The H8 antigen of pathogenic Neisseriae

We cloned and sequenced the H8 gene from N. meningitidis FAM18. The predicted amino acid sequence included a consensus lipoprotein signal sequence processing site, consistent with lipid modification that could account for the unusual electrophoretic and solubilization properties of H8. The amino acid sequence was rich in alanine and proline, especially in an imperfectly periodic region near the amino terminus, which encompassed the epitope recognized by available monoclonal antibodies. In a panel of neisserial strains, the presence of DNA homologous to the H8 gene correlated with the expression of an H8 protein. We cloned a gene from N. meningitidis JB515 that was distinct from the H8 gene but encoded a protein also recognized by an anti-H8 monoclonal antibody. Mice were not protected from meningococcemia by passive immunization with such an antibody.     

The Development of an Experimental Multiple Serogroups Vaccine for Neisseria meningitidis

A native outer membrane vesicles (NOMV) vaccine was developed from three antigenically diverse strains of Neisseria meningitidis that express the L1,8, L2, and L3,7 lipooligosaccharide (LOS) immunotypes, and whose synX, and lpxL1 genes were deleted.. Immunogenicity studies in mice showed that the vaccine induced bactericidal antibody against serogroups B, C, W, Y and X N. meningitidis strains. However, this experimental NOMV vaccine was not effective against serogroup A N. meningitidis strains. N. meningitidis capsular polysaccharide (PS) from serogroups A, C, W and Y were effective at inducing bactericidal antibody when conjugated to either tetanus toxoid or the fHbp1-fHbp2 fusion protein fHbp(1+2). The combination of the NOMV vaccine and the N. meningitidis serogroup A capsular polysaccharide (MAPS) protein conjugate was capable of inducing bactericidal antibodies against a limited number of N. meningitidis strains from serogroups A, B, C, W, Y and X tested in this study.     

Antigenic variation of pilin regulates adhesion of Neisseria meningitidis to human epithelial cells

Pili have been shown to play an essential role in the adhesion of Neisseria meningitidis to epithelial cells. However, among piliated strains, both inter- and intrastrain variability exist with respect to their degree of adhesion to epithelial cells in vitro (Virji et al., 1992). This suggests that factors other than the presence of pili per se are involved in this process. The N. meningitidis pilin subunit undergoes extensive antigenic variation. Piliated low- and high-adhesive derivatives of the same N. meningitidis strain were selected and the nucleotide sequence of the pilin gene expressed in each was determined. The highly adhesive derivatives had the same pilin sequence. The alleles encoding the pilin subunit of the low-adhesive derivatives were completely different from the one found in the high-adhesive isolates. Using polyclonal antibodies raised against one hyperadhesive variant, it was confirmed that the low-adhesive piliated derivatives expressed pilin variants antigenically different from the highly adhesive strains. The role of antigenic variation in the adhesive process of N. meningitidis was confirmed by performing allelic exchanges of the pilE locus between low-and high-adhesive isolates. Antigenic variation has been considered a means by which virulent bacteria evade the host immune system. This work provides genetic proof that a bacterial pathogen, N. meningitidis, can use antigenic variation to modulate their degree of virulence.     

Expression of meningococcal epitopes in LamB of Escherichia coli and the stimulation of serosubtype-specific antibody responses

