Protective role of interferon gamma, tumor necrosis factor alpha and interleukin-6 in Mycobacterium tuberculosis and M. avium infections

Unique Reciprocal Association Seen Between Latent Tuberculosis Infection and Diabetes Is Due to Immunoendocrine Modulation (DM-LTB-1)

Aim

The prevalence of latent tuberculosis infection (LTBI) among diabetes patients is poorly studied. In the present study, the prevalence of LTBI among pre-diabetes and diabetes patients was studied, along with immunoendocrine biomarkers (n = 804).

Methods

LTBI was screened by Quantiferon TB gold in Normal glucose tolerance [(NGT); n = 170, [Pre-diabetes (PDM; n = 209), Newly diagnosed diabetes (NDM; n = 165) and Known diabetes (KDM; n = 260) subjects. CRP, TNF-α, IL-6, IL-1β, IFN-β, IL-12, IFN-γ, IL-2, insulin, leptin, and adiponectin levels in serum and IFN-γ levels in quantiferon supernatants were quantified by ELISA. The expression of T-bet was quantified using qRT-PCR. Serum TBARS and nitrite levels were quantified by colorimetry.

Results

The LTBI prevalence was 32% in NGT, 23% in PDM, 24% in NDM, and 32% in KDM groups, with an adjusted OR of 0.61 (p < 0.05). Downregulation of CRP, TNF-α, and nitrites and upregulation of adiponectin could be responsible for LTBI mediated protection against insulin resistance (IR), while the high levels of IL-1β, IL-12, and leptin could be responsible for IR mediated anti-TB immunity. The defective antigen-specific IFN-γ response, as seen in the KDM group, could be responsible for the low detection rate of LTBI and high probability of endogenous reactivation.

Conclusion

There appears to be a biphasic relationship between diabetes-latent tuberculosis: At the early stages of diabetes it is reciprocal, while at a late stage it is synergistic, this important phenomenon obviously needs further research.

[A case of neuromyelitis optica associated with pulmonary Mycobacterium avium complex disease]

A 62-year-old woman suffering from pulmonary Mycobacterium avium complex (MAC) disease was admitted to our hospital with fever, visual impairment, and lower limb weakness. MRI detected lesions in the optic chiasm and spinal cord extending the length of 6 vertebrae. The anti-aquaporin 4 (AQP4) antibody titer determined by ELISA was elevated to 8.3 IU/l. On the basis of these findings, the patient was diagnosed as having neuromyelitis optica (NMO), when chest CT also demonstrated exacerbation of pulmonary lesions. Methylprednisolone pulse therapy and double-filtered plasma exchange ameliorated the symptoms, and the EDSS score improved from 8.5 to 6.5. Six months later, visual impairment recurred, although ELISA showed that the anti-AQP4 antibody titer had become undetectable. Also, the CSF interleukin-6 (IL-6) level was elevated to 34.8 pg/ml. There have been few reports of NMO associated with pulmonary MAC disease. An increase of IL-6 is considered to exacerbate the clinical picture of NMO, whereas it may suppress progression of the pulmonary MAC disease. Exacerbation of the pulmonary MAC disease and the following internal counteraction with IL-6 may have resulted in a NMO relapse. The present patient was therefore administered eculizumab but not satralizumab, a humanized anti-IL-6 receptor antibody, for prevention of NMO recurrence.

De novo histidine biosynthesis protects Mycobacterium tuberculosis from host IFN-γ mediated histidine starvation

Intracellular pathogens including Mycobacterium tuberculosis (Mtb) have evolved with strategies to uptake amino acids from host cells to fulfil their metabolic requirements. However, Mtb also possesses de novo biosynthesis pathways for all the amino acids. This raises a pertinent question- how does Mtb meet its histidine requirements within an in vivo infection setting? Here, we present a mechanism in which the host, by up-regulating its histidine catabolizing enzymes through interferon gamma (IFN-γ) mediated signalling, exerts an immune response directed at starving the bacillus of intracellular free histidine. However, the wild-type Mtb evades this host immune response by biosynthesizing histidine de novo, whereas a histidine auxotroph fails to multiply. Notably, in an IFN-γ^-/- mouse model, the auxotroph exhibits a similar extent of virulence as that of the wild-type. The results augment the current understanding of host-Mtb interactions and highlight the essentiality of Mtb histidine biosynthesis for its pathogenesis.

The double-edged sword of Tregs in M tuberculosis, M avium, and M absessus infection

Immunity against different Mycobacteria species targeting the lung requires distinctly different pulmonary immune responses for bacterial clearance. Many parameters of acquired and regulatory immune responses differ quantitatively and qualitatively from immunity during infection with Mycobacteria species. Nontuberculosis Mycobacteria species (NTM) Mycobacterium avium- (M avium), Mycobacterium abscessus-(M abscessus), and the Mycobacteria species Mycobacterium tuberculosis-(Mtb). Herein, we discuss the potential implications of acquired and regulatory immune responses in the context of animal and human studies, as well as future directions for efforts to treat Mycobacteria diseases.

The New Frontier of Host-Directed Therapies for Mycobacterium avium Complex

Mycobacterium avium complex (MAC) is an increasingly important cause of morbidity and mortality, and is responsible for pulmonary infection in patients with underlying lung disease and disseminated disease in patients with AIDS. MAC has evolved various virulence strategies to subvert immune responses and persist in the infected host. Current treatment for MAC is challenging, requiring a combination of multiple antibiotics given over a long time period (for at least 12 months after negative sputum culture conversion). Moreover, even after eradication of infection, many patients are left with residual lung dysfunction. In order to address similar challenges facing the management of patients with tuberculosis, recent attention has focused on the development of novel adjunctive, host-directed therapies (HDTs), with the goal of accelerating the clearance of mycobacteria by immune defenses and reducing or reversing mycobacterial-induced lung damage. In this review, we will summarize the evidence supporting specific adjunctive, HDTs for MAC, with a focus on the repurposing of existing immune-modulatory agents targeting a variety of different cellular pathways. We also highlight areas meriting further investigation.

Nicotine modulates molecules of the innate immune response in epithelial cells and macrophages during infection with M. tuberculosis

Smoking increases susceptibility to becoming infected with and developing tuberculosis. Among the components of cigarette smoke, nicotine has been identified as the main immunomodulatory molecule; however, its effect on the innate immune system is unknown. In the present study, the effect of nicotine on molecules of the innate immune system was evaluated. Lung epithelial cells and macrophages were infected with Mycobacterium tuberculosis (Mtb) and/or treated with nicotine. The results show that nicotine alone decreases the expression of the Toll-like receptors (TLR)-2, TLR-4 and NOD-2 in all three cell types, as well as the production of the SP-D surfactant protein in type II pneumocytes. Moreover, it was observed that nicotine decreases the production of interleukin (IL)-6 and C-C chemokine ligand (CCL)5 during Mtb infection in epithelial cells (EpCs), whereas in macrophages derived from human monocytes (MDMs) there is a decrease in IL-8, IL-6, tumor necrosis factor (TNF)-α, IL-10, CCL2, C-X-C chemokine ligand (CXCL)9 and CXCL10 only during infection with Mtb. Although modulation of the expression of cytokines and chemokines appears to be partially mediated by the nicotinic acetylcholine receptor α7, blocking this receptor found no effect on the expression of receptors and SP-D. In summary, it was found that nicotine modulates the expression of innate immunity molecules necessary for the defense against tuberculosis.

