Spike (B.1.617.2.1; Delta Plus Variant) Pseudotyped Lentivirus (Luc Reporter)
The pandemic coronavirus disease 2019 (COVID-19) is caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). As the first step of the viral replication, the virus attaches to the host cell surface before entering the cell. The viral Spike protein recognizes and attaches to the Angiotensin-Converting Enzyme 2 (ACE2) receptor found on the surface of type I and II pneumocytes, endothelial cells, and ciliated bronchial epithelial cells. Drugs targeting the interaction between the Spike protein of SARS-CoV-2 and ACE2 may offer protection against the viral infection. A variant called B.1.617.2.1 (also known as the Delta Plus Variant) was identified in India in the spring of 2021. This variant has a number of mutations that increase morbidity and mortality and allow the virus to spread more easily and quickly than other variants.
The Spike (B.1.617.2.1 Variant) (SARS-CoV-2) Pseudotyped Lentiviruses were produced with SARS-CoV-2 B.1.617.2.1 Variant Spike (Genbank Accession #QHD43416.1 with B.1.617.2.1 mutations; see below for details) as the envelope glycoproteins instead of the commonly used VSV-G. Compared to the Delta variant (B.1.617.2), variant Delta Plus has an additional mutation, K417N. These pseudovirions contain the firefly luciferase gene driven by a CMV promoter (Figure 1), therefore, the spike-mediated cell entry can be measured via luciferase activity. The Spike (B.1.617.2.1 Variant) (SARS-CoV-2) pseudotyped lentivirus can be used to measure the activity of neutralizing antibody against SARS-CoV-2 B.1.617.2.1 variant in a Biosafety Level 2 facility.
Spike interacts with host cells by binding to membrane receptor ACE2 (angiotensin converting enzyme 2). Based on experiments performed by scientists at BPS Bioscience, we know that the wild-type SARS-CoV-2 spike pseudotyped lentiviruses transduce the following cells with great efficiency: ACE2-HEK293 cells (BPS Bioscience #79951), ACE2-CHO cells (BPS Bioscience #79959), ACE2-HeLa cells (BPS Bioscience #79958). They also efficiently transduce TMPRSS2-Vero E6 cells (BPS Bioscience #78081), which express high endogenous levels of ACE2 and were stably transfected with human serine protease TMPRSS2 required for the priming of Spike and fusion of the virion with the plasma membrane. By contrast, it has been shown by others that SARS-CoV-2 spike pseudotyped lentiviruses do not transduce parental Calu3 and Vero E6 cells very well [Neerukonda et al. 2021, PlosOne PMID: 33690649; Tandon et al. 2020, Scientific Reports PMID: 33154514; Condor Capcha et al. 2021, Front. Cardiovasc. Med. PMID: 33521067; Pisil et al. 2021, Pathogens PMID: 33540924].
SARS-CoV-2 variant pseudoviruses have been validated using ACE2-HEK293 cells but have not been tested in other cells.
As recommended in our protocol, 5 µl of virus/well in a 96-well plate provides a sufficient signal-to-noise ratio to perform inhibition studies. The amount of virus added to the cells can also be scaled down according to the user’s need.
Spike Mutations in B.1.617.2 Variant:
T19R
G142D
156/157 DELETION
R158G
K417N
L452R
T478K
D614G
P681R
D950N
Figure 1. Schematic of the Luciferase Reporter in SARS-CoV-2 Spike (B.1.617.2.1 Variant) Pseudovirion
Name | Ordering Information |
Thaw Medium 1 or HEK293 Growth Medium | BPS Bioscience, #60187 |
ACE2-HEK293 Recombinant Cell Line | BPS Bioscience, #79951 |
Spike S1 Neutralizing Antibody (Clone C-A11) (SARS-CoV-2) | BPS Bioscience, #101024 |
96-well tissue culture treated, white clear-bottom assay plate | Corning, #3610 |
ONE-Step™ luciferase assay system | BPS Bioscience, #60690 |
The lentiviruses were produced from HEK293T cells. Supplied in medium containing 90% DMEM + 10% FBS.
Media Formulation:
Thaw Medium 1 (BPS Bioscience, #60187): MEM medium supplemented with 10% FBS, 1% non-essential amino acids, 1 mM Na pyruvate, 1% Penicillin/Streptomycin.