Interaction of measles virus vectors with Auger electron emitting radioisotopes

A recombinant measles virus (MV) expressing the sodium iodide symporter (NIS) is being considered for therapy of advanced multiple myeloma. Auger electrons selectively damage cells in which the isotope decays. We hypothesized that the Auger electron emitting isotope 125I can be used to control viral proliferation. MV was engineered to express both carcinoembryonic antigen and NIS (MV-NICE). Cells were infected with MV-NICE and exposed to 125I with appropriate controls. MV-NICE replication in vitro is inhibited by the selective uptake of 125I by cells expressing NIS. Auger electron damage is partly 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. MV-NICE does not replicate faster in the presence of radiation. Auger electron emitting isotopes effectively stop propagation of MV vectors expressing NIS in vitro. Additional work is necessary to translate these observations in vivo.

Measles virus exploits dendritic cells to suppress CD4+ T-cell proliferation via expression of surface viral glycoproteins independently of T-cell trans-infection

Dendritic cells (DC) have been proposed to play a pivotal role in transient immune suppression induced by measles virus (MV) infection. In the present study, we show that DC-induced suppression of T-cell proliferation was not mediated by IL-10 or IFNalpha/beta, which are released following infection of DC, but required cell contacts between MV-infected DC and T cells. Human sera containing neutralizing anti-MV antibodies, as well as anti-MV hemagglutinin (HA) or fusion protein (F) mAbs, were found (i) to reverse suppression and (ii) to restore DC allostimulatory capacity. Interestingly, DC-induced T-cell suppression was associated with both phenotypic and functional DC maturation, as demonstrated by IL-12 production and chemotaxis to MIP-3beta. These data suggest that MV infection turns on the maturation program of DC allowing migration to draining lymph nodes, where potent T-cell immune suppression might be achieved via cell surface expression of HA and F glycoproteins, independently of T cell trans-infection.

Induction of the measles virus receptor SLAM (CD150) on monocytes

Wild-type strains of measles virus (MV) isolated in B95a cells use the signalling lymphocyte activation molecule (SLAM; also known as CD150) as a cellular receptor, whereas the Edmonston strain and its derivative vaccine strains can use both SLAM and the ubiquitously expressed CD46 as receptors. Among the major target cells for MV, lymphocytes and dendritic cells are known to express SLAM after activation, but monocytes have been reported to be SLAM-negative. In this study, SLAM expression on monocytes was examined under different conditions. When freshly isolated from the peripheral blood, monocytes did not express SLAM on the cell surface. However, monocytes became SLAM-positive after incubation with phytohaemagglutinin, bacterial lipopolysaccharide or MV. Anti-SLAM monoclonal antibodies efficiently blocked infection of activated monocytes with a wild-type strain of MV. These results indicate that SLAM is readily induced and acts as a monocyte receptor for MV.

Disruption of Akt kinase activation is important for immunosuppression induced by measles virus

Surface-contact-mediated signaling induced by the measles virus (MV) fusion and hemagglutinin glycoproteins is necessary and sufficient to induce T-cell unresponsiveness in vitro and in vivo. To define the intracellular pathways involved, we analyzed interleukin (IL)-2R signaling in primary human T cells and in Kit-225 cells. Unlike IL-2-dependent activation of JAK/STAT pathways, activation of Akt kinase was impaired after MV contact both in vitro and in vivo. MV interference with Akt activation was important for immunosuppression, as expression of a catalytically active Akt prevented negative signaling by the MV glycoproteins. Thus, we show here that MV exploits a novel strategy to interfere with T-cell activation during immunosuppression.

