Mycobacterium tuberculosis evades host immunity by recruiting mesenchymal stem cells

Cotreatment With Clofazimine and Rapamycin Eliminates Drug-Resistant Tuberculosis by Inducing Polyfunctional Central Memory T-Cell Responses

Mycobacterium tuberculosis, the causative agent of tuberculosis, is acquiring drug resistance at a faster rate than the discovery of new antibiotics. Therefore, alternate therapies that can limit the drug resistance and disease recurrence are urgently needed. Emerging evidence indicates that combined treatment with antibiotics and an immunomodulator provides superior treatment efficacy. Clofazimine (CFZ) enhances the generation of T central memory (TCM) cells by blocking the Kv1.3+ potassium channels. Rapamycin (RAPA) facilitates M. tuberculosis clearance by inducing autophagy. In this study, we observed that cotreatment with CFZ and RAPA potently eliminates both multiple and extensively drug-resistant (MDR and XDR) clinical isolates of M. tuberculosis in a mouse model by inducing robust T-cell memory and polyfunctional TCM responses. Furthermore, cotreatment reduces the expression of latency-associated genes of M. tuberculosis in human macrophages. Therefore, CFZ and RAPA cotherapy holds promise for treating patients infected with MDR and XDR strains of M. tuberculosis.

A Key Role of CD8+ T Cells in Controlling of Tuberculosis Infection

The main role in the control of tuberculosis infection is played by macrophages and Th1 and CD8+ T cells. The study aimed to identify the most diagnostically significant CD8+ T cell subsets in tuberculosis patients.

METHODS

Peripheral blood samples from patients with clinical, radiological, and bacteriologically confirmed pulmonary tuberculosis (TB, n = 32) and healthy subjects (HC, n = 31) were collected and analyzed using 10-color flow cytometry.

RESULTS

The frequency of the EM4 CD3+CD8+ cells was reduced in the peripheral blood of patients with pulmonary tuberculosis, while the relative and absolute number of EM1 CD3+CD8+ cells increased compared to the control group. CD57 expression was reduced in patients with pulmonary tuberculosis on EM1, EM2, and pE1 CD3+CD8+ cells, whereas the EM3 cells had a high level of CD57 expression. The relative and absolute number of Tc2 (CCR6-CXCR3-) cells in peripheral blood in patients with pulmonary tuberculosis was increased, while the frequency of Tc1 (CCR6-CXCR3+) was decreased, compared to healthy donors.

CONCLUSIONS

Patients with pulmonary tuberculosis have an abnormal CD3+CD8+ cell profile and demonstrate their impaired maturation and functional activity.

Revisiting the role of mesenchymal stem cells in tuberculosis and other infectious diseases

Mesenchymal stem cells (MSCs) play diverse roles ranging from regeneration and wound healing to immune signaling. Recent investigations have indicated the crucial role of these multipotent stem cells in regulating various aspects of the immune system. MSCs express unique signaling molecules and secrete various soluble factors that play critical roles in modulating and shaping immune responses, and in some other cases, MSCs can also exert direct antimicrobial effects, thereby helping with the eradication of invading organisms. Recently, it has been demonstrated that MSCs are recruited at the periphery of the granuloma containing Mycobacterium tuberculosis and exert "Janus"-like functions by harboring pathogens and mediating host protective immune responses. This leads to the establishment of a dynamic balance between the host and the pathogen. MSCs function through various immunomodulatory factors such as nitric oxide (NO), IDO, and immunosuppressive cytokines. Recently, our group has shown that M.tb uses MSCs as a niche to evade host protective immune surveillance mechanisms and establish dormancy. MSCs also express a large number of ABC efflux pumps; therefore, dormant M.tb residing in MSCs are exposed to a suboptimal dose of drugs. Therefore, it is highly likely that drug resistance is coupled with dormancy and originates within MSCs. In this review, we discussed various immunomodulatory properties of MSCs, their interactions with important immune cells, and soluble factors. We also discussed the possible roles of MSCs in the outcome of multiple infections and in shaping the immune system, which may provide insight into therapeutic approaches using these cells in different infection models.

Mesenchymal Stem Cells and MSCs-Derived Extracellular Vesicles in Infectious Diseases: From Basic Research to Clinical Practice

Mesenchymal stem cells (MSCs) are attractive in various fields of regenerative medicine due to their therapeutic potential and complex unique properties. Basic stem cell research and the global COVID-19 pandemic have given impetus to the development of cell therapy for infectious diseases. The aim of this review was to systematize scientific data on the applications of mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles (MSC-EVs) in the combined treatment of infectious diseases. Application of MSCs and MSC-EVs in the treatment of infectious diseases has immunomodulatory, anti-inflammatory, and antibacterial effects, and also promotes the restoration of the epithelium and stimulates tissue regeneration. The use of MSC-EVs is a promising cell-free treatment strategy that allows solving the problems associated with the safety of cell therapy and increasing its effectiveness. In this review, experimental data and clinical trials based on MSCs and MSC-EVs for the treatment of infectious diseases are presented. MSCs and MSC-EVs can be a promising tool for the treatment of various infectious diseases, particularly in combination with antiviral drugs. Employment of MSC-derived EVs represents a more promising strategy for cell-free treatment, demonstrating a high therapeutic potential in preclinical studies.

Antibiotic Resistance to Mycobacterium tuberculosis and Potential Use of Natural and Biological Products as Alternative Anti-Mycobacterial Agents

Background: Tuberculosis (TB) is an infectious disease caused by the bacillus Mycobacterium tuberculosis (Mtb). TB treatment is based on the administration of three major antibiotics: isoniazid, rifampicin, and pyrazinamide. However, multi-drug resistant (MDR) Mtb strains are increasing around the world, thus, allowing TB to spread around the world. The stringent response is demonstrated by Mtb strains in order to survive under hostile circumstances, even including exposure to antibiotics. The stringent response is mediated by alarmones, which regulate bacterial replication, transcription and translation. Moreover, the Mtb cell wall contributes to the mechanism of antibiotic resistance along with efflux pump activation and biofilm formation. Immunity over the course of TB is managed by M1-macrophages and M2-macrophages, which regulate the immune response against Mtb infection, with the former exerting inflammatory reactions and the latter promoting an anti-inflammatory profile. T helper 1 cells via secretion of interferon (IFN)-gamma, play a protective role in the course of TB, while T regulatory cells secreting interleukin 10, are anti-inflammatory. Alternative therapeutic options against TB require further discussion. In view of the increasing number of MDR Mtb strains, attempts to replace antibiotics with natural and biological products have been object of intensive investigation. Therefore, in this review the anti-Mtb effects exerted by probiotics, polyphenols, antimicrobial peptides and IFN-gamma will be discussed. All the above cited compounds are endowed either with direct antibacterial activity or with anti-inflammatory and immunomodulating characteristics.

Antibody-Mediated LILRB2-Receptor Antagonism Induces Human Myeloid-Derived Suppressor Cells to Kill Mycobacterium tuberculosis

Tuberculosis is a leading cause of death in mankind due to infectious agents, and Mycobacterium tuberculosis (Mtb) infects and survives in macrophages (MФs). Although MФs are a major niche, myeloid-derived suppressor cells (MDSCs) are an alternative site for pathogen persistence. Both MФs and MDSCs express varying levels of leukocyte immunoglobulin-like receptor B (LILRB), which regulate the myeloid cell suppressive function. Herein, we demonstrate that antagonism of LILRB2 by a monoclonal antibody (mab) induced a switch of human MDSCs towards an M1-macrophage phenotype, increasing the killing of intracellular Mtb. Mab-mediated antagonism of LILRB2 alone and its combination with a pharmacological blockade of SHP1/2 phosphatase increased proinflammatory cytokine responses and phosphorylation of ERK1/2, p38 MAPK, and NF-kB in Mtb-infected MDSCs. LILRB2 antagonism also upregulated anti-mycobacterial iNOS gene expression and an increase in both nitric oxide and reactive oxygen species synthesis. Because genes associated with the anti-mycobacterial function of M1-MФs were enhanced in MDSCs following mab treatment, we propose that LILRB2 antagonism reprograms MDSCs from an immunosuppressive state towards a pro-inflammatory phenotype that kills Mtb. LILRB2 is therefore a novel therapeutic target for eradicating Mtb in MDSCs.

