Dr. Overbaugh's laboratory has a long-standing interest in understanding the mechanisms of HIV transmission and pathogenesis. A major hypothesis for the studies in her lab is that the variants of HIV-1 that are transmitted are a selected subset of all the viruses that evolve during the course of infection. Thus, an overarching goal of Dr. Overbaugh's research is to determine whether some variants are more transmissible and others are more pathogenic in the host and to define the mechanisms underlying these differences. Her lab has shown that there is a genetic bottleneck in the sequences that are transmitted, leading to selection of just one or a few HIV variants in a new host. Her lab's studies have shown that people already infected by HIV can become re-infected/superinfected with HIV from another source partner. Her laboratory is exploring the immune responses in individuals who become superinfected to determine if they have deficits in immunity that may explain their susceptibility to re-infection, which has implication for defining immune correlates of vaccine protection. Her lab is exploring similar question in the context of mother-infant transmission, where the infant is infected in the presence of maternal HIV-specific antibodies.
Much of the HIV research in the lab is focused on populations in Africa because this is where the AIDS epidemic is most severe. Studies include analyses of antiretroviral drug resistance, which has become increasingly important as HIV treatments become available in Africa. The laboratory is part of a larger team, comprising researchers in both Seattle and Kenya (The Nairobi HIV/STD Project), that is studying the molecular epidemiology of HIV transmission. The project is also examining the efficacy of various intervention strategies to limit the spread of HIV, particularly those that may be practical to implement in Africa and other parts of the developing world.