Mixed genotypes in Hepatitis C virus infection

BARÉ PATRICIA; PÉREZ BIANCO RAÚL

Hemophilia

Intech Open Access Publisher

Año: 2012; p. 97 - 110

Virtually, all hemophiliacs who received clotting factor concentrates prior to implementation of viral inactivation techniques became infected with hepatitis C virus at the time of the first infusion (Morfini M et al, Vox Sang 1994; Lee C et al, Haemophilia 2002; Ragni M, Haemophilia 2010). Prevalence rates of HCV infection up to 100% were reported in hemophilia patients treated with concentrates before 1985 (Yee TT, Gut 2000). Even though the introduction of heat-treated factor concentrates progressively decreased HCV transmission, the true risk ended when blood donor screening for antibodies against HCV was introduced in 1992 (Morfini M et al, Vox Sang 1994; Franchini et al, 2001; Lee C and Dusheiko G, 2002; Tagliaferri A et al, Haemophilia 2010). Nowadays, viral inactivation and recombinant technologies have effectively prevented transfusion-transmitted viral pathogens in hemophilia. Though, due to the past chronic infections that occurred before viral inactivation procedures, transmissible agents continue to affect hemophilic population and hepatitis C represents a leading cause of morbidity and mortality in patients with hemophilia (Plug I et al, J Thromb Haemost, 2006). HCV mixed genotype infections Since clotting factor concentrates were manufactured from many thousand of donors, the same patient was likely to undergo multiple exposures to the hepatitis C virus (Jarvis LM et al, Haemophilia 1995, Zoulim F et al, J Hepatol 1999). Consequently, several HCV genotypes circulating simultaneously were observed in adults with hemophilia (Eyster, M.E. J Infect Dis 1999; Schröter M J Clin Virol 2003). Moreover, the transmission of more than one genotype from a single factor concentrate has also been reported, suggesting equal transmission of all viral strains with a subsequent selection of the dominant strains (Nainan OV, J Gen Virol. 2006). When individuals are infected with more than one genotype, different factors may cause that one viral variant prevail upon the others and their correct identification is difficult to achieve. As a result of immunologic pressure, genetic interaction between virus and host, or treatment intervention, the establishment of the dominant genotype may change over time (Schröter M J Clin Virol 2003, Eyster, M.E. J Infect Dis 1999). The existence of different genotypes in different tissues of the same patient has been previously demonstrated (Radkowski M et al, J Virol 2002, Roy K M et al, J Med Virol 1998). Particularly, peripheral blood mononuclear cells (PBMC) can harbor distinct HCV variants that are not detected in plasma samples (Di Liberto G et al, Gastroenterology 2006, Roque-Afonso AM et al, J Virol 2005). Importance of HCV genotype analysis Hepatitis C virus (HCV) genotype has been described as an independent response predictor for antiviral therapy. Its analysis, in combination with viral load, serves to optimize the therapeutic regimen (Zeuzem S et al, J Hepatol 2004). Considering the fact some genotypes could be more resistant than others (Hayashi N et al, J Gastroenterol 2006), most treatment protocols require the correct identification of the infecting HCV genotype to provide the dose and duration of antiviral therapy. The currently available genotyping techniques are not suitable to detect multiple HCV genotypes due to the fact that they are designed to identify only the dominant HCV genotype. When several genotypes are present, direct sequencing methodologies still may not detect the minor genotypes (Hnatyszyn HJ. Antivir Ther 2005; Blackard J.T., K.E. Sherman J Infect Dis 2007; Nainan OV, J Gen Virol. 2006). Despite the fact that cloning would be the correct technique to assess their identification, it is complex to achieve in a routine diagnostic laboratory. Hence the detection of HCV mixed infections is still a matter of concern in clinical practice. Revealing the occult genotypes might be necessary to choose the adequate antiviral therapy because strains that are not detected could have an unexpected impact on treatment. Furthermore, recurrence from this reservoir has been suggested (de Felipe B et al, J Viral Hepat 2008; Lee WM, J Infect Dis 2005). Evidence of occult HCV infections in cell culture experiments With the use of a cell culture system that allows the detection of the HCV genome during prolonged time periods (Baré P et al, JGen Virol 2005), we investigated the presence of HCV in peripheral blood mononuclear cells of a group of hemophilic patients. Investigating HCV genotypes associated to lymphoid cells and comparing them to the HCV genotypes found in plasma samples, we previously demonstrated the presence of occult HCV mixed-genotype infections in 62% of 16 patients with hemophilia (Parodi C et al, Haemophilia 2008). Using the same non-stimulated cell culture system, we also analyzed the persistence of HCV genotypes up to 10 years of infection in HCV-HIV coinfected patients (abstract 1055, Liver Meeting 2010, publication in process). In our experiments, distinct HCV genotypes associated to PBMC and not present in serial plasma samples were verified but also maintained for long-time periods (7 to 10 years) in coinfected subjects. Therefore, mononuclear cells might be acting as an independent viral reservoir in this cohort whether or not HCV replicates inside these cells. In addition, our data suggested that genotypes of past infections may remain. Given that cell culture and cloning methodologies are time-consuming and difficult to perform, the use of a reliable genotyping technique in combination with the analysis of multiple time points could contribute to the correct identification of the infecting HCV genotypes and in consequence, it might help to provide the proper dose and duration of antiviral therapy. The clinical and therapeutic implications of lymphotropic HCV variants related to their persistence requires further investigation, especially in hemophilic HIV/HCV coinfected persons. The following issues will be discussed in the chapter: 1. Difficulties of assessing the correct genotype identification in hemophiliacs in which mixed-infections are present, 2. Different factors that could be associated to their presence and long-term persistence in hemophilic patients (ex: HIV coinfection) 3. HCV lymphotropism and its consequences 4. Evidence in agreement and against HCV replication in lymphoid cells. 5. Long-term persistence of HCV lymphotropic variants. Its potential clinical impact.