The secretion profile of mesenchymal stem cells and potential applications in treating human diseases

Mesenchymal stromal/stem cells (MSCs) possess multi-lineage differentiation and self-renewal potentials. MSCs-based therapies have been widely utilized for the treatment of diverse inflammatory diseases, due to the potent immunoregulatory functions of MSCs. An increasing body of evidence indicates that MSCs exert their therapeutic effects largely through their paracrine actions. Growth factors, cytokines, chemokines, extracellular matrix components, and metabolic products were all found to be functional molecules of MSCs in various therapeutic paradigms. These secretory factors contribute to immune modulation, tissue remodeling, and cellular homeostasis during regeneration. In this review, we summarize and discuss recent advances in our understanding of the secretory behavior of MSCs and the intracellular communication that accounts for their potential in treating human diseases.

Dormancy: There and Back Again

Many cells are capable of maintaining viability in a non-dividing state with minimal metabolism under unfavorable conditions. These are germ cells, adult stem cells, and microorganisms. Unfortunately, a resting state, or dormancy, is possible for tuberculosis bacilli in a latent form of the disease and cancer cells, which may later form secondary tumors (metastases) in different parts of the body. These cells are resistant to therapy that can destroy intensely dividing cells and to the host immune system. A cascade of reactions that allows cells to enter and exit dormancy is triggered by regulatory factors from the microenvironment in niches that harbor the cells. A ratio of forbidding and permitting signals dictates whether the cells become dormant or start proliferation. The only difference between the cell dormancy regulation in normal and pathological conditions is that pathogens, mycobacteria, and cancer cells can influence their own fate by changing their microenvironment. Certain mechanisms of these processes are considered in the review.

The multi-faceted roles of TGF-β in regulation of immunity to infection

Transforming Growth Factor-β is a potent regulator of the immune system, acting at every stage from thymic differentiation, population of the periphery, control of responsiveness, tissue repair and generation of memory. It is therefore a central player in the immune response to infectious pathogens, but its contribution is often clouded by multiple roles acting on different cells in time and space. Hence, context is all-important in understanding when TGF-β is beneficial or detrimental to the outcome of infection. In this review, a full range of infectious agents from viruses to helminth parasites are explored within this framework, drawing contrasts and general conclusions about the importance of TGF-β in these diseases.

Is Mycobacterium tuberculosis carcinogenic to humans?

We highlight the ability of the tuberculosis (TB) causing bacterial pathogen, Mycobacterium tuberculosis (Mtb), to induce key characteristics that are associated with established IARC classified Group 1 and Group 2A carcinogenic agents. There is sufficient evidence from epidemiological case-control, cohort and meta-analysis studies of increased lung cancer (LC) risk in pre-existing/active/old TB cases. Similar to carcinogens and other pathogenic infectious agents, exposure to aerosol-containing Mtb sprays in mice produce malignant transformation of cells that result in squamous cell carcinoma. Convincing, mechanistic data show several characteristics shared between TB and LC which include chronic inflammation, genomic instability and replicative immortality, just to name a few cancer hallmarks. These hallmarks of cancer may serve as precursors to malignant transformation. Together, these findings form the basis of our postulate that Mtb is a complete human pulmonary carcinogen. We also discuss how Mtb may act as both an initiating agent and promoter of tumor growth. Forthcoming experimental studies will not only serve as proof-of-concept but will also pivot our understanding of how to manage/treat TB cases as well as offer solutions to clinical conundrums of TB lesions masquerading as tumors. Clinical validation of our concept may also help pave the way for next generation personalized medicine for the management of pulmonary TB/cancer particularly for cases that are not responding well to conventional chemotherapy or TB drugs.

Mesenchymal Stem Cells and Tuberculosis: Clinical Challenges and Opportunities

Tuberculosis (TB) is one of the communicable diseases caused by Mycobacterium tuberculosis (Mtb) infection, affecting nearly one-third of the world's population. However, because the pathogenesis of TB is still not fully understood and the development of anti-TB drug is slow, TB remains a global public health problem. In recent years, with the gradual discovery and confirmation of the immunomodulatory properties of mesenchymal stem cells (MSCs), more and more studies, including our team's research, have shown that MSCs seem to be closely related to the growth status of Mtb and the occurrence and development of TB, which is expected to bring new hope for the clinical treatment of TB. This article reviews the relationship between MSCs and the occurrence and development of TB and the potential application of MSCs in the treatment of TB.

Bartonella henselae Persistence within Mesenchymal Stromal Cells Enhances Endothelial Cell Activation and Infectibility That Amplifies the Angiogenic Process

Some bacterial pathogens can manipulate the angiogenic response, suppressing or inducing it for their own ends. In humans, Bartonella henselae is associated with cat-scratch disease and vasculoproliferative disorders such as bacillary angiomatosis and bacillary peliosis. Although endothelial cells (ECs) support the pathogenesis of B. henselae, the mechanisms by which B. henselae induces EC activation are not completely clear, as well as the possible contributions of other cells recruited at the site of infection. Mesenchymal stromal cells (MSCs) are endowed with angiogenic potential and play a dual role in infections, exerting antimicrobial properties but also acting as a shelter for pathogens. Here, we delved into the role of MSCs as a reservoir of B. henselae and modulator of EC functions. B. henselae readily infected MSCs and survived in perinuclearly bound vacuoles for up to 8 days. Infection enhanced MSC proliferation and the expression of epidermal growth factor receptor (EGFR), Toll-like receptor 2 (TLR2), and nucleotide-binding oligomerization domain-containing protein 1 (NOD1), proteins that are involved in bacterial internalization and cytokine production. Secretome analysis revealed that infected MSCs secreted higher levels of the proangiogenic factors vascular endothelial growth factor (VEGF), fibroblast growth factor 7 (FGF-7), matrix metallopeptidase 9 (MMP-9), placental growth factor (PIGF), serpin E1, thrombospondin 1 (TSP-1), urokinase-type plasminogen activator (uPA), interleukin 6 (IL-6), platelet-derived growth factor D (PDGF-D), chemokine ligand 5 (CCL5), and C-X-C motif chemokine ligand 8 (CXCL8). Supernatants from B. henselae-infected MSCs increased the susceptibility of ECs to B. henselae infection and enhanced EC proliferation, invasion, and reorganization in tube-like structures. Altogether, these results indicate MSCs as a still underestimated niche for persistent B. henselae infection and reveal MSC-EC cross talk that may contribute to exacerbate bacterium-induced angiogenesis and granuloma formation.

Heterogeneous Host-Pathogen Encounters Coordinate Antibiotic Resilience in Mycobacterium tuberculosis

Successful treatment of tuberculosis (TB) depends on the eradication of its causative agent Mycobacterium tuberculosis (Mtb) in the host. However, the emergence of phenotypically drug-resistant Mtb in the host environment tempers the ability of antibiotics to cure disease. Host immunity produces diverse microenvironmental niches that are exploited by Mtb to mobilize adaptation programs. Such differential interactions amplify pre-existing heterogeneity in the host-pathogen milieu to influence disease pathology and therapy outcome. Therefore, comprehending the intricacies of phenotypic heterogeneity can be an empirical step forward in potentiating drug action. With this goal, we review the interconnectedness of the lesional, cellular, and bacterial heterogeneity underlying phenotypic drug resistance. Based on this information, we anticipate the development of new therapeutic strategies targeting host-pathogen heterogeneity to cure TB.

