Recombinant gamma interferon stimulates signal transduction and gene expression in alveolar macrophages in vitro and in tuberculosis patients

Geraniin inhibits whole blood IFN-γ and IL-6 and promotes IL-1β and IL-8, and stimulates calcium-dependent and sucrose-sensitive erythrocyte death

Correlations between circulating cytokine levels and disease states are well established, and pharmacological modulation of the immune response is thus an important aspect of the assessment of investigational new drugs. Moreover, chemotherapy-related anemia is a major obstacle in cancer treatment. Geraniin (GRN), a tannin extracted from Geranium and other plants, possesses promising antitumor potential. However, the effect of GRN on whole blood (WB) cytokine response and RBC physiology remains unexplored. Heparinized blood from consented, healthy adults was challenged with 100 ng/mL of lipopolysaccharide (LPS) with and without pretreatment with 10 μM of GRN for 24 h at 37 °C, and tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1β (IL-1β), IL-6, IL-8, and IL-10 were assayed by ELISA. Moreover, single-cell RBC suspensions were treated with 5-100 μM of GRN for 24 or 48 h at 37 °C and cytotoxicity and canonical eryptotic markers were examined by flow cytometry. It was revealed that GRN significantly attenuated LPS-induced IFN-γ levels, increased IL-1β, decreased IL-6 only in absence of LPS, and aggravated LPS-induced IL-8 while together with LPS significantly diminished IL-10. Furthermore, GRN induced dose-responsive, Ca²⁺-dependent, and sucrose-sensitive hemolysis, along with phosphatidylserine exposure and Ca²⁺ accumulation with no appreciable cell shrinkage or oxidative damage. GRN was also selectively toxic to platelets, significantly delayed reticulocyte maturation, and significantly disrupted leukocyte proportions. In conclusion, GRN regulates the WB cytokine response and promotes premature hemolysis and eryptosis. This study provides insights into the therapeutic utility of GRN in a highly relevant cellular model system.

ESAT-6 modulates Calcimycin-induced autophagy through microRNA-30a in mycobacteria infected macrophages

OBJECTIVE

Mycobacterium tuberculosis (M. tb) has a sumptuous repertoire of effector molecules to counter host defenses. Some of these antigens inhibit autophagy but the exact mechanism of this inhibition is poorly understood.

METHODS

Purified protein derivative (PPD) was fractionated using 10 (PPD 10, antigenic molecular weight > 10 kDa) and 3 (PPD 3, mol. weight > 3 kDa) kDa cutters. Effect of these fractions on Calcimycin-induced autophagy and intracellular mycobacterial viability was then studied using different experimental approaches.

RESULT

We found significant downregulation of autophagy by PPD 3 pre-treatment in Calcimycin-treated dTHP-1 cells compared to PPD 10. This reduction in autophagy also corroborated with the enhanced survival of mycobacteria in macrophages. We demonstrate that recombinant early secreted antigenic target 6 (rESAT-6) is responsible to inhibit Calcimycin-induced autophagy and enhance intracellular survival of mycobacteria. We also show that pre-treatment with rESAT-6 upregulates microRNA (miR)-30a-3p expression and vis-a-vis downregulates miR-30a-5p expression in Calcimycin-treated dTHP-1 cells. Transfection studies with either miR-30a-3p inhibitor or miR-30a-5p mimic clearly elucidated the opposing roles of miR-30a-3p and miR-30a-5p in rESAT-6 mediated mycobacterial survival through autophagy inhibition.

CONCLUSION

Taken together, our result evidently highlights that rESAT-6 enhances intracellular survival of mycobacteria by modulating miR-30a-3p and miR-30a-5p expression.

Translational Potential of Therapeutics Targeting Regulatory Myeloid Cells in Tuberculosis

Despite recent advances in tuberculosis (TB) drug development and availability, successful antibiotic treatment is challenged by the parallel development of antimicrobial resistance. As a result, new approaches toward improving TB treatment have been proposed in an attempt to reduce the high TB morbidity and mortality rates. Host-directed therapies (HDTs), designed to modulate host immune components, provide an alternative approach for improving treatment outcome in both non-communicable and infectious diseases. Many candidate immunotherapeutics, designed to target regulatory myeloid immune components in cancer, have so far proven to be of value as repurposed HDT in TB. Several of these studies do however lack detailed description of the mechanism or host pathway affected by TB HDT treatment. In this review, we present an argument for greater appreciation of the role of regulatory myeloid cells, such as myeloid-derived suppressor cells (MDSC), as potential targets for the development of candidate TB HDT compounds. We discuss the role of MDSC in the context of Mycobacterium tuberculosis infection and disease, focussing primarily on their specific cellular functions and highlight the impact of HDTs on MDSC frequency and function.

Inhaled drug treatment for tuberculosis: Past progress and future prospects

Since the 1990s the rising incidence of multiple drug resistant TB, particularly in the context of human immunodeficiency virus co-infected patients, has threatened global TB control. At that time funding agencies began to support formal investigation of aerosol therapy which until then had been the subject of case reports of individual investigators. Over the last decade, proponents of aerosol therapy have increased in number within the TB research community as the incidence of multiple and extremely drug resistant TB has increased dramatically around the world. Aerosol therapy offers the potential to deliver drug at target concentrations directly into the lungs, use the alveolar-capillary interface to achieve systemic levels, while reducing the risk of systemic toxicity seen with parentally administered doses. In addition, there are insufficient new drugs in the pipeline to anticipate the appearance of a new regimen in time to assure future control of drug resistance. Consequently, alternative strategies are critical to achieving global TB control, and inhaled therapies should be considered as one such strategy.

