Replication-incompetent Sendai virus can suppress the antiviral action of type I interferon

Altered baby hamster kidney (BHK-R) cells, which were established by serial passage of BHK cells in the presence of Sendai virus (SeV), allowed vesicular stomatitis virus (VSV) to replicate despite treatment with type I interferon (IFN). We have analyzed here mechanisms of the unresponsiveness to IFN. BHK-R cells cultured in the absence of SeV for 10 days under the conditions of no cell division (BHK-R10D) became sensitive to IFN. Studies on induction of unresponsiveness to IFN in BHK-R10D cells revealed that entry of SeV nucleocapsids into a cell was essential. Interestingly, even UV-inactivated SeV but not Newcastle disease virus was found to be able to confer resistance to IFN on HeLa or BHK cells as well as on BHK-R10D cells, suggesting that the IFN-resistance resulted from functions of SeV independent of replication of the viral genome but not from mutations of the cellular genome. Furthermore immunofluorescent experiments demonstrated that UV-inactivated SeV could rescue VSV replication from the antiviral action of IFN without expression of SeV antigens, confirming that the secondary transcription resulting in synthesis of large amounts of viral proteins was dispensable for the IFN-resistance. Thus we have revealed a unique strategy of SeV against the antiviral action of IFN.

Acidic pH enhancement of the fusion of Newcastle disease virus with cultured cells

Fusion of the lentogenic strain "Clone 30" of Newcastle disease virus (NDV) with the cell line COS-7 has been studied. Fusion was monitored using the octadecylrhodamine B chloride dequenching assay [Hoekstra, D., de Boer, T., Klappe, K. and Wilschut, J. (1984). Biochemistry 23, 5675-5681]. In the present work, fusion of NDV with COS-7 cells was found to occur in a time- and temperature-dependent fashion. Significant dequenching of the probe occurred at temperatures higher than 28 degrees C. A 20-fold excess of unlabeled virus inhibited fusion by about 53% compared with the control, whereas 62% inhibition of fusion was obtained after digestion of viral glycoproteins with trypsin. The data are discussed in terms of the nonfusion transfer of the probe. In addition, preincubation of cells with 50 mM ammonium chloride or 0.1% sodium azide prevented NDV from fusing with COS-7 cells by about 30% in comparison with the control. The cytopathic effect of NDV infection in cell culture in the presence of ammonium chloride was reduced compared with control. Moreover, viral preincubation at pH 5 yielded a mild inhibition of fusogenic activity. Our results suggest that NDV may use the endocytic pathway as a complementary way of entering cells by direct fusion with the plasma membrane.

A rapid virus neutralization assay for Newcastle disease virus with the swine testicular continuous cell line

Five continuous cell lines, swine testicular (ST), human rectal tumor (HRT 18), fetal rhesus monkey kidney (MA104), bovine turbinate (BT), and quail tracheal (QT35), were evaluated and compared with chicken embryo fibroblasts (CEFs) for their ability to propagate B1 or Texas GB strains of Newcastle disease virus (NDV). The NDV Texas GB strain replicated in all the continuous cell lines used in this study. Only the ST and QT35 cells produced a cytopathic effect (CPE) similar to that produced in CEFs. However, the ST cell line remained attached while displaying CPE, whereas infected QT35 cells detached, as did the CEFs. The B1 strain of NDV replicated in ST cells, MA104 cells, and CEFs but with less CPE as compared with the Texas GB strain. Pretreatment with trypsin did not enhance CPE with either NDV strain at the level tested. Sera evaluated for neutralizing antibody titers to NDV were significantly higher in titer when the ST cell line was used and compared with CEFs. A high correlation was found between the microscopic examination and the tetrazolium dye (MTT) microassay methods for determining the viral neutralization endpoint, thus suggesting the ST cell line and MTT microassay could be used as an alternative to CEFs and microscopic examination for evaluating neutralizing antibodies titers to NDV.

