Airways infection with virulent Mycobacterium tuberculosis delays the influx of dendritic cells and the expression of costimulatory molecules in mediastinal lymph nodes

The Use of Viral Vectors for Gene Therapy and Vaccination in Tuberculosis

Tuberculosis (TB), an infection caused by Mycobacterium tuberculosis (Mtb), is one of the primary causes of death globally. The treatment of TB is long and based on several drugs, producing problems in compliance and toxicity, increasing Mtb resistance to first-line antibiotics that result in multidrug-resistant TB and extensively drug-resistant TB. Thus, the need for new anti-TB treatments has increased. Here, we review some model strategies to study gene therapy based on the administration of a recombinant adenovirus that encodes diverse cytokines, such as IFNγ, IL12, GM/CSF, OPN, TNFα, and antimicrobial peptides to enhance the protective immune response against Mtb. These models include a model of progressive pulmonary TB, a model of chronic infection similar to latent TB, and a murine model of pulmonary Mtb transmission to close contacts. We also review new vaccines that deliver Mtb antigens via particle- or virus-based vectors and trigger protective immune responses. The results obtained in this type of research suggest that this is an alternative therapy that has the potential to treat active TB as an adjuvant to conventional antibiotics and a promising preventive treatment for latent TB reactivation and Mtb transmission. Moreover, Ad vector vaccines are adequate for preventing infectious diseases, including TB.

Pathological and protective roles of dendritic cells in Mycobacterium tuberculosis infection: Interaction between host immune responses and pathogen evasion

Dendritic cells (DCs) are principal defense components that play multifactorial roles in translating innate immune responses to adaptive immunity in Mycobacterium tuberculosis (Mtb) infections. The heterogeneous nature of DC subsets follows their altered functions by interacting with other immune cells, Mtb, and its products, enhancing host defense mechanisms or facilitating pathogen evasion. Thus, a better understanding of the immune responses initiated, promoted, and amplified or inhibited by DCs in Mtb infection is an essential step in developing anti-tuberculosis (TB) control measures, such as host-directed adjunctive therapy and anti-TB vaccines. This review summarizes the recent advances in salient DC subsets, including their phenotypic classification, cytokine profiles, functional alterations according to disease stages and environments, and consequent TB outcomes. A comprehensive overview of the role of DCs from various perspectives enables a deeper understanding of TB pathogenesis and could be useful in developing DC-based vaccines and immunotherapies.

Interplay between alveolar epithelial and dendritic cells and Mycobacterium tuberculosis

The innate response plays a crucial role in the protection against tuberculosis development. Moreover, the initial steps that drive the host-pathogen interaction following Mycobacterium tuberculosis infection are critical for the development of adaptive immune response. As alveolar Mϕs, airway epithelial cells, and dendritic cells can sense the presence of M. tuberculosis and are the first infected cells. These cells secrete mediators, which generate inflammatory signals that drive the differentiation and activation of the T lymphocytes necessary to clear the infection. Throughout this review article, we addressed the interaction between epithelial cells and M. tuberculosis, as well as the interaction between dendritic cells and M. tuberculosis. The understanding of the mechanisms that modulate those interactions is critical to have a complete view of the onset of an infection and may be useful for the development of dendritic cell-based vaccine or immunotherapies.

Mycobacterium tuberculosis-infected alveolar epithelial cells modulate dendritic cell function through the HIF-1α-NOS2 axis

Tuberculosis kills more than 1 million people every year, and its control depends on the effective mechanisms of innate immunity, with or without induction of adaptive immune response. We investigated the interaction of type II alveolar epithelial cells (AEC-II) infected by Mycobacterium tuberculosis with dendritic cells (DCs). We hypothesized that the microenvironment generated by this interaction is critical for the early innate response against mycobacteria. We found that AEC-II infected by M. tuberculosis induced DC maturation, which was negatively regulated by HIF-1α-inducible NOS2 axis, and switched DC metabolism from an early and short peak of glycolysis to a low energetic status. However, the infection of DCs by M. tuberculosis up-regulated NOS2 expression and inhibited AEC-II-induced DC maturation. Our study demonstrated, for the first time, that HIF-1α-NOS2 axis plays a negative role in the maturation of DCs during M. tuberculosis infection. Such modulation might be useful for the exploitation of molecular targets to develop new therapeutic strategies against tuberculosis.

