Coronavirus disease 2019 (COVID‐19) remains a major public health concern, and vaccine unavailability, hesitancy, or failure underscore the need for discovery of efficacious antiviral drug therapies. Numerous approved drugs target protein kinases associated with viral life cycle and symptoms of infection. Repurposing of kinase inhibitors is appealing as they have been vetted for safety and are more accessible for COVID‐19 treatment. However, an understanding of drug mechanism is needed to improve our understanding of the factors involved in pathogenesis. We tested the in vitro activity of three kinase inhibitors against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), including inhibitors of AXL kinase, a host cell factor that contributes to successful SARS‐CoV‐2 infection. Using multiple cell‐based assays and approaches, gilteritinib, nintedanib, and imatinib were thoroughly evaluated for activity against SARS‐CoV‐2 variants. Each drug exhibited antiviral activity, but with stark differences in potency, suggesting differences in host dependency for kinase targets. Importantly, for gilteritinib, the amount of compound needed to achieve 90% infection inhibition, at least in part involving blockade of spike protein‐mediated viral entry and at concentrations not inducing phospholipidosis (PLD), approached a clinically achievable concentration. Knockout of AXL, a target of gilteritinib and nintedanib, impaired SARS‐CoV‐2 variant infectivity, supporting a role for AXL in SARS‐CoV‐2 infection and supporting further investigation of drug‐mediated AXL inhibition as a COVID‐19 treatment. This study supports further evaluation of AXL‐targeting kinase inhibitors as potential antiviral agents and treatments for COVID‐19. Additional mechanistic studies are needed to determine underlying differences in virus response.

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Tissue-based T cells are important effectors in the prevention and control of mucosal viral infections -less is known about tissue-based B cells. We demonstrate that B cells and antibodysecreting cells (ASCs) are present in inflammatory infiltrates in skin biopsies of persons during symptomatic HSV2 reactivation and early healing. Both CD20 + B cells, most of which are antigen-inexperienced by co-expression of IgD, and ASCs, characterized by dense IgG RNA expression in combination with CD138, IRF4 and Blimp1 RNA, are seen to colocalize with T cells.ASCs are found clustered with CD4 + T cells, suggesting potential for crosstalk. HSV2-specific antibodies to virus surface antigens are also present in tissue and increase in concentration during HSV2 reactivation and healing, unlike in serum where concentrations remain static over time. B cells, ASCs, and HSV-specific antibody were rarely detected in biopsies of unaffected skin. Evaluation of serial biopsies demonstrate that B cells and ASCs follow a more migratory than resident pattern of infiltration in HSV-affected genital skin, in contrast to T cells. Together, these observations suggest distinct phenotypes of B cells in HSV-affected tissue; dissecting their role in reactivation may reveal new therapeutic avenues to control these infections.

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The SARS-CoV-2 pandemic has caused widespread illness, loss of life, and socioeconomic disruption that is unlikely to resolve until vaccines are widely adopted, and effective therapeutic treatments become established. Here, a well curated and annotated library of 6710 clinical and preclinical molecules, covering diverse chemical scaffolds and known host targets was evaluated for inhibition of SARS-CoV-2 infection in multiple infection models. Multi-concentration, high-content immunocytofluorescence-based screening identified 172 strongly active small molecules, including 52 with submicromolar potencies. The active molecules were extensively triaged by in vitro mechanistic assays, including human primary cell models of infection and the most promising, obatoclax, was tested for in vivo efficacy. Structural and mechanistic classification of compounds revealed known and novel chemotypes and potential host targets involved in each step of the virus replication cycle including BET proteins, microtubule function, mTOR, ER kinases, protein synthesis and ion channel function. In the mouse disease model obatoclax effectively reduced lung virus load by 10-fold. Overall, this work provides an important, publicly accessible, foundation for development of novel treatments for COVID-19, establishes human primary cell-based pharmacological models for evaluation of therapeutics and identifies new insights into SARS-CoV-2 infection mechanisms.