Morphometric analysis of Th1 and Th2 cytokine expression in human pulmonary tuberculosis

A meta-analysis of Th1 and Th2 cytokine profiles differentiating tuberculous from malignant pleural effusion

To clarify the predominance of Th1 or Th2 immune responses in malignant and tuberculous pleural effusion (MPE and TPE, respectively), we performed a meta-analysis of previously published results of the levels of Th1/Th2 cytokines associated with these two types of pleural effusion to evaluate the use of Th1/Th2 cytokine profiles in distinguishing TPE from MPE. We searched the PubMed and EMBASE databases for studies indexed from 2000 to March 2021. We included studies that (a) diagnosed TPE and MPE based on culture or pleural tissue biopsy and that (b) compared levels of Th1/Th2 cytokines between TPE and MPE. Pooled data based on a random-effects model or fixed-effects model and standardized mean differences (SMDs) across studies were used to compare TPE and MPE. We also performed Egger’s test to assess publication bias. Of 917 identified studies, a total of 42 studies were selected for the meta-analysis. Compared with MPE subjects, TPE subjects had a significantly higher level of TNF-α [2.22, (1.60–2.84)], an elevated level of IFN-γ [3.30, (2.57–4.40)] in pleural effusion, a situation where the Th1 immune response dominated. Conversely, the levels of interleukin-4 (IL-4) and IL-10 (Th2 cytokines) were higher in the MPE subjects than in the TPE subjects, showing statistically nonsignificant tiny effects [−0.15, (−0.94 to 0.63) and −0.04, (−0.21 to 0.12), respectively]. We confirmed that TPE, a situation in which the Th1 cytokines are predominant. The slight preponderance of Th2 cytokines in MPE, which is not convincing enough to prove.

STAT1 and CXCL10 involve in M1 macrophage polarization that may affect osteolysis and bone remodeling in extrapulmonary tuberculosis

OBJECTIVE

This study was aimed to reveal the molecular mechanism of bone destruction due to macrophage polarization leading to during extrapulmonary tuberculosis (EPTB) infection.

METHODS

The dataset GSE83456 was downloaded from the GEO database, and the xCell tool was used to obtain the 64 types of immune cells. The flow cytometry was performed to identified the differences between M1 and M2 macrophages between EPTB and the healthy controls (HCs). The enrichment analyses were performed on the differentially expressed genes (DEGs) and their functionally related modules. The hub genes were screened out, and their relationships with EPTB and the immune cell subtypes were further analyzed.

RESULTS

The flow cytometric analysis validated this hypothesis of M1-macrophage polarization correlated with the pathogenesis of EPTB. Of the obtained 103 DEGs, 97 genes were upregulated, and 6 genes were downregulated. The GO and KEGG pathway analyses showed that the DEGs were particularly involved in the immune-related processes. The hub genes (STAT1 and CXCL10) might be involved in M1-macrophage polarization and correlated with the pathogenesis of EPTB. STAT1 and CXCL10 could also behave as biomarkers for EPTB.

CONCLUSION

STAT1 and CXCL10 were involved in the M1-macrophage polarization and correlated with the pathogenesis of EPTB. Besides, both of them could also behave as biomarkers for EPTB diagnosis and provide the required clues for targeted therapy in the future.

Association of IL-15 and IP-10 Serum Levels with Cytomegalovirus Infection, CMV Viral Load and Cyclosporine Level after Kidney Transplantation

BACKGROUND

Cytomegalovirus (CMV) infection is the most common complications following kidney transplantation. Natural killer (NK) cells demonstrated critical anti-viral role in controlling and elimination of CMV after transplantation. Interleukin-15 (IL-15) is a pleiotropic cytokine that promotes the activity of NK cells and strengthens the acquired immune system. Also, IP10 (CXCL10) is a chemotactic factor which regulates NK cell recruitment and antiviral immune response. We aimed to determine the correlation between the serum levels of IL-15 and IP-10 cytokines with CMV infection, CMV viral load, and cyclosporine as a major immunosuppressive treatment after transplantation.

METHODS

Fifty-eight kidney transplant recipient patients without evidence of CMV virus disease before transplantation surgery were included in the study. From the day of transplant surgery, the patients were evaluated based on the presence of CMV Ag pp65, CMV viral load, serum levels of IL-15 & IP-10, Cyclosporine levels (C0 & C2), Glomerular Filtration Rate (GFR), and hematological & biochemical Index, up to 75 days.

RESULTS

Comparison analysis of serum levels of IL-15 and IP-10 showed no significant association with CMV infection in kidney transplant recipients. In addition, CMV viral load and cyclosporine levels at C0 and C2 did not affect patients' IL-15 and IP-10 levels.

CONCLUSION

The levels of IP-10 and IL-15 cytokines are not affected with CMV infection, even if a viral infection occurs in the early days after transplantation or long afterwards. In addition, taking the different levels of cyclosporine did not affect the cytokines levels. Other mechanisms may play a role in maintaining the levels of these cytokines.

Immunological characterization of chimeras of high specificity antigens from Mycobacterium tuberculosis H37Rv

Tuberculosis remains a serious global health problem. BCG is the only prophylactic TB vaccine and it shows variable protective efficacy. Chimeric protein subunit vaccines hold great potential as stand-alone vaccines or heterologous BCG prime boosters. We have designed a protein chimera, PP31, by combining Mtb ESAT-6 family antigen Rv1198 and MoCo biosynthesis family antigen Rv3111. Further, PP31 was extended by addition of latency antigen Rv1813c to yield PP43. Immunization of BALB/c mice with PP31 or PP43 with FIA adjuvant elicited strong humoral immune response. Restimulation of splenocytes of the immunized mice lead to significant proliferation of lymphocytes, secretion of cytokines IFN-γ, TNF, IL-2 of the Th1 class, IL-17A of the Th17 class, and IL-6. PP31 and PP43 also induced intracellular cytokine expression (IFN-γ, TNF, and IL-2) from both CD4+-CD44high and CD8+-CD44high T-cells. Antigen-specific IFN-γ+/IL-2+ double positive CD4+ T-cells were significantly higher in case of PP43 than PP31-immunized mice and control group. PP43 showed protection equivalent to heat-inactivated BCG in response to challenge of the immunized mice with Mtb H37Ra. Based on its immunogenicity and protective efficacy, PP43 appears to be a potential candidate for further development as a subunit vaccine against TB.

