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Longitudinal study of homosexual couples discordant for HIV-1 antibodies in the Baltimore MACS Study
J Palenicek1, R Fox, J Margolick
1Department of Epidemiology, Johns Hopkins School of Hygiene and Public Health, Baltimore, MD 21205.
Insights
Despite engaging in high-risk sexual activity, HIV-1 seronegative partners in discordant couples showed no signs of infection. The reasons for this lack of transmission remain unexplained, despite extensive testing and analysis.
Area of Science:
- Virology
- Immunology
- Epidemiology
Background:
- Human Immunodeficiency Virus type 1 (HIV-1) transmission dynamics within serodiscordant couples are crucial for understanding and preventing spread.
- Previous studies suggest sexual contact is a primary mode of HIV-1 transmission, particularly unprotected anal intercourse.
Purpose of the Study:
- To investigate the potential for HIV-1 infection in antibody-negative partners within serodiscordant couples.
- To identify factors associated with the lack of HIV-1 transmission from seropositive to seronegative partners.
Main Methods:
- Assessment of 36 HIV-1 serologically discordant couples from the Baltimore Multicenter AIDS Cohort Study (MACS).
- Concurrent follow-up of HIV-1 seropositive and seronegative couples for comparison over 1 year.
- Utilized viral culture, p24 antigen testing, and polymerase chain reaction (PCR) for HIV-1 DNA to detect infection in seronegative partners.
- Analyzed T-lymphocyte subsets (CD4, CD8), natural killer cells, and antibodies to common viruses (HSV-1, EBV, CMV, HSV-2).
Main Results:
- None of the HIV-1 seronegative partners in discordant couples showed evidence of HIV-1 infection despite reported high-risk sexual activity.
- No significant differences were observed in CD4, CD8, or natural killer cell counts between discordant and concordant couples.
- Discordant seronegative men had a lower prevalence of antibodies to herpes simplex virus type 2 compared to their seropositive partners.
Conclusions:
- The study found no detectable HIV-1 infection in seronegative partners of discordant couples, even with high-risk sexual behavior.
- The mechanisms preventing HIV-1 transmission in these cases remain unexplained.
- Factors such as sexual activity, immune cell profiles, or viral stage did not appear to be associated with the lack of transmission.
Abstract:
Thirty-six sexually active couples serologically discordant for human immunodeficiency virus, type 1 (HIV-1), within the Baltimore Multicenter AIDS Cohort Study (MACS) were assessed to determine whether evidence of HIV-1 infection could be detected in the HIV-1-antibody-negative partners and whether factors associated with lack of transmission of HIV from the seropositive to the seronegative partner could be ascertained. Six HIV-1 seropositive couples and 18 seronegative couples were followed concurrently for comparison. None of the seropositive subjects had an AIDS-defining illness at entry into the study, and all subjects were followed for 1 year. A separate evaluation of unprotected anal receptive and insertive intercourse between discordant couples indicated high-risk activities for a median of 40 months, as reported by the HIV seropositive partner. Despite this finding, none of the HIV-1 seronegative men in discordant couples had evidence of HIV-1 infection by viral culture, p24 antigen testing, or polymerase chain reaction for HIV-1 DNA. Discordant seronegatives and seropositives did not differ from concordant seronegatives and seropositives in numbers of circulating CD4, CD8, and natural killer lymphocytes or in prevalence of antibodies to herpes simplex virus, type 1, Epstein-Barr virus, or cytomegalovirus, except that discordant seronegative men were less likely than their seropositive partners to have antibodies to herpes simplex virus, type 2. The reason for the apparent lack of HIV-1 infection in seronegative discordant individuals remains unexplained and did not appear to be associated with type of sexual activity, T-lymphocyte subsets or natural killer cells, or early stage of HIV-1 disease.