It is likely that SIgA antibodies will contribute to preventing serious diseases when they are formed after a vaccination, after previous infections, or when they are produced quickly following a new infection.
Moderna and Pfizer-BioNTech mRNA vaccines played an important role in the prevention of severe COVID-19-related deaths and infections. Researchers are still working on alternative vaccines, and how they can be administered. Michael W. Russell, an immunologist, and microbiologist at the University at Buffalo explain the process of nasal vaccines and where they are at the moment in their development.
How does the immune system combat pathogens?
Two distinct parts make up the immune system: mucosal, and circulatory.
The mucosal immune system protects the mucosal surfaces. These include the eyes, mouth, mammary, middle ear, respiratory, and urogenital tracts. These surfaces are covered by antibodies as well as a range of anti-microbial proteins in sticky secrets. Immune cells in the lining of these surfaces also attack invading pathogens.
The circulatory component of the immune system produces antibodies and immune cells. These immune cells are then transported through the bloodstream into the internal tissues and other organs. The circulating antibodies don’t reach the mucosal surface in sufficient quantities to be effective. The immune system’s mucosal, circulatory, and other compartments are distinct.
What are the main players in mucosal immunity?
People are most familiar with the immune components known as antibodies or immunoglobulins. In response to invaders, the immune system produces antibodies.
Antibodies can bind to specific antigens, which are the parts or products of pathogens that trigger an immune response. Antibodies can either kill bacteria by binding to antigens, just as they do with viruses and toxins or inactivate them using additional immune proteins.
A specialized type of antibody known as secretory IgA or SIgA is produce by the mucosal immune system. SIgA is found in saliva, tears, intestinal secretions, and breast milk. It is resistant to other forms of anti-antibodies. It also has a higher rate of neutralizing viruses and toxins than other immunoglobulins and prevents bacteria from attaching and invading cells on organ surfaces.
Many other key players are also involved in the mucosal immune system. These include different anti-microbial protein types that kill pathogens as well as immune cells which generate antibodies.
Mucus is one central secretion of the mucosal immune system.
How does COVID-19 enter the body?
Most infectious diseases that are transmitted to humans and animals can through contact with mucosal surfaces (eating, drinking, or sexual contact). There are some exceptions to this rule, such as infections caused by wounds or parasites transmitted via tick bites.
SARS-CoV-2, the virus that causes COVID-19 enters your body via droplets and aerosols. These droplets get into your eyes, nose, mouth, or eyes. If it gets into the lungs, it can cause serious disease and trigger a hyperactive, inflammatory immune reaction.
This suggests that the virus is likely to first come into contact with the immune system through the nasal, mouth, and throat surfaces. This is confirmed by the presence of SIgA antibodies against SARS–CoV-2 within the secretions of infected persons, which include saliva, tears, and nasal fluid. These areas, particularly the tonsils, are able to trigger mucosal immune reactions.
The SIgA antibodies are likely to contribute to the prevention of serious diseases if they are formed as a result of vaccination or previous infections, or if they are produced quickly in response to a newly acquired infection.
What is the working principle of nasal vaccines?
Vaccines can give via mucosal routes through the mouth or nose. This triggers an immune response by stimulating areas of the mucosal immune system, leading to mucosal secretions that produce SIgA antibodies.
There are many mucosal vaccinations that can take by mouth. The flu vaccine is currently only available nasally.
The nasal vaccines would stimulate the immune system by allowing the virus antigens to take up within the tonsils or lining of the nose. Researchers believe that nasal vaccines work in the same way as oral mucosal vaccinations. However, it is not clear how they work in humans. The vaccine causes B cells to develop into plasma cells by releasing IgA from the vaccine. The IgA is then secreted into mucosal secretions throughout your body, where it becomes SIgA.
The SIgA antibodies found in the throat, mouth, and nose could target SARS-CoV-2 to neutralize the virus.
What are the advantages of mucosal vaccinations against COVID-19
My belief is that the best way to protect someone against COVID-19, or at the very least, to keep it from entering the upper respiratory tract where it can inflict relatively minimal damage, is to either block it at the point of entry or to confine it there.
To control epidemics, it is essential to break the chains of viral transmission. Researchers have discovered that COVID-19 is spread by normal breathing and speech. It can exacerbate when people sneeze, cough, shout, sing, or do other exertion. These emissions are mainly caused by saliva and nasal secretions. SIgA is the predominant form of anti-virus antibody. It stands to reason that sufficient SIgA antibodies could secrete against the virus to neutralize it and reduce its transmissibility.
Existing vaccines do not cause SIgA antibodies. Injected vaccines induce circulating IgG antibodies that are useful in preventing serious diseases in the lungs. The nasal vaccines induce SIgA antibodies in salivary and nasal secretions. This is where the virus is first acquired and can be more effective at preventing transmission.
The use of nasal vaccines can be useful as an adjunct to injections for those with severe infections. They don’t need needles and may help to overcome vaccine hesitancy due to fear of injections.
Is it possible to create a nasal COVID-19 vaccination?
More than 100 nasal or oral COVID-19 vaccines have been developed all over the world.
Many of these drugs have been tested or are being tested in animal models. Many reported causing protective antibodies in blood and secretions and preventing infection in these animals. Few have been tested in humans. Many were abandoned without reporting all details.
The World Health Organization reports that 14 nasal COVID-19 vaccinations were in clinical trials at the end of 2022. According to reports from China, inhaled and nasal vaccines have been approved for these countries. However, there is not much information available on the findings of these studies.