IL-10 underlies distinct susceptibility of BALB/c and C57BL/6 mice to Mycobacterium avium infection and influences efficacy of antibiotic therapy

The Significance of the Cell-Mediated Host Immune Response in Syphilis

Syphilis, caused by the highly invasive pathogen Treponema pallidum, remains one of the oldest and most significant public health challenges. According to the World Health Organization (WHO), the number of new syphilis cases among adults aged 15-49 years in 2022 was estimated at approximately 8 million, with notable increases observed in Europe, the Americas, and Africa. The cellular immune response plays a critical role in combating this infection, and its insufficient activity may contribute to chronic progression of the disease. T. pallidum effectively evades the host immune response, enabling its prolonged survival within the host and increasing the risk of late complications such as neurosyphilis and cardiovascular syphilis. This review article discusses the mechanisms of cellular immune responses in T. pallidum infection, including T lymphocyte activation, proinflammatory cytokine production, and the roles of macrophages and dendritic cells in pathogen recognition and elimination. Additionally, it examines the immune evasion strategies employed by T. pallidum, such as the low immunogenicity of its antigens and its ability to suppress the activation of effector cells. A comprehensive understanding of the current knowledge regarding cellular immune mechanisms may contribute to the development of more effective diagnostic and therapeutic approaches in syphilis management.

Elevated IL-10 serum levels are associated with slower serological response following syphilis treatment during pregnancy

BACKGROUND

Approximately 50% of pregnant individuals treated for syphilis do not achieve a decline in non-treponemal titers by delivery. The serological response in pregnant persons is significantly slower compared to non-pregnant individuals, with unclear pathogenesis and clinical significance. This study aimed to determine the association between the host immune response and serological outcome in pregnant individuals with syphilis.

METHODS

Twenty-four females with early syphilis, including 14 pregnant individuals, were included. Pro-inflammatory and regulatory cytokines (IFN-γ, TNF-α, IL-4, IL-1β, IL-10, TGF-β) were measured before treatment and 6 months after penicillin injection.

RESULTS

The median time to serological cure was 5 months for pregnant individuals and 2 months for non-pregnant females. Pregnant individuals had significantly higher serum levels of IL-10 and TGF-β at baseline and at 6 months post-treatment compared to non-pregnant individuals (p < .05).

CONCLUSIONS

A robust regulatory immune response to syphilis may be associated with a slower serological response to therapy during pregnancy.

Chronic hyperglycemia impairs anti-microbial function of macrophages in response to Mycobacterium tuberculosis infection

Diabetes mellitus (DM) is a major risk factor for tuberculosis (TB), though the underlying mechanisms linking DM and TB remain ambiguous. Macrophages are a key player in the innate immune response and their phagocytic ability is enhanced in response to microbial infections. Upon infection or inflammation, they also repel invading pathogens by generating; reactive oxygen species (ROS), reactive nitrogen species (RNS), pro-inflammatory cytokines (IL-1β and IL-6), and anti-inflammatory cytokines (IL-10). However, the robustness of these innate defensive capabilities of macrophages when exposed to hyperglycemia remains unclear. In our current work, we explored the production of these host defense molecules in response to challenge with Mycobacterium tuberculosis (Mtb) infection and lipopolysaccharide (LPS) stimulation. Utilizing peritoneal macrophages from high-fat diet + streptozotocin induced diabetic mice and hyperglycemic THP-1-derived macrophages as model systems; we found that LPS stimulation and Mtb infection were ineffective in stimulating the production of ROS, RNS, and pro-inflammatory cytokines in cells exposed to hyperglycemia. On the contrary, an increase in production of anti-inflammatory cytokines was observed. To confirm the mechanism of decreased anti-bacterial activity of the diabetic macrophage, we explored activation status of these compromised macrophages and found decreased surface expression of activation (TLR-4) and differentiation markers (CD11b and CD11c). We postulate that this could be the cause for higher susceptibility for Mtb infection among diabetic individuals.

Cysteinyl leukotriene receptor-1 as a potential target for host-directed therapy during chronic schistosomiasis in murine model

Schistosomiasis remains the most devastating neglected tropical disease, affecting over 240 million people world-wide. The disease is caused by the eggs laid by mature female worms that are trapped in host's tissues, resulting in chronic Th2 driven fibrogranulmatous pathology. Although the disease can be treated with a relatively inexpensive drug, praziquantel (PZQ), re-infections remain a major problem in endemic areas. There is a need for new therapeutic drugs and alternative drug treatments for schistosomiasis. The current study hypothesized that cysteinyl leukotrienes (cysLTs) could mediate fibroproliferative pathology during schistosomiasis. Cysteinyl leukotrienes (cysLTs) are potent lipid mediators that are known to be key players in inflammatory diseases, such as asthma and allergic rhinitis. The present study aimed to investigate the role of cysLTR1 during experimental acute and chronic schistosomiasis using cysLTR1-/- mice, as well as the use of cysLTR1 inhibitor (Montelukast) to assess immune responses during chronic Schistosoma mansoni infection. Mice deficient of cysLTR1 and littermate control mice were infected with either high or low dose of Schistosoma mansoni to achieve chronic or acute schistosomiasis, respectively. Hepatic granulomatous inflammation, hepatic fibrosis and IL-4 production in the liver was significantly reduced in mice lacking cysLTR1 during chronic schistosomiasis, while reduced liver pathology was observed during acute schistosomiasis. Pharmacological blockade of cysLTR1 using montelukast in combination with PZQ reduced hepatic inflammation and parasite egg burden in chronically infected mice. Combination therapy led to the expansion of Tregs in chronically infected mice. We show that the disruption of cysLTR1 is dispensable for host survival during schistosomiasis, suggesting an important role cysLTR1 may play during early immunity against schistosomiasis. Our findings revealed that the combination of montelukast and PZQ could be a potential prophylactic treatment for chronic schistosomiasis by reducing fibrogranulomatous pathology in mice. In conclusion, the present study demonstrated that cysLTR1 is a potential target for host-directed therapy to ameliorate fibrogranulomatous pathology in the liver during chronic and acute schistosomiasis in mice.

Bioinformatics characteristics and expression analysis of IL-8 and IL-10 in largemouth bass (Micropterus salmoides) upon Nocardia seriolae infection

IL-8 and IL-10 are crucial inflammatory cytokines that participate in defending host cells against infections. To demonstrate the function of the two interleukin genes in largemouth bass (Micropterus salmoides), we initially cloned and identified the cDNA sequences of il-8 and il-10 in largemouth bass, referred to as Msil-8 and Msil-10, respectively. The open reading frame (ORF) of Msil-8 was 324 bp in length, encoding 107 amino acids, while the ORF of Msil-10 consisted of 726 bp and encoded 241 amino acids. Furthermore, the functional domains of the SCY domain in MsIL-8 and the IL-10 family signature motif in MsIL-10 were highly conserved across vertebrates. Additionally, both MsIL-8 and MsIL-10 showed close relationships with M. dolomieu. Constitutive expression of Msil-8 and Msil-10 was observed in various tissues, with the highest level found in the head kidney. Subsequently, largemouth bass were infected with Nocardia seriolae via intraperitoneal injection to gain a further understanding of the function of these two genes. Bacterial loads were initially detected in the foregut, followed by the midgut, hindgut, and liver. The mRNA expression of Msil-8 was significantly down-regulated after infection, especially at 2 days post-infection (DPI), with a similar expression to Msil-10. In contrast, the expression of Msil-8 and Msil-10 was significantly upregulated in the foregut at 14 DPI. Taken together, these results reveal that the function of IL-8 and IL-10 was likely hindered by N. seriolae, which promoted bacterial proliferation and intercellular diffusion.

