MicroRNA miR-155 affects antiviral effector and effector Memory CD8 T cell differentiation

The ability of microRNAs to regulate the immune response in ischemia/reperfusion inflammatory pathways

MicroRNAs play a crucial role in regulating the immune responses induced by ischemia/reperfusion injury. Through their ability to modulate gene expression, microRNAs adjust immune responses by targeting specific genes and signaling pathways. This review focuses on the impact of microRNAs on the inflammatory pathways triggered during ischemia/reperfusion injury and highlights their ability to modulate inflammation, playing a critical role in the pathophysiology of ischemia/reperfusion injury. Dysregulated expression of microRNAs contributes to the pathogenesis of ischemia/reperfusion injury, therefore targeting specific microRNAs offers an opportunity to restore immune homeostasis and improve patient outcomes. Understanding the complex network of immunoregulatory microRNAs could provide novel therapeutic interventions aimed at attenuating excessive inflammation and preserving tissue integrity.

Functionalized nanowires for miRNA-mediated therapeutic programming of naïve T cells

Cellular programming of naïve T cells can improve the efficacy of adoptive T-cell therapy. However, the current ex vivo engineering of T cells requires the pre-activation of T cells, which causes them to lose their naïve state. In this study, cationic-polymer-functionalized nanowires were used to pre-program the fate of primary naïve CD8+ T cells to achieve a therapeutic response in vivo. This was done by delivering single or multiple microRNAs to primary naïve mouse and human CD8+ T cells without pre-activation. The use of nanowires further allowed for the delivery of large, whole lentiviral particles with potential for long-term integration. The combination of deletion and overexpression of miR-29 and miR-130 impacted the ex vivo T-cell differentiation fate from the naïve state. The programming of CD8+ T cells using nanowire-delivered co-delivery of microRNAs resulted in the modulation of T-cell fitness by altering the T-cell proliferation, phenotypic and transcriptional regulation, and secretion of effector molecules. Moreover, the in vivo adoptive transfer of murine CD8+ T cells programmed through the nanowire-mediated dual delivery of microRNAs provided enhanced immune protection against different types of intracellular pathogen (influenza and Listeria monocytogenes). In vivo analyses demonstrated that the simultaneous alteration of miR-29 and miR-130 levels in naïve CD8+ T cells reduces the persistence of canonical memory T cells whereas increases the population of short-lived effector T cells. Nanowires could potentially be used to modulate CD8+ T-cell differentiation and achieve a therapeutic response in vivo without the need for pre-activation.

MicroRNA‑155 modulation of CD8+ T‑cell activity personalizes response to disease‑modifying therapies of patients with relapsing‑remitting multiple sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disease where activated immune cells can attack oligodendrocytes causing damage to the myelin sheath. Several molecular mechanisms are responsible for the auto-activation of immune cells such as RNA interference (RNAi) through microRNAs (miRNAs or miRs). In the present study, the role of miR-155 in regulating CD8⁺ T-cell activity in patients with relapsing-remitting multiple sclerosis (RRMS) was investigated, in terms of its migratory functions with regard to intracellular adhesion molecule-1 (ICAM1) and integrin subunit β2 (ITGB2), and its cytotoxic proteins, perforin and granzyme B. Gene expression of miR-155, ICAM1, ITGB2, perforin and granzyme B was evaluated following epigenetic modulations using reverse transcription-quantitative polymerase chain reaction in CD8⁺ T-cells isolated from blood samples of patients with RRMS and compared to healthy controls. The ectopic expression of miR-155 resulted in a persistent downregulation in all genes of interest related to CD8⁺ T-cell activation that were positively correlated with the Expanded Disability Status Scale of patients. The present study revealed the interplay between miR-155, ICAM1, and ITGB2, shedding light on their beneficial use as possible therapeutic regulators and diagnostic biomarkers of disease. Moreover, epigenetic modulations enhancing the efficacy of disease-modifying therapies (DMTs) may be employed as personalized therapy, to decrease the side effects of DMTs and improve the outcomes of patients.

Antigen-specific downregulation of miR-150 in CD4 T cells promotes cell survival

MicroRNA-150 (miR-150) has been shown to play a general role in the immune system, but very little is known about its role on CD4+ T cell responses. During T cell responses against superantigen Staphylococcal Enterotoxin A, miR-150 expression was down-regulated in antigen-specific CD4+ T cells but up-regulated in CD8+ T cells. CD4+ and CD8+ T cell clonal expansion was greater in miR-150-KO mice than in WT mice, but miR-150 selectively repressed IL-2 production in CD4+ T cells. Transcriptome analysis of CD4+ T cells demonstrated that apoptosis and mTOR pathways were highly enriched in the absence of miR-150. Mechanistic studies confirmed that miR-150 promoted apoptosis specifically in antigen-specific CD4+ T cells, but not in bystander CD4+ nor in CD8+ T cells. Furthermore, inhibition of mTOR-linked mitochondrial superoxidedismutase-2 increased apoptosis in miR-150-/- antigen-specific CD4+ T. Thus, miR-150 impacts CD4+ T cell helper activity by attenuating IL-2 production along with clonal expansion, and suppresses superoxidedismutase to promote apoptosis.

MIR155HG Plays a Bivalent Role in Regulating Innate Antiviral Immunity by Encoding Long Noncoding RNA-155 and microRNA-155-5p

MIR155HG encodes a precursor RNA of microRNA-155 (miRNA-155). We previously identified this RNA also as a long noncoding RNA (lncRNA) that we call lncRNA-155. To define the functions of miRNA-155 and lncRNA-155, we generated miRNA-155 knockout (KO) mice lacking only 19 bp of the miRNA-155 core sequence without affecting the expression of lncRNA-155. Surprisingly, compared with the miRNA-155KO mice, previously generated lncRNA-155KO mice were more susceptible to both influenza virus (RNA virus) and pseudorabies virus (DNA virus) infection, as characterized by lower survival rate, higher body weight loss, and higher viral load. We found that miRNA-155-5p enhanced antiviral responses by positively regulating activation of signal transducer and activator of transcription 1 (STAT1), but the STAT1 activity differed greatly in the animals (lncRNA-155KO < miRNA-155KO < wild type). In line with this, expression levels of several critical interferon-stimulated genes (ISGs) were also significantly different (lncRNA-155KO < miRNA-155KO < wild type). We found that lncRNA-155 augmented interferon beta (IFN-β) production during the viral infection, but miRNA-155 had no significant effect on the virus-induced IFN-β expression. Furthermore, we observed that lncRNA-155 loss in mice resulted in dramatic inhibition of virus-induced activation of interferon regulatory factor 3 compared to both miRNA-155KO and wild-type (WT) animals. Moreover, lncRNA-155 still significantly suppressed the viral infection even though the miRNA-155 derived from lncRNA-155 was deleted or blocked. These results reveal that lncRNA-155 and miRNA-155 regulate antiviral responses through distinct mechanisms, indicating a bivalent role for MIR155HG in innate immunity. IMPORTANCE Here, we found that lncRNA-155KO mice lacking most of the lncRNA-155 sequences along with pre-miRNA-155, were more susceptible to influenza virus or pseudorabies virus infection than miRNA-155KO mice lacking only 19 bp of the miRNA-155 core sequence without affecting the expression of lncRNA-155, as evidenced by faster body weight loss, poorer survival, and higher viral load, suggesting an additional role of lncRNA-155 in regulating viral pathogenesis besides via processing miRNA-155. Congruously, miRNA-155-deleted lncRNA-155 significantly attenuated the viral infection. Mechanistically, we demonstrated miRNA-155-5p potentiated antiviral responses by promoting STAT1 activation but could not directly regulate the IFN-β expression. In contrast, lncRNA-155 enhanced virus-induced IFN-β production by regulating the activation of interferon regulatory factor 3. This finding reveals a bivalent role of MIR155HG in regulating antiviral responses through encoding lncRNA-155 and miRNA-155-5p and provides new insights into complicated mechanisms underlying interaction between virus and host innate immunity.

