Banging on the B..eat SH1

I have been banging on about B cells for what seems like the last decade, but when ever I suggest that MS drugs may be working by targeting B cells, the reviewers say “What about T cells? Because the drugs all work through T cells! and I am scared of reading your thoughts, if you don’t mention T cells, T cells, T cells”.

It is not surprising as the great and the good MS-researchers have spent their lives selling the idea of a complex network and as they flip-flop in their ideas, B cells this week, Th17 the next and CD8 the week and so on. No wonder there is confusion.

Just look at the CD20-antibodies and ask how they work?

We have already dismissed the view for a major activity via antibody depletion as antibody producing cells do not express CD20, but isn’t it funny that for the last forever, we have ignored antibodies and focussed on T cells and now we are seeing study after study saying hey we can find antibodies to Epstein Barr Virus that cross react to CNS proteins to cause damage. This is often based on linear peptide sequences, when we have been told pathogenic antibodies recognise shapes.

Is this scientific Amnesia?

One of the ways that CD20-depleting antibodies could work is by depleting the EBV viral reservoir as it makes and lives in memory B cells.

Every drug that works in MS can influence memory B cells and agents that deplete these B cells will reduce viral load. I could give many ways this could occur.

However there is a prevailing view that CD20-depleting antibodies work because they are targeting antigen-presenting B cells and so indirectly work because they are affecting T cells…..Yeah its always T-time when you are made to eat SH1

Initially we had the idea that it was stopping B cells activating T cells and more recently we had the “sloppy kissing-idea” that is when a B cell activates a T cell, it donates a bit of the B cell membrane to the T cell, which then incorporates into it’s coat and so the T cell expresses CD20. Then the CD20-depleting antibodies work because they are killing the tiny population of CD20+ T cells….Simples. This is called trogocytosis.

Is this an idea of troglodytes?

However, it is now T-time and antibodies against a T cell markers are being tested in MS again.

Fadul CE, Mao-Draayer Y, Ryan KA, Noelle RJ, Wishart HA, Channon JY, Kasper IR, Oliver B, Mielcarz DW, Kasper LH. Safety and Immune Effects of Blocking CD40 Ligand in Multiple Sclerosis. Neurol Neuroimmunol Neuroinflamm. 2021; 8(6):e1096. doi: 10.1212/NXI.0000000000001096.

Background and Objectives. Costimulation by CD40 and its ligand CD40L (CD154) is important for the functional differentiation of T cells. (So it’s T-time) Preclinical studies have recognized the importance of this costimulatory interaction in the pathogenesis of experimental models of multiple sclerosis (MS). To determine safety, pharmacokinetics, and immune effect of a humanized monoclonal antibody (mAb) against CD40 ligand (toralizumab/IDEC-131) in patients with relapsing-remitting MS (RRMS).

Methods This single-institution open-label dose-escalation study (phase I) enrolled 12 patients with RRMS to receive 4 doses of 1, 5, 10, or 15 mg/kg of humanized αCD40L (toralizumab) IV infusion every other week. Patients were followed up to 18 weeks, annually, and finally at 5 years. In addition to safety and pharmacokinetics, other secondary and exploratory measurements are immune effects, clinical, MRI, laboratory, and neuropsychological evaluations.

Results Fifteen adverse events, all of mild to moderate severity, were considered to be of possible or of unknown relationship to treatment. No serious adverse events, including thromboembolic events (This is relevant because the first generation anti-CD40 ligand antibodies caused clotting and vessel problems halting studies so they engineered the antibodies so they would not be bound by phogocytes or activate cell destruction), occurred during the 18-week defined study period. Annual and long-term follow-up at 5 years revealed no delayed toxicity. Pharmacokinetics were nonlinear between the 5 and 10 mg/kg dose groups. The serum half-life of toralizumab was consistent between the dose groups with a mean of 15.3 days (SD = 1.9). Flow cytometry revealed no depletion of lymphocyte subsets. An increase in the CD25+/CD3+ and CD25+/CD4+ ratio and a shift toward an anti-inflammatory cytokine response were seen after treatment.

Discussion. Our study suggests that blocking CD40L is safe and well tolerated in patients with RRMS while increasing CD25 ⁺ T cells and anti-inflammatory cytokine profile. These findings support further studies to assess the efficacy of blocking CD40L as a potential treatment of RRMS

So there you have it, block CD40 ligand and you get a T regulatory cell response as ever……..Yarn.

How would toralizumab work?. It’s affecting T regs (T regulatory cells) as this is the only mechanism for control of MS based on dogma when the study was done. I would say daclizumab worked and that did the opposite but maybe one can think of other explanations….but not if you are a troglodyte:-)

T cells have CD40 Ligand and dendritic cells have CD40 and the pair are immune checkpoint inhibitors. that have go halt activities. Notably, CD40 is a member of tumour necrosis factor superfamily and these receptors deliver survival signals and therefore on can guess that influencing CD40L and CD40 will impact on survival. So agents may have disease control potential

As ever pharma are like sharks and hunt in packs so where there’s one that has surfaced, there are more

Now there are a few CD40 ligand specific antibody-based agents in development that have been engineered to stop the clotting complications of the first generation inhibitors. One is called Dapirolizumab pegol (anti-CD40L), which is is being tested in Lupus. Another is called Frexalimab and has been in a proof-of-concept Study in Relapsing Multiple Sclerosis. that has shown activity and this T cell inhibitor works in relapsing MS…Hot off the press. ProfG is showing the study this week in Colorado.

