As a consequence of shared risk factors for exposure, HIV and hepatitis C virus (HCV) are often found concurrently [1,2]. In most instances, a neutral or negative interaction results. HCV-RNA levels are increased, fibrosis rates are accelerated, and morbidity and mortality are increased [3–5]. CD4 T-lymphocyte recovery after the initiation of combination antiretroviral therapy is blunted in HIV/HCV co-infection . Furthermore, the incidence of liver-specific adverse events related to antiretroviral therapy are increased and the efficacy of HCV drug therapy is diminished [7–9].
In contrast to this prevailing negative relationship between these two chronic viral infections, there is some evidence that the abnormal lipid profile observed in many patients after the initiation of HAART may be less pronounced in those with HIV/HCV co-infection . Although compelling, this work is limited by the cross-sectional nature of the analysis. A lipid-modifying effect of HCV infection has been demonstrated in those with HCV mono-infection [11–14]. To explore this phenomenon in HIV disease further, we evaluated a cohort of HAART-treated, HIV-infected individuals followed within an academic-based clinical and research unit. Given concerns pertaining to HAART-related metabolic abnormalities and lipodystrophy, identifying factors that may perturb these effects seems relevant.
We identified HIV, HIV/HCV and HIV/hepatitis B virus (HBV) co-infected individuals initiating HAART or interferon-based HCV therapy at our Ottawa Hospital Infectious Diseases Clinics between January 1996 and June 2005 using an SPSS version 12.0 (SPSS, Inc., Chicago, Illinois, USA) computerized database. The Ottawa Hospital Research Ethics Board reviewed and approved the collection and analysis of this dataset. HIV levels and CD4 T-lymphocyte counts were recorded in the study database at baseline and at 3-month intervals thereafter. Laboratory variables including alanine aminotransferase, aspartate aminotransferase, total cholesterol, LDL, HDL, and triglycerides were collected at similar intervals. Measures closest to but not after the first day of HAART were entered as the baseline value. Qualitative HCV-RNA levels were measured using the Roche Amplicor 2.0 system (Alameda, California, USA), which possesses a lower limit of detection of 100 IU/ml. HCV-seropositive patients without a blood HCV-RNA measurement were classified as HCV infected. HCV-seropositive patients with negative HCV-RNA measurements were classified as HCV uninfected.
The date of first HAART initiation, the duration of that regimen in months, and the specific antiretroviral medications used were recorded. HAART was defined as the combination use of three or more antiretroviral agents. Patients with previous single or dual nucleoside reverse transcriptase inhibitor exposure were classified as antiretroviral experienced.
Changes in lipid levels from baseline were compared and contrasted between HIV, HIV/HCV or HIV/HBV co-infected patients by Student's t-tests. These comparisons were made at 3-month intervals after HAART initiation. Factors potentially influencing lipid levels were assessed by univariate and multivariate regression analysis. These included age, sex, HCV co-infection, HBV co-infection, alcohol use while on HAART, a history of injection drug use, baseline CD4 T-cell count, baseline HIV RNA, stavudine use and protease inhibitor-based HAART. Lipid measurements during interferon-based HCV therapy and 6 months after the completion of treatment were compared by χ2 and Student's t-tests between HIV/HCV patients achieving a sustained virological response (SVR) and those who did not.
A total of 589 HIV-mono-infected, 210 HIV/HCV and 28 HIV/HBV-co-infected subjects initiated HAART between January 1996 and June 2005. Total cholesterol or triglyceride baseline data were available on 357 (61%), 115 (55%) and 24 (86%) patients initiating HAART, respectively (Table 1). The primary lipid analysis was conducted on these patients.
A consistent, persistent and significant increase in total cholesterol from baseline was noted in HIV mono-infection but not in those with HIV/HCV co-infection (P < 0.01 at months 3, 6, 9, 12, 15, 18; P < 0.05 at months 21, 24, 27, 30; Fig. 1a). Similar trends were observed with LDL-cholesterol (P < 0.05 at months 3 and 12; Fig. 1b) and triglycerides (Fig. 1c). Changes in HIV/HBV lipid profiles from baseline after the initiation of first HAART were similar to HIV mono-infection.
The influence of HCV infection on the change in total cholesterol from baseline remained significant when controlled for key variables with the potential to influence lipid profiles, including age, sex, previous nucleoside experience, stavudine use and protease inhibitor use. These findings were consistent and persistent up to and including month 21 of therapy (P < 0.05 at each 3-month interval). In addition to HCV co-infection, the use of protease inhibitor-based therapy was consistently associated with a greater increase in total cholesterol from baseline. Despite the greater use of protease inhibitor-based therapy, dual protease inhibitor-containing regimens and high-dose ritonavir (i.e. ≥ 800 mg/day) in those with HIV/HCV co-infection (Table 1), the increase in total cholesterol was still smaller than in HIV mono-infection.
Metabolic complications including those related to lipid abnormalities resulted in the interruption of HAART in HIV mono-infection (8%) but not in those with HCV (< 1%) or HBV (< 1%) co-infection (χ2, P < 0.001). Anti-lipid drug use data were available for 70% (557/799) of first time HIV and HIV/HCV-co-infected recipients of HAART. Eight per cent of HIV-mono-infected (33/426) and no HIV/HCV-co-infected subject (0/131) initiated lipid-lower therapy while on their first regimen of HAART (P < 0.001).
