Citations

Abstract Background: Viral vectors based on the Edmonston strain of measles virus (MV-Edm) selectively destroy all tumor cell lines tested in vitro. The oncolytic activity of the virus is enhanced by expression of the thyroidal sodium iodide symporter (MV-NIS) that allows selective 131I uptake by infected tumor cells and eliminates myeloma tumor xenografts that are resistant to the parent virus. MV-NIS is being considered for therapy of patients with relapsed or refractory multiple myeloma. Advanced myeloma is associated with significant immunosuppression with the potential risk of uncontrolled virus proliferation. The number of agents with activity against MV is limited. Low energy (Auger) electrons have a short path length and selectively damage cells in which the isotope decays. Thus, we hypothesized that the Auger electron emitting isotope 125I, selectively taken up by cells expressing NIS, can be used to control viral proliferation. Methods: A replication competent MV that expressed both a soluble form of carcinoembryonic antigen (CEA) and NIS (MV-NICE) was rescued and characterized. Cells were infected with MV-NICE or control vectors and exposed to 125I with appropriate controls. CEA expression and viral titers were determined at different time points. The role of free radical generation on virus replication was explored. In vivo control of MV-NICE replication with 125I was attempted. Results: MV-NICE replication in vitro is inhibited by the selective uptake of 125I by cells expressing NIS. Extracellular decay of the isotope has no effect on virus proliferation. Auger electron damage is in part mediated by free radicals and abrogated by glutathione. In myeloma xenografts, control of MV-NICE with 125I was not possible under the conditions of the experiment. Conclusion: MV-NICE does not replicate faster in the presence of radiation under our experimental conditions. Auger electron emitting isotopes effectively stop propagation of MV vectors expressing NIS in vitro. Additional work is necessary to translate these observations in vivo.

Abstract Among the best-characterized genetic alterations in gliomas is the amplification of the epidermal growth factor receptor (EGFR) gene, present in ∼40% of glioblastoma multiforme, and frequently associated with the EGFRvIII gene rearrangement. We have previously shown that attenuated vaccine strains of measles virus have potent antitumor activity against gliomas, and identified H protein mutations, which ablate recognition of the natural measles virus receptors CD46 and SLAM. Retargeted recombinant viruses were generated from the measles Edmonston-NSe vaccine strain displaying a single-chain antibody against EGFRvIII at the COOH terminus of H and containing the marker green fluorescent protein (GFP) gene in position 1. Two different H mutants were employed: HSNS (V451S, Y481N, and A527S)-CD46 blind, and HAA (Y481A and R533A)-CD46 and SLAM blind. MV-GFP virus was used as a positive control. Both EGFRvIII-retargeted viruses had significant antitumor activity against EGFRvIII-expressing glioblastoma multiforme but no cytopathic effect against normal cells. In an orthotopic model of EGFRvIII-expressing GBM39 xenografts, there was comparable therapeutic efficacy between retargeted strains and unmodified MV-GFP and statistically significant prolongation of survival in treated animals compared with the control group (P = 0.001). Formation of syncytia was observed in tumors treated with retargeted viruses, with a surrounding infiltrate consisting of macrophages and natural killer cells. In summary, EGFRvIII-retargeted oncolytic measles virus strains have comparable therapeutic efficacy with the unmodified MV-GFP strain against EGFRvIII-expressing glioma lines and xenografts with improved therapeutic index, a finding with potential translational implications in glioma virotherapy. (Cancer Res 2006; 66(24): 11840-50)

A transgenic mouse containing the complete human SLAM (hSLAM/CD150) gene, including its endogenous promoter for transcription, was generated by using human genomic DNA cloned into a bacterial artificial chromosome. hSLAM, the primary receptor for measles viruses (MV), was expressed on activated B, T, and dendritic cells with an expression profile equivalent to that of humans. We demonstrated that hSLAM + cells obtained from the transgenic mouse, including activated B, T, and dendritic cells, were susceptible to MV infection in a receptor-dependent manner. Evidence was provided for transient infection in the nasal lymph nodes of hSLAM + mice after intranasal inoculation. Virus was rapidly cleared without signs of secondary replication. To improve the efficiency of MV production, the hSLAM + mice were bred with mice having a Stat1 -deficient background. These mice were more susceptible to MV infection and produced more virus particles. After intranasal and intraperitoneal inoculation of these mice with MV, infections of the thymus, spleen, nasal, mesenteric, and leg lymph nodes were detected. Upon necropsy, enlarged lymph nodes and spleen were apparent. Flow cytometric analysis showed that abnormally large numbers of mature neutrophils and natural killer cells caused the splenomegaly. The hSLAM transgenic mouse constitutes an improved rodent model for studying the interaction of MV with immune cells that more accurately reflects the infection pattern found in humans.

