NOD2/RIG-I Activating Inarigivir Adjuvant Enhances the Efficacy of BCG Vaccine Against Tuberculosis in Mice

Tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) kills about 1.5 million people each year and the widely used Bacille Calmette-Guérin (BCG) vaccine provides a partial protection against TB in children and adults. Because BCG vaccine evades lysosomal fusion in antigen presenting cells (APCs), leading to an inefficient production of peptides and antigen presentation required to activate CD4 T cells, we sought to boost its efficacy using novel agonists of RIG-I and NOD2 as adjuvants. We recently reported that the dinucleotide SB 9200 (Inarigivir) derived from our small molecule nucleic acid hybrid (SMNH)^® platform, activated RIG-I and NOD2 receptors and exhibited a broad-spectrum antiviral activity against hepatitis B and C, Norovirus, RSV, influenza and parainfluenza. Inarigivir increased the ability of BCG-infected mouse APCs to secrete elevated levels of IL-12, TNF-α, and IFN-β, and Caspase-1 dependent IL-1β cytokine. Inarigivir also increased the ability of macrophages to kill MTB in a Caspase-1-, and autophagy-dependent manner. Furthermore, Inarigivir led to a Capsase-1 and NOD2- dependent increase in the ability of BCG-infected APCs to present an Ag85B-p25 epitope to CD4 T cells in vitro. Consistent with an increase in immunogenicity of adjuvant treated APCs, the Inarigivir-BCG vaccine combination induced robust protection against tuberculosis in a mouse model of MTB infection, decreasing the lung burden of MTB by 1-log10 more than that afforded by BCG vaccine alone. The Inarigivir-BCG combination was also more efficacious than a muramyl-dipeptide-BCG vaccine combination against tuberculosis in mice, generating better memory T cell responses supporting its novel adjuvant potential for the BCG vaccine.

Mesenchymal stem cells internalize Mycobacterium tuberculosis through scavenger receptors and restrict bacterial growth through autophagy

Human mesenchymal stem cells (MSCs) express scavenger receptors that internalize lipids, including oxidized low-density lipoprotein (oxLDL). We report that MSCs phagocytose Mycobacterium tuberculosis (Mtb) through two types of scavenger receptors (SRs; MARCO and SR-B1), as blockade of the receptors with antibodies or siRNA knockdown decreased the uptake of Mtb. MSCs also expressed mannose receptor (MR) that was found to endocytose rhodamine-labeled mannosylated BSA (rMBSA), though the receptor was not involved in the uptake of Mtb. Dil-oxLDL and rMBSA taken up into MSC endosomes colocalized with Mtb phagosomes, thus suggesting that the latter were fusion competent. Phagocytosed Mtb did not replicate within MSCs, thus suggesting an intrinsic control of bacterial growth. Indeed, MSCs exhibited intrinsic autophagy, which was up-regulated after activation with rapamycin. SiRNA knockdown of autophagy initiator beclin-1 enhanced Mtb survival, whereas rapamycin-induced autophagy increased intracellular killing of Mtb. In addition, MSCs secreted nitric oxide after Mtb infection, and inhibition of NO by N(G)-monomethyl-L-arginine enhanced intracellular survival of Mtb. MSCs can be grown in large numbers in vitro, and autologous MSCs transfused into tuberculosis patients have been found to be safe and improve lung immunity. Thus, MSCs are novel phagocytic cells with a potential for immunotherapy in treating multidrug-resistant tuberculosis.

