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Results for “Persistent Infection”

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PubMed2002

Synthesis and expression of viral antigens in Vero cells persistently infected with Junin virus.

Two Vero cell lines persistently infected with XJCl3 and Cl67 strains of Junin virus and named V3 and V7, respectively, have been characterized with respect to the presence and expression of the nucleoprotein (N) and the glycoprotein precursor (GPC) viral genes. After the acute phase of infection, where a marked CPE and high titers of virus were obtained, JV persistently infected cells became morphologically undistinguishable from Vero cells and virus production dropped to undetectable levels. V3 and V7 were resistant to the superinfection with antigenically related viruses. This fact could not be attributed to the presence of defective interfering particles or non-infectious virus in the supernatant. Expression of N was consistently detected in both cultures and accumulation of two degradation products of N was evident during the late passages. Although no G1 (main surface glycoprotein) expression was observed, a marked fusogenic capacity was detected in both cultures indicating at least, the synthesis of a GPC derived fusogenic glycoprotein. Cell lysates from V3 and V7 subjected to RT-PCR, using specific primers for N gene, or to a nested RT-PCR using specific primers for GPC (G1 region) confirmed the presence of both viral genes. No viral DNA sequences could be detected in JV persistently infected cells.

Animals↗

PubMed2005

Cytokine response of lymphocytes persistently infected with Chlamydia pneumoniae.

Chlamydia pneumoniae infection of lymphocytes in blood has been documented, and it is apparent that control of this pathogen in lymphocytes as well as immune functions of the infected lymphocytes may be critical in the development of chronic inflammatory diseases associated with infection by this bacterium. Since immune function of lymphocytes infected with C. pneumoniae has not been well studied, the cytokine response of lymphocytes infected with this pathogen was analyzed using an in vitro infection model of the Molt-4 human lymphoid cell line. C. pneumoniae infection of the cells showed a persistent infection without any vigorous growth of the bacteria. Analysis of the cytokine response of the cells persistently infected with C. pneumoniae showed minimum induction of inflammatory cytokine TNF-alpha message, determined by real-time reverse transcription (RT)-PCR in the lymphocytes, even though the infection of THP-1 monocytic cells showed a marked induction of this cytokine messages. BIC (a lymphocyte activation marker gene) as well as IFN-gamma messages were also minimally induced by the infection in Molt-4 lymphocytes. In contrast, constitutive expression of interleukin 8 (IL-8) messages of Molt-4 cells was suppressed by the infection. Thus, these results suggest that lymphocytes persistently infected with C. pneumoniae may have attenuated cytokine responses.

Chlamydia Infections↗

PubMed1976

Persistent infection of tissue culture cells by RNA viruses.

In this paper, the characteristics of cultured cells persistently infected with RNA viruses, other than leuko viruses are described. The roles that the host cell, interferon, virus mutants and defective interfering particles may play in the establishment and maintenance of persistent infection are discussed. It is proposed that the interaction of viruses with certain types of host cells can lead to persistent infection. The differences in virus-host interactions may be attributable to differences in membrane properties of various cells. Defective interfering particles may play a role in the establishment of persistent infections in cells which normally undergo lytic virus development. Mutant types of virus appear to be prominent in the virus released from persistently infected cells, but the role that various mutants play in the maintenance of persistent infections remains unclear.

Antibodies, Viral↗

PubMed1982

Persistent infection with bovine herpesvirus type 1: rabbit model.

Persistent infection with bovine herpesvirus type 1 (BHV-1) was established in all rabbits after conjunctival inoculation of virus. Spontaneous reactivations of BHV-1 with and without the appearance of recurrent ocular lesions were observed in persistently infected rabbits. BHV-1 was reactivated predictably and shed from all persistently infected rabbits after the administration of dexamethasone. During all reactivations, BHV-1 isolation was restricted to the inoculated eye.

Animals↗

PubMed1997

Superinfection exclusion of alphaviruses in three mosquito cell lines persistently infected with Sindbis virus.

