SARS MERS Spike Antibody
Description
Introduction to SARS-MERS Spike Antibodies
SARS-MERS spike antibodies are immunoglobulins targeting conserved or shared epitopes on the spike (S) glycoproteins of SARS-CoV and MERS-CoV. These antibodies often exhibit cross-reactivity due to structural similarities in the S2 subunit, which facilitates viral membrane fusion and host cell entry. Their development is critical for pan-coronavirus therapeutic strategies and vaccine design, particularly against emerging variants and zoonotic coronaviruses .
Epitope Conservation and Cross-Reactivity
The S2 subunit of coronaviruses contains highly conserved regions across β-coronaviruses, enabling cross-reactive antibody responses:
Key Conserved Regions:
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Stem Helix (residues 1230–1243 in MERS-CoV): Targeted by antibodies 1.6C7 and 28D9, which bind prefusion spikes of SARS-CoV, MERS-CoV, and SARS-CoV-2 .
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S2 Apex Hinge (residues 980–1006 in SARS-CoV-2): Recognized by antibody RAY53, which binds MERS-CoV and SARS-CoV-2 spikes .
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Fusion Peptide: Targeted by C20.119, neutralizing SARS-CoV-2 variants, SARS-CoV-1, and zoonotic sarbecoviruses .
Table 1: Cross-Reactive Antibody Epitopes
RAY53
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Mechanism: Binds the S2 hinge region, enabling antibody-dependent cellular phagocytosis (ADCP) and cytotoxicity (ADCC).
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Affinity: Effective K<sub>d</sub> of 100 nM for SARS-CoV-2 spike .
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Limitation: Epitope accessibility depends on spike conformational dynamics (e.g., occluded in Omicron BA.1) .
1.6C7 and 28D9
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Mechanism: Destabilize prefusion spike stem helices or block postfusion six-helix bundle formation .
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Efficacy: Prophylactic and therapeutic protection against lethal MERS-CoV in mice (100% survival at 10 mg/kg) .
IgG22
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Mechanism: Targets a conserved S2 coiled-coil region, validated by cryo-EM and crystal structures .
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Cross-Protection: Passive transfer protects mice against MERS-CoV and SARS-CoV-2 .
In Vitro Neutralization
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MERS-CoV Pseudovirus: 5/11 antibodies from COVID-19 convalescents showed weak neutralization (IC<sub>50</sub>: 10–100 µg/mL) .
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Broad Neutralizers: C20.119 neutralizes SARS-CoV-2 XBB and BQ.1.1 variants (IC<sub>50</sub>: 0.2–1.1 µg/mL) .
Effector Functions
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ADCP/ADCC: RAY53 mediates phagocytosis (THP-1 cells) and cytotoxicity (NK-92 cells) against SARS-CoV-2 spike .
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Fc-Dependent Activity: S2-targeting antibodies from SARS-CoV-2 convalescents show ADCC against MERS-CoV and HCoV-HKU1 .
Table 2: Clinical Trial Insights
Clinical and Therapeutic Implications
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Vaccination Cross-Boosting: COVID-19 vaccines enhance pre-existing anti-MERS-CoV S2 antibodies in 84.8% of MERS-recovered patients .
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Pan-Coronavirus Strategies: Stem helix and fusion peptide epitopes are prioritized for universal vaccine design .
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Therapeutic Cocktails: Combining S1-RBD and S2-core antibodies (e.g., S309 + RAY53) may overcome variant evasion .
Challenges and Future Directions
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Epitope Occlusion: Omicron BA.1 and other variants reduce S2-core antibody accessibility via spike conformational changes .
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Affinity-Activity Mismatch: High-affinity antibodies (e.g., RAY53) may not improve neutralization if spike opening is rate-limiting .
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Structural Optimization: Stabilized prefusion S2 stems (e.g., MERS SS) enhance immunogenicity and cross-reactive responses .
Product Specs
The Middle East Respiratory Syndrome Coronavirus (MERS-CoV) has been a concern since April 2012, with cases identified globally. Belonging to the coronavirus family, which also includes the common cold and SARS (severe acute respiratory syndrome), coronaviruses are known for causing severe illnesses with high mortality rates. MERS-CoV, a novel type of SARS within this family, leads to severe pneumonia characterized by sudden and serious respiratory illness, also associated with high mortality rates. As of January 27th, 2015, the World Health Organization (WHO) has reported 956 human cases, including 351 deaths, with expectations of further cases. A key structural protein in MERS-CoV, similar to other coronaviruses, is the large surface spike glycoprotein. This protein, situated on the virion surface, facilitates binding and entry into the target cell. The spike protein consists of two domains, S1 and S2. The S1 domain plays a crucial role in cellular tropism and interaction with the target cell, while the S2 domain is responsible for membrane fusion. The C-terminal region of the S1 domain houses a receptor binding domain, making it a potential target for vaccine development and serving as an antigen for diagnosis.