Intracellular and in vivo activities of oxazolidinone drugs against Mycobacterium avium complex infection

The prevalence of Mycobacterium avium complex-pulmonary disease (MAC-PD) has become a growing concern worldwide, and current treatments involving macrolides (clarithromycin [CLR] or azithromycin), ethambutol, and rifampicin have limited success, highlighting the need for better therapeutic strategies. Recently, oxazolidinone drugs have been identified as novel anti-tuberculosis drugs effective against drug-resistant M. tuberculosis. However, the effects of these drugs against MAC are still controversial due to limited data. Here, we first evaluated the intracellular anti-MAC activities of two oxazolidinone drugs, linezolid (LZD) and delpazolid (DZD), against 10 macrolide-susceptible MAC strains and one macrolide-resistant M. avium strain in murine bone marrow-derived macrophages (BMDMs) and found that both drugs demonstrated similar potential. The synergistic efficacies with CLR were then determined in a chronic progressive MAC-PD murine model by initiating a 4-week treatment at 8 weeks post-infection. Upon assessment of bacterial burdens and inflamed lesions, oxazolidinone drugs exhibited no anti-MAC effect, and there was no significant difference in the synergistic effect of CLR between LZD and DZD. These findings suggest that oxazolidinone drugs inhibit intracellular bacterial growth, even against macrolide-resistant MAC, but their clinical application requires further consideration.

Chronic Mycobacterium avium infection differentially affects the cytokine expression profile of three mouse strains, but has no effect on behavior

One of the most remarkable findings in the immunology and neuroscience fields was the discovery of the bidirectional interaction between the immune and the central nervous systems. This interplay is tightly regulated to maintain homeostasis in physiological conditions. Disruption in this interplay has been suggested to be associated with several neuropsychiatric disorders. Most studies addressing the impact of an immune system disruption on behavioral alterations focus on acute pro-inflammatory responses. However, chronic infections are highly prevalent and associated with an altered cytokine milieu that persists over time. Studies addressing the potential effect of mycobacterial infections on mood behavior originated discordant results and this relationship needs to be further addressed. To increase our understanding on the effect of chronic infections on the central nervous system, we evaluated the role of Mycobacterium avium infection. A model of peripheral chronic infection with M. avium in female from three mouse strains (Balb/c, C57BL/6, and CD-1) was used. The effect of the infection was evaluated in the cytokine expression profile (spleen and hippocampus), hippocampal cell proliferation, neuronal plasticity, serum corticosterone production and mood behavior. The results show that M. avium peripheral chronic infection induces alterations not just in the peripheral immune system but also in the central nervous system, namely in the hippocampus. Interestingly, the cytokine expression profile alterations vary between mouse strains, and are not accompanied by hippocampal cell proliferation or neuronal plasticity changes. Accordingly, no differences were observed in locomotor, anxious and depressive-like behaviors, in any of the mouse strains used. We conclude that the M. avium 2447 infection-induced alterations in the cytokine expression profile, both in the periphery and the hippocampus, are insufficient to alter hippocampal plasticity and behavior.

Virulence of Mycobacterium intracellulare clinical strains in a mouse model of lung infection - role of neutrophilic inflammation in disease severity

BACKGROUND

Mycobacterium intracellulare is a major etiological agent of Mycobacterium avium-intracellulare pulmonary disease (MAC-PD). However, the characteristics of the virulence of M. intracellulare and the in vivo chemotherapeutic efficacy remain unclear. In this study, we examined the virulence of nine M. intracellulare strains with different clinical phenotypes and genotypes in C57BL/6 mice.

RESULTS

We classified three types of virulence phenotypes (high, intermediate, and low) based on the kinetics of the bacterial load, histological lung inflammation, and neutrophilic infiltration. High virulence strains showed more severe neutrophilic infiltration in the lungs than intermediate and low virulence strains, with 6.27-fold and 11.0-fold differences of the average percentage of neutrophils in bronchoalveolar lavage fluid, respectively. In particular, the high virulence strain M.i.198 showed the highest mortality in mice, which corresponded to the rapid progression of clinical disease. In mice infected with the drug-sensitive high virulence strain M019, clarithromycin-containing chemotherapy showed the highest efficacy. Monotherapy with rifampicin exacerbated lung inflammation with increased lymphocytic and neutrophilic infiltration into the lungs.

CONCLUSIONS

The virulence phenotypes of clinical strains of M. intracellulare were diverse, with high virulence strains being associated with neutrophilic infiltration and disease progression in infected mice. These high virulence strains were proposed as a useful subject for in vivo chemotherapeutic experiments.

Vaccination inducing durable and robust antigen-specific Th1/Th17 immune responses contributes to prophylactic protection against Mycobacterium avium infection but is ineffective as an adjunct to antibiotic treatment in chronic disease

Mycobacterium avium complex (MAC) causing pulmonary disease in humanshas emerged worldwide. Thus, effective strategies simultaneously aiming to prevent MAC infection and accelerate therapeutic efficacy are required. To this end, subunit vaccine-induced protection against a well-defined virulent Mycobacterium avium (Mav) isolate was assessed as a preventative and therapeutic modality in murine models. Mav-derived culture filtrate antigen (CFA) was used as a vaccine antigen with glucopyranosyl lipid A stable emulsion (GLA-SE) or GLA-SE plus cyclic-di-GMP (GLA-SE/CDG), and we compared the immunogenicities, protective efficacies and immune correlates. Interestingly, CFA+GLA-SE/CDG immunization induced greater CFA-specific Th1/Th17 responses in both the lung and spleen than among the tested groups. Consequently, protective efficacy was optimally achieved with CFA+GLA-SE/CDG by significantly reducing bacterial loads along with long-lasting maintenance of antigen-specific Th1/Th17 cytokine-producing multifunctional T cell responses and relevant cytokine productions. Thus, we employed this subunit vaccine as an adjunct to antibiotic treatment. However, this vaccine was ineffective in further reducing bacterial loads. Collectively, our study demonstrates that strong Mav CFA-specific Th1/Th17 responses are critical for preventative protection against Mav infection but may be ineffective or even detrimental in an established and progressive chronic disease, indicating that different approaches to combating Mav infection are necessary according to vaccination purposes.

Evaluation of the immunomodulatory effects of interleukin-10 on peripheral blood immune cells of COVID-19 patients: Implication for COVID-19 therapy

Objective

Several therapies with immune-modulatory functions have been proposed to reduce the overwhelmed inflammation associated with COVID-19. Here we investigated the impact of IL-10 in COVID-19, through the ex-vivo assessment of the effects of exogenous IL-10 on SARS-CoV-2-specific-response using a whole-blood platform.

Methods

Two cohorts were evaluated: in “study population A”, plasma levels of 27 immune factors were measured by a multiplex (Luminex) assay in 39 hospitalized “COVID-19 patients” and 29 “NO COVID-19 controls” all unvaccinated. In “study population B”, 29 COVID-19 patients and 30 NO COVID-19-Vaccinated Controls (NO COVID-19-VCs) were prospectively enrolled for the IL-10 study. Whole-blood was stimulated overnight with SARS-COV-2 antigens and then treated with IL-10. Plasma was collected and used for ELISA and multiplex assay. In parallel, whole-blood was stimulated and used for flow cytometry analysis.

