Genetic characteristics of serogroup A meningococci circulating in China, 1956–2005

Safety and immunogenicity of meningococcal (Groups A and C) polysaccharide vaccine in children 2 to 6 y of age in China: a randomized, active-controlled, non-inferiority study

Meningococcal serogroups A and C cause significant numbers of cases in China. The Sanofi Pasteur meningococcal polysaccharide A + C vaccine (Men-AC) was licensed in China in 1995. Immunogenicity and safety of a single dose of Men-AC against a similar marketed vaccine, the Lanzhou Institute serogroups A and C vaccine (Lanzhou-AC), were evaluated in children 2 to 6 y of age. Antibody titers were determined before and on Day 30 after vaccination using a serum bactericidal assay using baby rabbit complement (SBA-BR). Immunogenicity endpoints included rates of seroconversion (postvaccination antibody titers ≥4-fold higher) and seroprotection (postvaccination titers ≥1:8). Unsolicited systemic adverse events (AEs) within 30 minutes after vaccination, solicited injection site and systemic reactions between Days 0 and 7, unsolicited non-serious AEs within 30 d, and serious adverse events (SAEs) throughout were recorded. Seroconversion rates against serogroups A and C were 97.0% (95% confidence interval [CI], 94.5-98.6) and 94.7% (95% CI, 91.6-97.0), respectively, in the Men-AC group and 97.7% (95% CI, 95.4-99.1) and 94.8% (95% CI, 91.7-97.0), respectively, in the Lanzhou-AC group, while seroprotection rates were 98.0% (95% CI, 95.8-99.3) and 97.0% (95% CI, 94.5-98.6), respectively, in the Men-AC group and 99.0% (95% CI, 97.2-99.8) and 96.8% (95% CI, 94.1-98.4), respectively, in the Lanzhou-AC group. Non-inferiority of Men-AC with regard to immunogenicity was demonstrated since the lower bounds of the 95% CIs of the differences in rates between the two groups were > -5% for both serogroups. Both vaccines were well tolerated.

The everchanging epidemiology of meningococcal disease worldwide and the potential for prevention through vaccination

Neisseria meningitidis is a major cause of bacterial meningitis and septicaemia worldwide and is associated with high case fatality rates and serious life-long complications among survivors. Twelve serogroups are recognised, of which six (A, B, C, W, X and Y) are responsible for nearly all cases of invasive meningococcal disease (IMD). The incidence of IMD and responsible serogroups vary widely both geographically and over time. For the first time, effective vaccines against all these serogroups are available or nearing licensure. Over the past two decades, IMD incidence has been declining across most parts of the world through a combination of successful meningococcal immunisation programmes and secular trends. The introduction of meningococcal C conjugate vaccines in the early 2000s was associated with rapid declines in meningococcal C disease, whilst implementation of a meningococcal A conjugate vaccine across the African meningitis belt led to near-elimination of meningococcal A disease. Consequently, other serogroups have become more important causes of IMD. In particular, the emergence of a hypervirulent meningococcal group W clone has led many countries to shift from monovalent meningococcal C to quadrivalent ACWY conjugate vaccines in their national immunisation programmes. Additionally, the recent licensure of two protein-based, broad-spectrum meningococcal B vaccines finally provides protection against the most common group responsible for childhood IMD across Europe and Australia. This review describes global IMD epidemiology across each continent and trends over time, the serogroups responsible for IMD, the impact of meningococcal immunisation programmes and future needs to eliminate this devastating disease.

Prevalence and genetic characteristics of 4CMenB and rLP2086 vaccine candidates among Neisseria meningitidis serogroup B strains, China

OBJECTIVE

To systematically investigate the prevalence and genetic characteristics of 4CMenB and rLP2086 vaccine candidates among Neisseria meningitidis serogroup B (NmB) in China.

METHODS

A total of 485 NmB strains isolated in 29 provinces of China between 1968 and 2016 were selected from the culture collection of the national reference laboratory according to the isolation year, location, and source. Multi-locus sequence typing (MLST) and porA gene sequencing were performed on all 485 study strains; PCR was used to detect the fHbp, nadA, and nhba gene of 432 strains; positive amplification products from the fHbp and nadA genes from all strains, as well as those of the nhba gene from 172 representative strains, were sequenced.

