Diverse facets of MDSC in different phases of chronic HBV infection: Impact on HBV-specific T-cell response and homing

Dual Oxygen-Supply Immunosuppression-Inhibiting Nanomedicine to Avoid the Intratumoral Recruitment of Myeloid-Derived Suppressor Cells

Myeloid-derived suppressor cells (MDSCs) are reported to be responsible for the negative prognosis of colorectal cancer (CRC) patients due to the mediated immunosuppressive tumor microenvironment (TME). The selective and chronic circumvention of tumor-infiltrated MDSCs has potential clinical significance for CRC treatment, which unluckily remains a technical challenge. Because tumor hypoxia makes a significant contribution to the recruitment of MDSCs in tumor sites, a dual oxygen-supplied immunosuppression-inhibiting nanomedicine (DOIN) is demonstrated for overcoming tumor hypoxia, which achieves selective and long-term inhibition of intratumoral recruitment of MDSCs. The DOIN is constructed by the encasement of perfluorooctyl bromide (PFOB) and 4-methylumbelliferone (4-MU) into a TME-responsive amphiphilic polymer. This nanoplatform directly carries oxygen to the tumor region and simultaneously loosens the condensed tumor extracellular matrix for the normalization of tumor vasculature, which selectively remodels the TME toward one adverse to the intratumoral recruitment of MDSCs. Importantly, this nanoplatform offers a long-acting alleviation of the hypoxic TME, chronically avoiding the comeback of tumor-infiltrated MDSCs. Consequently, the immunosuppressive TME is relieved, and T cells are successfully proliferated and activated into cytotoxic T lymphocytes, which boosts a systemic immune response and contributes to lasting inhibition of tumor growth with a prolonged survival span of xenograft.

Insights of immune cell heterogeneity, tumor-initiated subtype transformation, drug resistance, treatment and detecting technologies in glioma microenvironment

BACKGROUND

With the gradual understanding of glioma development and the immune microenvironment, many immune cells have been discovered. Despite the growing comprehension of immune cell functions and the clinical application of immunotherapy, the precise roles and characteristics of immune cell subtypes, how glioma induces subtype transformation of immune cells and its impact on glioma progression have yet to be understood.

AIM OF THE REVIEW

In this review, we comprehensively center on the four major immune cells within the glioma microenvironment, particularly neutrophils, macrophages, lymphocytes, myeloid-derived suppressor cells (MDSCs), and other significant immune cells. We discuss (1) immune cell subtype markers, (2) glioma-induced immune cell subtype transformation, (3) the mechanisms of each subtype influencing chemotherapy resistance, (4) therapies targeting immune cells, and (5) immune cell-associated single-cell sequencing. Eventually, we identified the characteristics of immune cell subtypes in glioma, comprehensively summarized the exact mechanism of glioma-induced immune cell subtype transformation, and concluded the progress of single-cell sequencing in exploring immune cell subtypes in glioma.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In conclusion, we have analyzed the mechanism of chemotherapy resistance detailly, and have discovered prospective immunotherapy targets, excavating the potential of novel immunotherapies approach that synergistically combines radiotherapy, chemotherapy, and surgery, thereby paving the way for improved immunotherapeutic strategies against glioma and enhanced patient outcomes.

CD44 expression on murine hepatic stellate cells promotes the induction of monocytic and polymorphonuclear myeloid-derived suppressor cells

In chronic inflammation, regulatory immune cells, such as regulatory T cells and myeloid-derived suppressor cells, can develop. Local signals in the inflamed tissue, such as cytokines and eicosanoids, but also contact-dependent signals, can promote myeloid-derived suppressor cell development. In the liver, hepatic stellate cells may provide such signals via the expression of CD44. Myeloid-derived suppressor cells generated in the presence of hepatic stellate cells and anti-CD44 antibodies were functionally and phenotypically analyzed. We found that both monocytic and polymorphonuclear myeloid-derived suppressor cells generated in the presence of αCD44 antibodies were less suppressive toward T cells as measured by T-cell proliferation and cytokine production. Moreover, both monocytic and polymorphonuclear myeloid-derived suppressor cells were phenotypically altered. Monocytic myeloid-derived suppressor cells mainly changed their expression of CD80 and CD39, and polymorphonuclear myeloid-derived suppressor cells showed altered expression of CD80/86, PD-L1, and CCR2. Moreover, both polymorphonuclear and monocytic myeloid-derived suppressor cells lost expression of Nos2 messenger RNA, whereas monocytic myeloid-derived suppressor cells showed reduced expression of TGFb messenger RNA and polymorphonuclear myeloid-derived suppressor cells reduced expression of Il10 messenger RNA. In summary, the presence of CD44 in hepatic stellate cells promotes the induction of both monocytic and polymorphonuclear myeloid-derived suppressor cells, although the mechanisms by which these myeloid-derived suppressor cells may increase suppressive function due to interaction with CD44 are only partially overlapping.

