mab-5 Antibody
Description
Mab5 Against SARS-CoV-2
Mab5 is a murine monoclonal antibody initially developed to neutralize SARS-CoV-1 but later found to cross-react with SARS-CoV-2. It targets the conserved HR2 region within the S2 subunit of the spike protein, enabling broad activity against emerging variants .
Key Findings:
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Neutralization Efficacy:
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In Vivo Protection:
| Parameter | Mab5 | Mab3-2 |
|---|---|---|
| IC₅₀ (μg/mL) | 12.3 | 87.4 |
| K<sub>D</sub> (pM) | 4.88 | 32.85 |
| Survival Rate (250 μg) | 100% | 0% (control) |
Mechanism:
Mab5 binds the CB-119 epitope in the S2 subunit, disrupting viral entry by blocking membrane fusion . Its humanized form (hMab5.17) maintained slow off-rate kinetics (10<sup>−6</sup>/s), enhancing therapeutic durability .
Mab5 Against Acinetobacter baumannii
This Mab5 is a humanized IgG2a monoclonal antibody targeting the O-antigen capsular carbohydrates of the drug-resistant pathogen A. baumannii. It was developed to expand coverage beyond existing therapies like bispecific antibody C73 .
Key Findings:
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Binding Breadth:
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In Vivo Efficacy:
| Panel | Mab5 Binding | BsAb C73 Binding |
|---|---|---|
| U.S. Isolates (n = 300) | 72.24% | 32.1% |
| International Isolates (n = 250) | 29.32% | 18.4% |
Mechanism:
Mab5 mediates opsonization and enhances phagocytosis by binding O-antigen polysaccharides, critical for immune evasion in A. baumannii .
Comparative Analysis
Both Mab5 antibodies exemplify the versatility of mAbs in targeting structurally distinct pathogens:
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SARS-CoV-2 Mab5: Focuses on viral membrane fusion inhibition.
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A. baumannii Mab5: Disrupts bacterial capsule integrity.
Challenges:
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Variant Escape: SARS-CoV-2 Mab5 requires continuous evaluation against VOCs .
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Coverage Gaps: A. baumannii Mab5 shows lower efficacy against non-U.S. strains, necessitating complementary mAbs .
Clinical and Research Implications
Product Specs
Constituents: 50% Glycerol, 0.01M PBS, pH 7.4
Target Background
- EGL-20 mediates an acute inhibition of anterior migration independently of BAR-1 and MAB-5. Subsequently, a possible transcriptional response mediated by BAR-1 and MAB-5 occurs. PMID: 26863303
- Genes regulated by MAB-5 are enriched for those encoding secreted and transmembrane molecules that affect the extracellular matrix. PMID: 23642123
- Research demonstrates that wild-type mab-5 function is necessary for normal P(9-11).p fate. PMID: 20478294
- MAB-5 plays a role during ray formation. Studies suggest that functional specificity is conferred by the N-terminal arm and helix I, but not helix II, of the homeodomain. PMID: 12538523
- mab-5 expression was investigated in the neuroblast lineage of this nematode. PMID: 12930745
- In the P11 lineage, a complex between MAB-5 and the Pbx homolog CEH-20 directly regulates transcription of the BH3 domain gene egl-1 to initiate programmed cell death. PMID: 16421192
Q&A
Basic Research Questions
What is the primary antigenic target and mechanism of action of Mab-5 antibody?
Mab-5 targets the S2 subunit of the SARS-CoV-2 spike protein, a conserved region critical for viral membrane fusion. Its mechanism involves high-affinity binding (dissociation constant K D = 4.88 pM) to block conformational changes required for viral entry . Methodologically, epitope mapping was performed using competitive binding assays and cryo-electron microscopy (cryo-EM) to resolve structural interactions .
How is neutralizing activity quantified for Mab-5 in preclinical studies?
Neutralization is evaluated via plaque reduction neutralization tests (PRNT), with results expressed as IC50 values (concentration inhibiting 50% of viral activity). For Mab-5, IC50 against SARS-CoV-2 was 12.3 μg/mL, validated using in vitro assays with Vero-E6 cells and crystal violet staining .
What experimental models validate Mab-5 efficacy?
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In vitro: Neutralization assessed using pseudovirus or live-virus assays in cell lines (e.g., Vero-E6) .
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In vivo: Syrian hamster models show reduced viral load and pathology post-infection .
Advanced Research Questions
How does humanization impact Mab-5’s binding affinity and therapeutic utility?
Humanization involves grafting murine Mab-5 variable regions onto human IgG frameworks. Post-humanization (hMab5.17), affinity slightly decreased (K D = 13 pM), but neutralizing activity remained comparable (IC50 = 12.2 μg/mL). Stability was confirmed via biolayer interferometry (BLI) and in vivo challenge models .
What structural insights explain Mab-5’s cross-reactivity with SARS-CoV-2 variants?
Cryo-EM of Mab-5 bound to the BA.5 RBD reveals interactions with conserved residues (e.g., N856, K854) in the S2 subunit. This explains neutralization of Omicron subvariants (XBB.1.16, EG.5) but not JN.1, which carries S:L455S/F456L mutations disrupting the epitope .
| Variant | Neutralization (PRNT50) | Key Epitope Mutations |
|---|---|---|
| BA.5 | 8.7 ng/mL | None |
| XBB.1.16 | 15.2 ng/mL | F486P, F490S |
| JN.1 | No activity | S:L455S, F456L |
How do methodological differences in antibody engineering affect immunogenicity?
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Chimerization: Fusion of murine variable regions with human constant domains (ChiMab5) retains neutralization but risks anti-drug antibodies (ADAs) .
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Deimmunization: Computational tools predict T-cell epitopes in variable regions; iterative mutagenesis reduces immunogenicity while preserving affinity .
What strategies resolve discrepancies between in vitro and in vivo efficacy data?
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Pharmacokinetic profiling: Adjust dosing intervals based on half-life (e.g., Syrian hamsters showed protection at 10 mg/kg q48h) .
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Tissue penetration assays: Confocal microscopy quantifies antibody distribution in lung epithelium .
Methodological Best Practices
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Epitope Binning: Use BLI or surface plasmon resonance (SPR) to map overlapping epitopes and avoid redundant antibody candidates .
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ADA Risk Mitigation: Employ in silico tools like EpiMatrix to predict T-cell epitopes during humanization .
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Variant Testing: Prioritize in vitro pseudotyping with mutant spikes before live-virus challenges .