LB02

Poster

Disease-modifying therapy

Frexalimab, a CD40L Inhibitor, in Relapsing Multiple Sclerosis: Results from a Randomized Controlled Phase 2 Trial

It works and is in the realm of the T& B and B cell depleters.. It inhibits lesions compared to placebo by about 98 percent according to the manufacturers press release. So a T cell effect and as has been pointed out by a blog reader T and B cells clearly work together to make a T cell response or a B cell response. I guess it depends where you want to put the emphasis.

How am I going to explain this? Because explain we must!

Do I have to (B) eat SH1 again?

Antibodies against CD154 are being tested in MS and other autoimmune conditions. CD154 is also known as CD40LG meaning CD40 ligand (known by some as CD40L) meaning something that binds to CD40. CD40 is the receptor to the ligand and what does it do?

CD40 is expressed by dendritic cells and antigen presenting cells and so it will influence CD40Ligand expressing T cells and so you can get T cell inhibition………

But that is probably not why pharma went after CD40 Ligand. I suggest that it is because CD40 is a key driver of B cell activity. Block the input signal i.e. CD40L and inhibited B cell activity.

We know this is important as immunoglobulin/antibody deficiencies occur in CD40L (CD154)-impaired patients with hyper-IgM syndrome (but low IgG, IgA) and served to underscore the central role of CD40 in mature B cell functions.

CD40 stimulates B cells to divide and differentiate and to produce IgA and IgG from IgM (class switching). CD40L has three binding partners: CD40, α5β1 integrin and integrin αIIbβ3. CD154 acts as a costimulatory molecule and is particularly important on a subset of T cells called T follicular helper cells (T_FH cells). On T_FH cells, CD154 promotes B cell maturation and function by engaging CD40 on the B cell surface and therefore facilitating cell-cell communication. A defect in this gene results in an inability to develop antibodies.

CD40 ligand (CD154) is primarily expressed on CD4+ T lymphocytes but is also found in a soluble form. While CD40L was originally described on T lymphocytes, its expression has since been found on a wide variety of cells, including platelets, mast cells, macrophages, basophils, and natural killer cells

Expression data microarray from http://www.proteinatlas.org (HPA dataset)

The antibodies against CD54 are not depleting so they do not deplete the targets, so does it:

(a) Block CD40L signaling something to the T cell?

(b) Does it block some function of other cells that express CD40L?

(c) Does it block the CD40L/CD40 interaction and block B cell function? or

(d) do something else?

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The easy answer is that is blocks B cell co-stimulation stopping B cell activation driven via CD40 to block B cell function and so it is really blocking B cells, B cells B cells. Ha Ha, Explained…..Read it, See it Sorted

Next up I can throw the same argument in the face of the T cell imunnologists and say when the T cells kiss the B cells not only does CD20 go from the B cell to the T cell, in this sloppy-kiss some T cell bits go back to the B cell and so some B cells express CD40L and the antibody binds to this on B cells and blocks its function….QED…Stick that up your T cell pipe and smoke it. (OK don’t smoke). Where does it stop? Why not eat the B cell receptor and the T cell becomes a B cell

Put that idea to ProfG and we get “trogocytosis my armpits…sloppy kissing my buttocks”. OK he doesn’t talk like that. Look at this and you can see that CD40LG is expressed by B cells when they are infected with EBV….it’s EBV, EBV EBV. Indeed with a inactivated genome EBV, it induced neither CD40L nor a viral gene, EBNA1, indicating that expression of viral gene(s) is required for CD40L induction and this protects the cells from death and thereby facilitating persistent infection of EBV.

Time after EBV infection B cells. Black blobs are expression over 96 hours EBNA1 is EBV, beta actin is a control as it is part of the cell skeleton. 0-24 is where the action is.

Imadome K, Shirakata M, Shimizu N, Nonoyama S, Yamanashi Y. CD40 ligand is a critical effector of Epstein-Barr virus in host cell survival and transformation. Proc Natl Acad Sci U S A. 2003;100:7836-40

Sneaky F’ing EBV I say. It means you can activate B cells without T cells in two ways. It mimics the signal of CD40 activation with Latent membrane protein one LMP1 and this CD40L expression means you can get B cell-B cell interaction of CD40L binding to CD40 expressing B cells and activating them. Add to the fact that EBV makes B cells growth and differentiation factors yet it is called viral interleukin 10, it means it keeps them B cells going…meaning the virus can hang around until it wants to reproduce, when the cell will get destroyed, but it means EBV activates them B cells and I bet some of them cause autoimmunity!

One of those autoimmunities may be called multiple sclerosis…even more simples unless you are a troglodyte of course:-(

So from T cells to B cells to EBV how much more of an answer do we need?…………………………………………..

One that incorporates T cells apparently:-(

COi None…..ProfG is presenting the trial results.

Disclaimer..My views and not anybody elses.