Perforin: a key pore-forming protein for immune control of viruses and cancer

Tumor-infiltrating lymphocytes in patients undergoing esophagectomy following neoadjuvant DCF therapy

BACKGROUND

Accumulating evidence suggests that expression levels of tumor-infiltrating (TI) cells may play a prognostic role in patients with esophageal cancer who have undergone esophagectomy. However, its effect on patients undergoing neoadjuvant docetaxel, cisplatin, and 5-fluorouracil (DCF) therapy followed by esophagectomy for esophageal squamous cell carcinoma (ESCC) remains unclear. Therefore, this study aimed to elucidate the prognostic impact of TI cells in patients who underwent esophagectomy following neoadjuvant DCF therapy.

METHODS

Overall, 81 patients with ESCC who underwent curative esophagectomy following neoadjuvant DCF therapy were included. The number of TI CD8+ cells was determined using light microscopy at ×400 in tumor invasive margins. Receiver operative characteristic curve was used to determine the cutoff values for mortality for continuous variables; the patients were separated into high and low TI CD8+ cell groups and their backgrounds and clinical outcomes were compared.

RESULTS

Overall and relapse-free survival were significantly worse in the TI CD8+-low group than that in the TI CD8+-high group (p < 0.01). Multivariate analysis revealed that positive ypN (hazard ratio [HR], 3.12; 95% confidence interval [CI], 1.08-9.02) and low TI CD8+ cell levels (HR, 2.77; 95% CI, 1.31-5.85) were independent prognostic factors for overall survival. Furthermore, positive venous invasion (HR, 2.63; 95% CI, 1.29-5.35) and low TI CD8+ cell levels (HR, 2.77; 95% CI, 1.70-5.46) were significant prognostic factors for relapse-free survival.

CONCLUSIONS

Low TI CD8+ cell level was a prominent prognostic factor for patients with ESCC undergoing neoadjuvant DCF therapy followed by esophagectomy.

Partial loss of Sorting Nexin 27 resembles age- and Down syndrome-associated T cell dysfunctions

BACKGROUND

Sorting Nexin 27 (SNX27)-retromer complex facilitates cargo recycling from endosomes to the plasma membrane. SNX27 downregulation in neurons, as the result of Trisomy 21 (T21), has been linked with cognitive deficits due to impairment of AMPA and NMDA receptor recycling. Studies in human T cell lines likewise demonstrated that SNX27 regulates the correct delivery of cargoes to the immune synapse limiting the activation of pro-inflammatory pathways. Nevertheless, the physiological consequences of partial SNX27 loss in T cell homeostasis are still unclear.

RESULTS

In this study, we have explored the consequences of T cell specific partial SNX27 downregulation in mice. T cells with partial SNX27 deficiency show a marked deficit in the CD4+ T cell pool, a hallmark of aging in mice and humans, and a well-characterized comorbidity of individuals with Down syndrome (DS). When analyzed ex vivo, CD4+ T cells with partial SNX27 deletion demonstrate enhanced proliferation but diminished IL-2 production. In contrast, the CD8+ population show enhanced expression of pro-inflammatory cytokines and lytic enzymes.

CONCLUSIONS

This mouse model supports the relevance of SNX27 in the organization of the immune synapse, previously described in cell lines, as well as in the control of T cell homeostasis. Individuals with DS experiment an acceleration of the aging process, which particularly affects the immune and central nervous systems. Thus, we hypothesize that reduced SNX27 expression in DS could contribute to the dysregulation of these systems and further research in SNX27 will shed light on the molecular factors underlying the phenotypes observed in people with DS and its contribution to aging.

Regulation and distribution of European sea bass perforins point to their role in the adaptive cytotoxic response against NNV

Cell-mediated cytotoxicity is a complex immune mechanism that involves the release of several killing molecules, being perforin (PRF) one of the most important effector players. Perforin is synthesized by T lymphocytes and natural killer cells in mammals and responsible for the formation of pores on the target cell membrane during the killing process. Although perforin has been extensively studied in higher vertebrates, this knowledge is very limited in fish. Therefore, in this study we have identified four prf genes in European sea bass (Dicentrarchus labrax) and evaluated their mRNA levels. All sea bass prf genes showed the typical and conserved domains of its human orthologue and were closely clustered by the phylogenetic analysis. In addition, all genes showed constitutive and ubiquitous tissular expression, being prf1.9 gene the most highly expressed in immune tissues. Subsequently, in vitro stimulation of head-kidney (HK) cells with phytohemagglutinin, a T-cell activator, showed an increase of all prf gene levels, except for prf1.3 gene. European sea bass HK cells increased the transcription of prf1.2 and prf1.9 during the innate cell-mediated cytotoxic activity against xenogeneic target cells. In addition, sea bass infected with nodavirus (NNV) showed a similar expression pattern of all prf in HK and brain at 15 days post-infection, except for prf1.3 gene and in the gonad. Finally, the use of a polyclonal antibody against PRF1.9 showed an increase of positive cells in HK, brain and gonad from NNV-infected fish. Taken together, the data seem to indicate that all prf genes, except prf1.3, appear to be involved in the European sea bass immunity, and probably in the cell-mediated cytotoxic response, with PRF1.9 playing the most important role against nodavirus. The involvement of the PRFs and the CMC activity in the vertical transmission success of the virus is also discussed.

