Down regulation of defensin genes during SARS-CoV-2 infection

Defensins, crucial components of the innate immune system, play a vital role against infection as part of frontline immunity. Association of SARS-CoV-2 infection with defensins has not been investigated. In this study, we have investigated the expression of defensin genes in the buccal cavity from patients with COVID-19 infection along with negative control samples. Nasopharyngeal/oropharyngeal swab samples collected for screening SARS-CoV-2 infection in early 2020 from Hyderabad, India, were analyzed for the expression of major defensin genes by the quantitative real-time reverse transcription polymerase chain reaction, qRT-PCR. Forty SARS-CoV-2 infected positive and 40 negative swab samples were selected for this study. Based on the qRT-PCR analysis involving gene specific primers for defensin genes, 9 defensin genes were found to be expressed in the nasopharyngeal/oropharyngeal cavity. Four defensin genes were found to be significantly down regulated in SARS-CoV-2 infected patients in comparison with the control samples based on differential expression analysis. The significantly down regulated genes were defensin beta 4A/B, 106B, 107B, and 103A. Down regulation of human beta defensin 2, 3, 6 and 7 suggests that antiviral innate immune response provided by defensins may be compromised in SARS-CoV-2 infection resulting in progression of the disease. Correction of the down regulation process through appropriate defensin peptide-based therapy could be an attractive method of treatment.