Spike Protein induces intestinal barrier dysfunction via Galectin-9

And CEACAM5...

This article was supposed to be published yesterday but I got lost writing a short story lol.

As I have mentioned multiple times, it takes a “nudge” or a literal word, and puzzle pieces fall into place at an astounding rate. I will mention him again, but I would like to thank Bob for his remarkable and insightful comments in many of my articles.

It is unrelated to this one, but this one is related to what he hinted to me. Credit where credit is due, especially when the intellect is of a degree that deserves it.

Notes on Omicron

One of the hallmarks of every single variant since the Wuhan Original (trademark pending) has been its intestinal tropism, the viral behavior of “liking to go into the gut”, which is rich in ACE2, the virus-favored receptor. Each subsequent variant had a stronger tropism to the gut, Omicron had such an aggressive “homing” to our guts that for over a year, its defining clinical characteristic was gastrointestinal symptoms. In China “Feels like the flu, has gastrointestinal symptoms ? Treat for Covid while awaiting tests”, and tests often came back positive.

The intestinal mucosal barrier is your primary defense against both different pathogens and especially toxins from getting into your blood (thus going anywhere), a hallmark of severe Covid, Long Covid, and even vaccine injury is a fucked up gut. A “leaky gut”, with clear observations of lasting changes in the microbial families living in your gut, when good ones decrease, bad ones increase. The question so far is how it does it, the how is very important because there are multiple ways for a pathogen to “do it”.

A summary by the author’s themselves so you can just jump to what this all mean if you wish.

In summary, our results demonstrated for the first time that the low expression of CEACAM5 upon SARS-CoV-2 spike stimulation induced intestinal barrier dysfunction through the interaction between CEACAM5 and Galectin-9. Increased expression of Galectin-9 promoted the polarization of CD4+ T cells towards pro-inflammatory phenotype. Then it elevated the production of proinflammatory cytokines, inhibited the PI3K/AKT/mTOR pathway, and increased apoptosis of CD4+ T cells, eventually resulting in intestinal barrier dysfunction. Overexpression of CEACAM5 and knockdown of Galectin-9 displayed an important role in maintaining intestinal barrier integrity. Based on these findings, targeting CEACAM5 and Galectin-9 could provide novel therapeutic strategies in intestinal barrier dysfunction of severe COVID patients and the potential underlying mechanism remains to be further explored.

SARS-Cov-2 spike induces intestinal barrier dysfunction through the interaction between CEACAM5 and Galectin-9

Given how CEACAM5 isn’t widely known here are the author’s own words.

Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5, also known as CEA or CD66e) was firstly reported as a tumor marker for colorectal cancer in 1965 (20). Besides, CEACAM5 has been demonstrated to modulate the systemic immune response through multiple pathways. CEACAM5 expressed on intestinal epithelial cells (IECs) can bind with CD8α on CD8+ suppressor T cells, leading to the inhibition of CD8+ suppressor T cell activation and the increasing proliferation of CD4+ T cells in inflammatory bowel disease (IBD) patients (21, 22). CEACAM5-derived peptide can activate CD8+ regulatory T cells to restore mucosal homeostasis (23). CEACAM5 mutation can inhibit TGF-β signaling and increase cell proliferation and colony formation in colorectal adenocarcinomas (24). Besides, high levels of CEACAM5 might increase the susceptibility of peripheral blood mononuclear cells (PBMCs) to Middle East respiratory syndrome-coronavirus (MERS-CoV) infection and promote disease progression (25). Through fecal multi-omics analysis, we found a decrease in CEACAM5 levels in COVID-19 patients (17). Moreover, expression of CEACAM5 was positively correlated with the abundance of Tyzzerella nexilis (beneficial gut bacteria), but negatively correlated with Bacteroides coprophilus (pathogenic gut bacteria) (17). However, the regulatory role and molecular mechanism of CEACAM5 in intestinal barrier dysfunction upon SARS-CoV-2 infection remains unclear.

Here we discussed the underlying working mechanisms of CEACAM5 in intestinal barrier dysfunction induced by SARS-Cov-2 spike, which may provide promising therapeutic targets for alleviating GI symptoms in COVID-19 patients and further enhance the treatment of SARS-Cov-2 infection.

A clarification before going further, here they injected the mice with recombinant Spike Protein-Fc containing RBD, the Fc stands for Fragment Crystallizable region of the IgG1 antibody. It can be used to enhance the stability of the protein, increase its half-life in the body, and promote a stronger immune response too.

To validate reduced CEACAM5 expression observed in the feces of Covid patients and explore its functions, the mice were injected with said Spike-Fc-RBD directly into the intraperitoneal region (lower abdomen). As with Covid patients, mice had lower levels of CEACAM5, they examined the intestinal barrier and found lower levels of Zona Occludens 1 (ZO-1), a protein that is important for maintaining the integrity of the intestinal barrier, consistent with increased levels of LPS in severe Covid patients compared to non-severe ones.

