Elena Fattori

Interleukin-6 deficient mice are protected from bone loss caused by estrogen depletion.

Interleukin‐6 (IL‐6) is a multifunctional cytokine whose circulating levels are under physiological conditions below detection, but whose production is rapidly and strongly induced by several pathological and inflammatory stimuli. IL‐6 has been implicated in a number of cell functions connected to immunity and hematopoiesis. Recently, it has been proposed to act as a stimulator of osteoclast formation and activity, in particular following estrogen depletion. The purpose of this study was to gain additional insights into the role of IL‐6 during development, as well as in physiological and pathological conditions. We report here that IL‐6 deficient mice generated by gene targeting are viable and do not present any evident phenotypic abnormality. However, analysis of bone metabolism revealed a specific bone phenotype. IL‐6 deficient female mice have a normal amount of trabecular bone, but higher rates of bone turnover than control littermates. Estrogen deficiency induced by ovariectomy causes in wild type animals a significant loss of bone mass together with an increase in bone turnover rates. Strikingly, ovariectomy does not induce any change in either bone mass or bone remodeling rates in the IL‐6 deficient mice. These findings indicate that IL‐6 plays an important role in the local regulation of bone turnover and, at least in mice, appears to be essential for the bone loss caused by estrogen deficiency.

Interleukin 6 causes growth impairment in transgenic mice through a decrease in insulin-like growth factor-I. A model for stunted growth in children with chronic inflammation.

Stunted growth is a major complication of chronic inflammation and recurrent infections in children. Systemic juvenile rheumatoid arthritis is a chronic inflammatory disorder characterized by markedly elevated circulating levels of IL-6 and stunted growth. In this study we found that NSE/hIL-6 transgenic mouse lines expressing high levels of circulating IL-6 since early after birth presented a reduced growth rate that led to mice 50-70% the size of nontransgenic littermates. Administration of a monoclonal antibody to the murine IL-6 receptor partially reverted the growth defect. In NSE/hIL-6 transgenic mice, circulating IGF-I levels were significantly lower than those of nontransgenic littermates; on the contrary, the distribution of growth hormone pituitary cells, as well as circulating growth hormone levels, were normal. Treatment of nontransgenic mice of the same strain with IL-6 resulted in a significant decrease in IGF-I levels. Moreover, in patients with systemic juvenile rheumatoid arthritis, circulating IL-6 levels were negatively correlated with IGF-I levels. Our findings suggest that IL-6-mediated decrease in IGF-I production represents a major mechanism by which chronic inflammation affects growth.

Lymphoproliferative disorder and imbalanced T-helper response in C/EBP beta-deficient mice.

C/EBP beta is considered a key element of interleukin‐6 (IL‐6) signalling as well as an important transcriptional regulator of the IL‐6 gene itself. We describe here how mice lacking C/EBP beta develop a pathology similar to mice overexpressing IL‐6 and nearly identical to multicentric Castlemans disease in human patients, with marked splenomegaly, peripheral lymphadenopathy and enhanced haemopoiesis. Humoral, innate and cellular immunity are also profoundly distorted, as shown by the defective activation of splenic macrophages, the strong impairement of IL‐12 production, the increased susceptibility to Candida albicans infection and the altered T‐helper function. Our data show that C/EBP beta is crucial for the correct functional regulation and homeostatic control of haemopoietic and lymphoid compartments.

A T-cell HCV vaccine eliciting effective immunity against heterologous virus challenge in chimpanzees.

Three percent of the worlds population is chronically infected with the hepatitis C virus (HCV) and at risk of developing liver cancer. Effective cellular immune responses are deemed essential for spontaneous resolution of acute hepatitis C and long-term protection. Here we describe a new T-cell HCV genetic vaccine capable of protecting chimpanzees from acute hepatitis induced by challenge with heterologous virus. Suppression of acute viremia in vaccinated chimpanzees occurred as a result of massive expansion of peripheral and intrahepatic HCV-specific CD8+ T lymphocytes that cross-reacted with vaccine and virus epitopes. These findings show that it is possible to elicit effective immunity against heterologous HCV strains by stimulating only the cellular arm of the immune system, and suggest a path for new immunotherapy against highly variable human pathogens like HCV, HIV or malaria, which can evade humoral responses.

IL-6 Expression in Neurons of Transgenic Mice Causes Reactive Astrocytosis and Increase in Ramified Microglial Cells but no Neuronal Damage

Growing evidence suggests that aberrant production of inflammatory cytokines within the central nervous system (CNS) contributes to the development of pathological conditions. To test the cause—effect relationship between the overproduction of interleukin‐6 (IL‐6) in the CNS and the onset of neuropathological changes, we have generated transgenic mice in which human IL‐6 expression has been targeted to the neurons by using the rat neuron‐specific enolase promoter. These mice develop reactive astrocytosis and an increase in ramified microglial cells but do not show histological or behavioural signs of neuron damage at the light microscope level. We thus conclude that a constant release of human IL‐6 by neuronal subpopulations in mice is sufficient to activate cells potentially capable of modulating the local immune response, but at the same time is compatible with normal neuron functions.

