Relative importance of STAT4 in murine tuberculosis

Immunoinhibitory effects of anti-tuberculosis therapy induce the host vulnerability to tuberculosis recurrence

The host immune responses play a pivotal role in the establishment of long-term memory responses, which effectively aids in infection clearance. However, the prevailing anti-tuberculosis therapy, while aiming to combat tuberculosis (TB), also debilitates innate and adaptive immune components of the host. In this study, we explored how the front-line anti-TB drugs impact the host immune cells by modulating multiple signaling pathways and subsequently leading to disease relapse. Administration of these drugs led to a reduction in innate immune activation and also the cytokines required to trigger protective T cell responses. Moreover, these drugs led to activation-induced cell death in the mycobacterial-specific T cell leading to a reduced killing capacity. Furthermore, these drugs stalled the T cell differentiation into memory subsets by modulating the activation of STAT3, STAT4, FOXO1, and NFκB transcription factors and hampering the Th1 and Th17-mediated long-term host protective memory responses. These findings suggest the urgent need to augment directly observed treatment, short-course (DOTS) therapy with immunomodulatory agents to mitigate the adverse effects linked to the treatment.IMPORTANCEAs a central component of TB eradication initiatives, directly observed treatment, short-course (DOTS) therapy imparts immune-dampening effects during the course of treatment. This approach undermines the host immune system by delaying the activation process and lowering the immune response. In our investigation, we have unveiled the impact of DOTS on specific immune cell populations. Notably, the signaling pathways involving STAT3 and STAT4 critical for memory responses and NFκβ associated with pro-inflammation were substantially declined due to the therapy. Consequently, these drugs exhibit limited effectiveness in preventing recurrence of the disease. These observations highlight the imperative integration of immunomodulators to manage TB infection.

Intranasal immunization with peptide-based immunogenic complex enhances BCG vaccine efficacy in a murine model of tuberculosis

Prime-boost immunization strategies are required to control the global tuberculosis (TB) pandemic, which claims approximately 3 lives every minute. Here, we have generated an immunogenic complex against Mycobacterium tuberculosis (M.tb), consisting of promiscuous T cell epitopes (M.tb peptides) and TLR ligands assembled in liposomes. Interestingly, this complex (peptide–TLR agonist–liposomes; PTL) induced significant activation of CD4⁺ T cells and IFN-γ production in the PBMCs derived from PPD⁺ healthy individuals as compared with PPD^– controls. Furthermore, intranasal delivery of PTL significantly reduced the bacterial burden in the infected mice by inducing M.tb-specific polyfunctional (IFN-γ⁺IL-17⁺TNF-α⁺IL-2⁺) immune responses and long-lasting central memory responses, thereby reducing the risk of TB recurrence in DOTS-treated infected animals. The transcriptome analysis of peptide-stimulated immune cells unveiled the molecular basis of enhanced protection. Furthermore, PTL immunization significantly boosted the Bacillus Calmette-Guerin–primed (BCG-primed) immune responses against TB. The greatly enhanced efficacy of the BCG-PTL vaccine model in controlling pulmonary TB projects PTL as an adjunct vaccine against TB.

Th1-Th2 Cross-Regulation Controls Early Leishmania Infection in the Skin by Modulating the Size of the Permissive Monocytic Host Cell Reservoir

The impact of T helper (Th) 1 versus Th2 immunity on intracellular infections is attributed to classical versus alternative activation of macrophages leading to resistance or susceptibility. However, observations in multiple infectious settings demonstrate deficiencies in mediators of Th1-Th2 immunity, which have paradoxical or no impact. We report that prior to influencing activation, Th1/Th2 immunity first controls the size of the permissive host cell reservoir. During early Leishmania infection of the skin, IFN-γ- or STAT6-mediated changes in phagocyte activation were counteracted by changes in IFN-γ-mediated recruitment of permissive CCR2⁺ monocytes. Monocytes were required for early parasite expansion and acquired an alternatively activated phenotype despite the Th1 dermal environment required for their recruitment. Surprisingly, STAT6 did not enhance intracellular parasite proliferation, but rather modulated the size and permissiveness of the monocytic host cell reservoir via regulation of IFN-γ and IL-10. These observations expand our understanding of the Th1-Th2 paradigm during infection.

Comprehensive analysis of long non-coding RNAs expression pattern in the pathogenesis of pulmonary tuberculosis

BACKGROUND

Long non-coding RNAs (lncRNAs) play crucial roles in the progression and pathogenesis of cancer. Right now, less is known about the association between the expression of lncRNAs and the pathogenesis of pulmonary tuberculosis (PTB).

METHODS

In present study, the expression profiles of lncRNAs were investigated by transcriptome sequencing from PTB patients vs. healthy individuals.