Apoptotic contraction drives target cell release by cytotoxic T cells

Cytotoxic T lymphocytes (CTLs) fight intracellular pathogens and cancer by identifying and destroying infected or transformed target cells1. To kill, CTLs form a specialized cytotoxic immune synapse (IS) with a target of interest and then release toxic perforin and granzymes into the interface to elicit programmed cell death2-5. The IS then dissolves, enabling CTLs to search for additional prey and professional phagocytes to clear the corpse6. While the mechanisms governing IS assembly have been studied extensively, far less is known about target cell release. Here, we applied time-lapse imaging to explore the basis for IS dissolution and found that it occurred concomitantly with the cytoskeletal contraction of apoptotic targets. Genetic and pharmacological perturbation of this contraction response indicated that it was both necessary and sufficient for CTL dissociation. We also found that mechanical amplification of apoptotic contractility promoted faster CTL detachment and serial killing. Collectively, these results establish a biophysical basis for IS dissolution and highlight the importance of mechanosensory feedback in the regulation of cell-cell interactions.

Designing Cancer Immunotherapies That Engage T Cells and NK Cells

T cells and natural killer (NK) cells have complementary roles in tumor immunity, and dual T cell and NK cell attack thus offers opportunities to deepen the impact of immunotherapy. Recent work has also shown that NK cells play an important role in recruiting dendritic cells to tumors and thus enhance induction of CD8 T cell responses, while IL-2 secreted by T cells activates NK cells. Targeting of immune evasion mechanisms from the activating NKG2D receptor and its MICA and MICB ligands on tumor cells offers opportunities for therapeutic intervention. Interestingly, T cells and NK cells share several important inhibitory and activating receptors that can be targeted to enhance T cell- and NK cell-mediated immunity. These inhibitory receptor-ligand systems include CD161-CLEC2D, TIGIT-CD155, and NKG2A/CD94-HLA-E. We also discuss emerging therapeutic strategies based on inhibitory and activating cytokines that profoundly impact the function of both lymphocyte populations within tumors.

The Actin Regulators Involved in the Function and Related Diseases of Lymphocytes

Actin is an important cytoskeletal protein involved in signal transduction, cell structure and motility. Actin regulators include actin-monomer-binding proteins, Wiskott-Aldrich syndrome (WAS) family of proteins, nucleation proteins, actin filament polymerases and severing proteins. This group of proteins regulate the dynamic changes in actin assembly/disassembly, thus playing an important role in cell motility, intracellular transport, cell division and other basic cellular activities. Lymphocytes are important components of the human immune system, consisting of T-lymphocytes (T cells), B-lymphocytes (B cells) and natural killer cells (NK cells). Lymphocytes are indispensable for both innate and adaptive immunity and cannot function normally without various actin regulators. In this review, we first briefly introduce the structure and fundamental functions of a variety of well-known and newly discovered actin regulators, then we highlight the role of actin regulators in T cell, B cell and NK cell, and finally provide a landscape of various diseases associated with them. This review provides new directions in exploring actin regulators and promotes more precise and effective treatments for related diseases.

Identification of Biomarkers Related to Immune Cell Infiltration with Gene Coexpression Network in Myocardial Infarction

Background

There is evidence that the immune system plays a key critical role in the pathogenesis of myocardial infarction (MI). However, the exact mechanisms associated with immunity have not been systematically uncovered.

Methods

This study used the weighted gene coexpression network analysis (WGCNA) and the CIBERSORT algorithm to analyze the MI expression data from the Gene Expression Omnibus database and then identify the module associated with immune cell infiltration. In addition, we built the coexpression network and protein-protein interactions network analysis to identify the hub genes. Furthermore, the relationship between hub genes and NK cell resting was validated by using another dataset GSE123342. Finally, receiver operating characteristic (ROC) curve analyses were used to assess the diagnostic value of verified hub genes.

Results

Monocytes and neutrophils were markedly increased, and T cell CD8, T cell CD4 naive, T cell CD4 memory resting, and NK cell resting were significantly decreased in MI groups compared with stable coronary artery disease (CAD) groups. The WGCNA results showed that the pink model had the highest correlation with the NK cell resting infiltration level. We identified 11 hub genes whose expression correlated to the NK cell resting infiltration level, among which, 7 hub genes (NKG7, TBX21, PRF1, CD247, KLRD1, FASLG, and EOMES) were successfully validated in GSE123342. And these 7 genes had diagnostic value to distinguish MI and stable CAD.

Conclusions

NKG7, TBX21, PRF1, CD247, KLRD1, FASLG, and EOMES may be a diagnostic biomarker and therapeutic target associated with NK cell resting infiltration in MI.