Results

Baseline levels of several immune factors, including IL-10, were significantly elevated in COVID-19 patients compared with NO COVID-19 subjects in “study population A”. Among them, IL-2, FGF, IFN-γ, and MCP-1 reached their highest levels within the second week of infection and then decreased. To note that, MCP-1 levels remained significantly elevated compared with controls. IL-10, GM-CSF, and IL-6 increased later and showed an increasing trend over time. Moreover, exogenous addition of IL-10 significantly downregulated IFN-γ response and several other immune factors in both COVID-19 patients and NO COVID-19-VCs evaluated by ELISA and a multiplex analysis (Luminex) in “study population B”. Importantly, IL-10 did not affect cell survival, but decreased the frequencies of T-cells producing IFN-γ, TNF-α, and IL-2 (p<0.05) and down-modulated HLA-DR expression on CD8⁺ and NK cells.

Conclusion

This study provides important insights into immune modulating effects of IL-10 in COVID-19 and may provide valuable information regarding the further in vivo investigations.

Enhanced immune effects and protection conferred by simultaneously targeting GAPDH, SeM, and EAG of S. equi via TLR4

Strangles, which is caused by Streptococcus equi subspecies equi, is one of the most prevalent equine infectious diseases and poses heavy economic losses worldwide. Although various vaccines have been used for decades, they seemed to be sub-optimal to demonstrate effective protection, and the antigen component of vaccines against S. equi remains to be optimized. In the present study, three target antigens (M-like protein, α2-macroglobulin and IgG-binding protein, and glyceraldehyde-3-phosphate dehydrogenase) were selected and expressed. Mice were immunized and challenged, and their immune response and efficacy were evaluated. The results revealed that this optimized multi-antigen treatment elicited a high expression level of T-cell receptor, major histocompatibility complex I, toll-like receptor TLR-4, and increased specific antibody. In addition, the challenge experiment showed an evidently improved protection efficacy. The present work demonstrated that these three proteins might be used as a promising multicomponent subunit vaccine candidate against S. equi infection.

A murine model of dengue virus infection in suckling C57BL/6 and BALB/c mice

Dengue is a significant public health concern across tropical and subtropical regions worldwide, principally causing disease in children. Very young children are at increased risk of severe manifestations of dengue infection. The mechanism of dengue disease in this population is not fully understood. In this study, we present a murine model of dengue virus primary infection in suckling C57BL/6 and BALB/c mice in order to investigate disease pathogenesis. Three-day-old C57BL/6 mice intraperitoneally infected with DENV-2 NGC were more susceptible to infection than BALB/c mice, showing increased liver enzymes, extended viremia, dissemination to organs and histological alterations in liver and small intestine. Furthermore, the immune response in DENV-infected C57BL/6 mice exhibited a marked Th1 bias compared to BALB/c mice. These findings highlight the possibility of establishing an immunocompetent mouse model of DENV-2 infection in suckling mice that reproduces certain signs of disease observed in humans and that could be used to further study age-related mechanisms of dengue pathogenesis.

Optimized GAPDH-truncated immunogen of Streptococcus equi elicits an enhanced immune response and provides effective protection in a mouse model

Strangles is an acute and frequently diagnosed infectious disease caused by Streptococcus equi subsp. equi. Infection with this pathogen can cause grave losses to the equine industry. The present work investigates glyceraldehyde-3-phosphate dehydrogenase (GAPDH), an important surface-localized virulence factor of S. equi, to determine whether it could be developed into an efficacious and suitable subunit vaccine against strangles. Two different recombinant fragments of S. equi GAPDH, namely, GAPDH-L and GAPDH-S, were constructed and expressed. Further, the antigenicity and immunogenicity of these two recombinant proteins were compared and evaluated in a mouse model. Our results revealed that immune responses were efficiently induced by the proteins in immunized mice. Remarkably, higher survival rates and significantly lower bacterial loads in the lung, liver, kidney, and spleen were observed in the GAPDH-S group compared with the GAPDH-L group after challenge with S. equi. High levels of specific antibodies, elevated antibody titers, and increased proportions of CD8 + T cells further indicated that GAPDH-S elicited better humoral and cellular immune responses than GAPDH-L. Furthermore, the induction of TCR, TLR-2, TLR-3, and TLR-4 significantly increased in the GAPDH-S group compared with those in the GAPDH-L and negative control groups. In summary, our results indicate that the optimized recombinant protein GAPDH-S is a promising candidate construct that may be further developed into a multivalent subunit vaccine for strangles.

Target the Host, Kill the Bug; Targeting Host Respiratory Immunosuppressive Responses as a Novel Strategy to Improve Bacterial Clearance During Lung Infection

The lung is under constant pressure to protect the body from invading bacteria. An effective inflammatory immune response must be tightly orchestrated to ensure complete clearance of any invading bacteria, while simultaneously ensuring that inflammation is kept under strict control to preserve lung viability. Chronic bacterial lung infections are seen as a major threat to human life with the treatment of these infections becoming more arduous as the prevalence of antibiotic resistance becomes increasingly commonplace. In order to survive within the lung bacteria target the host immune system to prevent eradication. Many bacteria directly target inflammatory cells and cytokines to impair inflammatory responses. However, bacteria also have the capacity to take advantage of and strongly promote anti-inflammatory immune responses in the host lung to inhibit local pro-inflammatory responses that are critical to bacterial elimination. Host cells such as T regulatory cells and myeloid-derived suppressor cells are often enhanced in number and activity during chronic pulmonary infection. By increasing suppressive cell populations and cytokines, bacteria promote a permissive environment suitable for their prolonged survival. This review will explore the anti-inflammatory aspects of the lung immune system that are targeted by bacteria and how bacterial-induced immunosuppression could be inhibited through the use of host-directed therapies to improve treatment options for chronic lung infections.

The immunomodulatory effects of mesenchymal stem cells on long term pulmonary complications in an animal model exposed to a sulfur mustard analog

INTRODUCTION

Sulfur Mustard (SM) is one of the most lethal chemicals with major complications manifested in the lungs. Although the pathogenesis behind SM-induced lung injury still remains poorly understood, prolonged activation and the imbalance of two major macrophage populations (M1 and M2) have been suggested to be involved. Here, we tried to investigate the effectiveness of adipose-derived mesenchymal stem cells (AD-MSC) on long-term lesions induced by CEES, an SM analog. The modulation of pulmonary immune cells and alveolar macrophage phenotype alteration was studied in the animal model used.

METHODS

Histopathological changes were investigated in the lungs and analysis of surface markers of alveolar macrophages as well as their cytokine expression in the BAL fluid was carried out by flow cytometry and ELISA, respectively.

RESULTS

Treatment of mice with AD-MSC after intraperitoneal administration of CEES (10 mg/kg) reduces progressive histopathologic changes in the lung. Flow cytometric analysis of isolated alveolar macrophages in the bronchoalveolar lavage showed that the accumulation of both M1 and M2 macrophages in response to CEES was reduced by MSC administration. AD-MSCs caused a marked reduction in the CD86- and CD206-expressing macrophages compared to the untreated groups. The modulating effect of AD-MSCs in the M1-subset was much more significant compared to M2. These findings suggest that AD-MSCs understand their environment and restore the balance in disorders associated with Th1 or Th2 imbalance. Our results indicate that MSCs may represent an effective approach to repair lung injury induced by mustards.

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.

