Scientists from Dartmouth Medical School (DMS) have reported results of their clinical trial of this new vaccine against TB -- Mycobacterium vaccae (MV) -- in the January 29 online issue of the journal AIDS. The study will be published in the March print issue of the journal. Principal investigator Ford von Reyn from DMS said, "Since development of a new vaccine against TB is a major international health priority, especially for patients with HIV infection, we and our Tanzanian collaborators are very encouraged by the results of the study." The vaccine is a type known as an inactivated, whole-cell mycobacterial vaccine and is expected to be economical to produce and distribute. Von Reyn described the trial as a "significant milestone -- the first to demonstrate that any type of vaccine can prevent an infectious complication of HIV in adults". He added that the next steps are to improve the manufacturing methods to support the production of the larger quantities of the TB vaccine needed for further studies and subsequent clinical use.
Since newly-infected HIV patients risk contracting TB almost immediately, investigators are targeting a strategy for immunization with MV before patients need to start taking antiretroviral drugs. The scientific team at Dartmouth began Phase-I human studies with MV in the United States in 1994 and demonstrated that a multiple-dose series of MV was safe in both healthy subjects and patients with HIV infection. The group then conducted Phase-II studies in larger groups of adults in Zambia and in Finland. In the Zambian trial, researchers found that MV boosted immune responses against TB that had first been primed in childhood with the current TB vaccine, BCG. Subsequently, the DarDar group received NIH funding to conduct the large Phase-III efficacy trial among HIV-infected patients with prior BCG immunization in Tanzania.
HIV patients are particularly vulnerable to TB because their immune systems are compromised. The vaccine works by boosting the immune responses of patients who have already been given the BCG vaccine earlier in life.
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