SUMMARY
UCLA researchers in the Department of Microbiology, Immunology and Molecular Genetics have developed a novel lentiviral vector encapsulated/coated with the spike (S) glycoprotein from novel SARS-CoV-2 virus. The novel lentiviral vector not only maintains the high infectivity seen in the widely used d19 spike pseudotype – which removes the final 19 amino acids of the cytoplasmic tail – but it also elicits a greater specificity for Angiotensin-converting enzyme 2 (ACE2) expressing cells, thereby, aiding development of therapeutics against SARS-Cov-2 virus.
BACKGROUND
ACE2 receptors are extensively expressed on cell membranes of airway epithelial cells. The novel coronavirus SARS-CoV-2 entry into host cells is primarily mediated by binding of its spike glycoprotein to the ACE2 receptor. An antibody response is elicited by the host in response to SARS-CoV-2 infection. A hosts’ ability to protect themselves from reinfection and/or disease progression is dependent upon high affinity binding and virus neutralizing capabilities of their antibodies.
Antibody neutralization activity is measured by co-culturing, a patient’s plasma sample with SARS-CoV-2, which is highly infectious and replication-competent, thus, necessitating the testing to be conducted within a biosafety level-3 laboratory. Therefore, it is a critical to develop pseudotyped spike glycoprotein non-replicative viral particles specific to ACE2 expressing cells thereby, providing a high-throughput quantification method for measuring the neutralization activity of plasma antibodies.
Current SARS-CoV-2 pseudotypes utilize a spike glycoprotein that contains a deletion of the final 19 amino acids (d19). Although this pseudotype maintains high infectivity of ACE2 expressing cells, it also elicits off-target infection of non-ACE2 expressing cells, a characteristic that is not shared with replicative SARS-CoV-2 virus. Consequently, it is crucial to develop a pseudotyped spike with greater specificity to ACE2 expressing cells than the current d19 pseudotype to accurately study SARS-CoV-2 infection in hACE2 transgenic mouse models or lung models such as air-liquid interface cultures.
INNOVATION
Dr. Donald Kohn and colleagues in the Department of Microbiology, Immunology and Molecular Genetics at UCLA have developed a safe, non-replicative lentiviral vector pseudotyped with S glycoprotein from SARS-Cov-2 Spike with high specificity for ACE2 expressing cells. This novel lentiviral vector’s spike glycoprotein was generated through three major modifications i.e., codon optimizations, amino acid substitutions, and cytoplasmic tail (CT) modifications. This unique pseudotyped lentiviral vector can be used to develop therapeutics, vaccines, and diagnostics against SARS-Cov-2 virus.
APPLICATION
- Covid-19 diagnostics
- Covid-19 vaccine development
- Covid-19 drug screening
- Covid-19 antibody testing
ADVANTAGES
- High viral titers
- Safe
- Non-replicative
- High infectivity of ACE2 expressing cells
- High specificity for ACE2 expressing cells and negligible off-target infectivity
- Eliminate the need for biosafety-level-3 laboratories when developing Covid-19 therapeutics
State of Development
The group has generated the lentiviral vector that expresses mutant SARS-Cov-2 Spike glycoprotein. They have shown that this construct is capable of transducing HEK-293T cells expressing ACE2 and air liquid interface cultures of primary airway epithelial cells.
Related Papers (from the inventors only)
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