IL-5 and IL-17A are critical for the chronic IgE response and differentiation of long-lived antibody-secreting cells in inflamed tissues

Elevation of IgE in patients with psoriasis: Is it a paradoxical phenomenon?

Immunoglobulin E (IgE) elevation is a hallmark of allergic conditions such as atopic dermatitis (AD). The pathogenesis of AD is typically associated with high levels of IL-4 and IL-13 produced by activated T helper 2 (Th2) cells. Psoriasis, on the other hand, is an inflammatory skin disease mainly driven by Th17 cells and their related cytokines. Although the immunopathologic reactions and clinical manifestations are often easily distinguished in the two skin conditions, patients with psoriasis may sometimes exhibit AD-like manifestations, such as elevated IgE and persistent pruritic lesions. Given the fact that the effective T cells have great plasticity to re-differentiate in response to innate and environmental factors, this unusual skin condition could be a consequence of a cross-reaction between distinct arms of T-cell and humoral immunity. Here we review the literature concerning the roles of IgE in the development of AD and psoriasis, showing that elevated IgE seems to be an important indicator for this non-typical psoriasis.

Anaphylaxis induced by Thalassophryne nattereri venom in mice is an IgE/IgG1-mediated, IL-4-dependent phenomenon

We hypothesized that beyond the Thalassophryne nattereri venoms ability to induce in mice a strong specific-Th2 response with high levels of specific IgE/IgG1, it would be able to trigger anaphylaxis in sensitized individuals. To investigate whether the venom is capable of inducing an allergic reaction in mice and characterize soluble and cellular mediators involved in this process, BALB/c female mice were sensitized intraperitoneally with decreasing-dose of venom at weekly intervals for 4 weeks and challenged by intraperitoneal, oral or epicutaneous routes with venom 2 weeks later. Our data show that sensitized-mice challenged by all routes showed intense symptoms of anaphylaxis, dependent on the anaphylactic IgG1 and IgE antibodies and mast cells. The late-phase reaction developed after initial symptoms was characterized by the influx of eosinophils, dependent on IL-5, IL-17A and eotaxin produced by Th2 cells in inflamed lungs and skin draining lymph-nodes. Using C57BL/6 deficient mice we demonstrated that IL-4 KO mice failed to develop anaphylactic symptoms or local Th2 inflammation, producing low levels of IgG1 and increased levels of IgG2a. Together our results demonstrated that the venom of T. nattereri has allergenic proteins that can trigger an allergic process, a phenomenon IgE-IgG1 dependent, IL-4-mediated and negatively regulated by IFN-γ.

Combined Blockade of TNF-α and IL-17A Alleviates Progression of Collagen-Induced Arthritis without Causing Serious Infections in Mice

The cytokines TNF-α and IL-17A are elevated in a variety of autoimmune diseases, including rheumatoid arthritis. Both cytokines are targets of several biologic drugs used in the clinic, but unfortunately many patients are refractory to these therapies. IL-17A and TNF-α are known to mediate signaling synergistically to drive expression of inflammatory genes. Hence, combined blockade of TNF-α and IL-17A represents an attractive treatment strategy in autoimmune settings where monotherapy is not fully effective. However, a major concern with this approach is the potential predisposition to opportunistic infections that might outweigh any clinical benefits. Accordingly, we examined the impact of individual versus combined neutralization of TNF-α and IL-17A in a mouse model of rheumatoid arthritis (collagen-induced arthritis) and the concomitant susceptibility to infections that are likely to manifest as side effects of blocking these cytokines (oral candidiasis or tuberculosis). Our findings indicate that combined neutralization of TNF-α and IL-17A was considerably more effective than monotherapy in improving collagen-induced arthritis disease even when administered at a minimally efficacious dose. Encouragingly, however, dual cytokine blockade did not cooperatively impair antimicrobial host defenses, as mice given combined IL-17A and TNF-α neutralization displayed infectious profiles and humoral responses comparable to mice given high doses of individual anti-TNF-α or anti-IL-17A mAbs. These data support the idea that combined neutralization of TNF-α and IL-17A for refractory autoimmunity is likely to be associated with acceptable and manageable risks of opportunistic infections associated with these cytokines.

