Myeloid CD169/Siglec1: An immunoregulatory biomarker in viral disease

Siglecs-mediated immune regulation in neurological disorders

The surfaces of various immune cells are rich in glycan chains, including the sialic-acid-binding immunoglobulin-like lectins (Siglecs) family. As an emerging glyco-immune checkpoint, Siglecs have the ability to bind and interact with various glycoproteins, thereby eliciting a series of downstream reactions to modulate the immune response. The impact of Siglecs has been extensively studied in tumor immunotherapy. However, research in neurological disorders and neurological diseases is very limited, and therapeutic options involving Siglecs need further exploration. Siglecs play a crucial role in the development, homeostasis, and repair processes of the nervous system, especially in degenerative diseases. This review summarizes studies on the immunomodulatory role mediated by Siglecs expressed on different immune cells in various neurological disorders, elucidates how dysregulated sialic acid contributes to several psychiatric disorders, and discusses the progress and limitations of research on the treatment of neurological disorders.

Dysregulation of SIGLEC1 in non-small cell lung cancer: prognostic implications and immunomodulatory role-a multicenter cohort study

PURPOSE

To investigate the clinical significance and functional role of SIGLEC1-positive cells in non-small cell lungcancer (NSCLC) patients, focusing on their prognostic impact and therapeutic response.

METHODS

A multicenter retrospective cohort analysis was conducted, integrating data from multiple sources. Weanalyzed SIGLEC1 expression in NSCLC tissues, clinicopathological features, overall survival outcomes,chemotherapy responsiveness, and sensitivity to targeted therapies. We also developed a prognostic model basedon SIGLEC1 expression and clinical variables.

RESULTS

SIGLEC1 expression was significantly downregulated in NSCLC tissues, and the density of SIGLEC1-positivecells was inversely correlated with various clinicopathological features. Notably, patients with high infiltration ofSIGLEC1-positive cells exhibited significantly better overall survival outcomes. Furthermore, elevated SIGLEC1expression was associated with improved responsiveness to chemotherapy and demonstrated distinct patterns ofsensitivity to targeted therapies. A robust prognostic model was developed by integrating SIGLEC1 expression andclinical variables.

CONCLUSIONS

This study highlighted the downregulation of SIGLEC1 in NSCLC tissues and its significant associationwith patient prognosis and therapeutic response. The findings suggested that SIGLEC1 played a critical role inmodulating the tumor immune microenvironment and has potential as both a prognostic biomarker and therapeutictarget in NSCLC.

Leukocyte activation patterns in hospitalized children: comparing SARS-CoV-2, bacterial infections, and inflammatory pathologies

In adults, monocytes and neutrophils play important roles in the hyperinflammatory responses characteristic of severe forms of SARS-CoV-2 infection. We assessed leukocyte activation in 55 children attending the emergency department for acute fever between March 2020 and September 2021. The following markers were analyzed by flow cytometry: CD169 and HLA-DR on monocytes, CD64 and CD16 on neutrophils, and CD38 on lymphocytes TCD8. Fifteen of the children had SARS-CoV-2 infection, 15 had bacterial infections, and 15 had inflammatory diseases. We observed overexpression of CD169 on monocytes and CD38 on T lymphocytes in all patients with a diagnosis of SARS-CoV-2, while overexpression of CD64 on neutrophils was observed with bacterial infections and inflammatory diseases. There was a decrease in the expression of HLA-DR on monocytes in the bacterial infection and inflammatory pathology groups. Leukocyte analysis identifies distinct activation patterns in children during SARS-CoV-2 infections, bacterial infections, and inflammatory diseases.

The Dysregulation of the Monocyte-Dendritic Cell Interplay Is Associated with In-Hospital Mortality in COVID-19 Pneumonia

Background: The monocyte-phagocyte system (MPS), including monocytes/macrophages and dendritic cells (DCs), plays a key role in anti-viral immunity. We aimed to analyze the prognostic value of the MPS components on in-hospital mortality in a cohort of 58 patients (M/F; mean age ± SD years) with COVID-19 pneumonia and 22 age- and sex-matched healthy controls. Methods: We measured frequencies and absolute numbers of peripheral blood CD169+ monocytes, conventional CD1c+ and CD141+ (namely cDC2 and cDC1), and plasmacytoid CD303+ DCs by means of multi-parametric flow cytometry. A gene profile analysis of 770 immune-inflammatory-related human genes and 20 SARS-CoV-2 genes was also performed. Results: Median frequencies and absolute counts of CD169-expressing monocytes were significantly higher in COVID-19 patients than in controls (p 0.04 and p 0.01, respectively). Conversely, percentages and absolute numbers of all DC subsets were markedly depleted in patients (p < 0.0001). COVID-19 cases with absolute counts of CD169+ monocytes above the median value of 114.68/μL had significantly higher in-hospital mortality (HR 4.96; 95% CI: 1.42-17.27; p = 0.02). Interleukin (IL)-6 concentrations were significantly increased in COVID-19 patients (p < 0.0001 vs. controls), and negatively correlated with the absolute counts of circulating CD1c+ cDC2 (r = -0.29, p = 0.034) and CD303+ pDC (r = -0.29, p = 0.036) subsets. Viral genes were upregulated in patients with worse outcomes along with inflammatory mediators such as interleukin (IL)-1 beta, tumor necrosis-α (TNF-α) and the anticoagulant protein (PROS1). Conversely, surviving patients had upregulated genes related to inflammatory and anti-viral-related pathways along with the T cell membrane molecule CD4. Conclusions: Our results suggest that the dysregulated interplay between the different components of the MPS along with the imbalance between viral gene expression and host anti-viral immunity negatively impacts COVID-19 outcomes. Although the clinical scenario of COVID-19 has changed over time, a deepening of its pathogenesis remains a priority in clinical and experimental research.

