The controversial origins of HIV

This East African HIV/AIDS hotspot is close to the Congo basin, where chimpazees and monkeys still live close to humans. The Simian Immunodeficiency Virus (SIV) that infects African monkeys and chimps is a close relative of HIV. And there are strong indications that HIV may have originated from the area around the Congo and East Africa. This is almost the same area where we find Uganda, a country where the first AIDS vaccine trials were done. What factors likely make this region conducive for the origin of HIV/AIDS? In this article, Kazhila Chinsembu explores the literature on the controversial origins of HIV. HIV is a lentivirus, and like all viruses of this type, it attacks the immune system. Lentiviruses are in turn part of a larger group of viruses known as retroviruses. The name ‘lentivirus’ literally means ‘slow virus’ because they take such a long time to produce any adverse effects in the body. They have been found in a number of different animals, including cats, sheep, horses and cattle. However, the most interesting lentivirus in terms of the investigation into the origins of HIV is the Simian Immunodeficiency Virus (SIV) that affects monkeys. In February 1999 a group of researchers from the University of Alabama announced that they had found a type of SIVcpz that was almost identical to HIV-1. This particular strain was identified in a frozen sample taken from a sub-group of chimpanzees known as Pan troglodytes troglodytes, which were once common in west-central Africa. The researchers (lead by Paul Sharp of Nottingham University and Beatrice Hahn of the University of Alabama) made the discovery during the course of a 10-year long study into the origins of the virus. They claimed that this sample proved that chimpanzees were the source of HIV-1, and that the virus had at some point crossed species from chimps to humans. Their final findings were published two years later in Nature magazine. In this article, they concluded that wild chimps had been infected simultaneously with two different simian immunodeficiency viruses which had “viral sex” to form a third virus that could be passed on to other chimps and, more significantly, was capable of infecting humans and causing AIDS. These two different viruses were traced back to a SIV that infected red-capped mangabeys and one found in greater spot-nosed monkeys. They believe that the hybridisation took place inside chimps that had become infected with both strains of SIV after they hunted and killed the two smaller species of monkey. How could HIV have crossed species? It has been known for a long time that certain viruses can pass between species. Indeed, the very fact that chimpanzees obtained SIV from two other species of ape shows just how easily this crossover can occur. As animals ourselves, we are just as susceptible. When a viral transfer between animals and humans takes place, it is known as zoonosis. Below are some of the most common theories about how this ‘zoonosis’ took place, and how SIV became HIV in humans: The ‘Hunter’ Theory The most commonly accepted theory is that of the ‘hunter’. In this scenario, SIVcpz was transferred to humans as a result of chimps being killed and eaten or their blood getting into cuts or wounds on the hunter. Normally the hunter’s body would have fought off SIV, but on a few occasions it adapted itself within its new human host and become HIV-1. The fact that there were several different early strains of HIV, each with a slightly different genetic make-up (the most common of which was HIV-1 group M), would support this theory: every time it passed from a chimpanzee to a man, it would have developed in a slightly different way within his body, and thus produced a slightly different strain. An article published in The Lancet in 2004, also shows how retroviral transfer from primates to hunters is still occurring even today. In a sample of 1099 individuals in Cameroon , they discovered to ten (1%) were infected with SFV (Simian Foamy Virus), an illness which, like SIV, was previously thought only to infect primates. All these infections were believed to have been acquired through the butchering and consumption of monkey and ape meat. Discoveries such as this have lead to calls for an outright ban on bushmeat hunting to prevent simian viruses being passed to humans. The Oral Polio Vaccine (OPV) theory Some other rather controversial theories have contended that HIV was transferred iatrogenically (i.e. via medical experiments). One particularly well-publicised idea is that polio vaccines played a role in the transfer. In the Kano province in Northern Nigeria, which operates under Sharia (Muslim religious law), the immunisation campaign was suspended in September 2003 when prominent Muslim leaders said they suspected that vaccines supplied by Western donors were adulterated to reduce fertility and spread HIV as part of a U.S.