New Strains of AIDS Virus Are Identified
Researchers have identified as many as 30 different strains of the AIDS virus that often elude conventional tests used to detect their presence in blood, a Belgian researcher said here Monday.
The new strains, first isolated in the Central African country of Cameroon, have never been detected in the United States and present no threat now to the American blood supply, J. Richard George of the U.S. Centers for Disease Control and Prevention told the 10th International Conference on AIDS.
But French scientists have identified the viruses, collectively called HIV-1 subtype O, in at least 10 people in Paris, some of whom have no connection to Cameroon. Existing blood tests may eventually have to be modified to ensure they detect the new strains as well, a recent meeting at the World Health Organization concluded.
In a separate development, Dr. Robert Gallo, co-discoverer of the AIDS virus, announced that he may have found the first effective treatment for Kaposi’s sarcoma, the form of cancer that is often a distinguishing feature of acquired immune deficiency syndrome.
Although he reported only animal data, Gallo said his new approach is supported by indirect evidence in humans and that it should be put into clinical trial immediately.
AIDS activists have long criticized the scientific Establishment for devoting insufficient effort toward development of a treatment for Kaposi’s and its disfiguring tumors. If Gallo’s results are validated in humans, it could represent a significant advance in treatment, they said.
The human immunodeficiency virus mutates extremely rapidly, as much as 1 million times faster than most other organisms; that instability has led to a proliferation of strains of HIV. Genetic information in these different strains can vary by a fraction of a percent or by as much as 30%.
Nonetheless, the viruses can be grouped together in various ways. Two main types are recognized--HIV-1 and HIV-2.
HIV-1 is the family that causes disease in most of the world, while HIV-2 predominates in areas of West Africa. These two families can further be broken down into eight subtypes, labeled A through H; all these subtypes are readily recognized by existing tests.
The new strains are called subtype O, for “outliers,” because they lie outside the existing subtypes. The subtype O strains do not necessarily resemble each other, however.
The first subtype O HIV was, in fact, reported at the 1988 International AIDS Conference by Guido van der Groen of the Institute of Tropical Medicine in Antwerp, Belgium. It was dismissed as a “curiosity” of no importance, said Dr. Peter Piot of WHO.
But Van der Groen reported here Monday that as many as 10% of AIDS patients in Cameroon have antibodies to one of the subtype O viruses. The strains are also found in as many as 6% of AIDS patients in neighboring Niger and Gabon but not in other nearby countries, he said.
Similar results were reported by Josef Eberle of the Max von Pettenkofer Institut in Munich, Germany. He and his colleagues found that as many as 30% of infections by new subtypes could not be detected by one or more tests normally used to monitor HIV infections.
“More disturbing,” he said, were similar problems in the more sophisticated tests, called western blots, that are used to confirm results in the preliminary tests.
French researchers reported earlier this summer in the medical journal the Lancet that they had identified HIV-1 subtype O in nine AIDS patients in Paris, most of whom had connections to Cameroon. The virus went undetected in at least one instance when subjected to each blood test normally used to test for HIV infection; one test missed the virus in blood from all nine patients and is no longer used in France.
Dr. Luc Montagnier of the Pasteur Institute in Paris, co-discoverer of the AIDS virus, said Monday that he had also isolated a subtype O strain from a French woman who has apparently harbored the virus since at least 1978 and who has no known risk factors for infection.
Van der Groen said at least 30 subtype O strains are now known.
Experts said there is no immediate threat from the new strains but noted that HIV-2 was first discovered in the same fashion. The growing number of cases in Cameroon suggests that the virus is spreading, Van der Groen said. But he emphasized that “there is no reason why there has to be changes in existing HIV tests.”
Gallo’s work on Kaposi’s sarcoma at the National Cancer Institute involved basic research on the mechanism of tumor formation.
Among other things, Gallo developed an “immortal” line of Kaposi’s cells that can be grown in the laboratory and injected into immunodeficient mice to produce the first animal model of the disease, he said.
Using these cells, he discovered that Kaposi’s cells are controlled by a hormone that is produced during pregnancy, called human chorionic gonadotropin or hCG. This hormone, he said, can prevent the formation of Kaposi’s tumors when injected into the immunodeficient mice along with the malignant Kaposi’s cells. It can also cure a tumor when injected into mice after the tumor has had time to establish itself.
Gallo noted that another female hormone, called luteinizing hormone, is about 85% identical to hCG and may, thus, aid in controlling the tumor. “That may provide the first explanation for why men get Kaposi’s far more often than women do,” he said.