Scientist Finds No Evidence of Insect Transfer of AIDS Virus

The French scientist who reported detecting genes from the AIDS virus in a variety of insects from Central Africa said Tuesday that his findings do not constitute evidence that insects can transmit the deadly disease.

“Insects can be contaminated with the virus but we have no evidence about the transmission of the virus,” Dr. Jean-Claude Chermann of the Pasteur Institute in Paris said in a telephone interview, in which he elaborated on earlier news reports of his findings.

“If you look at the epidemiology, sexual and blood transmission (of the virus) is enough to explain the number of cases of AIDS,” the French scientist said. “All the epidemiology we know argues against” insect transmission of the virus.

The presence of genes of the AIDS virus in an insect does not prove that the virus can reproduce or that the insect can subsequently infect other species with the virus, Chermann said.

A case in point is the Hepatitis B virus, which is more infectious for humans than the acquired immune deficiency syndrome virus. Parts of the Hepatitis B virus have been isolated from insects, although there is no evidence that they transmit the disease, which causes liver inflammation.

Chermann also said that he had not actually isolated living particles of the AIDS virus from insects collected in the Central African Republic and Zaire.

Assembled Data

Instead, using recombinant DNA techniques, his research team assembled data at the molecular level that they interpreted as showing that genes from the AIDS virus were present in the genetic material of dead African insects, such as mosquitoes, cockroaches, tsetse flies and bed bugs.

Chermann said that virtually all of about 50 insects he studied from Zaire showed such evidence of “contamination” with the AIDS virus, while only ticks and mosquitoes from the Central African Republic showed traces of the virus. No evidence of the virus was found in insects collected near Paris.

In a related experiment, Chermann mixed cells from fruit fly embryos and mosquito larvae with the AIDS virus in the laboratory. The AIDS virus did not reproduce in these cells.

But Chermann said the virus attached itself to a “receptor” on the surface of the cells. Subsequently, he said, genes from the virus combined with the genetic material in the nucleus of the cells.

Chermann said his research is now focusing on the mechanisms by which the AIDS virus binds to insect cells in the laboratory; he believes this may lead to a better understanding of how the virus gains access to human cells.

Chermann, who works with the French team that co-discovered the AIDS virus, announced his results last week at the 14th International Cancer Conference in Budapest.

“I hope that a lot of people now will try to verify our results and look for the AIDS virus in insects from other parts of the world,” Chermann said.

A leading AIDS researcher at the federal Centers for Disease Control on Tuesday agreed that any role insects may play in transmitting the AIDS virus is far from certain.

“There is still a lot to know yet,” said Dr. James W. Curran, the center’s director of AIDS programs. “It is unclear how real the results are and what they actually mean.”

Curran cautioned that genes from other viruses could have been present in the African insects. These genes may have cross-reacted with the materials used to detect genes from the AIDS virus, leading to erroneous results.