Pathogenesis of CCR5-restricted HIV-1

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Human immunodeficiency virus type 1 (HIV-1) causes AIDS and, to date, has infected approximately 20 thousand people in Australia and more than 40 million worldwide. People infected with HIV-1 first experience a period of 5-7 years where they remain healthy, ofter assisted by the use of anti-HIV-1 drugs, and this period is referred to as the asymptomatic period. After this period, infected individuals become sick due to their immune system being destroyed, and this is referred to as AIDS. Research into how HIV-1 causes AIDS has shown us that the virus changes over time to make itself better able to kill cells of the immune system, by at least 2 mechanisms. The first mechanism, which is the best characterised one, is where the virus changes the way it infects cells, whereby it can infect many more cells in the body by taking advantage of an alternate receptor molecule on the cell called CXCR4. This molecule is very widely expressed on immune cells, and thus the virus can now infect and kill many more cells. However, in about 50% of infected people who eventually get AIDS, the virus does not change this way. The virus instead uses it's original receptor to infect cells, called CCR5. Our preliminary studies, as well as other published reports, suggest that the virus changes itself another way to make it kill immune cells better, without using CXCR4. However, the mechanism by which HIV-1 does this is poorly understood. This proposal aims to better understand this mechanism. We expect to find that, in this group of patients, the Env proteins on the virus change to be able to bind CCR5 more tightly, and thus be able to use fewer molecules of CCR5 to infect cells. We believe that these forms of the virus are now better able to kill immune cells, leading to AIDS. This study will contribute to a greater understanding of how HIV-1 causes AIDS, which is necessary for the development of new drugs to treat HIV-1 infection.