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At least 37 records · Page 2Linked to original sources
PubMed1984

Persistent infection with influenza A virus: evolution of virus mutants.

A persistent infection (persistent infection I) of baby hamster kidney (BHK) cells with the WSN (H1N1) strain of influenza A virus was established using a virus stock which contained a high proportion of defective-interfering (DI) particles. Virus recovered from passage 92 (388 days) of persistent infection I was used to establish a second persistent infection (persistent infection II) in BHK cells. A number of phenotypic changes were identified in the virus isolated during the first 50 passages of persistent infection I (early pi virus). These included a decrease in the size of plaques, the appearance of temperature-sensitive mutants, and a decreased ability of amplified pi virus to agglutinate chicken erythrocytes. The decreased ability to cause hemagglutination was associated with a 20- to 30-fold increase in viral neuraminidase activity. Virus isolated after passage 63 of persistent infection I could not be amplified in eggs or in a number of cell lines. Although very little infectious virus was produced when cells were infected with these late pi viruses, cytopathology frequently occurred and an unusual pattern of viral protein synthesis was observed. The NP protein was the predominant protein synthesized, while the synthesis of M protein was drastically reduced relative to its synthesis in cells infected with parental WSN virus. The HA, NS1, and NS2 proteins were not detected; however, a virus-specific protein which migrates faster than NS2 was observed. Virus recovered from persistent infection II interfered with the replication of parental WSN virus in a mixed infection. The pattern of protein synthesis in such mixed infections resembled that in cells singly infected with late pi virus. DI particles did not appear to play a significant role either in the maintenance of the persistent infection, in the expression of the pi protein synthesis phenotype, or in the pi virus-mediated interference.

Animals↗
PubMed1997

A new small RNA virus persistently infecting an established cell line of Galleria mellonella, induced by a heterologous infection.

A persistent infection in a Galleria mellonella cell line was revealed when infected with a maize stem borer picorna-like virus isolated on Sesamia cretica (MSBV). The new virus, completely different from the MSBV, is designated as G. mellonella cell line virus (GmclV), induces spectacular cytopathic effects, and is also considered efficient in vivo. The GmclV is a 29-nm-diameter isometric virus, with single-strand RNA of 2.9 x 10(6) Da molecular weight with a poly(A) tract. Its capsid is constituted of only two major polypeptides, of 34,500 and 32,500 Da, and no minor bands could be detected. The characteristics of the GmclV do not permit us to classify it with assurance. Even though it has not yet been identified as a picornavirus, it can be classified in the small RNA virus group of the Picornaviridae. G. mellonella represents a very interesting model, owing to the fact that two different persistent viruses belonging to the same family were isolated in vivo and in vitro, to further the understanding of the general phenomenon of persistency and induction.

Animals↗
PubMed1995

Characteristics of cloned cerebrovascular endothelial cells following infection with Theiler's virus. II. Persistent infection.

Cloned cerebrovascular endothelial cells (CVE) persistently infected with Theiler's virus (PI-CVE) have been established and characterized. The CVE were derived from strains of mice that are susceptible (SJL/J and CBA) and resistant (BALB/c) to Theiler's virus-induced demyelination (TVID). The cells were persistently infected with either the BeAn or GDVII strains of Theiler's virus in vitro and studied at various passage levels for infectious virus, viral antigen and the expression of major histocompatibility complex (MHC) Class I and II antigens. The virus replicated to lower titers than in acutely infected CVE and appeared to be more cell-associated. Flow cytometric analysis revealed that 18-39% of the PI-CVE contained viral antigen. Persistently infected CVE derived from SJL/J and CBA mice expressed high levels of MHC Class I, whereas BALB/c PI-CVE did not. MHC Class II was upregulated by IFN-gamma in SJL/J PI-CVE albeit at a slightly lower level than in uninfected CVE. In addition, the PI-CVE demonstrated increased levels of mRNA for IL-1 beta when compared to uninfected CVE.

Animals↗
PubMed1971

Cells persistently infected with Newcastle disease virus. 3. Thermal stability of hemagglutinin and neuraminidase of a mutant isolated from persistently infected L cells.

Data were obtained which indicated the possible cause of the defective elution from erythrocytes of the mutant virus (NDV(pi)) isolated from L cells persistently infected with the Herts strain of Newcastle disease virus (NDV(o)). The chicken erythrocyte receptors for the mutant and wild-type viruses were equally sensitive to the action of Vibrio cholera filtrate neuraminidase; this suggests that the failure of NDV(pi) to elute from chicken erythrocytes is not due to a specific neuraminidase-resistant receptor for this virus on the erythrocyte membrane. There was no difference in the enzyme content of the intact virions of NDV(o) and NDV(pi) when tested with a soluble substrate, indicating that the inefficient elution of NDV(pi) was not due to a reduced enzyme content. The neuraminidase activity of intact NDV(pi) virions was significantly more stable at 55 C than the enzyme of NDV(o) virions, whereas the dissociated enzymes of the two viruses were inactivated at the same rate. On the basis of these findings, it seems likely there is a structural difference between the two viruses. The neuraminidase protein of the mutant NDV(pi) may be incorporated into the viral envelope in such a manner that it is prevented from reacting with the substrate in the erythrocyte membrane, although it can react with a soluble substrate. The hemagglutinin activity of both intact and disrupted NDV(pi) was significantly more resistant to thermal inactivation than that of the wild-type NDV(o). This finding suggests a genetic difference in the hemagglutinin protein of the two viruses.

