Differentiation, distribution and gammadelta T cell-driven regulation of IL-22-producing T cells in tuberculosis

A Brief Molecular History of Vγ9Vδ2 TCR-Mediated Phosphoantigen Sensing

Vγ9Vδ2 T-cells are universally present in humans and represent one of the most prevalent TCR reactivities, evolutionarily conserved across diverse mammalian species. They are an innate-like subset featuring a semi-invariant TCR repertoire that drives their well-recognized reactivity to small, non-peptidic phosphoantigens (pAg). Crucially, they can distinguish between highly immunostimulatory microbially derived pAg and much less potent host-derived pAg, with the former effectively acting as a pathogen associated molecular pattern (PAMP) and the Vγ9Vδ2 TCR as a surrogate pattern recognition receptor (PRR). Ample evidence supports important Vγ9Vδ2-mediated contributions to immunity against diverse pathogenic bacteria and parasites, mediated by their potent effector and immunoregulatory functions. The molecular basis of the pAg sensing mechanism underpinning such responses has, however, remained highly mysterious. Despite this, past studies have established that pAg sensing is MHC-independent, extremely fast, exquisitely pAg-sensitive, and dependent upon target cell expression of key BTN-family molecules, notably BTN3A and BTN2A1. Here we contextualize these findings and several recent studies addressing pAg sensing. We integrate these into a single unified theory of pAg sensing interpretable from different perspectives, both intracellular and extracellular, biophysical, and topological. We prioritize critical questions to address in the context of this proposed model. Finally, we suggest the model will provide a molecular template for antigen recognition by other related γδ T-cell subsets.

Helper T cell bias following tuberculosis chemotherapy identifies opportunities for therapeutic vaccination to prevent relapse

Therapeutic vaccines have promise as adjunctive treatment for tuberculosis (TB) or as preventives against TB relapse. An important development challenge is the limited understanding of T helper (Th) cell roles during these stages of disease. A murine model of TB relapse was used to identify changes in Th populations and cytokine microenvironment. Active TB promoted expansion of Th1, Th2, Th17, and Th22 cells and cytokines in the lung. Following drug therapy, pulmonary Th17 and Th22 cells contracted, Th1 cells remained elevated, while Th cells producing IL-4 or IL-10 expanded. At relapse, Th22 cells failed to re-expand in the lung despite a moderate re-expansion of Th1 and Th17 cells and an increase in Th cytokine polyfunctionality. The dynamics of Th populations further differed by tissue compartment and disease presentation. These outcomes identify immune bias by Th subpopulations during TB relapse as candidate mechanisms for pathogenesis and targets for therapeutic vaccination.

Double-edged sword: γδ T cells in mucosal homeostasis and disease

The mucosa is a tissue that covers numerous body surfaces, including the respiratory tract, digestive tract, eye, and urogenital tract. Mucosa is in direct contact with pathogens, and γδ T cells perform various roles in the tissue. γδ T cells efficiently defend the mucosa from various pathogens, such as viruses, bacteria, and fungi. In addition, γδ T cells are necessary for the maintenance of homeostasis because they select specific organisms in the microbiota and perform immunoregulatory functions. Furthermore, γδ T cells directly facilitate pregnancy by producing growth factors. However, γδ T cells can also play detrimental roles in mucosal health by amplifying inflammation, thereby worsening allergic responses. Moreover, these cells can act as major players in autoimmune diseases. Despite their robust roles in the mucosa, the application of γδ T cells in clinical practice is lacking because of factors such as gaps between mice and human cells, insufficient knowledge of the target of γδ T cells, and the small population of γδ T cells. However, γδ T cells may be attractive targets for clinical use due to their effector functions and low risk of inducing graft-versus-host disease. Therefore, robust research on γδ T cells is required to understand the crucial features of these cells and apply these knowledges to clinical practices.

Current Knowledge of Th22 Cell and IL-22 Functions in Infectious Diseases

T helper 22 (Th22) cells, a newly defined CD4+ T-cell lineage, are characterized by their distinct cytokine profile, which primarily consists of IL-13, IL-22 and TNF-α. Th22 cells express a wide spectrum of chemokine receptors, such as CCR4, CCR6 and CCR10. The main effector molecule secreted by Th22 cells is IL-22, a member of the IL-10 family, which acts by binding to IL-22R and triggering a complex downstream signaling system. Th22 cells and IL-22 have been found to play variable roles in human immunity. In preventing the progression of infections such as HIV and influenza, Th22/IL-22 exhibited protective anti-inflammatory characteristics, and their deleterious proinflammatory activities have been demonstrated to exacerbate other illnesses, including hepatitis B and Helicobacter pylori infection. Herein, we review the current understanding of Th22 cells, including their definition, differentiation and mechanisms, and the effect of Th22/IL-22 on human infectious diseases. According to studies on Th22 cells, Th22/IL-22 may be a promising therapeutic target and an effective treatment strategy for various infections.

Role of interleukin-22 in tuberculosis patients

OBJECTIVES

Disease progression of tuberculosis (TB) depends on the balance between the microorganism's virulence and the host defense systems (mainly T cell-mediated immune response). Interleukin-22 (IL-22) helps in cell proliferation and regeneration and provides protection against microbial diseases. The IL-22-producing T cells can migrate into the granulomas during TB infection. However, disparity exists in literature regarding its role. The present study aims to compare serum IL-22 levels and its' expression in TB patients and healthy controls.

METHODS

87 TB patients and 85 healthy subjects were enrolled in the study. Under aseptic conditions, venous blood was withdrawn. Serum IL-22 levels were estimated using enzyme-linked immunosorbent assay, and its gene expression was assessed using SYBR green-based quantitative PCR technology. A statistical analysis was performed using SPSS.

RESULTS

The median (interquartile range) of serum IL-22 levels was significantly lower in TB patients (18.55 (5.08) pg/mL) when compared to controls (49.38 (162.88) pg/mL) (p<0.0001). The IL-22 expression was significantly upregulated with a fold change value of 29.44 in TB patients.

CONCLUSIONS

The IL-22 levels were found to be significantly decreased in patients, contradictory to its expression, which is upregulated. It plays a crucial role for the modulation of tissues in response to TB infection.

Characterization of Mycobacterium tuberculosis-Specific Th22 Cells and the Effect of Tuberculosis Disease and HIV Coinfection

The development of a highly effective tuberculosis (TB) vaccine is likely dependent on our understanding of what constitutes a protective immune response to TB. Accumulating evidence suggests that CD4+ T cells producing IL-22, a distinct subset termed "Th22" cells, may contribute to protective immunity to TB. Thus, we characterized Mycobacterium tuberculosis-specific Th22 (and Th1 and Th17) cells in 72 people with latent TB infection or TB disease, with and without HIV-1 infection. We investigated the functional properties (IFN-γ, IL-22, and IL-17 production), memory differentiation (CD45RA, CD27, and CCR7), and activation profile (HLA-DR) of M. tuberculosis-specific CD4+ T cells. In HIV-uninfected individuals with latent TB infection, we detected abundant circulating IFN-γ-producing CD4+ T cells (median, 0.93%) and IL-22-producing CD4+ T cells (median, 0.46%) in response to M. tuberculosis The frequency of IL-17-producing CD4+ T cells was much lower, at a median of 0.06%. Consistent with previous studies, IL-22 was produced by a distinct subset of CD4+ T cells and not coexpressed with IL-17. M. tuberculosis-specific IL-22 responses were markedly reduced (median, 0.08%) in individuals with TB disease and HIV coinfection compared with IFN-γ responses. M. tuberculosis-specific Th22 cells exhibited a distinct memory and activation phenotype compared with Th1 and Th17 cells. Furthermore, M. tuberculosis-specific IL-22 was produced by conventional CD4+ T cells that required TCR engagement. In conclusion, we confirm that Th22 cells are a component of the human immune response to TB. Depletion of M. tuberculosis-specific Th22 cells during HIV coinfection may contribute to increased risk of TB disease.

Nanocages engineered from Bacillus Calmette-Guerin facilitate protective Vγ2Vδ2 T cell immunity against Mycobacterium tuberculosis infection

Tuberculosis (TB), induced by Mycobacterium tuberculosis (Mtb) infection, remains a top killer among infectious diseases. While Bacillus Calmette-Guerin (BCG) is the sole TB vaccine, the clumped-clustered features of BCG in intradermal immunization appear to limit both the BCG protection efficacy and the BCG vaccination safety. We hypothesize that engineering of clumped-clustered BCG into nanoscale particles would improve safety and also facilitate the antigen-presenting-cell (APC)’s uptake and the following processing/presentation for better anti-TB protective immunity. Here, we engineered BCG protoplasts into nanoscale membraned BCG particles, termed as “BCG-Nanocage” to enhance the anti-TB vaccination efficiency and safety. BCG-Nanocage could readily be ingested/taken by APC macrophages selectively; BCG-Nanocage-ingested macrophages exhibited better viability and developed similar antimicrobial responses with BCG-infected macrophages. BCG-Nanocage, like live BCG bacilli, exhibited the robust capability to activate and expand innate-like T effector cell populations of Vγ2+ T, CD4+ T and CD8+ T cells of rhesus macaques in the ex vivo PBMC culture. BCG-Nanocage immunization of rhesus macaques elicited similar or stronger memory-like immune responses of Vγ2Vδ2 T cells, as well as Vγ2Vδ2 T and CD4+/CD8+ T effectors compared to live BCG vaccination. BCG-Nanocage- immunized macaques developed rapidly-sustained pulmonary responses of Vγ2Vδ2 T cells upon Mtb challenge. Furthermore, BCG- and BCG-Nanocage- immunized macaques, but not saline controls, exhibited undetectable Mtb infection loads or TB lesions in the Mtb-challenged lung lobe and hilar lymph node at endpoint after challenge. Thus, the current study well justifies a large pre-clinical investigation to assess BCG-Nanocage for safe and efficacious anti-TB vaccination, which is expected to further develop novel vaccines or adjuvants.