The class 1 outer membrane protein (OMP), a major variable surface antigen of Neisseria meningitidis, is a component of novel meningococcal vaccines currently in field trials. Serological variants of the protein are also used to serosubtype meningococci. Most of the amino acid changes that give rise to antigenic variants of the protein occur in two variable regions (VR1 and VR2) that are thought to form loops on the cell surface. The polymerase chain reaction (PCR) was used to amplify the nucleotide sequences encoding VR1 and VR2 from the chromosomal DNA of N. meningitidis strain M1080. These were cloned in frame into the lamB gene of the Escherichia coli expression vector pAJC264. Whole-cell enzyme-linked immunosorbent assays (ELISAs), using monoclonal antibodies, and SDS PAGE confirmed that, upon induction, strains of E. coli carrying these constructs expressed hybrid LamB proteins containing the N. meningitidis surface loops. These strains were used to immunize rabbits and the resultant polyclonal antisera reacted specifically with the class 1 OMP of reference strain M1080 (P1.7). Immunogold labelling of meningococcal cells and whole-cell dot-blot analyses with these antisera showed that the variable epitopes were exposed on the cell surface and confirmed that this approach could be used to obtain serosubtype-specific antisera. The binding profiles of the antisera were determined from their reactions with overlapping synthetic peptides and their reactivity compared with that of relevant serosubtype-specific monoclonal antibodies. This approach was used successfully to raise antisera against two other class 1 OMP VR2s. A fourth antiserum raised against a VR2, including the P1.1 epitope, was not subtype specific.     

The role of glyceraldehyde 3-phosphate dehydrogenase (GapA-1) in <Emphasis Type="Italic">Neisseria meningitidis</Emphasis> adherence to human cells

Background  

Glyceraldehyde 3-phosphate dehydrogenases (GAPDHs) are cytoplasmic glycolytic enzymes, which although lacking identifiable secretion signals, have also been found localized to the surface of several bacteria (and some eukaryotic organisms); where in some cases they have been shown to contribute to the colonization and invasion of host tissues. Neisseria meningitidis is an obligate human nasopharyngeal commensal which can cause life-threatening infections including septicaemia and meningitis. N. meningitidis has two genes, gapA-1 and gapA-2, encoding GAPDH enzymes. GapA-1 has previously been shown to be up-regulated on bacterial contact with host epithelial cells and is accessible to antibodies on the surface of capsule-permeabilized meningococcal cells. The aims of this study were: 1) to determine whether GapA-1 was expressed across different strains of N. meningitidis; 2) to determine whether GapA-1 surface accessibility to antibodies was dependant on the presence of capsule; 3) to determine whether GapA-1 can influence the interaction of meningococci and host cells, particularly in the key stages of adhesion and invasion.     

1H, 13C and 15N assignment of the C-terminal domain of GNA2132 from Neisseria meningitidis

GNA2132 (Genome-derived Neisseria Antigen 2132) is a surface-exposed lipoprotein discovered by reverse vaccinology and expressed by genetically diverse Neisseria meningitidis strains (Pizza et al. 2000). The protein induces bactericidal antibodies against most strains of Meningococccus and has been included in a multivalent recombinant vaccine against N. meningitidis serogroup B. Structure determination of GNA2132 is important for understanding the antigenic properties of the protein in view of increased efficiency vaccine development. We report practically complete ¹H, ¹³C and ¹⁵N assignment of the detectable spectrum of a highly conserved C-terminal region of GNA2132 (residues 245–427) in micellar solution, a medium used to improve the spectral quality. The first 32 residues of our construct up to residue 277 were not visible in the spectrum, presumably because of line broadening due to solvent and/or conformational exchange. Secondary structure predictions based on chemical shift information indicate the presence of an all β-protein with eight β strands.     

Surface antigen analysis of group B Neisseria meningitidis outer membrane by monoclonal antibodies: Identification of bactericidal antibodies to class 5 protein

Twenty-four monoclonal antibodies (mAbs) against group B Neisseria meningitidis surface antigens were analyzed by immunoenzymatic assays and by a bactericidal test. Two mAbs were specific to polysaccharide B and one to lipopolysaccharide. The others were directed against outer membrane proteins ranging in molecular mass from 25 to 200 kDa. The outer membrane protein epitopes recognized by the mAbs were not conformational and were located on the outer surface of the microorganism. Linear epitopes on the class 5 protein, exposed on the surface of the membrane, were able to induce bactericidal antibodies to the homologous strain. The susceptibility of Neisseria meningitidis to these antibodies was unchanged when this organism was cultivated under conditions of iron depletion. These results demonstrate that peptides derived from class 5 proteins are potentially important in synthetic peptide or in recombinant protein vaccines containing linear bactericidal epitopes.     