IL-4 subverts mycobacterial containment in Mycobacterium tuberculosis-infected human macrophages

Protective immunity against Mycobacterium tuberculosis is poorly understood. The role of interleukin (IL)-4, the archetypal T-helper type 2 (Th2) cytokine, in the immunopathogenesis of human tuberculosis remains unclear.Blood and/or bronchoalveolar lavage fluid (BAL) were obtained from participants with pulmonary tuberculosis (TB) (n=23) and presumed latent TB infection (LTBI) (n=22). Messenger RNA expression levels of interferon (IFN)-γ, IL-4 and its splice variant IL-4δ2 were determined by real-time PCR. The effect of human recombinant (hr)IL-4 on mycobacterial survival/containment (CFU·mL^-1) was evaluated in M. tuberculosis-infected macrophages co-cultured with mycobacterial antigen-primed effector T-cells. Regulatory T-cell (Treg) and Th1 cytokine levels were evaluated using flow cytometry.In blood, but not BAL, IL-4 mRNA levels (p=0.02) and the IL-4/IFN-γ ratio (p=0.01) was higher in TB versus LTBI. hrIL-4 reduced mycobacterial containment in infected macrophages (p<0.008) in a dose-dependent manner and was associated with an increase in Tregs (p<0.001), but decreased CD4⁺Th1 cytokine levels (CD4⁺IFN-γ⁺ p<0.001; CD4⁺TNFα⁺ p=0.01). Blocking IL-4 significantly neutralised mycobacterial containment (p=0.03), CD4⁺IFNγ⁺ levels (p=0.03) and Treg expression (p=0.03).IL-4 can subvert mycobacterial containment in human macrophages, probably via perturbations in Treg and Th1-linked pathways. These data may have implications for the design of effective TB vaccines and host-directed therapies.

Vitamin A Metabolism by Dendritic Cells Triggers an Antimicrobial Response against Mycobacterium tuberculosis

Epidemiological evidence correlates low serum vitamin A (retinol) levels with increased susceptibility to active tuberculosis (TB); however, retinol is biologically inactive and must be converted into its bioactive form, all-trans retinoic acid (ATRA). Given that ATRA triggers a Niemann-Pick type C2 (NPC2)-dependent antimicrobial response against Mycobacterium tuberculosis, we investigated the mechanism by which the immune system converts retinol into ATRA at the site of infection. We demonstrate that granulocyte-macrophage colony-stimulating factor (GM-CSF)-derived dendritic cells (DCs), but not macrophages, express enzymes in the vitamin A metabolic pathway, including aldehyde dehydrogenase 1 family, member a2 (ALDH1A2) and short-chain dehydrogenase/reductase family, member 9 (DHRS9), enzymes capable of the two-step conversion of retinol into ATRA, which is subsequently released from the cell. Additionally, mRNA and protein expression levels of ALDH1A2 and DC marker CD1B were lower in tuberculosis lung tissues than in normal lung. The conditioned medium from DCs cultured with retinol stimulated antimicrobial activity from M. tuberculosis-infected macrophages, as well as the expression of NPC2 in monocytes, which was blocked by specific inhibitors, including retinoic acid receptor inhibitor (RARi) or N,N-diethylaminobenzaldehyde (DEAB), an ALDH1A2 inhibitor. These results indicate that metabolism of vitamin A by DCs transactivates macrophage antimicrobial responses.IMPORTANCE Tuberculosis (TB) is the leading cause of death by a single infectious agent worldwide. One factor that contributes to the success of the microbe is the deficiency in immunomodulatory nutrients, such as vitamin A (retinol), which are prevalent in areas where TB is endemic. Clinical trials show that restoration of systemic retinol levels in active TB patients is ineffective in mitigating the disease; however, laboratory studies demonstrate that activation of the vitamin A pathway in Mycobacterium tuberculosis-infected macrophages triggers an antimicrobial response. Therefore, the goal of this study was to determine the link between host retinol levels and retinoic acid-mediated antimicrobial responses against M. tuberculosis By combining established in vitro models with in situ studies of lung tissue from TB patients, this study demonstrates that the innate immune system utilizes transcellular metabolism leading to activation between dendritic cells and macrophages as a means to combat the pathogen.

Cellular immune response in MDR-TB patients to different protein expression of MDR and susceptible Mycobacterium tuberculosis: Rv0147, a novel MDR-TB biomarker

Tuberculosis (TB) is a crucial public health problem with prevalence of multidrug resistant (MDR) rising. An accurate TB biomarker is urgently needed to monitor the response to treatment in patients with MDR tuberculosis. To analyze interaction between selected MDR-TB purified protein and immune cells, dendritic cells from MDR-TB patients and healthy subjects were stimulated by 55KDa protein fractions (Rv0147). The purified proteins identified by proteomic techniques (two-dimensional gel electrophoresis, mass spectrometry) and peptide sequences are known to bind a MHC class I alleles which are extracted from the Immune Epitope Database and Analysis Resource database ( www.iedb.org ). T cells were isolated from PBMC by negative selection and cells were cultured in RPMI-1640 at 37 °C and 5% CO₂. Cell culture was assayed for cytokine IL-10 and INF-γ by ELISA. We found that INF-γ production was significantly (335 ± 35.5 pg/ml, P ˂ 0.05) upregulated after protein candidate (Rv0147) stimulation by dendritic cells from MDR-TB patients, whereas IL-10 production was greatly reduced compared with production in healthy subjects (212 ± 9.94 pg/ml, P ˂ 0.05). In fact, the purified protein, Rv0147, stimulated dendritic cells from MDR-TB patients, failed to produce IL-10 and directly stimulates INF-γ production by T cells. These results suggest that the purified protein, Rv0147, may stimulate Th1 type protective cytokine response in MDR-TB patients but not in normal subjects. The production of INF-γ but not IL-10 in the presence of purified protein, Rv0147, may be shifted to Th1 responses in MDR-TB patients and supports its potential as protein vaccine candidates against TB.

Influence of vitamin D deficiency on T cell subsets and related indices during spinal tuberculosis

The present study investigated the effects of vitamin D deficiency on T cell subsets in patients with spinal tuberculosis. In addition, the influence of vitamin D deficiency was investigated on the expression of cytokines IL-1β, IL-6 and TNF-α in intervertebral disc lesions of patients. One hundred and seventeen patients with spinal tuberculosis who received operative treatment in the Department of Orthopedics in Wuhan City Third Hospital from March 2012 to March 2015 were collected. The patients were divided depending upon vitamin D content into the control group (64 cases, vitamin D content <25 nmol/l) and experimental group (53 cases, vitamin D content >50 nmol/l). Immunofluorescence method was applied to determine the content of T cell subsets in both groups of patients. Intervertebral disc lesion tissues of two groups of patients were obtained during surgery then treated with HE staining and immunohistochemical staining. The values of average optical density obtained under light microscope were observed as the expression quantities of IL-1β, IL-6 and TNF-α, to explore the relationship between vitamin D and the expression of cytokines. When vitamin D is lacking, the expression of T lymphocyte subsets in patients with spinal tuberculosis significantly decreased. Compared with experimental group, the difference was statistically significant (P<0.05). Further, the expression of cytokines IL-1β, IL-6 and TNF-α in intervertebral disc lesion tissues of patients with spinal tuberculosis were significantly higher than those of patients with spinal tuberculosis whose vitamin D content was normal (P<0.05). In the control group, vitamin D content was negatively correlated with the expression of IL-1β, IL-6 and TNF-α. The expression of T lymphocyte subsets in patients with vitamin D deficiency was significantly reduced, and the immune function decreased. The expression of IL-1β, IL-6 and TNF-α in lesions were significantly higher than those of patients with normal vitamin D content. In addition, the lower the content of vitamin D was, the more active the expression of inflammatory factors were, which was not conducive to the recovery of tuberculosis lesions.