Mesencephalic Astrocyte-derived Neurotrophic Factor Supports Hepatitis B Virus-induced Immunotolerance

BACKGROUND & AIMS

The immune tolerance induced by hepatitis B virus (HBV) is a major challenge for achieving effective viral clearance, and the mechanisms involved are not well-understood. One potential factor involved in modulating immune responses is mesencephalic astrocyte-derived neurotrophic factor (MANF), which has been reported to be increased in patients with chronic hepatitis B. In this study, our objective is to examine the role of MANF in regulating immune responses to HBV.

METHODS

We utilized a commonly used HBV-harboring mouse model, where mice were hydrodynamically injected with the pAAV/HBV1.2 plasmid. We assessed the HBV load by measuring the levels of various markers including hepatitis B surface antigen, hepatitis B envelope antigen, hepatitis B core antigen, HBV DNA, and HBV RNA.

RESULTS

Our study revealed that following HBV infection, both myeloid cells and hepatocytes exhibited increased expression of MANF. Moreover, we observed that mice with myeloid-specific MANF knockout (ManfMye-/-) displayed reduced HBV load and improved HBV-specific T cell responses. The decreased HBV-induced tolerance in ManfMye-/- mice was associated with reduced accumulation of myeloid-derived suppressor cells (MDSCs) in the liver. Restoring MDSC levels in ManfMye-/- mice through MDSC adoptive transfer reinstated HBV-induced tolerance. Mechanistically, we found that MANF promoted MDSC expansion by activating the IL-6/STAT3 pathway. Importantly, our study demonstrated the effectiveness of a combination therapy involving an hepatitis B surface antigen vaccine and nanoparticle-encapsulated MANF siRNA in effectively clearing HBV in HBV-carrier mice.

CONCLUSION

The current study reveals that MANF plays a previously unrecognized regulatory role in liver tolerance by expanding MDSCs in the liver through IL-6/STAT3 signaling, leading to MDSC-mediated CD8+ T cell exhaustion.

MSC microvesicles loaded G-quadruplex-enhanced circular single-stranded DNA-9 inhibits tumor growth by targeting MDSCs

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) promote tumor growth, metastasis, and lead to immunotherapy resistance. Studies revealed that miRNAs are also expressed in MDSCs and promote the immunosuppressive function of MDSCs. Currently, few studies have been reported on inducible cellular microvesicle delivery of nucleic acid drugs targeting miRNA in MDSCs for the treatment of malignant tumors.

RESULTS AND CONCLUSION

In this study, we designed an artificial DNA named G-quadruplex-enhanced circular single-stranded DNA-9 (G4-CSSD9), that specifically adsorbs the miR-9 sequence. Its advanced DNA folding structure, rich in tandem repeat guanine (G-quadruplex), also provides good stability. Mesenchymal stem cells (MSCs) were prepared into nanostructured vesicles by membrane extrusion. The MSC microvesicles-encapsulated G4-CSSD9 (MVs@G4-CSSD9) was delivered into MDSCs, which affected the downstream transcription and translation process, and reduced the immunosuppressive function of MDSCs, so as to achieve the purpose of treating melanoma. In particular, it provides an idea for the malignant tumor treatment.

Myeloid-derived suppressor cells in cancer: therapeutic targets to overcome tumor immune evasion

Paradoxically, tumor development and progression can be inhibited and promoted by the immune system. After three stages of immune editing, namely, elimination, homeostasis and escape, tumor cells are no longer restricted by immune surveillance and thus develop into clinical tumors. The mechanisms of immune escape include abnormalities in antitumor-associated immune cells, selection for immune resistance to tumor cells, impaired transport of T cells, and the formation of an immunosuppressive tumor microenvironment. A population of distinct immature myeloid cells, myeloid-derived suppressor cells (MDSCs), mediate immune escape primarily by exerting immunosuppressive effects and participating in the constitution of an immunosuppressive microtumor environment. Clinical trials have found that the levels of MDSCs in the peripheral blood of cancer patients are strongly correlated with tumor stage, metastasis and prognosis. Moreover, animal experiments have confirmed that elimination of MDSCs inhibits tumor growth and metastasis to some extent. Therefore, MDSCs may become the target of immunotherapy for many cancers, and eliminating MDSCs can help improve the response rate to cancer treatment and patient survival. However, a clear definition of MDSCs and the specific mechanism involved in immune escape are lacking. In this paper, we review the role of the MDSCs population in tumor development and the mechanisms involved in immune escape in different tumor contexts. In addition, we discuss the use of these cells as targets for tumor immunotherapy. This review not only contributes to a systematic and comprehensive understanding of the essential role of MDSCs in immune system reactions against tumors but also provides information to guide the development of cancer therapies targeting MDSCs.

