Secret trials have been underway for several months at the USC Medical School of a controversial AIDS immunization therapy based on the theories of Dr. Jonas Salk, the creator of the first successful polio vaccine, The Times has learned.
The therapy is being tried on a small number of individuals who are infected with the AIDS virus but who have yet to develop symptoms of acquired immune deficiency syndrome. It is not being tested as a vaccine for uninfected individuals.
The treatment involves injections of whole AIDS virus particles that have been killed, or in scientific parlance, inactivated. The use of whole virus particles sets the Salk approach apart from other known AIDS immunization therapies now undergoing human trials and is the source of the controversy surrounding it.
Salk's theory is that the injected virus will strengthen an infected individual's immune system and thereby prevent the development of AIDS. Salk used a similar approach in creating his polio vaccine.
"The study is at a very preliminary stage and has produced no definitive results to date," Dr. Brian E. Henderson, director of USC's Kenneth Norris Jr. Cancer Hospital, said in an interview Wednesday.
"At the moment, we are just testing an idea," Salk said in a telephone interview from Chicago where he was attending a medical meeting. "We are doing very limited preliminary experiments."
The study is one of the first to be authorized by the state Department of Health Services under a 1987 law that allows California researchers to test new AIDS therapies within the state without seeking the approval of the federal Food and Drug Administration. Apparently it is the only AIDS immunization testing underway in the United States without FDA approval.
Salk said the research team would seek federal approval for expanded tests if preliminary experiments here are successful. But neither he nor Henderson would say when the experiments began, how many patients are involved and how long the current tests are expected to last.
Salk said it was his decision to conduct the tests without any public announcement. "My preference is not to engage in making promissory notes but rather to deliver results when they become available," he said. "I did the work on polio for quite a long time before there was any notice or attention."
Salk, 73, one of America's most widely known scientists, first described his theories on this type of AIDS therapy in an article in Nature, a British science journal, in June. The article attracted widespread comment among AIDS researchers.
AIDS destroys the body's immune system, leaving it powerless against certain cancers and otherwise rare infections. The goal of all immunization therapies against the AIDS virus is to prevent this breakdown.
Salk's approach using the entire virus particle differs from others, which generally incorporate only a small piece of the protein coat that is the outer shell of the AIDS virus.
The key, in Salk's view, may be the long period between the time a person is infected with the AIDS virus and when they become ill with the disease--in some cases many years. He believes that the body initally can ward off any damage to the immune system caused by the virus. AIDS only develops, according to this theory, when the immune system is eventually worn down.
The immunization therapy being tested is intended to reinforce the immune system, enabling it to keep the AIDS virus in check indefinitely.
Salk and other proponents of his theories believe that treatments based on the entire AIDS virus--not just part of the virus--are more likely to be effective in boosting the immune system.
Salk achieved his polio vaccine success in the early 1950s by using an inactivated polio virus. Successful vaccines against many other diseases are based on a similar approach.
But some AIDS researchers fear this approach might backfire. Some are concerned that the injected inactivated AIDS virus particles might overstimulate the immune system, causing it to wear out sooner. That might hasten the onset of AIDS.
In addtion, if the procedures to inactivate the AIDS virus turned out to be less than 100% effective, then a patient treated with Salk's preparation might be injected with some live virus.
Salk said that nine months of study of the therapy in chimpanzees have adequately answered such questions. "There was no evidence of toxicity and no evidence of AIDS virus infection," he said.
The results of the animal studies were reviewed by the state before permission for the human trials was granted, Salk said. He added that he is preparing to publish his results in a medical journal.
However, one researcher who is working with Salk on the animal tests said that important safety issues remain unresolved, adding that she would want to see more animal test results before moving to human trials.