Adenoviral vector-mediated GM-CSF gene transfer improves anti-mycobacterial immunity in mice - role of regulatory T cells

Granulocyte macrophage-colony stimulating factor (GM-CSF) is a hematopoietic growth factor involved in differentiation, survival and activation of myeloid and non-myeloid cells with important implications for lung antibacterial immunity. Here we examined the effect of pulmonary adenoviral vector-mediated delivery of GM-CSF (AdGM-CSF) on anti-mycobacterial immunity in M. bovis BCG infected mice. Exposure of M. bovis BCG infected mice to AdGM-CSF either applied on 6h, or 6h and 7days post-infection substantially increased alveolar recruitment of iNOS and IL-12 expressing macrophages, and significantly increased accumulation of IFNγ^pos T cells and particularly regulatory T cells (Tregs). This was accompanied by significantly reduced mycobacterial loads in the lungs of mice. Importantly, diphtheria toxin-induced depletion of Tregs did not influence mycobacterial loads, but accentuated immunopathology in AdGM-CSF-exposed mice infected with M. bovis BCG. Together, the data demonstrate that AdGM-CSF therapy improves lung protective immunity against M. bovis BCG infection in mice independent of co-recruited Tregs, which however critically contribute to limit lung immunopathology in BCG-infected mice. These data may be relevant to the development of immunomodulatory strategies to limit immunopathology-based lung injury in tuberculosis in humans.

Mass spectrometry applied to the identification of Mycobacterium tuberculosis and biomarker discovery

An adequate and effective tuberculosis (TB) diagnosis system has been identified by the World Health Organization as a priority in the fight against this disease. Over the years, several methods have been developed to identify the bacillus, but bacterial culture remains one of the most affordable methods for most countries. For rapid and accurate identification, however, it is more feasible to implement molecular techniques, taking advantage of the availability of public databases containing protein sequences. Mass spectrometry (MS) has become an interesting technique for the identification of TB. Here, we review some of the most widely employed methods for identifying Mycobacterium tuberculosis and present an update on MS applied for the identification of mycobacterial species.

Efficacy of gene-therapy based on adenovirus encoding granulocyte-macrophage colony-stimulating factor in drug-sensitive and drug-resistant experimental pulmonary tuberculosis

Tuberculosis (TB), although a curable disease, remains a major cause of morbidity and mortality worldwide. It is necessary to develop a short-term therapy with reduced drug toxicity in order to improve adherence rate and control disease burden. Granulocyte-macrophage colony-stimulating factor (GM-CSF) may be a key cytokine in the treatment of pulmonary TB since it primes the activation and differentiation of myeloid and non-myeloid precursor cells, inducing the release of protective Th1 cytokines. In this work, we administrated by intratracheal route recombinant adenoviruses encoding GM-CSF (AdGM-CSF). This treatment produced significant bacterial elimination when administered in a single dose at 60 days of infection with drug sensitive or drug resistant Mtb strains in a murine model of progressive disease. Moreover, AdGM-CSF combined with primary antibiotics produced more rapid elimination of pulmonary bacterial burdens than conventional chemotherapy suggesting that this form of treatment could shorten the conventional treatment.

Mycobacterium tuberculosis PE27 activates dendritic cells and contributes to Th1-polarized memory immune responses during in vivo infection

A gradual understanding of the proline-glutamate (PE) and proline-proline-glutamate (PPE) families, which compromise 10% of the coding regions in the Mycobacterium tuberculosis (Mtb) genome, has uncovered unique roles in host-pathogen interactions. However, the immunological function of PE27 (Rv2769c), the largest PE member, remains unclear. Here, we explored the functional roles and related signaling mechanisms of PE27 in the interaction with dendritic cells (DCs) to shape the T cell response. PE27 phenotypically and functionally induces DC maturation by up-regulating CD80, CD86, MHC class I and MHC class II expression on the DC surface to promote the production of TNF-α, IL-1β, IL-6, and IL-12p70 but not IL-10. Additionally, we found that PE27-mediated DC activation requires the participation of mitogen-activated protein kinases (MAPKs) and nuclear factor κB (NF-κB) signaling pathways. Interestingly, PE27-treated DCs directed naïve CD4(+) T cells to secrete IFN-γ and activate T-bet but not GATA-3. PE27 also induced IFN-γ-producing memory T cell responses in Mtb-infected mice, indicating that PE27 contributes to Th1-polarization. Taken together, these findings suggest that PE27 possesses Th1-polarizing potential through DC maturation and could be useful in the design of TB vaccines.

