Biomedical subjects

Eyal Raz

Publications and source records attributed to Eyal Raz.

At least 37 records · Page 2Linked to original sources

PubMed2004

Induction of antigen cross-presentation by Toll-like receptors.

Cross-presentation is the pathway by which exogenous antigens are routed for presentation on MHC class I for activation of CD8(+) T cells. This pathway is important for the development of CD8(+) cytotoxic T lymphocyte responses against tumors and infectious pathogens that do not directly infect APC. We review studies showing that certain Toll-like receptors mediate cross-presentation by dendritic cells, initiating cytosolic processing of antigen after inducing dendritic cell maturation. The implications of these studies for understanding CD8(+) T cell activation and implementing novel vaccine strategies is considered.

Animals↗

PubMed2004

Immunostimulatory oligonucleotides attenuate airways remodeling in allergic monkeys.

To determine whether inhaled immunostimulatory DNA sequence oligonucleotides containing CpG motifs mitigate the pathophysiologic manifestation of the asthmatic phenotype (airways hyperresponsiveness and airways remodeling), rhesus monkeys with experimentally induced allergic airways disease were treated seven times with inhaled immunostimulatory oligonucleotides (or sham) periodically for 33 weeks. Airways hyperresponsiveness was reduced twofold in immunostimulatory DNA sequence-treated compared with sham-treated monkeys. Airways from immunostimulatory oligonucleotide-treated monkeys had thinner reticular basement membranes, fewer mucous cells, fewer eosinophils, and fewer mast cells than sham-treated allergic monkeys. We conclude that inhaled immunostimulatory oligonucleotides can attenuate the magnitude of airway hyperreactivity and airways remodeling produced in nonhuman primates with experimentally induced allergic airways disease.

Administration, Inhalation↗

PubMed2004

Necessity of oligonucleotide aggregation for toll-like receptor 9 activation.

Toll-like receptor 9 (TLR9), a member of the interleukin-1 (IL-1) family of pathogen-associated molecular pattern receptors, is activated by unmethylated CpG-containing sequences in bacterial DNA or synthetic oligonucleotides (ODNs) in the endosomal compartment. The stimulation of an IL-1 response is thought to require the aggregation of its receptor. By analogy, we postulated that the potency of a TLR9 ligand should depend first on its ability to enter cells and gain access to TLR9 and second on its capacity to form a multimeric complex capable of cross-linking these receptors. Previously, we selected from a random library a series of phosphodiester ODNs with enhanced ability to permeate cells. Here, we studied the structural requirements for these penetrating ODNs to elicit a functional TLR9 response, as assessed by cytokine production from bone marrow-derived mouse mononuclear cells. The presence of a prototypic murine immunostimulatory DNA hexameric sequence (purine-purine-CG-pyrimidine-pyrimidine) in the ODNs was not sufficient for stimulation. In addition, the TLR9-activating ODNs had to have the ability to form aggregates and often to form secondary structures near the core CpG motifs. Multimerization was promoted by the presence of a guanine-rich 3'-terminus. The phosphodiester ODNs with CpG motifs that did not aggregate antagonized the effects of the multimeric TLR9 activators. These findings suggest that an optimal TLR9 agonist needs to contain a spatially distinct multimerization domain and a receptor binding CpG domain. This concept may prove useful for the design of new TLR9-modulating agents.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Cutting edge: activation of Toll-like receptor 2 induces a Th2 immune response and promotes experimental asthma.

Recognition of microbial components by APCs and their activation through Toll-like receptors (TLR) leads to the induction of adaptive immune responses. In this study, we show that activation of TLR2 by its synthetic ligand Pam3Cys, in contrast to activation of TLR9 by immunostimulatory DNA (ISS-ODN), induces a prominent Th2-biased immune response. Activation of APCs by Pam3Cys resulted in the induction of Th2-associated effector molecules like IL-13, and IL-1beta, GM-CSF and up-regulation of B7RP-1, but low levels of Th1-associated cytokines (IL-12, IFNalpha, IL-18, IL-27). Accordingly, TLR2 ligands aggravated experimental asthma. These data indicate that the type of TLR stimulation during the initial phase of immune activation determines the polarization of the adaptive immune response and may play a role in the initiation of Th2-mediated immune disorders, such as asthma.

Adjuvants, Immunologic↗

PubMed2004

Toll-like receptor 9 signaling mediates the anti-inflammatory effects of probiotics in murine experimental colitis.

