Hepatitis C virus: An infectious molecular clone of a second major genotype (2a) and lack of viability of intertypic 1a and 2a chimeras

Of the six major genotypes of hepatitis C virus (HCV), infectious cDNA clon es of only genotype 1 have been reported. Here, we report the construction of an infectious cDNA clone representing a second major HCV genotype, genot ype 2. This infectious clone (pJ6CF) encodes the consensus polyprotein of s train HC-J6(CH), genotype 2a. Its encoded polyprotein differs from those of the infectious clones of genotypes la and Ib by approximately 30%. Interty pic chimeric cDNA clones constructed from infectious clones of genotypes la and 2a of HCV were not infectious. RNA transcripts of four chimeras contai ning the 2a structural genes (C, E1, and 52) in the backbone of an infectio us genotype 1a clone (pCV-H77C) were not viable in a chimpanzee regardless of whether p7 was from the 1a or 2a clone. However, the chimpanzee was subs equently infected with RNA transcripts of each of the two infectious parent clones, indicating that the inability of the chimeras to replicate was int rinsic to the clones and not the result of preexisting protective immune re sponses.