The New York Times - December 13, 1986
Lawrence K. Altman

Thus far only cells of the immune system such as lymphocytes have been found to be infected by the virus. Lymphocytes are types of white blood cells that play crucial immunological roles in fighting infections. As a result of the destruction of these white cells, people with the AIDS virus suffer weakened immune systems and fall prey to a variety of infections and diseases.

If confirmed in further research, the findings suggest that the virus that causes acquired immune deficiency syndrome could spread during anal intercourse without breakage in tissue. The virus would apparently attack the cell directly.

The new finding may help to explain the high incidence of AIDS among male homosexuals practicing anal intercourse.

Doubts on Earlier Theory

Most experts have believed that male homosexuals become infected through tears that develop in rectal tissues during anal intercourse. According to this theory, the tears allow passage of the virus from contaminated semen into the recipient's bloodstream, where it can attack the type of white blood cells that many believe is the primary target of the virus.

However, Dr. Malcolm A. Martin, chief of the laboratory of molecular microbiology at the National Institute of Allergy and Infectious Diseases in Bethesda, Md., said the findings made by his team were "provocative" because they indicated that rectal and colon cells could be directly infected without the occurrence of "trauma," or anal tears. "But we haven't shown it directly in a person," Dr. Martin said.

Nevertheless, Dr. Martin added, the fact that the AIDS virus "can do that in the laboratory and in a tissue culture flask, raises the obvious possibility that it could occur in living people."

According to the results of the laboratory studies, the AIDS virus can infect and multiply in the rectal and colon cells and release additional viruses for more than 10 weeks after such infection.

This finding, Dr. Martin's team reported in the January issue of The Journal of Virology, suggests that infected cells of the colon and rectum could be sources of continued spread of the AIDS virus to the brain and other organs in the body.

AIDS researchers are handicapped by the lack of an animal model in which they can carry out experiments in the laboratory. Although tests have shown that some species of primates can be infected with the AIDS virus, the animals do not develop the disease. Because it is unethical to infect humans with the AIDS virus, many such experiments must be conducted in test-tube experiments in the laboratory. #14 Types of Cells Tested Dr. Martin tested 14 types of cells representing a wide range of human tissues such as breast, lung, pancreas and ovary.

The scientists used cancerous forms of the 14 cells because they can grow continuously in test tubes and the corresponding normal cells cannot.

Three of the five cell samples from the colon and rectum could be infected with the AIDS virus, while none of other types of cells studied were susceptible, Dr. Martin's team said.

Experts believe that AIDS is a sexually transmitted disease and that in addition to spread among male homosexuals, the AIDS virus can spread through sexual intercourse among heterosexuals if one person is already infected. However, scientists have never been certain how the virus is transmitted in the sexual act.

Dr. Martin said his findings suggested that the AIDS virus "may infect vaginal cells, too." However, Dr. Martin said cells from the vagina were not tested in his study because cancerous cells from that tissue that can grow in test tubes were not available to his team at the time it began the experiments.

The scientists also found that the colon and rectal cells produced the genetic material RNA, or ribonucleic acid, which in turn directs production of a molecule called CD-4. This same molecule is found on the surface of the T-4 lymphocyte and the other immune system cells attacked by the AIDS virus. The 13 breast and other nonimmune cell types that were not susceptible to the AIDS virus did not produce the CD-4 RNA.

Thus, the researchers theorized that the cells of the lower bowel may be one site of entry of the AIDS virus because of the presence of the CD-4 molecule on their surface.

Dr. Martin said that in future research his and other teams would try to detect the AIDS virus in biopsies taken from the rectums of people infected with the AIDS virus rather than from the cancer cells that were purposely infected in test tubes.

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