Prevalence and Risk Factors of Infection with High Risk Human Papilloma Viruses among HIV-Positive Women with Clinical Manifestations of Tuberculosis in a Middle-Income Country

Women living with HIV-1 are at high risk of infection with human papillomavirus of high carcinogenic risk (HR HPVs). M. tuberculosis (TB) promotes HPV infection and increases the risk to develop HPV-associated cancer. Our knowledge of persisting HR HPVs genotypes, and of the factors promoting HR HPV infection in people living with HIV-1 with clinical TB manifestations is sparse. Here, we analyzed 58 women living with HIV-1 with clinical TB manifestations (WLWH with TB) followed up in specialized centers in Russia, a middle income country endemic for HIV-1 and TB, for the presence in cervical smears of DNA of twelve HR HPV genotypes. DNA encoding HPV16 E5, E6/E7 was sequenced. Sociodemographic data of patients was collected by questionnaire. All women were at C2-C3 stages of HIV-infection (by CDC). The majority were over 30 years old, had secondary education, were unemployed, had sexual partners, experienced 2–3 pregnancies and at least one abortion, and were smokers. The most prevalent was HPV16 detected in the cervical smears of 38% of study participants. Altogether 34.5% of study participants were positive for HR HPV types other than HPV16; however, but none of these types was seen in more than 7% of tested samples. Altogether, 20.7% of study participants were positive for several HR HPV types. Infections with HPVs other than HPV16 were common among WLWH with generalized TB receiving combined ART/TB-therapy, and associated with their ability to work, indirectly reflecting both their health and lifestyle. The overall prevalence of HR HPVs was associated with sexual activity of women reflected by the number of pregnancies, and of HPV 16, with young age; none was associated to CD4+-counts, route of HIV-infection, duration of life with HIV, forms of TB-infection, or duration of ART, characterizing the immune status. Thus, WLWH with TB—especially young—were predisposed to infection with HPV16, advancing it as a basis for a therapeutic HPV vaccine. Phylogenetic analysis of HPV16 E5, E6/E7 DNA revealed no common ancestry; sequences were similar to those of the European and American HPV16 strains, indicating that HPV vaccine for WLWH could be the same as HPV16 vaccines developed for the general population. Sociodemographic and health correlates of HR HPV prevalence in WLWH deserve further analysis to develop criteria/recommendations for prophylactic catch-up and therapeutic HPV vaccination of this highly susceptible and vulnerable population group.

Exosomes derived from mycobacterium tuberculosis-infected MSCs induce a pro-inflammatory response of macrophages

Tuberculosis (TB) is a common infectious disease caused by Mycobacterium tuberculosis (M.tb), and macrophages serve as the primary natural host of M.tb. Mesenchymal stem cells (MSCs)-derived exosomes play an essential role in inflammatory responses. This study aimed to determine the role of exosomes derived from M.tb-infected MSCs (Exo-MSCs-M.tb) on macrophages in vitro and in vivo and the underlying mechanisms. Here, we demonstrated that M.tb infection promoted the production of Exo-MSCs-M.tb, but did not influence MSCs proliferation. Exo-MSCs-M.tb were taken up by macrophages and then induced the pro-inflammatory response of macrophages through elevating the production of TNF-α, RANTES, and iNOS. Also, pro-inflammatory response induced by Exo-MSCs-M.tb displayed a time-dependent pattern in macrophages, in which the highest level of inflammatory response was observed at 72 hours post-infection of MSCs. In addition, the effect of Exo-MSCs-M.tb was mediated through TLR2/4 and MyD88 signaling pathways. Furthermore, Exo-MSCs-M.tb could induce the pro-inflammatory response in mice in vivo, and exosomes isolated from Exo-MSCs-M.tb-treated mice could also promote the pro-inflammatory response. Taken together, these results indicate that Exo-MSCs-M.tb induced the pro-inflammatory response of macrophages through TLRs signaling. This study provides new insight into the potential of MSCs-derived exosomes for the treatment of TB.

Inhibition of JAK-STAT Signaling Pathway Alleviates Age-Related Phenotypes in Tendon Stem/Progenitor Cells

Diminished regeneration or healing capacity of tendon occurs during aging. It has been well demonstrated that tendon stem/progenitor cells (TSPCs) play a vital role in tendon maintenance and repair. Here, we identified an accumulation of senescent TSPCs in tendon tissue with aging. In aged TSPCs, the activity of JAK-STAT signaling pathway was increased. Besides, genetic knockdown of JAK2 or STAT3 significantly attenuated TSPC senescence in aged TSPCs. Pharmacological inhibition of JAK-STAT signaling pathway with AG490 similarly attenuated cellular senescence and senescence-associated secretory phenotype (SASP) of aged TSPCs. In addition, inhibition of JAK-STAT signaling pathway also restored the age-related dysfunctions of TSPCs, including self-renewal, migration, actin dynamics, and stemness. Together, our findings reveal the critical role of JAK-STAT signaling pathway in the regulation of TSPC aging and suggest an ideal therapeutic target for the age-related tendon disorders.

Initiation of Post-Primary Tuberculosis of the Lungs: Exploring the Secret Role of Bone Marrow Derived Stem Cells

Mycobacterium tuberculosis (Mtb), the causative organism of pulmonary tuberculosis (PTB) now infects more than half of the world population. The efficient transmission strategy of the pathogen includes first remaining dormant inside the infected host, next undergoing reactivation to cause post-primary tuberculosis of the lungs (PPTBL) and then transmit via aerosol to the community. In this review, we are exploring recent findings on the role of bone marrow (BM) stem cell niche in Mtb dormancy and reactivation that may underlie the mechanisms of PPTBL development. We suggest that pathogen's interaction with the stem cell niche may be relevant in potential inflammation induced PPTBL reactivation, which need significant research attention for the future development of novel preventive and therapeutic strategies for PPTBL, especially in a post COVID-19 pandemic world. Finally, we put forward potential animal models to study the stem cell basis of Mtb dormancy and reactivation.

The suppressive effect of bacterial-feeding nematodes on hemocyte spreading of Galleria mellonella

Insect parasitic nematodes have developed a mechanism to escape from the cellular immunity of their insect hosts for successful parasitism. However, the detailed mechanism whereby they achieve this remains unclear. In our previous study, we demonstrated that non-parasitic nematodes such as Caenorhabditis elegans potentially have the ability to escape from the cellular immunity of the greater wax moth Galleria mellonella. Here we aimed to clarify the effect of non-parasitic and parasitic nematodes on the spreading of hemocytes-an essential cellular reaction for adhering to a foreign substance -from G. mellonella larvae. The hexane/methanol extract of C. elegans inhibited the spreading of hemocytes. Using 2D-TLC and reversed-phase HPLC, we detected a single peak that inhibited the spreading of hemocytes. In addition, the spreading of hemocytes recovered from C. elegans-injected insects was significantly delayed. Western blotting analysis showed that phosphorylated extracellular signal-regulated protein kinase (ERK) -an essential signaling component for spreading in hemocytes-was decreased by the injection of C. elegans, and that plasma from nematode-injected insects contained the factor that causes the decrease of phosphorylated ERK. We also observed this phenomenon using other non-parasitic and parasitic bacterial-feeding nematodes. These results suggest that the factors inhibiting hemocyte adhesion and delaying the spreading of hemocytes are conserved in bacterial-feeding nematodes and could be a pre-adaptation for parasitism.

Inhibition of ABCG2 efflux pumps renders the Mycobacterium tuberculosis hiding in mesenchymal stem cells responsive to antibiotic treatment

The lengthy TB chemotherapeutic regimen, resulting in the emergence of drug resistance strains, poses a serious problem in the cure of the disease. Further, one-quarter of the world's population is infected with dormant M.tb, which creates a lifetime risk of reactivation. M.tb has a remarkable tendency to escape the host immune responses by hiding in unconventional niches. Recent studies have shown that bone-marrow mesenchymal stem cells (BM-MSCs) can serve as a reservoir of the pathogen and have been suggested to keep them beyond the reach of anti-TB drugs. In this study, we have shown that M.tb infects and grows inside BM-MSCs and were unresponsive to the anti-TB drugs rifampicin and isoniazid when compared to the pathogen residing inside THP-1 macrophages. It was further shown that the ABCG2 efflux pumps of the BM-MSCs were upregulated upon exposure to rifampicin, which may be the contributing factor for the antibiotic unresponsiveness of the bacteria inside these cells. Subsequently, it was shown that inhibition of ABCG2 efflux pumps along with administration of anti-TB drugs led to an increased susceptibility and consequently an enhanced killing of the M.tb inside BM-MSCs. These findings for the first time show that the MIC₉₉ values of anti-TB drugs increase many folds for the M.tb residing in BM-MSCs as compared to M.tb residing inside macrophages and the involvement of ABCG2 efflux pumps in this phenomenon. Our study substantiates that these BM-MSCs acts as a useful niche for M.tb wherein they can survive by escaping the antibiotic assault that can be attributed to the host ABCG2 efflux pumps. Inhibiting these efflux pumps can be an attractive adjunctive chemotherapy to eliminate the bacteria from this protective niche.