Targeting of PBP1 by β-lactams determines recA/SOS response activation in heterogeneous MRSA clinical strains

The SOS response, a conserved regulatory network in bacteria that is induced in response to DNA damage, has been shown to be associated with the emergence of resistance to antibiotics. Previously, we demonstrated that heterogeneous (HeR) MRSA strains, when exposed to sub-inhibitory concentrations of oxacillin, were able to express a homogeneous high level of resistance (HoR). Moreover, we showed that oxacillin appeared to be the triggering factor of a β-lactam-mediated SOS response through lexA/recA regulators, responsible for an increased mutation rate and selection of a HoR derivative. In this work, we demonstrated, by selectively exposing to β-lactam and non-β-lactam cell wall inhibitors, that PBP1 plays a critical role in SOS-mediated recA activation and HeR-HoR selection. Functional analysis of PBP1 using an inducible PBP1-specific antisense construct showed that PBP1 depletion abolished both β-lactam-induced recA expression/activation and increased mutation rates during HeR/HoR selection. Furthermore, based on the observation that HeR/HoR selection is accompanied by compensatory increases in the expression of PBP1,-2, -2a, and -4, our study provides evidence that a combination of agents simultaneously targeting PBP1 and either PBP2 or PBP2a showed both in-vitro and in-vivo efficacy, thereby representing a therapeutic option for the treatment of highly resistant HoR-MRSA strains. The information gathered from these studies contributes to our understanding of β-lactam-mediated HeR/HoR selection and provides new insights, based on β-lactam synergistic combinations, that mitigate drug resistance for the treatment of MRSA infections.

Cutting edge: Nicastrin and related components of γ-secretase generate a peptide epitope facilitating immune recognition of intracellular mycobacteria, through MHC class II-dependent priming of T cells

Bacillus Calmette-Guérin (BCG), the antituberculosis vaccine, localizes within immature phagosomes of macrophages and dendritic cells (APCs), and avoids lysosomal degradation. BCG-derived antigenic peptides are thus inefficiently processed by APCs, and we investigated alternate mechanisms of Ag processing. Proteomics identified that BCG phagosomes are enriched for nicastrin, APH, and presenilin components of γ-secretase, a multimeric protease. Using an in vitro Ag presentation assay and BCG-infected APCs, we found γ-secretase components to cleave BCG-derived Ag85B to produce a peptide epitope, which, in turn, primed IL-2 release from Ag85B-specific T cell hybridoma. siRNA knockdown or chemical inhibition of γ-secretase components using L685458 decreased the ability of BCG or Mycobacterium tuberculosis-infected APCs to present Ag85B. In addition, L685485 inhibition of γ-secretase led to a decreased ability of BCG-dendritic cells to immunize mice and induce Ag85B-specific CD4 T cells in vivo. Because BCG and M. tuberculosis sequester within APCs preventing immune recognition, γ-secretase components appear to fortuitously process the immunodominant Ag85B, facilitating immune recognition.

Label-free proteomics and systems biology analysis of mycobacterial phagosomes in dendritic cells and macrophages

Proteomics has been applied to study intracellular bacteria and phagocytic vacuoles in different host cell lines, especially macrophages (Mφs). For mycobacterial phagosomes, few studies have identified over several hundred proteins for systems assessment of the phagosome maturation and antigen presentation pathways. More importantly, there has been a scarcity in publication on proteomic characterization of mycobacterial phagosomes in dendritic cells (DCs). In this work, we report a global proteomic analysis of Mφ and DC phagosomes infected with a virulent, an attenuated, and a vaccine strain of mycobacteria. We used label-free quantitative proteomics and bioinformatics tools to decipher the regulation of phagosome maturation and antigen presentation pathways in Mφs and DCs. We found that the phagosomal antigen presentation pathways are repressed more in DCs than in Mφs. The results suggest that virulent mycobacteria might co-opt the host immune system to stimulate granuloma formation for persistence while minimizing the antimicrobial immune response to enhance mycobacterial survival. The studies on phagosomal proteomes have also shown promise in discovering new antigen presentation mechanisms that a professional antigen presentation cell might use to overcome the mycobacterial blockade of conventional antigen presentation pathways.