The Neisseria meningitidis haemoglobin receptor: its role in iron utilization and virulence

The Neisseris meningitidis haemoglobin receptor gene, hmbR, was cloned by complementation in a porphyrin-requiring Escherichia coli mutant. hmbR encodes an 89.5 kDa outer membrane protein which shares amino acid homology with the TonB-dependent receptors of Gram-negative bacteria. HmbR had the highest similarity to Neisseria transferrin and lactoferrin receptors. The utilization of haemoglobin as an iron source required internalization of the haemin moiety by the cell. The mechanism of haemin internalization via the haemoglobin receptor was TonB-dependent in E. coli. A N. meningitidis hmbR mutant was unable to use haemoglobin but could still use haemin as a sole iron source. The existence of a second N. meningitidis receptor gene, specific for haemin, was shown by the isolation of cosmids which did not hybridize with the hmbR probe, but which were able to complement an E. coli hemA aroB mutant on haemin-supplemented plates. The N. meningitidis hmbR mutant was attenuated in an infant rat model for meningococcal infection, indicating that haemoglobin utilization is important for N. meningitidis virulence.     

Role of interspecies transfer of chromosomal genes in the evolution of penicillin resistance in pathogenic and commensal Neisseria species

Summary The two pathogenic species of Neisseria, N. meningitidis and N. gonorrhoeae, have evolved resistance to penicillin by alterations in chromosomal genes encoding the high molecular weight penicillin-binding proteins, or PBPs. The PBP 2 gene (penA) has been sequenced from over 20 Neisseria isolates, including susceptible and resistant strains of the two pathogenic species, and five human commensal species. The genes from penicillin-susceptible strains of N. meningitidis and N. gonorrhoeae are very uniform, whereas those from penicillin-resistant strains consist of a mosaic of regions resembling those in susceptible strains of the same species, interspersed with regions resembling those in one, or in some cases, two of the commensal species. The mosaic structure is interpreted as having arisen from the horizontal transfer, by genetic transformation, of blocks of DNA, usually of a few hundred base pairs. The commensal species identified as donors in these interspecies recombinational events (N. flavescens and N. cinerea) are intrinsically more resistant to penicillin than typical isolates of the pathogenic species. Transformation has apparently provided N. meningitidis and N. gonorrhoeae with a mechanism by which they can obtain increased resistance to penicillin by replacing their penA genes (or the relevant parts of them) with the penA genes of related species that fortuitously produce forms of PBP 2 that are less susceptible to inhibition by the antibiotic. The ends of the diverged blocks of DNA in the penA genes of different penicillin-resistant strains are located at the same position more often than would be the case if they represent independent crossovers at random points along the gene. Some of these common crossover points may represent common ancestry, but reasons are given for thinking that some may represent independent events occurring at recombinational hotspots. Offprint requests to: B.G. Spratt     

Induction of antimeningitis immunity by the synthetic peptides: I. The immunoactive synthetic fragments of porin A fromNeisseria meningitidis

Fourteen peptides corresponding to sequences of all the exposed and some of the transmembrane protein regions of porin A from the outer membrane ofNeisseria meningitidis strain B:15:P1.7,16 were synthesized. Mice of various lines were immunized with the free peptides not conjugated with any protein carrier. It was shown that the majority of the peptides possess immunogenic properties. Two peptides were identified binding to antibodies present in the serum of mice after meningitis. Protective properties of a number of the synthesized peptides were studied, and three peptide sequences inducing mice protection to an experimental infection withN. meningitidis were identified.     

