Hepatitis C Virus and Hepatoma between U.S.A. and Japan

最近的研究表明，丙型肝炎病毒(HCV)与日本的肝细胞癌密切相关。虽然美国的丙型肝炎病毒抗体阳性率与日本几乎相同，但美国的肝细胞癌的发生率低于日本。为了了解美国和日本之间的差异，我们比较了来自日本和美国的丙型肝炎病毒的序列。我们从一个肝细胞癌患者那里获得了丙型肝炎病毒的基因。与日本分离株和美国分离株的核苷酸序列同源性分别为90.7%~91.4%和78.4%~78.8%。3株来自日本的分离物被归入日本型(类型II，Okamoto)，3株来自美国的分离物被归入美国型(类型I，Oakamoto)。当我们对38例接受干扰素治疗的慢性丙型肝炎患者进行分类时，28例(75%)为日本型。另一方面，在美国的33名患者中，只有7人(21%)是日本型的。这些发现表明，在日本和美国至少有两种类型的丙型肝炎病毒，其中一种在日本为主的类型在美国并不常见。需要进一步的研究来阐明丙型肝炎病毒株的差异在两国肝细胞癌患病率差异中的可能作用。

Recent studies have demonstrated that hepatitis C virus (HCV) is closely related with hepatocellular carcinoma in Japan. Although positive rate for antibody against HCV in the United States is nearly same as that in Japan, the occurrence rate of hepatocellular carcinoma in the United States is smaller than that in Japan. To understand the difference between the United States and Japan, we compared sequences of HCV obtained from Japanese patients with those from the United States.We obtained HCV-cDNA from a patient with hepatocellular carcinoma. It has 90.7-91.4% homology in nucleotide sequences of two isolates obtained in Japan while 78.4-78.8% with two isolates obtained in the United States. Those three isolates from Japan were classified into Japanese-type (type II, Okamoto) and three from United States into American-type (type I, Oakamoto). When we classified 38 patients with chronic hepatitis C treated with Interferon, 28 (75%) were Japanese-type. On the other hand, only 7 (21%) out of 33 patients in the United States were Japanese-type.These findings suggest that there are at least two types of HCV in Japan and United States and a type which is major in Japan is not common in the United States. Further studies are necessary to elucidate the possible role of the difference of HCV strains on the difference of prevalence of prevalence in hepatocellular carcinoma in both countries.