Brucella intracellular replication requires trafficking through the late endosomal/lysosomal compartment

Upon entry into mammalian cells, the intracellular pathogen Brucella abortus resides within a membrane-bound compartment, the Brucella-containing vacuole (BCV), the maturation of which is controlled by the bacterium to generate a replicative organelle derived from the endoplasmic reticulum (ER). Prior to reaching the ER, Brucella is believed to ensure its intracellular survival by inhibiting fusion of the intermediate BCV with late endosomes and lysosomes, although such BCVs are acidic and accumulate the lysosomal-associated membrane protein (LAMP-1). Here, we have further examined the nature of intermediate BCVs using confocal microscopy and live cell imaging. We show that BCVs rapidly acquire several late endocytic markers, including the guanosine triphosphatase Rab7 and its effector Rab-interacting lysosomal protein (RILP), and are accessible to fluid-phase markers either delivered to the whole endocytic pathway or preloaded to lysosomes, indicating that BCVs interact with late endosomes and lysosomes. Consistently, intermediate BCVs are acidic and display proteolytic activity up to 12 h post-infection. Expression of dominant-negative Rab7 or overexpression of RILP significantly impaired the ability of bacteria to convert their vacuole into an ER-derived organelle and replicate, indicating that BCV maturation requires interactions with functional late endosomal/lysosomal compartments. In cells expressing dominant-negative Rab7[T22N], BCVs remained acidic, yet displayed decreased fusion with lysosomes. Taken together, these results demonstrate that BCVs traffic along the endocytic pathway and fuse with lysosomes, and such fusion events are required for further maturation of BCVs into an ER-derived replicative organelle.

Brucella modulates secretory trafficking via multiple type IV secretion effector proteins

The intracellular pathogenic bacterium Brucella generates a replicative vacuole (rBCV) derived from the endoplasmic reticulum via subversion of the host cell secretory pathway. rBCV biogenesis requires the expression of the Type IV secretion system (T4SS) VirB, which is thought to translocate effector proteins that modulate membrane trafficking along the endocytic and secretory pathways. To date, only a few T4SS substrates have been identified, whose molecular functions remain unknown. Here, we used an in silico screen to identify putative T4SS effector candidate proteins using criteria such as limited homology in other bacterial genera, the presence of features similar to known VirB T4SS effectors, GC content and presence of eukaryotic-like motifs. Using β-lactamase and CyaA adenylate cyclase reporter assays, we identified eleven proteins translocated into host cells by Brucella, five in a VirB T4SS-dependent manner, namely BAB1_0678 (BspA), BAB1_0712 (BspB), BAB1_0847 (BspC), BAB1_1671 (BspE) and BAB1_1948 (BspF). A subset of the translocated proteins targeted secretory pathway compartments when ectopically expressed in HeLa cells, and the VirB effectors BspA, BspB and BspF inhibited protein secretion. Brucella infection also impaired host protein secretion in a process requiring BspA, BspB and BspF. Single or combined deletions of bspA, bspB and bspF affected Brucella ability to replicate in macrophages and persist in the liver of infected mice. Taken together, these findings demonstrate that Brucella modulates secretory trafficking via multiple T4SS effector proteins that likely act coordinately to promote Brucella pathogenesis.

The usher N terminus is the initial targeting site for chaperone-subunit complexes and participates in subsequent pilus biogenesis events

Pilus biogenesis on the surface of uropathogenic Escherichia coli requires the chaperone/usher pathway, a terminal branch of the general secretory pathway. In this pathway, periplasmic chaperone-subunit complexes target an outer membrane (OM) usher for subunit assembly into pili and secretion to the cell surface. The molecular mechanisms of protein secretion across the OM are not well understood. Mutagenesis of the P pilus usher PapC and the type 1 pilus usher FimD was undertaken to elucidate the initial stages of pilus biogenesis at the OM. Deletion of residues 2 to 11 of the mature PapC N terminus abolished the targeting of the usher by chaperone-subunit complexes and rendered PapC nonfunctional for pilus biogenesis. Similarly, an intact FimD N terminus was required for chaperone-subunit binding and pilus biogenesis. Analysis of PapC-FimD chimeras and N-terminal fragments of PapC localized the chaperone-subunit targeting domain to the first 124 residues of PapC. Single alanine substitution mutations were made in this domain that blocked pilus biogenesis but did not affect targeting of chaperone-subunit complexes. Thus, the usher N terminus does not function simply as a static binding site for chaperone-subunit complexes but also participates in subsequent pilus assembly events.