BACKGROUND & AIMS: We tested whether the attenuation of experimental colitis by live probiotic bacteria is due to their immunostimulatory DNA, whether toll-like receptor (TLR) signaling is required, and whether nonviable probiotics are effective. METHODS: Methylated and unmethylated genomic DNA isolated from probiotics (VSL-3), DNAse-treated probiotics and Escherichia coli (DH5 alpha) genomic DNA were administered intragastrically (i.g.) or subcutaneously (s.c.) to mice prior to the induction of colitis. Viable or gamma-irradiated probiotics were administered i.g. to wild-type mice and mice deficient in different TLR or in the adaptor protein MyD88, 10 days prior to administration of dextran sodium sulfate (DSS) to their drinking water and for 7 days thereafter. RESULTS: Intragastric and s.c. administration of probiotic and E. coli DNA ameliorated the severity of DSS-induced colitis, whereas methylated probiotic DNA, calf thymus DNA, and DNase-treated probiotics had no effect. The colitis severity was attenuated to the same extent by i.g. delivery of nonviable gamma-irradiated or viable probiotics. Mice deficient in MyD88 did not respond to gamma-irradiated probiotics. The severity of DSS-induced colitis in TLR2 and TLR4 deficient mice was significantly decreased by i.g. administration of gamma-irradiated probiotics, whereas, in TLR9-deficient mice, gamma-irradiated probiotics had no effect. CONCLUSIONS: The protective effects of probiotics are mediated by their own DNA rather than by their metabolites or ability to colonize the colon. TLR9 signaling is essential in mediating the anti-inflammatory effect of probiotics, and live microorganisms are not required to attenuate experimental colitis because nonviable probiotics are equally effective.

Absorption↗

PubMed2004

Toll-like receptor ligands: hygiene, atopy and therapeutic implications.

PURPOSE OF REVIEW: Allergic and certain other inflammatory diseases have become more common in industrialized countries over the past few decades. One potential explanation for such trends is that with a decreased incidence of microbial exposures, as a result of modern public health practices, an important source of immune stimulation has been lost, with a consequent increase in inflammatory responses and their associated diseases. This review will focus on our current understanding of how microbial exposures impact on host immunity and the pathogenesis of allergic diseases. RECENT FINDINGS: In the past decade, it has become clear that a number of molecular interactions between immunocytes and microbial compounds are mediated by Toll-like receptors on host cells. Moreover, recent investigations have suggested that ligands for different Toll-like receptors have the potential both to inhibit and promote the development of allergic hypersensitivities and diseases. SUMMARY: On the basis of studies discussed herein, we speculate that physiological exposures to Toll-like receptor ligands have important yet complex effects on immune homeostasis and host susceptibility towards atopic diseases. Moreover, we anticipate that a fuller understanding of how physiological Toll-like receptor ligand exposures impact on immune development will lead to novel therapeutic interventions for the prevention and treatment of atopic diseases.

Animals↗

PubMed2004

Antigen-immunostimulatory oligonucleotide conjugates: mechanisms and applications.

Conjugation of protein antigen with immunostimulatory oligonucleotides creates a potent immunogen. Physical linking of oligonucleotides to antigen enhances antigen uptake and targets the adjuvant properties of the oligonucleotides to the antigen-presenting cell. In addition, the conjugated oligonucleotides appear to have improved immunostimulatory abilities compared to free oligonucleotides, presumably due to enhanced activation of Toll-like receptor 9. Immunization with these conjugate preparations elicits antigen-specific antibody responses, a T-helper cell 1-biased cytokine profile from CD4 T cells, and CD8 cytotoxic T-lymphocyte activity that is CD4 independent. The humoral and cellular immune responses induced by these conjugates suggest they can be used to create effective vaccines against infectious pathogens and tumors and to beneficially modulate allergic responses. Indeed, recent clinical trial data show symptom relief and immunomodulation of the allergic response in patients with allergic rhinitis. This review considers the mechanisms of action of antigen-oligonucleotide conjugates and discusses available data regarding their use for the prevention and treatment of infectious, oncologic, and allergic diseases.

Adjuvants, Immunologic↗

PubMed2004

Allergen-independent immunostimulatory sequence oligodeoxynucleotide therapy attenuates experimental allergic rhinitis.