Mesenchymal stem cells protect against malaria pathogenesis by reprogramming erythropoiesis in the bone marrow

Malaria remains a major public health problem worldwide. The immune mechanisms that mediate protection against malaria are still unclear. Previously, we reported that mesenchymal stem cells (MSCs) play a critical role in host protection against malaria by altering the dynamic balance of T regulatory cells and effector T cells producing inflammatory cytokines. Here, we report that MSCs reprogram haematopoiesis in primary (bone marrow) and secondary (spleen) lymphoid organs to provide host protection against malaria. Adoptive transfer of MSCs from malaria-infected mice to naïve recipient mice that were subsequently infected with malaria parasites dramatically accelerated the formation of colony-forming units-erythroid cells in the bone marrow. Adoptively transferred MSCs also induced expression of the key erythroid cell differentiation factor GATA-1 in the spleen of recipient animals. Interestingly, we further observed a subtle increase in the CD34⁺ hematopoietic stem and progenitor cells in lymphoid organs, including spleen and lymph nodes. Infusion of MSCs also enhanced T cell proliferation, resulting in increased numbers of both CD4⁺ and CD8⁺ T cells in the spleen. MSCs also inhibited the induction of the negative co-stimulatory receptor programmed death-1 by T cells in recipient animals upon infection with malaria parasites. Taken together, our findings suggest that MSCs play a critical role in host protection against malaria infection by modulating erythropoiesis and lymphopoiesis.

Lung gene expression signatures suggest pathogenic links and molecular markers for pulmonary tuberculosis, adenocarcinoma and sarcoidosis

Previous reports have suggested a link between pulmonary tuberculosis (TB), which is caused by Mycobacterium tuberculosis (Mtb), and the development of lung adenocarcinoma (LUAD) and sarcoidosis. Furthermore, these lung diseases share certain clinical similarities that can challenge differential diagnosis in some cases. Here, through comparison of lung transcriptome-derived molecular signatures of TB, LUAD and sarcoidosis patients, we identify certain shared disease-related expression patterns. We also demonstrate that MKI67, an over-expressed gene shared by TB and LUAD, is a key mediator in Mtb-promoted tumor cell proliferation, migration, and invasion. Moreover, we reveal a distinct ossification-related TB lung signature, which may be associated with the activation of the BMP/SMAD/RUNX2 pathway in Mtb-infected macrophages that can restrain mycobacterial survival and promote osteogenic differentiation of mesenchymal stem cells. Taken together, these findings provide novel pathogenic links and potential molecular markers for better understanding and differential diagnosis of pulmonary TB, LUAD and sarcoidosis.

Previous work has suggested potential links between Mycobacterium tuberculosis infection and the development of both lung cancer and sarcoidosis, in addition to tuberculosis. Here, Qiyao Chai, Zhe Lu, Zhidong Liu and colleagues report a transcriptomic analysis of lung tissue from tuberculosis, lung adenocarcinoma, and sarcoidosis patients and find that while many disease-linked expression changes are shared between the three diseases, each also has distinct transcriptional signatures that could be useful as molecular markers.

Mycobacterium tuberculosis programs mesenchymal stem cells to establish dormancy and persistence

Tuberculosis (TB) remains a major infectious disease worldwide. TB treatment displays a biphasic bacterial clearance, in which the majority of bacteria clear within the first month of treatment, but residual bacteria remain nonresponsive to treatment and eventually may become resistant. Here, we have shown that Mycobacterium tuberculosis was taken up by mesenchymal stem cells (MSCs), where it established dormancy and became highly nonresponsive to isoniazid, a major constituent of directly observed treatment short course (DOTS). Dormant M. tuberculosis induced quiescence in MSCs and promoted their long-term survival. Unlike macrophages, where M. tuberculosis resides in early-phagosomal compartments, in MSCs the majority of bacilli were found in the cytosol, where they promoted rapid lipid synthesis, hiding within lipid droplets. Inhibition of lipid synthesis prevented dormancy and sensitized the organisms to isoniazid. Thus, we have established that M. tuberculosis gains dormancy in MSCs, which serve as a long-term natural reservoir of dormant M. tuberculosis. Interestingly, in the murine model of TB, induction of autophagy eliminated M. tuberculosis from MSCs, and consequently, the addition of rapamycin to an isoniazid treatment regimen successfully attained sterile clearance and prevented disease reactivation.

T Cell Immunity to Bacterial Pathogens: Mechanisms of Immune Control and Bacterial Evasion

The human body frequently encounters harmful bacterial pathogens and employs immune defense mechanisms designed to counteract such pathogenic assault. In the adaptive immune system, major histocompatibility complex (MHC)-restricted αβ T cells, along with unconventional αβ or γδ T cells, respond to bacterial antigens to orchestrate persisting protective immune responses and generate immunological memory. Research in the past ten years accelerated our knowledge of how T cells recognize bacterial antigens and how many bacterial species have evolved mechanisms to evade host antimicrobial immune responses. Such escape mechanisms act to corrupt the crosstalk between innate and adaptive immunity, potentially tipping the balance of host immune responses toward pathological rather than protective. This review examines the latest developments in our knowledge of how T cell immunity responds to bacterial pathogens and evaluates some of the mechanisms that pathogenic bacteria use to evade such T cell immunosurveillance, to promote virulence and survival in the host.

Understanding the Relationship between Glutathione, TGF-β, and Vitamin D in Combating Mycobacterium tuberculosis Infections

Tuberculosis (TB) remains a pervasive global health threat. A significant proportion of the world's population that is affected by latent tuberculosis infection (LTBI) is at risk for reactivation and subsequent transmission to close contacts. Despite sustained efforts in eradication, the rise of multidrug-resistant strains of Mycobacteriumtuberculosis (M. tb) has rendered traditional antibiotic therapy less effective at mitigating the morbidity and mortality of the disease. Management of TB is further complicated by medications with various off-target effects and poor compliance. Immunocompromised patients are the most at-risk in reactivation of a LTBI, due to impairment in effector immune responses. Our laboratory has previously reported that individuals suffering from Type 2 Diabetes Mellitus (T2DM) and HIV exhibited compromised levels of the antioxidant glutathione (GSH). Restoring the levels of GSH resulted in improved control of M. tb infection. The goal of this review is to provide insights on the diverse roles of TGF- β and vitamin D in altering the levels of GSH, granuloma formation, and clearance of M. tb infection. We propose that these pathways represent a potential avenue for future investigation and development of new TB treatment modalities.

Reece S, R. Martineau A, P. Kateete D. Detection of Mycobacterium tuberculosis DNA in CD34 + peripheral blood mononuclear cells of Ugandan adults with latent infection: a cross-sectional and nested prospective study

Background: Tuberculin skin test and interferon gamma release assay (IGRA) show limitations in diagnosing latent tuberculosis infection (LTBI) and poorly predict progression to active tuberculosis. This study will explore detection of Mycobacterium tuberculosis ( M.tb) DNA in CD34 + peripheral blood mononuclear cells (PBMCs) as a biomarker for LTBI and monitoring chemoprophylaxis response. Methods: In a cross-sectional study, 120 household contacts (60 HIV positive and 60 HIV negative) will be recruited. Also, 10 patients with sputum positive pulmonary tuberculosis and 10 visitors from low incidence countries with no history of TB treatment will be recruited as positive and negative controls, respectively. Participants will donate 100 ml (50 ml for TB patients) of blood to isolate PBMCs using density gradient centrifugation. Isolated PBMCs will be separated into CD34 + and CD34 - enriched cellular fractions. DNA from each fraction will be purified, quantified and subjected to droplet digital PCR targeting IS6110 (a M.tb Complex multi-copy gene) and rpoB, a single copy gene. Also, 4 ml of blood will be drawn for IGRA. In a nested prospective study, 60 HIV positive participants will be given 300 mg of Isoniazid Preventive Therapy (IPT) daily for six months, after which they will donate a second 100 ml blood sample that will be processed as described above. Data from the cross-sectional study will be analysed to determine the proportion of individuals in whom M.tb DNA is detectable in CD34 + and CD34 - fractions and number of M.tb genomes present. Data from the prospective study will be analysed to compare the proportion of individuals with detectable M.tb DNA in CD34 + and CD34 - fractions, and median M.tb genome copy number, post vs pre-IPT. Discussion: This study will determine whether detection of M.tb DNA in CD34 + PBMCs holds promise as a biomarker for LTBI and monitoring chemoprophylaxis response.

