Microbial heat shock protein 70 stimulatory properties have different TLR requirements

A nod to the bond between NOD2 and mycobacteria

Mycobacteria are responsible for several human and animal diseases. NOD2 is a pattern recognition receptor that has an important role in mycobacterial recognition. However, the mechanisms by which mutations in NOD2 alter the course of mycobacterial infection remain unclear. Herein, we aimed to review the totality of studies directly addressing the relationship between NOD2 and mycobacteria as a foundation for moving the field forward. NOD2 was linked to mycobacterial infection at 3 levels: (1) genetic, through association with mycobacterial diseases of humans; (2) chemical, through the distinct NOD2 ligand in the mycobacterial cell wall; and (3) immunologic, through heightened NOD2 signaling caused by the unique modification of the NOD2 ligand. The immune response to mycobacteria is shaped by NOD2 signaling, responsible for NF-κB and MAPK activation, and the production of various immune effectors like cytokines and nitric oxide, with some evidence linking this to bacteriologic control. Absence of NOD2 during mycobacterial infection of mice can be detrimental, but the mechanism remains unknown. Conversely, the success of immunization with mycobacteria has been linked to NOD2 signaling and NOD2 has been targeted as an avenue of immunotherapy for diseases even beyond mycobacteria. The mycobacteria-NOD2 interaction remains an important area of study, which may shed light on immune mechanisms in disease.

Immunotherapeutic Activities of a DNA Plasmid Carrying the Mycobacterial hsp65 Gene (DNAhsp65)

DNA vaccines have become relevant subject matter, and efforts for their development have been increasing due to their potential as technology platforms applicable for prophylactic and therapeutic approaches for infectious diseases and for cancer treatment, allergies, and autoimmune diseases. This review aimed to summarize current knowledge about the plasmid DNA vaccine carrying the mycobacterial hsp65 gene (DNAhsp65), which demonstrates immunomodulatory and immunoregulatory properties of both the innate and adaptive immune systems. The possible mechanisms associated with the modulation and regulatory role of DNAhsp65 in the control of various conditions is also discussed.

BCG constitutively expressing the adenylyl cyclase encoded by Rv2212 increases its immunogenicity and reduces replication of M. tuberculosis in lungs of BALB/c mice

Mycobacterium tuberculosis remains as a threat to public health around the world with 1.7 million cases of TB-associated deaths during 2016. Despite the use of Bacillus Calmette-Guerin (BCG) vaccine, control of the infection has not been successful. Because of this, several efforts have been made in order to develop new vaccines capable of boosting previous immunization or attempted for replacing current BCG. We previously showed that over expression of the M. tuberculosis adenylyl cyclase encoding gene Rv2212 in BCG bacilli (BCG-Rv2212), induced an attenuated phenotype when administered in BALB/c mice. Moreover, two-dimensional proteomic analysis showed that heat shock proteins such as GroEL2 and DnaK were overexpressed in this BCG-Rv2212. In this report, we show that immunization of mice with BCG-Rv2212 significantly increments IFN-γ⁺ CD4⁺ and CD8⁺ T-lymphocytes after PPD stimulation in comparison with BCG vaccinated mice. Mice vaccinated with BCG-Rv2212 significantly reduced the bacterial load in lungs after four-month post infection with M. tuberculosis H37Rv but was similar to BCG after 6 month-post-challenge. Survival experiment showed that both vaccines administered separately in mice induce similar levels of protection after 20-week post-challenge with M. tuberculosis H37Rv. Virulence experiments developed in nude mice, showed that BCG-Rv2212 and BCG bacilli were equally safe. Our results suggest that BCG-Rv2212 is capable of stimulating cellular immune response effectively and reduce bacterial burden in lungs of mice after challenge. Particularly, it seems to be more effective in controlling bacterial burden during the first steps of infection.

