HIV superinfection

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. These can form a recombinant strain that co-exists with the strain from the initial infection, as well as the strain from the new virus, and may cause more rapid disease progression or carry multiple resistances to certain HIV medications. 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. These can form a recombinant strain that co-exists with the strain from the initial infection, as well as the strain from the new virus, and may cause more rapid disease progression or carry multiple resistances to certain HIV medications. HIV superinfection may be interclade, where the second infecting virus is phylogenetically distinct from the initial virus, or intraclade, where the two strains are monophyletic. 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. Cases have been reported globally and studies have shown the incidence rate to be 0-7.7% per year. 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. 'If a person is infected with a second virus before seroconversion to the first virus has taken place, it is termed a dual infection. Infection with a second strain after seroconversion is known as superinfection.' A study conducted in Kenya in 2007 shows that superinfection tends to occur during the course of the initial infection, that is during acute infection, or 1–5 years after initial infection, but not during the latency period. Thus, superinfection occurs after an immune response to the initial infection has already been established. 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. Immune responses to initial infection with a particular strain of HIV do not provide protection against superinfection with a different strain. The effect of neutralizing antibodies (NAb) is also unknown, but it has been shown that individuals with HIV tend not to have a NAb response prior to superinfection. 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. The finding that superinfection occurs within and between HIV subtypes suggests that an immune response to initial HIV infection provide limited protection against infection by a new viral strain. This means that HIV-vaccine strategies made to replicate the host's immune response to HIV infection may not prevent new infections. Studies indicate that superinfection causes a spike in HIV viral load and a decrease in CD4+ cell count similar to those reported during primary HIV infection. Early studies of HIV superinfection analysed these spikes to diagnose cases of superinfection. It is unclear whether superinfection causes a sustained increase in viral load. The effect of superinfection on the progression of HIV infection is unclear because of its ambiguous effects on surrogate markers for the disease, such as an increase in viral load or a decrease in CD4 cell count. The potential of superinfection to cause rapid disease progression depends on viral and host factors. Cases of superinfection are yet to be identified in sufficient numbers to conduct detailed studies on the effect of superinfection on the host immune response.