SARS-CoV-2 antigens | Miltenyi Biotec

The scientific community is working at full speed to investigate and fight severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Miltenyi Biotec stands committed to assisting those researchers in getting to the bottom of COVID-19.

SARS-CoV-2 antigens and ACE2

SARS-CoV-2 antigens offer researchers the possibility to investigate virus-specific immune responses, including antigen-specific B cells and antibodies.

Overview of our antigens for SARS-CoV-2 research. All antigens are available with or without biotinylation:

Protein	Sequence part	Production specification
ACE2	Full length (with CLD)	Recombinant protein
ACE2	Truncated (w/o CLD)	Recombinant protein
Spike protein	Receptor binding domain (RBD)	Recombinant protein
Nucleoprotein	Full length	Recombinant protein
Envelope protein	C-Terminus	Synthetic polypeptide
	N-Terminus	Synthetic polypeptide
	Helical segment 2 (H2)	Synthetic polypeptide

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Applications of SARS-CoV-2 antigens

Overview of possible applications

Detection of patient-derived antibodies
Characterization of patient-specific immune responses
Detection and phenotyping of virus-specific B cells
Enrichment of virus-specific B cells
Analysis of virus binding to host cells
Protein detection assays

Detection of SARS-CoV-2–specific antibodies in serum samples

Detection of patient-derived antibodies against SARS-CoV-2 antigens via a bead-based immunoassay

Biotinylated recombinant proteins coupled to streptavidin-coated PMMA beads can be applied to detect SARS-CoV-2–specific antibodies in plasmapheresis samples of COVID-19⁺ patients.

Bead-based immunoassay for detection of patient-derived SARS-CoV-2 antibodies

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Analysis of patient-derived SARS-CoV-2 antibodies

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Analysis of different plasma dilutions illustrates that our SARS-CoV-2 antigens enable a highly sensitive detection of patient-derived anti–SARS-CoV-2 antibodies.

Quantification of captured SARS-CoV-2 antibodies at different plasma dilutions

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Quantification of captured SARS-CoV-2 antibodies at different plasma dilutions shows the high specificity of our SARS-CoV-2 antigens.

Detection of RBD binding to ACE2

Cell-based assay to analyze the binding of RBD to native ACE2

The combination of recombinant RBD and ACE2-expressing cells can be used to mimic the binding of SARS-CoV-2 to its host cells in vitro. Such binding assays can be applied to study inhibitory/neutralizing effects of components or antibodies.

Binding assay for the detection of recombinant RBD bound to cell surface ACE2

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Analysis of RBD binding to cell surface ACE2

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Immunofluorescent staining visualizes RBD bound to ACE2-expressing cells. Comparison of the percentage of stained cells at different RBD concentrations shows a titratable, high-affinity binding of recombinant RBD to cell surface ACE2.

This assay can be applied to analyze the potential of certain components to disrupt RBD/ACE2 binding, which would result in a reduced number of stained cells.

Available antigens for your SARS-CoV-2 research

ACE2

Angiotensin-converting enzyme 2 (ACE2, also known as ACEH) is a transmembrane protein, which acts as receptor for SARS-CoV, SARS-CoV-2, and other coronaviruses. The large extracellular peptidase domain of ACE2 is known to interact with the spike protein of coronaviruses. The small C-terminal collectrin-like domain (CLD) has recently been described to mediate homo-dimerization of ACE2.

We offer recombinant human ACE2 produced in HEK cells including C-terminal CLD or insect cell–derived ACE2 lacking CLD. The potential influence of the CLD domain is indicated by the exemplary analysis below.

Recombinant human ACE2

Sequence	Tag	Source	Biotinylated	Filling	Order no.
Q18 to S740	His, AviTag™	HEK	No	100 µg	130-127-516
			No	25 µg	130-127-456
			Yes	50 µg	130-127-465
			Yes	10 µg	130-127-442
Q18 o D615		Insect cells	No	100 µg	130-127-466
			No	25 µg	130-127-444
			Yes	50 µg	130-127-464
			Yes	10 µg	130-127-468

RBD binding affinity of ACE2 is increased upon dimerization

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RBD binding affinity of ACE2 is increased upon dimerization

Comparison of recombinant ACE2 with and without CLD shows that ACE2 dimerization results in increased affinity to viral RBD. Furthermore, our HEK-derived full-length protein (with CLD) also displays a higher RBD-binding affinity than the full-length competitor product. The higher binding affinity enables a more sensitive detection of RBD.