Vaccination with an Attenuated Ferritin Mutant Protects Mice against Virulent Mycobacterium tuberculosis

Mycobacterium tuberculosis the causative agent of tuberculosis affects millions of people worldwide. New tools for treatment and prevention of tuberculosis are urgently needed. We previously showed that a ferritin (bfrB) mutant of M. tuberculosis has altered iron homeostasis and increased sensitivity to antibiotics and to microbicidal effectors produced by activated macrophages. Most importantly, M. tuberculosis lacking BfrB is strongly attenuated in mice, especially, during the chronic phase of infection. In this study, we examined whether immunization with a bfrB mutant could confer protection against subsequent infection with virulent M. tuberculosis in a mouse model. The results show that the protection elicited by immunization with the bfrB mutant is comparable to BCG vaccination with respect to reduction of bacterial burden. However, significant distinctions in the disease pathology and host genome-wide lung transcriptome suggest improved containment of Mtb infection in animals vaccinated with the bfrB mutant, compared to BCG. We found that downmodulation of inflammatory response and enhanced fibrosis, compared to BCG vaccination, is associated with the protective response elicited by the bfrB mutant.

Extracellular traps and macrophages: new roles for the versatile phagocyte

MΦ are multipurpose phagocytes with a large repertoire of well-characterized abilities and functions, including regulation of inflammation, wound healing, maintenance of tissue homeostasis, as well as serving as an integral component of the innate-immune defense against microbial pathogens. Working along with neutrophils and dendritic cells, the other myeloid-derived professional phagocytes, MΦ are one of the key effector cells initiating and directing the host reaction to pathogenic organisms and resolving subsequent responses once the threat has been cleared. ETs are a relatively novel strategy of host defense involving expulsion of nuclear material and embedded proteins from immune cells to immobilize and kill bacteria, fungi, and viruses. As research on ETs expands, it has begun to encompass many immune cell types in unexpected ways, including various types of MΦ, which are not only capable of generating METs in response to various stimuli, but recent preclinical data suggest that they are an important agent in clearing ETs and limiting ET-mediated inflammation and tissue damage. This review aims to summarize historical and recent findings of biologic research regarding ET formation and function and discuss the role of MΦ in ET physiology and associated pathologies.

Adenosine deaminase acting on RNA-1 (ADAR1) inhibits HIV-1 replication in human alveolar macrophages

While exploring the effects of aerosol IFN-γ treatment in HIV-1/tuberculosis co-infected patients, we observed A to G mutations in HIV-1 envelope sequences derived from bronchoalveolar lavage (BAL) of aerosol IFN-γ-treated patients and induction of adenosine deaminase acting on RNA 1 (ADAR1) in the BAL cells. IFN-γ induced ADAR1 expression in monocyte-derived macrophages (MDM) but not T cells. ADAR1 siRNA knockdown induced HIV-1 expression in BAL cells of four HIV-1 infected patients on antiretroviral therapy. Similar results were obtained in MDM that were HIV-1 infected invitro. Over-expression of ADAR1 in transformed macrophages inhibited HIV-1 viral replication but not viral transcription measured by nuclear run-on, suggesting that ADAR1 acts post-transcriptionally. The A to G hyper-mutation pattern observed in ADAR1 over-expressing cells invitro was similar to that found in the lungs of HIV-1 infected patients treated with aerosol IFN-γ suggesting the model accurately represented alveolar macrophages. Together, these results indicate that ADAR1 restricts HIV-1 replication post-transcriptionally in macrophages harboring HIV-1 provirus. ADAR1 may therefore contribute to viral latency in macrophages.

Optimization of conditions for expression of recombinant interferon-γ in E.coli

Interferon gamma (IFN-γ) is an important immunoregulatory cytokine that has a central role against viral and bacterial infections. In this study, the cDNA encoding 141 amino acids of mature IFN-γ from mice splenocytes was cloned in a prokaryotic expression vector pQE 30. Optimization of expression conditions resulted in high IFN-γ protein. Western blot showed that recombinant IFN-γ was specifically recognized by its counterpart anti-mouse IFN-γ antibodies. In vitro dose-dependent studies, with A549 and HeLa cell lines, showed that cloned IFN-γ was safe and had no effect on cell proliferation. The protein prediction and analysis using SOPMA program, revealed that IFN-γ had 80 α-helices, 8 β-turns jointed by 9 extended strands and 44 random coils. A total of four major clusters were observed with murine IFN-γ sharing 39 % homology with human IFN-γ. Pair-wise alignment studies with human revealed 26 % identity and 43.3 % similarity. The recovery of bioactive proteins from inclusion bodies (IBs) is a complex process and various protocols have been developed. We report here a simple, robust and inexpensive purification approach for obtaining recombinant IFN-γ protein expressed as IBs in E.coli.

Host-directed therapeutics for tuberculosis: can we harness the host?

Treatment of tuberculosis (TB) remains challenging, with lengthy treatment durations and complex drug regimens that are toxic and difficult to administer. Similar to the vast majority of antibiotics, drugs for Mycobacterium tuberculosis are directed against microbial targets. Although more effective drugs that target the bacterium may lead to faster cure of patients, it is possible that a biological limit will be reached that can be overcome only by adopting a fundamentally new treatment approach. TB regimens might be improved by including agents that target host pathways. Recent work on host-pathogen interactions, host immunity, and host-directed interventions suggests that supplementing anti-TB therapy with host modulators may lead to shorter treatment times, a reduction in lung damage caused by the disease, and a lower risk of relapse or reinfection. We undertook this review to identify molecular pathways of the host that may be amenable to modulation by small molecules for the treatment of TB. Although several approaches to augmenting standard TB treatment have been proposed, only a few have been explored in detail or advanced to preclinical and clinical studies. Our review focuses on molecular targets and inhibitory small molecules that function within the macrophage or other myeloid cells, on host inflammatory pathways, or at the level of TB-induced lung pathology.

Function and Potentials of M. tuberculosis Epitopes

Study of the function of epitopes of Mycobacterium tuberculosis antigens contributed significantly toward better understanding of the immunopathogenesis and to efforts for improving infection and disease control. Characterization of genetically permissively presented immunodominant epitopes has implications for the evolution of the host–parasite relationship, development of immunodiagnostic tests, and subunit prophylactic vaccines. Knowledge of the determinants of cross-sensitization, relevant to other pathogenic or environmental mycobacteria and to host constituents has advanced. Epitope-defined IFNγ assay kits became established for the specific detection of infection with tubercle bacilli both in humans and cattle. The CD4 T-cell epitope repertoire was found to be more narrow in patients with active disease than in latently infected subjects. However, differential diagnosis of active TB could not be made reliably merely on the basis of epitope recognition. The mechanisms by which HLA polymorphism can influence the development of multibacillary tuberculosis (TB) need further analysis of epitopes, recognized by Th2 helper cells for B-cell responses. Future vaccine development would benefit from better definition of protective epitopes and from improved construction and formulation of subunits with enhanced immunogenicity. Epitope-defined serology, due to its operational advantages is suitable for active case finding in selected high disease incidence populations, aiming for an early detection of infectious cases and hence for reducing the transmission of infection. The existing knowledge of HLA class I binding epitopes could be the basis for the construction of T-cell receptor-like ligands for immunotherapeutic application. Continued analysis of the functions of mycobacterial epitopes, recognized by T cells and antibodies, remains a fertile avenue in TB research.

