Molecular and clinical rationale for therapeutic targeting of interleukin-5 and its receptor.

Interleukin-5 is a Th2 homodimeric cytokine involved in the differentiation, maturation, migration, development, survival, trafficking and effector function of blood and local tissue eosinophils, in addition to basophils and mast cells. The IL-5 receptor (IL-5R) consists of an IL-5-specific α subunit that interacts in conformationally dynamic ways with the receptor's ßc subunit, an aggregate of domains it shares with binding sites of IL-3 and granulocyte-macrophage colony-stimulating factor. IL-5 and IL-5R drive allergic and inflammatory immune responses characterizing numerous diseases, such as asthma, atopic dermatitis, chronic obstructive pulmonary disease, eosinophilic gastrointestinal diseases, hyper-eosinophilic syndrome, Churg-Strauss syndrome and eosinophilic nasal polyposis. Although corticosteroid therapy is the primary treatment for these diseases, a substantial number of patients exhibit incomplete responses and suffer side-effects. Two monoclonal antibodies have been designed to neutralize IL-5 (mepolizumab and reslizumab). Both antibodies have demonstrated the ability to reduce blood and tissue eosinophil counts. One additional monoclonal antibody, benralizumab (MEDI-563), has been developed to target IL-5R and attenuate eosinophilia through antibody-dependent cellular cytotoxicity. All three monoclonal antibodies are being clinically evaluated. Antisense oligonucleotide technology targeting the common ßc IL-5R subunit is also being used therapeutically to inhibit IL-5-mediated effects (TPI ASM8). Small interfering RNA technology has also been used therapeutically to inhibit the expression of IL-5 in animal models. This review summarizes the structural interactions between IL-5 and IL-5R and the functional consequences of such interactions, and describes the pre-clinical and clinical evidence supporting IL-5R as a therapeutic target.

Identification of a murine homolog of the human adenosine deaminase thymic enhancer.

We have identified a 236-bp first intron segment of the mouse adenosine deaminase gene (ADA) that shares 71.1% identity with the human ADA thymic enhancer. This segment has the same natural orientation as the human enhancer and a relative location within the first intron very analogous to that of the human enhancer. Four highly conserved regions were defined within this segment, including a 72-bp region having 83.6% identity with a segment containing the critical human enhancer core. Several consensus binding sequences were also conserved within these regions. Transient transfection assays in human and murine T-cell lines revealed that a 1.8-kb murine genomic fragment harboring the 236-bp segment functions as a weak activator of both the human and mouse ADA promoters. In contrast, a 2.3-kb human enhancer fragment exhibited high-level activation in conjunction with either the human or mouse ADA promoter in both the MOLT 4 (human) and S49 (murine) T-cell lines. Interestingly, the murine ADA promoter is significantly stronger than the human promoter in driving cat expression in transient transfection assays in all the T-cell lines tested.

Pathology of the pancreas in severe combined immunodeficiency and DiGeorge syndrome: acute graft-versus-host disease and unusual viral infections.

Review of autopsies of 28 children with severe combined immunodeficiency (SCID) or combined immunodeficiency (CID) and three with DiGeorge syndrome showed a high incidence of acute graft-versus-host disease (GVHD) in the pancreas. Acute GVHD (seven cases: four SCID, two CID, and one DiGeorge syndrome) was characterized by lymphocytes around large to medium ducts, damage to ductal epithelium (focal necrosis, reactive nuclear changes, inspissated secretions in duct lumens), and periductal edema. Changes were judged indeterminate but suspicious for GVHD when ductal damage was slight (six cases: three SCID, two CID, and one DiGeorge syndrome). All patients with pancreatic GVHD had received allogeneic bone marrow, fetal liver or thymus transplant, or nonirradiated blood products and had evidence of GVHD in other organs. Immunoperoxidase stain for HLA-DR showed strong-to-moderate staining of duct epithelium in two of four GVHD cases for which blocks were available. This change was nonspecific; weaker staining for HLA-DR was seen in cases with nonspecific abnormalities and in viral pancreatitis. Four cases had histological evidence of viral infection: two had cytomegalovirus pancreatitis, one had patchy parenchymal necrosis caused by adenovirus, and one had giant cell pancreatitis caused by parainfluenza virus. Mild nonspecific changes, such as focal fat necrosis or acinar dilatation, were seen in seven cases. One case had unexplained marked pancreatic atrophy and fibrosis. Acute pancreatic GVHD is not uncommon in autopsies of children with congenital immune deficiencies with GVHD of other organs; however, this finding may not have strong clinical implications in this group of patients. Careful attention to pancreatic ducts is necessary for diagnosis. Unusual viral pancreatitis may also be seen in this group, as well as nonspecific abnormalities.

Pathology of the liver in severe combined immunodeficiency and DiGeorge syndrome.

