Preclinical Mechanisms of Topical PRN473, a Bruton Tyrosine Kinase Inhibitor, in Immune-Mediated Skin Disease Models.

The expression of Bruton tyrosine kinase (BTK) in B cells and innate immune cells provides essential downstream signaling for BCR, Fc receptors, and other innate immune cell pathways. The topical covalent BTK inhibitor PRN473 has shown durable, reversible BTK occupancy with rapid on-rate and slow off-rate binding kinetics and long residence time, resulting in prolonged, localized efficacy with low systemic exposure in vivo. Mechanisms of PRN473 include inhibition of IgE (FcεR)-mediated activation of mast cells and basophils, IgG (FcγR)-mediated activation of monocytes, and neutrophil migration. In vivo, oral PRN473 was efficacious and well tolerated in the treatment of canine pemphigus foliaceus. In this study, we evaluated in vitro selectivity and functionality, in vivo skin Ab inflammatory responses, and systemic pharmacology with topically administered PRN473. Significant dose-dependent inhibition of IgG-mediated passive Arthus reaction in rats was observed with topical PRN473 and was maintained when given 16 h prior to challenge, reinforcing extended activity with once-daily administration. Similarly, topical PRN473 resulted in significant dose-dependent inhibition of the mouse passive cutaneous anaphylaxis IgE-mediated reaction. Multiday treatment with topical PRN473 in rodents resulted in low-to-no systemic accumulation, suggesting that efficacy was mainly due to localized exposure. Reduced skin Ab inflammatory activity was also confirmed with oral PRN473. These preclinical studies provide a strong biologic basis for targeting innate immune cell responses locally in the skin, with rapid onset of action following once-daily topical PRN473 administration and minimal systemic exposure. Dose-dependent inhibition in these preclinical models of immune-mediated skin diseases support future clinical studies.

CD22 and CD72 cooperatively contribute to the development of the reverse Arthus reaction model.

BACKGROUND: Local type III hypersensitivity reactions are acute inflammatory events induced by immune complex (IC) deposition. CD22 and CD72 are B cell-specific cell surface molecules that negatively regulate B cell function. OBJECTIVE: To elucidate the roles of CD22 and CD72 in the development of IgG-mediated type III hypersensitivity reactions. METHOD: The reverse Arthus reaction model in the skin was induced in mice lacking CD22 (CD22-/-), CD72 (CD72-/-), and both of them (CD22-/-/CD72-/-). Edema at 4h and hemorrhage at 8h after IC challenge were evaluated. Inflammatory cell infiltration and cytokine and chemokine expression were also examined. RESULTS: Edema and hemorrhage were significantly reduced in CD22-/-/CD72-/- mice compared with wild-type mice. The loss of both membrane proteins resulted in a greater decrease in edema at 4h, but not hemorrhage at 8h, than the loss of each protein alone. Infiltration of neutrophils, macrophages, and T cells, and the expression of TNF-α, IL-6, MIP-1α, and CCR5 mRNA were also diminished in the knockout mice compared to wild-type mice, and most significantly reduced in CD22-/-/CD72-/- mice. Regulatory T (Treg) cells in the spleen were significantly increased in all knockout mice at 4h. Significant differences in the severity of edema and hemorrhage between wild-type and knockout mice were lost when Treg cells were depleted in the knockout mice. CONCLUSION: These results demonstrate that CD22 and CD72 expression contribute to the development of the reverse Arthus reaction model and CD22 and CD72 might be therapeutic targets for human IC-mediated diseases.

Anti-TWEAK monoclonal antibodies reduce vascular damage and leucocyte infiltration in a mouse model of cutaneous reverse passive Arthus reaction.

