| Summary: | 碩士 === 高雄醫學大學 === 醫學檢驗生物技術學研究所 === 100 === In Taiwan, Coxsackievirus B1 (CV-B1) has been isolated almost annually since 1989. Since interserotypic genetic recombination is very common in enterovirus, this study characterized interserotypic genetic recombination in sporadic enterovirus isolates. The VP1 (276 nt, 87 strains) and polymerase 3D (414 nt, 36 strains) nucleotide sequences of twenty-two Taiwan isolates of CV-B1 (1989-2010) were compared with those of other CV-B1 strains isolated worldwide and with those of the CVB2-6 prototype strains as the outgroup. Phylogenetic analyses were performed by Neighbor-Joining, Maximum Likelihood, and Markov Chain Monte Carlo methods. All methods consistently showed the same topology, and each of three genotypes (designated GI-GIII) were identified in the VP1 and 3D regions. The VP1 tree showed a branch support by bootstrap (BS) or posterior probability (PP) > 70%. The CV-B1 can be clustered into three genetic groups, Genotype I (GI) in the Americas and Taiwan (1948-1989); Genotype II (GII), which appeared in 1971, and Genotype III (GIII), which appeared in 1989. The GII and GIII strains, which have co-circulated until recently, have been isolated in the United States, Asia, Europe and elsewhere and tend to be clustered in the same geographic regions. Unlike the VP1 tree, however, the 3D tree showed that the strains did not tend to cluster by serotype. For example, the CV-B3 prototype strain was clustered together with a CV-B1 strain (AY 37320) with a significant branch support (BS or pp >73%). Intergenotypic inconsistencies between the VP1 and 3D trees were also noted. The positions of the GII strains, and particularly the positions of the GIII strains, in the VP1 tree were reversed in the 3D tree. For example, in the VP1 tree, eleven Taiwan isolates were clustered in the GIII strain, and four were clustered in the GI strain. In the 3D tree, however, two Taiwan isolates were clustered in the GII strain. The incongruencies in the VP1 and 3D tree topologies in terms of serotype and genotype clustering showed that the circulating CV-B1 had recombined not only with itself, but also with other enteroviruses. Because the new mutant is often the main cause of an enterovirus epidemic, continuous molecular epidemiological studies of sporadic viruses are essential for effective enterovirus surveillance.
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