Human mesenchymal stem cell based intracellular dormancy model of Mycobacterium tuberculosis

Understanding the biology of the tuberculosis pathogen during dormant asymptomatic infection, called latent tuberculosis is crucial to decipher a resilient therapeutic strategy for the disease. Recent discoveries exhibiting presence of pathogen's DNA and bacilli in mesenchymal stem cells (MSCs) of human and mouse despite completion of antitubercular therapy, indicates that these specific cells could be one of the niches for dormant Mycobacterium tuberculosis in humans. To determine if in vitro infection of human MSCs could recapitulate the in vivo characteristics of dormant M. tuberculosis, we examined survival, phenotype, and drug susceptibility of the pathogen in MSCs. When a very low multiplicity of infection (1:1) was used, M. tuberculosis could survive in human bone marrow derived MSCs for more than 22 days without any growth. At this low level of infection, the pathogen did not cause any noticeable host cell death. During the later phase of infection, MSC-residing M. tuberculosis exhibited increased expression of HspX (a 16-kDa alpha-crystallin homolog) with a concurrent increase in tolerance to the frontline antitubercular drugs Rifampin and isoniazid. These results present a human MSC-based intracelllular model of M. tuberculosis infection to dissect the mechanisms through which the pathogen acquires and maintains dormancy in the host.

Mesenchymal stem cells offer a drug-tolerant and immune-privileged niche to Mycobacterium tuberculosis

Anti-tuberculosis (TB) drugs, while being highly potent in vitro, require prolonged treatment to control Mycobacterium tuberculosis (Mtb) infections in vivo. We report here that mesenchymal stem cells (MSCs) shelter Mtb to help tolerate anti-TB drugs. MSCs readily take up Mtb and allow unabated mycobacterial growth despite having a functional innate pathway of phagosome maturation. Unlike macrophage-resident ones, MSC-resident Mtb tolerates anti-TB drugs remarkably well, a phenomenon requiring proteins ABCC1, ABCG2 and vacuolar-type H⁺ATPases. Additionally, the classic pro-inflammatory cytokines IFNγ and TNFα aid mycobacterial growth within MSCs. Mechanistically, evading drugs and inflammatory cytokines by MSC-resident Mtb is dependent on elevated PGE2 signaling, which we verify in vivo analyzing sorted CD45^-Sca1⁺CD73⁺-MSCs from lungs of infected mice. Moreover, MSCs are observed in and around human tuberculosis granulomas, harboring Mtb bacilli. We therefore propose, targeting the unique immune-privileged niche, provided by MSCs to Mtb, can have a major impact on tuberculosis prevention and cure.

Mesenchymal Stem Cells: A New Generation of Therapeutic Agents as Vehicles in Gene Therapy

In recent years, mesenchymal stem cells (MSCs) as a new tool for therapeutic gene delivery in clinics have attracted much attention. Their advantages cover longer lifespan, better isolation, and higher transfection efficiency and proliferation rate. MSCs are the preferred approach for cell-based therapies because of their in vitro self-renewal capacity, migrating especially to tumor tissues, as well as anti-inflammatory and immunomodulatory properties. Therefore, they have considerable efficiency in genetic engineering for future clinical applications in cancer gene therapy and other diseases. For improving therapeutic efficiency, targeted therapy of cancers can be achieved through the sustained release of therapeutic agents and functional gene expression induction to the intended tissues. The development of a new vector in gene therapy can improve the durability of a transgene expression. Also, the safety of the vector, if administered systemically, may resolve several problems, such as durability of expression and the host immune response. Currently, MSCs are prominent candidates as cell vehicles for both preclinical and clinical trials due to the secretion of therapeutic agents in several cancers. In the present study, we discuss the status of gene therapy in both viral and non-viral vectors along with their limitations. Throughout this study, the use of several nano-carriers for gene therapy is also investigated. Finally, we critically discuss the promising advantages of MSCs in targeted gene delivery, tumor inhibition and their utilization as the gene carriers in clinical situations.

Clofazimine enhances the efficacy of BCG revaccination via stem cell-like memory T cells

Tuberculosis (TB) is one of the deadliest diseases, claiming ~2 million deaths annually worldwide. The majority of people in TB endemic regions are vaccinated with Bacillus Calmette Guerin (BCG), which is the only usable vaccine available. BCG is efficacious against meningeal and disseminated TB in children, but protective responses are relatively short-lived and fail to protect against adult pulmonary TB. The longevity of vaccine efficacy critically depends on the magnitude of long-lasting central memory T (T_CM) cells, a major source of which is stem cell-like memory T (T_SM) cells. These T_SM cells exhibit enhanced self-renewal capacity as well as to rapidly respond to antigen and generate protective poly-functional T cells producing IFN-γ, TNF-α, IL-2 and IL-17. It is now evident that T helper Th 1 and Th17 cells are essential for host protection against TB. Recent reports have indicated that Th17 cells preserve the molecular signature for T_SM cells, which eventually differentiate into IFN-γ-producing effector cells. BCG is ineffective in inducing Th17 cell responses, which might explain its inadequate vaccine efficacy. Here, we show that revaccination with BCG along with clofazimine treatment promotes T_SM differentiation, which continuously restores T_CM and T effector memory (T_EM) cells and drastically increases vaccine efficacy in BCG-primed animals. Analyses of these T_SM cells revealed that they are predominantly precursors to host protective Th1 and Th17 cells. Taken together, these findings revealed that clofazimine treatment at the time of BCG revaccination provides superior host protection against TB by increasing long-lasting T_SM cells.

Tuberculosis (TB) is one of the deadliest diseases, claiming ~2 million deaths annually worldwide. Bacillus Calmette Guerin (BCG) is the only usable vaccine available and exhibits efficacy against meningeal and disseminated TB in children. Consequently, the vast majority of people in TB endemic regions are vaccinated with BCG. However, host protective immune responses diminish over time due to gradual depletion of T central memory (T_CM) cells, which are responsible for long-term host protection. Here, we provide evidence that revaccination with BCG along with the clofazimine, an approved drug for treatment of leprosy and drug-resistant TB, induces stem cell-like memory T (T_SM) cells. T_SM cells are precursors to T_CM cells, and provide long-term host protection to TB by continuous supply of T_CM cells. Interestingly, these T_SM cells were generated from IL-17-producing T helper (Th)17 cells. These T_SM cells differentiated into T_CM and T effector memory (T_EM) cells and maintained a stable pool of critically important Th1 and Th17 cells to provide optimal host protection against TB.

Anatomic and Cellular Niches for Mycobacterium tuberculosis in Latent Tuberculosis Infection

Latent tuberculosis has been recognized for over a century, but discovery of new niches, where Mycobacterium tuberculosis resides, continues. We evaluated literature on M.tuberculosis locations during latency, highlighting that mesenchymal and hematopoietic stem cells harbor organisms in sensitized asymptomatic individuals.

Curcumin Nanoparticles Enhance Mycobacterium bovis BCG Vaccine Efficacy by Modulating Host Immune Responses

Tuberculosis (TB) is one of the deadliest diseases, causing ∼2 million deaths annually worldwide. Mycobacterium bovis bacillus Calmette-Guérin (BCG), the only TB vaccine in common use, is effective against disseminated and meningeal TB in young children but is not effective against adult pulmonary TB.