When studying isolated cells they observed a significant drop in CD4+ T cells, and they detected increased levels of IL-5, IFN-Gamma, IL-10 and IL-17 increasing to different degrees, both of these observed after stimulating them to Spike-Fc-RBD, observable inflammation in the duodenum (first part of the small intestine).

Next, the authors did proteomic analysis (analyzing a ton of proteins and how many of them there are) of many parts of the intestine. They also observed higher levels of LPS at 6 hours and day 2 indicating dysfunction in the gut barrier. Among the 1985 proteins identified, 549 were differently expressed, they had a fold change greater than 1.2 and a p-value less than 0.05, meaning it was significant. The last step in this part was using KEGG (a bioinformatics tool to how all the proteins connect, and which pathways are more active or not, among other uses), and the proteins differentially expressed were mostly in Covid019 related to tight junction, focal adhesion, adherens junction, and PI3K-Akt signaling pathway.

Most proteins are not “promiscuous” meaning they won’t interact with every other protein around, so by looking into a few of the differentially expressed ones they looked into proteins that could potentially interact with CEACAM5. Among them, there was Galectin-9 and their proteomic results showed higher levels of Gal-9 in the duodenum at 6 hours and at the ileum at 4 days after exposure to Spike-Fc-RBD.

To understand how the virus can potentially damage the intestinal barrier they tested the interaction between CEACAM5 and Gal-9 in the intestines of mice, finding that these two might interact. While seeing higher levels of Gal-9, they found lower levels of PI3K, p-AKT, and p-mTOR, and also found lower levels of CD4+ T cells. When they added Caco-2 cells (intestinal cells used in labs), and found after adding CD4+ cells to the Caco-2 and stimulated with Spike-Fc-RBD ZO-1 and CEACAM-5. This means the damage may be mediated by CD4+ cells.

Similar to above, when adding Caco-2 cells to the mix to investigate the protein levels in the CD4+ cells, they saw a increase in Galectin-9and a decrease in P13K, p-AKT, and p-mTOR, they also found higher levels of IL-4 and IL-17, and also observed higher levels of apoptotic (meaning dying) CD4+ T cells. Meaning the virus might cause the CD4+ T cells to become more inflammatory, inhibit the PI3K/AKT/mTOR pathway, and increase cell death, leading to damage to the intestinal barrier.

What does all this mean, what is the significance ?

At face value, this paper itself would be “bad” in the sense it shows how effectively the viral infection can “eat away” the gut protective layer and cause both a change in the microbiome and an influx of bacteria and toxins themselves into the blood (this equals to systemic distribution). But as my readers are aware by now, a Galectin-9 rich response is the de facto dominant immune response of most Omicron variants, and a Th17 response can also be seen in individuals with post-infection effects and damage, including Long Covid.

A leaky gut will also inevitably affect the brain, and the entire immune system, exposure to bacterial and fungal toxins from your gut will inevitably cause a change in systemic immune response (one of these being Endotoxic Tolerance). The virus is also killing many of our immune cells, and this form of exposure leads to even more death of our immune cells. What is more concerning to me is the intestinal barrier dysfunction.

Many other viruses can cause one of these, but there is only one virus that has all these hallmarks, it doesn’t completely share the exact pathways, but it mimics this very well. Human immunodeficiency virus, HIV. One of the hallmarks of long-term problems with HIV is precisely “bacterial translocation” caused by “intestinal barrier dysfunction”, meaning the gut barrier becomes very weak, and bad bacteria escapes elsewhere.

This can also create another one of our known doom loops. Exposure to viral elements or endotoxin (LPS) will increase Galectin-9 and IFN-y, and these on the other hand directly influence neuroinflammation and the Kynurenine Pathway.

Another paper of interest “Gal-9 may drive HIV pathogenesis by rendering CD8 T cells dysfunctional as well as contribute to ongoing persistent inflammation in the setting of viral suppression.” Galectin-9 isn’t as multifunctional as Gal-3, but it is 3 powerful sister, and participates in clear states of immunosuppression. These pathways can explain some of the oddities in the many forms of Long Covid, and how other pathogens can contribute so much.

Before finishing this with a snark remark and a schedule, recently a group of fantastic researchers uploaded a pre-print in which they explored the metabolic anomalies in Covid infection and Long Covid (called post-covid syndrome by some) using Machine Learning. Let us see what they found…

Color me… not surprised… (last article talks about how taurine supplementation helps, with a lot of references).

The many biomarkers for Long Covid

The "Covid brain" and zombie cells

Sequential infection, inflammaging and the microbiome

Now… I do really wonder if there is one single thing, a protein, or enzyme that can connect not only these but most dots I connected to this day. One could say a Protein to rule them all (and in toxins bind them).

This will be the title of the upcoming article, but before I will focus for a few days on the simplified, layperson-friendly supplementation guide, and then many days on that one. And yes, when I publish the Rule Them All, you will understand why I said this is probably one of the most important papers published this year, very significant at least to me.

I may publish a conspiracy sunday, or my short story if there is interest, or something unrelated in the meantime.

Your support is both appreciated and welcomed =) thank you.