RESULTS

A total of 449 differentially expressed (DE) (fold change ≥2, false discovery rate ≤ 0.05) lncRNAs were screened out from the PTB patients. Lnc-HNRNPU-1:7 and lnc-FAM76B-4:1 was found the most upregulated lncRNAs and downregulated lncRNAs in PTB patients, respectively. GO annotation and KEGG analysis were used to explore the potential roles of these DE lncRNAs. The JAK/STAT and TGF-β signaling pathways related to PTB pathogenesis were enriched in PTB patients. The co-expressed of a few lncRNAs and mRNAs on chromosome were shown by cis-regulatory gene analysis. Trans analysis indicated that STAT1, STAT2 and TAF7 transcription factors regulated the expression of lncRNA and mRNA. The constructed lncRNA ceRNA network suggested that lncRNAs regulating mRNAs expression may mediate by sponged miRNAs.

CONCLUSION

We comprehensively analyzed the expression profiles of lncRNAs in PTB patients, thus providing new clues for exploring the regulatory mechanisms of dysregulated lncRNAs in the pathogenesis of PTB.

Granulomas and Inflammation: Host-Directed Therapies for Tuberculosis

Tuberculosis (TB) remains a leading global health problem that is aggravated by emergence of drug-resistant strains, which account for increasing number of treatment-refractory cases. Thus, eradication of this disease will strongly require better therapeutic strategies. Identification of host factors promoting disease progression may accelerate discovery of adjunct host-directed therapies (HDTs) that will boost current treatment protocols. HDTs focus on potentiating key components of host anti-mycobacterial effector mechanisms, and limiting inflammation and pathological damage in the lung. Granulomas represent a pathological hallmark of TB. They are comprised of impressive arrangement of immune cells that serve to contain the invading pathogen. However, granulomas can also undergo changes, developing caseums and cavities that facilitate bacterial spread and disease progression. Here, we review current concepts on the role of granulomas in pathogenesis and protective immunity against TB, drawing from recent clinical studies in humans and animal models. We also discuss therapeutic potential of inflammatory pathways that drive granuloma progression, with a focus on new and existing drugs that will likely improve TB treatment outcomes.

Using GWAS to identify genetic predisposition in hepatic autoimmunity

Primary biliary cirrhosis (PBC), primary sclerosing cholangitis (PSC) and autoimmune hepatitis (AIH) represent the three major hepatic autoimmune conditions. Patient morbidity and mortality remain high across these three diseases, and an unmet need for rational therapy exists. Disease understanding has focused on combining clinical and laboratory based science to provide better insights into the joint host and environmental factors necessary for the initiation, and perpetuation, of hepato-biliary inflammation. Twin studies, family studies, population studies and an inter-relationship with other autoimmune phenomena suggest a genetic component to risk for each disease. Until recently, understanding of this genetic risk has been limited to HLA haplotypes. Associations with risk-conferring and protective HLA haplotypes are present in all three diseases. Over the last few years, genome-wide association studies (GWAS), and related genetic association studies, have greatly increased understanding of the genetic risk signature of these three diseases and autoimmunity in general. Here we consider the rationale for GWAS in general and with specific reference to hepatic autoimmunity. We consider the process of GWAS, and highlight major findings to date. Potential functional implications of key findings are discussed including the IL-12/STAT4 pathway in PBC and the CD28/IL-2 pathway in PSC. We describe the marked pleiotropy demonstrated by PBC and PSC, which is consistent with other autoimmune diseases. Further, we focus on specific gene associations including SH2B3, which is common to all three diseases, and FUT2 in PSC, which represents a link between environment and genetics. We review attempts to translate GWAS findings into basic laboratory models including in vivo systems and highlight where clinical observations relate to genetics. Finally we describe deficiencies in GWAS to date and consider future study of genetics in hepatic autoimmunity.

Transcription factor regulatory network for early lung immune response to tuberculosis in mice

Numerous transcription factors (TFs) have been suggested to have a role in Mycobacterium tuberculosis infection; however, the TFs involved in the early immune response of lung cells remains to be fully elucidated. The present study aimed to identify TFs which may have a role in the early immune response to tuberculosis and the gene regulatory networks in which they are involved. Gene expression data obtained from microarray analysis of the early lung immune response to tuberculosis (Gene Expression Omnibus; accession no. GSE23014) was integrated with data for TF binding sites and protein-protein interactions in order to construct a TF regulatory network. The role of TFs in protein complexes, active modules, topology of the network and regulation of immune processes were investigated. The results demonstrated that the constructed gene regulatory network harbored 1,270 differentially expressed (DE) genes with 4,070 regulatory and protein-protein interactions. In addition, it was revealed that 17 DE TFs were involved in the positive regulation of numerous immunological and biological processes, including T cell activation, T cell proliferation and tuberculosis-associated gene expression, in the constructed regulatory network. Signal transducer and activator of transcription 4, interferon regulatory factor 8, spleen focus-forming virus proviral integration 1, enhancer of zeste homolog 2 and kruppel-like factor 4 were predicted to be the primary TFs regulating the DE genes during early lung infection by M. tuberculosis, as determined through various analyses of the gene regulatory network. In conclusion, the present study identified novel TFs involved in the early response to M. tuberculosis infection, which may enhance current understanding of the molecular mechanism underlying tuberculosis infection and introduced potential targets for novel tuberculosis therapies.

