Human Defensin-5 (HD-5) and HD-6 mRNA Produced by Intestinal Crypt Paneth Cells are Decreased in Fecal Samples of Patients Positive for SARSCoV2

Abstract Alpha-defensins (AD) are antimicrobial peptides (AMP) that are found on mucosal surfaces, providing innate immune defense against pathogens. Human defensin-5 (HD-5) and HD-6 are AD produced only by Paneth cells of small intestinal crypts. SARS-CoV2 virus has been shown to infect the small intestinal cells via the ACE2 receptor and suppress inflammation in the gut. HD-5 and HD-6 bind ACE2 to prevent entry to intestinal cells. Based on the observation that human beta defensin-1 (hBD-1) is downregulated by influenza virus in airway epithelial cells, we hypothesized that HD-5 and HD-6 could be similarly downregulated by SARS-CoV2. To examine this in situ, we sampled patient cohorts with similar co-morbidities, with and without SARS-CoV2 positivity, for HD-5 and HD-6 gene expression via qRT-PCR. Stool samples were collected from all patients, diluted in Qiagen RNA Later and frozen at −80°C prior to total RNA extraction. Results revealed a significant decrease in both HD-5 (p=0.000006) and HD-6 (p=0.002) of SARS-CoV2 positive patients compared with non-Covid19 patients negative for SARS-CoV2. The results were consistent in fecal swabs or fecal streams. Gene expression in other significant markers of inflammation were also blunted: sPLA-2 (p=0.006), alpha-1-anti-trypsin (p=0.0001) and trypsin 2 (p=0.005). Other gut inflammatory markers PSTI, HIP/PAP, trypsin 3 and IL-8 were unchanged. There was a trend in IL-8 upregulation in Covid19 patients. This is the first demonstration of defensin mRNA detection in stool samples. The results suggest that decreasing AMPs may be a mechanism by which the virus increases its chance for survival. Supported by R21DE028378