Latent tuberculosis infection: myths, models, and molecular mechanisms

The aim of this review is to present the current state of knowledge on human latent tuberculosis infection (LTBI) based on clinical studies and observations, as well as experimental in vitro and animal models. Several key terms are defined, including "latency," "persistence," "dormancy," and "antibiotic tolerance." Dogmas prevalent in the field are critically examined based on available clinical and experimental data, including the long-held beliefs that infection is either latent or active, that LTBI represents a small population of nonreplicating, "dormant" bacilli, and that caseous granulomas are the haven for LTBI. The role of host factors, such as CD4(+) and CD8(+) T cells, T regulatory cells, tumor necrosis factor alpha (TNF-α), and gamma interferon (IFN-γ), in controlling TB infection is discussed. We also highlight microbial regulatory and metabolic pathways implicated in bacillary growth restriction and antibiotic tolerance under various physiologically relevant conditions. Finally, we pose several clinically important questions, which remain unanswered and will serve to stimulate future research on LTBI.

Inhibition of nuclear factor-kappa B activation decreases survival of Mycobacterium tuberculosis in human macrophages

Nuclear factor-kappa B (NFκB) is a ubiquitous transcription factor that mediates pro-inflammatory responses required for host control of many microbial pathogens; on the other hand, NFκB has been implicated in the pathogenesis of other inflammatory and infectious diseases. Mice with genetic disruption of the p50 subunit of NFκB are more likely to succumb to Mycobacterium tuberculosis (MTB). However, the role of NFκB in host defense in humans is not fully understood. We sought to examine the role of NFκB activation in the immune response of human macrophages to MTB. Targeted pharmacologic inhibition of NFκB activation using BAY 11-7082 (BAY, an inhibitor of IκBα kinase) or an adenovirus construct with a dominant-negative IκBα significantly decreased the number of viable intracellular mycobacteria recovered from THP-1 macrophages four and eight days after infection. The results with BAY were confirmed in primary human monocyte-derived macrophages and alveolar macrophages. NFκB inhibition was associated with increased macrophage apoptosis and autophagy, which are well-established killing mechanisms of intracellular MTB. Inhibition of the executioner protease caspase-3 or of the autophagic pathway significantly abrogated the effects of BAY. We conclude that NFκB inhibition decreases viability of intracellular MTB in human macrophages via induction of apoptosis and autophagy.

In silico analysis and experimental validation of Mycobacterium tuberculosis -specific proteins and peptides of Mycobacterium tuberculosis for immunological diagnosis and vaccine development

Comparative analyses of the Mycobacterium tuberculosis genome with the genomes of other mycobacteria have led to the identification of several genomic regions of difference (RDs) between M. tuberculosis and M. bovis BCG. The identification of immunodominant and HLA-promiscuous antigens and peptides encoded by these RDs could be useful for diagnosis and the development of new vaccines against tuberculosis. The analysis of RD proteins and peptides by in silico methods (using computational programs to predict major and HLA-promiscuous antigenic proteins and peptides) and experimental validations (using peripheral blood mononuclear cells and sera from tuberculosis patients and BCG-vaccinated healthy subjects to assess antigen-specific cellular and humoral immune responses in vitro) identified several major antigens and peptides. To evaluate the in vivo potentials, the genes of immunodominant antigens were cloned and expressed in DNA vaccine vectors. Immunizations of experimental animals with the recombinant constructs induced antigen-specific cellular responses. Further experiments showed that each of these proteins had several T and B cell epitopes scattered throughout their sequence, which confirmed their strong immunogenicity. In conclusion, the bioinformatics-based in silico identification of promiscuous antigens and peptides of M. tuberculosis is a useful approach to identify new candidates important for diagnosis and vaccine applications.

25(OH)D(3) affects the maturation and function of mouse bone marrow-derived dendritic cells stimulated by Mycobacterium bovis BCG

It has been shown that vitamin D deficiency increases an individual's susceptibility to tuberculosis (TB). However, very little is known about the effect of vitamin D on the immune response to Mycobacterium tuberculosis (M. tb) in dendritic cells (DCs). Because DCs play an important role in TB infection, we investigated the phenotypic characteristics and functional capabilities of mouse bone marrow-derived dendritic cells (BMDCs) after stimulation with Bacillus Calmette-Guérin (BCG) in the presence or absence of 25(OH)D(3)(100 nM). Bone marrow cells from mice were cultured with GM-CSF (20 ng/ml) and were then treated with 25(OH)D(3) for 7 days. On day 6, 5 µg/ml of BCG (≥1.0×10(6) CFU/mg) was added to the cells for 24 hours, and on day 7, the non-adherent cells were harvested for phenotypic and functional analyses. After incubation with 25(OH)D(3), the expression levels of MHC-II and CD86 on the surface of the dendritic cells (DCs) and the ability of the DCs to stimulate proliferation of allogeneic mixed lymphocytes were lower than control cells (p<0.05). Furthermore, the level of Interleukin (IL) -4 secreted by the BMDCs in the 25(OH)D(3) culture was lower than that in the control culture (p<0.01). However, the BMDCs cultured with 25(OH)D(3) produced significantly higher levels of IL-2, IL-6, IL-10 and interferon gamma(IFN-γ) than those in the control culture (p<0.05). These findings suggest that 25(OH)D(3) modulates the immune response during mycobacterial infection by affecting the maturation and function of DCs.

Helminths and skewed cytokine profiles increase tuberculin skin test positivity in Warao Amerindians

The immune regulatory mechanisms involved in the acquisition of Mycobacterium tuberculosis infection in children are largely unknown. We investigated the influence of parasitic infections, malnutrition and plasma cytokine profiles on tuberculin skin test (TST) positivity in Warao Amerindians in Venezuela. Pediatric household contacts of sputum smear-positive tuberculosis (TB) cases were enrolled for TST, chest radiograph, plasma cytokine analyses, QuantiFERON-TB Gold In-Tube (QFT-GIT) testing and stool examinations. Factors associated with TST positivity were studied using generalized estimation equations logistic regression models. Of the 141 asymptomatic contacts, 39% was TST-positive. After adjusting for age, gender and nutritional status, TST positivity was associated with Trichuris trichiura infections (OR 3.5, 95% CI 1.1-11.6) and low circulating levels of T helper 1 (Th1) cytokines (OR 0.51, 95% CI 0.33-0.79). Ascaris lumbricoides infections in interaction with Th2- and interleukin (IL)-10-dominated cytokine profiles were positively associated with TST positivity (OR 3.1, 95% CI 1.1-8.9 and OR 2.4, 95% CI 1.04-5.7, respectively). A negative correlation of QFT-GIT mitogen responses with Th1 and Th2 levels and a positive correlation with age were observed (all p < 0.01). We conclude that helminth infections and low Th1 cytokine plasma levels are significantly associated with TST positivity in indigenous Venezuelan pediatric TB contacts.