Analysis of phagosomal proteomes: from latex-bead to bacterial phagosomes

Phagosomal proteome characterization has contributed significantly to the understanding of host-pathogen interaction and the mechanism of infectious diseases caused by intracellular bacteria. The latex bead-containing phagosome has been widely used as a model system to study phagosomal proteomes at a global level. In contrast, the study of bacteria-containing phagosomes at a similar level has just begun. A number of intracellular microbial species are studied for their proteomes during the invasion of a host, providing insight into their metabolic adaptation in host cells and interaction with host-cell antimicrobial environments. In this review, we attempt to summarize the most recent advancements in the proteomic study of microbial phagosomes, especially those originating from mouse or human cells. We also briefly describe the proteomics of latex bead-containing phagosomes because they are often used as model phagosomes for study. We provide descriptions on major biological and technological components in phagosomal proteome studies. We also discuss the role of phagosomal proteome study in the broader horizon of systems biology and the technological challenges in phagosomal proteome characterization.

Cadmium chloride-induced disruption of testicular steroidogenesis in rainbow trout, Oncorhynchus mykiss

Cadmium (Cd) is a known endocrine disruptor with the ability to affect the production of hormones involved in the regulation of reproductive processes. In the present study, the effects of CdCl(2) on unstimulated and stimulated testicular steroidogenesis were examined with the intention of furthering the understanding of the potential site(s) of action in the signaling pathway for 11-KT synthesis in teleosts. In short-term (2-h) exposures, CdCl(2 )stimulated 11-KT production (29% and 28% over controls) in minced testicular tissues at concentrations of 10 and 100 microM, respectively. However, 11-KT production was significantly lower than in controls (54%, 62%, and 54%) when tissues were incubated for 18 h with 1, 10, and 100 microM Cd. Incubation of testicular tissues with 100 IU/ml human chorionic gonadotropin (hCG) and 5 mM dibutyryl-cAMP (dbcAMP), which activate rate-limiting steps in steroid synthesis, or 1.3 microM 25-hydroxycholesterol (25-OHC), which augments production, resulted in significant increases in steroidogenesis over controls. hCG-stimulated steroidogenesis was reduced to 54% and 62% that of stimulated controls when tissues were incubated with CdCl(2) at 1 and 10 microM, respectively. 11-KT production in dbcAMP-stimulated and 25-OHC-augmented tissues was not affected by Cd exposure. The results of this study indicate that one site of action of Cd in the signaling steroidogenic pathway is located prior to cAMP formation. This impairment could be overcome when higher concentrations of Cd were used in hCG-stimulated cells, suggesting the presence of a stimulatory site at, or following, hCG receptor binding.

The Delta fbpA mutant derived from Mycobacterium tuberculosis H37Rv has an enhanced susceptibility to intracellular antimicrobial oxidative mechanisms, undergoes limited phagosome maturation and activates macrophages and dendritic cells

Mycobacterium tuberculosis H37Rv (Mtb) excludes phagocyte oxidase (phox) and inducible nitric oxide synthase (iNOS) while preventing lysosomal fusion in macrophages (MPhis). The antigen 85A deficient (Delta fbpA) mutant of Mtb was vaccinogenic in mice and the mechanisms of attenuation were compared with MPhis infected with H37Rv and BCG. Delta fbpA contained reduced amounts of trehalose 6, 6, dimycolate and induced minimal levels of SOCS-1 in MPhis. Blockade of oxidants enhanced the growth of Delta fbpA in MPhis that correlated with increased colocalization with phox and iNOS. Green fluorescent protein-expressing strains within MPhis or purified phagosomes were analysed for endosomal traffick with immunofluorescence and Western blot. Delta fbpA phagosomes were enriched for rab5, rab11, LAMP-1 and Hck suggesting enhanced fusion with early, recycling and late endosomes in MPhis compared with BCG or H37Rv. Delta fbpA phagosomes were thus more mature than H37Rv or BCG although, they failed to acquire rab7 and CD63 preventing lysosomal fusion. Finally, Delta fbpA infected MPhis and dendritic cells (DCs) showed an enhanced MHC-II and CD1d expression and primed immune T cells to release more IFN-gamma compared with those infected with BCG and H37Rv. Delta fbpA was thus more immunogenic in MPhis and DCs because of an enhanced susceptibility to oxidants and increased maturation.