BACKGROUND: Tumour necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) is a pro-inflammatory cytokine, which is closely associated with the pathogenesis of various types of cutaneous vasculitis (CV). AIM: To investigate the therapeutic effects of an anti-TWEAK monoclonal antibody (mAb) in a mouse model of cutaneous reverse passive Arthus (RPA) reaction. METHODS: Cutaneous RPA reaction was induced in BALB/c mice by intradermal injection of anti-ovalbumin IgG into the left ear followed immediately by intravenous injection of chicken ovalbumin. After treatment, haemorrhagic lesions in the mouse skin were scored semiquantitatively. The amount of extravasated fluorescein isothiocyanate (FITC)-labelled bovine serum albumin (BSA) in the ears was detected spectrophotometrically. Expression of myeloperoxidase (MPO) was detected by immunohistochemical staining, while mRNA expression of TNF-α and interleukin (IL)-6 in lesional skin was detected by real-time quantitative (q)PCR. RESULTS: Our results indicated that anti-TWEAK mAb significantly attenuated the clinical and histopathological changes in immune complex (IC)-induced mice, and also reduced the semiquantitative haemorrhage score, FITC-labelled BSA extravasation and MPO activity. Real-time qPCR showed that anti-TWEAK mAb significantly inhibited mRNA expression of TNF-α and IL-6 in lesional skin from IC-induced mice. CONCLUSION: These data suggest that anti-TWEAK mAb can block vascular damage and leucocyte infiltration in IC-induced mice. TWEAK might be a candidate immunotherapeutic medicine for suppression of IC-induced CV.

Interaction between CX3CL1 and CX3CR1 regulates vasculitis induced by immune complex deposition.

A type III hypersensitivity reaction induced by an immune complex, such as leukocytoclastic vasculitis, is mediated by inflammatory cell infiltration that is highly regulated by multiple adhesion molecules. CX3CL1, a ligand for CX3C chemokine receptor 1 (CX3CR1), has recently been identified as a key mediator of leukocyte adhesion that functions without the recruitment of integrins or selectin-mediated rolling. To elucidate the role of CX3CL1 and CX3CR1 in the development of leukocytoclastic vasculitis, the cutaneous and peritoneal reverse Arthus reactions, classic experimental models for immune complex-mediated tissue injury, were examined in mice lacking CX3CR1. CX3CL1 expression in sera and lesional skin of patients with polyarteritis nodosa (PN) and healthy controls was also examined. Edema and hemorrhage were significantly reduced in CX3CR1(-/-) mice compared with wild-type mice. Infiltration of neutrophils and mast cells and expression of IL-6 and tumor necrosis factor-α were also decreased in CX3CR1(-/-) mice. CX3CL1 was expressed in endothelial cells during the cutaneous reverse Arthus reactions. Furthermore, serum CX3CL1 levels were significantly higher in patients with PN than in healthy controls. Endothelial cells in lesional skin of patients with PN strongly expressed CX3CL1. These results suggest that interactions between CX3CL1 and CX3CR1 may contribute to the development of leukocytoclastic vasculitis by regulating neutrophil and mast cell recruitment and cytokine expression.

Exogenous application of hydrogen sulfide donor attenuates inflammatory reactions through the L-selectin-involved pathway in the cutaneous reverse passive Arthus reaction.

H2S has been highlighted recently as an endogenous, gaseous signaling molecule, especially in inflammations. The deposition of IC induces an acute inflammatory response with tissue injury. To assess the roles of H2S in the IC-induced diseases, the cutaneous, reverse passive Arthus reaction was conducted using NaHS as a H2S donor. Furthermore, we conducted similar experiments using selectin(-/-) mice to determine the involvement of selectin molecules in the H2S-mediated pathway. Exogenous application of NaHS dramatically attenuated inflammatory reactions in WT mice associated with Arthus reaction. Namely, mRNA expressions of TNF-α, IFN-γ, and neutrophil numbers were reduced significantly in the lesional skins of NaHS-treated WT mice relative to untreated ones. NaHS treatment significantly reduced these three parameters in the lesional skins of E- and P-selectin(-/-) mice but not in those of L-selectin(-/-) mice. Quite similar results were obtained in the blocking study using WT mice injected with mAb to E-, P-, and L-selectin. Our results indicated that the exogenous application of NaHS attenuates inflammatory responses in reverse passive Arthus reaction through a L-selectin-involved pathway but not through E- or P-selectin pathways.

Isoflurane inhibits neutrophil recruitment in the cutaneous Arthus reaction model.