RESULTS

MLST results showed that the predominant (putative) clonal complexes (CCs) of NmB isolates have changed over time in China. While strains that could not be assigned to existing (p)CCs were the biggest proportion, CC4821 was the most prevalent lineage (36.0%) since 2005. PCR and sequence analysis revealed that the 4CMenB and rLP2086 vaccine candidates were highly diverse. Respectively, 152 PorA genotypes and 83 VR2 sequences were identified with significant diversity within a single CC; the complete nadA gene was found in ten of 432 study strains; fHbp was present in most strains (422/432) with variant 2 predominating (82.9%) in both patient- and carrier- derived isolates; almost all strains harbored the nhba gene while sequences were diverse.

CONCLUSIONS

With regards to clonal lineages and vaccine candidate proteins, NmB isolates from China were generally diverse. Further studies should be performed to evaluate the cross-protection of present vaccines against Chinese NmB strains.

Capsule switching of Neisseria meningitidis sequence type 7 serogroup A to serogroup X

OBJECTIVES

The bacterial pathogen Neisseria meningitidis is able to escape the currently available capsule-based vaccines by undergoing capsule switching. In this study, we investigated whether capsule switching has occurred in a recently emerged sequence type (ST) 7 serogroup X isolate in China, for which currently no vaccine is available.

METHODS

To identify capsule switching breakpoints, the capsule locus and flanking regions of the ST-7 serogroup X isolate and three endemic ST-7 serogroup A isolates were sequenced and compared. To obtain further insight into capsule switching frequency and length of DNA fragments involved, capsule switching assays were performed using genomic DNA containing combinations of antibiotic selection markers at various locations in the capsule locus and flanking regions.

RESULTS

Sequence analyses showed that capsule switching has occurred and involved a 8450 bp serogroup X DNA fragment spanning the region from galE to ctrC. Capsule switching assays indicate that capsule switching occurs at a frequency of 6.3 × 10^-6 per bacterium per μg of DNA and predominantly involved DNA fragments of about 8.1-9.6 kb in length.

CONCLUSIONS

Our results show that capsule switching in N. meningitidis occurs at high frequency and involves recombination in the flanking regions of the capsule biosynthesis genes.

Effects of meteorological factors on the incidence of meningococcal meningitis

BACKGROUND AND OBJECTIVES

Substantial climate changes have led to the emergence and re-emergence of various infectious diseases worldwide, presenting an imperative need to explore the effects of meteorological factors on serious contagious disease incidences such as that of meningococcal meningitis (MCM).

METHODS

The incidences of MCM and meteorology data between 1981 and 2010 were obtained from Chaoyang city. Structure Equation Modeling was used to analyze the relationships between meteorological factors and the incidence of MCM, using the LISREL software.

RESULTS

The SEM results showed that Adjusted Goodness of Fit Index (AGFI) = 0.30, Goodness of Fit Index (GFI) = 0.63, and Root Mean Square Error of Approximation (RMSEA) = 0.31. Humidity and temperature both had negative correlations with MCM incidence, with factor loads of -0.32 and -0.43, while sunshine was positively correlated with a factor load of 0.42. For specific observable variables, average air pressure, average evaporation, average air temperature, and average ground temperature exerted stronger influence, with item loads between observable variables and MCM incidence being -0.42, 0.34, -0.32, and -0.32 respectively.

CONCLUSION

Public health institutions should pay more attention to the meteorological variables of humidity, sunshine, and temperature in prospective MCM control and prevention.

Perceptions of measles, pneumonia, and meningitis vaccines among caregivers in Shanghai, China, and the health belief model: a cross-sectional study

BACKGROUND

In China, the measles vaccine is offered for free whereas the pneumococcal vaccine is a for-fee vaccine. This difference has the potential to influence how caregivers evaluate whether a vaccine is important or necessary for their child, but it is unclear if models of health behavior, such as the Health Belief Model, reveal the same associations for different diseases. This study compares caregiver perceptions of different diseases (measles, pneumonia and meningitis); and characterizes associations between Health Belief Model constructs and both pneumococcal vaccine uptake and perceived vaccine necessity for pneumonia, measles, and meningitis.