IL12Rβ1: the cytokine receptor that we used to know

Human IL12RB1 encodes IL12Rβ1, a type I transmembrane receptor that is an essential component of the IL12- and IL23-signaling complex. IL12RB1 is well-established as being a promoter of delayed type hypersensitivity (DTH), the immunological reaction that limits tuberculosis. However, recent data demonstrate that in addition to promoting DTH, IL12RB1 also promotes autoimmunity. The contradictory roles of IL12RB1 in human health raises the question, what are the factors governing IL12RB1 function in a given individual, and how is inter-individual variability in IL12RB1 function introduced? Here we review recent data that demonstrate individual variability in IL12RB1 function is introduced at the epigenetic, genomic polymorphism, and mRNA splicing levels. Where and how these differences contribute to disease susceptibility and outcome are also reviewed. Collectively, recent data support a model wherein IL12RB1 sequence variability - whether introduced at the genomic or post-transcriptional level - contributes to disease, and that human IL12RB1 is not as simple a gene as we once believed.

Bioactivities of alcohol based extracts of Phyllanthus emblica branches: antioxidation, antimelanogenesis and anti-inflammation

Phyllanthus emblica is an euphorbiaceous plant that has long been used in traditional medicines for health promotion, anti-aging and also for treatment of wide ranges of symptoms and diseases. The aim of this study is to investigate the pharmacological activity of the plant branch. Alcohol based extracts of P. emblica branch were prepared in 50 % ethanolic extract by maceration (EPE) and methanolic extract by Soxhlet apparatus (MPE). EPE and MPE contained high total phenolic content and strong antioxidative activity. By HPLC analysis, gallic acid and vanillic acid are the major phenolic compounds of these extracts. Both EPE and MPE inhibited tyrosinase activity stronger than the ethanolic extract of P. emblica fruit (IC50 of 247.37 ± 18.57 and 193.75 ± 44.90 versus 4346.95 ± 166.23 μg/ml). EPE significantly inhibited the mRNA expressions of tyrosinase, and tyrosinase related proteins (TRP-1 and TRP-2) in B16 murine melanoma cells and suppressed the expression of LPS-induced pro-inflammatory genes (COX-2, iNOS, TNF-α, IL-16 and IL-6) in RAW 264.7 murine macrophage cells in a dose-dependent manner. These extracts significantly suppressed the carrageenan-induced paw edema in rats in a dose-dependent manner.

Mycobacterial Infection in MyD88-Deficient Mice

MyD88 is an adaptor protein that plays a major role in TLR/IL-1 receptor family signaling. To understand the role of MyD88 in the development of murine tuberculosis in vivo, MyD88 knockout (KO) mice aerially were infected with Mycobacterium tuberculosis. Infected MyD88 mice were not highly susceptible to M. tuberculosis infection, but they developed granulomatous pulmonary lesions with neutrophil infiltration which were larger than those in wild-type (WT) mice (P < 0.01). The pulmonary tissue levels of mRNA for iNOS and IL-18 were slightly lower, but levels of mRNA for IL-1 beta, IL-2, IL-4, IL-6, IL-10, IFN-gamma, and TGF-beta were higher in MyD88 KO mice. IFN-gamma, TNF-alpha, IL-1 beta, and IL-12 also were high in the sera of MyD88 KO mice. There were no statistically significant differences in the expression of TNF-alpha, IL-12, and ICAM-1 mRNA between MyD88 KO and WT mice. Thus, MyD88 deficiency did not influence the development of murine tuberculosis. NF-kappa B activity was similar in the alveolar macrophages from the lung tissues of MyD88 KO and WT mice. Also, there may be a TLR2-specific, MyD88-independent IL-1 receptor/TLR-mediated pathway to activate NF-kappa B in the host defense against mycobacterial infection.

Cytotoxic and immunomodulatory effects of polyhydroxyoctane isolated from Lentinus polychrous mycelia

A polyhydroxyoctane, 6-methylheptane-1,2,3,4,5-pentaol (MHP), was first isolated from mycelia of the Thai edible mushroom Lentinus polychrous. MHP was evaluated for its cytotoxic and immunomodulatory effects in vitro. MHP was slightly cytotoxic to murine splenocytes but not to RAW264.7 cells or peripheral blood mononuclear cells. MHP decreased nitric oxide and intracellular O2 (-) production from lipopolysaccharide- and phorbol-12-myristate-13-acetate-activated RAW264.7 cells at levels of 78.98 ± 4.72 and 78.48 ± 2.41 % of controls, respectively. The mRNA expression of pro-inflammatory mediators, including iNOS, TNF-α, IL-1β, IL-6, COX-1 and COX-2, were significantly suppressed by MHP. In addition, MHP significantly increased the proliferation of phytohemagglutinin and pokeweed mitogen-induced splenocytes. These results indicate that MHP is able to modulate inflammatory responses and the proliferation of both T- and B-lymphocyte cells, suggesting that MHP may be a good natural immunomodulator.

