A new method for determining HCV RNA genotype using 5′ UTR sequence *
The determination of HCV genotype and viral load are important in the evaluation of interferon therapy for chronic hepatitis C. The type-specific PCR method employing type-specific primers in the core region and the immuno serological method (ELISA) are commonly used for genotype classification. However, especially with the ELISA method, it is often impossible to do genotype classification in low dose RNA serum. We developed a new method for precise genotype determination based on differences in the nucleotide sequence of the 5' UTR region. 290 samples of HCV RNA positive serum were examined using this 5' UTR method, and compared with type-specific PCR results (Okamoto's method) or serogroup findings (Kohara's method). The combination of three nucleotides (-167, -163, -161) of 5' UTR could determine genotypes, 1 b is equivalent to T, A, G, 2 a to T, G, G, and 2 b to T, G, A. The correlation with Okamoto's method was 99.7% (289/290). With the serogroup method, 41 cases (14.1%) were judged as suspended, but with the 5' UTR genotype method, these suspended cases were classified. The minimum viral loads necessary for differntiation of genotype were examined by serial dilution of each type of serum. Determination of genotype could be achieved with 100 copy/ml of RNA. This new method seems to be useful since the determiation of genotype and examination of HCV RNA can be done at the same time. (Accepted on August 18, 2001) Kawasaki Igakkaishi 27(3): 193- 200, 2001
