Mycobacteria activate γδ T-cell anti-tumour responses via cytokines from type 1 myeloid dendritic cells: a mechanism of action for cancer immunotherapy

γδ T cells: Major advances in basic and clinical research in tumor immunotherapy

ABSTRACT

γδ T cells are a kind of innate immune T cell. They have not attracted sufficient attention because they account for only a small proportion of all immune cells, and many basic factors related to these cells remain unclear. However, in recent years, with the rapid development of tumor immunotherapy, γδ T cells have attracted increasing attention because of their ability to exert cytotoxic effects on most tumor cells without major histocompatibility complex (MHC) restriction. An increasing number of basic studies have focused on the development, antigen recognition, activation, and antitumor immune response of γδ T cells. Additionally, γδ T cell-based immunotherapeutic strategies are being developed, and the number of clinical trials investigating such strategies is increasing. This review mainly summarizes the progress of basic research and the clinical application of γδ T cells in tumor immunotherapy to provide a theoretical basis for further the development of γδ T cell-based strategies in the future.

BCG-activation of leukocytes is sufficient for the generation of donor-independent innate anti-tumor NK and γδ T-cells that can be further expanded in vitro

Bacillus Calmette-Guérin (BCG), the nonpathogenic Mycobacterium bovis strain used as tuberculosis vaccine, has been successfully used as treatment for non-muscle invasive bladder cancer for decades, and suggested to potentiate cellular and humoral immune responses. However, the exact mechanism of action is not fully understood. We previously described that BCG mainly activated anti-tumor cytotoxic NK cells with upregulation of CD56 and a CD16⁺ phenotype. Now, we show that stimulation of human peripheral blood mononuclear cells with iBCG, a preparation based on BCG-Moreau, expands oligoclonal γδ T-cells, with a cytotoxic phenotype, together with anti-tumor CD56^high CD16⁺ NK cells. We have used scRNA-seq, flow cytometry, and functional assays to characterize these BCG-activated γδ T-cells in detail. They had a high IFNγ secretion signature with expression of CD27⁺ and formed conjugates with bladder cancer cells. BCG-activated γδ T-cells proliferated strongly in response to minimal doses of cytokines and had anti-tumor functions, although not fully based on degranulation. BCG was sufficient to stimulate proliferation of γδ T-cells when cultured with other PBMC; however, BCG alone did not stimulate expansion of purified γδ T-cells. The characterization of these non-donor restricted lymphocyte populations, which can be expanded in vitro, could provide a new approach to prepare cell-based immunotherapy tools.

Suppression of the malignancy of mammary tumor in mice model by inactivated preparation of Mycobacterium obuense

Breast cancer (BC) is a significant cause of global mortality in women. This study was aimed to evaluate the immune-activation of malignant BC via the administration of attenuated Mycobacterium obuense. For this purpose, an in vivo model was developed with BALB/c mice. Mice were injected with 2.00 × 10⁶ 4T1 cells with breast tumor cell line. Forty-two mice were equally divided into control as well as low dose (0.20 mg 100 µL^-1) and high dose (0.50 mg 100 µL^-1) groups of M. obuense to investigate gene expression in the antitumor effects of M. obuense. In one group, paclitaxel was administrated as a choice drug in BC treatment. Antitumor manners were characterized by cytotoxicity against tumor target cells, size of the tumor and the expression of some BC metastatic genes together with pathology. The MTT assay demonstrated that different concentrations of both low and a high dose of bacteria did present no cytotoxicity effect on 4T1 cells. According to our findings, M. obuense significantly repressed tumor growth. M. obuense downregulated the expression of collagen type I alpha 1 (COLIA1), cFos, alkaline phosphatase (ALP), claudin 3 (cldn3), and conversely, activated transcription factor 4 (ATF4) and Twist related protein-1 (Twist1). All these alternations induced a decrease in the migratory and invasive capabilities of BC. The result of pathology was indicative of tumor regression in the paclitaxel and HK- M. obuense -recipient group. Thus, it seems most likely that M. obuense might impinge upon cell growth and metastatic behavior of malignant cells exerting anti-tumor activity in BC.

γδ T Cells in the Tumor Microenvironment-Interactions With Other Immune Cells

A growing number of studies have shown that γδ T cells play a pivotal role in mediating the clearance of tumors and pathogen-infected cells with their potent cytotoxic, cytolytic, and unique immune-modulating functions. Unlike the more abundant αβ T cells, γδ T cells can recognize a broad range of tumors and infected cells without the requirement of antigen presentation via major histocompatibility complex (MHC) molecules. Our group has recently demonstrated parts of the mechanisms of T-cell receptor (TCR)-dependent activation of Vγ9Vδ2+ T cells by tumors following the presentation of phosphoantigens, intermediates of the mevalonate pathway. This process is mediated through the B7 immunoglobulin family-like butyrophilin 2A1 (BTN2A1) and BTN3A1 complexes. Such recognition results in activation, a robust immunosurveillance process, and elicits rapid γδ T-cell immune responses. These include targeted cell killing, and the ability to produce copious quantities of cytokines and chemokines to exert immune-modulating properties and to interact with other immune cells. This immune cell network includes αβ T cells, B cells, dendritic cells, macrophages, monocytes, natural killer cells, and neutrophils, hence heavily influencing the outcome of immune responses. This key role in orchestrating immune cells and their natural tropism for tumor microenvironment makes γδ T cells an attractive target for cancer immunotherapy. Here, we review the current understanding of these important interactions and highlight the implications of the crosstalk between γδ T cells and other immune cells in the context of anti-tumor immunity.

Bacillus Calmette-Guerin (BCG) induces superior anti-tumour responses by Vδ2+ T cells compared with the aminobisphosphonate drug zoledronic acid

Vδ2⁺ T cells can recognize malignantly transformed cells as well as those infected with mycobacteria. This cross-reactivity supports the idea of using mycobacteria to manipulate Vδ2⁺ T cells in cancer immunotherapy. To date, therapeutic interventions using Vδ2⁺ T cells in cancer have involved expanding these cells in or ex vivo using zoledronic acid (ZA). Here, we show that the mycobacterium Bacillus Calmette–Guérin (BCG) also causes Vδ2⁺ T-cell expansion in vitro and that resulting Vδ2⁺ cell populations are cytotoxic toward tumour cell lines. We show that both ZA and BCG-expanded Vδ2+ cells effectively killed both Daudi and THP-1 cells. THP-1 cell killing by both ZA and BCG-expanded Vδ2+ cells was enhanced by treatment of targets cells with ZA. Although no difference in cytotoxic activity between ZA- and BCG-expanded Vδ2+ cells was observed, BCG-expanded cells degranulated more and produced a more diverse range of cytokines upon tumour cell recognition compared to ZA-expanded cells. ZA-expanded Vδ2+ cells were shown to upregulate exhaustion marker CD57 to a greater extent than BCG-expanded Vδ2+ cells. Furthermore, ZA expansion was associated with upregulation of inhibitory markers PD-1 and TIM3 in a dose-dependent manner whereas PD-1 expression was not increased following expansion using BCG. Intradermal BCG vaccination of rhesus macaques caused in vivo expansion of Vδ2⁺ cells. In combination with the aforementioned in vitro data, this finding suggests that BCG treatment could induce expansion of Vδ2⁺ T cells with enhanced anti-tumour potential compared to ZA treatment and that either ZA or BCG could be used intratumourally as a means to potentiate stronger anti-tumour Vδ2⁺ T-cell responses.

