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Antiviral Assay for Variants of Concern

Amino acid changes that occur during the virus life cycle have led to the emergence of new coronavirus variants. There are 4 “variants of concern” (Alpha, Beta, Gamma and Delta variants) on the  World Health Organization  (WHO) and the CDC watchlist.  The  “variants of concern” designation is assigned based on increased transmissibility, resistance to  public health measures and/or virulence. The ongoing evolution of SARS-CoV-2 requires continuous research and development to create a  pipeline of effective therapies against COVID-19.

IBT Bioservices offers solutions for research and development challenges to identifying broadly neutralizing candidates to stem the ongoing pandemic. Our recombinant rVSV-SARS-CoV-2 assay can now be used to determine the neutralization potency (IC50 value) of anti-infectives against spike-mediated infectivity of Coronavirus variants of concern.  The platform can evaluate proteins, antibodies, as well as small or large molecules.  If you would like to screen your antiviral candidates, use the form below to contact IBT Bioservices.

Fig. 1. Relative light units (luciferase activity) recorded upon infection of Vero cells using IBT’s rVSV-pseudotype SARS-CoV2 Spike.

                    Fig. 1. Luciferase activity (RLU) in Vero cells infected with rVSV-pseudotype SARS-CoV2 Spike.

Key advantages: The spike protein is a key determinant of host and cell tropism, antigenicity and immunogenicity, interspecies transmission as well as pathogenesis1. These traits make the S protein an attractive target for antiviral inhibitors and vaccines2,3,4. Recombinant VSV pseudotyped with the corona-virus Spike proteins are efficient tools for evaluating mechanisms of virus entry and efficacy of anti-infective  candidates. 

Spike Variants List 

Common Name (Origin)
Pango Lineage
Spike Amino Acid
Mutations
Wild-type
(Wuhan)
Parental Strain
--
Alpha
(United Kingdom)
 
B.1.1.7/
501Y.V1
del69–70 HV, del144 Y, N501Y, A570D, D614G, P681H, T761I, S982A, D1118H
Beta
(South Africa)
 
B.1.351
K417N, E484K, N501Y, D614G, A701V
 
Gamma (Brazil)
 
P.1
L18F, T20N, P26S, D138Y, R190S, K417T, E484K, N501Y, D614G, H655Y, T1027I
Delta (India)
B.1.617
L452R, E484Q
Epsilon
(California, USA)
B.1.427
B.1.429
L452R, D614G
SS13I, W152C, L452R, D614G
D614G (--)
--
D614G

Better reagents, Better results!

IBT Bioservices also offers antibodies that target the C- and N- terminus of the S1 region, the C-terminus of the S2 region of the Spike protein and the receptor binding domain (RBD).  The specificity of these affinity purified polyclonal (rabbit) antibodies has been confirmed by Western blot and ELISA. These polyclonal antibodies and antigens are key discovery tools for detection and as control proteins for immunoassays. 

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Fig. 1 Survival after challenge with INFV H1N1 A/Pert/261/2009 (Tamiflu-resistant strain). Inoculum 1xLD90=1.0E+05 PFU/mouse
Survival after challenge with INFV H1N1 A/Pert/261/2009 (Tamiflu-resistant strain) 1.0E+05 PFU/mouse
Survival and weight change in BALB/c mice challenged with INFV A/ Texas/36/91 (H1N1) and treated with antiviral Osletamivir Phosphate (Tamiflu)
Lung viral load and Survival (30 % weight loss cut-off) in BALB/c mice challenged with INFV H3N2 A/HK/1/68.

Alpha (UK) – B. 1.1.7 / 501Y.V1

amino acid mutations: del69–70 HV, del144 Y, N501Y, A570D, D614G, P681H, T761I, S982A, D1118H

Beta (South Africa) – B.1.351

amino acid mutations: K417N, E484K, N501Y, D614G, A701V

Gamma (Brazil) – P.1

amino acid mutations: L18F, T20N, P26S, D138Y, R190S, K417T, E484K, N501Y, D614G, H655Y, T1027I

Epsilon (Ca, USA) B.1.427

amino acid mutations: L452R, D614G

SARS-CoV-2 Parental Strain Wild Type (Wuhan)
SARS-CoV-2 D614G Variant

amino acid mutations: D614G

Epsilon (Ca, USA) B.1.429

amino acid mutations: S13I, W152C, L452R, D614G

SARS-CoV-2 Delta Variant

amino acid mutations: L452R, E484Q