Identification and functional analysis of the perforin-1 like gene in disease resistance in half smooth tongue sole (Cynoglossus semilaevis)

The pore-forming protein perforin is one of the effectors of cell-mediated killing via the granule exocytosis pathway. In this study, a genome-wide association study was conducted in Vibrio harveyi disease-resistant and disease-susceptible families of half smooth tongue sole (Cynoglossus semilaevis) to determine the genes accounting for host resistance, and a perforin homologue was identified, designated perforin-1 like (CsPRF1l). The full-length cDNA of CsPRF1l is 1835 bp, and encodes 514 amino acids. The CsPRF1l gene consists of 10 exons and 9 introns, spanning approximately 7 kb. The amino acid sequence of CsPRF1l shows 60.35, 54.03, 41.92, and 34.17% identities to Morone saxatilis PRF1l, Oryzias melastigma PRF1l, Danio rerio PRF1.5 and Homo sapiens PRF, respectively. Sequence analysis revealed the presence of membrane attack complex/perforin (MACPF) and C2 domains in CsPRF1l. Quantitative real-time PCR showed that CsPRF1l presented a higher intestinal expression level in disease-resistant families than in susceptible families. Tissue expression pattern analysis showed that CsPRF1l is present in most of the tested tissues and highly expressed in the intestine, brain, stomach and gills. After challenge with V. harveyi, CsPRF1l mRNA was markedly upregulated in the liver, spleen, kidney, intestine, gills and skin. In addition, the recombinant CsPRF1l protein exhibited obvious antimicrobial activity against V. harveyi in vitro and in a zebrafish model. Collectively, these data indicate that CsPRF1l modulates host immune defense against V. harveyi invasion and provide clues about the efficacy of rCsPRF1l in fish that will give rise to useful therapeutic applications for V. harveyi infection in C. semilaevis.

Summary and comparison of the perforin in teleosts and mammals: A review

Perforin, a pore-forming glycoprotein, has been demonstrated to play key roles in clearing virus-infected cells and tumour cells due to its ability of forming 'pores' on the cell membranes. Additionally, perforin is also found to be associated with human diseases such as tumours, virus infections, immune rejection and some autoimmune diseases. Until now, plenty of perforin genes have been identified in vertebrates, especially the mammals and teleost fish. Conversely, vertebrate homologue of perforin gene was not identified in the invertebrates. Although recently there have been several reviews focusing on perforin and granzymes in mammals, no one highlighted the current advances of perforin in the other vertebrates. Here, in addition to mammalian perforin, the structure, evolution, tissue distribution and function of perforin in bony fish are summarized, respectively, which will allow us to gain more insights into the perforin in lower animals and the evolution of this important pore-forming protein across vertebrates.

Knocking 'em Dead: Pore-Forming Proteins in Immune Defense

Immune cells use a variety of membrane-disrupting proteins [complement, perforin, perforin-2, granulysin, gasdermins, mixed lineage kinase domain-like pseudokinase (MLKL)] to induce different kinds of death of microbes and host cells, some of which cause inflammation. After activation by proteolytic cleavage or phosphorylation, these proteins oligomerize, bind to membrane lipids, and disrupt membrane integrity. These membrane disruptors play a critical role in both innate and adaptive immunity. Here we review our current knowledge of the functions, specificity, activation, and regulation of membrane-disrupting immune proteins and what is known about the mechanisms behind membrane damage, the structure of the pores they form, how the cells expressing these lethal proteins are protected, and how cells targeted for destruction can sometimes escape death by repairing membrane damage.

Interfacial actin protrusions mechanically enhance killing by cytotoxic T cells

Cytotoxic T lymphocytes (CTLs) kill by forming immunological synapses with target cells and secreting toxic proteases and the pore-forming protein perforin into the intercellular space. Immunological synapses are highly dynamic structures that boost perforin activity by applying mechanical force against the target cell. Here, we used high-resolution imaging and microfabrication to investigate how CTLs exert synaptic forces and coordinate their mechanical output with perforin secretion. Using micropatterned stimulatory substrates that enable synapse growth in three dimensions, we found that perforin release occurs at the base of actin-rich protrusions that extend from central and intermediate locations within the synapse. These protrusions, which depended on the cytoskeletal regulator WASP and the Arp2/3 actin nucleation complex, were required for synaptic force exertion and efficient killing. They also mediated physical deformation of the target cell surface during CTL-target cell interactions. Our results reveal the mechanical basis of cellular cytotoxicity and highlight the functional importance of dynamic, three-dimensional architecture in immune cell-cell interfaces.

Centrioles control the capacity, but not the specificity, of cytotoxic T cell killing

Immunological synapse formation between cytotoxic T lymphocytes (CTLs) and the target cells they aim to destroy is accompanied by reorientation of the CTL centrosome to a position beneath the synaptic membrane. Centrosome polarization is thought to enhance the potency and specificity of killing by driving lytic granule fusion at the synapse and thereby the release of perforin and granzymes toward the target cell. To test this model, we employed a genetic strategy to delete centrioles, the core structural components of the centrosome. Centriole deletion altered microtubule architecture as expected but surprisingly had no effect on lytic granule polarization and directional secretion. Nevertheless, CTLs lacking centrioles did display substantially reduced killing potential, which was associated with defects in both lytic granule biogenesis and synaptic actin remodeling. These results reveal an unexpected role for the intact centrosome in controlling the capacity but not the specificity of cytotoxic killing.

