SARS-CoV-2 Spike RBD Proteins
InvivoGen offers a collection of Spike RBD (receptor binding domain) fusion proteins from a selection of SARS-CoV-2 variants, including the variants of concern (VOC). These proteins feature either a His, Fc, or Lucia luciferase tag for easy detection, depending on your applications:
- His-tag: a C-terminal poly-histidine (6xHis) sequence
- Fc-Tag: a C-terminal human IgG1 Fc region
- Lucia-tag: a C-terminal Lucia luciferase reporter
Detection is performed using either conjugated anti-His or anti-Fc antibodies, or QUANTI-Luc, a luciferase detection reagent.
Potential applications for Spike RBD-tagged proteins
Vaccination or immunization studies can be carried out using RBD-His or RBD-Fc proteins. However, caution should apply for RBD-Fc, as the Fc portion may induce anti-species immune responses. RBD-Lucia are not suitable because of the luciferase immunogenicity.
Detection of the ACE2 cellular receptor for the SARS-CoV-2 Spike protein can be achieved using RBD-His, RBD-Fc, or RBD-Lucia proteins.
Screening of small molecules or antibodies, able to block the SARS-CoV-2 RBD interaction with the ACE2 receptor can be performed using RBD-His, RBD-Fc, or RBD-Lucia proteins.
Screening of RBD-specific monoclonal or polyclonal antibodies can be run using RBD-His, RBD-Fc, or RBD-Lucia proteins with ELISA. However, caution should apply for RBD-Fc, as the secondary anti-Fc antibody may cross-react with the Fc region of the tested antibody(ies), thus increasing the background signal. RBD-Lucia proteins are highly suitable for screening antibodies with LIPS (luciferase immunoprecipitation system), a solution-phase assay that allows the detection of antibodies against both linear and conformational epitopes.
Advantages of RBD-Lucia proteins
Lucia luciferase provides a larger dynamic range than the commonly used HRP detection.
In an ELISA, RBD-Lucia proteins can be used to easily compare the binding affinity of a given mAb (e.g. Anti-RBD mAbs) to different SARS-CoV-2 Spike variants.
- In a LIPS assay, they favor more precise monitoring of antibody responses in the sera of recovered COVID 19 patients and/or vaccinees. Indeed, this solution-phase assay allows broader detection of antibodies, against both linear and conformational epitopes of the RBD. Moreover, the greater detection range of Lucia luciferase activity allows delineation of response profiles, based on antibody levels.