miR-150 promotes progressive T cell differentiation via inhibiting FOXP1 and RC3H1

T cells used in immune cell therapy, represented by T cell receptor therapy (TCR-T), are usually activated and proliferated in vitro and are induced to a terminally differentiated phenotype, with limited viability after transfusion back into the body. T cells exhibited a robust proliferative potential and in vivo viability in the early stages of progressive differentiation. In this study, we identified microRNAs that regulate T cell differentiation. After microRNA sequencing of the four subsets: Naïve T cells (T_N), stem cell-like memory T cells (T_SCM), central memory T cells (T_CM）, and effector memory T cells (T_EM), miR-150 was identified as the most highly expressed miRNA among the four subsets and was lowly expressed in the T_SCM cells. We predicted the target genes of miR-150 miRNA and performed Gene Ontology and Kyoto Encyclopaedia of Genes and Genomes analyses. We observed that the target genes of miR-150 were enriched in pathways associated with T-cell differentiation. FOXP1 and RC3H1 were identified as key target genes of miR-150 in the regulation of T-cell function. We examined the effects of miR-150 on the differentiation and function of healthy donor T-cells. We observed that miR-150 overexpression promoted T-cell differentiation to effector T-cells and effector memory T-cells, enhanced apoptosis, inhibited cell proliferation and increased secretion of pro-inflammatory cytokines such as IFN-γ and TNF-α. In addition, the expressions of early differentiation-related genes (ACTN1, CERS6, BCL2, and EOMES), advanced differentiation-related genes (KLRG1), and effector-function-related genes (PRF1 and GZMB) were significantly decreased after overexpression of miR-150. Collectively, our results suggested that miR-150 can promote progressive differentiation of T cells and the downmodulation of miR-150 expression while performing adoptive immunotherapy may inhibit T-cell differentiation and increase the proliferative potential of T cells.

Perspectives on the Use of Small Noncoding RNAs as a Therapy for Severe Virus-Induced Disease Manifestations and Late Complications

Many viruses appear each year. Some of these viruses result in severe disease and even death. The frequency of epidemics and pandemics is growing at an alarming rate. The lack of virus-specific etiopathogenic drugs necessitates the search for new tools for the complex treatment of severe viral diseases and their late complications. Small noncoding RNAs and their antagonists may be effective therapeutic tools for preventing virus-induced damage to targeted epithelial cells and surrounding tissues in the manifestation stage. Moreover, sncRNAs could interfere with the virus-interacting host genes that trigger the malignant transformation of target cells as a late complication of severe viral diseases.

Molecular Mechanisms of Immunosenescene and Inflammaging: Relevance to the Immunopathogenesis and Treatment of Multiple Sclerosis

Aging is characterized, amongst other features, by a complex process of cellular senescence involving both innate and adaptive immunity, called immunosenescence and associated to inflammaging, a low-grade chronic inflammation. Both processes fuel each other and partially explain increasing incidence of cancers, infections, age-related autoimmunity, and vascular disease as well as a reduced response to vaccination. Multiple sclerosis (MS) is a lifelong disease, for which considerable progress in disease-modifying therapies (DMTs) and management has improved long-term survival. However, disability progression, increasing with age and disease duration, remains. Neurologists are now involved in caring for elderly MS patients, with increasing comorbidities. Aging of the immune system therefore has relevant implications for MS pathogenesis, response to DMTs and the risks mediated by these treatments. We propose to review current evidence regarding markers and molecular mechanisms of immunosenescence and their relevance to understanding MS pathogenesis. We will focus on age-related changes in the innate and adaptive immune system in MS and other auto-immune diseases, such as systemic lupus erythematosus and rheumatoid arthritis. The consequences of these immune changes on MS pathology, in interaction with the intrinsic aging process of central nervous system resident cells will be discussed. Finally, the impact of immunosenescence on disease evolution and on the safety and efficacy of current DMTs will be presented.

MicroRNA-139 Expression Is Dispensable for the Generation of Influenza-Specific CD8+ T Cell Responses

MicroRNAs (miRNAs/miRs) are small, endogenous noncoding RNAs that are important post-transcriptional regulators with clear roles in the development of the immune system and immune responses. Using miRNA microarray profiling, we characterized the expression profile of naive and in vivo generated murine effector antiviral CD8⁺ T cells. We observed that out of 362 measurable mature miRNAs, 120 were differentially expressed by at least 2-fold in influenza-specific effector CD8⁺ CTLs compared with naive CD8⁺ T cells. One miRNA found to be highly downregulated on both strands in effector CTLs was miR-139. Because previous studies have indicated a role for miR-139-mediated regulation of CTL effector responses, we hypothesized that deletion of miR-139 would enhance antiviral CTL responses during influenza virus infection. We generated miR-139^-/- mice or overexpressed miR-139 in T cells to assess the functional contribution of miR-139 expression in CD8⁺ T cell responses. Our study demonstrates that the development of naive T cells and generation or differentiation of effector or memory CD8⁺ T cell responses to influenza virus infection are not impacted by miR-139 deficiency or overexpression; yet, miR-139^-/- CD8⁺ T cells are outcompeted by wild-type CD8⁺ T cells in a competition setting and demonstrate reduced responses to Listeria monocytogenes Using an in vitro model of T cell exhaustion, we confirmed that miR-139 expression similarly does not impact the development of T cell exhaustion. We conclude that despite significant downregulation of miR-139 following in vivo and in vitro activation, miR-139 expression is dispensable for influenza-specific CTL responses.

DNA Methylation and Immune Memory Response

The generation of memory is a cardinal feature of the adaptive immune response, involving different factors in a complex process of cellular differentiation. This process is essential for protecting the second encounter with pathogens and is the mechanism by which vaccines work. Epigenetic changes play important roles in the regulation of cell differentiation events. There are three types of epigenetic regulation: DNA methylation, histone modification, and microRNA expression. One of these epigenetic changes, DNA methylation, occurs in cytosine residues, mainly in CpG dinucleotides. This brief review aimed to analyse the literature to verify the involvement of DNA methylation during memory T and B cell development. Several studies have highlighted the importance of the DNA methyltransferases, enzymes that catalyse the methylation of DNA, during memory differentiation, maintenance, and function. The methylation profile within different subsets of naïve activated and memory cells could be an interesting tool to help monitor immune memory response.

MicroRNA-155 and antiviral immune responses

The microRNA, miR-155 regulates both adaptive and innate immune responses. In viral infections, miR-155 can affect both innate immunity (interferon response, natural killer cell activity, and macrophage polarization) and adaptive immunity (including generation of anti-viral antibodies, CD8⁺ cytotoxic T lymphocytes, Th17, Th2, Th1, Tfh and Treg cells). In many viral infections, the proper and timely regulation of miR-155 expression is critical for the induction of an effective anti-virus immune response and viral clearance without any harmful immunopathologic consequences. MiR-155 may also exert pro-viral effects, mainly through the inhibition of the anti-viral interferon response. Thus, dysregulated expression of miR-155 can result in virus persistence and disruption of the normal response to viral infections. This review provides a thorough discussion of the role of miR-155 in immune responses and immunopathologic reactions during viral infections, and highlights its potential as a therapeutic target.

