Vaccine potential of meningococcal FrpB: studies on surface exposure and functional attributes of common epitopes

doi:10.1016/0264-410X(94)90314-X

Vaccine

Volume 12, Issue 6, May 1994, Pages 535-541

https://doi.org/10.1016/0264-410X(94)90314-X Get rights and content

Abstract

Neisseria meningitidis expresses several novel outer membrane proteins (OMPs) in vivo and when grown under iron limitation in vitro. One of the most prominent is a 70 kDa iron-regulated protein (FrpB). FrpB was purified by elution from SDS—polyacrylamide gels and rabbit polyclonal antiserum (R-70) was raised against it. R-70 was bactericidal against homologous, but not heterologous, strains in the presence of human complement. The bactericidal activity was retained when R-70 was adsorbed with formaldehyde-fixed iron-replete cells (i.e. not expressing FrpB), but lost when adsorbed with fixed iron-restricted cells (which express FrpB). A murine monoclonal anti-FrpB antibody (mAb M70) was raised against a common epitope which showed complete cross-reaction on Western blots of OMPs from other serogroups and serotypes of N. meningitidis and some commensal Neisseriae species. However, it failed to kill the organism. Immunogold electron microscopy on ultrathin sections, using the R-70 antiserum adsorbed with fixed iron-replete cells, showed labelling on 40% of the cells, whereas the R-70 adsorbed with fixed iron-restricted cells and mAb M70 failed to label. However, none of these sera labelled whole cells, suggesting lack of surface accessibility. It appears that the highly conserved cross-reactive epitopes of FrpB only become exposed in the process of generating the antigen, whereas the surface-exposed epitopes recognized in killing assays are immunologically variable among different strains. Therefore, despite the strong immunogenicity of the common epitopes of FrpB in vivo, their apparent lack of surface exposure and the failure of antibodies against them to kill meningococci do not support consideration of this protein alone as the sole component of a broadly cross-protective vaccine.

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Cited by (37)

