Silvia Campo

Pivotal Advance: Inhibition of MyD88 dimerization and recruitment of IRAK1 and IRAK4 by a novel peptidomimetic compound.

MyD88 is an adaptor protein, which plays an essential role in the intracellular signaling elicited by IL‐1R and several TLRs. Central to its function is the ability of its Toll/IL‐1R translation initiation region (TIR) domain to heterodimerize with the receptor and to homodimerize with another MyD88 molecule to favor the recruitment of downstream signaling molecules such as the serine/threonine kinases IL‐1R‐associated kinase 1 (IRAK1) and IRAK4. Herein, we have synthesized and tested the activity of a synthetic peptido‐mimetic compound (ST2825) modeled after the structure of a heptapeptide in the BB‐loop of the MyD88‐tIR domain, which interferes with MyD88 signaling. ST2825 inhibited MyD88 dimerization in coimmunoprecipitation experiments. This effect was specific for homodimerization of the TIR domains and did not affect homodimerization of the death domains. Moreover, ST2825 interfered with recruitment of IRAK1 and IRAK4 by MyD88, causing inhibition of IL‐1β‐mediated activation of NF‐κB transcriptional activity. After oral administration, ST2825 dose‐dependently inhibited IL‐1β‐induced production of IL‐6 in treated mice. Finally, we observed that ST2825 suppressed B cell proliferation and differentiation into plasma cells in response to CpG‐induced activation of TLR9, a receptor that requires MyD88 for intracellular signaling. Our results indicate that ST2825 blocks IL‐1R/TLR signaling by interfering with MyD88 homodimerization and suggest that it may have therapeutic potential in treatment of chronic inflammatory diseases.

Exogenous Pentraxin 3 Restores Antifungal Resistance and Restrains Inflammation in Murine Chronic Granulomatous Disease

Chronic granulomatous disease (CGD) is a primary immunodeficiency characterized by life-threatening bacterial and fungal infections and hyperinflammation. The susceptibility to aspergillosis in experimental CGD (p47phox−/− mice) is associated with the failure to control the inherent inflammatory response to the fungus and to restrict the activation of inflammatory Th17 cells. We assessed whether pentraxin (PTX)3, a member of a family of multimeric pattern-recognition proteins with potent anti-Aspergillus activity, could limit pathogenic inflammation in p47phox−/− mice by curbing the IL–23/Th17 inflammatory axis in response to the fungus. We found that the production of PTX3 was delayed in CGD mice in infection but exogenous administration of PTX3 early in infection restored antifungal resistance and restrained the inflammatory response to the fungus. This occurred through down-regulation of IL-23 production by dendritic cells and epithelial cells which resulted in limited expansion of IL-23R+ γδ+ T cells producing IL-17A and the emergence of Th1/Treg responses with minimum pathology. Thus, PTX3 could be therapeutically used for the exploitation of NADPH-independent mechanism(s) of antifungal immune protection with limited immunopathology in CGD.

PTX3 Binds MD-2 and Promotes TRIF-Dependent Immune Protection in Aspergillosis

The long pentraxin 3 (PTX3) modulates different effector pathways involved in innate resistance to Aspergillus fumigatus, including complement activation or promotion of phagocytosis by interacting with FcγRs. However, whether and how TLRs modulate PTX3 mediates antifungal resistance is not known. In this study, we demonstrate that PTX3 binds myeloid differentiation protein 2 (MD-2) in vitro and exerts its protective antifungal activity in vivo through TLR4/MD-2–mediated signaling. Similar to Tlr4−/− mice, Md2−/− mice displayed high susceptibility to pulmonary aspergillosis, a phenotype associated with a proinflammatory cytokine profile and impaired antifungal activity of polymorphonuclear neutrophils. Treating Md2−/− mice with PTX3 failed to confer immune protection against the fungus, whereas adoptive transfer of MD-2–competent polymorphonuclear neutrophils restored it. Mechanistically, engagement of MD-2 by PTX3-opsonized Aspergillus conidia activated the TLR4/Toll/IL-1R domain-containing adapter inducing IFN-β–dependent signaling pathway converging on IL-10. Thus, we have identified a novel receptor mechanism, involving the TLR4/MD-2/Toll/IL-1R domain-containing adapter inducing IFN-β–mediated signaling, whereby PTX3 elicits antifungal resistance with limited immunopathology in A. fumigatus infection.