The Effect of Immunosuppressive Adjuvant Kynurenine on Type 1 Diabetes Vaccine

Inducing antigen-specific tolerance is a promising treatment for preventing or reversing Type 1 diabetes (T1D). In contrast to a vaccine that induces immune responses against pathogens, a tolerogenic vaccine can suppress immunity against antigens causing diseases by administrating a mixture of self-antigens with an adjuvant that decreases the strength of antigen-specific response. Kynurenine (Kyn) is an endogenous substance that can inhibit the natural killer cell and T cell proliferation and promote the differentiation of naïve T cells into regulatory T cells (T_regs). In this study, we evaluated the efficacy of Kyn as a novel suppressive adjuvant. Kyn was co-immunized with GAD65 phage vaccine to induce T_reg cells and tolerogenic responses for the prevention of T1D in NOD mouse model. Mice were subcutaneously immunized two times with 10¹¹ Pfu (100μL,10¹² Pfu/ml) GAD65 phage vaccine doses mixed with 200 μg of Kyn. Serum antibodies and cytokines were detected by ELISA and electrochemiluminescence, respectively. Flow cytometry assay was used to analyze DC and Treg. MTS was used for the analysis of spleen lymphocyte proliferation. RNA sequencing was used to investigate mRNA and miRNA expression profiles in spleen lymphocytes. Compared to GAD65 phage vaccine alone, co-immunization of Kyn and GAD65 phage vaccine resulted in the prevention of hyperglycemia in 60% of mice for at least one month. Further, Kyn enhances GAD65-specific Th2-mediated immune responses; regulates the Th1/Th2 imbalance and increases the secretion of Th2 cytokines and the number of CD4⁺CD25⁺Foxp3⁺T cells; suppresses DC maturation and GAD65-specific T lymphocyte proliferation. Moreover, we integrated Kyn related miRNA and mRNA expression profiles obtained from the spleen lymphocyte RNA-sequencing which was stimulated by Kyn in vitro. These data provide an important basis for understanding the mechanisms underlying Kyn as an immunosuppressive adjuvant which regulated the immune response. These findings suggest that Kyn can serve as an effective suppressive adjuvant candidate for Type 1 diabetes vaccines.

The emerging role of microRNA in regulating the mTOR signaling pathway in immune and inflammatory responses

The mechanistic/mammalian target of rapamycin (mTOR) is considered to be an atypical protein kinase that plays a critical role in integrating different cellular and environmental inputs in the form of growth factors, nutrients and energy and, subsequently, in regulating different cellular events, including cell metabolism, survival, homeostasis, growth and cellular differentiation. Immunologically, mTOR is a critical regulator of immune function through integrating numerous signals from the immune microenvironment, which coordinates the functions of immune cells and T cell fate decisions. The crucial role of mTOR in immune responses has been lately even more appreciated. MicroRNAs (miRNAs) are endogenous, small, noncoding single-stranded RNAs that act as molecular regulators involved in multiple processes during immune cells development, homeostasis, activation and effector polarization. Several studies have recently indicated that a range of miRNAs are involved in regulating the phosphoinositide 3-kinase/protein kinase B/mTOR (PI3K/AKT/mTOR) signaling pathway by targeting multiple components of this signaling pathway and modulating the expression and function of these targets. Current evidence has revealed the interplay between miRNAs and the mTOR pathway circuits in various immune cell types. The expression of individual miRNA can affect the function of mTOR signaling to determine the cell fate decisions in immune responses through coordinating immune signaling and cell metabolism. Dysregulation of the mTOR pathway/miRNAs crosstalk has been reported in cancers and various immune-related diseases. Thus, expression profiles of dysregulated miRNAs could influence the mTOR pathway, resulting in the promotion of aberrant immunity. This review summarizes the latest information regarding the reciprocal role of the mTOR signaling pathway and miRNAs in orchestrating immune responses.

Diurnal Variation of Plasma Extracellular Vesicle Is Disrupted in People Living with HIV

BACKGROUND

Several types of extracellular vesicles (EVs) secreted by various immune and non-immune cells are present in the human plasma. We previously demonstrated that EV abundance and microRNA content change in pathological conditions, such as HIV infection. Here, we investigated daily variations of large and small EVs, in terms of abundance and microRNA contents in people living with HIV (PLWH) receiving antiretroviral therapy (HIV+ART) and uninfected controls (HIV-).

METHODS

Venous blood samples from n = 10 HIV+ART and n = 10 HIV- participants were collected at 10:00 and 22:00 the same day. Large and small plasma EVs were purified, counted, and the mature miRNAs miR-29a, miR-29b, miR-92, miR-155, and miR-223 copies were measured by RT-PCR.

RESULTS

Large EVs were significantly bigger in the plasma collected at 10:00 versus 22:00 in both groups. There was a significant day-night increase in the quantity of 5 miRNAs in HIV- large EVs. In HIV+ART, only miR-155 daily variation has been observed in large EVs. Finally, EV-miRNA content permits to distinguish HIV- to HIV+ART in multivariate analysis.

CONCLUSION

These results point that plasma EV amount and microRNA contents are under daily variation in HIV- people. This new dynamic measure is disrupted in PLWH despite viral-suppressive ART. This study highlights a significant difference concerning EV abundance and their content measured at 22:00 between both groups. Therefore, the time of blood collection must be considered in the future for the EV as biomarkers.

MicroRNA-155 Regulates MAIT1 and MAIT17 Cell Differentiation

Mucosal-associated invariant T (MAIT) cells are innate-like T cells that develop in the thymus through three maturation stages to acquire effector function and differentiate into MAIT1 (T-bet⁺) and MAIT17 (RORγt⁺) subsets. Upon activation, MAIT cells release IFN-γ and IL-17, which modulate a broad spectrum of diseases. Recent studies indicate defective MAIT cell development in microRNA deficient mice, however, few individual miRNAs have been identified to regulate MAIT cells. MicroRNA-155 (miR-155) is a key regulator of numerous cellular processes that affect some immune cell development, but its role in MAIT cell development remains unclear. To address whether miR-155 is required for MAIT cell development, we performed gain-of-function and loss-of-function studies. We first generated a CD4Cre.miR-155 knock-in mouse model, in which miR-155 is over-expressed in the T cell lineage. We found that overexpression of miR-155 significantly reduced numbers and frequencies of MAIT cells in all immune organs and lungs and blocked thymic MAIT cell maturation through downregulating PLZF expression. Strikingly, upregulated miR-155 promoted MAIT1 differentiation and blocked MAIT17 differentiation, and timely inducible expression of miR-155 functionally inhibited peripheral MAIT cells secreting IL-17. miR-155 overexpression also increased CD4^–CD8⁺ subset and decreased CD4^–CD8^– subset of MAIT cells. We further analyzed MAIT cells in conventional miR-155 knockout mice and found that lack of miR-155 also promoted MAIT1 differentiation and blocked MAIT17 differentiation but without alteration of their overall frequency, maturation and function. Overall, our results indicate that adequate miR-155 expression is required for normal MAIT1 and MAIT17 cell development and function.

MicroRNA-155 Controls iNKT Cell Development and Lineage Differentiation by Coordinating Multiple Regulating Pathways

The development of invariant natural killer T (iNKT) cells requires a well-attuned set of transcription factors, but how these factors are regulated and coordinated remains poorly understood. MicroRNA-155 (miR-155) is a key regulator of numerous cellular processes that affects cell development and homeostasis. Here, we found that miR-155 was highly expressed in early iNKT cells upon thymic selection, and then its expression is gradually downregulated during iNKT cell development. However, the mice with miR-155 germline deletion had normal iNKT cell development. To address if downregulated miR-155 is required for iNKT cell development, we made a CD4Cre.miR-155 knock-in (KI) mouse model with miR-155 conditional overexpression in the T cell lineage. Upregulated miR-155 led to interruption of iNKT cell development, diminished iNKT17 and iNKT1 cells, augmented iNKT2 cells, and these defects were cell intrinsic. Furthermore, defective iNKT cells in miR-155KI mice resulted in the secondary innate-like CD8 T cell development. Mechanistically, miR-155 modulated multiple targets and signaling pathways to fine tune iNKT cell development. MiR-155 modulated Jarid2, a critical component of a histone modification complex, and Tab2, the upstream activation kinase complex component of NF-κB, which function additively in iNKT development and in promoting balanced iNKT1/iNKT2 differentiation. In addition, miR-155 also targeted Rictor, a signature component of mTORC2 that controls iNKT17 differentiation. Taken together, our results indicate that miR-155 serves as a key epigenetic regulator, coordinating multiple signaling pathways and transcriptional programs to precisely regulate iNKT cell development and functional lineage, as well as secondary innate CD8 T cell development.

