Biología molecular del virus de la Hepatitis C en la toma de decisiones clínicas

Abstract

The search for markers that can predict this natural history of the disease facilitates clinical decision making. The identification of genetic markers facilitates the management of the information, due to they are markers that remain stable throughout the entire infectious process without alteration with the evolution of the disease. This fact is an improvement over the classic biochemical marker, which itself is influenced by the state of the disease in which it is determined. Immunological genetic markers are of great interest. Natural immunity is the main defense barrier against viruses. In addition, they are related to inflammatory processes, so they are in direct connection with some of the complications that result from infection with the hepatitis C virus (HCV). The aim of this work is to search for immunological genetic markers that can explain the natural evolution of hepatitis C virus infection in the patient coinfected with the human immunodeficiency virus (HIV), addressing three clinical points of especial interest, such liver fibrosis progression, identification of patients with high likelihood of experience spontaneous viral clearance, and early prediction of treatment induced side-effect. Liver fibrosis progression is the main complication of HCV chronic infection. This paulatine liver fibrosis progression lead to liver cirrhosis, end-stage liver disease and, finally hepatocellular carcinoma. It should be noted that the liver fibrosis progression is not cause by the HCV it-self (non-cytopatic virus), but mediated by host immune system. Consequently, the study of immunological markers could be essential in sense to predict liver fibrosis progression. In this sense, this doctoral tesis project is constituted by two studies designed to evaluate the influence of human leukocyte antigens type B (HLA-B) on the progress of liver fibrosis. The first of these studies, is a retrospective longitudinal study, which includes non-cirrhotic HIV/HCV co-infected patients naïve to HCV therapy. The evolution of liver fibrosis was measured using an indirect and validated proceduce as liver stiffness. The main outcome variable was liver fibrosis progression, defined as an increase of liver fibrosis stage of at least with one degree. The study included 104 patients HIV/HCV co-infected patients. Baseline liver fibrosis stage distribution of the population was: 62 patients with liver fibrosis stage consistent with F0-F1 (59.6%), 22 patients with liver fibrosis stage consistent with F2 (21.2%), and 20 patients with liver fibrosis stage consistent with F3 (19.2%). During a mean follow-up of 54.6 months, it was observed that those patients bearing HLA-B*18 showed a higher (73.3%) and faster liver fibrosis progression (24 [IQR: 8-29] months) than those not carrying HLA-B*18 (38.2%, 34.5 [IQR: 14.7-51.2] months). This association was also observed when was considered the development of F3-F4 liver fibrosis as end-point among F0-F2 patients (HLA-B*18pos: 69.2%; 18 months [6.5–37] vs HLA-B*18neg: 28.2%; 37 months [IQR: 19–52]; p = incluir). In the second study, it was evaluated if HLA-B*18 had a strong influence on liver fibrosis progression in patients who had previously failed to therapy. The study had the same design that the previous study with the main outcomes. Sixty-five HIV/HCV treatment experienced co-infected with mean follow-up of 53 months. As we have observed in HIV/HCV untreated patients, HLA-B*18 carrying treatment experienced patients showed a higher and faster liver fibrosis progression (81.1%; 24 months [IQR: 8-43]) than those not bearing HLA-B*18 patients (38.9%; 39.5 months [IQR: 14.7-56.2]). This relationship was also observed in the development of cirrhosis (F3-F4) from minimal fibrosis stage (F0-F2) (HLA-B*18pos patients: 77.7% vs. HLA-B*18neg patients: 29.2%). From both studies, it can be concluded that HLA-B*18 is related with a higher and rapid liver fibrosis progression in HIV/HCV both naïve and treatment experienced patients. The determination of the HLA-B*18 couCL help to identified those patients in which treatment shouCL be implemented prioritary due to the higher risk of develop advanced liver fibrosis stage at short-term. The polymorphisms of the interleukin 28B gene are of interest to differentiate patients who are going to show spontaneous clearance of HCV during the acute phase of the infection. The positive predictive value of this marker has been estimated on 60-64%, clearly inefficient in clinical decision making. Consequently, despite international clinical guidelines recognize the value of the IL28B, can not recommend the implementation of this marker in