HIV superinfection (also called HIV reinfection) is a condition in which a person with an established "human immunodeficiency virus infection acquires a second "strain of HIV, often of a different "subtype. The HIV superinfection strain (a recombinant strain) appears when a person becomes simultaneously infected by two different strains, allowing the two viruses to exchange genetic material, resulting in a new unique strain that can possess the resistances of both previous strains. This new strain co-exists with the two prior strains and may cause more rapid disease progression or carry multiple "resistances to certain HIV medications.
People with HIV risk superinfection by the same actions that would place a non-infected person at risk of acquiring HIV. These include sharing needles and forgoing condoms with HIV-positive sexual partners. For many years superinfection was thought to occur mainly in high-risk populations. Research from "Uganda published in 2012 indicates that HIV superinfection among HIV-infected individuals within a general population remains unknown. Further research from "The Journal of Infectious Diseases indicates that there have been 16 documented cases of superinfection since 2002.
It is unknown what aspects of the natural "immune response to HIV may protect someone from superinfection, but it has been shown that cytotoxic lymphocyte responses do not seem to be protective. In addition, it has been demonstrated that superinfection can occur in individuals that demonstrate a robust anti-HIV antibody response. The anti-HIV antibody response broadens and strengthens in individuals post-superinfection. Taken with the finding that super-infection is common and occurs within and between HIV subtypes it has been suggested that the immune response elicited by primary infection may confer limited protection and raises concerns that HIV-vaccine strategies designed to replicate the natural anti-HIV immune response may have limited effectiveness in preventing new infections. However at the same time, HIV-infected individuals at high risk for super-infection who do not become superinfected may also provide a very interesting avenue for new "vaccine research.
A study in the "New England Journal of Medicine titled "Inhibition of HIV-1 Disease Progression by Contemporaneous HIV-2 Infection" revealed that people who are HIV-positive with the two major subtypes have a slower progression towards AIDS than people with only "HIV-1 or "HIV-2. This challenges the notion of superinfection by illustrating that contemporaneous infection can offset itself.