Vesicular Stomatitis Virus Yield Research Articles

Molecular characterization and antiviral effects of canine interferon regulatory factor 1 (CaIRF1)

BackgroundInterferon regulatory factor 1 (IRF1) is an important transcription factor that activates the type I interferon (IFN-I) response and plays a vital role in the antiviral immune response. Although IRF1 has been identified in several mammals, little information related to its function in canines has been described.ResultsIn this study, canine IRF1 (CaIRF1) was cloned. After a series of bioinformatics analyses, we found that the CaIRF1 protein structure was similar to that of other animal IRF1 proteins, including a conserved DNA-binding domain (DBD), an IRF-association domain 2 (IAD2) domain and two nuclear localization signals (NLSs). An indirect immunofluorescence assay (IFA) revealed that CaIRF1 was mainly distributed in the nucleus. Overexpression of CaIRF1 in Madin-Darby canine kidney cells (MDCK) induced high levels of interferon β (IFNβ) and IFN-stimulated response element (ISRE) promoter activation and induced interferon-stimulated gene (ISG) expression. Subsequently, we assayed the antiviral activity of CaIRF1 against vesicular stomatitis virus (VSV) and canine parvovirus type-2 (CPV-2) in MDCK cells. Overexpression of CaIRF1 effectively inhibited the viral yields of VSV and CPV-2, while knocking down of CaIRF1 expression mildly increased viral gene copies.ConclusionsCaIRF1 is involved in the cellular IFN-I signaling pathway and plays an important role in the antiviral response.

Dengue virus induced changes in Ca2+ homeostasis in human hepatic cells that favor the viral replicative cycle

The role of Ca2+ during dengue virus (DENV) replication is unknown; thus, changes in Ca2+ homeostasis in DENV infected human hepatic HepG2 and Huh-7 cells were analyzed. Infected HepG2 cells, but not Huh-7 cells, showed a significant increase in plasma membrane permeability to Ca2+, while both cell lines showed marked reduced levels of Ca2+ stored in the endoplasmic reticulum. While the expression levels of STIM1 and ORAI1 showed no changes, STIM1 and ORAI1 were shown to co-localized in infected cells, indicating activation of the store-operated Ca2+ entry (SOCE) pathway. Finally, manipulation in the infected cells of the intra and extracellular Ca2+ levels by chelators (BAPTA-AM and EGTA), SOC inhibitor (SKF96365), IP3 Receptor antagonist (2APB) or increase of extracellular [Ca2+], significantly reduced DENV yield, but not vesicular stomatitis virus yield, used as a control. These results show that DENV infection alters cell Ca2+ homeostasis and that such changes favor viral replication.

Retinoic Acid-inducible Gene I-inducible miR-23b Inhibits Infections by Minor Group Rhinoviruses through Down-regulation of the Very Low Density Lipoprotein Receptor

In mammals, viral infections are detected by innate immune receptors, including Toll-like receptor and retinoic acid inducible gene I (RIG-I)-like receptor (RLR), which activate the type I interferon (IFN) system. IFN essentially activates genes encoding antiviral proteins that inhibit various steps of viral replication as well as facilitate the subsequent activation of acquired immune responses. In this study, we investigated the expression of non-coding RNA upon viral infection or RLR activation. Using a microarray, we identified several microRNAs (miRNA) specifically induced to express by RLR signaling. As suggested by Bioinformatics (miRBase Target Data base), one of the RLR-inducible miRNAs, miR-23b, actually knocked down the expression of very low density lipoprotein receptor (VLDLR) and LDLR-related protein 5 (LRP5). Transfection of miR-23b specifically inhibited infection of rhinovirus 1B (RV1B), which utilizes the low density lipoprotein receptor (LDLR) family for viral entry. Conversely, introduction of anti-miRNA-23b enhanced the viral yield. Knockdown experiments using small interfering RNA (siRNA) revealed that VLDLR, but not LRP5, is critical for an efficient infection by RV1B. Furthermore, experiments with the transfection of infectious viral RNA revealed that miR-23b did not affect post-entry viral replication. Our results strongly suggest that RIG-I signaling results in the inhibitions of infections of RV1B through the miR-23b-mediated down-regulation of its receptor VLDLR.