Measles virus-induced promotion of dendritic cell maturation by soluble mediators does not overcome the immunosuppressive activity of viral glycoproteins on the cell surface

Measles virus (MV) infection promotes maturation of dendritic cells (DC), but also interferes with DC functions, and MV renders the DC inhibitory for T cell proliferation. We now describe that MV infection triggers the release of type I IFN from monocyte-derived DC (Mo-DC) which contributes to DC maturation. There is no evidence that soluble mediators are released interfering with the stimulatory activity of uninfected DC. Since inhibition of allogeneic T cell proliferation was unaffected by a fusion inhibitory peptide (Z-fFG), MV infection of T cells did not contribute to inhibition. Allogeneic T cell proliferation depended on the percentage of DC expressing MV F/H glycoproteins within the DC population and their surface expression levels, was induced upon addition of UV-inactivated MV to a mixed lymphocyte reaction stimulated by lipopolysaccharide-matured DC, and was not induced by DC infected with a recombinant MV encoding the ectodomain of vesicular stomatitis virus G protein (MG/FV) instead of the MV glycoproteins. Similarly, DC infected with MV, but not with MG/FV inhibited mitogen-induced proliferation of T cells. Thus, a dominant inhibitory signal is delivered to T cells by the MV glycoproteins on the surface of DC overcoming positive signals by co-stimulatory molecules promoted by maturation factors released from infected DC.

Failure of measles virus to activate nuclear factor-kappa B in neuronal cells: implications on the immune response to viral infections in the central nervous system

Neurons are postmitotic cells that foster virus persistence. These cells lack the HLA class I molecules required for clearance of infected cells. Previously, we showed that HLA class I is induced by measles virus (MV) on glial cells, which is primarily mediated by IFN-beta. In contrast, MV was unable to induce HLA class I or IFN-beta in neuronal cells. This failure was associated with lack of NF-kappa B binding to the positive regulatory domain II element of the IFN-beta promoter, which is essential for virus-induced IFN-beta gene activity. In this study, we demonstrate that the failure to activate NF-kappa B in neuronal cells is due to the inability of MV to induce phosphorylation and degradation of I kappa B, the inhibitor of NF-kappa B. In contrast, TNF-alpha induced degradation of I kappa B alpha in the neuronal cells, suggesting that failure to induce I kappa B alpha degradation is likely due to a defect in virus-mediated signaling rather than to a defect involving neuronal I kappa B alpha. Like MV, mumps virus and dsRNA failed to induce I kappa B alpha degradation in the neuronal cells, suggesting that this defect may be specific to viruses. Autophosphorylation of the dsRNA-dependent protein kinase, a kinase possibly involved in virus-mediated I kappa B alpha phosphorylation, was intact in both cell types. The failure of virus to induce I kappa B alpha phosphorylation and consequently to activate NF-kappa B in neuronal cells could explain the repression of IFN-beta and class I gene expression in virus-infected cells. These findings provide a potential mechanism for the ability of virus to persist in neurons and to escape immune surveillance.

Receptor (CD46)- and replication-mediated interleukin-6 induction by measles virus in human astrocytoma cells

A major source of inflammatory cytokines in the measles virus (MV)-infected brain are astrocytes, which produce a variety of soluble mediators including interferons-alpha/beta (IFN-alpha/beta), interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6). Using the MV-strain Edmonston (ED) and the recombinant MV-strain MGV in which the MV-envelope proteins H and F have been replaced by the vesicular stomatitis virus (VSV) envelope protein G, we investigated IL-6 induction in human U-251 astrocytoma cells in the presence and absence of a MV-specific receptor (CD46) interaction. The CD46-MV interaction did not inhibit the induction of cytokines. Similar multiplicities of infection of MGV induced generally lower levels of IL-6 than MV-ED. UV-inactivated replication-incompetent MV-ED induced low levels of IL-6. In contrast, MGV did not induce IL-6 after inactivation with UV light, indicating that the MV-ED-receptor interaction or the uptake of viral particles by membrane fusion induced IL-6, whereas interaction with the VSV-G receptor and uptake of viral particles by endocytosis did not induce IL-6. Crosslink of the MV-receptor CD46 with antibodies and treatment of cells with purified viral glycoproteins led to the induction of small but significant amounts of IL-6. Our data suggest that triggering of CD46 and associated protein kinases can lead to the induction of low levels of IL-6, whereas the replication of the negative strand RNA virus constitutes the major stimulus leading to the synthesis of high levels of IL-6 in astrocytes.