Th22 Cells Are a Major Contributor to the Mycobacterial CD4+ T Cell Response and Are Depleted During HIV Infection

HIV-1 infection substantially increases the risk of developing tuberculosis (TB). Mechanisms such as defects in the Th1 response to Mycobacterium tuberculosis in HIV-infected persons have been widely reported. However, Th1-independent mechanisms also contribute to protection against TB. To identify a broader spectrum of defects in TB immunity during HIV infection, we examined IL-17A and IL-22 production in response to mycobacterial Ags in peripheral blood of persons with latent TB infection and HIV coinfection. Upon stimulating with mycobacterial Ags, we observed a distinct CD4+ Th lineage producing IL-22 in the absence of IL-17A and IFN-γ. Mycobacteria-specific Th22 cells were present at high frequencies in blood and contributed up to 50% to the CD4+ T cell response to mycobacteria, comparable in magnitude to the IFN-γ Th1 response (median 0.91% and 0.55%, respectively). Phenotypic characterization of Th22 cells revealed that their memory differentiation was similar to M. tuberculosis-specific Th1 cells (i.e., predominantly early differentiated CD45RO+CD27+ phenotype). Moreover, CCR6 and CXCR3 expression profiles of Th22 cells were similar to Th17 cells, whereas their CCR4 and CCR10 expression patterns displayed an intermediate phenotype between Th1 and Th17 cells. Strikingly, mycobacterial IL-22 responses were 3-fold lower in HIV-infected persons compared with uninfected persons, and the magnitude of responses correlated inversely with HIV viral load. These data provide important insights into mycobacteria-specific Th subsets in humans and suggest a potential role for IL-22 in protection against TB during HIV infection. Further studies are needed to fully elucidate the role of IL-22 in protective TB immunity.

Characterization of membrane-bound IL-22+ T cell subsets in HIV-1 patients coinfected with Mycobacterium tuberculosis

BACKGROUND

Previously, we have found that IL-22 could be not only secreted outside of cells, but also highly expressed on the T cells membrane in HIV-1 negative patients with tuberculosis (TB). However, the study on membrane-bound IL-22+ cells of HIV-1 infected patients is rare. Therefore, we investigated antigen-specific membrane-bound IL-22+ T cell subsets in Mycobacterium tuberculosis (M.tb) coinfection of HIV-1 infected individuals.

METHODS

A case-control study that enrolled 74 HIV-1 infected participants was carried out, including HIV-1 monoinfection (HIV+TB-, n = 43), HIV-1 infected patients with latent TB (HIV+LTB, n = 18) and HIV-1 coinfected patients with active TB (HIV+TB+, n = 13). We made use of an IFN-γ release assay (IGRA) to screen LTB individuals. Purified protein derivative (PPD) and phosphoantigen (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP) were used as specific-stimulators to detect the levels of peripheral blood membrane-bound IL-22+ T cell subsets via cell surface staining and flow cytometry among three groups.

RESULTS

An approximate rate of 24.3% (n = 18 out of 74) of latent M.tb infection among HIV-1 positive population in Eastern China. Interestingly, HMBPP-specific CD3+Vγ2+ T cells were impaired in HIV+TB+patients compared with HIV+LTB patients (P < 0.05). Furthermore, increases of PPD-specific and HMBPP-specific membrane-bound IL-22+ T cell subsets including CD3+, CD3+CD4+ and CD3+Vγ2+ T cells were observed in HIV+TB+group rather than HIV+LTB groups (all P < 0.05).

CONCLUSION

Antigen-specific membrane-bound IL-22+ T cells were highly expressed in M.tb coinfection of HIV-1 infected individuals, and may play an important role in anti-TB immune response during coinfection with HIV-1.

The role of donor-unrestricted T-cells, innate lymphoid cells, and NK cells in anti-mycobacterial immunity

Vaccination strategies against mycobacteria, focusing mostly on classical T‐ and B‐cells, have shown limited success, encouraging the addition of alternative targets. Classically restricted T‐cells recognize antigens presented via highly polymorphic HLA class Ia and class II molecules, while donor‐unrestricted T‐cells (DURTs), with few exceptions, recognize ligands via genetically conserved antigen presentation molecules. Consequently, DURTs can respond to the same ligands across diverse human populations. DURTs can be activated either through cognate TCR ligation or via bystander cytokine signaling. TCR‐driven antigen‐specific activation of DURTs occurs upon antigen presentation via non‐polymorphic molecules such as HLA‐E, CD1, MR1, and butyrophilin, leading to the activation of HLA‐E–restricted T‐cells, CD1‐restricted T‐cells, mucosal‐associated invariant T‐cells (MAITs), and TCRγδ T‐cells, respectively. NK cells and innate lymphoid cells (ILCs), which lack rearranged TCRs, are activated through other receptor‐triggering pathways, or can be engaged through bystander cytokines, produced, for example, by activated antigen‐specific T‐cells or phagocytes. NK cells can also develop trained immune memory and thus could represent cells of interest to mobilize by novel vaccines. In this review, we summarize the latest findings regarding the contributions of DURTs, NK cells, and ILCs in anti–M tuberculosis, M leprae, and non‐tuberculous mycobacterial immunity and explore possible ways in which they could be harnessed through vaccines and immunotherapies to improve protection against Mtb.

Fast-acting γδ T-cell subpopulation and protective immunity against infections

Unique Vγ2Vδ2 (Vγ9Vδ2) T cells existing only in human and non-human primates, account for the majority of circulating γδ T cells in human adults. Vγ2Vδ2 T cells are the sole γδ T-cell subpopulation capable of recognizing the microbial (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP) produced by selected pathogens during infections. Recent seminal studies in non-human primate models have demonstrated that the unique HMBPP-specific Vγ2Vδ2 T cells are fast-acting, multi-functional, and protective during infections. This article reviews the recent seminal observations of Vγ2Vδ2 T cells in protective mechanisms against tuberculosis and other infections.

Macrophage-Targeted Isoniazid-Selenium Nanoparticles Promote Antimicrobial Immunity and Synergize Bactericidal Destruction of Tuberculosis Bacilli

Pathogenesis hallmarks for tuberculosis (TB) are the Mycobacterium tuberculosis (Mtb) escape from phagolysosomal destruction and limited drug delivery into infected cells. Several nanomaterials can be entrapped in lysosomes, but the development of functional nanomaterials to promote phagolysosomal Mtb clearance remains a big challenge. Here, we report on the bactericidal effects of selenium nanoparticles (Se NPs) against Mtb and further introduce a novel nanomaterial-assisted anti-TB strategy manipulating Ison@Man-Se NPs for synergistic drug-induced and phagolysosomal destruction of Mtb. Ison@Man-Se NPs preferentially entered macrophages and accumulated in lysosomes releasing Isoniazid. Surprisingly, Ison@Man-Se/Man-Se NPs further promoted the fusion of Mtb into lysosomes for synergistic lysosomal and Isoniazid destruction of Mtb. Concurrently, Ison@Man-Se/Man-Se NPs also induced autophagy sequestration of Mtb, evolving into lysosome-associated autophagosomal Mtb degradation linked to ROS-mitochondrial and PI3K/Akt/mTOR signaling pathways. This novel nanomaterial-assisted anti-TB strategy manipulating antimicrobial immunity and Mtb clearance may potentially serve in more effective therapeutics against TB and drug-resistant TB.

Tuberculosis patients display a high proportion of CD8+ T cells with a high cytotoxic potential

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (Mtb) and remains a major cause of morbidity and mortality worldwide. In the host's immune response system, T cells play a critical role in mediating protection against Mtb infection, but the role of CD8⁺ T cells is still controversial. We evaluated the phenotypical characterization and cytotoxic ability of CD8⁺ T cells by flow cytometry‐based assay. Cytokine levels in serum were measured by multiplex cytokine assay. Our data show that cells from TB patients have an increased percentage of peripheral blood CD8⁺αβ⁺ T (p = 0.02) and CD56⁺CD8⁺ T (p = 0.02) and a decreased frequency of NKG2D⁺CD8⁺ T (p = 0.02) compared with healthy donors. Unlike CD8⁺ T cells from healthy donors, CD8⁺ T cells from TB patients exhibit greater cytotoxicity, mediated by HLA class I molecules, on autologous monocytes in the presence of mycobacterial antigens (p = 0.005). Finally, TB patients have a proinflammatory profile characterized by serum high level of TNF‐α (p = 0.02) and IL‐8 (p = 0.0001), but, interestingly, IL‐4 (p = 0.002) was also increased compared with healthy donors. Our data show evidence regarding the highly cytotoxic status of CD8⁺ T cells in Mtb infection. These cytotoxic cells restricted to HLA‐A, B, and C could be used to optimize strategies for designing new TB vaccines or for identifying markers of disease progression.

