The origin of AIDS -  Was a polio vaccine involved? 

Current evidence suggests that SIVcpz (the chimpanzee form of simian immunodeficiency virus) entered the human population in central Africa as early as the 1930’s or 40’s. This date is based on computer modeling. Until recently this was suggested have happened in the area that is now known as the Republic of Congo. It is possible that infection resulted from contamination of the human recipient with chimpanzee blood (perhaps through a cut). Probably the virus that infected humans and caused disease was first localized to a small area of central  Africa and only spread rapidly as a result of urbanization and possibly the use of contaminated needles in medical procedures.  

In a Rolling Stone article and in a book called The River (and in a subsequent movie), the journalist Edward Hooper proposed a new idea concerning the origin of HIV infections in humans. Mr Hooper’s contention is that the virus entered the human population much later, as a result of contaminated polio vaccine that was tested near Kingali in the Republic of Congo in the 1960’s. His main evidence is the co-incidence of the geographical distribution of the presumed first AIDS cases and the test areas of the vaccine.  

The polio vaccine tested near Kingali is not one that is now used. In the 1950’s, the first vaccine was a formalin-inactivated (killed) vaccine that was developed by Dr Jonas Salk. This was replaced by an attenuated live vaccine developed by Dr Albert Sabin. At the same time as Sabin was developing his vaccine, Dr Hilary Koprowski at the Wistar Institute was developing another attenuated vaccine.  In addition to the Congo, this vaccine was tested in Burundi, Rwanda and in some European countries from 1957 and 1960. The virus particles in attenuated polio vaccines were (and still are) made in cultured cells derived from monkey kidneys. Mr Hooper contends that Dr Koprowski’s vaccine became contaminated with SIVcpz because chimpanzee kidneys were used instead. African Green Monkeys, the usual source of cells for polio vaccine production do not harbor SIV viruses (although they do harbor simian virus 40 (SV40) and this did contaminate some early attenuated polio vaccines, although there is no evidence that disease resulted). In fact, it is known that chimpanzees were used by Dr Koprowski but this was for testing the efficacy of the vaccine and not for its production. 

In order to sort out this controversy, it was suggested that any remaining samples of the Koprowski vaccine be analyzed. Some were found though, of course, these were not the same vials of vaccine that were used in Africa. In these analyses, the investigators looked for primate mitochondrial DNA and for HIV or SIV RNA. The tests for the viruses were negative and the mitochondrial DNA showed that the vaccine viruses were grown on monkey and not chimpanzee cells. In the movie, Mr Hooper contends that there is further evidence to suggest the use of chimpanzees. He claims that two people remember that they used chimpanzee cells to make the vaccine but this has been denied by others who worked on the project.

If SIVcpz did infect humans from the vaccine, it would be expected that HIV-1 would most closely resemble the stains of SIVcpz in the area of central Africa in which the vaccine was made and tested. In fact, HIV-1 is most closely related to the SIVcpz strains found in west African chimpanzees (Cameroon) and not to the strains circulating in chimpanzees in the region of the vaccine study.

Mr Hooper also contends that the evolutionary tree made up by the various HIV strains found around the world suggests the entry of multiple SIVcpz viruses into the human population at one time, that is multiple HIV strains arose simultaneously. This could happen if many chimpanzees were used to make the vaccine that was then given to more than one million vacinees. However, if one looks at the region of the Congo where the vaccine trial took place, there are not the multiple strains that would be predicted.  It is therefore likely that the different HIV-1 strains infected humans at different times and in different places.

Further evidence that the vaccine did not contain HIV comes from the fact that the same lot of vaccine that was used in the trials in the Congo was also used in Poland and HIV did not arise there. AIDS arose only in central Africa.

Thus, it seems unlikely that SIVcpz contaminated the test polio vaccine that was used in central Africa and the fact that AIDS may have arisen in this area is purely coincidence.