"This is the first prospective study that suggests we might be able to decrease the probability of transmission of HIV using antiretroviral drugs," said Dr. Bruce L. Gilliam, who led the research at the University of North Carolina at Chapel Hill.
"Because the AIDS virus doesn't transmit very well, in the United States it is thought that there is about one transmission for every 1,000 exposures, and we might be able to reduce that further."
Still, people should never rely on such treatment to avoid contracting or spreading the virus, he cautioned. Abstinence remains the best way to avoid the illness, and using condoms is second best.
Gilliam directed the investigation while a fellow in infectious diseases at the UNC-CH School of Medicine. He now is a research physician at the Henry M. Jackson Foundation for the Advancement of Military Medicine in Rockville, Md.
A report on the findings appears in the May 1 issue of the Journal of Acquired Immune Deficiency Syndromes and Human Retrovirology, published today (Monday, July 7).
The study involved collecting semen and blood from 11 HIV-positive men before they were given what's called reverse transcriptase inhibitor therapy with delavirdine, zidovudine and didanosine. Researchers measured virus particles in those specimens and then counted them in new samples eight to 18 weeks after treatment began and again in five patients at least a year later. For comparison, the scientists also measured the AIDS virus in 11 men not receiving delavirdine and the other drugs or whose treatment had not changed for at least two months before the study started.
No significant change was observed in virus levels in the control group volunteers, who were monitored for up to 26 weeks. In the treatment group, however, levels dropped markedly, and in eight of the 11 subjects, HIV could not be detected at all. Similar results were found in blood samples.
"This study provides the first convincing evidence that reverse transcriptase inhibitor therapy effectively reduces shedding of HIV-1 in semen and may therefore reduce the spread of infection within populations," Gilliam said.
Besides Gilliam, UNC-CH authors include Drs. John R. Dyer, Susan Fiscus, Myron S. Cohen and Joseph J. Eron Jr. and registered nurse Cheryl Marcus. Other authors are Drs. Susan Zhou of the Jackson Foundation and Lynne Wathen and William W. Freimuth of the Pharmacia & Upjohn Co. of Kalamazoo, Mich.
Pharmacia & Upjohn manufactures delavirdine, Glaxo-Wellcome Pharmaceuticals produces zidovudine and Bristol-Myers Squibb makes didanosine.
"This work confirms what many AIDS researchers thought would be the case, but no one had looked at in a prospective way before," Gilliam said. "Because it also resolves the uncertainties of several earlier studies with conflicting results, we think the response will be very positive."
In the United States and Europe, antiretroviral therapy holds promise for slowing the AIDS epidemic, but also increases the possibility of transmitting resistant strains of HIV, he said. Such therapy would not be practical in Africa and the Far East because countries there and most people cannot afford the drugs.
Because the study population was small, the scientists were not able to determine which of the antitretroviral drugs was most effective in curtailing the virus.
The National Institutes of Health's General Clinical Research Centers Program and Pharmacia & Upjohn Co. supported the research.
Note: Gilliam can be reached at (301) 217-9410, Ext. 1055 (w) or 947-8004 (h). His beeper number is (301) 215-1035. Cohen's numbers are (919) 966-2536 (w) and 933-9434 (h).