The Effects of IL10 and NK Cells on the Susceptibility to Mouse Cytomegalovirus in BALB/c Mice despite the Compensation of IFNγ

OBJECTIVE

The aim of this study was to determine which factors lead to the susceptibility to mouse cytomegalovirus (MCMV) in the spleens of BALB/c mice.

METHODS

BALB/c and C57BL/6 mice were randomly divided into a control group and an infection group and sacrificed on day 0, 1, 3, 7, 14, and 28 postinfection. The cytotoxicity of NK cells was determined by evaluating lactate dehydrogenase contents. Flow cytometry was used to analyze activated NK cells, IFNγ+ NK cells, and total NK cells in the spleen. The pathological changes of spleens in each group were analyzed by HE staining. The expression of IL10, IL18, IFNγ, Thpok, and IFNβ of spleens was determined by quantitative reverse transcriptase PCR. The viral loads of MCMV in spleens and salivary glands were also detected.

RESULTS

We found that spleen NK cells and IL10 in C57BL/6 mice possessed more powerful immunity to MCMV than BALB/c mice. In BALB/c mice, combined effects of the cytotoxicity of NK cells and IFNγ in spleens still ended up with deficient control of infection.

CONCLUSION

The functional shortage of NK cells and inappropriate expression of IL10 result in the susceptibility to MCMV in BALB/c mice.

Early Resistance of Non-virulent Mycobacterial Infection in C57BL/6 Mice Is Associated With Rapid Up-Regulation of Antimicrobial Cathelicidin Camp

Early clearance of tuberculosis is the successful eradication of inhaled bacteria before the development of an adaptive immune response. We previously showed, by utilizing a non-virulent mycobacteria infection model, that C57BL/6 mice are more efficient than BALB/c in their control of bacterial growth in the lungs during the first weeks of the infection. Here, we assessed early (within 1–3 days) innate immune events locally in the lungs to identify factors that may contribute to the control of non-virulent mycobacterial burden. We confirmed that C57BL/6 mice are more resistant to infection compared with BALB/c after intranasal inoculation with mycobacterium. Transcriptomic analyses revealed a remarkably silent signature in C57BL/6 mice despite effective control of bacterial growth. In contrast, BALB/c mice up-regulated genes associated with neutrophil and myeloid cell chemotaxis and migration. Flow cytometry analyses corroborated the transcriptomic analyses and demonstrated influx of both neutrophil and myeloid cell populations in BALB/c mice, while these did not increase in C57BL/6 mice. We further detected increased release of TNF-α from BALB/c lung cells but limited release from C57BL/6-derived cells. However, C57BL/6 mice showed a marked early up-regulation of the Camp gene, encoding the cathelicidin CRAMP peptide, post-mycobacterial exposure. CRAMP (LL-37 in human) expression in the lungs was confirmed using immunofluorescence staining. Altogether, these findings show that C57BL/6 mice can clear the mycobacterial infection early and that this early control is associated with high CRAMP expression in the lungs without concomitant influx of immune cells. The role of CRAMP/LL-37 during mycobacterial infection may be relevant for novel protective strategies, and warrants further studies of human cohorts.

Differences in innate IFNγ and IL-17 responses to Bordetella pertussis between BALB/c and C57BL/6 mice: role of γδT cells, NK cells, and dendritic cells

Cell-mediated immune responses characterized by the secretion of IFNγ and IL-17 play an important role in the immune response to Bordetella pertussis (B. pertussis). We investigated innate sources of IFNγ and IL-17 upon stimulation of spleen cells from BALB/c (B/c) and C57BL/6 (B6) mice with heat-killed B. pertussis (hkBp). Spleen cells from B/c mice secreted less IFNγ and more IL-17 than those from B6 mice. Innate IFNγ was produced predominantly by NK cells in B/c mice and by CD8 T cells and NK cells in B6 mice. Innate IL-17 was produced primarily by γδT cells in both mouse strains. The secretion of IFNγ was abrogated by anti-IL-12, and the production of IL-17 was abolished by anti-IL-1β- and anti-IL23-neutralizing antibodies. B/c dendritic cells (DCs) stimulated with hkBp secreted significantly more IL-1β and less IL-12 than B6 DCs. Differences in JNK phosphorylation in DCs suggest that this pathway plays a role in the differences between B/c and B6 strains. Mixed cultures of DCs and γδT cells from B/c and B6 showed that cytokines from DCs as well as γδT cell-intrinsic factors contributed to the robust innate IL-17 response in B/c strain. Stimulation of γδT cells with IL-1β and IL-23 was sufficient for IL-17 secretion whereas IL-12 inhibited the secretion of IL-17. A larger fraction of γδT cells were γδT-17 cells in B/c mice than B6 mice. Our data indicate important roles for genetically determined factors in the innate IFNγ and IL-17 responses to B. pertussis.

STAT3 expression by myeloid cells is detrimental for the T- cell-mediated control of infection with Mycobacterium tuberculosis

STAT3 is a master regulator of the immune responses. Here we show that M. tuberculosis-infected stat3^fl/fllysm cre mice, defective for STAT3 in myeloid cells, contained lower bacterial load in lungs and spleens, reduced granuloma extension but higher levels of pulmonary neutrophils. STAT3-deficient macrophages showed no improved control of intracellular mycobacterial growth. Instead, protection associated to elevated ability of stat3^fl/fllysm cre antigen-presenting cells (APCs) to release IL-6 and IL-23 and to stimulate IL-17 secretion by mycobacteria-specific T cells. The increased IL-17 secretion accounted for the improved control of infection since neutralization of IL-17 receptor A in stat3^fl/fllysm cre mice hampered bacterial control. APCs lacking SOCS3, which inhibits STAT3 activation via several cytokine receptors, were poor inducers of priming and of the IL-17 production by mycobacteria-specific T cells. In agreement, socs3^fl/flcd11c cre mice deficient of SOCS3 in DCs showed increased susceptibility to M. tuberculosis infection. While STAT3 in APCs hampered IL-17 responses, STAT3 in mycobacteria-specific T cells was critical for IL-17 secretion, while SOCS3 in T cells impeded IL-17 secretion. Altogether, STAT3 signalling in myeloid cells is deleterious in the control of infection with M. tuberculosis.

We studied the role of STAT3, a major regulator of immunity, in the control of the infection with M. tuberculosis. Stat3^fl/fllysm cre mice, deficient in STAT3 in myeloid cells, showed lower bacterial levels in organs and reduced extension of lung granulomas after infection with M. tuberculosis. STAT3-deficient APCs stimulated with innate receptor agonists released high levels of IL-6 and IL-23, and promoted IL-17 production by mycobacteria-specific CD4+ T cells. Increased IL-17 levels accounted for the increased resistance to M. tuberculosis of the STAT3-deficient mice. Instead, stat3^fl/fllysm cre macrophages showed no improved control of mycobacterial growth. SOCS3 is a negative regulator of STAT3 activation. The ability of socs3^fl/fllysm cre APCs to secrete IL-6 and IL-23 and to stimulate IL-17 production by antigen-specific T cells was reduced. In agreement, mice lacking SOCS3 in DCs showed increased susceptibility to M. tuberculosis infection. Different to a role in myeloid cells, STAT3 expression by mycobacteria-specific T cells was required for IL-17 secretion while SOCS3 in T cells hampered IL-17 production. Therefore, despite STAT3 expression in T cells is required for Th17 differentiation, STAT3 in APCs hampers secretion of Th17 promoting cytokines and the secretion of IL-17 by mycobacteria-specific T cells and reduces the resistance of mice to infection with M. tuberculosis.