Nontuberculous mycobacterium M. avium infection predisposes aged mice to cardiac abnormalities and inflammation

Biological aging dynamically alters normal immune and cardiac function, favoring the production of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) and increased instances of cardiac distress. Cardiac failure is the primary reason for hospitalization of the elderly (65+ years). The elderly are also increasingly susceptible to developing chronic bacterial infections due to aging associated immune abnormalities. Since bacterial infections compound the rates of cardiac failure in the elderly, and this phenomenon is not entirely understood, the interplay between the immune system and cardiovascular function in the elderly is of great interest. Using Mycobacterium avium, an opportunistic pathogen, we investigated the effect of mycobacteria on cardiac function in aged mice. Young (2-3 months) and old (18-20 months) C57BL/6 mice were intranasally infected with M. avium strain 104, and we compared the bacterial burden, immune status, cardiac electrical activity, pathology, and function of infected mice against uninfected age-matched controls. Herein, we show that biological aging may predispose old mice infected with M. avium to mycobacterial dissemination into the heart tissue and this leads to cardiac dysfunction. M. avium infected old mice had significant dysrhythmia, cardiac hypertrophy, increased recruitment of CD45+ leukocytes, cardiac fibrosis, and increased expression of inflammatory genes in isolated heart tissue. This is the first study to report the effect of mycobacteria on cardiac function in an aged model. Our findings are critical to understanding how nontuberculous mycobacterium (NTM) and other mycobacterial infections contribute to cardiac dysfunction in the elderly population.

Genetic Variation/Evolution and Differential Host Responses Resulting from In-Patient Adaptation of Mycobacterium avium

Members of the Mycobacterium avium complex (MAC) are characterized as nontuberculosis mycobacteria and are pathogenic mainly in immunocompromised individuals. MAC strains show a wide genetic variability, and there is growing evidence suggesting that genetic differences may contribute to a varied immune response that may impact the infection outcome.

Members of the Mycobacterium avium complex (MAC) are characterized as nontuberculosis mycobacteria and are pathogenic mainly in immunocompromised individuals. MAC strains show a wide genetic variability, and there is growing evidence suggesting that genetic differences may contribute to a varied immune response that may impact the infection outcome. The current study aimed to characterize the genomic changes within M.avium isolates collected from single patients over time and test the host immune responses to these clinical isolates. Pulsed-field gel electrophoresis and whole-genome sequencing were performed on 40 MAC isolates isolated from 15 patients at the Department of Medical Microbiology at St. Olavs Hospital in Trondheim, Norway. Isolates from patients (patients 4, 9, and 13) for whom more than two isolates were available were selected for further analysis. These isolates exhibited extensive sequence variation in the form of single-nucleotide polymorphisms (SNPs), suggesting that M. avium accumulates mutations at higher rates during persistent infections than other mycobacteria. Infection of murine macrophages and mice with sequential isolates from patients showed a tendency toward increased persistence and the downregulation of inflammatory cytokines by host-adapted M. avium strains. The study revealed the rapid genetic evolution of M. avium in chronically infected patients, accompanied by changes in the virulence properties of the sequential mycobacterial isolates.

Nanocarriers for DNA Vaccines: Co-Delivery of TLR-9 and NLR-2 Ligands Leads to Synergistic Enhancement of Proinflammatory Cytokine Release

Adjuvants enhance immunogenicity of vaccines through either targeted antigen delivery or stimulation of immune receptors. Three cationic nanoparticle formulations were evaluated for their potential as carriers for a DNA vaccine, and muramyl dipeptide (MDP) as immunostimulatory agent, to induce and increase immunogenicity of Mycobacterium tuberculosis antigen encoding plasmid DNA (pDNA). The formulations included (1) trimethyl chitosan (TMC) nanoparticles, (2) a squalene-in-water nanoemulsion, and (3) a mineral oil-in-water nanoemulsion. The adjuvant effect of the pDNA-nanocomplexes was evaluated by serum antibody analysis in immunized mice. All three carriers display a strong adjuvant effect, however, only TMC nanoparticles were capable to bias immune responses towards Th1. pDNA naturally contains immunostimulatory unmethylated CpG motifs that are recognized by Toll-like receptor 9 (TLR-9). In mechanistic in vitro studies, activation of TLR-9 and the ability to enhance immunogenicity by simultaneously targeting TLR-9 and NOD-like receptor 2 (NLR-2) was determined by proinflammatory cytokine release in RAW264.7 macrophages. pDNA in combination with MDP was shown to significantly increase proinflammatory cytokine release in a synergistic manner, dependent on NLR-2 activation. In summary, novel pDNA-Ag85A loaded nanoparticle formulations, which induce antigen specific immune responses in mice were developed, taking advantage of the synergistic combinations of TLR and NLR agonists to increase the adjuvanticity of the carriers used.

Immunoevasion and immunosuppression of the macrophage by Mycobacterium tuberculosis

By virtue of their position at the crossroads between the innate and adaptive immune response, macrophages play an essential role in the control of bacterial infections. Paradoxically, macrophages serve as the natural habitat to Mycobacterium tuberculosis (Mtb). Mtb subverts the macrophage's mechanisms of intracellular killing and antigen presentation, leading ultimately to the development of tuberculosis (TB) disease. Here, we describe mechanisms of Mtb uptake by the macrophage and address key macrophage functions that are targeted by Mtb-specific effector molecules enabling this pathogen to circumvent host immune response. The macrophage functions described in this review include fusion between phagosomes and lysosomes, production of reactive oxygen and nitrogen species, antigen presentation and major histocompatibility complex class II expression and trafficking, as well as autophagy and apoptosis. All these are Mtb-targeted key cellular pathways, normally working in concert in the macrophage to recognize, respond, and activate 'proper' immune responses. We further analyze and discuss major molecular interactions between Mtb virulence factors and key macrophage proteins and provide implications for vaccine and drug development.

