Introduction
In Europe and the USA, about 30% of HIV -positive individuals are coinfected with the hepatitis C virus (HCV) [1] HIV -infected men have been reported. HCV/HIV coinfection is characterized by more rapid progression toward severe liver disease [2–4] [5] [1,6] HIV -infected patients, especially after the dramatic decline in morbidity and mortality due to opportunistic diseases following the introduction of HAART in 1996. Previous historical studies suggest that individuals with concomitant HIV infection are far less likely to spontaneously clear HCV than patients with HCV monoinfection. It is currently recommended that individuals who are acutely infected with HCV should undergo monitoring of HCV viral load levels to determine whether spontaneous clearance is likely or whether the opportunity for early treatment should be considered [7]
At the moment, combination of pegylated interferon-α with ribavirin represents the backbone of HCV-specific therapy . With interferon-based combination therapy sustained viral response (SVR) is, however, achieved in only about 40% of chronically infected patients [1] [8]
HCV genotype and HCV viral load are major determinants of response to treatment in HCV infection. Nevertheless, host genetic factors have also been shown to influence the natural course of infection as well as response to treatment.
Cytokines play a key role in regulating antiviral immune responses and a variety of cytokine gene polymorphisms have been shown to affect natural course of and treatment response in HCV monoinfection. Transforming growth factor (TGF)-β is a multifunctional cytokine that is involved in control of cell growth, differentiation, and apoptosis of cells. In addition, TGF-β has a major regulatory role in hepatic fibrosis and cirrhosis. Importantly, the TGF-β gene is polymorphic (codon 10 and 25) leading to differences in cytokine production. Thus, patients can be classified in high, intermediate, or low producers of TGF-β according to their TGF-β genotype.
Here, we analyzed the impact of the TGF-polymorphism in response to HCV-specific therapy in HIV -positive patients with acute hepatitis C.
Patients and methods
Design and study populations
Sixty HIV -positive white patients with acute hepatitis C were enrolled into this study. Acute hepatitis C was diagnosed when at least two of the following three criteria were fulfilled within the past 4 months prior to the diagnosis of HCV infection: HCV seroconversion; alanine aminotransferase (ALT) more than 350 IU with prior normal aminotransferases, and risk exposure to HCV (modified from [9] HIV coinfected patients were treated with pegylated interferon-α and ribavirin (800 mg/day) for 24 (HCV genotypes 2 and 3) or 48 weeks (genotypes 1 and 4). Patients who were HCV RNA negative 6 months after the end of treatment were classified as sustained virological responders. All other patients were considered to be non-responders.
As a control, 148 HCV monoinfected, 201 HIV monoinfected patients, and 100 healthy individuals were included to analyze the distribution of the TGF-β genotypes.
Informed consent was obtained from each patient prior to inclusion into the study, and the study conformed to the ethical guidelines of the Helsinki declaration as approved by the local ethics committees.
Cytokine genotyping
TGF-β genotypes (TGF-β codon 10T/C and codon 25G/C) were analyzed using the cytokine genotyping tray (One Lambda, Canoga Park, California, USA) following the manufacturer's protocol allowing classification into TGF-β high (10T/T 25G/G; 10T/C 25G/G), intermediate (10T/C 25G/C; 10C/G 25G/G; 10T/T 25G/C), and low (10C/C 25G/C; 10C/C 25C/C; 10T/T 26C/C; 10T/C 25C/C) producers.
Statistics
Cytokine genotype distribution as well as treatment response rates in patients with different cytokine genotypes were analyzed using 2 × 2 contingency tables. For statistical comparisons between the groups, χ 2 statistics, Fisher's exact test, and Mann–Whitney U test were used as appropriate. To determine the effect of the TGF-β genotype in comparison to HCV load and genotype, the main established predictors of response, we stratified our patient data as HCV genotype 1 versus non-HCV genotype 1, and HCV RNA 2.0 million copies/ml or less versus more than 2.0 million copies/ml [8,9] P values less than 0.05 (two-sided) were regarded as significant.
Results
Study population
Sixty HIV -positive patients with acute hepatitis C [age, mean (range) 39.2 (25–70) years; CD4 cell count, 498.2 (148–969) cells/μl; HIV load, 26.6 × 103 (50–341 × 103 ) copies/ml; ALT, 558.4 (24–3089) IU/ml; γ-glutamyl transpeptidase (GT), 396.6 (77–962) IU/ml; HCV load, 6.5 × 106 (4.5 × 103 –47 × 106 ) copies/ml] were enrolled into this study (Table 1 ). Patients were treated with pegylated interferon-α plus body weight adapted doses of ribavirin for 24 (genotypes 2 and 3) and 48 (genotypes 1 and 4) weeks, respectively. Overall, an end-of-treatment response (ETR) was seen in 76.7% (46/60) and a SVR rate was achieved in 68.3% (41/60) of treated patients.
Table 1: Patient characteristics.
