Polymorphism of nadA gene of Neisseria meningitidis in China

Objective To understand the polymorphism of nadA gene of Neisseria meningitidis isolates in China, investigate the epidemiological significance of NadA protein of major N. meningitidis strains circulated in China and explore the feasibility of developing NadA protein based N. meningitidis vaccine. Methods Totally 230 N. meningitidis strains isolated in 26 provinces from 1963 to 2012 were analyzed by using muliti locus sequence typing(MLST), PCR, dot blotting assay and gene sequencing. The sequences of nadA genes were aligned by using BioEdit and Mega 4.0 software. Results Of the 230 N. meningitidis strains, only 55 were nadA positive. All the nadA positive N.meningitidis strains belonged to serogroup A(ST-5 complex) and serogroup W135(ST-11 complex). No nadA positive strains were found in serogroup B, C and others serogroups. NadA variant 3 included five different subvariants(NadA V3.1-3.5) with high homology up to 99%. Of 55 nadA positive N. meningitidis strains,54 were variant 3. Conclusion In China, NadA protein was only present in serogroup A(ST-5 complex) and serogroup W135(ST-11 complex) and absent in serogroup B of N. meningitidis isolates. Variants 3 NadA protein is not suitable for using as candidate protein of N. meningitidis B vaccine in China.