N-dihydrogalactochitosan reduces mortality in a lethal mouse model of SARS-CoV-2

The rapid emergence and global dissemination of SARS-CoV-2 that causes COVID-19 continues to cause an unprecedented global health burden resulting in nearly 7 million deaths. While multiple vaccine countermeasures have been approved for emergency use, additional treatments are still needed due to sluggish vaccine rollout, vaccine hesitancy, and inefficient vaccine-mediated protection. Immunoadjuvant compounds delivered intranasally can guide non-specific innate immune responses during the critical early stages of viral replication, reducing morbidity and mortality. N- dihydro g alacto c hitosan (GC) is a novel mucoadhesive immunostimulatory polymer of β- 0-4-linked N-acetylglucosamine that is solubilized by the conjugation of galactose glycans with current applications as a cancer immunotherapeutic. We tested GC as a potential countermeasure for COVID-19. GC was well-tolerated and did not produce histopathologic lesions in the mouse lung. GC administered intranasally before and after SARS-CoV-2 exposure diminished morbidity and mortality in humanized ACE2 receptor expressing mice by up to 75% and reduced infectious virus levels in the upper airway. Fluorescent labeling of GC shows that it is confined to the lumen or superficial mucosa of the nasal cavity, without involvement of adjacent or deeper tissues. Our findings demonstrate a new application for soluble immunoadjuvants such as GC for preventing disease associated with SARS-CoV-2 and may be particularly attractive to persons who are needle-averse. IMPORTANCE The ongoing COVID-19 pandemic necessitates new approaches to reduce disease caused by SARS-CoV-2. We tested the immunoadjuvant N-dihydro g alacto c hitosan (GC), used previously as an immunostimulant for tumor therapy and adjuvant for viral vaccines, as a potential COVID-19 countermeasure. When GC was administered before and after inoculation of a lethal dose of SARS-CoV-2 into the nose of humanized mice expressing an entry receptor for the virus, fewer mice showed weight loss and died compared to mice that received only the vehicle but no GC. GC-treated mice also had lower levels of infectious SARS-CoV-2 in their upper airway. These results suggest that GC may be a candidate to prevent or treat COVID-19. Single Sentence Summary The immunoadjuvant N-dihydrogalactochitosan diminishes SARS-CoV-2 disease in humanized ACE2 mice, representing a new countermeasure against COVID-19. ### Competing Interest Statement TH, CFW, SSKL declare a conflict of interest as employees with minority ownership stakes of Immunophotonics, Inc., the manufacturer of the proprietary immune stimulant GC. RML declares a conflict of interest as an advisor with minority ownership stake in Immunophotonics.