CD11c(+) CD103(+) cells of Mycobacterium tuberculosis-infected C57BL/6 but not of BALB/c mice induce a high frequency of interferon-γ- or interleukin-17-producing CD4(+) cells

The magnitude of the cellular adaptive immune response is critical for the control of Mycobacterium tuberculosis infection in the chronic phase. In addition, the genetic background is equally important for resistance or susceptibility to tuberculosis. In this study, we addressed whether lung populations of dendritic cells, obtained from genetically different hosts, would play a role in the magnitude and function of CD4(+) populations generated after M. tuberculosis infection. Thirty days post-infection, C57BL/6 mice, which generate a stronger interferon-γ (IFN-γ)-mediated immune response than BALB/c mice, exhibited a higher number and frequency of lung CD11c(+)  CD11b(-)  CD103(+) cells compared with BALB/c mice, which exhibited a high frequency of lung CD11c(+)  CD11b(+)  CD103(-) cells. CD11c(+)  CD11b(-)  CD103(+) cells, purified from lungs of infected C57BL/6 mice, but not from infected BALB/c mice, induced a higher frequency of IFN-γ-producing or interleukin-17 (IL-17)-producing CD4(+) cells. Moreover, CD4(+) cells also arrive at the lung of C57BL/6 mice faster than in BALB/c mice. This pattern of immune response seems to be associated with higher gene expression for CCL4, CCL19, CCL20 and CCR5 in the lungs of infected C57BL/6 mice compared with infected BALB/c mice. The results described here show that the magnitude of IFN-γ-producing or IL-17-producing CD4(+) cells is dependent on CD11c(+)  CD11b(-)  CD103(+) cells, and this pattern of immune response is directly associated with the host genetic background. Therefore, differences in the genetic background contribute to the identification of immunological biomarkers that can be used to design human assays to predict progression of M. tuberculosis infection.

ESAT-6 Targeting to DEC205+ Antigen Presenting Cells Induces Specific-T Cell Responses against ESAT-6 and Reduces Pulmonary Infection with Virulent Mycobacterium tuberculosis

Airways infection with Mycobacterium tuberculosis (Mtb) is contained mostly by T cell responses, however, Mtb has developed evasion mechanisms which affect antigen presenting cell (APC) maturation/recruitment delaying the onset of Ag-specific T cell responses. Hypothetically, bypassing the natural infection routes by delivering antigens directly to APCs may overcome the pathogen's naturally evolved evasion mechanisms, thus facilitating the induction of protective immune responses. We generated a murine monoclonal fusion antibody (α-DEC-ESAT) to deliver Early Secretory Antigen Target (ESAT)-6 directly to DEC205+ APCs and to assess its in vivo effects on protection associated responses (IFN-γ production, in vivo CTL killing, and pulmonary mycobacterial load). Treatment with α-DEC-ESAT alone induced ESAT-6-specific IFN-γ producing CD4+ T cells and prime-boost immunization prior to Mtb infection resulted in early influx (d14 post-infection) and increased IFN-γ+ production by specific T cells in the lungs, compared to scarce IFN-γ production in control mice. In vivo CTL killing was quantified in relevant tissues upon transferring target cells loaded with mycobacterial antigens. During infection, α-DEC-ESAT-treated mice showed increased target cell killing in the lungs, where histology revealed cellular infiltrate and considerably reduced bacterial burden. Targeting the mycobacterial antigen ESAT-6 to DEC205+ APCs before infection expands specific T cell clones responsible for early T cell responses (IFN-γ production and CTL activity) and substantially reduces lung bacterial burden. Delivering mycobacterial antigens directly to APCs provides a unique approach to study in vivo the role of APCs and specific T cell responses to assess their potential anti-mycobacterial functions.