A clear, colorless solution that has been sterilized by filtration.
The solution has a concentration of 1mg/ml and contains the following components: Phosphate-Buffered Saline (pH 7.4), 0.02% Sodium Azide, and 10% Glycerol.
For short-term storage (up to 1 month), keep at 4°C. For extended storage, store at -20°C. It's important to avoid repeated freezing and thawing cycles.
The product is stable for 12 months when stored at -20°C and for 1 month at 4°C.
The SARS MERS Spike antibody has undergone ELISA analysis to verify its specificity and reactivity. However, optimal results require titration for each specific application due to varying experimental conditions.
Middle East respiratory syndrome coronavirus, Human betacoronavirus 2c EMC/2012, MERS-CoV, MERS, MERSCoV SP, Spike glycoprotein, S glycoprotein, S, Spike protein, E2, Peplomer protein.
SARS MERS Spike antibody was purified from mouse ascitic fluids by protein-A affinity chromatography.
PAT40G7AT
Recombinant MERS-CoV Spike (18-1296aa) purified from Baculovirus.
IgG1 kappa.
Q&A
What are the structural differences between SARS-CoV, MERS-CoV, and SARS-CoV-2 spike proteins that affect antibody recognition?
SARS-CoV-2 shares approximately 78% sequence homology with SARS-CoV and about 50% with MERS-CoV at the genetic level . These similarities explain the potential for cross-reactive antibodies targeting conserved epitopes across these coronaviruses. The spike protein consists of two primary subunits: S1, which contains the receptor-binding domain (RBD) and is highly variable between coronaviruses, and S2, which mediates membrane fusion and contains more conserved regions across coronavirus species.
The S1 subunit shows greater divergence between coronavirus species and is immunodominant, making it the primary target for neutralizing antibodies but also more susceptible to escape mutations . In contrast, the S2 subunit harbors conserved epitopes, particularly in the stem helix regions, that can be targeted by broadly reactive antibodies . These structural characteristics directly influence antibody binding specificity, cross-reactivity potential, and neutralization capacity across different coronaviruses.
How do antibody responses to different structural proteins (S1, S2, N) vary in coronavirus infections?
Research data demonstrates significant variation in antibody responses to different viral structural proteins. In SARS-CoV-2 infection, approximately 87.5% of infected individuals develop IgG responses to the S1 subunit and 88.25% to the nucleocapsid (N) protein . Interestingly, only about 14.44% of subjects display significant antibody responses to the S2 subunit despite its conserved nature .
The antibody response profile also correlates with disease severity. Patients with severe COVID-19 demonstrate significantly higher antibody titers against both S1 and N proteins compared to asymptomatic individuals (p ≤ 0.0001) . Approximately 72.73% of severe cases develop high IgG responses to S1, compared to only 10.81% of asymptomatic individuals . Additionally, individuals with prolonged symptoms (long COVID-19) show greater IgG response profiles than those with shorter symptom duration .
What evidence exists for cross-reactive antibody responses between SARS-CoV-2 and MERS-CoV infections?
Multiple studies have demonstrated significant cross-reactivity between antibodies generated against SARS-CoV-2 and MERS-CoV. Over 60% of sera from COVID-19 convalescent individuals show binding activity against MERS-CoV spike protein, compared to less than 8% in the general population, indicating that SARS-CoV-2 infection boosts antibodies with cross-reactivity against MERS-CoV .
When specifically examining the S2 subunit, 34 out of 60 convalescent serum samples showed binding activity against MERS-CoV S2, with endpoint titers positively correlated with the titers to SARS-CoV-2 S2 . From single memory B cells isolated from COVID-19 convalescents, researchers constructed 38 monoclonal antibodies (mAbs), of which 11 demonstrated binding activity with MERS-CoV S2 . Further analysis revealed that 9 of these mAbs exhibited potent cross-reactivity with spike proteins across multiple coronaviruses, including alphacoronaviruses (229E and NL63) and betacoronaviruses (SARS-CoV-1, SARS-CoV-2, OC43, and HKU1) .
Does prior MERS-CoV exposure affect immune responses to SARS-CoV-2 vaccination?
A cohort study of 14 patients with previous MERS-CoV infection revealed that COVID-19 vaccination significantly enhanced pre-existing immunity against MERS-CoV and SARS-CoV . Post-vaccination samples showed significantly higher levels of total antibodies, IgG, and IgA targeting SARS-CoV-2 S protein compared to pre-vaccination samples (mean total antibodies: 8955.0 AU/mL; p = 0.002) .