Distribution of transforming growth factor-β genotypes
Distribution of TGF-β genotypes in HIV /HCV coinfected patients [high producer 48/60 (80.4%), intermediate producer 11/60 (18.3%), low producer 1/60 (1.6%)] was comparable with that seen in healthy individuals [high producer 82/100 (82%), intermediate producer 18 (18%), low producer 0 (0%)], HIV monoinfected patients [high producer 158/201 (78.6%), intermediate producer 43/201 (21.4%), low producer 0 (0%)], and HCV monoinfected subjects [low producer 111/148 (75%), intermediate producer 35/148 (23.6%), low producer 2/148 (1.3%)], respectively. All distributions were in accordance with the Hardy–Weinberg equilibrium. Furthermore, no significant differences could be detected for demographic variables, route of infection, liver enzymes, HCV genotype, HCV or HIV load between the TGF-β genotypes in HCV/HIV coinfected patients (data not shown).
Transforming growth factor-β genotype and treatment responseRegarding the low prevalence of the low producer genotype, data analysis was based on patients with a high-producer genotype in comparison to carriers of other genotypes (non-high producer).
Patients with a high-producer genotype were more likely to achieve an ETR as compared to carriers of a non-high-producer genotype (82.4 versus 58.3%), although this difference failed to reach statistical significance (Fig. 1 a, left graph). We, however, found coinfected carriers of a high-producer genotype to have a significantly higher SVR rate than non-high-producer patients (75 versus 41.7%; P = 0.039) (Fig. 1 b, left graph).
Fig. 1: ETR and SVR rates in relation to TGF-β genotype in HIV -infected patients with acute hepatitis C. (a) ETR rates (%) in HCV/HIV coinfected patients in for subjects with a TGF-β high-producer genotype in comparison to patients with other genotypes (non-high producer ). The graph on the left gives data for all patients, irrespective of the infecting HCV genotype, whereas the graph on the right illustrates data for patients coinfected with HCV genotype 1 (left columns) or non-HCV genotype 1 (right) separately. (b) Illustrates SVR rates in HIV -infected patients with acute hepatitis C in comparison to the TGF-β genotype for all patients (left graph) and after stratification with respect to the infecting HCV genotype (right graph).
When patients were stratified according to HCV genotypes, patients with genotype 1 infection had a lower SVR rate as compared to patients infected with non-HCV genotype 1 infection (66.7 versus 76.9.6%; P = n.s.).
Importantly, an effect of the TGF-β genotypes on treatment outcome was only seen in the subgroup of patients with HCV genotypes 1 (P = 0.013), whereas SVR rates were not significantly affected by the TGF-β genotype in patients infected with other HCV genotypes (Fig. 1 b, right graph).
In addition, we analyzed our data in a stepwise forward-conditional regression model (Table 2 ). In the model the TGF-β high-producer genotype remained a strong predictor for SVR therapy (odds ratio 5.6; 95% confidence interval CI 1.3–25.7; P = 0.02), whereas HCV load and age were removed from the final regression model.
Table 2: Multivariate regression model for sustained virological response in acute HCV/HIV coinfection .
Discussion
Response to HCV-specific therapy depends on both viral and host factors. Among the host factors, cytokine gene polymorphisms have been shown to affect the response to antiviral therapy . For instance, the tumor necrosis factor-α promoter polymorphism at position −308 [10] [11] therapy in HCV infection.
Here, we studied the impact of the TGF-β gene polymorphism in response to HCV-specific treatment in HIV (+) patients with acute hepatitis C and identified the TGF-β high-producer genotype as an independent predictor of SVR. Performing a subgroup analysis, we found that the association between the TGF-β genotype and treatment response was restricted to patients with a HCV genotype 1 infection. This observation, however, needs to be balanced against the relatively small number of patients infected with a genotype other than genotype 1 in our study. Thus, we cannot exclude with certainty that the TGF-β genotype also affects treatment response in HIV -positive patients infected with HCV genotypes other than genotype 1.
TGF-β is a profibrinogenic cytokine, which has been shown to be involved in development of fibrosis in hepatocytes of patients with chronic viral hepatitis. In addition, TGF-β has been implicated in suppression of immune responses and downmodulation of growth promoting activities. Therefore, the identification of the TGF-β high-producer genotype as a predictor of response to HCV therapy is primarily counterintuitive. Supportive data are, however, obtained by Tambur et al . [12] et al. [13] et al. reported that TGF-β can downregulate HIV -1 viral replication in vitro . With respect to hepatitis C, HCV NS5A-mediated suppression of TGF-β signaling has been suggested as a step in HCV pathogenesis. Thus, the TGF-β high-producer genotype might partially compensate for the HCV-induced inhibition of TGF-β signaling thereby enabling the generation of a type 1 response. In this context it is important to note that strong antiviral type 1 immune responses have been proposed to be associated with viral clearance both during the acute phase of primary HCV infection and antiviral therapy of chronic hepatitis [14–16]
Whether TGF-β polymorphisms also affects spontaneous elimination of HCV in HIV -positive subjects remains to be clarified. Kimura et al. [17] HIV coinfected subjects displayed a similar TGF-β genotype distribution to that of healthy controls and HIV monoinfected subjects, argues against a significant impact on the natural course of HCV infection. Accordingly, Suzuki et al. [18] et al . [19] et al. [20]
Our data, however, support the importance of genetic factors for the response to HCV-specific therapy in HIV -infected patients with acute hepatitis C.
Acknowledgement
This work was supported by the Hector-Stiftung (M42).
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