Response of turkeys to simultaneous vaccination with hemorrhagic enteritis and Newcastle disease viruses

The effects of single and combined vaccination of turkeys against hemorrhagic enteritis virus (HEV) and Newcastle disease virus (NDV) were investigated. Dual vaccination of turkeys with NDV-B1 and HEVp30 or marble spleen disease virus (MSDV) enhanced white mottling of the spleens and the apoptosis rate in spleen cells (P < 0.05). In addition, simultaneously vaccinated turkeys had fewer HEV-infected spleen cells at 4 days postvaccination than turkeys given HEVp30 or MSDV alone. The anti-HEV antibody response was significantly reduced at 14 days postvaccination (P < 0.05), whereas the anti-NDV antibody response was enhanced (P < 0.05) in turkeys vaccinated with HEVp30 + NDV-B1. Further, the effect of dual vaccination on macrophage function was studied. Spleen cells from NDV-B1-vaccinated turkeys were primed to produce nitric oxide (NO) after stimulation in vitro with lipopolysaccharide. Spleen cells from HEVp30- or MSDV-vaccinated turkeys did not produce NO after in vitro stimulation. In dual-vaccinated turkeys, the priming effect of NDV-B1 was reduced in comparison with single-inoculated birds.

Human tumor cell modification by virus infection: an efficient and safe way to produce cancer vaccine with pleiotropic immune stimulatory properties when using Newcastle disease virus

Direct infection of tumor cells with viruses transferring protective or therapeutic genes, a frequently used procedure for production of tumor vaccines in human gene therapy, is an approach which is often limited by the number of tumor cells that can reliably be infected as well as by issues of selectivity and safety. We report an efficient, selective and safe way of infecting human tumor cells with a natural virus with interesting pleiotropic immune stimulatory properties, the avian paramyxovirus Newcastle disease virus (NDV). Two of the six viral genes (HN and F) modify the tumor cell surface by introduction of new adhesion molecules for lymphocyte interactions and other viral genes stimulate host cell genes and local production of cytokines and chemokines which can recruit a broad antitumor response in vivo. A large variety of human tumor cells is shown to be efficiently infected by NDV with viral replication being independent of tumor cell proliferation. Such properties make NDV a suitable agent for modification of noncultured freshly isolated and gamma-irradiated patient-derived tumor cells. For the apathogenic non-lytic strain NDV-Ulster which is used in our clinical vaccine trials, we demonstrate selective replication in tumor cells as compared with corresponding normal cells. Furthermore, we present evidence that new virions produced by infected tumor cells are non-infectious using three different quantitative test methods. Our results demonstrate feasibility and broad applicability of this strategy of human tumor vaccine modification. Post-operative vaccination with the autologous virus-modified vaccine ATV-NDV thus provides a reasonable potential for pleiotropic modifications of the immune response of cancer patients against their own tumor.

Differential viral induction of distinct interferon-alpha genes by positive feedback through interferon regulatory factor-7

Interferon (IFN) genes are among the earliest transcriptional responses to virus infection of mammalian cells. Although the regulation of the IFNbeta gene has been well characterized, the induction of the large family of IFNalpha genes has remained obscure. We report that the IFNalpha genes can be divided into two groups: an immediate-early response gene (IFNalpha4) which is induced rapidly and without the need for ongoing protein synthesis; and a set of genes that display delayed induction, consisting of at least IFNalpha2, 5, 6 and 8, which are induced more slowly and require cellular protein synthesis. One protein that must be synthesized for induction of the delayed gene set is IFN itself, presumably IFNalpha4 or IFNbeta, which stimulates the Jak-Stat pathway through the IFN receptor, resulting in activation of the transcription factor interferon-stimulated gene factor 3 (ISGF3). Among the IFN-stimulated genes induced through this positive feedback loop is the IFN regulatory factor (IRF) protein, IRF7. Induction of IRF7 protein in response to IFN and its subsequent activation by phosphorylation in response to virus-specific signals, involving two C-terminal serine residues, are required for induction of the delayed IFNalpha gene set.

Interferon yield and MHC antigen expression of human medulloblastoma cells and its suppression during dibutyryl cyclic AMP-induced differentiation: do medulloblastoma cells derive from bipotent neuronal and glial progenitors?