Tuberculosis (TB) is one of the deadliest diseases, causing ∼2 million deaths annually worldwide. Mycobacterium bovis bacillus Calmette-Guérin (BCG), the only TB vaccine in common use, is effective against disseminated and meningeal TB in young children but is not effective against adult pulmonary TB. T helper 1 (Th1) cells producing interferon gamma (IFN-γ) and Th17 cells producing interleukin-17 (IL-17) play key roles in host protection against TB, whereas Th2 cells producing IL-4 and regulatory T cells (Tregs) facilitate TB disease progression by inhibiting protective Th1 and Th17 responses. Furthermore, the longevity of vaccine efficacy critically depends on the magnitude of long-lasting central memory T (T_CM) cell responses. Hence, immunomodulators that promote T_CM responses of the Th1 and Th17 cell lineages may improve BCG vaccine efficacy. Here, we show that curcumin nanoparticles enhance various antigen-presenting cell (APC) functions, including autophagy, costimulatory activity, and the production of inflammatory cytokines and other mediators. We further show that curcumin nanoparticles enhance the capacity of BCG to induce T_CM cells of the Th1 and Th17 lineages, which augments host protection against TB infection. Thus, curcumin nanoparticles hold promise for enhancing the efficacy of TB vaccines.

CD73 expression in tissue granulomas in distinguishing intestinal tuberculosis from Crohn's disease in a South African cohort

INTRODUCTION

Overlap of clinical, endoscopic and radiographic features, coupled with a poor microbiological yield makes differentiating Crohn's disease (CD) from intestinal tuberculosis (ITB) challenging. A potential histological differentiating mechanism is the use of immunohistochemical staining for the mesenchymal stem cell marker CD73, as a pilot study showed ITB but not CD granulomas stained positive for this marker. The aim of this study was to assess the value of CD73 in differentiating ITB from CD granulomas in a South African cohort.

METHODS

Patients with confirmed CD or ITB were identified from a pathology database. Tissue sections were reviewed by a pathologist to confirm the presence of granulomas. These were then stained with a mouse monoclonal anti-CD73 antibody. The slides were examined together by a pathologist and gastroenterologist in a blinded manner for anti-CD73 staining around granulomas.

RESULTS

Ninety six cases were available for analysis; 50 cases of ITB and 46 cases of CD. Thirty percent of CD granulomas (14/46) stained positive for CD73, whereas CD73 positivity was seen in 52% (26/50) of cases of ITB. This was statistically significant (OR 2.48, 95% CI 1.1-5.72, p = .03). The area under the curve (AUC) was 0.61. Sensitivity of CD73 in predicting ITB was 52% and specificity was 70%. Overall CD73 staining of granulomas correctly classified only 60% of cases.

CONCLUSIONS

In our study we have shown that significantly more patients with ITB express CD73 in their granulomas than those with CD. However the relatively poor sensitivity, specificity and AUC make this test unlikely to be of value in our clinical practice.

Effect of binding immunoglobulin protein on induction of regulatory B cells with killer phenotype during inflammation and disease

Immune responses result from different immune cells acting in synergy to successfully fight infections. This requires a high degree of regulation to prevent excessive production of inflammatory products leading to other disease forms. Regulatory B cells are classified based on surface immunoglobulin expression. These cells are reported to resolve inflammation during chronic or autoimmune diseases. However, during chronic inflammation, their frequencies have been shown to be affected, and they can be induced by exposure to extracellular binding immunoglobulin protein (BiP). This review focuses on the effects on immune cells by extracellular or secreted BiP during various chronic inflammatory responses. For example, cell stress associated with Mycobacterium tuberculosis infection leads to accumulation of unfolded proteins that subsequently activate BiP and its three signal transducers intracellularly. Furthermore, BiP can be translocated from the endoplasmic reticulum to the extracellular environment where it binds immune cells as an autoantigen and leads to functional changes.

Immune responses during tuberculosis disease require balanced cell interactions. These include antigen-presenting cells, effector cells and regulatory cells. B lymphocytes can mediate regulatory function during chronic diseases and lead to better disease outcome. These specialized cells mediate this function through both surface and soluble protein expression. Their development can be facilitated by different stimuli including binding immunoglobulin protein. This protein resides in the endoplasmic reticulum where it functions in proper protein folding; however, it can escape this location to the extracellular phase, where it affects immune cell function leading to development of regulatory traits on B cells.

Cell-cell contact with proinflammatory macrophages enhances the immunotherapeutic effect of mesenchymal stem cells in two abortion models

Mesenchymal stem cells (MSCs), which are pluripotent cells with immunomodulatory properties, have been considered good candidates for the therapy of several immune disorders, such as inflammatory bowel diseases, concanavalin A-induced liver injury, and graft-versus-host disease. The embryo is a natural allograft to the maternal immune system. A successful pregnancy depends on the timely extinction of the inflammatory response induced by embryo implantation, followed by the switch to a tolerant immune microenvironment in both the uterus and the system. Excessive infiltration of immune cells and serious inflammatory responses are triggers for embryo rejection, which results in miscarriage. Here, we demonstrated that adoptive transfer of MSCs could prevent fetal loss in a lipopolysaccharide (LPS)-induced abortion model and immune response-mediated spontaneous abortion model. The immunosuppressive MSCs alleviated excessive inflammation by inhibiting CD4⁺T cell proliferation and promoting the decidual macrophage switch to M2 in a tumor necrosis factor-stimulated gene-6 (TSG-6)-dependent manner. Cell-to-cell contact with proinflammatory macrophages increased the TSG-6 production by the MSCs, thereby enhancing the suppressive regulation of T cells and macrophages. Moreover, proinflammatory macrophages in contact with the MSCs upregulated the expression of CD200 on the stem cells and facilitated the reprogramming of macrophages towards an anti-inflammatory skew through the interaction of CD200 with CD200R on proinflammatory macrophages. Therefore, the results demonstrate that a TSG-6-mediated paracrine effect, reinforced by cell-to-cell contact between MSCs and proinflammatory macrophages, is involved in the mechanism of MSC-mediated abortion relief through the induction of immune tolerance. Our study also indicates the potential application of MSCs in clinical recurrent miscarriages.

The level of the endoplasmic reticulum stress chaperone protein, binding immunoglobulin protein (BiP), decreases following successful tuberculosis treatment

An increased Mycobacterium tuberculosis burden inside the host leads to higher demand of response proteins. This in turn results in metabolic shift and cellular stress, which is caused by the accumulation and trafficking of these proteins within the endoplasmic reticulum (ER). To resolve this, cells trigger the unfolded protein response (UPR), which is mainly mediated by binding immunoglobulin protein (BiP)/glucose-regulated protein 78 (GRP78) chaperone, and this in turn upregulates its transcription. This chaperone protein facilitates proper protein folding within the ER; however, it can also be passively secreted into the extracellular environment or be expressed on cell surfaces attached to anchor proteins and transmembrane proteins. This notion has been shown in studies on chronic inflammation, including cancer and arthritis, with the detection of BiP-specific antibodies from different sample types. The present study analysed secreted BiP from plasma samples collected from healthy participants and patients with newly diagnosed tuberculosis (TBdx), seen over the course of TB treatment at week 1 (W1), month 2 (M2), and month 6 (M6). The results revealed that during the initial TB disease and treatment period, cells are subjected to stress conditions resulting in metabolic shifts, which lead to the secretion of the intracellular UPR-mediating chaperone protein, BiP. This was indicated by mean differences between TBdx (mean 40.88ng/ml) and W1 (68.57ng/ml) in the TB participant groups. However, no difference was observed between the healthy group (mean 42.64ng/ml) and TBdx group (mean 40.88ng/ml). Analysis of paired time-point visits revealed increased BiP secretion during early TB treatment. The detection of BiP in plasma samples was found to decrease after successful TB treatment to levels comparable to those in the healthy controls. Evaluation of BiP levels in larger TB treatment studies may lead to the identification of a new target for early TB diagnosis and host-directed immunotherapy.

Effects of preventive therapy for latent tuberculosis infection and factors associated with treatment abandonment: a cross-sectional study

Background

Routine data on the use of preventive therapy (PT) for latent tuberculosis infection (LTBI) in students are scarce in high tuberculosis (TB) burden countries. This study aimed to investigate the effects of PT and identify factors related to PT abandonment during the school TB epidemic in Guangzhou, southern China.