Three Aedes albopictus (mosquito) cell lines persistently infected with Sindbis virus excluded the replication of both homologous (various strains of Sindbis) and heterologous (Aura, Semliki Forest, and Ross River) alphaviruses. In contrast, an unrelated flavivirus, yellow fever virus, replicated equally well in uninfected and persistently infected cells of each line. Sindbis virus and Semliki Forest virus are among the most distantly related alphaviruses, and our results thus indicate that mosquito cells persistently infected with Sindbis virus are broadly able to exclude other alphaviruses but that exclusion is restricted to members of the alphavirus genus. Superinfection exclusion occurred to the same extent in three biologically distinct cell clones, indicating that the expression of superinfection exclusion is conserved among A. albopictus cell types. Superinfection of persistently infected C7-10 cells, which show a severe cytopathic effect during primary Sindbis virus infection, by homologous virus does not produce cytopathology, consistent with the idea that cytopathology requires significant levels of viral replication. A possible model for the molecular basis of superinfection exclusion, which suggests a central role for the alphavirus trans-acting protease that processes the nonstructural proteins, is discussed in light of these results.

Aedes↗

PubMed1997

Detection of calves persistently infected with bovine pestivirus in a sample of dairy calves in south-eastern Queensland.

OBJECTIVE: To determine the proportion and incidence of calves persistently infected with bovine pestivirus in calves (n = 1521) supplied to the Tick Fever Research Centre and to assess the test regime to detect calves persistently infected with bovine pestivirus. DESIGN: Calves, 1 to 6 weeks old, selected for use in the production of the tick fever vaccine were collected from 21 properties in 56 separate groups between October 1990 and December 1996. Each group was examined for the presence of calves persistently infected with bovine pestivirus. PROCEDURE: All calves were routinely tested for antibody to bovine pestivirus and bovine pestivirus antigen using a serum neutralisation test and an antigen-capture ELISA, respectively. Pooled lymphocyte samples from calves were also monitored for bovine pestivirus by inoculation of sheep. Whole herd testing was carried out in eight herds, using a serum neutralisation test as a screen test followed by an antigen-capture ELISA of cattle with a serum neutralisation test titre of less than 32. RESULTS: Fourteen of the 1521 calves tested (0.9%), were detected as persistently infected and the incidence ranged from 0.0 to 3.0% per year over 6 years. Persistently infected calves were found in 13 of the 59 groups and originated from 7 of the 21 herds used. In whole herd testing on the properties of origin, cattle persistently infected with bovine pestivirus were detected in four of the eight herds tested. CONCLUSIONS: The proportion of calves persistently infected with bovine pestivirus is similar to that in other countries and indicates that bovine pestivirus could be a significant cause of economic loss in Australian cattle herds. In detecting calves persistently infected with bovine pestivirus, the combination of sheep inoculation, paired antigen-capture ELISA and serum neutralisation tests appeared to be highly sensitive and specific.

Animals↗

PubMed1979

Comparison of the antigens produced by foamy virus in a cytolytic and a persistent infection of HEp2 cells.

The antigens from cytolytic infections of HEp2 cells by type I simian foamy virus produced two multicomponent precipitation lines when tested by immunodiffusion with the homologous hyperimmune rabbit antiserum. The antigens obtained from a non-productive infection of MK5 virus in HEp2 cells produced only those precipitation lines which corresponded with the inner lines obtained from the cytolytic infection. Similarly, hyperimmune rabbit antiserum against antigens extracted from the persistent infection lacked the antibody which was responsible for the outer lines of precipitation. Indirect immunofluorescence with acetone-fixed and unfixed cells using the homologous and heterologous sera confirmed the absence of antigens in the persistent infection and showed that an antigen is produced in the persistently infected cells which is either absent or present in very small amounts in cytolytically infected cells. Neutralization experiments and ether treatment suggested that the missing antigens in the persistent infection were the envelope components of foamy virus. It is proposed that the persistent infection has properties in common with some infections by RNA tumour viruses.

Antigens, Viral↗

PubMed2005

Bactericidal activity of first-choice antibiotics against gamma interferon-induced persistent infection of human epithelial cells by Chlamydia trachomatis.

