Antibodies, T cells, and Population Immunity

A lot of additional research in the last week on the adaptive immune response to CV-19 infection and cross-reactivity with the seasonal coronaviruses.  Here is a good example, just published in the journal Immunity.  (Imm. Article)  The big picture finding was that patients develop a response that lasts for at least 5 to 7 months.  The authors used two assays to independently assess antibody presence and strength.  They validated the accuracy of these assays themselves.  They looked for spike protein, nucleocapsid and receptor binding domain antibodies.  Then they tested about 5800 individuals from the community.   They found that almost all who had been infected, had strong neutralizing antibody responses.  As have some other studies, these researchers also found that persons with severe disease tended to have greater antibody responses, but that all patients, including those who were asymptomatic, had a response.

Here is another similar result, but this time looking for antibodies in mucosal tissues as well as blood.  (Science Study)   The researchers found blood and saliva antibodies to CV-19 lasted for at least three months.  439 blood samples and 128 saliva samples were used from CV-19 patients.  This finding of neutralizing antibodies in the mucosal tissue is important because that is obviously where any re-exposure to CV-19 is likely to occur.

This study looked at antibody and T cell responses in health care workers.  (Medrxiv Paper)   136 workers, 76 of whom had confirmed mild or asymptomatic infections, were used for the study.  Neutralizing antibodies were present in 90% of the workers and strength did not appear to correlate with disease severity.  T cell reponses also were present, and those did tend to be stronger in persons with more severe disease.  Even those patients who did not have measurable neutralizing antibodies showed some T cell response.  The response was still present after at least four months.

And this paper appears to reach a conclusion contradictory to one I reported on earlier in the week.  The current paper found that antibodies to seasonal coronavirus were associated with less severe CV-19 infection.  (Medrxiv Paper)   Sixty patients with a spectrum of CV-19 disease were included.  Those with lower antibodies levels for seasonal CV had more severe disease.

I want to stress again too that people should ignore the reinfection nonsense.  It happens with every infectious disease and it doesn’t in any manner mean that there isn’t a durable adaptive immune response in like 99.99999% of the population.  The media and our politicians tend to present things in a simplistic manner and anything involving the immune system is not simple.  I have used this example before.  The adaptive immune system is not a physical barrier that prevents a person from ever being exposed to the virus again.  We all have a likelihood of repeated exposure.  It is like a rapid reaction force that once you are exposed, can clear the virus before it gains cell entry and starts replicating.  People who get infected are developing that rapid reaction force, they won’t become infectious on re-exposure and they do contribute to population immunity.