Analysis of Host Genetic Factors in the Occurrence of Anemia and on the Virological Response to a Peg-interferon/Ribavirin Therapy in HIV-HCV Co-infected Patients

The treatment of HCV (hepatitis C virus) infection has made significant progress over the past decade with the therapy combining pegylated interferon (Peg-IFN) to ribavirin (RBV). The cure of HCV infection which consists to obtain a sustained virological response (SVR) (undetectable HCV RNA 24 weeks after end of treatment) is reached in more than 50% of patients infected with HCV. However, this rate is much lower, around 30 to 40% in HIV-HCV co-infected patients and sometimes can be less than 20% for patients infected with HCV genotype 1. Haemolytic anemia is a dose-limiting adverse effect which occurs frequently under RBV therapy. RBV-induced anemia represents the main cause of treatment discontinuation or dose reduction of RBV, thus limiting the chances of achieving a SVR. RBV has a large inter-individual pharmacokinetic variability and a relationship between the occurrence of anemia and RBV concentration was clearly demonstrated. However, other factors, including genetic factors, could be predictive of hematotoxicity and/or a better efficiency. In particular, IL-28B polymorphism analysis, in patients infected with HCV genotype 1, before starting antiviral therapy could predict the response to treatment (positive predictive value). The genetic polymorphism of inosine triphosphate pyrophosphatase (ITPA) is also strongly associated to a protective effect towards the RBV-induced-anemia. But most of these data are issued from studies performed in a Japanese HCV mono-infected population treated with Peg-IFN-RBV therapy for which there is no other causal variant that the rs1127354. Only few studies are reported in the literature in caucasian HIV-HCV co-infected patients. Moreover, data on RBV plasma exposure are very scarce in all these studies showing an impact of the ITPA polymorphism on the occurrence of anemia. In addition, others polymorphisms of SCL29A1/A2 and SCL28A2/A3 coding for RBV transporters, ENT (equilibrative nucleoside transporter) et CNT (concentrative nucleoside transporter) would be associated to either rapid virological response or anemia in HCV infected patients treated by Peg-IFN plus RBV. No study considering both polymorphisms of ITPA, IL-28B, SCL29A1/A2 and SCL28A2/A3 genes and RBV plasma exposure data has so far been conducted in HIV-HCV co-infected patients.

Thus, it would be interesting in a first time to assess the impact of the ITPA polymorphism on both the RBV plasma exposure and the protective effect towards RBV-induced anemia in HIV-HCV co-infected patients. This study could be helpful to the literature for possible further RBV dose adjustments according to ITPA activity.

Then, it would be relevant to further complete these data by assessing other genetic polymorphisms as IL-28B, SCL29A1/A2 and SCL28A2/A3 and thus evaluate the overall pharmacogenetic relationships towards RBV-induced anaemia and/or virological response to a Peg-IFN/RBV therapy.