1. Human medulloblastoma (ONS-76), a central nervous system (CNS)-derived undifferentiated cell line, was found to possess glial characteristics as defined by responses in the interferon (IFN) system; ONS-76 cells produced as much IFN-beta as human fibroblast and glioma cells by viral infection and poly(I):poly(C) induction. 2. Major histocompatibility complex (MHC) class I antigens were also induced under IFN-beta stimulation. ONS-76 cells expressed neurofilament protein, as shown by Northern blot analysis, and morphological differentiation was induced by dibutyryl cyclic AMP (dcAMP). 3. Expression of IFN-beta and MHC class I antigens was suppressed in ONS-76 cells during the dcAMP-induced differentiation. 4. These results showed that ONS-76 cells possessed a glial property in IFN system responses and a neuronal property in cytoskeleton protein, suggesting that the precursors of medulloblastoma may be characterized as bipotent neuronal and glial progenitors in CNS.

Primary activation of interferon A and interferon B gene transcription by interferon regulatory factor 3

The family of interferon (IFN) regulatory factors (IRFs) encodes DNA-binding transcription factors, some of which function as modulators of virus-induced signaling. The IRF-3 gene is constitutively expressed in many tissues and cell types, and neither virus infection nor IFN treatment enhances its transcription. In infected cells, however, IRF-3 protein is phosphorylated at the carboxyl terminus, which facilitates its binding to the CBP/p300 coactivator. In the present study, we demonstrate that overexpression of IRF-3 significantly enhances virus-mediated transcription of the IFNA and IFNB genes in infected cells as well as IFN synthesis. IRF-3-mediated activation of IFN genes depends in part on carboxyl-terminal phosphorylation of a cluster of Ser/Thr residues, because a mutant with Ser/Thr to Ala substitutions activates the IFN promoter less efficiently. However, overexpression of IRF-3 in human 2FTGH cells alone results in the induction of an antiviral state, which depends on functional IFN signaling, because IRF-3 does not induce an antiviral state in mutant 2FTGH cells defective in either JAK-1 or p48 functions; also no antiviral effect of IRF-3 could be demonstrated in Vero cells that lack the IFNA and IFNB genes. This finding indicates that the observed antiviral activity of IRF-3 in 2FTGH cells results mainly from the induction of IFNs. Furthermore, E1A protein inhibited IRF-3-mediated stimulation of the IFNA4 promoter in transient expression assays; this inhibition could be reversed partially by overexpression of CBP/p300 and was not demonstrated with the mutant of E1A that does not bind p300. These results identify IRF-3 and CBP/p300 as integral components of the virus-induced complex that stimulates type 1 IFN gene transcription. The observation that adenovirus E1A antagonizes IRF-3 mediated activation suggests that E1A and IRF-3 may compete for binding to CBP/p300 and implicates a novel mechanism by which adenovirus may overcome the antiviral effects of the IFN pathway.

The role of leucine residues in the structure and function of a leucine zipper peptide inhibitor of paramyxovirus (NDV) fusion

To investigate the molecular mechanisms involved in paramyxovirus-induced cell fusion, the function and structure of synthetic peptide analogs of the sequence from the leucine zipper region (heptad repeat region 2) of the Newcastle disease virus fusion protein (F) were characterized. As previously reported (Young et al., Virology, 238, 291), a peptide with the sequence ALDKLEESNSKLDKVNVKLT (amino acids 478-497 of the F protein) inhibited syncytia formation after transfection of Cos cells with the hemagglutinin-neuraminidase and F protein cDNAs. A peptide analog which had an alanine residue in place of the first leucine residue in the zipper motif (ALDKAEESNSKLDKVNVKLT) retained inhibitory activity but less than the original peptide. Further loss in activity was observed in a peptide in which two of the leucine residues were replaced with alanine (ALDKAEESNSKADKVNVKLT), and a peptide which had all leucine residues in the zipper motif replaced with alanine (ALDKAEESNSKADKVNVKLT) had no inhibitory activity. The three-dimensional conformations of these peptides in aqueous solution were determined through the use of nuclear magnetic spectroscopy and molecular modeling. Results showed that while the wild-type peptide formed a helix with properties between an alpha-helix and a 3(10) helix with leucine residues aligned along one face of the helix, progressive substitution of leucine residues with alanine resulted in the progressive loss of helical structure. The results suggest that alterations of leucine residues in the zipper motif disrupt secondary structure of the peptide and that this structure is critical to the inhibitory activity of the peptide.