Studies on the interaction of propranolol with erythrocyte membranes

The interaction of propranolol with erythrocyte membranes at concentrations stabilizing intact erythrocytes against hypotonic hemolysis produced corresponding perturbations in membrane protein and particularly membrane phospholipid components as monitored by increases in the reactivity of membrane amino and sulfhydryl groups towards trinitrobenzenesulfonic acid and 5,5'-dithio-bis(2-nitro-benzoic acid), respectively. Membrane-propranolol interactions were also analyzed in terms of alterations produced in the kinetic properties of membrane enzymes. These experiments provided evidence that propranolol-induced perturbations were sufficiently generalized as to influence the activity of enzymatic processes associated with both inner and outer membrane surfaces. Configurational changes in membrane phospholipids were implicated in these effects of propranolol, which included alterations in functionally significant membrane-cation interactions, It is suggested that the findings described here may provide a basis for understanding molecular aspects of membrane stabilization in other systems.

Age-dependent choice of sexual partners and the transmission dynamics of HIV in Sub-Saharan Africa

A mathematical model of the transmission of HIV-1 within heterosexual populations in Sub-Saharan Africa is described and its properties analysed. The model incorporates epidemiological and demographic processes and extends previous work in this area via the inclusion of age and sex dependency in rates of sexual partner change, and sexual partner choice dependent on age. Parameter assignments are made on the basis of current data on the transmission dynamics of HIV-1 and the demography of human populations in Africa. Both age-dependent rates of sexual activity and the sexual contact of males with females younger than themselves act to enhance the predicted demographic impact. With realistic parameter values, the model suggests AIDS is able to reverse the sign of population growth rates from positive to negative values over a timescale of a few decades. The sensitivity of this prediction is examined in relation to changes in the pattern of sexual contact between different age classes of females and males, different patterns of change in the age-dependent rate of sexual partner change, different assumptions concerning the doubling time of the epidemic in its early stages, and the relative efficiencies of viral transmission between men and women, and vice versa. The impact AIDS is predicted to have on the number of young and elderly persons as a fraction of the number of productive adults (the dependancy ratio) is examined under various assumptions concerning the weighting to be applied to mirror the burden imposed by the care of those with AIDS. The paper includes an assessment of the influence of the timing of changes in sexual behaviour, or the promotion of the use of condoms, on the predicted course of the epidemic. The paper concludes with a discussion of data needs and the model refinements required to more accurately mirror current understanding of the epidemiology of HIV-1.

Adoptive cell therapy using antigen-specific CD4⁻CD8⁻T regulatory cells to prevent autoimmune diabetes and promote islet allograft survival in NOD mice

AIMS/HYPOTHESIS

A new differentiation pathway for CD4(-)CD8(-) (DN) T cells has recently been identified that exhibits the potent function of peripheral converted DN T cells in suppressing immune responses and provides the potential to treat autoimmune diseases. The aim of this study was to determine if the DN T cells converted from CD4(+) T cells of NOD mice retain the antigen-specific regulatory capacity and prevent autoimmune diabetes in vivo. We also sought to determine if the combination of DN T cells with rapamycin promotes islet allograft survival in autoimmune diabetic NOD recipients.

METHODS

NOD CD4(+) T cells were converted to DN T cells in an in vitro mixed-lymphocyte reaction, with or without GAD65 peptide, as previously reported. The antigen-specific DN T cells were adoptively transferred to NOD/SCID mice, new-onset diabetic NOD mice or islet-allograft-recipient NOD mice as the part of cell-based therapy. The development of diabetes and allograft survival was assessed by monitoring blood glucose levels.

