A Whiff of Protection: Mucosal Vaccines
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Daniel Hoft, M.D., Ph.D.
Credit: Dr. Hoft |
To most people, vaccines mean needles. Daniel Hoft, M.D., Ph.D., of Saint Louis University in Missouri, is developing a different kind of vaccine—one that anyone fearful of a needle’s jab should welcome. Dr. Hoft is working on a mucosal vaccine for TB that might be delivered as a squirt up the nose.
Most vaccines elicit a body-wide protective immune response. In contrast, mucosal vaccines target immune cells in the body’s mucous membranes, such as the tissues lining the nose, mouth, lung, gut, and urogenital tract. Unlike watertight skin, mucosal surfaces allow substances to pass through. Oxygen and carbon dioxide move across the mucosa of the lungs as we breathe, for example. Mycobacterium tuberculosis (M. tb), which lodge in the lower lung, take advantage of the openness of mucosa to invade our bodies, notes Dr. Hoft.
The current TB vaccine, BCG, limits the growth of TB bacteria in their actively dividing stage, but does not prevent infection itself. Also, BCG’s protection appears to fade over time. This means vaccinated individuals who become infected may develop active disease when age or disease weaken immune responses and allow latent M. tb to reactivate, says Dr. Hoft.
The goal of a mucosal TB vaccine, he explains, is to stimulate sub-groups of immune system cells in the lung mucosa, thereby preventing or reducing infection in the first place. Because TB is so prevalent worldwide, Dr. Hoft adds, even a 50 percent reduction in infection rate would translate to enormous health benefits in endemic areas.
Dr. Hoft and his colleagues recently began research in mice on a vaccination strategy that combines a “prime” of one or more M. tb proteins delivered as a nose spray (the mucosal vaccine) with a “boost” of BCG. After determining which prime-boost combinations stimulate the most potent protective responses in the widest range of immune cells, the scientists will expose vaccinated mice to M. tb to test its effectiveness.
References
de Vallière, S. et al. Enhancement of innate and cell-mediated immunity by antimycobacterial antibodies. Infect Immun. 2005 Oct;73(10):6711-20.
Worku, S. Differential effects of control and antigen-specific T cells on intracellular mycobacterial growth. Infect Immun. 2003 Apr;71(4):1763-73.
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