Team:SMMU-China/Description

Background:

COVID-19 is a highly infectious respiratory disease caused by a new coronavirus known as SARS-CoV-2. This novel coronavirus infection, which began as an outbreak of unusual viral pneumonia in Wuhan, has evolved into a global health crisis. Although the fatality rate is not high, the number of people infected is large and still millions of people dying. Ongoing trials are testing antiviral therapies, immune modulators and anticoagulants. However, there have been no conclusive series of reproducible randomized clinical trials demonstrating the efficacy of any one drug or therapy for COVID-19, especially severe cases.

What’s the main problem?

The mild or severe cytokine storms in severe patients can mainly account for severe cases’ death. Current medicine and therapy mainly focus on interrupting the viral life-cycle of SARS-CoV-2 or preventing cytokine storms. However, there is no specific medicine and highly efficient treating method for severe cases. Specifically, for those severe patients, mechanical ventilation might aggravate the lung damage. Also, some medicine such as dexamethasone and remdesivir are reported to improve the time to recovery but still have using limits respectively and there isn’t enough clinical evidence to prove their efficacy. And human vaccine is still under development and a number of challenges must be overcome in this process, such as technical barriers, the feasibility of large-scale production and regulation and so on. Here, we hope to develop a radical cure that is can be widely used and with less side effect. Subsequently, our ideas for curing severe COVID-19 cases came into being.

What do we do？

We developed a series of CAR (chimeric antigen receptors) MERTK-Macrophages using synthetic biology technology .The CAR consists of three specific elements: the extracellular domain targeted at the distinctive S protein of the SARS-CoV-2, the transmenbrane domain permitting the signal transduction and the intracellular domain activating the phagocytosis process. There are actually four different kinds of CARs marked with the intracellular domain as follow: common γ subunit of Fc receptors (CARγ), MEGF10 (CARMEGF10), MERTK (CARMERTK) and CD3ζ (CARζ).We confirmed the virus clearance of the CAR-macrophage and detected the inflammatory factors in the four coculture systems.CAR MERTK combined with macrophages has the ability to decrease the rise of systemic inflammatory reaction syndrome and lower the chance of acute respiratory distress syndrome and this was testified by the trials we made.

Why do we choose CAR MERTK-Macrophages?

The success of CAR-T cell therapies highlights the promise of programmed immunity and suggests that applying CAR strategies to other immune cell lineages may be beneficial. Macrophages serve as critical effector of the innate immune system, mainly responsible for engulfing debris and pathogens and they are capable of penetrating solid tumor, making their way inside tumors and traveling to harmful cancers that the rest of the immune system cannot reach. As clinical research shows that cytokine storms mainly account for the death of severe cases and S protein targeted at MERTK belonging to TAM receptors is able to activate phagocytic clearance without upregulating immune responses. Hence, we creatively put forward an idea that combining macrophages with CAR MERTK to treat patients with severe COVID-19.

Conclusion:

We demonstrate that our concept: a ‘silent CAR’ (CAR-Macrophage) can successfully eliminate SARS-CoV-2 while causing barely cytokine release. After constructing 4 types of , we conducted experiments concerning their phagocytic capacity, cell lytic effect and virion internalization property to demonstrate that all types of CAR-Macrophages show significant virus eliminating efficiency. Subsequently, we conducted cytokine analysis assay and observed strongly increased induction of cytokines in all CAR-Macrophages except for CARMERTK cells. Thus demonstrating that our concept to construct a "silent CAR" that can effectively remove virus particles without inflammatory response is realized. Furthermore, we demonstrated the protective role of CAR macrophages in SARS-CoV-2 infection by using coculture model, serving as an extended application on cell level. Finally, we ruled out the possibility that macrophages being infected by SARS-CoV-2, demonstrating the safety and reliability of our COVID-19 targeted therapy.

References:

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