Chronic pulmonary cavitary tuberculosis in rabbits: a failed host immune response

The molecular determinants of the immune response to Mycobacterium tuberculosis HN878 infection in a rabbit model of pulmonary cavitary tuberculosis were studied. Aerosol infection of rabbits resulted in a highly differentially expressed global transcriptome in the lungs at 2 weeks, which dropped at 4 weeks and then gradually increased. While IFNγ was progressively upregulated throughout the infection, several other genes in the IFNγ network were not. T-cell activation network genes were gradually upregulated and maximally induced at 12 weeks. Similarly, the IL4 and B-cell activation networks were progressively upregulated, many reaching high levels between 12 and 16 weeks. Delayed peak expression of genes associated with macrophage activation and Th1 type immunity was noted. Although spleen CD4(+) and CD8(+) T cells showed maximal tuberculosis antigen-specific activation by 8 weeks, macrophage activation in lungs, lymph nodes and spleen did not peak until 12 weeks. In the lungs, infecting bacilli grew exponentially up to 4 weeks, followed by a steady-state high bacillary load to 12 weeks that moderately increased during cavitation at 16 weeks. Thus, the outcome of HN878 infection of rabbits was determined early during infection by a suboptimal activation of innate immunity and delayed T-cell activation.

In vivo and in vitro anti-inflammatory activity of Lentinus polychrous extract

ETHNOPHARMACOLOGICAL RELEVANCE

Lentinus polychrous is a Thai local edible mushroom, traditionally used for the treatments of fever and inflammation due to snake or scorpion envenomation.

AIM OF STUDY

The present study aimed to investigate an anti-inflammatory effect of Lentinus polychrous mycelial extract (LPME) both in vitro and in vivo.

MATERIALS AND METHODS

The cytotoxicity and suppressive effects of LPME on nitric oxide production, intracellular O2(-) production, pro-inflammatory mediator expression, TNF-α production were determined by using LPS-activated RAW 264.7 cells. In addition, Anti-inflammatory effect of LPME was evaluated by using carageenan-induced paw edema in rats.

RESULTS

The LPME exhibited cytotoxicity with 50% inhibitory concentration (IC50) of 280.25 ± 10.10 μg/ml and significantly suppressed the productions of NO and intracellular O2(-) with dose-dependent manner. LPME decreased the expressions of iNOS, IL-1β, IL-6, TNF-α and COX-2 and significantly decreased the TNF-α production in LPS-activated macrophage with dose-dependent manners. Moreover, LPME showed significant suppressive effect on paw edema in rats.

CONCLUSION

The results clearly revealed that the LPME inhibited NO and pro-inflammatory productions by down-regulating the gene expressions of pro-inflammatory mediators leading to the decrease paw edema in rat which support the traditional use.

Revisiting the role of the granuloma in tuberculosis

The granuloma, which is a compact aggregate of immune cells, is the hallmark structure of tuberculosis. It is historically regarded as a host-protective structure that 'walls off' the infecting mycobacteria. This Review discusses surprising new discoveries--from imaging studies coupled with genetic manipulations--that implicate the innate immune mechanisms of the tuberculous granuloma in the expansion and dissemination of infection. It also covers why the granuloma can fail to eradicate infection even after adaptive immunity develops. An understanding of the mechanisms and impact of tuberculous granuloma formation can guide the development of therapies to modulate granuloma formation. Such therapies might be effective for tuberculosis as well as for other granulomatous diseases.

Immune response to Mycobacterium tuberculosis infection in the parietal pleura of patients with tuberculous pleurisy

The T lymphocyte-mediated immune response to Mycobacterium tuberculosis infection in the parietal pleura of patients with tuberculous pleurisy is unknown. The aim of this study was to investigate the immune response in the parietal pleura of tuberculous pleurisy compared with nonspecific pleuritis. We have measured the numbers of inflammatory cells particularly T-cell subsets (Th1/Th2/Th17/Treg cells) in biopsies of parietal pleura obtained from 14 subjects with proven tuberculous pleurisy compared with a control group of 12 subjects with nonspecific pleuritis. The number of CD3+, CD4+ and CCR4+ cells and the expression of RORC2 mRNA were significantly increased in the tuberculous pleurisy patients compared with the nonspecific pleuritis subjects. The number of toluidine blue+ cells, tryptase+ cells and GATA-3+ cells was significantly decreased in the parietal pleura of patients with tuberculous pleurisy compared with the control group of nonspecific pleuritis subjects. Logistic regression with receiver operator characteristic (ROC) analysis for the three single markers was performed and showed a better performance for GATA-3 with a sensitivity of 75%, a specificity of 100% and an AUC of 0.88. There was no significant difference between the two groups of subjects in the number of CD8, CD68, neutrophil elastase, interferon (IFN)-γ, STAT4, T-bet, CCR5, CXCR3, CRTH2, STAT6 and FOXP3 positive cells. Elevated CD3, CD4, CCR4 and Th17 cells and decreased mast cells and GATA-3+ cells in the parietal pleura distinguish patients with untreated tuberculous pleurisy from those with nonspecific pleuritis.

