Potent in vitro activity of β-D-4'-chloromethyl-2'-deoxy-2'-fluorocytidine against Nipah virus

Nipah virus (NiV) is a highly pathogenic zoonotic paramyxovirus that continues to cause outbreaks in humans characterized by high mortality and significant clinical sequelae in survivors. Currently, no therapeutics are approved for use in humans against NiV infection. Here, we report that 4'-chloromethyl-2'-deoxy-2'-fluorocytidine (ALS-8112) inhibits NiV. ALS-8112 is the parent nucleoside of lumicitabine, which has been evaluated in phase I and II clinical trials to treat pediatric and adult respiratory syncytial virus infection. In this study, we tested ALS-8112 against NiV and other major human respiratory pneumo- and paramyxoviruses in 2 human lung epithelial cell lines, and demonstrated the ability of ALS-8112 to reduce infectious wild-type NiV yield by over 6 orders of magnitude with no apparent cytotoxicity. However, further cytotoxicity testing in primary cells and bone marrow progenitor cells indicated cytotoxicity at higher concentrations of ALS-8112. Our results warrant the evaluation of lumicitabine against NiV infection in relevant animal models.

Interferon-Induced Transmembrane Protein 1 Restricts Replication of Viruses That Enter Cells via the Plasma Membrane

The acute antiviral response is mediated by a family of interferon-stimulated genes (ISGs), providing cell-intrinsic immunity. Mutations in genes encoding these proteins are often associated with increased susceptibility to viral infections. One family of ISGs with antiviral function is the interferon-inducible transmembrane proteins (IFITMs), of which IFITM3 has been studied extensively. In contrast, IFITM1 has not been studied in detail. Since IFITM1 can localize to the plasma membrane, we investigated its function with a range of enveloped viruses thought to infect cells by fusion with the plasma membrane. Overexpression of IFITM1 prevented infection by a number of Paramyxoviridae and Pneumoviridae, including respiratory syncytial virus (RSV), mumps virus, and human metapneumovirus (HMPV). IFITM1 also restricted infection with an enveloped DNA virus that can enter via the plasma membrane, herpes simplex virus 1 (HSV-1). To test the importance of plasma membrane localization for IFITM1 function, we identified blocks of amino acids in the conserved intracellular loop (CIL) domain that altered the subcellular localization of the protein and reduced antiviral activity. By screening reported data sets, 12 rare nonsynonymous single nucleotide polymorphisms (SNPs) were identified in human IFITM1, some of which are in the CIL domain. Using an Ifitm1-/- mouse, we show that RSV infection was more severe, thereby extending the range of viruses restricted in vivo by IFITM proteins and suggesting overall that IFITM1 is broadly antiviral and that this antiviral function is associated with cell surface localization.IMPORTANCE Host susceptibility to viral infection is multifactorial, but early control of viruses not previously encountered is predominantly mediated by the interferon-stimulated gene (ISG) family. There are upwards of 300 of these genes, the majority of which do not have a clearly defined function or mechanism of action. The cellular location of these proteins may have an important effect on their function. One ISG located at the plasma membrane is interferon-inducible transmembrane protein 1 (IFITM1). Here we demonstrate that IFITM1 can inhibit infection with a range of viruses that enter via the plasma membrane. Mutant IFITM1 proteins that were unable to localize to the plasma membrane did not restrict viral infection. We also observed for the first time that IFITM1 plays a role in vivo, and Ifitm1-/- mice were more susceptible to viral lung infection. These data contribute to our understanding of how ISGs prevent viral infections.

4'-Azidocytidine (R1479) inhibits henipaviruses and other paramyxoviruses with high potency

The henipaviruses Nipah virus and Hendra virus are highly pathogenic zoonotic paramyxoviruses which have caused fatal outbreaks of encephalitis and respiratory disease in humans. Despite the availability of a licensed equine Hendra virus vaccine and a neutralizing monoclonal antibody shown to be efficacious against henipavirus infections in non-human primates, there remains no approved therapeutics or vaccines for human use. To explore the possibility of developing small-molecule nucleoside inhibitors against henipaviruses, we evaluated the antiviral activity of 4'-azidocytidine (R1479), a drug previously identified to inhibit flaviviruses, against henipaviruses along with other representative members of the family Paramyxoviridae. We observed similar levels of R1479 antiviral activity across the family, regardless of virus genus. Our brief study expands the documented range of viruses susceptible to R1479, and provides the basis for future investigation and development of 4'-modified nucleoside analogs as potential broad-spectrum antiviral therapeutics across both positive and negative-sense RNA virus families.

