A Safe Inhaled Alkaline Treatment That Inhibits Respiratory Viral Infections

Abstract

Introduction: Viral respiratory infection causes significant mortality and morbidity, particularly in patients with chronic airways diseases such as cystic fibrosis. In order to enter host cells and replicate, most respiratory viruses require an acidic intracellular and endosomal environment. We study the beneficial effects of airway alkalinization by an inhaled drug, Optate, that we currently have demonstrated is safe to inhale by healthy subjects and those with stable airways disease. We have recently shown that Optate safely inhibits SARS-CoV-2 infection in primary human airway epithelial cells (HAECs). We hypothesized that Optate would also inhibit other viral infections. Methods: Viral isolates of influenza A (FluA), influenza B (FluB), respiratory syncytial virus (RSV), and human rhinovirus (HRV) were obtained clinically from patients symptomatic of viral respiratory infection. RhMK cells were infected with isolates and treated with 120 mM Optate or placebo. Cells in each group were stained with FITC-conjugated antibodies for the corresponding virus;viral particles were imaged with fluorescent microscopy and images were quantified in ImageJ. Cytopathic effect (CPE) was also evaluated in each group by visual microscopy. Results: FluA, FluB, and RSV infection were significantly inhibited in cells treated with Optate compared to placebo, demonstrated by a significant decrease in fluorescent intensity (n = 4, p 0.05). No visual signs of CPE were noted in the Optate treated FluA, FluB, and RSV groups (< 5% of cells showed signed of injury) compared to the placebo FluA, FluB, and RSV groups (∼ 50% of cells showed signs of injury. CPE was similar between Optate and placebo HRV groups (∼50% of cells showed signs of injury). Conclusions: Optate inhibits FluA, FluB, and RSV infection without causing CPE, similar to its inhibition of SARS-CoV-2 infection. HRV infection was not affected by Optate treatment, suggesting HRV may not require acidic endosomal pH to enter cells and replicate. These findings suggest that Optate may be an inhaled therapeutic for patients with respiratory viral infections.