-led drive against Islam. In his book, The River, the journalist Edward Hooper suggested that HIV could be traced to the testing of an oral polio vaccine called Chat, given to about a million people in the Belgian Congo , Ruanda and Urundi in the late 1950s. To be reproduced, live polio vaccine needs to be cultivated in living tissue, and Hooper’s belief is that Chat was grown in kidney cells taken from local chimps infected with SIVcmz. This, he claims, would have resulted in the contamination of the vaccine with chimp SIV, and a large number of people subsequently becoming infected with HIV-1. The fact that the OPV theory accounts for just one (group M) of several different groups of HIV also suggests that transfer must have happened in other ways too. The final element that suggests that the OPV theory is not credible as the sole method of transmission is the argument that HIV existed in humans before the vaccine trials were ever carried out. The Contaminated Needle Theory This is an extension of the original ‘hunter’ theory. In the 1950s, the use of disposable plastic syringes became commonplace around the world as a cheap, sterile way to administer medicines. However, to African healthcare professionals working on inoculation and other medical programmes, the huge quantities of syringes needed would have been very costly. It is therefore likely that one single syringe would have been used to inject multiple patients without any sterilisation in between. This would rapidly have transferred any viral particles (within a hunter’s blood for example) from one person to another, creating huge potential for the virus to mutate and replicate in each new individual it entered, even if the SIV within the original person infected had not yet converted to HIV. The Colonialism Theory The colonialism or ‘Heart of Darkness’ theory, is one of the more recent theories to have entered into the debate. It is again based on the basic ‘hunter’ premise, but more thoroughly explains how this original infection could have lead to an epidemic. It was first proposed in 2000 by Jim Moore, an American specialist in primate behaviour, who published his findings in the journal AIDS Research and Human Retroviruses. During the late 19th and early 20th century, much of Africa was ruled by colonial forces. In areas such as French Equatorial Africa and the Belgian Congo, colonial rule was particularly harsh and many Africans were forced into labour camps where sanitation was poor, food was scare and physical demands were extreme. These factors alone would have been sufficient to create poor health in anyone, so SIV could easily have infiltrated the labour force and taken advantage of their weakened immune systems to become HIV. A stray and perhaps sick chimpanzee with SIV would have made a welcome extra source of food for the workers. Moore also believes that many of the labourers would have been inoculated with unsterile needles against diseases such as smallpox (to keep them alive and working), and that many of the camps actively employed prostitutes to keep the workers happy, creating numerous possibilities for onward transmission. A large number of labourers would have died before they even developed the first symptoms of AIDS, and those that did get sick would not have stood out as any different in an already disease-ridden population. Even if they had been identified, all evidence (including medical records) that the camps existed was destroyed to cover up the fact that a staggering 50% of the local population were wiped out there. One final factor Moore uses to support his theory, is the fact that the labour camps were set up around the time that HIV was first believed to have passed into humans ‘ the early part of the 20th century. The Conspiracy Theory Some say that HIV is a ‘conspiracy theory’ or that it is ‘man-made’. A recent survey carried out in the US for example, identified a significant number of African Americans who believe HIV was manufactured as part of a biological warfare programme, designed to wipe out large numbers of black and homosexual people. Many say this was done under the auspices of the US federal ‘Special Cancer Virus Program’ (SCVP), possibly with the help of the CIA. Some even believe that the virus was spread (either deliberately or inadvertently) to thousands of people all over the world through the smallpox inoculation programme, or to gay men through Hepatitis B vaccine trials. While none of these theories can be definitively disproved, the evidence they are based on is tenuous at best, and often ignores the clear link between SIV and HIV, or the fact that the virus has been identified in people as far back as 1959. They also fail to take into consideration the lack of genetic-engineering technology available to ‘create’ the virus at the time that AIDS first appeared. Links: http://www.avert.org/origins.html http://en.wikipedia.org/wiki/Polio

April 2006
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