IP-10 release assays in the diagnosis of tuberculosis infection: current status and future directions

The current state-of-the-art tests for infection with Mycobacterium tuberculosis - the IFN-γ release assays - rely on accurate measurement of the cytokine IFN-γ. Many other potential biomarkers are expressed in concert with IFN-γ, and IP-10 in particular has shown promising results. IP-10 is produced in large amounts, allowing for the development of new and simplified test platforms, such as lateral flow. In this review, we summarize the results of 22 clinical studies exploring the use of IP-10 as an alternative marker to IFN-γ. The studies report that diagnostic accuracy of IP-10 is on par with IFN-γ, but also that IP-10 may be more robust in young children and in HIV-infected individuals with low CD4 cell counts. We conclude the review by presenting limitations of the published works and outline recent developments and future directions.

Evaluation of immunogenicity and protective efficacy against Mycobacterium tuberculosis infection elicited by recombinant Mycobacterium bovis BCG expressing human Interleukin-12p70 and Early Secretory Antigen Target-6 fusion protein

ESAT-6 protein of Mycobacterium tuberculosis is absent in Mycobacterium bovis BCG and Mycobacterium microti and has been demonstrated to stimulate strong cell-mediated immunity. IL-12 can play crucial roles in regulating IFN-γ production and Th1 effectors production. In this study, we constructed three rBCG vaccines that could express proteins of human IL-12p70 and/or ESAT-6 and evaluated their immunogenicity and protective efficacy in mice. Our experiments illustrated that the rBCG-IE (expressing a fusion protein of human IL-12p70 and ESAT-6) was capable of inducing stronger Th1 type cell-mediated immune responses than conventional BCG, or rBCG-I (expressing human IL-12p70), or rBCG-E (expressing ESAT-6). However, the results of protective experiments showed that rBCG-IE could only confer similar and even lower protective efficacy against M. tuberculosis H37Rv infection compared with BCG vaccine.

IL-32 expression in the airway epithelial cells of patients with Mycobacterium avium complex lung disease

Lung disease due to Mycobacterium avium complex (MAC) organisms is increasing. A greater understanding of the host immune response to MAC organisms will provide a foundation to develop novel therapies for these recalcitrant infections. IL-32 is a newly described pro-inflammatory cytokine that enhances host immunity against various microbial pathogens. Cytokines that induce IL-32 such as interferon-gamma, IL-18, IL-12 and tumor necrosis factor-alpha are of considerable importance to mycobacterial immunity. We performed immunohistochemistry and morphometric analysis to quantify IL-32 expression in the lungs of 11 patients with MAC lung disease and 10 controls with normal lung tissues. After normalizing for basement membrane length, there was a profound increase in IL-32 expression in the airway epithelial cells of the MAC-infected lungs compared with controls. Following normalization for alveolar surface area, there was a trend toward increased IL-32 expression in type II alveolar cells and alveolar macrophages in the lungs of MAC patients. Human airway epithelial cells (BEAS-2B) infected with M. avium produced IL-32 by a nuclear factor-kappa B-dependent mechanism. In both BEAS-2B cells and human monocyte-derived macrophages, exogenous IL-32γ significantly reduced the growth of intracellular M. avium. This finding was corroborated by an increase in the number of intracellular M. avium recovered from THP-1 monocytes silenced for endogenous IL-32 expression. The anti-mycobacterial effect of IL-32 may be due, in part, to increased apoptosis of infected cells. These findings indicate that IL-32 facilitates host defense against MAC organisms but may also contribute to the airway inflammation associated with MAC pulmonary disease.

Characterization of Th1- and Th2-type immune response in human multidrug-resistant tuberculosis

Multidrug-resistant tuberculosis (MDR-TB) has become a lethal global threat. Insights into the immune regulation of MDR-TB are urgently needed for the development of new treatments; however, the T cell response to an MDR-TB infection in human remains unclear. In the present study, the proportion of Th1 and Th2 cell subsets and the level of related T cell subset cytokines in peripheral blood were investigated. We detected that an MDR-TB infection resulted in suppressed Th1 and Th2 cell activation, which was more remarkable in patients with MDR-TB than that in drug-sensitive tuberculosis (DS-TB) sufferers when compared to healthy controls (HCs). In addition, MDR-TB infection down-regulated the expression of IFN-γ, IL-2, and IL-10, and up-regulated IL-4, IL-6, and TNF-α expression. Our data suggest that the disturbance between protective and pathogenic effects induced by the immunosuppression of Th1- and Th2-type responses is a substantial characteristic of MDR-TB infections.

A review of murine models of latent tuberculosis infection

The mechanisms of latency and the causes of reactivation of Mycobacterium tuberculosis remain poorly understood; an important reason for this gap in knowledge is the absence of a standardized animal model of latent tuberculosis infection (LTBI). A complete LTBI model should incorporate 2 aspects of LTBI: a persistent infection model with a low bacterial load and a latent infection model that is modified from the Cornell model. Many parameters must be carefully considered to establish an LTBI model, including the inoculating dose, the route of infection, the time interval between infection and the initiation of antibiotic therapy, and the genetic background of the host animal. The responsiveness of this mouse model of LTBI can be assessed through the integrated use of indices, including Karnofsky performance status, bacterial load in spleen and lungs, induced levels of interferon-gamma and tumour necrosis factor-alpha, expression of interleukin (IL)-10 and IL-4 in tissues, specific antigen load in organs, time required for hormone-induced TB relapse, expression level of dormancy genes, and CD4 T-cell count.

Cytokines in response to proteins predicted in genomic regions of difference of Mycobacterium tuberculosis

Cellular immune responses are responsible for both protection and pathogenesis in tuberculosis, and are mediated/regulated by a complex network of pro-inflammatory, T helper (Th) type 1 and type 2 cytokines. In this study, the secretion of pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, IL-8 and IL-1β; Th1 cytokines interferon-gamma (IFN-γ), IL-2 and tumor necrosis factor-beta (TNF-β); and Th2 cytokines IL-4, IL-5 and IL-10 by the peripheral blood mononuclear cells (PBMCs) of pulmonary tuberculosis patients was studied. PBMCs were cultured in vitro in the absence and presence of complex mycobacterial antigens and peptides corresponding to 11 regions of difference (RD) of Mycobacterium tuberculosis that are deleted/absent in all vaccine strains of Mycobacterium bovis bacillus Calmette-Guérin (BCG). The culture supernatants were tested for secreted cytokines by FlowCytomix assay. PBMCs from the majority of patients (53-100%) spontaneously secreted detectable concentrations of all cytokines tested, except for IL2 (29%) and IL-10 (41%). The profiles of proinflammatory cytokines were largely similar for various complex antigens or RD peptides. However, with respect to Th1 and Th2 cytokines, the antigens could be divided into three groups; the first with Th1-bias (culture filtrate of M. tuberculosis, RD1, RD5, RD7, RD9 and RD10), the second with Th2-bias (whole cells and cell walls of M. tuberculosis, RD12, RD13 and RD15), and the third without Th1/Th2-bias (M. bovis BCG, RD4, RD6 and RD11). Complex mycobacterial antigens and RD proteins with Th1- and Th2-biases may have roles in protection and pathogenesis of tuberculosis, respectively.