MicroRNA control of B cell tolerance, autoimmunity and cancer

Since the discovery of the first microRNA (miRNA) in 1993, thousands of miRNAs have been identified in humans and mice and many of them have been shown to control a large variety of cellular processes in different cell types including those composing the immune system. MicroRNAs regulate virtually all aspects of immune cell development, differentiation and function. Studies have shown that these molecules are involved in the maintenance of lymphocyte tolerance and, when dysregulated, promote the development of autoimmune diseases. In this review, we focus on the current knowledge about the roles of miRNAs in B cell tolerance and their contribution to autoimmunity, highlighting additional roles for some of these miRNAs in T cell tolerance. Finally, we will comment on miRNAs that promote both autoimmunity and lymphoma.

The emerging role of microRNAs in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection

The novel coronavirus disease 2019 (COVID-19) pandemic has imposed significant public health problems for the human populations worldwide after the 1918 influenza A virus (IVA) (H1N1) pandemic. Although numerous efforts have been made to unravel the mechanisms underlying the coronavirus, a notable gap remains in our perception of the COVID-19 pathogenesis. The innate and adaptive immune systems have a pivotal role in the fate of viral infections, such as COVID-19 pandemic. MicroRNAs (miRNAs) are known as short noncoding RNA molecules and appear as indispensable governors of almost any cellular means. Several lines of evidence demonstrate that miRNAs participate in essential mechanisms of cell biology, regulation of the immune system, and the onset and progression of numerous types of disorders. The immune responses to viral respiratory infections (VRIs), including influenza virus (IV), respiratory syncytial virus (RSV), and rhinovirus (RV), are correlated with the ectopic expression of miRNAs. Alterations of the miRNA expression in epithelial cells may contribute to the pathogenesis of chronic and acute airway infections. Hence, analyzing the role of these types of nucleotides in antiviral immune responses and the characterization of miRNA target genes might contribute to understanding the mechanisms of the interplay between the host and viruses, and in the future, potentially result in discovering therapeutic strategies for the prevention and treatment of acute COVID-19 infection. In this article, we present a general review of current studies concerning the function of miRNAs in different VRIs, particularly in coronavirus infection, and address all available therapeutic prospects to mitigate the burden of viral infections.

Serum levels of hsa-miR-16-5p, hsa-miR-29a-3p, hsa-miR-150-5p, hsa-miR-155-5p and hsa-miR-223-3p and subsequent risk of chronic lymphocytic leukemia in the EPIC study

Chronic lymphocytic leukemia (CLL) is an incurable disease accounting for almost one-third of leukemias in the Western world. Aberrant expression of microRNAs (miRNAs) is a well-established characteristic of CLL, and the robust nature of miRNAs makes them eminently suitable liquid biopsy biomarkers. Using a nested case-control study within the European Prospective Investigation into Cancer and Nutrition (EPIC), the predictive values of five promising human miRNAs (hsa-miR-16-5p, hsa-miR-29a-3p, hsa-miR-150-5p, hsa-miR-155-5p and hsa-miR-223-3p), identified in a pilot study, were examined in serum of 224 CLL cases (diagnosed 3 months to 18 years after enrollment) and 224 matched controls using Taqman based assays. Conditional logistic regressions were applied to adjust for potential confounders. The median time from blood collection to CLL diagnosis was 10 years (p25-p75: 7-13 years). Overall, the upregulation of hsa-miR-150-5p, hsa-miR-155-5p and hsa-miR-29a-3p was associated with subsequent risk of CLL [OR1∆Ct-unit increase (95%CI) = 1.42 (1.18-1.72), 1.64 (1.31-2.04) and 1.75 (1.31-2.34) for hsa-miR-150-5p, hsa-miR-155-5p and hsa-miR-29a-3p, respectively] and the strongest associations were observed within 10 years of diagnosis. However, the predictive performance of these miRNAs was modest (area under the curve <0.62). hsa-miR-16-5p and hsa-miR-223-3p levels were unrelated to CLL risk. The findings of this first prospective study suggest that hsa-miR-29a, hsa-miR-150-5p and hsa-miR-155-5p were upregulated in early stages of CLL but were modest predictive biomarkers of CLL risk.

Differential expression of miRNAs and their target genes: Exploring a new perspective of acquired aplastic anemia pathogenesis

INTRODUCTION

MicroRNAs (miRNAs) play a critical role in orchestrating T cell differentiation and activation and may thus play a vital role in acquired aplastic anemia (aAA). The study aimed to evaluate the differential expression of selected miRNAs and their relevant target genes in bone marrow samples of aAA patients.

METHODS

Differential expression of 8 miRNAs viz; hsa-miR-126-3p, miR-145-5p, miR-155-5p, miR-150-5p, miR-146b-5p, miR-34a, miR-29a, and miR-29b was evaluated in the bone marrow mononuclear cells of aAA patients. TaqMan microRNA assay was performed for preparing the cDNA of specific miRNA, followed by expression analysis using qRT-PCR. Data were normalized using two endogenous controls, RNU6B and RNU48. Delta-delta CT method was used to calculate the fold change (FC) of miRNA expression in individual samples, and a FC of >1.5 was taken as significant. Target genes of these miRNAs were evaluated by qRT-PCR.

RESULTS

Thirty five samples of aAA patients and 20 controls were evaluated. Irrespective of the disease severity, five miRNAs were found to be deregulated; miR-126 (FC-0.348; P-value-.0001) and miR-145 (FC-0.31; P-value-.0001) were downregulated, while miR-155 (FC-3.50; P-value-.0067), miR-146 (FC-3.13; P-value-.0105), and miR-150 (FC-5.78; P-value-.0001) were upregulated. Target gene study revealed an upregulation of PIK3R2, MYC, SOCS1, and TRAF-6, and downregulation of MYB.

CONCLUSION

This is the first study from the Indian subcontinent demonstrating the presence of altered miRNA expression in the bone marrow samples of aAA patients, suggesting their role in the pathogenesis of the disease. A comprehensive study focusing on the effect of these miRNA-mRNA interactions is likely to open new avenues of management.

Airway mir-155 responses are associated with TH1 cytokine polarization in young children with viral respiratory infections

BACKGROUND

MicroRNAs (miRs) control gene expression and the development of the immune system and antiviral responses. MiR-155 is an evolutionarily-conserved molecule consistently induced during viral infections in different cell systems. Notably, there is still an unresolved paradox for the role of miR-155 during viral respiratory infections. Despite being essential for host antiviral TH1 immunity, miR-155 may also contribute to respiratory disease by enhancing allergic TH2 responses and NFkB-mediated inflammation. The central goal of this study was to define how airway miR-155 production is related to TH1, TH2, and pro-inflammatory cytokine responses during naturally occurring viral respiratory infections in young children.

METHODS

Normalized nasal airway levels of miR-155 and nasal protein levels of IFN-γ, TNF-α, IL-1β, IL-13, IL-4 were quantified in young children (≤2 years) hospitalized with viral respiratory infections and uninfected controls. These data were linked to individual characteristics and respiratory disease parameters.

RESULTS

A total of 151 subjects were included. Increased miR-155 levels were observed in nasal samples from patients with rhinovirus, RSV and all respiratory viruses analyzed. High miR-155 levels were strongly associated with high IFN-γ production, increased airway TH1 cytokine polarization (IFN-γ/IL-4 ratios) and increased pro-inflammatory responses. High airway miR-155 levels were linked to decreased respiratory disease severity in individuals with high airway TH1 antiviral responses.

CONCLUSIONS

The airway secretion of miR-155 during viral respiratory infections in young children is associated with enhanced antiviral immunity (TH1 polarization). Further studies are needed to define additional physiological roles of miR-155 in the respiratory tract of human infants and young children during health and disease.

