Team:Technion-Israel/Description

• Description
• The Problem | COVID-19 Pandemic
• Present Day Solutions
• ACT.

The Problem | COVID-19 Pandemic

The world’s way of life has been under siege for the past year by the novel coronavirus strain, designated "Severe Acute Respiratory Syndrome CoronaVirus 2” (SARS-CoV-2). This strain is accounted for the COVID-19 disease, which reached the scale of a global pandemic circa March 2020. By the end of August, the virus has spread into 215 countries and territories around the world, causing the death of over 806,000 people and infecting over 23 million^[1].

The main transmission route of respiratory viruses (such as SARS-CoV-2) comes in the form of coughing and sneezing droplets, each containing up to millions of viral particles. Smaller droplets remain airborne for longer periods of time; thus, increasing the virus’s chance of being inhaled by a susceptible host. Aside from the airborne transmission, some evidence suggests that contaminated fomites also play a key role in the spread of viral infections^[2]. Fomites are inanimate objects, which can spread infections passively. Once a fomite-to-skin transference occurs, it is usually a matter of time until the virus reaches an available mucus layer (eyes, mouth, nose, etc.) and the person becomes infected^[3].

In the case of COVID-19, the infection is facilitated by the virus’s spike proteins (designated Spike proteins) which bind to angiotensin-converting enzyme 2 (ACE2) receptor. Thus, COVID-19 is a disease of the molecular kind, to which the tailored responses should be molecular as well.

SARS-CoV-2

SARS-CoV-2 is the seventh known strain from the family of beta-coronavirus. The viral genome is a positive single stranded RNA (ssRNA+) and its virion is about 80-100nm in diameter^[4][5].

Virions are enveloped by a lipid bilayer membrane, containing around 25 heavily glycosylated trimers, designated Spikes or Spike proteins. The spikes have an area of ~6 amino acids, which form the receptor-binding domain (RBD) that enables their binding to a specific enzyme, found on the surface of human lung cells (among other human cell types). This enzyme is known as ACE2. The linkage between the Spike protein and the ACE2 causes a structural rearrangement of the proteins that assemble the connected viral spike. This rearrangement contributes to the initiation of the cascade leading to membranal fusion, which ends with the insertion of the viral RNA into the human cell^[6][7].

COVID-19 is almost exclusively mild in children^[8], while older individuals, as well as those with specific preexisting illnesses, are more likely to develop severe syndromes that relate to severe pneumonia and may require intensive care^[9].

ACE2

Angiotensin-converting enzyme 2 (ACE2) is an enzyme attached to the cell membranes of cells in the lungs, arteries, heart, kidney, and intestines. Its primary physiological role is in the maturation of angiotensin, a peptide hormone that controls vasoconstriction and blood pressure^[10].

ACE2 is also the cellular receptor for SARS-CoV-2. The RBD of the Spike protein is recognized by the extracellular peptidase domain (PD) of ACE2 mainly through polar residues. Thus, the enzyme is “hijacked” by some coronaviruses and sets the path that allows the infection of human host cells^[11].

Present Day Solutions

Among the measures which have been taken against this pandemic, the most prominent ones are mandatory mask-wearing and social distancing, the latter has been the cause of increased depression cases all over the world^[12]. Other measures are mostly taken against fomite transmissions and consist of glove-wearing, frequent use of alcohol-based sanitizers and detergents (hand soap). All three of which have their own disadvantages.

Single-use gloves are widely misused by people that behave as if the gloves provide some kind of "viral immunity", and thus they contribute to the spread (by using the same gloves for long periods of time and touching their phones and faces). Another rising phenomenon is the unnecessary use of the gloves ("to be on the safe side"), worsening the global scatter of non-perishable plastics.

Alcohol-based sanitizers, while being almost completely effective against the virus, are unfortunately also very effective against our skin’s microbiome (the delicate balance of bacteria, viruses, and fungus that live on our skin^[13]). In addition to the damage, it causes to the beneficial bacteria, hand sanitizers could also contribute to the development of more resistant bacteria^[14].

Hand soap is by far the most useful way to kill present membrane enveloped viruses on our skin. It is cheap, effective, and safe. The main problem with the use of hand soap as the preeminent mean of protection is that it is not available at all times and places and the damage (infection) might be already done by the time it is used. The two latter (sanitizers and soap) might kill the viruses that transferred to our hands, but do not prevent future transfers.

ACT.

We suggest a more prophylactic approach that aims to reduce viral transference from fomites and therefore aid in flattening the curve, reducing the load on the health systems and the economies worldwide, and hopefully, saving lives.