T-cell independent IgM and enduring protective IgG antibodies induced by chimeric measles viruses

B-cell activation depends on the intensity of B-cell receptor cross-linking. Studies of haptenated antigens and vesicular stomatitis virus (VSV) have demonstrated a correlation between antigen repetitiveness and the degree to which B-cell activation is independent of T cells. Here, we compare neutralizing antibody responses to inactivated VSV with those to two inactivated human pathogenic viruses: highly cytopathic poliovirus (PV) and poorly cytopathic measles virus (MV). The rigidly structured PV efficiently induced neutralizing IgM antibodies independent of T cells. In contrast, neutralizing antibodies to the pleomorphic MV were dependent on helper T cells. To test whether this resulted from the differences in virus structure or the capacity of MV to induce cell fusion and/or immunosuppression, we analyzed antibody responses to chimeric MV expressing VSV glycoprotein instead of MV fusion protein and hemagglutinin. IgM antibodies were independent of T cells; in addition, we found IgG responses dependent on T-cell help that were enduring and protective against lethal VSV infection. Because chimeric MV viruses look like MV ultrastructurally, we conclude that not only structural differences in the envelope but also the ability of MV to induce immunosuppression may limit its capacity to directly activate B cells. These findings are relevant for our understanding of B-cell activation by two prototypic human pathogenic viruses and for the design of new recombinant vaccines.

UV-inactivated measles virus stimulates human and mice naive lymphocytes to proliferate in vitro

Ultra violet (UV) light-inactivated measles virus was used for the lymphocyte proliferation assay, where it caused consistently adult human peripheral blood monolymphocytes (PBML) proliferation which was not dependent on the measles virus complement fixation titre in the donor's sera. When the cord blood lymphocytes from newborn baby and spleen lymphocytes from unprimed Balb/c, C57bl and CBA mice were used in the proliferation assay, all the lymphocytes were stimulated by the UV-inactivated measles virus in a dose-dependent manner. These results suggest that: (1) lymphotropic measles virus can also activate lymphocytes in vitro, and (2) this activation appeared to be neither species- nor major histocompatibility complex (MHC)-restricted. These results may have important implications for measles vaccination and the understanding of the immunopathogenesis of measles virus infection.

Measles virus induction of human endothelial cell tissue factor procoagulant activity in vitro

Measles virus infection of microvascular endothelium in vivo and ensuing endothelial cell activation may be important in the pathogenesis of subsequent inflammation in target organs. This study investigated the capacity of measles virus to induce procoagulant activity, in vitro, in endothelial cells isolated from human umbilical cord veins. Endothelial cells were infected with a clinical isolate of measles virus propagated in Vero cells. Cells were also incubated with bacterial lipopolysaccharide (10 micrograms/ml), herpes simplex virus type 1, cytomegalovirus or culture medium alone as positive and negative controls, respectively. Endothelial cell procoagulant activity was measured in a one-stage clotting assay. Measles virus stimulated both a time and dose-dependent endothelial cell procoagulant response by the induction of tissue factor synthesis, confirmed by both immunocytochemistry and its dependence on factor VII for activity. This activity was reduced by u.v.-irradiation of the virus. Infected cells were analysed by double immunofluorescent staining for both tissue factor and measles virus N-protein, and examined using confocal scanning laser microscopy. Cells expressing tissue factor were also positive for the measles virus N-protein. Low levels of interleukin-1 were detected in some viral inocula derived from measles virus-infected Vero cells, however neutralising antibody to interleukin-1 failed to inhibit the endothelial cell procoagulant response to measles virus, whereas it significantly reduced procoagulant activity induced in endothelial cells by recombinant interleukin-1. The capacity of measles virus to induce endothelial tissue factor in vitro, may be relevant to the thrombotic vasculopathy associated with measles virus infection in vivo.