RESULTS

NOD CD4(+) T cells were converted in vitro to DN T cells at a rate of 50% and expressed unique cell features. The DN T cells from NOD donors blocked autoimmunity and prevented diabetes in NOD models, and these effects were even greater for GAD65-peptide-primed DN T cells. DN T cells acted in conjunction with rapamycin to suppress alloantigen-triggered T cell proliferation, promoted apoptosis and prolonged islet allograft survival in NOD recipients.

CONCLUSIONS/INTERPRETATION

Administration of the islet beta cell antigen-specific DN T cells can prevent the development of autoimmune diabetes and promote islet allograft survival in NOD mice.

Function of the usher N-terminus in catalysing pilus assembly

The chaperone/usher (CU) pathway is a conserved bacterial secretion system that assembles adhesive fibres termed pili or fimbriae. Pilus biogenesis by the CU pathway requires a periplasmic chaperone and an outer membrane (OM) assembly platform termed the usher. The usher catalyses formation of subunit-subunit interactions to promote polymerization of the pilus fibre and provides the channel for fibre secretion. The mechanism by which the usher catalyses pilus assembly is not known. Using the P and type 1 pilus systems of uropathogenic Escherichia coli, we show that a conserved N-terminal disulphide region of the PapC and FimD ushers, as well as residue F4 of FimD, are required for the catalytic activity of the ushers. PapC disulphide loop mutants were able to bind PapDG chaperone-subunit complexes, but did not assemble PapG into pilus fibres. FimD disulphide loop and F4 mutants were able to bind chaperone-subunit complexes and initiate assembly of pilus fibres, but were defective for extending the pilus fibres, as measured using in vivo co-purification and in vitro pilus polymerization assays. These results suggest that the catalytic activity of PapC is required to initiate pilus biogenesis, whereas the catalytic activity of FimD is required for extension of the pilus fibre.

The influence of different sexual-contact patterns between age classes on the predicted demographic impact of AIDS in developing countries

A model is developed to describe the spread of HIV within heterosexual communities and the demographic impact of AIDS. The model combines epidemiologic and demographic processes and is designed to mirror the impact of AIDS in sub-Saharan Africa. Refinements on past work in this area include unequal probabilities for transmission from females to males and from males to females, the inclusion of an age- and sex-dependent sexual-partner choice function and distributed incubation plus infectious periods. Numerical studies suggest that unequal transmission probabilities (weighted to a greater probability from males to females than vice versa), and the tendency of males to choose sexual partners of the opposite sex younger than themselves, both act to increase the demographic impact of AIDS over that predicted with equal transmission between the sexes and partner choice restricted within given age classes. Analyses support the conclusions of past work that the epidemic will only have a small detrimental impact on the dependency ratio of a population (the ratio of dependents to working adults) even when a weighting is added to take account of the extra burden imposed by the care of adult AIDS patients. However, a small increase in the ratio can imply a significant rise in the number of dependents within the population. Stimulation studies of the impact of changes in behavior to reduce transmission highlight to the need to induce such changes as early as possible in the course of the epidemic in order to minimize its impact. Directions for future research are discussed emphasizing the need to acquire quantitative data on sexual habits and to construct models to represent heterogeneity in sexual behavior.

The differential affinity of the usher for chaperone-subunit complexes is required for assembly of complete pili

Attachment to host cells via adhesive surface structures is a prerequisite for the pathogenesis of many bacteria. Uropathogenic Escherichia coli assemble P and type 1 pili for attachment to the host urothelium. Assembly of these pili requires the conserved chaperone/usher pathway, in which a periplasmic chaperone controls the folding of pilus subunits and an outer membrane usher provides a platform for pilus assembly and secretion. The usher has differential affinity for pilus subunits, with highest affinity for the tip-localized adhesin. Here, we identify residues F21 and R652 of the P pilus usher PapC as functioning in the differential affinity of the usher. R652 is important for high-affinity binding to the adhesin whereas F21 is important for limiting affinity for the PapA major rod subunit. PapC mutants in these residues are specifically defective for pilus assembly in the presence of PapA, demonstrating that differential affinity of the usher is required for assembly of complete pili. Analysis of PapG deletion mutants demonstrated that the adhesin is not required to initiate P pilus biogenesis. Thus, the differential affinity of the usher may be critical to ensure assembly of functional pilus fibres.

