There are two types of HIV, HIV-1 and HIV-2, which can lead to AIDS. HIV-1, with global spread, is the more aggressive and infectious virus. The reason for the difference in pathogenesis between HIV-1 and HIV-2 is not yet clear, and neither is the inhibiting effect that HIV-2 has on HIV-1 in dually infected understood. Our research is focused on understanding the interactions between the immune system and these viruses. We are analyzing cellular and humoral immunity in HIV-1 and/or HIV-2 infected individuals, in relation to viral and clinical markers of disease progression. In parallel, we study the interaction by various in vitro infection models, including lymphoid tissue. We are also trying to find out how the immune system is affected by HIV-1-tuberculosis (TB) coinfection. Our collaborators include clinics and scientists in Guinea-Bissau, a West African country where both HIV-1 and HIV-2 are circulating, as well as in Ethiopia, a country with many HIV-TB coinfected, and several other national and international researchers. Taken together, in addition to basic knowledge on HIV pathogenesis, we anticipate that our studies may contribute to optimized treatment and provide clues to how an effective HIV vaccine should work.