Mika Saitoh, Makoto Takeda, Koichi Gotoh, Fumihiko Takeuchi, Tsuyoshi Sekizuka, Makoto Kuroda, Katsumi Mizuta, Akihide Ryo, Ryota Tanaka, Haruyuki Ishii, Hayato Takada, Kunihisa Kozawa, Ayako Yoshida, Masahiro Noda, Nobuhiko Okabe, Hirokazu Kimura

We studied the molecular evolution of H gene in four prevalent Asian genotypes (D3, D5, D9, and H1) of measles virus (MeV). We estimated the evolutionary time scale of the gene by the bayesian Markov Chain Monte Carlo (MCMC) method. In addition, we predicted the changes in structure of H protein due to selective pressures. The phylogenetic tree showed that the first division of these genotypes occurred around 1931, and further division of each type in the 1960-1970s resulted in four genotypes. The rate of molecular evolution was relatively slow (5.57×10(-4) substitutions per site per year). Only two positively selected sites (F476L and Q575K) were identified in H protein, although these substitutions might not have imparted significant changes to the structure of the protein or the epitopes for phylactic antibodies. The results suggested that the prevalent Asian MeV genotypes were generated over approximately 30-40 years and H protein was well conserved.