Potential application of new diagnostic methods for controlling bovine tuberculosis in Brazil

Bovine tuberculosis, a chronic infection in cattle caused by Mycobacterium bovis, remains an economic and public health problem for several countries. Due to its economic impact on international trade, contagious nature, and implications for human health, global programs to eradicate the disease were implemented worldwide. Those programs are based on slaughtering PPD-reactive animals. Despite the National Programs in Brazil, complete eradication has not been achieved, and the disease remains, albeit at a lower prevalence. The central purpose of this review is to address diagnostic tests for tuberculosis. Considering the course of the infection in cattle, at least two tests, ideally complementary to one another, may be necessary for an adequate diagnosis: the first based on the cellular response, and the second capable of identifying anergic animals by detection of specific anti-M.bovis antibodies.

Diagnosis of gastrointestinal tuberculosis: Using cytomorphological, microbiological, immunological and molecular techniques - A study from Central India

The present study included three groups: (A) age and gender matched control (n=24) with no previous signs of M. tuberculosis complex (MTBC) infection, (B) patients (n=28) diagnosed with gastro-intestinal TB (GITB), (C) patients (n=50) with clinical and histo-pathological signs of GITB, but were culture and AFB negative. Real time assay performed using fluorescence resonance energy transfer hybridization probes showed a positivity index of 36 % in group C, i.e. 18 were found reactive from the total 50 cases studied. In addition, immune characterization of these 18 cases showed depleted CD(4) (+) count and increased levels of IFN-γ and TNF-α cytokines. No positive case was found in group A, while in group B, out of total 28 cases studied 27 were found positive. A combinatorial diagnostic approach for rapid detection and characterization of GITB might provide specific therapeutic strategies for prevention and treatment of the infection in future.

Characterization of human cellular immune responses to Mycobacterium tuberculosis proteins encoded by genes predicted in RD15 genomic region that is absent in Mycobacterium bovis BCG

RD15 is a genomic region of difference (RD) present in Mycobacterium tuberculosis H37Rv but absent in all strains of Mycobacterium bovis BCG. RD15 contains genes encoding proteins of mammalian cell entry (Mce3A-F), important for the invasion and survival of M. tuberculosis in host cells. In this study, we have evaluated cellular immune responses to RD15 proteins using peripheral blood mononuclear cells (PBMC) from pulmonary tuberculosis patients and M. bovis BCG-vaccinated healthy subjects. PBMC were tested for T-helper (Th) type 1 [antigen-induced proliferation and interferon (IFN)-gamma secretion] and anti-inflammatory [interleukin (IL)-10 secretion] responses to complex mycobacterial antigens and peptides corresponding to proteins of RD1 and RD15. In Th1 assays, complex mycobacterial antigens induced strong responses in both donor groups, and RD1 induced strong responses in tuberculosis patients and moderate responses in healthy subjects, whereas RD15 induced weak responses in tuberculosis patients and strong to moderate responses in healthy subjects. IL-10 secretion in both donor groups was strong to moderate in response to complex mycobacterial antigens, but weak in response to RD1 and RD15. Analysis of IFN-gamma : IL-10 ratios showed strong Th1 biases to complex mycobacterial antigens and RD1 in both donor groups, and to RD15 and RD1504 (Mce3A) in healthy subjects only. These results suggest that RD1504 is the best Th1-stimulating antigen present in RD15, and therefore may be a potential vaccine candidate against TB.

IL-32 is a host protective cytokine against Mycobacterium tuberculosis in differentiated THP-1 human macrophages

Macrophages provide a first line of defense against Mycobacterium tuberculosis. However, in instances where macrophage activation for killing is suboptimal, M. tuberculosis is capable of surviving intracellularly. IL-32 is a recently described cytokine induced by M. tuberculosis in a variety of cell types including human monocytes and macrophages. In this study, we investigated the biological significance of IL-32 in an in vitro model of M. tuberculosis infection in differentiated THP-1 human macrophages in which IL-32 expression was silenced using stable expression of short hairpin RNA (shRNA). Inhibition of endogenous IL-32 production in THP-1 cells that express one of three distinct shRNA-IL-32 constructs significantly decreased M. tuberculosis induction of TNF-alpha by approximately 60%, IL-1beta by 30-60%, and IL-8 by 40-50% and concomitantly increased the number of cell-associated M. tuberculosis bacteria compared with THP-1 cells stably expressing a scrambled shRNA. In THP-1 cells infected with M. tuberculosis and stimulated with rIL-32, a greater level of apoptosis was observed compared with that with M. tuberculosis infection alone. Obversely, there was significant abrogation of apoptosis induced by M. tuberculosis and a concomitant decrease in caspase-3 activation in cells depleted of endogenous IL-32. rIL-32gamma significantly reduced the number of viable intracellular M. tuberculosis bacteria, which was modestly but significantly abrogated with a caspase-3 inhibitor. We conclude that IL-32 plays a host defense role against M. tuberculosis in differentiated THP-1 human macrophages.

Impaired activation of Stat1 and c-Jun as a possible defect in macrophages of patients with active tuberculosis

Studies of patients with active tuberculosis (TB) and infected healthy individuals have shown that interferon (IFN)-gamma is present in sites of Mycobacterium tuberculosis infection in comparable levels. This suggests that there is a deficiency in the macrophage response to IFN-gamma in TB patients. We used recombinant human IFN-gamma to stimulate adherent monocyte-derived macrophages from three groups of people: patients with active tuberculosis (TBP), their healthy household contacts (HHC) and healthy uninfected controls from the community (CC). We then evaluated the ability of the macrophages to inhibit the growth of M. tuberculosis H37Rv as well as their cytokine profile at early in infection (48 h). After IFN-gamma treatment, macrophages of healthy individuals (HHC and CC) controlled M. tuberculosis growth and produced mainly nitric oxide (NO) and interleukin (IL)-12p70, whereas TBP macrophages did not kill M. tuberculosis. Additionally, TBP macrophages produced low levels of NO and IL-12p70 and high levels of tumour necrosis factor (TNF)-alpha and IL-10. Transforming growth factor (TGF)-beta levels were similar among all three groups. M. tuberculosis infection had little effect on the cytokine response after IFN-gamma stimulus, but infection alone induced more IL-10 and TGF-beta in TBP macrophages. There were no differences in Stat1 nuclear translocation and DNA binding between the groups. However, the phosphorylated Stat1 and c-Jun (AP-1) in nuclear protein extracts was diminished in TBP macrophages compared to macrophages of healthy individuals. These results indicate an impairment of Stat1-dependent and Stat1-independent IFN-gamma signalling in macrophages of people with active tuberculosis, suggesting a different molecular regulation that could impact macrophage functionality and disease outcome.