Relating olfactory neurotoxicity to altered olfactory-mediated behaviors in rainbow trout exposed to three currently-used pesticides

Odor-evoked neurophysiological responses can form the basis for behavioral responses. Here we first characterized olfactory-mediated behavioral and neurophysiological responses of juvenile rainbow trout to the amino acid l-histidine, then looked at whether there were similar responses to the carbamate antisapstain IPBC and the herbicides atrazine and Roundup, and lastly explored how exposures to these pesticides modified the l-histidine responses. Trout were behaviorally attracted to 10(-7)M l-histidine (as assayed in a counter-current olfactometer), but this preference behavior switched to indifference with higher histidine concentrations. Neurophysiologically, the summed electrical responses of peripheral olfactory neurons, as measured using electro-olfactogram (EOG), was 0.843+/-0.252 mV to 10(-7)M l-histidine. Of the pesticides, only Roundup evoked EOGs, indicating the amino acid-based pesticide may have acted as an odorant, and generated a behavioral response: it was avoided at active ingredient [AI; glyphosate isopropyl amine] concentrations > or =10 mg/l. With 30 min pesticide exposures, 10(-7)M l-histidine preference behavior was eliminated following exposure to 1 microg/l IPBC and atrazine, and 100 microg/l AI Roundup. Similarly, 10(-7)M l-histidine-evoked EOGs were significantly reduced by exposure to 1 microg/l IPBC, 10 microg/l atrazine, and 100 microg/l AI Roundup. When combined together, the results demonstrate that typical preference behavior can be abolished when neurophysiological responses are reduced by >60% of control. This asymmetry in response thresholds suggests that behavioral responses may be more sensitive toxicological endpoints than neurophysiological responses.

Biosynthetic capacity of rainbow trout (Oncorhynchus mykiss) interrenal tissue after cadmium exposure

The disruption of endocrine system function in wildlife species, including teleosts, by contaminants such as metals is presently of major environmental concern. Recently, it has been shown that cadmium (Cd) exposure results in significant reductions in corticosteroid secretion by fish interrenal steroidogenic cells, likely through an inhibition of intracellular cortisol synthesis. In the present study, the effects of CdCl(2) on unstimulated and stimulated interrenal steroidogenesis in rainbow trout were examined with the intention of furthering an understanding of the site(s) of Cd toxic action. CdCl(2) alone reduced cortisol secretion in minced interrenal tissues to 59% and 55% of control values when exposed to 10 and 100 microM, respectively. Incubation of interrenal tissues with 0.01 IU/mL adrenocorticotropic hormone (ACTH), which activates rate-limiting steps in steroid synthesis, resulted in significant stimulation of steroidogenesis in controls. However, ACTH-stimulated steroidogenesis was reduced when tissues were previously incubated with Cd. Maximal rates of unstimulated cortisol secretion were achieved by augmentation using 5 microM 25-hydroxycholesterol (25-OHC) or 0.8 microL/mL synthetic cholesterol [SyntheChol(SC)]. Steroidogenesis augmentation by 25-OHC was significantly reduced in tissues incubated with Cd. Interestingly, cortisol secretion was significantly higher in SC-augmented tissue exposed to 1 and 10 microM Cd when compared to augmented control tissues. The results of this study show that Cd affects both stimulated and unstimulated steroidogenesis in rainbow trout, and that one major site(s) of action of Cd in the cortisol synthesis pathway is likely prior to cytochrome P450 side chain cleavage.