A genetic variant in the CD40 gene is related to HBV infection in the Chinese Han population

BACKGROUND

CD40 is an important immune costimulatory molecule that has recently been found to be associated with chronic hepatitis B. This study aims to explore the association between CD40 polymorphisms and HBV infection, as well as to investigate the impact of different rs1883832 genotypes on CD40 expression and its effect on the progression of chronic HBV infection.

METHODS

We genotyped rs1883832 in 3433 individuals using MassARRAY, and quantified the CD40 expression, including CD40 mRNA, sCD40, and mCD40. The CD40 and HBV infection indicators were assessed to investigate the potential function of rs1883832 in suppressing HBV replication in HepG2.2.15 and HepAD38, CD40L in cytotoxic t lymphocytes (CTLs) and interferon-γ, TNF-α, granzyme B, and perforin were measured to elucidate the mechanism by which CD40 inhibits HBV replication.

RESULTS

Our study revealed that the frequencies of CC genotype and C allele of rs1883832 were significantly higher in immune recovery compared to chronic hepatitis B. Individuals with CC genotype exhibited significantly elevated CD40 in serum and B cells compared to TT genotypes in chronic hepatitis B. Additionally, CD40 is capable of inhibiting HBV replication and transcription in hepatocytes by means of interaction with CD40L. A significant negative correlation was found between HBV DNA, HBeAg, and mCD40. Conversely, the expressions of ALT and mCD40 showed a positive correlation, which aligns with the trend of CD40L.

CONCLUSIONS

rs1883832 C allele may have a protective role in HBV immune recovery. This protective effect could potentially be attributed to the regulation of CD40 expression. The activation of the anti-HBV immune response, which occurs through binding CD40L on CTL, can suppress HBV DNA replication and potentially facilitate immune recovery in HBV infection.

Recent advances in understanding T cell activation and exhaustion during HBV infection

Chronic hepatitis B virus (HBV) infection remains a major public health concern globally, and T cell responses are widely believed to play a pivotal role in mediating HBV clearance. Accordingly, research on the characteristics of HBV-specific T cell responses, from activation to exhaustion, has advanced rapidly. Here, we summarize recent developments in characterizing T cell immunity in HBV infection by reviewing basic and clinical research published in the last five years. We provide a comprehensive summary of the mechanisms that induce effective anti-HBV T cell immunity, as well as the latest developments in understanding T cell dysfunction in chronic HBV infection. Furthermore, we briefly discuss current novel treatment strategies aimed at restoring anti-HBV T cell responses.

Immune response and treatment targets of chronic hepatitis B virus infection: innate and adaptive immunity

Chronic hepatitis B virus (HBV) infection is a major global public health risk that threatens human life and health, although the number of vaccinated people has increased. The clinical outcome of HBV infection depends on the complex interplay between viral replication and the host immune response. Innate immunity plays an important role in the early stages of the disease but retains no long-term immune memory. However, HBV evades detection by the host innate immune system through stealth. Therefore, adaptive immunity involving T and B cells is crucial for controlling and clearing HBV infections that lead to liver inflammation and damage. The persistence of HBV leads to immune tolerance owing to immune cell dysfunction, T cell exhaustion, and an increase in suppressor cells and cytokines. Although significant progress has been made in HBV treatment in recent years, the balance between immune tolerance, immune activation, inflammation, and fibrosis in chronic hepatitis B remains unknown, making a functional cure difficult to achieve. Therefore, this review focuses on the important cells involved in the innate and adaptive immunity of chronic hepatitis B that target the host immune system and identifies treatment strategies.

Lower frequency of MDSCs was significantly related to functional cure in CHB patients treated with peginterferon

BACKGROUND AND AIMS

Myeloid-derived suppressor cells (MDSCs) and CD4⁺ regulatory T cells (Tregs) expand during chronic hepatitis B virus (HBV) infection and inhibit antiviral immunity. However, the relationship between antiviral effect and the frequencies of those immune suppressive cells after pegylated interferon α-2a (PegIFNα-2a) therapy is not clearly understood. This study aimed to investigate the contribution of monocytic MDSCs (mMDSCs) and CD4⁺ Tregs to functional cure (HBsAg seroclearance) after PegIFNα-2a therapy and evaluate the effect of PegIFNα-2a therapy on these cells.