Interaction of the CD43 Sialomucin with the Mycobacterium tuberculosis Cpn60.2 Chaperonin Leads to Tumor Necrosis Factor Alpha Production

Mycobacterium tuberculosis is the causal agent of tuberculosis. Tumor necrosis factor alpha (TNF-α), transforming growth factor β (TGF-β), and gamma interferon (IFN-γ) secreted by activated macrophages and lymphocytes are considered essential to contain Mycobacterium tuberculosis infection. The CD43 sialomucin has been reported to act as a receptor for bacilli through its interaction with the chaperonin Cpn60.2, facilitating mycobacterium-macrophage contact. We report here that Cpn60.2 induces both human THP-1 cells and mouse-derived bone marrow-derived macrophages (BMMs) to produce TNF-α and that this production is CD43 dependent. In addition, we present evidence that the signaling pathway leading to TNF-α production upon interaction with Cpn60.2 requires active Src family kinases, phospholipase C-γ (PLC-γ), phosphatidylinositol 3-kinase (PI3K), p38, and Jun N-terminal protein kinase (JNK), both in BMMs and in THP-1 cells. Our data highlight the role of CD43 and Cpn60.2 in TNF-α production and underscore an important role for CD43 in the host-mycobacterium interaction.

Dynamic interactions of Plasmodium spp. with vascular endothelium

Plasmodial species are protozoan parasites that infect erythrocytes. As such, they are in close contact with microvascular endothelium for most of the life cycle in the mammalian host. The host-parasite interactions of this stage of the infection are responsible for the clinical manifestations of the disease that range from a mild febrile illness to severe and frequently fatal syndromes such as cerebral malaria and multi-organ failure. Plasmodium falciparum, the causative agent of the most severe form of malaria, is particularly predisposed to modulating endothelial function through either direct adhesion to endothelial receptor molecules, or by releasing potent host and parasite products that can stimulate endothelial activation and/or disrupt barrier function. In this review, we provide a critical analysis of the current clinical and laboratory evidence for endothelial dysfunction during severe P. falciparum malaria. Future investigations using state-of-the-art technologies such as mass cytometry and organs-on-chips to further delineate parasite-endothelial cell interactions are also discussed.

miRNA-133 augments coelomocyte phagocytosis in bacteria-challenged Apostichopus japonicus via targeting the TLR component of IRAK-1 in vitro and in vivo

In this study, we explored the potential roles of miRNA-133 in regulating TLR pathways in the sea cucumber Apostichopus japonicus. Target screening of RNA-Seq data successfully identified interleukin-1 receptor-associated kinase (AjIRAK−1) as a putative target of miR-133. This result was further validated by negative expression profiles in Vibrio splendidus-challenged coelomocytes and lipopolysaccharide (LPS)-exposed cell cultures. HEK-293T cells transfected with a dual-luciferase reporter fused to the 3′UTR of wild-type or mutant AjIRAK-1 exhibited a 52.9% reduction in luciferase activity (p < 0.01) compared to controls. Co-infection with a miR-133 mimics or a specific siRNA targeting AjIRAK-1 significantly repressed the mRNA and protein expression levels of AjIRAK-1 and its downstream molecules, such as AjTRAF6 and Ajp105, in primary coelomocytes. In contrast, a miR-133 inhibitor significantly increased the expression of these TLR pathway members. The injection of miR-133 agomir or AjIRAK-1 siRNA into sea cucumbers not only decreased the expression of AjIRAK-1 and its downstream molecules but also significantly increased V. splendidus coelomocyte phagocytosis. All of the present data provide direct evidence that miR-133 is involved in TLR cascade modulation through AjIRAK-1 targeting to promote V. splendidus coelomocyte phagocytosis in these non-model invertebrates.

Mesoporous silica particles potentiate antigen-specific T-cell responses

AIM

To study the adjuvant effect of mesoporous silica particles and their capability of modifying an already existing allergic Th2-like immune response.

MATERIALS & METHODS

The adjuvant effect of Santa Barbara Amorphous-15 (SBA-15) mesoporous silica particles was studied in an antigen-specific ovalbumin (OVA) system in vitro and in vivo. The capacity of the OVA-loaded SBA-15 particles (SBA-15-OVA) to modify an existing immune response was assessed in a murine allergy model.