Elevated IP-10 and IL-6 from bronchoalveolar lavage cells are biomarkers of non-cavitary tuberculosis

BACKGROUND

Active TB disease can destroy lung parenchyma leading to cavities. Immune responses that predispose or protect individuals from lung damage during TB are poorly defined.

OBJECTIVE

To sample lung immune cells and assay bronchoalveolar lavage (BAL) cell cytokine production.

DESIGN

Enrolled subjects (n = 73) had bilateral infiltrates and underwent BAL.

RESULTS

All had sputum culture demonstrating Mycobacterium tuberculosis and 22/73 (30%) had cavities on their chest radiograph. Those with cavities at presentation had a higher percentage of polymorphonuclear neutrophils (PMN) in BAL as well as lower inducible protein (IP) 10 (P < 0.01) and interleukin (IL) 6 (P = 0.013) in BAL cell supernatants compared to those without cavities. There was no correlation between cavities and other BAL or serum cytokines. IP-10 was negatively associated with BAL PMN. IP-10 and IL-6 expression above median reduces the odds of cavities by 79% and 78% in logistic regression models. IP-10 and IL-6 clustered with interferon-gamma and tumour necrosis factor-alpha in a principal component analysis, while IL-4 clustered with PMN.

CONCLUSION

Increasing IP-10 and IL-6 production by BAL cells is associated with non-cavitary TB in patients who present with radiographically advanced TB. IP-10 and IL-6 may reflect an effective T-helper 1 immune control pathway for TB, attenuating tuberculous lung destruction.

Wedelolactone, a naturally occurring coumestan, enhances interferon-γ signaling through inhibiting STAT1 protein dephosphorylation

Signal transducers and activators of transcription 1 (STAT1) transduces signals from cytokines and growth factors, particularly IFN-γ, and regulates expression of genes involved in cell survival/death, proliferation, and migration. STAT1 is activated through phosphorylation on its tyrosine 701 by JAKs and is inactivated through dephosphorylation by tyrosine phosphatases. We discovered a natural compound, wedelolactone, that increased IFN-γ signaling by inhibiting STAT1 dephosphorylation and prolonging STAT1 activation through specific inhibition of T-cell protein tyrosine phosphatase (TCPTP), an important tyrosine phosphatase for STAT1 dephosphorylation. More interestingly, wedelolactone inhibited TCPTP through interaction with the C-terminal autoinhibition domain of TCPTP. We also found that wedelolactone synergized with IFN-γ to induce apoptosis of tumor cells. Our data suggest a new target for anticancer or antiproliferation drugs, a new mechanism to regulate PTPs specifically, and a new drug candidate for treating cancer or other proliferation disorders.

The effect of combination IFN-alpha-2a with usual antituberculosis chemotherapy in non-responding tuberculosis and diabetes mellitus: a case report and review of the literature

A limited number of publications indicate that certain interferons (IFNs) may have a role in difficult-to-treat tuberculosis. We present a 48-year-old male diabetic patient who was referred to our department with the presumptive diagnosis of multidrug resistant tuberculosis. During the previous 8 months, he had been treated initially with a four-drug regimen (rifampicin, isoniazid, pyrazinamide, and ethambutol), which was later modified by the addition of streptomycin and ciprofloxacin, but his clinical condition had not improved and his sputum smear microscopy had remained positive to acid-fast bacilli. Cultured Mycobacterium tuberculosis from his sputum was sensitive to rifampicin and isoniazid. We administered IFN-alpha-2a at a low dose of 3 million IU intramuscularly weekly, in combination with isoniazid, rifampicin, ethambutol, and pyrazinamide. Two months after initiation of this therapy, sputum smears became negative, and a dramatic improvement in the patient's clinical and radiological findings occurred. During a 4-year follow-up, all consecutive sputum cultures remain negative. This case provides additional confirmation that certain IFNs could, potentially, be useful as therapeutic adjuncts for selected cases of non-responding tuberculosis and, therefore, merit further consideration.

Cytokine therapy of tuberculosis at the crossroads

Drug treatment is the key strategy in TB control. However, the treatment course lasts 6-9 months because the current anti-TB drugs are poorly effective against nondividing (i.e., persistent) bacilli. As a result, completion rates are unsatisfactory, leading to emergence and spread of multidrug-resistant infection. It would, therefore, be very desirable to design a form of complementary treatment that could speed up the recovery process for people afflicted with TB and reduce the relapse rates. With the advancement of our understanding of the immunopathogenesis of TB, it has become increasingly possible to develop novel adjunctive immunotherapies for both drug-susceptible and drug-resistant TB. Notably, cytokines probably offer the most promising prospect of such a therapy being introduced in routine clinical practice. However, in many ways, the cytokine therapy of TB has reached a crossroad, since, although the initial promise failed to live up to expectations, sufficient encouraging evidence exists to warrant further exploration. There are clear arguments in favor as well as against such treatments. This review aims to provide a rationale for cytokine treatment of TB, to describe the current status of several cytokines that have been considered for that purpose and, ultimately, to make a case for the need for further clinical trials.