METHODS

Flow cytometry analysis was performed along with longitudinal immune monitoring of 97 hepatitis B e antigen (HBeAg) negative chronic hepatitis B (CHB) patients receiving PegIFNα-2a weekly for 48 weeks.

RESULTS

The frequencies of mMDSCs and CD4⁺ Tregs increased in all HBV patients, and they were higher in the HBsAg persistence group than in the HBsAg seroclearance group. A significant decline in the frequency of mMDSCs was found in patients who realized functional cure after PegIFNα-2a treatment. In contrast, the frequency of CD4⁺ Tregs in both the HBsAg seroclearance and persistence groups significantly increased. Multivariate analyses indicated that the baseline serum HBsAg levels (p < .001) and mMDSCs frequency (p = .027) were independently associated with the HBsAg clearance, and the combined marker (HBsAg plus mMDSCs) displayed the highest specificity (93.1%) than any other markers in predicting HBsAg seroclearance.

CONCLUSIONS

These results suggest that a poor response to PegIFNα-2a treatment in CHB patients may be related to the frequencies of immune suppressive cells, while the therapeutic targeting of these cells might be effective in boosting anti-HBV immunity.

Deciphering the roles of myeloid derived suppressor cells in viral oncogenesis

Myeloid derived suppressor cells (MDSCs) are a heterogenous population of myeloid cells derived from monocyte and granulocyte precursors. They are pathologically expanded in conditions of ongoing inflammation where they function to suppress both innate and adaptive immunity. They are subdivided into three distinct subsets: monocytic (M-) MDSC, polymorphonuclear (or neutrophilic) (PMN-) MDSC and early-stage (e-) MDSC that may exhibit differential function in different pathological scenarios. However, in cancer they are associated with inhibition of the anti-tumour immune response and are universally associated with a poor prognosis. Seven human viruses classified as Group I carcinogenic agents are jointly responsible for nearly one fifth of all human cancers. These viruses represent a large diversity of species, including DNA, RNA and retroviridae. They include the human gammaherpesviruses (Epstein Barr virus (EBV) and Kaposi's Sarcoma-Associated Herpesvirus (KSHV), members of the high-risk human papillomaviruses (HPVs), hepatitis B and C (HBV, HCV), Human T cell leukaemia virus (HTLV-1) and Merkel cell polyomavirus (MCPyV). Each of these viruses encode an array of different oncogenes that perturb numerous cellular pathways that ultimately, over time, lead to cancer. A prerequisite for oncogenesis is therefore establishment of chronic infection whereby the virus persists in the host cells without being eradicated by the antiviral immune response. Although some of the viruses can directly modulate the immune response to enable persistence, a growing body of evidence suggests the immune microenvironment is modulated by expansions of MDSCs, driven by viral persistence and oncogenesis. It is likely these MDSCs play a role in loss of immune recognition and function and it is therefore essential to understand their phenotype and function, particularly given the increasing importance of immunotherapy in the modern arsenal of anti-cancer therapies. This review will discuss the role of MDSCs in viral oncogenesis. In particular we will focus upon the mechanisms thought to drive the MDSC expansions, the subsets expanded and their impact upon the immune microenvironment. Importantly we will explore how MDSCs may modulate current immunotherapies and their impact upon the success of future immune-based therapies.

Abnormally primed CD8 T cells: The Achilles' heel of CHB

Chronic hepatitis B virus (HBV) infection continues to be a significant public health challenge, and more than 250 million people around world are infected with HBV. The clearance of HBV with virus-specific CD8 T cells is critical for a functional cure. However, naïve HBV-specific CD8 T cells are heavily hindered during the priming process, and this phenomenon is closely related to abnormal cell and signal interactions in the complex immune microenvironment. Here, we briefly summarize the recent progress in understanding the abnormal priming of HBV-specific CD8 T cells and some corresponding immunotherapies to facilitate their functional recovery, which provides a novel perspective for the design and development of immunotherapy for chronic HBV infection (CHB). Finally, we also highlight the balance between viral clearance and pathological liver injury induced by CD8 T-cell activation that should be carefully considered during drug development.

