The Prevalence And Genetic Diversity Of PilE、nadA And Other Genes Of Neisseria Meningitidis

Neisseria meningitidis (Nm), a strictly human pathogen that asymptomatically colonizes the upper respiratory tract in the human population, is a leading cause of invasive bacterial infections globally, with devastating morbidity and mortality. Each year, an estimated about100,000cases of N. meningitidis infection are reported worldwide, with a constant fatality rate of approximately10%. Based on the immunochemistry of the capsular polysaccharide, Neisseria meningitidis can be classified into one of12serogroups. Serogroups A, B, C, Y, W135and X are responsible for the majority of meningococcal disease globally. The epidemic of meningococcal disease showed regional characteristics. Serogroup A caused two global pandemics in last century. Serogroup B (ST-8clonal complex, ST-32clonal complex, ST-41/44clonal complex), C (ST-11clonal complex) and Y (ST-23clonal complex) meningococci mainly caused regional epidemic of invasive meningococcal disease in North American and Europe. In China, ST-5clonal complex serogroup A and ST-4821clonal complex serogroup C were the main cause of meningococcal disease. ST-11clonal complex serogroup W135strains caused an outbreak in2000and have subsequently caused sporadic disease and epidemics worldwide.Currently, meningococcal poiysaccharide or polysaccharide-protein conjugate vaccines against serogroup A, C, W135and Y have become available, prevention of meningococcal. The MenB (Serogroup B Meningococcus) capsular polysaccharide is poorly immunogenic as it is antigenically similar to the human foetal neural cell adhesion molecule. The development of a universal vaccine against serogroup B has been extremely challenging. NadA (Neisseria adhesion A) and PilE (the major pilin)are the main adhesion proteins of Neisseria meningitidis, playing an important role in adhesion and invasion of human cells. PorA, PorB and FetA are the major immunodominant antigen component of the outer membrane vesicle (OMV) vaccines which have proven highly effective against NmB epidemics. FHbp (factor H binding protein), identified by reverse vaccinology, was a newly attractive candidate antigen.First of all, a total of230Neisseria meningitidis, isolated from26provinces between1963to2012. were investigated by using MLST (Muliti-Locus Sequence Typing), PCR, dot blotting and the gene results of nucleotide or amino acid sequences were aligned by cluster analysis using BioEdit and MEGA4.0software. We found that of the230N. meningitidis, only55isolates were nadA positive. Nm strains with nadA positive were exclusively belonging to serogroup A (ST-5clonal complex) and serogroup W135(ST-11clonal complex). No nadA positive strains were found in serogroup B, C and others serogroups Nm strains. NadA variant3included five different subvariants (NadA V3.1-3.5) showing high homology up to99%. In China, NadA protein was absent in serogroup B Nm isolates. Variants3NadA protein is not available for being one candidate protein of MenB protein-based vaccine in China.In this study, the prevalence and genetic diversity of pilE and nadA were investigated among the prevalent serogroups and clonal complexes (cc) of144Neisseria meningitidis isolated in China. All serogroup A strains belonging to ST-1clonal complex (ccl) and ST-5clonal complex (cc5) and all ST-11clonal complex (cc11) serogroup W135strains were clustered into Class â…¡ PilE clades. All serogroup C and most of serogroup B isolates except ST-8clonal complex (cc8) and ST5642were Class â…  PilE clades. Class â…¡ pilE sequences were highly conserved. All isolates belonging to Class â…  PilE isolates were nadA negative. However, nadA positive strains were exclusively found in cc5and cc11isolates (Class â…¡ PilE). This study showed that PilE and NadA may be related to epidemic or endemic of meningococcal disease.By MLST,porA,porB,fetA,fHbp and nadA analysis,167serogoup B Neisseria meningitidis isolated in China were investigated. cc4821was the most common lineage (19.6%,32/163) in the collection and predominated in the present prevalence, and this transformation tendency of the dominant clonal complexes of serogroup B meningococci have seen obviously according to our data. The data presented in our study indicated the high degree diversity of PorA, with a large range of VR families (34VR1,54VR2) and the combinations of VR families as many as83. No predominant PorA type was found. Among the remaining78divergent porA types, up to54porA types were merely presented in one isolate. PorB variants of the whole serogoup B isolates were exclusively belonged to family three, and were mostly associated with cc4821. The five most common FetA types identified in this study were F5-5, F5-8, F5-2, F1-5and F3-3, which accounted for36.36%(60/165) of isolates. The predominant fHbp variant among the serogoup B isolates was variant2(84.67%), which was inconsistent with previously reports. Furthermore, the most common subvariant2.16was account for21.3%of the whole analyzed strains, and meanwhile, this subvariant was mostly associated with cc4821as well. However, most of the strains were devoid of nadA.In summary, the epidemic of meningococcal disease showed regional characteristics. Only cc11serogroup W135strains and serogroup A strains belonging to ccl and cc5were related to epidemic of meningococcal disease so far. Our study suggested that, the adhesion ability of Neisseria meningitidis in different serogroups might have relationships with the potential epidemic of meningococcal disease. The antigen genes sequencing typing of Serogroup B Meningococcus in China were distinctive. Therefor, in Chian, the research and development of MenB protein vaccines should be based on the antigenic characteristics of Chinese Neisseria meningitidis strains.