EIF3i affects vesicular stomatitis virus growth by interacting with matrix protein

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VSV M protein interacts with the i subunit of eIF3.

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The region of M that interacts with eIF3i is located within the 122- to -181 amino acids.

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M–eIF3i interaction affects VSV growth.

The matrix protein of vesicular stomatitis virus (VSV) performs multiple functions during viral genome replication and virion production and is involved in modulating multiple host signaling pathways that favor virus replication. To perform numerous functions within infected cells, the M protein needs to recruit cellular partners. To better understand the role of M during VSV replication, we looked for interacting partners by using the two-hybrid system. The eukaryotic translation initiation factor 3, subunit i (eIF3i) was identified to be an M-binding partner, and this interaction was validated by GST pull-down and laser confocal assays. Through a mutagenesis analysis, we found that some mutants of M between amino acids 122 and 181 impaired but did not completely abolish the M–eIF3i interaction. Furthermore, the knockdown of eIF3i by RNA interference decreased viral replication and transcription in the early stages but led to increase in later stages. VSV transcription was increased at 4 h post-infection but was not changed at 8 and 12 h post-infection after the over-expression of eIF3i. Finally, we also demonstrated that VSV could inhibit the activity of Akt1 and that the knockdown of eIF3i inhibited the expression of the ISGs regulated by phospho-Akt1. These results indicated that eIF3i may affect VSV growth by regulating the host antiviral response in HeLa cells.

OBTAINING OF THE TRANSGENIC HELIANTHUS TUBEROSUS L. PLANTS, CALLUS AND "HAIRY" ROOT CULTURES ABLE TO EXPRESS THE RECOMBINANT HUMAN INTERFERON ALPHA-2b GENE

This work is the first to our knowledge to describe the successful attempt of Agrobacterium rhizogenes-mediated transformation of topinambour in order to obtain the transgenic H. tuberosus plants, callus and "hairy" root cultures. The plasmid vectors contained the sequence of interferon gene fused with Nicotiana plumbagenifolia L. calreticulin apoplast targeting signal driven by 35S CaMV promoter or root-specific Mll promoter. Nearly 75% isolated Ri-root lines and callus cultures were proved (by PCR analysis) to contain HuINFa-2b transgene. We also managed to obtain H. tuberosus transgenic plants through somatic embryogenesis on the transgenic "hairy" root culture. The obtained transgenic H. tuberosus cultures exhibited high-level antiviral activity that ranged from 2000 to 54500 IU/g FW that makes this crop considered a promising source of recombinant interferon alpha 2b protein.

Cell-Specific Inhibition of Paramyxovirus Maturation by Proteasome Inhibitors

Effects of proteasome inhibitors on the replication of a paramyxovirus in comparison with the effects on replication of an orthomyxovirus and rhabdovirus were investigated. Treatment of Sendai virus (SeV)-infected LLC-MK2 cells with 50 microM MG132 reduced virus growth to ca. 1/10,000, and treatment with different concentrations of MG132 reduced virus growth in a dose-dependent manner. Released amounts of viral proteins were reduced in correspondence with decrease in infectivity. The inhibition of virus maturation was confirmed by an SeV-like particle formation system. Lactacystin also impaired SeV growth and zLL impaired the growth to a lesser extent, suggesting involvement of proteasomes in the restriction of virus growth. In the presence of MG132, localizations of the M protein and viral F and HN glycoproteins on the cell membrane appeared to be partly dissociated, although the viral glycoproteins were normally transported to the cell surface. These results suggest that an early step of SeV assembly was disturbed by proteasome inhibitors. The relationship of the results with ubiquitin is also discussed. SeV maturation was less susceptible and resistant to MG132 in CV1 cells and A549 cells, respectively, indicating cell specificity of the drug effect. Release of vesicular stomatitis virus also showed high susceptibility to MG132 and release of influenza virus A/WSN/33 was only mildly susceptible to the drug in LLC-MK2 cells. Effects of proteasome inhibitors on virus maturation are thus highly cell-specific and partly virus-specific.

[Production of purified human recombinant alpha2b-interferon]

Technology for producing biologically active recombinant alpha2b-interferon is based on creating a bacterial producer strain containing the cDNA of human interferon alpha. The authors have obtained two producers of recombinant alpha2b-interferon, the synthesis of the target protein in them occurs in the inclusion bodies. The schemes of isolation and purification of biologically active recombinant alpha2b-interferon have been developed. The drug purity was approximately 97-98%. Biological activity in the culture of sensory cells in the cytopathic test was 4.2*10(8)ME/mg.

SIRT1 stabilizes PML promoting its sumoylation

SIRT1, the closest mammalian homolog of yeast Sir2, is an NAD(+)-dependent deacetylase with relevant functions in cancer, aging, and metabolism among other processes. SIRT1 has a diffuse nuclear localization but is recruited to the PML nuclear bodies (PML-NBs) after PML upregulation. However, the functions of SIRT1 in the PML-NBs are unknown. In this study we show that primary mouse embryo fibroblasts lacking SIRT1 contain reduced PML protein levels that are increased after reintroduction of SIRT1. In addition, overexpression of SIRT1 in HEK-293 cells increases the amount of PML protein whereas knockdown of SIRT1 reduces the size and number of PML-NBs and the levels of PML protein in HeLa cells. SIRT1 stimulates PML sumoylation in vitro and in vivo in a deacetylase-independent manner. Importantly, the absence of SIRT1 reduces the apoptotic response of vesicular stomatitis virus-infected cells and favors the extent of this PML-sensitive virus replication. These results show a novel function of SIRT1 in the control of PML and PML-NBs.

Suppression of virus replication via down-modulation of mitochondrial short chain enoyl-CoA hydratase in human glioblastoma cells

Several viruses have been demonstrated to be the etiologic agent in chronic progressive diseases, associated with persistence; however, major questions concerning the pathogenic mechanisms of viral persistence are still unanswered. With the aim of identifying host cellular proteins that may play a role in viral replication, we established long-term persistently infected human glioblastoma cell lines with mutant measles virus (MV) and analyzed the host proteins by two-dimensional gel electrophoresis (2-DE) with mass spectrometry. We observed significant down-modulation in the expression of mitochondrial short chain enoyl-CoA hydratase (ECHS), which catalyzes the beta-oxidation pathway of fatty acid. Knockdown of this gene by a short interference RNA (siRNA) apparently impaired wild-type MV replication and the cytopathic effects (CPEs) of MV were significantly reduced in siRNA-transfected cells. These findings will shed light upon a new important notion for the interaction between virus replication and lipid metabolism in host cells and might provide a new strategy for virus control.

Vesicular stomatitis virus vectors expressing avian influenza H5 HA induce cross-neutralizing antibodies and long-term protection

Given the lethality of H5N1 avian influenza viruses (AIV) and the recurring spread from poultry to humans, an effective vaccine against H5N1 viruses may be needed to prevent a pandemic. We generated experimental vaccine vectors based on recombinant vesicular stomatitis virus (VSV) expressing the H5 hemagglutinin (HA) from an H5N1 virus isolated in 1997. The HA gene was expressed either from an attenuated wild-type VSV vector or from a single-cycle vector containing a deletion of the VSV G gene. We found that all of the vectors induced potent neutralizing antibody titers against the homologous and antigenically heterologous H5N1 viruses isolated in 2004 and 2005. Vaccination of mice with any combination of prime or prime/boost vectors provided long-lasting protection (>7 months) against challenge with AIV, even in animals receiving a single dose of single-cycle vaccine. Our data indicate that these recombinants are promising vaccine candidates for pandemic influenza.

