P1-S5.05 The emergence of HIV pandemic: who lifted the lid of the African SIV-HIV Pot? A hypothesis

Abstract

: A series of studies established that HIV infection in humans originated from multiple episodes of zoonotic transmission of CD4 T cell-tropic lentiviruses infecting African monkey species-Simian Immunodeficiency Viruses (SIV). HIV-1 derives from the chimpanzee (Pan troglodytes)-SIVcpz, while HIV-2 derives from SIVsm, which naturally infects the Sooty mangabey (Cercocebus atys). Pan troglodytes is present across West Central Africa. Cercocebus atys have their natural habitat in West Africa (Guinea-Bissau to Cote d'Ivoire). Timing the emergence of HIV-1 in humans: four of the earliest known instances of HIV-1 infection are as follows: A plasma sample taken in 1959 from an adult male living in the Democratic Republic of the Congo. A lymph node sample taken in 1960 from an adult female, also from the Democratic Republic of the Congo. HIV-1 found in tissue samples from an American teenager who died in St. Louis in 1969. HIV-1 found in tissue samples from a Norwegian sailor who died around 1976. An 1998 analysis of the plasma sample dated 1959 suggested that HIV-1 was introduced into humans around the 1940s or the early 1950s. In 2000 the results of a new study suggested that HIV-1 infection occurred around 1931 in West Africa. However, a study in 2008 dated the origin of HIV to between 1884 and 1924. Timing the emergence of HIV-2 in human population: in 2003 molecular timing analysis of two subtypes of HIV-2 (A and B) and SIVsm samples led to conclusion that subtype A had passed into humans around 1940 and subtype B in 1945. The data evidence that Africa was the continent where the transfer of emerged HIV-1 and HIV-2 to humans first occurred. What caused the HIV epidemic to spread so suddenly from African pot in late 70s and early 80s? In this connection let's recall the largest successful worldwide medical intervention in human history-the WHO Smallpox Eradication Programme (1967-1977). Smallpox epidemics had inflicted mankind throughout history, and during 1967 some 10-15 million cases were occurring in 30 endemic countries. In WHO monograph Smallpox and Its Eradication "the chronology and precise timing of the Programme progress was well documented including Africa region: at the end of 1971 smallpox was endemic in only three African countries and was completely eradicated by 1977. Can there be a possible link between the HIV-1/HIV-2 pandemic emergence from West and Central Africa and smallpox eradication?. Smallpox was endemic for most of the countries of West and Central Africa where HIV's originated. Smallpox may be fatal for the most of the HIV-infected immunocompromised persons resulting in interruption of HIV spread. Thus smallpox could be considered as a natural barrier that limited prevalence of newly emerged HIV-1/HIV-2 in local human population. Smallpox eradication probably was the key factor which may contribute the widespread of HIV's in the population of West and Central Africa and the subsequent HIV pandemic emergence"., (C) 2011 BMJ Publishing Group Ltd