Enhancing B- and T-Cell Immune Response to a Hepatitis C Virus E2 DNA Vaccine by Intramuscular Electrical Gene Transfer

ABSTRACT We describe an improved genetic immunization strategy for eliciting a full spectrum of anti-hepatitis C virus (HCV) envelope 2 (E2) glycoprotein responses in mammals through electrical gene transfer (EGT) of plasmid DNA into muscle fibers. Intramuscular injection of a plasmid encoding a cross-reactive hypervariable region 1 (HVR1) peptide mimic fused at the N terminus of the E2 ectodomain, followed by electrical stimulation treatment in the form of high-frequency, low-voltage electric pulses, induced more than 10-fold-higher expression levels in the transfected mouse tissue. As a result of this substantial increment of in vivo antigen production, the humoral response induced in mice, rats, and rabbits ranged from 10- to 30-fold higher than that induced by conventional naked DNA immunization. Consequently, immune sera from EGT-treated mice displayed a broader cross-reactivity against HVR1 variants from natural isolates than sera from injected animals that were not subjected to electrical stimulation. Cellular response against E2 epitopes specific for helper and cytotoxic T cells was significantly improved by EGT. The EGT-mediated enhancement of humoral and cellular immunity is antigen independent, since comparable increases in antibody response against ciliary neurotrophic factor or in specific anti-human immunodeficiency virus type 1 gag CD8+ T cells were obtained in rats and mice. Thus, the method described potentially provides a safe, low-cost treatment that may be scaled up to humans and may hold the key for future development of prophylactic or therapeutic vaccines against HCV and other infectious diseases.

Gene Electrotransfer Results in a High-Level Transduction of Rat Skeletal Muscle and Corrects Anemia of Renal Failure

We have investigated the efficacy of a gene transfer strategy based on plasmid DNA electroinjection for the correction of anemia associated with renal failure. An expression plasmid encoding the rat erythropoietin (EPO) cDNA under the control of the CMV promoter as constructed and utilized for this work. Electroinjection of pCMV/rEPO in different rat muscles yielded sustained and long-term EPO production and secretion. The muscle-produced EPO corrected the anemia in five of six nephrectomized rats, used as a model of renal failure. The efficiency of muscle transduction was comparable in rats and mice injected with equivalent amounts of DNA per kilogram of body weight. These results demonstrate that gene electrotransfer can be applied to produce therapeutically significant levels of erythropoietin in chronic renal failure.

Modulation of the immune response induced by gene electrotransfer of a hepatitis C virus DNA vaccine in nonhuman primates.

Induction of multispecific, functional CD4+ and CD8+ T cells is the immunological hallmark of acute self-limiting hepatitis C virus (HCV) infection in humans. In the present study, we showed that gene electrotransfer (GET) of a novel candidate DNA vaccine encoding an optimized version of the nonstructural region of HCV (from NS3 to NS5B) induced substantially more potent, broad, and long-lasting CD4+ and CD8+ cellular immunity than naked DNA injection in mice and in rhesus macaques as measured by a combination of assays, including IFN-γ ELISPOT, intracellular cytokine staining, and cytotoxic T cell assays. A protocol based on three injections of DNA with GET induced a substantially higher CD4+ T cell response than an adenovirus 6-based viral vector encoding the same Ag. To better evaluate the immunological potency and probability of success of this vaccine, we have immunized two chimpanzees and have compared vaccine-induced cell-mediated immunity to that measured in acute self-limiting infection in humans. GET of the candidate HCV vaccine led to vigorous, multispecific IFN-γ+CD8+ and CD4+ T lymphocyte responses in chimpanzees, which were comparable to those measured in five individuals that cleared spontaneously HCV infection. These data support the hypothesis that T cell responses elicited by the present strategy could be beneficial in prophylactic vaccine approaches against HCV.

Gene electro-transfer of an improved erythropoietin plasmid in mice and non-human primates.

Anemia due to impaired erythropoietin (EPO) production is associated with kidney failure. Recombinant proteins are commonly administered to alleviate the symptoms of this dysfunction, whereas gene therapy approaches envisaging the delivery of EPO genes have been tried in animal models in order to achieve stable and long‐lasting EPO protein production. Naked DNA intramuscular injection is a safe approach for gene delivery; however, transduction levels show high inter‐individual variability in rodents and very poor efficiency in non‐human primates. Transduction can be improved in several animal models by application of electric pulses after DNA injection.

Gene electro-transfer improves transduction by modifying the fate of intramuscular DNA

Intramuscular gene delivery through injection of plasmid DNA has long been considered a promising approach for safe and simple in vivo gene expression for vaccination and gene therapy purposes. Recently, intramuscular gene delivery has been improved by applying low‐voltage electric pulses after plasmid injection, a procedure that has been variably called gene electro‐transfer, in vivo electroporation or electrical stimulation. Different types of electrical treatments have been used with excellent results both in terms of transgene expression levels and immunization outcome. This approach, therefore, holds promise for safe gene delivery to animals and humans designed for non‐viral gene therapy and DNA‐based vaccination. The molecular mechanisms underlying this increment in transduction efficiency are, however, still unclear.