Inhalable Vaccine Candidate Blocks SARS-CoV-2 Transmission to Prevent Virus From Infecting the Lungs

COVID-19 has caused over 5.5 million deaths worldwide. The virus that causes the disease has been mutating and ravaging communities, especially those areas with limited access to injectable COVID-19 vaccines or have a high rate of vaccine hesitancy. Due to this, scientists are exploring the effectiveness of an inhalable vaccine showing promise in clinical trials.

Researchers from Penn State said that the inhalable aerogel is loaded with DNA that encodes SARS-CoV-2 spike protein to induce an immune response against COVID-19. The inhalable aerogel can be used to create an inhalable vaccine that prevents viral infection to the lungs to block COVID-19 transmission.

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A laboratory worker tests a nasal spray at the Pharma and Beauty factory in Saint-Chamas, southeastern France, on January 21, 2021.

Importance of Alveolar Macrophages in COVID-19 Infection

Macrophages play a crucial role in the body's immune system. According to the British Society for Immunology, these specialized cells are involved in detecting, phagocytosis, and destructing foreign bodies, including bacteria and viruses that enter the body. Additionally, they also present antigens to T cells to release cytokinesis to activate other cells and initiate inflammation.

In the lungs, there are alveolar macrophages that are in close contact with the alveolar epithelium. These macrophages are the first line of defense against invading pathogens.

News Medical Life Sciences reported that when SARS-CoV-2 enters the body, the activated alveolar macrophages generate contradictory biological effects, one type initiates important antiviral defense mechanisms while the other produces "Trojan horse" macrophage hosts that promotes binding of the virus within the lungs that might circulate and spread to distal organs and cause infection.

Considering the importance of macrophages in the COVID-19 infection, researchers from Penn State speculated on creating an inhalable aerogel that can be used for the inhalable vaccine to target SARS-CoV-2 antigens in these cells. They believe that such non-invasive immunization may yield a potent prophylactic mucosal immunity.

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How Does the Inhalable Vaccine Works?

Researchers of the study are concerned that current vaccines do not do well at preventing transmission because they still allow the replication of SARS-CoV-2 in the body, Science Daily reported.

They propose that the inhalable vaccine would elicit local immunity at the primary site of the infection where the virus could be quickly neutralized and eliminated without triggering inflammation like the injectable COVID-19 vaccines.

They previously developed a gel-like material called aerogel that could carry antimicrobials to the lungs to treat bacterial lung infections, such as tuberculosis. Now, they have decided to use to combine aerogel with DNA that encodes SARS-CoV02 proteins. They were able to develop the COVID-19 formulation, which they call coronavirus mimetic particle (CoMiP), to target alveolar macrophages that are the first ones to get infected with the virus.

CoMiPs are designed to trick alveolar macrophages into thinking they are expressing the SARS-CoV-2 spike protein. Then the alveolar macrophages would show it to the rest of the immune system to learn to recognize the protein during SARS-CoV-2 infection.

Laboratory tests revealed that macrophages readily ingest CoMiPs. Then they optimized its formulation to identify the maximum safe dose in cells in vitro before testing it on their mice model. Researchers noted that both laboratory and mice experiments resulted in good expression of the proteins and increased antibodies in the lungs that provided the mice with some protection.

Although this is not yet at the level that they would like it to be, the team is optimistic about the results, given its potential use as an inhalable vaccine. They described CoMiPs in full detail in their study, titled "Inhalable SARS-CoV-2 Mimetic Particles Induce Pleiotropic Antigen Presentation," published in the journal Biomacromolecules.