Debulking SARS-CoV-2 in saliva using angiotensin converting enzyme 2 in chewing gum to decrease oral virus transmission and infection

Abstract

To advance a novel concept of debulking virus in the oral cavity, the primary site of viral replication, virus-trapping proteins CTB-ACE2 were expressed in chloroplasts and clinical-grade plant material was developed to meet FDA requirements. Chewing gum (2 g) containing plant cells expressed CTB-ACE2 up to 17.2 mg ACE2/g dry weight (11.7% leaf protein), have physical characteristics and taste/flavor like conventional gums, and no protein was lost during gum compression. CTB-ACE2 gum efficiently (>95%) inhibited entry of lentivirus spike or VSV-spike pseudovirus into Vero/CHO cells when quantified by luciferase or red fluorescence. Incubation of CTB-ACE2 microparticles reduced SARS-CoV-2 virus count in COVID-19 swab/saliva samples by >95% when evaluated by microbubbles (femtomolar concentration) or qPCR, demonstrating both virus trapping and blocking of cellular entry. COVID-19 saliva samples showed low or undetectable ACE2 activity when compared with healthy individuals (2,582 versus 50,126 DRFU; 27 versus 225 enzyme units), confirming greater susceptibility of infected patients for viral entry. CTB-ACE2 activity was completely inhibited by pre-incubation with SARS-CoV-2 receptor-binding domain, offering an explanation for reduced saliva ACE2 activity among COVID-19 patients. Chewing gum with virus-trapping proteins offers a general affordable strategy to protect patients from most oral virus re-infections through debulking or minimizing transmission to others.

Hybrid measurement of respiratory aerosol reveals a dominant coarse fraction resulting from speech that remains airborne for minutes

“…The importance of speech droplets in SARS-CoV-2 transmission is highlighted by a review of documented superspreader events ( 75 ), with the vast majority found in places such as bars, restaurants, conferences, and cocktail receptions, all of which involve loud speech, and none reported for movie theaters or libraries, where speech activity is minimal ( 76 ). The high viral loads identified in saliva ( 77 ), in particular prior to the onset of symptoms ( 72 ), are consistent with the importance of speech aerosols in transmission of SARS-CoV-2 and suggest that reducing the concentration of viable virus in saliva may be effective at curbing transmission ( 78 ).…”

Mucosal immune response in BNT162b2 COVID-19 vaccine recipients

“…38 Studies on oral mucosal vaccination, which represents the main route of SARS-CoV-2 transmission are still preliminary. 39 On the other hand, governments have recently approved the administration of the booster dose for the mRNA vaccines (i.e., the third dose), and data about the development of specific mucosal immune response could clarify the role of these vaccines in protecting against the infection, since the systemic evoked response seems stronger than after the primary vaccination cycle. 40…”

COVID-19 therapies: do we see substantial progress?

“…Direct inhibition of SARS-CoV-2 entry and replication in the oral cavity was proposed to be achieved by using a chewing gum that contained recombinant ACE2 expressed in plant cells. In vitro and human subject studies have indicated both viral particle trapping and cellular entry blocking by microparticle-conjugated ACE2 [ 86 ].…”