Mechanotransduction in T Cell Development, Differentiation and Function

Cells in the body are actively engaging with their environments that include both biochemical and biophysical aspects. The process by which cells convert mechanical stimuli from their environment to intracellular biochemical signals is known as mechanotransduction. Exemplifying the reliance on mechanotransduction for their development, differentiation and function are T cells, which are central to adaptive immune responses. T cell mechanoimmunology is an emerging field that studies how T cells sense, respond and adapt to the mechanical cues that they encounter throughout their life cycle. Here we review different stages of the T cell's life cycle where existing studies have shown important effects of mechanical force or matrix stiffness on a T cell as sensed through its surface molecules, including modulating receptor-ligand interactions, inducing protein conformational changes, triggering signal transduction, amplifying antigen discrimination and ensuring directed targeted cell killing. We suggest that including mechanical considerations in the immunological studies of T cells would inform a more holistic understanding of their development, differentiation and function.

The pharmalogical reactivation of p53 function improves breast tumor cell lysis by granzyme B and NK cells through induction of autophagy

Cytotoxic T lymphocytes (CTL) and natural killer cells (NK)-mediated elimination of tumor cells is mostly dependent on Granzyme B apoptotic pathway, which is regulated by the wild type (wt) p53 protein. Because TP53 inactivating mutations, frequently found in human tumors, could interfere with Granzyme B-mediated cell death, the use of small molecules developed to reactivate wtp53 function in p53-mutated tumor cells could optimize their lysis by CTL or NK cells. Here, we show that the pharmalogical reactivation of a wt-like p53 function in p53-mutated breast cancer cells using the small molecule CP-31398 increases their sensitivity to NK-mediated lysis. This potentiation is dependent on p53-mediated induction of autophagy via the sestrin-AMPK-mTOR pathway and the ULK axis. This CP31398-induced autophagy sequestrates in autophagosomes several anti-apoptotic proteins, including Bcl-X_L and XIAP, facilitating Granzyme B-mediated mitochondrial outer membrane permeabilization, caspase-3 activation and Granzyme B- or NK cell-induced apoptosis. Together, our results define a new way to increase cytotoxic lymphocyte-mediated lysis of p53-mutated breast cancer cell, through a p53-dependent autophagy induction, with potential applications in combined immunotherapeutic approaches.

When and how NK cell-induced programmed cell death benefits immunological protection against intracellular pathogen infection

NK cells are innate lymphoid cells that exert a key role in immune surveillance through the recognition and elimination of transformed cells and viral, bacterial, and protozoan pathogen-infected cells without prior sensitization. Elucidating when and how NK cell-induced intracellular microbial cell death functions in the resolution of infection and host inflammation has been an important topic of investigation. NK cell activation requires the engagement of specific activating, co-stimulatory, and inhibitory receptors which control positively and negatively their differentiation, memory, and exhaustion. NK cells secrete diverse cytokines, including IFN-γ, TNF-α/β, CD95/FasL, and TRAIL, as well as cytoplasmic cytotoxic granules containing perforin, granulysin, and granzymes A and B. Paradoxically, NK cells also kill other immune cells like macrophages, dendritic cells, and hyper-activated T cells, thus turning off self-immune reactions. Here we first provide an overview of NK cell biology, and then we describe and discuss the life–death signals that connect the microbial pathogen sensors to the inflammasomes and finally to cell death signaling pathways. We focus on caspase-mediated cell death by apoptosis and pro-inflammatory and non-caspase-mediated cell death by necroptosis, as well as inflammasome- and caspase-mediated pyroptosis.

Intracellular Delivery by Membrane Disruption: Mechanisms, Strategies, and Concepts

Intracellular delivery is a key step in biological research and has enabled decades of biomedical discoveries. It is also becoming increasingly important in industrial and medical applications ranging from biomanufacture to cell-based therapies. Here, we review techniques for membrane disruption-based intracellular delivery from 1911 until the present. These methods achieve rapid, direct, and universal delivery of almost any cargo molecule or material that can be dispersed in solution. We start by covering the motivations for intracellular delivery and the challenges associated with the different cargo types-small molecules, proteins/peptides, nucleic acids, synthetic nanomaterials, and large cargo. The review then presents a broad comparison of delivery strategies followed by an analysis of membrane disruption mechanisms and the biology of the cell response. We cover mechanical, electrical, thermal, optical, and chemical strategies of membrane disruption with a particular emphasis on their applications and challenges to implementation. Throughout, we highlight specific mechanisms of membrane disruption and suggest areas in need of further experimentation. We hope the concepts discussed in our review inspire scientists and engineers with further ideas to improve intracellular delivery.

Macrophages: Their Untold Story in T Cell Activation and Function

The complexity of T cell activation to maintain homeostasis and provide host defense is highlighted by the intricate step-wise process which is coordinated by multiple cell types. Crucial to T cell activation is the requirement of antigen-presenting cells (APCs) such as macrophages at each step of the activation and effector stages. Macrophages are central regulators in T cell activation and are involved in each step including initiating the series of events leading to T cell activation. Macrophages identify and present foreign antigens in classes I and II major histocompatibility complexes (MHC) to T cells, which recognize the MHC-antigen complex through their T cell receptor. This initial step is all in vain if additional costimulatory and cytokine signaling does not occur concurrently. Macrophages can mediate and provide the required costimulatory signaling and cytokine secretion required for effective T cell activation. While other cell types, especially other APCs, may be capable of playing a role during different stages of T cell activation, this review will focus on how macrophages can modulate T cell activation and effector function. This is in no way an attempt to minimize the role of other APCs but instead to bring to light to the role macrophages can play during this process. Here, the role macrophages play in cancer to either activate or inhibit T cells based on macrophage phenotype, costimulatory molecules, and cytokine secretion is highlighted as an example of how macrophages can significantly alter T cell activation and effector function in human disease.

