VISTA drives macrophages towards a pro-tumoral phenotype that promotes cancer cell phagocytosis yet down-regulates T cell responses.

BACKGROUND: VISTA is a well-known immune checkpoint in T cell biology, but its role in innate immunity is less established. Here, we investigated the role of VISTA on anticancer macrophage immunity, with a focus on phagocytosis, macrophage polarization and concomitant T cell activation. METHODS: Macrophages, differentiated from VISTA overexpressed THP-1 cells and cord blood CD34+ cell-derived monocytes, were used in phagocytosis assay using B lymphoma target cells opsonized with Rituximab. PBMC-derived macrophages were used to assess the correlation between phagocytosis and VISTA expression. qRT-PCR, flow cytometry, and enzyme-linked immunosorbent assay were performed to analyze the impact of VISTA on other checkpoints and M1/M2-like macrophage biology. Additionally, flow cytometry was used to assess the frequency of CD14+ monocytes expressing VISTA in PBMCs from 65 lymphoma patients and 37 healthy donors. RESULTS: Ectopic expression of VISTA in the monocytic model cell line THP-1 or in primary monocytes triggered differentiation towards the macrophage lineage, with a marked increase in M2-like macrophage-related gene expression and decrease in M1-like macrophage-related gene expression. VISTA expression in THP-1 and monocyte-derived macrophages strongly downregulated expression of SIRPα, a prominent 'don't eat me' signal, and augmented phagocytic activity of macrophages against cancer cells. Intriguingly, expression of VISTA's extracellular domain alone sufficed to trigger phagocytosis in ∼ 50% of cell lines, with those cell lines also directly binding to recombinant human VISTA, indicating ligand-dependent and -independent mechanisms. Endogenous VISTA expression was predominantly higher in M2-like macrophages compared to M0- or M1-like macrophages, with a positive correlation observed between VISTA expression in M2c macrophages and their phagocytic activity. VISTA-expressing macrophages demonstrated a unique cytokine profile, characterized by reduced IL-1ß and elevated IL-10 secretion. Furthermore, VISTA interacted with MHC-I and downregulated its surface expression, leading to diminished T cell activation. Notably, VISTA surface expression was identified in monocytes from all lymphoma patients but was less prevalent in healthy donors. CONCLUSIONS: Collectively, VISTA expression associates with and drives M2-like activation of macrophages with a high phagocytic capacity yet a decrease in antigen presentation capability to T cells. Therefore, VISTA is a negative immune checkpoint regulator in macrophage-mediated immune suppression.

COVID-19 can lead to rapid progression of cervical intraepithelial neoplasia by dysregulating the immune system: A hypothesis.

COVID-19 is a multisystem disease and cause of a global pandemic. Lately, cases of disease progression of HPV-infected CIN under SARS-CoV-2 infection were reported giving rise to the hypothesis of direct virus-infection induced pro-carcinogenic effect of SARS-CoV-2. We herein present a case of rapid progression from HPV-induced CIN 2 to microinvasive carcinoma within three months under COVID-19 without direct virus infection. Histopathologic evaluation, Fluorescence-in-situ hybridization and qRT-PCR against SARS-CoV-2 RNA as well as gene expression analysis were performed from the available FFPE-tissue and accompanied by an analysis of white blood cell differential. No signs of direct SARS-CoV-2 infection or COVID-19 typical alterations of cervical tissue were found. As expected, p53 decreased in expression with progression of dysplasia, while APOBEC3A and VISTA showed a decrease in expression contrary to observations in dysplasia progression. PD-L1 was expressed consistently or increased slightly but did not show the expected strong induction of expression. DNMT1 showed an increase in expression in CIN III and a slight decrease in carcinoma, while DNMT3a is consistently expressed in CIN II and decreased in carcinoma. Blood tests after COVID-19 showed substantial reduction of lymphocytes, eosinophils, T-cells, and NK-cells. Our results hint at an indirect effect of COVID-19 on the cervical neoplasm. We conclude that the immune system might be preoccupied and exhausted by the concurring COVID-19 disease, leading to less immunological pressure on the HPV-infected cervical dysplasia enabling rapid disease progression. Further, indirect proangiogenic and proinflammatory micromilieu due to the multisystemic effects of COVID-19 might play an additional role.

IL-6-induced FOXO1 activity determines the dynamics of metabolism in CD8 T cells cross-primed by liver sinusoidal endothelial cells.

Liver sinusoidal endothelial cells (LSECs) are liver-resident antigen (cross)-presenting cells that generate memory CD8 T cells, but metabolic properties of LSECs and LSEC-primed CD8 T cells remain understudied. Here, we report that high-level mitochondrial respiration and constitutive low-level glycolysis support LSEC scavenger and sentinel functions. LSECs fail to increase glycolysis and co-stimulation after TLR4 activation, indicating absence of metabolic and functional maturation compared with immunogenic dendritic cells. LSEC-primed CD8 T cells show a transient burst of oxidative phosphorylation and glycolysis. Mechanistically, co-stimulatory IL-6 signaling ensures high FOXO1 expression in LSEC-primed CD8 T cells, curtails metabolic activity associated with T cell activation, and is indispensable for T cell functionality after re-activation. Thus, distinct immunometabolic features characterize non-immunogenic LSECs compared with immunogenic dendritic cells and LSEC-primed CD8 T cells with memory features compared with effector CD8 T cells. This reveals local features of metabolism and function of T cells in the liver.