Interleukin-22 receptor 1 is expressed in multinucleated giant cells: A study on intestinal tuberculosis and Crohn's disease

BACKGROUND

It is challenging to distinguish intestinal tuberculosis from Crohn's disease due to dynamic changes in epidemiology and similar clinical characteristics. Recent studies have shown that polymorphisms in genes involved in the interleukin (IL)-23/IL-17 axis may affect intestinal mucosal immunity by affecting the differentiation of Th17 cells.

AIM

To investigate the specific single-nucleotide polymorphisms (SNPs) in genes involved in the IL-23/IL-17 axis and possible pathways that affect susceptibility to intestinal tuberculosis and Crohn's disease.

METHODS

We analysed 133 patients with intestinal tuberculosis, 128 with Crohn's disease, and 500 normal controls. DNA was extracted from paraffin-embedded specimens or whole blood. Four SNPs in the IL23/Th17 axis (IL22 rs2227473, IL1β rs1143627, TGFβ rs4803455, and IL17 rs8193036) were genotyped with TaqMan assays. The transcriptional activity levels of different genotypes of rs2227473 were detected by dual luciferase reporter gene assay. The expression of IL-22R1 in different intestinal diseases was detected by immunohistochemistry.

RESULTS

The A allele frequency of rs2227473 (P = 0.030, odds ratio = 0.60, 95% confidence interval: 0.37-0.95) showed an abnormal distribution between intestinal tuberculosis and healthy controls. The presence of the A allele was associated with a higher IL-22 transcriptional activity (P < 0.05). In addition, IL-22R1 was expressed in intestinal lymphoid tissues, especially under conditions of intestinal tuberculosis, and highly expressed in macrophage-derived Langhans giant cells. The results of immunohistochemistry showed that the expression of IL-22R1 in patients with Crohn's disease and intestinal tuberculosis was significantly higher than that in patients with intestinal polyps and colon cancer (P < 0.01).

CONCLUSION

High IL-22 expression seems to be a protective factor for intestinal tuberculosis. IL-22R1 is expressed in Langhans giant cells, suggesting that the IL-22/IL-22R1 system links adaptive and innate immunity.

Immunization of Vγ2Vδ2 T cells programs sustained effector memory responses that control tuberculosis in nonhuman primates

Despite the urgent need for a better tuberculosis (TB) vaccine, relevant protective mechanisms remain unknown. We previously defined protective phosphoantigen (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP)–specific Vγ2Vδ2 T cells as a unique subset in primates, and, here, we immunized them selectively for protection against TB. A single respiratory vaccination of macaques with attenuated HMBPP-producing Listeria monocytogenes (Lm ΔactA prfA*), but not an HMBPP-lacking ΔgcpE Listeria strain, expanded Vγ2Vδ2 T cells, elicited Th1-like Vγ2Vδ2 T cell responses, and reduced TB infection/pathology after moderate-dose TB challenge. Such protection correlated with rapid memory-like, Th1-like Vγ2Vδ2 T cell responses, the presence of tissue-resident Vγ2Vδ2 T effectors coproducing IFN-γ/perforin and inhibiting intracellular Mycobacterium tuberculosis growth, and enhanced CD4⁺/CD8⁺ T cell responses. These findings establish a concept incorporating immunization of human Vγ2Vδ2 T cells for TB vaccine development.

Tuberculosis (TB) remains a leading killer among infectious diseases, and a better TB vaccine is urgently needed. The critical components and mechanisms of vaccine-induced protection against Mycobacterium tuberculosis (Mtb) remain incompletely defined. Our previous studies demonstrate that Vγ2Vδ2 T cells specific for (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP) phosphoantigen are unique in primates as multifunctional effectors of immune protection against TB infection. Here, we selectively immunized Vγ2Vδ2 T cells and assessed the effect on infection in a rhesus TB model. A single respiratory vaccination of macaques with an HMBPP-producing attenuated Listeria monocytogenes (Lm ΔactA prfA*) caused prolonged expansion of HMBPP-specific Vγ2Vδ2 T cells in circulating and pulmonary compartments. This did not occur in animals similarly immunized with an Lm ΔgcpE strain, which did not produce HMBPP. Lm ΔactA prfA* vaccination elicited increases in Th1-like Vγ2Vδ2 T cells in the airway, and induced containment of TB infection after pulmonary challenge. The selective immunization of Vγ2Vδ2 T cells reduced lung pathology and mycobacterial dissemination to extrapulmonary organs. Vaccine effects coincided with the fast-acting memory-like response of Th1-like Vγ2Vδ2 T cells and tissue-resident Vγ2Vδ2 effector T cells that produced both IFN-γ and perforin and inhibited intracellular Mtb growth. Furthermore, selective immunization of Vγ2Vδ2 T cells enabled CD4⁺ and CD8⁺ T cells to mount earlier pulmonary Th1 responses to TB challenge. Our findings show that selective immunization of Vγ2Vδ2 T cells can elicit fast-acting and durable memory-like responses that amplify responses of other T cell subsets, and provide an approach to creating more effective TB vaccines.

Multidrug-resistant tuberculosis (MDR-TB) strain infection in macaques results in high bacilli burdens in airways, driving broad innate/adaptive immune responses

Tuberculosis (TB) has become the most deadly infectious diseases due to epidemics of HIV/AIDS and multidrug-resistant/extensively drug-resistant TB (MDR-/XDR-TB). Although person-to-person transmission contributes to MDR-TB, it remains unknown whether infection with MDR strains resembles infection with drug-sensitive (DS) TB strains, manipulating limited or broad immune responses. To address these questions, macaques were infected with MDR strain V791 and a drug-sensitive Erdman strain of TB. MDR bacilli burdens in the airway were significantly higher than those of the Erdman control after pulmonary exposure. This productive MDR strain infection upregulated the expression of caspase 3 in macrophages/monocytes and induced appreciable innate-like effector responses of CD3-negative lymphocytes and Ag-specific γδ T-cell subsets. Concurrently, MDR strain infection induced broad immune responses of T-cell subpopulations producing Th1, Th17, Th22, and CTL cytokines. Furthermore, MDR bacilli, like the Erdman strain, were capable of inducing typical TB disease characterized by weight loss, lymphocytopenia, and severe TB lesions. For the first time, our results suggest that MDR-TB infection acts like DS to induce high bacterial burdens in the airway (transmission advantage), innate/adaptive immune responses, and disease processes. Because nonhuman primates are biologically closer to humans than other species, our data may provide useful information for predicting the effects of primary MDR strain infection after person-to-person transmission. The findings also support the hypothesis that a vaccine or host-directed adjunctive modality that is effective for drug-sensitive TB is likely to also impact MDR-TB.

IL-22: An Underestimated Player in Natural Resistance to Tuberculosis?

Approximately 10% of individuals latently infected with Mycobacterium tuberculosis (Mtb) develop active tuberculosis (TB) during their lifetime. Although it is well recognized that T-helper 1 immune responses are crucial for containing latent TB infection, the full array of host factors conferring protective immunity from TB progression are not completely understood. IL-22 is produced by cells of the innate and adaptive immune system including innate lymphoid cells, and natural killer cells as well as T lymphocytes (Th1, Th17, and Th22) and binds to its cognate receptor, the IL-22R1, which is expressed on non-hematopoietic cells such as lung epithelial cells. However, recent studies suggest that Mtb induces expression of the IL-22R1 on infected macrophages and multiple studies have indicated a protective role of IL-22 in respiratory tract infections. Reduced concentrations of circulating IL-22 in active TB compared to latent TB and decreased percentages of Mtb-specific IL-22 producing T cells in TB patients compared to controls designate this cytokine as a key player in TB immunology. More recently, it has been shown that in type 2 diabetes (T2D) and TB co-morbidity serum IL-22 concentrations are further reduced compared to TB patients without co-morbidities. However, whether a causative link between low IL-22 and increased susceptibility to TB and disease severity of TB exists remains to be established. This review summarizes the contribution of IL-22, a potentially under-appreciated key player in natural resistance to TB, at the interface between the immune response to Mtb and the lung epithelium.

The crucial roles of Th17-related cytokines/signal pathways in M. tuberculosis infection

Interleukin-17 (IL-17), IL-21, IL-22 and IL-23 can be grouped as T helper 17 (Th17)-related cytokines because they are either produced by Th17/Th22 cells or involved in their development. Here, we review Th17-related cytokines/Th17-like cells, networks/signals and their roles in immune responses or immunity against Mycobacterium tuberculosis (Mtb) infection. Published studies suggest that Th17-related cytokine pathways may be manipulated by Mtb microorganisms for their survival benefits in primary tuberculosis (TB). In addition, there is evidence that immune responses of the signal transducer and activator of transcription 3 (STAT3) signal pathway and Th17-like T-cell subsets are dysregulated or destroyed in patients with TB. Furthermore, Mtb infection can impact upstream cytokines in the STAT3 pathway of Th17-like responses. Based on these findings, we discuss the need for future studies and the rationale for targeting Th17-related cytokines/signals as a potential adjunctive treatment.

