Wuhan strain of SARS-CoV-2 triggers activation of immune evasion machinery similar to the one operated by cancer cells, 2025, Abooali et al.

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Wuhan strain of SARS-CoV-2 triggers activation of immune evasion machinery similar to the one operated by cancer cells
Abooali, Maryam ; Yasinska, Inna M. ; Thapa, Gauri ; Lei, Xi ; da Costa, Kelly A. S. ; Schlichtner, Stephanie ; Berger, Steffen M. ; Fasler-Kan, Elizaveta ; Temperton, Nigel J. ; Vuono, Romina ; Sumbayev, Vadim V.

In the last 2 years, there has been an increasing concern that SARS-CoV-2 infection may represent a marker of undiagnosed cancers. A potential connection between COVID-19/long COVID and malignant transformation/cancer progression was reported in a number of studies. It is, however, unclear if the virus itself can cause malignant transformation or if it has a potential to support malignant processes in human body.

We analyzed nasopharyngeal swabs collected from individuals infected with Wuhan strain of SARS-CoV-2 and conducted in vitro studies using BEAS-2B human bronchial epithelial cells.

Here we report that Wuhan strain of SARS-CoV-2 and its spike protein induce activation of hypoxia-inducible factor 1 (HIF-1) transcription complex in infected cells. This effect is achieved through conversion of cellular 2-oxoglutarate into 2-hydroxy-glutarate, which most likely blocks the activity of HIF-1α prolyl hydroxylation. As such, it leads to activation of HIF-1, which triggers production of transforming growth factor–β type 1 (TGF-β). TGF-β induces expression of immune checkpoint proteins, such as galectin-9, programmed death-ligand 1, and indoleamine-2,3-dioxygenase, an enzyme, which is involved in production of immunosuppressive amino acid called L-kynurenine.

These immune checkpoint pathways were capable of suppressing both helper and cytotoxic activities of T lymphocytes and, as such, could potentially support malignant processes in infected tissues.

Link | PDF | Frontiers in Immunology [Open Access]

 

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Summary abbreviated quotes from introduction and results —

Here, we report, for the first time, that Wuhan strain of SARSCoV-2 and its spike protein (S) induce activation of hypoxia-inducible factor 1 (HIF-1) transcription complex possibly by triggering conversion of cellular 2 oxoglutarate into 2-hydroxy-glutarate, which most likely blocks prolyl hydroxylation/degradation of inducible alpha subunit of HIF-1 (HIF-1a). Active HIF-1 induces production of transforming growth factor–b type 1 (TGF-b), which triggers expression of immune checkpoint proteins, such as galectin-9, PD-L1, and IDO1.

First of all, we investigated nasopharyngeal swabs (taken in the active phase […]) obtained from five non-hospitalized individuals affected by Wuhan strain of SARS-CoV-2 virus versus five healthy individuals. We found that […] the levels of galectin-9, TGF-b, and LKU [L-kynurenine] were highly upregulated compared to those of healthy individuals.

Interestingly, mRNA levels of both HIF-1a and VEGF […] were significantly increased in the swabs of COVID-19 individuals. […] However, we were keen to understand the cause of this effect because the tissues subjected to taking the swabs cannot have highly decreased oxygen availability. On the other hand, the S protein of SARS-CoV-2 was reported to upregulate aerobic glycolysis leading to translocation of all the pyruvate into mitochondria. This can leave existing lactate dehydrogenase (LDH) A enzyme molecules “unemployed.” In addition, in this case, LDH A can in theory convert cytosolic 2OG into L-2-OH-G. The latter cannot be used as a cofactor in HIF-1a PHD reaction, leading to attenuation of this reaction and stabilization/accumulation of HIF-1a protein.

To investigate this hypotheis of 2-OG conversion/removal, we measured D-2-OH-G in swabs of both SARS-CoV-2–infected and healthy individuals. We found that 2-OH-G was not detectable at all in the swabs of all healthy individuals and was clearly detectable in swabs of COVID-19 individuals. As such, we hypothesized that this process triggers activation of HIF-1, which was shown to upregulate TGF-b production, and TGF-b is known to induce expression of galectin-9, PD-L1, and IDO1 (converts amino acid L-tryptophan into formyl-kynurenine, which is then turned into LKU) via the Smad3 pathway.

To verify the finding and hypotheses described above in the in vitro cell culture model, we used human bronchial epithelium BEAS-2B cells. Cells were transfected with Wuhan SARS-CoV-2 S protein expression plasmid (S-SC2W) vs. empty vector (EV; control).

We also found that 2-OH-G was not detectable in wild-type BEAS-2B cells as well as in the cells transfected with EV. But in the cells transfected with S-SC2W, it was clearly detectable. [LDHA] was obviously higher in S protein-containing BEAS-2B cells. At the same time, when LDHA inhibitor was added […] conversion of 2-OG was significantly downregulated confirming the ability of LDHA to act on 2-OG. This led to attenuation of HIF-1a PHD activity as well as high upregulation of HIF-1 DNA-binding activity and TGF-b production

As a result, glycolysis was significantly upregulated in S-containing BEAS-2B cells compared to that in controls. […] Phospho-Smad3 was highly upregulated […]. IDO1 activity and respectively LKU release were highly increased in S-SC2W–containing BEAS-2B cells. We also verified the role of HIF-1 in TGF-b expression[…] We confirmed the direct interaction of HIF-1 with TGF-b gene promoter region. As such, we can confirm that Wuhan SARS-CoV-2 S protein upregulates glycolysis, and we uncovered the mechanism underlying this process. This mechanism also leads to activation of immune evasion machinery similar to the one operated by cancer cells.

 

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Selected summary quotes from discussion —

we have demonstrated that this virus manages to trigger a complex pathway leading to activation of HIF-1 transcription complex. This was found to be triggered specifically by S protein, which is in line with previous observations on S protein–dependent upregulation of glycolysis, the process, which is downstream of HIF-1 signaling. By activating energy metabolism, which is required for virus replication, it manages to make LDHA and possibly other enzymes to convert cellular 2-OG into 2-OH-G

It was reported previously that S protein of different coronaviruses including SARSCoV, which caused an outbreak in 2003, induces heavy endoplasmic reticulum stress. SARS-CoV-2 is not an exception and was also reported to trigger severe ER stress. This kind of reaction is likely to promote aerobic glycolysis, thus leading to generation of pyruvate which is then translocated into mitochondria.

Generated 2-OH-G cannot be used as a co-factor in HIF-1a PHD reaction, which required 2-OG. PHD reaction (2-OG–dependent) would normally lead to degradation of HIF-1a protein. As it does not take place, this makes HIF-1 transcription complex highly active.

Active HIF-1 triggers expression of TGFb, as observed previously and confirmed in our study using ChIP assay. TGF-b displays autocrine activity and, through Smad3 pathway, induces activation of immune checkpoint proteins —galectin-9, PD-L1, and IDO1

As we have recently reported, both TGF-b and IFN-g are capable of inducing IDO1 activity, leading to increased LKU production.

Our work highlights the importance of consideration to apply different approaches, which would allow to downregulate TGF-b signaling in COVID-19 patients in order to reduce the immune evasion effects of the virus