THE EFFECTS OF INHALATION OF DIESEL EXHAUST ON MURINE MYCOBACTERIAL INFECTION

The authors investigated the effects of inhalation of diesel exhaust (DE) on murine mycobacterial infection in vivo. Eight-week-old female BALB/c mice were exposed to DE (3 mg/m3 of diesel exhaust particles [DEPs]) for 1 month, 2 months, or 6 months (for 7 hours a day, 5 days a week). Control mice were housed in a clean room for the same periods. On the day following the last DE exposure, control mice and DE-exposed mice were aerially infected with Mycobacterium tuberculosis (1 x 10(6) colony-forming units (CFU), Kurono strain). At 7 weeks after mycobacterial infection, the authors examined the lung tissues for histopathological changes and performed reverse transcriptase-polymerase chain reaction (RT-PCR) to measure the messenger RNA (mRNA) expression of several proinflammatory cytokines and inducible nitric oxide synthase (iNOS). Then, the homogenates of lungs and spleens were cultured on 1% (v/v) Ogawa's egg slant medium, and after a 4-week incubation period at 37 degrees C, colonies on the medium were counted. After 1 month of DE exposure, the mycobacterial infection had slightly ameliorated. After 2 months of DE exposure, the expression levels of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-12p40, interferon (IFN)-gamma, and iNOS mRNAs were slightly increased. However, after 6 months of DE exposure, the expression levels of IL-1beta , IL-12p40, IFN-gamma, and iNOS mRNAs were decreased, and the infection as measured by increased lung burden (CFU) actually increased. These results indicate that long-term DE exposure may increase pulmonary mycobacterial burden.

Higher susceptibility of type 1 diabetic rats to Mycobacterium tuberculosis infection

An association between diabetes mellitus and tuberculosis has been implicated for a long time. We have previously reported that Goto Kakizaki type 2 diabetic rats are highly susceptible to Mycobacterium (M.) tuberculosis infection. As a next step, we attempted to clarify whether type 1 diabetic rats are more susceptible to M. tuberculosis than non-diabetic wild-type (WT) rats. Here, we used the Komeda diabetes-prone (KDP) rat, as a model of type 1 diabetes mellitus. The infected KDP rats developed large granulomas without central necrosis in their lungs, liver or spleen. This was consistent with a significant increase in the number of colony-forming units (cfu) of M. tuberculosis in the lungs and spleen (p < 0.01). Insulin treatment resulted in significant reduction of tubercle bacilli in the infected KDP rats (p < 0.01). Pulmonary levels of interferon-gamma, tumor necrosis factor-alpha and interleukin-1beta mRNAs were higher in the infected diabetic rats than in WT rats. Alveolar macrophages from KDP rats were not fully activated by M. tuberculosis infection because the macrophages did not secrete nitric oxide (NO) that can kill M. tuberculosis (p < 0.01), but no significant difference in phagocytosis of tubercle bacilli by alveolar macrophages was observed between KDP and WT rats. Taken together, our findings indicate that type 1 diabetic rats are more susceptible to M. tuberculosis that WT rats.

Signal transducer and activator of transcription 4 (STAT4), but not IL-12 contributes to Pseudomonas aeruginosa-induced lung inflammation in mice

Pseudomonas aeruginosa is a major opportunistic pathogen in immune-compromised individuals and cystic fibrosis patients. This organism stimulates a complex inflammatory response in the lung, including production of various cytokines and chemokines. The specific contribution of these mediators in the host defense against this bacterium has yet to be fully characterized. Interleukin-12 (IL-12) is commonly known as a master regulator of innate and adaptive immunity. IL-12 induces its biological effects through its associated intracellular signaling molecule, the signal transducer and activator of transcription 4 (STAT4). To examine a specific role of IL-12 and STAT4 in P. aeruginosa lung infection in mice, STAT4-deficient (STAT4-/-) and IL-12 p40-deficient (IL-12 p40-/-) mice were infected with P. aeruginosa intranasally. Interestingly, STAT4-/- mice, but not IL-12 p40-/- mice after 24h infection showed impaired production of the pro-inflammatory cytokines tumor necrosis factor, interleukin-1beta, and macrophage-inflammatory protein-2. However, neither STAT4 nor IL-12 p40 deficiency significantly affected INFgamma production or bacterial clearance compared to wild-type mice. Similarly, neutrophil recruitment was not affected in the STAT4-/- and IL-12 p40-/- mice. These results suggest that STAT4 contributes to P. aeruginosa-induced inflammation, but it is not essential for bacterial clearance. Although IL-12 is essential for the host defense against various pathogens, this cytokine is likely not a major player in the host response to P. aeruginosa lung infection.

Transcriptional control of lung morphogenesis

The vertebrate lung consists of multiple cell types that are derived primarily from endodermal and mesodermal compartments of the early embryo. The process of pulmonary organogenesis requires the generation of precise signaling centers that are linked to transcriptional programs that, in turn, regulate cell numbers, differentiation, and behavior, as branching morphogenesis and alveolarization proceed. This review summarizes knowledge regarding the expression and proposed roles of transcription factors influencing lung formation and function with particular focus on knowledge derived from the study of the mouse. A group of transcription factors active in the endodermally derived cells of the developing lung tubules, including thyroid transcription factor-1 (TTF-1), beta-catenin, Forkhead orthologs (FOX), GATA, SOX, and ETS family members are required for normal lung morphogenesis and function. In contrast, a group of distinct proteins, including FOXF1, POD1, GLI, and HOX family members, play important roles in the developing lung mesenchyme, from which pulmonary vessels and bronchial smooth muscle develop. Lung formation is dependent on reciprocal signaling among cells of both endodermal and mesenchymal compartments that instruct transcriptional processes mediating lung formation and adaptation to breathing after birth.