Cloning, gene expression and characterization of a novel bacterial NAD-dependent non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase from Neisseria meningitidis strain Z2491

Alignment of the amino acid sequence of some archaeal, bacterial and eukaryotic non-phosphorylating glyceraldehydes-3-phosphate dehydrogenases (GAPNs) and aldehyde dehydrogenases (ALDHs) with the sequence of a putative GAPN present in the genome of the Gram-negative bacterium Neisseria meningitidis strain Z2491 demonstrated the conservation of residues involved in the catalytic activity. The predicted coding sequence of the N. meningitidis gapN gene was cloned in Escherichia coli XL1-blue under the expression of an inducible promoter. The IPTG-induced GAPN was purified ca. 48-fold from E. coli cells using a procedure that sequentially employed conventional ammonium sulfate fractionation as well as anion-exchange and affinity chromatography. The purified recombinant enzyme was thoroughly characterized. The protein is a homotetramer with a 50-kDa subunit, exhibiting absolute specificity for NAD and a broad spectrum of aldehyde substrates. Isoelectric focusing analysis with the purified fraction showed the presence of an acidic polypeptide with an isoelectric point of 6.3. The optimum pH of the purified enzyme was between 9 and 10. Studies on the effect of increasing temperatures on the enzyme activity revealed an optimal value ca. 64 °C. Molecular phylogenetic data suggest that N. meningitidis GAPN has a closer relationship with archaeal GAPNs and glyceraldehyde dehydrogenases than with the typical NADP-specific GAPNs from Gram-positive bacteria and photosynthetic eukaryotes.     

Characterization of serogroup C meningococci isolated from 14 provinces of China during 1966–2005 using comparative genomic hybridization

Neisseria meningitidis is a major cause of bacterial meningitis and septicemia worldwide. In China, serogroup A strains were responsible for over 95% of the cases, while serogroup C strains were only recovered from a few sporadic cases. However, a sudden increase in the number of cases due to serogroup C strains occurred during 2003–2005 in Anhui Province, China. Many cases were found in other provinces at the same time. Multilocus sequence typing (MLST) results indicated that the unique sequence type 4821 clone meningococci, a new hyper-virulent lineage, was responsible for the serogroup C meningitis outbreaks. We have completed the project of sequencing the whole genome of the Chinese N. meningitidis serogroup C representative isolate 053442. We fabricated a whole-genome microarray of N. meningitidis isolate 053442 and analyzed the genome composition differences among 81 serogroup C isolates which were isolated from 14 provinces of China during 1966–2005. The comparative genomic hybridization (CGH) result shows that the genome compositions of nearly all serogroup C isolates are similar to that of 053442. The products of many absent open reading frames (ORFs) are conserved hypothetical proteins. The results will provide a valuable resource from which one can analyze the genome composition and genetic background of serogroup C meningococci in China.     

Induction of Antimeningitis Immunity by Synthetic Peptides: III. Immunoactive Synthetic Fragments of the NspA Protein from Neisseria meningitidis

Four potentially immunoactive peptide fragments of the NspA protein from the outer membrane of the Neisseria meningitidis bacterium were synthesized in order to create a synthetic vaccine against meningococcal infection by the serogroup B bacterium. Mice of various lines were immunized with free peptides nonconjugated with a protein carrier. All the synthetic peptides were shown to induce the production of the antipeptide antibodies in mice. A peptide capable of inducing a decrease in the number of bacteria in blood and the protection of infected animals from death was found in the experiments on the protection of the animals infected with two strains of the Neisseria meningitidis serogroup B.     

Analysis in Neisseria meningitidis and other Neisseria species of genes homologous to the FKBP immunophilin family