RESULTS

SBA-15-OVA induced significantly stronger OVA-specific splenocyte proliferation compared with OVA alone. Significantly higher IFN-γ production was observed in ex vivo OVA-stimulated splenocytes from SBA-15-OVA-immunized mice compared with mice injected with only SBA-15 or OVA. Treatment of OVA-sensitized mice with SBA-15-OVA modified the immune response with significantly lower serum levels of OVA-specific IgE and higher IgG levels compared with the alum-OVA-treated group.

CONCLUSION

The results are promising for the continued development of mesoporous silica materials for therapeutic applications.

A central role for inducible heat-shock protein 70 in autoimmune vitiligo

Inducible heat-shock protein 70 (HSP70i) is a protein regulated by stress that protects cells from undergoing apoptosis. Such proteins are marvellously well conserved throughout evolution, which has placed them in the spotlight for helping to understand the intriguing relationship between infection and immunity. In the presence of stress proteins, dendritic cells (DCs) will sense this alarm signal and respond by recruiting immune cells of different plumage to fit the occasion. In times of stress, melanocytes will secrete antigen-bound HSP70i to act as an alarm signal in activating DCs that comes equipped with an address of origin to drive the autoimmune response in vitiligo. Here we pose that if the autoimmune response is funnelled through HSP70i, then blocking the stress protein from activating DCs can lend new treatment opportunities for vitiligo.

Eimeria tenella heat shock protein 70 enhances protection of recombinant microneme protein MIC2 subunit antigen vaccination against E. tenella challenge

Heat shock proteins have been reported to stimulate the immune system via innate receptors. Our study found that the novel immunopotentiator, Eimeria tenella (E. tenella) heat shock protein 70 (HSP70), enhanced protective immunity elicited by E. tenella antigen microneme protein 2 (EtMIC2) against avian coccidiosis. It demonstrated that the expression of TLR2 and TLR4 were strongly upregulated in EtHSP70 and EtMIC2 plus EtHSP70 stimulated chicken embryo fibroblasts (CEF) compared with untreated controls and EtMIC2 alone. In addition, the same treatment induced high levels of interleukin (IL)-12 and interferon (IFN)-γ that are critical cytokines of innate immunity. In vivo experiments involved using broiler chickens subcutaneously immunized with EtMIC2 alone or EtMIC2 plus EtHSP70 at 7 and 14 days post-hatch, which were then orally challenged with live E. tenella at 7 days following secondary immunization. Body weight gains, cecal lesion scores, fecal oocyst shedding, serum antibody responses against MIC2, and intestinal cytokine transcript levels were assessed as measures of protective immunity. Chickens immunized with EtMIC2 plus EtHSP70 showed increased body weight gains, decreased oocyst shedding, increased serum antibody responses, and high levels of IL-12, IFN-γ, and IL-17 compared with the EtMIC2 only or control groups. Moreover, chickens immunized with EtHSP70 alone showed significantly protective effect against E. tenella infection. In summary, this study provides the first evidence of the immunoenhancing activities of EtHSP70 in poultry.

Identification of HLA-A∗02:01-restricted CTL epitopes in Trypanosoma cruzi heat shock protein-70 recognized by Chagas disease patients

CD8(+) cytotoxic T lymphocyte (CTL) response is critical for controlling the infection of the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease. Since only a few CD8 antigens have been described in Chagas disease patients, the identification of new class I-restricted epitopes is urgently needed for the development of immunotherapies against T. cruzi infection. In this study, bioinformatic methods were used to predict HLA-A∗02:01-binders, and 30 peptides were selected, synthesized and tested for HLA-A∗02:01 binding. Among them, sixteen peptides with medium-to-high affinity were assayed for their recognition by CTL from HSP70-immunized or T. cruzi-infected transgenic B6-A2/K(b) mice. Our results show that four immunodominant epitopes (HSP70(210-8), HSP70(255-63), HSP70(316-24) and HSP70(345-53)) are contained in the T. cruzi HSP70 antigen. Indeed two of them (HSP70(210-8) and HSP70(316-24)) were also recognized by CTL of HLA-A∗02:01(+) Chagas disease patients, indicating that these peptides are processed and displayed as MHC class I epitopes during the natural history of T. cruzi infection. The HLA-A∗02:01 restriction was evidenced using peptide-pulsed K562-A2 cells as antigen-presenting cells. Both cytotoxic and cytokine-secreting activities were detected in response to the former two peptides and, moreover, 10/12 patients (83%) recognized at least one of these two HSP70-derived CD8(+) epitopes.

