Genetic analysis of recent Taiwanese isolates of a variant of coxsackievirus A24

Epidemics of acute hemorrhagic conjunctivitis (AHC) caused by a variant of coxsackievirus A24 (CA24v) reappeared in Taiwan in 1990 and 1994, following the first two epidemics of 1985-86 and 1988-89. To analyze the genetic div ersity of recent CA24v in Taiwan, 7 Taiwanese strains isolated during the 1 990-94 period were studied together with one Japanese and two Thai strains isolated in 1993. A fragment of 674 nucleotides between the carboxy termina l 3A and the amino terminal 3D polymerase, including the entire 3C protease (3C(pro)), was amplified by a reverse transcription-polymerase chain react ion (RT PCR) and the nucleotide sequences were determined. In the 549 nucle otides (183 amino acids) of the entire 3C(pro), we found nucleotide differe nces at 80 positions between 10 strains and the prototype strain, EH24/70, one of the earliest strains of CA24v. Most of the nucleotide changes were s ynonymous substitutions and only nine amino acid changes were found. The nu cleotide sequence homologies among 71 strains worldwide were 88-100%. These 71 nucleotide sequences were then analyzed by Neighbor-joining method and phylogenetically separated into three distinct genotypes. Genotype I consis ted of early strains isolated in 1970-71 from Singapore and Hong Kong. Geno type II included isolates from Singapore and Thailand obtained in 1975. Gen otype III comprised strains from the eastern hemisphere isolated in 1985-94 from Japan, Taiwan, China, Hong Kong, Thailand, Singapore, Pakistan and Gh ana. They were further divided chronologically into six clusters. The recen t isolates from Taiwan obtained in 1985/1986, 1988/1989 and 1990-94 were cl assified into genotype III Clusters 1, 5, and 6 respectively. The evolution ary rate was re-estimated to be 3x10(-3) 30 years after the emergence of th e virus. J. Med. Virol. 64:269-274, 2001. (C) 2001 Wiley-Liss, Inc.