The immunophilin family of FK506-binding proteins (FKBPs), involved in eukaryotic protein folding and cell regulation, have recently been found to have prokaryotic homologues. Genes with sequences homologous to those encoding human FKBPs were examined in Neisseria species. An FKBP DNA sequence was present, as shown by the polymerase chain reaction and Southern blotting experiments, in the chromosome of Neisseria meningitidis (14 strains) and in all 11 different commensal Neisseria spp. studied, but was not found in Neisseria gonorrhoeae (11 strains tested) or in Moraxella catarrhalis. The nucleotide and predicted protein sequences of the FKBP-encoding domain from five of the meningococcal strains were highly conserved (e.g. ≥97% homologous). The meningococcal nucleotide sequence was ≥93% homologous and the consensus meningococcal protein sequence was ≥97% homologous to FKBP sequences found in seven different commensal Neisseria spp. The meningococcal nucleotide and predicted protein sequences were ≥59% homologous to the conserved C-terminus of the human FKBP gene family. The FKBP nucleotide sequence was present as a single copy in the chromosome of commensal Neisseria spp. and in most strains of N. meningitidis. The FKBP gene was linked to the silent pilin locus, pilS, in class II-piliated meningococcal strains. In meningococcal strains expressing class I pili, the FKBP gene was linked to one of several pilS loci but not the pilE locus present in these strains. FKBP genes found in commensal Neisseria spp. were not linked to known pilin loci.     

Induction of Anti-Meningitis Immunity by Synthetic Peptides: II. Immunoactive Synthetic Fragments of the OpaB Protein from Neisseria meningitidis

Mice of various lines were immunized by 11 synthetic peptides that correspond to the sequences of fragments of the OpaB protein from the outer membrane of Neisseria meningitidis involving the known human T-helper epitopes and all the potential mouse T-helper epitopes calculated for the protein. The mice were immunized with the free peptides without their conjugation with a protein carrier. Most of the peptides were found to induce in mice the production of antipeptide antibodies. Mice protection against the experimental infection by a virulent strain of N. meningitidis of the B serotype was studied, and two peptides were shown to exert the most pronounced protective effect.     

Genetic Diversity of Neisseria meningitidis Serogroup C ST-4821 in China Based on Multiple-Locus Variable Number Tandem Repeat Analysis

Neisseria meningitidis sequence type (ST)-4821 was first reported in China in 2003, and a new hyper-virulent lineage has been designated as the ST-4821 complex. A large number of N. meningitidis ST-4821 strains have been identified in China since 2003; however, the microevolution characteristics of this complex are unclear. Different combinations of variable number of tandem repeats (VNTR) loci were used in multiple-locus VNTR analysis (MLVA) to analyze 118 N. meningitidis serogroup C ST-4821 strains isolated from seventeen provinces between 2003 and 2012. Additionally, MLVA with five VNTR loci was performed due to its high discriminatory power. One hundred and eighteen isolates were found to comprise 112 subtypes based on MLVA, and 16 outbreak-associated strains were clustered into one group. These data indicate a high level of diversity for N. meningitidis ST-4821 due to microevolution in the last decade. In addition, the results revealed high similarity between isolates from the same geographic origins, which is helpful when monitoring the spread of N. meningitidis serogroup C ST-4821 and will provide valuable information for the control and prevention of bacterial meningitis in China.     

Characterization of serogroup C meningococci isolated from 14 provinces of China during 1966—2005 using comparative genomic hybridization

Neisseria meningitidis is a major cause of bacterial meningitis and septicemia worldwide. In China, serogroup A strains were responsible for over 95% of the cases, while serogroup B strains were mainly the cause of localized outbreaks and sporadic cases. Before 2003, serogroup C strains were only re-covered from a few sporadic cases. However, a sudden increase in the number of cases due to sero-group C strains occurred during 2003—2005 in Anhui Province, China. Many cases were found in other provinces at the same time. Multilocus sequence typing (MLST) results indicated that the unique se-quence type 4821 clone meningococci, a new hyper-virulent lineage, was responsible for the serogroup C meningitis outbreaks. We have completed the project of sequencing the whole genome of the Chi-nese N. meningitidis serogroup C representative isolate 053442. We fabricated a whole-genome mi-croarray of N. meningitidis isolate 053442 and analyzed the genome composition differences among 81 serogroup C isolates which were isolated from 14 provinces of China during 1966—2005. The com-parative genomic hybridization (CGH) result shows that the genome compositions of nearly all sero-group C isolates are similar to that of 053442. The products of many absent open reading frames (ORFs) are conserved hypothetical proteins. The results will provide a valuable resource from which one can analyze the genome composition and genetic background of serogroup C meningococci in China.     