Mycobacterium tuberculosis employs Cpn60.2 as an adhesin that binds CD43 on the macrophage surface

CD43 is a large sialylated glycoprotein found on the surface of haematopoietic cells and has been previously shown to be necessary for efficient macrophage binding and immunological responsiveness to Mycobacterium tuberculosis. Using capsular material from M. tuberculosis and recombinant CD43-Fc, we have employed affinity chromatography to show that Cpn60.2 (Hsp65, GroEL), and to a lesser extent DnaK (Hsp70), bind to CD43. Competitive inhibition using recombinant protein and polyclonal F(ab')(2) antibody-mediated epitope masking studies were used to evaluate M. tuberculosis binding to CD43(+/+) versus CD43(-/-) macrophages. Results showed that Cpn60.2, but not DnaK, acts as a CD43-dependent mycobacterial adhesin for macrophage binding. Assessment of the specific binding between Cpn60.2 and CD43 showed it to be saturable, with a comparatively weak affinity in the low micromolar range. We have also shown that the ability of Cpn60.2 to competitively inhibit M. tuberculosis binding to macrophages is shared by the Escherichia coli homologue, GroEL, but not by the mouse and human Hsp60 homologues. These findings add to a growing field of research that implicates molecular chaperones as having extracellular functions, including bacterial adherence to host cells. Thus, CD43 may act as a Pattern Recognition Receptor (PRR) for bacterial homologues of the 60 kDa molecular chaperone.

Gene expression profiles in peripheral blood mononuclear cells can distinguish patients with non-small cell lung cancer from patients with nonmalignant lung disease

Early diagnosis of lung cancer followed by surgery presently is the most effective treatment for non-small cell lung cancer (NSCLC). An accurate, minimally invasive test that could detect early disease would permit timely intervention and potentially reduce mortality. Recent studies have shown that the peripheral blood can carry information related to the presence of disease, including prognostic information and information on therapeutic response. We have analyzed gene expression in peripheral blood mononuclear cell samples including 137 patients with NSCLC tumors and 91 patient controls with nonmalignant lung conditions, including histologically diagnosed benign nodules. Subjects were primarily smokers and former smokers. We have identified a 29-gene signature that separates these two patient classes with 86% accuracy (91% sensitivity, 80% specificity). Accuracy in an independent validation set, including samples from a new location, was 78% (sensitivity of 76% and specificity of 82%). An analysis of this NSCLC gene signature in 18 NSCLCs taken presurgery, with matched samples from 2 to 5 months postsurgery, showed that in 78% of cases, the signature was reduced postsurgery and disappeared entirely in 33%. Our results show the feasibility of using peripheral blood gene expression signatures to identify early-stage NSCLC in at-risk populations.

Identification of novel Leishmania donovani antigens that help define correlates of vaccine-mediated protection in visceral leishmaniasis

Visceral leishmaniasis (VL), caused by the intracellular parasite Leishmania donovani is a major public health problem in the developing world. But there is no effective and safe vaccine approved for clinical use against any form of leishmaniasis. Through reactivity with kala-azar patient and cured sera, polypeptides ranging from 91 to 31-kDa from L. donovani promastigotes were previously identified as potential protective vaccine candidates. In this study four polypeptides 91(LD91), 72 (LD72), 51(LD51) and 31 (LD31)-kDa were purified using sodium dodecyl sulfate polyacrylamide gel electrophoresis followed by electroelution. We compared the vaccine efficacy of these antigens encapsulated in cationic liposomes in BALB/c mice against challenge infection with L. donovani. Our results demonstrated that liposomal LD31 (74%-77%) and LD51 (72%-75%) vaccination reduced parasite burden to the greatest degree followed by liposomal LD72 (65%-67%) and LD91 (46%-49%). Analysis of the cytokine responses in immunized mice revealed that all the vaccinated groups produced prechallenge interferon-gamma, interleukin-12 and interleukin-4. Interestingly, the degree of reduction in parasite load could be predicted by the magnitude of the cytokine responses which correlated inversely with the parasite burden both in liver and spleen. The 31, 51 and 72-kDa bands were identified as ATP synthase alpha chain, beta-tubulin and heat shock 70-related protein 1 precursor of L. major, respectively using matrix-assisted laser desorption ionization-time of flight (MALDI-TOF/TOF) mass spectrometry. These three leishmanial antigens have not been described before as successful vaccine candidates examined against in vivo VL model. Thus, these antigens can be potential components of future antileishmaniasis vaccines.

