A novel biopolymer for mucosal adjuvant against respiratory pathogens

Mucosal vaccinations for respiratory pathogens provide superior protection as they stimulate localized cellular and humoral immunity at the site of infection. Currently, the major limitation of the intranasal vaccination is using effective adjuvants capable of withstanding the harsh environment imposed by the mucosa. Herein, we describe the efficacy of using a novel biopolymer, N-dihydrogalactochitosan (GC), as a nasal mucosal vaccine adjuvant against respiratory infections. Specifically, using COVID as an example, we mixed GC with recombinant SARS-CoV-2 trimeric spike (S) and nucleocapsid (NC) proteins to intranasally vaccinate K18-hACE2 transgenic mice, in comparison with Addavax (AV), an MF-59 equivalent. In contrast to AV, intranasal application of GC induces a robust, systemic antigen-specific antibody response and increases the number of T cells in the cervical lymph nodes. Moreover, GC+S+NC vaccinated animals were largely resistant to lethal SARS-CoV-2 challenge and experienced drastically reduced morbidity and mortality, with the animal weights and behavior returning to normal 22 days post infection. In contrast, animals intranasally vaccinated by AV+S+NC experienced severe weight loss, mortality, and respiratory distress, with none surviving beyond 6 days post infection. Our findings demonstrate that GC can serve as a potent mucosal vaccine adjuvant against SARS-CoV-2 and potentially other respiratory viruses.

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 more than 4 million deaths in the 20 months since the virus was discovered. While multiple vaccine countermeasures have been approved for emergency use, additional treatments are still needed due to sluggish vaccine rollout and vaccine hesitancy. Immunoadjuvant compounds delivered intranasally can guide non-specific innate immune responses during the critical early stages of viral replication, reducing morbidity and mortality. N-dihydrogalactochitosan (GC) is a novel mucoadhesive immunostimulatory polymer of {beta}-0-4-linked N-acetylglucosamine that is solubilized by the conjugation of galactose glycans. We tested GC as a potential countermeasure for COVID-19. 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 and lungs. Our findings demonstrate a new application for soluble immunoadjuvants like GC for preventing severe disease associated with SARS-CoV-2. Single Sentence SummaryThe immunoadjuvant N-dihydrogalactochitosan diminishes SARS-CoV-2 disease in humanized ACE2 mice representing a new countermeasure against COVID-19.