In vitro differentiation of human macrophages with enhanced antimycobacterial activity

Mycobacterium tuberculosis causes widespread, persistent infection, often residing in macrophages that neither sterilize the bacilli nor allow them to cause disease. How macrophages restrict growth of pathogens is one of many aspects of human phagocyte biology whose study relies largely on macrophages differentiated from monocytes in vitro. However, such cells fail to recapitulate the phenotype of tissue macrophages in key respects, including that they support early, extensive replication of M. tuberculosis and die in several days. Here we found that human macrophages could survive infection, kill Mycobacterium bovis BCG, and severely limit the replication of M. tuberculosis for several weeks if differentiated in 40% human plasma under 5%-10% (physiologic) oxygen in the presence of GM-CSF and/or TNF-α followed by IFN-γ. Control was lost with fetal bovine serum, 20% oxygen, M-CSF, higher concentrations of cytokines, or premature exposure to IFN-γ. We believe that the new culture method will enable inquiries into the antimicrobial mechanisms of human macrophages.

New drugs and regimens for treatment of TB

Tools for effective TB control have been available for years. Case finding, active medications, case management and directly observed therapy are the foundations for the management of TB. The current TB epidemic, centered in resource-limited settings is fueled by the HIV-1 epidemic. Lack of ability to diagnose and treat drug-resistant TB has led to development of more extensive patterns of resistance. Among the currently available drugs, there is reason to hope that rifamycins paired with fluoroquinolones will lead to shorter treatment regimens for drug-susceptible TB. As the result of novel public-private collaborations and investments of resources, new drugs are being developed. These include TMC207, already shown to have activity early in the treatment of multidrug-resistant TB and others that are likely to be active against persistor organisms, and have the prospect to dramatically shorten treatment courses for active and latent TB. Given that these drugs have novel mechanisms of action, combinations have the prospect to be highly active even against multidrug-resistant organisms.

Human lung immunity against Mycobacterium tuberculosis: insights into pathogenesis and protection

The study of human pulmonary immunity against Mycobacterium tuberculosis (M.tb) provides a unique window into the biological interactions between the human host and M.tb within the broncho-alveolar microenvironment, the site of natural infection. Studies of bronchoalveolar cells (BACs) and lung tissue evaluate innate, adaptive, and regulatory immune mechanisms that collectively contribute to immunological protection or its failure. In aerogenically M.tb-exposed healthy persons lung immune responses reflect early host pathogen interactions that may contribute to sterilization, the development of latent M.tb infection, or progression to active disease. Studies in these persons may allow the identification of biomarkers of protective immunity before the initiation of inflammatory and disease-associated immunopathological changes. In healthy close contacts of patients with tuberculosis (TB) and during active pulmonary TB, immune responses are compartmentalized to the lungs and characterized by an exuberant helper T-cell type 1 response, which as suggested by recent evidence is counteracted by local suppressive immune mechanisms. Here we discuss how exploring human lung immunity may provide insights into disease progression and mechanisms of failure of immunological protection at the site of the initial host-pathogen interaction. These findings may also aid in the identification of new biomarkers of protective immunity that are urgently needed for the development of new and the improvement of current TB vaccines, adjuvant immunotherapies, and diagnostic technologies. To facilitate further work in this area, methodological and procedural approaches for bronchoalveolar lavage studies and their limitations are also discussed.

Clinical Use of Interferon-gamma

Interferon gamma (IFN-gamma), a pleotropic cytokine, has been shown to be important to the function of virtually all immune cells and both innate and adaptive immune responses. In 1986, early clinical trials of this cytokine began to evaluate its therapeutic potential. The initial studies focused on the tolerability and pharmacology of IFN-gamma and systematically determined its antitumor and anti-infection activities. In the 20-plus years since those first trials, IFN-gamma has been used in a wide variety of clinical indications, which are reviewed in this article.

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.

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.

Inhaled therapeutics for prevention and treatment of pneumonia

The lungs are the most common site of serious infection owing to their large surface area exposed to the external environment and minimum barrier defense. However, this architecture makes the lungs readily available for topical therapy. Therapeutic aerosols include those directed towards improving mucociliary clearance of pathogens, stimulation of innate resistance to microbial infection, cytokine stimulation of immune function and delivery of antibiotics. In our opinion inhaled antimicrobials are underused, especially in patients with difficult-to-treat lung infections. The use of inhaled antimicrobial therapy has become an important part of the treatment of airway infection with Pseudomonas aeruginosa in cystic fibrosis and the prevention of invasive fungal infection in patients undergoing heart and lung transplantation. Cytokine inhaled therapy has also been explored in the treatment of neoplastic and infectious disease. The choice of pulmonary drug delivery systems remains critical as air-jet and ultrasonic nebulizer may deliver sub-optimum drug concentration if not used properly. In future development of this field, we recommend an emphasis on the study of the use of aerosolized hypertonic saline solution to reduce pathogen burden in the airways of subjects infected with microbes of low virulence, stimulation of innate resistance to prevent pneumonia in immunocompromised subjects using cytokines or synthetic pathogen-associated molecular pattern analogues and more opportunities for the use of inhaled antimicrobials. These therapeutics are still in their infancy but show great promise.

Management of multidrug-resistant tuberculosis: Update 2007

Multidrug-resistant tuberculosis (MDR-TB) with bacillary resistance to at least isoniazid and rifampicin in vitro is a worldwide phenomenon. Hot spots of the disease are found scattered in different continents. Prevention of its development through good tuberculosis control programmes operating under the directly observed therapy, short-course (DOTS) strategy is of paramount importance. However, with established MDR-TB, treatment with alternative and specific chemotherapy is necessary to achieve a beneficial outcome. Such an approach on a programme basis is currently known as the 'DOTS-Plus' strategy. Second-line (reserve) drugs utilized in the treatment of MDR-TB are generally less potent and more toxic, perhaps with the notable exceptions of some fluoroquinolones and injectable agents. Surgery has a distinct adjunctive role for the management of MDR-TB in selected patients. The emergence of extensively drug-resistant tuberculosis (XDR-TB), that is, MDR-TB with additional bacillary resistance to the fluoroquinolones and injectables, has provided a very alarming challenge to global health, as the disease currently has a low cure rate and high mortality. In order to combat XDR-TB, strengthening of DOTS and DOTS-Plus programmes is mandatory, especially in the face of surging HIV infection. Furthermore, more attention needs to be focused on developing new drugs with potent bactericidal and sterilizing activities and low side-effects, and above all, drugs that are affordable for communities worldwide.