Interferon regulatory factor 3 and CREB-binding protein/p300 are subunits of double-stranded RNA-activated transcription factor DRAF1

Cells respond to viral infection or double-stranded RNA with the transcriptional induction of a subset of alpha/beta interferon-stimulated genes by a pathway distinct from the interferon signal pathway. The transcriptional induction is mediated through a DNA sequence containing the alpha/beta interferon-stimulated response element (ISRE). We previously identified a novel transcription factor, designated double-stranded RNA-activated factor 1 (DRAF1), that recognizes this response element. The DNA-binding specificity of DRAF1 correlates with transcriptional induction, thereby distinguishing it as a positive regulator of alpha/beta interferon-stimulated genes. Two of the components of DRAF1 have now been identified as interferon regulatory factor 3 (IRF-3) and the transcriptional coactivator CREB-binding protein (CBP)/p300. We demonstrate that IRF-3 preexists in the cytoplasm of uninfected cells and translocates to the nucleus following viral infection. Translocation of IRF-3 is accompanied by an increase in serine and threonine phosphorylation. Coimmunoprecipitation analyses of endogenous proteins demonstrate an association of IRF-3 with the transcriptional coactivators CBP and p300 only subsequent to infection. In addition, antibodies to the IRF-3, CBP, and p300 molecules react with DRAF1 bound to the ISRE target site of induced genes. The cellular response that leads to DRAF1 activation and specific gene expression may serve to increase host survival during viral infection.

Direct triggering of the type I interferon system by virus infection: activation of a transcription factor complex containing IRF-3 and CBP/p300

It has been hypothesized that certain viral infections directly activate a transcription factor(s) which is responsible for the activation of genes encoding type I interferons (IFNs) and interferon-stimulated genes (ISGs) via interferon regulatory factor (IRF) motifs present in their respective promoters. These events trigger the activation of defense machinery against viruses. Here we demonstrate that IRF-3 transmits a virus-induced signal from the cytoplasm to the nucleus. In unstimulated cells, IRF-3 is present in its inactive form, restricted to the cytoplasm due to a continuous nuclear export mediated by nuclear export signal, and it exhibits few DNA-binding properties. Virus infection but not IFN treatment induces phosphorylation of IRF-3 on specific serine residues, thereby allowing it to complex with the co-activator CBP/p300 with simultaneous nuclear translocation and its specific DNA binding. We also show that a dominant-negative mutant of IRF-3 could inhibit virus-induced activation of chromosomal type I IFN genes and ISGs. These findings suggest that IRF-3 plays an important role in the virus-inducible primary activation of type I IFN and IFN-responsive genes.

Analysis of a peptide inhibitor of paramyxovirus (NDV) fusion using biological assays, NMR, and molecular modeling

To investigate the molecular mechanisms involved in paramyxovirus-induced cell fusion, the function and structure of a peptide with a 20-amino-acid sequence from the leucine zipper region (heptad repeat region 2) of the Newcastle disease virus fusion protein (F) were characterized. A peptide with the sequence ALDKLEESNSKLDKVNVKLT (amino acids 478-497 of the F protein) was found to inhibit syncytia formation after virus infection and after transfection of Cos cells with the HN (hemagglutinin-neuraminidase) and F protein cDNAs. Using an F protein gene that requires addition of exogenous trypsin for cleavage, it was shown that the peptide exerted its inhibitory effect prior to cleavage. The three-dimensional conformation of the peptide in aqueous solution was determined through the use of NMR and molecular modeling. Results showed that the peptide formed a helix with properties between an alpha-helix and a 3(10)-helix and that leucine residues aligned along one face of the helix. Side chain salt bridges and hydrogen bonds likely contributed to the stability of the peptide secondary structure. Analysis of the aqueous solution conformation of the peptide suggested mechanisms for specificity of interaction with the intact F protein.