Distributions of epistasis in microbes fit predictions from a fitness landscape model

How do the fitness effects of several mutations combine? Despite its simplicity, this question is central to the understanding of multilocus evolution. Epistasis (the interaction between alleles at different loci), especially epistasis for fitness traits such as reproduction and survival, influences evolutionary predictions "almost whenever multilocus genetics matters". Yet very few models have sought to predict epistasis, and none has been empirically tested. Here we show that the distribution of epistasis can be predicted from the distribution of single mutation effects, based on a simple fitness landscape model. We show that this prediction closely matches the empirical measures of epistasis that have been obtained for Escherichia coli and the RNA virus vesicular stomatitis virus. Our results suggest that a simple fitness landscape model may be sufficient to quantitatively capture the complex nature of gene interactions. This model may offer a simple and widely applicable alternative to complex metabolic network models, in particular for making evolutionary predictions.

Vesicular stomatitis viruses resistant to the methylase inhibitor sinefungin upregulate RNA synthesis and reveal mutations that affect mRNA cap methylation

Sinefungin (SIN), a natural S-adenosyl-L-methionine analog produced by Streptomyces griseolus, is a potent inhibitor of methyltransferases. We evaluated the effect of SIN on replication of vesicular stomatitis virus (VSV), a prototype of the nonsegmented negative-strand RNA viruses. The 241-kDa large polymerase (L) protein of VSV methylates viral mRNA cap structures at the guanine-N-7 (G-N-7) and ribose-2'-O (2'-O) positions. By performing transcription reactions in vitro, we show that both methylations are inhibited by SIN and that methylation was more sensitive at the G-N-7 than at 2'-O position. We further show that SIN inhibited growth of VSV in cell culture, reducing viral yield by 50-fold and diminishing plaque size. We isolated eight mutants that were resistant to SIN as judged by their growth characteristics. The SIN-resistant (SINR) viruses contained mutations in the L gene, the promoter for L gene expression provided by the conserved sequence elements of the G-L gene junction and the M gene. Five mutations resulted in amino acid substitutions to conserved regions II/III and VI of the L protein. For each mutant, we examined viral gene expression in cells and cap methylation in vitro. SINR mutants upregulated RNA synthesis in the presence of SIN, which may be responsible for their resistance. We also found that some SINR viruses with L gene mutations were defective in cap methylation in vitro, yet their methylases were less sensitive to SIN inhibition than those of the wild-type parent. These studies show that the VSV methylases are inhibited by SIN, and they define new regions of L protein that affect cap methylation. These studies also provide experimental evidence that inhibition of cap methylases is a potential strategy for development of antiviral therapeutics against nonsegmented negative-strand RNA viruses.

Sulfated homologues of heparin inhibit hepatitis C virus entry into mammalian cells

The mechanism of entry of hepatitis C virus (HCV) through interactions between the envelope glycoproteins and specific cell surface receptors remains unclear at this time. We have previously shown with the vesicular stomatitis virus (VSV)/HCV pseudotype model that the hypervariable region 1 of the HCV E2 envelope glycoprotein helps in binding with glycosaminoglycans present on the cell surface. In this study, we have examined the binding of HCV envelope glycoproteins with chemically modified derivatives of heparin. Furthermore, we have determined the functional relevance of the interaction of heparin derivatives with HCV envelope glycoproteins for infectivity by using a human immunodeficiency virus (HIV)/HCV pseudotype, a VSV/HCV pseudotype, and cell culture-grown HCV genotype 1a. Taken together, our results suggest that the HCV envelope glycoproteins rely upon O-sulfated esters of a heparin homologue to facilitate entry into mammalian cells.

Synergistic attenuation of vesicular stomatitis virus by combination of specific G gene truncations and N gene translocations

A variety of rational approaches to attenuate growth and virulence of vesicular stomatitis virus (VSV) have been described previously. These include gene shuffling, truncation of the cytoplasmic tail of the G protein, and generation of noncytopathic M gene mutants. When separately introduced into recombinant VSV (rVSV), these mutations gave rise to viruses distinguished from their "wild-type" progenitor by diminished reproductive capacity in cell culture and/or reduced cytopathology and decreased pathogenicity in vivo. However, histopathology data from an exploratory nonhuman primate neurovirulence study indicated that some of these attenuated viruses could still cause significant levels of neurological injury. In this study, additional attenuated rVSV variants were generated by combination of the above-named three distinct classes of mutation. The resulting combination mutants were characterized by plaque size and growth kinetics in cell culture, and virulence was assessed by determination of the intracranial (IC) 50% lethal dose (LD(50)) in mice. Compared to virus having only one type of attenuating mutation, all of the mutation combinations examined gave rise to virus with smaller plaque phenotypes, delayed growth kinetics, and 10- to 500-fold-lower peak titers in cell culture. A similar pattern of attenuation was also observed following IC inoculation of mice, where differences in LD(50) of many orders of magnitude between viruses containing one and two types of attenuating mutation were sometimes seen. The results show synergistic rather than cumulative increases in attenuation and demonstrate a new approach to the attenuation of VSV and possibly other viruses.

Antiviral activity and RNA polymerase degradation following Hsp90 inhibition in a range of negative strand viruses

We have analyzed the effectiveness of Hsp90 inhibitors in blocking the replication of negative-strand RNA viruses. In cells infected with the prototype negative strand virus vesicular stomatitis virus (VSV), inhibiting Hsp90 activity reduced viral replication in cells infected at both high and low multiplicities of infection. This inhibition was observed using two Hsp90 inhibitors geldanamycin and radicicol. Silencing of Hsp90 expression using siRNA also reduced viral replication. Hsp90 inhibition changed the half-life of newly synthesized L protein (the large subunit of the VSV polymerase) from >1 h to less than 20 min without affecting the stability of other VSV proteins. Both the inhibition of viral replication and the destabilization of the viral L protein were seen when either geldanamycin or radicicol was added to cells infected with paramyxoviruses SV5, HPIV-2, HPIV-3, or SV41, or to cells infected with the La Crosse bunyavirus. Based on these results, we propose that Hsp90 is a host factor that is important for the replication of many negative strand viruses.

Analysis of CD8+ T cell-mediated anti-viral responses in mice with targeted deletions of the M1 or M5 muscarinic cholinergic receptors

A number of studies have demonstrated that non-neuronal acetylcholine can play a role in the regulation of T cell function. Recently, we reported that CD8(+) T cells, from mice with a targeted deletion of the M(1) muscarinic receptor, had a defect in differentiating into cytolytic T lymphocytes when stimulated in vitro. In the current report, we analyze the in vivo function of CD8(+) T cells from mice with targeted deletions of either M(1) or M(5) muscarinic receptors. M(1) or M(5) knockout mice were infected with either lymphocytic choriomeningitis virus or vesicular stomatitis virus. Expansion of anti-viral CD8(+) T cells was monitored by staining with tetramer reagents specific for the immunodominant peptides of the viruses. No defect in expansion of CD8(+) T cells was observed in either M(1) or M(5) knockout mice. The extent to which one can draw a generalized conclusion that M(1) and M(5) are not involved in anti-viral immunity depends upon issues of antigen strength, genetic background, induction of redundant receptors, and the potential for qualitative defects in the expanded CD8(+) T cells.