[Peripheral blood T cell TNF-α and IFN-γ production stimulated by low molecular peptide of Mycobacterium tuberculosis heat-resistant antigen for differential diagnosis between pulmonary tuberculosis and latent tuberculosis infection]

OBJECTIVE

To investigate the effects of low molecular peptide of Mycobacterium tuberculosis heat-resistant antigen (Mtb-HAg-10k) on the production of tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) in peripheral blood T cells and test the feasibility of differential diagnosis between pulmonary tuberculosis (PTB) and latent tuberculosis infection (LTBI) by assessing the number of Mtb-HAg-10k-stimulated IFN-γ-producing T cells.

METHODS

Peripheral blood mononuclear cells (PBMCs) were separated from the peripheral blood of 10 healthy adults, 6 individuals with LTBI and 13 patients with PTB. The PBMCs were cultured in the presence of Mtb-HAg-10k obtained by ultrafiltration centrifugation, with Mtb-HAg and phytohaemagglutinin (PHA) as the controls. The proportions of TNF-α- and IFN-γ-producing cells in the T cell subsets were detected by flow cytometry (FCM), and the number of IFN-γ-producing cells from patients with PTB and LTBI was detected with ELISPOT.

RESULTS

Flow cytometry showed that Mtb-HAg-10k exposure resulted in a significantly higher proportion of TNF-α-producing γδT cells than that of IFN-γ-producing γδT cells in the PBMCs (P<0.01). Compared with the PBMCs exposed to PHA, the PBMCs exposed to Mtb-HAg-10k exhibited a significantly greater proportion of γδT cells that produced both TNF-α and IFN-γ (P<0.01) but a significantly lower proportion of αβT cells producing both TNF-α and IFN-γ (P<0.01). Mtb-HAg-10k exposure of the PBMCs caused a significant reduction in the number of IFN-γ-producing cells as compared with Mtb-HAg and PHA treatments (P<0.01), and this reduction was more obvious in PBMCs from patients with PTB than in those from individuals with LTBI (P<0.01).

CONCLUSION

Mtb-HAg-10k can markedly induce γδT cells in the PBMCs to produce TNF-α and IFN-γ, and detection of the number of IFN-γ-producing cells in the PBMCs following Mtb-HAg-10k stimulation helps in the differential diagnosis between pulmonary tuberculosis and latent tuberculosis infection.

[Peripheral blood T cell TNF-α and IFN-γ production stimulated by low molecular peptide of Mycobacterium tuberculosis heat-resistant antigen for differential diagnosis between pulmonary tuberculosis and latent tuberculosis infection]

OBJECTIVE

To investigate the effects of low molecular peptide of Mycobacterium tuberculosis heat-resistant antigen (Mtb-HAg-10k) on the production of tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) in peripheral blood T cells and test the feasibility of differential diagnosis between pulmonary tuberculosis (PTB) and latent tuberculosis infection (LTBI) by assessing the number of Mtb-HAg-10k-stimulated IFN-γ-producing T cells.

METHODS

Peripheral blood mononuclear cells (PBMCs) were separated from the peripheral blood of 10 healthy adults, 6 individuals with LTBI and 13 patients with PTB. The PBMCs were cultured in the presence of Mtb-HAg-10k obtained by ultrafiltration centrifugation, with Mtb-HAg and phytohaemagglutinin (PHA) as the controls. The proportions of TNF-α- and IFN-γ-producing cells in the T cell subsets were detected by flow cytometry (FCM), and the number of IFN-γ-producing cells from patients with PTB and LTBI was detected with ELISPOT.

RESULTS

Flow cytometry showed that Mtb-HAg-10k exposure resulted in a significantly higher proportion of TNF-α-producing γδT cells than that of IFN-γ-producing γδT cells in the PBMCs (P<0.01). Compared with the PBMCs exposed to PHA, the PBMCs exposed to Mtb-HAg-10k exhibited a significantly greater proportion of γδT cells that produced both TNF-α and IFN-γ (P<0.01) but a significantly lower proportion of αβT cells producing both TNF-α and IFN-γ (P<0.01). Mtb-HAg-10k exposure of the PBMCs caused a significant reduction in the number of IFN-γ-producing cells as compared with Mtb-HAg and PHA treatments (P<0.01), and this reduction was more obvious in PBMCs from patients with PTB than in those from individuals with LTBI (P<0.01).

CONCLUSION

Mtb-HAg-10k can markedly induce γδT cells in the PBMCs to produce TNF-α and IFN-γ, and detection of the number of IFN-γ-producing cells in the PBMCs following Mtb-HAg-10k stimulation helps in the differential diagnosis between pulmonary tuberculosis and latent tuberculosis infection.

Measuring bovine γδ T cell function at the site of Mycobacterium bovis infection

Bovine γδ T cells are amongst the first cells to accumulate at the site of Mycobacterium bovis infection; however, their role in the developing lesion remains unclear. We utilized transcriptomics analysis, in situ hybridization, and a macrophage/γδ T cell co-culture system to elucidate the role of γδ T cells in local immunity to M. bovis infection. Transcriptomics analysis revealed that γδ T cells upregulated expression of several novel, immune-associated genes in response to stimulation with M. bovis antigen. BCG-infected macrophage/γδ T cell co-cultures confirmed the results of our RNAseq analysis, and revealed that γδ T cells from M. bovis-infected animals had a significant impact on bacterial viability. Analysis of γδ T cells within late-stage M. bovis granulomas revealed significant expression of IFN-γ and CCL2, but not IL-10, IL-22, or IL-17. Our results suggest γδ T cells influence local immunity to M. bovis through cytokine secretion and direct effects on bacterial burden.

IL-22 induces Reg3γ and inhibits allergic inflammation in house dust mite-induced asthma models

Previous studies have shown that IL-22, one of the Th17 cell-related cytokines, plays multiple roles in regulating allergic airway inflammation caused by antigen-specific Th2 cells; however, the underlying mechanism remains unclear. Here, we show that allergic airway inflammation and Th2 and Th17 cytokine production upon intratracheal administration of house dust mite (HDM) extract, a representative allergen, were exacerbated in IL-22-deficient mice. We also found that IL-22 induces Reg3γ production from lung epithelial cells through STAT3 activation and that neutralization of Reg3γ significantly exacerbates HDM-induced eosinophilic airway inflammation and Th2 cytokine induction. Moreover, exostatin-like 3 (EXTL3), a functional Reg3γ binding protein, is expressed in lung epithelial cells, and intratracheal administration of recombinant Reg3γ suppresses HDM-induced thymic stromal lymphopoietin and IL-33 expression and accumulation of type 2 innate lymphoid cells in the lung. Collectively, these results suggest that IL-22 induces Reg3γ production from lung epithelial cells and inhibits the development of HDM-induced allergic airway inflammation, possibly by inhibiting cytokine production from lung epithelial cells.

Lung-resident γδ T cells and their roles in lung diseases

γδ T cells are greatly enriched in mucosal and epithelial sites, such as the skin, respiratory, digestive and reproductive tracts, and they are defined as tissue-resident immune cells. In these tissues, the characteristics and biological roles of γδ T cells are distinguished from each other. The lungs represent the most challenging immunological dilemma for the host, and they have their own effective immune system. The abundance of γδ T cells, an estimated 8-20% of resident pulmonary lymphocytes in the lung, maintains lung tissue homeostasis. In this review, we summarize the recent research progress regarding lung-resident γδ T cells, including their development, residency and immune characteristics, and discuss the involvement of γδ T cells in infectious diseases of the lung, including bacterial, viral and fungal infections; lung allergic disease; lung inflammation and fibrosis; and lung cancer.

Novel role for IL-22 in protection during chronic Mycobacterium tuberculosis HN878 infection

Approximately 2 billion people are infected with Mycobacterium tuberculosis (Mtb), resulting in 1.4 million deaths every year. Among Mtb-infected individuals, clinical isolates belonging to the W-Beijing lineage are increasingly prevalent, associated with drug resistance, and cause severe disease immunopathology in animal models. Therefore, it is exceedingly important to identify the immune mechanisms that mediate protection against rapidly emerging Mtb strains, such as W-Beijing lineage. IL-22 is a member of the IL-10 family of cytokines with both protective and pathological functions at mucosal surfaces. Thus far, collective data show that IL-22 deficient mice are not more susceptible to aerosolized infection with less virulent Mtb strains. Thus, in this study we addressed the functional role for the IL-22 pathway in immunity to emerging Mtb isolates, using W-Beijing lineage member, Mtb HN878 as a prototype. We show that Mtb HN878 stimulates IL-22 production in TLR2 dependent manner and IL-22 mediates protective immunity during chronic stages of Mtb HN878 infection in mice. Interestingly, IL-22-dependent pathways in both epithelial cells and macrophages mediate protective mechanisms for Mtb HN878 control. Thus, our results project a new protective role for IL-22 in emerging Mtb infections.