Therapeutic effect of recombinant adenovirus encoding interferon-gamma in a murine model of progressive pulmonary tuberculosis

We constructed recombinant adenoviruses encoding murine interferon-gamma (AdIFNgamma) and tested its therapeutic efficiency in a well characterized model of progressive pulmonary tuberculosis (TB) in Balb/c mice, infected through the trachea with the laboratory drug-susceptible H37Rv strain or multidrug-resistant (MDR) clinical isolate. When the disease was in a late phase, 2 months after infection, we administered by intratracheal cannulation a single dose [1.7 x 10(9) plaque forming units (pfu)] of AdIFNgamma or the control adenovirus. Groups of mice were killed at different time-points and the lungs were examined to determine bacilli colony forming units (CFU), cytokine/chemokine gene expression, and CD4/CD8 subpopulations, and also subjected to automated histomorphometry. In comparison with the control group, after 2 weeks of treatment and during the next 6 months, AdIFNgamma-treated animals infected with either the H37Rv strain or the MDR strain showed significantly lower bacilli loads and tissue damage (pneumonia), higher expressions of IFN-gamma, tumor necrosis factor (TNF), and inducible nitric oxide synthase (iNOS), and bigger granulomas. When compared with the results from conventional chemotherapy or AdIFNgamma treatment alone, the combined treatment with AdIFNgamma plus conventional chemotherapy shortened the time taken for reduction of bacillary load. This shows that gene therapy with AdIFNgamma efficiently reconstituted the protective immune response and controlled the progress of pulmonary TB produced by MDR or non-MDR strains.

The immunopathogenesis of chronic obstructive pulmonary disease: insights from recent research

Chronic obstructive pulmonary disease (COPD) progression is characterized by accumulation of inflammatory mucous exudates in the lumens of small airways, and thickening of their walls, which become infiltrated by innate and adaptive inflammatory immune cells. Infiltration of the airways by polymorphonuclear and mononuclear phagocytes and CD4 T cells increases with COPD stage, but the cumulative volume of the infiltrate does not change. By contrast, B cells and CD8 T cells increase in both the extent of their distribution and in accumulated volume, with organization into lymphoid follicles. This chronic lung inflammation is also associated with a tissue repair and remodeling process that determines the ultimate pathologic phenotype of COPD. Why these pathologic abnormalities progress in susceptible individuals, even after removal of the original noxious stimuli, remains mysterious. However, important clues are emerging from analysis of pathologic samples from patients with COPD and from recent discoveries in basic immunology. We consider the following relevant information: normal limitations on the innate immune system's ability to generate adaptive pulmonary immune responses and how they might be overcome by tobacco smoke exposure; the possible contribution of autoimmunity to COPD pathogenesis; and the potential roles of ongoing lymphocyte recruitment versus in situ proliferation, of persistently activated resident lung T cells, and of the newly described T helper 17 (Th17) phenotype. We propose that the severity and course of acute exacerbations of COPD reflects the success of the adaptive immune response in appropriately modulating the innate response to pathogen-related molecular patterns ("the Goldilocks hypothesis").

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.

IFN-γTherapy of Tuberculosis and Related Infections

It is firmly established that interferon-gamma (IFN-gamma) plays a mandatory role in acquired protective immunity to pathogenic mycobacteria and other intracellular pathogens. Therefore, it seems conceivable that application of recombinant IFN-gamma could be exploited for the treatment of tuberculosis. However, the results of experimental studies and clinical trials, conducted mostly in patients with multidrug resistant (MDR) disease, have thus far been only moderately encouraging. Further studies are now needed to determine if a greater clinical benefit from IFN-gamma could be obtained for the prophylactic treatment of latent tuberculosis infection and for shortening of the protracted standard chemotherapy regimen. Thus, aerosolized IFN-gamma treatment could be particularly beneficial to AIDS patients at high risk of developing mycobacterial infections, that is, those with significantly declined CD4(+) T cell counts. This review describes the current state of research on IFN-gamma interventions in tuberculosis and related infections and highlights some of the future opportunities.

Subcutaneously administered interferon-gamma for the treatment of multidrug-resistant pulmonary tuberculosis

OBJECTIVE

We evaluated the clinical and laboratory effects of subcutaneously administered interferon-gamma (IFN-gamma) in the treatment of chronic and advanced multidrug-resistant tuberculosis (MDR-TB).

DESIGN

Eight patients with sputum smear and culture persistently positive MDR-TB were subcutaneously administered 2 million international units of recombinant human IFN-gamma three times a week for 24 weeks (72 doses total) between December 2002 and May 2003. Subjects also received a customized drug regimen containing second- and third-line antituberculosis agents based upon drug susceptibility testing and previous treatment history.

RESULTS

Body weight remained stable or slightly decreased in all subjects during the study period, and none displayed radiographic improvement on serial chest computed tomography scanning. Sputum smears and cultures remained positive for all patients, and there was no increase in the mean time to yield a positive culture (from 16.5+/-6.4 to 11.8+/-4.9 days). There was no enhancement of cell-mediated immune responses in terms of production of IFN-gamma or IL-10, or of composition of lymphocytes among peripheral blood mononuclear cells. In four patients, therapy was discontinued because of adverse reactions.

CONCLUSION

In patients with chronic and advanced MDR-TB, subcutaneous IFN-gamma treatment did not result in improvement in clinical, radiologic, microbiologic, or immunologic parameters.

Inhaled cytokines and cytokine antagonists

Cytokine and cytokine antagonist have provided novel and effective therapies for many human diseases. A number of approved cytokines including the interferons (alpha, beta and gamma), interleukin-2 (IL-2), granulocyte macrophage colony stimulating factor (GM-CSF) as well as novel cytokine antagonists have been administered by the pulmonary route for both local lung disease and as a non-invasive method for systemic delivery. We review the published clinical experience of inhaled cytokines and cytokine antagonists. We discuss the limitations of the existing data and the type of clinical data desired to establish the advantages and safety of inhaled cytokines and cytokine antagonists.

Mucosal immunotherapy of tuberculosis: is there a value in passive IgA?