Toll-like receptor 4 signalling regulates antibody response to adenoviral vector-based vaccines by imprinting germinal centre quality

Adenoviral vectors (AdV) are considered promising candidates for vaccine applications. A prominent group of Toll-like receptors (TLRs) participate in the adenovirus-induced adaptive immune response, yet there is little information regarding the role of TLR4 in AdV-induced immune responses in recent literature. We investigated the function of TLR4 in both adaptive and innate immune responses to an AdV-based anthrax vaccine. By immunizing wild-type and TLR4 knockout (TLR4-KO) mice, we revealed the requirement of TLR4 in AdV-induced innate responses. We also showed that TLR4 functions are required for germinal centre responses in immunized mice, as expression of the apoptosis-related marker Fas was down-regulated on germinal centre B cells from TLR4-KO mice. Likewise, decreased expression of inducible costimulator on follicular T helper cells was observed in immunized TLR4-KO mice. Moreover, a potent protective antigen-specific humoral immune response was mimicked using an adjuvant system containing the TLR4 agonist monophosphoryl lipid A. Overall, our findings showed that very rapid antigen-specific antibody production is correlated with the TLR4-imprinted germinal centre response to AdV-based vaccine. These results provide additional evidence for the use of the AdV and a TLR agonist to induce humoral responses. Our findings offer new insights into rational vaccine design.

The Immunomodulatory Imbalance in Patients with Ketamine Cystitis

The pathogenesis of ketamine cystitis (KC) has been recently linked with immune response to patients but the same has not yet been established. Hence, this study aims to propose a possible immune mechanism of irreversible bladder damage caused by KC. A total of 53 KC patients and 21 healthy volunteers as controls have been retrospectively assessed. The levels of serum immunoglobulin E (IgE), IL-6, and IFN-γ of KC patients were significantly higher than those of controls, whereas the TGF-β levels of KC patients substantially reduced but the IL-2 and IL-4 levels of KC patients were comparable to those of controls. Moreover, the KC patients had significantly higher counts of T_H1, T_H2, and T_H17 cells than those of controls. The immune response of KC users may begin with the IL-6 production and differentiation of T_H17 and may be followed by alternating between high expressions of T_H1 and T_H2. The IL-6 may further suppress the T_REG cells which can aggravate chronic inflammation in KC patients and the imbalance in T_H17 and T_REG cells may involve the pathogenesis of KC. Further investigation is needed to define the role of IL-6 in T_H1/T_H2/T_H17-regulated signaling pathway in ketamine-induced cystitis.

Neutrophils releasing IL-17A into NETs are essential to plasma cell differentiation in inflamed tissue dependent on IL-1R

Interleukin (IL) 17A in chronic inflammation is also produced by innate immune cells as neutrophils. Mice with chronic humoral response induced by venom of Thalassophryne nattereri (VTn) proved to be a good tool for evaluating the impact of IL-17A on the development of long-lived plasma cells in the inflamed peritoneal cavity. Here, we report that VTn induces IL-17A production by neutrophils accumulating in the peritoneal cavity and triggers the extrusion of IL-17A along with neutrophil extracellular traps (NETs). Neutrophil depletion reduced the number of IL17A-producing cells in VTn-immunized mice and blocked the differentiation of long-lived plasma cells. Specific antibody production and survival of long-lived plasma cells was ablated in VTn-immunized mice deficient in CD4, while CD28 signaling had the opposite effect on differentiation of long-lived plasma cells. Further, maturation of long-lived plasma cells in inflamed peritoneal cavity was IL-1R1 and COX-2 dependent. Finally, when both the Raf-MEK-ERK pathway and the IL-17A or IL-1R1 activities were blocked, neutrophils were unable to promote the differentiation of memory B cells into long-lived plasma cells, confirming the essential role of neutrophils and IL-17A along with NETs in an IL-1/IL-1R-dependent manner as the novel helping partner for plasma cell differentiation in chronically inflamed tissues.

Interleukin-17A Promotes CD8+ T Cell Cytotoxicity To Facilitate West Nile Virus Clearance

CD8⁺ T cells are crucial components of immunity and play a vital role in recovery from West Nile virus (WNV) infection. Here, we identify a previously unrecognized function of interleukin-17A (IL-17A) in inducing cytotoxic-mediator gene expression and promoting CD8⁺ T cell cytotoxicity against WNV infection in mice. We find that IL-17A-deficient (Il17a^-/-) mice are more susceptible to WNV infection and develop a higher viral burden than wild-type (WT) mice. Interestingly, the CD8⁺ T cells isolated from Il17a^-/- mice are less cytotoxic and express lower levels of cytotoxic-mediator genes, which can be restored by supplying recombinant IL-17A in vitro and in vivo Importantly, treatment of WNV-infected mice with recombinant IL-17A, as late as day 6 postinfection, significantly reduces the viral burden and increases survival, suggesting a therapeutic potential for IL-17A. In conclusion, we report a novel function of IL-17A in promoting CD8⁺ T cell cytotoxicity, which may have broad implications in other microbial infections and cancers.

