Recombinant Neisseria meningitidis serogroup C Translation initiation factor IF-2 (infB), partial

What is the biological role of translation initiation factor IF-2 (infB) in Neisseria meningitidis?

Translation initiation factor IF-2 (infB) is a critical component of the bacterial protein synthesis machinery in N. meningitidis. It promotes the correct positioning of the initiator fMet-tRNAi during the early stages of translation, as noted in research on bacterial translation mechanisms . The protein plays an essential role in enabling the bacterium to synthesize proteins necessary for survival, metabolism, and virulence.

During the complex infection process where N. meningitidis must adapt to different host environments, proper protein synthesis regulation becomes critical. Transcriptome analysis has revealed that infB expression may be regulated during interaction with host cells , suggesting its important role in the bacterium's adaptation during infection.

How does infB expression change during N. meningitidis infection of human cells?

When N. meningitidis adheres to host epithelial and endothelial cells, specific gene expression patterns emerge that support bacterial survival and virulence. As noted in one study, "The availability of epitope recognition patterns obtained from single sera permitted to correlate the immune reactivity to specific protein fragment with the functional activity of the antibodies" , highlighting the importance of protein expression during infection stages.

What expression systems yield optimal results for recombinant N. meningitidis infB?

According to product specifications, recombinant infB can be expressed in multiple systems including:

• E. coli

• Yeast

• Baculovirus

• Mammalian cells

Among these, yeast is frequently used for commercial preparations of meningococcal proteins, as indicated in product documentation . The selection of an appropriate expression system depends on research requirements, particularly regarding protein folding and potential post-translational modifications.

For functional studies, researchers should consider that N. meningitidis proteins expressed in E. coli may lack specific post-translational modifications present in the native bacterium, while eukaryotic expression systems might introduce modifications not present in bacteria.

What purification strategies yield highest functional recovery of recombinant infB?

High-purity recombinant infB (typically ≥85% as determined by SDS-PAGE) is generally achieved through multi-step purification protocols:

• Initial capture using affinity chromatography (tag-dependent)

• Intermediate purification via ion exchange chromatography

• Polishing step using size exclusion chromatography

During protein handling, it's critical to maintain appropriate buffer conditions to preserve native structure. According to product specifications, reconstitution should be performed in deionized sterile water to a concentration of 0.1-1.0 mg/mL, with 5-50% glycerol added for long-term storage .

What techniques are most effective for structural characterization of recombinant infB?

To fully characterize recombinant infB structure and function, researchers should employ a complementary set of analytical techniques:

Studies examining bacterial translation factors have demonstrated that functional characterization should include ribosome binding assays and GTP hydrolysis measurements to confirm activity .

How can researchers effectively monitor infB interactions with host immune components?

To investigate potential interactions between infB and host immune components, researchers can employ several approaches:

• Surface Plasmon Resonance (SPR): Enables real-time monitoring of binding kinetics between purified infB and various host factors.

• Pull-down assays followed by mass spectrometry: Useful for identifying novel interaction partners from complex biological samples.

• Immunoprecipitation: Can capture specific infB-host protein complexes from infection models.

• ELISA-based binding assays: Quantitative measurement of specific binding interactions.

These methods are particularly relevant given findings that N. meningitidis proteins can interact with host factors like complement proteins. For example, the factor H binding protein (fHbp) has been extensively studied for its interactions with human complement factor H: "fHbp provides a mechanism for immune evasion by binding human complement factor H (CFH) to protect it from complement-mediated killing" .

What approaches can reveal infB regulation during meningococcal infection processes?

To study infB regulation during infection, researchers can utilize several complementary approaches:

• RNA-Seq analysis: Transcriptome studies have been successfully used to identify genes differentially expressed during host cell interactions. As demonstrated in several studies, N. meningitidis undergoes substantial transcriptional reprogramming when exposed to host cells or human blood .

• qRT-PCR validation: For targeted quantification of infB expression levels under different conditions.

• Reporter gene constructs: Fusing the infB promoter to reporter genes like GFP or luciferase to monitor expression in real-time during infection.

• ChIP-Seq: To identify transcription factors that bind to the infB promoter.

One study examining meningococcal gene expression during human cell interaction noted that "cell-surface-adherent bacteria were dissociated from the HEp-2 cells by treatment with trypsin-EDTA and recovered by centrifugation... more than 95% of the bacteria could be removed from the cell surface and RNA could be extracted from over 90% of the bacteria in total" , demonstrating effective methodologies for isolating bacteria for expression analysis.