PURPOSE: Neutrophil recruitment to the inflammatory sites is regulated by a variety of adhesion molecules including ß2 integrins. The dependency of neutrophil recruitment on ß2 integrins is variable in different tissues, but has not yet been verified in the cutaneous passive reverse Arthus reaction. We examined this question and also evaluated the impact of isoflurane on neutrophil recruitment to the skin because we previously showed in vitro that isoflurane binds and inhibits ß2 integrins. METHODS: The dependency on ß2 integrins in neutrophil recruitment to the skin in the Arthus reaction was examined using αL, αM and ß2 knockout mice. Then, we evaluated the effect of isoflurane on neutrophil recruitment to the skin. In addition, the effects of isoflurane on neutrophil binding to intercellular adhesion molecule-1 (ICAM-1), one of the ß2 integrin ligands, were studied in vitro using cell adhesion assays. RESULTS: Neutrophil recruitment to the skin in the Arthus reaction model was totally dependent on ß2 integrins, as ß2 knockout mice completely abolished it. However, the defect of only one of the ß2 integrins was not sufficient to abolish neutrophil recruitment. Isoflurane reduced neutrophil recruitment to the skin by approximately 90 %. Also, isoflurane inhibited neutrophil adhesion to ß2 integrin ligand ICAM-1. CONCLUSIONS: We demonstrated that (1) neutrophil recruitment to the skin was totally dependent on ß2 integrins, and (2) isoflurane significantly impaired neutrophil recruitment. Based on the previous studies on the contribution of other adhesion molecules in neutrophil recruitment, it is likely that isoflurane at least partially affects on ß2 integrins in this model.

Gαi2 is the essential Gαi protein in immune complex-induced lung disease.

Heterotrimeric G proteins of the Gα(i) family have been implicated in signaling pathways regulating cell migration in immune diseases. The Gα(i)-protein-coupled C5a receptor is a critical regulator of IgG FcR function in experimental models of immune complex (IC)-induced inflammation. By using mice deficient for Gα(i2) or Gα(i3), we show that Gα(i2) is necessary for neutrophil influx in skin and lung Arthus reactions and agonist-induced neutrophilia in the peritoneum, whereas Gα(i3) plays a less critical but variable role. Detailed analyses of the pulmonary IC-induced inflammatory response revealed several shared functions of Gα(i2) and Gα(i3), including mediating C5a anaphylatoxin receptor-induced activation of macrophages, involvement in alveolar production of chemokines, transition of neutrophils from bone marrow into blood, and modulation of CD11b and CD62L expression that account for neutrophil adhesion to endothelial cells. Interestingly, C5a-stimulated endothelial polymorphonuclear neutrophil transmigration, but not chemotaxis, is enhanced versus reduced in the absence of neutrophil Gα(i3) or Gα(i2), respectively, and knockdown of endothelial Gα(i2) caused decreased transmigration of wild-type neutrophils. These data demonstrate that Gα(i2) and Gα(i3) contribute to inflammation by redundant, overlapping, and Gα(i)-isoform-specific mechanisms, with Gα(i2) exhibiting unique functions in both neutrophils and endothelial cells that appear essential for polymorphonuclear neutrophil recruitment in IC disease.

Platelets control leukocyte recruitment in a murine model of cutaneous arthus reaction.

Platelets have been shown to be important in inflammation, but their role in the cutaneous Arthus reaction remains unclear. To assess the role of platelets in this pathogenetic process, the cutaneous Arthus reaction was examined in wild-type mice and mice lacking E-selectin, P-selectin, or P-selectin glycoprotein ligand-1 (PSGL-1) with or without platelet depletion by busulfan, a bone marrow precursor cell-specific toxin. Edema and hemorrhage induced by immune complex challenge significantly decreased in busulfan-treated wild-type mice compared with untreated mice. Busulfan treatment did not affect edema and hemorrhage in P-selectin- or PSGL-1-deficient mice, suggesting that the effect by busulfan is dependent on P-selectin and PSGL-1 expression. The inhibited edema and hemorrhage paralleled reduced infiltration of neutrophils and mast cells and reduced levels of circulating platelets. Increased cutaneous production of interleukin-6, tumor necrosis factor-alpha, and platelet-derived chemokines during Arthus reaction was inhibited in busulfan-treated wild-type mice relative to untreated mice, which paralleled the reduction in cutaneous inflammation. Flow cytometric analysis showed that immune complex challenge generated blood platelet-leukocyte aggregates that decreased by busulfan treatment. In thrombocytopenic mice, the cutaneous inflammation after immune complex challenge was restored by platelet infusion. These results suggest that platelets induce leukocyte recruitment into skin by forming platelet-leukocyte aggregates and secreting chemokines at inflamed sites, mainly through the interaction of P-selectin on platelets with PSGL-1 on leukocytes.