Virulence and immunogenicity of genetically defined human and porcine isolates of M. avium subsp. hominissuis in an experimental mouse infection

Mycobacterium avium subsp. hominissuis (Mah) represents a health concern for humans and to a lesser extent for pigs, but its zoonotic potential remains elusive. Using multispacer sequence typing (MST) we previously identified 49 different genotypes of Mah among Belgian clinical and porcine isolates, with 5 MSTs shared by both hosts. Using experimental intranasal infection of BALB/c mice, we compared the virulence and immunogenicity of porcine and clinical human isolates with shared genotype or with a genotype only found in humans or pigs. Bacterial replication was monitored for 20 weeks in lungs, spleen and liver and mycobacteria specific spleen cell IFN-γ, IL-10 and IL-17 production as well as serum antibody responses were analyzed. Isolates varied in virulence, with human and porcine isolates sharing MST22 genotype showing a thousand fold higher bacterial replication in lungs and more dissemination to spleen and liver than the human and porcine MST91 isolates. Virulent MST22 type was also associated with progressive suppression of IFN-γ and IL-17 responses, and increased IL-10 production. Whole genome sequencing of the two virulent isolates with MST22 genotype and two avirulent isolates of genotype MST91 and comparison with two well-studied M. avium subsp. hominissuis reference strains i.e. Mah 104 and Mah TH135, identified in the two MST22 isolates nine specific virulence factors of the mammalian cell entry family, that were identical with Mah 104 strain. Despite the obvious limitations of the mouse model, a striking link of virulence and identity at the genome level of porcine and human isolates with the same multisequence type, for which no correlation of place of residence (humans) or farm of origin (pigs) was observed, seems to point to the existence in the environment of certain genotypes of Mah which may be more infectious both for humans and pigs than other genotypes.

The role of IL-10 in Mycobacterium avium subsp. paratuberculosis infection

Mycobacterium avium subsp. paratuberculosis (MAP) is an intracellular pathogen and is the causative agent of Johne's disease of domestic and wild ruminants. Johne's disease is characterized by chronic granulomatous enteritis leading to substantial economic losses to the livestock sector across the world. MAP persistently survives in phagocytic cells, most commonly in macrophages by disrupting its early antibacterial activity. MAP triggers several signaling pathways after attachment to pathogen recognition receptors (PRRs) of phagocytic cells. MAP adopts a survival strategy to escape the host defence mechanisms via the activation of mitogen-activated protein kinase (MAPK) pathway. The signaling mechanism initiated through toll like receptor 2 (TLR2) activates MAPK-p38 results in up-regulation of interleukin-10 (IL-10), and subsequent repression of inflammatory cytokines. The anti-inflammatory response of IL-10 is mediated through membrane-bound IL-10 receptors, leading to trans-phosphorylation and activation of Janus Kinase (JAK) family receptor-associated tyrosine kinases (TyKs), that promotes the activation of latent transcription factors, signal transducer and activators of transcription 3 (STAT3). IL-10 is an important inhibitory cytokine playing its role in blocking phagosome maturation and apoptosis. In the current review, we describe the importance of IL-10 in early phases of the MAP infection and regulatory mechanisms of the IL-10 dependent pathways in paratuberculosis. We also highlight the strategies to target IL-10, MAPK and STAT3 in other infections caused by intracellular pathogens.

A Rhesus Macaque Model of Pulmonary Nontuberculous Mycobacterial Disease

In this study, we sought to develop a nonhuman primate model of pulmonary Mycobacterium avium complex (MAC) disease. Blood and bronchoalveolar lavage fluid were collected from three female rhesus macaques infected intrabronchially with escalating doses of M. avium subsp. hominissuis. Immunity was determined by measuring cytokine levels, lymphocyte proliferation, and antigen-specific responses. Disease progression was monitored clinically and microbiologically with serial thoracic radiographs, computed tomography scans, and quantitative mycobacterial cultures. The animal subjected to the highest inoculum showed evidence of chronic pulmonary MAC disease. Therefore, rhesus macaques could provide a robust model in which to investigate host-pathogen interactions during MAC infection.

Delivery of LLKKK18 loaded into self-assembling hyaluronic acid nanogel for tuberculosis treatment

Tuberculosis (TB), a disease caused by the human pathogen Mycobacterium tuberculosis, recently joined HIV/AIDS on the top rank of deadliest infectious diseases. Low patient compliance due to the expensive, long-lasting and multi-drug standard therapies often results in treatment failure and emergence of multi-drug resistant strains. In this scope, antimicrobial peptides (AMPs) arise as promising candidates for TB treatment. Here we describe the ability of the exogenous AMP LLKKK18 to efficiently kill mycobacteria. The peptide's potential was boosted by loading into self-assembling Hyaluronic Acid (HA) nanogels. These provide increased stability, reduced cytotoxicity and degradability, while potentiating peptide targeting to main sites of infection. The nanogels were effectively internalized by macrophages and the peptide presence and co-localization with mycobacteria within host cells was confirmed. This resulted in a significant reduction of the mycobacterial load in macrophages infected in vitro with the opportunistic M. avium or the pathogenic M. tuberculosis, an effect accompanied by lowered pro-inflammatory cytokine levels (IL-6 and TNF-α). Remarkably, intra-tracheal administration of peptide-loaded nanogels significantly reduced infection levels in mice infected with M. avium or M. tuberculosis, after just 5 or 10 every other day administrations. Considering the reported low probability of resistance acquisition, these findings suggest a great potential of LLKKK18-loaded nanogels for TB therapeutics.

Trehalose 6,6-Dimycolate from Mycobacterium tuberculosis Induces Hypercoagulation

Tuberculosis (TB) remains a global health concern. Trehalose 6'6-dimycolate (TDM) activates innate inflammation and likely also stimulates chronic inflammation observed during disease progression. Noninfectious models using purified TDM oil/water emulsions elicit pathologic findings observed in patients with TB. We introduce a new TDM model that promotes inflammatory lung pathologic findings and vascular occlusion and hemorrhage. C57BL/6 and BALB/c mice were injected with 10 μg of i.p. TDM in light mineral oil (TDM-IP). At day 7, another injection of 10 μg of i.v. TDM in oil/water emulsion was given (TDM-IV). The i.p./i.v. TDM (TDM-IVIP) group was compared with mice injected once with i.v. or i.p. TDM. The responses to TDM-IP, TDM-IV, or TDM-IPIV were consistent between mouse strains. Mice that received TDM-IV and TDM-IPIV had inflammatory pathologic findings with increases in inflammatory and T-cell cytokines, and the TDM-IPIV group had further enhancement of IL-10 and granulocyte-macrophage colony-stimulating factor. The TDM-IPIV group had increased CD4(+) T cells in lung tissue, significantly increased coagulation, decreased clot formation time, and increased maximum clot firmness. Masson's trichrome staining revealed increased deposition of collagen in the occluded vasculature. TDM-IPIV promotes a hypercoagulopathy state, independent of inflammation. This new model argues that TDM is sufficient to generate the hypercoagulopathy observed in patients with TB.

