Citations

ABSTRACT In addition to humans, only certain nonhuman primates are naturally susceptible to measles virus (MeV) infection. Disease severity is species dependent, ranging from mild to moderate for macaques to severe and even lethal for certain New World monkey species. To investigate if squirrel monkeys ( Saimiri sciureus ), which are reported to develop a course of disease similar to humans, may be better suited than macaques for the identification of virulence determinants or the evaluation of therapeutics, we infected them with a green fluorescent protein-expressing MeV. Compared to cynomolgus macaques ( Macaca fascicularis ) infected with the same virus, the squirrel monkeys developed more-severe immunosuppression, higher viral load, and a broader range of clinical signs typical for measles. In contrast, infection with an MeV unable to interact with the epithelial receptor nectin-4, while causing immunosuppression, resulted in only a mild and transient rash and a short-lived elevation of the body temperature. Similar titers of the wild-type and nectin-4-blind MeV were detected in peripheral blood mononuclear cells and lymph node homogenates, but only the wild-type virus was found in tracheal lavage fluids and urine. Thus, our study demonstrates the importance of MeV interactions with nectin-4 for clinical disease in the new and better-performing S. sciureus model of measles pathogenesis. IMPORTANCE The characterization of mechanisms underlying measles virus clinical disease has been hampered by the lack of an animal model that reproduces the course of disease seen in human patients. Here, we report that infection of squirrel monkeys ( Saimiri sciureus ) fulfills these requirements. Comparative infection with wild-type and epithelial cell receptor-blind viruses demonstrated the importance of epithelial cell infection for clinical disease, highlighting the spread to epithelia as an attractive target for therapeutic strategies.

ABSTRACT After the contagion measles virus (MV) crosses the respiratory epithelium within myeloid cells that express the primary receptor signaling lymphocytic activation molecule (SLAM), it replicates briskly in SLAM-expressing cells in lymphatic organs. Later, the infection spreads to epithelia expressing nectin-4, an adherens junction protein expressed preferentially in the trachea, but how it gets there is not understood. To characterize the mechanisms of spread, we infected groups of 5 or 6 cynomolgus monkeys ( Macaca fascicularis ) with either a wild-type MV or its “N4-blind” derivative, which is unable to enter nectin-4-expressing cells because of the targeted mutation of two hemagglutinin residues. As expected, both viruses caused similar levels of immunosuppression, as monitored by reductions in white blood cell counts and lymphocyte proliferation activity. However, monkeys infected with the N4-blind MV cleared infection more rapidly. Wild-type virus-infected monkeys secreted virus, while marginal virus titers were detected in tracheal lavage fluid cells of N4-blind MV-infected hosts. Analyses of tracheal rings obtained at necropsy (day 12) documented widespread infection of individual cells or small cell clusters in the subepithelial lamina propria of monkeys infected with either virus. However, only wild-type MV spread to the epithelium, forming numerous infectious centers comprised of many contiguous columnar cells. Infected CD11c + myeloid (macrophage or dendritic) cells were frequently observed in the lamina propria below epithelial infectious centers. Thus, MV may use myeloid cells as vehicles not only immediately after contagion but also to infect epithelia of tissues expressing nectin-4, including the trachea.

ABSTRACT Hepatitis C virus (HCV) infection remains a serious public health problem worldwide. Treatments are limited, and no preventive vaccine is available. Toward developing an HCV vaccine, we engineered two recombinant measles viruses (MVs) expressing structural proteins from the prototypic HCV subtype 1a strain H77. One virus directs the synthesis of the HCV capsid (C) protein and envelope glycoproteins (E1 and E2), which fold properly and form a heterodimer. The other virus expresses the E1 and E2 glycoproteins separately, with each one fused to the cytoplasmic tail of the MV fusion protein. Although these hybrid glycoproteins were transported to the plasma membrane, they were not incorporated into MV particles. Immunization of MV-susceptible, genetically modified mice with either vector induced neutralizing antibodies to MV and HCV. A boost with soluble E2 protein enhanced titers of neutralizing antibody against the homologous HCV envelope. In animals primed with MV expressing properly folded HCV C-E1-E2, boosting also induced cross-neutralizating antibodies against two heterologous HCV strains. These results show that recombinant MVs retain the ability to induce MV-specific humoral immunity while also eliciting HCV neutralizing antibodies, and that anti-HCV immunity can be boosted with a single dose of purified E2 protein. The use of MV vectors could have advantages for pediatric HCV vaccination.

