Rectal herpes increases HIV plasma levels and rectal HIV shedding

Active herpes simplex virus-2 (HSV-2) in the rectum can increase the shedding of HV in the rectal tissue of HIV-positive men, according to research presented to the 44^th Infectious Diseases Society of America (IDSA) meeting in Toronto on October 12^th. High levels of shedding of HIV from the rectum could increase the risk of HIV transmission to the insertive partner during unprotected sex.

Study group and methods

The research team looked at a small group of MSM who had enrolled in a study of STIs. Six of these men were recently infected with HIV (an average of four months); 17 were chronically infected (had had HIV for a longer time). The group was relatively young (27 years old on average); slightly over half had had receptive anal intercourse in the past three months.

Participants were tested for HIV RNA by blood test (RT-PCR), and for HIV and HSV by rectal swab, at each of three study visits. HIV RNA was detectable for all men in all of the blood tests, and from over 90% of the rectal swabs.

Reasons for the study

HIV RNA levels can be higher in rectal tissue than in blood plasma. There is therefore a real risk of HIV transmission from the receptive to the insertive partner during anal sex.

Herpes typically alternates between dormant periods and active outbreaks, so called “reactivations.” HIV levels in the blood have been found to increase during HSV-2 reactivations. Previous studies have found that the risk of sexual HIV transmission is higher when other active sexually transmitted infections (STIs) are present, and that women with genital herpes have higher vaginal levels of HIV.

A team of investigators from the U.S. and Peru therefore chose to study rectal HIV “shedding” (and hence, possibly sexual infectiousness) in men who have sex with men (MSM) – particularly, how such shedding is affected by rectal herpes infection.

Herpes activation raised HIV levels

Rectal swabs tested positive for herpes virus DNA – indicating herpes reactivation – 23% of the time. There were no significant differences between visits, or between recently-infected and chronically-infected men. However, the men whose rectal swabs tested positive for active shedding of herpes virus showed higher HIV RNA levels, in both rectal swabs and blood plasma. A 10-fold (1 log₁₀) increase in rectal HSV DNA was associated with 1.38-fold higher (0.14 log₁₀) rectal HIV RNA levels. There was a similar trend for HIV in the blood plasma: for a 10-fold increase in rectal HSV DNA, the researchers found a 1.29-fold increase (0.11 log₁₀) in plasma HIV RNA levels.

The researchers acknowledged that more frequent measurements may have led to greater accuracy, and that other factors may have affected the results – such as rectal inflammation due to other causes, or even the rectal presence of semen containing HIV. Despite these limitations, they concluded that “rectal HIV shedding is frequent in men with both early and established HIV infections, rectal HIV RNA levels were on average higher than plasma HIV RNA levels, [and] concurrent rectal HSV reactivation was associated with higher rectal and plasma HIV levels ... [Herpes virus] reactivation may thus increase HIV-1 infectiousness and disease progression.”