Despite conventional medical and surgical treatments, malignant pleural mesothelioma (MPM) remains incurable. Oncovirotherapy (i.e., the use of replication-competent virus for cancer treatment) is currently explored in clinical trials. In this study, we investigated the antineoplastic potential of a new oncolytic viral agent, a live-attenuated measles virus (MV) strain derived from the Edmonston vaccine lineage (Schwarz strain). We evaluated both oncolytic activity and immunoadjuvant properties of the MV vaccine strain on mesothelioma tumor cells. Infectivity, syncytium formation, and cytolytic activity of MV were studied on a panel of mesothelioma cells derived from pleural effusions of MPM patients. We observed that MV infected preferentially MPM cell lines in comparison with nontransformed mesothelial cells, leading to an efficient killing of a significant fraction of tumor cells. A cytoreductive activity was also evidenced through formation of multinuclear cellular aggregates (syncytia). The susceptibility of MPM cell lines to measles infection was assessed by the analysis of cell surface expression of the MV vaccine receptor (CD46). We also evaluated whether MV infection of mesothelioma cells could elicit an autologous antitumor immune response. We showed that MV Schwarz strain induced apoptotic cell death of infected mesothelioma cells, which were efficiently phagocytosed by dendritic cells (DC). Loading of DCs with MV-infected MPM cells induced DC spontaneous maturation, as evidenced by the increased expression of MHC and costimulatory molecules along with the production of proinflammatory cytokines. Priming of autologous T cells by DCs loaded with MV-infected MPM cells led to a significant proliferation of tumor-specific CD8 T cells. Altogether, these data strongly support the potential of oncolytic MV as an efficient therapeutic agent for mesothelioma cancer. [Cancer Res 2008;68(12):4882-92]

Human APOBEC3 enzymes deaminate single stranded DNA. At least five can deaminate mitochondrial DNA in the cytoplasm, while three can deaminate viral DNA in the nucleus. However, only one, APOBEC3A, can hypermutate genomic DNA. We analysed the distribution and function of the two APOBEC3A isoforms p1 and p2 in transfected cell lines. Both can translocate to the nucleus and hypermutate CMYC DNA and induce DNA double strand breaks as visualized by the detection of ©H2AX or Chk2. APOBEC3A induced G1 phase cell cycle arrest and triggered several members of the intrinsic apoptosis pathway. Activation of purified human CD4+ T lymphocytes with PHA, IL2 and interferon α resulted in C->T hypermutation of genomic DNA and double stranded breaks suggesting a role for APOBEC3A in pro-inflammatory conditions. As chronic inflammation underlies many diseases including numerous cancers, it is possible that APOBEC3A induction may generate many of the lesions typical of a cancer genome.

The use of DNA constructs encoding leptospiral proteins is a promising new approach for vaccination against leptospirosis. In previous work we determined that immunization with hemolysis-associated protein 1 (Hap1) (LipL32) expressed by adenovirus induced significant protection against a virulent Leptospira challenge in gerbils. To avoid the use of the adenovirus vector, we checked for clinical protection against lethal challenge by DNA vaccination. A DNA vaccine expressing Hap1 was designed to enhance the direct gene transfer of this protein into gerbils. A challenge was performed 3 weeks after the last immunization with a virulent strain of serovar canicola. Our results show that the cross-protective effect with pathogenic strains of Leptospira, shared by Hap1, could be mediated by the DNA plasmid vector. This finding should facilitate the design and development of a new generation of vaccines against bacteria, particularly Leptospira interrogans sensu lato.

(1) Asbestos exposure is the main factor involved in MPM pathogenesis. Management of MPM patients remains difficult (2) because diagnosis is usually established late in disease evolution, making patient prognosis poor (survival rate ranging from 4 to 12 months). Moreover, differential diagnosis between MPM and pleural benign diseases (often induced by asbestos exposure), lung adenocarcinoma, or pleural metastasis of diverse origins remains uncertain. Significant advances in MPM treatment suggest the development of early and reliable diagnostic tests, and thus require a better knowledge of MPMspecific markers.Mesothelin has been suggested to significantly improve the panel of MPM-associated markers.(3) Mesothelin is a cellsurface GPI-anchored glycoprotein that has putative functions in cell-to-cell adhesion.(4) This differentiation antigen is present at low levels in a restricted set of normal adult tissues, including the mesothelium, but is overexpressed aberrantly by several cancers, such as mesothelioma, and pancreatic and ovarian carcinomas. (4,5) The primary product of the human mesothelin gene is a 71-kDa precursor protein, which is cleaved physiologically by a furine-like protease to produce a 31-kDa N-terminal fragment (N-ERK/mesothelin or MPF) secreted into the blood (6) and a 40-kDa C-terminal fragment (mesothelin) expressed at the cell surface. (5) Additionally, Scholler et al. detected SMRP in culture supernatants of several carcinomas.(7) It has since been reported that the levels of SMRP are more elevated in sera from mesothelioma patients than in patients with other cancers, inflammatory diseases, or in healthy controls.(8-10) Moreover, a raised SMRP concentration in pleural effusions was also demonstrated to be relevant to discriminate MPM from benign pleural lesions and other malignant diseases. (11,12) Today, the clinical relevance of clarifying SMRP origin relies potentially on the identification of molecules that could be quantified in association with SMRP in order to establish an earlier and more reliable MPM diagnosis. Another benefit relies on the development of less-invasive diagnostic tests rather than actual standard diagnostic procedures based on immunohistochemical staining of tumor biopsies. Although several hypotheses have already been proposed, the mechanisms involved in soluble mesothelin production by tumor cells remain largely unknown. (4) To understand these mechanisms, we explored two alternative possibilities: release of an aberrant RNA splicing product (mesothelin variant 3) or enzyme-mediated shedding of membranebound mesothelin (phospholipases, proteases). These in vitro experiments were conducted on epithelioid mesothelioma cell lines established in our laboratory from pleural effusions of MPM patients. Materials and MethodsPatients. The MPM patients had received no anticancer therapy before the study. Pleural effusions were collected by thoracocentesis. Diagnosis was established by immunohistochemical and immunocytochemical labelings. All patients gave signed, informed c...