Molecular characterization of three enteroviral strains isolated in Kuwait from young children with serious conditions

Abstract

Introduction: Human enteroviruses are single stranded RNA viruses associated with many serious diseases such as encephalitis and myocarditis. They consist of up to 100 immunologically and genetically distinct types. Three enteroviral isolates, 2104, 3936 and 3988, were previously isolated from patients with neurological disorders or sepsis-like illness. In this study, the molecular characterization of the three isolates was investigated. Methodology: A full genome sequencing was performed by Sanger method, followed by phylogenetic and bootscanning analyses. A detailed analysis of genetic differences between the clinical and prototype isolates were investigated by mapping polymorphisms at nucleotide and amino acid levels, and by comparing RNA secondary structure in the noncoding regions. Results: Based on the phylogenetic analysis of the VP1 gene and complete genome, 2104 was typed as coxsackievirus B1, 3936 as coxsackievirus B5, and 3988 as echovirus 7. Similarity and bootscan plots provided support for intra- and intertypic recombination crossover points occurring mainly along the nonstructural coding regions of the isolates. A sequence divergence of 12 to 14% was detected in the 5’-noncoding region between the clinical isolates and their corresponding prototype strains. Synonymous and nonsynonymous substitutions could be also mapped to different coding regions of the isolates, including those coding for the Puff, Knob and the hydrophobic pocket of the capsid. Examination of relative frequencies of synonymous and nonsynonymous substitutions in different coding regions of enteroviral isolates showed no evidence for selective pressure. Conclusion: The results provided a better understanding of the genetic variations, evolution and adaptation of enteroviruses in Kuwait.