How can researchers identify environmental signals that modulate infB expression?

To identify specific environmental cues that influence infB expression, researchers should:

• Design experiments with controlled variation of parameters such as:

  • Temperature (37°C vs. fever temperatures up to 40°C)

  • pH (neutral vs. acidic or basic conditions)

  • Oxygen levels (aerobic vs. microaerobic or anaerobic)

  • Nutrient availability (rich vs. minimal media)

  • Presence of specific host molecules (serum factors, iron sources)

• Use high-throughput approaches like RNA-Seq or microarray analysis to capture global expression changes.

• Employ reporter systems with the infB promoter to directly measure transcriptional responses.

Studies of meningococcal virulence regulation have shown that environmental cues can substantially impact gene expression. For instance, "fHbp is regulated in vivo by environmental cues (such as oxygen levels and temperature)" , suggesting translation factors may be similarly regulated.

How can researchers determine if infB contributes to N. meningitidis virulence?

To assess infB's potential role in virulence, researchers should consider a multi-faceted approach:

What techniques can assess infB's role in meningococcal adaptation to different host environments?

To investigate infB's role in bacterial adaptation to different host niches, researchers can employ:

• Time-course experiments: Analyzing infB expression at different stages of infection, similar to studies that examined "time course experiment of ex vivo bacteremia, with the aim of identifying regulatory RNAs differentially expressed during this step of meningococcal pathogenesis" .

• Tissue-specific models: Comparing bacterial behavior in models representing different host environments (nasopharyngeal tissue, blood, CSF).

• Proteomics analysis: Examining translation profiles under different conditions to determine if infB activity varies.

• In situ hybridization: Localizing infB expression within infected tissues.

Research has shown that "N. meningitidis is a human-adapted pathogen that causes meningitis and sepsis worldwide" , and its ability to adapt to different host environments is crucial for pathogenesis.

How does infB sequence conservation compare across different N. meningitidis serogroups?

To analyze infB conservation:

• Multiple sequence alignment: Compare infB sequences from serogroups A, B, C, W, Y, and others.

• Phylogenetic analysis: Construct evolutionary trees to determine relationships between variants.

• Structure prediction: Map sequence variations onto predicted protein structures to identify functionally relevant differences.

• Selective pressure analysis: Calculate dN/dS ratios to identify regions under positive or purifying selection.

Whole genome sequencing studies have been employed to analyze genetic relationships between meningococcal strains, showing that "N. meningitidis is structured in phylogenetic clades" and that "each clade has acquired and remodeled specific genomic tracts, with the potential to impact on the commensal and virulence behavior" .

What structural or functional differences exist between infB from N. meningitidis and related pathogens?

Translation initiation factor IF-2 is present across diverse bacterial species, but specific adaptations may exist in N. meningitidis. To investigate these differences:

• Comparative structural analysis: Compare crystal structures or homology models of infB from N. meningitidis, N. gonorrhoeae, and other related bacteria.

• Domain organization analysis: Identify specific insertions, deletions, or domain rearrangements.

• Functional complementation studies: Test whether infB from one species can functionally replace that of another.

The close relationship between N. meningitidis and N. gonorrhoeae makes comparative studies particularly interesting. Research has shown that "N. gonorrhoeae and N. meningitidis are closely-related bacteria that cause a significant global burden of disease" , and some antigens are conserved between them, raising the possibility that translation factors might also share important features.

What is the potential of infB as a target for vaccine development against N. meningitidis?

While not typically considered a primary vaccine antigen candidate due to its intracellular location, infB may still have relevance for vaccine research:

• Antigen accessibility assessment: Determine if any portions of infB become surface-exposed during infection.

• T-cell epitope analysis: Identify peptides that could stimulate T-cell responses.

• Cross-protection potential: Investigate whether immune responses against infB might provide protection against multiple strains or even related species.

Current meningococcal vaccines primarily target surface-exposed antigens. For example, the 4CMenB vaccine contains "three major 4CMenB antigenic components (fHbp, NHBA and NadA)" , and studies have shown that "The high level of human anti-gonococcal NHBA antibodies generated by Bexsero vaccination may provide additional cross-protection against gonorrhoea" .

