So what is important for the immune response to COVID?
In this COVID survivor we see the kinetics of the immune response as it generates after infection. To me it is as expected. It is a combination of T and B cells and the innate (monocytes etc). immune response and occurs according to Immunology 101. B cell responses take a few days to generate and antibody producing cells are elevated by about 8 days after symptom onset, with recovery from day 10. The antibody ramps up after that, because this is what is going to do. It creates a response that is going to be rapidly produced on next encounter and is designed to stop you getting re-infected. This is what antibodies do.
I bet when the sequences of the B cell receptor are cloned and made, you will see some of them being made are to the “Spike protein” of the virus, which it uses to infect the lungs.
The T cells and notably the CD8 T cell response is there by 7 days and is highest by day 9 and is again consistent with immunology 101 that CD8 T cells are the best beasties for kicing some viral butt. There was an increase in CD4, not a mega increase and they will be doing what they do and that is help B cells to make antibody and help CD8 T cells to kill virus. Does that make them top dog. In the eyes of the MS immunologist it seems so. The Immune system is a system and uses more than one thing to get the job done, which is kill the infection.
I guess it doesn’t tell us what would happen if one of the cell types are not there, but you can see the viral load is already dropping dramatically at day 7 when the antibody level has yet to really pick up and I think it says “CD8 cavalry to the rescue” along with the innate system. They are probably not in the blood because they are in the lung doing their job.
Therefore, you may be at early risk with alemtuzumab because these cells, notably the CD8 T cell are depleted. In reallity cladribine is a magnitude less active on these cells and really does not do alot of damage to the innate immune system at the dose used in MS. Also ocrelizumab is an another order of magnitude lower at depleting CD8 T cells. Whilst it may cause a blunted antibody response…if CD8 T cells and the innate immune response at the front line in ridding people of the the COVID virus it makes one wonder if we should be lumping all IRTS together. It perhaps says that to suggest that the agents have the same risk does not seem to take into account the biology. Also this risk will change with time, because once the treatments are gone the cells come back. HSCT is going to be at top of the tree, as it depletes CD8 T cells alot and B cells alot and so much so that you have to re-do vaccinations.
However the authors put the emphasis of the antibody secreteing cells and the follicular T helper cells.
Remeber this person was not really treated and the the course was mild. There was no increase in cytokines like-interleukin 6, which ahs been associated with a worsening.
Where would you put your emphasis
Thevarajan I et al. Breadth of concomitant immune responses prior to patient recovery: a case report of non-severe COVID-19.Nature medicine (2020).