Nontuberculous mycobacterial osteomyelitis

Osteomyelitis caused by nontuberculous mycobacteria (NTM) can have severe consequences and a poor prognosis. Physicians therefore need to be alert to this condition, especially in immunocompromised patients. Although the pathogenesis of NTM osteomyelitis is still unclear, studies in immunodeficient individuals have revealed close relationships between NTM osteomyelitis and defects associated with the interleukin-12-interferon-γ-tumor necrosis factor-α axis, as well as human immunodeficiency virus infection, various immunosuppressive conditions, and diabetes mellitus. Culture and species identification from tissue biopsies or surgical debridement tissue play crucial roles in diagnosing NTM osteomyelitis. Suitable imaging examinations are also important. Adequate surgical debridement and the choice of appropriate, combined antibiotics for long-term anti-mycobacterial chemotherapy, based on in vitro drug susceptibility tests, are the main therapies for these bone infections. Bacillus Calmette-Guerin vaccination might have limited prophylactic value. The use of multiple drugs and long duration of treatment mean that the therapeutic process needs to be monitored closely to detect potential side effects. Adequate duration of anti-mycobacterial chemotherapy together with regular monitoring with blood and imaging tests are key factors determining the recovery outcome in patients with NTM osteomyelitis.

Cellular and humoral immune responses in sheep vaccinated with candidate antigens MAP2698c and MAP3567 from Mycobacterium avium subspecies paratuberculosis

Control of Johne's disease, caused by Mycobacterium avium subspecies paratuberculosis (MAP) in ruminants using commercially available vaccine reduces production losses, mortality, fecal shedding and histopathological lesions but does not provide complete protection from infection and interferes with serological diagnosis of Johne's disease and bovine tuberculosis. At this time no recombinant antigens have been found to provide superior protection compared to whole killed or live-attenuated MAP vaccines. Therefore, there is a need to evaluate more candidate MAP antigens. In this study recombinant MAP antigens MAP2698c and MAP3567 were formulated with four different MONTANIDE™ (ISA 50V2, 61VG, 71VG, and 201VG) adjuvants and evaluated for their ability to produce specific immune responses in vaccinated sheep. The cellular immune response was measured with an interferon-gamma (IFN-γ) release assay and the humoral immune response was measured by antibody detection enzyme linked immunosorbent assay. Recombinant vaccine formulation with the antigen MAP2698c and MONTANIDE™ ISA 201VG adjuvant produced strong whole-MAP as well as MAP2698c-specific IFN-γ responses in a high proportion of the vaccinated sheep. The formulation caused less severe injection site lesions in comparison to other formulations. The findings from this study suggest that the MAP2698c + 201VG should be evaluated in a challenge trial to determine the efficacy of this vaccine candidate.

Host response to nontuberculous mycobacterial infections of current clinical importance

The nontuberculous mycobacteria are a large group of acid-fast bacteria that are very widely distributed in the environment. While Mycobacterium avium was once regarded as innocuous, its high frequency as a cause of disseminated disease in HIV-positive individuals illustrated its potential as a pathogen. Much more recently, there is growing evidence that the incidence of M. avium and related nontuberculous species is increasing in immunocompetent individuals. The same has been observed for M. abscessus infections, which are very difficult to treat; accordingly, this review focuses primarily on these two important pathogens. Like the host response to M. tuberculosis infections, the host response to these infections is of the TH1 type but there are some subtle and as-yet-unexplained differences.

Role of IL-6 in Mycobacterium avium--associated immune reconstitution inflammatory syndrome

Immune reconstitution inflammatory syndrome (IRIS) is a major adverse event of antiretroviral therapy in HIV infection, and paradoxically occurs as HIV viremia is suppressed and CD4 T cell numbers recover. IRIS reflects pathogenic immune responses against opportunistic infections acquired during the period of immunodeficiency, but little is understood about the mechanisms of inflammatory pathology. In this study, we show that IL-6 and C-reactive protein levels transiently rise at the time of the IRIS event in HIV-infected patients, unmasking Mycobacterium avium complex infection after starting antiretroviral therapy. To directly test the role of IL-6 in IRIS pathology, we used a model of experimentally inducible IRIS in which M. avium-infected T cell-deficient mice undergo a fatal inflammatory disease after reconstitution with CD4 T cells. We find that IL-6 neutralization reduces C-reactive protein levels, alleviates wasting disease, and extends host survival during experimental IRIS. Moreover, we show that combined blockade of IL-6 and IFN-γ further reduces IRIS pathology, even after the onset of wasting disease. The combination of these clinical and experimental-model data show that the IL-6 pathway is not only a biomarker of mycobacterial IRIS but also a major mediator of pathology distinct from IFN-γ and may be a useful target for therapeutic intervention.

A functional single-nucleotide polymorphism in the promoter of the gene encoding interleukin 6 is associated with susceptibility to tuberculosis

BACKGROUND

Genetic variation influences susceptibility or resistance to tuberculosis. Interleukin 6 (IL-6) contributes to protection against tuberculosis in mice. However, its role in regulating susceptibility or resistance to tuberculosis in humans is unclear.

METHODS

Genotyping of polymorphisms in IL-6 and IL-6R (CD126) genes was performed in 2 independent cohorts, an experimental population (495 cases and 358 controls) and a validation population (1383 cases and 1149 controls). The associations of the variants with tuberculosis were tested using 2 case-control association studies. In addition, the regulatory effects of single-nucleotide polymorphism rs1800796 (-572C > G) on IL-6 production in plasma and CD14(+) monocyte cultures stimulated with a Mycobacterium tuberculosis (M. tuberculosis) product were assessed.

RESULTS

The rs1800796 polymorphism is associated with increased resistance to tuberculosis (odds ratio [OR], 0.771; 95% confidential interval, .684-.870). The rs1800796GG genotype is strongly associated with reduced risk to tuberculosis (OR, 0.621; 95% CI, .460-.838). Interestingly, CD14(+) monocytes isolated from individuals with rs1800796GG genotype produced significantly less IL-6 in response to M. tuberculosis 19-kDa lipoprotein than those with CC or CG genotype.

CONCLUSIONS

We identified a genetic polymorphism in the IL-6 promoter that regulates cytokine production and host resistance to pulmonary tuberculosis in Chinese populations.

Mycobacterium Tuberculosis Infection and Inflammation: what is Beneficial for the Host and for the Bacterium?

Tuberculosis is still a major health problem in the world. Initial interactions between Mycobacterium tuberculosis and the host mark the pathway of infection and the subsequent host inflammatory response. This inflammatory response is tightly regulated by both the host and the bacterium during different stages of infection. As infection progresses, the initial intense pro-inflammatory response observed is regulated by suppressive mediators balancing inflammation. In this environment, M. tuberculosis battles to survive interfering with the host inflammatory response. In this review we discuss the major effector molecules involved in inflammation in relation to the different stages of M. tuberculosis infection.

[Reactivation of tuberculosis during dual therapy with pegylated interferon and ribavirin for chronic hepatitis C]

Hepatitis C viral infection can be associated with other infectious diseases including viral and bacterial infections such as tuberculosis. Mycobacterium tuberculosis infection may be latent for many years and revealed during an immunodeficiency state. The responsibility of antiviral treatment in the reactivation of tuberculosis is controversial. We report two cases of tuberculous reactivation during bitherapy with pegylated interferon and ribavirin for chronic hepatitis C. A rapid viral response was obtained in both cases. Tuberculous reactivation occurred at 12 and 13 weeks of antiviral treatment, respectively. Tuberculosis involved urinary tract in one patient and lymph nodes in the other. Antituberculous treatment was given and antiviral treatment maintained. The outcome of tuberculosis was favourable and a sustained viral response was obtained for both patients.