routinary clinical practice. This is due to IL28B miss-classified a large number of patients. Thus, there are patients bearing interleukin 28B CC who do reach spontaneous viral resolution, and, in contrast, patients carrying the unfavorable polymorphisms who experience viral clearance. Due to this spontaneous viral resolution is mediated by host immune system, we evaluated the impact of HLA molecules and Natural Killers (NK) killer immunoglobulin-like recpetors (KIRs) on the rate of spontaneous viral clearance in HIV/HCV co-infected patients. A prospective transversal study incluiding HIV/HCV coinfected patients was conducted. It was included two groups of patients: i) patients who experienced spontaneous viral clearance, defined as presence of HCV-antibodies confirmed by RIBA-III with undetectable viral load non-induced by therapy; ii) HCV chronically infected patients, defined as detectable serum HCV viral load of more than one year. The study population was constituted by 138 patients, 57 patients (41.3%) with self-limiting infection, and 81 patients (58.7%) with chronic infection. In our study, IL28B showed a negative predictive value of 81.5% and a positive predictive value of 61.6% for spontaneous viral clearance. We identified HLA-B*44, HLA-C*12 and KIR3DS1 variants to be associated with spontaneous HCV clearance, showing a negative predictive value of 77.4%, 85.7% and 86.2%, respectively. We developed an algorithm including HLA-B*44, HLA-C*12, and KIR3DS1 in sense to optimize the prediction of spontaneous viral clearance. The presence of at least one of the three markers (defined as an unfavorable genetic profile [UGP]), in combination with IL28B unfavorable genotype showed a negative predictive value for spontaneous viral clearance of 100%. In the same way, the absence of these three genetic markers (defined as favorable genetic profile [FGP]) in combination with the IL28B CC genotype reach a positive predictive value for spontaneous viral clearance of 74.1%. We concluded that the determination HLA-B*44, HLA-C*12, and KIR3DS1 significantly improves the predictive value for spontaneous HCV clearance, identifying those patients with a high likelyhood of develop HCV chronic infection. espite the current standar of HCV therapy consist on the combination of at least two direct-acting antiviral drugs (DAAs) in absence of interferon (IFN), there stil are some situation where IFN use is recommended. For example, in those patients infected with HCV genotype 3, population with lower treatment-induced healing rate, inclusion of pegylated interferon-based to DAAs is recommended in sense to increase the likelyhood to have a success treatment outcome. However, the use of IFN significantly increase the rate of side effects and discontinuation of therapy by this reason. The main adverse effect related to IFN-use is the development of thrombocytopenia. Currently, the mechanism of IFN-induced thrombocytopenia is unknown. Nevertheless, it has been suggested that, due to administration of pegylated interferon modulates the activity of the immune system (especially NK lymphocytes), the induction of thrombocytopenia could be immune-mediated. We conducted a prospective longitudinal study including HIV/HCV chronically infected patients treated with Peg-IFN/RBV to evaluate the impact of KIRs genotypes in the development of thrombocytopenia secondary to pegylated interferon-based regimens. A total of 58 HIV/HCV co-infected naïve patients were scheduled to receive their first course with pegylated interferon plus ribavirin. Platelet count was determined at baseline and at weeks 1, 2, 4, 8 and 12 of the treatment. The end point of the study was the presence of thrombocytopenia, considering platelet count <150,000 cells/mL. The 34.4% of patients developed thrombocytopenia. We identified the absence of KIR2DS2 as risk factor for the development of thrombocytopenia. In this sense, the 54.2% of patients with absence of KIR2DS2 and the 22.5% of patients bearing KIR2DS2 developed thrombocytopenia (p = poner). Furthermore, the development of thrombocytopenia was faster in those patients with absence of KIR2DS2 than in those bearing this immune-genetic marker (6.6 weeks vs. 10.3 weeks; p = incluir). In conclusion, our study found that the absence of KIR2DS2 is associated with a greater decline in total platelet count, lead in a faster development of thrombocytopenia during pegylated interferon-based regimens in HIV/HCV coinfected patients. Our results provide the first step forward to the development of a biomarker with capacity to predict one of the most significant adverse events during IFN therapy, which could be applied in different scenarios where this drug is used (such HCV genotype 3 treatment).