Deconstructing tick saliva: non-protein molecules with potent immunomodulatory properties.

Dendritic cells (DCs) are powerful initiators of innate and adaptive immune responses. Ticks are blood-sucking ectoparasite arthropods that suppress host immunity by secreting immunomodulatory molecules in their saliva. Here, compounds present in Rhipicephalus sanguineus tick saliva with immunomodulatory effects on DC differentiation, cytokine production, and costimulatory molecule expression were identified. R. sanguineus tick saliva inhibited IL-12p40 and TNF-α while potentiating IL-10 cytokine production by bone marrow-derived DCs stimulated by Toll-like receptor-2, -4, and -9 agonists. To identify the molecules responsible for these effects, we fractionated the saliva through microcon filtration and reversed-phase HPLC and tested each fraction for DC maturation. Fractions with proven effects were analyzed by micro-HPLC tandem mass spectrometry or competition ELISA. Thus, we identified for the first time in tick saliva the purine nucleoside adenosine (concentration of ∼110 pmol/µl) as a potent anti-inflammatory salivary inhibitor of DC cytokine production. We also found prostaglandin E(2) (PGE(2) ∼100 nM) with comparable effects in modulating cytokine production by DCs. Both Ado and PGE(2) inhibited cytokine production by inducing cAMP-PKA signaling in DCs. Additionally, both Ado and PGE(2) were able to inhibit expression of CD40 in mature DCs. Finally, flow cytometry analysis revealed that PGE(2), but not Ado, is the differentiation inhibitor of bone marrow-derived DCs. The presence of non-protein molecules adenosine and PGE(2) in tick saliva indicates an important evolutionary mechanism used by ticks to subvert host immune cells and allow them to successfully complete their blood meal and life cycle.

IL-4 regulates susceptibility to intestinal inflammation in murine food allergy.

Allergies involve a state of immediate hypersensitivity to antigens, including food proteins. The mechanism underlying the initiation and development of allergic responses involves IL-4 that directly induces the differentiation of committed effector Th2 lymphocytes. Although it is clear that Th2 responses play a pivotal role in the development of allergic responses, it remains unclear which mechanisms are involved in the development of the intestinal damages observed in food allergy. Accordingly, this work aimed to study the role of Th2/IL-4-dependent responses in the development of food allergy and intestinal pathology. C57BL/6 wild-type (WT) and IL-4-/- mice were sensitized with peanut proteins, challenged with peanut seeds, and followed for the development of food allergy and intestinal inflammation. Results demonstrated that exposure to peanut seeds led to weight loss in WT but not in IL-4-/- mice that preserved gut integrity with no signs of mucosal inflammation. These animals presented increased levels of IgG2a in sera, suggesting a role for allergic antibodies in the pathogenesis of WT animals. Most importantly, results also showed that lack of IL-4 modulated gut mucosal response in food allergy through diminished expression of TNF-alpha mRNA, increased Th1 IFN-gamma, IL-12p40, regulatory cytokines, and Foxp3, demonstrating their relevance in the control of allergic inflammatory processes, especially in the intestine. Finally, this study highlighted some of the complex mechanisms involved in the pathogenesis of allergic responses to food antigens in the gut, thereby providing valuable tools for directing novel therapeutic or preventive strategies to the control of allergic enteropathy.

The involvement of CD4+CD25+ T cells in the acute phase of Trypanosoma cruzi infection.

The infection with Trypanosoma cruzi leads to a vigorous and apparently uncontrolled inflammatory response in the heart. Although the parasites trigger specific immune response, the infection is not completely cleared out, a phenomenon that in other parasitic infections has been attributed to CD4+CD25+ T cells (Tregs). Then, we examined the role of natural Tregs and its signaling through CD25 and GITR in the resistance against infection with T. cruzi. Mice were treated with mAb against CD25 and GITR and the parasitemia, mortality and heart pathology analyzed. First, we demonstrated that CD4+CD25+GITR+Foxp3+ T cells migrate to the heart of infected mice. The treatment with anti-CD25 or anti-GITR resulted in increased mortality of these infected animals. Moreover, the treatment with anti-GITR enhanced the myocarditis, with increased migration of CD4+, CD8+, and CCR5+ leukocytes, TNF-alpha production, and tissue parasitism, although it did not change the systemic nitric oxide synthesis. These data showed a limited role for CD25 signaling in controlling the inflammatory response during this protozoan infection. Also, the data suggested that signaling through GITR is determinant to control of the heart inflammation, parasite replication, and host resistance against the infection.

Tick saliva inhibits the chemotactic function of MIP-1alpha and selectively impairs chemotaxis of immature dendritic cells by down-regulating cell-surface CCR5.

