Effect of acidic amino acid substitution at the pr-M junction of dengue type 2 virus on prM cleavage and virus replication

Abstract

Cleavage by furin of the envelope glycoprotein, prM, is required for maturation and infectivity of the dengue virus. Highly conserved acidic amino acid, aspartate in DENV-1 and -3 or glutamate in DENV-2 and -4, at a P3 position proximal to the furin cleavage site, infl uences the level of prM cleavage during virus replication. However, the signifi cance of this inter-serotypic variation of P3 acidic residue has not been elucidated. The aim of this study was to defi ne the effect of acidic amino acid variation at this P3 position in the pr-M junction on the extent of prM cleavage and virus replication. The mutant virus, strain E203D, containing a P3 glutamate-to-aspartate substitution was generated by site-directed mutagenesis of a full-length cDNA clone of the dengue serotype 2 virus, strain 16681. The level of prM cleavage, as determined by the metabolic labeling method employing 35S-Cys/Met, in the strain E203D was comparable to the parent virus. When virus replicative ability was assessed in single and multi-step multiplication studies, no difference existed in the kinetics of replication between the strain E203D and the parent virus. A glutamate-to-aspartate substitution in prM at the polyprotein position 203 does not appear to affect the level of prM cleavage or viral replication in the dengue serotype 2 virus.