Chlamydia trachomatis is responsible for clinically important chronic inflammatory diseases of humans, including trachoma and pelvic inflammatory disease. Persistent infection of mucosal sites may contribute to the development of these chronic inflammatory diseases. Standard clinical therapy results in satisfactory cure rates of acute infections; however, chronic infection associated with persistence has been suggested to be less responsive to antibiotic therapy. We report the efficiency of two first-line chlamydial antibiotics, azithromycin and doxycycline, under conditions of eradication of C. trachomatis persistent infection using the in vitro model of gamma interferon (IFN-gamma)-mediated persistence and reactivation from persistence. Doxycycline was superior in eradicating acute (minimal bactericidal concentration [MBC](100) = 2.5 to 5.0 microg/ml) compared to persistent (MBC(100) = 10 to 50 mirog/ml) infection. In contrast, azithromycin was significantly more effective in eradicating persistent infection (MBC(100) = 2.5 to 5.0 microg/ml) than acute infection (MBC(100) = 10 to 50 microg/ml). The superior bactericidal effect of azithromycin against persistent infection was found to correlate with the enhanced uptake of the drug by IFN-gamma-treated infected epithelial cells. Based on these findings, we hypothesize that azithromycin should be a particularly efficacious anti-infective agent for the eradication of IFN-gamma-induced chlamydial persistent infection in vivo.

Anti-Bacterial Agents↗

PubMed1992

Heterologous resistance to superinfection by louping ill virus persistently infected cell cultures.

Louping ill virus, a tick-borne arbovirus readily established a persistent infection in porcine kidney (PS) cells after initially inducing minor cytopathic changes. Nucleotide sequence analysis of the envelope glycoprotein of the viral RNA recovered from the persistently infected cells showed no changes as compared with the virus used to establish persistent infections. More than 80 per cent of the cells contained virus specific antigen when analysed by indirect immunofluorescence microscopy. This persistently infected cell line resisted superinfection with either homologous or most heterologous flaviviruses. However, the yellow fever French neurotropic virus (YF FNV) multiplied in the persistently infected cells and evidence of dual infections in these cells was obtained using specific monoclonal antibodies in double labelling immunofluorescence tests. The relevance of these observations is discussed in the light of other evidence that tick-borne viruses can survive for long periods in wild animal species.

Animals↗

PubMed2004

Recombinant Sendai viruses with L1618V mutation in their L polymerase protein establish persistent infection, but not temperature sensitivity.

The Sendai virus pi strain (SeVpi) isolated from cells persistently infected with SeV shows mainly two phenotypes: (1) temperature sensitivity and (2) an ability of establishing persistent infection (steady state). Three amino acid substitutions are found in the Lpi protein and are located at aa 1088, 1618, and 1664. Recombinant SeV(Lpi) (rSeV(Lpi)) having all these substitutions is temperature sensitive and is capable of establishing persistent infection (steady state). rSeVs carrying the fragment containing L1618V show both phenotypes. rSeV(L1618V), in which leucine at aa 1618 is replaced with valine, has the ability of establishing persistent infection, but is not a temperature-sensitive mutant, indicating that the ability of a virus to establish persistent infection can be separated from temperature sensitivity. The amino acid change at 1618(L-->V) coexisting with aa 1169 threonine is required for acquirement of a temperature-sensitive phenotype. Three amino acid substitutions are also found in the Ppi protein, but rSeV(Ppi) does not show these phenotypes.

Amino Acid Sequence↗

PubMed1981

Establishment and maintenance of a persistent infection of L132 cells by human coronavirus strain 229E.

A persistent infection by human coronavirus 229E (HCV/229E) was established in a human continuous cell line (L132). Following the initial infection with stock HCV/229E, several cultures were established of which two (HV1 and HV4) have been maintained by continuous passage for two years. These cultures have shed high titres of infectious virus continuously into the supernatant fluid since their initiation. The persistently infected cells were resistant to homologous super-infection but supported polio virus replication to normal titres. Preliminary tests indicated that 50-100 percent of the cells contain virus. Neither interferon nor reverse transcriptase could be detected in these cultures and the presence of defective interfering particles could not be demonstrated. VH1 and VH4 coronaviruses, isolated from these persistently infected cultures (HV) and identified by 229E antiserum neutralization, were more cytocidal than the parent virus as judged by plaque characteristics and CPE, however they were indistinguishable on the basis of density, EM morphology, and genome size. Present evidence indicated that temperature plays an important but as yet undetermined role in the establishment and maintenance of stable 229E persistently infected cell cultures.