Human γδ T Cell Subsets and Their Clinical Applications for Cancer Immunotherapy

Simple Summary

Research into the immunotherapeutic potential of T cells has predominantly focused on conventional alpha beta (αβ) T cells, which recognize peptide antigens presented by polymorphic major histocompatibility complex (MHC) class I and class II molecules. However, innate-like T cells, such as gamma delta (γδ) T cells, also play important roles in antitumor immunity. Here, we review the current understanding of γδ T cells in antitumor immunity and discuss strategies that could potentially maximize their potential in cancer immunotherapy.

Abstract

Gamma delta (γδ) T cells are a minor population of T cells that share adaptive and innate immune properties. In contrast to MHC-restricted alpha beta (αβ) T cells, γδ T cells are activated in an MHC-independent manner, making them ideal candidates for developing allogeneic, off-the-shelf cell-based immunotherapies. As the field of cancer immunotherapy progresses rapidly, different subsets of γδ T cells have been explored. In addition, γδ T cells can be engineered using different gene editing technologies that augment their tumor recognition abilities and antitumor functions. In this review, we outline the unique features of different subsets of human γδ T cells and their antitumor properties. We also summarize the past and the ongoing pre-clinical studies and clinical trials utilizing γδ T cell-based cancer immunotherapy.

Potential of Mycobacterium tuberculosis chorismate mutase (Rv1885c) as a novel TLR4-mediated adjuvant for dendritic cell-based cancer immunotherapy

For clinical application by dendritic cell (DC)-based cancer immunotherapy, a proper adjuvant system to elicit a strong anticancer immune response is needed. Here, we investigated the potential of chorismate mutase (TBCM, Rv1885c), a putative Mycobacterium tuberculosis (TB) virulence factor, as an immunoadjuvant in DC-based tumor immunotherapy. First, we found that TBCM functionally activated DCs by upregulating costimulatory molecules, increasing the secretion of proinflammatory cytokines, enhancing migration and inducing the Th1-type immune response in a dose-dependent manner via TLR4-mediated signaling. In addition, subcutaneous injection of TBCM-activated DCs loaded with cell lysates led to reduced tumor mass, enhanced mouse survival and lowered tumor incidence in lung carcinoma (LLC) cell-bearing mice. This is mainly mediated by functional cytotoxic T lymphocyte-mediated oncolytic activity and inhibition of cancer proliferation- and metastasis-related genes. Moreover, TBCM-induced DCs can also generate memory CD4 T cells and exert long-term tumor prevention effects. In conclusion, our findings suggest that TBCM (Rv1885c), a novel TLR4 agonist, could be used as an immunoadjuvant for DC-based cancer immunotherapy.

Rapidly Growing Mycobacterium Species: The Long and Winding Road from Tuberculosis Vaccines to Potent Stress-Resilience Agents

Inflammatory diseases and stressor-related psychiatric disorders, for which inflammation is a risk factor, are increasing in modern Western societies. Recent studies suggest that immunoregulatory approaches are a promising tool in reducing the risk of suffering from such disorders. Specifically, the environmental saprophyte Mycobacterium vaccae National Collection of Type Cultures (NCTC) 11659 has recently gained attention for the prevention and treatment of stress-related psychiatric disorders. However, effective use requires a sophisticated understanding of the effects of M. vaccae NCTC 11659 and related rapidly growing mycobacteria (RGMs) on microbiome–gut–immune–brain interactions. This historical narrative review is intended as a first step in exploring these mechanisms and provides an overview of preclinical and clinical studies on M. vaccae NCTC 11659 and related RGMs. The overall objective of this review article is to increase the comprehension of, and interest in, the mechanisms through which M. vaccae NCTC 11659 and related RGMs promote stress resilience, with the intention of fostering novel clinical strategies for the prevention and treatment of stressor-related disorders.

Cheap and Commonplace: Making the Case for BCG and γδ T Cells in COVID-19

Antigen-specific vaccines developed for the COVID-19 pandemic demonstrate a remarkable achievement and are currently being used in high income countries with much success. However, new SARS-CoV-2 variants are threatening this success via mutations that lessen the efficacy of antigen-specific antibodies. One simple approach to assisting with this issue is focusing on strategies that build on the non-specific protection afforded by the innate immune response. The BCG vaccine has been shown to provide broad protection beyond tuberculosis disease, including against respiratory viruses, and ongoing studies are investigating its efficacy as a tool against SARS-CoV-2. Gamma delta (γδ) T cells, particularly the Vδ2 subtype, undergo rapid expansion after BCG vaccination due to MHC-independent mechanisms. Consequently, γδ T cells can produce diverse defenses against virally infected cells, including direct cytotoxicity, death receptor ligands, and pro-inflammatory cytokines. They can also assist in stimulating the adaptive immune system. BCG is affordable, commonplace and non-specific, and therefore could be a useful tool to initiate innate protection against new SARS-CoV-2 variants. However, considerations must also be made to BCG vaccine supply and the prioritization of countries where it is most needed to combat tuberculosis first and foremost.

Listeria monocytogenes-infected human monocytic derived dendritic cells activate Vγ9Vδ2 T cells independently of HMBPP production

Gamma-delta (γδ) T cells express T cell receptors (TCR) that are preconfigured to recognize signs of pathogen infection. In primates, γδ T cells expressing the Vγ9Vδ2 TCR innately recognize (E)-4-hydroxy-3-methyl-but- 2-enyl pyrophosphate (HMBPP), a product of the 2-C-methyl-D-erythritol 4- phosphate (MEP) pathway in bacteria that is presented in infected cells via interaction with members of the B7 family of costimulatory molecules butyrophilin (BTN) 3A1 and BTN2A1. In humans, Listeria monocytogenes (Lm) vaccine platforms have the potential to generate potent Vγ9Vδ2 T cell recognition. To evaluate the activation of Vγ9Vδ2 T cells by Lm-infected human monocyte-derived dendritic cells (Mo-DC) we engineered Lm strains that lack components of the MEP pathway. Direct infection of Mo-DC with these bacteria were unchanged in their ability to activate CD107a expression in Vγ9Vδ2 T cells despite an inability to synthesize HMBPP. Importantly, functional BTN3A1 was essential for this activation. Unexpectedly, we found that cytoplasmic entry of Lm into human dendritic cells resulted in upregulation of cholesterol metabolism in these cells, and the effect of pathway regulatory drugs suggest this occurs via increased synthesis of the alternative endogenous Vγ9Vδ2 ligand isoprenyl pyrophosphate (IPP) and/or its isomer dimethylallyl pyrophosphate (DMAPP). Thus, following direct infection, host pathways regulated by cytoplasmic entry of Lm can trigger Vγ9Vδ2 T cell recognition of infected cells without production of the unique bacterial ligand HMBPP.

