First Evidence of Pathogenic HERV-W Envelope Expression in T Lymphocytes in Association with the Respiratory Outcome of COVID-19 Patients

Background: Despite an impressive effort in clinical research, no standard therapeutic approach for coronavirus disease 2019 (COVID-19) patients has been established, highlighting the need to identify early biomarkers for predicting disease progression and new therapeutic intervention for patient management. The present study aimed to evaluate the involvement of the human endogenous retrovirus -W envelope (HERV-W ENV) in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection considering recent findings that HERVs are activated in response to infectious agents and lead to various immunopathological effects. We analysed HERV-W ENV expression in blood cells of COVID-19 patients in correlation with clinical characteristics and have discussed its potential role in the outcome of the disease.<br><br>Methods: We analysed HERV-W ENV expression in blood samples of Covid-19 patients and healthy donors by flow cytometry and quantitative reverse transcriptase PCR analysis, and evaluated its correlation with clinical signs, inflammatory markers, cytokine expression, and disease progression.<br><br>Findings: HERV-W ENV was highly expressed in&nbsp;the leukocytes of COVID-19 patients but not in those of healthy donors. Its expression correlated with the markers of T-cell differentiation and exhaustion and blood cytokine levels. The percentage of HERV-W ENV-positive lymphocytes correlated with inflammatory markers and pneumonia severity in COVID-19 patients. Notably, HERV-W ENV expression reflects the respiratory outcome of patients during hospitalization.<br><br>Interpretation: Given the known immuno- and neuro-pathogenicity of HERV-W ENV protein, it could promote certain pathogenic features of COVID-19 and therefore serve as a biomarker to predict clinical progression of disease and as a potential therapeutic target.<br><br>Funding: Genero Innovation<br><br>Declaration of Interests: C.M. reports grant from Gilead, outside the submitted work; L.S. reports personal fees and other from Merck, Gilead, and Abbvie, grants from Gilead, outside the submitted work; HP and BC receive compensation for their work by Geneuro-Innovation. The other authors declare no competing interests.<br><br>Ethics Approval Statement: Ethical approval for the collection and use of human samples was obtained from the ethical board of the Hospital, COronaVIrus Disease: Safety and Efficacy of Experimental Treatment (COVID_SEET prot.7562/2020, 9th April 2020, experimental register 46.20).