RNA adenosine deaminase ADAR1 deficiency leads to increased activation of protein kinase PKR and reduced vesicular stomatitis virus growth following interferon treatment

Two size forms of ADAR1 adenosine deaminase are known, one constitutively expressed (p110) and the other interferon (IFN)-induced (p150). To test the role of ADAR1 in viral infection, HeLa cells with ADAR1 stably knocked down and 293 cells overexpressing ADAR1 were utilized. Overexpression of p150 ADAR1 had no significant effect on the yield of vesicular stomatitis virus. Likewise, reduction of p110 and p150 ADAR1 proteins to less than approximately 10 to 15% of parental levels (ADAR1-deficient) had no significant effect on VSV growth in the absence of IFN treatment. However, inhibition of virus growth following IFN treatment was approximately 1 log(10) further reduced compared to ADAR1-sufficient cells. The level of phosphorylated protein kinase PKR was increased in ADAR1-deficient cells compared to ADAR1-sufficient cells following IFN treatment, regardless of viral infection. These results suggest that ADAR1 suppresses activation of PKR and inhibition of VSV growth in response to IFN treatment.

The Role of TRAF2 Binding to the Type I Interferon Receptor in Alternative NFκB Activation and Antiviral Response

Type I interferons (IFNs) play critical roles in the host defense by modulating gene expression through the IFN-dependent activation of STAT and NFkappaB transcription factors. Previous studies established that IFN activates NFkappaB through a classical NFkappaB pathway that results in IkappaBalpha degradation and formation of p50-containing NFkappaB complexes, as well as an alternative pathway that involves NFkappaB-inducing kinase and TRAF2, which results in the formation of p52-containing NFkappaB complexes. In this study, we examined the interaction of TRAF proteins with the type I IFN receptor. We found that TRAF2 was directly coupled to the signal-transducing IFNAR1 subunit of the IFN receptor. By immunoprecipitation, overexpression of epitope-tagged IFNAR1 constructs, and glutathione S-transferase pulldown experiments, we demonstrate that TRAF2 rapidly binds to the IFNAR1 subunit of the IFN receptor upon IFN binding. The membrane proximal half of the IFNAR1 subunit was found to directly bind TRAF2. Moreover, analysis of mouse embryo fibroblasts derived from TRAF2 knock-out mice demonstrated that TRAF2 plays a critical role in the activation of the alternative NFkappaB pathway by IFN, but not the classical NFkappaB pathway, as well as in the antiviral action of IFN. Our results place TRAF2 directly in the signaling pathway transduced through the IFNAR1 subunit of the IFN receptor. These findings provide an important insight into the molecular mechanisms by which IFN generates signals to induce its biological effects.

Matrix protein of Vesicular stomatitis virus harbours a cryptic mitochondrial-targeting motif

Vesicular stomatitis virus (VSV) is a rhabdovirus that has attracted attention of late as an oncolytic virus and as a vaccine vector. Mutations in the matrix (M) gene of VSV yield attenuated strains that may be very useful in both settings. As a result of this interest in the M protein, this study analysed various M-green fluorescent protein (GFP) fusion constructs. Remarkably, fusion of the N terminus of the M protein to GFP targeted the fluorescent protein to the surface of mitochondria. Mutational analysis indicated that a mitochondrial-targeting motif exists within aa 33-67. Expression of these fusion proteins led to loss of mitochondrial membrane permeability and to an alteration in mitochondrial organization mirroring that seen during viral infection. In addition, a portion of the M protein present in infected cells co-purified with mitochondria. This work may indicate a novel function for this multifunctional viral protein.

Effects of thyroid-stimulating hormone on the replicative cycle of vesicular stomatitis virus in primary cultured sheep thyroid cells

Sheep thyroid cells in primary culture are highly sensitive to thyroid stimulating hormone (TSH). We infected thyroid cells with vesicular stomatitis virus (VSV) in the course of studies on cell polarity, and we found that TSH augmented the speed of the replicative cycle of VSV but did not affect the final yield of the virus. Three hours post-infection, at a multiplicity of infection of 10, the virus was detected in the cell layer of the cultures incubated with TSH but not in those without TSH. Five hours post-infection, there was a 100-fold increase in the medium in the yield of VSV and a 60-fold increase in the cell-associated virus in the TSH-treated cells compared with the cells without TSH. We found that the early stages of infection were accelerated by TSH. This effect appears to be due, at least in part, to increased processing in the lysosomes, thus allowing deposition of the transcriptionally-active nucleocapsid into the cytoplasm. These studies show that TSH is critically involved in the infectivity of VSV and that by manipulating cell culture conditions, an increased rate of virus production can be achieved.

Thyroid hormone potentiates the antiviral action of interferon-gamma in cultured human cells.

