Screening for regulators of SARS CoV-2 infection and inflammation

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications & trials

Abstract

Cells of the innate immune system, such as dendritic cells and macrophages, constantly patrol host mucosal surfaces and peripheral tissues for signs of infection or injury. Since many people infected with SARS-CoV-2 clear the virus without developing symptoms, aspects of the innate immune response may hold the key to defeating this virus and its variants. The potential for an adverse cytokine storm depends on the interaction of different cell types at the site of infection. This highlights the need to study the immune response to SARS-CoV-2 in a combined environment of both epithelial cells, which are the primary target of infection, and innate immune cells such as macrophages, which are crucial drivers of inflammation. In FY2022, we obtained access to the NIAID SARS Virology Core lab (SVC), and we have since established a co-culture assay with human epithelial cells, an established CoV-2-permissive cell, and human macrophages. Using an antibody specific to the SARS-CoV-2 spike protein, we have been able to measure viral infection of the epithelial cells and how this can be modulated by the macrophage state. In a related project, we have investigated how biologically active small molecules can impart modulatory effects in immune cells, in some cases, providing extended long-term memory. In a screen of biologically active small molecules for regulators of TNF induction, we identified several compounds with the ability to induce training effects on human macrophages. Among these compounds, a Syk kinase inhibitor (SYKi IV) screen hit promoted an enhanced response to LPS similar to that previously reported for beta-glucan. Macrophages trained with SYKi IV showed a high degree of resistance to influenza A. To extend these studies to coronavirus, we first determined that macrophages trained with SYKi IV showed reduced infection with the OC43 seasonal coronavirus. We then investigated effects in the epithelial/macrophage co-culture assays for SARS CoV-2, and found that SYKi IV macrophage training led to dramatically reduced epithelial cell infection. We find similar results with a broad panel of SYK kinase inhibitors, highlighting a potential application of SYK targeting as a modulator of SARS-CoV-2 susceptibility. This work was recently accepted for publication in Cell Reports. We continue to evaluate the logistics of running large scale screen to identify gene perturbations or small molecules that can influence SARS-CoV-2 infection in the context of innate immune modulation. We are also developing additional output assays to evaluate host cell responses to infection, such as multiplex high content microscopy-based single cell analysis of gene induction. Such assays can be conducted in fixed cells and as such, could be run outside the BSL-3 lab after the viral infection step.