A quantitative comet assay: imaging and analysis of virus plaques formed with a liquid overlay

Although the plaque assay defines a "gold-standard" for measuring virus infectivity, its reliance on plaque counting limits its sensitivity. When the assay is performed with a liquid overlay, instead of agar overlay, spontaneous flows can promote a uni-directional spread of infection, creating elongated regions of cytopathology that resemble comets. As a model system comet and plaque cultures of vesicular stomatitis virus (VSV) on baby hamster kidney (BHK-21) cells were compared. Host-cell monolayers were infected with VSV particles, incubated 15 h in the presence of liquid or agar overlays and stained. VSV formed significantly larger comets than plaques, consistent with a mechanism of flow-enhanced spread. When antiviral drug (5-fluorouracil) was incorporated into the liquid overlay, comet sizes were reduced in a dose-dependent manner. Images of infected monolayers, acquired using a simple digital scanner, enabled a quantification of the inhibitory effect of the drug on infectivity. The resulting measure of drug susceptibility was found to be 18-fold more sensitive than the IC(50) measure attained by the traditional plaque-reduction assay. This quantitative comet assay has the potential to similarly enhance the sensitivity of infection measures for other plaque-forming viruses.

Overproduction of double-stranded RNA in vesicular stomatitis virus-infected cells activates a constitutive cell-type-specific antiviral response

In a companion paper (D. Ostertag, T. M. Hoblitzell-Ostertag, and J. Perrault, J. Virol. 81:492-502, 2007), we provided indirect evidence that cell-type-specific growth restriction of the vesicular stomatitis virus (VSV) polR mutants may be due to enhanced production of double-stranded RNA (dsRNA). We show here that polR growth in mouse L-929 cells was rescued by vaccinia virus coinfection and that sole expression of the vaccinia virus dsRNA-binding E3L protein, via coinfection with an engineered VSV minigenome, also restored polR growth. Expression of dsRNA-binding protein NS1A or NS1B from influenza virus, but not C protein from Sendai virus, which does not bind dsRNA, likewise effected polR rescue. The N-terminal dsRNA-binding domain of NS1A, only 73 amino acids in length, but not a full-size mutant NS1A lacking dsRNA-binding activity, restored polR growth. Both key aspects of polR growth restriction, namely inhibition of genome replication and release of low-infectivity virus particles, were countered by expression of the dsRNA-binding proteins. We tested the effects of overproducing dsRNA in wild-type VSV infections by coinfecting cells with a VSV recombinant expressing the sense strand of the enhanced green fluorescent protein gene (VSV-GFP) and one expressing the antisense strand (VSV-PFG). These coinfections mimicked all aspects of polR restriction, including host range, lack of effect on transcription, reduced virus particle infectivity, and insensitivity to inhibition of host gene transcription or dsRNA-activated protein kinase activity. We conclude that, for some cell types, overproduction of dsRNA during VSV infection triggers an immediate and constitutive host cell antiviral effector response independent of interferon induction or signaling.

Cell-type-specific growth restriction of vesicular stomatitis virus polR mutants is linked to defective viral polymerase function

Vesicular stomatitis virus polR mutants synthesize defective RNA replication products in vitro and display growth restriction in some cultured cells (J. L. Chuang, R. L. Jackson, and J. Perrault, Virology 229:57-67, 1997). We show here that a recombinant virus carrying the polR N protein mutation (R179H) yielded approximately 100-fold- and approximately 40-fold-lower amounts of infectious virus than the wild type in mouse L-929 and rat 3Y1 cells, respectively, but only approximately 3-fold less in hamster BHK cells. Virus genome accumulation was inhibited 6- to 10-fold in restricting cells, but transcription was not affected. No defect in encapsidation of replication products was detected, but virus protein accumulation was reduced two- to threefold in both restricting and nonrestricting cells. polR virus particles released from the latter were 5- to 10-fold less infectious than the wild type but showed no difference in protein composition. Phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF-2alpha) was enhanced approximately 3-fold in polR versus wild-type virus-infected L-929 cells, but neither inhibition of host gene transcription nor inhibition of double-stranded RNA (dsRNA)-activated protein kinase showed significant effects on restriction. Conditioned medium studies revealed no evidence for secretion of antiviral factors from restricting cells. We conclude that the block in polR growth is due to the combined effect of reduced genome replication and lower infectivity of released virus particles and may be due to overproduction of dsRNA. An accompanying paper (D. Ostertag, T. M. Hoblitzell-Ostertag, and J. Perrault, J. Virol. 81:503-513, 2007) provides compelling evidence for the role of dsRNA in this unique restriction phenomenon.

The role of the proteasome-ubiquitin pathway in regulation of the IFN-gamma mediated anti-VSV response in neurons

Pharmacologic inhibition of the proteasome resulted in increased NOS-1 protein levels and increased NO production by neuronal cells. This correlated with an increased antiviral effect of IFN-gamma against the replication of vesicular stomatitis virus (VSV) replication in vitro. We also observed that a regulatory protein, Protein Inhibitor of NOS-1 (PIN) was down-regulated by IFN-gamma treatment, and more ubiquitinated PIN accumulated in IFN-gamma treated neurons. In cells of the reticuloendothelial system, IFN-gamma treatment induces the expression of a set of low molecular weight MHC-encoded proteins (LMPs), which replace the beta-subunit of the proteasome complex during the proteasome neosynthesis, resulting in a complex termed the immunoproteasome. LMP2, -7, and -10 were induced and the immunoproteasome was generated by IFN-gamma treatment in neuronal cells. Importantly, we observed that IFN-gamma induced inhibition of VSV protein synthesis was not dependent on ubiquitination.

Evaluation of immunological paradigms in a virus model: are dendritic cells critical for antiviral immunity and viral clearance?

We have examined the role of dendritic cells (DCs) in the antiviral immune response and viral clearance using a transgenic mouse model (CD11c-diphtheria toxin (DT) receptor GFP) that allows for their conditional ablation in vivo. DT administration systemically ablated conventional and IFN-producing plasmacytoid DCs (pDCs) in transgenic, but not nontransgenic littermates, without elimination of splenic macrophages. Unexpectedly, early (12 and 48 h postinfection) viral clearance of vesicular stomatitis virus was normal in DC-depleted mice despite markedly reduced serum titers of type I IFN. DC-depleted mice remained virus-free with the exception of a subset (approximately 30%) that developed overwhelming and fatal brain infections 6 days postinfection. However, DT treatment profoundly inhibited clonal expansion of naive CD8+ vesicular stomatitis virus-specific T cells without altering the primary Th1 and Th2 cytokine response. Optimal clonal expansion required pDCs because selective elimination of these cells in vivo with a depleting Ab also suppressed expansion of tetramer+ cells, although Th1/Th2 cytokine production remained unaltered. Collectively, these data indicate that conventional DCs and to a lesser extent pDCs are critical for proliferation of naive antiviral T cells. However, other components of the primary adaptive immune response (Th1/Th2 cytokines) are essentially normal in the absence of DCs, which may account for the efficient viral clearance seen in DC-depleted mice. Thus, sufficient redundancy exists in the immune system to sustain efficient viral clearance despite loss of an APC considered essential for induction of a primary antiviral immune response.