Additionally, significantly higher anti-SARS S1 IgG levels were detected following vaccination (mean reactivity index: 55.4; p = 0.001), suggesting enhanced cross-reactivity with multiple coronaviruses . Neutralizing antibodies were significantly boosted against SARS-CoV-2 (50.5% neutralization; p < 0.001) after vaccination in these individuals . These findings indicate that sequential exposure to different coronavirus antigens (through infection and then vaccination) may enhance broad coronavirus immunity.
What methodologies are effective for isolating and characterizing cross-reactive coronavirus antibodies?
Effective methodologies for isolating cross-reactive coronavirus antibodies include:
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Serum screening: Initial screening of convalescent sera against multiple coronavirus spike proteins to identify samples with cross-reactivity potential . This typically employs enzyme-linked immunosorbent assays (ELISA) to detect binding antibodies.
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Single B cell sorting: Isolation of memory B cells from individuals with cross-reactive serum profiles, followed by single-cell sorting using fluorescence-activated cell sorting (FACS) with labeled coronavirus antigens .
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Monoclonal antibody construction: Generation of monoclonal antibodies from sorted B cells through cloning of antibody genes and expression in suitable systems .
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Cross-reactivity assessment: Systematic testing of isolated antibodies against panels of coronavirus spike proteins from different genera and strains using binding assays .
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Neutralization assays: Evaluation of functional activity using pseudovirus or authentic virus neutralization assays to distinguish binding from neutralizing antibodies .
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Epitope mapping: Determination of binding sites through techniques including alanine scanning mutagenesis, competition assays, X-ray crystallography, and cryo-electron microscopy .
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In vivo protection studies: Validation of protective efficacy through passive transfer experiments in animal models challenged with relevant coronaviruses .
How can researchers effectively design stabilized spike protein constructs for cross-reactive antibody development?
The design of stabilized spike protein constructs, particularly those targeting conserved epitopes in the S2 subunit, involves several strategic approaches:
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S1 subunit removal: Removing the immunodominant but poorly conserved S1 subunit focuses immune responses on the more conserved S2 region. This approach was successfully implemented in creating MERS-CoV stabilized stem (SS) constructs: MERS SS.V1 and MERS SS.V2 .
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Structure-guided engineering: Using high-resolution structural data to identify regions requiring stabilization, particularly focusing on the prefusion conformation of the S2 subunit .
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Strategic disulfide bond introduction: Introducing disulfide bonds at key positions to lock the protein in the desired conformation and prevent unwanted structural transitions .
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Proline substitutions: Introducing proline residues at critical fusion machinery hinge points to prevent conformational changes associated with the fusion process .
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Glycan shielding modification: Manipulating glycosylation sites to either shield or expose specific epitopes of interest .
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Trimerization domain addition: Incorporating heterologous trimerization domains to ensure proper oligomeric presentation of the spike protein .
This structure-guided approach has proven successful, as vaccination with MERS SS constructs elicited cross-reactive β-coronavirus antibody responses and protected mice against lethal MERS-CoV challenge .
How does disease severity correlate with spike antibody responses across different coronaviruses?
Disease severity demonstrates significant correlation with antibody response patterns across coronavirus infections. In SARS-CoV-2 infection, patients with severe disease develop substantially higher antibody responses to both the S1 subunit and N protein compared to asymptomatic individuals . Specifically, 72.73% of severe cases develop high IgG responses to S1, while only 10.81% of asymptomatic individuals show comparable responses .
Additionally, only a minority of individuals with severe COVID-19 (6.06%) develop low titers of IgG antibodies against S1, suggesting a robust correlation between disease severity and antibody production . The duration of symptoms also influences antibody responses, with individuals experiencing prolonged symptoms (long COVID-19) demonstrating greater IgG response profiles than those with shorter symptom duration .
The heightened antibody response in severe cases may reflect both increased viral replication and a more intense inflammatory response, potentially contributing to immunopathology while simultaneously providing stronger immune protection against reinfection .
What are the key challenges in developing a pan-coronavirus vaccine targeting conserved spike epitopes?
Key challenges in developing pan-coronavirus vaccines targeting conserved spike epitopes include:
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Immunodominance of variable regions: The S1 subunit, particularly the RBD, tends to dominate the immune response during natural infection or conventional vaccination, diverting responses away from more conserved but less immunogenic regions .
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Limited natural S2 responses: Only a small percentage of infected individuals (approximately 14.44%) develop robust antibody responses to the S2 subunit despite its conservation across coronavirus species .
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Epitope accessibility: Many conserved regions in the S2 subunit may be poorly accessible to antibodies in the native prefusion conformation of the spike protein .
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Balancing breadth and potency: Cross-reactive antibodies often demonstrate reduced neutralization potency against individual viruses compared to strain-specific antibodies .
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Structural constraints: Designing stable immunogens that properly present conserved epitopes while maintaining their native conformational structure is technically challenging .