Urothelial bladder cancer may suppress perforin expression in CD8+ T cells by an ICAM-1/TGFβ2 mediated pathway

The immune system plays a significant role in urothelial bladder cancer (UBC) progression, with CD8⁺ T cells being capable to directly kill tumor cells using perforin and granzymes. However, tumors avoid immune recognition by escape mechanisms. In this study, we aim to demonstrate tumor immune escape mechanisms that suppress CD8⁺ T cells cytotoxicity. 42 patients diagnosed with UBC were recruited. CD8⁺ T cells from peripheral blood (PB), sentinel nodes (SN), and tumor were analyzed in steady state and in vitro-stimulated conditions by flow cytometry, RT-qPCR, and ELISA. Mass spectrometry (MS) was used for identification of proteins from UBC cell line culture supernatants. Perforin was surprisingly found to be low in CD8⁺ T cells from SN, marked by 1.8-fold decrease of PRF1 expression, with maintained expression of granzyme B. The majority of perforin-deficient CD8⁺ T cells are effector memory T (T_EM) cells with exhausted Tc2 cell phenotype, judged by the presence of PD-1 and GATA-3. Consequently, perforin-deficient CD8⁺ T cells from SN are low in T-bet expression. Supernatant from muscle invasive UBC induces perforin deficiency, a mechanism identified by MS where ICAM-1 and TGFβ2 signaling were causatively validated to decrease perforin expression in vitro. Thus, we demonstrate a novel tumor escape suppressing perforin expression in CD8⁺ T cells mediated by ICAM-1 and TGFβ2, which can be targeted in combination for cancer immunotherapy.

Post-operative unadjuvanted therapeutic xenovaccination with chicken whole embryo vaccine suppresses distant micrometastases and prolongs survival in a murine Lewis lung carcinoma model

Immunotherapy in the form of anticancer vaccination relies on the mobilization of the patient's immune system against specific cancer antigens. Instead of focusing on an autologous cell lysate, which is not always available in clinical practice, the present study investigates vaccines utilizing xenogeneic foetal tissue that are rich in oncofoetal antigens. Lewis lung carcinoma (LLC)-challenged C57BL/6 mice were treated with either a xenogeneic vaccine made from chicken whole embryo, or a xenogeneic vaccine made from rat embryonic brain tissue, supplemented with a Bacillus subtilis protein fraction as an adjuvant. Median and overall survival, size of metastatic foci in lung tissue and levels of circulating CD8a⁺ T cells were evaluated and compared with untreated control mice. Following primary tumour removal, a course of three subcutaneous vaccinations with xenogeneic chicken embryo vaccine led to significant increase in overall survival rate (100% after 70 days of follow-up vs. 40% in untreated control mice), significant increase in circulating CD8a⁺ T cells (18.18 vs. 12.6% in untreated control mice), and a significant decrease in the area and incidence of metastasis foci. The xenogeneic rat brain tissue-based vaccine did not improve any of the investigated parameters, despite promising reports in other models. We hypothesize that the proper selection of antigen source (tissue) can constitute an effective immunotherapeutic product.

Differential Expression of CD8+ T Cell Cytotoxic Effector Molecules in Blood and Gastrointestinal Mucosa in HIV-1 Infection

We previously reported that CD8⁺ T cells in human gastrointestinal mucosa exhibit reduced perforin expression and weak or impaired cytotoxic capacity compared with their counterparts in blood. Nevertheless, these cells degranulate and express cytokines and chemokines in response to cognate Ag. In addition to weak expression of perforin, earlier studies suggested differential regulation of perforin and granzymes (Gzms), with GzmA and B expressed by significantly higher percentages of mucosal CD8⁺ T cells than perforin. However, this topic has not been fully explored. The goal of this study was to elucidate the expression and coexpression patterns of GzmA, B, and K in conjunction with perforin in rectosigmoid CD8⁺ T cells during HIV-1 infection. We found that expression of both perforin and GzmB, but not GzmA or GzmK, was reduced in mucosa compared with blood. A large fraction of rectosigmoid CD8⁺ T cells either did not express Gzms or were single-positive for GzmA. Rectosigmoid CD8⁺ T cells appeared skewed toward cytokine production rather than cytotoxic responses, with cells expressing multiple cytokines and chemokines generally lacking in perforin and Gzm expression. These data support the interpretation that perforin and Gzms are differentially regulated, and display distinct expression patterns in blood and rectosigmoid T cells. These studies may help inform the development of strategies to combat HIV-1 and other mucosal pathogens.