Review of liver biopsy or autopsy material from 33 patients with severe combined immunodeficiency or combined immunodeficiency and four patients with DiGeorge syndrome revealed a wide range of hepatic pathology. The most common abnormality was graft-versus-host disease (16 patients), followed by viral infection (4 patients had adenovirus hepatitis, 3 had cytomegalovirus hepatitis). Centrilobular fibrosis with or without veno-occlusive disease was seen in five patients. Three patients had nonspecific hepatitis, four had changes attributed to total parenteral nutrition, and two had lymphoproliferative disorders involving the liver. Both patients with lymphoproliferative disorders had received transplants. Two patients had resolving necrosis probably secondary to non-A, non-B hepatitis. One had atypical mycobacterial infection. Hemosiderosis was a common nonspecific abnormality, seen in nine patients. All patients with hepatic graft-versus-host disease had received transplants or nonirradiated blood products. Hepatic graft-versus-host disease varied in severity from hepatic necrosis with destruction of both large and small bile ducts in a transfusion-associated case to subtle damage to interlobular bile ducts. Even minimal bile duct changes correlated with the clinical impression of graft-versus-host disease in these patients. Late chronic graft-versus-host disease was not seen in any patient, although acute graft-versus-host disease sometimes occurred late after transplant.

A 26-month-old child with Marden-Walker syndrome and pyloric stenosis.

We recently examined a 26-month-old boy with abnormal face, blepharophimosis, hypertelorism, apparently low-set ears, micrognathia, arachnodactyly, talipes equinovarus, and joint contractures. Subsequently he manifested failure to thrive, respiratory infections, and developmental delay. These congenital anomalies and associated findings are consistent with a diagnosis of the Marden-Walker syndrome. He also had mild pyloric stenosis and duodenal bands, not previously reported in this syndrome. This syndrome appears to be an autosomal recessive trait in some families. A summary of findings of the 16 previous published patients is presented.

Pretranslational regulation of type I collagen, fibronectin, and a 50-kilodalton noncollagenous extracellular protein by dexamethasone in rat fibroblasts.

The effect of dexamethasone on the synthesis of total cellular and extracellular proteins and specifically on the synthesis of type I procollagen chains, fibronectin, and a 50-kDa extracellular noncollagenous polypeptide was examined in cultured rat dermal fibroblasts. A slight but consistent inhibition of total protein synthesis by dexamethasone was dose and time dependent. Treatment of cells with 1 microM dexamethasone for 24 h while abolishing procollagen synthesis nearly completely (less than 95%) had the opposite effect (5-7-fold increase) on the synthesis of an extracellular noncollagenous 50-kDa polypeptide. Dexamethasone did not significantly affect the rates of synthesis of fibronectin. Cell-free translation of mRNA from dexamethasone-treated cells revealed corresponding changes in the steady-state levels of functional mRNAs coding for procollagens, the 50-kDa polypeptide, and fibronectin. Northern blot hybridization using nick-translated cDNA plasmids coding for pro-alpha 1(I), fibronectin, and cytoplasmic beta-actin mRNA corroborated the data obtained from cell-free translation experiments. Run-off transcription assays using nuclei from cells treated with 1 microM dexamethasone for 24 h revealed that glucocorticoid treatment did not significantly affect the rate of transcription of type I collagen genes; similarly, the rate of transcription of fibronectin and cytoplasmic beta-actin genes also remained unchanged under these conditions. An analysis of the kinetics of decay of radiolabeled mRNA coding for pro-alpha 1(I), pro-alpha 2(I), and fibronectin in dexamethasone-treated cells revealed that procollagen mRNAs were turned over at an accelerated rate in glucocorticoid-treated cells. These data suggest that dexamethasone regulates type I collagen gene expression by preferentially decreasing the stability of pro-alpha 1(I) and pro-alpha2(I) mRNAs. Although dexamethasone increased the levels of translatable mRNAs coding for a 50-kDa polypeptide, the molecular mechanism(s) of how hormone exerts this effect remains unknown.

Transcriptional regulation of type I collagen genes in cultured fibroblasts by a factor isolated from thioacetamide-induced fibrotic rat liver.

Recently Hatahara and Seyer (Hatahara, T., and Seyer, J.M. Biochim. Biophys. Acta (1982) 716, 377-382) isolated a factor from fibrotic rat liver which stimulates collagen synthesis in cultured fibroblasts without affecting their rate of proliferation. To investigate the mechanism of fibrogenic factor-mediated enhancement of type I collagen synthesis, we quantitated the levels of mRNAs coding for pro-alpha 1(I) and pro-alpha 2(I) chains in rat dermal fibroblasts. Cell-free translation experiments revealed that the fibrogenic factor caused greater than 5-fold increase in the translatable levels of type I mRNAs. We also quantitated collagen mRNAs by techniques of Northern blotting of glyoxylated poly(A+) RNA followed by hybridization to nick-translated human cDNA clones containing the coding sequence of pro-alpha 1(I) and pro-alpha 2(I) chains. Furthermore, we investigated the relative rates of collagen mRNA transcription in the isolated nuclei of treated and control fibroblasts. Similar quantitation of beta-actin mRNA transcription, which remains unaffected by the treatment with fibrogenic factor, was used as an internal control. We demonstrate that the fibrogenic factor causes a 4-6-fold increase in the rate of transcription of pro-alpha 1(I) and pro-alpha 2(I) genes. Finally, we also show that the rate of intracellular degradation of collagen is not significantly altered in cells treated with fibrogenic factor. These results combined with data on cell-free translation strongly suggest that the increased accumulation of type I collagen mRNA in fibrogenic factor-treated fibroblasts is a consequence of enhanced rates of collagen mRNA transcription.