Dr. Klotman’s BCM video update this week has nothing about COVID. Things are fairly quiet in the world of respiratory viruses right now, and that’s a good thing. The video is devoted to a chat with one of BCM’s outstanding neuroscientists.
This gives me a chance to post about an interesting COVID report that I read in the last few days. It was a report on a study of human antibody response to m-RNA COVID vaccines (Pfizer and Moderna). One of the things that vaccinology experts have noted about the vaccines is that they call forth a strong IgG antibody response but not an IgA response. What the hell are IgG and IgA, you say? I’m glad you asked.
The human immune system consists of a variety of responses to bacterial, viral, fungal, and parasitic attacks. One of those responses is carried out by white blood cells of various kinds that respond selectively to bacteria, fungi, or parasites.
Another response is based on messenger molecules that are involved in calling forth the white blood cell response and in modulating the inflammatory response. Those molecules are called cytokines, and there are many kinds of them. You may recall that at the beginning of the COVID pandemic one hypothesis for the extensive damage caused by the SARS-CoV-2 virus was thought to be cytokine storm – a kind of uncontrolled cytokine release that caused extensive self-injury. Attempts at using immunomodulating drugs to control COVID mortality by reducing cytokine release didn’t really pan out. Alas.
The part of the immune system that responds most briskly is the antibody system – special proteins that fit key-in-lock with foreign proteins. There are several kinds of antibodies: IgM, IgG, IgA, and IgE. Ig means ImmunoGlobulin – med-speak for antibody. Each of these antibody classes has a focused role:
- IgE is the antibody class that responds to allergens. Think of IgE as the hay fever and asthma antibodies
- IgM is the first antibody that our plasma cells (the makers of antibodies) create in response to a newly detected foreign proteins circulating in the bloodstream
- IgGs (there are several kinds) are more specific antibodies that plasma cells create after their initial IgM response
- IgA is the antibody class that is found in mucosal membranes
What? Now we have membranes? Let me elaborate. The internal linings of our airways, oral, nasal, and digestive tracts, as well as urinary and reproductive tracts are very different from our skin. All of these membranes are moist (stick you finger in your mouth for proof). These moist surfaces have plasma cells that produce IgA antibodies that protect the membranes from foreign proteins – proteins like viruses.
One of the downsides of m-RNA and the older protein vaccines is that they do not stimulate the production of IgA antibodies. We inject them into the muscle, and we get an IgG response – antibodies that circulate in the blood but that do not reach the mucosal membranes. I hate it when that happens.
So, this recent study showed that folks who had previously been infected with COVID responded to subsequent m-RNA vaccination with a mucosal IgA response that COVID-naïve folks did not. It’s as if the vaccine boosted their mucosal plasma cells that had been primed by prior infection. Pretty cool, I’d say.
In any case, Dr. Hotez at Baylor College of Medicine and other vaccinologists have suggested for years that an inhaled or nasal spray coronavirus vaccine would be a boon – easy to administer, and capable of stimulating an IgA antibody response that would serve as the first line of defense against subsequent coronavirus infections. We can only hope that such a thing is developed before the next coronavirus pandemic.
And trust me, there will eventually be another even if it isn’t in my lifetime. We need to get prepared for it.