Adoptive Transfer of Phosphoantigen-Specific γδ T Cell Subset Attenuates Mycobacterium tuberculosis Infection in Nonhuman Primates

The dominant Vγ2Vδ2 T cell subset recognizes phosphoantigen and exists only in humans and nonhuman primates. Despite the discovery of γδ T cells >30 y ago, a proof-of-concept study has not been done to prove the principle that the Vγ2Vδ2 T cell subset is protective against Mycobacterium tuberculosis and other infections. In this study, we used an adoptive cell-transfer strategy to define the protective role of Vγ2Vδ2 T cells in a primate tuberculosis (TB) model. Vγ2Vδ2 T cells for adoptive transfer displayed central/effector memory and mounted effector functions, including the production of anti-M. tuberculosis cytokines and inhibition of intracellular mycobacteria. They also expressed CXCR3/CCR5/LFA-1 trafficking/tissue-resident phenotypes and consistently trafficked to the airway, where they remained detectable from 6 h through 7 d after adoptive transfer. Interestingly, the test group of macaques receiving transfer of Vγ2Vδ2 T cells at weeks 1 and 3 after high-dose (500 CFU) M. tuberculosis infection exhibited significantly lower levels of M. tuberculosis infection burdens in lung lobes and extrapulmonary organs than did the control groups receiving PBLs or saline. Consistently, adoptive transfer of Vγ2Vδ2 T cells attenuated TB pathology and contained lesions primarily in the infection site of the right caudal lung lobe, with no or reduced TB dissemination to other lobes, spleen, or liver/kidney; in contrast, the controls showed widespread TB dissemination. The proof-of-concept finding supports the view that the dominant Vγ2Vδ2 T cell subset may be included in the rational design of a TB vaccine or host-directed therapy.

Regulatory T Cells and Pro-inflammatory Responses Predominate in Children with Tuberculosis

Background

Following infection with Mycobacterium tuberculosis (M.tb), children are more susceptible to develop disease particularly extrapulmonary disease than adults. The exact mechanisms required for containment of M.tb are not known, but would be important to identify correlates of protection.

Objective

To comprehensively analyze key immune responses to mycobacteria between HIV-negative children with extrapulmonary TB (EPTB) compared to children with pulmonary TB (PTB) or healthy controls.

Methods

Whole blood was stimulated in vitro with mycobacteria for 24 h or 6 days to induce effector and memory responses. CD4, CD8, γδ, regulatory T cells, and their related cytokines were measured. Samples of children with tuberculosis (TB) disease were analyzed both at time of diagnosis and at the end of TB treatment to determine if any differences were due to TB disease or an underlying host phenotype.

Results

Seventy-six children with TB disease (48 with PTB and 28 with EPTB) and 83 healthy controls were recruited to the study. The frequency of CD4⁺CD25⁺CD39⁺FOXP3⁺ regulatory T cells and secreted IL10 were significantly higher in children with TB compared to healthy controls. IFNγ-, IL17-, and IL22-producing γδ T cells, IL22-producing CD4⁺ T cells and secreted pro-inflammatory cytokines (IFNγ, IL1β, and TNFα) were significantly lower in children with TB disease compared to healthy controls. IFNγ-producing CD4⁺ T cells and Ki67⁺-proliferating CD4⁺ T cells, however, were present in equal numbers in both groups. Following treatment, these immune parameters recovered to “healthy” levels or greater in children with PTB, but not those with extrapulmonary TB.

Conclusion

In children with TB disease, a predominantly immune regulatory state is present. These immune findings do not distinguish between children with PTB and EPTB at the time of diagnosis. Following treatment, these inflammatory responses recover in PTB, suggesting that the effect is disease specific rather than due to an underlying host defect.

Cytokines and Chemokines in Mycobacterium tuberculosis Infection

Chemokines and cytokines are critical for initiating and coordinating the organized and sequential recruitment and activation of cells into Mycobacterium tuberculosis-infected lungs. Correct mononuclear cellular recruitment and localization are essential to ensure control of bacterial growth without the development of diffuse and damaging granulocytic inflammation. An important block to our understanding of TB pathogenesis lies in dissecting the critical aspects of the cytokine/chemokine interplay in light of the conditional role these molecules play throughout infection and disease development. Much of the data highlighted in this review appears at first glance to be contradictory, but it is the balance between the cytokines and chemokines that is critical, and the "goldilocks" (not too much and not too little) phenomenon is paramount in any discussion of the role of these molecules in TB. Determination of how the key chemokines/cytokines and their receptors are balanced and how the loss of that balance can promote disease is vital to understanding TB pathogenesis and to identifying novel therapies for effective eradication of this disease.

A Subset of Protective γ9δ2 T Cells Is Activated by Novel Mycobacterial Glycolipid Components

γ₉δ₂ T cells provide a natural bridge between innate and adaptive immunity, rapidly and potently respond to pathogen infection in mucosal tissues, and are prominently induced by both tuberculosis (TB) infection and bacillus Calmette Guérin (BCG) vaccination. Mycobacterium-expanded γ₉δ₂ T cells represent only a subset of the phosphoantigen {isopentenyl pyrophosphate [IPP] and (E)-4-hydroxy-3-methyl-but-2-enylpyrophosphate [HMBPP]}-responsive γ₉δ₂ T cells, expressing an oligoclonal set of T cell receptor (TCR) sequences which more efficiently recognize and inhibit intracellular Mycobacterium tuberculosis infection. Based on this premise, we have been searching for M. tuberculosis antigens specifically capable of inducing a unique subset of mycobacterium-protective γ₉δ₂ T cells. Our screening strategy includes the identification of M. tuberculosis fractions that expand γ₉δ₂ T cells with biological functions capable of inhibiting intracellular mycobacterial replication. Chemical treatments of M. tuberculosis whole-cell lysates (MtbWL) ruled out protein, nucleic acid, and nonpolar lipids as the M. tuberculosis antigens inducing protective γ₉δ₂ T cells. Mild acid hydrolysis, which transforms complex carbohydrate to monomeric residues, abrogated the specific activity of M. tuberculosis whole-cell lysates, suggesting that a polysaccharide was required for biological activity. Extraction of MtbWL with chloroform-methanol-water (10:10:3) resulted in a polar lipid fraction with highly enriched specific activity; this activity was further enriched by silica gel chromatography. A combination of mass spectrometry and nuclear magnetic resonance analysis of bioactive fractions indicated that 6-O-methylglucose-containing lipopolysaccharides (mGLP) are predominant components present in this active fraction. These results have important implications for the development of new immunotherapeutic approaches for prevention and treatment of TB.

Protective immune responses of major Vγ2Vδ2 T-cell subset in M. tuberculosis infection

Recent observation that prenyl pyrophosphates bind the Ig superfamily protein butyrophilin 3A1 (BTN3A1) suggests that modifying BTN3A1 activates major γδ T-cell subset, Vγ2Vδ2 T cells. Studies also show that microbial phosphoantigen HMBPP is required for expansion, pulmonary response, effector functions and memory polarization of Vγ2Vδ2 T cells during infections. Broad repertoires of cytokines involve expansion, recall-like expansion and effector functions of Vγ2Vδ2 T cells after Mtb infection or vaccination. Finally, mechanistic studies in nonhuman primate TB model demonstrate early expansion and differentiation of Vγ2Vδ2 T cells during Mtb infection can increase immune resistance to TB in macaques, with a potential mechanism of early/sustained IFN-γ production and CTL killing.

Interleukin-22 is elevated in lavage from patients with lung cancer and other pulmonary diseases

BACKGROUND

Interleukin-22 (IL-22) is involved in lung diseases such as pneumonia, asthma and lung cancer. Lavage mirrors the local environment, and may provide insights into the presence and role of IL-22 in patients.

METHODS

Bronchoscopic lavage (BL) samples (n = 195, including bronchoalveolar lavage and bronchial washings) were analysed for IL-22 using an enzyme-linked immunosorbent assay. Clinical characteristics and parameters from lavage and serum were correlated with lavage IL-22 concentrations.

RESULTS

IL-22 was higher in lavage from patients with lung disease than in controls (38.0 vs 15.3 pg/ml, p < 0.001). Patients with pneumonia and lung cancer had the highest concentrations (48.9 and 33.0 pg/ml, p = 0.009 and p < 0.001, respectively). IL-22 concentration did not correlate with systemic inflammation. IL-22 concentrations did not relate to any of the analysed cell types in BL indicating a potential mixed contribution of different cell populations to IL-22 production.

CONCLUSIONS

Lavage IL-22 concentrations are high in patients with lung cancer but do not correlate with systemic inflammation, thus suggesting that lavage IL-22 may be related to the underlying malignancy. Our results suggest that lavage may represent a distinct compartment where the role of IL-22 in thoracic malignancies can be studied.