Efficacy of PTX3 in a Rat Model of Invasive Aspergillosis

ABSTRACT Pentraxin 3 (PTX3) is an acute-phase glycoprotein with a nonredundant function in the host resistance to Aspergillus fumigatus. PTX3 activity was evaluated against pulmonary aspergillosis in rats immunosuppressed with cortisone acetate. PTX3 enhanced the survival rate and reduced the lung fungal burden of infected rats in both therapeutic and prophylactic modalities. Thus, we extended the protective activity of PTX3 in pulmonary aspergillosis to corticosteroid-induced immunodeficiency, which is a relevant clinical condition in graft-versus-host disease and in solid organ transplant.

Low and High Tenascin-Expressing Tumors Are Efficiently Targeted by ST2146 Monoclonal Antibody

ST2146biot is a biotinylated anti-tenascin monoclonal antibody (mAb) to be used for Pretargeted Antibody Guided Radioimmunotherapy (PAGRIT) of solid tumors. In vivo biodistribution studies of 125I-labeled ST2146biot were done in nude mice transplanted with human HT-29 colon carcinoma and/or human U-118MG glioblastoma cells characterized for low and high tenascin expression, respectively. In vitro results show that ST2146 retains immunoreactivity upon biotinylation, in contrast to other anti-tenascin mAbs. In vivo biodistribution of ST2146 shows specific tumor accumulation up to 10 days after the i.v. injection, with no relevant differences between biotinylated and nonbiotinylated ST2146. A dose of 4 μg/mouse saturates the low tenascin-expressing human colon carcinoma HT-29, whereas the high tenascin-expressing human glioblastoma U-118MG seems to be saturated at a ST2146biot dose between 320 and 640 μg/mouse. The percentage of injected dose per gram of tumor ranges from 10% to 30%, corresponding to an amount of ST2146biot/g of tumor of ∼400 ng/g and >200 μg/g for HT-29 and U-118MG, respectively. Tumor to normal organs uptake ratios are between 15 and 60, confirming high tumor selectivity of ST2146biot despite its cross-reactivity with the tenascin expressed at low level in the normal mouse organs. The ST2146biot localization data are substantially confirmed even when both low and high tenascin-expressing tumors are implanted in the same animal. To our knowledge, the absolute amount of ST2146biot, specifically localized in xenotransplanted human tumors, is the highest thus far described and supports the clinical use of this mAb in PAGRIT®.

LPS-induced serum TNF production and lethality in mice: effect of L-carnitine and some acyl-derivatives

The effect of L-carnitine and some of its acyl derivatives on serum TNF production and lethality in a murine experimental endotoxin shock model was investigated. In some instances, serum IL-6 production was also evaluated. In this experimental model, C57BL/6 mice received 30 mg/kg LPS (E. cell 055:B5) injected intraperitoneally, while L-carnitine and its derivatives were administered according to different schedules. Serum levels of TNF and IL-6 were evaluated 1 h following LPS injection. The treated animals were also monitored daily for differences in body temperature, feeding, and survival for 10 days after LPS injection. Although some derivatives were able to significantly affect TNF production, the marked decrease in serum TNF levels of LPS-treated mice was not paralleled by a substantial increase in survival.

Effect of PTX3 and Voriconazole Combination in a Rat Model of Invasive Pulmonary Aspergillosis

ABSTRACT This study evaluated the pharmacological activity of PTX3, administered in combination with voriconazole, in a rat model of pulmonary aspergillosis. The data indicated additive therapeutic activities of these compounds, as demonstrated by the amelioration of respiratory function changes, reduction of lung fungal burden, and increased survival. Overall, we provide clear evidence that the combination of PTX3 with a suboptimal dose of voriconazole might represent a therapeutic option under those clinical conditions where the use of voriconazole alone is not warranted for efficacy and tolerability reasons.