Non-coding RNAs in CD8 T cell biology

CD8 T cells are among the most vigorous soldiers of the immune system that fight viral infections and cancer. CD8 T cell development, maintenance, activation and differentiation are under the tight control of multiple transcriptional and post-transcriptional networks. Over the last two decades it has become clear that non-coding RNAs (ncRNAs), which consist of microRNAs (miRNAs) and long ncRNAs (lncRNAs), have emerged as global biological regulators. While our understanding of the function of specific miRNAs has increased since the discovery of RNA interference, it is still very limited, and the field of lncRNAs is just starting to blossom. Here we will summarize our knowledge on the role of ncRNAs in CD8 T cell biology, including differentiation into memory and exhausted cells.

miR-155 Overexpression in OT-1 CD8+ T Cells Improves Anti-Tumor Activity against Low-Affinity Tumor Antigen

Therapy by adoptive transfer of ex vivo-expanded tumor-infiltrating or genetically modified T cells may lead to impressive clinical responses. However, there is a need to improve in vivo persistence and functionality of the transferred T cells, in particular, to face the highly immunosuppressive environment of solid tumors. Here, we investigate the potential of miR-155, a microRNA known to play an important role in CD8+ T cell fitness. We show that forced expression of miR-155 in tumor antigen-specific T cells improves the tumor control of B16 tumors expressing a low-affinity antigen ligand. Importantly, miR-155-transduced T cells exhibit increased proliferation and effector functions associated with a higher glycolytic activity independent of exogenous glucose. Altogether, these data suggest that miR-155 may optimize the antitumor activity of adoptively transferred low-affinity tumor-infiltrating lymphocytes (TILs), in particular, by rendering them more resistant to the glucose-deprived environment of solid tumors. Thus, transgenic expression of miR-155 may enable therapeutic targeting of self-antigen-specific T cells in addition to neoantigen-specific ones.

Overexpression of microRNA-155 enhances the efficacy of dendritic cell vaccine against breast cancer

MicroRNA 155 (miR-155) plays important roles in the regulation of the development and functions of a variety of immune cells. We previously revealed a vital role of miR-155 in regulating the function of dendritic cells (DCs) in breast cancer. miR-155 deficiency in DCs impaired their maturation, migration, cytokine production, and ability to activate T cells. In the current study, to exploit the therapeutic value of miR-155 for breast cancer, we examined the impact of overexpression of miR-155 on antitumor responses generated by DC vaccines. We boosted miR-155 expression in DCs by generating a miR-155 transgenic mouse strain (miR-155tg) or using lentivirus transduction. DCs overexpressing miR-155 exhibited enhanced functions in response to tumor antigens. Using miR-155 overexpressing DCs, we generated a DC vaccine and found that the vaccine resulted in enhanced antitumor immunity against established breast cancers in mice, demonstrated by increased effector T cells in the mice, suppressed tumor growth, and drastically reduced lung metastasis. Our current study suggests that in future DC vaccine development for breast cancer or other solid tumors, introducing forced miR155 overexpression in DCs via various approaches such as viral transduction or nanoparticle delivery, as well as including other adjuvant agents such as TLR ligands or immune stimulating cytokines, may unleash the full therapeutic potential of the DC vaccines.

MicroRNA regulation of CD8+ T cell responses

MicroRNAs (miRNAs) are a class of short noncoding RNAs that play critical roles in the regulation of a broad range of biological processes. Like transcription factors, miRNAs exert their effects by modulating the expression of networks of genes that operate in common or convergent pathways. CD8⁺ T cells are critical agents of the adaptive immune system that provide protection from infection and cancer. Here, we review the important roles of miRNAs in the regulation of CD8⁺ T cell biology and provide perspectives on the broader emerging principles of miRNA function.

Immune promotive effect of bioactive peptides may be mediated by regulating the expression of SOCS1/miR-155

The present study was designed to evaluate the effect of bioactive hepatic peptide (BHP) on the immune function of mice and to examine the mechanism mediated by the related factors cytokine suppressor of cytokine signaling 1 (SOCS1) and microRNA (miR)-155. The mice were divided into eight groups, including a normal mouse group, normal peptide groups (low-dose, mid-dose and high-dose), an immunosuppressed group, and immunosuppressed with peptide groups (low-dose, mid-dose and high-dose). The proliferative ability of splenic lymphocytes was determined in vitro using a Cell Counting kit-8 assay. Wright's staining was used to assess the phagocytic function of macrophages. Histological changes in the spleen were evaluated by hematoxylin-eosin staining. The relevant factors SOCS1/miR-155 were assessed by immunohistochemistry and reverse transcription fluorescence-quantitative polymerase chain reaction analysis. The levels of the cytokines TGF-β1, IL-10 and IL-17A were determined by enzyme-linked immunosorbent assay. First, the organ index, percentage of lymphocytes, phagocytosis experiments and splenic lymphocyte proliferation test results revealed that the immunodeficient mouse model had been successfully established. Second, compared with the control mice, the normal peptide group mice exhibited increased spleen and thymus indices, percentages of lymphocyte subsets, macrophage phagocytosis percentages, phagocytic indices, splenic lymphocyte proliferation and expression of miR-155; however, the expression of SOCS1 was decreased in the normal peptide groups to varying extents. In addition, the expression of SOCS1 was upregulated, whereas that of miR-155 was downregulated in the immunosuppressed group. Compared with the mice in the immunosuppressed group, the mice in the immunosuppressed with peptide groups had increased spleen and thymus indices, percentages of lymphocyte subsets, macrophage phagocytosis percentages, phagocytic indices, splenic lymphocyte proliferation and expression of miR-155; however, the expression of SOCS1 was decreased in the immunosuppressed with peptide groups to varying extents. Following treatment with BHP, the secretion of TGF-β1 in the spleen of the normal mice and immunosuppressed mice was significantly decreased, and the secretion of IL-10 was significantly increased. No significant difference in the expression of IL-17A was observed among the groups. In summary, BHP improved the immune function of the normal mice and immunosuppressed mice. This data provides a scientific basis for the development of bioactive peptide health products.

Increased Levels of miR-155 are Related to Higher T-Cell Activation in the Peripheral Blood of Patients with Chronic Hepatitis B

OBJECTIVES

MicroRNA-155 (miR-155) is an important regulator of immune responses in humans. However, its role in T-cell activation in hepatitis B virus (HBV) infection remains unclear.

MATERIALS AND METHODS

Eighty-one patients with chronic hepatitis B (CHB), 77 HBV carriers, and 51 healthy controls were recruited. HBV DNA and serologic tests were carried out for each subject. Levels of miR-155 in peripheral blood were detected by quantitative reverse transcription/polymerase chain reaction. Immune activation of T-cells was determined by detection of surface molecules CD38 and HLA-DR using flow cytometry.

RESULTS

We found higher miR-155 levels in CD4⁺ and CD8⁺ T-cells of CHB patients than HBV carriers or healthy controls (p < 0.01), moreover, miR-155 levels in the CD8⁺ T-cells of HBV carriers were higher than in healthy controls (p < 0.01). Furthermore, immune activation of CD4⁺ and CD8⁺ T-cells in CHB patients was much higher than in healthy controls (p < 0.01).

CONCLUSION

Our findings suggest that miR-155 expression positively correlates with T-cell activation, especially in CHB patients, and is a potential biomarker for immune activation and disease progression in HBV infection.

miR-143 Regulates Memory T Cell Differentiation by Reprogramming T Cell Metabolism

MicroRNAs are an important regulator for T cell immune response. In this study, we aimed to identify microRNAs with the potential to regulate T cell differentiation. The influence of miR-143 on differentiation and function of CD8+ T cells from healthy donors were detected, and it was found that miR-143 overexpression could significantly increase the differentiation of central memory T (Tcm) CD8+ cells, decrease cell apoptosis, and increase proinflammatory cytokine secretion. Furthermore, the specific killing of HER2-CAR T cells against esophageal cancer cell line TE-7 was enhanced by miR-143 overexpression. Glucose transporter 1 (Glut-1) was identified as the critical target gene of miR-143 in the role of T cell regulation. By inhibition Glut-1, miR-143 inhibited glucose uptake and glycolysis in T cell to regulated T cell differentiation. Tcm cell populations were also suppressed in parallel with the downregulation of miR-143 in tumor tissues from 13 patients with esophagus cancer. IDO and its metabolite kynurenine in the tumor microenvironment were screened as an upstream regulator of miR-143. IDO small interfering RNA significantly increased the expression of miR-143 and Tcm cell population. In conclusion, our results show that miR-143 enhanced antitumor effects of T cell by promoting memory T cell differentiation and metabolism reprogramming through Glut-1. Our findings will encourage the development of new strategies targeting miR-143 in both cancer cells and T cells.