Human interferon-gamma (hIFN gamma) exhibits a number of biological effects, including antiviral activity in homologous cells. The antiviral activity of recombinant (r) hIFN gamma, estimated by inhibition of vesicular stomatitis virus yield, was potentiated up to 120-fold in human fibroblast (BG-9) cells exposed to free L-T4 (0.5 x 10(-10) mol/L). Thyroid hormone alone did not induce the antiviral state in BG-9 cells. L-T3 also potentiated the antiviral action of rhIFN gamma, but D-T4 and D-T3 were ineffective. The antiviral effect of hIFN alpha in BG-9 cells was not influenced by thyroid hormone. Exposure of rhIFN gamma-treated BG-9 cells to L-T4 for only 3 h was sufficient to potentiate hIFN gamma-mediated antiviral activity. Similar potentiation by L-T4 of the antiviral effect of rhIFN gamma in HeLa cell cultures was also observed. Although the mechanism of potentiation of rhIFN gamma action by thyroid hormone is incompletely understood, the absence of antiviral activity of thyroid hormone alone indicates that the iodothyronine effect does not depend upon hormonal action on genes able to be stimulated by IFN gamma.

Induction of beta interferon by human immunodeficiency virus type 1 and its gp120 protein in human monocytes-macrophages: role of beta interferon in restriction of virus replication

In vitro cultivated human monocytes show a time-dependent differentiation into macrophages, characterized by an increased expression of macrophage-specific antigens. Monocytes-macrophages were infected with human immunodeficiency virus type 1 strain Ba-L (HIV-1Ba-L) at different stages of differentiation. When 7-day cultured macrophages were infected in the presence of antibodies to beta interferon (IFN-beta), a significant increase in HIV-1 p24 release was detected. This effect was not observed in 1-day monocytes. This finding suggests that IFN-beta secreted by the infected macrophages inhibits p24 release. Treatment of cultured macrophages with recombinant gp120 (rgp120) protein resulted in the induction of IFN-beta mRNA and in an antiviral state to vesicular stomatitis virus. This rgp120-induced antiviral state was largely neutralized by antibodies to IFN-beta, whereas anti-IFN-alpha antibodies were ineffective. In cultured macrophages, 0.1 IU of IFN-beta per ml was sufficient to induce a marked inhibition of vesicular stomatitis virus yield, whereas this dose was ineffective in 1-day monocytes. These results indicate that (i) HIV-1 (possibly in part through its gp120 protein) induces low levels of IFN-beta in macrophages and (ii) this IFN-beta is very effective in inducing an antiviral state in differentiated macrophages.

Effects of different biological response modifiers on interferon expression in bacterial lipopolysaccharide (LPS)-responsive and LPS-hyporesponsive mouse peritoneal macrophages

We have previously shown that the antiviral state of explanted mouse peritoneal macrophages (PM) decays during in vitro culture and that this decay is much more rapid in Lpsd PM than it is in Lpsn PM. Moreover, Lpsn PM can transfer the antiviral state to other cells, whereas Lpsd PM cannot. In vitro treatment of Lpsn PM with different agents [i.e., bacterial lipopolysaccharide (LPS), interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha, macrophage colony-stimulating factor (M-CSF) and antibody to Mac-1 antigen] induced an antiviral state to vesicular stomatitis virus (VSV) which was inhibited by antibodies to IFN-beta. Treatment of Lpsn PM with LPS or IFN-gamma resulted in greater accumulation of IFN-beta mRNA, whereas no change in the barely detectable levels of IFN-alpha mRNA was observed. Marked accumulation of IFN-beta mRNA was also observed in PM after TNF-alpha treatment. M-CSF and IFN-gamma (but not LPS) also induced an IFN-mediated antiviral state in Lpsd PM. Low levels of spontaneous transcription of IFN-beta mRNA were detected in nuclei from Lpsd PM. Treatment of Lpsd PM with IFN-gamma for 3 h resulted in the accumulation of IFN-beta mRNA without any concomitant increase in the transcription of the IFN-beta gene, as determined by run-on transcription assays with isolated nuclei. The addition of as little as I international unit/ml of IFN-gamma to PM resulted in a 100-fold inhibition of VSV yield. As antibodies to IFN-alpha/beta inhibited only a portion of the IFN-gamma-induced antiviral state, such an antiviral state might reflect the synergism between IFN-gamma and endogenous IFN-beta. In fact, the addition of low doses of both IFN-gamma and IFN-beta to either Lpsn or Lpsd PM resulted in synergistic antiviral effects. In vivo treatment of Lpsd mice with granulocyte-macrophage (GM)-CSF, M-CSF, IFN-gamma or Newcastle disease virus rendered peritoneal cells capable of transferring an antiviral state. These results indicate that (i) various stimuli can induce IFN-beta production by PM, (ii) Lpsd PM spontaneously transcribe low levels of IFN-beta mRNA, even though they cannot transfer an antiviral state, (iii) different stimuli, but not LPS, induce a normal IFN response in Lpsd PM, (iv) IFN-gamma increases the accumulation of IFN-beta mRNA in Lpsd PM by post-transcriptional mechanisms and (v) IFN-gamma may act synergistically with endogenous IFN-beta in inducing a potent antiviral state to VSV in PM.