Mycobacterial antigen-induced T helper type 1 (Th1) and Th2 reactivity of peripheral blood mononuclear cells from diabetic and non-diabetic tuberculosis patients and Mycobacterium bovis bacilli Calmette-Guérin (BCG)-vaccinated healthy subjects

Patients with diabetes mellitus are more susceptible to tuberculosis (TB), and the clinical conditions of diabetic TB patients deteriorate faster than non-diabetic TB patients, but the immunological basis for this phenomenon is not understood clearly. Given the role of cell-mediated immunity (CMI) in providing protection against TB, we investigated whether CMI responses in diabetic TB patients are compromised. Peripheral blood mononuclear cells (PBMC) obtained from diabetic TB patients, non-diabetic TB patients and Mycobacterium bovis bacilli Calmette-Guérin (BCG)-vaccinated healthy subjects were cultured in the presence of complex mycobacterial antigens and pools of M. tuberculosis regions of difference (RD)1, RD4, RD6 and RD10 peptides. The PBMC were assessed for antigen-induced cell proliferation and secretion of T helper 1 (Th1) [interferon (IFN)-gamma, interleukin (IL)-2, tumour necrosis factor (TNF)-beta], and Th2 (IL-4, IL-5, IL-10) cytokines as CMI parameters. All the complex mycobacterial antigens and RD1(pool) stimulated strong proliferation of PBMC of all groups, except moderate responses to RD1(pool) in healthy subjects. In response to complex mycobacterial antigens, both IFN-gamma and TNF-beta were secreted by PBMC of all groups whereas diabetic TB patients secreted IL-10 with concentrations higher than the other two groups. Furthermore, in response to RD peptides, IFN-gamma and IL-10 were secreted by PBMC of diabetic TB patients only. The analyses of data in relation to relative cytokine concentrations showed that diabetic TB patients had lower Th1 : Th2 cytokines ratios, and a higher Th2 bias. The results demonstrate a shift towards Th2 bias in diabetic TB patients which may explain, at least in part, a faster deterioration in their clinical conditions.

Immunomodulation with recombinant interferon-gamma1b in pulmonary tuberculosis

BACKGROUND

Current treatment regimens for pulmonary tuberculosis require at least 6 months of therapy. Immune adjuvant therapy with recombinant interferon-gamma1b (rIFN-gammab) may reduce pulmonary inflammation and reduce the period of infectivity by promoting earlier sputum clearance.

METHODOLOGY/PRINCIPAL FINDINGS

We performed a randomized, controlled clinical trial of directly observed therapy (DOTS) versus DOTS supplemented with nebulized or subcutaneously administered rIFN-gamma1b over 4 months to 89 patients with cavitary pulmonary tuberculosis. Bronchoalveolar lavage (BAL) and blood were sampled at 0 and 4 months. There was a significant decline in levels of inflammatory cytokines IL-1beta, IL-6, IL-8, and IL-10 in 24-hour BAL supernatants only in the nebulized rIFN-gamma1b group from baseline to week 16. Both rIFN-gamma1b groups showed significant 3-fold increases in CD4+ lymphocyte response to PPD at 4 weeks. There was a significant (p = 0.03) difference in the rate of clearance of Mtb from the sputum smear at 4 weeks for the nebulized rIFN-gamma1b adjuvant group compared to DOTS or DOTS with subcutaneous rIFN-gamma1b. In addition, there was significant reduction in the prevalence of fever, wheeze, and night sweats at 4 weeks among patients receiving rFN-gamma1b versus DOTS alone.

CONCLUSION

Recombinant interferon-gamma1b adjuvant therapy plus DOTS in cavitary pulmonary tuberculosis can reduce inflammatory cytokines at the site of disease, improve clearance of Mtb from the sputum, and improve constitutional symptoms.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00201123.

Mycobacterium tuberculosis WhiB3 maintains redox homeostasis by regulating virulence lipid anabolism to modulate macrophage response

The metabolic events associated with maintaining redox homeostasis in Mycobacterium tuberculosis (Mtb) during infection are poorly understood. Here, we discovered a novel redox switching mechanism by which Mtb WhiB3 under defined oxidizing and reducing conditions differentially modulates the assimilation of propionate into the complex virulence polyketides polyacyltrehaloses (PAT), sulfolipids (SL-1), phthiocerol dimycocerosates (PDIM), and the storage lipid triacylglycerol (TAG) that is under control of the DosR/S/T dormancy system. We developed an in vivo radio-labeling technique and demonstrated for the first time the lipid profile changes of Mtb residing in macrophages, and identified WhiB3 as a physiological regulator of virulence lipid anabolism. Importantly, MtbΔwhiB3 shows enhanced growth on medium containing toxic levels of propionate, thereby implicating WhiB3 in detoxifying excess propionate. Strikingly, the accumulation of reducing equivalents in MtbΔwhiB3 isolated from macrophages suggests that WhiB3 maintains intracellular redox homeostasis upon infection, and that intrabacterial lipid anabolism functions as a reductant sink. MtbΔwhiB3 infected macrophages produce higher levels of pro- and anti-inflammatory cytokines, indicating that WhiB3-mediated regulation of lipids is required for controlling the innate immune response. Lastly, WhiB3 binds to pks2 and pks3 promoter DNA independent of the presence or redox state of its [4Fe-4S] cluster. Interestingly, reduction of the apo-WhiB3 Cys thiols abolished DNA binding, whereas oxidation stimulated DNA binding. These results confirmed that WhiB3 DNA binding is reversibly regulated by a thiol-disulfide redox switch. These results introduce a new paradigmatic mechanism that describes how WhiB3 facilitates metabolic switching to fatty acids by regulating Mtb lipid anabolism in response to oxido-reductive stress associated with infection, for maintaining redox balance. The link between the WhiB3 virulence pathway and DosR/S/T signaling pathway conceptually advances our understanding of the metabolic adaptation and redox-based signaling events exploited by Mtb to maintain long-term persistence.

Currently, approximately one-third of the world's population is latently infected with Mycobacterium tuberculosis (Mtb), the bacterium that causes tuberculosis (TB). A central question in TB research is to identify the mechanisms that allow the organism to persist for long periods of time in humans. The mycobacterial cell wall has a high lipid content and contains several important lipid groups, including poly- and di-acyltrehaloses (PAT/DAT), sulfolipids (SL-1), and phthiocerol dimycocerosates (PDIM). These lipids are produced and actively secreted during infection to subvert the host immune system, eventually leading to Mtb persistence. We have discovered that the regulatory protein WhiB3 controls the differential production of PAT, DAT, SL-1, and PDIM and the storage lipid triacylglycerol (TAG) in response to fluctuations in the intracellular redox environment. We demonstrated that WhiB3 directly regulates lipid production by binding to the promoter regions of lipid biosynthetic genes in a redox-dependent manner. We also discovered that through this regulatory process, WhiB3 controls fatty acid metabolism and maintains intracellular redox homeostasis by channeling toxic reducing equivalents into lipid anabolism. Thus, our results suggest that Mtb lipid anabolism functions as a reductant sink to neutralize the reductive stress associated with the catabolism of host lipids during infection. These findings may serve as a model foundation for how pathogens adjust their metabolism to cope with stresses encountered during infection.

