A recent symposium was held in the UK (28-29 April 2021) that examined various aspects of COVID-19 and our immunologic system.  (Collaborative Covid Immunology/ UK Covid Immunology Consortium [UK- CIC] and the British Society for Immunology.). While the immune responses to COVID-19 are clear, we have little information about potential long-term effects.  Which is why I will share the results of  several very interesting papers presented at the symposium.

In a nutshell, it seems that those of us who develop severe COVID-19 develop persistent immunological problems- including the fact that our immune system may experience what would be termed early senescence.

First, lets consider the poster session authored by N. Duggal, T Vennith, A Richter, F Sian, and J Lord (all from the University of Birmingham).  This paper (#15 of the symposium), entitled Accelerated immune aging in COVID-19 infection survivors, examined 46 patients (ranging in age from 30 to 68) hospitalized with severe COVID-19.  These folks – some three months after discharge from the hospital- all demonstrated age-related decline in their ability to mount an immune response.

In particular, their B and T cells (termed naïve cells; a naïve cell is one that has never been exposed to an antigen- once exposed to the antigen, the cell either is converted to a memory cell or a plasma cell ([that secretes antibodies specific to the antigen to which it was initially bound]) are diminished in number.  Moreover, there is an accumulation of memory cells remaining in circulation (ready to respond to reinfection). When this is coupled with excess senescent T cells (highly inflammatory, secreting cytotoxic mediators and natural killer cell receptors [NKR] regardless of antigen specificity) which secrete chemicals, exacerbating inflammation related to many age-related diseases.  While the patients were mostly under the age of 60, they still demonstrated immunosenescence associated with subjects over the age of 60.

Another paper of interest was presented by Drs. Lydia Becker and Verena Kaestele (University of Manchester), Immune profiling reveals ongoing neutrophil dysfunction in COVID-19 patients post-hospitalization.  The researchers examined some 50 folks who experienced severe COVID-19.

A neutrophil is a “general purpose” immune cell that attacks invading bacteria and promote inflammation.  These cells comprise 2/3 of all the white cells in our body- which increase dramatically during an infection and the return to normal levels once the infection has cleared.  (When my current disease was rampant, my white cell count was through the roof; weeks later the levels returned to normal.) Those folks with severe COVID-19 demonstrated neutrophil levels at 90% of all white blood cells; the demand is so high that their bodies (actually their bone marrows) can’t keep up with the demand and therefore secrete immature neutrophils (not really functional), which lets the disease become more severe; the condition also promotes excessive blood clotting. This condition remained some 9 months after hospitalization discharge (which may better explain long-term COVID-19).

The third paper of interest was presented by Dr. Aimee Hanson (U Cambridge), the Differential recovery of immunological perturbations in severe COVID-19.  The results of this study demonstrated that there were persistent changes in the gene expression of the patients’ immune systems. What this means is not known, but may be related to long-term COVID.

None of these studies are fully conclusive, since the number of patients were so lowin each of their studies.  But, they do present avenues for further investigation so we can address the situation of long-term COVID-19.

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