ABSTRACTSignaling lymphocytic activation molecule (SLAM, CD150) is the universal morbillivirus receptor. Based on the identification of measles virus (MV) hemagglutinin (H) amino acids supporting human SLAM-dependent cell entry, we mutated canine distemper virus (CDV) H and identified residues necessary for efficient canine SLAM-dependent membrane fusion. These residues are located in two nearby clusters in a new CDV H structural model. To completely abolish SLAM-dependent fusion, combinations of mutations were necessary. We rescued a SLAM-blind recombinant CDV with six mutations that did not infect ferret peripheral blood mononuclear cells while retaining full infectivity in epithelial cells.

ABSTRACT The efficiency of viruses in cancer therapy is enhanced by proteins that mediate the fusion of infected cells with their neighbors. It was reported that replication-competent adenovirus particles can spread between nuclei within fusion-generated syncytia. To assess this conjecture, we generated fusogenic adenoviruses that express a balanced ratio of the F and H glycoproteins of measles virus. The viruses displayed enhanced cytotoxicity but largely unchanged replication efficiencies compared to a nonfusogenic virus. Most notably, the virus genomes did not spread through fusion-generated multinuclear cells. Hence, adenovirus replication in syncytia remains largely restricted to initially transduced nuclei.

ABSTRACTMeasles virus (MV) enters cells either through the signaling lymphocyte activation molecule SLAM (CD150) expressed only in immune cells or through the ubiquitously expressed regulator of complement activation, CD46. To identify residues on the attachment protein hemagglutinin (H) essential for fusion support through either receptor, we devised a strategy based on analysis of morbillivirus H-protein sequences, iterative cycles of mutant protein production followed by receptor-based functional assays, and a novel MV H three-dimensional model. This model uses the Newcastle disease virus hemagglutinin-neuraminidase protein structure as a template. We identified seven amino acids important for SLAM- and nine for CD46 (Vero cell receptor)-induced fusion. The MV H three-dimensional model suggests (i) that SLAM- and CD46-relevant residues are located in contiguous areas in propeller β-sheets 5 and 4, respectively; (ii) that two clusters of SLAM-relevant residues exist and that they are accessible for receptor contact; and (iii) that several CD46-relevant amino acids may be shielded from direct receptor contacts. It appears likely that certain residues support receptor-specific H-protein conformational changes. To verify the importance of the H residues identified with the cell-cell fusion assays for virus entry into cells, we transferred the relevant mutations into genomic MV cDNAs. Indeed, we were able to recover recombinant viruses, and we showed that these replicate selectively in cells expressing SLAM or CD46. Selectively receptor-blind viruses will be used to study MV pathogenesis and may have applications for the production of novel vaccines and therapeutics.

ABSTRACTMeasles virus (MV) is typically spread by aerosol droplets and enters via the respiratory tract. The progression of MV infection has been widely studied; yet, the pathway for virus entry in polarized human airway epithelia has not been investigated. Herein we report the use of a replication-competent Edmonston vaccine strain of MV expressing enhanced green fluorescent protein (MV-eGFP) to infect primary cultures of well-differentiated human airway epithelia. Previous studies with polarized Caco-2 cells (intestine-derived human epithelia) and MDCK cells (kidney-derived canine epithelia) demonstrated that MV primarily infected and exited the apical surface. In striking contrast, our results indicate that MV preferentially transduces human airway cells from the basolateral surface; however, virus release remains in an apical direction. When MV-eGFP was applied apically or basolaterally to primary cultures of airway epithelia, discrete foci of eGFP expression appeared and grew; however, the cell layer integrity was maintained for the duration of the study (7 days). Interestingly, utilizing immunohistochemistry and confocal microscopy, we observed widespread expression of the receptor for the vaccine strain of MV (CD46) at greatest abundance on the apical surface of the differentiated human airway epithelia as well as in human tracheal tissue sections. These data suggest that the progression of MV infection through the respiratory epithelium may involve pathways other than direct binding and entry through the apical surface of airway epithelia.