MicroRNAs as modulators of T cell functions in cancer

MicroRNAs (miRNAs) are short RNA molecules that regulate gene expression post-transcriptionally. They have emerged as important modulators of T lymphocyte biology, influencing cell activation, differentiation and proliferation in response to environmental signals. Here, we will discuss how miRNAs expressed by T cells can influence two key aspects of tumorigenesis, namely the direct, cell-intrinsic oncogenic transformation of T lymphocytes, as well as the indirect effects on tumor growth mediated by altered immune surveillance. We will specifically focus on three miRNAs that have been shown to regulate different aspects of T cell biology in both physiological and pathological conditions, namely miR-155, miR-146a and miR-181a. We aim at providing examples of the fundamental importance of miRNA-regulated networks in determining the fate of T lymphocytes during oncogenic transformation and in the control of tumor growth.

Long-Term Persistence of Exhausted CD8 T Cells in Chronic Infection Is Regulated by MicroRNA-155

Persistent viral infections and tumors drive development of exhausted T (TEX) cells. In these settings, TEX cells establish an important host-pathogen or host-tumor stalemate. However, TEX cells erode over time, leading to loss of pathogen or cancer containment. We identified microRNA (miR)-155 as a key regulator of sustained TEX cell responses during chronic lymphocytic choriomeningitis virus (LCMV) infection. Genetic deficiency of miR-155 ablated CD8 T cell responses during chronic infection. Conversely, enhanced miR-155 expression promoted expansion and long-term persistence of TEX cells. However, rather than strictly antagonizing exhaustion, miR-155 promoted a terminal TEX cell subset. Transcriptional profiling identified coordinated control of cell signaling and transcription factor pathways, including the key AP-1 family member Fosl2. Overexpression of Fosl2 reversed the miR-155 effects, identifying a link between miR-155 and the AP-1 transcriptional program in regulating TEX cells. Thus, we identify a mechanism of miR-155 regulation of TEX cells and a key role for Fosl2 in T cell exhaustion.

miR-150 Regulates Memory CD8 T Cell Differentiation via c-Myb

MicroRNAs play an important role in T cell responses. However, how microRNAs regulate CD8 T cell memory remains poorly defined. Here, we found that miR-150 negatively regulates CD8 T cell memory in vivo. Genetic deletion of miR-150 disrupted the balance between memory precursor and terminal effector CD8 T cells following acute viral infection. Moreover, miR-150-deficient memory CD8 T cells were more protective upon rechallenge. A key circuit whereby miR-150 repressed memory CD8 T cell development through the transcription factor c-Myb was identified. Without miR-150, c-Myb was upregulated and anti-apoptotic targets of c-Myb, such as Bcl-2 and Bcl-xL, were also increased, suggesting a miR-150-c-Myb survival circuit during memory CD8 T cell development. Indeed, overexpression of non-repressible c-Myb rescued the memory CD8 T cell defects caused by overexpression of miR-150. Overall, these results identify a key role for miR-150 in memory CD8 T cells through a c-Myb-controlled enhanced survival circuit.

miR-150-Mediated Foxo1 Regulation Programs CD8+ T Cell Differentiation

MicroRNA (miR)-150 is a developmental regulator of several immune-cell types, but its role in CD8⁺ T cells is largely unexplored. Here, we show that miR-150 regulates the generation of memory CD8⁺ T cells. After acute virus infection, miR-150 knockout (KO) mice exhibited an accelerated differentiation of CD8⁺ T cells into memory cells and improved production of effector cytokines. Additionally, miR-150 KO CD8⁺ T cells displayed an enhanced recall response and improved protection against infections with another virus and bacteria. We found that forkhead box O1 (Foxo1) and T cell-specific transcription factor 1 (TCF1) are upregulated during the early activation phase in miR-150 KO CD8⁺ T cells and that miR-150 directly targets and suppresses Foxo1. These results suggest that miR-150-mediated suppression of Foxo1 regulates the balance between effector and memory cell differentiation, which might aid in the development of improved vaccines and T cell therapeutics.

Long Non-Coding RNAs: Novel Players in Regulation of Immune Response Upon Herpesvirus Infection

Herpesviruses have developed a variety of sophisticated immune evasion strategies to establish lifelong latent infection, including the use of long non-coding RNAs (lncRNAs). In this review, we summarize the lncRNA action modes, i.e., RNA-protein, RNA-RNA, and RNA-DNA interactions, involved in regulating important aspects of immunity by controlling gene expression at various stages. Upon herpesvirus infection, host lncRNAs, such as nuclear paraspeckle assembly transcript 1, negative regulator of antiviral, and B-cell integration cluster have been functionally characterized as negative or positive antiviral regulators in the immune response. Herpesviruses have also evolved multiple strategies to modulate the host immune response using lncRNAs, such as latency-associated transcript, β 2.7 RNA, 5 kb and 7.2 kb lncRNAs, Epstein-Barr virus-encoded non-coding RNA, BamH I-A rightward transcripts, polyadenylated nuclear, and herpesvirus saimiri U-rich RNAs. We discuss the various mechanisms of immune-related lncRNAs, and their diversified and important functions in the modulation of innate and adaptive immunity upon herpesvirus infection as well as in host-pathogen interactions, which will facilitate our understanding of rational design of novel strategies to combat herpesvirus infection.

Peripheral blood lymphocyte subset levels differ in patients with hepatocellular carcinoma

We investigated the levels of target lymphocyte subsets in peripheral blood lymphocyte samples from patients with hepatocellular carcinoma (HCC). A total of 715 high-risk patients with primary HCC were recruited in Guangxi, China as the case group. The control group included 100 patients who received health examinations at the same hospital during the same period. Fasting elbow venous blood (10 mL) was collected from each participant, and flow cytometry was used to detect the levels of NK cells and CD3⁺, CD4⁺ and CD19⁺ T cells in peripheral blood samples. All included patients with prmary HCC were treated by surgical resection, and followed up for one year. The levels of CD19⁺ and NK cells were lower in cases than in controls (both P < 0.05). In addition, the level of CD8⁺ cells was greater in the case group than in the control group (P < 0.05). In the high-HCC-risk population, CD8⁺, CD19⁺ and NK cell levels all differed between male and female patients, patients in TNM stages I–II and stages III–IV, patients with and without extrahepatic metastasis, and patients with and without HBV infection (all P < 0.05). After follow-up, detected recurrence and survival rate was 33.71% and 83.64%, respectively. CD8⁺ levels was reduced following surgical resection, whereas the levels of CD19⁺ and NK cells were increased (all P < 0.05). In conclusion, altered levels of CD8⁺, CD19⁺ and NK cell levels may be used as reference values for monitoring immune function in certain populations with high HCC risk, and as potential evidence for the clinical diagnosis and treatment of HCC.

Deregulation of microRNA-155 and its transcription factor NF-kB by polychlorinated biphenyls during viral infections

Polychlorinated biphenyls (PCBs), and similar environmental contaminants, have been linked to virus outbreaks and increased viral induced mortality since the 1970s. Yet the mechanisms behind this increased susceptibility remain elusive. It has recently been illustrated that the innate immune viral detection system is tightly regulated by small non-coding RNAs, including microRNAs (miRNAs). For virus infections miRNA-155 expression is an important host response against infection, and deregulation of this miRNA is closely associated with adverse outcomes. Thus, we designed a targeted in vitro study using primary chicken fibroblasts, first exposed to a mixture of PCBs (Arochlor-1250) before being stimulated with a synthetic RNA virus (poly I:C), to determine if PCBs have the potential to deregulate miRNA-155. In this paper, we provide the first data for the deregulation of miRNA-155 when a host is exposed to a mixture of PCBs before a virus infection. Thus, we provide important evidence that PCBs can be involved in the deregulation of important miRNA pathways involved in the immune system; thereby demonstrating novel insights into the mechanism of PCB toxicity on the immune system.

