Hepatitis C virus. Aspects on natural history, antibody response, and viral quantification

Abstract

Hepatitis C virus (HCV) is the major cause of parenterally transmitted non-A, non-B hepatitis, and is associated with chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Despite the screening of blood products nosocomial spread of HCV continues to occur. We investigated an outbreak of HCV involving three patients following percutaneous coronary intervention, and found that the most likely mode of transmission was contamination of a multidose vial of saline used for the flushing of intravenous catheters. It may thus be prudent to restrict the use of multidose vials in addition to the implementation of vigorous adherence to standard hygienic procedures to prevent recurrence of similar outbreaks.To investigate the role of the HCV glycoproteins in the viral infection of mammalian cells, we developed a VSV/HCV pseudotyped virus. Genomic regions encoding the putative ectodomain of the HCV E1 (amino acids 174 to 359) and E2 (amino acids 371 to 742) glycoproteins were appended to the transmembrane domain and cytoplasmic tail of vesicular stomatitis virus (VSV) G protein. When infected with a temperature-sensitive VSV mutant (ts045) and grown at 40.5°C, cells transiently expressing the E1 or E2 chimeric glycoprotein generated VSV/HCV pseudotyped virus. The resulting pseudotyped virus exhibited the ability to infect mammalian cells and sera derived from chimpanzees immunized with the homologous HCV envelope glycoproteins neutralized infectivity.Using the pseudotyped viruses, we analyzed sera from acute, chronic and HCV RNA negative seropositive untreated patients. Sequential sera from 9 out of 10 patients collected during the acute phase of infection were found to have intermittent viremia, elevated ALT level, and detectable neutralization activity against pseudotype virus. Patients with chronic HCV infection displayed detectable HCV RNA without a significant variation in ALT level, and a majority (>90 %) failed to display a detectable neutralizing activity.In order to evaluate the progression of liver fibrosis associated with HCV infection, two liver biopsy specimens obtained prior to anti-viral therapy from 98 patients with HCV were scored and evaluated using statistical methods appropriate for ordered categorical data. Greater progression of fibrosis was seen with increasing time between the biopsies. Likewise, the change in fibrosis score was significantly more pronounced in the 11 patients whose first biopsy was obtained within the first year after acquiring HCV. A multivariate logistic regression analysis showed that interface hepatitis in both biopsies, the time interval between the biopsies, and age at first biopsy were associated with change in the fibrosis score. In addition we found that higher age at the time of infection was associated with development of cirrhosis, that moderate intake of alcohol was associated with fibrosis progression, and that an inflammatory response in the form of moderate interface hepatitis in the first biopsy was not necessarily associated with greater progression of fibrosis if the second biopsy showed mild interface hepatitis. However, having moderate interface hepatitis later in the course of infection as reflected by the second biopsy may be detrimental.An enzyme immunoassay (EIA) has recently been developed for the HCV core antigen. To evaluate the association between core antigen and HCV RNA levels with regards to the change in liver histology over time, as well as to study the effect of duration of storage on viral load results, sequential sera were analyzed from 45 patients. A relatively strong association was found between the core antigen and HCV RNA concentrations (rs=0.8), with a core antigen level of 1 pg/ml corresponding to approximately 1,000 IU/mL. No association was found between HCV RNA or core antigen levels and stage of fibrosis, progression of fibrosis, necroinflammatory grade, steatosis, genotype, alanine aminotransferase (ALT), or alcohol consumption. However, a significant association was demonstrated between the storage time of the samples and both HCV RNA and core antigen concentrations.