While effective for the prevention and treatment of allergic rhinitis (AR) symptoms, currently available medications do not reverse allergen specific hypersensitivities. Therefore, pharmacotherapeutics are not curative and their daily use is often required for years. These investigations were conducted to determine whether immunostimulatory sequence oligodeoxynucleotide (ISS-ODN) delivery protects previously sensitized mice from AR hypersensitivity responses and modulates their allergen specific immune profiles. Mice were first sensitized with ovalbumin (OVA) and alum, twenty-four hr before beginning a series of seven daily intranasal (i.n.) allergen challenges, subsets of mice received a single i.n. or intradermal (i.d.) dose of ISS-ODN or control oligodeoxynucleotide (C-ODN), a single intraperitoneal (i.p.) injection of dexamethasone (DXM), or no intervention. Mice receiving i.d. or i.n. ISS-ODN were found to have attenuated immediate and late phase effector cell responses to i.n. OVA challenge. Specifically, ISS-ODN treated mice had less histamine and cysteinyl leukotriene release and eosinophilic inflammation in their nasal passages than mice treated with C-ODN. In addition, splenocytes from ISS-ODN but not C-ODN treated mice displayed attenuated OVA-specific interleukin (IL)-4, IL-5, and IL-13 but increased interferon-gamma responses. Finally, ISS-ODN was generally a more effective treatment than DXM, both in blunting AR hypersensitivity responses and in shifting T helper 2 Th2-biased immune parameters towards Th1 dominance. As ISS-ODN delivery rapidly attenuated effector cell responses in this AR model in an allergen independent manner, the present results suggest that therapy with ISS-ODN alone may be an effective alternative to corticosteroid medications for the clinical management of AR.

Administration, Intranasal↗

PubMed2004

Inhibition of experimental asthma by indoleamine 2,3-dioxygenase.

Epidemiological evidence points to the inverse relationship between microbial exposure and the prevalence of allergic asthma and autoimmune diseases in Westernized countries. The molecular basis for this observation has not yet been completely delineated. Here we report that the administration of certain toll-like receptor (TLR) ligands, via the activation of innate immunity, induces high levels of indoleamine 2,3-dioxygenase (IDO), the rate-limiting enzyme of tryptophan catabolism in various organs. TLR9 ligand-induced pulmonary IDO activity inhibits Th2-driven experimental asthma. IDO activity expressed by resident lung cells rather than by pulmonary DCs suppressed lung inflammation and airway hyperreactivity. Our results provide a mechanistic insight into the various formulations of the hygiene hypothesis and underscore the notion that activation of innate immunity can inhibit adaptive Th cell responses.

Adoptive Transfer↗

PubMed2003

Immunostimulatory DNA inhibits transforming growth factor-beta expression and airway remodeling.

Immunostimulatory sequences of DNA (ISS) inhibit eosinophilic airway inflammation, Th2 responses, and airway hyperreactivity (AHR) in mouse models of acute ovalbumin (OVA)-induced airway inflammation. To determine whether ISS inhibits airway remodeling, we developed a mouse model of airway remodeling in which OVA-sensitized mice were repeatedly exposed to intranasal OVA administration for 1-6 mo. Mice chronically exposed to OVA developed sustained eosinophilic airway inflammation and sustained AHR to methacholine compared with control mice. In addition, the mice chronically exposed to OVA developed features of airway remodeling, including thickening of the peribronchial smooth muscle layer, peribronchial myofibroblast accumulation, expression of the profibrotic growth factor transforming growth factor-beta, and subepithelial collagen deposition (assessed by quantitation of the area of peribronchial trichrome staining using image analysis, and immunostaining with anti-collagen V antibodies). Administration of ISS systemically every other week significantly inhibited the development of AHR, eosinophilic inflammation, airway mucus production, and importantly, airway remodeling in mice chronically exposed to OVA for 3-6 mo. In addition, ISS significantly reduced bronchoalveolar lavage and lung levels of the profibrotic cytokine transforming growth factor-beta. These studies demonstrate that ISS prevents not only Th2-mediated airway inflammation in response to acute allergen challenge, but also airway remodeling associated with chronic allergen challenge.

Animals↗

PubMed2003

Accumulation of peribronchial mast cells in a mouse model of ovalbumin allergen induced chronic airway inflammation: modulation by immunostimulatory DNA sequences.

Few peribronchial mast cells are noted either in the lungs of naive mice or in the lungs of OVA-sensitized mice challenged acutely with OVA by inhalation. In this study, we demonstrate that OVA-sensitized mice exposed to repetitive OVA inhalation for 1-6 mo have a significant accumulation of peribronchial mast cells. This accumulation of peribronchial mast cells is associated with increased expression of the Th2 cell-derived mast cell growth factors, including IL-4 and IL-9, but not with the non-Th2 cell-derived mast cell growth factor, stem cell factor. Pretreating mice with immunostimulatory sequences (ISS) of DNA containing a CpG motif significantly inhibited the accumulation of peribronchial mast cells and the expression of IL-4 and IL-9. To determine whether mast cells express Toll-like receptor-9 (TLR-9; the receptor for ISS), TLR-9 expression by mouse bone marrow-derived mast cells (MBMMCs) was assessed by RT-PCR. MBMMCs strongly expressed TLR-9 and bound rhodamine-labeled ISS. However, incubation of MBMMCs with ISS in vitro neither inhibited MBMMC proliferation nor inhibited Ag/IgE-mediated MBMMC degranulation, but they did induce IL-6. Overall these studies demonstrate that mice exposed to repetitive OVA challenge, but not acute OVA challenge, have an accumulation of peribronchial mast cells and express increased levels of mast cell growth factors in the lung. Although mast cells express TLR-9, ISS does not directly inhibit mast cell proliferation in vitro, suggesting that ISS inhibits accumulation of peribronchial mast cells in vivo by indirect mechanism(s), which include inhibiting the lung expression of Th2 cell-derived mast cell growth factors.