METHODS

Caregivers of infants and young children between 8 months and 7 years of age from Shanghai (n = 619) completed a written survey on their perceptions of measles, pneumonia, and meningitis. We used logistic regression models to assess predictors of pneumococcal vaccine uptake and vaccine necessity.

RESULTS

Only 25.2% of children had received a pneumococcal vaccine, although most caregivers believed that pneumonia (80.8%) and meningitis (92.4%), as well as measles (93.2%), vaccines were serious enough to warrant a vaccine. Perceived safety was strongly associated with both pneumococcal vaccine uptake and perceived vaccine necessity, and non-locals had 1.70 times higher odds of pneumonia vaccine necessity than non-locals (95% CI: 1.01, 2.88).

CONCLUSIONS

Most factors had a similar relationship with vaccine necessity, regardless of disease, indicating a common mechanism for how Chinese caregivers decided which vaccines are necessary. Because more caregivers believed meningitis needed a vaccine than pneumonia, health care workers should emphasize pneumococcal vaccination's ability to protect against meningitis.

Genetic Analysis of Neisseria meningitidis Sequence Type 7 Serogroup X Originating from Serogroup A

Neisseria meningitidis causes meningococcal disease, often resulting in fulminant meningitis, sepsis, and death. Vaccination programs have been developed to prevent infection of this pathogen, but serogroup replacement is a problem. Capsular switching has been an important survival mechanism for N. meningitidis, allowing the organism to evolve in the present vaccine era. However, related mechanisms have not been completely elucidated. Genetic analysis of capsular switching between diverse serogroups would help further our understanding of this pathogen. In this study, we analyzed the genetic characteristics of the sequence type 7 (ST-7) serogroup X strain that was predicted to arise from ST-7 serogroup A at the genomic level. By comparing the genomic structures and sequences, ST-7 serogroup X was closest to ST-7 serogroup A, whereas eight probable recombination regions, including the capsular gene locus, were identified. This indicated that serogroup X originated from serogroup A by recombination leading to capsular switching. The recombination involved approximately 8,540 bp from the end of the ctrC gene to the middle of the galE gene. There were more recombination regions and strain-specific single-nucleotide polymorphisms in serogroup X than in serogroup A genomes. However, no specific gene was found for each serogroup except those in the capsule gene locus.

Burden of Neisseria meningitidis infections in China: a systematic review and meta-analysis

BACKGROUND

Neisseria meningitidis is a leading cause of bacterial meningitis and septicemia in children and young adults worldwide. The disease burden associated with N. meningitidis infections has not been systematically assessed in China. Therefore, we undertook this study to determine the burden of meningococcal disease in China.

METHOD

We performed a systematic review and meta-analysis of articles on N. meningitidis incidence, carriage, seroprevalence and mortality rates in China by searching the Chinese BioMedical Database (CBM), China National Knowledge Infrastructure (CNKI), Wanfang database and PubMed for publications from January 2005 to Aug 2015.

RESULTS

In total, 50 articles were included in our analysis. The overall incidence of meningococcal disease and associated mortality were estimated to be 1.84 (95% confidence interval (CI) 0.91-3.37) per 100 000 persons per year and 0.33 (95% CI 0.12-0.86) per 100 000 persons per year, respectively. N. meningitidis carriage rate among the healthy population was estimated to be 2.7% (95% CI 2.0-3.5%). Prevalence of antibodies against N. meningitidis serogroup A and C were estimated to be 77.3% (95% CI 72.4%-81.6%) and 33.5% (95% CI 27.0%-40.8%), respectively. No studies were found for serogroup specific disease burden.

CONCLUSIONS

The overall incidence of meningococcal disease in China is low. The lower seroprevalence of serogroup C within the population suggests that it may pose a greater risk for meningococcal disease outbreak than serogroup A. The lack of data on serogroup disease burden by age groups suggests the implementation of laboratory based meningococcal surveillance systems are urgently needed in China.