Repeated exposure to low-dose diesel exhaust after allergen challenge exaggerates asthmatic responses in mice

BACKGROUND

In conjunction with allergens, diesel exhaust particles act as an adjuvant to enhance IgE responses, inducing expression of cytokines/chemokines and adhesion molecules, and increasing airway hyper-responsiveness (AHR). As most studies were designed to expose animals to diesel exhaust throughout the periods of both sensitization and allergen challenge, it remains unclear whether diesel exhaust (DE) exposure exaggerates airway responses in asthmatic animals.

OBJECTIVE

To study effects of exposure to low-dose DE on AHR and allergic airway inflammation in asthmatic mice.

METHODS

BALB/c mice were sensitized by intraperitoneal injection of ovalbumin and challenged by intranasal administration with ovalbumin. They were exposed to low-dose DE for 7 h/day, 5 days/week, for up to 12 weeks. AHR to methacholine was evaluated by whole-body plethysmography as well as bronchoalveolar lavage cell analysis and cytokine gene expression in lungs.

RESULTS

Repeated exposure of asthmatic mice to low-dose DE resulted in increased AHR and gene expression of several pro-asthmatic cytokines/chemokines, but these effects rapidly subsided with continued exposure to DE.

CONCLUSION

Repeated exposure to low-dose DE after ovalbumin challenge exaggerates allergic responses in mice, but effects are not prolonged with continuous DE exposure.

Protective efficacy of recombinant (Ag85A) BCG Tokyo with Ag85A peptide boosting against Mycobacterium tuberculosis-infected guinea pigs in comparison with that of DNA vaccine encoding Ag85A

A recombinant form of BCG Tokyo with an Ag85A gene insert was administered once subcutaneously to guinea pigs and its protective efficacy was compared with that of a DNA vaccine encoding Ag85A from Mycobacterium tuberculosis administered twice to guinea pigs by epidermal gene gun bombardment. Vaccination with either the recombinant BCG Tokyo or Ag85A DNA significantly reduced the severity of pulmonary pathology and the number of pulmonary and splenic colony-forming units (cfu) (p<0.001). The recombinant BCG Tokyo was better than Ag85A DNA in terms of protective efficacy against M. tuberculosis. When immunogenic synthetic Ag85A peptide was further used as a booster together with recombinant BCG Tokyo (Ag85A) or Ag85A DNA, lung pathology was improved significantly and the number of pulmonary CFU was reduced significantly. Neither recombinant BCG Tokyo, Ag85A DNA, nor the parental BCG Tokyo protected the guinea pigs from hematogenous spread of tubercle bacilli to the spleen because splenic granulomas without central necrosis were recognized. The spleen tissues from guinea pigs vaccinated with recombinant BCG Tokyo or Ag85A DNA expressed IFN-gamma and IL-2 mRNA at significantly high levels (p<0.001) as evaluated by reverse transcription polymerase chain reaction. It is concluded that peptide boosting is important for the induction of higher protective efficacy by recombinant BCG Tokyo or a tuberculosis DNA vaccine and both recombinant BCG Tokyo (Ag85A) and Ag85A DNA vaccine induce Th2 cytokine mRNA expression significantly.

Nude rat (F344/N-rnu) tuberculosis

As many mononuclear cells from Mycobacterium tuberculosis-infected lung tissues are not available for fluorescence-activated cell sorter (FACS) analysis and the tuberculin test is not feasible in a mouse tuberculosis model, we attempted to develop a rat tuberculosis model. We have previously reported that rat tuberculosis is associated with granulomas that lack central necrosis. In order to develop a better animal model of tuberculosis in immunocompromised humans (tuberculosis associated with HIV infection or tuberculosis of the elderly), we infected F344/N-rnu nude rats with M. tuberculosis via the airborne route. The animals developed pulmonary granulomas with central necrosis encapsulated by dense collagen fibres, closely resembling those of human tuberculosis. The nude rats died of disseminated tuberculosis by the 85th day after aerosol infection, while F344 wild-type rats did not. Interestingly, T-cells that were reactive with anti-CD4 antibody and anti-CD8 antibody, indicating the presence of remnant thymus, were observed in the infected lung tissues of the nude rats. Therefore, T-cell precursors may be present in nude rats. The nude rat tuberculosis model mimics tuberculosis in immunocompromised humans and may provide a suitable model for immunological studies in vivo.

STAT4: a critical regulator of inflammation in vivo

Signal transducer and activator of transcription 4 (STAT4) is a central mediator in generating inflammation during protective immune responses and immune-mediated diseases. In the 8 yr since their first description, STAT4-deficient mice have defined the role of STAT4 in a variety of in vivo model systems. Despite the extensive study and use of these mice, the exact role of STAT4 in vivo is still unclear. In this review, I focus on describing the phenotypes of STAT4-deficient immune responses to pathogens and in diseases. Comparing the effects of STAT4 deficiency among numerous model systems will further enhance the development of a systemic model of STAT4 function in vivo.

