It is now known that the rate of nucleotide substitution for the genes of HIV (Human Immunodeficiency Virus) and HCV (Hepatitis C Virus), is a million times higher than that for human genes. This characteristic feature of pathogenic viruses gives us a unique opportunity to observe the generating mechanism of genetic variability, even withing a single host. Indeed, it is rather common practice to obtain a viral isolate from a single patient or carrier at several time points after infection. The isolated viral clones have been sequenced and the nucleotide sequences compared with each other to estimate the numbers of nucleotide substitutions. By using the substitution numbers, we successfully constructed a phylogenetic tree for the clones isolated from a single host. The phylogentic tree obtained showed that the homogeneous populations of viral clones present at the initial stage, gradually accumulated genetic variability within the human body. We also found that there was a particular period of time when amino acid substitutions were significantly favored. This implies that some sort of positive selection is taking place during this time, in order for viruses to escape from the immune system of the host. These results will be useful in analyzing the evolutionary interaction between the viruses and their hosts.
|Original language||English (US)|
|Number of pages||1|
|Journal||Japanese Journal of Human Genetics|
|State||Published - 1997|
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