Current understanding of PTX3 protective activity on Aspergillus fumigatus infection.

Infection caused by Aspergillus fumigatus remains a major therapeutic challenge in immunocompromised individuals. Innate immunity represents the first line of defense against pathogens. In the last 20 years, several proteins belonging to this arm of the immune system have been characterized as being endowed with antifungal activity. Among these, the prototype long pentraxin PTX3 has been identified as a non-redundant protective factor against infections caused by A. fumigatus. A number of relevant animal models of invasive aspergillosis have indicated that PTX3 exerts its protective activity in several conditions of immunosuppression. In this article, we review the current understanding of PTX3 mechanisms of action that might be of help in further exploration of the pharmacological activity of this protein against A. fumigatus.

In vivo and in vitro cytokine modulatory activity of newly synthesised 2-aminotetraline derivatives.

In the present study, the protective effect of newly synthesised 2-aminotetralines was investigated in murine models of toxic shock. A few derivatives protected mice against lethality induced by lipopolysaccharide from different bacterial strains and shock induced by staphylococcal enterotoxin B in mice sensitized by D-Galactosamine (D-Galn). Notably, one derivative, S(−)-2-amino-6-fluoro-7-methoxy-1,2,3,4 tetrahydronaphthalene hydrochloride (ST1214), was also effective when administered orally (30 mg kg−1) in a therapeutic regimen. ST1214 markedly inhibited the production of the proinflammatory cytokines, such as tumor necrosis factor-&agr; (TNF-&agr;), Interleukin-1&bgr; (IL-1&bgr;), Interleukin-12 (IL-12), interferon-&ggr; (IFN-&ggr;), as well as the inflammatory mediator nitric oxide (NO), and concurrently enhanced the production of the anti-inflammatory cytokine IL-10. Moreover, ST1214 dose-dependently reduced TNF-&agr; production by human peripheral blood mononuclear cells and promonocytic THP-1 cells in vitro. In the latter, ST1214 was found to inhibit lipopolysaccharide-induced TNF-&agr; secretion but not cytokine mRNA accumulation. These results suggest that the mechanism of action of ST1214 involves blockade of posttranscriptional events of TNF-&agr; production, apparently independent of p38 and ERK kinase activity. These results show beneficial effects of 2-aminotetralines in murine shock models and indicate a distinct counter-regulatory activity in down-regulating proinflammatory cytokine response, and upregulating IL-10. One derivative, i.e., ST1214, can be regarded as a lead compound in the development of novel drugs effective in anti-inflammatory strategies.

Efficacy of a Nanocochleate-Encapsulated 3,5-Diaryl-s-Triazole Derivative in a Murine Model of Graft-Versus-Host Disease

We have previously demonstrated that the compound 3-(2-ethylphenyl)-5-(3-methoxyphenyl)-1H-1,2,4-triazole exerts immunosuppressive effects in several experimental models of autoimmunity. These results were achieved by subcutaneously administering ST1959 after dissolution in an oily vehicle, because of its poor water solubility. To circumvent this problem, we sought to determine whether nanocochleate technology could be successfully exploited to deliver ST1959 and protect mice undergoing lethal acute graft-versus-host disease (GVHD). Orally-administered encochleated ST1959 significantly protected animals from lethality, resulting in survival rates of 57% and 100% at doses of 2 and 10 mg/kg, respectively, whereas oral administration of 2 mg/kg ST1959, mixed with empty nanocochleates, was completely inactive. Increased survival was associated with diminished serum chemokine levels and donor CD8+ T cells in the spleen of ST1959-treated mice. Moreover, ST1959 treatment significantly counteracted GVHD-induced normocitic anemia by increasing hemoglobin, hematocrit, platelet, and red and white blood cell counts. Overall, these data show that orally-administered encochleated ST1959 significantly protects mice from GVHD.