Role of MR-proADM and Monocyte CD169 in Predicting In-Hospital and 60-Day Mortality in COVID-19 Patients

Objectives

Mid-regional pro-adrenomedullin (MR-proADM) and monocyte CD169 (CD169) are valuable prognostic indicators of severe COVID-19.

Methods

We assessed the predictive ability of a single measurement of MR-proADM and CD169 at emergency department (ED) admission to forecast in-hospital and 60-day mortality in adult COVID-19 patients. We analyzed clinical and laboratory data, with in-hospital mortality as the primary endpoint and 60-day mortality as the secondary endpoint. We examined associations with clinical and laboratory variables through univariate and multivariate analyses.

Results

Data from 382 patients over 14 months were analyzed. Significant predictors of in-hospital mortality included age ⩾ 70 years (hazard ratio [HR] 8.1; 95% confidence interval [CI] 2.2-29.5), CD169 ratio ⩾ 20 (HR: 2.4; 95%CI: 1.6-5.6), MR-proADM ⩾ 1.1 mmol/L (HR: 5.1; 95%CI: 1.7-15.6), the need for invasive mechanical ventilation (HR: 6.8; 95%CI: 2.4-19.1), and active cancer (HR: 5.2; 95%CI: 1.8-15.2). For 60-day mortality, only elevated MR-proADM levels showed predictive value (HR: 6.7; 95%CI: 1.7-25.0), while high serologic titer was protective (HR: 0.4; 95%CI: 0.1-0.9).

Conclusion

A single MR-proADM and CD169 measurement upon ED admission has prognostic value for in-hospital mortality, with MR-proADM also predicting 60-day mortality.

Persistence of circulating CD169+monocytes and HLA-DR downregulation underline the immune response impairment in PASC individuals: the potential contribution of different COVID-19 pandemic waves

The use of CD169 as a marker of viral infection has been widely discussed in the context of COVID-19, and in particular, its crucial role in the early detection of SARS-CoV-2 infection and its association with the severity and clinical outcome of COVID-19 were demonstrated. COVID-19 patients show relevant systemic alteration and immunological dysfunction that persists in individuals with post-acute sequelae of SARS-CoV-2 infection (PASC). It is critical to implement the characterization of the disease, focusing also on the possible impact of the different COVID-19 waves and the consequent effects found after infection. On this basis, we evaluated by flow cytometry the expression of CD169 and HLA-DR on monocytes from COVID-19 patients and PASC individuals to better elucidate their involvement in immunological dysfunction, also evaluating the possible impact of different pandemic waves. The results confirm CD169 RMFI is a good marker of viral infection. Moreover, COVID-19 patients and PASC individuals showed high percentage of CD169+ monocytes, but low percentage of HLA-DR+ monocytes and the alteration of systemic inflammatory indices. We have also observed alterations of CD169 and HLA-DR expression and indices of inflammation upon different COVID-19 waves. The persistence of specific myeloid subpopulations suggests a role of CD169+ monocytes and HLA-DR in COVID-19 disease and chronic post-infection inflammation, opening new opportunities to evaluate the impact of specific pandemic waves on the immune response impairment and systemic alterations with the perspective to provide new tools to monitoring new variants and diseases associated to emerging respiratory viruses.

Malaria-specific Type 1 regulatory T cells are more abundant in first pregnancies and associated with placental malaria

BACKGROUND

Malaria in pregnancy (MIP) causes higher morbidity in primigravid compared to multigravid women; however, the correlates and mechanisms underlying this gravidity-dependent protection remain incompletely understood. We aimed to compare the cellular immune response between primigravid and multigravid women living in a malaria-endemic region and assess for correlates of protection against MIP.

METHODS

We characterised the second trimester cellular immune response among 203 primigravid and multigravid pregnant women enrolled in two clinical trials of chemoprevention in eastern Uganda, utilizing RNA sequencing, flow cytometry, and functional assays. We compared responses across gravidity and determined associations with parasitaemia during pregnancy and placental malaria.