Direct incorporation of the NKT-cell activator α-galactosylceramide into a recombinant Listeria monocytogenes improves breast cancer vaccine efficacy

Background:

Immune suppression in the tumour microenvironment remains a major limitation to successful immunotherapy of cancer. In the current study, we analysed whether the natural killer T cell-activating glycolipid α-galactosylceramide could overcome immune suppression and improve vaccination against metastatic breast cancer.

Methods:

Mice with metastatic breast cancer (4T1 model) were therapeutically treated with a Listeria monocytogenes-based vaccine expressing tumour-associated antigen Mage-b followed by α-galactosylceramide as separate agents, or as a complex of α-galactosylceramide stably incorporated into Listeria-Mage-b. Effects on metastases, tumour weight, toxicity and immune responses were determined.

Results:

Sequential treatments of mice with established 4T1 breast carcinomas using Listeria-Mage-b followed by α-galactosylceramide as a separate agent was highly effective at reducing metastases, but was accompanied by severe liver toxicity. In contrast, combined therapy using Listeria-Mage-b modified by incorporation of α-galactosylceramide resulted in nearly complete elimination of metastases without toxicity. This was associated with a significant increase in the percentage of natural killer T cells in the spleen, and an increase in natural killer cell activity and in T cell responses to Mage-b.

Conclusions:

Our results suggest that direct incorporation of α-galactosylceramide into a live bacterial vaccine vector is a promising non-toxic new approach for the treatment of metastatic breast cancer.

Improving Mycobacterium bovis bacillus Calmette-Guèrin as a vaccine delivery vector for viral antigens by incorporation of glycolipid activators of NKT cells

Recombinant Mycobacterium bovis bacillus Calmette-Guèrin (rBCG) has been explored as a vector for vaccines against HIV because of its ability to induce long lasting humoral and cell mediated immune responses. To maximize the potential for rBCG vaccines to induce effective immunity against HIV, various strategies are being employed to improve its ability to prime CD8+ T cells, which play an important role in the control of HIV infections. In this study we adopted a previously described approach of incorporating glycolipids that activate CD1d-restricted natural killer T (NKT) cells to enhance priming of CD8+ T cells by rBCG strains expressing an SIV Gag antigen (rBCG-SIV gag). We found that the incorporation of the synthetic NKT activating glycolipid α-galactosylceramide (α-GC) into rBCG-SIV gag significantly enhanced CD8+ T cell responses against an immunodominant Gag epitope, compared to responses primed by unmodified rBCG-SIV gag. The abilities of structural analogues of α-GC to enhance CD8+ T cell responses to rBCG were compared in both wild type and partially humanized mice that express human CD1d molecules in place of mouse CD1d. These studies identified an α-GC analogue known as 7DW8-5, which has previously been used successfully as an adjuvant in non-human primates, as a promising compound for enhancing immunogenicity of antigens delivered by rBCG.vectors. Our findings support the incorporation of synthetic glycolipid activators of NKT cells as a novel approach to enhance the immunogenicity of rBCG-vectored antigens for induction of CD8+ T cell responses. The glycolipid adjuvant 7DW8-5 may be a promising candidate for advancing to non-human primate and human clinical studies for the development of HIV vaccines based on rBCG vectors.