Mycobacterial trehalose 6,6′-dimycolate preferentially induces type 1 helper T cell responses through signal transducer and activator of transcription 4 protein

Mycobacterium tuberculosis is an intracellular pathogen of tuberculosis and its pathogenicity is related to the ability to escape killing by ingested macrophages and induce delayed-type hypersensitivity (DTH). A major component of the cell wall of M. tuberculosis is trehalose 6,6'-dimycolate (TDM), which has been implicated as a pathogenetic factor. The expression of DTH and cell-mediated immunity is dependent on the macrophage-cytokine-type 1 helper T (Th1) lymphocyte axis. Cytokines, interleukin-12 (IL-12) and interferon-gamma (IFN-gamma), play a critical role in the process and IL-12-activated signal transducer and activator of transcription (STAT) 4 is required for the development of fully functional Th1 cells. To clarify host responses to mycobacterial TDM, we have analyzed footpad reaction, histopathology and cytokine profile of experimental granulomatous lesions using STAT4-deficient mice. In the present study, we have demonstrated that mycobacterial TDM selectively induces the Th1 response through the STAT4 signaling pathway, because mice lacking STAT4 protein significantly reduced to develop DTH, hypersensitivity granulomas, and Th1 cytokine responses, when compared to BALB/c mice. These results shed light on the molecular pathogenesis of mycobacterial disease. Taken together with previous studies, TDM is a pleiotropic molecule against the host and participates in the pathogenesis.

Signaling by IL-12 and IL-23 and the immunoregulatory roles of STAT4

Produced in response to a variety of pathogenic organisms, interleukin (IL)-12 and IL-23 are key immunoregulatory cytokines that coordinate innate and adaptive immune responses. These dimeric cytokines share a subunit, designated p40, and bind to a common receptor chain, IL-12R beta 1. The receptor for IL-12 is composed of IL-12R beta 1 and IL-12R beta 2, whereas IL-23 binds to a receptor composed of IL-12R beta 1 and IL-23R. Both cytokines activate the Janus kinases Tyk2 and Jak2, the transcription factor signal transducer and activator of transcription 4 (STAT4), as well as other STATs. A major action of IL-12 is to promote the differentiation of naive CD4+ T cells into T-helper (Th) 1 cells, which produce interferon (IFN)-gamma, and deficiency of IL-12, IL-12R subunits or STAT4 is similar in many respects. In contrast, IL-23 promotes end-stage inflammation. Targeting IL-12, IL-23, and their downstream signaling elements would therefore be logical strategies for the treatment of immune-mediated diseases.

Characterization of colonic and mesenteric lymph node dendritic cell subpopulations in a murine adoptive transfer model of inflammatory bowel disease

Ulcerative colitis and Crohn's disease, collectively termed inflammatory bowel diseases (IBD), are chronic inflammatory diseases of the intestine that afflict more than 4 million people worldwide. Intestinal inflammation is characterized by an abnormal mucosal immune response to normally harmless antigens in the gut flora. In Crohn's disease, the pathogenic mucosal immune response is a typical T helper (TH1) type cell response, whereas ulcerative colitis is predominantly associated with a TH2 response. We are interested in the role of dendritic cells in early immunologic events leading to T cell activation and chronic intestinal inflammation. Using a murine adoptive transfer model of IBD, we found an accumulation of dendritic cells in colon and mesenteric lymph nodes during the early stage of IBD before the appearance of epithelial lesions and tissue degradation. In situ immunostaining and flow-cytometric analysis revealed that approximately 50% of colonic dendritic cells were CD11b B220 myeloid dendritic cells and 50% expressed the CD11b B220 plasmacytoid phenotype. In corresponding mesenteric lymph nodes, approximately 16% were plasmacytoid dendritic cells. Colonic myeloid dendritic cells were shown to express the co-stimulatory molecule CD40. Both, colonic myeloid and plasmacytoid dendritic cells released interferon-alpha in situ and stimulated T cell proliferation ex vivo. Our results show that dendritic cells can mature in the intestine without migrating to mesenteric lymph nodes. Mature intestinal dendritic cells may form a nucleation site for a local T cell response and play an important role in the pathogenesis of IBD.

