Comparison of amino acid sequences in hypervariable region-1 of hepatitis C virus clones between human inocula and the infected chimpanzee sera

We analyzed nucleic and amino acid sequences of the hypervariable region (HVR)-1 of the hepatitis C virus (HCV) from inocula and the infected chimpanzee sera. One milliliter each of 10−5, 10−3 and 10−2 dilutions of serum no. 4, and those of 10−4, 10−5 and 10−6 dilutions of serum no. 6 were inoculated to six different chimpanzees. Both inocula nos. 4 and 6 contained 107 copies of HCV RNA/ml. The two chimpanzees inoculated with 10−4 and 10−5 dilutions of no. 6 were infective, while none of the dilutions from inoculum no. 4 were infective. Our results indicated that HCV RNA titer in sera did not correlate with in vivo infectivity. RNA from both inocula and the infected chimpanzee sera were extracted and transcribed to cDNA. The PCR products amplifying the HCV HVR-1 were incorporated into a vector, followed by transformation. Twenty colonies were picked up randomly from each sample. DNA was extracted and the DNA and amino acid sequences were determined. Genetic variations of 20 clones from inoculum no. 6 were divided into six groups, whereas, 40 clones from infected chimpanzees were completely identical to the major quasispecies of inoculum no. 6 in amino acid sequences. The study suggested that the major quasispecies in the diluted inocula were transmitted and replicated.