Genetic characteristics of measles virus strains causing two outbreaks in Guizhou province

Abstract

Objective To analyze the genetic characteristics of measles virus strains causing two outbreaks in Guizhou province from November 2014 to March 2015. Methods Throat swab samples collected from measles cases in two outbreaks were inoculated into Vero/SLAM cells. Viral RNAs were extracted from positive cultures. Nucleoprotein genes were amplified by using reverse transcription-polymerase chain reaction (RT-PCR) and the PCR products were sequenced and analyzed. Results Eleven strains of wild-type measles virus were isolated from the two measles outbreaks and all of them belonged to H1a sub-genotype. Phylogenetic analysis showed that those strains were clustered into two distinct branches. Differences in nucleotide and amino acid genetic distances between the 11 strains of measles virus and the WHO reference strain of H1a sub-genotype (Chin9322) were 1.1%-1.6% and 0.7%-3.4%, respectively. Compared with the reference strain Chin9322 and Guizhou epidemic strains in recent years, six strains showed amino acid sequence mutations in 47 (G to S), 82 (S to G) and 122 (R to K) sites and two strains had a mutation in 98 (P-L) site. Conclusion H1a sub-genotype measles virus was the predominant pathogen causing two measles outbreaks in Guizhou province during 2014 to 2015. Moreover, it was also a predominant sub-genotype circulating in China and Guizhou province. Different measles virus strains of H1a sub-genotype continued to be prevalent in Guizhou province. This study provided some scientific data for the control and elimination of measles in Guizhou province. Key words: Measles virus; Outbreak; Genotype; Sequence analysis