Assembly of recombinant Newcastle disease virus nucleocapsid protein into nucleocapsid-like structures is inhibited by the phosphoprotein

A recombinant baculovirus expressing the nucleocapsid gene (NP) of Newcastle disease virus (NDV), a member of the genus Rubulavirus, has been generated and shown to express the native protein to high levels in insect cells. In contrast to the NP protein of the rubulavirus human parainfluenza virus 2, the NDV protein has been demonstrated by electron microscopy and caesium chloride gradient analysis to be capable of self-assembly in vivo to form nucleocapsid-like structures in the absence of other NDV proteins. These structures, which contained RNA that was resistant to micrococcal nuclease digestion, were also observed when the protein was expressed in E. coli, a phenomenon which was not inhibited by the presence of a 40 amino acid fusion region at the amino terminus of the protein. Further, the formation of these structures was inhibited by the co-expression of the phosphoprotein (P). Therefore, we conclude that the P protein acts as a chaperone, preventing uncontrolled encapsidation of non-viral RNA by NP protein.

Synergism between multiple virus-induced factor-binding elements involved in the differential expression of interferon A genes

Comparative transfection analysis of murine interferon A4 and interferon A11 promoter constructs transiently transfected in mouse L929 and human HeLa S3 cells infected with Newcastle disease virus showed that the second positive regulatory domain I-like domain (D motif), located between nucleotides -57 and -46 upstream of the transcription start site, contributes to the activation of virus-induced transcription of the interferon (IFN)-A4 gene promoter by cooperating with the positive regulatory domain I-like and TG-like domains previously described. Electrophoretic mobility shift assay performed with the virus-inducible fragments containing these motifs indicated that the binding activity that we have denoted as virus-induced factor (Génin, P., Bragança, J., Darracq, N., Doly, J., and Civas, A. (1995) Nucleic Acids Res. 23, 5055-5063) is different from interferon-stimulated gene factor 3. It binds to the D motif but not to the virus-unresponsive form of the D motif disrupted by a G-57 --> C substitution. We show that the low levels of IFN-A11 gene expression are caused essentially by the lack of two inducible enhancer domains disrupted by the A-78 --> G and the G-57 --> C substitutions. These data suggest a model taking account of the differential regulation of IFN-A gene family members. They also suggest that virus-induced factor may correspond to the primary transcription factor directly activated by virus that is involved in the initiation of IFN-A gene transcription.

A differential scanning calorimetric study of Newcastle disease virus: identification of proteins involved in thermal transitions

The irreversible thermal denaturation of Newcastle disease virus was investigated using different techniques including high-sensitivity differential scanning calorimetry, thermal gel analysis intrinsic fluorescence, and neuraminidase activity assays. Application of a successive annealing procedure to the scanning calorimetric endotherm of Newcastle disease virus furnished four elementary thermal transitions below the overall endotherm; these were further identified as coming from the denaturation of each viral protein. The shape of these transitions, as well as their scanrate dependence, was explained by assuming that thermal denaturation takes place according to the kinetic scheme N-->(k)D, where k is a first-order kinetic constant that changes with temperature, as given by the Arrhenius equation; N is the native state; and D is the denatured state. On the basis of this model, activation energy values were calculated. The data obtained with the other methods used in this work support the proposed two-state kinetic model.

Tumor-cell number and viability as quality and efficacy parameters of autologous virus-modified cancer vaccines in patients with breast or ovarian cancer

PURPOSE

We investigated quality and efficacy criteria of an autologous, physically and immunologically purified, Newcastle disease virus (NDV)-modified, irradiated tumor-cell vaccine (ATV-NDV) by analyzing three independent cohorts (a through c) of patients vaccinated between 1991 and 1995.

MATERIALS AND METHODS

Included were 63 patients with primary breast cancer (a), 27 with metastatic pretreated breast cancer (b), and 31 with metastatic pretreated ovarian cancer (c). In addition to vaccine, cohorts b and c received nonspecific immunotherapy as supportive treatment. After cryoconservation and purification, the vaccines varied in applied numbers of viable cells and dead cell contaminations. We retrospectively hypothesized that an immunogenic vaccine should contain at least 1.5 x 10(6) viable tumor cells and viability should be at least 33%. Each cohort was thus divided into two groups; one that received vaccine type A (A), fulfilling both criteria; and the other type B (B), missing one or both criteria.

