COVID-19 Treatments: Researchers from Rutgers New Jersey Medical School Advocate Using Immunotherapy Involving CAR-NK Cells To Treat COVID-19
: Researchers from Rutgers New Jersey Medical School reports the potential of a new class of drugs called CAR NK cells, which could be used off-the-shelf to treat COVID-19.
Their research findings were published on a preprint server and have yet to be peer-reviewed. https://www.biorxiv.org/content/10.1101/2020.08.11.247320v1
Present medical interventions in COVID-19 comprise three types of therapy: antiviral treatments, immunomodulators, and supporting treatments. The first category includes remdesivir, ribavirin and other antivirals (though none are officially approved to treat COVID-19, remdesivir is only under EUA status) often used in combinations.
In the case of immune response reduction protocols, attempts are made using antibodies to the IL-6 receptors, corticosteroids, and non-steroidal anti-inflammatory drugs (NSAIDs).
Whereas supportive management includes mechanical ventilation and supplementary oxygen, as well as the use of convalescent plasma.
Currently multiple immunotherapeutic techniques are also being tried out.
Interestingly, in this research, the study team proposes a novel approach to modulating cell-based immunity involves the use of chimeric antigen receptor (CAR) technology with natural killer (NK) cells. These are isolated from peripheral blood and can be adapted to express CAR in order to treat multiple infectious and neoplastic conditions.
In past immunotherapy protocols, CAR T cells have been used in some tumor therapies.
But importantly to treat COVID-19, the T cells have to be derived from affected individuals who have lymphopenia. On the other hand, the CAR NK cells can be sourced from a third party, allowing them to be used off-the-shelf, at reduced costs and with broader app.
The research team used NK cells, which they then modified with a CAR molecule that binds specifically to the SARS-CoV-2 spike (S) protein. Prior research has shown the significant similarity between the genomes of this virus and the earlier SARS-CoV, as well as a cross-reactive neutralizing antibody CR3022.
The study team therefore, transduced the scFv domain of the antibody into a viral vector containing IgG1 hinge and other parts of the immunoglobulin molecule. This antibody CR3022 has potent binding activity against the spike proteins of both viruses. (scFvs or Single-chain variable fragments are recombinant molecules in which the variable regions of light and heavy immunoglobulin chains encoding antigen-binding domains are engineered into a single polypeptide.)
The study team first generated CR3022-CAR expression on the NK cells in a human NK-92 cell line using plasmids containing the chimeric antigen. After sorting the resulting cells using flow cytometry, the CR3022-expressing cells were maintained for 2 months to confirm that CAR was consistently expressed.
Upon stable expression of CAR on the cell membrane being established, the team confirmed that the pattern of receptor expression of the chimeric cells was similar to that of the parent NK cells.
m then evaluated how well these cells bound to the receptor-binding domain (RBD) of the virus. On co-incubation, they found that as expected, the CR3022-CAR-NK cells bound to the RBD protein.
The researchers then looked at the binding activity of the CR3022-CAR-NK cells to pseudotyped SARS-CoV-2 viral particles.
The team found that just like the binding of the RBD to the natural receptor, ACE2, which promotes viral entry into the host cell, these chimeric NK cells also bound to the pseudoviruses. In fact, the pseudovirus binding to a cell culture line expressing human ACE2 was weaker than the binding to the CR3022-CAR-NK-92MI cells, which indicates a higher affinity of this cell line to the spike protein than its natural ACE2 receptor.
The researchers then expressed the RBD on a cell line expressing the ACE2 receptor, which was activated after culturing with these cells. They then examined the efficiency of binding and activation of CR3022-CAR-NK cells by these target cells. They found that that the activation molecule CD107 on the surface of the CR3022-CAR-NK cells increased when cultured with the ACE2- and RBD-expressing cells.
Significantly, the levels of the activation products TNF-alpha and perforin also shot up in these CR3022-CAR-NK-92MI cells after co-culturing with these 293T-hACE2 cells expressing the spike RBD target. They observed that CR3022-CAR-NK cells were able to kill cells infected with SARS-CoV-2, supporting this modality for clinical use.
Corresponding author, Dr Dongfang Liu from Center for Immunity and Inflammation, Rutgers New Jersey Medical School told Thailand Medical News, “The research shows that CR3022-CAR-NK cells can be activated by SARS-CoV-2 spike protein receptor-binding domain expressing infected target cells and specifically kill their susceptible target cells. The cells used in the study have malignant potential and must be irradiated before use in patients to prevent them from taking permanent root in the recipient.”
The study team however noted as natural SARS-CoV-2 particles was not tested, nor was an animal model used. Such studies will be required to demonstrate the relevance of these observations in the clinical setting, by showing the effectiveness and safety of the CR3022-CAR-NK cells.
However they stressed that this study could promote more advanced preclinical studies and perhaps the production of a line of universally applicable readymade CAR-NK-based immunotherapy for COVID-19.
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