Immunotherapeutic approaches, which have been considered for tuberculosis (TB), include immuno-potentiating or suppressing agents, cytokines, antibodies, DNA vaccines, non-pathogenic mycobacteria and mycobacterial extracts. While most or all of these potential agents showed at least some degree of promise in various experimental models, few progressed to clinical trials, yielding only moderately encouraging, though controversial results. Consequently, further research is required, as the need for an immunological agent, adjunct to chemotherapy, remains strongly justified. Its purpose is to shorten the currently protracted (6-9 months) drug treatment and thus increase compliance rates, which are most disappointing in areas with the highest disease prevalence. Using a mouse model of Mycobacterium tuberculosis (Mtb) infection, we recently reported, that an intranasally given monoclonal IgA antibody significantly reduced the bacterial load in the infected lungs, and that this protective effect of IgA could be further extended by co-inoculation with interferon gamma (IFNgamma). In this review, we describe the main features of IgA and its cellular receptors, the extent and possible mechanisms of passive vaccination with an IgA monoclonal antibody against the alpha-crystallin antigen of Mtb and discuss the potentials of this approach in the wider context of immunotherapy of TB.

Infectious lung complications in patients with HIV/AIDS

PURPOSE OF REVIEW

The aim of this article is to review recent observations in the area of infectious lung complications in individuals with human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS). Since the immunodeficiency was first characterized, it has been associated with enhanced susceptibility to opportunistic infection, and life-threatening infections of the lung in particular. In the past few years there have been a large number of reports documenting the changes to this disease profile in the age of highly active antiretroviral therapy (HAART). Furthermore, there have been considerable advances in our understanding of the immunology and vaccinology of many of the pathogens implicated in pulmonary infections in this context, including Mycobacterium tuberculosis, Streptococcus pneumoniae and Pneumocystis pneumonia.

RECENT FINDINGS

In considering the time-course and spectrum of HIV-associated respiratory infections, the field must now be divided into studies undertaken in parts of the world where HAART is accessible and those where it is not. Despite the enormous impact of HAART, it has brought with it a new set of concerns, including the effects of immune restoration disease (IRD), and the complex interplay between HAART and tuberculosis therapy.

SUMMARY

The overriding conclusion from recent experience is that HAART, in those parts of the world where it is readily available, has changed the clinical picture of infections associated with HIV, and needs to be available to patients across the developing world as well. Furthermore there have been important developments in vaccination programs against pathogens involved in HIV-associated pneumonia.

Interleukin-10 induces inhibitory C/EBPbeta through STAT-3 and represses HIV-1 transcription in macrophages

Pulmonary tuberculosis (TB) has been characterized by inflammation with increased pro- or anti-inflammatory cytokines produced by macrophages. We have reported that IFN produces inhibitory C/EBPbeta and represses transcription of the HIV-1 LTR in macrophages. STAT-1 and type I IFN receptor knockout mice have macrophages that are defective in IFN signaling, yet LPS stimulation induces inhibitory C/EBPbeta, demonstrating that other cytokines can induce this repressor. LPS or Mycobacterium tuberculosis-derived lipoarabinomannan induce the anti-inflammatory cytokine interleukin (IL)-10, which represses the HIV-1 LTR in differentiated THP-1 macrophages by inducing inhibitory C/EBPbeta. In contrast, in undifferentiated THP-1 monocytes, IL-10 did not inhibit HIV-1 replication or induce C/EBPbeta. IL-10 signal transduction uses STAT-3, and macrophages from STAT-3-/- mice fail to produce inhibitory C/EBPbeta after LPS or IL-10 stimulation. Transfection of STAT-3 into THP-1 cells enhances C/EBPbeta promoter activity. THP-1 differentiation also increases STAT-3 protein, but not STAT-3 gene transcription, and induces a translational regulator, CUG-binding protein, that was essential for production of C/EBPbeta. Differentiation induced post-transcriptional regulation is required to produce inhibitory C/EBPbeta in response to IL-10. Only macrophages are able to repress HIV-1 LTR promoter activity and inhibit viral replication in response to IL-10 or type I IFN.

Randomized, double-blind, placebo-controlled, dose-escalating study of aerosolized interferon gamma-1b in patients with mild to moderate cystic fibrosis lung disease

Interferon gamma-1b (IFN-gamma1b) is a pleiotropic cytokine with immunomodulatory activities that could decrease bacterial burden, inflammation, and obstruction in patients with CF. Patients with CF (> or =12 years old, FEV1 > or =40% predicted) were randomly assigned to sequential dose cohorts inhaling 500 microg IFN-gamma1b, 1,000 microg IFN-gamma1b, or placebo by Respirgard II nebulizer thrice weekly for 12 weeks. Sputum bacterial density and spirometry were measured. Safety, antibiotic use, hospitalization, and sputum neutrophils, elastase, DNA, IL-8, and myeloperoxidase were also evaluated. Sixty-six patients (mean age, 24 years, with mean baseline FEV1 of 74 +/- 20 (SD) percent predicted) were studied. One patient had bronchospasm after the first dose of IFN-gamma1b; the overall withdrawal rate was 15% (5 in the placebo group, 2 in the 500-microg IFN-gamma1b group, and 3 in the 1,000 microg IFN-gamma1b group). The 500-microg IFN-gamma1b dose was well-tolerated, but the 1,000-mug dose cohort, who had a higher baseline bacterial density than placebo patients (mean difference, 1.2 log(10) CFU/g sputum, 95% confidence interval (CI), 0.1,2.8, P=0.04), had 24% more hospitalizations for exacerbation than placebo patients (95% CI, 2,45%, P=0.05). There was a 0.12-l difference between the 500-microg IFN-gamma1b and placebo groups with respect to the 12-week change in FEV1 (active group minus placebo group, 95% CI, -0.03,0.26, P=0.11), as compared to a 0.01-l difference between the 1,000-microg IFN-gamma1b and placebo groups (95% CI, -0.16,0.17, P=0.96). No effects of IFN-gamma1b were seen in sputum bacterial density or inflammatory biomarkers at 12 weeks. Aerosolized IFN-gamma1b did not improve pulmonary function, reduce sputum bacterial density, or affect inflammatory sputum markers in patients with mild-moderate lung disease.