Phylogenetic study of clonal complex (CC)198 capsule null locus (cnl) genomes: A distinctive group within the species Neisseria meningitidis

Capsule null locus (cnl) strains, one type of specific unencapsulated Neisseria spp., only have regions D and E of the capsule gene cluster which encodes the genes for capsule biosynthesis, modification, and transportation. Compared with encapsulated strains, regions A and C of cnl strains have been replaced by 113 or 114 bp conserved non-coding sequences. Cnl strains include multiple clonal complexes (CC). According to previous studies, CC198 is the major clonal lineage in both cnl patients and healthy cnl carriers. We hypothesized that CC198 possesses different genome characteristics compared with other cnl strains. In this study, we obtained the draft genomes of two CC198 strains from healthy carriers. Using 75071 single nucleotide polymorphisms located in 1163 core genes, we constructed the phylogenetic relationships between a batch of representative Neisseria meningitidis genomes. CC198 and CC1136 clustered together, but apart from other N. meningitidis strains including CC53. We also aligned the sequences of genes located in regions D and E of the capsule gene locus from encapsulated and unencapsulated strains. A number of possible recombination events were identified in the galE and tex genes between different serogroups of encapsulated N. meningitidis and CC53 strains, especially in tex. In contrast, there is almost no recombination in N. meningitidis CC198 strains. These results showed that CC198 belongs to a phylogenetically distinct group within the species N. meningitidis, which may be directly derived from the cnl-type ancestor of N. meningitidis. The encapsulated strains may acquire other necessary genes for capsule formation by horizontal transfer.

Clonal characteristics of invasive Neisseria meningitidis following initiation of an A + C vaccination program in China, 2005-2012

OBJECTIVES

To reveal the population structure of invasive Neisseria meningitidis isolates after the initiation of an A + C vaccination program in China.

METHODS

Multilocus sequence typing (MLST) and PorA typing were used to characterize 238 invasive N. meningitidis isolates collected in China between 2005 and 2012.

RESULTS

During this period, sequence type (ST)-5, ST-4821 and ST-11 complexes were dominant among serogroups A, C and W, accounting for 100%, 98.5% and 100% of each serogroup, respectively. P1.20,9, P1.7-2,14 and P1.5,2 were the dominant PorA types of serogroups A, C and W, respectively. Serogroup B showed high genetic diversity with two dominant lineages: ST-4821 complex and ST-5662 subgroup.

CONCLUSIONS

The population of 238 invasive N. meningitidis isolates was primarily composed of a select group of recognized hypervirulent lineages. Among these clonal complexes, ST-7 serogroup A and ST-11 serogroup W are distributed globally, and other three clones exist only in China.

Genetic diversity and clonal characteristics of ciprofloxacin-resistant meningococcal strains in China

The purpose of the present study was to identify the clonal characteristics and gyrA gene diversity of ciprofloxacin-resistant meningococcal strains in China. One hundred and forty-one ciprofloxacin-resistant and 103 ciprofloxacin-susceptible meningococcal strains were selected for multilocus sequence typing. Of these, 54 ciprofloxacin-resistant and 42 ciprofloxacin-susceptible strains were selected for gyrA gene sequencing. Of the three clonal complexes prevalent in China, serogroup A of ST-5 complex (CC5) and serogroup C/B strains of CC4821 had a high proportion of ciprofloxacin resistance, whereas CC11 serogroup W strains were all susceptible. Nucleotide and amino acid sequences of the gyrA gene among ciprofloxacin-resistant strains showed more diversity than those among ciprofloxacin-susceptible strains. All ciprofloxacin-resistant strains had a T91I mutation and the ciprofloxacin-susceptible strains had no T91I mutation. Phylogenetic analysis showed that the gyrA gene sequences of CC4821 serogroup B/C strains, CC11 serogroup W, CC1 serogroup A, ciprofloxacin-susceptible CC5 serogroup A and reference strains had high similarity. By contrast, the ciprofloxacin-resistant CC5 serogroup A strains had a highly conserved gyrA gene sequence which was different (94.8% similarity) from that in the above strains. The results of our investigation showed that the high proportion of ciprofloxacin resistance in Neisseria meningitidis is associated with certain sequence types (STs) or clonal complexes (CCs). The prevalence of certain CCs with a high proportion of ciprofloxacin resistance can facilitate the spread of ciprofloxacin resistance.