Our solution aspires to be more effective than the use of disposable gloves, less damaging to our skin than alcohol-based hand sanitizers, and provide active skin protection for hours after every use (unlike hand soap and other sanitizers).

Hence, we present – ACT. Anti COVID-19 Technology, a hydrogel-based skin-screen containing proteins that act as “decoy proteins”, aimed to block infection of host cells by the SARS-CoV-2 virus.

Fishing rod, hook, and bait

It is simpler to describe our system as a fishing rod, hook, and bait (the fish is the virus):

As a bait, we aspire to use two possible proteins: mutated ACE2 with enhanced binding affinity to the Spike proteins, and "Sybodies"- synthetic single-domain antibodies (nanobodies) with the ability to strongly bind the Spike proteins (designed by Walter et al)^[15].

As for the hook, we worked on two different "protein carriers" approaches: First, Bacillus subtilis spore surface display (BSSD) approach, by synthetically causing the B.subtilis cells to express one of the "bait" proteins once sporulation is induced. Second is coordinatively linking the "bait" proteins to special microgel-beads containing Ni⁺ (by His tagging the proteins).

To make it spreadable on our skin, we chose a thermo-responsive hydrogel (based on Pluronic F-127^[16]) as the “fishing rod”. The gel will contain one of the hooks with one or both baits.

References

1. World health organization. WHO Coronavirus Disease (COVID-19) Dashboard website.Updated October 2, 2020. https://covid19.who.int/table. Accessed September 29, 2020
2. Kampf G, Todt D, Pfaender S, Steinmann E. Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents. J Hosp Infect. 2020;104(3):246-251.
3. CDC Centers for Disease Control and Prevention. Coronavirus Disease 2019 (COVID-19). Updated September 21, 2020. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/how-covid-spreads.html. Accessed September 29, 2020.
4. Walls AC, Park YJ, Tortorici MA, Wall A, McGuire AT, Veesler D. Structure, Function, and Antigenicity of the SARS-CoV-2 Spike Glycoprotein. Cell. 2020;181(2):281-292.e6.
5. Ke Z, Oton J, Qu K, et al. Structures and distributions of SARS-CoV-2 spike proteins on intact virions. Nature. August 2020:1-7.
6. Ke Z, Oton J, Qu K, et al. Structures, conformations and distributions of SARS-CoV-2 spike protein trimers on intact virions. bioRxiv. January 2020:2020.06.27.174979.
7. Procko E. The sequence of human ACE2 is suboptimal for binding the S spike protein of SARS coronavirus 2. bioRxiv Prepr Serv Biol. May 2020.
8. Brodin P. Why is COVID-19 so mild in children? Acta Paediatr Int J Paediatr. 2020;109(6):1082-1083.
9. Guan W, Ni Z, Hu Y, et al. Clinical Characteristics of Coronavirus Disease 2019 in China. N Engl J Med. 2020;382(18):1708-1720.
10. Hamming I, Timens W, Bulthuis MLC, Lely AT, Navis GJ, van Goor H. Tissue distribution of ACE2 protein, the functional receptor for SARS coronavirus. A first step in understanding SARS pathogenesis. J Pathol. 2004;203(2):631-637.
11. Yan R, Zhang Y, Li Y, Xia L, Guo Y, Zhou Q. Structural basis for the recognition of SARS-CoV-2 by full-length human ACE2. Science (80- ). 2020;367(6485):1444-1448.
12. Nirmita Panchal, Rabah Kamal, Kendal Orgera, et al. The Implications of COVID-19 for Mental Health and Substance Use | KFF. Kaiser Fam Found. 2020.
13. NIH News in Health. Your Microbes and You. November 2012. https://newsinhealth.nih.gov/2012/11/your-microbes-you. Accessed September 29, 2020.
14. Pidot SJ, Gao W, Buultjens AH, et al. Increasing tolerance of hospital Enterococcus faecium to handwash alcohols. Sci Transl Med. 2018;10(452):6115.
15. Walter JD, Hutter CAJ, Zimmermann I, et al. Synthetic nanobodies targeting the SARS-CoV-2 receptor-binding domain. bioRxiv. April 2020:2020.04.16.045419.
16. Gioffredi E, Boffito M, Calzone S, et al. Pluronic F127 Hydrogel Characterization and Biofabrication in Cellularized Constructs for Tissue Engineering Applications. In: Procedia CIRP. Vol 49. Elsevier B.V.; 2016:125-132.