Proteinase 3 and neutrophil elastase enhance inflammation in mice by inactivating antiinflammatory progranulin.

Neutrophil granulocytes form the body's first line of antibacterial defense, but they also contribute to tissue injury and noninfectious, chronic inflammation. Proteinase 3 (PR3) and neutrophil elastase (NE) are 2 abundant neutrophil serine proteases implicated in antimicrobial defense with overlapping and potentially redundant substrate specificity. Here, we unraveled a cooperative role for PR3 and NE in neutrophil activation and noninfectious inflammation in vivo, which we believe to be novel. Mice lacking both PR3 and NE demonstrated strongly diminished immune complex-mediated (IC-mediated) neutrophil infiltration in vivo as well as reduced activation of isolated neutrophils by ICs in vitro. In contrast, in mice lacking just NE, neutrophil recruitment to ICs was only marginally impaired. The defects in mice lacking both PR3 and NE were directly linked to the accumulation of antiinflammatory progranulin (PGRN). Both PR3 and NE cleaved PGRN in vitro and during neutrophil activation and inflammation in vivo. Local administration of recombinant PGRN potently inhibited neutrophilic inflammation in vivo, demonstrating that PGRN represents a crucial inflammation-suppressing mediator. We conclude that PR3 and NE enhance neutrophil-dependent inflammation by eliminating the local antiinflammatory activity of PGRN. Our results support the use of serine protease inhibitors as antiinflammatory agents.

Targeting immune complex-mediated hypersensitivity with recombinant soluble human FcgammaRIA (CD64A).

Binding of Ag-Ab immune complexes to cellular FcgammaR promotes cell activation, release of inflammatory mediators, and tissue destruction characteristic of autoimmune disease. To evaluate whether a soluble FcgammaR could block the proinflammatory effects of immune complexes, recombinant human (rh) versions of FcgammaRIA, FcgammaRIIA, and FcgammaRIIIA were prepared. Binding of rh-FcgammaRIA to IgG was of high affinity (KD=1.7x10(-10) M), whereas rh-FcgammaRIIA and rh-FcgammaRIIIA bound with low affinity (KD=0.6-1.9x10(-6) M). All rh-FcgammaR reduced immune complex precipitation, blocked complement-mediated lysis of Ab-sensitized RBC, and inhibited immune complex-mediated production of IL-6, IL-13, MCP-1, and TNF-alpha by cultured mast cells. Local or systemic delivery only of rh-FcgammaRIA, however, reduced edema and neutrophil infiltration in the cutaneous Arthus reaction in mice. 125I-labeled rh-FcgammaRIA was cleared from mouse blood with a rapid distribution phase followed by a slow elimination phase with a t1/2gamma of approximately 130 h. The highest percentage of injected radioactivity accumulated in blood approximately liver approximately carcass>kidney. s.c. dosing of rh-FcgammaRIA resulted in lower serum levels of inflammatory cytokines and prevented paw swelling and joint damage in a murine model of collagen Ab-induced arthritis. These data demonstrate that rh-FcgammaRIA is an effective inhibitor of type III hypersensitivity.

Immune complex pathophysiology.

Antigen-antibody (Ab) interactions that lead to the formation of immune complexes (ICs) are subtle biochemical processes determining health or disease according to the outcome. Good laboratory practice (GLP)-acknowledged IC detection methods reveal that plasma levels of up to 15 microg/mL heat-aggregated immunoglobulin G (IgG) equivalents are normal, indicating the physiological role of ICs. Among the major variables that influence the equilibrium association constant Ka, are specificity and epitope density of the antigen, Ig class/subclass of the Ab, IC complement (C)-activating capacity, Fc receptor (FcR) interaction, and cytokine activation pattern. The Ka of antigen-Ab binding at approximately 20 degrees C ranges from low affinity (105) to high affinity (107-1011). Beneficial ICs serve to remove and/or neutralize infectious or toxic antigens, following an infectious attack in immune and vaccinated hosts. Circulating ICs are more prone for benefit than tissue-bound ICs, which reflect in situ formation and/or undesired deposition in tissues due to overflow from insufficient reticuloendothelial system (RES) removal. The classical textbook topic on ICs still holds true but is under revision because of the improved knowledge of effector systems, such as C, cytokine, and FcR apparatus. Therapeutic options to treat IC-associated diseases include intravenous immunoglobulins (IVIG) at their onset and monoclonal antibodies (mAb) directed at C activation products and/or cytokines.