Viral vectors expressing group B meningococcal outer membrane proteins induce strong antibody responses but fail to induce functional bactericidal activity
2022, Journal of Infection
Adenoviral vectored vaccines, with the appropriate gene insert, induce cellular and antibody responses against viruses, parasites and intracellular pathogens such as Mycobacterium tuberculosis. Here we explored their capacity to induce functional antibody responses to meningococcal transmembrane outer membrane proteins.
Vectors expressing porin A and ferric enterobactin receptor A antigens were generated, and their immunogenicity assessed in mice using binding and bactericidal assays.
The viral vectors expressed the bacterial proteins in an in vitro cell-infection assay and, after immunisation of mice, induced higher titres (>10⁵ end-point titre) and longer lasting (>32 weeks) transgene-specific antibody responses in vivo than did outer membrane vesicles containing the same antigens. However, bactericidal antibodies, which are the primary surrogate of protection against meningococcus, were undetectable, despite different designs to support the presentation of the protective B-cell epitopes.
These results demonstrate that, while the transmembrane bacterial proteins expressed by the viral vector induced strong and persistent antigen-specific antibodies, this platform failed to induce bactericidal antibodies. The results suggest that conformation or post-translational modifications of bacterial outer membrane antigens produced in eukaryote cells might not result in presentation of the necessary epitopes for induction of functional antibodies.
A novel meningococcal outer membrane vesicle vaccine with constitutive expression of FetA: A phase I clinical trial
2015, Journal of Infection
Citation Excerpt :
This means that multiple PorA types are required to cover different strains.17–19 FetA is an additional vaccine candidate, being a variable subcapsular antigen that has been shown to induce bactericidal antibodies in animal models20–23 and to a certain extent during clinical trials, where immune responses against FetA can be detected.21,24–26 As a consequence of iron-dependent regulation of its expression during culture,27 the amount of FetA is variable in OMV vaccines, ranging from 0 to 9% of the total protein content of MenBVac and MeNZB, used in Norway and New Zealand, respectively.28,29
Outer membrane vesicle (OMV) vaccines are used against outbreaks of capsular group B Neisseria meningitidis (MenB) caused by strains expressing particular PorA outer membrane proteins (OMPs). Ferric enterobactin receptor (FetA) is another variable OMP that induces type-specific bactericidal antibodies, and the combination of judiciously chosen PorA and FetA variants in vaccine formulations is a potential approach to broaden protection of such vaccines.
The OMV vaccine MenPF-1 was generated by genetically modifying N. meningitidis strain 44/76 to constitutively express FetA. Three doses of 25 μg or 50 μg of MenPF-1 were delivered intra-muscularly to 52 healthy adults.
MenPF-1 was safe and well tolerated. Immunogenicity was measured by serum bactericidal assay (SBA) against wild-type and isogenic mutant strains. After 3 doses, the proportion of volunteers with SBA titres ≥1:4 (the putative protective titre) was 98% for the wild-type strain, and 77% for the strain 44/76 FetA_onPorA_off compared to 51% in the strain 44/76 FetA_offPorA_off, demonstrating that vaccination with MenPF-1 simultaneously induced FetA and PorA bactericidal antibodies.
This study provides a proof-of-concept for generating bactericidal antibodies against FetA after OMV vaccination in humans. Prevalence-based choice of PorA and FetA types can be used to formulate a vaccine for broad protection against MenB disease.
Serogroup B meningococcal vaccines-an unfinished story
2010, The Lancet Infectious Diseases
Citation Excerpt :
Iron-regulated proteins (eg, FetA, LbpA, and LbpB) are upregulated in conditions where the concentration of iron is low, so the amount present in outer membrane vesicle vaccines is dependent on growth conditions during manufacture. FetA induced serum bactericidal antibody in rabbits,115 and an outer membrane vesicle vaccine with high expression of FetA is in development, aiming to overcome strain restriction by eliciting antibodies against both PorA and FetA. Other proposed candidates include outer membrane vesicles with overexpression of LbpA, purified LbpB, and recombinant Opa, which have all induced bactericidal antibodies in mice.113,116
Most invasive meningococcal disease in developed countries is caused by Neisseria meningitidis with a serogroup B capsule. However, despite availability of vaccines for other serogroups since the 1960s, no serogroup B vaccine exists. In this Review we look at the development of serogroup B vaccines over the past 40 years. Outer membrane vesicle vaccines have been successfully used to control geographically isolated epidemics, but most have not been highly immunogenic in young children or provided broad cross-protection from infections with other strains. Vaccines based on subcapsular antigens have recently produced promising results in early clinical trials, and the disease burden might be substantially reduced over the next few years.
A common gene pool for the Neisseria FetA antigen
2009, International Journal of Medical Microbiology
Meningococcal FetA is an iron-regulated, immunogenic outer membrane protein and vaccine component. The most diverse region of this protein is a previously defined variable region (VR) that has been shown to be immunodominant. In this analysis, a total of 275 Neisseria lactamica isolates, collected during studies of nasopharyngeal bacterial carriage in infants, were examined for the presence of a fetA gene. The fetA VR nucleotide sequence was determined for 217 of these isolates, with fetA apparently absent from 58 isolates, the majority of which belonged to the ST-624 clonal complex. The VR in N. lactamica was compared to the same region in N. meningitidis, N. gonorrhoeae, and a number of other commensal Neisseria. Identical fetA variable region sequences were identified among commensal and pathogenic Neisseria, suggesting a common gene pool, differing from other antigens in this respect. Carriage of commensal Neisseria species, such as N. lactamica, that express FetA may be involved in the development of natural immunity to meningococcal disease.
Shielding of immunogenic domains in Neisseria meningitidis FrpB (FetA) by the major variable region
2007, Vaccine
Citation Excerpt :
Its vaccine potential was previously investigated [22–25]. Immunization of laboratory animals with formulations containing FrpB resulted in strain-specific bactericidal antibodies [22–24]. Some of these antibodies were shown to recognize synthetic peptides derived from a variable region of FrpB, which is in agreement with their strain-specificity [23].
The meningococcal iron-limitation-inducible outer membrane protein FrpB (FetA) has been shown to induce bactericidal antibodies, and is, therefore, considered a vaccine candidate. However, these antibodies are strain specific and, consistently, epitope mapping showed that they are directed against a region, located in a surface-exposed loop, L5, that displays considerable sequence variability between strains. Here, we attempted to redirect the immune response to more conserved domains of the protein by deleting L5. Immunization with an FrpB protein lacking L5 resulted in a bactericidal antibody response, and epitope mapping showed that these antibodies were directed against loop L3, which also displays considerable sequence variability. To re-direct the immune response further, immunizations were performed with an FrpB protein lacking both L5 and L3. The antibodies obtained were not bactericidal. Furthermore, the bactericidal antibodies against L3 were only bactericidal in the absence of L5, and immunofluorescence microscopy experiments showed that L5 efficiently shields other immunogenic cell surface-exposed epitopes outside of this region on living cells. Whereas the ability of micro-organisms to vary surface-exposed domains that are targets for protective immunity has long been established, the current work shows that such domains can be remarkably efficient in shielding other, more conserved epitopes.
The identification of two protective DNA vaccines from a panel of five plasmid constructs encoding Brucella melitensis 16M genes
2007, Vaccine
Citation Excerpt :
Iron regulation in Brucella is known to be linked with virulence (for review see [22]), and thus immune intervention of the iron regulation proteins was hypothesised to contribute to control of infection. Moreover, Brucella frpB was shown to exhibit homology to Neisseria meningitidis frpB which has demonstrable immunogenicity [23]. The fliC candidate was selected as a potentially significant surface antigen or secreted protein previously unstudied in Brucella.
Five candidate genes from the Brucella melitensis 16M genome were selected. Eukaryotic expression plasmids encoding these antigens were constructed and expression was verified in vitro from transfected Cos7 cells. Each vaccine was assessed for protective efficacy in a BALB/c mouse brucellosis infection model. From these experiments two protective DNA vaccines were identified: p-omp25 and p-ialB. The Omp25 antigen (BMEI1249) has previously been studied in terms of Brucella virulence, serodiagnosis and as a protective antigen. However, this study represents the first report of a significant protective effect achieved against B. melitensis 16M challenge using the Omp25 antigen in a DNA vaccine approach. The other protective vaccine identified in this study was p-ialB. The ialB candidate (BMEI1584) was selected based upon its’ putative function as an invasion protein which was assigned due to shared identity with the invasion protein B (ialB) of Bartonella bacilliformis. This candidate has not previously been investigated with regard to Brucella virulence or pathogenesis. This study is the first report to identify the Brucella invasion protein B (BMEI1584) as a novel protective antigen for brucellosis.

