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PubMed1981

Interference induced in GL-V3 monkey kidney cells by rabies virus strains.

Resistance to superinfection with vesicular stomatitis virus (VSV) occurred in GL-V3 monkey kidney cells infected with the CVS-11, Pitman Moore, LEP Flury, but not the ERA strain of rabies virus. Specific immunofluorescent staining of intracellular rabies antigen showed that the number and size of fluorescent foci increased after the onset of interference, and that this was paralleled by increasing yields of infectious virus. Although CVS-11 and ERA differed in their ability to induce interference, the virus yields from monolayers infected with either strain were similar. Interference apparently had no effect on the replication or dissemination of the inducing virus, and seems unrelated to the long incubation period or aberrant forms of infection in vivo.

Animals↗
PubMed2003

Interference between avian endogenous ev/J 4.1 and exogenous ALV-J retroviral envelopes.

A new family of avian retroviral endogenous sequences designated ev/J or EAV-HP has been identified recently. Here an additional avian ev/J 4.1 endogenous sequence, ev/J 4.1 Rb, is reported. ev/J 4.1 Rb has the most extensive amino acid identity ever described for an endogenous envelope protein with the ALV-J avian leukosis virus. Here, we also demonstrate that ev/J 4.1 Rb functionally pseudotypes murine leukaemia virions and leads to a complete reciprocal interference with ALV-J envelopes. This is the first demonstration of such a high level of envelope interference between endogenous and exogenous avian retroviruses. Our results provide additional clues on the co-evolution of retroviral sequences among vertebrates.

Amino Acid Sequence↗
PubMedDate not supplied

[Combined experimental infection of Microtus gregalis by tick-borne encephalitis and rabies viruses and probable interference].

Narrow-skulled voles (Microtus gregalis) were inoculated with tick-borne encephalitis (TBE) and rabies (RV) viruses isolated in the steppe zone of West Siberia. TBE infection was asymptomatic and nonlethal in all voles. The virus was eliminated from the voles between days 14 and 60 postinoculation. Only 1 of 26 tested animals produced anti-TBE antibodies in titer 1:20. RV infection was acute and lethal. All sick animals contained RV in the brain, 42.1% in salivary glands, 5.3% in the lungs and kidneys. The voles which survived RV inoculation had no RV. The voles inoculated with RV after TBE were less sensitive and had a longer incubation period in comparison with the animals challenged with RV alone. The differences augmented from day 0 to day 14 after TBE inoculation and became statistically significant on day 14. Later, 21 day after challenge with TBE virus, the differences almost disappeared. The role of possible interference in the evolution of virus-host interaction of Lyssaviruses is discussed.

Animals↗
PubMed1979

Epidemiologic interference of virus populations.

There are a few simulation studies for interference models in the literature but the present paper discusses an analytical model for the competition of two interfering virus populations in a community. The mathematical model consist of eight coupled differential equations which have up to four equilibrium points. Criteria for local stability are given.

Disease Outbreaks↗
PubMedDate not supplied

[Sensitivity of normal and Rous virus-transformed lines of Armenian hamster cells to infectious viruses].

The capacity of normal (NHET) and Rous virus-transformed cell line of armenian hamster both producing (SHET Sh-R) and not producing (SHET K-3) virus to support reproduction of vaccinia and Newcastle disease viruses was demonstrated. The former of these viruses replicated in the cell cultures with cytopathic effect, the latter did so without causing cell degeneration. The degree of Newcastle disease virus reproduction in all 3 cultures was the same whereas vaccinia virus synthesis in SHET Sh-R was inhibited as compared with NHET and SHET K-3 cultures. Interference between Rous virus and vaccinia virus in SHET Sh-R culture was not due to interferon. The infectious viruses under study caused no activation of Rous virus genome in the virogenic SHET K-3 cell line.

Animals↗
PubMed1977

Multiple free viral DNA copies in polyoma virus-transformed mouse cells surviving productive infection.

Mouse 3T6 cells were infected with polyoma virus at high multiplicity, and survivors were isolated. Clones from single cells were then established and were found to be resistant to a second infection. However, in some clones viral functions could at least be partially expressed during reinfection, as judged from a stimulation of nuclear tumor antigen expression. One such clone was studied in detail. These cells were transformed and produced low amounts of virus (less than 1 PFU per cell per generation). The persistent infection did not seem to be a carrier-state phenomenon, since infectious-center assays showed that most cells produced virus. The resistance of the cells to reinfection can be explained by interference from viral DNA present in the cells, averaging about 1,500 "free" copies per cell. This DNA had the normal physical characteristics of polyoma DNA. However, it had a slightly larger size than authentic polyoma DNA. Mapping with restriction endonucleases showed that the addition to the DNA was about 5% of the wild-type genome and was located close to the origin of DNA replication. This DNA was infectious, although it had a 10-fold lower infectivity than wild-type polyoma DNA. Both virus and DNA from the polyoma-resistant cells had a small-plaque morphology, as opposed to the large-plaque morphology of the virus used for the initial selection of cells.

