Sexual role and transmission of HIV Type 1 among men who have sex with men, in Peru

Abstract

In Latin America, men who have sex with men (MSM) have traditionally practiced role segregation--that is, the adoption of a fixed role (insertive or receptive) rather than a versatile role (both practices) during anal sex. Previous modeling has shown that role segregation may yield a lower incidence of human immunodeficiency virus (HIV) type 1 infection, compared with role versatility; however, the modeling assumed no risk of acquiring HIV-1 during insertive sex, which is now recognized as unlikely. We reexamine the issue by use of a deterministic model incorporating bidirectional transmission and data from a cohort study of MSM in Lima, Peru, to demonstrate the potential effects of role segregation on the trajectory of the HIV-1 epidemic. In Lima, 67% of MSM reported segregated roles in their recent male partnerships. A population of MSM with identical contact rates but complete role versatility would have twice the prevalence of HIV-1 infection throughout the epidemic's first 3 decades. Preferential mixing among versatile MSM does not change overall prevalence but affects which individuals become infected.

Figures

Figure 1

Sexual identity, role identity, and reported role with last 3 male partners, for cohort of 254 Peruvian men who have sex with men (MSM).

Figure 2

Association of role identity with sexual identity (A) and role behavior (B). A, P<10-11, Fisher’s exact test for independence, excluding nonresponders. B, Underlined nos. indicate concordant identity and behavior. Likelihood ratio tests on nested log-linear models were done for (main effects, concordance) vs. (main effects) (P<.001).

Figure 3

Respondent role identity and respondent’s perception of partner’s role identity (n = 582), for any of the last 3 partners.

Figure 4

HIV-1 prevalence in 3 simulated populations of men who have sex with men (MSM), by year of epidemic. The mean no. of partners/ year was 24 in all populations, and the proportion of MSM with versatile sexual behavior was 30% (line A; comparable to the Peruvian cohort), 100% (line B), and 10% (line C). All populations had random mixing and a 5-fold difference in infectivity, for receptive vs. insertive behavior.

Figure 5

HIV-1 prevalence in simulated populations of men who have sex with men, by year of epidemic. Models were run with a 2-fold (A) and a 10-fold (B) difference in infectivity, for receptive vs. insertive behavior, and with no infectivity for insertive behavior (C). All populations had random mixing. In each graph, the 3 lines correspond to the same parameter sets as in figure 4.

Figure 6

Disease prevalence at year 20 of epidemic, across all model runs. A, Natural log of overall HIV-1 prevalence in 605 model runs. This is seen to be mostly a function of contact rate (which determines section in which points are plotted) and the initial fraction of the population that is versatile (which possesses a strong positive correlation with the log value for HIV-1 prevalence within each contact level). B, Relative-risk measure (described in Results) as a function of role assortativity.