COVID-19. Chitosan as prevention. Can it work?
Introduction
There is a question that should be answered today: while waiting for an approved vaccine, is it possible to contain the spread of the COVID-19 epidemic with a low toxicity drug that inhibits the virus/receptor ratio so as to prevent its entry?
Discussion
Coronaviruses usually cause only colds in healthy individuals and in the initial phase, while in the subsequent phase, the disease can lead to pneumonia with serious consequences in adults above the age of 60 and/or immunodepressed. Influenza epidemics explode every year between autumn and winter and, worldwide, infect about 3/5 million people with 250/500,000 deaths (1-2).
Let us now consider the typology in percentage of people affected by the virus: about 80% over 40 years old while the percentage is drastically reduced to 5.3% between 0 and 20 years old (3). The mortality rate was 2.8% for men and 1.7% for women while the highest mortality rate was 14.8% in the 80-year-old age group. Influences predominantly affect males, both in the older population and in the younger population (4) with a male-to-woman ratio of 1.3 in Europe and women develop a higher innate and adaptive immune response, which can be beneficial when encountering pathogens (5). These data confirm that the virus can enter more easily and cause more damage in those age groups where the immune system is less protected.
Now, since immunodepression is the facilitated way for the virus to create damage, a viable route could be to block the entry of the virus by first strengthening the immune system with natural antibacterial products and using a broad spectrum inhibitor to block the interactivity relationship between the virus and the human ACE2 receptor, a zincopeptidase membrane converted by angiotensin which is found distributed in the human body and more concentrated in kidney, testicles, heart. In particular, this blocking attempt must be made before the virus has entered our system as it may be contraindicated if the virus is already present (6).
It has been shown that the expression of ADA2 and several Ada2-mediated cell wall related genes (ALS2, PGA45, and ACE2) and efflux transporter genes (MDR1 and CDR1) have been significantly inhibited by chitosan (7) and the action of chitosan has been widely described by recent studies (8), so let us examine the likely benefits of this component.
Chitosan is a naturally abundant polysaccharide and has demonstrated excellent biocompatibility, biodegradability, mechanical strength and low toxicity.
It is obtained by alkaline N-deacetylation of chitin, which is the main component of the exoskeleton of crustaceans, such as shrimps, crabs and lobsters (9).
Many studies have focused on its function as a vector, in regenerative medicine, of bioactive molecules (10), of bone tissue regenerator (11), of its potential for tissue engineering on articular cartilage (12).
In vivo experiments showed that unmodified Chitosan nanoparticles were able to reverse fibrosis with a 100% survival rate at the end of the study, indicating the ability of Chitosan nanoparticles to provide functional collagenase to the fibrotic liver and making the use of collagen binding peptides unnecessary (13).
Because of its low toxicity and biodegradability properties, Chitosan has been used as an antimicrobial agent (14).
Chitosan and cationically modified chitosan (HTCC) are biomaterials that can be used to improve immune efficacy and improve immune response due to their promising mucoadhesive properties (15).
Conclusion
The combined action of a robust strengthening of immune defences combined with the intake of chitosan could be a preventive way of protection against COVID-19.
References__________________________________________________________________
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COVID-19. Chitosan as prevention. Can it work? 