Interferon-alpha genes from Bos and Bubalus bubalus

Interferon-a genes were cloned from six breeds of three species of two genera (three Chinese native cattle breeds of yellow cattle, wild yak and HuanHu domestic yak, one European breed of Holstein cow, and two water buffalo breeds of FuAn water buffalo and FuZhong water buffalo) by direct PCR. The PCR products were directly inserted into the expression vector to be sequenced and expressed. Sequence analysis showed that IFN-a genes of six clones were composed of 498 nucleotides, encoding a mature polypeptide with 166 amino acids. Compared with the published BoIFN-a subtypes, the IFN-a gene of Holstein cow had only one point mutation with the BoIFN-aA subtype. The IFN-a gene of yellow cattle was similar to the BoIFN-aD subtype with amino acid identity of 97.0% and may be considered as a new subtype, namely, BoIFN-aD1. The other four IFN-a genes, cloned from wild yak and HuanHu domestic yak, FuAn water buffalo, and FuZhong water buffalo, represented four new subtypes, namely, BoIFN-aI, BoIFN-aJ, BuIFN-a1, and BuIFN-a2, respectively. Each of the six clones was expressed in E. coli with molecular weight of approximately 20 kDa by SDS-PAGE and Western blot analyses. Antiviral activity assays showed that the six recombinant IFN-a (rIFN-a) all exhibited 1,000 times higher antiviral activity in the MDBK/VSV cell line than in the CEF/VSV one. Moreover, the rIFN-as could inhibit infectious bovine rhinotracheitis virus replication in the MDBK cell line using CPE inhibition method. The results suggested that rIFN-as a potential agent for clinical application against virus diseases in cattle industry.

Long-acting interferon-alpha 2a modified with a trimer-structured polyethylene glycol: preparation, in vitro bioactivity, in vivo stability and pharmacokinetics

The proper selection of size and shape for polyethylene glycol (PEG) is one of the most important points in PEGylation technology. Therefore, PEGs of various sizes and shapes have been widely developed to endow specific properties. In this study, a unique, trimer-structured, 43 kDa PEG was conjugated to interferon-alpha 2a (IFN) by forming an amide bond to improve the pharmacokinetic properties and minimize the loss of IFN bioactivity. Mono-PEGylated IFN (PEG(3)-IFN) prepared by utilizing this unique PEG was purified and characterized by cation-exchange chromatography and MALDI-TOF mass spectrometry. The in vitro bioactivity, in vivo stability, and pharmacokinetics of PEG(3)-IFN were examined and compared to those of native IFN. PEG(3)-IFN exhibited comparable in vitro bioactivities to native IFN and an excellent stability of the conjugation linkage in rat serum and various organs following subcutaneous injection. Furthermore, it showed slow absorption and markedly reduced clearance in rats, thereby increasing the biological half-life by about 40-fold compared to that of native IFN. This is the first report on the application of unique, trimer-structured PEG to bioactive proteins. The results suggest that unique, trimer-structured 43 kDa PEG can provide some advantages to improve the pharmacokinetic properties and to maintain the bioactivity of therapeutic proteins in clinical use.

Compatibility of lyotropic liquid crystals with viruses and mammalian cells that support the replication of viruses

We report a study that investigates the biocompatibility of materials that form lyotropic liquid crystals (LCs) with viruses and mammalian cells that support the replication of viruses. This study is focused on aqueous solutions of tetradecyldimethyl-amineoxide (C(14)AO) and decanol (D), or disodium cromoglycate (DSCG; C(23)H(14)O(11)Na(2)), which can form optically birefringent, liquid crystalline phases. The influence of these materials on the ability of vesicular stomatitis virus (VSV) to infect human epitheloid cervical carcinoma (HeLa) cells was examined by two approaches. First, VSV was dispersed in aqueous C(14)AO+ D or DSCG, and then HeLa cells were inoculated by contacting the cells with the aqueous C(14)AO + D or DSCG containing VSV. The infectivity of VSV to the HeLa cells was subsequently determined. Second, VSV was incubated in LC phases of either C(14)AO + D or DSCG for 4 h, and the concentration (titer) of infectious virus in the LC was determined by dilution into cell culture medium and subsequent inoculation of HeLa cells. Using these approaches, we found that the LC containing C(14)AO + D caused inactivation of virus as well as cell death. In contrast, we determined that VSV retained its infectivity in the presence of aqueous DSCG, and that greater than 74-82% of the HeLa cells survived contact with aqueous DSCG (depending on concentration of DSCG). Because VSV maintained its function (and we infer structure) in LCs formed from DSCG, we further explored the influence of the virus on the ordering of the LC. Whereas the LC formed from DSCG was uniformly aligned on surfaces prepared from self-assembled monolayers (SAMs) of HS(CH(2))(11)(OCH(2)CH(2))(4)OH on obliquely deposited films of gold in the absence of VSV, the introduction of 10(7)-10(8) infectious virus particles per milliliter caused the LC to assume a non-uniform orientation and a colorful appearance that was readily distinguished from the uniformly aligned LCs. Control experiments using cell lysates with equivalent protein concentrations but no virus did not perturb the uniform alignment of the LC.

Vesicular stomatitis virus induces apoptosis in the Wong–Kilbourne derivative of the Chang conjunctival cell line

BACKGROUND

Virotherapy represents a novel therapeutic modality for the treatment of malignant diseases. Vesicular stomatitis virus (VSV) has been shown to exert antitumor effect in several tumor types. Since the potential oncolytic activity of VSV has not yet been evaluated in epithelial tumors of the conjunctiva, we set out to investigate the susceptibility of the immortalized Wong-Kilbourne derivative of the Chang conjunctival cell line (WK) to VSV and analyze the role of apoptosis in VSV-mediated induction of cell death.

METHODS

WK cells were infected with VSV at various multiplicities and maintained for different periods of time. VSV-infected cells were analyzed by inverted microscopy for the development of cytopathic effects (CPE). Virus replication was measured by indirect immunofluorescence assay, Western blot analysis and plaque titration. The apoptotic response of the infected cells was quantitated by ELISA detecting the enrichment of nucleosomes in the cytoplasm. Western blot analysis was used to determine the levels of Bcl-2 and Bax proteins.

RESULTS

The WK cell line was highly permissive to VSV replication and was highly susceptible for the CPE of this virus. VSV infection elicited the apoptotic death of WK cells. Mock-infected cells exhibited endogenous expression of Bcl-2 and p21 Bax proteins. VSV infection caused a significant decrease in the expression level of Bcl-2. Moreover, in parallel with a slight decrease in the level of p21 Bax, p18 Bax protein accumulated in VSV-infected WK cells.

CONCLUSIONS

VSV is a powerful inducer of apoptosis in immortalized WK cells. The VSV-mediated alterations in the expressions of Bcl-2 and Bax proteins may play important roles in the apoptotic responses of infected cells and may also sensitize to other apoptotic stimuli. This virus may possess oncolytic activity in epithelial tumors of the conjunctiva.

Prophylactic alpha interferon treatment increases the therapeutic index of oncolytic vesicular stomatitis virus virotherapy for advanced hepatocellular carcinoma in immune-competent rats

Vesicular stomatitis virus (VSV) is a negative-strand RNA virus with intrinsic oncolytic specificity due to substantially attenuated antiviral responses in many tumors. We have recently reported that recombinant VSV vector can be used as an effective oncolytic agent to safely treat multifocal hepatocellular carcinoma (HCC) in the livers of immune-competent rats via hepatic artery infusion. When administered at doses above the maximum tolerated dose (MTD), however, the animals suffered from neurotoxicity and/or acute lethal hepatotoxicity. Since VSV is extremely sensitive to the antiviral actions of alpha/beta interferon (IFN-alpha/beta) in normal cells, we tested if prophylactic treatment with rat IFN-alpha would enhance VSV safety without compromising treatment efficacy in tumor-bearing rats. We found that VSV retained its replication potential in human and rat HCC cells after preincubation with relatively high doses of rat and human IFN-alpha in vitro, and its MTD in tumor-bearing rats treated systemically with rat IFN-alpha at 66 IU/g body weight (BW), equivalent to a human IFN-alpha dose that is currently prescribed for patients with viral hepatitis, was elevated by more than 1/2 log unit. Furthermore, we demonstrate that intratumoral replication of VSV was not attenuated by administration of 66 IU/g BW rat IFN-alpha, as tumor response and survival advantage in VSV-treated rats in the presence or absence of rat IFN-alpha were equivalent. The results suggest that prophylactic rat IFN-alpha treatment elevates the therapeutic index of hepatic arterial VSV therapy for multifocal HCC in rats. Since human IFN-alpha is currently in clinical use, its prophylactic application should be considered in future clinical translational protocols for VSV-mediated oncolytic virotherapy as a novel therapeutic modality in patients with advanced HCC, as well as other types of cancer.

