Origins of HIV and the AIDS Epidemic

September 11-12, 2000, The Royal Society, London, United Kingdom

Jonathan Weber, FRCP, FRCPath, FmedSci, Keith Alcorn, Medical Writer

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In This Article

Lot 10a/11 Yields its Secrets

Investigators of the OPV theory have repeatedly called for the remaining lots of CHAT vaccine to be tested for SIV and HIV and for mitochondrial DNA to be analyzed to establish which species' cells were used to propagate the vaccine. Two lots of vaccine are known to have survived into the 1990s: one lot (10a/11) is held by the Wistar Institute, while the other was held by the Karolinska Institute in Stockholm and was tested for HIV a few years ago. The Wistar Institute recently released its stock of CHAT vaccine to be tested under the supervision of an independent panel headed by Dr. Claudio Basilico of New York University School of Medicine. Basilico reported the results of those tests at the Royal Society meeting.

Using Roche Amplicor polymerase chain reaction, the collaborative group responsible for testing found no evidence of HIV-1 RNA or SIV RNA in any of the samples. Most important, mitochondrial DNA was detected in these samples, despite their age, and was shown in independent laboratories on blinded samples to be macaque in origin. No chimpanzee DNA was detected in any sample.

The HIV-1 assay had a limit of detection of 100 copies/mL, while the SIV assay had a detection limit of 1000 copies/mL. Philippe Lena of the Pasteur Institute in Paris used more sensitive DNA tests to examine whether SIV could persist in macaque kidney cells when they were prepared in the fashion employed by vaccine developers. He reported that kidney tissue from a macaque with plasma SIV RNA of 122 x106 copies/mL contained 571 SIV DNA copies/mcg of tissue, and replication-competent virus, which persisted in CEMX174 co-culture after 6 passages. Lena concluded that while the quantities of DNA were possibly too small to be infectious in this case, macrophages, which could harbor retrovirus infection, were detectable in the kidney cell monolayer, "whizzing about all over the place" as Robin Weiss put it in his summary of the meeting.

However, John Garrett of the UK's National Institute of Biological Standards and Control (NIBSC) assessed the viability of HIV and SIV in monkey kidney monolayers exposed to trypsin, an agent used in the preparation of the cells used to culture polio vaccine in macaque kidneys. HIV and SIV did not replicate in the presence of trypsin in the NIBSC experiments. Edward Hooper has suggested that trypsin was not routinely used in the late 1950s, but John Beale argued that it would not have been possible to achieve the polio virus titers reported by Stanley Plotkin unless trypsinization took place. Beale showed that the process used to prepare polio virus vaccine from macaque kidney cell monolayers would lead to a 10 to 12 log10 reduction in SIV infectivity. Indeed, polio virus vaccine continued to be prepared from African green monkey kidney cell monolayers in the 1970s and 1980s. Although these monkeys harbor an SIVagm virus, the process for OPV has not lead to SIV contamination of OPV.

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