Tuesday, July 23, 2013
Africans with HIV are more susceptible to TB
Tuberculosis is the leading cause of death by infectious disease, causing 1.5 million deaths around the world each year. Its prevalence is rising because of drug resistance and an increasing number of patients who are co-infected with HIV. They represent nearly 30% of all TB-related deaths. The convergence of these epidemics is particularly prominent on the African continent, which has the highest rates of TB cases and deaths — 80% of which occur in people living with HIV. Globally, a higher incidence of tuberculosis is known to occur in Africans and African-Americans than in American or European whites, and genetic susceptibility has long been suspected. Researchers found that a low-expressing version of the immune response gene known as macrophage migration inhibitory factor (MIF) — a cell-signaling molecule secreted by the body's innate immune system — conferred a two-and-a-half two and a half-fold increased risk for severe tuberculosis in a group of patients from Uganda. Low-expressers of MIF are almost twice as common among people of African ancestry as whites. "This helps to explain the increased incidence of TB in Africa," said senior author Richard Bucala, M.D., professor of rheumatology, pathology, and epidemiology at Yale School of Medicine and Yale School of Public Health.