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Validation across diverse coronaviruses: Demonstrating protection against both existing coronaviruses and potential future emergent strains requires extensive cross-species challenge studies .
Recent research has made progress in addressing these challenges through structure-guided engineering approaches, such as developing stabilized stem constructs that focus immune responses on conserved S2 regions .
How might sequential exposures to different coronavirus antigens enhance broad protective immunity?
Sequential exposure to different coronavirus antigens appears to enhance broad protective immunity through several mechanisms:
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Boosting cross-reactive memory B cells: Exposure to SARS-CoV-2 antigens (through vaccination) in individuals previously infected with MERS-CoV significantly boosted cross-reactive neutralizing antibody responses . This suggests that sequential exposures can preferentially expand pre-existing cross-reactive memory B cell populations.
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Refining antibody affinity: Multiple exposures to related but distinct antigens may drive affinity maturation that selects for antibodies recognizing truly conserved epitopes while reducing strain-specific binding .
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Broadening epitope recognition: A cohort study found that individuals exposed to both MERS-CoV infection and SARS-CoV-2 vaccination developed significantly boosted cross-reactive immune responses toward multiple human coronaviruses, with the strongest cross-recognition between SARS-CoV-2, SARS-CoV, and MERS-CoV .
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Enhanced neutralization breadth: Post-vaccination samples from MERS-CoV patients showed significantly higher neutralizing antibody activity against SARS-CoV-2 (50.5% neutralization; p < 0.001), suggesting that sequential exposures improve functional antibody responses .
This phenomenon could inform vaccination strategies that use prime-boost approaches with different coronavirus antigens or that specifically target shared epitopes to generate broadly protective immunity against both existing and potentially emergent coronaviruses .
Antibody Response Profiles Across Different COVID-19 Clinical Severities
| Clinical Profile | Anti-S1 IgG Response | Anti-N IgG Response | Anti-S2 IgG Response | Notable Characteristics |
|---|---|---|---|---|
| Asymptomatic | 10.81% high response | Lower titers | Generally low | 35.14% showed medium levels |
| Mild-Moderate | Intermediate levels | Intermediate levels | Generally low | Progressive increase with severity |
| Severe | 72.73% high response | High titers | Generally low | Only 6.06% had low S1 titers |
| Long COVID-19 | Greater response | Greater response | Data limited | Stronger response than short-duration cases |
Data compiled from analysis of antibody responses across different coronavirus structural proteins in varying COVID-19 clinical profiles .
Product Science Overview
The Middle East Respiratory Syndrome Coronavirus (MERS-CoV) is a highly pathogenic virus that emerged in 2012 in Saudi Arabia. It belongs to the betacoronavirus genus and is known for causing severe respiratory illness in humans. The virus is characterized by its spike (S) protein, which plays a crucial role in the virus’s ability to infect host cells. The spike protein is a primary target for neutralizing antibodies and vaccine development.
The spike protein of MERS-CoV is a class I fusion protein that facilitates the virus’s entry into host cells. It consists of two subunits: S1 and S2. The S1 subunit contains the receptor-binding domain (RBD), which binds to the host cell receptor dipeptidyl peptidase 4 (DPP4 or CD26). The S2 subunit mediates the fusion of the viral and host cell membranes, allowing the viral genome to enter the host cell .
Mouse anti MERS-CoV spike antibodies are monoclonal antibodies produced by immunizing mice with the MERS-CoV spike protein or its fragments. These antibodies are highly specific to the spike protein and are used in various research and diagnostic applications.
Production
The production of mouse anti MERS-CoV spike antibodies involves several steps:
- Immunization: Mice are immunized with the MERS-CoV spike protein or its fragments. The immunogen can be produced using recombinant DNA technology in cell lines such as Chinese Hamster Ovary (CHO) cells.
- Hybridoma Formation: B cells from the immunized mice are fused with myeloma cells to create hybridoma cells. These hybridomas can produce large quantities of monoclonal antibodies.
- Screening and Selection: Hybridomas are screened for the production of antibodies that specifically bind to the MERS-CoV spike protein. Positive clones are selected and expanded.
- Purification: The monoclonal antibodies are purified from the hybridoma culture supernatant using protein A or G affinity chromatography .
Applications
Mouse anti MERS-CoV spike antibodies are used in various applications, including:
- Enzyme-Linked Immunosorbent Assay (ELISA): These antibodies are used to detect the presence of MERS-CoV spike protein in samples.
- Western Blotting: They are used to identify and quantify the spike protein in cell lysates or purified preparations.
- Flow Cytometry: These antibodies can be used to analyze the expression of the spike protein on the surface of infected cells.
- Neutralization Assays: They are used to assess the ability of the antibodies to neutralize the virus by blocking the interaction between the spike protein and the host cell receptor .