Differential activation of dendritic cells by Mycobacterium tuberculosis Beijing genotype

Mycobacterium tuberculosis (Mtb) inhibits dendritric cells (DC) function in order to delay T cell response. Furthermore, there is increasing evidence that genetic diversity of Mtb strains can affect their interaction with the immune system. Beijing genotype has attracted attention because of its high prevalence and multi-drug resistance. Although it is known that this genotype is hypervirulent and differentially activates macrophages when compared to other genotypes, little is known about its interaction with DC. In order to address this issue, murine bone marrow derived DC (BMDC) were stimulated with soluble extracts (SE) from BCG, H37Rv, Canetti and Beijing genotypes. We observed that unlike other mycobacteria strains, SE-Beijing was unable to induce maturation of DC as assessed by cell surface MHC-II expression. DC stimulated with SE-Beijing failed to produce IL-12 and TNF-α, but did secrete IL-10. Interestingly, SE-Beijing induced CCR7 and PDL-1 on BMDC, but did not induce the expression of CD86. When BMDC stimulated with SE-Beijing were used to activate CD4+ cells they were unable to induce a Th1 response when compared with less virulent genotypes. These results indicate that Beijing is able to modulate DC activation and function, which may be related to the pathogenesis induced by this genotype.

Immunotherapeutic effects of recombinant adenovirus encoding granulocyte-macrophage colony-stimulating factor in experimental pulmonary tuberculosis

BALB/c mice with pulmonary tuberculosis (TB) develop a T helper cell type 1 that temporarily controls bacterial growth. Bacterial proliferation increases, accompanied by decreasing expression of interferon (IFN)-γ, tumour necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS). Activation of dendritic cells (DCs) is delayed. Intratracheal administration of only one dose of recombinant adenoviruses encoding granulocyte-macrophage colony-stimulating factor (AdGM-CSF) 1 day before Mycobacterium tuberculosis (Mtb) infection produced a significant decrease of pulmonary bacterial loads, higher activated DCs and increased expression of TNF-α, IFN-γ and iNOS. When AdGM-CSF was given in female mice B6D2F1 (C57BL/6J X DBA/2J) infected with a low Mtb dose to induce chronic infection similar to latent infection and corticosterone was used to induce reactivation, a very low bacilli burden in lungs was detected, and the same effect was observed in healthy mice co-housed with mice infected with mild and highly virulent bacteria in a model of transmissibility. Thus, GM-CSF is a significant cytokine in the immune protection against Mtb and gene therapy with AdGM-CSF increased protective immunity when administered in a single dose 1 day before Mtb infection in a model of progressive disease, and when used to prevent reactivation of latent infection or transmission.

Mycobacterium tuberculosis manipulates pulmonary APCs subverting early immune responses

Alveolar macrophages (AM) and dendritic cells (DCs) are the main antigen presenting cells (APCs) in the respiratory tract. Whereas macrophages have been extensively studied in tuberculosis, in situ interactions of DC with Mycobacterium tuberculosis (Mtb) are poorly explored. We aimed to characterize lung APCs during pulmonary tuberculosis in Balb/C mice infected with Mtb H37Rv. Mtb-infection via the airways induced a delayed and continuous accumulation of DCs and AM in the lungs. While lung DCs increased after day 3 post-infection, macrophages increased after 2-3 weeks. Although both populations accumulated in lungs during the infection, DCs decreased in the late stages. Infection induced differential expression of co-stimulatory molecules in these lung APCs, decreasing to basal levels in both APCs in the late stages. A remarkable segregation was found regarding bacillary burden. Many macrophages contained numerous bacilli, but DC contained scarce mycobacteria or none. Mtb-infection also induced delayed accumulation of DC in draining lymph nodes. This delayed recruitment was not associated with a lack of IL-12p40, which was detected from day 3 post-infection. Although AM and lung DCs behave differently during pulmonary tuberculosis, Mtb apparently manipulates both lung APCs subverting early protective responses resulting in disease progression.

Cellular and humoral mechanisms involved in the control of tuberculosis

Mycobacterium tuberculosis (Mtb) infection is a major international public health problem. One-third of the world's population is thought to have latent tuberculosis, a condition where individuals are infected by the intracellular bacteria without active disease but are at risk for reactivation, if their immune system fails. Here, we discuss the role of nonspecific inflammatory responses mediated by cytokines and chemokines induced by interaction of innate receptors expressed in macrophages and dendritic cells (DCs). We also review current information regarding the importance of several cytokines including IL-17/IL-23 in the development of protective cellular and antibody-mediated protective responses against Mtb and their influence in containment of the infection. Finally, in this paper, emphasis is placed on the mechanisms of failure of Mtb control, including the immune dysregulation induced by the treatment with biological drugs in different autoimmune diseases. Further functional studies, focused on the mechanisms involved in the early host-Mtb interactions and the interplay between host innate and acquired immunity against Mtb, may be helpful to improve the understanding of protective responses in the lung and in the development of novel therapeutic and prophylactic tools in TB.

