Genetic Predisposition and AIDS

Researchers studying the relationship between genetic predisposition and infectious diseases have linked two specific genes to higher and lower levels of susceptibility to HIV/AIDS.

Investigators at the University of Texas Health Science Center (San Antonio, USA) and the Wilford Hall Medical Center (Lackland Air Force Base, TX, USA) analyzed more than 4,300 blood samples from individuals, both HIV-positive and -negative, from various ethnic origins to determine the number of copies of CCL3L1, a gene that encodes a potent HIV-blocking protein, carried by each person.

They reported in the January 6, 2005, online issue of Science Express, that among the healthy group, African-American adults had an average of four CCL3L1 copies, while European and Hispanic-American adults averaged two and three copies, respectively. When HIV-positive individuals possessed fewer than the average number of copies for their ethnic type, they had a 39-260% higher risk of rapid progression to AIDS than did those with the average number of copies. An above-average number of copies provided additional protection against progressing to active AIDS. Each additional CCL3L1 copy lowered the risk 4.5-10.5%, depending on ethnic background.

The protective effect of the CCL3L1 protein was linked to its interaction with CCR5, a major HIV-receptor protein. Individuals who possessed a lower-than-average number of CCL3L1 copies as will as certain CCR5 variants had a substantially higher risk of HIV acquisition and rate of progression to AIDS.