How can researchers evaluate cross-reactivity between antibodies against infB and other Neisseria species proteins?

To assess potential cross-reactivity:

• ELISA-based cross-reactivity testing: Using purified recombinant infB proteins from different species.

• Western blot analysis: Testing antibody recognition of native proteins from multiple species.

• Epitope mapping: Identifying specific regions recognized by cross-reactive antibodies.

• Protein microarray technology: Similar to approaches used in vaccine research where "protein microarray to study the immune response induced by the three major 4CMenB antigenic components (fHbp, NHBA and NadA) in individual sera from vaccinated infants, adolescents and adults" .

Cross-reactivity studies are particularly relevant given findings that some meningococcal vaccine components can generate antibodies recognizing related species: "Bexsero induces antibodies in humans that recognize gonococcal proteins" .

How can CRISPR-Cas9 technology be optimized for studying infB function in N. meningitidis?

CRISPR-Cas9 offers powerful tools for genetic manipulation, but requires careful optimization for N. meningitidis:

• Design of guide RNAs: Select target sequences within infB with minimal off-target effects, considering the high GC content of Neisseria genomes.

• Delivery methods: Optimize transformation protocols for CRISPR components, which can be challenging in N. meningitidis.

• Conditional systems: Since complete knockout of infB would likely be lethal, design inducible or partial disruption strategies.

• Validation strategies: Employ RNA-Seq, proteomics, and functional assays to confirm and characterize the effects of genetic modifications.

Genetic manipulation studies have been successful in identifying novel virulence factors in N. meningitidis. For example, one study "investigated the mechanisms by which Neisseria meningitidis serogroup B (MenB) survives at the physiological concentrations of human and mouse cathelicidin" and identified that "when either of the 2 genes was deleted, MenB resistance to cathelicidins was impaired in vitro" .

What high-throughput approaches can identify infB interaction partners during infection?

To comprehensively map infB interactions during infection:

• Proximity labeling proteomics: Using BioID or APEX2 fusions to capture proteins in close proximity to infB during infection.

• Crosslinking mass spectrometry (XL-MS): To identify direct protein-protein interactions.

• RNA immunoprecipitation (RIP): To identify RNA molecules interacting with infB.

• Ribosome profiling: To assess changes in translation dynamics when infB function is altered.

These approaches can provide insights similar to those gained in studies of other bacterial factors, where researchers identified "a circuit of regulatory RNA elements used by N. meningitidis to adapt to proliferate in human blood" .

What are the critical parameters for maintaining stability of recombinant infB during storage and experimental use?

To maintain optimal stability and functionality of recombinant infB:

• Storage conditions: Store at -20°C for routine use, or -80°C for extended storage .

• Reconstitution protocol: Use deionized sterile water to a concentration of 0.1-1.0 mg/mL, with addition of 5-50% glycerol for long-term storage .

• Working aliquots: Store at 4°C for up to one week to avoid repeated freeze-thaw cycles .

• Buffer optimization: Consider testing different buffer compositions (varying pH, salt concentration, and additives) to identify conditions that maximize stability.

• Stabilizing agents: Addition of specific stabilizers like glycerol, sucrose, or bovine serum albumin might improve stability.

The shelf life of liquid form is typically 6 months at -20°C/-80°C, while lyophilized preparations may remain stable for 12 months when properly stored .

How can researchers overcome common challenges in functional assays involving recombinant infB?

Common challenges and solutions for infB functional assays include:

• Protein aggregation: Use freshly prepared protein, optimize buffer conditions, consider adding mild detergents or chaperones.

• Low activity: Ensure proper folding by testing different expression and purification conditions, verify that all cofactors (like GTP) are present.

• Non-specific interactions: Increase washing stringency in binding assays, include competitors to reduce background.

• Reproducibility issues: Standardize protein concentration measurement methods, ensure batch-to-batch consistency.

• Assay interference: Test for potential interfering compounds in your experimental system, include appropriate controls.

Functional assays for translation factors often require reconstituted systems with purified components, as suggested by studies examining "core activities of the ribosome" where factors like "bacterial initiation factor 2, IF2, promotes correct positioning of the initiator" .

What emerging technologies might advance our understanding of infB's role in N. meningitidis pathogenesis?