Reducing the spread of HIV infection in sub-Saharan Africa: some demographic and economic implications

Any reduction in the rate of spread of HIV infection has consequences for the incidence and demographic effects of AIDS. In this paper, output from a published mathematical model of the dynamics of HIV transmission through heterosexual contact is used to study the implications of reducing HIV transmission on demographic patterns and national health budgets in sub-Saharan Africa. The major conclusion is that both the timing and the effectiveness of reducing HIV transmission are non-linearly related to their potential demographic and economic effects. The analysis emphasizes the benefits to be gained from a concerted effort to reduce the spread of HIV infection as early as possible in the time course of the epidemic.

Spontaneous resolution of acute rejection and tolerance induction with IL-2 fusion protein in vascularized composite allotransplantation

Vascularized composite allotransplantation (VCA) has emerged as a treatment option for treating nonlife-threatening conditions. Therefore, in order to make VCA a safe reconstruction option, there is a need to minimize immunosuppression, develop tolerance-inducing strategies and elucidate the mechanisms of VCA rejection and tolerance. In this study we explored the effects of hIL-2/Fc (a long-lasting human IL-2 fusion protein), in combination with antilymphocyte serum (ALS) and short-term cyclosporine A (CsA), on graft survival, regulatory T cell (Treg) proliferation and tolerance induction in a rat hind-limb transplant model. We demonstrate that hIL-2/Fc therapy tips the immune balance, increasing Treg proliferation and suppressing effector T cells, and permits VCA tolerance as demonstrated by long-term allograft survival and donor-antigen acceptance. Moreover, we observe two distinct types of acute rejection (AR), progressive and reversible, within hIL-2/Fc plus ALS and CsA treated recipients. Our study shows differential gene expression profiles of FoxP3 versus GzmB, Prf1 or interferon-γ in these two types of AR, with reversible rejection demonstrating higher Treg to Teff gene expression. This correlation of gene expression profile at the first clinical sign of AR with VCA outcomes can provide the basis for further inquiry into the mechanistic aspects of VCA rejection and future drug targets.

The optical mouse as an inexpensive region-of-interest position recorder in optical microscopy

In optical microscopy, the microscopic features of interest typically have to be derived from regions that are spatially distributed over the sample. While the features to be analyzed may be minute, the regions from where they must be obtained from may be located quite far apart from one another. If the features are not distinct enough to allow easy visual discrimination, it would be tedious and time-consuming to attempt to recall and revisit these regions of interest. One method to overcome this difficulty would be to note and record the graduated markings on the microscope, or to use built-in position encoders. The former is tedious while the latter is generally expensive. Here, a region-of-interest position-recording implement based on the use of an optical mouse is presented. It is inexpensive and easily adaptable to the manual stage of any optical microscope.

Vascularized osteomyocutaneous allografts are permissive to tolerance by induction-based immunomodulatory therapy

Vascularized composite allografts (VCAs) are unique among transplanted organs in that they are composed of multiple tissues with disparate antigenic and immunologic properties. As the predominant indications for VCAs are non-life-threatening conditions, there is an immediate need to develop tolerance induction strategies and to elucidate the mechanisms of VCA rejection and tolerance using VCA-specific animal models. In this study, we explore the effects of in vitro induced donor antigen-specific CD4(-) CD8(-) double negative (DN) Treg-based therapy, in a fully MHC mismatched mouse VCA such as a vascularized osteomyocutaneous as compared to a non-VCA such as a full thickness skin (FTS) transplantation model to elucidate the unique features of VCA rejection and tolerance. We demonstrate that combined therapy with antigen-induced CD4 derived DN Tregs and a short course of anti-lymphocyte serum, rapamycin and IL-2/Fc fusion protein results in donor-specific tolerance to VCA, but not FTS allografts. Macrochimerism was detected in VCA but not FTS allograft recipients up to >60 days after transplantation. Moreover, a significant increase of CD4(+) Foxp3(+) Tregs was found in the peripheral blood of tolerant VCA recipients. These data suggest that VCA are permissive to tolerance induced by DN Treg-based induction therapy.