Antigen-loaded exosomes alone induce Th1-type memory through a B-cell-dependent mechanism

Exosomes are nanovesicles harboring proteins important for antigen presentation. We compared the potency of differently loaded exosomes, directly loaded with OVA(323-339) peptide (Pep-Exo) or exosomes from OVA-pulsed DCs (OVA-Exo), for their ability to induce specific T-cell proliferation in vitro and in vivo. Both Pep-Exo and OVA-Exo elicited specific transgenic T-cell proliferation in vitro, with the Pep-Exo being more efficient. In contrast, only OVA-Exo induced specific T-cell responses in vivo highlighting the importance of indirect loading strategies in clinical applications. Coadministration of whole OVA overcame the unresponsiveness with Pep-Exo but still elicited a lower response compared with OVA-Exo. In parallel, we found that OVA-Exo not only augmented the specific T-cell response but also gave a Th1-type shift and an antibody response even in the absence of whole OVA. We detected IgG2a and interferon-gamma production from splenocytes showing the capability of exosomes to provide antigen for B-cell activation. Furthermore, we found that B cells are needed for exosomal T-cell stimulation because Bruton tyrosine kinase-deficient mice showed abrogated B- and T-cell responses after OVA-Exo immunization. These findings reveal that exosomes are potent immune regulators and are relevant for the design of vaccine adjuvants and therapeutic intervention strategies to modulate immune responses.

Proteomic dissection of agonist-specific TLR-mediated inflammatory responses on macrophages at subcellular resolution

Upon stimulation by distinct bacterial/viral products/agonists, APCs including macrophages tend to express particular TLR molecules to coordinate the signaling that ultimately target at chromatin and mediate the activity of downstream transcriptional factors in regulating characteristic sets of gene expression for innate immune response. To investigate largely unknown regulatory mechanism underlying agonist-specific TLR-mediated innate immune responses, at subcellular resolution, we first analyzed Pam3CSK4-induced proteome changes in living macrophages and identified the differentially expressed proteins in the cytosol and chromatin-associated fractions, respectively, by using AACT/SILAC-based quantitative proteomic approach. In the cytosol fraction, we found that the proteins with notable Pam3CSK4-induced expression changes were primarily involved in post-translational events, energy metabolism, protein transporting, and apoptosis. Among them, a ubiquitous and highly conserved iron-binding protein, Ferritin, was further characterized as a modulator for the expression of a TLR2-specific cytokine IL-10 in murine macrophage cells by using small-interfering RNA (siRNA). Interestingly, we simultaneously identified multiple apoptosis-related proteins showing opposite trend in their regulated expressions, which clearly indicated the existence of systems regulation in differentially modulating the signal for the cross-road balance between protecting cell from apoptosis and the apoptosis of infected cells. For those regulated proteins identified in the nuclear fraction, we integrated bioinformatics to find the interactions of certain chromatin-associated proteins, which suggested their interconnected involvements in proteasome-ubiquitin pathway, DNA replication, and post-translational activity upon Pam3CSK4 stimulation. Certain regulated proteins in our quantitative proteomic data set showed the similar trend of up-regulation in both Pam3CSK4- and LPS-stimulated macrophages (Nature 2007, 447, 972), suggesting their belonging to the recently identified class of pro-inflammatory genes. The regulatory discrepancy between both data sets for other set of genes indicated their agonist-specific nature in innate immune responses.