Effects of total flavonoids of sea buckthorn ( Hippophae rhamnoides L.) on cytotoxicity of NK92-MI cells

Sea buckthorn (Hippophae rhamnoides L.) has multifarious medicinal properties including immunoregulatory effect. The total flavonoids of Hippophae rhamnoides L. (TFH) are the main active components isolated from berries of sea buckthorn. The aim of this study was to evaluate the effects of TFH on the cytotoxicity of NK92-MI cells and its possible mechanisms. NK92-MI cells were treated with TFH (2.5 or 5.0 mg/L) or phosphate-buffered saline (PBS) for 24 h, the cytotoxicity against K562 was detected by measuring the release of lactate dehydrogenase (LDH), expression levels of NCRs (NKp30, NKp44, NKp46) and NKG2D were detected by flow cytometry, and expression levels of perforin and granzyme B were detected by western blot. Cytokine Antibody Arrays with 80 cytokine proteins were used to profile the effect of TFH on cytokines. Western blot was adopted to detect the effects of TFH on STAT1, STAT4, and STAT5 signal pathway. Compared with the normal control group, TFH could significantly enhance NK92-MI cell cytotoxicity against K562 cells, upregulate expressions of NKp44, NKp46, perforin, and granzyme B. TFH could upregulate expressions of IL-1α, IL-2, IL-7, IL-15, CSF-2, CSF-3, MCP-1, MIG, IFN-γ, TNF-α, and TNF-β and downregulate expressions of IL-16, MIP-1β, CX3CL-1, and MIF. TFH could increase expressions of phospho-STAT1 and phospho-STAT5. The results suggest that TFH stimulated NK92-MI cells to activate and enhance cytotoxicity of NK92-MI cells.

Predominance of weakly cytotoxic, T-betLowEomesNeg CD8+ T-cells in human gastrointestinal mucosa: implications for HIV infection

The gastrointestinal mucosa is an important site of HIV acquisition, viral replication, and pathogenesis. Immune cells in mucosal tissues frequently differ in phenotype and function from their non-mucosal counterparts. Although perforin-mediated cytotoxicity as measured in blood is a recognized correlate of HIV immune control, its role in gastrointestinal tissues is unknown. We sought to elucidate the cytotoxic features of rectal mucosal CD8⁺ T-cells in HIV infected and uninfected subjects. Perforin expression and lytic capacity were significantly reduced in rectal CD8⁺ T-cells compared with their blood counterparts, regardless of HIV clinical status; granzyme B (GrzB) was reduced to a lesser extent. Mucosal perforin and GrzB expression were higher in participants not on antiretroviral therapy compared with those on therapy and controls. Reduction in perforin and GrzB was not explained by differences in memory/effector subsets. Expression of T-bet and Eomesodermin was significantly lower in gut CD8⁺ T-cells compared with blood, and in vitro neutralization of TGF-β partially restored perforin expression in gut CD8⁺ T-cells. These findings suggest that rectal CD8⁺ T-cells are primarily non-cytotoxic, and phenotypically shaped by the tissue microenvironment. Further elucidation of rectal immune responses to HIV will inform the development of vaccines and immunotherapies targeted to mucosal tissues.

Network Analysis-Based Approach for Exploring the Potential Diagnostic Biomarkers of Acute Myocardial Infarction

Acute myocardial infarction (AMI) is a severe cardiovascular disease that is a serious threat to human life. However, the specific diagnostic biomarkers have not been fully clarified and candidate regulatory targets for AMI have not been identified. In order to explore the potential diagnostic biomarkers and possible regulatory targets of AMI, we used a network analysis-based approach to analyze microarray expression profiling of peripheral blood in patients with AMI. The significant differentially-expressed genes (DEGs) were screened by Limma and constructed a gene function regulatory network (GO-Tree) to obtain the inherent affiliation of significant function terms. The pathway action network was constructed, and the signal transfer relationship between pathway terms was mined in order to investigate the impact of core pathway terms in AMI. Subsequently, constructed the transcription regulatory network of DEGs. Weighted gene co-expression network analysis (WGCNA) was employed to identify significantly altered gene modules and hub genes in two groups. Subsequently, the transcription regulation network of DEGs was constructed. We found that specific gene modules may provide a better insight into the potential diagnostic biomarkers of AMI. Our findings revealed and verified that NCF4, AQP9, NFIL3, DYSF, GZMA, TBX21, PRF1 and PTGDR genes by RT-qPCR. TBX21 and PRF1 may be potential candidates for diagnostic biomarker and possible regulatory targets in AMI.