Arrested spread of vesicular stomatitis virus infections in vitro depends on interferon-mediated antiviral activity

A quantitative understanding of the innate immune response will enable its recruitment against emerging, poorly characterized, or weaponized viral pathogens. To gain insights into how the innate responses can limit viral spread, we used quantitative focal infections to study how the spread of recombinant vesicular stomatitis viruses (VSV) on baby hamster kidney (BHK) and delayed brain tumor (DBT) cell monolayers is affected by innate cellular antiviral responses. We observed that rates of infection spread correlated with one-step growth rankings for four ectopic VSV strains: N1, N2, N3, and N4. However, this correlation was lost for M51R, a recombinant VSV mutant that lacks the ability to shut-off host gene expression. In BHK cells, M51R spread at two-thirds the rate of the recombinant control virus, XK3.1, even though their one-step growth was comparable. In DBT cells, M51R infections failed to spread beyond the site of inoculation. Addition of anti-interferon antibody restored M51R spread and one-step growth to wild-type levels. Interestingly, the antibody enhanced the spread of wild-type virus but not its growth. These results suggest that while the rate of viral spread generally correlates with the rate of viral growth, the induction of cellular antiviral activities can be in some cases, the overriding factor in both spread and growth. In summary, focal infections enabled us to visualize and quantify how viral spread was inhibited by cellular antiviral activities. This study demonstrates a mechanism for quantifying how innate cellular responses can mitigate infection spread in vitro.

RNA interference is an antiviral defence mechanism in Caenorhabditis elegans

RNA interference (RNAi) is an evolutionarily conserved sequence-specific post-transcriptional gene silencing mechanism that is well defined genetically in Caenorhabditis elegans. RNAi has been postulated to function as an adaptive antiviral immune mechanism in the worm, but there is no experimental evidence for this. Part of the limitation is that there are no known natural viral pathogens of C. elegans. Here we describe an infection model in C. elegans using the mammalian pathogen vesicular stomatitis virus (VSV) to study the role of RNAi in antiviral immunity. VSV infection is potentiated in cells derived from RNAi-defective worm mutants (rde-1; rde-4), leading to the production of infectious progeny virus, and is inhibited in mutants with an enhanced RNAi response (rrf-3; eri-1). Because the RNAi response occurs in the absence of exogenously added VSV small interfering RNAs, these results show that RNAi is activated during VSV infection and that RNAi is a genuine antiviral immune defence mechanism in the worm.

Pseudotypes of vesicular stomatitis virus with CD4 formed by clustering of membrane microdomains during budding

Many plasma membrane components are organized into detergent-resistant membrane microdomains referred to as lipid rafts. However, there is much less information about the organization of membrane components into microdomains outside of lipid rafts. Furthermore, there are few approaches to determine whether different membrane components are colocalized in microdomains as small as lipid rafts. We have previously described a new method of determining the extent of organization of proteins into membrane microdomains by analyzing the distribution of pairwise distances between immunogold particles in immunoelectron micrographs. We used this method to analyze the microdomains involved in the incorporation of the T-cell antigen CD4 into the envelope of vesicular stomatitis virus (VSV). In cells infected with a recombinant virus that expresses CD4 from the viral genome, both CD4 and the VSV envelope glycoprotein (G protein) were found in detergent-soluble (nonraft) membrane fractions. However, analysis of the distribution of CD4 and G protein in plasma membranes by immunoelectron microscopy showed that both were organized into membrane microdomains of similar sizes, approximately 100 to 150 nm. In regions of plasma membrane outside of virus budding sites, CD4 and G protein were present in separate membrane microdomains, as shown by double-label immunoelectron microscopy data. However, virus budding occurred from membrane microdomains that contained both G protein and CD4, and extended to approximately 300 nm, indicating that VSV pseudotype formation with CD4 occurs by clustering of G protein- and CD4-containing microdomains.

Use of influenza C virus glycoprotein HEF for generation of vesicular stomatitis virus pseudotypes

Influenza C virus contains two envelope glycoproteins: CM2, a putative ion channel protein; and HEF, a unique multifunctional protein that performs receptor-binding, receptor-destroying and fusion activities. Here, it is demonstrated that expression of HEF is sufficient to pseudotype replication-incompetent vesicular stomatitis virus (VSV) that lacks the VSV glycoprotein (G) gene. The pseudotyped virus showed characteristic features of influenza C virus with respect to proteolytic activation, receptor usage and cell tropism. Chimeric glycoproteins composed of HEF ectodomain and VSV-G C-terminal domains were efficiently incorporated into VSV particles and showed receptor-binding and receptor-destroying activities but, unlike authentic HEF, did not mediate efficient infection, probably because of impaired fusion activity. HEF-pseudotyped VSV efficiently infected polarized Madin-Darby canine kidney cells via the apical plasma membrane, whereas entry of VSV-G-complemented virus was restricted to the basolateral membrane. These findings suggest that pseudotyping of viral vectors with HEF might be useful for efficient apical gene transfer into polarized epithelial cells and for targeting cells that express 9-O-acetylated sialic acids.

Vector competence of Culicoides sonorensis (Diptera: Ceratopogonidae) for vesicular stomatitis virus

To determine the vector competence of Culicoides sonorensis Wirth & Jones midges for vesicular stomatitis virus (VSV)-New Jersey, insects were experimentally infected per os and sampled over time. Viral replication, as determined by in situ hybridization, was seen in epithelial, neural, and hemolymph cell types throughout the insect. Spatial and temporal distribution of virus was determined by immunohistochemical examination of sequentially sampled insects. Tissues of the alimentary canal were infected in a temporal pattern that paralleled the route of digestion/absorption: foregut and midgut by day 1, surrounding hemolymph and Malpighian tubules by day 3, and finally the midgut/ hindgut junction, hindgut, and rectal region by day 5. The circulation of virus in the hemolymph by day 3 coincided with infection of the dermis and fat bodies, the salivary glands, eyes, cerebral and subthoracic ganglia, and the ovaries. Oviduct epithelium and ovarial sheaths were infected by day 3, followed by infection of the developing oocytes by day 5. Interestingly, neural infections were seen in the subabdominal ganglia innervating the midgut in 33% of insects by 1 d postfeeding in the absence of positive staining in the hemolymph or surrounding tissues. A retrograde axonal transport infection route for these ganglia is discussed. The disseminated, productive, noncytolytic infection in Culicoides is consistent with that of an efficient biological vector for VSV. Virus readily replicated throughout the insect, passing both midgut and salivary gland infection barriers and reaching transmission-related organs in 3 d. Establishing the competence of this insect vector for VSV provides the foundation for animal transmission studies in the future. The possibility of horizontal, transovarial, and mechanical transmission is discussed.

