Using the common cold virus as a naturally occurring vaccine to prevent COVID-19: Lessons from Edward Jenner

Three recent papers published in Nature, Science and Cell, all present clear evidence that there is cross-reactive T-cell immunity between human coronaviruses (229E, NL63, OC43, and HKU1), linked with the common cold, and SARS-CoV-2, the causative agent of COVID-19. Can we use this information to design and build a new vaccine based on the less pathogenic, common cold coronaviruses, for the prevention of COVID-19? If we look at the history of medicine and vaccine development, from the point of view of Edward Jenner, the answer just might be yes.

For example, there are four human coronaviruses that are known to cause the common cold, namely 229E, NL63, OC43, and HKU1, which lead to mild upper respiratory infections (URI's) [1][2][3][4]. According to the CDC, their route of transmission appears to be similar to SARS-CoV-2, but the onset of symptoms is quite mild in comparison. https://www.cdc.gov/coronavirus/ general-information.html All five viruses contain a viral spike glycoprotein (VSG), which is the main target of SARS-CoV-2 vaccine development world-wide.
One attractive hypothesis is that inoculation with the common cold coronavirus (229E, NL63, OC43, or HKU1) or, more likely, an attenuated version, could provide immunity against SARS-CoV-2. If that was the case, then we might already have a naturally-occurring vaccine at hand, that could soon be implemented, off the shelf.
To begin to test this hypothesis, we retrieved the protein sequences of the relevant viral spike glycoproteins from a variety of available databases, such as UniProt/ FASTA, and analysed their shared protein sequence similarity and identity using BLASTP.  most similar to that of SARS-CoV-2, with nearly 38% identity and up to 53% similarity ( Figure 1). In fact, the viral spike glycoproteins of coronavirus OC43 and HKU1 are also quite similar to each other, sharing 64% identity ( Figure 2). So, both OC43 and HKU1 would possibly be good candidates for developing a potential vaccine to SARS-CoV-2.
Is there any clinical evidence to support these assertions?  Three recent papers published in Nature, Science and Cell have begun to look at the existence of crossreactive immunity in a variety of patient populations, especially patients infected with the SARS-CoV-2 (with frank COVID-19 or asymptomatic) and uninfected patients. The results are all quite encouraging, directly demonstrating cross-reactive Tcell immunity between SARS-CoV-2 and the existing known human cold coronaviruses (229E, NL63, OC43, and HKU1) [5][6][7]. One of the papers also detected cross-reactive serum IgG as well.
These reports clearly provide tantalizing clinical evidence for the feasibility of using a human cold coronavirus, such as attenuated OC43 or HKU1, as a potential vaccine for the prevention of COVID-19. What would Edward Jenner suggest, if he was living today?
Further support for this idea has recently appeared in the popular press and was supported by data from the National Institutes of Health (NIH), because there is significant shared serological cross-reactivity between SARS-CoV-2, OC43 and HKU1 [8,9].
Fortunately, two live coronaviruses, OC43 and 229E, associated with the common cold, are actually commercially available from the American Type Culture Collection (ATCC), which could greatly facilitate their potential use in new, off-the-self, vaccine development. https://www.lgcstandards-atcc.org/products/all/VR-1558.aspx https://www.lgcstandards-atcc.org/products/all/VR-740.aspx Moreover, the VSGs from OC43 and HKU1, may also be sufficient to convey cross-reactive immunity, when recombinantly-inserted in another non-pathogenic viral vector, specifically designed for live or attenuated vaccine immunizations (Figure 3).
Ultimately, this may be a safer approach, than using the VSG from SARS-CoV-2, which may have mild negative, or even pathogenic, side-effects. Only time will tell.
Nature may have already done the "experiment" or "clinical trial" for us, as so many people that are SARS-CoV-2 virus-positive, are asymptomatic and show evidence of cross-reactive immunity, to both SARS-CoV-2 and the common cold coronaviruses.
These findings have been independently confirmed now, in several different laboratories world-wide.

AUTHOR CONTRIBUTIONS
FS and MPL conceived the ideas presented, performed the protein sequence homology analysis and wrote the text of the article. MPL prepared the figures. Both authors edited and approved the final version of the article, prior to journal submission.