Suppression of IFNgamma+mycobacterial lipoarabinomannan-induced NO by IL-4 is due to decreased IRF-1 expression

In mice, and possibly in humans, nitric oxide (NO) is an important host-defense molecule against Mycobacterium tuberculosis. Inducible nitric oxide synthase (iNOS) and NO are upregulated in murine macrophages stimulated with interferon-gamma (IFNgamma) and mannose-capped lipoarabinomannan (ManLAM), a major lipoglycan in the cell wall of M. tuberculosis. Interleukin-4 (IL-4) can inhibit NO expression and may impair host immune response to M. tuberculosis. Therefore, we sought to determine the mechanism by which IL-4 inhibits IFNgamma+ManLAM-induced NO production. Since l-arginine is the substrate for both iNOS and arginase, and IL-4 increases arginase activity by inducing its production, a plausible mechanism of IL-4 inhibition of NO expression is via depletion of l-arginine through increased arginase activity. Herein, we show that IL-4 inhibited iNOS gene expression at the transcriptional level, suggesting an inhibitory mechanism that is independent of the competition for l-arginine between iNOS and arginase. Furthermore, pharmacologic inhibition of IL-4-induced arginase activity did not abrogate IL-4 inhibition of IFNgamma+ManLAM-induced NO expression. Instead, inhibition by IL-4 was mediated principally by the ability of IL-4 to inhibit the production of IFNgamma-induced interferon-gamma response factor-1 (IRF-1) protein, a critically important transcriptional element that enhances expression of IFNgamma-inducible genes such as iNOS.

Characterization of human cellular immune responses to novel Mycobacterium tuberculosis antigens encoded by genomic regions absent in Mycobacterium bovis BCG

Comparative genomics has identified several regions of differences (RDs) between the infectious Mycobacterium tuberculosis and the vaccine strains of Mycobacterium bovis BCG. We aimed to evaluate the cellular immune responses induced by antigens encoded by genes predicted in 11 RDs. Synthetic peptides covering the sequences of RD1, RD4 to RD7, RD9 to RD13, and RD15 were tested for antigen-induced proliferation and secretion of Th1 cytokine, gamma interferon (IFN-gamma), by peripheral blood mononuclear cells (PBMC) obtained from culture-proven pulmonary tuberculosis (TB) patients and M. bovis BCG-vaccinated healthy subjects. Among the peptide pools, RD1 induced the best responses in both donor groups and in both assays. In addition, testing of TB patients' PBMC for secretion of proinflammatory cytokines (tumor necrosis factor alpha [TNF-alpha], interleukin 6 [IL-6], IL-8, and IL-1beta), Th1 cytokines (IFN-gamma, IL-2, and TNF-beta), and Th2 cytokines (IL-4, IL-5, and IL-10) showed differential effects of RD peptides in the secretion of IFN-gamma and IL-10, with high IFN-gamma/IL-10 ratios (32 to 5.0) in response to RD1, RD5, RD7, RD9, and RD10 and low IFN-gamma/IL-10 ratios (<1.0) in response to RD12, RD13, and RD15. Peptide-mixing experiments with PBMC from healthy subjects showed that secretion of large quantities of IL-10 in response to RD12 and RD13 correlated with inhibition of Th1 responses induced by RD1 peptides. In conclusion, our results suggest that M. tuberculosis RDs can be divided into two major groups--one group that activates PBMC to preferentially secrete IFN-gamma and another group that activates preferential secretion of IL-10--and that these two groups of RDs may have roles in protection against and pathogenesis of TB, respectively.

Gene expression profiles of bronchoalveolar cells in pulmonary TB

The host response to Mycobacterium tuberculosis includes macrophage activation, inflammation with increased immune effector cells, tissue necrosis, and cavity formation, and fibrosis, distortion, and bronchiectasis. To evaluate the molecular basis of the immune response in the lungs of patients with active pulmonary tuberculosis (TB), we used bronchoalveolar lavage to obtain cells at the site of infection. Affymetrix GeneChip microarrays and cDNA nylon filter microarrays interrogated gene expression in bronchoalveolar lavage (BAL) cells from 11 healthy controls and 17 patients with active pulmonary TB. We found altered gene expression for 69 genes in TB versus normal controls that included cell surface markers, cytokines, chemokines, receptors, transcription factors, and complement components. In addition, TB BAL cell gene expression patterns segregated into 2 groups: one suggestive of a T helper type 1 (Th1) cellular immune response with increased signal transducer and activator of transcription-4 (STAT-4), interferon-gamma (IFN-gamma receptor), and monokine induced by IFN-gamma (MIG) expression with increased IFN-gamma protein levels in BAL fluid; the other group displayed characteristics of Th2 immunity with increased STAT-6, CD81, and IL-10 receptor expression. We were able to demonstrate that a Th2 presentation could change to a Th1 pattern after anti-tuberculous treatment in 1 TB patient studied serially. These gene expression data support the conclusion that pulmonary TB produces a global change in the BAL cell transcriptome with manifestations of either Th1 or Th2 immunity.

Evaluation of T cell immune responses in multi-drug-resistant tuberculosis (MDR-TB) patients to Mycobacterium tuberculosis total lipid antigens

Mycobacterium tuberculosis lipid antigens produce significant T cell responses in healthy tuberculin reactor [purified protein derivative (PPD-positive] individuals. In the present study, proliferation and interferon (IFN)-gamma/interleukin (IL)-4 responses were analysed to M. tuberculosis total lipid antigens in T lymphocytes from 25 patients with multi-drug-resistant tuberculosis (MDR-TB). The obtained results were compared with those of 30 asymptomatic healthy PPD-positive and 30 healthy tuberculin skin test negative (PPD-negative) subjects. Peripheral blood mononuclear cells (PBMCs) and T cells (CD4(+) and CD8(+)) were stimulated using autologous immature dendritic cells. Proliferation responses were assessed using 3-{4,5-dimethylthiazol-2-yl}-2,5 diphenyl tetrazolium bromide (MTT). IFN-gamma/IL-4 concentrations in the supernatant of the CD4(+) and CD8(+)T cells were measured by enzyme-linked immunosorbent assay. Proliferation assay showed that the peripheral blood mononuclear cells and CD4(+) T cells from the MDR-TB patients responded significantly less to the M. tuberculosis total lipid antigens than to the CD4(+) T cells in the PPD-positive subjects. Total lipid antigen-specific proliferative responses in the CD8(+) T cells from the MDR-TB patients were minimally detected and the responses were similar to those of the PPD-positive subjects. IFN-gamma production by the CD4(+) T cells stimulated by total lipid antigens from the MDR-TB patients was decreased significantly compared with the PPD-positive individuals, whereas IL-4 production in the patients was elevated. IFN-gamma and IL-4 production in the CD8(+) T cells of the MDR-TB patients was similar to those of the PPD-positive subjects. In conclusion, it is suggested that stimulated CD4(+) T cells by M. tuberculosis total lipid antigens may be shifted to T helper 2 responses in MDR-TB patients.