Association of Interleukin-10 promoter polymorphisms with neurosyphilis

Interleukin 10 (IL-10) is a potent anti-inflammatory cytokine. Increased production of IL-10 has been found in late syphilis, presumably creating favorable conditions for bacteria persistence. Single-nucleotide polymorphisms (SNPs) within the promoter of IL-10 gene have been found to influence IL-10 production. We investigated whether SNPs in the IL-10 gene promoter are associated with cerebrospinal fluid (CSF) levels of IL-10 and neurosyphilis. Polymorphisms in the gene for IL-10 (G→A mutation at the position -1084 and C→A mutation at the position -592) were sought in 35 patients with syphilis and 24 healthy volunteers. CSF examination (i.e. routine laboratory tests and IL-10 levels) was performed in all syphilis patients. Neurosyphilis was defined as reactive CSF VDRL test or CSF white blood cells⩾5/μL and CSF protein concentration⩾45mg/dL. Overall, 31% of patients with syphilis had neurosyphilis. CSF IL-10 levels were significantly higher in patients with neurosyphilis when compared to those with syphilis but not neurosyphilis. -1082 GG and -592 CC genotypes were significantly associated with higher CSF IL-10 levels. Moreover, these genotypes were found to be more frequent in individuals with neurosyphilis in comparison to those without neurosyphilis. Anti-inflammatory immune response seems to be important in pathogenesis of neurosyphilis. Our data suggest that host-related factors, such as SNPs of immune regulatory genes may influence the susceptibility to neurosyphilis.

Foxp3+ T cells inhibit antitumor immune memory modulated by mTOR inhibition

Inhibition of mTOR signaling enhances antitumor memory lymphocytes. However, pharmacologic mTOR inhibition also enhances regulatory T-cell (Treg) activity. To counter this effect, Treg control was added to mTOR inhibition in preclinical models. Tregs were controlled with CD4-depleting antibodies because CD4 depletion has high translational potential and already has a well-established safety profile in patients. The antitumor activity of the combination therapy was CD8 dependent and controlled growth of syngeneic tumors even when an adoptive immunotherapy was not used. Lymphocytes resulting from the combination therapy could be transferred into naïve mice to inhibit aggressive growth of lung metastases. The combination therapy enhanced CD8 memory formation as determined by memory markers and functional studies of immune recall. Removal of FoxP3-expressing T lymphocytes was the mechanism underlying immunologic memory formation following CD4 depletion. This was confirmed using transgenic DEREG (depletion of regulatory T cells) mice to specifically remove Foxp3(+) T cells. It was further confirmed with reciprocal studies where stimulation of immunologic memory because of CD4 depletion was completely neutralized by adoptively transferring tumor-specific Foxp3(+) T cells. Also contributing to tumor control, Tregs that eventually recovered following CD4 depletion were less immunosuppressive. These results provide a rationale for further study of mTOR inhibition and CD4 depletion in patients.

Pattern recognition receptors and cytokines in Mycobacterium tuberculosis infection--the double-edged sword?

Tuberculosis, an infectious disease caused by Mycobacterium tuberculosis (Mtb), remains a major cause of human death worldwide. Innate immunity provides host defense against Mtb. Phagocytosis, characterized by recognition of Mtb by macrophages and dendritic cells (DCs), is the first step of the innate immune defense mechanism. The recognition of Mtb is mediated by pattern recognition receptors (PRRs), expressed on innate immune cells, including toll-like receptors (TLRs), complement receptors, nucleotide oligomerization domain like receptors, dendritic cell-specific intercellular adhesion molecule grabbing nonintegrin (DC-SIGN), mannose receptors, CD14 receptors, scavenger receptors, and FCγ receptors. Interaction of mycobacterial ligands with PRRs leads macrophages and DCs to secrete selected cytokines, which in turn induce interferon-γ- (IFNγ-) dominated immunity. IFNγ and other cytokines like tumor necrosis factor-α (TNFα) regulate mycobacterial growth, granuloma formation, and initiation of the adaptive immune response to Mtb and finally provide protection to the host. However, Mtb can evade destruction by antimicrobial defense mechanisms of the innate immune system as some components of the system may promote survival of the bacteria in these cells and facilitate pathogenesis. Thus, although innate immunity components generally play a protective role against Mtb, they may also facilitate Mtb survival. The involvement of selected PRRs and cytokines on these seemingly contradictory roles is discussed.

Heme catabolism by heme oxygenase-1 confers host resistance to Mycobacterium infection

Heme oxygenases (HO) catalyze the rate-limiting step of heme degradation. The cytoprotective action of the inducible HO-1 isoform, encoded by the Hmox1 gene, is required for host protection against systemic infections. Here we report that upregulation of HO-1 expression in macrophages (M) is strictly required for protection against mycobacterial infection in mice. HO-1-deficient (Hmox1(-/-)) mice are more susceptible to intravenous Mycobacterium avium infection, failing to mount a protective granulomatous response and developing higher pathogen loads, than infected wild-type (Hmox1(+/+)) controls. Furthermore, Hmox1(-/-) mice also develop higher pathogen loads and ultimately succumb when challenged with a low-dose aerosol infection with Mycobacterium tuberculosis. The protective effect of HO-1 acts independently of adaptive immunity, as revealed in M. avium-infected Hmox1(-/-) versus Hmox1(+/+) SCID mice lacking mature B and T cells. In the absence of HO-1, heme accumulation acts as a cytotoxic pro-oxidant in infected M, an effect mimicked by exogenous heme administration to M. avium-infected wild-type M in vitro or to mice in vivo. In conclusion, HO-1 prevents the cytotoxic effect of heme in M, contributing critically to host resistance to Mycobacterium infection.

IL-10 inhibits mature fibrotic granuloma formation during Mycobacterium tuberculosis infection

Protective immunity and latent Mycobacterium tuberculosis infection in humans are associated with the formation of mature protective granulomas within the lung. Unfortunately, understanding the importance of such structures has been hindered by the lack of small-animal models that can develop mature granulomas. In this article, we describe for the first time, to our knowledge, the formation of mature, fibrotic M. tuberculosis-containing pulmonary granulomas in a mouse model of IL-10 deficiency (CBA/J IL-10(-/-)). Long-term control of M. tuberculosis infection in the absence of IL-10 was also associated with an early and enhanced capacity for Ag presentation and a significant increase in the generation of multifunctional T cells. Although IL-10 deficiency is known to enhance Th1 immune responses in general, we demonstrate in this study using transient anti-IL-10R treatment that it is the presence of IL-10 in vivo during the first month of M. tuberculosis infection that plays a definitive role in the inhibition of optimum protective immunity that can establish the environment for mature granuloma formation. Although the importance of IL-10 during M. tuberculosis infection has been debated, our data demonstrate that in CBA/J mice, IL-10 plays a significant early inhibitory role in preventing the development of protective immunity associated with containment of M. tuberculosis infection.

Role of interleukin 10 transcriptional regulation in inflammation and autoimmune disease

Interleukin 10 (IL-10) is a cytokine with potent anti-inflammatory properties that plays a central role in limiting host immune response to pathogens, thereby preventing damage to the host and maintaining normal tissue homeostasis. Dysregulation of IL-10 is associated with enhanced immunopathology in response to infection as well as increased risk for development of many autoimmune diseases. Thus a fundamental understanding of IL-10 gene expression is critical for our comprehension of disease progression and resolution of host inflammatory response. In this review, we discuss modes of regulation of IL-10 gene expression in immune effector cell types, including signal transduction, epigenetics, promoter architecture, and post-transcriptional regulation, and how aberrant regulation contributes to immunopathology and disease progression.

