RESUMO
Helicobacter pylori infection causes chronic active gastritis that after many years of infection can develop into peptic ulceration or gastric adenocarcinoma. The bacterium is highly adapted to surviving in the gastric environment and a key adaptation is the virulence factor urease. Although widely postulated, the requirement of urease expression for persistent infection has not been elucidated experimentally as conventional urease knockout mutants are incapable of colonization. To overcome this constraint, conditional H. pylori urease mutants were constructed by adapting the tetracycline inducible expression system that enabled changing the urease phenotype of the bacteria during established infection. Through tight regulation we demonstrate that urease expression is not only required for establishing initial colonization but also for maintaining chronic infection. Furthermore, successful isolation of tet-escape mutants from a late infection time point revealed the strong selective pressure on this gastric pathogen to continuously express urease in order to maintain chronic infection. In addition to mutations in the conditional gene expression system, escape mutants were found to harbor changes in other genes including the alternative RNA polymerase sigma factor, fliA, highlighting the genetic plasticity of H. pylori to adapt to a changing niche. The tet-system described here opens up opportunities to studying genes involved in the chronic stage of H. pylori infection to gain insight into bacterial mechanisms promoting immune escape and life-long infection. Furthermore, this genetic tool also allows for a new avenue of inquiry into understanding the importance of various virulence determinants in a changing biological environment when the bacterium is put under duress.
Assuntos
Gastrite/genética , Inativação Gênica/fisiologia , Infecções por Helicobacter/imunologia , Helicobacter pylori/genética , Urease/metabolismo , Animais , Proteínas de Bactérias/metabolismo , Doença Crônica , Mucosa Gástrica/microbiologia , Gastrite/microbiologia , Expressão Gênica/genética , Camundongos , Neoplasias Gástricas/genéticaRESUMO
PURPOSE: To determine the efficacy of rAAV.sFlt-1-mediated gene therapy in a transgenic mouse model of retinal neovascularization (trVEGF029) and to assess whether rAAV.sFlt-1 administration generated any deleterious, long-lasting immune response that could affect efficacy. METHODS: trVEGF029 mice were injected subretinally with rAAV.sFlt-1 or phosphate-buffered saline. Fluorescein angiography and electroretinography were used to compare the extent of fluorescein leakage from retinal vessels and retinal function, respectively. A group of eyes was enucleated, and the retinal vasculature and morphology were studied by confocal and light microscopy. Cells were isolated from the posterior eyecups and spleens of a further group, and immune cell subset populations were investigated by flow cytometry. sFlt-1 protein levels in the eyes were evaluated by ELISA. RESULTS: After a single rAAV.sFlt-1 injection, sFlt-1 protein levels were upregulated, and there was a reduction in fluorescein leakage from the retinal vessels and an improvement in retinal function. Confocal microscopy of isolectin-IB4-labeled retinal wholemounts showed more normal-appearing capillary beds in rAAV.sFlt-1-injected than in PBS-injected trVEGF029 mouse eyes. Light microscopy demonstrated retinal morphology preservation, with fewer aberrant vessels invading the outer nuclear layer of rAAV.sFlt-1-injected eyes. Furthermore, the immune response to subretinal injection of rAAV.sFlt-1 was limited to a transient increase in CD45(+) leukocytes that disappeared by 4 weeks after injection. This transient increase was localized to the eye and did not affect long-term therapeutic efficacy. CONCLUSIONS: The data support the notion that rAAV.sFlt-1 gene therapy is safe and effective for the long-term inhibition of deleterious blood vessel growth in the eye.
Assuntos
Dependovirus/genética , Terapia Genética , Imunidade Celular/imunologia , Neovascularização Retiniana/imunologia , Neovascularização Retiniana/terapia , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/genética , Animais , Formação de Anticorpos/imunologia , Linfócitos B/imunologia , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , Dependovirus/imunologia , Modelos Animais de Doenças , Eletrorretinografia , Ensaio de Imunoadsorção Enzimática , Citometria de Fluxo , Angiofluoresceinografia , Técnica Indireta de Fluorescência para Anticorpo , Vetores Genéticos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Microscopia Confocal , Neovascularização Retiniana/patologia , Vasos Retinianos/metabolismo , Vasos Retinianos/patologia , Regulação para Cima , Fator A de Crescimento do Endotélio Vascular/genética , Fator A de Crescimento do Endotélio Vascular/metabolismo , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/imunologiaRESUMO
Coramsine is a novel chemotherapeutic agent isolated from Solanum linnaeanum (devil's apple). Topical treatment provides clinical benefit for skin tumors. To evaluate the potential broader applicability of the drug, its in vivo anticancer efficacy in a murine model of malignant mesothelioma and its mode of action were investigated. Systemic administration of coramsine slowed tumor growth and prolonged survival time. Importantly, the antitumor efficacy of coramsine was enhanced when treatment was combined with stimulation of innate immunity using unmethylated CpG-containing oligodeoxynucleotides (ODNs). Combination treatment further slowed tumor growth and provided a survival benefit. Coramsine seems to kill tumor cells by direct cell lysis. Using 2 different assays to detect apoptosis (caspase activation and DNA fragmentation), we found no evidence that coramsine induces any form of programmed cell death. The fact that the efficacy of coramsine is potentiated by CpG ODNs suggests that coramsine-induced cell death is an immunologic null event.
Assuntos
Adjuvantes Imunológicos/farmacologia , Antineoplásicos/farmacologia , Neoplasias Experimentais/imunologia , Neoplasias Experimentais/terapia , Oligodesoxirribonucleotídeos/farmacologia , Preparações de Plantas/farmacologia , Alcaloides de Solanáceas/farmacologia , Animais , Apoptose/efeitos dos fármacos , Apoptose/imunologia , Linhagem Celular Tumoral , Terapia Combinada , Sinergismo Farmacológico , Imunidade Inata/efeitos dos fármacos , Imunoterapia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Transplante de Neoplasias , Neoplasias Experimentais/patologia , SolanumRESUMO
The cross-arming of effector CTL in response to cross-presented tumor Ags is predicted to fail in the absence of CD40 stimulation. However, questions remain regarding the role of CD40 signaling and additional CD4+ T cell-derived signals in this process. To address this, we have analyzed the cross-arming of tumor-specific CTL effectors in vivo in a mouse model of established tumor and tumor regression following CD40 activation. We found that tumor-specific CTL were constitutively cross-armed in tumor-draining lymph nodes during tumor growth and that systemic CD40 activation did not alter CTL cross-arming in the tumor-draining lymph nodes. Rather, CD40 activation induced peripheral dissemination of tumor-specific CTL effectors that required continual CD40 stimulation to maintain peripheral CTL and tumor regression. These data indicate that CD40 activation enhances the peripheral survival of constitutively cross-armed CTL and that persistent CD4+ T cell signals are required for their long-term activity.