Identification of Autophagy-Inhibiting Factors of Mycobacterium tuberculosis by High-Throughput Loss-of-Function Screening

The interaction of host cells with mycobacteria is complex and can lead to multiple outcomes ranging from bacterial clearance to progressive or latent infection. Autophagy is recognized as one component of host cell responses that has an essential role in innate and adaptive immunity to intracellular bacteria. Many microbes, including Mycobacterium tuberculosis, have evolved to evade or exploit autophagy, but the precise mechanisms and virulence factors are mostly unknown. Through a loss-of-function screening of an M. tuberculosis transposon mutant library, we identified 16 genes that contribute to autophagy inhibition, six of which encoded the PE/PPE protein family. Their expression in Mycobacterium smegmatis confirmed that these PE/PPE proteins inhibit autophagy and increase intracellular bacterial persistence or replication in infected cells. These effects were associated with increased mammalian target of rapamycin (mTOR) activity and also with decreased production of tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β). We also confirmed that the targeted deletion of the pe/ppe genes in M. tuberculosis resulted in enhanced autophagy and improved intracellular survival rates compared to those of wild-type bacteria in the infected macrophages. Differential expression of these PE/PPE proteins was observed in response to various stress conditions, suggesting that they may confer advantages to M. tuberculosis by modulating its interactions with host cells under various conditions. Our findings demonstrated that multiple M. tuberculosis PE/PPE proteins are involved in inhibiting autophagy during infection of host phagocytes and may provide strategic targets in developing therapeutics or vaccines against tuberculosis.

Current efforts and future prospects in the development of live mycobacteria as vaccines

The development of more effective vaccines against Mycobacterium tuberculosis (Mtb) remains a major goal in the effort to reduce the enormous global burden of disease caused by this pathogen. Whole-cell vaccines based on live mycobacteria with attenuated virulence represent an appealing approach, providing broad antigen exposure and intrinsic adjuvant properties to prime durable immune responses. However, designing vaccine strains with an optimal balance between attenuation and immunogenicity has proven to be extremely challenging. Recent basic and clinical research efforts have broadened our understanding of Mtb pathogenesis and created numerous new vaccine candidates that have been designed to overcome different aspects of immune evasion by Mtb. In this review, we provide an overview of the current efforts to create improved vaccines against tuberculosis based on modifications of live attenuated mycobacteria. In addition, we discuss the use of such vaccine strains as vectors for stimulating protective immunity against other infectious diseases and cancers.

Transcriptome Analysis of Mycobacteria-Specific CD4+ T Cells Identified by Activation-Induced Expression of CD154

Analysis of Ag-specific CD4⁺ T cells in mycobacterial infections at the transcriptome level is informative but technically challenging. Although several methods exist for identifying Ag-specific T cells, including intracellular cytokine staining, cell surface cytokine-capture assays, and staining with peptide:MHC class II multimers, all of these have significant technical constraints that limit their usefulness. Measurement of activation-induced expression of CD154 has been reported to detect live Ag-specific CD4⁺ T cells, but this approach remains underexplored and, to our knowledge, has not previously been applied in mycobacteria-infected animals. In this article, we show that CD154 expression identifies adoptively transferred or endogenous Ag-specific CD4⁺ T cells induced by Mycobacterium bovis bacillus Calmette-Guérin vaccination. We confirmed that Ag-specific cytokine production was positively correlated with CD154 expression by CD4⁺ T cells from bacillus Calmette-Guérin-vaccinated mice and show that high-quality microarrays can be performed from RNA isolated from CD154⁺ cells purified by cell sorting. Analysis of microarray data demonstrated that the transcriptome of CD4⁺ CD154⁺ cells was distinct from that of CD154^- cells and showed major enrichment of transcripts encoding multiple cytokines and pathways of cellular activation. One notable finding was the identification of a previously unrecognized subset of mycobacteria-specific CD4⁺ T cells that is characterized by the production of IL-3. Our results support the use of CD154 expression as a practical and reliable method to isolate live Ag-specific CD4⁺ T cells for transcriptomic analysis and potentially for a range of other studies in infected or previously immunized hosts.

