inactivation of a nontuberculous mycobacteria. MV immunization may reduce the risk of HIV-associated dMTB. The purpose of this study is to define risk factors for HIV-associated dMTB and to assess the safety and effectiveness of an MV vaccine for the prevention of HIV-associated pulmonary and disseminated tuberculosis.

HIV positive patients with prior BCG immunization and HIV negative controls will be entered in a 5-year study in Tanzania. Participants will be randomized to receive a 5-dose series of MV or placebo over 12 months, with a repeat skin test at Month 14. Baseline evaluation will include medical history, chest x-ray, skin tests with purified protein derivative (PPD), and blood tests to evaluate interferon-gamma production. Participants with PPD reactions greater than or equal to 5 mm will receive 6 months of prophylaxis with isoniazid. Participants will be followed every 3 months for 3 to 5 years to assess new pMTB (microbiologic or clinical diagnosis) or dMTB (microbiologic diagnosis). Potential risk factors for dMTB will also be assessed.