Adjuvants, Immunologic↗

PubMed2003

Molecular basis for the immunostimulatory activity of guanine nucleoside analogs: activation of Toll-like receptor 7.

Certain C8-substituted and N7, C8-disubstituted guanine ribonucleosides comprise a class of small molecules with immunostimulatory activity. In a variety of animal models, these agents stimulate both humoral and cellular immune responses. The antiviral actions of these guanosine analogs have been attributed to their ability to induce type I IFNs. However, the molecular mechanisms by which the guanosine analogs potentiate immune responses are not known. Here, we report that several guanosine analogs activate Toll-like receptor 7 (TLR7). 7-Thia-8-oxoguanosine, 7-deazaguanosine, and related guanosine analogs activated mouse immune cells in a manner analogous to known TLR ligands, inducing cytokine production in mouse splenocytes (IL-6 and IL-12, type I and II IFNs), bone marrow-derived macrophages (IL-6 and IL-12), and in human peripheral blood leukocytes (type I IFNs, tumor necrosis factor alpha and IL-12). The guanosine congeners also up-regulated costimulatory molecules and MHC I/II in dendritic cells. Genetic complementation studies in human embryonic kidney 293 cells confirmed that the guanosine analogs activate cells exclusively via TLR7. The stimulation of TLR7 by the guanosine analogs in human cells appears to require endosomal maturation because inhibition of this process with chloroquine significantly reduced the downstream activation of NF-kappaB. However, TLR8 activation by R-848 and TLR2 activation by [S-[2,3-bis(palmitoyloxy)-(2-RS)-propyl]-N-palmitoyl-R-Cys-S-Ser-Lys4-OH, trihydrochloride)] were not inhibited by chloroquine, whereas TLR9 activation by CpG oligodeoxynucleotides was abolished. In summary, we present evidence that guanosine analogs activate immune cells via TLR7 by a pathway that requires endosomal maturation. Thus, the B cell-stimulating and antiviral activities of the guanosine analogs may be explained by their TLR7-activating capacity.

Animals↗

PubMed2003

A subset of Toll-like receptor ligands induces cross-presentation by bone marrow-derived dendritic cells.

Dendritic cells (DCs) are capable of cross-presenting exogenous Ag to CD8(+) CTLs. Detection of microbial products by Toll-like receptors (TLRs) leads to activation of DCs and subsequent orchestration of an adaptive immune response. We hypothesized that microbial TLR ligands could activate DCs to cross-present Ag to CTLs. Using DCs and CTLs in an in vitro cross-presentation system, we show that a subset of microbial TLR ligands, namely ligands of TLR3 (poly(inosinic-cytidylic) acid) and TLR9 (immunostimulatory CpG DNA), induces cross-presentation. In contrast to presentation of Ag to CD4(+) T cells by immature DCs, TLR-induced cross-presentation is mediated by mature DCs, is independent of endosomal acidification, and relies on cytosolic Ag processing machinery.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Do microbes influence the pathogenesis of allergic diseases? Building the case for Toll-like receptor ligands.

The prevalence and severity of allergic diseases and other diseases of immune dysregulation are increasing in industrialized countries. One explanation for these trends is that decreased exposure to microbes, due to modern public health practices, has resulted in the loss of a main source of immune provocation, and a consequent increase in pathogenic immune responses and their associated diseases. It is now clear that molecular interactions between immunocytes and microbes are mediated largely by Toll-like receptors (TLRs) on host cells and a diversity of ligands produced by viruses, bacteria and fungi. Physiological exposures to TLR ligands are also likely to have an important yet complex role in host immune homeostasis and predisposition towards atopy.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Resolution of airway inflammation following ovalbumin inhalation: comparison of ISS DNA and corticosteroids.