Antigens, Viral↗
PubMed2002

Inhibition of HIV-1 infection by small interfering RNA-mediated RNA interference.

RNA interference (RNAi) is an ancient antiviral response that processes dsRNA and associates it into a nuclease complex that identifies RNA with sequence homology and specifically cleaves it. We demonstrate that RNAi mediated by 21-bp dsRNA specifically inhibits HIV-1 infection of permanent cell lines and primary CD4(+) T cells. Inhibition of HIV replication was measured by p24 Gag protein content in supernatant, Northern blot analysis, and DNA PCR for products of reverse transcription. The inhibition occurred at two points in the viral life cycle, after fusion and before reverse transcription and during transcription of viral RNA from integrated provirus. Treatment of HIV-infected activated CD4(+) T cells with a fluorine-derivatized siRNA that is resistant to RNase A yielded similar inhibition of HIV infection. In addition, the derivatized siRNA could be delivered without lipofectin complexing and in the presence of serum. The identification of RNAi activity against HIV-1 presents a new approach to study viral infections and a proof of concept of RNAi antiviral activity in mammalian cells.

Anti-HIV Agents↗
PubMed1991

In vitro homotypic and heterotypic interference by defective interfering particles of West Nile virus.

Defective interfering (DI) particles of the flavivirus West Nile (WN) were generated after as few as two high multiplicity serial passages in Vero and LLC-MK2 cells. Six cell lines (Vero, LLC-MK2, L929, HeLa, BHK-21 and SW13) were used to assay interference by DI particles in a yield reduction assay. Interference was found to vary depending on the cell type used. The highest levels of interference were obtained in LLC-MK2 cells, whereas no detectable effect was observed in BHK-21 and SW13 cells. The ability of DI virus to be propagated varied depending on the cell line used; no detectable propagation of DI virus was observed in SW13 cells. Optimum interference was obtained following co-infection of cells with DI virus and standard virus at a multiplicity of 5. Interference between DI and standard viruses occurred only when they were co-infected or when cells were infected with DI virus 1 h before standard virus. Investigation of heterotypic interference by DI particles of WN virus strains from Sarawak, India and Egypt revealed that interference was dependent on the strain of WN virus or flavivirus used as standard virus. A measure of the similarity between five strains of WN virus and other flaviviruses was made on the basis of interference by DI viruses, and was found to be similar to that based on haemagglutination inhibition tests using a panel of monoclonal antibodies.

Animals↗
PubMed1975

Production of defective interfering virus in the brains of mice by an avirulent, in contrast with a virulent, strain of Semliki forest virus.

An avirulent strain (A7) of Semliki Forest virus formed nearly as much haemagglutinating and complement fixing antigen in the brains of adult mice as a virulent (V13) strain, yet the infectivities of the brain tissues were different by about 100-fold. It appeared therefore that defective virus particles were fomed by A7 but these were not demonstrated by fluorescent antibody studies. In short-term organ cultures of adult mouse brain, A7 derived from mouse brain showed a typical interference pattern in inoculum infectivity response curves. Furthermore, when mixed suspensions of brain-grown V13 and A7 with equal infectivities were inoculated the inoculum infectivity response patterns showed significant depressions of the V13 response at higher inocula. Such interference was not detected if chick cell grown A7 and V13 were substituted for the mouse grown virus. The avirulence of A7 in adult mice and its rapid protective effect against lethal V13 infection could be due to the production of defective interfering virus particles in the brain.

Animals↗
PubMed2004

Quantification of infectious HIV-1 plasma viral load using a boosted in vitro infection protocol.

Methods currently used for HIV-1 viral load measurements are very sensitive, but cannot distinguish between infectious and noninfectious particles. Here we describe the development of a novel, sensitive, and highly reproducible method that allows rapid isolation and quantification of infectious particles from patient plasma. By immobilizing HIV-1 particles in human plasma to platelets using polybrene, we observed a 10- to 1000-fold increase in infectivity over infection protocols using free virus particles. Using this method, we evaluated infectivity in plasma from 52 patients at various disease stages. At plasma viral loads of 1000-10000 HIV-1 RNA copies/ml 18%, at 10,000-50,000 copies/ml 73%, at 50,000-100,000 copies/ml 90%, and above 100,000 copies 96% of cultures were positive. We found that infectious titers among patients vary distinctively but are characteristic for a patient over extended time periods. Furthermore, we demonstrate that by evaluating infectious titers in conjunction with total HIV RNA loads, subtle effects of treatment intervention on viremia levels can be detected. The immobilization procedure does not interfere with viral entry and does not restore the infectivity of neutralized virus. Therefore, this assay system can be utilized to investigate the influence of substances that specifically affect virion infectivity such as neutralizing antibodies, soluble CD4, or protease inhibitors. Measuring viral infectivity may thereby function as an additional, useful marker in monitoring disease progression and evaluating efficacy of antivirals in vivo.