Antibodies, Viral↗

PubMed2000

Sequence variability of Borna disease virus: resistance to superinfection may contribute to high genome stability in persistently infected cells.

The RNA genome of Borna disease virus (BDV) shows extraordinary stability in persistently infected cell cultures. We performed bottleneck experiments in which virus populations from single infected cells were allowed to spread through cultures of uninfected cells and in which RNase protection assays were used to identify virus variants with mutations in a 535-nucleotide fragment of the M-G open reading frames. In one of the cell cultures, the major virus species (designated 2/1) was a variant with two point mutations in the G open reading frame. When fresh cells were infected with a low dose of a virus stock prepared from 2/1-containing cells, only a minority of the resulting persistently infected cultures contained detectable levels of the variant, whereas the others all seemed to contain wild-type virus. The BDV variant 2/1 remained stable in the various persistently infected cell cultures, indicating that the cells were resistant to superinfection by wild-type virus. Indeed, cells persistently infected with prototype BDV He/80 were also found to resist superinfection with strain V and vice versa. Our screen for mutations in the viral M and G genes of different rat-derived BDV virus stocks revealed that only one of four stocks believed to contain He/80 harbored virus with the original sequence. Two stocks mainly contained a novel virus variant with about 3% sequence divergence, whereas the fourth stock contained a mixture of both viruses. When the mixture was inoculated into the brains of newborn mice, the novel variant was preferentially amplified. These results provide evidence that the BDV genome is mutating more frequently than estimated from its invariant appearance in persistently infected cell cultures and that resistance to superinfection might strongly select against novel variants.

Animals↗

PubMed1986

Persistent infection of Aedes albopictus C6/36 cells by Bunyamwera virus.

Two cell lines persistently infected with Bunyamwera virus have been established from the C6/36 clone of Aedes albopictus cells. The cells express Bunyamwera virus antigens as detected by immunofluorescence and are resistant to superinfection with Bunyamwera virus and other bunyaviruses, but not Dugbe virus (Nairovirus) nor vesicular stomatitis virus. The virus released from the persistently infected cells developed an altered cloudy or "bull's-eye" plaque morphology with increasing passage level, and a greater temperature sensitivity at 39.5 degrees than standard virus. The persistent virus interfered strongly with the replication of standard Bunyamwera virus in normal C6/36 cells and to a much lesser extent in BHK cells. Interference was not noted with other bunyaviruses or vesicular stomatitis virus. The persistent virus from one cell line, C6/36-PI LO, had a slower migrating nucleocapsid protein on polyacrylamide gels. Analysis of the RNA in persistently infected cells or in persistent virus by Northern blot hybridization with cloned cDNA probes showed that the major viral RNA species was the S segment, while the L and M RNA segments were barely detectable. Our results indicate that Bunyamwera virus can readily establish persistent infections in mosquito cells, and that persistence is accompanied by the generation of viruses with variable genetic and phenotypic characteristics.

Aedes↗

PubMed1976

Genesis and maintenance of a persistent infection by canine distemper virus.

Vero cells were persistently infected with canine distemper virus by continuous undiluted passage of virus harvests. The cells were refractory to superinfection by both measles virus and canine distemper virus. These persistently infected cells produced and released into the medium a labile component which had a potent and selective inhibitory effect on the replication of canine distemper and measles virus. The inhibitory agent was not inactivated by u.v.-irradiation or sedimented by ultracentrifugation. Antisera against canine distemper virus or SSPE sera were able to block this inhibitory effect. We propose that these persistently infected cells produce an excess of a virus-induced regulatory protein.