Identification of Intrinsic Airway Acidification in Pulmonary Tuberculosis

Exhaled breath condensate acidification reflects the presence of airway acidification. Mycobacterium tuberculosis is an organism particularly sensitive to acidity. We aimed to determine if there is evidence of airway acidification in a cross section of patients with active tuberculosis.We enrolled 51 subjects with active tuberculosis in Ghana and Thailand, and compared them to control subjects. We collected exhaled breath condensate, and assayed for pH after gas standardization.Exhaled breath condensate pH from the control group revealed a median of 7.9 (7.7 - 8.0, n = 21), significantly higher than the active pulmonary tuberculosis patients who had a median pH of 7.4 (7.0 - 7.7; n = 51; p=0.002). Presence or absence of antibiotic therapy did not affect EBC pH values.These exhaled breath condensate data support the theory that airways become acidic in active tuberculosis infection. This may be a mechanism of immune response and pathology not previously considered.

Osteopontin: a novel cytokine involved in the regulation of Mycobacterium avium subspecies paratuberculosis infection in periparturient dairy cattle

Osteopontin (Opn), an important mediator of the cell-mediated immune response, enhances the host immune response against mycobacterial infections. Infections caused by Mycobacterium avium ssp. paratuberculosis (MAP) have a devastating effect on the dairy industry. We sought to characterize Opn at the level of gene and protein expression in periparturient dairy cows naturally infected with MAP. Peripheral blood mononuclear cells (PBMC) were isolated from control, subclinical, and clinical periparturient dairy cows naturally infected with MAP beginning 3 wk precalving to 5 wk postcalving and incubated with medium alone (non-stimulated: NS), concanavalin A (ConA), or a whole-cell sonicate of MAP (MPS). Real-time PCR was performed to evaluate expression of Opn and classical Th1 and Th2 cytokines. Results demonstrated greater Opn expression in nonstimulated PBMC isolated from subclinical cows compared with control and clinical cows. For clinical cows, there was a strong correlation between Opn expression and expression of the Th1 cytokines IFN-gamma and IL-1 alpha for nonstimulated PBMC and IFN-gamma and IL-12 for PBMC stimulated with MPS. Expression of tumor necrosis factor-alpha was greater in clinical cows than the other groups. Nonstimulated, ConA, and MPS-stimulated PBMC from subclinical cows secreted more IFN-gamma, and MPS-stimulated PBMC from clinical cows secreted more IL-4 compared with the other groups. Immunoblot analysis of PBMC detected 4 Opn proteins at 60, 52, 34, and 27 kDa. This is the first study to evaluate the role of Opn on the immune response of dairy cows naturally infected with MAP, and results suggest Opn may be a key regulator against MAP infection.

Enhancement of BCG-induced Th1 immune response through Vγ9Vδ2 T cell activation with non-peptidic drugs

Since drug-activated gammadelta T cells promote dendritic cell (DC) maturation, we analyzed the effect of combining gammadelta T cell specific drugs with BCG in vitro. BCG-induced DC maturation was increased by bromohydrin-pirophosphate (BrHPP) or zoledronate (Zol)-activated gammadelta T cells. Specifically, the co-culture with activated Vgamma9Vdelta2 T cells with BCG-infected DC resulted in a significant increase of the expression of CD80, CD86, CD40 and CD25 molecules on DC. Moreover, DC were able to produce increased levels of TNF-alpha and synthesize ex novo IL-15 without altering the IL-10/IL-12 immunoregulatory pathway. Finally, the Th1 immunity induced by BCG-infected DC on naïve CD4 T cells was increased by gammadelta T cell activation with BrHpp or Zol. These data indicate that gammadelta T cell triggering drugs could be used to enhance the BCG induced Th1 immunity.

Gene expression profiling of monocyte-derived macrophages following infection with Mycobacterium avium subspecies avium and Mycobacterium avium subspecies paratuberculosis

Mycobacterium avium subspecies paratuberculosis (MAP) and Mycobacterium avium subspecies avium (MAA) represent two closely related intracellular bacteria with vastly different associated pathologies. MAA can cause severe respiratory infections in immune compromised humans but is nonpathogenic in ruminants and is more readily controlled by the bovine immune system than MAP. MAP causes a fatal wasting syndrome in ruminants, typified by granulomatous enteritis localized in the small intestine. MAP has also been cited as a potential cause of human Crohn's disease. We used a bovine immune-specific microarray (BOTL-5) to compare the response of mature bovine monocyte-derived macrophages (MDM cells) to MAP and MAA. Statistical analysis of microarray data revealed 21 genes not appreciably expressed in resting MDM cells that were activated following infection with either MAA or MAP. Further analysis revealed 144 genes differentially expressed in MDM cells following infection with MAA and 99 genes differentially expressed following infection with MAP. Of these genes, 37 were affected by both types of mycobacteria, with three being affected in opposite directions. Over 41% of the differentially expressed genes in MAA and MAP infected MDM cells were members of, regulated by, or regulators of the MAPK pathways. Expression of selected genes was validated by quantitative real-time reverse transcriptase PCR and in several key genes (i.e., IL-2 receptor, tissue inhibitor of matrix metalloproteinases-1, and Fas-ligand) MAA was found to be a stronger activating factor than MAP. These gene expression patterns were correlated with prolonged activation of p38 MAPK and ERK1/2 by MAA, relative to MAP.

Activation of ERK1/2 and TNF-α production are mediated by calcium/calmodulin, and PKA signaling pathways during Mycobacterium bovis infection

Mycobacterium bovis bacillus Calmette-Guérin (BCG)-induced tumor necrosis factor (TNF)-alpha secretion via an extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase-dependent mechanism is an important host defence mechanism against Mycobacterium tuberculosis in human monocytes. We now define distinct signaling pathways that regulate induction of TNF-alpha and activation of ERK1/2 by intracellular signaling mechanisms during M. bovis infection. We determined that M. bovis BCG-induced ERK 1/2 activation occurs through a mechanism that requires intracellular calcium and likely involves a calmodulin-sensitive step. In contrast, M. bovis BCG can induce p38 mapk activation by a calcium (Ca2+)/calmodulin-independent mechanism. Interestingly, we present evidence that M. bovis BCG activates protein kinase A (PKA), since pretreatment of monocytes with H-89, a inhibitor of PKA activity, blocked the ability of M. bovis BCG to induce ERK1/2 activation. These results were further supported by the fact that treatment of cells with KT5720, another well-described inhibitor of PKA activity, significantly diminished the effect of M. bovis BCG on ERK1/2 activation. Furthermore, secretion of TNF-alpha in M. bovis-infected human monocytes was also dependent on Ca2+/calmodulin, and PKA pathways. Finally, addition of H-89 significantly diminished TNF-alpha mRNA expression in M. bovis-infected human monocytes. These results indicate that the Ca2+/calmodulin, and PKA pathways play important regulatory roles in monocyte signaling upon M. bovis infection.

