Scientists trace the AIDS virus in humans to 1920s

The AIDS virus was already well established in humans by the 1920s, long before the earliest confirmed case was discovered in a 1959 blood sample, according to a newly published study. The virus crossed from chimpanzees to humans as early as the 17th century, according to the findings.

An international group of scientists including experts from the Virus Reference Laboratory at University College Dublin have developed a unique new way to time the evolution of viruses. Their "molecular clock analysis" was developed during a study of Irish women infected with hepatitis C.

The researchers' findings have just been released in a new scientific journal published only on the Internet, FASEB (Federation of American Societies for Experimental Biology). They describe their new method for analysing viral evolution as a way to understand a virus's origins and also to predict how it might change.

"We know that the genetic material of viruses is constantly evolving," explained Prof William Hall, director of the Virus Reference Laboratory and a consultant microbiologist at St Vincent's Hospital, Dublin. "The virus is ticking away. What the analysis does is enable us to look at its clock."

The research group included the UCD team and scientists from major research centres in Belgium, Germany, France and Senegal. A key to the effort however was a study in Dublin of the Irish women who got hepatitis C when given infected Anti-D serum by the Blood Transfusion Service Board.

The Health Research Board had funded a major study of hepatitis C in these women in an effort to understand the virus, Prof Hall said. The researchers realised that the virus had evolved, changing from its original form when given in 1977 to when it was analysed in 1998.

The group then began looking for the origins of the AIDS virus, HIV. They found that all of the various "subtypes" of HIV already existed by the 1920s and 1930, a situation that could only have arisen in the context of significant human infection.

This predates the current earliest confirmed HIV case, found in an African plasma sample.

Winding the molecular clock back even further, the researchers compared HIV with the closely related simian disease, SIV. They estimated that the two viruses derived from a single common ancestor some time around 1675.

The FASEB website is http://www.fasebj.org