IL-10 down-regulates costimulatory molecules on Mycobacterium tuberculosis-pulsed macrophages and impairs the lytic activity of CD4 and CD8 CTL in tuberculosis patients

Activation of T cells requires both TCR-specific ligation and costimulation through accessory molecules during T cell priming. IFNgamma is a key cytokine responsible for macrophage activation during Mycobacterium tuberculosis (Mtb) infection while IL-10 is associated with suppression of cell mediated immunity in intracellular infection. In this paper we evaluated the role of IFNgamma and IL-10 on the function of cytotoxic T cells (CTL) and on the modulation of costimulatory molecules in healthy controls and patients with active tuberculosis (TB). gamma-irradiated-Mtb (i-Mtb) induced IL-10 production from CD14(+) cells from TB patients. Moreover, CD3(+) T cells of patients with advanced disease also produced IL-10 after i-Mtb stimulation. In healthy donors, IL-10 decreased the lytic activity of CD4(+) and CD8(+) T cells whereas it increased gammadelta-mediated cytotoxicity. Furthermore, we found that the presence of IL-10 induced a loss of the alternative processing pathways of antigen presentation along with a down-regulation of the expression of costimulatory molecule expression on monocytes and macrophages from healthy individuals. Conversely, neutralization of endogenous IL-10 or addition of IFNgamma to either effector or target cells from TB patients induced a strong lytic activity mediated by CD8(+) CTL together with an up-regulation of CD54 and CD86 expression on target cells. Moreover, we observed that macrophages from TB patients could use alternative pathways for i-Mtb presentation. Taken together, our results demonstrate that the presence of IL-10 during Mtb infection might contribute to mycobacteria persistence inside host macrophages through a mechanism that involved inhibition of MHC-restricted cytotoxicity against infected macrophages.

Mycobacterium tuberculosis-induced CXCR4 and chemokine expression leads to preferential X4 HIV-1 replication in human macrophages

Opportunistic infections such as pulmonary tuberculosis (TB) increase local HIV-1 replication and mutation. As AIDS progresses, alteration of the HIV-1 gp120 V3 sequence is associated with a shift in viral coreceptor use from CCR5 (CD195) to CXCR4 (CD184). To better understand the effect of HIV/TB coinfection, we screened transcripts from bronchoalveolar lavage cells with high density cDNA arrays and found that CXCR4 mRNA is increased in patients with TB. Surprisingly, CXCR4 was predominately expressed on alveolar macrophages (AM). Mycobacterium tuberculosis infection of macrophages in vitro increased CXCR4 surface expression, whereas amelioration of disease reduced CXCR4 expression in vivo. Bronchoalveolar lavage fluid from TB patients had elevated levels of CCL4 (macrophage inflammatory protein-1beta), CCL5 (RANTES), and CX3CL1 (fractalkine), but not CXCL12 (stromal-derived factor-1alpha). We found that M. tuberculosis infection of macrophages in vitro increased viral entry and RT of CXCR4-using [corrected] HIV-1, but not of CCR5-using [corrected] HIV-1. Lastly, HIV-1 derived from the lung contains CD14, suggesting that they were produced in AM. Our results demonstrate that TB produces a permissive environment for replication of CXCR4-using virus by increasing CXCR4 expression in AM and for suppression of CCR5-using HIV-1 by increasing CC chemokine expression. These changes explain in part why TB accelerates the course of AIDS. CXCR4 inhibitors are a rational therapeutic approach in HIV/TB coinfection.

Specific engagement of TLR4 or TLR3 does not lead to IFN-beta-mediated innate signal amplification and STAT1 phosphorylation in resident murine alveolar macrophages

The innate immune response must be mobilized promptly yet judiciously via TLRs to protect the lungs against pathogens. Stimulation of murine peritoneal macrophage (PMphi) TLR4 or TLR3 by pathogen-associated molecular patterns (PAMPs) typically induces type I IFN-beta, leading to autocrine activation of the transcription factor STAT1. Because it is unknown whether STAT1 plays a similar role in the lungs, we studied the response of resident alveolar macrophages (AMphi) or control PMphi from normal C57BL/6 mice to stimulation by PAMPs derived from viruses (polyriboinosinic:polyribocytidylic acid, specific for TLR3) or bacteria (Pam(3)Cys, specific for TLR2, and repurified LPS, specific for TLR4). AMphi did not activate STAT1 by tyrosine phosphorylation on Y701 following stimulation of any of these three TLRs, but readily did so in response to exogenous IFN-beta. This unique AMphi response was not due to altered TLR expression, or defective immediate-early gene response, as measured by expression of TNF-alpha and three beta chemokines. Instead, AMphi differed from PMphi in not producing bioactive IFN-beta, as confirmed by ELISA and by the failure of supernatants from TLR-stimulated AMphi to induce STAT1 phosphorylation in PMphi. Consequently, AMphi did not produce the microbicidal effector molecule NO following TLR4 or TLR3 stimulation unless exogenous IFN-beta was also added. Thus, murine AMphi respond to bacterial or viral PAMPs by producing inflammatory cytokines and chemokines, but because they lack the feed-forward amplification typically mediated by autocrine IFN-beta secretion and STAT1 activation, require exogenous IFN to mount a second phase of host defense.

Regional Deposition of Aerosolized Interferon-γ in Pulmonary Tuberculosis

STUDY OBJECTIVES

Aerosol interferon-gamma (IFN-gamma) is a potential immunomodulator in the treatment of pulmonary tuberculosis (TB). Previous investigations demonstrated conversion of sputum smears in five patients with multidrug-resistant TB after 12 treatments over 1 month, and induction of signaling molecules in 10 of 11 drug-sensitive TB patients using BAL. The objective of the current study was to evaluate particle size and deposition pattern in patients with TB receiving aerosol IFN-gamma treatment.

DESIGN

Particle size was determined with a cascade impactor, and deposition of IFN-gamma mixed with (99m)Tc-labeled human serum albumin was assessed using a gamma camera. Local levels of IFN-gamma were measured in BAL using enzyme-linked immunosorbent assays. Study patients/intervention: Fourteen patients with pulmonary TB received IFN-gamma aerosol (500 micro g) for 12 treatments in addition to antimycobacterial therapy with BAL before and after IFN-gamma aerosol treatment. Eight patients with minimal-to-moderate parenchymal involvement underwent deposition studies. Deposited (99m)Tc-labeled IFN-gamma aerosol was partitioned between upper airways and lungs using attenuation correction measurements. (133)Xe equilibrium scanning, (133)Xe washout, and (99m)Tc- macroaggregate injection defined regional lung volume, ventilation, and perfusion.