Selenium mitigates the inhibitory effect of TBBPA on NETs release by regulating ROS/MAPK pathways-induced carp neutrophil apoptosis and necroptosis

Tetrabromobisphenol A (TBBPA) is one of the most common and persistent organic pollutants found in the environment. When TBBPA is ingested by organisms through various pathways and stored in the body, it shows obvious harmful effects. Selenium (Se) works as an antioxidant in the body, allowing it to withstand the poisonous effects of dangerous substances. The effects and mechanisms of Se and TBBPA on carp neutrophil immune function, apoptosis, and necroptosis, however, are unknown. As a result, we created TBBPA exposure and Se antagonism models using carp neutrophils as study objects, and we investigated the expression of genes implicated in extracellular traps (NETs), cytokines, apoptosis, and necroptosis. The findings demonstrated that extracellular traps neutrophils in the TBBPA group displayed the inhibition of NETs, apoptosis, and necrosis, as well as an increase in Reactive oxygen species (ROS) levels and activation of the MAPK pathway. The expression of genes related to the mitochondrial apoptosis pathway (Bax, Cyt-c, Bcl-2 and Caspase-3) and necroptosis pathway (MLKL, RIPK1, RIPK3, Caspase-8 and FADD) were activated. The expression of inflammatory factors IL-1 and TNF-α were increased, and the expression of IL-2 and IFN-γ were decreased. But an appropriate concentration of Se can mitigate the effects of TBBPA. Our results suggest that Se can mitigate the inhibitory effect of TBBPA on NETs release by regulating apoptosis and necroptosis of carp neutrophil via ROS/MAPK pathways. These results provide a basis information for exploring the toxicity of TBBPA, and enrich the anti-toxicity mechanism of trace element Se in the body.

Methionine enkephalin inhibits colorectal cancer by remodeling the immune status of the tumor microenvironment

There is evidence that methionine enkephalin (MENK), an opioid peptide, promotes anti-tumor immune responses. In this study, the effect of MENK on colorectal cancer (CRC) and its mechanisms of action were examined in vivo. The intraperitoneal administration of 20 mg/kg MENK effectively inhibited MC38 subcutaneous colorectal tumor growth in mice. MENK inhibited tumor progression by increasing the immunogenicity and recognition of MC38 cells. MENK down-regulated the oncogene Kras and anti-apoptotic Bclxl and Bcl2, suppressed Il1b, Il6, iNOS, and Arg1 (encoding inflammatory cytokines), and increased Il17a and Il10 levels. MENK promoted a tumor suppressive state by decreasing the immune checkpoints Pd-1, Pd-l1, Lag3, Flgl1, and 2b4 in CRC. MENK also altered the immune status of the tumor immune microenvironment (TIME). It increased the infiltration of M1-type macrophages, CD8⁺T cells, and CD4⁺T cells and decreased the proportions of G-MDSCs, M-MDSCs, and M2-type macrophages. MENK accelerated CD4⁺T_EM and CD8⁺T_EM cell activation in the TIME and up-regulated IFN-γ, TNF-α, and IL-17A in CD4⁺T cells and Granzyme B in CD8⁺T cells. In addition, analyses of PD-1 and PD-L1 expression indicated that MENK promoted the anti-tumor immune response mediated by effector T cells. Finally, OGFr was up-regulated at the protein and mRNA levels by MENK, and the inhibitory effects of MENK on tumor growth were blocked by NTX, a specific blocker of OGFr. These finding indicate that MENK remodels the TIME in CRC to inhibit tumor progression by binding to OGFr. MENK is a potential therapeutic agent for CRC, especially for improving the efficacy of immunotherapy.

Plasticity of monocytes and macrophages in cirrhosis of the liver

Cirrhosis of the liver is a systemic condition with raising prevalence worldwide. Patients with cirrhosis are highly susceptible to develop bacterial infections leading to acute decompensation and acute-on-chronic liver failure both associated with a high morbidity and mortality and sparse therapeutic options other than transplantation. Mononuclear phagocytes play a central role in innate immune responses and represent a first line of defence against pathogens. Their function includes phagocytosis, killing of bacteria, antigen presentation, cytokine production as well as recruitment and activation of immune effector cells. Liver injury and development of cirrhosis induces activation of liver resident Kupffer cells and recruitment of monocytes to the liver. Damage- and pathogen-associated molecular patterns promote systemic inflammation which involves multiple compartments besides the liver, such as the circulation, gut, peritoneal cavity and others. The function of circulating monocytes and tissue macrophages is severely impaired and worsens along with cirrhosis progression. The underlying mechanisms are complex and incompletely understood. Recent 'omics' technologies help to transform our understanding of cellular diversity and function in health and disease. In this review we point out the current state of knowledge on phenotypical and functional changes of monocytes and macrophages during cirrhosis evolution in different compartments and their role in disease progression. We also discuss the value of potential prognostic markers for cirrhosis-associated immuneparesis, and future immunotherapeutic strategies that may reduce the need for transplantation and death.