Dual mechanisms of pestiviral superinfection exclusion at entry and RNA replication

For many viruses, primary infection has been shown to prevent superinfection by a homologous second virus. In this study, we investigated superinfection exclusion of bovine viral diarrhea virus (BVDV), a positive-sense RNA pestivirus. Cells acutely infected with BVDV were protected from superinfection by homologous BVDV but not with heterologous vesicular stomatitis virus. Superinfection exclusion was established within 30 to 60 min but was lost upon passaging of persistently infected cells. Superinfecting BVDV failed to deliver a translatable genome into acutely infected cells, indicating a block in viral entry. Deletion of structural protein E2 from primary infecting BVDV abolished this exclusion. Bypassing the entry block by RNA transfection revealed a second block at the level of replication but not translation. This exclusion did not require structural protein expression and was inversely correlated with the level of primary BVDV RNA replication. These findings suggest dual mechanisms of pestivirus superinfection exclusion, one at the level of viral entry that requires viral glycoprotein E2 and a second at the level of viral RNA replication.

Following the very initial growth of biological RNA viral clones

Due to their extremely high genetic diversity, which is a direct consequence of high mutation rates, RNA viruses are often described as molecular quasispecies. According to this theory, RNA virus populations cannot be understood in terms of individual viral clones, as they are clouds of interconnected mutants, but this prediction has not yet been demonstrated experimentally. The goal of this study was to determine the fitness of individual clones sampled from a given RNA virus population, a necessary previous step to test the above prediction. To do so, limiting dilutions of a vesicular stomatitis virus population were employed to isolate single viral clones and their initial growth dynamics were followed, corresponding to the release of the first few hundred viral particles. This technique is useful for estimating basic fitness parameters, such as intracellular growth rate, viral yield per cell, rate at which cells are infected and time spent in cell-to-cell transmission. A combination of these parameters allows estimation of the fitness of individual clones, which seems to be determined mainly by their ability to complete infection cycles more quickly. Interestingly, fitness was systematically higher for initial clones than for their derived populations. In addition to environmental changes, such as cellular defence mechanisms, these differences are attributable to high RNA virus mutation rates.

Functional analysis of late-budding domain activity associated with the PSAP motif within the vesicular stomatitis virus M protein

A PPPY motif within the M protein of vesicular stomatitis virus (VSV) functions as a late-budding domain (L-domain); however, L-domain activity has yet to be associated with a downstream PSAP motif. VSV recombinants with mutations in the PPPY and/or PSAP motif were recovered by reverse genetics and examined for growth kinetics, plaque size, and budding efficiency by electron microscopy. Results indicate that unlike the PPPY motif, the PSAP motif alone does not possess L-domain activity. Finally, the insertion of the human immunodeficiency virus type 1 p6 L-domain and flanking sequences into the PSAP region of M protein rescued budding of a PPPY mutant of VSV to wild-type levels.

Phosphorylation of vesicular stomatitis virus phosphoprotein P is indispensable for virus growth

The phosphoprotein (P) of vesicular stomatitis virus (VSV) is an essential subunit of the viral RNA-dependent RNA polymerase (RdRp) complex. It is phosphorylated at two different domains. Using defective interfering (DI) RNA or minigenomic RNA templates, we previously demonstrated that phosphorylation within the amino-terminal domain I is essential for transcription, whereas phosphorylation within the carboxy-terminal domain II is necessary for replication. For the present study, we examined the role of the phosphorylation of residues in these domains in the life cycle of VSV. Various mutant P coding sequences were inserted into a full-length cDNA clone of VSV, and the virus recovery, kinetics of growth, and mRNA and protein synthesis were examined. We observed that virus recovery was completely abolished when all three phosphate acceptor sites in domain I or both sites in domain II were replaced with alanine. Single or double mutations in domain I (with the exception of P60/64) or single mutations in domain II had no adverse effect on virus recovery. VSVP227, carrying alanine at position 227, showed reduced kinetics of virus growth but increased kinetics of viral mRNA synthesis in infected cells. More interestingly, this particular virus exhibited a significantly reduced cytopathic effects and apoptosis in infected cells, implying that P may be involved in these processes. Furthermore, we found that DI RNAs of different sizes were generated by high-multiplicity passaging of various mutant VSVs, indicating that the viral RdRp may play a significant role in the process of DI particle generation. Taken together, our results suggest that the phosphorylation of residues in domains I and II of VSV P is indispensable for virus growth.

Budding of PPxY-containing rhabdoviruses is not dependent on host proteins TGS101 and VPS4A

Viral matrix proteins of several enveloped RNA viruses play important roles in virus assembly and budding and are by themselves able to bud from the cell surface in the form of lipid-enveloped, virus-like particles (VLPs). Three motifs (PT/SAP, PPxY, and YxxL) have been identified as late budding domains (L-domains) responsible for efficient budding. L-domains can functionally interact with cellular proteins involved in vacuolar sorting (VPS4A and TSG101) and endocytic pathways (Nedd4), suggesting involvement of these pathways in virus budding. Ebola virus VP40 has overlapping PTAP and PPEY motifs, which can functionally interact with TSG101 and Nedd4, respectively. As for vesicular stomatitis virus (VSV), a PPPY motif within M protein can interact with Nedd4. In addition, M protein has a PSAP sequence downstream of the PPPY motif, but the function of PSAP in budding is not clear. In this study, we compared L-domain functions between Ebola virus and VSV by constructing a chimeric M protein (M40), in which the PPPY motif of VSV M is replaced by the L domains of VP40. The budding efficiency of M40 was 10-fold higher than that of wild-type (wt) M protein. Overexpression of a dominant negative mutant of VPS4A or depletion of cellular TSG101 reduced the budding of only M40-containing VLPs but not that of wt M VLPs or live VSV. These findings suggest that the PSAP motif of M protein is not critical for budding and that there are fundamental differences between PTAP-containing viruses (Ebola virus and human immunodeficiency virus type 1) and PPPY-containing viruses (VSV and rabies virus) regarding their dependence on specific host factors for efficient budding.

Block of vesicular stomatitis virus endocytic and exocytic pathways by 1-cinnamoyl-3,11-dihydroxymeliacarpin, a tetranortriterpenoid of natural origin

Previously, it has been shown that 1-cinnamoyl-3,11-dihydroxymeliacarpin (CDM), a natural compound isolated from leaf extracts ofMelia azedarachL., inhibits the vesicular stomatitis virus (VSV) multiplication cycle when added before or after infection. Here, we have established that the lack of VSV protein synthesis in CDM pre-treated Vero cells is ascribed to the inhibition of an initial step during virus multiplication, although indirect immunofluorescence (IFI) studies confirmed that the binding and uptake of [35S]methionine-labelled VSV was not affected by CDM pre-treatment. Instead, our findings revealed that this compound impedes the uncoating of VSV nucleocapsids in pre-treated Vero cells, since the antiviral action of CDM was partially reversed by inducing VSV direct fusion at the plasma membrane, and VSV M protein fluorescence was confined to the endosomes, even 2 h post-internalization. Furthermore, CDM induced cytoplasmic alkalinization, as shown by acridine orange staining, consistent with the inhibition of virus uncoating. Although VSV proteins are synthesized when CDM is added after infection, IFI studies revealed that G protein was absent from the surface of infected cells and co-localized with a Golgi marker. Therefore, CDM inhibits the transport of G protein to the plasma membrane. Taken together, these findings indicate that CDM exerts its antiviral action on the endocytic and exocytic pathways of VSV by pre- or post-treatment, respectively.

Mannosyl glycodendritic structure inhibits DC-SIGN-mediated Ebola virus infection in cis and in trans

We have designed a glycodendritic structure, BH30sucMan, that blocks the interaction between dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) and Ebola virus (EBOV) envelope. BH30sucMan inhibits DC-SIGN-mediated EBOV infection at nanomolar concentrations. BH30sucMan may counteract important steps of the infective process of EBOV and, potentially, of microorganisms shown to exploit DC-SIGN for cell entry and infection.

