Abstract Body

Background: Since 2000, incidence of sexually acquired hepatitis C virus (HCV) infection has increased among HIV infected men who have sex with men (MSM). Only a few case-control and cohort studies evaluating transmission risk factors were conducted, and most of these studies initially were not designed to study HCV, but HIV-related behavior and characteristics. The MOSAIC study provides a unique opportunity to study risk factors for acute HCV infection in HIV-infected MSM.

Methods: From 2009 onwards, HIV-infected MSM with an acute HCV infection (cases) were prospectively included and followed at five hospitals in the Netherlands. For each case, one to two unmatched controls were recruited from the population of HIV-infected MSM without HCV. Written questionnaires were administered, covering socio-demographics, blood-borne risk factors for HCV infection, sexual risk behavior, and drug use. Clinical data on HIV-and HCV were acquired through linkage with databases from the Dutch HIV Monitoring Foundation. Determinants of HCV infection were analyzed using logistic regression.

Results: Among 213 MSM (82 MSM with and 131 MSM without HCV infection), median age was 45.7 years (IQR:41.0-52.2). Ulcerative STI (OR:5.26,95%CI:1.72-16.1), receptive unprotected anal intercourse (rUAI;OR:5.05,95%CI:1.63-15.6), sharing sex toys (OR:3.98,95%CI:1.12-14.2), sharing straws when snorting drugs (OR:3.46,95%CI:1.41-8.47), unprotected fisting (OR:2.54,95%CI:1.01-6.42), and CD4 cell count at the last HCV negative visit prior to study entry (OR:1.74 per cube root lower, 95%CI:1.18-2.56) were independently associated with HCV acquisition. Of interest, injecting drug use was reported by only 12 men, and was not significantly associated in multivariable analysis; nor were anal rinsing, rectal bleeding, number of sex partners, meeting location, and group sex participation. No interactions were found.

Conclusions: To our knowledge, this is the largest case-control study focusing on transmission of HCV among HIV-infected MSM. Besides known risk factors for HCV (rUAI, STI, fisting, and sharing of sex toys), associations between the sharing of straws when snorting drugs, and lower CD4 cell count and HCV acquisition were found. Our study confirms sexual transmission and a role of non-injecting drug use as a risk factor for HCV transmission. Further studies are needed on the role of CD4 cell count, as it is still unclear whether a lower CD4 cell count facilitates HCV infection or is a result of acute HCV infection itself (or both).