Does the outcome of HCV infection vary with the infecting virus type?
Posted by ajcann on September 26, 2007
Hepatitis C virus (HCV) infection is a major cause of chronic liver disease that can lead to appreciable morbidity including cirrhosis and hepatocellular carcinoma (HCC). HCV can be classified into several genotypes based on variations in the nucleotide sequence of its genome. The infecting HCV type has been shown to be clinically important because it predicts response to antiviral therapy, with infection by type 1 being associated with the most resistance to treatment. There is no consensus as to whether differences in the clinical and histological severity of liver disease can be explained by differences in the infecting type. Several studies suggest genotype 1b to be associated with more severe disease, but most have found little or no influence of genotype on disease progression. Similar ambiguity surrounds the study of the role of HCV genotypes in spontaneous viral clearance. Some studies have found no association between the viral type and the spontaneous clearance of HCV RNA, with host factors like sex seeming to be more important, while other studies have suggested that infection by genotype 1 or 1b might be less likely to clear spontaneously when compared with infection by other genotypes.
The aim of this study was to investigate whether the HCV type might influence the clinical outcome of infection. Study serum samples were assembled from 749 individuals enrolled into the UK HCV National Register from which data on clinical outcomes were determined. The prevalence of HCV type 1 among those who cleared infection was 69% and among those who remained HCV RNA positive was 51%: type 1 infections were more likely to be HCV RNA negative than non-1 types. Type 1 infections were also more likely to be associated with histological stage scores above the median when compared with non-1 types. In conclusion, HCV type 1 infection was more often HCV RNA negative, suggesting that spontaneous clearance may occur more commonly with this type. Among the RNA-positive infections, type 1 infection may be more aggressive than types 2/3.
September 27, 2007 at 7:18 pm
HCV is really interesting. Quasispecies or intragenotypic differences within a same genotype, that too in the same person is characteristic of hepatitis C virus. Don’t know whether this specific term is ascribed to any other pathogen.
March 3, 2008 at 7:31 am
Quasiespecies is a term that was first ascribed to HIV due to its high variability at the genotypic level. This variability is the result of the high mutation rate of the HIV reverse transcriptase. HCV in that sense is very much like HIV and that is why just like HIV, it is able to “escape” from the immune response that is generated by the body. In both cases, the vigorous antibody response that the body generates to clear the infectiou becomes essentially useless since by the time the antibodies are generated, the virus has mutated enough not to be “recognized” by these antibodies.