Inhibition of IL-10 production by maternal antibodies against Group B Streptococcus GAPDH confers immunity to offspring by favoring neutrophil recruitment

Group B Streptococcus (GBS) is the leading cause of neonatal pneumonia, septicemia, and meningitis. We have previously shown that in adult mice GBS glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is an extracellular virulence factor that induces production of the immunosuppressive cytokine interleukin-10 (IL-10) by the host early upon bacterial infection. Here, we investigate whether immunity to neonatal GBS infection could be achieved through maternal vaccination against bacterial GAPDH. Female BALB/c mice were immunized with rGAPDH and the progeny was infected with a lethal inoculum of GBS strains. Neonatal mice born from mothers immunized with rGAPDH were protected against infection with GBS strains, including the ST-17 highly virulent clone. A similar protective effect was observed in newborns passively immunized with anti-rGAPDH IgG antibodies, or F(ab')₂ fragments, indicating that protection achieved with rGAPDH vaccination is independent of opsonophagocytic killing of bacteria. Protection against lethal GBS infection through rGAPDH maternal vaccination was due to neutralization of IL-10 production soon after infection. Consequently, IL-10 deficient (IL-10^−/−) mice pups were as resistant to GBS infection as pups born from vaccinated mothers. We observed that protection was correlated with increased neutrophil trafficking to infected organs. Thus, anti-rGAPDH or anti-IL-10R treatment of mice pups before GBS infection resulted in increased neutrophil numbers and lower bacterial load in infected organs, as compared to newborn mice treated with the respective control antibodies. We showed that mothers immunized with rGAPDH produce neutralizing antibodies that are sufficient to decrease IL-10 production and induce neutrophil recruitment into infected tissues in newborn mice. These results uncover a novel mechanism for GBS virulence in a neonatal host that could be neutralized by vaccination or immunotherapy. As GBS GAPDH is a structurally conserved enzyme that is metabolically essential for bacterial growth in media containing glucose as the sole carbon source (i.e., the blood), this protein constitutes a powerful candidate for the development of a human vaccine against this pathogen.

Streptococcus agalactiae (Group B streptococcus, GBS) is the leading infectious cause of morbidity and mortality among neonates. However, there is still no satisfactory explanation of why neonates are so susceptible to GBS infections. Intrapartum antibiotic prophylaxis (IAP) was implemented in many countries but led to the emergence of antibiotic-resistant GBS strains. Therefore, maternal vaccination represents an attractive alternative to IAP. Here, we show that the high susceptibility of newborn mice to GBS infections is associated with their propensity to produce elevated amounts of immunosuppressive cytokine IL-10. We also demonstrate that IL-10 impairs neutrophil recruitment into infected organs thus preventing bacterial clearance. We identified extracellular GAPDH as the GBS factor that induces the high IL-10 production detected early upon neonatal infection. We show that maternal vaccination with recombinant GAPDH confers robust protective immunity against lethal infection with a GBS hyper-virulent strain in mice offspring. This protection can also be obtained either by antibody neutralization of GBS GAPDH or by blocking IL-10 binding to its receptor. As GBS GAPDH is an essential protein for bacterial growth, it is present in all GBS strains and thus constitutes an appropriate target antigen for a global effective vaccine against this pathogen.

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

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

Immune evasive mechanisms contributing to persistent Leishmania donovani infection

The protozoan parasite Leishmania donovani, a causative agent of visceral leishmaniasis, has evolved several strategies to interfere with the immune system and establish persistent infections that are potentially lethal. In this article, we discuss two mechanisms of immune evasion adopted by the parasite: the induction of immune suppressive IL-10 responses and the generation of poor and functionally impaired CD8(+) T-cell responses.

Strain-specific outcomes of repeated social defeat and chronic fluoxetine treatment in the mouse

Social stress is a risk factor for affective disorders in vulnerable individuals. Although the biological nature of stress susceptibility/resilience remains to be elucidated, genetic variation is considered amongst the principal contributors to brain disorders. Furthermore, genetic predisposition may be determinant for the therapeutic outcome, as proposed for antidepressant treatments. In the present studies we compared the inherently diverse genetic backgrounds of 2 mouse strains by assessing the efficacy of a chronic antidepressant treatment in a repeated social stress procedure. C57BL/6J and BalbC mice underwent 10-day social defeats followed by 28-day fluoxetine treatment (10 mg/kg/mL, p.o.). In C57BL/6J, most of the social defeat-induced changes were of metabolic nature including persistently altered feed efficiency and decreased abdominal fat stores that were ameliorated by fluoxetine. BalbC mouse behavior was persistently affected by social defeat both in the social avoidance and the forced swim tests, and in either procedure it was restored by chronic fluoxetine, whereas their endocrine parameters were mostly unaffected. The highlighted strain-specific responsivity to the metabolic and behavioral consequences of social defeat and to the chronic antidepressant treatment offers a promising research tool to further explore the underlying neural mechanisms and genetic basis of stress susceptibility and treatment response.

Enhanced protection to Mycobacterium tuberculosis infection in IL-10-deficient mice is accompanied by early and enhanced Th1 responses in the lung

IL-10 regulates the balance of an immune response between pathogen clearance and immunopathology. We show here that Mycobacterium tuberculosis (Mtb) infection in the absence of IL-10 (IL-10(-/-) mice) results in reduced bacterial loads in the lung. This reduction was preceded by an accelerated and enhanced IFN-γ response in the lung, an increased influx of CD4(+) T cells into the lung, and enhanced production of chemokines and cytokines, including CXCL10 and IL-17, in both the lung and the serum. Neutralization of IL-17 affected neither the enhanced production of CXCL10 nor the accumulation of IFN-γ-producing T cells in the lungs, but led to reduced numbers of granulocytes in the lung and reduced bacterial loads in the spleens of Mtb-infected mice. This suggests that IL-17 may contribute to dissemination of Mtb.

Polymorphisms in the gene encoding bovine interleukin-10 receptor alpha are associated with Mycobacterium avium ssp. paratuberculosis infection status

Background

Johne's disease is a chronic inflammatory bowel disease (IBD) of ruminants caused by Mycobacterium avium ssp. paratuberculosis (MAP). Since this pathogen has been implicated in the pathogenesis of human IBDs, the goal of this study was to assess whether single nucleotide polymorphism (SNPs) in several well-known candidate genes for human IBD are associated with susceptibility to MAP infection in dairy cattle.

Methods

The bovine candidate genes, interleukin-10 (IL10), IL10 receptor alpha/beta (IL10RA/B), transforming growth factor beta 1 (TGFB1), TGFB receptor class I/II (TGFBR1/2), and natural resistance-associated macrophage protein 1 (SLC11A1) were sequenced for SNP discovery using pooled DNA samples, and the identified SNPs were genotyped in a case-control association study comprised of 242 MAP negative and 204 MAP positive Holstein dairy cattle. Logistic regression was used to determine the association of SNPs and reconstructed haplotypes with MAP infection status.

Results

A total of 13 SNPs were identified. Four SNPs in IL10RA (984G > A, 1098C > T, 1269T > C, and 1302A > G) were tightly linked, and showed a strong additive and dominance relationship with MAP infection status. Haplotypes AGC and AAT, containing the SNPs IL10RA 633C > A, 984G > A and 1185C > T, were associated with an elevated and reduced likelihood of positive diagnosis by serum ELISA, respectively.

Conclusions

SNPs in IL10RA are associated with MAP infection status in dairy cattle. The functional significance of these SNPs warrants further investigation.