Inhibition of Vesicular Stomatitis Virus Replication in Dexamethasone-Treated L929 Cells

We previously demonstrated that dexamethasone treatment of L929 cells inhibited plaque formation by vesicular stomatitis virus (VSV), encephalomyocarditis virus, or vaccinia virus. We now have characterized the antiviral effects of glucocorticoids in L929 cells. Dexamethasone did not directly inactivate VSV nor did steroid treatment of L929 cells affect virion adsorption or penetration. The VSV yield in L929 cells treated with dexamethasone for a period of only 4 or 8 hr was decreased by 50% when cells were infected the day following steroid treatment. Treating L929 cells with dexamethasone for a longer period resulted in greater inhibitions of virus synthesis. Interferon activity (less than 5 units/ml) was not detected in L929 cell culture fluids and cell sonicates from steroid-treated cells and the addition of antiserum to murine alpha/beta-interferon had no effect on the ability of dexamethasone to inhibit VSV replication. Dexamethasone treatment of L929 cells did not induce the production of double-stranded RNA-dependent protein kinase but did result in a slight elevation of 2-5A oligoadenylate synthetase activity, two enzymatic activities associated with the antiviral state induced by interferon. However, the elevated 2-5A synthetase activity was not associated with an inhibition of VSV RNA accumulation in dexamethasone-treated L929 cells. By contrast, the synthesis of all five VSV proteins was reduced by 50-75% in dexamethasone-treated L929 cells as early as 4 hr after infection. Thus, the dexamethasone-mediated inhibition of VSV replication in L929 cells is associated with decreased production of VSV structural proteins.

Effects of prednisone, aspirin, and acetaminophen on an in vivo biologic response to interferon in humans

In healthy volunteers receiving a single intramuscular dose of 18 X 10(6) U interferon alone or after 24 hours of an 8-day course of prednisone (40 mg/day), aspirin (650 mg every 4 hours), or acetaminophen (650 mg every 4 hours), the magnitude of the biologic response to interferon was quantified by measuring the time course of the induction of 2'-5'-oligoadenylate synthetase and resistance to vesicular stomatitis virus infection in human peripheral blood mononuclear cells. Prednisone decreased the AUC of 2'-5'-oligoadenylate synthetase activity (p less than 0.05), whereas administration of aspirin or acetaminophen did not affect this biologic response. No measurable effect was seen during administration of prednisone, aspirin, or acetaminophen on the duration or intensity of vesicular stomatitis virus yield reduction. The side effects seen with interferon administration at the dose tested were not altered in a clinically meaningful manner by prednisone, aspirin, or acetaminophen.

Interferons-α/β- and -γ-Resistant Friend Cell Variants Exhibiting Receptor Sites for Interferons but No Induction of 2-5A Synthetase and 67K Protein Kinase

A number of Friend leukemia cell variants with a interferon-gamma (IFN-gamma)-resistant phenotype have been isolated. They appear resistant to the antiproliferative action of IFN-gamma and to the induction of the antiviral state assessed by Friend leukemia virus release and vesicular stomatitis virus yield. Selection was performed via a prolonged exposure to increasing amounts of highly purified recombinant IFN-gamma of wild-type Friend cells or of variant clones thereof already resistant to IFN-alpha/beta (Affabris et al., 1982, Virology 120, 441-452). Only the clones derived from IFN-alpha/beta-resistant variants showed a phenotype fully resistant to IFN-gamma treatment while keeping their previously acquired resistance to IFN-alpha/beta. These cells are not deficient in high-affinity receptors for IFN-gamma so that their resistant phenotype appears to be mediated by events distal to binding of IFN-gamma to its receptors. Furthermore, analysis of IFN-induced dsRNA-dependent 2-5A synthetase and 67K protein kinase enzymatic activities, biochemical markers for cellular responses to IFN, showed that both these activities were not induced in IFN-alpha/beta and IFN-gamma-resistant clones when treated with either type of IFN. Accordingly, no increased expression of 2-5A synthetase mRNA(s) could be detected by probing poly(A)+-enriched RNA from cells exposed to IFN-alpha/beta or IFN-gamma treatment with murine or human specific cDNAs. On the other hand, no major changes in restriction patterns of 2-5A synthetase gene(s) were observed in these variant cells by restriction endonuclease digestion and Southern blotting. In addition, analysis of 2-5A synthetase mRNA induction, performed on wild-type cells, showed that the kinetic of induction due to IFN-gamma treatment is slower than that obtained with IFN-alpha/beta.