The Transcription Factor T-Bet Is Regulated by MicroRNA-155 in Murine Anti-Viral CD8+ T Cells via SHIP-1

We report here that the expression of the transcription factor T-bet, which is known to be required for effector cytotoxic CD8⁺ T lymphocytes (CTL) generation and effector memory cell formation, is regulated in CTL by microRNA-155 (miR-155). Importantly, we show that the proliferative effect of miR-155 on CD8⁺ T cells is mediated by T-bet. T-bet levels in CTL were controlled in vivo by miR-155 via SH2 (Src homology 2)-containing inositol phosphatase-1 (SHIP-1), a known direct target of miR-155, and SHIP-1 directly downregulated T-bet. Our studies reveal an important and unexpected signaling axis between miR-155, T-bet, and SHIP-1 in in vivo CTL responses and suggest an important signaling module that regulates effector CTL immunity.

Invariant natural killer T-cell development and function with loss of microRNA-155

Invariant natural killer T (iNKT) cells are adaptive T cells with innate-like characteristics including rapid cytokine production and a proliferative response to stimulation. Development of these cells in the thymus is dependent on expression of the microRNA (miRNA) processing enzyme Dicer, indicating that iNKT cells probably have distinct miRNA requirements for gene regulation during development. The miRNA miR-155 has previously been shown to have numerous roles in T cells, including regulation of proliferation and differentiation, and positive modulation of interferon-γ expression. We examined the role of miR-155 in the development and function of iNKT cells. Using germline-deficient miR-155 mice, we showed that loss of miR-155 resulted in unchanged iNKT cell frequency and cell number. Although miR-155 was up-regulated in iNKT cells upon activation with α-galactosylceramide, loss of miR-155 did not affect cytokine production or proliferation by iNKT cells. Hence, cytokine production occurs in iNKT cells independently of miR-155 expression.

Elevated expression of miR-155 is associated with the differentiation of CD8+ T cells in patients with HIV-1

The differentiation and response ofCD8+ T cells is vital in host defense against human immunodeficiency virus type 1 (HIV-1). MicroRNA (miR)‑155 is an important regulator of T cell differentiation. However, the profile of miR-155 in HIV‑1 infected individuals and its association with CD8+ T cell differentiation remain to be fully elucidated. The present cross‑sectional study was performed involving 63 HIV‑1‑infected patients undergoing highly active antiretroviral therapy (HAART), 31 HAART‑naïve patients and 35 healthy controls. The levels of miR‑155 in CD8+ T cells were detected using reverse transcription‑quantitative polymerase chain reaction analysis. Subsets of CD8+ T cell differentiation were detected using flow cytometry. The results revealed that the discord controllers and HAART‑naïve patients showed higher percentages of effector and effector memory cells, and lower percentages of naïve cells (P<0.05). The levels of miR‑155 in CD8+ T cells from the HIV‑1‑infected patients were higher, particularly in the discord controllers and HAART naïve patients (P<0.01). The expression levels of miR‑155 were positively correlated with the percentages of effector and effector memory CD8+ T cells, and negatively correlated with the percentages of naïve and central memory CD8+ T cells (P<0.01). Taken together, these findings suggested that the levels of miR‑155 in CD8+ T cells of patients with HIV-1 were increased and asso-ciated with CD8+ T cell differentiation.

Enhanced immunogenicity following miR-155 incorporation into the influenza A virus genome

Influenza A vaccine efficacy in the elderly is generally poor and so identification of novel molecular adjuvants to improve immunogenicity is important to reduce the overall burden of disease. Short non-coding RNAs, known as microRNAs (miRNAs) are known to regulate gene expression and have the potential to influence immune responses. One such miRNA, miR-155, has been shown to modulate T and B cell development and function. We incorporated miR-155 into the influenza A virus (IAV) genome creating a self-adjuvanting 'live vaccine' with the ability to modify immunogenicity. Infection of mice with a recombinant influenza virus encoding miR-155 in the NS gene segment altered epitope-specific expansion of influenza-specific CD8⁺ T cells and induced significantly higher levels of neutralising antibody.

MicroRNA-155 is a biomarker of T-cell activation and immune dysfunction in HIV-1-infected patients

OBJECTIVES

MicroRNA-155 (miR-155) regulates T-cell differentiation and activation. It has also been associated with HIV infection. However, it remains unclear whether miR-155 is related to the T-cell response in HIV-infected individuals (e.g. T-cell activation and exhaustion).

METHODS

We performed a cross-sectional study involving 121 HIV-1-infected patients on highly active antiretroviral therapy (HAART) and 43 HAART-naïve patients. MiR-155 levels in the peripheral blood were determined by quantitative reverse transcription-polymerase chain reaction (PCR). T-cell immune activation, exhaustion, and homeostasis were measured by determining the expression of CD38, programmed death 1 (PD-1) and CD127 via flow cytometry.

RESULTS

The levels of miR-155 in total peripheral blood mononuclear cells, CD4 T cells and CD8 T cells from HIV-1-infected patients were increased (P < 0.01). Nonresponders and HAART-naïve patients also exhibited a higher percentage of CD8⁺ CD38⁺ T cells and a lower percentage of CD4⁺ CD127⁺ and CD8⁺ CD127⁺ T cells (P < 0.05). We also found higher levels of PD-1 expression on the CD4⁺ and CD8⁺ T cells of HIV-1-infected patients (P < 0.05).

CONCLUSIONS

Our findings suggest that miR-155 levels in the peripheral blood of HIV-1-infected patients are increased and associated with T-cell activation. Therefore, miR-155 is a potential biomarker of the immune response following HIV-1 infection.

Dicer Regulates the Balance of Short-Lived Effector and Long-Lived Memory CD8 T Cell Lineages

MicroRNAs constitute a major post-transcriptional mechanism for controlling protein expression, and are emerging as key regulators during T cell development and function. Recent reports of augmented CD8 T cell activation and effector differentiation, and aberrant migratory properties upon ablation of Dicer/miRNAs in naïve cells have established a regulatory role of miRNAs during priming. Whether miRNAs continue to exert similar functions or are dispensable during later stages of CD8 T cell expansion and memory differentiation remains unclear. Here, we report a critical role of Dicer/miRNAs in regulating the balance of long-lived memory and short-lived terminal effector fates during the post-priming stages when CD8 T cells undergo clonal expansion to generate a large cytotoxic T lymphocyte (CTL) pool and subsequently differentiate into a quiescent memory state. Conditional ablation of Dicer/miRNAs in early effector CD8 T cells following optimal activation and expression of granzyme B, using unique dicer^fl/flgzmb-cre mice, led to a strikingly diminished peak effector size relative to wild-type antigen-specific cells in the same infectious milieu. Diminished expansion of Dicer-ablated CD8 T cells was associated with lack of sustained antigen-driven proliferation and reduced accumulation of short-lived effector cells. Additionally, Dicer-ablated CD8 T cells exhibited more pronounced contraction after pathogen clearance and comprised a significantly smaller proportion of the memory pool, despite significantly higher proportions of CD127^Hi memory precursors at the effector peak. Combined with previous reports of dynamic changes in miRNA expression as CD8 T cells differentiate from naïve to effector and memory states, these findings support distinct stage-specific roles of miRNA-dependent gene regulation during CD8 T cell differentiation.

Atractylenolide I modulates ovarian cancer cell-mediated immunosuppression by blocking MD-2/TLR4 complex-mediated MyD88/NF-κB signaling in vitro

BACKGROUND

TLR4/MD-2 complex-mediated MyD88-dependent activation of NF-κB and Akt promotes tumor-associated immunosuppression in epithelial ovarian cancer (EOC) via induction of immunesuppressive cytokines and indoleamine 2,3-dioxygenase (IDO). Atractylenolide I (AO-1) is a naturally occurring sesquiterpene lactone known to change the conformational ensemble of human MD-2 on EOC cells. This study examined the modulation by AO-1 of TLR4/MD-2 complex-mediated MyD88/NF-κB signaling.