STAT4 is a critical mediator of early innate immune responses against pulmonary Klebsiella infection

Bacterial pneumonia is a leading cause of morbidity and mortality in the U.S. An effective innate immune response is critical for the clearance of bacteria from the lungs. IL-12, a key T1 cytokine in innate immunity, signals through STAT4. Thus, understanding how STAT4 mediates pulmonary immune responses against bacterial pathogens will have important implications for the development of rational immunotherapy targeted at augmenting innate immunity. We intratracheally administered Klebsiella pneumoniae to wild-type BALB/c and STAT4 knockout (STAT4-/-) mice. Compared with wild-type controls, STAT4-/- mice had decreased survival following intratracheal Klebsiella administration, which was associated with a higher lung and blood bacterial burden. STAT4-/- animals also displayed impaired pulmonary IFN-gamma production and decreased levels of proinflammatory cytokines, including the ELR- CXC chemokines IFN-gamma-inducible protein-10 and monokine induced by IFN-gamma. Although total lung leukocyte populations were similar between STAT4-/- and wild-type animals following infection, alveolar macrophages isolated from infected STAT4-/- mice had decreased production of proinflammatory cytokines, including IFN-gamma, compared with infected wild-type mice. The intrapulmonary overexpression of IFN-gamma concomitant with the systemic administration of IFN-gamma partially reversed the immune deficits observed in STAT4-/- mice, resulting in improved bacterial clearance from the blood. Collectively, these studies demonstrate that STAT4 is required for the generation of an effective innate host defense against bacterial pathogens of the lung.

Pathological and immunological profiles of rat tuberculosis

To investigate the pathological and immunological profiles of rat tuberculosis, Lewis female rats were infected aerially with Mycobacterium tuberculosis. Histopathology, immunological profiles of mononuclear cells from M. tuberculosis-infected rat lung tissue, and the expression patterns of cytokine and iNOS mRNAs were examined over time. M. tuberculosis induced granulomatous lesions in the lungs, spleen, lymph nodes and liver, but these lesions lacked central necrosis. Multinucleate giant cells were observed in late-phase tuberculosis. CD4(+) and CD8(+) T cells increased with time and reached a peak 5 weeks after infection, decreasing gradually thereafter. ED1 antigen, suggestive of alveolar macrophages, was expressed at a high level in early phase tuberculosis and remained at the same level even in the late phase. OX62 antigen increased gradually and reached a peak 5 weeks after infection. Interferon-gamma, tumour necrosis factor-alpha and iNOS mRNAs were expressed strongly over time, but their expression decreased 12 weeks after infection. Because rat tuberculosis is very similar to murine tuberculosis and it is easy to obtain mononuclear cells from M. tuberculosis-infected rat lung tissue, the rat tuberculosis model appears to be suitable for immunological studies in vivo.

STAT1 knockout mice are highly susceptible to pulmonary mycobacterial infection

This study was designed to determine the roles of STAT1 protein in defense against mycobacterial infection. Airborne infection of STAT1 knockout (KO) mice with a Mycobacterium tuberculosis Kurono strain induced multiple necrotic lesions in lungs, spleen and liver, while that in wild-type (WT) mice did not. The STAT1 KO mice succumbed to mycobacterial infection by the 35th day after infection. Compared with the levels in WT mice, inducible nitric oxide synthase (iNOS), tumor necrosis factor-alpha, interferon-gamma and IL-12 mRNA levels were significantly lower in the lung of STAT1 KO mice. Interestingly, granulomatous lesion development in STAT1 KO mice was inhibited significantly by treatment with exogenous recombinant murine IL-12. Therefore, STAT1 regulates IL-12 expression and appears to be a critical transcription factor in controling mycobacterial infection.

Rat neutrophils prevent the development of tuberculosis

To understand the role of neutrophils in the development of rat tuberculosis in vivo, we utilized lipopolysaccharide (LPS)-induced neutrophilia in the lungs. LPS (50 micro g/ml) was administered intratracheally to male Fischer rats. Rats were then infected with Mycobacterium tuberculosis by an airborne route. Intratracheal injection of LPS significantly blocked the development of pulmonary granulomas and significantly reduced pulmonary CFU (P < 0.01). LPS treatment with amphotericin B (an LPS inhibitor) or neutralizing anti-rat neutrophil antibody reversed the development of pulmonary lesions. LPS-induced transient neutrophilia prevented early mycobacterial infection. The timing of LPS administration was important. When given intratracheally at least 10 days after aerial infection, LPS did not prevent development of tuberculosis. Neutrophils obtained by bronchoalveolar lavage killed M. tuberculosis cells. These results indicate clearly that neutrophils participate actively in defense against early-phase tuberculosis.

Vaccination of guinea pigs with DNA encoding Ag85A by gene gun bombardment

A DNA vaccine encoding Ag85A from Mycobacterium tuberculosis was administered to guinea pigs by epidermal gene gun bombardment and its protective efficacy was determined. Vaccination with Ag85A DNA twice significantly reduced the severity of pulmonary pathology and number of pulmonary colony-forming units (CFU) (p<0.01). When immunogenic synthetic Ag85A peptide was used as a booster, lung pathology was improved significantly and pulmonary CFU were reduced dramatically. Neither Ag85A DNA nor BCG Tokyo protected the guinea pigs from hematogenous spread of tubercle bacilli to the spleen because splenic granulomas without central necrosis were recognized. When the vaccinated guinea pigs were followed up for 7 months, the pulmonary lesions became fibrotic in guinea pigs vaccinated with Ag85A DNA plus Ag85A peptide, or BCG Tokyo, and no tubercle bacilli were detected. The protective efficacy of the tuberculosis Ag85A DNA vaccine was improved significantly by peptide boosting. It is concluded that dosage and peptide boosting are important in the induction of higher protective efficacy by a tuberculosis DNA vaccine.