In vitro antiviral activity of a series of wild berry fruit extracts against representatives of Picorna-, Orthomyxo- and Paramyxoviridae

Wild berry species are known to exhibit a wide range of pharmacological activities. They have long been traditionally applied for their antiseptic, antimicrobial, cardioprotective and antioxidant properties. The aim of the present study is to reveal the potential for selective antiviral activity of total methanol extracts, as well as that of the anthocyanins and the non-anthocyanins from the following wild berries picked in Bulgaria: strawberry (Fragaria vesca L.) and raspberry (Rubus idaeus L.) of the Rosaceae plant family, and bilberry (Vaccinium myrtillis L.) and lingonberry (Vaccinium vitis-idaea L) of the Ericaceae. The antiviral effect has been tested against viruses that are important human pathogens and for which chemotherapy and/or chemoprophylaxis is indicated, namely poliovirus type 1 (PV-1) and coxsackievirus B1 (CV-B1) from the Picornaviridae virus family, human respiratory syncytial virus A2 (HRSV-A2) from the Paramyxoviridae and influenza virus A/H3N2 of Orthomyxoviridae. Wild berry fruits are freeze-dried and ground, then total methanol extracts are prepared. Further the extracts are fractioned by solid phase extraction and the non-anthocyanin and anthocyanin fractions are eluted. The in vitro antiviral effect is examined by the virus cytopathic effect (CPE) inhibition test. The results reveal that the total extracts of all tested berry fruits inhibit the replication of CV-B1 and influenza A virus. CV-B1 is inhibited to the highest degree by both bilberry and strawberry, as well as by lingonberry total extracts, and influenza A by bilberry and strawberry extracts. Anthocyanin fractions of all wild berries strongly inhibit the replication of influenza virus A/H3N2. Given the obtained results it is concluded that wild berry species are a valuable resource of antiviral substances and the present study should serve as a basis for further detailed research on the matter.

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.

Efficacy of oral ribavirin in hematologic disease patients with paramyxovirus infection: analytic strategy using propensity scores

Few antiviral agents are available for treating paramyxovirus infections, such as those involving respiratory syncytial virus (RSV), parainfluenza virus (PIV), and human metapneumovirus (hMPV). We evaluated the effect of oral ribavirin on clinical outcomes of paramyxovirus infections in patients with hematological diseases. All adult patients with paramyxovirus were retrospectively reviewed over a 2-year period. Patients who received oral ribavirin were compared to those who received supportive care without ribavirin therapy. A propensity-matched case-control study and a logistic regression model with inverse probability of treatment weighting (IPTW) were performed to reduce the effect of selection bias in assignment for oral ribavirin therapy. A total of 145 patients, including 64 (44%) with PIV, 60 (41%) with RSV, and 21 (15%) with hMPV, were analyzed. Of these 145 patients, 114 (78%) received oral ribavirin and the remaining 31 (21%) constituted the nonribavirin group. Thirty-day mortality and underlying respiratory death rates were 31% (35/114) and 12% (14/114), respectively, for the oral ribavirin group versus 19% (6/31) and 16% (5/31), respectively, for the nonribavirin group (P = 0.21 and P = 0.56). In the case-control study, the 30-day mortality rate in the ribavirin group was 24% (5/21) versus 19% (4/21) in the nonribavirin group (P = 0.71). In addition, the logistic regression model with IPTW revealed no significant difference in 30-day mortality (adjusted hazard ratio of 1.3; 95% confidence interval [95% CI] of 0.3 to 5.8) between the two groups. Steroid use (adjusted odds ratio, 5.67; P = 0.01) and upper respiratory tract infection (adjusted odds ratio, 0.07; P = 0.001) was independently associated with mortality. Our data suggest that oral ribavirin therapy may not improve clinical outcomes in hematologic disease patients infected with paramyxovirus.

[Experimental investigation of Ingavirin antiviral activity against human parainfluenza virus]

The Ingavirin antiviral properties with respect to the parainfluenza virus, as an actual human respiratory tract pathogen, were investigated by two methods, i.e. immunoenzymatic analysis and microtetrazolium test. The results showed that along with the immediate antiviral activity Ingavirin had nonspecific cytoprotective properties. While affecting the virus proteins synthesis, Ingavirin lowered the virus cytopathogenic action. The drug significantly decreased the portion of the bronchial epithelium cells killed at the stage of acute infection.

