When you think about vaccines these days, you most likely picture someone getting a shot. Yet, SARS-CoV-2 enters our body through the respiratory tract and not via an injection. Since vaccinations are meant as “training” for our immune system so that the body can learn to recognize the pathogen, wouldn’t it make sense to design a vaccine against coronavirus that mimics its route of infection? This is exactly what researchers from the Tianjin University in China sought out as they created an “inhalable nanovaccine with biomimetic coronavirus structure to trigger mucosal immunity of respiratory tract against COVID-19” (Zheng et al.).
The mucosal membrane, or mucosa, is the lining of the internal passages and cavities in our body that can come into contact with material from the outside of the body. There are many different mucosa: gastric mucosa in our stomach, intestinal mucosa in our gut, the endometrium lining the uterus, palpebral conjunctiva lining the inside of the eyelids, and so on. But the most relevant mucosa in terms of airborne infections is, of course, the respiratory mucosa lining the respiratory tract. Mucosa takes its name from the mucus—viscous fluid covering this tissue. In fact, your snot is basically excess nasal mucus.
It is the job of the mucus to protect the airways from irritants and pathogens; it does so both mechanically—by trapping the particles to be swept away by the cilia—and chemically with antimicrobials (Lillehoj & Kim).
There are also “mucosa-associated lymphoid tissues (MALT)” that represent a major part of the immune system (Holmgren and Czerkinsky). The respiratory tract mucosa is the body’s “first line of defense” against respiratory diseases, which makes mucosal immunity a desired target (Zheng et al.).
So far, almost all of the vaccine efforts have focused on injections. Yet, “a recent report suggests that, while patients may be asymptomatic after COVID-19 vaccination, they can still harbor the SARS-2-CoV coronavirus in the upper airways and be able to transmit the infection to others'' (Doyle). Indeed, these systemic “routes [of vaccination] are poorly effective at generating mucosal immune responses,” which would be able to successfully neutralize coronavirus particles in the respiratory tract. However, mucosal immune responses “can only be induced by mucosal routes of immunization” (Russell et al.).
Luckily, Bin Zheng and his colleagues found that “in contrast to traditional injectable vaccines, [their] inhalable nanovaccine can better inspire respiratory mucosal immunity and secrete large amounts of sIgA [secretory immunoglobulin A] on the mucosal surface as a barrier against virus invasion.” The cool feature of their inhalable vaccine is that it is “biomimetic,” meaning their inhalable vaccine is a nanoparticle synthesized to resemble SARS-Cov-2:
The similarity can trick our immune system into thinking it is facing COVID-19 and build up immunity in the nose!
So, for all those afraid of pointy needles and dripping blood, we may have a solution for vaccines that avoids all your fears — inhalable vaccines!
Doyle, Ken. “Intranasal COVID-19 Vaccines: What the Nose Knows - Promega Connections.” Promega Connections, https://www.promegaconnections.com/intranasal-covid-19-vaccines-coronavirus/. Accessed 4 Apr. 2021.
Holmgren, Jan, and Cecil Czerkinsky. “Mucosal Immunity and Vaccines.” Nature Medicine, vol. 11, no. 4, Nature Publishing Group, Apr. 2005, p. S45, doi:10.1038/nm1213.
Lillehoj, Erik P., and K. Chul Kim. “Airway Mucus: Its Components and Function.” Archives of Pharmacal Research, vol. 25, no. 6, Pharmaceutical Society of Korea, 31 Dec. 2002, pp. 770–80, doi:10.1007/BF02976990.
Russell, Michael W., et al. “Mucosal Immunity in COVID-19: A Neglected but Critical Aspect of SARS-CoV-2 Infection.” Frontiers in Immunology, vol. 11, Frontiers Media S.A., Nov. 2020, p. 3221, doi:10.3389/fimmu.2020.611337.
Zheng, Bin, et al. “Inhalable Nanovaccine with Biomimetic Coronavirus Structure to Trigger Mucosal Immunity of Respiratory Tract against COVID-19.” Chemical Engineering Journal, vol. 418, no. March 2021.
Last Fact Checked on May 20th, 2021.