Cytokine/Chemokine Release Patterns and Transcriptomic Profiles of LPS/IFNγ-Activated Human Macrophages Differentiated with Heat-Killed Mycobacterium obuense, M-CSF, or GM-CSF

Macrophages (Mφs) are instrumental regulators of the immune response whereby they acquire diverse functional phenotypes following their exposure to microenvironmental cues that govern their differentiation from monocytes and their activation. The complexity and diversity of the mycobacterial cell wall have empowered mycobacteria with potent immunomodulatory capacities. A heat-killed (HK) whole-cell preparation of Mycobacterium obuense (M. obuense) has shown promise as an adjunctive immunotherapeutic agent for the treatment of cancer. Moreover, HK M. obuense has been shown to trigger the differentiation of human monocytes into a monocyte-derived macrophage (MDM) type named Mob-MDM. However, the transcriptomic profile and functional properties of Mob-MDMs remain undefined during an activation state. Here, we characterized cytokine/chemokine release patterns and transcriptomic profiles of lipopolysaccharide (LPS)/interferon γ (IFNγ)-activated human MDMs that were differentiated with HK M. obuense (Mob-MDM(LPS/IFNγ)), macrophage colony-stimulating factor M-MDM(LPS/IFNγ)), or granulocyte/macrophage colony-stimulating factor (GM-MDM(LPS/IFNγ)). Mob-MDM(LPS/IFNγ) demonstrated a unique cytokine/chemokine release pattern (interleukin (IL)-10^low, IL-12/23p40^low, IL-23p19/p40^low, chemokine (C-x-C) motif ligand (CXCL)9^low) that was distinct from those of M-MDM(LPS/IFNγ) and GM-MDM(LPS/IFNγ). Furthermore, M-MDM(LPS/IFNγ) maintained IL-10 production at significantly higher levels compared to GM-MDM(LPS/IFNγ) and Mob-MDM(LPS/IFNγ) despite being activated with M1-Mφ-activating stimuli. Comparative RNA sequencing analysis pointed to a distinct transcriptome profile for Mob-MDM(LPS/IFNγ) relative to both M-MDM(LPS/IFNγ) and GM-MDM(LPS/IFNγ) that comprised 417 transcripts. Functional gene-set enrichment analysis revealed significant overrepresentation of signaling pathways and biological processes that were uniquely related to Mob-MDM(LPS/IFNγ). Our findings lay a foundation for the potential integration of HK M. obuense in specific cell-based immunotherapeutic modalities such as adoptive transfer of Mφs (Mob-MDM(LPS/IFNγ)) for cancer treatment.

The subtle interplay between gamma delta T lymphocytes and dendritic cells: is there a role for a therapeutic cancer vaccine in the era of combinatorial strategies?

Human gamma delta (γδ) T cells represent heterogeneous subsets of unconventional lymphocytes with an HLA-unrestricted target cell recognition. γδ T cells display adaptive clonally restricted specificities coupled to a powerful cytotoxic function against transformed/injured cells. Dendritic cells (DCs) are documented to be the most potent professional antigen-presenting cells (APCs) able to induce adaptive immunity and support the innate immune response independently from T cells. Several data show that the cross-talk of γδ T lymphocytes with DCs can play a crucial role in the orchestration of immune response by bridging innate to adaptive immunity. In the last decade, DCs, as well as γδ T cells, have been of increasing clinical interest, especially as monotherapy for cancer immunotherapy, even though with unpredictable results mainly due to immune suppression and/or tumor-immune escape. For these reasons, new vaccine strategies have to be explored to reach cancer immunotherapy's full potential. The effect of DC-based vaccines on γδ T cell is less extensively investigated, and a combinatorial approach using DC-based vaccines with γδ T cells might promote a strong synergy for long-term tumor control and protection against escaping tumor clones. Here, we discuss the therapeutic potential of the interaction between DCs and γδ T cells to improve cancer vaccination. In particular, we describe the most relevant and updated evidence of such combinatorial approaches, including the use of Zoledronate, Interleukin-15, and protamine RNA, also looking towards future strategies such as CAR therapies.

Repurposing Infectious Diseases Vaccines Against Cancer

Vaccines used to prevent infections have long been known to stimulate immune responses to cancer as illustrated by the approval of the Bacillus Calmette-Guérin (BCG) vaccine to treat bladder cancer since the 1970s. The recent approval of immunotherapies has rejuvenated this research area with reports of anti-tumor responses with existing infectious diseases vaccines used as such, either alone or in combination with immune checkpoint inhibitors. Here, we have reviewed and summarized research activities using approved vaccines to treat cancer. Data supporting a cancer therapeutic use was found for 16 vaccines. For 10 (BCG, diphtheria, tetanus, human papillomavirus, influenza, measles, pneumococcus, smallpox, typhoid and varicella-zoster), clinical trials have been conducted or are ongoing. Within the remaining 6, preclinical evidence supports further evaluation of the rotavirus, yellow fever and pertussis vaccine in carefully designed clinical trials. The mechanistic evidence for the cholera vaccine, combined with the observational data in colorectal cancer, is also supportive of clinical translation. There is limited data for the hepatitis B and mumps vaccine (without measles vaccine). Four findings are worth highlighting: the superiority of intravesical typhoid vaccine instillations over BCG in a preclinical bladder cancer model, which is now the subject of a phase I trial; the perioperative use of the influenza vaccine to limit and prevent the natural killer cell dysfunction induced by cancer surgery; objective responses following intratumoral injections of measles vaccine in cutaneous T-cell lymphoma; objective responses induced by human papillomavirus vaccine in cutaneous squamous cell carcinoma. All vaccines are intended to induce or improve an anti-tumor (immune) response. In addition to the biological and immunological mechanisms that vary between vaccines, the mode of administration and sequence with other (immuno-)therapies warrant more attention in future research.