High throughput screening assay for negative single stranded RNA virus polymerase inhibitors

The Paramyxoviridae form a large family of viruses containing many human and veterinary pathogens for which a need for antiviral treatment is emphasized, particularly following the recent emergence of new viruses. The viral RNA-dependent RNA polymerase constitutes an obvious target for antiviral compounds. An in vitro assay was developed that allows high throughput screening of compounds potentially inhibiting the Sendai virus RNA-dependent RNA polymerase. Screening relies on the detection of the Photinus pyralis luciferase produced in a transcription/translation coupled assay using a mini-replicon virus. It contains an internal control for possible adverse effects of the tested compounds on translation or on luciferase activity. It is estimated that the mini-replicon template produced in one fertilized egg is sufficient to run 5000-10,000 reactions. This assay constitutes a simple, sensitive and easily automated method to perform high throughput screening of Paramyxoviridae RNA-dependent RNA polymerase inhibitors.

Antiviral activity of cholesteryl esters of cinnamic acid derivatives

Cholesteryl 3",4"-dimethoxycinnamate (7) and a new synthesized o-coumaroyl ester of 3 beta-(2'-hydroxyethoxy)-cholest-5-en (13) exhibited a marked activity against poliovirus type 1 (Mahoney). Compound 7 showed an approximately 20-fold greater selectivity in its antiviral activity than compound 13. These compounds were selected from thirteen steryl esters of cinnamic acid derivatives through an in vitro antiviral screening against viruses belonging to taxonomic groups with causative agents of important human infectious diseases to which chemotherapy is indicated, i.e. Picornaviridae, Orthomyxoviridae, Paramyxoviridae and Herpesviridae.

A colorimetric LDH assay for the titration of infectivity and the evaluation of anti-viral activity against ortho- and paramyxoviruses

A rapid and precise screening assay was developed for in vitro evaluation of anti-orthomyxo- and anti-paramyxovirus agents. The procedure is spectrophotometrical assessment for viability of cells via extracellular leakage of lactic dehydrogenase (LDH). HMV-II cells, a human melanoma cell line was found to be suitable for the titration of virus infectivity and screening of anti-viral agents for orthomyxo- and paramyxoviruses. Comparative titration of infectivity of stock viruses by the LDH and the MTT in site reduction of 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) methods with HMV-II cells as well as plaque titration with MDCK, Vero and HeLa cells was carried out. The LDH method was comparable or more sensitive for influenza viruses (FLUV)-A, B, C, parainfluenza viruses (PFLUV)-1, 2 and less sensitive for PFLUV-3, mumps virus (MPSV), measles viruses (MLSV) and respiratory syncytial virus (RSV) than the plaque titration. The 50% effective concentration (EC50) of 1-beta-D-ribofuranosyl-1, 2, 4-triazol-3-carboxamide (ribavirin) and 5-ethynyl-1-beta-D-ribofuranosyl-imidazole-4-carboxamide (EICAR) against orthomyxo- and paramyxoviruses were examined comparatively by the LDH, MTT and plaque reduction (PR) methods. The EC50 values of FLUV-C and PFLUV-1 were able to be evaluated only by the LDH but not by the MTT and PR methods. The LDH method with HMV-II cells simplifies the assay procedure and permits the evaluation of a large number of compounds for anti-orthomyxo- and anti-paramyxoviruses activity in vitro.

A comparative study of the effect of dextran sulfate on the fusion and the in vitro replication of influenza A and B, Semliki Forest, vesicular stomatitis, rabies, Sendai, and mumps virus

The effect of dextran sulfate on the fusion of a series of enveloped viruses, bearing specifically different fusion proteins, was investigated. The fusion with model- and with biological membranes was monitored by an R18 fluorescence-dequenching fusion assay. Dextran sulfate strongly suppresses the fusion of orthomxyo- (influenza A (H1N1 and H3N2 subtypes) and influenza B), of toga- (Semliki Forest virus), and of rhabdoviruses (vesicular stomatitis and rabies virus). The fusion of the paramyxo-viruses Sendai and mumps was not significantly affected by the anionic polysaccharide. The response to dextran sulfate was virus-specific, and identical for the different members of one virusfamily, bearing the same fusion protein. It was shown that dextran sulfate attaches with high affinity to the viruses studied, but not to erythrocytes. The anionic polymer appears to attach to the fusion epitope of the viral membrane. The inhibition of virus replication in vitro shows a remarkable correlation with the observed anti-fusion effects of dextran sulfate.