Methods

Purified protein derivative (PPD) skin testing was performed on all staff and students in a vocational school in Guangzhou, southern China during December 2014. Subjects (n=362) with a reactive PPD induration ≥15 mm, or with papules, blisters, and a normal chest X-ray image were recommended for PT. The subjects were assigned to a PT group (n=156) and control group (n=206), respectively, on a voluntary basis. Subjects in the PT group received isoniazid (INH) combined with rifampicin (RFP) for 3 consecutive months; after which, the incidence of TB and protective rate of PT for reducing TB were observed during a 2-year follow up period. An improved questionnaire was used to identify factors that influenced treatment abandonment. All data were subjected to univariate and multivariate logistic regression analyses.

Results

Two cases in the PT group and 20 cases in the control group developed TB. The protective rate of PT for reducing TB was 86.8%. In the PT group, 69 cases finished PT, with a completion rate of 44.2%, and the incidence rates of adverse events and hepatotoxicity were 12.2% and 1.9%, respectively. Among 362 LTBI cases, a total of 293 cases abandoned PT. Discrimination (OR =7.173, 95% CI, 3.361-15.307), worry about adverse drug reactions (OR =2.752, 95% CI, 1.459-5.192), a low parental education level (OR =2.605, 95% CI, 1.420-4.777), and accepting the opinion of a non-TB specialist (OR =6.017, 95% CI, 3.077-11.765) were identified as high-risk factors for abandoning PT.

Conclusions

A PT regimen consisting of INH combined with RFP for 3 consecutive months is reasonable for use in schools. Discrimination, worry about adverse drug reactions, a low parental education level, and accepting the opinion of a non-TB specialist are all factors that may increase the risk for treatment abandonment among LTBI cases. To overcome psychological obstacles is critical for improving treatment adherence.

The use of immunotherapy for the treatment of tuberculosis

INTRODUCTION

Tuberculosis (TB) is the first cause of mortality by a single infectious agent in the world, causing more than one million deaths worldwide as reported by the World Health Organization (WHO). For the optimal control of TB infection, a protective immune response that limits bacterial spread without causing damage to the host is essential. Although most healthy individuals are capable of generating protective responses, patients who suffer pulmonary TB commonly present a defective immune function. Areas covered: We intend to highlight the potential of novel immunotherapeutic strategies that enhance and promote effective immune responses. The following methodology was undertaken for establishing a literature search: the authors used PubMed to search for 'Pulmonary Tuberculosis' and keywords that denoted the novel immunotherapeutic strategies discussed in length in the text including antibodies, antimicrobial peptides, cell therapy, cytokines and gene therapy. Expert commentary: The current therapeutic regimens for this disease are complex and involve the prolonged use of multiple antibiotics with diverse side effects that lead to therapeutic failure and bacterial resistance. The standard appliance of immunotherapy and its deployment to vulnerable populations will require coordinated work and may serve as a powerful tool to combat the ensuing threat of TB.

Mesenchymal stem cells internalize Mycobacterium tuberculosis through scavenger receptors and restrict bacterial growth through autophagy

Human mesenchymal stem cells (MSCs) express scavenger receptors that internalize lipids, including oxidized low-density lipoprotein (oxLDL). We report that MSCs phagocytose Mycobacterium tuberculosis (Mtb) through two types of scavenger receptors (SRs; MARCO and SR-B1), as blockade of the receptors with antibodies or siRNA knockdown decreased the uptake of Mtb. MSCs also expressed mannose receptor (MR) that was found to endocytose rhodamine-labeled mannosylated BSA (rMBSA), though the receptor was not involved in the uptake of Mtb. Dil-oxLDL and rMBSA taken up into MSC endosomes colocalized with Mtb phagosomes, thus suggesting that the latter were fusion competent. Phagocytosed Mtb did not replicate within MSCs, thus suggesting an intrinsic control of bacterial growth. Indeed, MSCs exhibited intrinsic autophagy, which was up-regulated after activation with rapamycin. SiRNA knockdown of autophagy initiator beclin-1 enhanced Mtb survival, whereas rapamycin-induced autophagy increased intracellular killing of Mtb. In addition, MSCs secreted nitric oxide after Mtb infection, and inhibition of NO by N(G)-monomethyl-L-arginine enhanced intracellular survival of Mtb. MSCs can be grown in large numbers in vitro, and autologous MSCs transfused into tuberculosis patients have been found to be safe and improve lung immunity. Thus, MSCs are novel phagocytic cells with a potential for immunotherapy in treating multidrug-resistant tuberculosis.

Mouse Bone Marrow Sca-1+ CD44+ Mesenchymal Stem Cells Kill Avirulent Mycobacteria but Not Mycobacterium tuberculosis through Modulation of Cathelicidin Expression via the p38 Mitogen-Activated Protein Kinase-Dependent Pathway

Mycobacterium tuberculosis primarily infects lung macrophages. However, a recent study showed that M. tuberculosis also infects and persists in a dormant form inside bone marrow mesenchymal stem cells (BM-MSCs) even after successful antibiotic therapy. However, the mechanism(s) by which M. tuberculosis survives in BM-MSCs is still not known. Like macrophages, BM-MSCs do not contain a well-defined endocytic pathway, which is known to play a central role in the clearance of internalized mycobacteria. Here, we studied the fate of virulent and avirulent mycobacteria in Sca-1⁺ CD44⁺ BM-MSCs. We found that BM-MSCs were able to kill avirulent Mycobacterium smegmatis and Mycobacterium bovis BCG but not the pathogenic species M. tuberculosis Further mechanistic studies revealed that pathogenic M. tuberculosis dampens the antibacterial response of BM-MSCs by downregulating the expression of the cationic antimicrobial peptide cathelicidin. In contrast, avirulent mycobacteria were effectively killed by inducing the Toll-like receptor 2/4 (TLR2/4) pathway-dependent expression of cathelicidin, while small interfering RNA (siRNA)-mediated cathelicidin silencing increased the survival of M. bovis BCG in BM-MSCs. We also showed that M. bovis BCG infection caused increased expression levels of MyD88, phospho-interleukin-1 receptor-associated kinase 4 (pIRAK-4), and the p38 mitogen-activated protein kinase (MAPK) signaling pathway. Further downstream investigations demonstrated that IRAK-4-p38 activation increased the nuclear translocation of NF-κB, which subsequently induced the expression of cathelicidin and the cytokine interleukin-1β (IL-1β), resulting in the decreased survival of M. bovis BCG. On the other hand, inhibition of TLR2/4, pIRAK-4, p38, and NF-κB nuclear translocation decreased cathelicidin and IL-1β expression levels and therefore increased the survival of avirulent mycobacteria. This is the first report that demonstrates that virulent mycobacteria manipulate the TLR2/4-MyD88-IRAK-4-p38-NF-κB-Camp-IL-1β pathway to survive inside bone marrow stem cells.

Cellular Architecture of Spinal Granulomas and the Immunological Response in Tuberculosis Patients Coinfected with HIV

Mycobacterium tuberculosis (M.tb) and HIV are individually responsible for the most deaths worldwide among all infectious agents, and coinfection with M.tb and HIV is a significant public health challenge in the developing world. Although the lung is the primary target organ for tuberculosis (TB), M.tb can also cause extrapulmonary tuberculosis (EPTB) such as in the bones and joints. Treatment of EPTB is much more challenging than treatment of pulmonary TB. The hallmark of the host immune response against TB is the formation of organized structures called granulomas that are infiltrated with immune cells and are rich in cytokines and chemokines. Inside granulomas, the host confines the M.tb bacteria to a particular region of the organ and avoids dispersion. In this study, we analyzed immune cells in bone granulomas of patients with EPTB that are also coinfected with HIV. We found that HIV-infected TB patients have dispersed bone granulomas, with reduced T cell numbers and a concomitant increase in plasma cells. Additionally, HIV-infected patients exhibited dramatically increased serum levels of IgM and IgG1 antibodies, which is indicative of T-cell-independent B-cell activation and mucosal T-cell activation, respectively. Interestingly, we also observed that CD29⁺ stem cells are increased in HIV-TB coinfection, suggesting a link with HIV infection. Therefore, our work provides new insights into the architecture of spinal TB granulomas and the role of B-cells and humoral immunity against a highly infectious intracellular pathogen. We propose that our findings will inform biomarker identification for EPTB and possibly the development of related therapeutics and/or vaccines to protect HIV-infected patients against disseminated TB.