Efficient MHC class II-restricted presentation of measles virus to T cells relies on its targeting to its cellular receptor human CD46 and involves an endosomal pathway

The role of the measles virus (MV) receptor, human CD46, in the uptake of MV and antigen presentation by Major Histocompatibility Complex (MHC) class II molecules was investigated. Expression of CD46 in murine B cells resulted in cells highly efficient in capturing UV-inactivated MV particles and presenting both envelope hemagglutinin H and nucleoprotein N to specific T cell hybridomas. Although MV fuse with the plasma membrane of its target cells, presentation of both MV-H and -N was sensitive to inhibition by chloroquine but was not affected by a tripeptide which prevents virus-cell fusion. Whereas 50 microM of chloroquine was required to inhibit presentation of MV-H, purified H or soluble N, only a two-fold lower concentration was required to inhibit that of MV-N. This shows that some CD46-mediated captured MV particles are endocytosed, then disrupted and processed in an endosome/lysosome compartment.

Development and evaluation of the TD97 measles virus vaccine

The TD97 strain vaccine virus was prepared from the Tanabe strain measles virus by low-temperature passages in primary cell cultures and ultraviolet (UV) mutagenesis. The TD97 strain exhibited the following characteristics: highly temperature sensitive, neither multiplying nor forming any plaques at 40 degrees C in Vero cells; genetically stable, maintaining high temperature sensitivity after ten successive passages in CE cells at 30 degrees C or 35 degrees C; and M proteins of this virus about 1 KD slower in mobility in SDS-PAGE than that of the Tanabe strain. The TD97 strain was further confirmed to be attenuated by an inoculation test into primate brain. In field trials, 752 healthy children were inoculated with a live virus vaccine prepared with this strain, and the following results were obtained: the seroconversion rate was 97% (517/533), and the average HI antibody titer was 2(5.2). An antibody-increasing effect was also observed in children who were initially seropositive. In children who seroconverted, the rates of fever were 15.7% (55/351) for 37.5 degrees C or higher and 4.0% (14/351) for 39 degrees C or higher. The rash rate was 7.7% (27/351), and the incidence of local reaction was 5.4% (19/351). The TD97 strain is thus considered to be suitable in use for an attenuated measles vaccine.

Effect of measles-virus infection and interferon treatment on invasiveness of Shigella flexneri in HEp2-cell cultures

The influence of measles-virus infection on the invasiveness of Shigella flexneri in HEp2-cell cultures was studied. Bacterial invasiveness was significantly enhanced in cell cultures incubated with virus before bacterial inoculation. This effect was a function of time after introduction of virus to the cell cultures and of the concentration of virus. The increase in bacterial invasiveness was observed before production of infectious virus particles and before a cytopathic effect was evident. A similar enhancement of invasiveness was demonstrated when cell cultures were pretreated with UV-inactivated measles virus. Pretreatment of cells with interferon did not influence invasiveness, although it reduced the effect of measles-virus infection.

Interferon induction by measles virus

Interferon induction in BSC-1 cells by measles virus isolates previously found to be interferon inducing (IF+) or interferon noninducing (IF-) was studied in different cell types. Lack of induction by the IF- viruses was not due to an inhibitory factor since BSC-1 cells coinfected with IF+ and IF- stocks produced interferon levels similar to those infected with IF+ stocks alone. Various tests indicated that the phenotypic expression of interferon induction by these isolates was dependent on an infectious virus genome, the cell type tested, and the passage history of the virus. In contrast to the in vitro results, the IF- phenotype was stable in vivo, whereas passage of the IF+ virus resulted in selection against the IF+ phenotype. The phenotypic expression of interferon induction by measles virus was, therefore, controlled by complex interactions between virus and host cell factors exerted both in vivo and in vitro.

Immunogenicity of UV-inactivated measles virus

By means of the antigen extinction limit test it was shown that a triple dose vaccination of guinea pigs with UV-inactivated measles virus gave better results, than a single dose vaccination which was proved by the very low immunogenicity index. For both vaccination schemes (single and triple) the immune response was only slightly influenced by a change of dose from 10(5) to 10(6) HadU50/ml or by the addition of aluminum adjuvant. In the antigen extinction limit test the antibody levels were determined by two methods (HIT and NT) the results of which were statistically equivalent. The UV-inactivated measles virus was also found to induce hemolysis-inhibiting antibodies.

Thermal and ultraviolet inactivation of plaque purified measles virus clones

Three plaque-purified measles virus clones exhibited remarkable differences in their kinetics of inactivation only after heating at 45 degrees C and none after UV-irradiation. A hypothesis is discussed of the possible dependence, in fast inactivating populations, of thermolability on a relative incompleteness of the virions.