Effects of protease inhibitors on replication of various myxoviruses

We studied the effects of eight protease inhibitors on the multicycle replications of various orthomyxoviruses and paramyxoviruses. Among the compounds, nafamostat mesilate, camostat mesilate, gabexate mesilate, and aprotinin, which are widely used in the treatment of pancreatitis, inhibited influenza virus A and B replication at concentrations that were significantly lower than their cytotoxic thresholds in vitro. None of the protease inhibitors had activity against respiratory syncytial virus, measles virus, or parainfluenza virus type 3 at the highest concentrations tested. Camostat mesilate was found to be the most selective inhibitor. Its 50% effective concentration for influenza virus A replication was 2.2 micrograms/ml, and the selectivity index, which was based on the ratio of the 50% inhibitory concentration for host cell proliferation to the 50% effective concentration for influenza virus A replication, was 680. When the in ovo antiviral activity of the compounds was tested by using chicken embryos, camostat mesilate at a dose of 10 micrograms/g markedly reduced the hemagglutinin titers of influenza viruses A and B.

Antiviral activities of ribavirin, 5-ethynyl-1-beta-D-ribofuranosylimidazole-4-carboxamide, and 6'-(R)-6'-C-methylneplanocin A against several ortho- and paramyxoviruses

5-Ethynyl-1-beta-D-ribofuranosylimidazole-4-carboxamide (EICAR) and 6'-(R)-6'-C-methylneplanocin A (TJ13025) are two novel antiviral agents which are targeted against IMP dehydrogenase and S-adenosylhomocysteine hydrolase, respectively. These compounds have been examined for their activities against various strains of orthomyxoviruses (influenza virus) and paramyxoviruses (parainfluenza virus, mumps virus, measles virus, and respiratory syncytial virus) in vitro. EICAR was 10- to 59-fold more active than ribavirin and TJ13025 was 32- to 330-fold more active than ribavirin against parainfluenza virus types (2 and 3), mumps virus, and measles virus. EICAR was also more active than ribavirin against respiratory syncytial virus and influenza virus, whereas TJ13025 was virtually inactive against these viruses. The 50% virus-inhibitory concentrations of EICAR and TJ13025 were generally within the 0.1- to 1-microgram/ml range. Although the compounds did not prove cytotoxic to stationary host cells (HeLa, Vero, MDCK, and LLCMK2) at a concentration of 200 micrograms/ml, concentrations of 4 to 13 micrograms/ml inhibited the growth of dividing cells. EICAR and TJ13025 should be further pursued as candidate drugs for the treatment of ortho- and paramyxovirus infections.

Inhibitory effect of a new antibiotic, guanine 7-N-oxide, on the replication of several RNA viruses

Guanine 7-N-oxide (G-7-Ox) was examined for its antiviral activity against 9 viruses based on plaque reduction, neuraminidase activity reduction, a fluorescent antibody technique or ELISA. The following viruses were included in the tests: influenza, Sendai, simian virus 5 (SV5), respiratory syncytial, western equine encephalitis, Japanese encephalitis, vesicular stomatitis, rabies and polio. G-7-Ox showed broad anti-RNA viral activity against all viruses tested, except for poliovirus. Inhibition of persistent SV5 infection by G-7-Ox indicates that its antiviral activity is independent of cytotoxicity.

Polypeptides of pneumonia virus of mice. II. Characterization of the glycoproteins

The kinetics of synthesis and the nature of the oligosaccharides of the glycoproteins of pneumonia virus of mice (PVM) were studied. Tryptic peptide mapping showed that the two major glycosylated polypeptides G1 and G2 were different forms of the same protein. G2 was derived from G1 which in turn appeared to be derived from an unidentified precursor. The G1/G2 protein of PVM is probably a haemagglutinin since a monoclonal antibody directed against it has a high haemagglutination inhibition titre. On the basis of experiments with inhibitors and glycosidases it was deduced that G1 and G2 have both N-linked and O-linked oligosaccharides. The putative fusion protein-equivalent of PVM was shown to possess N-linked oligosaccharides. In the presence of tunicamycin a high mobility form (F1t) appeared to be derived from a precursor (F0t) with the same mobility as the fully glycosylated protein. If by analogy with other paramyxoviruses this represents a cleavage event, the difference in mobility of the precursor and product suggests that the putative F2 product is smaller than the corresponding F2 protein of other paramyxoviruses. However, no F2 candidate protein was detected and evidence for an F1,2 dimer was inconclusive. The glycoproteins of PVM resemble those of respiratory syncytial virus in terms of their pattern of glycosylation, but differ in their processing.