Atherogenesis and the humoral immune response to modified lipoproteins

Modified forms of LDL are immunogenic and activate both cell-mediated and humoral immune responses. Both types of responses are pro-inflammatory and are probably primary players in the perpetuation of the chronic inflammatory reaction characteristic of atherosclerosis. The immunologic response to modified LDL can be directed to MHC-II-associated peptides in the case of T helper cells, and to a variety of epitopes-modified lysine groups, modified phospholipids, proteins that become associated with oxidized LDL (such as beta2GP1)--in the case of B cell responses. T cell activation is likely to play a major role through cross-activation of macrophages. Humoral responses to modified LDL are pathogenic as a consequence of the formation of antigen-antibody complexes containing modified LDL and IgG antibodies. Those immune complexes induce cholesterol ester accumulation in macrophages and macrophage-like cells, and induce the release of pro-inflammatory cytokines, chemokines, oxygen active radicals, and matrix metalloproteinases from those cells. There is no conclusive evidence supporting a protective role for IgM antibodies in humans, possibly because autoantibodies to modified lipoproteins are predominantly of the IgG isotype.

Monocyte-derived dendritic cells from chagasic patients vs healthy donors secrete differential levels of IL-10 and IL-12 when stimulated with a protein fragment of Trypanosoma cruzi heat-shock protein-70

We analyzed the effect of the truncated heat-shock protein 70 from Trypanosoma cruzi on maturation of human dendritic cells (DCs) derived from monocytes of peripheral blood mononuclear cells from healthy donors and chagasic patients. The results show that the T-HSP70 is capable of maturing human DCs inducing an increase in the expression level of the CD83, CD86 and human leukocyte antigen-DR surface markers, as well as in the secretion of interleukin (IL)-12, tumor necrosis factor-alpha (TNF-alpha) and IL-6 cytokines. Results also show the existence of a differential functional activity of matured DCs from chagasic patients vs healthy donors in response to T-HSP70 protein and to HSP-70-derived A72 peptide, as only T-HSP70-matured DCs from chagasic patients have an enhanced secretion of IL-10 and a reduced secretion of IL-12. Moreover, the addition of A72 peptide to immature DCs from chagasic patients induced an increase in the percentage of cells expressing CD83 and CD86 molecules regarding to the expression level observed by cells from healthy donors. These findings suggest that T. cruzi HSP70 protein may induce a specific maturation profile on chagasic patients' DCs, which would favor the persistence of the parasite in the human host.

Sensitive detection of cereal fractions that are toxic to celiac disease patients by using monoclonal antibodies to a main immunogenic wheat peptide

BACKGROUND

Celiac disease is an immune-mediated enteropathy caused by the ingestion of gluten, a protein fraction found in certain cereals. Immunotoxic gluten peptides that are recalcitrant to degradation of digestive enzymes appear to trigger celiac syndromes. A 33-mer peptide from alpha-2 gliadin has been identified as a principal contributor to gluten immunotoxicity. A gluten-free diet is the usual first therapy for celiac disease patients; therefore, the characterization and quantification of the toxic portion of the gluten in foodstuffs is crucial to avoid celiac damage.

OBJECTIVE

We aimed to develop immunologic assays as a novel food analysis tool for measuring cereal fractions that are immunotoxic to celiac disease patients.

DESIGN

The design focused on the production of monoclonal antibodies against the gliadin 33-mer peptide and the development of enzyme-linked immunosorbent assays (ELISAs) and Western blot analysis with the use of novel antibodies.

RESULTS

A sandwich ELISA method showed a detection limit for wheat, barley, and rye of <1 ppm prolamine. However, the method required a sample that was > or =1 order of magnitude greater for the detection of low-toxic oats, and there was no signal with the safe cereals maize and rice. A competitive ELISA method was also developed for detection of the toxic peptide in hydrolyzed food, which had a detection limit of <0.5 ppm gliadin.

CONCLUSIONS

Both ELISAs designed for use with the toxic gliadin 33-mer peptide suggested a high correlation between the presence of the peptide and the amount of cereal that was toxic to celiac disease patients. The sensitivity was significantly higher than that of equivalent methods recognizing other gluten epitopes.