The Target Reaction in the Antiviral Action of Mouse Interferon against Vesicular Stomatitis Virus Multiplication

Treatment of mouse L929 cells with mouse interferon (IFN) lowered the yield of vesicular stomatitis virus (VSV) in a dose-dependent manner. Accumulation of viral proteins was severely inhibited in IFN-treated cells, whereas cellular protein synthesis was not, indicating that the virus-induced shutoff of cellular protein synthesis was prevented by IFN. In order to identify the major target of IFN action precisely, the effect of IFN treatment on the synthesis of viral RNAs and proteins at various stages during the course of viral replication was examined. Accumulation of viral RNAs late in infection was inhibited, as was the case with viral proteins, but the synthesis of leader RNA and mRNAs early in infection was not significantly inhibited by treatment with a moderate dose of IFN. On the other hand, viral protein synthesis at an early stage of infection was strongly inhibited by IFN. The results indicate that the major target reaction of antiviral action of IFN against VSV multiplication is the translation of viral mRNA.

Mechanism of interferon action: inhibition of vesicular stomatitis virus replication in human amnion U cells by cloned human gamma-interferon. I. Effect on early and late stages of the viral multiplication cycle.

The molecular basis of the inhibition of vesicular stomatitis virus (VSV) replication by pure recombinant gamma-interferon (IFN-gamma) in human amnion U cells was examined. A saturating concentration of IFN-gamma induced, at maximum, about a two log10 reduction in infectious VSV yield. The kinetics of induction of the antiviral activity by IFN-gamma were first order over the period of about 6-18 h, following a lag of about 3 h, after treatment with a saturating concentration of IFN-gamma. The relationship of the inhibition in VSV infectivity to the early and late events of the VSV multiplication cycle was investigated. IFN-gamma treatment had no detectable effect on the adsorption and penetration of VSV virions or on their uncoating to yield viral nucleocapsids. The polypeptides of adsorbed or uncoated VSV particles were neither preferentially degraded nor detectably altered in IFN-gamma-treated U cells, as compared to untreated U cells. Progeny virions isolated from IFN-gamma-treated U cells, although greatly reduced in number, were found to be equally as infectious as those isolated from untreated U cells. Progeny virions from IFN-gamma-treated cells also possessed the same composition of viral proteins as was observed for virions from untreated cells. These results suggest that conditions of IFN-gamma treatment sufficient to reduce the yield of infectious VSV progeny 100-fold do not detectably affect either the early or the late stages of the VSV multiplication cycle.

Mechanism of interferon action: inhibition of vesicular stomatitis virus replication in human amnion U cells by cloned human leukocyte interferon. I. Effect on early and late stages of the viral multiplication cycle.

The kinetics of induction in human amnion U cells of the antiviral activity against vesicular stomatitis virus (VSV) produced by a single molecularly cloned subspecies of human leukocyte interferon (IFN-alpha A) were examined. IFN-alpha A-induced inhibition was found to be biphasic over a period of 24 h with the major extent of VSV inhibition occurring within the first 6 h of IFN treatment. The relationship of this major phase of inhibition to the early and late events of the VSV multiplication cycle was investigated. IFN-alpha A treatment had no detectable effect on the adsorption and penetration of VSV virions or on their uncoating to yield viral nucleocapsids. The polypeptides of adsorbed or uncoated VSV particles were neither preferentially degraded nor detectably altered in IFN-treated cells, as compared to untreated cells. Progeny virions released from IFN-treated cells, although greatly reduced in number, were found to be equally as infectious as those released from untreated cells. Progeny virions from IFN-treated cells also had a normal complement of VSV proteins in the same ratios as were seen in virions from untreated cells; specifically, IFN treatment produced no reduction in the incorporation of G or M protein into assembled virions. These results suggest that conditions of IFN treatment sufficient to reduce the yield of infectious VSV progeny greater than 99% do not detectably affect either the early or the late stages of the VSV multiplication cycle.