RESULTS

Conventional prognostic factors were wall balanced between A and B in cohorts a and c. In cohort a, there was a benefit in survival (P = .026) and disease-free survival (P = .089) for A. In addition, in cohort a, the relative risk of dying in the group that received A as compared with B was 0.2 (univariate Cox model). There were also survival trends in favor of A versus B (P = .18 and P = .09, respectively) in cohorts b and c, with relative risks of 0.5 and 0.42, respectively. In cohort b, the survival benefit could not be ascribed to vaccine quality alone, because of prognostic imbalance in favor of A.

CONCLUSION

In cohort c, like in cohort a, the survival benefit for A may be ascribed to the ATV-NDV vaccine quality, since prognostic factors were not biased. This could imply clinical effectivity in breast and ovarian cancer with ATV-NDV high-quality vaccine. Furthermore, the data provide clinically relevant information for standardization and quality control of autologous tumor-cell vaccines. A randomized study is urgently needed.

Early induction of proinflammatory cytokine and type I interferon mRNAs following Newcastle disease virus, poly [rI:rC], or low-dose LPS challenge of the mouse

Numerous cytokines induce symptoms characteristic of the flu syndrome common to acute viral infections. To better characterize the cytokine mRNA profile associated with the early phase of this syndrome, we examined the induction of cytokine mRNAs in spleens of mice 1, 2, and 4 h following intraperitoneal inoculation of Newcastle disease virus (NDV). The reverse transcriptase-polymerase chain reaction was used to detect mRNAs for mouse proinflammatory cytokines [interleukin (IL)-1 alpha, IL-1 beta, IL-6, tumor necrosis factor-alpha (TNF-alpha), macrophage colony-stimulating factor (M-CSF), and interferon (IFN)-gamma] and type I IFNs (IFN-alpha 4 and IFN-beta). We observed a rapid (within 2 h) induction of most of these cytokine mRNAs in the mouse spleen following challenge with live NDV or the viral stimulant poly[rI:rC]. IL-1 beta, M-CSF, and IFN-gamma mRNAs were also induced by heat-inactivated NDV, suggesting the possibility of endotoxin contamination of the virus (confirmed by Limulus lysate assay). Examination of cytokine induction by comparable doses of lipopolysaccharide indicated that endotoxin contamination could account for the cytokine mRNA-inducing activity of the heat-inactivated virus. These studies point to a critical control (heat-inactivated virus) for viral cytokine studies. In addition, they indicate that certain cytokine mRNAs (IL-1 alpha, IL-6, M-CSF, IFN-gamma, IFN-alpha, and IFN-beta) are rapidly induced in the spleen when live virus is inoculated intraperitoneally, independently of contaminating endotoxin.

[Risk for the transmission of Newcastle disease by contaminated poultry products]

Poultry products contaminated with pathogenic strains of Newcastle disease virus are a source of virus transmission to susceptible poultry flocks. The probability of contamination varies according to the type of product. Research conducted by various laboratories in Europe has shown that pathogenic virus can be isolated from the carcasses of chickens, whether vaccinated or not, during a brief period after experimental infection. Eggs laid by hens infected with Newcastle disease virus present a very low risk. Furthermore, feathers, bones, blood and offal present potential risks if they are incorporated in poultry feed. Finally, poultry droppings used as a fertiliser can present a major risk of infection in certain circumstances.