Innate and adaptive immunity in female genital tract: cellular responses and interactions

The mucosal immune system in the female reproductive tract (FRT) has evolved to meet the unique requirements of dealing with sexually transmitted bacterial and viral pathogens, allogeneic spermatozoa, and the immunologically distinct fetus. Analysis of the FRT indicates that the key cells of the innate and adaptive immune systems are present and functionally responsive to antigens. Acting through Toll-like receptors in the Fallopian tubes, uterus, cervix, and in the vagina, epithelial cells, macrophages, natural killer cells, and neutrophils confer protection through the production of chemokines and cytokines, which recruit and activate immune cells, as well as bactericidal and virucidal agents, which confer protection at times when adaptive immunity is downregulated by sex hormones to meet the constraints of procreation. The overall goal of this paper is to define the innate immune system in the FRT and, where possible, to define the regulatory influences that occur during the menstrual cycle that contribute to protection from and susceptibility to potential pathogens. By understanding the nature of this protection and the ways in which innate and adaptive immunity interact, these studies provide the opportunity to contribute to the foundation of information essential for ensuring reproductive health.

Induction of Mycobacterium avium growth restriction and inhibition of phagosome-endosome interactions during macrophage activation and apoptosis induction by picolinic acid plus IFNgamma

Treatment of mouse macrophages with picolinic acid (PA) and gamma-interferon (IFNgamma) led to the restriction of Mycobacterium avium proliferation concomitant with the sequential acquisition of metabolic changes typical of apoptosis, mitochondrial depolarization, annexin V staining and caspase activation, over a period of up to 5 days. However, triggering of cell death by ATP, staurosporine or H(2)O(2) failed to affect mycobacterial viability. In contrast to untreated macrophages where extensive interactions between phagosomes and endosomes were observed, phagosomes from treated macrophages lost the ability to acquire endosomal dextran. N-Acetylcysteine was able to revert both the anti-mycobacterial activity of treated macrophages as well as the block in phagosome-endosome interactions. The treatment, however, induced only a minor increase in the acquisition of lysosomal markers, namely Lamp-1, and did not increase to any great extent the acidification of the phagosomes. These data thus suggest that the anti-mycobacterial activity of PA and IFNgamma depends on the interruption of intracellular vesicular trafficking, namely the blocking of acquisition of endosomal material by the microbe.

Multinutrient undernutrition dysregulates the resident macrophage proinflammatory cytokine network, nuclear factor-kappaB activation, and nitric oxide production

We have described previously a murine model of multinutrient undernutrition that reproduced the features of moderate human malnutrition and led to increased early dissemination of Leishmania donovani. Peritoneal cells from these malnourished mice produced decreased NO after stimulation with IFN-gamma/LPS. We hypothesized that malnutrition may cause a deficit in NF-kappaB activation, a principal transcription pathway for inducible NO synthase and proinflammatory cytokines. Macrophages from malnourished mice, stimulated with IFN-gamma/LPS, showed increased IL-6 production and decreased IL-10 and TNF-alpha production. Neutralization of TNF-alpha in macrophage cultures from the control mice mimicked the effect of malnutrition on NO and IL-10 production, whereas supplemental TNF-alpha added to cultures of macrophages from malnourished mice increased NO secretion. NF-kappaB nuclear binding activity in macrophages from the malnourished mice was reduced early after stimulation, but increased to supranormal values by 16- or 24-h poststimulation. Blocking NO production in the macrophages from the control mice reproduced the effect of malnutrition on the late activation of NF-kappaB, whereas supplemental NO decreased the late NF-kappaB activation in the malnourished mice. Thus, in macrophages from the malnourished mice, initial deficits in NF-kappaB activity probably lead to decreased TNF-alpha, which results in decreased NO; however, IL-6 is regulated independently from NF-kappaB and TNF-alpha. The late activation of NF-kappaB in the macrophages from malnourished mice is due to absence of negative feedback from NO.

Immunologie der Tuberkulose

Tuberculosis is an ancient health problem that is still not under control worldwide. High infection rates with the etiologic pathogen, Mycobacterium tuberculosis, persisting within the host organism and waiting for the opportunity to disseminate when the immune system is suppressed, and the long and cost-intensive chemotherapeutic treatment urgently require the development of a novel vaccine. This article reviews the immune response to M. tuberculosis infection resulting in new strategies for the improvement of the available vaccine Mycobacterium bovis BCG or for the development of alternative vaccines. A new vaccine should elicit a better immune response than the natural infection and reliably protect from TB disease, regardless if given prior or post infection with M. tuberculosis.

Infection of human monocytes with Mycobacterium bovis BCG induces production of CC-chemokines

DESIGN

CC-chemokines are potent leukocyte activators and chemoattractants, which have an important role in granuloma formation, function critical for the immune responses to mycobacterial infection. This study investigated whether infection of human monocytes with Mycobacterium bovis bacillus Calmette-Guérin (BCG) elicits secretion of RANTES, macrophage inflammatory protein (MIP)-1alpha and MIP-1beta.

METHODS

RANTES, MIP-1alpha and MIP-1beta synthesis was measured by the presence of protein secretion in the cell culture supernatant as determined by enzyme-linked immunosorbent assay. To investigate the mechanism of M. bovis BCG stimulation of RANTES, we carried out inhibition assays with antibodies to CD40 and we used an intracellular calcium chelator BAPTA-AM.

RESULTS

Infection of human monocytes with M. bovis BCG induced RANTES, MIP-1alpha and MIP-1beta secretion in a dose-dependent manner. This stimulation of CC-chemokines production was not attributed to LPS contamination. M. bovis-induced RANTES secretion was dependent upon bacterial uptake and on tumor necrosis factor (TNF)-alpha. Interestingly, the production of RANTES by M. bovis BCG-infected monocytes occurs through a mechanism that requires intracellular calcium and was significantly inhibited (P<0.05) with antibodies to CD40.

CONCLUSIONS

These results suggest that the ability of M. bovis BCG to produce CC-chemokines might lead to protection in the acquired immune response of mycobacterial infection and at the same time indicate that M. bovis BCG-induced RANTES secretion is mediated by CD40 and dependent on the intracellular calcium influx.