Pneumovirus-like characteristics of the mRNA and proteins of turkey rhinotracheitis virus

Electronmicroscopy has indicated that turkey rhinotracheitis virus (TRTV), the causative agent of an acute respiratory disease in turkeys, is a member of the Paramyxoviridae family. To determine if TRTV belongs to one of the three defined genera of this family (Paramyxovirus, Morbillivirus and Pneumovirus) we have analysed the RNA and proteins induced during replication of TRTV in Vero cells. Following replication in the presence of actinomycin D 10 polyadenylated RNA bands, ranging in Mr from 0.22 to 2.0 X 10(6), were detected in infected cells; some bands probably contained 2 or more RNA species. Viral proteins were studied after radiolabelling in the presence of [35S]methionine and [3H]glucosamine. Comparison of the polypeptides in mock-infected and infected cells, virions and nucleocapsids and after lentil-lectin chromatography and immunoprecipitation revealed seven virus-specific polypeptides (p), some of which were glycosylated (gp): gp82 (Mr 82K), gp68, gp53, gp15, p43, p40 and p35. These are considered to be analogous to the large glycopolypeptide (HN, H and G), fusion protein precursor F0, the F protein cleavage products F1 and F2, nucleocapsid (N), phosphorylated (P) and matrix (M) polypeptides, respectively, of the Paramyxoviridae. Two other polypeptides (Mr 200K and 22K) were also detected, as was a glycopolypeptide of Mr 97K, probably related to gp82. Tunicamycin inhibited glycosylation of gp53 and gp15 but gp82 was little affected, most glycans still being present on a glycopolypeptide of approximately 79K. This finding, indicating that gp82 has mostly O-linked glycans, considered with the mRNA profile and the molecular weight of the N protein shows that of the three genera in this family, TRTV most closely resembles the Pneumovirus genus.

Oligopeptides that specifically inhibit membrane fusion by paramyxoviruses: studies on the site of action

Previous studies from this laboratory showed that oligopeptides with amino acid sequences similar to the sequence of the N-terminal region of the F1 polypeptide of paramyxoviruses inhibited the membrane fusing activity of the F protein, and thereby inhibited virus infectivity at the level of penetration and virus-induced cell fusion and hemolysis. The site of action of these oligopeptide inhibitors has been investigated. Radioactively labeled oligopeptides were found to bind to cells, but not to virus. Pretreatment of cells, but not virus, at 4 degrees with oligopeptides inhibited the initiation of infection and hemolysis induced by measles virus. The binding of the oligopeptides to cells was reversible at 25 or 37 degrees. Oligopeptides were synthesized with a chloromethylketone group to enable them to bind irreversibly, or with an azido group to permit them to be cross-linked in situ by photoactivation. The results with these derivatized oligopeptides, which retained their inhibitory activity, confirmed that they bind to, and express their inhibitory activity on, cells and not virus. The results suggest that the oligopeptides react with receptor sites on the cell membrane and inhibit membrane-fusing activity by competing with the F1 polypeptide for such sites. A Scatchard analysis of the binding of an oligopeptide to CV-1 cells revealed that it bound with a dissociation constant of 1.2 X 10(-7) M and that there were approximately 3.0 X 10(6) binding sites per cell.

The uncoating of paramyxoviruses may not require a low pH mediated step

The effect of lysosomotropic agents, chloroquine and NH4Cl, on the replication of paramyxoviruses was compared with that on the other enveloped RNA viruses whose uncoating is known to be blocked by the agents. Under the conditions where vesicular stomatitis or influenza virus infection was strongly inhibited at an early step, the agents exhibited little inhibitory effect on the progress of infection by Newcastle disease virus and Sendai virus, allowing viral primary transcription to occur and neither inhibiting the virus production significantly nor reducing the number of infected cells. These results are incompatible with the previous report showing that paramyxovirus and the other enveloped RNA viruses may have in common an intracellular step sensitive to lysosomotropic agents (Miller and Lenard, Proc. Nat. Acad. Sci. USA 78, 3605-3609, 1981) and suggest that paramyxovirus uncoating may not require a low pH mediated lysosomal step.