Effects of Mycobacterium vaccae Aerosol Inhalation on Airway Inflammation in Asthma Mouse Model

Background: Mycobacterium vaccae vaccine, a composition of Mycobacterium proteins, has been known to have bidirectional immunomodulatory functions. Recent studies have shown that M. vaccae has a therapeutic potential for treating asthma. However, little is known regarding the effect of M. vaccae aerosol inhalation during allergen sensitization or challenge on asthma. The purpose of this study was to explore the effect and the underlying mechanism of M. vaccae aerosol inhalation during allergen sensitization or challenge on airway inflammation in an asthma mouse model. Methods: Asthma mouse models were established. Mice received aerosol inhalation with M. vaccae once daily during allergen sensitization or challenge for 5 days successively. Airway responsiveness, bronchoalveolar lavage fluid (BALF) cell count, histology, and cytokine concentrations (IL-4, IFN-γ, IL-10, and IL-17) were measured. The relative mRNA expression of ASC, caspase-1, TNF-α, and IL-1β was also determined. Expression of pulmonary NLRP3 and nuclear factor kappa B (NF-κB) protein was measured using immunohistochemistry and Western blot. Results: M. vaccae aerosol inhalation suppressed airway hyperresponsiveness and inflammation, reduced levels of IL-4, upregulated expression of IFN-γ and IL-10 in BALF, inhibited mRNA expression of pulmonary ASC, caspase-1, TNF-α, and IL-1β, and also inhibited expression of pulmonary NLRP3 and NF-κB protein during allergen sensitization or challenge. Conclusion: M. vaccae aerosol inhalation can suppress airway hyperresponsiveness and inflammation during allergen sensitization or challenge, and may be a promising approach for asthma therapy.

Trial Watch: Experimental Toll-like receptor agonists for cancer therapy

Toll-like receptors (TLRs) are prototypic pattern recognition receptors (PRRs) best known for their ability to activate the innate immune system in response to conserved microbial components such as lipopolysaccharide and double-stranded RNA. Accumulating evidence indicates that the function of TLRs is not restricted to the elicitation of innate immune responses against invading pathogens. TLRs have indeed been shown to participate in tissue repair and injury-induced regeneration as well as in adaptive immune responses against cancer. In particular, TLR4 signaling appears to be required for the efficient processing and cross-presentation of cell-associated tumor antigens by dendritic cells, which de facto underlie optimal therapeutic responses to some anticancer drugs. Thus, TLRs constitute prominent therapeutic targets for the activation/intensification of anticancer immune responses. In line with this notion, long-used preparations such as the Coley toxin (a mixture of killed Streptococcus pyogenes and Serratia marcescens bacteria) and the bacillus Calmette-Guérin (BCG, an attenuated strain of Mycobacterium bovis originally developed as a vaccine against tuberculosis), both of which have been associated with consistent anticancer responses, potently activate TLR2 and TLR4 signaling. Today, besides BCG, only one TLR agonist is FDA-approved for therapeutic use in cancer patients: imiquimod. In this Trial Watch, we will briefly present the role of TLRs in innate and cognate immunity and discuss the progress of clinical studies evaluating the safety and efficacy of experimental TLR agonists as immunostimulatory agents for oncological indications.

Mitigating Coronavirus Induced Dysfunctional Immunity for At-Risk Populations in COVID-19: Trained Immunity, BCG and "New Old Friends"

The novel, highly contagious coronavirus SARS-CoV-2 spreads rapidly throughout the world, leading to a deadly pandemic of a predominantly respiratory illness called COVID-19. Safe and effective anti-SARS-CoV-2 vaccines are urgently needed. However, emerging immunological observations show hallmarks of significant immunopathological characteristics and dysfunctional immune responses in patients with COVID-19. Combined with existing knowledge about immune responses to other closely related and highly pathogenic coronaviruses, this could forebode significant challenges for vaccine development, including the risk of vaccine failure. Animal data from earlier coronavirus vaccine efforts indicate that elderly people, most at risk from severe COVID-19 disease, could be especially at risk from immunopathologic responses to novel coronavirus vaccines. Bacterial "new old friends" such as Bacille Calmette-Guérin (BCG) or Mycobacterium obuense have the ability to elevate basal systemic levels of type 1 cytokines and immune cells, correlating with increased protection against diverse and unrelated infectious agents, called "trained immunity." Here we describe dysfunctional immune responses induced by coronaviruses, representing potentially difficult to overcome obstacles to safe, effective vaccine development for COVID-19, and outline how trained immunity could help protect high risk populations through immunomodulation with BCG and other "new old friends."

Mycobacteria-Based Vaccines as Immunotherapy for Non-urological Cancers

The arsenal against different types of cancers has increased impressively in the last decade. The detailed knowledge of the tumor microenvironment enables it to be manipulated in order to help the immune system fight against tumor cells by using specific checkpoint inhibitors, cell-based treatments, targeted antibodies, and immune stimulants. In fact, it is widely known that the first immunotherapeutic tools as immune stimulants for cancer treatment were bacteria and still are; specifically, the use of Mycobacterium bovis bacillus Calmette-Guérin (BCG) continues to be the treatment of choice for preventing cancer recurrence and progression in non-invasive bladder cancer. BCG and also other mycobacteria or their components are currently under study for the immunotherapeutic treatment of different malignancies. This review focuses on the preclinical and clinical assays using mycobacteria to treat non-urological cancers, providing a wide knowledge of the beneficial applications of these microorganisms to manipulate the tumor microenvironment aiming at tumor clearance.

Effects of Mycobacterium vaccae vaccine in a mouse model of tuberculosis: protective action and differentially expressed genes

BACKGROUND

Tuberculosis is a leading cause of death worldwide. BCG is an effective vaccine, but not widely used in many parts of the world due to a variety of issues. Mycobacterium vaccae (M. vaccae) is another vaccine used in human subjects to prevent tuberculosis. In the current study, we investigated the potential mechanisms of M. vaccae vaccination by determining differentially expressed genes in mice infected with M. tuberculosis before and after M. vaccae vaccination.

METHODS

Three days after exposure to M. tuberculosis H37Rv strain (5 × 10⁵ CFU), adult BALB/c mice randomly received either M. vaccae vaccine (22.5 μg) or vehicle via intramuscular injection (n = 8). Booster immunization was conducted 14 and 28 days after the primary immunization. Differentially expressed genes were identified by microarray followed by standard bioinformatics analysis.

RESULTS

M. vaccae vaccination provided protection against M. tuberculosis infection (most prominent in the lungs). We identified 2326 upregulated and 2221 downregulated genes in vaccinated mice. These changes could be mapped to a total of 123 signaling pathways (68 upregulated and 55 downregulated). Further analysis pinpointed to the MyD88-dependent TLR signaling pathway and PI3K-Akt signaling pathway as most likely to be functional.

CONCLUSIONS

M. vaccae vaccine provided good protection in mice against M. tuberculosis infection, via a highly complex set of molecular changes. Our findings may provide clue to guide development of more effective vaccine against tuberculosis.

Bacteria and cancer: Different sides of the same coin

Conventional cancer therapies such as chemotherapy, radiation therapy, and immunotherapy due to the complexity of cancer have been unsuccessful in the complete eradication of tumor cells. Thus, there is a need for new therapeutic strategies toward cancer. Recently, the therapeutic role of bacteria in different fields of medicine and pharmaceutical research has attracted attention in recent decades. Although several bacteria are notorious as cancer-causing agents, recent research revealed intriguing results suggesting the bacterial potential in cancer therapy. Thus, bacterial cancer therapy is an alternative anticancer approach that has promising results on tumor cells in-vivo. Moreover, with the aid of genetic engineering, some natural or genetically modified bacterial strains can directly target hypoxic regions of tumors and secrete therapeutic molecules leading to cancer cell death. Additionally, stimulation of immune cells by bacteria, bacterial cancer DNA vaccine and antitumor bacterial metabolites are other therapeutic applications of bacteria in cancer therapy. The present study is a comprehensive review of different aspects of bacterial cancer therapy alone and in combination with conventional methods, for improving cancer therapy.

