Abrogation of neutrophil inflammatory pathways and potential reduction of neutrophil-related factors in COVID-19 by intravenous immunoglobulin.

Pathogenesis of lung injury in COVID-19 is not completely understood, leaving gaps in understanding how current treatments modulate the course of COVID-19. Neutrophil numbers and activation state in circulation have been found to correlate with COVID-19 severity, and neutrophil extracellular traps (NETs) have been found in the lung parenchyma of patients with acute respiratory distress syndrome (ARDS) in COVID-19. Targeting the pro-inflammatory functions of neutrophils may diminish lung injury in COVID-19 and ARDS. Neutrophils were isolated from peripheral blood of healthy donors, treated ex vivo with dexamethasone, tocilizumab and intravenous immunoglobulin (IVIG) and NET formation, oxidative burst, and phagocytosis were assessed. Plasma from critically ill COVID-19 patients before and after clinical treatment with IVIG and from healthy donors was assessed for neutrophil activation-related proteins. While dexamethasone and tocilizumab did not affect PMA- and nigericin-induced NET production ex vivo, IVIG induced a dose-dependent abrogation of NET production in both activation models. IVIG also reduced PMA-elicited reactive oxygen species production, but did not alter phagocytosis. COVID-19 patients were found to have elevated levels of cell-free DNA, neutrophil elastase and IL-8 as compared to healthy controls. Levels of both cell-free DNA and neutrophil elastase were lower 5 days after 4 days of daily treatment with IVIG. The lack of impact of dexamethasone or tocilizumab on these neutrophil functions suggests that these therapeutic agents may not act through suppression of neutrophil functions, indicating that the door might still be open for the addition of a neutrophil modulator to the COVID-19 therapeutic repertoire.

Potent in vitro and in vivo antifungal activity of a small molecule host defense peptide mimic through a membrane-active mechanism.

Lethal systemic fungal infections of Candida species are increasingly common, especially in immune compromised patients. By in vitro screening of small molecule mimics of naturally occurring host defense peptides (HDP), we have identified several active antifungal molecules, which also exhibited potent activity in two mouse models of oral candidiasis. Here we show that one such compound, C4, exhibits a mechanism of action that is similar to the parent HDP upon which it was designed. Specifically, its initial interaction with the anionic microbial membrane is electrostatic, as its fungicidal activity is inhibited by cations. We observed rapid membrane permeabilization to propidium iodide and ATP efflux in response to C4. Unlike the antifungal peptide histatin 5, it did not require energy-dependent transport across the membrane. Rapid membrane disruption was observed by both fluorescence and electron microscopy. The compound was highly active in vitro against numerous fluconazole-resistant clinical isolates of C. albicans and non-albicans species, and it exhibited potent, dose-dependent activity in a mouse model of invasive candidiasis, reducing kidney burden by three logs after 24 hours, and preventing mortality for up to 17 days. Together the results support the development of this class of antifungal drug to treat invasive candidiasis.