Exploiting Pre-Existing CD4+ T Cell Help from Bacille Calmette-Guérin Vaccination to Improve Antiviral Antibody Responses

The continuing emergence of viral pathogens and their rapid spread into heavily populated areas around the world underscore the urgency for development of highly effective vaccines to generate protective antiviral Ab responses. Many established and newly emerging viral pathogens, including HIV and Ebola viruses, are most prevalent in regions of the world in which Mycobacterium tuberculosis infection remains endemic and vaccination at birth with M. bovis bacille Calmette-Guérin (BCG) is widely used. We have investigated the potential for using CD4⁺ T cells arising in response to BCG as a source of help for driving Ab responses against viral vaccines. To test this approach, we designed vaccines comprised of protein immunogens fused to an immunodominant CD4⁺ T cell epitope of the secreted Ag 85B protein of BCG. Proof-of-concept experiments showed that the presence of BCG-specific Th cells in previously BCG-vaccinated mice had a dose-sparing effect for subsequent vaccination with fusion proteins containing the Ag 85B epitope and consistently induced isotype switching to the IgG2c subclass. Studies using an Ebola virus glycoprotein fused to the Ag 85B epitope showed that prior BCG vaccination promoted high-affinity IgG1 responses that neutralized viral infection. The design of fusion protein vaccines with the ability to recruit BCG-specific CD4⁺ Th cells may be a useful and broadly applicable approach to generating improved vaccines against a range of established and newly emergent viral pathogens.

"Endocytic pH regulates cell surface localization of glycolipid antigen loaded CD1d complexes"

Invariant natural killer T (iNKT) cells recognize glycolipid antigens presented by CD1d, an antigen presenting protein structurally similar to MHC class I. Stimulation of iNKT cells by glycolipid antigens can induce strong immune responses in vivo, with rapid production of a wide variety of cytokines including those classically associated with either T helper type 1 (Th1) or type 2 (Th2) responses. Alterations in the lipid tails or other portions of CD1d-presented glycolipid ligands can bias the iNKT response towards production of predominantly Th1 or Th2 associated cytokines. However, the mechanism accounting for this structure-activity relationship remains controversial. The Th1-biasing glycolipids have been found to consistently form complexes with CD1d that preferentially localize to plasma membrane cholesterol rich microdomains (lipid rafts), whereas CD1d complexes formed with Th2-biasing ligands are excluded from these microdomains. Here we show that neutralization of endosomal pH enhanced localization of CD1d complexes containing Th2-biasing glycolipids to plasma membrane lipid rafts of antigen presenting cells (APC). Transfer of APCs presenting these "stabilized" CD1d/αGC complexes into mice resulted in immune responses with a more prominent Th1-like bias, characterized by increased NK cell transactivation and interferon-γ production. These findings support a model in which low endosomal pH controls stability and lipid raft localization of CD1d-glycolipid complexes to regulate the outcome of iNKT cell mediated responses.

Suppression of Th1 Priming by TLR2 Agonists during Cutaneous Immunization Is Mediated by Recruited CCR2+ Monocytes

Effective subunit vaccines require the incorporation of adjuvants that stimulate cells of the innate immune system to generate protective adaptive immune responses. Pattern recognition receptor agonists are a growing class of potential adjuvants that can shape the character of the immune response to subunit vaccines by directing the polarization of CD4 T cell differentiation to various functional subsets. In the current study, we applied a high-throughput in vitro screen to assess murine CD4 T cell polarization by a panel of pattern recognition receptor agonists. This identified lipopeptides with TLR2 agonist activity as exceptional Th1-polarizing adjuvants. In vivo, we demonstrated that i.v. administration of TLR2 agonists with Ag in mice replicated the findings from in vitro screening by promoting strong Th1 polarization. In contrast, TLR2 agonists inhibited priming of Th1 responses when administered cutaneously in mice. This route-specific suppression was associated with infiltrating CCR2⁺ cells in the skin-draining lymph nodes and was not uniquely dependent on any of the well characterized subsets of dendritic cells known to reside in the skin. We further demonstrated that priming of CD4 T cells to generate Th1 effectors following immunization with the Mycobacterium bovis bacillus Calmette-Guérin (BCG) strain, a lipoprotein-rich bacterium recognized by TLR2, was dependent on the immunization route, with significantly greater Th1 responses with i.v. compared with intradermal administration of BCG. A more complete understanding of route-dependent TLR2 responses may be critical for informed design of novel subunit vaccines and for improvement of BCG and other vaccines based on live-attenuated organisms.