METHODS

The expression and activation of NF-κB, Akt and IDO1 by MyD88(+) EOC SKOV3 cells was determined using western blot; the TLR4/MD-2 complex on SKOV3 cells and the phenotype of T lymphocytes were determined using flow cytometry; IDO activity was evaluated by measuring L-kynurenine; Immunesuppressive cytokines were detected using ELISA; T-cell proliferation to mitogen stimulation was assessed by MTT assay; the cytotoxicity of lymphocytes and NK cells was measured using LDH-cytotoxicity assay.

RESULTS

AO-1 could down-regulate expression of TLR4/MD-2 complex, resulting in downregulation of MyD88/NF-κB signaling and activation of NF-κB, Akt and IDO1 and secretion of IL-6, TGF-β1, VEGF and IL-17A by EOC SKOV3 cells, and further reduce increased levels of regulatory T cells (Treg cells) and improve decreased proliferative response and antitumor cytotoxicity of T lymphocytes exposed to EOC SKOV3 cell supernatant.

CONCLUSION

AO-1 may reverse EOC cell-mediated immunosuppression through blocking TLR4/MD-2 complex-mediated MyD88/NF-κB signaling.

Are We Eating Our Way to Prostate Cancer-A Hypothesis Based on the Evolution, Bioaccumulation, and Interspecific Transfer of miR-150

MicroRNAs (miRNAs) are well established epigenetic modifiers. There is a lot of work being done to identify the evolutionary transfer of miRNAs both at intra- and interspecific levels. In this hypothesis-driven review, we have suggested a possible reason as to why miR-150 can be a promising diagnostic biomarker for prostate cancer using theories of evolution, bio-accumulation, and interspecific transfer of miRNAs.

Enhancing adoptive T cell immunotherapy with microRNA therapeutics

Adoptive T cell-based immunotherapies can mediate complete and durable regressions in patients with advanced cancer, but current response rates remain inadequate. Maneuvers to improve the fitness and antitumor efficacy of transferred T cells have been under extensive exploration in the field. Small non-coding microRNAs have emerged as critical modulators of immune system homeostasis and T cell immunity. Here, we summarize recent advances in our understanding of the role of microRNAs in regulating T cell activation, differentiation, and function. We also discuss how microRNA therapeutics could be employed to fine-tune T cell receptor signaling and enhance T cell persistence and effector functions, paving the way for the next generation of adoptive immunotherapies.

MicroRNAs and Their Targets Are Differentially Regulated in Adult and Neonatal Mouse CD8+ T Cells

Immunological memory, which protects organisms from re-infection, is a hallmark of the mammalian adaptive immune system and the underlying principle of vaccination. In early life, however, mice and other mammals are deficient at generating memory CD8+ T cells, which protect organisms from intracellular pathogens. The molecular basis that differentiates adult and neonatal CD8+ T cells is unknown. MicroRNAs (miRNAs) are both developmentally regulated and required for normal adult CD8+ T cell functions. We used next-generation sequencing to identify mouse miRNAs that are differentially regulated in adult and neonatal CD8+ T cells, which may contribute to the impaired development of neonatal memory cells. The miRNA profiles of adult and neonatal cells were surprisingly similar during infection; however, we observed large differences prior to infection. In particular, miR-29 and miR-130 have significant differential expression between adult and neonatal cells before infection. Importantly, using RNA-Seq, we detected reciprocal changes in expression of messenger RNA targets for both miR-29 and miR-130. Moreover, targets that we validated include Eomes and Tbx21, key genes that regulate the formation of memory CD8+ T cells. Notably, age-dependent changes in miR-29 and miR-130 are conserved in human CD8+ T cells, further suggesting that these developmental differences are biologically relevant. Together, these results demonstrate that miR-29 and miR-130 are likely important regulators of memory CD8+ T cell formation and suggest that neonatal cells are committed to a short-lived effector cell fate prior to infection.

Physiological roles of miR-155

miR-155 is involved in non-coding microRNAs found in humans, mice and chickens of which the sequence is conserved. Historically, miR-155 was identified as a B-cell integration cluster (bic), which induces B-cell leucosis in chickens, by its activation through viral promoter insertion. Subsequent studies have shown that transgenic mice expressing miR-155 in B cells generated lymphoma, showing that miR-155 is oncogenic. Biochemical investigation identifies many substrates of miR-155, and one of them in B cells and macrophages is the SH2-domain containing inositol-5'-phosphatase 1. A deficiency of miR-155 in the immune system causes attenuated immune functions. Clinically, several types of malignancy including diffuse large B-cell lymphoma have high miR-155 expression levels.

Role of miR-155 in the pathogenesis of herpetic stromal keratitis

Ocular infection with herpes simplex virus 1 can result in a chronic immunoinflammatory stromal keratitis (SK) lesion that is a significant cause of human blindness. A key to controlling SK lesion severity is to identify cellular and molecular events responsible for tissue damage and to manipulate them therapeutically. Potential targets for therapy are miRNAs, but these are minimally explored especially in responses to infection. Here, we demonstrated that Mir155 expression was up-regulated after ocular herpes simplex virus 1 infection, with the increased Mir155 expression occurring mainly in macrophages and CD4(+) T cells and to a lesser extent in neutrophils. In vivo studies indicated that Mir155 knockout mice were more resistant to herpes SK with marked suppression of T helper cells type 1 and 17 responses both in the ocular lesions and the lymphoid organs. The reduced SK lesion severity was reflected by increased phosphatidylinositol-3,4,5-trisphosphate 5-phosphatase 1 and interferon-γ receptor α-chain levels in activated CD4(+) T cells in the lymph nodes. Finally, in vivo silencing of miR-155 by the provision of antagomir-155 nanoparticles to herpes simplex virus 1-infected mice led to diminished SK lesions and corneal vascularization. In conclusion, our results indicate that miR-155 contributes to the pathogenesis of SK and represents a promising target to control SK severity.

microRNAs function in CD8+T cell biology

During an immune response, CD8(+)T cells can differentiate into multiple types of effector and memory cells that are important components of immune surveillance. However, their dysregulation has been implicated in infection with viruses or intracellular bacteria and tumorigenesis. miRNAs have been identified as crucial regulators of gene expression, and they perform this function by repressing specific target genes at the post-transcriptional level. Most miRNAs expressed in a given cell type serve the function to impede broadly cell-type-inappropriate gene expression and potently deepen a pre-existing differentiation program. It is increasingly recognized that miRNAs directly modulate the concentration of many regulatory proteins that are required for the development of immune cells in the thymus and their responses in the periphery. This review outlines our current understanding of the function of miRNAs in CD8(+)T cell biology as it impacts expression of protein-coding genes in the context of proper development, infection, as well as oncogenesis. In addition, we conclude with a perspective on future challenges and the clinical relevance of miRNA biology.

Host miR155 promotes tumor growth through a myeloid-derived suppressor cell-dependent mechanism

miR155 is a regulator of immune cell development and function that is generally thought to be immunostimulatory. However, we report here that genetic ablation of miR155 renders mice resistant to chemical carcinogenesis and the growth of several transplanted tumors, suggesting that miR155 functions in immunosuppression and tumor promotion. Host miR155 deficiency promoted overall antitumor immunity despite the finding of defective responses of miR155-deficient dendritic cells and antitumor T cells. Further analysis of immune cell compartments revealed that miR155 regulated the accumulation of functional myeloid-derived suppressive cells (MDSC) in the tumor microenvironment. Specifically, miR155 mediated MDSC suppressor activity through at least two mechanisms, including SOCS1 repression and a reduced ability to license the generation of CD4(+)Foxp3(+) regulatory T cells. Importantly, we demonstrated that miR155 expression was required for MDSC to facilitate tumor growth. Thus, our results revealed a contextual function for miR155 in antitumor immunity, with a role in MDSC support that appears to dominate in tumor-bearing hosts. Overall, the balance of these cellular effects appears to be a root determinant of whether miR155 promotes or inhibits tumor growth.