Therapeutic vaccination immunomodulation: forming the basis of all cancer immunotherapy

Recent immunotherapy advances have convincingly demonstrated complete tumour removal with long-term survival. These impressive clinical responses have rekindled enthusiasm towards immunotherapy and tumour antigen vaccination providing 'cures' for melanoma and other cancers. However, many patients still do not benefit; sometimes harmed by severe autoimmune toxicity. Checkpoint inhibitors (anti-CTLA4; anti-PD-1) and interleukin-2 (IL-2) are 'pure immune drivers' of pre-existing immune responses and can induce either desirable effector-stimulatory or undesirable inhibitory-regulatory responses. Why some patients respond well, while others do not, is presently unknown, but might be related to the cellular populations being 'driven' at the time of dosing, dictating the resulting immune response. Vaccination is in-vivo immunotherapy requiring an active host response. Vaccination for cancer treatment has been skeptically viewed, arising partially from difficulty demonstrating clear, consistent clinical responses. However, this article puts forward accumulating evidence that 'vaccination' immunomodulation constitutes the fundamental, central, intrinsic property associated with antigen exposure not only from exogenous antigen (allogeneic or autologous) administration, but also from endogenous release of tumour antigen (autologous) from in-vivo tumour-cell damage and lysis. Many 'standard' cancer therapies (chemotherapy, radiotherapy etc.) create waves of tumour-cell damage, lysis and antigen release, thus constituting 'in-vivo vaccination' events. In essence, whenever tumour cells are killed, antigen release can provide in-vivo repeated vaccination events. Effective anti-tumour immune responses require antigen release/supply; immune recognition, and immune responsiveness. With better appreciation of endogenous vaccination and immunomodulation, more refined approaches can be engineered with prospect of higher success rates from cancer therapy, including complete responses and better survival rates.

Antitumor Effects of DC Vaccine With ALA-PDT-Induced Immunogenic Apoptotic Cells for Skin Squamous Cell Carcinoma in Mice

Targeted immunotherapy using dendritic cell vaccine has been employed for the treatment of solid tumors. Topical 5-aminolevulinic acid-mediated photodynamic therapy, an established approach for topical cancers, can induce an effective antitumor immune response. We have previously shown that 5-aminolevulinic acid-mediated photodynamic therapy–induced tumor lysates could considerably enhance antigen-presenting capacity of ex vivo-generated dendritic cells. The current study further demonstrates that 5-aminolevulinic acid-mediated photodynamic therapy dendritic cell vaccine can induce immune responses against cancers. Dendritic cells pulsed by photodynamic therapy–treated skin squamous cell carcinoma cells inhibited squamous cell carcinoma to a greater extent than tumor lysates treated by photodynamic therapy alone or dendritic cells pulsed by freeze–thawed treated tumor cells. Immunohistochemistry showed that photodynamic therapy dendritic cell vaccine could increase the activity of CD4⁺ and CD8⁺ T cells in the tumor implantation sites. Flow cytometry assays showed that CD4⁺ and CD8⁺ T cells in the spleens of photodynamic therapy dendritic cell vaccine immunized mice increased significantly. Furthermore, we observed increased amounts of interleukin 12 and Interferon gamma (IFN-γ) and decreased amounts of interleukin 10 in the splenocytes and peripheral blood of photodynamic therapy dendritic cell vaccine immunized mice by enzyme linked immunosorbent assay (ELISA). Taken together, our findings suggest that photodynamic therapy dendritic cell vaccination is an effective prophylactic therapy for squamous cell carcinoma.

Diabetic gut microbiota dysbiosis as an inflammaging and immunosenescence condition that fosters progression of retinopathy and nephropathy

The increased prevalence of type 2 diabetes mellitus (T2DM) and life expectancy of diabetic patients fosters the worldwide prevalence of retinopathy and nephropathy, two major microvascular complications that have been difficult to treat with contemporary glucose-lowering medications. The gut microbiota (GM) has become a lively field research in the last years; there is a growing recognition that altered intestinal microbiota composition and function can directly impact the phenomenon of ageing and age-related disorders. In fact, human GM, envisaged as a potential source of novel therapeutics, strongly modulates host immunity and metabolism. It is now clear that gut dysbiosis and their products (e.g. p-cresyl sulfate, trimethylamine‑N‑oxide) dictate a secretory associated senescence phenotype and chronic low-grade inflammation, features shared in the physiological process of ageing ("inflammaging") as well as in T2DM ("metaflammation") and in its microvascular complications. This review provides an in-depth look on the crosstalk between GM, host immunity and metabolism. Further, it characterizes human GM signatures of elderly and T2DM patients. Finally, a comprehensive scrutiny of recent molecular findings (e.g. epigenetic changes) underlying causal relationships between GM dysbiosis and diabetic retinopathy/nephropathy complications is pinpointed, with the ultimate goal to unravel potential pathophysiological mechanisms that may be explored, in a near future, as personalized disease-modifying therapeutic approaches.

Enhanced effect of checkpoint inhibitors when given after or together with IMM-101: significant responses in four advanced melanoma patients with no additional major toxicity

Background

The use of checkpoint inhibitors (ipilimumab, pembrolizumab, nivolumab) has revolutionised the treatment of metastatic melanoma. However still more than the half the patients do not respond to single-agent immunotherapy. This has led to the development of combining these agents in an attempt to enhance the anti-cancer activity. More than 300 different studies with 15 different drug doses are currently ongoing. Combining different checkpoint inhibitors (CPIs) does indeed lead to an increase in response rate, but this is associated with significant toxicity. IMM-101 is a heat killed Mycobacterium preparation which induces marked immune modulation and little systemic toxicity. It has been reported as having activity in melanoma as single agent and in pancreatic cancer in combination with gemcitabine, the latter in a randomised study.

Methods

Here we report the effect of adding CPIs to 3 patients who had previously been on IMM-101, either as a trial or a named patient programme and a patient who received the IMM-101 together with nivolumab.

Results

All 4 patients had rapid and very good responses, three of them maintained over 18 months with no significant additional toxicity.

Conclusions

The rapid and complete clinical responses seen in these patients may suggest that IMM-101 is activating a complementary pathway which is synergistic with CPI treatment.