Role of macrophage oxidative metabolism in resistance to vesicular stomatitis virus infection.

The role of oxygen metabolites in mediating virucidal activity was studied in two cloned macrophage-like cell lines. The parental cell line, J774.16, upon appropriate stimulation with either phorbol myristate acetate (PMA) or aggregated immunoglobulin, is induced to oxidize glucose via the hexose monophosphate shunt and produce O2- and H2O2. A variant derived from it, clone C3C, is defective in oxidative metabolism and cannot be stimulated to produce O2- or H2O2. Significant differences in yields of vesicular stomatitis virus (VSV) between stimulated clone 16 cells and unstimulated cells could be obtained only when low multiplicities were used for infection. Under the same conditions, PMA stimulation of the variant clone C3C produced no reduction in yields. The effect of PMA on virus yields in clone 16 was short-lived and dose dependent. PMA stimulation of either cell line had no effect on the number of infectious centers, suggesting that the antiviral effect was likely to be an extracellular, rather than an intracellular, one. Using glucose oxidase plus aglucose to generate H2O2 in solution, we observed that H2O2 alone is capable of killing limited amounts of VSV. The inactivation of VSV, both by H2O2 in solution and by activated clone 16 cells, could be inhibited by catalase. We conclude that intracellular resistance to VSV is primarily mediated through nonoxidative mechanisms, since activated macrophages can kill only a limited number of infectious virus particles extracellularly by means of secreted H2O2.

Broadly active inhibitor of viruses spontaneously produced by many cell types in culture.

A broadly active inhibitor of viruses (vaccinia, polio 1, and vesicular stomatitis) was found in the culture fluid from many types of normal human and mouse cells in culture. Virus plaque-inhibiting activity appeared in culture fluids within a few hour after incubation of cultures with fresh medium. Peak inhibitory activity occurred within 24 h. Blockade of cellular ribonucleic acid or protein synthesis decreased appearance of the inhibitor, thereby substantiating that it is a cell-produced viral inhibitor. Inhibition of virus required the simultaneous presence of inhibitor, virus, and cells (due to the reversible nature of the inhibition of virus attachment and penetration, as shown in the accompanying paper [T. K. Hughes et al., Infect Immun. 32:454-457, 1981]). The degree of inhibitory activity depended on the animal species of origin of the inhibitor, the cell type used for assay, and the virus type used for challenge. No cell species barrier against inhibitor action was found. Strong inhibition of multicycle yields of vesicular stomatitis virus and Sindbis virus was caused by low doses of inhibitor. These specific characteristics of the present inhibitor separate it from commonly recognized inhibitors. Possible biological significance of the inhibitor is discussed.

The production of high yields of infectious vesicular stomatitis virus in A. albopictus cells and comparisons with replication in BHK-21 cells

Yields of vesicular stomatitis virus (VSV) ranging between 6 × 10 8 and 3 × 10 9 PFU/ml were obtained from a clonally derived line (LT C-7) of A. albopictus cells which has been adapted to Eagle's medium. Both with respect to specific infectivity and PFUIHA ratio, VSV grown in A. albopictus cells (VSV A. albo ) could not be distinguished from virus grown in BHK cells. VSV A. albo however, contained less G and L protein (relative to N) than did VSV BHK. Although relative to the other viral proteins there was also less G protein in lysates of infected mosquito cells than in BHK cells, relative to the other viral messenger RNAs, the G protein mRNA was more abundant in A. albopictus cells than in BHK cells.

Sensitivity of group C arboviruses (bunyaviridae) to human amnion interferon.

The sensitivity of several group C arboviruses (Bunyaviridae) to human amnion interferon was compared to that of vesicular stomatitis virus (VSV) and Sindbis virus. In CPE inhibition assays. Apeu virus was the most sensitive of the group C arboviruses tested; it was significantly more inhibited than VSV, but was in the same range as Sindbis virus. In plaque reduction assays, the increasing order of sensitivity was Apeu, Marituba, VSV and Sindbis viruses. Single-cycle yields of VSV and Apeu virus were reduced to the same extent with 1-10 interferon units; with 230 units, VSV growth was inhibited to a much greater extent (100-fold) than Apeu virus.