Grasshoppers (Orthoptera: Acrididae) could serve as reservoirs and vectors of vesicular stomatitis virus

Vesicular stomatitis (VS) is an economically devastating disease of livestock in the Americas. Despite strong circumstantial evidence for the role of arthropods in epizootics, no hematophagous vector explains the field evidence. Based on the spatiotemporal association of grasshopper outbreaks and VS epizootics, we investigated the potential role of these insects as vectors and reservoirs of the disease. The critical steps in the grasshopper-bovine transmission cycle were demonstrated, including 1) 62% of grasshoppers [Melanoplus sanguinipes (F.)] fed vesicular stomatitis virus (VSV) from cell culture became infected, with titers reaching 40,000 times the inoculative dose; 2) 40% of grasshoppers that cannibalized VSV-infected grasshopper cadavers became infected, amplifying virus up to 1,000-fold; 3) one of three cattle consuming VSV-infected grasshopper cadavers contracted typical VS and shed virus in saliva; and 4) 15% of grasshoppers became infected when fed saliva from this infected cow. The ecological conditions and biological processes necessary for these transmissions to occur are present throughout much of the Americas. Field studies will be required to show these findings are relevant to the natural epidemiology of VSV.

Vesicular stomatitis virus infection and neuropathogenesis in the murine model are associated with apoptosis

This study examines apoptosis and viral neuropathogenesis in a murine model infected with vesicular stomatitis virus (VSV). VSV induces apoptotic cell death in cultured cell lines, raising the possibility that apoptosis of infected neurons and other target cells may contribute to disease and mortality. To determine whether or not VSV induces apoptosis in neural tissues, mice were inoculated intranasally with VSV. At 24, 48, 72, 96, and 120 hours postinfection, brain tissues were assayed for the presence of viral RNA by in situ hybridization and viral antigen by immunohistochemistry. Apoptosis was identified by in situ terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling and electron microscopy. Viral replication and lesions were observed predominantly in central nervous system neurons. Apoptotic cell death was restricted to the same regions of the brain in which infected cells and tissue injury were identified. Results suggest that VSV-induced apoptosis is a mechanism causing cell death, tissue injury, and mortality in VSV-infected mice.

Serum Interferon Inhibitor Declines in Patients with HIV‐1 Infection After a Change in Antiretroviral Therapy

An inhibitor of interferon antiviral activity, which is absent in healthy HIV-seronegative persons, was detected in the sera of all 29 HIV-seropositive study participants. The relationship of the level of interferon inhibitor to CD4 count and HIV-RNA copy number was statistically significant in distinct models. Levels of interferon inhibitor declined by an average of 41-60% in patients who underwent a change in anti-retroviral therapy. Interferon inhibitor levels appear to decline as CD4 cell count rises and HIV-RNA levels fall. This suggests that interferon inhibitor may have a significant role in the host immune response to HIV infection.

Organization of the vesicular stomatitis virus glycoprotein into membrane microdomains occurs independently of intracellular viral components

The glycoprotein (G protein) of vesicular stomatitis virus (VSV) is primarily organized in plasma membranes of infected cells into membrane microdomains with diameters of 100 to 150 nm, with smaller amounts organized into microdomains of larger sizes. This organization has been observed in areas of the infected-cell plasma membrane that are outside of virus budding sites as well as in the envelopes of budding virions. These observations raise the question of whether the intracellular virion components play a role in organizing the G protein into membrane microdomains. Immunogold-labeling electron microscopy was used to analyze the distribution of the G protein in arbitrarily chosen areas of plasma membranes of transfected cells that expressed the G protein in the absence of other viral components. Similar to the results with virus-infected cells, the G protein was organized predominantly into membrane microdomains with diameters of approximately 100 to 150 nm. These results indicate that internal virion components are not required to concentrate the G protein into membrane microdomains with a density similar to that of virus envelopes. To determine if interactions between the G protein cytoplasmic domain and internal virion components were required to create a virus budding site, cells infected with recombinant VSVs encoding truncation mutations of the G protein cytoplasmic domain were analyzed by immunogold-labeling electron microscopy. Deletion of the cytoplasmic domain of the G protein did not alter its partitioning into the 100- to 150-nm microdomains, nor did it affect the incorporation of the G protein into virus envelopes. These data support a model for virus assembly in which the G protein has the inherent property of partitioning into membrane microdomains that then serve as the sites of assembly of internal virion components.

Propagation of viruses on micropatterned host cells

We have developed a technique to characterize the in vitro propagation of viruses. Microcontact printing was used to generate linear arrays of alkanethiols on gold surfaces, which served as substrates for the patterned culture of baby hamster kidney (BHK-21) cells. Vesicular stomatitis virus (VSV) was added to unpatterned cell reservoirs adjacent to the patterned cells and incubated, setting in motion a continuously advancing viral infection into the patterned cells. At different incubation times, multiple arrays were chemically fixed to stop the viral propagation. Viral propagation distances into the patterned cells were determined by indirect immunofluorescent labeling and visualization of the VSV surface glycoprotein (G). The infection spread at approximately 50 microm/h in the 140-microm lines. Moreover, different temporal stages of the infection process were simultaneously visualized along individual lines. These stages included initiation of infection, based on G protein expression; cell-cell fusion, based on virus-induced clustering of cell nuclei; and cytoskeletal degradation, based on localized release of cells from the surface. This work sets a foundation for parallel, high-throughput characterization of viral and cellular processes.

Polymorphisms and the antiviral property of porcine Mx1 protein

We determined the cDNA sequences of the type I interferon-inducible proteins, pig Mx1 from PK(15) and LLC-PK1 cells, and compared the antiviral activities of both Mx proteins, including Mx1 polymorphisms against vesicular stomatitis virus (VSV). Mx1 cDNA derived from PK(15) cells had an 11 bp-deletion in the 3' end of the coding region, and was estimated to encode 8 amino acid substitutions and a 23 amino acid extension compared to that from LLC-PK1 cells. VSV replication was inhibited in the 3T3 cells expressing Mx1 mRNA after the cDNA was transfected. However, the efficiency of this inhibition was not different between the cells expressing Mx1 mRNA from both PK and LLC. These results indicate that pig Mx1 protein confers resistance to VSV.

IL-12, while beneficial, is not essential for the host response to VSV encephalitis

In this report, the role of STAT4 and local production of interleukin (IL)-12 in the central nervous system (CNS) were examined during experimental vesicular stomatitis virus (VSV) encephalitis. We have previously shown that IL-12 treatment is beneficial both in vitro and in vivo during experimental VSV infection. This inhibition of VSV replication was dependent on the production of nitric oxide (NO) by the neuronal isoform of nitric oxide synthase (NOS-1). In vitro, IL-12 induces the phosphorylation and nuclear localization of STAT4 in neuroblastoma cell lines. STAT4 expression was not required for host survival or clearance of virus during experimental VSV encephalitis. Taken together, these data suggest that while neurons can respond directly to IL-12 in vitro by signaling through STAT4, STAT4 is not required for survival. It is likely that redundant innate host inflammatory cytokine responses compensate for the absence of IL-12 signaling.