FINDINGS

Using whole blood RNA sequencing, no significant differentially expressed genes were identified between primigravid (n = 12) and multigravid (n = 11) women overall (log 2(FC) > 2, FDR < 0.1). However, primigravid (n = 49) women had higher percentages of malaria-specific, non-naïve CD4+ T cells that co-expressed IL-10 and IFNγ compared with multigravid (n = 85) women (p = 0.000023), and higher percentages of these CD4+ T cells were associated with greater risks of parasitaemia in pregnancy (Rs = 0.49, p = 0.001) and placental malaria (p = 0.0073). These IL-10 and IFNγ co-producing CD4+ T cells had a genomic signature of Tr1 cells, including expression of transcription factors cMAF and BATF and cell surface makers CTLA4 and LAG-3.

INTERPRETATION

Malaria-specific Tr1 cells were highly prevalent in primigravid Ugandan women, and their presence correlated with a higher risk of malaria in pregnancy. Understanding whether suppression of Tr1 cells plays a role in naturally acquired gravidity-dependent immunity may aid the development of new vaccines or treatments for MIP.

FUNDING

This work was funded by NIH (PO1 HD059454, U01 AI141308, U19 AI089674, U01 AI155325, U01 AI150741), the March of Dimes (Basil O'Connor award), and the Bill and Melinda Gates Foundation (OPP 1113682).

Sialoadhesin (CD169/Siglec-1) is an extended molecule that escapes inhibitory cis-interactions and synergizes with other macrophage receptors to promote phagocytosis

Sialoadhesin (CD169/Siglec-1, Sn) is a macrophage receptor that interacts with sialic acids on both host cells and pathogens. It is a type 1 membrane protein with an unusually large number of 17 extracellular immunoglobulin (Ig)-like domains, made up of an N-terminal V-set domain that binds sialic acid and 16 adjacent C2-set domains. The potential importance of 17 Ig domains in Sn for mediating cellular interactions has not been investigated experimentally. In the present study, Chinese Hamster Ovary (CHO) cells were stably transfected with full-length or truncated forms of Sn. Using human red blood cells (RBC) as a model system, CHO cells expressing truncated forms of Sn with 4 or less Ig domains were unable to bind RBC in comparison to the full-length protein. Immunoelectron microscopy of the CHO cells indicated that full-length Sn extends ~ 33 nm from the plasma membrane compared with ~ 14 nm for a truncated form with 6 N-terminal Ig domains. Co-expresssion of Sn-expressing CHO cells with heavily glycosylated membrane proteins of differing predicted lengths resulted in selective modulation of Sn-dependent binding to RBC and supported the hypothesis that Sn has evolved 17 Ig domains to escape inhibitory cis-interactions. The functional significance of the extended length of Sn was demonstrated in experiments with macrophages showing that Sn synergizes with phagocytic receptors FcR and TIM-4 to strongly promote uptake of IgG-opsonized and eryptotic RBC respectively.

Thymosin Alpha 1 Restores the Immune Homeostasis in lymphocytes during Post-Acute Sequelae of SARS-CoV-2 infection

The complex alterations of the immune system and the immune-mediated multiorgan injury plays a key role in host response to SARS-CoV-2 infection and in the pathogenesis of COVID-19, being also associated with adverse outcomes. Thymosin alpha 1 (Tα1) is one of the molecules used in the treatment of COVID-19, as it is known to restore the homeostasis of the immune system during infections and cancer. The use of Tα1 in COVID-19 patients had been widely used in China and in COVID-19 patients, it has been shown to decrease hospitalization rate, especially in those with greater disease severity, and reduce mortality by restoring lymphocytopenia and more specifically, depleted T cells. Persistent dysregulation with depletion of naive B and T cell subpopulations and expansion of memory T cells suggest a chronic stimulation of the immune response in individuals with post-acute sequelae of SARS-CoV-2 infection (PASC). Our data obtained from an ex vivo study, showed that in PASC individuals with a chronically altered immune response, Tα1 improve the restoration of an appropriate response, most evident in those with more severe illness and who need respiratory support during acute phase, and in those with specific systemic and psychiatric symptoms of PASC, confirming Tα1 treatment being more effective in compromised patients. The results obtained, along with promising reports on recent trials on Tα1 administration in patients with COVID-19, offer new insights into intervention also for those patients with long-lasting inflammation with post-infectious symptoms, some of which have a delayed onset.

The Blessed Union of Glycobiology and Immunology: A Marriage That Worked

In this article, we discuss the main aspects regarding the recognition of cell surface glycoconjugates and the immunomodulation of responses against the progression of certain pathologies, such as cancer and infectious diseases. In the first part, we talk about different aspects of glycoconjugates and delve deeper into the importance of N-glycans in cancer immunotherapy. Then, we describe two important lectin families that have been very well studied in the last 20 years. Examples include the sialic acid-binding immunoglobulin (Ig)-like lectins (siglecs), and galectins. Finally, we discuss a topic that needs to be better addressed in the field of glycoimmunology: the impact of oncofetal antigens on the cells of the immune system. New findings in this area are of great importance for advancement, especially in the field of oncology, since it is already known that cellular interactions mediated by carbohydrate-carbohydrate and/or carbohydrate proteins are able to modulate the progression of different types of cancer in events that compromise the functionality of the immune responses.