Immunodeficiency and autoimmune phenomena in female hyper-IgM syndrome.

We report an unusual case that highlights the clinical problems associated with autoimmune phenomena. A female (born 1972) was referred to our hospital with systemic lupus erythematosus (SLE) diagnosis. During the follow-up (7 years), we observed the appearance and the disappearance of a lot of autoantibodies detected. The history of recurrent bacterial sinopulmonary infections since puberty and enlargement of lymphonodes, elevated IgM, very low IgA and normal IgG levels, and the variable autoantibody profile oriented toward a "defective Ig class switch recombination" disorder: the hyper-IgM syndrome. Immunodeficiency and autoimmune phenomena may occur concomitantly in the same individual and sometimes the differential diagnosis is difficult.

Intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 cooperatively contribute to the cutaneous Arthus reaction.

Immune complex (IC)-induced inflammation is mediated by inflammatory cell infiltration, a process that is highly regulated by expression of multiple adhesion molecules. The roles and interactions of ICAM-1 and VCAM-1, the major regulators of leukocyte firm adhesion, were examined in the cutaneous reverse-passive Arthus reaction using ICAM-1-deficient (ICAM-1-/-) mice and blocking mAb against VCAM-1. Within 8 h, IC challenge of wild-type mice induced edema, hemorrhage, interstitial accumulation of neutrophils and mast cells, as well as production of TNF-alpha and IL-6. All of these inflammatory parameters were reduced significantly in ICAM-1-/- mice. The blockade of VCAM-1 in wild-type mice did not affect any inflammatory parameters. In contrast, ICAM-1-/- mice treated with anti-VCAM-1 mAb had significantly reduced edema, hemorrhage, and neutrophil infiltration. Furthermore, VCAM-1 blockade in ICAM-1-/- mice suppressed cutaneous TNF-alpha and IL-6 production. Thus, VCAM-1 plays a complementary role to ICAM-1 in the cutaneous Arthus reaction by regulating leukocyte accumulation and proinflammatory cytokine production.

Site of blood vessel damage and relevance of CD18 in a murine model of immune complex-mediated vasculitis.

How neutrophils (polymorphonuclear neutrophils, PMNs) damage vessels in leukocytoclastic vasculitis (LcV) mediated by immune complexes (ICs) is unclear. If degradative enzymes and oxygen radicals are released from PMNs while adhering to the inner side of the vessel wall, they could be washed away by the blood stream or neutralized by serum protease inhibitors. We investigated if in LcV PMNs could damage vessels from the tissue side after transmigration. We used CD18-deficient (CD18-/-) mice because the absence of CD18 excludes transmigration of PMNs. When eliciting the Arthus reaction in ears of CD18-/- mice, deposition of ICs was not sufficient to recruit PMNs or to induce IC-mediated LcV. Injection of PMNs intradermally in CD18-/- mice allowed us to investigate if bypassing diapedesis and placing PMNs exclusively on the abluminal side leads to vascular destruction. We found that injected PMNs gathered around perivascular ICs, but did not cause vessel damage. Only intravenous injection of wild-type PMNs could re-establish the Arthus reaction in CD18-/- mice. Thus, PMNs cause vessel damage during diapedesis from the luminal side, but not from the perivascular space. We suggest that in order to shield the cytotoxic products from the blood stream, ICs induce particularly tight interactions between them, PMNs and endothelial cells.

Immune complexes alter cerebral microvessel permeability: roles of complement and leukocyte adhesion.