Site-specific lipophilic modification of interferon-alpha

Interferon-alpha (IFNalpha), a cytokine with modulatory activities on many cell types, is useful for treating many types of cancer and infectious diseases. This study investigates whether modification of a protein, using IFNalpha as an example, with a lipophilic group can alter its distribution and kinetic properties in the body. Ser163 of IFNalpha2a was mutated to Cys to generate a free sulfhydryl group for site-specific chemical modification. IFNalpha2a(S163C) was conjugated by iodoacetamide derivatives of varying lengths, and the modified IFNalpha2a was purified by gel filtration chromatography. The biological activities of IFNalpha2a(S163C) and lipophilized IFNalpha2a(S163C) were similar to that of IFNalpha2a, as evidenced by their inhibitory effects on the growth of Daudi cells and on the replication of vesicular stomatitis virus in Madin-Darby bovine kidney cells. Lipophilized IFNalpha2a(S163C) bound to human serum albumin and cell membranes more readily than did IFNalpha2a. Future experiments will investigate whether lipophilized IFNalpha2a(S163C) has improved pharmacokinetic properties.

The importance of lytic and nonlytic immune responses in viral infections

Antiviral immune effector mechanisms can be divided broadly into lytic and nonlytic components. We use mathematical models to investigate the fundamental question of which type of response is required to combat different types of viral infection. According to our model, the relative roles of the two types of component depend on the cytopathicity of the virus relative to its rate of replication. If the viral cytopathicity is low relative to the rate of viral replication, the model predicts that a combination of lytic and nonlytic effector mechanisms is likely to be required to resolve the disease, particularly if the virus replicates at a fast rate. By contrast, if viral cytopathicity is high relative to the replication rate of the virus, then lytic and nonlytic mechanisms can, in principle, resolve the infection independently. We discuss our findings in the context of specific viral infections and use our model to interpret empirical data.

Polymorphisms and the differential antiviral activity of the chicken Mx gene

The nucleotide sequence of chicken Mx cDNA was reported earlier using the White Leghorn breed in Germany, but it showed no enhanced resistance to viruses. In this study, the nucleotide sequences of chicken Mx cDNA were determined in many breeds. A total of 25 nucleotide substitutions, of which 14 were deduced to cause amino acid exchanges, were detected, suggesting that the chicken Mx gene is very polymorphic. Transfected cell clones expressing chicken Mx mRNA were established after the Mx cDNA was constructed with an expression vector and introduced into mouse 3T3 cells, and the Mx genes from some breeds were demonstrated to confer positive antiviral responses to influenza virus and vesicular stomatitis virus. On the basis of the comparison among the antiviral activities associated with many Mx variations, a specific amino acid substitution at position 631 (Ser to Asn) was considered to determine the antivirally positive or negative Mx gene. Thus, a single amino acid substitution influences the antiviral activity of Mx in domesticated chickens.

Virus inactivation in hemoglobin solution by heat treatment

To increase the safety of stroma-free hemoglobin solution (SFH) as an artificial oxygen carrier source, we investigated the effect of heat treatment on virus inactivation in hemoglobin solution. The hemoglobin solution spiked with vesicular stomatitis virus (VSV) was treated at 60 degrees C for 1 hr under either an air or CO atmosphere. VSV was inactivated at >5.8 log10 and >6.0 log10 under the air and CO atmosphere, respectively. Although the methemoglobin rate increased after the heat treatment under the air atmosphere, no methemoglobin formation was observed by the treatment under the CO atmosphere. Isoelectric focusing analysis revealed the denaturation of hemoglobin after the heat treatment under the air, while hemoglobin banding was not altered in the carbonylated condition. Some protein bands other than hemoglobin were weakened or disappeared on SDS-PAGE after the heat treatment under both conditions. In addition, the hemoglobin concentration in the SFH was higher after the heat treatment than before the treatment. These findings indicate that the heat treatment under the CO atmosphere inactivates viruses without hemoglobin denaturation, and hence, this method is a promising approach to prepare a safer SFH as artificial oxygen carriers.

Intracellular chelation of iron by bipyridyl inhibits DNA virus replication: ribonucleotide reductase maturation as a probe of intracellular iron pools

The efficient replication of large DNA viruses requires dNTPs supplied by a viral ribonucleotide reductase. Viral ribonucleotide reductase is an early gene product of both vaccinia and herpes simplex virus. For productive infection, the apoprotein must scavenge iron from the endogenous, labile iron pool(s). The membrane-permeant, intracellular Fe(2+) chelator, 2,2'-bipyridine (bipyridyl, BIP), is known to sequester iron from this pool. We show here that BIP strongly inhibits the replication of both vaccinia and herpes simplex virus, type 1. In a standard plaque assay, 50 microm BIP caused a 50% reduction in plaque-forming units with either virus. Strong inhibition was observed only when BIP was added within 3 h post-infection. This time dependence was observed also in regards to inhibition of viral late protein and DNA synthesis by BIP. BIP did not inhibit the activity of vaccinia ribonucleotide reductase (RR), its synthesis, nor its stability indicating that BIP blocked the activation of the apoprotein. In parallel with its inhibition of vaccinia RR activation, BIP treatment increased the RNA binding activity of the endogenous iron-response protein, IRP1, by 1.9-fold. The data indicate that the diiron prosthetic group in vaccinia RR is assembled from iron taken from the BIP-accessible, labile iron pool that is sampled also by ferritin and the iron-regulated protein found in the cytosol of mammalian cells.

Antiviral activities of the soluble extracellular domains of type I interferon receptors

Alternative splicing leads to the expression of multiple isoforms of the subunits (IFNAR1 and IFNAR2) of the type I IFN receptor. Here we describe two transcripts representing extracellular forms of ovine IFNAR1 and show that soluble extracellular forms of both IFNAR2 and IFNAR1, prepared in recombinant form in Escherichia coli, have antiviral (AV) activity in the absence of IFN. Exposure of Madin-Darby bovine kidney cells to the extracellular domain (R2E) of IFNAR2 at concentrations as low as 10 nM afforded complete protection against vesicular stomatitis virus and led to the rapid activation of the transcription factors ISGF3 and GAF. Although R2E can bind IFN (K(d) approximately 70 nM), activity was observed irrespective of whether or not ligand was present. R2E was inactive on mouse L929 cells but active on L929 cells expressing a membraneanchored, ovine/human chimeric IFNAR2 with an ovine extracellular domain. The data suggest that AV activity is conferred by the ability of soluble R2E to associate with the transfected IFNAR2 subunit rather than resident murine IFNAR1. Soluble extracellular forms of IFNAR1 have lower AV activity than R2E on Madin-Darby bovine kidney cells but are less species-specific and protect wild-type L929 cells as efficiently as the transfected cell line, presumably by interacting with one of the murine receptor subunits.

Study on risk factors for transplacental viral infections; effect of bacterial factors and double viral infections on virus replication in placenta and amniotic membranes

Among risk factors for vertical transmission of HIV there are listed concomitant viral and bacterial infections. Therefore the influence on the viruses replication in human placenta and amniotic membrane cultures of double viral infection with two unrelated viruses - encephalomyocarditis (EMCV) and vesicular stomatitis virus (VSV) - was studied and compared with the replication of the viruses in single virus infection (EMCV or VSV) in the same organ cultures. Additionally effect of bacterial factors - lipopolysaccharide (LPS) Escherichia coli and sonicated Treponema pallidum antigens (Tpa) - on VSV replication in the same culture system was studied and compared with VSV replication in untreated explants. Two effects were observed in double-virus infected cultures and also in bacterial factors treated cultures: inhibition and stimulation of virus replication. The kind of effect in the both cases was dependent on the presence or absence of innate antiviral immunity. In virus-sensitive organs double infected or treated with LPS or Tpa, inhibition of virus titer (2-5 log TCID(50)/ml) was observed. In the organs expressing the innate immunity, stimulation (1-4 log TCID(50)/ml) of virus replication was noticed. Contribution of endogenous TNFalpha in both reactions (stimulation and inhibition) was confirmed using antibodies against the TNF.