Understanding delayed T-cell priming, lung recruitment, and airway luminal T-cell responses in host defense against pulmonary tuberculosis

Mycobacterium tuberculosis (M.tb), the causative bacterium of pulmonary tuberculosis (TB), is a serious global health concern. Central to M.tb effective immune avoidance is its ability to modulate the early innate inflammatory response and prevent the establishment of adaptive T-cell immunity for nearly three weeks. When compared with other intracellular bacterial lung pathogens, such as Legionella pneumophila, or even closely related mycobacterial species such as M. smegmatis, this delay is astonishing. Customarily, the alveolar macrophage (AM) acts as a sentinel, detecting and alerting surrounding cells to the presence of an invader. However, in the case of M.tb, this may be impaired, thus delaying the recruitment of antigen-presenting cells (APCs) to the lung. Upon uptake by APC populations, M.tb is able to subvert and delay the processing of antigen, MHC class II loading, and the priming of effector T cell populations. This delay ultimately results in the deferred recruitment of effector T cells to not only the lung interstitium but also the airway lumen. Therefore, it is of upmost importance to dissect the mechanisms that contribute to the delayed onset of immune responses following M.tb infection. Such knowledge will help design the most effective vaccination strategies against pulmonary TB.

The role of IL-10 in immune regulation during M. tuberculosis infection

During gaseous exchange the lungs are exposed to a vast variety of pathogens, allergens, and innocuous particles. A feature of the lung immune response to lung-tropic aerosol-transmitted bacteria such as Mycobacterium tuberculosis (Mtb) is a balanced immune response that serves to restrict pathogen growth while not leading to host-mediated collateral damage of the delicate lung tissues. One immune-limiting mechanism is the inhibitory and anti-inflammatory cytokine interleukin (IL)-10. IL-10 is made by many hematopoietic cells and a major role is to suppress macrophage and dendritic cell (DC) functions, which are required for the capture, control, and initiation of immune responses to pathogens such as Mtb. Here, we review the role of IL-10 on bacterial control during the course of Mtb infection, from early innate to adaptive immune responses. We propose that IL-10 is linked with the ability of Mtb to evade immune responses and mediate long-term infections in the lung.

Factors that deregulate the protective immune response in tuberculosis

Tuberculosis (TB) is a chronic infectious disease which essentially affects the lungs and produces profound abnormalities on the immune system. Although most people infected by the tubercle bacillus (90%) do not develop the disease during their lifetime, when there are alterations in the immune system, such as co-infection with HIV, malnutrition, or diabetes, the risk of developing active disease increases considerably. Interestingly, during the course of active disease, even in the absence of immunosuppressive conditions, there is a profound and prolonged suppression of Mycobacterium tuberculosis-specific protective immune responses. Several immune factors can contribute to downregulate the protective immunity, permitting disease progression. In general, many of these factors are potent anti-inflammatory molecules that are probably overproduced with the intention to protect against tissue damage, but the consequence of this response is a decline in protective immunity facilitating bacilli growth and disease progression. Here the most significant participants in protective immunity are reviewed, in particular the factors that deregulate protective immunity in TB. Their manipulation as novel forms of immunotherapy are also briefly commented.

Characterization of langerhans cells in epidermal sheets along the body of Armadillo (Dasypus novemcinctus)

Armadillos are apparently important reservoirs of Mycobacterium leprae and an animal model for human leprosy, whose immune system has been poorly studied. We aimed at characterizing the armadillo's langerhans cells (LC) using epidermal sheets instead of tissue sections, since the latter restrict analysis only to cut-traversed cells. Epidermal sheets by providing an en face view, are particularly convenient to evaluate dendritic morphology (cells are complete), spatial distribution (regular vs. clustered), and frequency (cell number/tissue area). Lack of anti-armadillo antibodies was overcome using LC-restricted ATPase staining, allowing assessment of cell frequency, cell size, and dendrites extension. Average LC frequency in four animals was 528 LC/mm(2), showing a rather uniform non-clustered distribution, which increased towards the animal's head, while cell size increased towards the tail; without overt differences between sexes. The screening of antibodies to human DC (MHC-II, CD 1a, langerin, CD86) in armadillo epidermal sheets, revealed positive cells with prominent dendritic morphology only with MHC-II and CD86. This allowed us to test DC mobilization from epidermis into dermis under topical oxazolone stimulation, a finding that was corroborated using whole skin conventional sections. We hope that the characterization of armadillo's LC will incite studies of leprosy and immunity in this animal model.