Functional CD40 expression induced following bacterial infection of mouse and human osteoblasts

Bacterially induced bone infections often result in significant local inflammatory responses which are coupled with loss of bone. However, the mechanisms necessary for the protective host response, or those responsible for pathogen-induced bone loss, are not clear. Recent evidence demonstrates that bacterially infected osteoblasts secrete chemokines and cytokines, suggesting that these cells may have an unappreciated role in supporting localized inflammation. In this study, mouse and human osteoblasts were investigated for their ability to express functional CD40 upon exposure to two important pathogens of bone, Staphylococcus aureus and Salmonella enterica serovar Dublin. Bacterial infection of cultured mouse or human osteoblasts resulted in increased CD40 mRNA and CD40 protein expression induced by either pathogen. Importantly, CD40 expression by osteoblasts was functional, as assessed by ligation of this molecule with recombinant, soluble CD154. CD40 activity was assessed by induction of interleukin-6 and granulocyte-macrophage colony-stimulating factor in osteoblasts following ligation. Cocultures of activated CD4(+) T lymphocytes and osteoblasts could interact via CD40 and CD154, since an antibody against CD40 could block macrophage inflammatory protein-1alpha secretion. Taken together, these studies conclusively demonstrate that infected osteoblasts can upregulate expression of functional CD40 molecules which mediate cytokine secretion. This surprising result further supports the notion that bone-forming osteoblasts can directly interact with CD154-expressing cells (i.e., T lymphocytes) and can contribute to the host response during bone infection.

Effect of Mycobacterium tuberculosis-specific 10-kilodalton antigen on macrophage release of tumor necrosis factor alpha and nitric oxide

Secreted proteins of Mycobacterium tuberculosis are major targets of the specific immunity in tuberculosis and constitute promising candidates for the development of more efficient vaccines and diagnostic tests. We show here that M. tuberculosis-specific antigen 10 (MTSA-10, originally designated CFP-10) can bind to the surface of mouse J774 macrophage-like cells and stimulate the secretion of the proinflammatory cytokine tumor necrosis factor alpha (TNF-alpha). MTSA-10 also synergized with gamma interferon (IFN-gamma) for the induction of the microbicidal free radical nitric oxide (NO) in J774 cells, as well as in bone marrow-derived and peritoneal macrophages. On the other hand, pretreatment of J774 cells with MTSA-10 markedly reduced NO but not TNF-alpha or interleukin 10 (IL-10) release upon subsequent stimulation with lipopolysaccharide or the cell lysate of M. tuberculosis. The presence of IFN-gamma during stimulation with M. tuberculosis lysate antagonized the desensitizing effect of MTSA-10 pretreatment on macrophage NO production. The activation of protein tyrosine kinases (PTK) and the serine/threonine kinases p38 MAPK and ERK was apparently required for MTSA-10 induction of TNF-alpha and NO release, as revealed by specific kinase inhibitors. However, only p38 MAPK activity, not PTK or ERK activity, was partly responsible for MTSA-10-mediated macrophage desensitization. The modulation of macrophage function by MTSA-10 suggests a novel mechanism for its involvement in immunopathogenesis of tuberculosis and might have implications for the prevention, diagnosis, and therapy of this disease.

Isolation of a 19-kDa mycobacterium, bovis-specific antigen, different from MPB70/80, by chromatofocusing

Two antigens, 19-kDa each, were purified from Mycobacterium bovis culture filtrate protein extract by chromatofocusing. Antigen I had a 4.5 pI, and its amino terminal (DPVDAVINTTCNYGQVVAALNATDP) showed a 100% homology with the hypothetical protein Rv1174c. Antigen II had a pI of 6.0 pI and its amino terminal (GDLVGPGCAEYAAANPTGPASVQGM) showed a 100% homology with M. bovis MPB70/80. Antigen I is a hetero-dimer formed by a glycosylated, 10.5-kDa, monomer and a non-glycosylated 8-kDa monomer with identical amino terminal sequences. Both antigens were recognized by the sera of PPD+ animals, but antigen I did not crossreact with sera of human PPD+ individuals. Antigen I was a weak inducer of lymphocyte proliferation and IFN-gamma production. Our results show that M. bovis expresses a 19 kDa glycoprotein, homologue to the product of M. tuberculosis gen Rv1174c, which may prove useful for bovine TB diagnostic assays.

Antigenicity of Mycobacterium paratuberculosis superoxide dismutase in mice

Mycobacterium paratuberculosis (MPT) is the etiologic agent of paratuberculosis. The disease is prevalent in cattle worldwide, and exacts a heavy financial toll. Effective control requires the development of acellular vaccines offering a better protection than the current available vaccines without side effects and allowing the discrimination between infected and vaccinated animals. We studied the immune response of mice to the MPT superoxide dismutase (SOD) alone or adjuvanted by Ribi. We cloned, overexpressed and purified this antigen in Escherichia coli. Spleen cells from immunized mice, after exposure to recombinant MPT SOD (MPT rSOD), produced significant levels of IFNgamma, TNFalpha and IL-6. IFNgamma and TNFalpha production was increased by the addition of Ribi. In contrast, low levels of NO, IL-4 and IL-10 were secreted by spleen cells culture from immunized mice. The immunoglobulin isotype distribution analysis showed that Ribi adjuvant clearly induced a significantly higher anti-MPT rSOD antibody production of all classes tested and decreased the IgG1/IgG2a ratio thus improving the Th1 response. Delayed-type hypersensitivity responses in mice footpads were observed only in mice immunized with MPT rSOD emulsified in Ribi. Vaccination of MPT rSOD emulsified with Ribi induced both a Th2 and Th1 type of immune response with the later slightly more pronounced. The results presented here on the immunogenicity of MPT SOD suggest that this antigen should be further tested as a candidate antigen for a future acellular vaccine against paratuberculosis.

Beta-chemokines are induced by Mycobacterium tuberculosis and inhibit its growth

Chemokines (CK) are potent leukocyte activators and chemoattractants and aid in granuloma formation, functions critical for the immune response to Mycobacterium tuberculosis. We hypothesized that infection of alveolar macrophages (AM) with different strains of M. tuberculosis elicits distinct profiles of CK, which could be altered by human immunodeficiency virus (HIV) infection. RANTES, macrophage inflammatory protein-1 alpha (MIP-1 alpha), and MIP-1 beta were the major beta-CK produced in response to M. tuberculosis infection. Virulent M. tuberculosis (H37Rv) induced significantly less MIP-1 alpha than did the avirulent strain (H37Ra), while MIP-1 beta and RANTES production was comparable for both strains. MIP-1 alpha and MIP-1 beta were induced by the membrane, but not cytosolic, fraction of M. tuberculosis. M. tuberculosis-induced CK secretion was partly dependent on tumor necrosis factor alpha (TNF-alpha). AM from HIV-infected individuals produced less TNF-alpha and MIP-1 beta than did normal AM in response to either M. tuberculosis strain. We tested the functional significance of decreased beta-CK secretion by examining the ability of beta-CK to suppress intracellular growth of M. tuberculosis. MIP-1 beta and RANTES suppressed intracellular growth of M. tuberculosis two- to threefold, a novel finding. Thus, beta-CK contribute to the innate immune response to M. tuberculosis infection, and their diminution may promote the intracellular survival of M. tuberculosis.