Protective potency of recombinant meningococcal IgA1 protease and its structural derivatives upon animal invasion with meningococcal and pneumococcal infections

Immunization of mice with recombinant IgA1 protease of Neisseria meningitidis or several structural derivatives thereof protects the animals infected with a variety of deadly pathogens, including N. meningitidis serogroups A, B, and C and 3 serotypes of Streptococcus pneumonia. In sera of rabbits immunized with inactivated pneumococcal cultures, antibodies binding IgA1-protease from N. meningitidis serogroup B were detected. Thus, the cross-reactive protection against meningococcal and pneumococcal infections has been demonstrated in vivo. Presumably it indicates the presence of common epitopes in the N. meningitidis IgA1 protease and S. pneumoniae surface proteins.     

Structure and function of repetitive sequence elements associated with a highly polymorphic domain of the Neisseria meningitidis PilQ protein

Secretins are a large family of proteins associated with membrane translocation of macromolecular complexes, and a subset of this family, termed PilQ proteins, is required for type IV pilus biogenesis. We analysed the status of PilQ expression in Neisseria meningitidis (Mc) and found that PilQ^? mutants were non-piliated and deficient in the expression of pilus-associated phenotypes. Sequence analysis of the 5′ portion of the pilQ ORF of the serogroup B Mc strain 44/76 showed the presence of seven copies of a repetitive sequence element, in contrast to the situation in N. gonorrhoeae (Gc) strains, which carry either two or three copies of the repeat. The derived amino acid sequence of the consensus nucleotide repeat was an octapeptide PAKQQAAA, designated as the small basic repeat (SBR). This gene segment was studied in more detail in a collection of 52 Mc strains of diverse origin by screening for variability in the size of the PCR-generated DNA fragments spanning the SBRs. These strains were found to harbour from four to seven copies of the repetitive element. No association between the number of copies and the serogroup, geographic origin or multilocus genotype of the strains was evident. The presence of polymorphic repeat elements in Mc PilQ is unprecedented within the secretin family. To address the potential function of the repeat containing domain, Mc strains were constructed so as to express chimeric PilQ molecules in which the number of SBR repeats was increased or in which the repeat containing domain was replaced in toto by the corresponding region of the Pseudomonas aeruginosa (Pa) PilQ protein. Although the strain expressing PilQ with an increased number of SBRs was identical to the parent strain in pilus phenotypes, a strain expressing PilQ with the equivalent Pa domain had an eightfold reduction in pilus expression level. The findings suggest that the repeat containing domain of PilQ influences Mc pilus expression quantitatively but not qualitatively.     

Application of Multiple-Locus Variable Number Tandem Repeat Analysis to Identify Outbreak-Associated Neisseria meningitides Serogroup C Sequence Type 4821 in China

Neisseria meningitidis (N. meningitidis) serogroup C sequence type (ST)-4821 caused an outbreak in 2010 in Shandong province of China. Twenty-one non-outbreak-associated strains were isolated, along with twenty-eight N. meningitides serogroup C ST-4821 isolates. Therefore, it’s essential to identify and clarify characterization of the real outbreak-associated strains with a rapid method during an outbreak investigation. In this study, multiple-locus variable number tandem repeat analysis (MLVA) was applied to analyze 84 N. meningitidis strains, among which 58 were recovered from two outbreaks and 26 were sporadic isolates. Three MLVA schemes with different combination of VNTR loci were tested, and two of them were suitable for isolates from China: scheme 2 with six loci was found to separate ST into finer resolution, and scheme 3 with five loci can be used to identify outbreak-associated isolates from the same outbreak that caused by N. meningitidis serogroup C ST-4821.