'Immunization' against airborne tuberculosis by an earlier primary response to a concurrent intravenous infection

Tuberculosis in mice is a lung disease. Airborne infection of this host species with Mycobacterium tuberculosis (Mtb) resulted in 20 days of Mtb growth in the lungs before further growth was inhibited and the level of infection stabilized. Inhibition of Mtb growth was associated with the production of interferon-gamma (IFN-gamma)-producing T cells in the lymph nodes and spleen and with the progressive accumulation of these cells in the lungs. Production of IFN-gamma-producing T cells was not discernable until about day 15 of infection, presumably because Mtb did not disseminate from the lungs to the draining lymph nodes and spleen until after an approximate 10-day delay. By contrast, in mice infected via the intravenous (i.v.) route, the spleen became infected almost immediately, resulting in much earlier production of IFN-gamma-producing T cells and earlier control of spleen and lung infection. In mice infected concurrently via both routes, earlier generation of immunity to the i.v. infection resulted in earlier accumulation of IFN-gamma-producing T cells in the lungs and earlier control of lung infection that was initiated via the airborne route. This protection against airborne infection afforded by an earlier primary immune response is equivalent to that expressed by mice vaccinated with bacillus Calmette-Guérin or certain other vaccines.

Low expression of antigen-presenting and costimulatory molecules by lung cells from tuberculosis patients

Costimulatory and antigen-presenting molecules are essential to the initiation of T cell immunity to mycobacteria. The present study analyzed by immunocytochemistry, using monoclonal antibodies and alkaline phosphatase-anti-alkaline phosphatase method, the frequency of costimulatory (CD86, CD40, CD40L, CD28, and CD152) and antigen-presenting (MHC class II and CD1) molecules expression on human lung cells recovered by sputum induction from tuberculosis (TB) patients (N = 22) and non-TB controls (N = 17). TB cases showed a statistically significant lower percentage of HLA-DR+ cells than control subjects (21.9 +/- 4.2 vs 50.0 +/- 7.2%, P < 0.001), even though similar proportions of TB cases (18/22) and control subjects (16/17, P = 0.36) had HLA-DR-positive-stained cells. In addition, fewer TB cases (10/22) compared to control subjects (16/17) possessed CD86-expressing cells (P = 0.04; OR: 0.05; 95%CI = 0.00-0.51), and TB cases expressed a lower percentage of CD86+ cells (P = 0.04). Moreover, TB patients with clinically limited disease ( pound1 lobe) on chest X-ray exhibited a lower percentage of CD86-bearing cells compared to patients with more extensive lung disease (>1 lobe) (P = 0.02). The lower expression by lung cells from TB patients of HLA-DR and CD86, molecules involved in antigen presentation and activation of T cells, may minimize T cell recognition of Mycobacterium tuberculosis, fostering an immune dysfunctional state and active TB.

High-risk human papilloma virus infection decreases the frequency of dendritic Langerhans' cells in the human female genital tract

Dendritic cells (DC) are often arranged in planar layers in tissues with high antigenic exposure, such as skin and mucosae. Providing an en face view, this arrangement optimizes in situ analysis regarding morphology (even of individual dendrites), topographic distribution (regular/clustered) and quantification. The few reports on human genital DC usually utilize single markers and conventional sections, restricting immunolabelling only to cell parts sectioned by the cut. To better assess DC in situ, we labelled epithelial sheets, prepared from fresh cervix biopsies, with antibodies to major histocompatibility complex (MHC)-CII, CD1a and Langerin, revealing (with each of these markers) a dense DC network in a planar-like, regular distribution. Using the hybrid capture system to detect the high-risk mucotropic human papilloma virus (HPV) group, 16 positive and five negative women were studied and the results were compared between these groups. DC frequency per area was substantially reduced (to approximately 50% for the three markers) in samples from all HPV-infected patients compared with samples from controls. Unlike HPV(-) samples, Langerin(+) DC in HPV(+) cervix exhibited a highly accentuated dendritic appearance. We believe this to be the first study using these three DC-restricted markers (Langerin, CD1a and MHC-CII) in cervical epithelial sheets from high-risk HPV(+) donors and also the first study to demonstrate the morphological and quantitative changes triggered by high-risk HPV infection. Cervical DC reduction in early, premalignant high-risk HPV infection might represent viral subversion strategies interfering with efficient antigen handling by the immune system's peripheral sentinels, the DC, perhaps hampering appropriate recruitment and subsequent development of effector (cytotoxic) T cells.

