INCREASED CATHEPSIN EXPRESSION CORRELATES WITH SARS-COV-2 INFECTION IN HUMAN IBD ENTEROIDS

Abstract

IntroductionCoronavirus Disease 2019 (COVID-19) is an ongoing public health crisis that has sickened or precipitated death in millions. The etiologic agent of COVID-19, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), infects the intestinal epithelium, with viral RNA shed in the stool, and can induce GI symptoms similar to the human inflammatory bowel diseases (IBD). An international surveillance epidemiology study, SECURE-IBD, reported that the standardized mortality ratio trends higher in IBD patients (1.5–1.8) and that 5-aminosalicylic acid (5-ASA) therapy correlates with poor outcome. Together these data indicate patients with IBD may represent a particularly vulnerable population during this COVID-19 pandemic.MethodsPublished datasets GSE75214 and GSE16879 were downloaded and expression levels of select genes were querried using RStudio. Primary human ileal spheroids (enteroids), derived from healthy donors and patients with Crohn’s disease (CD), were grown on 2D transwells until confluent. Cells were then differentiated for 3d before infection with a modified vesicular stomatitis virus expressing the SARS-CoV-2 spike protein (VSV-SARS-CoV-2) and green fluorescent protein (GFP) for 1 h at a multiplicity of infection (MOI) of ~0.5. Healthy enteroids were treated with 10 ng/ml of human Tumor Necrosis Factor alpha (TNF-α) for 24h before infection via the basolateral reservoir or 5-ASA 5h before infection via the apical reservoir. 24h after infection, cells were processed for immunofluorescence or RNA expression of select genes by qRT-PCR.ResultsVSV-SARS-CoV-2 was able to infect both healthy and CD enteroids as determined by co-staining of GFP, indicative of virus infection, and the viral receptor ACE2. However, levels of GFP fluorescence did not correlate with ACE2 expression in CD enteroids. A subset of CD enteroids exhibited enhanced protease expression (TMPRSS2, TMPRSS4, CTSL), each of which correlated with higher viral RNA levels (P=0.04, P=0.002, P=0.006, respectively). In Vero E6 cells, 5-ASA inhibited the replication of a clinical isolate of SARS-CoV-2 in a concentration-dependent manner. Treating healthy enteroids with 5-ASA did not have any effect on viral proliferation, while TNF-α pretreatment reduced viral RNA. 5-ASA treatment caused a reduction of ACE2 and an increase in CTSL expression.ConclusionsHost proteases, particularly the lysosomal protease CTSL, contribute to the infection of CD enteroids and may represent novel therapeutic targets in patients with IBD and COVID-19. 5-ASA modulates the expression of several epithelial genes relevant to SARS-CoV-2 infection, yet does not alter viral replication in healthy enteroids.