Host immune response to rapidly growing mycobacteria, an emerging cause of chronic lung disease

Rapidly growing mycobacteria (RGM) are environmental organisms classified under the broader category of nontuberculous mycobacteria. The most common RGM to cause human diseases are Mycobacterium abscessus, Mycobacterium chelonae, Mycobacterium fortuitum, and Mycobacterium massiliense. Infections due to the RGM are an emerging health problem in the United States. Chronic pulmonary disease and skin/soft-tissue infections are the two most common disorders due to these organisms. Clinical outcomes in the treatment of M. abscessus infections are generally disappointing. Because less is known about the nature of the immune response to M. abscessus than for tuberculosis, we herein highlight the major clinical features associated with infections due to M. abscessus and other RGM, and review the known host immune response to RGM, drawing from experimental animal and clinical studies. Based on in vitro and in vivo murine models, Toll-like receptor 2, dectin-1, tumor necrosis factor (TNF)-α, IFN-γ, leptin, T cells, and possibly neutrophils are important components in the host defense against RGM infections. However, excessive induction of TNF-α by the R morphotype of M. abscessus may allow it to be more pathogenic than the S morphotype. Clinical observations and/or genetic studies in humans corroborate many of the findings in animals in that those with cell-mediated immunodeficiency, genetic defects in IFN-γ-IL-12 axis, and those individuals on TNF-α blockers are at increased risk for nontuberculous mycobacteria infections, including the RGM. However, much remains to be discovered on why seemingly healthy individuals, particularly slender postmenopausal women with thoracic cage anomalies, appear to be at increased risk.

IL-10 is pathogenic during the development of coxsackievirus B4-induced chronic pancreatitis

Using a mouse model of coxsackievirus B4 (CVB4-V)-induced chronic pancreatitis, we investigated whether cytokines are involved in the progression of acute disease to chronic inflammatory disease. We show that IL-10 contributed to the development of chronic pancreatitis since acute disease resolved when IL-10 was absent or when IL-10 signaling was disrupted. We explored the underlying mechanisms by which IL-10 affected disease progression, using a novel approach to assess immunological events occurring in situ. Multiple markers that define functional innate immune responses and functional T cell responses were monitored over the course of CVB4-V infection of wild-type and IL-10 knockout mice, using a multiplex transcriptional profiling approach. We show that high levels of IL-10 early during infection were associated with delayed innate and T cell responses. Furthermore, high IL-10 production correlated with altered kinetics of T regulatory responses indicating a disruption in the balance between effector and regulatory T cell responses.

Resistance to mycobacterial infection: a pattern of early immune responses leads to a better control of pulmonary infection in C57BL/6 compared with BALB/c mice

In this study, we have compared the immunological responses associated with early pulmonary mycobacterial infection in two mouse strains, BALB/c and C57BL/6 known to exhibit distinct differences in susceptibility to infection with several pathogens. We infected mice via the intranasal route. We have demonstrated that BALB/c was less able to control mycobacterial growth in the lungs during the early phase of pulmonary infection. Our results showed that during the early phase (day 3 to week 1), BALB/c mice exhibited a delay in the production of TNF and IFN-gamma in the lungs compared to C57BL/6 mice. Levels of IL-12 and soluble TNF receptors (sTNFR) were comparable between the mouse strains. The cellular subset distribution in these mice before and after infection showed a higher increase in CD11b+ cells in the lungs of C57BL/6, compared to BALB/c as early as day 3 postinfection. At early time points, higher levels of monocyte chemoattractant protein (MCP)-1 and macrophage inflammatory protein 1 (MIP)-alpha were detected in C57BL/6 than BALB/c mice. In vitro, BCG-infected bone marrow derived macrophages (BMM) from both mouse strains displayed similar capacities to either phagocytose bacteria or produce soluble mediators such as TNF, IL-12 and nitric oxide (NO). Although IFN-gamma stimulation of infected BMM in both mouse strains resulted in the induction of antimycobacterial activity, BALB/c mice had a reduced capacity to kill ingested bacteria. The above observations indicate that the chain of early, possibly innate immunological events occurring during pulmonary mycobacterial infection may directly impact on increased susceptibility or resistance to infection.

Enzymatic removal of mannose moieties can increase the immune response to HIV-1 gp120 in vivo

The Env glycoproteins gp120 and gp41 are used in humoral immunity-based vaccines against human immunodeficiency virus (HIV-1) infection. One among many obstacles to such a vaccine is the structural defenses of Env glycoproteins that limit their immunogenicity. For example, gp120 mannose residues can induce immunosuppressive responses in vitro, including IL-10 expression, via mannose C-type lectin receptors on antigen-presenting cells. Here, we have investigated whether mannose removal alters gp120 immunogenicity in mice. Administering demannosylated gp120 (D-gp120) in the T(H)2-skewing adjuvant Alum induced approximately 50-fold higher titers of anti-gp120 IgG, compared to unmodified gp120. While the IgG subclass profile was predominantly T(H)2-associated IgG1, Abs of the T(H)1-associated IgG2a and IgG3 subclasses were also detectable in D-gp120 recipients. Immunizing with D-gp120 also improved T-cell responses. Giving an IL-10 receptor blocking MAb together with unmodified gp120 in Alum increased the anti-gp120 IgG titer, implicating IL-10 as a possible mediator of auto-suppressive responses to gp120.

Airway delivery of silica increases susceptibility to mycobacterial infection in mice: potential role of repopulating macrophages

Silica exposure results in an increased lifelong risk of developing mycobacterial pulmonary infections. To date, there are no animal models that replicate this finding to permit assessment of the mechanisms underlying susceptibility to mycobacterial infection. To test the hypothesis that prior silica exposure increases risk of mycobacterial infection, we intratracheally (I.T.) administered silica, a control dust (Al(2)O(3)) or saline into mechanically ventilated C57BL/6 mice. Later, the mice received Mycobacterium avium or Mycobacterium tuberculosis I.T. Mice were sacrificed at defined time points and mycobacteria in lung homogenates were quantified. M. avium or M. tuberculosis infection was markedly increased in silica-exposed mice compared with mice exposed to either Al(2)O(3) or saline beginning 3 wk after silica exposure. Similarly, lung sections from silica-exposed mice had many more acid fast bacilli(+) (AFB(+)) organisms than from control mice. Alveolar macrophages (AMs) from bronchoalveolar lavage of silica-exposed mice also revealed a higher number of mycobacteria compared with mice treated with Al(2)O(3) or saline. In addition, passive transfer of AMs from silica-exposed mice to control mice increased M. tuberculosis susceptibility. These results indicate that silica exposure converts mycobacteria-resistant mice into mycobacteria-susceptible mice via a process that likely involves a new population of AMs that are more susceptible to mycobacterial infection.

Interleukin-10: new perspectives on an old cytokine

Interleukin-10 (IL-10) has long been recognized to have potent and broad-spectrum anti-inflammatory activity, which has been unequivocally established in various models of infection, inflammation, and even in cancer. However, because of the marginal successes of the initial clinical trials using recombinant IL-10, some of the interest in this cytokine as an anti-inflammatory therapeutic has diminished. New work showing IL-10 production from regulatory T cells and even T-helper 1 T cells has reinvigorated the field and revealed the power of this cytokine to influence immune responses. Furthermore, new preclinical studies suggest that combination therapies, using antibodies to IL-10 along with chemotherapy, can be effective in treating bacterial, viral, or neoplastic diseases. Studies to understand IL-10 gene expression in the various cell types may lead to new therapeutics to enhance or inhibit IL-10 production. In this review, we summarize what is known about the regulation of IL-10 gene expression by various immune cells. We speculate on the promise that this cytokine holds to influence immune responses and mitigate immune pathologies.