RESULTS

Upper airway deposition was significant often exceeding lung deposition (53.9 +/- 7.09 micro g vs 35.8 +/- 2.73 micro g, respectively [mean +/- SE]). IFN-gamma levels measured in BAL fluid were significantly increased with aerosol treatment (0.83 +/- 0.43 micro g before vs 24.76 +/- 8.71 micro g after, p </= 0.017), and IFN-gamma levels correlated with regional deposition of IFN-gamma aerosol (r = 0.823). Four-quadrant analysis of regional lung deposition best correlated with regional perfusion (r = 0.422, p = 0.013) with penetration of aerosol into areas of obvious radiographic infiltration on chest radiograph.

CONCLUSIONS

Aerosol therapy with IFN-gamma in patients with pulmonary TB is widely distributed and results in significant enhancement of IFN-gamma levels in the lower respiratory tract. In patients without lung destruction, IFN-gamma aerosol may be an adjuvant to enhance the local immune response.

Aerosolized gamma interferon (IFN-gamma) induces expression of the genes encoding the IFN-gamma-inducible 10-kilodalton protein but not inducible nitric oxide synthase in the lung during tuberculosis

Gamma interferon (IFN-gamma) is critical in the immune response against Mycobacterium tuberculosis. In an ongoing trial of aerosol IFN-gamma in conjunction with standard drug therapy, we have observed activation of IFN signaling in bronchoalveolar lavage (BAL) cells from tuberculosis (TB) patients. We hypothesized that aerosol IFN-gamma treatment of pulmonary TB would increase expression of genes important for the control of TB. We investigated the expression of downstream genes by measuring inducible nitric oxide synthase (iNOS) and the chemokine IFN-inducible 10-kDa protein (IP-10) by real-time quantitative reverse transcription-PCR. In vitro, M. tuberculosis induced IP-10, and IFN-gamma stimulated this further, with no effect on iNOS expression. We studied 21 patients with pulmonary TB and 7 healthy subjects. Similar to the in vitro model, IP-10 mRNA was increased in BAL cells from TB patients and was augmented after treatment with aerosolized IFN-gamma. TB was also associated with elevated iNOS mRNA, but aerosolized IFN-gamma did not further enhance expression. Genomic analysis identified 1,300 of 4,058 genes expressed in BAL cells from six TB patients before and after 1 month of therapy, including aerosolized IFN-gamma. However, only 15 genes were differentially regulated by IFN-gamma. We conclude that iNOS and IP-10 mRNA expression is increased in TB but that aerosol IFN-gamma treatment increases expression of few genes in the human lung.

Exogenous gamma and alpha/beta interferon rescues human macrophages from cell death induced by Bacillus anthracis

During the recent bioterrorism-related outbreaks, inhalational anthrax had a 45% mortality in spite of appropriate antimicrobial therapy, underscoring the need for better adjuvant therapies. The variable latency between exposure and development of disease suggests an important role for the host's innate immune response. Alveolar macrophages are likely the first immune cells exposed to inhalational anthrax, and the interferon (IFN) response of these cells comprises an important arm of the host innate immune response to intracellular infection with Bacillus anthracis. Furthermore, IFNs have been used as immunoadjuvants for treatment of another intracellular pathogen, Mycobacterium tuberculosis. We established a model of B. anthracis infection with the Sterne strain (34F(2)) which contains lethal toxin (LeTx). 34F(2) was lethal to murine and human macrophages. Treatment with IFNs significantly improved cell viability and reduced the number of germinated intracellular spores. Infection with 34F(2) failed to induce the latent transcription factors signal transducer and activators of transcription 1 (STAT1) and ISGF-3, which are central to the IFN response. Furthermore, 34F(2) reduced STAT1 activation in response to exogenous alpha/beta IFN, suggesting direct inhibition of IFN signaling. Even though 34F(2) has LeTx, there was no mitogen-activated protein kinase kinase 3 cleavage and p38 was normally induced, suggesting that these early effects of B. anthracis infection in macrophages are independent of LeTx. These data suggest an important role for both IFNs in the control of B. anthracis and the potential benefit of using exogenous IFN as an immunoadjuvant therapy.

Surfactant protein A modulates the inflammatory response in macrophages during tuberculosis

Tuberculosis leads to immune activation and increased human immunodeficiency virus type 1 (HIV-1) replication in the lung. However, in vitro models of mycobacterial infection of human macrophages do not fully reproduce these in vivo observations, suggesting that there are additional host factors. Surfactant protein A (SP-A) is an important mediator of innate immunity in the lung. SP-A levels were assayed in the human lung by using bronchoalveolar lavage (BAL). There was a threefold reduction in SP-A levels during tuberculosis only in the radiographically involved lung segments, and the levels returned to normal after 1 month of treatment. The SP-A levels were inversely correlated with the percentage of neutrophils in BAL fluid, suggesting that low SP-A levels were associated with increased inflammation in the lung. Differentiated THP-1 macrophages were used to test the effect of decreasing SP-A levels on immune function. In the absence of infection with Mycobacterium tuberculosis, SP-A at doses ranging from 5 to 0.01 micro g/ml inhibited both interleukin-6 (IL-6) production and HIV-1 long terminal repeat (LTR) activity. In macrophages infected with M. tuberculosis, SP-A augmented both IL-6 production and HIV-1 LTR activity. To better understand the effect of SP-A, we measured expression of CAAT/enhancer binding protein beta (C/EBPbeta), a transcription factor central to the regulation of IL-6 and the HIV-1 LTR. In macrophages infected with M. tuberculosis, SP-A reduced expression of a dominant negative isoform of C/EBPbeta. These data suggest that SP-A has pleiotropic effects even at the low concentrations found in tuberculosis patients. This protein augments inflammation in the presence of infection and inhibits inflammation in uninfected macrophages, protecting uninvolved lung segments from the deleterious effects of inflammation.