Unsaturated free fatty acids inactivate animal enveloped viruses

Unsaturated free fatty acids such as oleic, arachidonic or linoleic at concentrations of 5-25 microgram/ml inactivate enveloped viruses such as herpes, influenza, Sendai, Sindbis within minutes of contact. At these concentrations the fatty acids are inocuous to animal host cells in vitro. Naked viruses, such as polio, SV40 or EMC are not affected by these acids. Saturated stearic acid does not inactivate any viruses at concentrations tested. Though the mode of action of unsaturated fatty acids is not understood, electronmicrographs of enveloped viruses treated by them indicate that the inactivation is associated with disintegration of the virus envelope.

A probable model of the inhibitory action of ceruloplasmin on the multiplication of some myxo- and paramyxoviruses

A model of the interaction between virus glycoprotein and the glycoprotein moeity of ceruloplasmia was developed on the ground of previous experimental data referring to the inhibitory action of this enzyme on the multiplication of some influenza and parainfluenza viruses and on their hemagglutinin and neuraminidase activities. The model makes evident the "trap" action exerted by ceruloplasmin on virus particles, both in the early and in the later phases of virus multiplication.

Recovery of infectious proviral DNA from mammalian cells infected with respiratory syncytial virus

The DNA fraction from a line of bovine embryonic kidney cells originally exposed as primary cultures several months earlier to a temperature-sensitive (ts) mutant of respiratory syncytial (RS) virus could be used to transfect human HEp-2 cells with the production of infectious RS virus. The DNA donor cells, designated BEK/RS ts, retained their healthy fibroblastic appearance during continuous cultivation at a temperature (39 degrees) restrictive for growth of the original infecting mutant and showed no evidence for RS virus replication or viral antigen synthesis when directly examined for these activities by conventional methods. The infectious property of the DNA from BEK/RS ts cells was abolished by exposure of the nucleic acid preparation to DNase (but not RNase) or by pretreatment of recipient HEp-2 cells with actinomycin D or mitomycin C. The latter drug treatments substantially enhanced the replication of infecting wild-type RS virus in HEp-2 cells. Viral isolates derived from the progeny of a DNA transfection included clones possessing several genetic markers of the RS ts mutant originally used to infect BEK/RS ts cells and other virus clones that appeared to be either hybrid or wild-type for phenotypic properties such as their temperature sensitivity. An infectious proviral DNA was also detected in a line of virogenic HEp-2 cells (HEp-2/RS) persistently infected with respiratory syncytial virus after exposure to the wild-type strain 2 years earlier.

Characterization of inactivation of myxoviruses and paramyxoviruses by hydroxylamine, N-methylhydroxylamine and O-methylhydroxylamine

A study of the mechanism of myxovirus and paramyxovirus inactivattion by hydroxylamine, O-methylhydroxylamine and N-methylhydroxylamine was conducted. Influenza A (WSN) was used as the sensitive myxovirus and Newcastle disease virus (NDV-L) was used as the relatively resistant paramyxovirus in certain experiments. Inactivation was found to be rapid (15 minutes) and mose effective at high concentrations (2M). All three compounds significantly decreased the hemagglutination titer of WSN treated at pH smaller than or equal to 5.0. There was no detectable change in NDV hemagglutination titer. Adsorption of hydroxylamine (pH 7.0) inactivated WSN appeared normal; however, the rate of adsorption was decreased when virus was inactivated by (pH 5.0) O-methylhydroxylamine. Equilibrium density gradient centrifugation in potassium tartrate showed no density changes in inactivated virus. WSN inactivated virus. WSN inactivated with 14C-O-methylhydroxylamine and subjected to RNA extraction showed greater than or equal to 35 percent of the 14C in the phenol phases and 21 per cent in the RNA. The 14C-O-methylhydroxylamine associated with the RNA of insensitive NDV was about 3 per cent of that associated with sensitive WSN-RNA. Hydroxylamine has no apparent effect on paramyxovirus (NDV) hemagglutination titer and less 14C-O-methylhydroxylamine is associated with the RNA of this virus. The results suggest these compounds may affect both the RNA and the envelope portion of myxoviruses (WSN) to produce inactivation.

Virus inactivation by ethylene oxide containing gases

Gases containing ethylene oxide mixed with carbon dioxide alone (Etox®) or together with methyl formate (Etoxiat®) were employed for virus treatment in a way that has been shown efficient for the killing of bacteria. A number of viruses selected for their capacity to withstand chemical or physical treatments were tested under varying conditions, including in a dried state in the presence of high amounts of organic matter (animal spillings). The viruses tested were enteroviruses, paramyxovirus (NDV), poxvirus and parvovirus, and they were all inactivated to a high degree.