If it is necessary to summarize what a nasal coronavirus vaccine is looking for, it could well qualify as a barrier to entry. Scientists were able to determine that SARS-CoV-2 enters the body through the nose and that it is there where the infection begins, and that is why they seek to emulate the strategy that has already shown its effectiveness against polio.
“A nasal vaccine is sought because intramuscular and subcutaneous injections do not generate IgA secretion and with good cellular immunity, if we add this immunity in combination, it would not be unreasonable to think about eradicating the virus, because as soon as you have contact with the virus, there is already a good immune response ”, stated Juan Ramón Curi (MN 120,679), Head of the Otorhinolaryngology Service of the Favaloro Foundation, in dialogue with TN.com.ar.
Why the Nose
There is no question that science and doctors learned how the coronavirus behaved as it spread across the world. However, one fact was almost undisputed: the infection begins in the nose. That is why, among the first recommended measures, the use of a mask was applied.
“From the beginning, it was suggested that to detect the disease, a nasopharyngeal swab had to be done because it is the site where the highest viral concentration is recorded,” said Curi. In the words of the specialist, the gateway to the body is the nose, where SARS-CoV-2 multiplies and infection begins.
Now, once the virus enters the body, the immune system takes over and its response is highly complex.
At this moment the antibodies bind to the intruder to mark it for recognition and elimination, while a little later the “experts” appear, the T lymphocytes, who not only come out in their support, but are also responsible for killing and remembering them. what they were like and how to kill them if they re-enter the body.
Soldiers (antibodies) who are in the first line of defense are called by different names. Those that are hidden in the mucosa are known as Immunoglobulin A (IgA), while those called Immunoglobulin M (IgM) are the first to fight an infection and are in the blood, and those called Immunoglobulin G (IgG) are the ones that they appear as “war veterans” and remain, for the most part, in body fluids.
The reason for this explanation is not random, but is closely related to the intention of putting the nose as the first barrier against the virus by its “fast soldiers”. “When we ‘dose’ a patient for antibodies against Covid-19 we see that the IgM rises in the infection and that the IgG appears as a scar left by the virus,” explains Curi. However, in this “equation” IgA is missing.
“IgG is the immunity generated by the vaccine and these titers with the vaccine are highly superior to those of infection, but subcutaneous or intramuscular vaccines do not generate IgA, which is secreted in the mucosa and the digestive tract. Precisely, with the nasal vaccine, that immunological concentration would be generated in the first defense site and where the highest viral load of a patient with Covid-19 infection is housed, ″ explained the otorhinolaryngologist.
The combination is strength
On several occasions, in order to explain the reasons for a decision, it is necessary to appeal to previous experiences. In this case, the best example is what happened with poliomyelitis, a disease that attacked children as young as four years old and that in the 1950s marked its peak in Argentina, when 6496 cases were registered.
The answer to this disease was a vaccine created by Jonas Salk in 1955. However, its disappearance was related to a second immunization, in this case oral, developed in 1962 by Albert Sabin.
Since 1984, Argentina no longer registered polio cases and the Americas were declared polio-free in 1994. However, these formulations are still administered in the country (at two, four, and six months, with a reinforcement upon admission to the primary disease) waiting for it to become the second disease to be eradicated worldwide, behind smallpox.
In the case of Covid-19, scientists are seeking to replicate this strategy that has already proven its fruits today. “Most of the virus is in the nose and the vaccine that is in phase one seeks to create a barrier in the first contact with the virus, which is through the nasopharynx after inhaling the microdroplets or by the Flügge drops that a patient infected aerosolized, ”said Curi.
“In some way, the intention is to immunize the mucosa and generate IgA immunity, with which the cellular immune response at the blood level would not be so fundamental if we neutralize the respiratory tract, since Waldeyer’s lymphatic ring is the first immunological barrier and it is a site where good IgA secretion is expected ”, continued the specialist.
Even though there are still several clinical stages (and a long time) to reach this vaccine, the possible results are more than encouraging. “It would not be unreasonable to think of two initial doses with an injectable vaccine and reinforce the IgA with a nasal vaccine,” said the Secretary of Press and Dissemination of the Argentine Federation of Otorhinolaryngology Societies (FASO).
“With good cellular immunity, if we add IgA immunity in a combination, it would be feasible to eradicate the virus, because as soon as you have contact with the virus there is already a good immune response,” Curi hoped, while emphasizing that “the development of a nasal vaccine does not replace an injectable vaccine. But it is promising and if it works, it would be very good. “