RESUMO
The adipokine, leptin, regulates blood glucose and the insulin secretory function of beta cells, while also modulating immune cell function. We hypothesized that the dual effects of leptin may prevent or suppress the autoreactive destruction of beta cells in a virally induced rodent model of type 1 diabetes. Nearly 100% of weanling BBDR rats treated with the combination of an innate immune system activator, polyinosinic:polycytidylic acid (pIC), and Kilham rat virus (KRV) become diabetic within a predictable time frame. We utilized this model to test the efficacy of leptin in preventing diabetes onset, remitting new onset disease, and preventing autoimmune recurrence in diabetic rats transplanted with syngeneic islet grafts. High doses of leptin delivered via an adenovirus vector (AdLeptin) or alzet pump prevented diabetes in>90% of rats treated with pIC+KRV. The serum hyperleptinemia generated by this treatment was associated with decreased body weight, decreased non-fasting serum insulin levels, and lack of islet insulitis in leptin-treated rats. In new onset diabetics, hyperleptinemia prevented rapid weight loss and diabetic ketoacidosis, and temporarily restored euglycemia. Leptin treatment also prolonged the survival of syngeneic islets transplanted into diabetic BBDR rats. In diverse therapeutic settings, we found leptin treatment to have significant beneficial effects in modulating virally induced diabetes. These findings merit further evaluation of leptin as a potential adjunct therapeutic agent for treatment of human type 1 diabetes.
Assuntos
Diabetes Mellitus Experimental/tratamento farmacológico , Diabetes Mellitus Tipo 1/tratamento farmacológico , Leptina/uso terapêutico , Infecções por Parvoviridae/imunologia , Parvovirus/imunologia , Animais , Glicemia , Diabetes Mellitus Experimental/imunologia , Diabetes Mellitus Experimental/patologia , Diabetes Mellitus Experimental/virologia , Diabetes Mellitus Tipo 1/patologia , Diabetes Mellitus Tipo 1/virologia , Cetoacidose Diabética/prevenção & controle , Humanos , Transplante das Ilhotas Pancreáticas , Leptina/administração & dosagem , Leptina/imunologia , Infecções por Parvoviridae/virologia , Poli I-C/administração & dosagem , Poli I-C/imunologia , Ratos , Ratos Endogâmicos BB , Resultado do TratamentoRESUMO
A variety of DNA vaccine prime and recombinant viral boost immunization strategies have been developed to enhance immune responses in humans, but inherent limitations to these strategies exist. There is still an overwhelming need to develop safe and effective approaches that raise broad humoral and T cell-mediated immune responses systemically and on mucosal surfaces. We have developed a novel mucosal immunization regimen that precludes the use of viral vectors yet induces potent T cell responses. Using hepatitis B surface Ag (HBsAg), we observed that vaccination of BALB/c mice with an i.m. HBsAg-DNA vaccine prime followed by an intranasal boost with HBsAg protein encapsulated in biologically inert liposomes enhanced humoral and T cell immune responses, particularly on mucosal surfaces. Intranasal live virus challenge with a recombinant vaccinia virus expressing HBsAg revealed a correlation between T cell immune responses and protection of immunized mice. A shortened immunization protocol was developed that was successful in both adult and neonatal mice. These results support the conclusion that this new approach is capable of generating a Th-type-1-biased, broad spectrum immune response, specifically at mucosal surfaces. The success of this design may provide a safe and effective vaccination alternative for human use.
Assuntos
Antígenos de Superfície da Hepatite B/imunologia , Vacinas contra Hepatite B/imunologia , Imunidade nas Mucosas/fisiologia , Imunização Secundária , Células Th1/imunologia , Vacinas de DNA/imunologia , Administração Intranasal , Animais , Animais Recém-Nascidos , Formação de Anticorpos/efeitos dos fármacos , Formação de Anticorpos/fisiologia , Feminino , Antígenos de Superfície da Hepatite B/farmacologia , Vacinas contra Hepatite B/farmacologia , Humanos , Imunidade nas Mucosas/efeitos dos fármacos , Lipossomos , Camundongos , Camundongos Endogâmicos BALB C , Vacinas de DNA/farmacologia , Vaccinia virus/imunologiaRESUMO
Peripheral T cells can be polarized towards type 1 or type 2 cytokine immune responses during TCR engagement. Because T cell selection by peptide plus self-MHC in the thymus requires TCR engagement, we hypothesized that type 1 cytokines may polarize developing T cells. We cultured thymi from BBDR rats in adult thymus organ cultures (ATOC) under type 1 cytokine conditions in the absence of exogenous antigen. Type 1 cytokine-conditioned ATOC generated cells that spontaneously secreted high levels of IFNgamma, but not IL-4. A second exposure to type 1 cytokines further increased IFNgamma secretion by these cells, most of which were blasts that expressed the activation markers CD25, CD71, CD86, and CD134. Studies using blocking antibodies and pharmacological inhibitors suggested that both IL-18 and cognate TCR-MHC/ligand interactions were important for activation. Blocking anti-MHC class I plus anti-MHC class II antibodies, neutralizing anti-IL-18 antibody, and the p38 MAP-kinase inhibitor SB203580 each reduced IFNgamma production by approximately 75-80%. Cyclosporin A, which prevents TCR signaling, inhibited IFNgamma production by approximately 50%. These data demonstrate that exposure to type 1 cytokines during intrathymic development can polarize differentiating T cells, and suggest a mechanism by which intrathymic exposure to type 1 cytokines may modulate T cell development.
Assuntos
Diferenciação Celular/fisiologia , Citocinas/metabolismo , Linfócitos T/metabolismo , Timo/fisiologia , Animais , Anticorpos/metabolismo , Interferon gama/metabolismo , Interleucina-18/imunologia , Interleucina-18/metabolismo , Complexo Principal de Histocompatibilidade/imunologia , Técnicas de Cultura de Órgãos , RatosRESUMO
Use of the BioBreeding (BB) rat to model human insulin-dependent diabetes mellitus (IDDM) is useful in that characteristics of diabetes in the BB rat closely parallel those observed in human IDDM. Diabetic animals can be biopsied, autopsied, and bred to study the genetic basis of IDDM. The genetic, immunological, and environmental components of the disease can all be investigated under controlled conditions. Two inbred lines of BB have been used in the majority of published studies using this model system; these rats are designated as diabetes prone (DP-BB/Wor) and diabetes resistant (DR-BB/Wor). This unit presents two protocols for the diagnosis and prevention of spontaneous IDDM in DP-BB/Wor rats. Two alternate protocols are given for the induction of autoimmune disease in DR-BB/Wor rats and for the adoptive transfer of autoimmunity into histocompatible athymic WAG nu/nu recipient rats. Support protocols are also given for diagnosis of insulitis, treatment of diabetic rats with insulin, and serological analysis of blood samples from sentinel rats to monitor the pathogen status of the colony.