Antiviral Agents↗

PubMed2004

Genetic characterization of equine arteritis virus during persistent infection of stallions.

Equine arteritis virus (EAV) causes a persistent infection of the reproductive tract of carrier stallions. The authors determined the complete genome sequences of viruses (CW96 and CW01) that were present 5 years apart in the semen of a carrier stallion (CW). The CW96 and CW01 viruses respectively had only 85.6 % and 85.7 % nucleotide identity to the published sequence of EAV (EAV030). The CW96 and CW01 viruses had two 1 nt insertions and a single 1 nt deletion in the leader sequence, and a 3 nt coding insertion in ORF1a; thus their genomes included 12 708 nt as compared to the 12 704 nt in EAV030. Variation between viruses present in the semen of stallion CW and EAV030 was especially marked in the replicase gene (ORF1a and 1b), and the greatest variation occurred in the portion of ORF1a encoding the nsp2 protein. The ORFs 3 and 5, which respectively encode the GP3 and GP5 envelope proteins, showed greatest variation amongst ORFs encoding structural EAV proteins. Comparative sequence analyses of CW96 and CW01 indicated that ORFs 1a, 1b and 7 were highly conserved during persistent infection, whereas there was substantial variation in ORFs 3 and 5. Although the variation that occurs in ORF5 results in the emergence of novel phenotypic viral variants as determined by neutralization assay, all variants were neutralized by high-titre polyclonal equine antisera, suggesting that immune evasion is unlikely to be responsible for the establishment of persistent EAV infection of carrier stallions. Northern blot analyses of RNA extracted from cell culture propagated viruses isolated from 10 different persistently infected stallions failed to demonstrate any large genomic deletions, suggesting that defective interfering particles are also unlikely to be important in either the maintenance or clearance of persistent EAV infection of the reproductive tract of carrier stallions.

Amino Acid Sequence↗

PubMed1982

Selection of temperature-sensitive mutants in persistent infection by parainfluenza virus type 3.

Vero cells persistently infected with parainfluenza virus type 3 (para 3) were examined for the production of temperature-sensitive (ts) mutants. After 6 months and 33 passages, ts mutants formed the great majority of the virus being shed into the supernatant fluid. Complementation studies gave evidence that the mutants shared a common lesion. Although ts mutants may play a role in the maintenance of persistent infection in this system, the mutants proved to be unstable when removed from the milieu of persistent infection. It is thus possible that their selection may be secondary to (an) unidentified factor(s) which play(s) a more primary role in the maintenance process.

Animals↗

PubMed1980

Characterization of measles virus recovered from persistently infected Vero cells.

Vero cells were persistently infected with measles virus in medium with antimeasles serum. When antiserum was not added to the medium, the persistently infected cells (VMAS cells) proliferated in a cyclical manner alternating between extensive cell destruction and renewed cell growth. When these cells were grown at 33 C and 40 C, they released temperature-sensitive and temperature-dependent viruses. However, these viruses, upon further propagation, reverted to the wild type suggesting that such temperature-related functions were phenotypically determined and regulated by host-cell factors. The spontaneous viral yield was dependent upon the active cell growth.

Animals↗

PubMed1979

Production of temperature-sensitive and pathogenic virus from Aedes albopictus cells (Singh) persistently infected with Chikungunya virus.

When A. albopictus, clone C6/36, cells were infected with chikungunya (CHIK) virus, high virus yield accompanied by a cytopathic effect in the acute stage of infection was followed by a relatively low yield of virus over a long period of time. Virus produced from persistently infected cultures became gradually of smaller plaque size and more temperature-sensitive; however, such virus still retained pathogenicity for suckling mice even after one year of infection. When the persistently infected cells were subcultured, a dissociation was observed between the time course of cell growth and that of virus production, suggesting some intracellular mechanisms that turn off virus production. The greater part of the interference against CHIK virus by the culture medium of the persistently infected cells appeared to be mediated by the infective virus in the medium. The infective virus was easily removed from the persistently infected cells either by subculture or by cloning in the presence of anti-CHIK serum, yielding cured cultures or virus-negative clones.

Aedes↗