IMPORTANCE

Interleukin-17A (IL-17A) and CD8⁺ T cells regulate diverse immune functions in microbial infections, malignancies, and autoimmune diseases. IL-17A is a proinflammatory cytokine produced by diverse cell types, while CD8⁺ T cells (known as cytotoxic T cells) are major cells that provide immunity against intracellular pathogens. Previous studies have demonstrated a crucial role of CD8⁺ T cells in recovery from West Nile virus (WNV) infection. However, the role of IL-17A during WNV infection remains unclear. Here, we demonstrate that IL-17A protects mice from lethal WNV infection by promoting CD8⁺ T cell-mediated clearance of WNV. In addition, treatment of WNV-infected mice with recombinant IL-17A reduces the viral burden and increases survival of mice, suggesting a potential therapeutic. This novel IL-17A-CD8⁺ T cell axis may also have broad implications for immunity to other microbial infections and cancers, where CD8⁺ T cell functions are crucial.

Bioactive components in fish venoms

Animal venoms are widely recognized excellent resources for the discovery of novel drug leads and physiological tools. Most are comprised of a large number of components, of which the enzymes, small peptides, and proteins are studied for their important bioactivities. However, in spite of there being over 2000 venomous fish species, piscine venoms have been relatively underrepresented in the literature thus far. Most studies have explored whole or partially fractioned venom, revealing broad pharmacology, which includes cardiovascular, neuromuscular, cytotoxic, inflammatory, and nociceptive activities. Several large proteinaceous toxins, such as stonustoxin, verrucotoxin, and Sp-CTx, have been isolated from scorpaenoid fish. These form pores in cell membranes, resulting in cell death and creating a cascade of reactions that result in many, but not all, of the physiological symptoms observed from envenomation. Additionally, Natterins, a novel family of toxins possessing kininogenase activity have been found in toadfish venom. A variety of smaller protein toxins, as well as a small number of peptides, enzymes, and non-proteinaceous molecules have also been isolated from a range of fish venoms, but most remain poorly characterized. Many other bioactive fish venom components remain to be discovered and investigated. These represent an untapped treasure of potentially useful molecules.

Induction of Protective Immune Responses Against Schistosomiasis haematobium in Hamsters and Mice Using Cysteine Peptidase-Based Vaccine

One of the major lessons we learned from the radiation-attenuated cercariae vaccine studies is that protective immunity against schistosomiasis is dependent on the induction of T helper (Th)1-/Th2-related immune responses. Since most schistosome larval and adult-worm-derived molecules used for vaccination uniformly induce a polarized Th1 response, it was essential to include a type 2 immune response-inducing molecule, such as cysteine peptidases, in the vaccine formula. Here, we demonstrate that a single subcutaneous injection of Syrian hamsters with 200 μg active papain, 1 h before percutaneous exposure to 150 cercariae of Schistosoma haematobium, led to highly significant (P < 0.005) reduction of >50% in worm burden and worm egg counts in intestine. Immunization of hamsters with 20 μg recombinant glyceraldehyde 3-phosphate dehydrogenase (rSG3PDH) and 20 μg 2-cys peroxiredoxin-derived peptide in a multiple antigen peptide construct (PRX MAP) together with papain (20 μg/hamster), as adjuvant led to considerable (64%) protection against challenge S. haematobium infection, similar to the levels reported with irradiated cercariae. Cysteine peptidases-based vaccination was also effective in protecting outbred mice against a percutaneous challenge infection with S. haematobium cercariae. In two experiments, a mixture of Schistosoma mansoni cathepsin B1 (SmCB1) and Fasciola hepatica cathepsin L1 (FhCL1) led to highly significant (P < 0.005) reduction of 70% in challenge S. haematobium worm burden and 60% reduction in liver egg counts. Mice vaccinated with SmCB1/FhCL1/rSG3PDH mixture and challenged with S. haematobium cercariae 3 weeks after the second immunization displayed highly significant (P < 0.005) reduction of 72% in challenge worm burden and no eggs in liver of 8-10 mice/group, as compared to unimmunized mice, associated with production of a mixture of type 1- and type 2-related cytokines and antibody responses.