Adult↗
PubMed2006

Down-regulation of MHC class I is a property common to papillomavirus E5 proteins.

The E5 protein family of papillomaviruses comprises small hydrophobic proteins which are associated with the cell endomembrane compartments. The functions of the E5 proteins, particularly those of HPV, are still far from clear. We have reported that the E5 proteins of BPV-1, BPV-4, HPV-16 and HPV-6 down-regulate MHC class I, potentially helping the virus evade the host immune response. Others have described MHC class I down-regulation by HPV-2 E5. We report here that another E5 protein, HPV-83 E5, likewise down-regulates MHC class I and propose that interference with expression, assembly and/or transport of MHC class I is a common property of all E5 proteins evolved by the virus to circumvent host immunosurveillance and thus establish productive infection.

Cell Line↗
PubMed1976

Interfering activity of virulent and attenuated influenza virus strains.

The interfering activity of influenza virus variants A/Hong Kong/1/68 (H3N202), A/Victoria/35/72(H3N2-3), B/14/55 and B/USSR/69 differing in the level of their reactogenicity for adults and children was studied. An inverse relationship was established between reactogenicity of the strains and their interfering activity in the resistant chick embryo cell (CEC) cultures. Virulent strains did not interfere with vesicular stomatitis virus. Vaccine strains used for commercial live influenza vaccine safe for adults but reactogenic in children were intermediate and showed moderate interfering activity. The highest capacity for interference was demonstrated in cold-adapted thermosensitive variants non-pathogenic for both adults and children. The interfering activity of the attenuated strains increased progressively with increasing inocula.

Adult↗
PubMed1998

Host range and interference studies of three classes of pig endogenous retrovirus.

Recent interest in the use of porcine organs, tissues, and cells for xenotransplantation to humans has highlighted the need to characterize the properties of pig endogenous retroviruses (PERVs). Analysis of a variety of pig cells allowed us to isolate and identify three classes of infectious type C endogenous retrovirus (PERV-A, PERV-B, and PERV-C) which have distinct env genes but have highly homologous sequences in the rest of the genome. To study the properties of these env genes, expression plasmids for the three env genes were constructed and used to generate retrovirus vectors bearing corresponding Env proteins. Host range analyses by the vector transduction assay showed that PERV-A and PERV-B Envs have wider host ranges, including several human cell lines, compared with PERV-C Env, which infected only two pig cell lines and one human cell line. All PERVs could infect pig cells, indicating that the PERVs have a potential to replicate in pig transplants in immunosuppressed patients. Receptors for PERV-A and PERV-B were present on cells of some other species, including mink, rat, mouse, and dog, suggesting that such species may provide useful model systems to study infection and pathogenicity of PERV. In contrast, no vector transduction was observed on nonhuman primate cell lines, casting doubt on the utility of nonhuman primates as models for PERV zoonosis. Interference studies showed that the three PERV strains use receptors distinct from each other and from a number of other type C mammalian retroviruses.

Animals↗
PubMed1978

[Passive immunization against rabies (author's transl)].

Passive immunization has proven an important complementary method for protection of an infected organism against rabies in the very first phase after virus contact. Passive-active immunization is by far superior compared to vaccination only. A few cases of human rabies after serovaccination in due time might be due to interference (immunosuppression) of active antibody formation after vaccination by passiively administered performed heterologous rabies immune globulin. This "interference phenomenon" can probably be explained as an imbalance of antigen and antibody in vivo, i.e. antigen masking and, hence, blocking of the immune reaction on its afferent branch. Both, 19S- and 7S- antibody moleculars, are able to induce interference. Whereas the old heterologous antisera from horse or mule, in an extremely high percentage, provoked moderate or severe side effects of such as urticaria, serum sickness, immune complex nephritis etc., the now available homologous Rabies Immune Globulin of Human Origin (RIGH) is very well tolerated, of long-lasting effectiveness and does not interfere with active antibody formation after application of HDCS-tissues culture vaccine, when an amount of 20 I.U./kg bodyweight of RIGH and 6 diseases of HDCS-vaccine on days, 0, 3, 7, 14, 30 and 90 (Essen schedule postexposure vaccination) is used.

Humans↗
PubMed1981

R-factor cointegrate formation in Salmonella typhimurium bacteriophage type 201 strains.

