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IMPACT OF HIV INFECTION ON HEPATITIS C VIRUS (HCV) PERSISTENCE AND RE-INFECTION AMONG INJECTION DRUG USERS (IDUS)

J Grebely¹, JD Raffa², B Conway¹, C Lai³, M Krajden⁴, MW Tyndall³
¹Department of Pharmacology and Therapeutics, ²Department of Statistics, University of Waterloo, Waterloo, Ontario ³BC Centre for Excellence in HIV/AIDS, ⁴BC Centre for Disease Control, Vancouver, British Columbia

In addition to host-related factors, pathogen-related factors such as HIV infection may lead to altered host immunity against HCV. We sought to determine the role of HIV infection on the rate and characteristics of virologic clearance in HCV-infected individuals and to compare the rate of new infection to that observed in previously uninfected individuals.
The CHASE Project is a cohort study of an inner city population (consisting mainly of IDUs). The cohort data was linked with a longitudinal (1992-2005) database at the BC Centre for Disease Control containing HCV antibody and PCR assay results. Retrospective analysis revealed persistently HCV uninfected subjects along with new infections, virologic clearance, and subsequent re-infections.
We identified 926 uninfected and 658 HCV viremic subjects at baseline, with 152/658 (23.1%) spontaneously clearing viremia. HCV clearance was associated with female sex (Adjusted OR 1.48; 0.97-2.27), Aboriginal ethnicity (AOR 3.24; 2.13-4.94) and previous HBV co-infection (AOR 2.44; 1.03-5.80) and inversely associated with age <40 (AOR 0.61; 0.40-0.94) and HIV infection (AOR 0.41; 0.21-0.80). Of 173 HIV infected subjects, we could establish the order of infection in 51 (29%). Of these, 48/51 (94%) were infected with HCV prior to becoming HIV-infected, including 11/11 HIV-infected patients that cleared viremia spontaneously. HCV clearance was 10.8%, 17.4%, 21.3%, 18.2% in subjects with a nadir CD4 count of <=50, >50-100, >100-200, >200, respectively (P=0.46). New infections were documented in 172/926 (18.6%) individuals (8.1 cases/100 person-years). HCV re-infection was documented in 14/152 (9.2%) individuals (1.8 cases/100 person-years). This included 2 patients with HCV clearance that subsequently became re-infected with HCV after acquiring HIV.
In this large retrospective analysis, HIV infection and a lower CD4 nadir was associated with HCV persistence. The rate of HCV re-infection following spontaneous clearance was much lower than primary infection. Further prospective studies are required to determine whether decreased immune function caused by HIV leads to either a recrudescence of low-level viremia or decreased protection against HCV re-infection.

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