Immune complexes (ICs) are potent inflammatory mediators in peripheral tissues. However, very few studies have examined the ability of ICs to induce inflammatory responses in the brain. Therefore, using preformed ICs or the reverse passive Arthus (RPA) model to localize ICs to the pial microvasculature of mice, we aimed to investigate the ability of ICs to induce an inflammatory response in the cerebral (pial) microvasculature. Application of preformed ICs immediately increased pial microvascular permeability, with a minimal change in leukocyte adhesion in pial postcapillary venules. In contrast, initiation of the RPA response in the pial microvasculature induced changes in cerebral microvascular permeability and increased leukocyte adhesion in pial postcapillary venules. The RPA response induced deposition of C3 in perivascular regions adjacent to sites of IC formation. Depletion of C3 abrogated RPA-induced microvascular permeability and leukocyte adhesion, indicating that the complement pathway was critical for this response. Inhibition of leukocyte adhesion via CD18 blockade also reduced IC-induced microvascular permeability. However, this did not require intercellular adhesion molecule-1, inasmuch as blockade of intercellular adhesion molecule-1 did not alter RPA-induced microvascular permeability and adhesion. These findings demonstrate that ICs are capable of rapidly inducing inflammatory responses in the cerebral microvasculature, with the complement pathway and leukocyte recruitment playing critical roles in microvascular dysfunction.

Macrophages induce the inflammatory response in the pulmonary Arthus reaction through G alpha i2 activation that controls C5aR and Fc receptor cooperation.

Complement and FcgammaR effector pathways are central triggers of immune inflammation; however, the exact mechanisms for their cooperation with effector cells and their nature remain elusive. In this study we show that in the lung Arthus reaction, the initial contact between immune complexes and alveolar macrophages (AM) results in plasma complement-independent C5a production that causes decreased levels of inhibitory FcgammaRIIB, increased levels of activating FcgammaRIII, and highly induced FcgammaR-mediated TNF-alpha and CXCR2 ligand production. Blockade of C5aR completely reversed such changes. Strikingly, studies of pertussis toxin inhibition show the essential role of G(i)-type G protein signaling in C5aR-mediated control of the regulatory FcgammaR system in vitro, and analysis of the various C5aR-, FcgammaR-, and G(i)-deficient mice verifies the importance of Galpha(i2)-associated C5aR and the FcgammaRIII-FcgammaRIIB receptor pair in lung inflammation in vivo. Moreover, adoptive transfer experiments of C5aR- and FcgammaRIII-positive cells into C5aR- and FcgammaRIII-deficient mice establish AM as responsible effector cells. AM lacking either C5aR or FcgammaRIII do not possess any such inducibility of immune complex disease, whereas reconstitution with FcgammaRIIB-negative AM results in an enhanced pathology. These data suggest that AM function as a cellular link of C5a production and C5aR activation that uses a Galpha(i2)-dependent signal for modulating the two opposing FcgammaR, FcgammaRIIB and FcgammaRIII, in the initiation of the inflammatory cascade in the lung Arthus reaction.

In vivo accumulation of self-assembling dye Congo red in an area marked by specific immune complexes: possible relevance to chemotherapy.

Supramolecular micellar structures have been proposed as carriers in aim-oriented drug transportation to a target marked by specific immune complexes. In this study, the self-assembling dye Congo red was used as a model supramolecular carrier and its accumulation in the target was studied in vivo. The target was created in vivo as the local specific inflammation provoked by subcutaneous injection of antigen to the ear of a previously immunized rabbit. The color caused by accumulation of Congo red after its intravenous injection was registered by pictures of the ear with suitably filtered visible light shining through it to distinguish Congo red against the background color of hemoglobin. The results confirmed the expected accumulation and retention of Congo red in the inflammation area marked by deposits of specific immune complexes. The role of albumin and its possible interference with transportation of drugs through the blood by supramolecular carriers was also subjected to preliminary examination. The results revealed that albumin collaborates rather than interferes with drug transportation; this is another factor making the use of supramolecular carriers for aim-oriented chemotherapy highly promising.

A peptide derived from the parasite receptor, complement C2 receptor inhibitor trispanning, suppresses immune complex-mediated inflammation in mice.