Attenuated Bacteria as Immunotherapeutic Tools for Cancer Treatment

The use of attenuated bacteria as cancer therapeutic tools has garnered increasing scientific interest over the past 10 years. This is largely due to the development of bacterial strains that maintain good anti-tumor efficacy, but with reduced potential to cause toxicities to the host. Because of its ability to replicate in viable as well as necrotic tissue, cancer therapy using attenuated strains of facultative anaerobic bacteria, such as Salmonella, has several advantages over standard treatment modalities, including chemotherapy and radiotherapy. Despite some findings suggesting that it may operate through a direct cytotoxic effect against cancer cells, there is accumulating evidence demonstrating that bacterial therapy acts by modulating cells of the immune system to counter the growth of the tumor. Herein, we review the experimental evidence underlying the success of bacterial immunotherapy against cancer and highlight the cellular and molecular alterations in the peripheral immune system and within the tumor microenvironment that have been reported following different forms of bacterial therapy. Our improved understanding of these mechanisms should greatly aid in the translational application of bacterial therapy to cancer patients.

Defining Genome-Wide Expression and Phenotypic Contextual Cues in Macrophages Generated by Granulocyte/Macrophage Colony-Stimulating Factor, Macrophage Colony-Stimulating Factor, and Heat-Killed Mycobacteria

Heat-killed (HK) Mycobacterium obuense (NCTC13365) is currently being evaluated in the clinic as an immunotherapeutic agent for cancer treatment. Yet, the molecular underpinnings underlying immunomodulatory properties of HK M. obuense are still largely undefined. To fill this void, we sought to perform immunophenotyping, chemokine/cytokine release analysis and genome-wide characterization of monocyte-derived macrophages (MDM) in which monocytes were originally isolated from healthy donors and differentiated by HK M. obuense (Mob-MDM) relative to macrophage colony-stimulating factor (M-MDM) and granulocyte/macrophage colony-stimulating factor (GM-MDM). Immunophenotyping and cytokine release analysis revealed downregulated surface expression of CD36, decreased spontaneous release of CCL2 and increased spontaneous secretion of CCL5, CXCL8/IL-8, IL-6, and TNF-α in Mob-MDM relative to M-MDM and GM-MDM. Analysis of cytostatic activity showed that Mob-MDM exhibited similar growth inhibitory effects on immortalized and malignant epithelial cells compared with GM-MDM but at an elevated rate relative to M-MDM. To understand global cues in Mob-MDM, we performed comparative RNA-sequencing (RNA-Seq) analysis of Mob-MDM relative to GM-MDM and M-MDM (n = 4 donors). Clustering analysis underscored expression profiles (n = 256) that were significantly modulated in Mob-MDM versus both M-MDM and GM-MDM including, among others, chemokines/cytokines and their receptors, enzymes and transcriptions factors. Topological functional analysis of these profiles identified pathways and gene sets linked to Mob-MDM phenotype including nitric oxide production, acute phase response signaling and microbe recognition pathways as well as signaling cues mediated by the proinflammatory cytokine, interferon-gamma, and the intracellular pattern recognition receptor, nucleotide-binding oligomerization domain-containing protein 2. Taken together, our study highlights molecular immune phenotypes and global signaling cues in Mob-MDM that may underlie immunomodulatory properties of HK M. obuense. Such properties could be of valuable use in immunotherapy approaches such as adoptive cell therapy against cancer.

Immunomodulatory effects of heat-killed Mycobacterium obuense on human blood dendritic cells

Heat-killed (HK) Mycobacterium obuense is a novel immunomodulator, currently undergoing clinical evaluation as an immunotherapeutic agent in the treatment of cancer. Here, we examined the effect of in vitro exposure to HK M. obuense on the expression of different categories of surface receptors on human blood myeloid (m) and plasmacytoid (p) DCs. Moreover, we have characterized the cytokine and chemokine secretion patterns of purified total blood DCs stimulated with HK M. obuense. HK M. obuense significantly up-regulated the expression of CD11c, CD80, CD83, CD86, CD274 and MHC class II in whole-blood mDCs and CD80, CD123 and MHC class II in whole-blood pDCs. Down-regulation of CD195 expression in both DC subpopulations was also noted. Further analysis showed that HK M. obuense up-regulated the expression of CD80, CD83 and MHC class II on purified blood DC subpopulations. TLR2 and TLR1 were also identified to be engaged in mediating the HK M. obuense-induced up-regulation of surface receptor expression on whole blood mDCs. In addition, our data demonstrated that HK M. obuense augmented the secretion of CCL4, CCL5, CCL22, CXCL8, IL-6, IL-12p40 and TNF-α by purified total blood DCs. Taken together, our data suggest that HK M. obuense exerts potent differential immunomodulatory effects on human DC subpopulations.

Immunobiography and the Heterogeneity of Immune Responses in the Elderly: A Focus on Inflammaging and Trained Immunity

Owing to its memory and plasticity, the immune system (IS) is capable of recording all the immunological experiences and stimuli it was exposed to. The combination of type, dose, intensity, and temporal sequence of antigenic stimuli that each individual is exposed to has been named “immunobiography.” This immunological history induces a lifelong continuous adaptation of the IS, which is responsible for the capability to mount strong, weak or no response to specific antigens, thus determining the large heterogeneity of immunological responses. In the last years, it is becoming clear that memory is not solely a feature of adaptive immunity, as it has been observed that also innate immune cells are provided with a sort of memory, dubbed “trained immunity.” In this review, we discuss the main characteristics of trained immunity as a possible contributor to inflammaging within the perspective of immunobiography, with particular attention to the phenotypic changes of the cell populations known to be involved in trained immunity. In conclusion, immunobiography emerges as a pervasive and comprehensive concept that could help in understanding and interpret the individual heterogeneity of immune responses (to infections and vaccinations) that becomes particularly evident at old age and could affect immunosenescence and inflammaging.

Randomised, open-label, phase II study of gemcitabine with and without IMM-101 for advanced pancreatic cancer

BACKGROUND

Immune Modulation and Gemcitabine Evaluation-1, a randomised, open-label, phase II, first-line, proof of concept study (NCT01303172), explored safety and tolerability of IMM-101 (heat-killed Mycobacterium obuense; NCTC 13365) with gemcitabine (GEM) in advanced pancreatic ductal adenocarcinoma.

METHODS

Patients were randomised (2 : 1) to IMM-101 (10 mg ml(-l) intradermally)+GEM (1000 mg m(-2) intravenously; n=75), or GEM alone (n=35). Safety was assessed on frequency and incidence of adverse events (AEs). Overall survival (OS), progression-free survival (PFS) and overall response rate (ORR) were collected.

RESULTS

IMM-101 was well tolerated with a similar rate of AE and serious adverse event reporting in both groups after allowance for exposure. Median OS in the intent-to-treat population was 6.7 months for IMM-101+GEM v 5.6 months for GEM; while not significant, the hazard ratio (HR) numerically favoured IMM-101+GEM (HR, 0.68 (95% CI, 0.44-1.04, P=0.074). In a pre-defined metastatic subgroup (84%), OS was significantly improved from 4.4 to 7.0 months in favour of IMM-101+GEM (HR, 0.54, 95% CI 0.33-0.87, P=0.01).

CONCLUSIONS

IMM-101 with GEM was as safe and well tolerated as GEM alone, and there was a suggestion of a beneficial effect on survival in patients with metastatic disease. This warrants further evaluation in an adequately powered confirmatory study.

