Measles Epidemics Among Children in Vietnam: Genomic Characterization of Virus Responsible for Measles Outbreak in Ho Chi Minh City, 2014

摘要

Background: Measles remains poorly controlled in Southeast Asia, including Vietnam.Objectives: The aimof this studywas to characterize genes of virus responsible for ameasles outbreak among childrenin Vietnam in 2014.Study design: Throat swab samples were collected from 122 pediatric patients with suspected measles. Furthermore,peripheral blood mononuclear cells (PBMCs) from 31 of these cases were also collected. Measles virus(MV) RNA was obtained directly from the clinical specimens, amplified by PCR, and then the N and H geneswere sequenced.Results:MV RNAwas detectable in throat swabs fromall 122 patients tested. Positive-strand viral RNA,which indicatesthe intermediate replicative form ofMV, was also detected in PBMCs from all 31 cases from whom thesecellswere collected. One hundred and eighteen strainswith theN genewere obtained by RT-PCR and sequenced.Using phylogenetic analysiswithmeasles reference sequences, all of the Vietnamese strains were found to be genotypeD8. However, all strains formed a distinct cluster within the genotype D8 group (D8-VNM) suggestingtheir own lineage. This distinct clusterwas supported by a branchwith a 99% bootstrap value and 3.3% nucleotidedivergence in the N-450 region of the N gene from the D8 reference strain. Notably, all of the D8-VNM variantstrains represented unique amino acid sequences consisting of R442, S451 and G452 in the N-450 region ofthe N gene.Conclusions: Measles viruses responsible for outbreaks in Southern Vietnam belonged to a genotype D8 variantgroup which had unique amino acid sequences in the N gene. Our report provides important genomic informationabout the virus for measles elimination in Southeast Asia.