Skin squames contribute to ammonia and volatile fatty acid production from bacteria colonizing in air-cooling units with odor complaints

One of the most notable Indoor Air Quality problems is odor emission. This study investigated the potential contribution of skin squames to the production of ammonia (NH₃ ) and volatile organic acids (VFAs) by 7 bacteria isolated from air-cooling (AC) units with complaints of urine and body odors. Our previous study showed that keratinolytic activity is higher in AC units with odor complaints than those without. In the offices where these units are located, the most likely source of keratins is from human skin squames. Most bacteria can produce NH₃ and VFAs in the skin squame culture. Some correlations between the levels of NH₃ , NH4+, VFAs, and keratinolytic activity were found. The odor production pathway with skin squames was proposed. Staphylococcus haemolyticus was abundant in the AC units with odor problems and had a high level of keratinolytic activity in addition to odor production. For long-term odor control, it is important to reduce the level of skin squames entering the AC units.

Generation of IL-3-Secreting CD4+ T Cells by Microbial Challenge at Skin and Mucosal Barriers

During Ag priming, naive CD4⁺ T cells differentiate into subsets with distinct patterns of cytokine expression that dictate to a major extent their functional roles in immune responses. We identified a subset of CD4⁺ T cells defined by secretion of IL-3 that was induced by Ag stimulation under conditions different from those associated with previously defined functional subsets. Using mouse models of bacterial and viral infections, we showed that IL-3–secreting CD4⁺ T cells were generated by infection at the skin and mucosa but not by infections introduced directly into the blood. Most IL-3–producing T cells coexpressed GM-CSF and other cytokines that define multifunctionality. Generation of IL-3–secreting T cells in vitro was dependent on IL-1 family cytokines and was inhibited by cytokines that induce canonical Th1 or Th2 cells. Our results identify IL-3–secreting CD4⁺ T cells as a potential functional subset that arises during priming of naive T cells in specific tissue locations.

Inexpensive color evaluation of dye-based pressure-sensitive films for plantar studies

Dye-based pressure-sensitive films are advantageous in plantar pressure studies due to their ease of use, cost-effectiveness, and ability to produce measurements within the shoe. To circumvent the use of proprietary equipment and software to relate the dye-stained film to load, an alternative approach of using a conventional flatbed scanner and generic image processing software is attempted here instead. The technique revealed high linear increasing and decreasing trends for the respective red and blue normalized intensities (R(2) > 0.95) and low standard deviation in all readings (<0.06) overall. By subtracting the blue from the red normalized intensity, it was discovered that the measurement sensitivity could be doubled. The results here confirm the viability of using a conventional flatbed scanner and generic image processing software to relate the dye-stained pressure films to load. The adoption of this approach promises substantial cost savings.

Construction and evaluation of high-quality n-ZnO nanorod/p-diamond heterojunctions

Vertically-aligned ZnO nanorods (NRs) arrays were synthesized by a low-temperature solution method on boron-doped diamond (BDD) films. The morphology, growth direction, and crystallinity of the ZnO NRs were studied by scanning electron microscopy, X-ray diffraction and cathodoluminescence. Electrical characterization of the ZnO NR/BBD heterostructures revealed characteristic p-n junction properties with an on/off ratio of about 50 at +/- 4 V and a small reverse leakage current approximately 1 microA. Moreover, the junctions showed an ideality factor around 1.0 at a low forward voltage from 0 to 0.3 V and about 2.1 for an increased voltage ranging from 1.2 to 3.0 V, being consistent with that of an ideal diode according to the Sah-Noyce-Shockley theory.