Model of differential susceptibility to mucosal Burkholderia pseudomallei infection

Burkholderia pseudomallei is the causative agent of melioidosis, an infectious disease with protean clinical manifestations. The major route of infection is thought to be through subcutaneous inoculation of contaminated soil and water, although ingestion and inhalation of contaminated aerosols are also possible. This study examines infection through the intranasal route in a murine model to mimic infection through inhalation. Two strains of mice, C57BL/6 and BALB/c, exhibit differential susceptibilities to the infection, with the C57BL/6 mice being considerably more resistant. To examine host factors that could contribute to this difference, bacterial loads and cytokine profiles in the two strains of mice were compared. We found that infected BALB/c mice exhibited higher bacterial loads in the lung and spleen and that they produced significantly higher levels of gamma interferon (IFN-gamma) in the serum than C57BL/6 mice. Although tumor necrosis factor alpha and interleukin-1 could be detected in the nasal washes and sera of both strains of mice, the production in serum was transient and much lower than that of IFN-gamma. C57BL/6 mice also exhibited memory responses to bacteria upon reinfection, with the production of serum immunoglobulin G (IgG) and mucosal IgA antibodies. Thus, it is possible that the production of systemic and mucosal antibodies is important for protection against disease in C57BL/6 mice.

Mycobacteria-induced TNF-alpha and IL-10 formation by human macrophages is differentially regulated at the level of mitogen-activated protein kinase activity

The clinical course of mycobacterial infections is linked to the capacity of pathogenic strains to modulate the initial antimycobacterial response of the macrophage. To elucidate some of the mechanisms involved, we studied early signal transduction events leading to cytokine formation by human monocyte-derived macrophages (MDM) in response to clinical isolates of Mycobacterium avium. TNF-alpha production induced by M. avium was inhibited by anti-CD14 mAbs, but not by Abs against the macrophage mannose receptor. Analysis of mitogen-activated protein (MAP) kinase activation (extracellular signal-regulated kinase 1/2, p38, and c-Jun NH(2)-terminal kinase) showed a rapid phosphorylation of all three subfamilies in response to M. avium, which was inhibited by anti-CD14 Abs. Using highly specific inhibitors of p38 (SB203580) and MAP kinase kinase-1 (PD98059), we found that activation of the extracellular signal-regulated kinase pathway, but not of p38, was essential for the M. avium-induced TNF-alpha formation. In contrast, IL-10 production was abrogated by the p38 inhibitor, but not by the MAP kinase kinase-1 inhibitor. In conclusion, M. avium-induced secretion of TNF-alpha and IL-10 by human macrophages is differentially regulated at the level of MAP kinase activity.

Global impact of influenza virus on cellular pathways is mediated by both replication-dependent and -independent events

Influenza virus, the causative agent of the common flu, is a worldwide health problem with significant economic consequences. Studies of influenza virus biology have revealed elaborate mechanisms by which the virus interacts with its host cell as it inhibits the synthesis of cellular proteins, evades the innate antiviral response, and facilitates production of viral RNAs and proteins. With the advent of DNA array technology it is now possible to obtain a large-scale view of how viruses alter the environment within the host cell. In this study, the cellular response to influenza virus infection was examined by monitoring the steady-state mRNA levels for over 4,600 cellular genes. Infections with active and inactivated influenza viruses identified changes in cellular gene expression that were dependent on or independent of viral replication, respectively. Viral replication resulted in the downregulation of many cellular mRNAs, and the effect was enhanced with time postinfection. Interestingly, several genes involved in protein synthesis, transcriptional regulation, and cytokine signaling were induced by influenza virus replication, suggesting that some may play essential or accessory roles in the viral life cycle or the host cell's stress response. The gene expression pattern induced by inactivated viruses revealed induction of the cellular metallothionein genes that may represent a protective response to virus-induced oxidative stress. Genome-scale analyses of virus infections will help us to understand the complexities of virus-host interactions and may lead to the discovery of novel drug targets or antiviral therapies.

Protection against virulent Mycobacterium avium infection following DNA vaccination with the 35-kilodalton antigen is accompanied by induction of gamma interferon-secreting CD4(+) T cells

Mycobacterium avium is an opportunistic pathogen that primarily infects immunocompromised individuals, although the frequency of M. avium infection is also increasing in the immunocompetent population. The antigen repertoire of M. avium varies from that of Mycobacterium tuberculosis, with the immunodominant 35-kDa protein being present in M. avium and Mycobacterium leprae but not in members of the M. tuberculosis complex. Here we show that a DNA vector encoding this M. avium 35-kDa antigen (DNA-35) induces protective immunity against virulent M. avium infection, and this protective effect persists over 14 weeks of infection. In C57BL/6 mice, DNA vaccines expressing the 35-kDa protein as a cytoplasmic or secreted protein, both induced strong T-cell gamma interferon (IFN-gamma) and humoral immune responses. Furthermore, the antibody response was to conformational determinants, confirming that the vector-encoded protein had adopted the native conformation. DNA-35 immunization resulted in an increased activated/memory CD4(+) T-cell response, with an accumulation of CD4(+) CD44(hi) CD45RB(lo) T cells and an increase in antigen-specific IFN-gamma production. The protective effect of the DNA-35 vectors against M. avium infection was comparable to that of vaccination with Mycobacterium bovis BCG and significantly greater than that for previous treated infection with M. avium. These results illustrate the importance of the 35-kDa protein in the protective response to M. avium infection and indicate that DNA vaccination successfully promotes a sustained level of protection during chronic M. avium infection.

Dysregulated production of interferon-gamma, interleukin-4 and interleukin-6 in early tuberculosis patients in response to antigen 85B of Mycobacterium tuberculosis

Both interferon-gamma (IFN-gamma) and interleukin (IL)-4 expression in T cells and IL-6 expression in cells of the monocyte/macrophage lineage were monitored using antigen 85B (Ag85B) protein and purified protein derivative (PPD) antigen in the early stages of tuberculosis (TB). We showed that the levels of cell-associated IFN-gamma and IL-4 (mRNA and intracellular cytokine) in Ag85B-stimulated T cells were significantly depressed in TB patients compared with those in healthy tuberculin reactors. On the other hand, the capacity of peripheral blood mononuclear cells (PBMC) to produce IL-6 spontaneously ex vivo was enhanced in patients (P < 0. 001), but their corresponding capacities to respond to Ag85B were not significantly different from those of normal donors. After 2 months of antituberculosis therapy, the mean blastogenic responses of Ag85B-stimulated PBMC from seven TB patients were increased 6. 1-fold (P = 0.011). Furthermore, the proportions of both IFN-gamma- (P < 0.01) and IL-4- (P = 0.05) producing T cells were significantly increased. However, those of IL-6-producing cells were diminished in response to Ag85B (P = 0.05). Our results suggest that there may be an altered regulation of IFN-gamma, IL-4 and IL-6 to Ag85B in the early stages of TB.