Ticks are blood-feeding arthropods that secrete immunomodulatory molecules through their saliva to antagonize host inflammatory and immune responses. As dendritic cells (DCs) play a major role in host immune responses, we studied the effects of Rhipicephalus sanguineus tick saliva on DC migration and function. Bone marrow-derived immature DCs pre-exposed to tick saliva showed reduced migration towards macrophage inflammatory protein (MIP)-1alpha, MIP-1beta and regulated upon activation, normal T cell expressed and secreted (RANTES) chemokines in a Boyden microchamber assay. This inhibition was mediated by saliva which significantly reduced the percentage and the average cell-surface expression of CC chemokine receptor CCR5. In contrast, saliva did not alter migration of DCs towards MIP-3beta, not even if the cells were induced for maturation. Next, we evaluated the effect of tick saliva on the activity of chemokines related to DC migration and showed that tick saliva per se inhibits the chemotactic function of MIP-1alpha, while it did not affect RANTES, MIP-1beta and MIP-3beta. These data suggest that saliva possibly reduces immature DC migration, while mature DC chemotaxis remains unaffected. In support of this, we have analyzed the percentage of DCs on mice 48h after intradermal inoculation with saliva and found that the DC turnover in the skin was reduced compared with controls. Finally, to test the biological activity of the saliva-exposed DCs, we transferred DCs pre-cultured with saliva and loaded with the keyhole limpet haemocyanin (KLH) antigen to mice and measured their capacity to induce specific T cell cytokines. Data showed that saliva reduced the synthesis of both T helper (Th)1 and Th2 cytokines, suggesting the induction of a non-polarised T cell response. These findings propose that the inhibition of DCs migratory ability and function may be a relevant mechanism used by ticks to subvert the immune response of the host.

Intercellular adhesion molecule-1 is required for the early formation of granulomas and participates in the resistance of mice to the infection with the fungus Paracoccidioides brasiliensis.

The migration of leukocytes to inflammatory sites elicited by Paracoccidioides brasiliensis is supposed to be coordinated by cytokines and chemokines. Here, we investigated the role of intercellular adhesion molecule-1 (ICAM-1) in recruiting inflammatory cells to lungs of mice infected with P. brasiliensis and in determining the outcome of the disease. Expression of ICAM-1 was up-regulated on T lymphocytes after infection with the fungus, and its expression was dependent on interferon-gamma, tumor necrosis factor-alpha, and interleukin-12. Moreover, the absence of ICAM-1 resulted in high susceptibility to the infection and delayed formation of granulomatous lesions. In addition, the absence of ICAM-1 resulted in increased growth and dissemination of fungus, decreased number of CD3+CD4+ and CD3+CD8+ T cells, and increased production of interleukin-4 in the inflammatory site. The organization of a granulomatous reaction in mice deficient of ICAM-1 was delayed, starting only on day 60 after infection, whereas in wild-type mice it was complete on day 30 of infection. These data show that ICAM-1 is effectively involved in cellular migration and in the organization of the granulomatous lesion caused by the fungus P. brasiliensis.

Tick saliva inhibits differentiation, maturation and function of murine bone-marrow-derived dendritic cells.

Haematophagous arthropod vectors such as mosquitoes, tsetse flies, sandflies and ticks have evolved salivary immunomodulatory factors that prevent the vertebrate host from rejecting them meanwhile enhancing pathogen transmission. As dendritic cells (DC) play a major role in host immune responses, we studied the effects of Rhipicephalus sanguineus tick saliva on DC differentiation and maturation. Flow cytometry analysis revealed that the addition of saliva to bone marrow cells inhibits the differentiation of DC and decreased the population of differentiated immature DC, increasing the levels of major histocompatibility complex (MHC) class II while not altering the expression of costimulatory (CD40, CD80 and CD86) and adhesion (CD54) molecules. Furthermore, maturation of DC stimulated by lipopolysaccharide (LPS) in the presence of saliva resulted in a lower expression of costimulatory molecules, but did not alter the up-regulation of MHC class II and CD54. The lipopolysaccharide (LPS)-matured DC cultured with saliva also presented reduced production of interleukin-12, whereas interleukin-10 production was unaltered. Assessment of the function of DC cultured with tick saliva revealed them to be poor stimulators of cytokine production by antigen-specific T cells. Our data indicate a novel modulatory role for the saliva of arthropod vectors at an initial step of the immune response through the inhibition of differentiation and maturation of DC into functional antigen-presenting cells.

Matrix metalloproteinases, their physiological inhibitors and osteoclast factors are differentially regulated by the cytokine profile in human periodontal disease.