The cells that mediate innate immune memory and their functional significance in inflammatory and infectious diseases

Immunological memory mediated by antigen-specific T and B cells is the foundation of adaptive immunity and is fundamental to the heightened and rapid protective immune response induced by vaccination or following re-infection with the same pathogen. While the innate immune system has classically been considered to be non-specific and devoid of memory, it now appears that it can be trained following exposure to microbes or their products and that this may confer a form of memory on innate immune cells. The evidence for immunological memory outside of T and B cells has been best established for natural killer (NK) cells, where it has been known for decades that NK cells have heighten responses following immunological re-challenge. Furthermore, recent studies have demonstrated that monocyte/macrophages, and probably dendritic cells, can be re-programmed through epigenetic modification, following exposure to pathogens or their products, resulting in heighted responses following a second stimulation. Unlike antigen-specific memory of the adaptive immune system, the second stimulation does not have to be with the same pathogen or antigen. Indirect evidence for this comes from reports on the non-specific beneficial effect of certain live vaccines, such as Bacillus Calmette Guerin (BCG) against unrelated childhood infectious diseases. It also appears that certain pathogen or pathogen-derived molecules can prime immune cells, especially macrophages, to secrete more anti-inflammatory and less pro-inflammatory cyokines, thus opening up the possibility of exploiting innate immune training as a new therapeutic approach for inflammatory diseases.

Generation of mouse and human dendritic cells in vitro

Dendritic cells (DC) that can orchestrate immune responses and maintain host homeostasis, are indispensable components of the immune system. Although distributed widely in many lymphoid and non-lymphoid tissues, their rarity in number has become a limiting factor for DC related research and therapies. Therefore, methods for efficiently generating large numbers of DC resembling their in vivo counterparts are urgently needed for DC related research and therapies. Herein we summarize the current methods for generating mouse and human DC in vitro and hope that these will facilitate both studies of DC biology and their clinical applications.

Vaccines versus immunotherapy: overview of approaches in deciding between options

This review compares the optimal use of vaccines vs. other forms of immunotherapy, which includes cytokines, such as IL-2, monoclonal antibodies, such as the 'checkpoint inhibitors', against CTLA-4 and PD-1. The review includes both prophylactic and therapeutic vaccines using a variety of technologies. It is already established that vaccines can be enhanced by other immunotherapies, such as cytokines (IL-2) and there is scope for combining both of these with the 'checkpoint' antibodies. Moreover, both can be enhanced with other modalities, such as radiotherapy, ablative therapy and both high and low dose chemotherapies.

Analysis of the immunomodulatory properties of two heat-killed mycobacterial preparations in a human whole blood model

The significant role played by mycobacteria in modulating immune responses through enhancing the crosstalk between innate and adaptive immunity has been highlighted in several studies. Owing to their unique antigenic profile, heat killed (HK) preparations of rapid-growing mycobacteria, currently undergoing clinical development, have been assessed as adjuvant therapy in various diseases. The purpose of this study is to investigate the regulation of leukocyte surface receptors, in whole blood from healthy donors, following in vitro stimulation with HK Mycobacterium vaccae (M. vaccae) or M. obuense. We have demonstrated the ability of both mycobacterial preparations to target monocytes and neutrophils and to regulate the surface expression of selected adhesion receptors, antigen-presenting and costimulatory receptors, pattern recognition receptors, complement and Fc receptors, as well as cytokine/chemokine receptors. Toll-like receptors (TLRs) 1 and 2 were also shown to be involved in mediating the M. obuense-induced upregulation of selected surface receptors on monocytes. Whole blood stimulation with M. vaccae or M. obuense resulted in a significant increase in the secretion of a specific set of cytokines and chemokines. Both mycobacterial preparations induced strong antigen-specific proliferative responses in peripheral blood mononuclear cells. Collectively, our data shows that M. vaccae and M. obuense have the potential to act as potent immunomodulators. Future research based on these findings may reveal novel immune pathways induced by these preparations with potential implication for their use in diverse immunotherapeutic approaches.

Draft Genome Sequence of Mycobacterium obuense Strain UC1, Isolated from Patient Sputum

We report the draft genome sequence of Mycobacterium obuense strain UC1 from a patient sputum sample. This is the first draft genome sequence of Mycobacterium obuense, a rapidly growing scotochromogenic mycobacterium.

Harnessing the power of Vδ2 cells in cancer immunotherapy

γδ T cells are a subset of T lymphocytes that have been implicated in immunosurveillance against infections and tumours. In the peripheral blood of humans the γδ T cell pool is made up predominantly of Vδ2 cells, which can detect both foreign and self-metabolites of the isoprenoid biosynthesis pathway. This unique axis of antigen recognition enables Vδ2 cells to respond to a range of pathogenic infections as well as perturbations in endogenous isoprenoid biosynthesis that can occur during cell stress and malignant transformation. There has been growing interest in Vδ2 cells as a potential avenue for cancer immunotherapy, and a number of strategies have been utilized in an attempt to boost the anti-tumour response of Vδ2 cells in patients. In this review we discuss critically the evidence that Vδ2 cells contribute to the cytotoxic response against tumours and evaluate current immunotherapeutic approaches that target these cells in cancer patients, with specific focus on their shortcomings and how they may be improved.

Empowering gamma delta T cells with antitumor immunity by dendritic cell-based immunotherapy

Gamma delta (γδ) T cells are the all-rounders of our immune-system with their major histocompatibility complex-unrestricted cytotoxicity, capacity to secrete immunosti-mulatory cytokines and ability to promote the generation of tumor antigen-specific CD8⁺ and CD4⁺ T cell responses. Dendritic cell (DC)-based vaccine therapy has the prospective to harness these unique features of the γδ T cells in the fight against cancer. In this review, we will discuss our current knowledge on DC-mediated γδ T cell activation and related opportunities for tumor immunologists.

Immune evasion in cancer: Mechanistic basis and therapeutic strategies

Cancer immune evasion is a major stumbling block in designing effective anticancer therapeutic strategies. Although considerable progress has been made in understanding how cancers evade destructive immunity, measures to counteract tumor escape have not kept pace. There are a number of factors that contribute to tumor persistence despite having a normal host immune system. Immune editing is one of the key aspects why tumors evade surveillance causing the tumors to lie dormant in patients for years through "equilibrium" and "senescence" before re-emerging. In addition, tumors exploit several immunological processes such as targeting the regulatory T cell function or their secretions, antigen presentation, modifying the production of immune suppressive mediators, tolerance and immune deviation. Besides these, tumor heterogeneity and metastasis also play a critical role in tumor growth. A number of potential targets like promoting Th1, NK cell, γδ T cell responses, inhibiting Treg functionality, induction of IL-12, use of drugs including phytochemicals have been designed to counter tumor progression with much success. Some natural agents and phytochemicals merit further study. For example, use of certain key polysaccharide components from mushrooms and plants have shown to possess therapeutic impact on tumor-imposed genetic instability, anti-growth signaling, replicative immortality, dysregulated metabolism etc. In this review, we will discuss the advances made toward understanding the basis of cancer immune evasion and summarize the efficacy of various therapeutic measures and targets that have been developed or are being investigated to enhance tumor rejection.

