Interpretation of undetectable hepatitis C virus RNA levels in HIV-hepatitis C virus co-infection

Individuals with positive hepatitis C virus (HCV) antibody titres, normal transaminase levels, and undetectable HCV-RNA levels are generally considered to have cleared previous hepatitis C infection. We report the emergence of plasma HCV RNA within a cohort of HIV and HCV seropositive/plasma HCV-RNA-negative patients initiating highly active antiretroviral therapy. Our observations challenge conventional wisdom that HCV polymerase chain reaction-negative patients with normal liver enzymes are ‘cured'. The diagnosis of chronic hepatitis C virus (HCV) is based on antibody serology and HCV-RNA testing. In general, individuals with positive HCV antibody titres, normal transaminase levels and undetectable HCV-RNA levels are considered to have cleared previous infection with HCV [1]. In several circumstances the reliance on these technologies for the diagnosis and exclusion of chronic viral infection may be misguided [2]. Using the example of hepatitis B, cases in which anti-hepatitis B serum-positive and hepatitis B serum antigen-negative patients have developed fulminate hepatitis in concert with the emergence of hepatitis B serum antigen positivity have been reported in transplantation patients [3,4]. This has also been reported in patients initiating highly active antiretroviral therapy (HAART) in HIV treatment [5]. We report the emergence of plasma HCV RNA within a cohort of HIV and HCV-seropositive/plasma HCV-RNA-negative patients initiating HAART. As part of an evaluation of the long-term effects of HAART on HCV-RNA levels in HIV–HCV-co-infected patients HCV-RNA levels were measured immediately before the initiation of HAART and 3, 6, and 12 months thereafter. Frozen (−70°C) plasma specimens collected between January 1996 and August 2001 at the Ottawa Hospital Immunodeficiency Clinic were tested using the Roche Amplicor 2.0 quantitative HCV-RNA assay (lower limit of detection 600 IU/ml) (Roche Diagnostics, Branchburg, NJ, USA). All HIV and HCV-seropositive individuals who received HAART for a minimum of 6 months and achieved HIV-RNA suppression below 500 copies/ml were identified. Of 108 HIV and HCV-seropositive patients who initiated HAART during this period, 50 met the inclusion criteria and had serial frozen plasma specimens available for testing. The baseline characteristics were similar between those included in the analysis and the 15 who were excluded because frozen specimens were unavailable (data not shown). Of the 50 HCV-seropositive individuals assessed, HCV-RNA levels were undetectable at baseline in 10. These individuals did not differ clinically from those with detectable HCV-RNA levels at baseline (Table 1). Baseline transaminase levels were within normal limits (i.e. < 40 IU/l) in eight of the 10 individuals and were within 1.5 times the upper limit of normal in the other two. In four cases, HCV-RNA levels subsequently became positive after the initiation of HAART. Transient increases in transaminase levels occurred concurrently with the emergence of HCV polymerase chain reaction (PCR) positivity. A review of medical records does not suggest acute re-infection during the period of evaluation. The other six individuals remained HCV-RNA negative at all measured timepoints.Table 1: Patients with undetectable hepatitis C virus RNA compared with the remaining cohort.Several factors potentially influencing these observations were considered. Individuals selected for this evaluation remained on HAART for at least 6 months, had relatively high CD4 T-lymphocyte counts, and lacked clinical or laboratory evidence of hepatic decompensation. The baseline transaminase levels in this cohort were within or near the normal range. These factors should be considered when applying the results of this study to other HIV-HCV-co-infected populations. The normal variability observed with the repeat testing of plasma HCV RNA is generally less than 1 log10 [6]. In all four cases, the increase in plasma HCV-RNA levels was greater thanhan 4 log10, suggesting that these results are not a reflection of normal measure to measure variability above and below the lower limit of detection. It is possible that PCR results reported as undetectable at all measures by the quantitative system may have been positive by more sensitive assays. The routine use of HCV-RNA detection systems with low limits of viral detection in the HIV-HCV-co-infected population is warranted. The preparation of specimens and the duration of frozen storage may effect quantitation of the HCV-RNA level [7]. However, the HCV-RNA levels at baseline and months 3, 6, and 12 were not found to correlate with the duration of frozen storage, suggesting that this parameter did not have a significant effect on these results (data not shown). Notwithstanding these limitations, our observations challenge conventional wisdom that HCV PCR-negative patients with normal liver enzymes are ‘cured'. In fact, it may be misguided to believe that infection with HCV is ever fully cleared. Even in those with normal transaminase levels and plasma HCV PCR negativity, low-grade or latent infection may remain, either within the parenchyma of the liver or in extrahepatic reservoirs, including dendritic cells and B lymphocytes [8,9]. The perturbation of this state, in these cases by the immune modifying effects or the direct liver toxicity of HAART, may lead to biochemical, virological, and clinical expression of chronic HCV infection.

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