Twenty-seven HIV/HCV-co-infected subjects received interferon-based HCV therapy for at least 12 weeks and had lipid results available for analysis. All but two were receiving HAART. All patients had well-compensated baseline liver function. At 3 and 6 months of treatment, and at the end of therapy, the mean cholesterol increased from baseline in those eventually achieving an SVR and remained unchanged in non-responders (P < 0.03 at each timepoint; Fig. 2). No consistent change in HDL or triglycerides was noted during or after interferon-based treatment irrespective of therapeutic outcome. A mean 0.85 mmol/l (SD 1.12) increase in total cholesterol was noted 6 months after completing treatment in eight subjects achieving an SVR. Total cholesterol increased (n = 6) or remained unchanged from baseline (n = 1) in all but one of the eight subjects. In contrast, there was no mean change from baseline in total cholesterol in subjects who did not achieve an SVR (mean −0.07 mmol/l; SD 0.65). This lipid outcome differed significantly between those with and without an SVR (P = 0.02).
Lower total cholesterol and LDL levels have been reported in those with HCV infection including those with and without advanced liver disease [11–14]. Our work suggests that this influence on the lipid profile extends to HAART-treated, HIV/HCV-co-infected patients.
The increase in total cholesterol observed in our HIV-mono-infected patients was comparable to that seen with traditional protease inhibitor plus nucleoside regimens . In contrast, minimal increases from baseline in total and LDL-cholesterol and in triglyceride levels were observed in those with HIV/HCV co-infection. This effect was consistent, persisted for at least 30 months after the initiation of therapy, and was evident irrespective of the use of protease inhibitor-containing treatment or stavudine.
As a consequence of this effect, lipid-lowering drugs were used less frequently in those with HIV/HCV co-infection on HAART in comparison with those with HIV mono-infection. This low use of lipid-lowering medication is in agreement with a cross-sectional study of 881 patients, of whom over 80% were on antiretroviral therapy . Although the long-term consequences of HIV and HAART-related hyperlipidemia is uncertain, the risk of cardiovascular disease may be increased [16,17]. These cohort studies have not consistently controlled for viral hepatitis co-infection. This seems justified on the basis of our findings.
To support the hypothesis further that HCV perturbs the effect on HIV and HAART on the lipid profiles of HIV/HCV-co-infected subjects, we evaluated the effect of interferon-based HCV therapy on lipid profiles. It has been reported that cholesterol and triglyceride levels increase in HCV-mono-infected patients receiving interferon-based therapy . Furthermore, interferon-based HCV treatment recipients achieving an SVR to therapy were found to have diminished steatosis 24 weeks after treatment completion . Our results suggest that lipid characteristics are also perturbed in HIV/HCV-co-infected subjects receiving interferon-based therapy. While on therapy, total and LDL-cholesterol levels increased in concert with a decline in HCV-RNA levels. These levels remained elevated only in those achieving an SVR.
There are several lines of evidence suggesting that lipid metabolism and the HCV life cycle are intertwined. It is known that in plasma HCV associates with LDL, very low density lipoprotein and HDL-cholesterol [20–23]. In particular, HCV envelope glycoprotein (E2) and HCV core protein associate with very low density lipoprotein and LDL particles [24–27], and HCV core protein has been identified within cellular lipid storage droplets . Furthermore, the HCV viral load is markedly reduced in HCV-infected patients after LDL plasmapheresis . HCV cell binding and entry may be dependent on LDL receptor expression [26,30,31], and HDL may facilitate HCV entry through the class B type 1 scavenger receptor . The use of these receptors may not only explain how HCV gains intracellular entrance, but may also provide a mechanism by which HCV perturbs the lipid profile (i.e. by enhanced cellular lipid uptake). There is also growing evidence that HCV perturbs lipid metabolism, assembly and excretion of lipid complexes from within the hepatocyte [33–35]. The true nature of this interaction remains to be fully determined.
There are limitations to consider when evaluating these findings. Data were not available at every timepoint for every parameter for every patient. Despite this, no relevant bias in data collection was identified. Although planned a priori, multiple comparisons were made during the course of this analysis. As a precaution, only statistically significant results that were consistent and persistent over time were reported. Diminishing numbers of patients on therapy over time limited our ability to compare HIV/HBV patients with the other groups after the first 6 months of therapy. This same issue influenced our ability and the appropriateness of comparison between HIV-mono-infected and HIV/HCV-co-infected patients beyond 30 months of HAART. HCV-RNA testing in HCV-seropositive patients was incomplete (60%), creating the potential for misclassification. This would serve to diminish the true effect size of HCV co-infection on the lipid profile.
Despite these concerns, our work demonstrates that HCV infection has a consistent and long-term influence on antiretroviral-related lipid changes after the initiation of HAART. As a clinical consequence, less lipid-lowering medication was required in those with HIV/HCV co-infection, and few co-infected patients interrupted their therapy as a result of HAART-related metabolic complications. This beneficial influence is lost in those patients who achieve an SVR with interferon-based HCV treatment. The long-term effect of this phenomenon on cardiovascular event rates merits closer evaluation.
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