Interleukin-10 Family and Tuberculosis: An Old Story Renewed

The interleukin-10 (IL-10) family of cytokines consists of six immune mediators, namely IL-10, IL-19, IL-20, IL-22, IL-24 and IL-26. IL-10, IL-22, IL-24 and IL-26 are critical for the regulation of host defense against Mycobacterium tuberculosis infections. Specifically, IL-10 and IL-26 can suppress the antimycobacterial immunity and promote the survival of pathogen, while IL-22 and IL-24 can generate protective responses and inhibit the intracellular growth of pathogen. Knowledge about the new players in tuberculosis immunology, namely IL-10 family, can inform novel immunity-based countermeasures and host directed therapies against tuberculosis.

Immunotherapy for tuberculosis: future prospects

Tuberculosis (TB) is still a major global health problem. A third of the world’s population is infected with Mycobacterium tuberculosis. Only ~10% of infected individuals develop TB but there are 9 million TB cases with 1.5 million deaths annually. The standard prophylactic treatment regimens for latent TB infection take 3–9 months, and new cases of TB require at least 6 months of treatment with multiple drugs. The management of latent TB infection and TB has become more challenging because of the spread of multidrug-resistant and extremely drug-resistant TB. Intensified efforts to find new TB drugs and immunotherapies are needed. Immunotherapies could modulate the immune system in patients with latent TB infection or active disease, enabling better control of M. tuberculosis replication. This review describes several types of potential immunotherapies with a focus on those which have been tested in humans.

Mycobacterium bovis Infection of Cattle and White-Tailed Deer: Translational Research of Relevance to Human Tuberculosis

Tuberculosis (TB) is a premier example of a disease complex with pathogens primarily affecting humans (i.e., Mycobacterium tuberculosis) or livestock and wildlife (i.e., Mycobacterium bovis) and with a long history of inclusive collaborations between physicians and veterinarians. Advances in the study of bovine TB have been applied to human TB, and vice versa. For instance, landmark discoveries on the use of Koch's tuberculin and interferon-γ release assays for diagnostic purposes, as well as Calmette and Guérin's attenuated M. bovis strain as a vaccine, were first evaluated in cattle for control of bovine TB prior to wide-scale use in humans. Likewise, recent discoveries on the role of effector/memory T cell subsets and polyfunctional T cells in the immune response to human TB, particularly as related to vaccine efficacy, have paved the way for similar studies in cattle. Over the past 15 years, substantial funding for development of human TB vaccines has led to the emergence of multiple promising candidates now in human clinical trials. Several of these vaccines are being tested for immunogenicity and efficacy in cattle. Also, the development of population-based vaccination strategies for control of M. bovis infection in wildlife reservoirs will undoubtedly have an impact on our understanding of herd immunity with relevance to the control of both bovine and human TB in regions of the world with high prevalence of TB. Thus, the one-health approach to research on TB is mutually beneficial for our understanding and control of TB in humans, livestock, and wildlife.

Tuberculous pleurisy drives marked effector responses of γδ, CD4+, and CD8+ T cell subpopulations in humans

Although tuberculous pleurisy (TP) presumably involves a hypersensitivity reaction, there is limited evidence indicating overreactive effector responses of γδ T cells and αβ T cells and their interrelation with Foxp3(+) Tregs in pleural and other compartments. We found that TP induced reciprocal representations of Foxp3(+) Tregs and Mtb phosphoantigen-specific Vγ2Vδ2 T cells in different anatomic compartments. Patients with TP exhibited appreciable numbers of "proliferating" Ki-67(+) Vγ2Vδ2 T cells in the airway where Foxp3(+) Tregs were not dominant, whereas striking increases in Foxp3(+) Tregs in the blood and pleural compartments coincided with low frequencies of Vγ2Vδ2 T cells. Interestingly, anti-tuberculosis chemotherapy control of Mtb infection in patients with TP reversed reciprocal representations of Foxp3(+) Tregs and proliferating Vγ2Vδ2 T cells. Surprisingly, despite high-level Foxp3(+) Tregs, TP appeared to drive overreactive responses of IFN-γ-producing Vγ2Vδ2, CD4(+)CD25(+), and CD8(+)CD25(+) T effector subpopulations, whereas IL-22-producing Vγ2Vδ2 T cells increased subtly. Th1 effector responses were sustained despite remarkable declines in Foxp3(+) Tregs at 1 mo after the treatment. Overreactive T effector responses of Mtb-reactive γδ T cells, αβ CD25(+)CD4(+), and CD25(+)CD8(+) T cell subpopulations appear to be immune features for TP. Increased Foxp3(+) Tregs might be responsive to overreactive TP but unable to influence T effector responses despite having an inverse relation with proliferating Vγ2Vδ2 T cells.

Characterization of CD4/CD8+ αβ and Vγ2Vδ2+ T cells in HIV-negative individuals with different Mycobacterium tuberculosis infection statuses

BACKGROUND

The immune responses of T cell subsets among patients with different Mycobacterium tuberculosis (M.tb) infection statuses [i.e., active tuberculosis (ATB), latent tuberculosis infection (LTBI) and non-infection (healthy control, HC)] have not been fully elucidated in HIV-negative individuals. Specifically, data are limiting in high tuberculosis epidemic regions in China. To investigate the distributions and functions of T cell subsets (i.e., CD3+, CD4+, CD8+ αβ and Vγ2Vδ2+ T cells) in HIV-negative subjects with different M.tb infection statuses, we conducted a case-control study that enrolled 125 participants, including ATB patients (n = 46), LTBI subjects (n = 34), and HC (n = 45).

RESULTS

An IFN-γ release assay (IGRA) was employed to screen LTBI subjects. Whole blood cell surface staining and flow cytometry were used to detect phenotypic distributions of T cells in the peripheral blood mononuclear cells (PBMCs) and tuberculous pleural fluid mononuclear cells (PFMCs). PPD and the phosphorylated antigen HMBPP were employed as stimulators for the detection of M.tb antigen-specific T cell functions via intracellular cytokine staining (ICS). The absolute numbers of T cell subsets, including CD3+ CD4+, CD3+ CD8+ αβ and Vγ2Vδ2+ T cells, were significantly reduced in active tuberculosis compared with latent tuberculosis or the healthy controls. Importantly, PPD-specific CD3+ CD4+ and CD3+ CD8+ αβ T cells and HMBPP-specific Vγ2Vδ2+ T cells in ATB patients were also significantly reduced compared to the LTBI/HC subjects (P<0.05). In contrast, the proportion of CD4+ T cells in PFMCs was higher compared to PBMCs, while CD8+ and Vγ2Vδ2+ T cells in PFMCs were lower compared to PBMCs (all P < 0.05). PPD-specific CD4+ T cells predominated among CD3+ T cells in PFMCs.

CONCLUSIONS

Cellular immune responses are impaired in ATB patients. Antigen-specific CD4+ T cell may migrate from the periphery to the lesion site, where they exert anti-tuberculosis functions.

Long noncoding RNA derived from CD244 signaling epigenetically controls CD8+ T-cell immune responses in tuberculosis infection

Molecular mechanisms for T-cell immune responses modulated by T cell-inhibitory molecules during tuberculosis (TB) infection remain unclear. Here, we show that active human TB infection up-regulates CD244 and CD244 signaling-associated molecules in CD8(+) T cells and that blockade of CD244 signaling enhances production of IFN-γ and TNF-α. CD244 expression/signaling in TB correlates with high levels of a long noncoding RNA (lncRNA)-BC050410 [named as lncRNA-AS-GSTT1(1-72) or lncRNA-CD244] in the CD244(+)CD8(+) T-cell subpopulation. CD244 signaling drives lncRNA-CD244 expression via sustaining a permissive chromatin state in the lncRNA-CD244 locus. By recruiting polycomb protein enhancer of zeste homolog 2 (EZH2) to infg/tnfa promoters, lncRNA-CD244 mediates H3K27 trimethylation at infg/tnfa loci toward repressive chromatin states and inhibits IFN-γ/TNF-α expression in CD8(+) T cells. Such inhibition can be reversed by knock down of lncRNA-CD244. Interestingly, adoptive transfer of lncRNA-CD244-depressed CD8(+) T cells to Mycobacterium tuberculosis (MTB)-infected mice reduced MTB infection and TB pathology compared with lncRNA-CD244-expressed controls. Thus, this work uncovers previously unidentified mechanisms in which T cell-inhibitory signaling and lncRNAs regulate T-cell responses and host defense against TB infection.

Tuberculosis specific responses following therapy for TB: Impact of HIV co-infection

Characterizing perturbations in the immune response to tuberculosis in HIV can develop insights into the pathogenesis of coinfection. HIV+ TB+ and TB monoinfected (TB+) subjects recruited from clinics in Bamako prior to initiation of TB treatment were evaluated at time-points following initiation of therapy. Flow cytometry assessed CD4+/CD8+ T cell subsets and activation markers CD38/HLA-DR. Antigen specific responses to TB proteins were assessed by intracellular cytokine detection and proliferation. HIV+ TB+ subjects had significantly higher markers of immune activation in the CD4+ and CD8+ T cells compared to TB+ subjects. HIV+ TB+ had lower numbers of TB-specific CD4+ T cells at baseline. Plasma IFNγ levels were similar between HIV+ TB+ and TB+ subjects. No differences were observed in in-vitro proliferative capacity to TB antigens between HIV+ TB+ and TB+ subjects. Subjects with HIV+ TB+ coinfection demonstrate in vivo expansion of TB-specific CD4+ T cells. Immunodeficiency associated with CD4+ T cell depletion may be less significant compared to immunosuppression associated with HIV viremia or untreated TB infection.