Selectin Ligand-Independent Priming and Maintenance of T Cell Immunity during Airborne Tuberculosis

Immunity to Mycobacterium tuberculosis infection is critically dependent on the timely priming of T effector lymphocytes and their efficient recruitment to the site of mycobacterial implantation in the lung. E-, P-, and L-selectin counterreceptors control lymphocyte homing to lymph nodes and leukocyte trafficking to peripheral sites of acute inflammation, their adhesive function depending on fucosylation by fucosyltransferases (FucT) IV and VII. To address the relative importance of differentially glycosylated selectin counterreceptors for priming of T cell effector functions in a model of mycobacteria-induced granulomatous pulmonary inflammation, we used aerosol-borne M. tuberculosis to infect FucT-IV-/-, FucT-VII-/-, FucT-IV-/-/FucT-VII-/-, or wild-type control mice. In lymph nodes, infected FucT-IV-/-/FucT-VII-/- and, to a lesser extent, FucT-VII-/- mice had severely reduced numbers of T cells and reduced Ag-specific effector responses. By contrast, recruitment of activated T cells into the lungs was similar in all four groups of mice during infection and expression of T cell, and macrophage effector functions were only delayed in lungs of FucT-IV-/-/FucT-VII-/- mice. Importantly, lungs from all groups expressed CXCL13, CCL21, and CCL19 and displayed organized follicular neolymphoid structures after infection with M. tuberculosis, which suggests that the lung served as a selectin ligand-independent priming site for immune responses to mycobacterial infection. All FucT-deficient strains were fully capable of restricting M. tuberculosis growth in infected organs until at least 150 days postinfection. Our observations indicate that leukocyte recruitment functions dictated by FucT-IV and FucT-VII-dependent selectin ligand activities are not critical for inducing or maintaining T cell effector responses at levels necessary to control pulmonary tuberculosis.

Foamy macrophages within lung granulomas of mice infected with Mycobacterium tuberculosis express molecules characteristic of dendritic cells and antiapoptotic markers of the TNF receptor-associated factor family

Highly vacuolated or foamy macrophages are a distinct characteristic of granulomas in the lungs of animals infected with Mycobacterium tuberculosis. To date these have usually been considered to represent activated macrophages derived from monocytes entering the lesions from the blood. However, we demonstrate in this study that foamy macrophages express high levels of DEC-205, a marker characteristic of dendritic cells (DCs). In addition to high expression of the DEC-205 marker, these cells were characterized as CD11b(+)CD11c(high)MHC class II(high), and CD40(high), which are additional markers typically expressed by DCs. Up-regulation of CD40 was seen only during the early chronic stage of the lung disease, and both the expression of CD40 and MHC class II markers were down-regulated as the disease progressed into the late chronic phase. Foamy cells positive for the DEC-205 marker also expressed high levels of TNFR-associated factor-1 (TRAF-1), TRAF-2, and TRAF-3, markers associated with resistance to apoptosis. These data indicate that in addition to the central role of DCs in initiating the acquired immune response against M. tuberculosis infection, they also participate in the granulomatous response.

Subcellular localization of mycobacteria in tissues and detection of lipid antigens in organelles using cryo-techniques for light and electron microscopy

The survival of intracellular pathogens within a host is determined by microbial evasion, which can be partially attributed to their subcellular trafficking strategies. Microscopic techniques have become increasingly important in understanding the cell biology of microbial infections. These recently developed techniques can be used for the subcellular localization of antigens not only in cultured cells but also within tissues such as Mycobacterium tuberculosis in lung and Mycobacterium leprae in skin. High-resolution immunofluorescence microscopy can be used in combination with cryo-immunogold electron microscopy using consecutive cryo-sections on the same tissue block forming a direct connection between the two microscopy techniques. The detection of mycobacterial lipid antigens in situ at an ultrastructural level is currently a challenge, but new modifications can be used to address this. These methods might be of interest to microbiologists and cell biologists who study host-pathogen interactions.