SARS-CoV-2 Uses CD4 to Infect T Helper Lymphocytes (preprint)

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the agent of a major global outbreak of respiratory tract disease known as coronavirus disease-2019 (COVID-19). SARS-CoV-2 infects the lungs and may cause several immune-related complications such as lymphocytopenia and cytokine storm which are associated with the severity of the disease and predict mortality . The mechanism by which SARS-CoV-2 infection may result in immune system dysfunction is not fully understood. Here we show that SARS-CoV-2 infects human CD4+ T helper cells, but not CD8+ T cells, and is present in blood and bronchoalveolar lavage T helper cells of severe COVID-19 patients. We demonstrated that SARS-CoV-2 spike glycoprotein (S) directly binds to the CD4 molecule, which in turn mediates the entry of SARS- CoV-2 in T helper cells in a mechanism that also requires ACE2 and TMPRSS2. Once inside T helper cells, SARS-CoV-2 assembles viral factories, impairs cell function and may cause cell death. SARS-CoV-2 infected T helper cells express higher amounts of IL-10, which is associated with viral persistence and disease severity. Thus, CD4-mediated SARS-CoV-2 infection of T helper cells may explain the poor adaptive immune response of many COVID- 19 patients.

Pharmacological inhibition of the kinin-kallikrein system in severe COVID-19 A proof-of-concept study (preprint)

Coronavirus disease-19 (COVID-19) can develop into a severe respiratory syndrome that results in up to 40% mortality. Acute lung inflammatory edema is a major pathological finding in autopsies explaining O2 diffusion failure and hypoxemia. Only dexamethasone has been shown to reduce mortality in severe cases, further supporting a role for inflammation in disease severity. SARS-CoV-2 enters cells employing angiotensin converting enzyme 2 (ACE2) as a receptor, which is highly expressed in lung alveolar cells. ACE2 is one of the components of the cellular machinery that inactivates the potent inflammatory agent bradykinin, and SARS-CoV-2 infection could interfere with the catalytic activity of ACE2, leading to accumulation of bradykinin. In this open-label, randomized clinical trial, we tested two pharmacological inhibitors of the kinin-kallikrein system that are currently approved for the treatment of hereditary angioedema, icatibant and inhibitor of C1 esterase/kallikrein, in a group of 30 patients with severe COVID-19. Neither icatibant nor inhibitor of C1 esterase/kallikrein resulted in significant changes in disease mortality and time to clinical improvement. However, both compounds promoted significant improvement of lung computed tomography scores and increased blood eosinophils, which has been reported as an indicator of disease recovery. In this small cohort, we found evidence for a beneficial role of pharmacological inhibition of the kinin-kallikrein system in two markers that indicate improved disease recovery.