The genetic and molecular properties of the plasmids in Salmonella typhimurium phase type 201 isolated are described. Such strains are resistant to streptomycin, tetracycline, chloramphenicol, ampicillin, kanamycin, and several other antimicrobial drugs, and are highly pathogenic for calves. These strains have been encountered with increasing frequency since 1972 in West Germany and The Netherlands. We show that isolates of this phage type constitute a very homogeneous group with regard to their extrachromosomal elements. These bacteria carry three small plasmids: pRQ3, a 4.2-megadalton (Md) colicinogenic plasmid; pRQ4, 3.4-Md plasmid that interferes with the propagation of phages; and pRQ5, a 3.2-Md cryptic plasmid. Tetracycline resistance resides on a conjugative 120-MD plasmid pRQ1, belonging to the incompatibility class H2. Other antibiotic resistance determinants are encoded by a nonconjugative 108-Md plasmid pRQ2. Transfer of multiple-antibiotic resistance to appropriate recipient strains was associated with the appearance of a 230-Md plasmid, pRQ6. It appears that pRQ6 is a stable cointegrate of pRQ1 and pRQ2. This cointegrate plasmid was transferable with the same efficiency as pRQ1. Other conjugative plasmids could mobilize pRQ2, but stable cointegrates were not detected in the transconjugants. Phase type 201 strains carry a prophage, and we show that phage pattern 201 reflects the interference with propagation of typing phages effected by this prophage and plasmid pRQ4 in strains of phage type 201.

Anti-Bacterial Agents↗
PubMed1996

A novel murine retrovirus identified during testing for helper virus in human gene transfer trials.

An important requirement for the use of retroviral vectors in human gene transfer experiments is the avoidance of human exposure to replication-competent (helper) retroviruses. To meet this requirement, we used a sensitive marker rescue assay for helper virus to screen vector-transduced cells prior to reinfusion into patients. This assay utilized Mus dunni cells harboring a retroviral vector that can be rescued by helper retroviruses. The assay indicated the presence of helper virus in medium exposed to hematopoietic cells from all patients tested, including six patients with various cancers and one patient with Gaucher's disease, whether or not the patient cells had been exposed to retroviral vectors. All of the helper viruses were in a single interference group. We have now shown that treatment of the M. dunni marker rescue assay cells with 5-iodo-2'-deoxyuridine or hydrocortisone can activate production of an apparently identical helper virus, which we have named M. dunni endogenous virus (MDEV). Thus, production of virus in the assays of patient materials was likely due to exposure of the marker rescue assay cells to the hydrocortisone present in the hematopoietic cell growth medium. MDEV does not belong to any of the known murine leukemia virus groups by interference analysis, and we have called the new group multitropic because of the wide range of cells from different species that MDEV can infect.

Animals↗
PubMed1982

Low infectivity of HSV-1 DNA caused by defective-interfering genomes.

The infectivity of herpes simplex virus, type 1, strain ANG progeny DNA from standard virus infections and of progeny DNA from infections involving defective-interfering virus particles (DI DNA) was compared in transfection assays. No difference in infectivity of virus DNA isolated either from infected cells or from progeny virus was found for a given type of infection. However, the values for two types of infection differed markedly, with DI progeny DNA being less infectious by more than 2 log10. The low infectivity was mainly due to the presence of interfering DNA molecules in DI progeny DNA, regardless of whether intracellular DNA or DNA extracted from mature virions was analysed. The interfering capacity of DI progeny DNA did not depend on the integrity of the genomes. The physical proximity provided by simultaneous precipitation of infectious and of interfering DNA is an important factor influencing the degree to which DI DNA interferes. Interference by DI DNA in the transfection assay can be partly reversed by the addition of XbaI fragments of standard DNA; in control experiments this fragmented DNA was shown to lead to a reduction rather than to an enhancement of the infectivity of standard virus DNA.

Animals↗
PubMed2005

Interference between mild and pathogenic strains of infectious bursal disease virus in chickens.

Infectious bursal disease virus is a contagious, immunosuppressive disease of young chickens that is controlled by vaccination. Cross-protection occurs between different strains of the virus as a result of shared neutralizing epitopes. However, interactions between two antigenically similar strains (a mild and a pathogenic) coinfecting the same host have not been investigated. Groups of specific-pathogen-free chickens were inoculated with a mild strain followed by a pathogenic strain at 0, 16, 24, or 48 hr postinoculation (PI) with a mild strain. Virus persistence and the predominant strain of the virus were determined by reverse transcriptase-polymerase chain reaction and restriction fragment length polymorphism analysis, respectively, in bursas at 2, 4, 8, 14, and 21 days PI with the pathogenic strain. Severity of infection was assessed by the bursa/body weight ratios and histopathologic lesion scores. The mild virus interfered with replication of the pathogenic virus. The greatest interference was observed when the pathogenic strain was inoculated 24 hr PI with the mild strain. The interference phenomenon observed might be due to competition for host receptor sites or production of cytokine(s). This interference phenomenon could have practical implications for vaccine usage and protection.

Animals↗