Caspases in COVID-19 Disease and Sequela and the Therapeutic Potential of Caspase Inhibitors

Currently, there is no effective vaccine and only one FDA approved early-stage therapy against SARS-CoV-2 infection as an indication to prevent disease progression. Cellular caspases play a role in the pathophysiology of a number of disorders that the co-morbid conditions seen in severe COVID-19 disease. In this study, we assessed transcriptional states of caspases in blood cells from COVID-19 patients. Gene expression levels of select caspases were increased in in vitro SARS-CoV-2 infection models and single cell RNA-Seq data of blood from COVID-19 patients showed a distinct caspase expression in T cells, neutrophils, and dendritic cells. Flow cytometric evaluation of CD4 T cells showed up-regulation of caspase-1 in hospitalized COVID-19 patients compared to unexposed controls. Convalescent COVID-19 patients with lingering symptoms ("long haulers") showed persistent up-regulation of caspase-1 in CD4 T cells that was attenuated ex vivo following co-culture with a select pan-caspase inhibitor. Further, we observed elevated caspase-3 levels in red blood cells from COVID-19 patients compared to controls that were responsive to caspase inhibition. Our results expose an exuberant caspase response in COVID-19 that may facilitate immune-related pathological processes leading to severe outcomes. Pan-caspase inhibition could emerge as a therapeutic strategy to ameliorate or prevent severe COVID-19 outcomes.

Novel SARS-CoV-2 specific antibody and neutralization assays reveal wide range of humoral immune response during COVID-19

Development of antibody protection during SARS-CoV-2 (CoV-2) infection is a pressing question for public health and for vaccine development. We developed highly sensitive CoV-2-specific antibody and neutralization assays. CoV-2 Spike protein or Nucleocapsid protein specific IgG antibodies at titers more than 1:100,000 were detectable in all PCR+ subjects (n=87) and were absent in the negative controls. Other isotype antibodies (IgA, IgG1-4) were also detected. CoV-2 neutralization was determined in COVID-19 and convalescent plasma up to 10,000-fold dilution, using Spike protein pseudotyped lentiviruses, which was also blocked by neutralizing antibodies (NAbs). Hospitalized patients had up to 3000-fold higher antibody and neutralization titers compared to outpatients or convalescent plasma donors. Further, subjects who donated plasma further out from the diagnosis of COVID-19 appeared to have lower titers. Interestingly, some COVID-19 patients also contained NAbs against SARS Spike protein pseudovirus. Together these results demonstrate the high specificity and sensitivity of our assays, which may impact understanding the quality or duration of the antibody response during COVID-19 and in determining the effectiveness of potential vaccines.