[HCV subtypes and their clinical significance]

We immunologically isolated a clone with a 177-bp DNA fragment, designated as #2-22, that had homology to the NS-5 region of a HCV genome. To classify this HCV isolate, we sequenced several clones (2028 bases in total) from a cDNA library constructed from a #2-22-positive patient's blood. They showed distinct similarity to the HC-J8 genome (type II b), among the known HCV subtypes. Using this #2-22 sequence for PCR, we screened the HCV-positive blood samples from Southern Kyushu, we could identify 27% of them as type II b. In another cDNA library, from a single blood donor, who did not have multiple infections of HCV, we found two clones that might have arisen from an ancestral (or previous or historical) intergenomic recombination. They had reversed orders of similarity to different HCV subtypes, that is, the first 149-bp clone had 94% identical bases with a segment of HC-J8 and 78% with the corresponding sequence of HC-J6, but the second 814-bp clone had 85% identical bases with a segment of HC-J8 and 94% to the corresponding sequence of HC-J6. The importance of subtype analysis is discussed in relation to its clinical application, such as diagnostics development.