The reduced bactericidal function of complement C5-deficient murine macrophages is associated with defects in the synthesis and delivery of reactive oxygen radicals to mycobacterial phagosomes

Complement C5-deficient (C5(-/-)) macrophages derived from B.10 congenic mice were found to be defective in killing intracellular Mycobacterium tuberculosis (MTB). They were bacteriostatic after activation with IFN-gamma alone but bactericidal in the combined presence of IFN-gamma and C5-derived C5a anaphylatoxin that was deficient among these macrophages. Reduced killing correlated with a decreased production of reactive oxygen species (ROS) in the C5(-/-) macrophages measured using fluorescent probes. Furthermore, a lack of colocalization of p47(phox) protein of the NADPH oxidase (phox) complex with GFP-expressing MTB (gfpMTB) indicated a defective assembly of the phox complex on phagosomes. Reconstitution with C5a, a known ROS activator, enhanced the assembly of phox complex on the phagosomes as well as the production of ROS that inhibited the growth of MTB. Protein kinase C (PKC) isoforms are involved in the phosphorylation and translocation of p47(phox) onto bacterial phagosomes. Western blot analysis demonstrated a defective phosphorylation of PKC (alpha, beta, delta) and PKC-zeta in the cytosol of C5(-/-) macrophages compared with C5 intact (C5(+/+)) macrophages. Furthermore, in situ fluorescent labeling of phagosomes indicated that PKC-beta and PKC-zeta were the isoforms that are not phosphorylated in C5(-/-) macrophages. Because Fc receptor-mediated phox assembly was normal in both C5(-/-) and C5(+/+) macrophages, the defect in phox assembly around MTB phagosomes was specific to C5 deficiency. Reduced bactericidal function of C5(-/-) macrophages thus appears to be due to a defective assembly and production of ROS that prevents effective killing of intracellular MTB.

Processing and presentation of a mycobacterial antigen 85B epitope by murine macrophages is dependent on the phagosomal acquisition of vacuolar proton ATPase and in situ activation of cathepsin D

Mycobacterium tuberculosis (strain H37Rv) and bacillus Calmette-Guérin (BCG) vaccine inhibit phagosome maturation in macrophages and their effect on processing, and presentation of a secreted Ag85 complex B protein, Ag85B, by mouse macrophages was analyzed. Macrophages were infected with GFP-expressing mycobacterial strains and analyzed for in situ localization of vacuolar proton ATPase (v-ATPase) and cathepsin D (Cat D) using Western blot analysis and immunofluorescence. H37Rv and BCG phagosomes excluded the v-ATPase and maintained neutral pH while the attenuated H37Ra strain acquired v-ATPase and acidified. Mycobacterial phagosomes acquired Cat D, although strains BCG and H37Rv phagosomes contained the inactive 46-kDa form, whereas H37Ra phagosomes had the active 30-kDa form. Infected macrophages were overlaid with a T cell hybridoma specific for an Ag85B epitope complexed with MHC class II. Coincident with active Cat D, H37Ra-infected macrophages presented the epitope to T cells inducing IL-2, whereas H37Rv- and BCG-infected macrophages were less efficient in IL-2 induction. Bafilomycin inhibited the induction of macrophage-induced IL-2 from T cells indicating that v-ATPase was essential for macrophage processing of Ag85B. Furthermore, the small interfering RNA interference of Cat D synthesis resulted in a marked decrease in the levels of macrophage-induced IL-2. Thus, a v-ATPase-dependent phagosomal activation of Cat D was required for the generation of an Ag85B epitope by macrophages. Reduced processing of Ag85B by H37Rv- and BCG-infected macrophages suggests that phagosome maturation arrest interferes with the efficient processing of Ags in macrophages. Because Ag85B is immunodominant, this state may lead to a decreased ability of the wild-type as well as the BCG vaccine to induce protective immunity.

Cystitis emphysematosa caused by Candida albicans

Cystitis emphysematosa was diagnosed ante mortem in a white male severe diabetic amputee with a history of recurrent urinary tract infection and long-term Foley catheter drainage. Laboratory cultures before and during surgery, including histology, demonstrated invasive Candida albicans as the etiologic agent. This is the first case reported of cystitis emphysematosa caused by Candida albicans.