ABSTRACTRecent studies of primate models suggest that wild-type measles virus (MV) infects immune cells located in the airways before spreading systemically, but the identity of these cells is unknown. To identify cells supporting primary MV infection, we took advantage of mice expressing the MV receptor human signaling lymphocyte activation molecule (SLAM, CD150) with human-like tissue specificity. We infected these mice intranasally (IN) with a wild-type MV expressing green fluorescent protein. One, two, or three days after inoculation, nasal-associated lymphoid tissue (NALT), the lungs, several lymph nodes (LNs), the spleen, and the thymus were collected and analyzed by microscopy and flow cytometry, and virus isolation was attempted. One day after inoculation, MV replication was documented only in the airways, in about 2.5% of alveolar macrophages (AM) and 0.5% of dendritic cells (DC). These cells expressed human SLAM, and it was observed that MV infection temporarily enhanced SLAM expression. Later, MV infected other immune cell types, including B and T lymphocytes. Virus was isolated from lymphatic tissue as early as 2 days post-IN inoculation; the mediastinal lymph node was an early site of replication and supported high levels of infection. Three days after intraperitoneal inoculation, 1 to 8% of the mediastinal LN cells were infected. Thus, MV infection of alveolar macrophages and subepithelial dendritic cells in the airways precedes infection of lymphocytes in lymphatic organs of mice expressing human SLAM with human-like tissue specificity.

Abstract Combination chemotherapy regimen incorporating CD20 antibodies are commonly used in the treatment of CD20-positive non–Hodgkin's lymphoma (NHL). Fludarabine phosphate (F-araAMP), cyclophosphamide, and CD20 antibodies (Rituximab) constitute the FCR regimen for treating selected NHL, including aggressive mantle cell lymphoma (MCL). As an alternative to the CD20 antibody, we generated a CD20-targeted measles virus (MV)–based vector. This vector was also armed with the prodrug convertase purine nucleoside phosphorylase (PNP) that locally converts the active metabolite of F-araAMP to a highly diffusible substance capable of efficiently killing bystander cells. We showed in infected cells that early prodrug administration controls vector spread, whereas late administration enhances cell killing. Control of spread by early prodrug administration was also shown in an animal model: F-araAMP protected genetically modified mice susceptible to MV infection from a potentially lethal intracerebral challenge. Enhanced oncolytic potency after extensive infection was shown in a Burkitt's lymphoma xenograft model (Raji cells): After systemic vector inoculation, prodrug administration enhanced the therapeutic effect synergistically. In a MCL xenograft model (Granta 519 cells), intratumoral (i.t.) vector administration alone had high oncolytic efficacy: All mice experienced complete but temporary tumor regression, and survival was two to four times longer than that of untreated mice. Cells from MCL patients were shown to be sensitive to infection. Thus, synergy of F-araAMP with a PNP-armed and CD20-targeted MV was shown in one lymphoma therapy model after systemic vector inoculation. [Cancer Res 2007;67(22):10939–47]

Abstract Cancer cells secrete matrix metalloproteinases (MMP) that degrade the extracellular matrix and are responsible for some hallmarks of malignant cancer. Many viruses, including a few currently used in oncolytic virotherapy clinical trials, depend on intracellular proteases to process their proteins and activate their particles. We show here for measles virus (MV) that particle activation can be made dependent of proteases secreted by cancer cells. The MV depends on the intracellular protease furin to process and activate its envelope fusion (F) protein. To make F protein activation cancer cell specific, we introduced hexameric sequences recognized by an MMP and identified the mutant proteins most effective in fusing MMP-expressing human fibrosarcoma cells (HT1080). We showed that an MMP inhibitor interferes with syncytia formation elicited by mutant F proteins and confirmed MMP-dependent cleavage by Edman degradation sequence analysis. We generated recombinant MVs expressing the modified F proteins in place of furin-activated F. These viruses spread only in cells secreting MMP. In nude mice, an MMP-activated MV retarded HT1080 xenograft growth as efficiently as the furin-activated MV vaccine strain. In MV-susceptible mice, the furin-activated virus caused lethal encephalitis upon intracerebral inoculation, whereas the MMP-activated did not. Thus, MV particle activation can be made dependent of proteases secreted by cancer cells, enhancing safety. This study opens the perspective of combining targeting at the particle activation, receptor recognition, and selective replication levels to improve the therapeutic index of MV and other viruses in ongoing clinical trials of oncolysis. (Cancer Res 2006; 66(15): 7694-700)