Thalassophryne nattereri fish venom: from the envenoming to the understanding of the immune system

Thalassophryne nattereri (niquim) is a venomous fish found off North and Northeast coast of Brazil, where it is known by the severity of the accidents involving humans. This review article is divided into four topics. The first one provides a brief description of the animal biology and its distribution off Brazilian coastal waters, the venom apparatus, signs and symptoms observed in envenomated humans and also describes envenomation in mice. The second topic describes the use of modern genetic approach and mass spectrometry for identification of highly expressed genes in its venom glands and the sequence of major toxins. The third chapter offers a detailed study of tissue injury induced by the venom and reveals the role of toxins that impair inflammation reduction. Finally, the fourth section expands the understanding of many extrinsic and intrinsic essential factors in maintaining survival of memory B cell compartment. Our results demonstrate the wide possibilities for research in the area of toxinology, also the necessity of interconnection among biochemistry, pharmacology and immunology areas for the expansion of knowledge and for generation of innovation.

Induction of protective immune responses against schistosomiasis using functionally active cysteine peptidases

Each year schistosomiasis afflicts up to 600 million people in 74 tropical and sub-tropical countries, predominantly in the developing world. Yet we depend on a single drug, praziquantel, for its treatment and control. There is no vaccine available but one is urgently needed especially since praziquantel-resistant parasites are likely to emerge at some time in the future. The disease is caused by several worm species of the genus Schistosoma. These express several classes of papain-like cysteine peptidases, cathepsins B and L, in various tissues but particularly in their gastrodermis where they employ them as digestive enzymes. We have shown that sub-cutaneous injection of recombinant and functionally active Schistosoma mansoni cathepsin B1 (SmCB1), or a cathepsin L from a related parasite Fasciola hepatica (FhCL1), elicits highly significant protection (up to 73%) against an experimental challenge worm infection in murine models of schistosomiasis. The immune modulating properties of this subcutaneous injection can boost protection levels (up to 83%) when combined with other S. mansoni vaccine candidates, glyceraldehyde 3-phosphate dehydrogenase (SG3PDH) and peroxiredoxin (PRX-MAP). Here, we discuss these data in the context of the parasite's biology and development, and provide putative mechanism by which the native-like cysteine peptidase induce protective immune responses.

The hierarchical process of differentiation of long-lived antibody-secreting cells is dependent on integrated signals derived from antigen and IL-17A

Switched CD19-positive memory B cells purified from mice with chronic immune response against Thalassophrynenattereri venom proteins were cultured with venom or cytokines. Our results confirm the existence of a hierarchic process of differentiation: activated memory B cells progressively acquire increasing levels of CD138 and decreasing levels of CD45R/B220 to finally arrive at ASC with B220^neg phenotype, which are IgG1-secreting cells. Only Bmem from peritoneal cavity or bone marrow of VTn immunized mice presented the capacity to generate ASC functionally active. IL-17A or IL-21/IL-23/IL-33 improves the ability of venom to induce intracellular IgG of peritoneal derived-ASC. Cognate stimulation with venom and IL-17A is sufficient to down-regulate the expression of CD45R/B220. BAFF-R is up-regulated in splenic or medullar derived-ASC stimulated by venom, CpG or cytokines. Only splenic derived-ASC up-regulate Bcl-2 expression after CpG or the combination of IL-21/IL-23/IL-33 stimulation. Finally, the activation of ASC for IgG1 secretion is triggered by venom proteins in peritoneal cavity and by IL-17A in medullar niche. These results show the importance of the integration of signals downstream of BCR and IL17-A receptors in modulating ASC differentiation, focusing in the microenvironment niche of their generation.