Complement C2 receptor inhibitor trispanning (CRIT) is a Schistosoma protein that binds the human complement protein, C2. We recently showed that peptides based on the ligand binding region of CRIT inhibit the classical pathway (CP) of complement activation in human serum, using hemolytic assays and so speculated that on the parasite surface CRIT has the function of evading human complement. We now show that in vitro the C2-binding 11-aa C terminus of the first extracellular domain of CRIT, a 1.3-kDa peptide termed CRIT-H17, inhibits CP activation in a species-specific manner, inhibiting mouse and rat complement but not that from guinea pig. Hitherto, the ability of CRIT to regulate complement in vivo has not been assessed. In this study we show that by inhibiting the CP, CRIT-H17 is able to reduce immune complex-mediated inflammation (dermal reversed passive Arthus reaction) in BALB/c mice. Upon intradermal injection of CRIT-H17, and similarly with recombinant soluble complement receptor type 1, there was a 41% reduction in edema and hemorrhage, a 72% reduction in neutrophil influx, and a reduced C3 deposition. Furthermore, when H17 was administered i.v. at a 1 mg/kg dose, inflammation was reduced by 31%. We propose that CRIT-H17 is a potential therapeutic agent against CP complement-mediated inflammatory tissue destruction.

Relative contributions of selectins and intercellular adhesion molecule-1 to tissue injury induced by immune complex deposition.

Immune complex-induced tissue injury is mediated by inflammatory cell infiltration that is highly regulated by multiple adhesion molecules. To assess the relative contribution of adhesion molecules, including selectins and ICAM-1, in this pathogenetic process, the cutaneous passive Arthus reaction was examined in mice lacking E-selectin, P-selectin, or both L-selectin and ICAM-1 with anti-P- or E-selectin mAbs. Edema and hemorrhage were significantly reduced in P-selectin(-/-) mice compared with wild-type mice while they were not inhibited in E-selectin(-/-) mice. Combined E- and P-selectin blockade resulted in more significant reduction relative to L-selectin/ICAM-1(-/-) as well as P-selectin(-/-) mice. Remarkably, both E- and P-selectin blockade in L-selectin/ICAM-1(-/-) mice completely abrogated edema and hemorrhage. The inhibited edema and hemorrhage paralleled reduced infiltration of neutrophils and mast cells that expressed significant levels of P-selectin glycoprotein ligand-1. Similarly reduced infiltration of neutrophils and mast cells was observed in the peritoneal Arthus reaction and was associated partly with the decreased production of tumor necrosis factor-alpha and interleukin-6. The results of this study indicate that both endothelial selectins contribute predominantly to the Arthus reaction by regulating mast cell and neutrophil infiltration and that the full development of the Arthus reaction is mediated cooperatively by all selectins and ICAM-1.

Optimized conjugation ratios lead to allergen immunostimulatory oligodeoxynucleotide conjugates with retained immunogenicity and minimal anaphylactogenicity.

BACKGROUND: Immunotherapy has gradually fallen out of favor for the treatment of many allergic diseases because of the overall convenience, safety, and efficacy of medications. However, investigations suggest that allergen/immunostimulatory sequence oligodeoxynucleotide (ISS-ODN) conjugates (AICs) might have improved safety and efficacy compared with allergen extracts. OBJECTIVE: We determined whether changes in the ISS-ODN conjugation ratio would effect the immunogenicity and allergenicity of AIC. METHODS: Immunogenicity was determined by means of AIC vaccination of mice, followed by analysis of antigen-specific antibody and cytokine responses. The allergenicity of AIC was determined in mast cell release studies and in murine models of anaphylaxis and the Arthus reaction. RESULTS: AIC induced a stronger immune response than allergen alone or allergen mixed with ISS-ODN, but higher-level ISS-ODN conjugation reduced its immunogenicity modestly. In mast cell degranulation studies AIC was approximately 100-fold less allergenic than native allergen, with stepwise increases in the ODN conjugation ratio leading to stepwise decreases in allergenicity. In anaphylaxis studies death rates were reduced from 100% with native allergen challenge to as low as 0% with high-ratio ISS-ODN AIC challenge. Similar results were obtained in an Arthus reaction model. CONCLUSION: These investigations establish that AIC is both significantly more immunogenic and less allergenic than native allergens and the techniques used might have further utility for the standardization and optimization of AIC formulations for use in allergic patients.