Life and death in the granuloma: immunopathology of tuberculosis

During tuberculosis (TB) infection, the granuloma provides the microenvironment in which antigen-specific T cells colocate with and activate infected macrophages to inhibit the growth of Mycobacterium tuberculosis. Although the granuloma is the site for mycobacterial killing, virulent mycobacteria have developed a variety of mechanisms to resist this macrophage-mediated killing. These surviving mycobacteria become dormant, however, if host cellular immunity or the signals maintaining granuloma structure wane, or if mycobacteria resume replication, leading to reactivation of TB. This balance of life and death applies not only to the mycobacterium but also to the host macrophages that may undergo apoptosis or necrosis, leading to the characteristic caseous necrosis within the granuloma, and the potential spread of TB infection. The immunological factors controlling the development and maintenance of the granuloma will be reviewed.

Assessment of in vitro immunity to Mycobacterium tuberculosis in a human peripheral blood infection model using a luciferase reporter construct of M. tuberculosis H37Rv

Protective immune responses to tuberculosis in man are primarily cell-mediated and require the interaction of specific T cells, cytokines and activated macrophages. In the present study, Mycobacterium tuberculosis H37Rv labelled with luciferase reporter enzyme was used to analyse the anti-mycobacterial immunity in man using an in vitro whole blood infection model. Peripheral blood samples obtained from M. bovis bacille Calmette-Guérin (BCG)-vaccinated tuberculin-positive healthy volunteers (n = 23) were cultured with M. tuberculosis H37Rv reporter strain. The growth of bacteria in the whole blood cultures was monitored after 48 and 96 h of infection. The results showed that the growth of M. tuberculosis was significantly inhibited after 96 h (P < 0.029) of culture. Among the cytokines studied, interleukin (IL)-10 and IL-12 were not detected at all, whereas low levels of interferon (IFN)-gamma after 96 h (0.4 IU/ml) and tumour necrosis factor (TNF)-alpha after 48 (135 pg/ml) and 96 h (47 pg/ml) of culture were detected in the supernatants of whole blood infected with M. tuberculosis. The magnitude of bacterial growth correlated directly with the concentration of TNF-alpha detected after 48 h (r = 0.722) and 96 h (r = 0.747) of culture (P <or= 0.0001 and P <or= 0.0001, respectively). However, the addition of monoclonal antibodies specific to TNF-alpha and IFN-gamma to the blood cultures did not alter mycobacterial growth indicating the role of other mechanisms/factors in restricting the growth of M. tuberculosis in whole blood cultures.

Cytokine expression profiles of bovine lymph nodes: effects of Mycobacterium bovis infection and bacille Calmette-Guérin vaccination

Cytokine expression in lymph nodes from cattle inoculated intranasally with Mycobacterium bovis was compared to that of non-infected animals using real-time polymerase chain reaction. The effect of M. bovis infection, 4 months post-challenge, was to suppress the expression of anti-inflammatory cytokines interleukin (IL)-4 and IL-10 as well as the pro-inflammatory cytokines tumour necrosis factor (TNF) and IL-6. Expression of interferon (IFN)-gamma and IL-12 was maintained. Animals vaccinated with bacille Calmette-Guérin responded differently to challenge with M. bovis. In particular, no decrease in expression of IL-4 or IL-6 was observed following challenge of vaccinated animals and decreased IFN-gamma was detected. Also, vaccinated animals had higher levels of IL-4 and IL-10 transcripts compared to unvaccinated animals following challenge. These changes in cytokine expression levels led to a significant shift in the IFN-gamma/IL-4 or IFN-gamma/IL-10 ratio within the lymph node following challenge. Challenged animals generally showed a strong Th1 bias that was not seen in animals vaccinated prior to challenge. An inverse correlation between the level of pathology and bacterial load within the lymph node and the expression of IL-4, IL-10 and TNF was also observed. These results suggest that in the lymph nodes of cattle with established tuberculosis and a persisting bacterial infection, maintenance of the pro-inflammatory response in combination with a suppressed anti-inflammatory response may control the infection but contribute to host-induced tissue damage. Vaccination, which reduces the bacterial load and consequently the IFN-gamma response, may result in less suppression of anti-inflammatory cytokines.

Immunohistochemical markers augment evaluation of vaccine efficacy and disease severity in bacillus Calmette–Guerin (BCG) vaccinated cattle challenged with Mycobacterium bovis

Development of necrotic granulomas in response to Mycobacterium bovis infection in cattle is pathognomonic for bovine tuberculosis. Previously our laboratory reported on M. bovis granuloma classification by stage of lesion advancement within bovine lymph nodes and developed immunohistochemical markers to further characterize these granulomas. In this study of bovine lymph node granulomas we applied this classification system to assess the dynamics of vaccination challenge. Lymph nodes collected from cattle vaccinated with M. bovis bacillus Calmette-Guerin (BCG) and subsequently challenged with virulent M. bovis were compared to lymph nodes from unvaccinated, challenged cattle. Expression of interferon-gamma (IFN-gamma), transforming growth factor-beta (TGF-beta), type I procollagen and cell marker identification of T cells, B cells, macrophages and WC1(+)gammadelta TCR+ cells were assessed. Granulomas formed in vaccinated cattle were greatly reduced in number, area, degree of necrosis and peripheral fibrosis and contained fewer Langhans' giant cells, acid fast bacilli, WC1(+)gammadelta TCR+ cells and less TGF-beta expression in comparison to controls. B cells clustered intensely along the outer granuloma margins within vaccinated calves, with significantly more IFN-gamma producing cells identified in the medullary regions of lymph nodes from BCG-vaccinated animals compared to unvaccinated controls. This may be indicative of immune activation and surveillance in regions not directly associated with ongoing disease. Lymph node evaluation using light microscopy and immunohistochemical markers is useful to assess the immune response and discriminate granulomas to determine vaccine efficacy and disease severity.

Increased specific T cell cytokine responses in patients with active pulmonary tuberculosis from Central Africa

An understanding of T cell responses that are crucial for control of Mycobacterium tuberculosis (MTB) has major implications for the development of immune-based interventions. We studied the frequency of purified protein derivative (PPD)-specific CD3) cells expressing interleukin-2 (IL)-2, gamma interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha and IL-10 in HIV-negative pulmonary tuberculosis patients (TB, n=30) as well as in healthy individuals (controls, n=21) from Central Africa. Increased frequencies of PPD-stimulated CD3+ cells expressing IL-2, IFN-gamma, and TNF-alpha in TB were seen when compared with frequencies of controls. The presence of type 1 cytokine biased responses in TB patients was supported by a shift in the distribution pattern of cytokine expression from exclusively IL-2 or TNF-alpha expression seen in controls towards an increased frequency of IFN-gamma/IL-2 or IFN-gamma/TNF-alpha co-expression in TB. Higher levels of PPD-induced IFN-gamma in the supernatants from TB patients than from controls were found, which correlated with its intracellular expression. PPD was a weak inducer of IL-10 in T cells and insufficient in promoting cytokine production in TCRgammadelta+CD3+ cells. Non-specific stimulation with PMA and ionomycin revealed increased frequencies of CD4+ cells expressing IFN-gamma in controls, while expression of IL-2, IL-4, IL-10, IL-13, and TNF-alpha was not different. Non-specific cytokine responses of TCRgammadelta+CD3+ cells were similar in all groups. Pulmonary TB in Central Africa is associated with enhanced expression and secretion of specifically induced cytokines that are frequently implicated in host defense against MTB.