Immuno-pharmacodynamics for evaluating mechanism of action and developing immunotherapy combinations

Immunotherapy has become a major modality of cancer treatment, with multiple new classes of immunotherapeutics recently entering the clinic and obtaining market approval from regulatory agencies. While the promise of these therapies is great, so is the number of possible combinations not only with each other but also with small molecule therapeutics. Furthermore, the observation of unusual dose-response relationships suggests a critical dependency of drug effectiveness on the dosage regimen (dose and schedule). Clinical pharmacodynamic (PD) biomarkers will be useful endpoints for confirming drug mechanism of action, evaluating combination therapies for synergy or antagonism, and identifying optimal dosage regimens. In contrast to conventional PD in which drug action occurs entirely within a single target cell (ie, is self-contained within the malignant cell), immunotherapy involves a complex mechanism of action with sequential steps that propagate through multiple cell types, both normal and malignant. Its intercellular pharmacology begins with molecular target engagement either on an immune effector cell or a malignant cell, followed by stimulatory biochemical and biological signals in immune effector cells, and then finally ends with activation of cell death mechanisms in malignant cells lying within a certain distance from the activated effector cells (immune cell-tumor cell proximity). Evaluating such "trans-cellular pharmacology," in which different steps of drug action are distributed across multiple cell types, requires novel microscopy and image analysis tools capable of quantifying PD-biomarker responses, mapping the responses onto the cellular geography of the tumor using phenotypic biomarkers to identify specific cell types, and finally analyzing the spatial relationships between biomarkers in the context of each cell's biological role. We have termed this form of nearest neighbor image analysis of drug action "proximity PD microscopy," to indicate the importance of the location of the PD-biomarker response within the cellular landscape of a tumor specimen. We discuss herein the major modes of immunotherapy, and lay out a blueprint for using PD assessment to optimize dosage regimens of single agents and guide development of combination immunotherapy regimens, using PD1/PD-L1 immune checkpoint inhibition as a case study.

Proinflammatory Caspase A Activation and an Antiviral State Are Induced by a Zebrafish Perforin after Possible Cellular and Functional Diversification from a Myeloid Ancestor

In mammals, perforins play a central role in the granule-dependent cell death induced by natural killer T cells and cytotoxic T lymphocytes, and participate both in the defense against virus-infected and neoplastic cells and in the recognition of nonself molecules by the immune system. Little is known about fish perforin genes. We examined the zebrafish with the aim of increasing our knowledge about the role of perforins. We characterized 6 perforin genes in the zebrafish genome, and we studied them at the evolutionary level in combination with expression patterns in several tissues and cell populations, during both larval development and in the course of a viral infection. Our results suggest the specialization of different cell types in the production of perforins. Moreover, functional diversification during the evolution of these molecules could be inferred from this study. In particular, one of the genes, prf19b, which is mainly produced by myeloid cells, seemed to be involved in antiviral defense, conferring protection after an in vivo infection.

A High Yield and Cost-efficient Expression System of Human Granzymes in Mammalian Cells

When cytotoxic T lymphocytes (CTL) or natural killer (NK) cells recognize tumor cells or cells infected with intracellular pathogens, they release their cytotoxic granule content to eliminate the target cells and the intracellular pathogen. Death of the host cells and intracellular pathogens is triggered by the granule serine proteases, granzymes (Gzms), delivered into the host cell cytosol by the pore forming protein perforin (PFN) and into bacterial pathogens by the prokaryotic membrane disrupting protein granulysin (GNLY). To investigate the molecular mechanisms of target cell death mediated by the Gzms in experimental in-vitro settings, protein expression and purification systems that produce high amounts of active enzymes are necessary. Mammalian secreted protein expression systems imply the potential to produce correctly folded, fully functional protein that bears posttranslational modification, such as glycosylation. Therefore, we used a cost-efficient calcium precipitation method for transient transfection of HEK293T cells with human Gzms cloned into the expression plasmid pHLsec. Gzm purification from the culture supernatant was achieved by immobilized nickel affinity chromatography using the C-terminal polyhistidine tag provided by the vector. The insertion of an enterokinase site at the N-terminus of the protein allowed the generation of active protease that was finally purified by cation exchange chromatography. The system was tested by producing high levels of cytotoxic human Gzm A, B and M and should be capable to produce virtually every enzyme in the human body in high yields.

MicroRNA profiling of CD3+ CD56+ cytokine-induced killer cells

Studies have proven that IL-2 and IL-15 showed contrasting roles during CIK cells preparation. By employing microarray, we analyzed miRNA expression profiles of PBMC, CIKIL-2 and CIKIL-15. Advanced bioinformatic analyses were performed to explore the key miRNAs which may regulate cell proliferation and anti-tumor activity of CIK. We identified 261 differentially expressed miRNAs (DEMs) between PBMC and CIKIL-2, and 249 DEMs between PBMC and CIKIL-15. MiR-143-3p/miR-145-5p was miRNA cluster which may positively regulate cell proliferation. In contrast, miR-340-5p/miR-340-3p cluster may negatively regulate cell proliferation via induction apoptosis, which may cause decreased cell proliferation capacity of CIKIL-2. MiRNA-target interaction analysis indicated that 10 co-downregulated miRNAs may synergistically turn on the expression of a pool of tumor cytotoxic genes in CIK cells. The DEMs between CIKIL-2 and CIKIL-15 may contribute to enhanced tumor cytotoxic capacity of CIKIL-2. Importantly, we found that repressed miR-193a-5p may regulate the expressions of inhibitory receptor KLRD1. The results of the validation assay have shown that KLRD1 were upregulated in CIK cells. Our findings have provided new insights into mechanisms of CIK cells production and tumor cytotoxic function, and shed light on their safety for clinical trial.

