Yuwei Guo
Smruti Nair
Hancheng Guan
Henry Daniell
| Yuwei Guo | Smruti Nair | Hancheng Guan | Henry Daniell |
Yuwei Guo, Hancheng Guan, Henry Daniell, Robert P RicciardI
Basic & Translational Sciences, University of Pennsylvania, School of Dental Medicine
Introduction
Although SARS-CoV-2 is transmitted nasally and orally, oral transmission is 3-5 orders of magnitude higher than nasal transmission. Speaking 4 words releases more virions than 1 hour of mask-less breathing, suggesting a decrease in oral viral load could have a substantial effect on virus transmission. SARS-CoV-2 spike protein binds to the Angiotensin Converting Enzyme (ACE2) in human saliva and enters cells via ACE2 receptors or GM1 co-receptors. We developed two novel anti-viral proteins with distinct viral-trapping mechanism. While CTB-ACE2 blocks SARS-CoV-2 strains by direct binding to spike protein, plant lectin FRIL from Lablab Purpureus bean entraps viruses that express complex type-N glycans on their outer envelopes. The efficacy of both viral trap proteins incorporated into chewing gums is evaluated for debulking or neutralizing different strains of SARS-CoV-2 or influenza viruses.
Methods
The debulking effect of CTB-ACE2 chewing gum (1.75 and 3.5 µg) and FRIL bean protein (20, 40, and 100 µg) was tested with 120 uL of omicron or delta variants of SARS-CoV-2 nasopharyngeal samples (Ronald G. Collman-IRB#823392). The anti-viral ability of FRIL bean powder and purified protein against Influenza virus, H1N1 and H3N2, and Coronavirus OC43 was tested using plaque reduction assay. The mechanism of FRIL's virus-trapping ability was investigated using negative-staining Electron Microscopy using H1N1.
Results
Low dosages of CTB-ACE2 and FRIL significantly lowered the microbubble count of patient samples (p<0.0001), suggesting that the viral-trapping proteins could effectively reduce viral load in COVID19 patients infected with different strains. In plaque reduction assay, FRIL bean powder exhibited EC50 of 0.25 against H1N1, 0.21 against H3N2, and 0.13 mg/mL against OC43. Purified FRIL showed EC50 of 0.95 against H1N1, 0.96 against H3N2, and 0.76 µg/mL against OC43. Negative staining EM of purified FRIL with H1N1 virus revealed the mechanism of FRIL inducing viral aggregation and thereby preventing cellular entry.
Conclusion
CTB-ACE2 has shown viral trapping ability towards a variety of SARS-CoV-2 variants. The natural plant lectin, FRIL, showed high potency against Influenza and Coronavirus, making it another strong candidate for virus-debulking chewing gum. Chewing gum containing FRIL could be manufactured and further investigated against other major transmissive viruses that contain complex-type N-glycans such as AIV and HBV.