Complete Genome Sequence of Neisseria meningitidis Serogroup A Strain NMA510612, Isolated from a Patient with Bacterial Meningitis in China

Serogroup A meningococcal strains have been involved in several pandemics and a series of epidemics worldwide in the past. Determination of the genome sequence of the prevalent genotype strain will help us understand the genetic background of the evolutionary and epidemiological properties of these bacteria. We sequenced the complete genome of Neisseria meningitidis NMA510612, a clinical isolate from a patient with meningococcal meningitis.

Prevalence and genetic diversity of two adhesion-related genes, pilE and nadA, in Neisseria meningitidis in China

The main Neisseria meningitidis adhesion molecules, type IV pili (Tfp) and Neisseria adhesion A (NadA), play important roles in the pathogenesis of invasive meningococcal disease. PilE is the major Tfp subunit. In this study, the prevalence and genetic diversity of pilE and nadA were investigated in the prevalent serogroups and clonal complexes (CC) of N. meningitidis isolated in China. All serogroup A strains belonging to CC1 and CC5 and all CC11 serogroup W135 strains were clustered into class II PilE clades. All serogroup C and most of serogroup B isolates except CC8 and ST5642 were class I PilE clades. Class II pilE sequences were highly conserved. All isolates belonging to class I PilE isolates were nadA negative. However, nadA-positive strains were exclusively found in CC5 and CC11 isolates (class II PilE). This study showed that PilE and NadA may be related to epidemic or endemic meningococcal disease.

Distribution of serogroups and sequence types in disease-associated and carrier strains of Neisseria meningitidis isolated in China between 2003 and 2008

Given the unpredictability of Neisseria meningitidis outbreaks and the increased prevalence of serogroup C strains following the introduction of serogroup A-based vaccines, we conducted an analysis of serogroups and sequence types (STs) in disease-associated and carrier N. meningitidis isolates that have emerged in China since 2003. We used multilocus sequence-typing techniques to investigate 371 N. meningitidis strains isolated from patients with meningitis and healthy carriers. Two lineages were identified in serogroup A and C isolates, genotyped as the ST5 complex and ST4821 complex, respectively. Both clonal complexes were found throughout China, although ST4821 was more concentrated in the eastern region of the country. The ST5 complex has been persistent in China since the late 1980s and has since spread across the entire country. Isolates belonging to the ST4821 complex have been a dominant lineage since 2003.

Safety and immunogenicity of a tetravalent polysaccharide vaccine against meningococcal disease

BACKGROUND/PURPOSE

Meningococcal disease, including meningitis and sepsis, usually follows an invasive infection by Neisseria meningitidis, and is a major cause of death and morbidity worldwide. Currently available meningococcal vaccines that consist of pure capsular polysaccharides (serogroups A, C, W-135 and Y) are generally safe and efficacious in adults and children aged > 2 years. The purpose of this study was to evaluate the immunogenicity, safety and reactogenicity of a single dose of GlaxoSmithKline Biologicals' Mencevax ACWY vaccine in healthy Taiwanese subjects aged 2-30 years.

METHODS

This open, single center, Phase III study was conducted in Taiwan. A single dose of the Mencevax ACWY vaccine was administered to subjects aged 2-30 years. Immunogenicity and safety of the vaccine were evaluated after vaccination.

RESULTS

The immunogenicity results obtained 1 month after vaccination with Mencevax ACWY vaccine indicated that the vaccine elicited a good immune response in vaccinees aged 2-30 years. This was both in terms of functional activity directed against meningococcal polysaccharide (A, C, W-135 and Y) as measured by serum bactericidal assay (> 93% activity against all serogroups), and specific IgG concentrations measured by ELISA (> 96% seropositivity to all serogroups).

CONCLUSION

The tetravalent polysaccharide Mencevax ACWY meningococcal vaccine was well tolerated and immunogenic in subjects aged 2-30 years in Taiwan.