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Abstract

References (31)

Effect of outer membrane vesicle vaccine against group B meningococcal disease in Norway

Lancet

The 70 kilodalton iron regulated protein Neisseria meningitidis is not the receptor for human transferrin

FEMS. Microbiol. Lett.

A rapid and sensitive method for the quantification of microgram quantities of protein utilizing the principle of protein-dye binding

Anal. Biochem.

Antigenic and molecular heterogenicity of the transferrin-binding proteins of Neisseria meningitidis

FEMS Microbiol. Lett.

Conventional laboratory agar media provide an iron-limited environment for bacterial growth

FEMS Microbiol. Lett.

The meningococcus and mechanisms of pathogenicity

Microbiol. Rev.

Immune response of infants and children to disseminated infection with Neisseria meningitidis

J. Infect. Dis.

Vaccine against group B Neisseria meningitidis: protection trial and mass vaccination results in Cuba

NIPH Ann.

Protective efficacy of a serogroup B meningococcal vaccine in Sao Paulo, Brazil

Lancet

Meningococcal serogroup B vaccine protection trial and follow-up studies in Chile

NIPH Ann.

Antibody responses to serogroup B meningococcal outer membrane antigens after vaccination and infection

J. Clin. Microbiol.

Immunisation against Neisseria meningitidis

Deduced amino acid sequences of class I protein (Por A) from three strains of Neisseria meningitidis

J. Exp. Med.

Comparison of the class 1 outer membrane proteins of eight serological reference strains of Neisseria meningitidis

Mol. Microbiol.

Expression of an inaccessible P1.7 subtype on meningococcal class 1 proteins

J. Med. Microbiol.

Cited by (37)

Viral vectors expressing group B meningococcal outer membrane proteins induce strong antibody responses but fail to induce functional bactericidal activity

A novel meningococcal outer membrane vesicle vaccine with constitutive expression of FetA: A phase I clinical trial

Serogroup B meningococcal vaccines-an unfinished story

A common gene pool for the Neisseria FetA antigen

Shielding of immunogenic domains in Neisseria meningitidis FrpB (FetA) by the major variable region

The identification of two protective DNA vaccines from a panel of five plasmid constructs encoding Brucella melitensis 16M genes

PaperVaccine potential of meningococcal FrpB: studies on surface exposure and functional attributes of common epitopes

Abstract

Lancet

FEMS. Microbiol. Lett.

Anal. Biochem.

FEMS Microbiol. Lett.

FEMS Microbiol. Lett.

The meningococcus and mechanisms of pathogenicity

Microbiol. Rev.

Immune response of infants and children to disseminated infection with Neisseria meningitidis

J. Infect. Dis.

Vaccine against group B Neisseria meningitidis: protection trial and mass vaccination results in Cuba

NIPH Ann.

Protective efficacy of a serogroup B meningococcal vaccine in Sao Paulo, Brazil

Lancet

Meningococcal serogroup B vaccine protection trial and follow-up studies in Chile

NIPH Ann.

Antibody responses to serogroup B meningococcal outer membrane antigens after vaccination and infection

J. Clin. Microbiol.

Immunisation against Neisseria meningitidis

Deduced amino acid sequences of class I protein (Por A) from three strains of Neisseria meningitidis

J. Exp. Med.

Comparison of the class 1 outer membrane proteins of eight serological reference strains of Neisseria meningitidis

Mol. Microbiol.

Expression of an inaccessible P1.7 subtype on meningococcal class 1 proteins

J. Med. Microbiol.

Paper
Vaccine potential of meningococcal FrpB: studies on surface exposure and functional attributes of common epitopes