We examined 24 C-type hepatitis specimens from Thailand and detected hepatitis C virus (HCV) RNA in all of them by RT-nested PCR for a portion of the HCV 5' non-coding (5' NC) region and a portion of the HCV core region. However, we failed to detect HCV RNA in 11 specimens by RT-nested PCR for a portion in the non-structural protein 5 (NS5) region that has been used commonly for HCV genotyping. We designed a new primer set for a separate portion of the NS5 region. Using this primer set, we succeeded in amplifying this portion in all 24 specimens. Two novel HCV genotypes, tentatively designated HCV-VII and HCV-VIII, were identified by sequencing these amplified regions. Our newly designed primers for RT-nested PCR may be useful for diagnosing infection as well as for genotyping unidentified HCV genomes.
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