Detection of Mycobacterium avium subsp. paratuberculosis in non-human primates

BACKGROUND

Due to a sporadic occurrence of Mycobacterium avium subsp. paratuberculosis (MAP) in non-human primates (NHP), the susceptibility of different NHP to MAP should be investigated.

METHODS

Fecal and tissue samples (ileum, ileocecal lymph node, bone marrow) of 20 animals (seven species) were analyzed by IS900-based PCRs and sequenced. Samples of MAP PCR positive NHP were further cultivated.

RESULTS

MAP DNA was detectable in two animals; the ileum of a cottontop tamarin and the bone marrow of a common marmoset. Cultivation of MAP failed. Sequence analysis revealed 100% homology to the MAP-K10 sequence. Pathohistological examinations offered no direct correlation to a MAP infection.

CONCLUSIONS

MAP was detected for the first time in a common marmoset. But as both NHP suffered from other diseases, an asymptomatic infection with MAP was assumed. The detection of MAP in the bone marrow might play a role in establishing latent paratuberculosis, as known from tuberculosis.

CD271+ Mesenchymal Stem Cells as a Possible Infectious Niche for Leishmania infantum

Visceral leishmaniasis (VL) is a serious and fatal disease. Therapeutic drugs are toxic and non-sterilizing. The etiological agents Leishmania infantum and Leishmania donovani cause active and asymptomatic diseases. Effective drugs to treat VL exist but unfortunately, post-treatment relapses are common. Little is known why drugs are non-sterilizing or how these intracellular pathogens can escape treatment. Here, using a murine model of VL we found that CD271+/Sca1+ bone marrow mesenchymal stem cells (BM-MSCs) are readily infected in vitro and in vivo by L. infantum. Because BM-MSCs express potent drug efflux pumps, e.g., ABCG2 it is possible that this unique intracellular infectious niche could allow L. infantum to escape anti-parasite drugs.

Blockade of the Kv1.3 K+ Channel Enhances BCG Vaccine Efficacy by Expanding Central Memory T Lymphocytes

Tuberculosis is the oldest known infectious disease, yet there is no effective vaccine against adult pulmonary tuberculosis. Emerging evidence indicates that T-helper 1 and T-helper 17 cells play important roles in host protection against tuberculosis. However, tuberculosis vaccine efficacy in mice is critically dependent on the balance between antigen-specific central memory T (Tcm) and effector memory T (Tem) cells. Specifically, a high Tcm/Tem cell ratio is essential for optimal vaccine efficacy. Here, we show that inhibition of Kv1.3, a potassium channel preferentially expressed by Tem cells, by Clofazimine selectively expands Tcm cells during BCG vaccination. Furthermore, mice that received clofazimine after BCG vaccination exhibited significantly enhanced resistance against tuberculosis. This superior activity against tuberculosis could be adoptively transferred to naive, syngeneic mice by CD4⁺ T cells. Therefore, clofazimine enhances Tcm cell expansion, which in turn provides improved vaccine efficacy. Thus, Kv1.3 blockade is a promising approach for enhancing the efficacy of the BCG vaccine in humans.

The role of primary infection of Schwann cells in the aetiology of infective inflammatory neuropathies

Numerous different pathogens are responsible for infective peripheral neuropathies and this is generally the result of the indirect effects of pathogen infection, namely anti pathogen antibodies cross reacting with epitopes on peripheral nerve, auto reactive T cells attacking myelin, circulating immune complexes and complement fixation. Primary infection of Schwann cells (SC) associated with peripheral nerve inflammation is rare requiring pathogens to cross the Blood Peripheral Nerve Barrier (BPNB) evade anti-pathogen innate immune pathways and invade the SC. Spirochetes Borrelia bourgdorferi and Trepomema pallidum are highly invasive, express surface lipo proteins, but despite this SC are rarely infected. However, Trypanosoma cruzi (Chaga's disease) and Mycobacterium leprae. Leprosy are two important causes of peripheral nerve infection and both demonstrate primary infection of SC. This is due to two novel strategies; T. cruzi express a trans-silalidase that mimics host neurotrophic factors and infects SC via tyrosine kinase receptors. M. leprae demonstrates multi receptor SC tropism and subsequent infection promotes nuclear reprogramming and dedifferentiation of host SC into progenitor stem like cells (pSLC) that are vulnerable to M. leprae infection. These two novel pathogen evasion strategies, involving stem cells and receptor mimicry, provide potential therapeutic targets relevant to the prevention of peripheral nerve inflammation by inhibiting primary SC infection.

Mesenchymal stem cells alter macrophage immune responses to Leishmania major infection in both susceptible and resistance mice

Mesenchymal stem cells (MSCs) are attracted to inflammation site and switch immune system to modulate inflammatory responses. This ability makes MSCs the best candidate cells for stem cell therapy of infection diseases. Therefore, we aimed to evaluate the modulatory effect of adipose-derived MSCs (AD-MSCs) on macrophages in Leishmania (L.) major infection. Macrophages and MSCs were isolated from both susceptible (BALB/c) and resistance (C57BL/6) strains. After co-culture of AD-MSCs with macrophages using a transwell system, we assessed MSCs-educated macrophage responses to L. major infection. Our results indicated suppression in levels of tumor necrosis factor α (TNF-α) and interleukin 10 (IL-10) of MSCs co-cultured macrophages in response to L. major infection. To clarify the effects of this suppression on inflammatory conditions, TNF-α/IL-10 ratio was calculated, indicating an increase in TNF-α/IL-10 ratio in MSCs co-cultured groups. The higher TNF-α/IL-10 ratio was observed in BALB/c macrophages co-cultured with BALB/c MSCs. Nitric oxide (NO) assay presented a significant reduction in the supernatant of all MSCs co-cultured groups compared to control. We observed a significant reduction in phagocytosis of MSCs co-cultured groups in response to L. major infection without any significant differences in the phagocytic index. In conclusion, our results represented a new spectrum of immunomodulation induced by MSCs co-cultured with macrophages in response to L. major infection. The magnitude of immunoregulation was different between BALB/c and C57BL/6 strains. Our findings also showed that MSCs exerted potential effect of M1 polarization due to unequal decrease in levels of TNF-α and IL-10 when we considered TNF-α and IL-10as representatives of M1 and M2 phenotypes, respectively. Induction of inflammatory cytokine milieu and reduction in level of IL-10 provides a new hope for stem cell therapy of leishmaniasis in susceptible models.

Distribution of Mycobacterium avium subsp. paratuberculosis in a Subclinical Naturally Infected German Fleckvieh Bull

Although it has been known for years that Mycobacterium avium subsp. paratuberculosis (MAP) is detectable in the reproductive organs and semen of infected bulls, only few studies have been conducted on this topic worldwide. This study surveyed the MAP status of a bull, naturally infected due to close contact with its subclinically infected parents over a period of 4 years. From the age of 7 weeks to necropsy, faecal, blood and, after sexual maturity, semen samples were drawn repeatedly. Already at the first sampling day, MAP-DNA was detected in faeces by semi-nested PCR. True infection was confirmed by the detection of MAP-DNA in blood at the age of 40 weeks. In total, MAP-DNA was present in 25% faecal (34/139), 16% blood (23/140) and 5% semen (4/89) samples, including MAP-free intervals of up to 9 weeks. MAP genome equivalents (MAP-GE) of up to 6.3 × 10⁶ /g faeces and 1.8 × 10⁵ /ml blood were determined. Cultivation of MAP occurred only in three of 137 faecal and two of 109 blood, but never in semen samples. Over the whole period, the bull was a serological negative MAP shedder. During necropsy, 42 tissue samples were collected. Neither macroscopic nor histological lesions characteristic of a MAP infection were observed. Cultivation of MAP in tissue sections failed. However, MAP-DNA was spread widely in the host, including in tissues of the lymphatic system (7/15), digestive tract (5/14) and the urogenital tract (5/9) with concentrations of up to 3.9 × 10⁶ MAP-GE/g tissue. The study highlighted the detection of MAP in male reproductive organs and semen. It supports the hypothesis that bulls may probably transmit MAP, at least under natural mating conditions. In artificial insemination, this might not be relevant, due to antibiotics included currently in semen extenders. However, the survivability of MAP in this microenvironment should be investigated in detail.