A five year study of 937 HIV-positive men receiving little or no anti-retroviral treatment has shown that men who had any unprotected receptive anal intercourse (RAI) and who were thus exposed to semen had more rapid CD4 cell declines than men who avoided unprotected RAI.
The study followed men recruited to the MACS cohort between 1984 and 1985, and tracked their sexual behaviour and CD4 counts during the period before anti-retroviral treatment became widespread, in order to get the purest possible information on the potential negative effects of unprotected RAI.
Most men reported only one or two RAI partners during the twelve months prior to their rapid CD4 cell loss, but this level of URAI was in itself associated with greater CD4 cell loss than avoidance of unprotected anal intercourse. Men who reported any U-RAI during the previous twelve months were twice as likely to experience a CD4 cell decline compared to men who avoided U-RAI. The risk of CD4 cell loss increased with each URAI partner reported during the previous 12 months. People who reported 8 or more RAI partners during the previous 12 months were at four times greater risk of experiencing a rapid CD4 decline during that period.
Paradoxically, men who consistently reported a high number of RAI partners throughout the study period were at much lower risk of rapid CD4 decline, a finding that the research group cannot explain. They suggest that these individuals (numbering less than 4% of the cohort) may have been naturally more resistant to the effects of HIV infection, as evidenced by their relative lack of CD4 decline.
The study cannot determine whether the cause of the CD4 decline was re-infection with HIV, exposure to other sexually transmitted infections, or some immunosuppressive effect of semen itself. Recreational drug use did not affect the rate of CD4 cell loss, and the only sexually transmitted infections analysed were syphilis and gonorrhoea. An episode of either of these infections increased the risk of a rapid CD4 decline by around 70% in any 12 month period.
The study cannot provide any information about the effects of U-RAI in individuals currently taking anti-retroviral treatment since too few men in the study received anti-retroviral treatment, and the effects of this treatment would have been modest in any case.
Reference
Wiley DJ et al. Evidence that anoreceptive intercourse with ejaculate exposure is associated with rapid CD4 cell loss. AIDS 14: 707-715, 2000.