Role of cytokines and other factors involved in the Mycobacterium tuberculosis infection

Mycobacterium tuberculosis (Mtb) is a pathogen that is widely distributed geographically and continues to be a major threat to world health. Bacterial virulence factors, nutritional state, host genetic condition and immune response play an important role in the evolution of the infection. The genetically diverse Mtb strains from different lineages have been shown to induce variable immune system response. The modern and ancient lineages strains induce different cytokines patterns. The immunity to Mtb depends on Th1-cell activity [interferon-γ (IFN-γ), interleukin-12 (IL-12) and tumor necrosis factor-α (TNF-α)]. IL-1β directly kills Mtb in murine and human macrophages. IL-6 is a requirement in host resistance to Mtb infection. IFN-γ, TNF-α, IL-12 and IL-17 are participants in Mycobacterium-induced granuloma formation. Other regulating proteins as IL-27 and IL-10 can prevent extensive immunopathology. CXCL 8 enhances the capacity of the neutrophil to kill Mtb. CXCL13 and CCL19 have been identified as participants in the formation of granuloma and control the Mtb infection. Treg cells are increased in patients with active tuberculosis (TB) but decrease with anti-TB treatment. The increment of these cells causes down- regulation of adaptive immune response facilitating the persistence of the bacterial infection. Predominance of Th2 phenotype cytokines increases the severity of TB. The evolution of the Mtb infection will depend of the cytokines network and of the influence of other factors aforementioned.

Interleukin-22: immunobiology and pathology

Interleukin-22 (IL-22) is a recently described IL-10 family cytokine that is produced by T helper (Th) 17 cells, γδ T cells, NKT cells, and newly described innate lymphoid cells (ILCs). Knowledge of IL-22 biology has evolved rapidly since its discovery in 2000, and a role for IL-22 has been identified in numerous tissues, including the intestines, lung, liver, kidney, thymus, pancreas, and skin. IL-22 primarily targets nonhematopoietic epithelial and stromal cells, where it can promote proliferation and play a role in tissue regeneration. In addition, IL-22 regulates host defense at barrier surfaces. However, IL-22 has also been linked to several conditions involving inflammatory tissue pathology. In this review, we assess the current understanding of this cytokine, including its physiologic and pathologic effects on epithelial cell function.

Th17-related cytokines contribute to recall-like expansion/effector function of HMBPP-specific Vγ2Vδ2 T cells after Mycobacterium tuberculosis infection or vaccination

Whether cytokines can influence the adaptive immune response by antigen-specific γδ T cells during infections or vaccinations remains unknown. We previously demonstrated that, during BCG/Mycobacterium tuberculosis (Mtb) infections, Th17-related cytokines markedly upregulated when phosphoantigen-specific Vγ2Vδ2 T cells expanded. In this study, we examined the involvement of Th17-related cytokines in the recall-like responses of Vγ2Vδ2 T cells following Mtb infection or vaccination against TB. Treatment with IL-17A/IL-17F or IL-22 expanded phosphoantigen 4-hydroxy-3-methyl-but-enyl pyrophosphate (HMBPP)-stimulated Vγ2Vδ2 T cells from BCG-vaccinated macaques but not from naïve animals, and IL-23 induced greater expansion than the other Th17-related cytokines. Consistently, Mtb infection of macaques also enhanced the ability of IL-17/IL-22 or IL-23 to expand HMBPP-stimulated Vγ2Vδ2 T cells. When evaluating IL-23 signaling as a prototype, we found that HMBPP/IL-23-expanded Vγ2Vδ2 T cells from macaques infected with Mtb or vaccinated with BCG or Listeria ΔactA prfA*-ESAT6/Ag85B produced IL-17, IL-22, IL-2, and IFN-γ. Interestingly, HMBPP/IL-23-induced production of IFN-γ in turn facilitated IL-23-induced expansion of HMBPP-activated Vγ2Vδ2 T cells. Furthermore, HMBPP/IL-23-induced proliferation of Vγ2Vδ2 T cells appeared to require APC contact and involve the conventional and novel protein kinase C signaling pathways. These findings suggest that Th17-related cytokines can contribute to recall-like expansion and effector function of Ag-specific γδ T cells after infection or vaccination.

γδ T Cell-Mediated Immune Responses in Disease and Therapy

The role of γδ T cells in immunotherapy has gained specific importance in the recent years because of their prominent function involving directly or indirectly in the rehabilitation of the diseases. γδ T cells represent a minor population of T cells that express a distinct T cell receptor (TCR) composed of γδ chains instead of αβ chains. Unlike αβ T cells, γδ T cells display a restricted TCR repertoire and recognize mostly unknown non-peptide antigens. γδ T cells act as a link between innate and adaptive immunity, because they lack precise major histocompatibility complex (MHC) restriction and seize the ability to recognize ligands that are generated during affliction. Skin epidermal γδ T cells recognize antigen expressed by damaged or stressed keratinocytes and play an indispensable role in tissue homeostasis and repair through secretion of distinct growth factors. γδ T cell based immunotherapy strategies possess great prominence in the treatment because of the property of their MHC-independent cytotoxicity, copious amount of cytokine release, and a immediate response in infections. Understanding the role of γδ T cells in pathogenic infections, wound healing, autoimmune diseases, and cancer might provide knowledge for the successful treatment of these diseases using γδ T cell based immunotherapy. Enhancing the human Vγ9Vδ2 T cells functions by administration of aminobisphosphonates like zoledronate, pamidronate, and bromohydrin pyrophosphate along with cytokines and monoclonal antibodies shows a hopeful approach for treatment of tumors and infections. The current review summarizes the role of γδ T cells in various human diseases and immunotherapeutic approaches using γδ T cells.

BTLA exhibits immune memory for αβ T cells in patients with active pulmonary tuberculosis

Despite past extensive studies, the role of B and T lymphocyte attenuator (BTLA) in αβ T cells in patients with active pulmonary tuberculosis (ATB) remains poorly understood. Here we demonstrate that BTLA expression on αβ T cells is decreased in patients with M. tuberculosis (Mtb) infection. Particularly, BTLA expression levels are likely critical for αβ T cells to manifest and maintain an active central memory phenotype with high capacity for secretion of IFN-γ and perforin, which are important for immune memory against TB infection. BTLA(high) αβ T cells also exhibited higher capacity in response to Mtb peptide stimulation. In contrast to the role of BTLA played for negative regulation of immune responses, our data in the current studies suggest that BTLA expression on αβ T cells is likely associated with protective immune memory against Mtb infection in the setting of patients with active pulmonary tuberculosis. This previous unappreciated role for BTLA may have implications for prevention and treatment of patients with Mtb infection.

In vitro effects of bisphosphonates on chemotaxis, phagocytosis, and oxidative burst of neutrophil granulocytes

OBJECTIVES

Bisphosphonate-associated osteonecrosis of the jaws is a serious side effect that mainly occurs in patients receiving highly potent, nitrogen-containing bisphosphonates. Usually the diagnosis is made due to exposed bone and a nonhealing wound. Neutrophil granulocytes are essential for sufficient wound healing; therefore, the influence of different bisphosphonates on neutrophil granulocytes was the focus of this study.

MATERIAL AND METHODS

The effect of nitrogen-containing bisphosphonates (ibandronate, pamidronate, and zoledronate) and one non-nitrogen-containing bisphosphonate (clodronate) on chemotaxis, phagocytosis, and oxidative burst of neutrophil granulocytes in human whole blood was analyzed using standard cytometric flow assays.

RESULTS

Chemotaxis of neutrophils was reduced by almost 50 % when cells were treated with ibandronate and zoledronate. All tested nitrogen-containing bisphosphonates moderately increased the percentage of phagocytizing neutrophils, whereas the percentage of oxidizing cells was extremely affected. Zoledronate increased the oxidative burst activity even at low concentrations. Treatment with ibandronate and pamidronate reached the same level, but only in at least 10 times the higher concentrations. The maximal burst activity of a single cell reached nearly 150 % compared to control. In this case, zoledronate also caused maximal effects even at low concentrations. Clodronate did not show any effects.

CONCLUSION

The results show a proinflammatory effect of the nitrogen-containing effect on neutrophil granulocytes which might contribute to the development of osteonecrosis.

CLINICAL RELEVANCE

The altered neutrophil defense might play a key role in the pathogenesis of bisphosphonate-associated osteonecrosis of the jaws, although the underlying causation between inflammatory reaction and the development of necrosis is yet unknown.