Several cutting-edge approaches offer promise for deeper insights into infB function:

• Cryo-electron microscopy: For high-resolution structural studies of infB in complex with the ribosome.

• Single-cell RNA-Seq: To examine heterogeneity in bacterial responses during infection.

• In vivo imaging: To track bacterial behavior and protein localization during infection.

• Organ-on-chip models: To better replicate the complex environments encountered during infection.

• Systems biology approaches: Integrating multiple data types to model the role of infB in the broader context of meningococcal physiology and pathogenesis.

These approaches could help answer questions about meningococcal adaptation during infection, similar to studies showing that "N. meningitidis accumulate in large organs during meningococcal septic shock" .

How might understanding infB function contribute to novel therapeutic approaches against N. meningitidis?

Insights into infB function could inform several therapeutic strategies:

• Small molecule inhibitors: Identifying compounds that specifically target N. meningitidis infB without affecting host translation.

• Peptide-based inhibitors: Designing peptides that interfere with specific infB interactions.

• Antisense strategies: Developing oligonucleotides that target infB mRNA.

• Host-directed therapies: Modulating host responses based on understanding how infB impacts host-pathogen interactions.

• Combination approaches: Targeting infB in conjunction with other bacterial factors to enhance efficacy of existing antibiotics.

These approaches are relevant given the ongoing challenges in controlling meningococcal disease, as "control of gonorrhoea is becoming increasingly difficult, due to widespread antibiotic resistance" , highlighting the need for novel therapeutic targets.

How does infB function intersect with metabolic adaptation of N. meningitidis during infection?

The relationship between translation and metabolism is bidirectional and likely critical during infection:

• Metabolic regulation of translation: Investigate how metabolic status (e.g., nutrient availability, energy state) affects infB activity and translation initiation efficiency.

• Translational control of metabolism: Examine how changes in translation machinery, including infB function, affect expression of metabolic enzymes.

• Coordinated responses: Study how infB-mediated translation control is integrated with metabolic adaptation during different infection stages.

Research has shown that "metabolic adaptation enables meningococci to exploit host resources, supporting the concept of nutritional virulence" , suggesting translation factors like infB may play a role in this adaptive process.

What methodologies can reveal links between infB and known virulence factors in N. meningitidis?

To explore connections between infB and established virulence factors:

• Co-expression analysis: Identify genes whose expression patterns correlate with infB during infection.

• Genetic interaction studies: Test for synthetic phenotypes between infB variants and mutations in virulence genes.

• Proteomics-based approaches: Examine how altering infB function affects the abundance of virulence factors.

• Mathematical modeling: Develop models that integrate translation regulation with virulence factor expression.

Such studies could build on findings showing that specific genes like factor H binding protein (fHbp) are crucial for virulence, as "bacterial genome-wide association study highlighted the role of fHbp determining whether strains harmlessly colonize an individual or cause IMD [invasive meningococcal disease]" .

How might infB-specific detection methods contribute to improved diagnosis of N. meningitidis infections?

While not a first-line diagnostic target, infB could have value in certain diagnostic contexts:

• Species-specific PCR: Developing primers targeting conserved regions of infB for species identification.

• Multiplex molecular assays: Including infB alongside other targets to enhance diagnostic specificity.

• Loop-mediated isothermal amplification (LAMP): Similar to approaches that have been developed "for rapid detection of N. meningitidis" .

• Antibody-based detection: Using anti-infB antibodies in immunoassays for bacterial detection.

Current molecular diagnostic approaches include methods where "LAMP reaction was set up and optimized by four primers" targeting specific genes in N. meningitidis , and similar approaches could potentially incorporate infB targets.

Can infB sequence variations serve as markers for tracking N. meningitidis serogroup C transmission?

To evaluate infB's potential as a molecular epidemiology marker:

• Whole genome sequencing: Analyze infB in the context of complete genomic data from clinical isolates.

• Single nucleotide polymorphism (SNP) analysis: Identify specific variations that might correlate with transmission patterns.

• Multilocus sequence typing (MLST): Determine if infB could complement existing MLST schemes.

• Comparative analysis with established markers: Assess whether infB provides additional discriminatory power compared to current typing methods.

Genomic epidemiology has proven valuable in meningococcal surveillance, as demonstrated in studies where "WGS showed a higher discrimination power and provided more accurate data on molecular characteristics and genetic relationships among invasive N. meningitidis isolates" .