CD8+ T cells in cutaneous leishmaniasis: the good, the bad, and the ugly

CD8(+) T lymphocytes are components of the adaptive immune response and play an important role in protection against many viral and bacterial infections. However, their role in parasitic infections is less well understood. In leishmaniasis, a disease caused by intracellular protozoan parasites of the genus Leishmania, CD8(+) T cells have been shown to be protective. However, increasing evidence indicates that CD8(+) T cells may also exacerbate disease. In this review, we will describe the situations where CD8(+) T cells are either good or bad for the outcome of the infection and attempt to reconcile the dual role played by CD8(+) T cells in cutaneous leishmaniasis.

How do viruses control mitochondria-mediated apoptosis?

There is no doubt that viruses require cells to successfully reproduce and effectively infect the next host. The question is what is the fate of the infected cells? All eukaryotic cells can "sense" viral infections and exhibit defence strategies to oppose viral replication and spread. This often leads to the elimination of the infected cells by programmed cell death or apoptosis. This "sacrifice" of infected cells represents the most primordial response of multicellular organisms to viruses. Subverting host cell apoptosis, at least for some time, is therefore a crucial strategy of viruses to ensure their replication, the production of essential viral proteins, virus assembly and the spreading to new hosts. For that reason many viruses harbor apoptosis inhibitory genes, which once inside infected cells are expressed to circumvent apoptosis induction during the virus reproduction phase. On the other hand, viruses can take advantage of stimulating apoptosis to (i) facilitate shedding and hence dissemination, (ii) to prevent infected cells from presenting viral antigens to the immune system or (iii) to kill non-infected bystander and immune cells which would limit viral propagation. Hence the decision whether an infected host cell undergoes apoptosis or not depends on virus type and pathogenicity, its capacity to oppose antiviral responses of the infected cells and/or to evade any attack from immune cells. Viral genomes have therefore been adapted throughout evolution to satisfy the need of a particular virus to induce or inhibit apoptosis during its life cycle. Here we review the different strategies used by viruses to interfere with the two major apoptosis as well as with the innate immune signaling pathways in mammalian cells. We will focus on the intrinsic mitochondrial pathway and discuss new ideas about how particular viruses could activately engage mitochondria to induce apoptosis of their host.

T cell-NF-κB activation is required for tumor control in vivo

BACKGROUND

T cells have the capacity to eliminate tumors but the signaling pathways by which they do so are incompletely understood. T cell priming requires activation of the transcription factors AP-1, NFAT and NF-κB downstream of the TCR, but whether activation of T cell-NF-κB in vivo is required for tumor control has not been addressed. In humans and mice with progressively growing tumors, the activity of T cell-intrinsic NF-κB is often reduced. However, it is not clear if this is causal for an inability to reject transformed cells, or if it is a consequence of tumor growth. T cell-NF-κB is important for T cell survival and effector differentiation and plays an important role in enabling T cells to reject cardiac and islet allografts, suggesting the possibility that it may also be required for tumor elimination. In this study, we tested whether normal T cell-NF-κB activation is necessary for the rejection of tumors whose growth is normally controlled by the immune system.

METHODS

Mice with genetically impaired T cell-NF-κB activity were subcutaneously injected with MC57-SIY tumor cells. Tumor growth was measured over time, and the anti-tumor immune response was evaluated using flow cytometry and cytokine detection assays.

RESULTS

Mice with impaired T cell-NF-κB activity were unable to reject tumors that were otherwise eliminated by wildtype mice, despite equal accumulation of tumor-reactive T cells. In addition, specific impairment of NF-κB signaling downstream of the TCR was sufficient to prevent tumor rejection. Tumor antigen-specific T cell-IFN-γ and TNF-α production, as well as cytotoxic ability, were all reduced in mice with impaired T cell-NF-κB, suggesting an important role for this transcription factor in the effector differentiation of tumor-specific effector T cells.

CONCLUSIONS

Our results have identified the NF-κB pathway as an important signaling axis in T cells, required for the elimination of growing tumors in vivo. Maintaining or enhancing T cell-NF-κB activity may be a promising avenue for anti-tumor immunotherapy.

Granzyme B-activated p53 interacts with Bcl-2 to promote cytotoxic lymphocyte-mediated apoptosis

Granzyme B (GzmB) plays a major role in CTLs and NK cell-mediated elimination of virus-infected cells and tumors. Human GzmB preferentially induces target cell apoptosis by cleaving the proapoptotic Bcl-2 family member Bid, which, together with Bax, induces mitochondrial outer membrane permeabilization. We previously showed that GzmB also induces a rapid accumulation of the tumor-suppressor protein p53 within target cells, which seems to be involved in GzmB-induced apoptosis. In this article, we show that GzmB-activated p53 accumulates on target cell mitochondria and interacts with Bcl-2. This interaction prevents Bcl-2 inhibitory effect on both Bax and GzmB-truncated Bid, and promotes GzmB-induced mitochondrial outer membrane permeabilization. Consequently, blocking p53-Bcl-2 interaction decreases GzmB-induced Bax activation, cytochrome c release from mitochondria, and subsequent effector caspases activation leading to a decreased sensitivity of target cells to both GzmB and CTL/NK-mediated cell death. Together, our results define p53 as a new important player in the GzmB apoptotic signaling pathway and in CTL/NK-induced apoptosis.