Imbalances between tumor necrosis factor-alpha and its soluble receptor forms, and interleukin-1beta and interleukin-1 receptor antagonist in BAL fluid of cavitary pulmonary tuberculosis

OBJECTIVES

We investigated the possibility that the large pulmonary cavity in tuberculosis (TB) lesions might result from imbalances between tumor necrosis factor-alpha (TNF-alpha) and soluble TNF-alpha receptor forms (sTNF-RI and sTNF-RII), and interleukin-beta (IL-1beta) and IL-1 receptor antagonist (IL-1RA) in sites of local inflammation.

PATIENTS AND METHODS

BAL was performed in 32 patients with active pulmonary TB, and the recovered BAL fluid (BALF) was examined for concentrations of TNF-alpha and its soluble receptor forms, IL-1beta, and IL-1RA. Patients were classified into two groups: group 1, patients with a large cavity (> or = 4 cm) on chest radiographs (n = 15); and group 2, patients with a small cavity (< 4 cm; n = 3) or no cavity (n = 14) on chest radiographs.

RESULTS

The concentrations of TNF-alpha, IL-1beta, and IL-1RA in BALF were significantly higher in group 1 patients than in group 2 patients before standardization. The difference was also statistically significant for TNF-alpha and IL-1beta after standardization with urea. Furthermore, group 1 patients had significantly higher ratios of TNF-alpha to sTNF-RI and sTNF-RII and IL-1beta to IL-1RA compared with group 2 patients.

CONCLUSIONS

These findings suggest that the relative abundance of TNF-alpha and IL-1beta associated with imbalances of secretion of soluble TNF-alpha receptor forms and IL-1RA may have caused tissue necrosis leading to cavity formation in patients with active pulmonary TB.

Role of cytokines in pulmonary antimicrobial host defense

Host defense of the lung is characterized by a fine balance between the generation of a vigorous inflammatory response to clear pathogens and maintenance of the integrity of the alveolar gas-exchange surface. The magnitude of the inflammatory response is therefore tightly regulated by pro- and anti-inflammatory cytokine mediators. This article summarizes current information on the roles of specific cytokines in pneumonia, with particular emphasis on ongoing investigations into the role of innate immunity in bacterial and fungal pneumonia.

Mycobacterium avium Infection of Mouse Macrophages Inhibits IFN-γ Janus Kinase-STAT Signaling and Gene Induction by Down-Regulation of the IFN-γ Receptor

Macrophage activation is required to control the growth of intracellular pathogens. Recent data indicate that macrophages become functionally deactivated during mycobacterial infection. We studied macrophage deactivation by examining the expression of a panel of IFN-γ-inducible genes and activation of Janus Kinase (JAK)-STAT pathway in Mycobacterium avium-infected macrophages. Reduced expression of IFN-γ-inducible genes—MHC class II gene Eβ; MHC class II transactivator; IFN regulatory factor-1; and Mg21, a gene coding for a GTP-binding protein—was observed in M. avium-infected macrophages. Decreased tyrosine phosphorylation and DNA binding activity of STAT1 in M. avium-infected macrophages stimulated with IFN-γ was observed. Tyrosine phosphorylation of JAK1, JAK2, and IFN-γRα was also reduced in infected cells. Northern and Western blot analyses showed that a down-regulation of IFN-γR α- and β-chain mRNA and protein occurred in M. avium-infected macrophages. The down-regulation of IFN-γR and inhibition of STAT1 activation were time dependent and required 4 h of infection for down-regulation of the IFN-γR and 8 h for STAT1 inhibition. These findings suggest that M. avium infection inhibits induction of IFN-γ-inducible genes in mouse macrophages by down-regulating IFN-γR, resulting in reduced phosphorylation of IFN-γRα, JAK1, JAK2, and STAT1.

Role of CD40 ligand in Mycobacterium avium infection

Mycobacterium avium is a common opportunistic pathogen in immunocompromised patients such as those infected with human immunodeficiency virus. Although M. avium is an intracellular organism replicating predominantly in macrophages, disseminated M. avium infection is seen in AIDS patients with CD4(+) cell counts of <50 cells/microliters, suggesting a possible involvement of a T cell-macrophage interaction for the elimination of M. avium. To determine whether CD40-CD40 ligand (CD40L) interactions play a role in M. avium infection, we studied the ability of CD40L to restrict M. avium replication in human monocyte-derived macrophages (MDM) in vitro. MDM were infected with M. avium and cocultured with CD40L-transfected 293 cells for 7 days. Intracellular growth of M. avium in these MDM was assessed by colony counting. CD40L-expressing cells inhibited growth of M. avium in MDM by 86.5% +/- 4.2% compared to MDM cultured with control cells. These findings were verified by assays using purified, soluble recombinant human CD40L (CD40LT). CD40LT (5 micrograms/ml) inhibited intracellular growth of M. avium by 76.9% +/- 18.0% compared to cells treated with medium alone. Inhibition by CD40LT was reduced by monoclonal antibodies (MAbs) against CD40 and CD40L. The inhibitory effect of CD40LT was not accompanied by enhancement of interleukin-12 (IL-12) production by M. avium-infected MDM, while CD40L-expressing cells stimulated IL-12 production by these cells. Treatment of M. avium-infected mice with MAb against murine CD40L resulted in recovery of larger numbers of organisms (0.8 to 1.0 log) from the spleens, livers, and lungs of these animals compared to infected mice which received normal immunoglobulin G. These results indicate that CD40-CD40L signaling may be an important step in host immune response against M. avium infection.

Treatment of mice with staphylococcal enterotoxin B enhances resolution of an induced Escherichia coli urinary tract infection and stimulates production of proinflammatory cytokines

Staphylococcal enterotoxin B (SEB) is a superantigen that causes mass proliferation of murine Vbeta8+ T cells via major histocompatibility complex (MHC) class II molecules and leads to their apoptosis or anergy. SEB also stimulates other MHC class II-bearing cells to proliferate and secrete cytokines, some of which might enhance early host defenses against urinary tract infections (UTIs). We investigated the effect of SEB administration on the course of an induced Escherichia coli UTI in mice. Treatment with SEB 3 or 7 days before the infection had no effect on UTI resolution. However, when SEB was administered at the time of infection, bacterial colonization in the bladders was reduced at time points between 6 h and 3 days. This reduction was not due to a physiological effect, such as increased urinary glycosaminoglycans, or altered pH, nor was SEB bactericidal for the inoculum. Cytokine production in the spleens and bladders of SEB-treated and/or infected mice was evaluated by reverse transcription-PCR. SEB treatment resulted in increased levels of interleukin-2 (IL-2), IL-4, IL-6, and IL-10 mRNAs in the spleen and IL-1alpha, IL-6, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor alpha transcripts in the bladder. Also, liver cells from SEB-treated mice expressed IL-6 mRNA, which induces the production of acute-phase proteins. These data indicate that SEB treatment in vivo leads to enhanced UTI resolution through a mechanism that may include direct stimulation of effector cells in the bladder, the action of cytokines induced in the spleen, or cytokine-mediated induction of acute-phase proteins.