Strain differences in the somnogenic effects of interferon inducers in mice

Increased slow-wave sleep accompanies influenza infection in C57BL/6 mice but not BALB/c mice. These strains of mice possess different alleles of the genetic lucus If-1, which codes for high (If-1h; C57BL/6) and low (If-1(1); BALB/c) production of interferon (IFN), a putative sleep-inducing cytokine. To evaluate the contribution of the If-1 gene to differences in murine sleep propensity, sleep patterns were evaluated in mice treated with the IFN inducers polyinosinic:polycytidilic acid (pIC) or Newcastle disease virus (NDV), with influenza virus, or with murine interferon (IFN-alpha) or IFN-alpha/beta. As compared with baseline values, C57BL/6 mice exhibited increased slow-wave sleep after all three challenges, but BALB/c mice did not. Congenic B6.C-H28c mice, which bear the BALB/c allele for low IFN production on the C57BL/6 genetic background, showed enhanced slow-wave sleep after influenza infection but not after NDV. Exogenous IFN did not enhance slow-wave sleep in either C57BL/6 or BALB/c mice. These data suggest that the If-1 allele may influence the somnogenic responsiveness of mice under some conditions but that additional mechanisms may contribute to sleep enhancement during infectious disease.

Replicating viruses as selective cancer therapeutics

Replication-competent viruses are used as selective cancer therapeutics and the mechanisms leading to tumor-specific replication and antitumoral efficacy are now becoming apparent. The specific viruses in development include tumor-targeting herpes simplex viruses, autonomous parvoviruses, Newcastle disease viruses and adenovirus. Information is also available on antiviral immunology and viral defenses against host-mediated immunity. This approach has many potential attributes, in addition to potential hurdles that must be overcome.

Efrapeptins block exocytic but not endocytic trafficking of proteins

During the course of screening studies to identify inhibitors of intracellular protein trafficking, we isolated efrapeptins as active principles. These compounds arrested syncytium formation (SF) and cytopathic effect (CPE) in Newcastle disease virus (NDV)- and vesicular stomatitis virus (VSV)-infected BHK cells, respectively, without profoundly affecting glycoprotein synthesis. Efrapeptins blocked cell surface expression of NDV-HN and VSV-G glycoproteins, but did not suppress intoxication by ricin or diphtheria toxin even after prolonged pretreatment. Efrapeptins are inhibitors of F-ATPase, or ATP synthase, but their inhibitory effect on SF and CPE was independent of the amount of intracellular ATP.

The production of colibacillosis in turkeys following sequential exposure to Newcastle disease virus or Bordetella avium, avirulent hemorrhagic enteritis virus, and Escherichia coli

Female large white turkeys were intranasally inoculated with either Newcastle disease virus (ND) or Bordetella avium (BA) at 4 weeks of age. This was followed by oral inoculation with an avirulent (vaccine) strain of hemorrhagic enteritis virus (HE) at 5 weeks and intravenous inoculation with Escherichia coli (EC) at 6 weeks. Control birds received ND, BA, or HE followed by EC; EC alone; or nothing at all. Turkeys receiving one agent prior to EC challenge did not experience a significant increase in mortality or pericarditis. Those exposed to ND or BA followed by HE and EC experienced a significant elevation in mortality and pericarditis. A highly significant positive correlation between the number of infectious agents encountered during primary exposure and the incidence of colibacillosis after EC challenge was demonstrated.

Experimental infection in turkeys and chickens with Ornithobacterium rhinotracheale

Ornithobacterium rhinotracheale was found to cause growth retardation in both turkeys and chickens after experimental intra-air sac administration and to cause growth retardation together with airsacculitis and pneumonia after aerosol administration. Both turkey and chicken isolates of O. rhinotracheale were able to induce the same kind of respiratory inflammations and weight-gain losses in chickens as well as turkeys. Turkey rhinotracheitis virus was found to have a triggering effect on the O. rhinotracheale infection in turkeys, and Newcastle disease virus and to a lesser extent infectious bronchitis virus showed triggering effects on the O. rhinotracheale infection in chickens. Ornithobacterium rhinotracheale could be reisolated from affected organs of experimentally infected birds.

Antiviral activity of some hydroxycoumarin derivatives

Esculetin (6,7-dihydroxycoumarin) and its diacetate exhibited a marked inhibitory effect on Newcastle disease virus replication in cell cultures at concentrations of 36 microM and 62 microM, respectively. These compounds were selected from ten hydroxycoumarin derivatives through an in vitro antiviral screen involving viruses of the picorna-, orthomyxo-, paramyxo-, and herpes virus families.