In this study we have compared the therapeutic effect of the administration of immunostimulatory DNA sequences (ISS) with that of corticosteroids on the resolution of airway inflammation and airway hyperreactivity (AHR) in a mouse model. Mice which had already developed significant levels of eosinophilic airway inflammation 24 h after allergen challenge were then treated with either ISS or corticosteroids, and the effect on AHR and airway inflammation assessed 6 d later. ISS inhibited AHR as effectively as corticosteroids. Combination therapy with ISS and corticosteroids was more effective than monotherapy with either ISS or corticosteroids in inhibiting AHR. In ovalbumin-challenged mice, levels of bronchoalveolar lavage (BAL) eosinophils were significantly reduced with either ISS or corticosteroids. ISS induced significant levels of BAL interferon-gamma, whereas corticosteroids did not induce expression of BAL interferon-gamma. Both ISS and corticosteroids significantly reduced levels of interleukin-5 in BAL, as well as the number of Periodic Acid Schiff-positive airway epithelial cells. Corticosteroids, but not ISS, increased the number of eosinophils in regional mediastinal lymph nodes. Very few apoptotic peribronchial cells were noted following ovalbumin challenge as assessed by TUNEL assay. Corticosteroids, but not ISS, induced an increase in the small number of apoptotic peribronchial cells. The mechanism by which either ISS or corticosteroids inhibit AHR is likely to be mediated by distinct and shared cellular pathways. The combination of the shared and distinct anti-inflammatory pathways may account for the additive effect of ISS and corticosteroids on inhibiting AHR.

Administration, Inhalation↗

PubMed2003

The therapeutic potential of antigen-oligonucleotide conjugates.

Conjugation of protein antigen with immunostimulatory oligonucleotides creates a potent immunogen that elicits antigen-specific antibody responses, a Th1-biased cytokine profile, and CD8 cytotoxic T lymphocyte activity. The wide range of humoral and cellular immune responses induced by these conjugates suggests they can be used to create effective vaccines against infectious pathogens and tumors and to beneficially modulate the immune responses seen in allergic diseases. This review summarizes the available data on the use of antigen-oligonucleotide conjugates and discusses their potential use for the treatment of infectious, oncologic, and allergic diseases in humans.

Animals↗

PubMed2002

Liposomal immunostimulatory DNA sequence (ISS-ODN): an efficient parenteral and mucosal adjuvant for influenza and hepatitis B vaccines.

Synthetic oligodeoxynucleotides (ODNs) containing immunostimulatory sequences (ISS-ODN, also known as CpG-ODNs) have been shown to display in experimental models potent Th1-biassed immunoadjuvant activity upon parenteral or mucosal co-administration with a variety of antigens. In an attempt to potentiate adjuvant activity, and to reduce dose and number of administrations, ISS-ODN was entrapped (up to 90% efficiency) in large (1.5 microm) multilamellar liposomes using a simple and fast (5 min) procedure. Mice were vaccinated once or twice intramuscularly (i.m.) or intranasally (i.n.) with subunit influenza vaccines (consisting of the viral hemagglutinin and neuraminidase, HN) or with hepatitis B surface antigen particles (HBsAg), either non-encapsulated or liposome-encapsulated, together with free or liposomal ISS-ODN (5-25 microg per dose). At 3-12 weeks post-vaccination, the humoral (systemic, mucosal) and cellular responses and protective immunity were assessed. Vaccine formulations containing liposomal ISS-ODN co-administered with either soluble antigen or liposomal antigen (in the same vesicles or in separate vesicles) were up to 30 times more effective than formulations containing un-encapsulated ISS-ODN in inducing: (a) antigen-specific serum and mucosal IgG2a and IgA antibodies; (b) splenocyte proliferative response, cytotoxic activity and IFNgamma production; (c) a DTH response; and (d) protection against virus challenge. The response was Th1-dominant in the influenza model and a mixed Th1+Th2 response in the hepatitis B model. No adverse reactions were noted. Thus, liposomal encapsulation of ISS-ODN further enhances its inherent adjuvant activity.

Adjuvants, Immunologic↗

PubMed2002

Plasmid DNA encoding the respiratory syncytial virus G protein protects against RSV-induced airway hyperresponsiveness.

Respiratory syncytial virus (RSV) is an important cause of childhood respiratory disease as well as exacerbations of asthma. Although previous studies have demonstrated that a DNA vaccine encoding the RSV G protein can inhibit RSV replication in mouse models of RSV infection, studies have not been performed to determine whether a DNA vaccine encoding the RSV G protein can protect against RSV induced mucus expression and airway hyperresponsiveness which was the focus of this study. The DNA-G vaccine we constructed significantly inhibited RSV viral replication, mucus expression, and importantly was associated with inhibition of RSV induced airway responsiveness.

Animals↗