OBJECTIVE: Inflammatory reactions raised in response to periodontopathogens are thought to trigger pathways of periodontal tissue destruction. We therefore investigated the expression of matrix metalloproteinases (MMPs) and the osteoclastogenic factor receptor activator of nuclear factor-kappaB ligand (RANKL), their respective tissue inhibitors of metalloproteinases (TIMPs) and osteoprotegerin (OPG) in different forms of human periodontal diseases (PDs), and the possible correlation with the expression of inflammatory and regulatory cytokines. MATERIAL AND METHODS: Quantitative polymerase chain reaction (real-time PCR) was performed with gingival biopsies mRNA from aggressive (AP) and chronic periodontitis (CP) patients. RESULTS: Periodontitis patients exhibit higher expression of all analyzed factors when compared with healthy tissues. The expression of MMPs and RANKL were similar in AP and CP, as well as the expression of TNF-alpha. On the other hand, the expression of TIMPs and OPG was higher in CP, and was associated with lower IFN-gamma and higher IL-10 expression, compared with AP. CONCLUSION: It is possible that the pattern of cytokines expressed determines the stable or progressive nature of the lesions and regulates the severity of PD, driving the balance between MMPs and TIMPs, RANKL and OPG expression in the gingival tissues controlling the breakdown of soft and bone tissues and, consequently, the disease severity.

Chemokine production and leukocyte recruitment to the lungs of Paracoccidioides brasiliensis-infected mice is modulated by interferon-gamma.

Chemokines and chemokine receptors play a role in cell recruitment during granulomatous inflammatory reactions. Here, we evaluated the expression of chemokines and chemokine receptors and their regulation by IFN-gamma in the course of Paracoccidioides brasiliensis (Pb) infection in mice. We found an association between KC and MIP-1alpha (CCL3) production and neutrophil infiltration in the lungs of Pb-infected mice during the early acute phase of infection. High levels of RANTES/CCL5, MCP-1/CCL2, IP-10/CXCL10, and Mig/CXCL9 simultaneously with mononuclear cell infiltration in the lungs was found. In the absence of IFN-gamma (GKO mice) we observed increased production of KC and MIP-1alpha and chronic neutrophilia. Moreover, we found a change in the chemokine receptor profiles expressed by wild-type (WT) versus GKO animals. Increased expression of CXCR3 and CCR5, and low levels of CCR3 and CCR4 were observed in the lungs of Pb-infected WT mice, whereas the opposite effect was observed in the lungs of GKO mice. Consistent with these results, infected cells from WT mice preferentially migrated in response to IP-10 (CXCR3 ligand), while those from GKO mice migrated in response to eotaxin/CCL11 (CCR3 ligand). These results suggest that IFN-gamma modulates the expression of chemokines and chemokine receptors as well as the kind of cells that infiltrate the lungs of Pb-infected mice.

Patterns of chemokines and chemokine receptors expression in different forms of human periodontal disease.

Current knowledge states that periodontal diseases are chronic inflammatory reactions raised in response to periodontopathogens. Many cell types and mediators, including Th1 and Th2 lymphocytes, cytokines and chemokines, appear to be involved in the immunopathogenesis of periodontal diseases. Chemokines, a family of chemotactic cytokines, bind to specific receptors and selectively attract different cell subsets to the inflammatory site. They can also interact with classical cytokines and modulate the local immune response. In order to study the role of chemokines in periodontal diseases, we examined the expression of chemokines, chemokine receptors and cytokines by means of reverse transcription-polymerase chain reaction (RT-PCR) techniques. Characteristic patterns of such factors' expression were found in gingival biopsies from patients presenting with aggressive periodontitis and chronic periodontitis. The expression of the chemokines macrophage inflammatory protein-1 alpha (MIP-1alpha) and interferon-gamma inducible protein 10 (IP-10) and of their respective receptors, CCR5 and CXCR3, were more prevalent and higher in aggressive periodontitis, and associated with higher interferon-gamma (IFN-gamma) expression and lower interleukin-10 (IL-10) expression. In contrast, chronic periodontitis patients exhibited a more frequent and higher expression of monocyte chemoattractant protein-1 (MCP-1) and its receptor CCR4, and higher expression of IL-10. It is possible that chemokines, in addition to the classical cytokines, are involved in the immunopathogenesis of periodontal disease, driving the migration and the maintenance of several inflammatory cell types such as polymorphonuclear leukocytes, dendritic cells (DCs), natural killer cells, macrophages, and subsets of lymphocytes in the gingival tissues. These cells are thought to participate in the inflammatory and immune reaction that takes place in periodontal disease, killing pathogens, presenting antigens, and producing cytokines. The selective recruitment of polarized lymphocyte subsets could result in differential cytokine production at the site of response, which is supposed to determine the stable or progressive nature of the lesion. Besides, the role of chemokines as activators and chemoattracts of osteclasts may be involved in the determination of disease severity.