Spike protein

The surface or spike (S) glycoprotein plays a critical role in coronavirus infection as it is crucial for recognition and fusion of the virus with the host cell membrane. Two different functional domains of the S protein are responsible for these individual processes: The S1 domain contains the receptor binding domain, which binds to the host cell receptor ACE2, whereas membrane fusion is mediated via the S2 domain. Furthermore, cleavage at the boundary of the S1 and S2 domains (aa residues 685 and 686) via cellular proteases primes the protein for entry into the host cell. Upon fusion of the viral envelope to the host cell membrane, the viral genome enters the host cell and viral replication starts.

Receptor binding domain

The receptor binding domain (RBD) locates C-terminally within the S1 subunit of the S protein. The S protein forms a homotrimeric structure on the surface of the SARS-CoV-2 virus. Recent studies have shown that the predominant activated form of the protein S trimer displays one RBD rotated up into an ACE2-accessible state. Binding of RBD to ACE2 is a major contributor for interaction of protein S with its target receptor.

We offer recombinant SARS-CoV-2 RBD produced in HEK or insect cells:

Sequence	Tag	Source	Biotinylated	Filling	Order no.
R319 to S591	His, AviTag™	HEK	No	100 µg	130-127-518
			No	25 µg	130-127-448
			Yes	50 µg	130-127-457
			Yes	10 µg	130-127-458
		Insect cells	No	100 µg	130-127-453
			No	25 µg	130-127-463
			Yes	50 µg	130-127-469
			Yes	10 µg	130-127-445

Dose response curve showing binding of RBD to cell surface ACE2

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RBD is biologically functional and binds cell surface ACE2

Biotinylated recombinant RBD bound to cell surface ACE2 can be detected by immunofluorescent staining. Quantification of stained cells at different RBD concentrations illustrates that Miltenyi Biotec's recombinant RBD is biologically functional and binds cell surface ACE2 with high affinity.

Nucleoprotein

The SARS-CoV-2 nucleoprotein (also known as nucleocapsid protein or protein N) is a key structural protein of the SARS-CoV-2 virus. The N-terminal RNA-binding domain (NTD) associates with the viral genome of SARS-CoV-2. An intrinsically disordered stretch connects the NTD domain with the C-terminal dimerization domain (CTD). A major function of protein N is the packaging of the viral genome into helical nucleocapsid structures. Additionally, it is involved in virus transcription and interacts with the viral membrane during virion assembly.

We offer recombinant SARS-CoV-2 nucleoprotein (full length):

Sequence	Tag	Source	Biotinylated	Filling	Order no.
Full length 2S-419A	His, AviTag™	HEK	No	100 µg	130-127-517
			No	25 µg	130-127-462
			Yes	50 µg	130-127-467
			Yes	10 µg	130-127-454

Envelope protein

The envelope protein (also known as envelope small membrane protein) is localized on the surface of the virus and represents one of the most relevant structural proteins of SARS-CoV-2. It acts as a viroporin and is involved in virus morphogenesis, assembly, and pathogenesis. Based on previous structural studies of highly similar envelope proteins from other coronaviruses and homology studies, it is assumed that the envelope protein forms a pentameric structure when integrated into the membrane of SARS-CoV-2.

We offer synthesized polypeptides for three parts of the envelope protein: C- terminus, N-terminus, and helical segment 2 (H2).

SARS-CoV-2 envelope antigens

Region	Sequence	Biotinylated	Filling	Order no.
C-terminus	L34 to 75V	No	100 µg	130-127-446
C-terminus	L34 to 75V	Yes	100 µg	130-127-451
N-terminus	M1 to 16S	No	100 µg	130-127-455
N-terminus	M1 to 16S	Yes	100 µg	130-127-461
Helical segment 2 (H2)	S55 to 75V	No	100 µg	130-127-450
Helical segment 2 (H2)	S55 to 75V	Yes	100 µg	130-127-452

Contact us for more information

If you have further questions or are interested in our proteins for SARS-CoV-2 research, please specify your question or request in the contact form and we will come back to you:

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Antigens for SARS-CoV-2 research