Global epidemiology of meningococcal disease

As reviewed in this paper, meningococcal disease epidemiology varies substantially by geographic area and time. The disease can occur as sporadic cases, outbreaks, and large epidemics. Surveillance is crucial for understanding meningococcal disease epidemiology, as well as the need for and impact of vaccination. Despite limited data from some regions of the world and constant change, current meningococcal disease epidemiology can be summarized by region. By far the highest incidence of meningococcal disease occurs in the meningitis belt of sub-Saharan Africa. During epidemics, the incidence can approach 1000 per 100,000, or 1% of the population. Serogroup A has been the most important serogroup in this region. However, serogroup C disease has also occurred, as has serogroup X disease and, most recently, serogroup W-135 disease. In the Americas, the reported incidence of disease, in the range of 0.3-4 cases per 100,000 population, is much lower than in the meningitis belt. In addition, in some countries such as the United States, the incidence is at an historical low. The bulk of the disease in the Americas is caused by serogroups C and B, although serogroup Y causes a substantial proportion of infections in some countries and W-135 is becoming increasingly problematic as well. The majority of meningococcal disease in European countries, which ranges in incidence from 0.2 to 14 cases per 100,000, is caused by serogroup B strains, particularly in countries that have introduced serogroup C meningococcal conjugate vaccines. Serogroup B also predominates in Australia and New Zealand, in Australia because of the control of serogroup C disease through vaccination and in New Zealand because of a serogroup B epidemic. Based on limited data, most disease in Asia is caused by serogroup A and C strains. Although this review summarizes the current status of meningococcal disease epidemiology, the dynamic nature of this disease requires ongoing surveillance both to provide data for vaccine formulation and vaccine policy and to monitor the impact of vaccines following introduction.

Quadrivalent meningococcal ACYW-135 glycoconjugate vaccine for broader protection from infancy

Invasive meningococcal disease is a global public-health concern, with infants and adolescents bearing the majority of the disease burden. Vaccination is the most rational strategy to prevent meningococcal disease. Control of serogroup C disease has largely been achieved by the introduction of glycoconjugate meningococcal C vaccines, initially in the UK in 1999, and subsequently in several other countries. The recent licensure of a quadrivalent glycoconjugate vaccine against serogroups A, C, Y and W-135 in the USA and Canada has broadened protection against Neisseria meningitidis in 2-55 year olds. The investigational quadrivalent meningococcal serogroup A, C, Y and W-135 glycoconjugate vaccine (MenACYW-CRM197), which is immunogenic from infancy, has the potential to extend protection to the most vulnerable age group. This article discusses this novel quadrivalent vaccine formulation and its potential to control invasive disease caused by N. meningitidis serogroups A, C, Y and W-135.

Distribution of surface-protein variants of hyperinvasive meningococci in China

OBJECTIVE

Information regarding the different types of FetA and PorB meningococci that circulate in various regions of the world is still scarce. The present study investigated the distribution of FetA and PorB variable region (VR) types among meningococci belonging to hyperinvasive lineages circulating in China.

METHODS

The approach consisted of genotypic analysis of 201 Neisseria meningitidis strains belonging to hyperinvasive lineages isolated in China during the period 1956-2006.

RESULTS

Sixteen different PorB types were found, 8 of which were newly identified. Of the 24 different FetA VR types, 3 were determined to be novel. Particular combinations of FetA and PorB types associated with distinct clonal complexes were also observed. Most cases of invasive disease were caused by five individual clones: A: P1.7-1,10: F5-5: ST-3 (cc1) with P3.6,11,10,7 (class 3 PorB protein; VR1-6, VR2-11, VR3-10, and VR4-7); A: P1.20,9: F3-1: ST-5 (cc5) with P3.4,11,10,7; A: P1.20,9: F3-1: ST-5 (cc5) with P3.9,11,10,7; A: P1.20,9: F3-1: ST-7 (cc5) with P3.4,11,10,7; and C: P1.7-2,14: F3-3: ST-4821 (cc4821) with P3.9,15,6,7.

CONCLUSION

A number of antigen-gene variants and combinations exhibited broad temporal and geographic distributions, although several invasive clones were mainly associated with a specified timeframe. The changes that are increasingly emerging in circulating strains and the prevalent clone replacement describe the molecular epidemiology of meningococcal disease in China. Our findings have implications for both public-health monitoring and further study of this organism.