TLR2, TLR4 and the MyD88 signaling are crucial for the in vivo generation and the longevity of long-lived antibody-secreting cells

This study was undertaken to gain better insights into the role of TLRs and MyD88 in the development and differentiation of memory B cells, especially of ASC, during the Th2 polarized memory response induced by Natterins. Our in vivo findings demonstrated that the anaphylactic IgG1 production is dependent on TLR2 and MyD88 signaling, and that TLR4 acts as adjuvant accelerating the synthesis of high affinity-IgE. Also, TLR4 (MyD88-independent) modulated the migration of innate-like B cells (B1a and B2) out of the peritoneal cavity, and the emigration from the spleen of B1b and B2 cells. TLR4 (MyD88-independent) modulated the emigration from the spleen of Bmem as well as ASC B220^pos. TLR2 triggered to the egress from the peritoneum of Bmem (MyD88-dependent) and ASC B220^pos (MyD88-independent). We showed that TLR4 regulates the degree of expansion of Bmem in the peritoneum (MyD88-dependent) and in BM (MyD88-independent) as well as of ASC B220^neg in the spleen (MyD88-independent). TLR2 regulated the intensity of the expansion of Bmem (MyD88-independent) and ASC B220^pos (MyD88-dependent) in BM. Finally, TLR4 signals sustained the longevity of ASC B220^pos (MyD88-independent) and ASC B220^neg into the peritoneum (MyD88-dependent) and TLR2 MyD88-dependent signaling supported the persistence of B2 cells in BM, Bmem in the spleen and ASC B220^neg in peritoneum and BM. Terminally differentiated ASC B220^neg required the cooperation of both signals through TLR2/TLR4 via MyD88 for longevity in peritoneum, whereas Bmem required only TLR2/MyD88 to stay in spleen, and ASC B220^pos rested in peritoneum dependent on TLR4 signaling. Our data sustain that earlier events on memory B cells differentiation induced in secondary immune response against Natterins, after secondary lymph organs influx and egress, may be the key to determining peripheral localization of innate-like B cells and memory B cells as ASC B220^pos and ASC B220^neg.

The longevity of Th2 humoral response induced by proteases natterins requires the participation of long-lasting innate-like B cells and plasma cells in spleen

The generation of long-lived antibody-secreting cells (ASC) and memory B cells are critical events for an effective vaccine and the choice of adjuvant can influence these processes. Various cellular and molecular mechanism involved in the protease action that determine Th2 responses have been identified. However, direct or indirect actions in the regulation of the induction, survival and longevity of ASC in differential compartments remain largely unknown. We investigated whether the proteolytic activity of proteins are determinant for the modulation of the memory immune response in mice, promoting the differentiation of memory B cells to terminally differentiated end stage cells. Here, we show that the proteolytic activity of Natterins, from the venom of Thalassophryne nattereri Brazilian fish, besides inducing a Th2 response with plasmatic titers of high-affinity antigen-specific IgE over extended periods is sufficient for the generation of signals that contribute to the formation of a survival niche in the spleen, essential for the longevity of the main subtype of ASC with B220^neg phenotype.

Inflammatory signalling associated with brain dead organ donation: from brain injury to brain stem death and posttransplant ischaemia reperfusion injury

Brain death is associated with dramatic and serious pathophysiologic changes that adversely affect both the quantity and quality of organs available for transplant. To fully optimise the donor pool necessitates a more complete understanding of the underlying pathophysiology of organ dysfunction associated with transplantation. These injurious processes are initially triggered by catastrophic brain injury and are further enhanced during both brain death and graft transplantation. The activated inflammatory systems then contribute to graft dysfunction in the recipient. Inflammatory mediators drive this process in concert with the innate and adaptive immune systems. Activation of deleterious immunological pathways in organ grafts occurs, priming them for further inflammation after engraftment. Finally, posttransplantation ischaemia reperfusion injury leads to further generation of inflammatory mediators and consequent activation of the recipient's immune system. Ongoing research has identified key mediators that contribute to the inflammatory milieu inherent in brain dead organ donation. This has seen the development of novel therapies that directly target the inflammatory cascade.

The pathologic and clinical intersection of atopic and autoimmune disease

Hypersensitivity reactions of the immune system have been broadly categorized into the atopic and autoimmune depending on whether the antigen triggering the reaction is endogenous (or self) or exogenous, the types of cellular and humoral components involved, and the clinical symptoms. Research into the pathophysiology of the resultant disease states has focused on a dichotomy between Th1 and Th2 T helper lymphocytes thought to govern autoimmune and atopic disease, respectively. Recent discoveries, however, have served to dispute this paradigm and have provided additional insight into the roles of Th17 cells, B-lymphocytes and T regulatory cells as well as the considerable communication and commonalities between the complex signaling pathways. Furthermore, clinical studies have served to challenge the idea that the presence of atopy and autoimmunity are mutually exclusive states. Finally, application of recent approaches to treatment-biologic targeted therapy in autoimmunity and induction of immune tolerance in atopic disease--to both disease states have shown mixed but promising results.