Hepatitis C virus is classified into multiple genotypes based on sequence differences in the viral genome. In this study, the investigators retrospectively studied 179 patients in the United States with chronic hepatitis C to determine how genotype related to epidemiology, pathogenicity, and response to therapy. Fifty-eight percent of patients had genotype 1a, 21% had 1b, 2% had 2a, 13% had 2b, 5% had 3a and 1% had 4a.
There was no association between genotype and mode of acquisition of infection. Patients with genotypes 1a and 1b had more severe hepatitis. Twenty-eight percent of patients with genotype 1a and 26% of patients with genotype 1b had a complete biochemical response to treatment with interferon-alpha for six months. In contrast, 71% of patients with genotype 2a or 2b had a complete response to interferon therapy.
This study confirms that 1a and 1b are the most predominant hepatitis C virus genotypes in the United States and that patients infected with these viral genotypes generally have more severe liver disease and lower rates of response to interferon therapy than patients infected with genotypes 2a or 2b.