Rationale for combining immunotherapy with chemotherapy

Immunotherapy has usually been considered as an alternative to more traditional modalities. Moreover, it has previously been felt that chemotherapy is inherently immunosuppressive and not suitable for combining with immunotherapy. In this review, the concept of combining different modalities that result in cell death, such as radiotherapy and chemotherapy, with immunotherapy is explored. Tumors actively cause immune suppression which can be reversed by their removal but when this is not possible, enhancing the immune response with nonspecific immune stimulation can enhance the response to other modalities, such as radiotherapy and chemotherapy. Additionally, several chemotherapy agents at low doses selectively inhibit regulatory and suppressor cells.

Zoledronic acid causes γδ T cells to target monocytes and down-modulate inflammatory homing

Zoledronic acid (ZA) is a potential immunotherapy for cancer because it can induce potent γδ T-cell-mediated anti-tumour responses. Clinical trials are testing the efficacy of intravenous ZA in cancer patients; however, the effects of systemic ZA on the activation and migration of peripheral γδ T cells remain poorly understood. We found that γδ T cells within ZA-treated peripheral blood mononuclear cells were degranulating, as shown by up-regulated expression of CD107a/b. Degranulation was monocyte dependent because CD107a/b expression was markedly reduced in the absence of CD14(+) cells. Consistent with monocyte-induced degranulation, we observed γδ T-cell-dependent induction of monocyte apoptosis, as shown by phosphatidylserine expression on monocytes and decreased percentages of monocytes in culture. Despite the prevailing paradigm that ZA promotes tumour homing in γδ T cells, we observed down-modulation of their tumour homing capacity, as shown by decreased expression of the inflammatory chemokine receptors CCR5 and CXCR3, and reduced migration towards the inflammatory chemokine CCL5. Taken together our data suggest that ZA causes γδ T cells to target monocytes and down-modulate the migratory programme required for inflammatory homing. This study provides novel insight into how γδ T cells interact with monocytes and the possible implications of systemic use of ZA in cancer.

γδ T cell and other immune cells crosstalk in cellular immunity

γδ T cells have been recognized as effectors with immunomodulatory functions in cellular immunity. These abilities enable them to interact with other immune cells, thus having the potential for treatment of various immune-mediated diseases with adoptive cell therapy. So far, the interactions between γδ T cell and other immune cells have not been well defined. Here we will discuss the interactivities among them and the perspective on γδ T cells for their use in immunotherapy could be imagined. The understanding of the crosstalk among the immune cells in immunopathology might be beneficial for the clinical application of γδ T cell.

Exosomes derived from Rab27a‑overexpressing tumor cells elicit efficient induction of antitumor immunity

Lung cancer is the leading cause of mortality worldwide. However, there is a lack of effective therapeutic strategies. Currently, tumor immunotherapy based on exosomes, which are secreted by a variety of cell types including tumor cells, has drawn particular attention and are suggested to have the potential for exploitation in tumor therapy. Nevertheless, the therapeutic efficacy mediated via tumor cell-derived exosomes is not satisfactory. Rab27a, one of the Rab family of small GTPases, has been suggested to be important in exosome secretion. Thus, the purpose of the present study was to examine whether exosomes derived from Rab27a‑overexpressing cells elicited more potent antitumor immunity. A Rab27a‑overexpressing line was established via transfection of a Rab27a overexpression vector into the human non-small-cell lung cancer cell line, A549. Exosomes were isolated and the typical exosomal protein markers, CD9, CD63, heat shock protein (Hsp) 70 and Hsp90, were found to be enriched in the exosomes derived from Rab27a‑overexpressing cells. Subsequently, these exosomes were demonstrated to be capable of upregulating major histocompatibility complex class II molecules as well as the co-stimulatory molecules CD80 and CD86 on dendritic cells (DCs), suggesting that more potent maturation of DCs was induced. Furthermore, DCs loaded with exosomes derived from Rab27-overexpressing cells significantly promoted CD4+ T cell proliferation in vitro. In addition, in vivo immunization of exosomes derived from Rab27a‑overexpressing cells inhibited tumor growth in a mouse model. It was also demonstrated that splenocytes from mice immunized with exosomes derived from Rab27-overexpressing cells expressed high levels of type I cytokines, including IL-2 and IFN-γ, which are important in the regulation of cell-mediated antitumor immunity. Collectively, it was demonstrated that exosomes derived from Rab27a‑overexpressing cancer cells elicited more potent antitumor immune effects, which may provide novel insights for the development of efficient exosome-based cancer vaccines.

Tripartite immune cell co-operation in the Bacillus Calmette Guérin-induced activation of γδ T cells

γδ T cells contribute to immunosurveillance of pathogenic infections and malignant transformations; however, mechanisms of activation have yet to be fully defined. In this study we demonstrate a novel mechanism by which human Vδ2(+) γδ T cells are activated by the model pathogen Bacillus Calmette Guérin (BCG). We show in vitro that Vδ2 cell cytokine production and cytotoxic activity in response to BCG are dependent on both dendritic cells (DCs) and memory CD4(+) αβ T cells (CD4 T cells). We found that Vδ2 cells are indirectly activated by BCG in an interleukin (IL)-12p70-dependent manner, and that DC production of the IL-12p70 responsible for Vδ2 cell activation requires Toll-like receptor 2/4 ligands from BCG and interferon (IFN)-γ from memory CD4 T cells. Our data suggest that Vδ2 cell responses to BCG are dependent on the activation of IFN-γ-producing memory CD4 T cells, and provide novel insight into the complex interplay between cells of the innate and adaptive immune response.

Can tissue-based immune markers be used for studying the natural history of cancer?

Increasing evidence suggests that altered immunity and chronic inflammation play a key role in the etiology of many malignancies, but the underlying biological mechanisms involved remain unclear. Systemic markers of immunity may not represent the clinically relevant, site-specific immune response, whereas tissue-based markers may more accurately reflect the local immunologic mechanisms by which precursor lesions develop into cancer. Tissues are often only available in individuals with disease. Previous studies have measured tumor-infiltrating lymphocytes to predict prognosis and survival, but it can be challenging to use tissue-based markers to study the natural history of cancer due to limitations with regard to temporality, the availability of appropriate comparison groups, and other epidemiologic issues. In this commentary, we discuss several epidemiologic study design and study population considerations to address these issues, including the strengths and limitations of using tissue-based markers to study immune response and cancer development. We also discuss how the use of tissue-based immune markers fits into the greater context of molecular epidemiology, which encompasses multiple technologies and techniques, and how implementation of tissue-based immune markers will provide an increased understanding of site-specific biological mechanisms involved in carcinogenesis.