Interleukin-22 promotes T helper 1 (Th1)/Th17 immunity in chlamydial lung infection

The role of interleukin-22 (IL-22) in intracellular bacterial infections is a controversial issue, although the contribution of this cytokine to host defense against extracellular bacterial pathogens has been well established. In this study, we focused on an intra-cellular bacterium, Chlamydia, and evaluated the production and function of IL-22 in host defense against chlamydial lung infection using a mouse model. We found that Chlamydia muridarum infection elicited quick IL-22 responses in the lung, which increased during infection and were reduced when bacterial loads decreased. More importantly, blockade of endogenous IL-22 using neutralizing anti-IL-22 monoclonal antibodies (mAb) resulted in more severe disease in the mice, leading to significantly higher weight loss and bacterial growth and much more severe pathological changes than treatment with isotype control antibody. Immunological analyses identified significantly lower T helper 1 (Th1) and Th17 responses in the IL-22-neutralized mice. In contrast, intranasal administration of exogenous IL-22 significantly enhanced protection following chlamydial lung infection, which was associated with a significant increase of Th17 response. The data demonstrate that IL-22 is a critical cytokine, mediating host defense against chlamydial lung infection and coordinating the function of distinct Th-cell subsets, particularly Th1 and Th17, in the process.

CD4+ T cells contain early extrapulmonary tuberculosis (TB) dissemination and rapid TB progression and sustain multieffector functions of CD8+ T and CD3- lymphocytes: mechanisms of CD4+ T cell immunity

The possibility that CD4(+) T cells can act as "innate-like" cells to contain very early Mycobacterium tuberculosis dissemination and function as master helpers to sustain multiple effector functions of CD8(+) T cells and CD3(-) lymphocytes during development of adaptive immunity against primary tuberculosis (TB) has not been demonstrated. We showed that pulmonary M. tuberculosis infection of CD4-depleted macaques surprisingly led to very early extrapulmonary M. tuberculosis dissemination, whereas CD4 deficiency clearly resulted in rapid TB progression. CD4 depletion during M. tuberculosis infection revealed the ability of CD8(+) T cells to compensate and rapidly differentiate to Th17-like/Th1-like and cytotoxic-like effectors, but these effector functions were subsequently unsustainable due to CD4 deficiency. Whereas CD3(-) non-T lymphocytes in the presence of CD4(+) T cells developed predominant Th22-like and NK-like (perforin production) responses to M. tuberculosis infection, CD4 depletion abrogated these Th22-/NK-like effector functions and favored IL-17 production by CD3(-) lymphocytes. CD4-depleted macaques exhibited no or few pulmonary T effector cells constitutively producing IFN-γ, TNF-α, IL-17, IL-22, and perforin at the endpoint of more severe TB, but they presented pulmonary IL-4(+) T effectors. TB granulomas in CD4-depleted macaques contained fewer IL-22(+) and perforin(+) cells despite the presence of IL-17(+) and IL-4(+) cells. These results implicate a previously unknown innate-like ability of CD4(+) T cells to contain extrapulmonary M. tuberculosis dissemination at very early stage. Data also suggest that CD4(+) T cells are required to sustain multiple effector functions of CD8(+) T cells and CD3(-) lymphocytes and to prevent rapid TB progression during M. tuberculosis infection of nonhuman primates.

Interleukin 22 inhibits intracellular growth of Mycobacterium tuberculosis by enhancing calgranulin A expression

Previously, we found that interleukin 22 (IL-22) inhibits intracellular growth of Mycobacterium tuberculosis in human monocyte-derived macrophages (MDMs). In the current study, we determined the mechanisms underlying these effects. We found that W7, a phagolysosomal fusion inhibitor, abrogates IL-22-dependent M. tuberculosis growth inhibition in MDMs, suggesting that IL-22 acts through enhanced phagolysosomal fusion. Our microarray analysis indicated that recombinant IL-22 (rIL-22) enhances the expression of an intracellular signaling molecule, calgranulin A. This was confirmed by real-time polymerase chain reaction, Western blot, and confocal microscopy. Calgranulin A small interfering RNA (siRNA) abrogated rIL-22-dependent growth inhibition of M. tuberculosis in MDMs. IL-22 enhanced Rab7 expression and downregulated Rab14 expression of M. tuberculosis-infected MDMs, and these effects were reversed by calgranulin A siRNA. These results suggest that M. tuberculosis growth inhibition by IL-22 depends on calgranulin A and enhanced phagolysosomal fusion, which is associated with increased Rab7 and reduced Rab14 expression.

Phosphoantigen/IL2 expansion and differentiation of Vγ2Vδ2 T cells increase resistance to tuberculosis in nonhuman primates

Dominant Vγ2Vδ2 T-cell subset exist only in primates, and recognize phosphoantigen from selected pathogens including M. tuberculosis(Mtb). In vivo function of Vγ2Vδ2 T cells in tuberculosis remains unknown. We conducted mechanistic studies to determine whether earlier expansion/differentiation of Vγ2Vδ2 T cells during Mtb infection could increase immune resistance to tuberculosis in macaques. Phosphoantigen/IL-2 administration specifically induced major expansion and pulmonary trafficking/accumulation of phosphoantigen-specific Vγ2Vδ2 T cells, significantly reduced Mtb burdens and attenuated tuberculosis lesions in lung tissues compared to saline/BSA or IL-2 controls. Expanded Vγ2Vδ2 T cells differentiated into multifunctional effector subpopulations capable of producing anti-TB cytokines IFNγ, perforin and granulysin, and co-producing perforin/granulysin in lung tissue. Mechanistically, perforin/granulysin-producing Vγ2Vδ2 T cells limited intracellular Mtb growth, and macaque granulysin had Mtb-bactericidal effect, and inhibited intracellular Mtb in presence of perforin. Furthermore, phosphoantigen/IL2-expanded Vγ2Vδ2 T effector cells produced IL-12, and their expansion/differentiation led to enhanced pulmonary responses of peptide-specific CD4+/CD8+ Th1-like cells. These results provide first in vivo evidence implicating that early expansion/differentiation of Vγ2Vδ2 T effector cells during Mtb infection increases resistance to tuberculosis. Thus, data support a rationale for conducting further studies of the γδ T-cell-targeted treatment of established TB, which might ultimately help explore single or adjunctive phosphoantigen expansion of Vγ2Vδ2 T-cell subset as intervention of MDR-tuberculosis or HIV-related tuberculosis.

Tuberculosis(TB), caused by Mycobacterium tuberculosis(Mtb), remains a leading cause of morbidity and mortality worldwide. While CD4+/CD8+ T cells are protective, role of γδ T cells in TB and other infections remains unknown in humans. Vγ2Vδ2 T cells exist only in primates, represent a dominant circulating γδ T-cell subpopulation, and recognize phosphoantigen from Mtb and some selected pathogens. Here, we determined whether earlier expansion/differentiation of Vγ2Vδ2 T cells during Mtb infection increased resistance to TB in macaques. Phosphoantigen plus IL-2 administration induced expansion and pulmonary accumulation of Vγ2Vδ2 T cells, significantly reduced Mtb counts and attenuated TB lesions in lung tissues. Expanded Vγ2Vδ2 T cells produced anti-TB cytokines IFNγ, perforin and granulysin, and co-produced perforin and granulysin in lung tissue. Perforin/granulysin-co-producing Vγ2Vδ2 T cells limited intracellular Mtb growth, and macaque granulysin killed Mtb bacteria, and inhibited intracellular Mtb in presence of perforin. Furthermore, expansion of Vγ2Vδ2 T effectors enhanced pulmonary responses of peptide-specific CD4+/CD8+ T cells, which correlated with the ability of Vγ2Vδ2 T effector cells to produce IL-12. These results provide first evidence implicating a protective role of Vγ2Vδ2 T effector cells in TB, supporting a rationale to explore Vγ2Vδ2 T-cell-targeted treatment of drug-resistant TB or HIV-related TB.

IL-22 from conventional NK cells is epithelial regenerative and inflammation protective during influenza infection

Influenza infection primarily targets the upper respiratory system, leading to a severe destruction of the epithelial cell layer. The role of immune cells in the regeneration of tracheal and bronchial epithelial cells is not well defined. Here, we investigated the production of pro-constructive cytokine, Interleukin-22 (IL-22), in the bronchoalveolar lavage (BAL), trachea, lung tissue, and spleen during influenza infection. We found that conventional natural killer (NK) cells (NCR1(+)NK1.1(+)CD127(-)RORγt(-)) were the predominant IL-22-producers in the BAL, trachea, and lung tissues. Tracheal epithelial cells constitutively expressed high levels of IL-22R and underwent active proliferation in response to IL-22 in the wild-type mice. Infection of IL-22(-/-) mice with influenza virus resulted in a severe impairment in the regeneration of tracheal epithelial cells. In addition, IL-22(-/-) mice continued to lose body weight even after 10 days post infection without any recovery. Tracheal epithelial cell proliferation was significantly reduced in IL-22(-/-) mice during influenza infection. Adoptive transfer of IL-22-sufficient but not IL-22-deficient NK cells into IL-22(-/-) mice restored the tracheal/bronchial epithelial cell regeneration and conferred protection against inflammation. Our findings strongly suggest that conventional NK cells have evolved to both kill virus-infected cells and also to provide vital cytokines for tissue regeneration.