Inhibition of lymphocyte stimulation by measles virus

The effect of measles virus on phytohemagglutinin-(PHA) induced stimulation of human peripheral blood mononuclear cells was investigated to delineate possible mechanisms for viral suppression of cell-mediated immunity (CMI). it was noted that medium which had several days contact with uninfected monolayers as well as unpurified measles virus preparations produced significant inhibition of 3H-thymidine incorporation by PHA-stimulated lymphocytes. When partially purified measles virus preparations were used, however, marked inhibition was observed and the inhibitory effect of cell-derived factors could be separated easily from the virus-induced inhibition. Experiments to determine the mechanisms of this virus-induced inhibition of 3H-thymidine incorporation showed the following: 1) live measles virus and not UV-irradiated or heat-inactivated virus produced inhibition; 2) the inhibitory effect observed was not the result of a viral-induced inhibitor being released from measles-infected lymphocytes; and 3) monocyte depletion had no effect on the ability of measles virus to inhibit 3H-thymide incorporation by PHA-stimulated lymphocytes. Since it was found that measles virus-infected lymphocytes display an impaired response to in vitro PHA stimulation, perhaps this dysfunction may be extended to mediator release and other functions associated with delayed cutaneous hypersensitivity (DCH) in vivo.

Host DNA synthesis-suppressing factor in culture fluid of tissue cultures infected with measles virus

Host DNA synthesis is suppressed by the culture fluid of cell cultures infected with measles virus. This activity in the culture fluid is initiated somewhat later than the growth of infectious virus. Ninety percent of host DNA synthesis in HeLa cells is inhibited by culture fluid of 3-day-old cell cultures of Vero or HeLa cells infected with measles virus. This suppressing activity is not a property of the virion, but is due to nonvirion-associated component which shows none of the activities of measles virus such as hemagglutination, hemolysis, or cell fusion nor does it have the antigenicity of measles virus as tested by complement-fixation or hemagglutination-inhibiting antibody blocking tests. Neutralization of the activity of this component is not attained with the pooled sera of convalescent measles patients. This component has molecular weights of about 45,000, 20,000, and 3,000 and appears to be a heat-stable protein. The production of host DNA suppressing factor (DSF) is blocked by cycloheximide. Neither UV-inactivated nor antiserum-neutralized measles virus produce DSF. Furthermore, such activity of nonvirion-associated component is not detected in the culture fluid of cultures infected with other RNA viruses such as poliovirus, vesicular stomatitis virus, or Sindbis virus.

Autoradiographic studies of cytogenetic effects induced by UV-inactivated measles virus (fusion factor) in human cells

Two types of extensive chromosome changes (pulverization and uncoiling) as well as a combination of these phenomena in the same cell were induced by exposure to UV-inactivated measles virus (FF). The DNA-labeling patterns of these nuclear events were investigated. These types of extensive changes not only appeared to be morphologically distinguishable but also to be induced at different stages of the cell cycle. Pulverization occurred in very actively DNA-synthesizing cells. In contrast, G₁, G₂, or M cells were sensitive to uncoiling changes.

Cytogenetic effects of measles virus fusion factor (FF) on human leukocytes

In human leukocyte cultures, <i>extensive chromosome changes </i>(pulverization, uncoiling, or a combination of these) induced by UV-inactivated measles virus (fusion factor or FF) (1) were virus specific, (2) showed a quantitative relationship to virus dose, and (3) were dependent upon length of virus treatment. In contrast to the above-defined extensive chromosome changes, <i>simple chromosomal breaks </i>showed none of these properties and could be induced by cell debris alone at rates comparable to infectious virus or FF. These observations indicate that extensive and simple chromosomal changes are morphologically distinct and sequentially unrelated, constituting two different populations of aberrations. Analysis of extensive chromosome changes after different virus exposures suggested that uncoiling is not an early and less severe form of pulverization. Localization of chromosome breakage induced by both infectious virus and FF as well as cell debris and control (medium) treated cultures was nonrandom and statistically indistinguishable.