SARS-CoV-2 Neutralizing Antibodies

SARS-CoV-2 Neutralizing AntibodiesThe ongoing COVID-19 pandemic has changed the world in a way that hasn't been seen in generations. The medical research community is exploring every avenue to find solutions for the prevention, detection, and treatment of the disease.

Neutralizing antibodies are of specific interest to scientists, as they can efficiently stop the infection by blocking the interaction between the SARS-CoV-2 virus and the host cells. Most neutralizing antibodies react to the receptor binding domain (RBD) of the spike protein, which directly binds with the cell surface receptor ACE2.

Sino Biological has developed three neutralizing antibodies against SARS-CoV-2. The activities of these antibodies have been extensively validated in both binding assays, and pseudovirus infection assays. These reagents can be used as reference antibodies in neutralization assays, and possibly animal studies as well.

Neutralization Efficacy Assay aganist SARS-CoV-2 Variants

SARS-CoV-2 keeps evolving by continual mutation which enable the virus to evade vaccines and immune systems. Some of the mutations ,the U.K. variant B.1.1.7, the Brazil variant P.1, the South Africa variant B.1.351 and the Indian variant B.1.617, may have allowed the virus to escape from neutralizing antibodies. To characterize these variants, a new panel of monoclonal antibodies have been launched. These antibodies demonstrate differential neutralizing activities against different variants validated by Competitive ELISA Assay. Notably, the B.1.351 and P.1 variants seem to be immune to a subset of the antibodies.

Neutralizing Antibodies WT RBD Recombinant RBD Recombinant S1
B.1.1.7 B.1.351 P.1 B.1.617 B.1.617 B.1.429
40150-D001 ++ + ++ ++ ++ ++ ++
40150-D002 ++ + + ++ ++ ++ ++
40591-MM43 ++ ++ ++ ++ ++ ++ ++
40592-R001 +++ +++ - - +++ +++ +++
40592-R118 +++ +++ - - + + +
40592-R117 +++ +++ - - +++ +++ +++
+: Neutralizing Capacity
The Aforementioned Recombinant RBD :
WT: 40592-V08B
B.1.1.7 | U.K. Variant: 40592-V08H82 (N501Y)
B.1.351 | South Africa Variant: 40592-V08H85 (K417N, E484K, N501Y)
P.1 | Brazil Variant: 40592-V08H86 (K417T, E484K, N501Y)
B.1.617 | India Variant: 40592-V08H88 (L452R, E484Q)
The Aforementioned Recombinant S1 :
B.1.617 | India Variant: 40591-V08H19 (E154K, E484Q, L452R, D614G, P681R)
B.1.429 | California Variant: 40591-V08H17 (W152C, L452R, D614G)

Neutralization Activity Assay (Measured by microneutralization assay in vitro)

The microneutralization assay was performed on 293T-ACE2 cells infected with SARS-CoV-2 Spike PSV. Neutralizing antibodies can effectively inhibit the infection of SARS-CoV-2 Spike pseudovirus on ACE2 overexpression 293T cells.

  • Anti-S1 (40591-MM43)
    Mouse MAb
    Conc. (µg/mL) Inhibition%
    100 96.39%
    10 94.57%
    1 42.24%
    0.1 -5.53%
    The IC50 is typically 1.41 µg/mL.
  • Anti-RBD (40592-MM57)
    Mouse MAb
    Conc. (µg/mL) Inhibition%
    100 95.51%
    10 93.32%
    1 75.69%
    0.1 10.11%
    The IC50 is typically 0.41 µg/mL.
  • Anti-RBD (40592-R001)
    Rabbit MAb
    Conc. (µg/mL) Inhibition%
    100 99.56%
    4 99.9%
    0.16 59.29%
    0.032 5.59%
    The IC50 is typically 0.11 µg/mL.

Competitive-ELISA Assay (Measured by Inhibitor Screening ELISA Kit )

Neutralizing ability was detected by SARS-CoV-2 Inhibitor Screening ELISA Kit (Catalog# KIT001) using competitive ELISA.

  • S1 Neutralizing Antibody
    Mouse MAb

    The IC50 is typically 0.857 nM
  • RBD Neutralizing Antibody
    Mouse MAb

    The IC50 is typically 3.694 nM
  • RBD Neutralizing Antibody
    Rabbit MAb

    The IC50 is typically 0.59 nM

Specificity Assay

SARS-CoV-2 shares 80% sequence identity to the 2003 SARS-CoV. Hence, antibodies raised against SARS-CoV-2 antigens often shows various degree of cross-reactivity with the corresponding antigens of 2003 SARS-CoV. On the other hand, the similarities between SARS-CoV-2 and other members of human coronavirus are very limited. The following two clones of anti-spike antibodies have been tested against all seven coronavirus, and are shown to be specific to SARS-CoV-2 spike.

  • S1 Neutralizing Antibody
  • RBD Neutralizing Antibody
  • The reactivity of the antibodies against the known coronavirus is assessed in ELISA. The reactivity (OD450) is illustrated in the figure left.

Affinity Assay

The binding between immobilized SARS-CoV-2 RBD protein (40592-V08B-B) and the anti-Spike antibody 40592-R001 in Octet RED assay.