Animals↗
PubMed1973

Persistent infection of cells in culture by measles virus. 3. Comparison of virus-specific RNA synthesized in primary persistent infection in HeLa cells.

The pattern of actinomycin D-resistant RNA synthesis was examined during primary infection of HeLa cells by virulent Edmonston measles virus and in two HeLa clones persistently infected by the same strain of virus. One of these clones, K11, produces infectious virus of low virulence for HeLa cells, and the other, K11A-HG-1, has thus far failed to yield infectious virus. The patterns of virus-specific RNA synthesized in these three types of infection are qualitatively similar to each other and to the patterns of virus-specific RNA synthesis in other paramyxovirus infections. There were, however, quantitative differences. In addition, virions of the virulent Edmonston strain of measles virus were found to contain high-molecular-weight RNA with a sedimentation constant identical to that of Newcastle disease virus.

Carbon Isotopes↗
PubMed1993

Long-term eradication of Chlamydia trachomatis genital infection after antimicrobial therapy. Evidence against persistent infection.

OBJECTIVE: To determine whether Chlamydia trachomatis urogenital infections persist or relapse after antimicrobial therapy by serial measurement of chlamydial-specific DNA using the polymerase chain reaction (PCR), cell cultures, and serological studies. DESIGN: Prospective evaluation of an inception cohort. SETTING: University student health clinic. PARTICIPANTS: Twenty women with culture-proven and PCR-proven C trachomatis urogenital infections. MEASUREMENTS: Incidence of persistent infection as determined by PCR, culture, and serial measurement of local and systemic antibody to C trachomatis for 5 months after doxycycline therapy. RESULTS: Prior to therapy, C trachomatis was isolated in cell culture from the cervix in 19 of 20 women, from the urethra in 13 women, and from the rectum in 13 women. All culture-positive specimens were also PCR-positive. Immediately after completion of antimicrobial therapy, all women had negative cell cultures for chlamydia. Ten of 20 culture-negative cervical specimens and two culture-negative urethral specimens had chlamydial DNA present immediately after treatment. In addition, three women had detectable DNA from cervical specimens 1 week after treatment. The presence of cervicitis (P = .01), high inclusion counts (P = .004), and serological evidence of recent infection (P = .0004) were each significantly associated with PCR positivity after treatment. All 384 subsequent cervical, rectal, and urethral specimens collected over 5 months were negative by both PCR and culture with the exception of one woman who was reinfected. Serum immunoglobulin M (IgM) titers, geometric mean serum immunoglobulin G (IgG) titers, and prevalence of local antibody to chlamydia progressively declined after treatment. CONCLUSIONS: Standard antimicrobial therapy is effective in the long-term microbiologic eradication of uncomplicated C trachomatis urogenital infections. The presence of chlamydial DNA after antimicrobial therapy is of short duration and reflects excretion of nonviable organisms rather than persistent infection.

Adult↗
PubMed1994

Presence of a truncated form of the Sendai virus P protein in a long-term persistent infection: implications for the maintenance of the persistent state.

In this report we have monitored viral gene expression, both at the RNA and protein level, after the establishment of a long-term persistent infection of Sendai virus. The persistent infection was initially established by infecting BHK cells with a viral stock containing a short (1.4 kb) copy-back DI (DIH4). After over 120 weeks in culture this short copy-back DI had been replaced by two large deletion DIs (approximately 7 and 12 kb) from which was expressed an N-terminally truncated form of the P protein. The mRNA for this protein was detected in cells and the deletion within the P gene was mapped by PCR cloning and sequencing of intracellular nucleocapsid RNA. This truncated P protein (derived by deleting the N-terminal half of the cloned Pwt gene) has already been shown to function as a dominant negative for DI replication when driven by cloned viral genes. Cloning and expression of the truncated P from the long-term persistent infection revealed that this protein had retained the dominant negative phenotype. The presence of such a protein would severely depress viral gene expression and may therefore play an important role in the maintenance of persistence.

Animals↗
PubMed1984

Isolation of cold-sensitive mutants of measles virus from persistently infected murine neuroblastoma cells.

Clone NS20Y of the mouse neuroblastoma C1300 was infected with wild-type Edmonston measles virus, and, after a transition to a carrier culture, became persistently infected. Persistently infected clones were derived and characterized morphologically by the appearance of multinucleate giant cells and nucleocapsid matrices in cytoplasm and nucleus, but very few budding virus particles. Antimeasles antibodies markedly suppressed the expression of viral antigens and giant cells, and the effect was totally reversible. When the cells were cultured at 33 degrees C, the number of giant cells began to diminish and ultimately disappeared; in contrast, when cultured at 39 degrees C, the cultures invariably lysed. Yields at 33 degrees C were ca. 2 logs lower than those at 39 degrees C. Cells cultured at 33 degrees C produced relatively high levels of interferon, whereas those at 39 degrees C produced little or no interferon. When the persistently infected cultures were exposed to anti-interferon alpha/beta serum at a nonpermissive temperature, there was a marked increase in multinucleate cells, suggesting that maintenance of the persistence state and its regulation by temperature may be related to the production of interferon. Viral isolates from cells cultured at 39 degrees C were obtained, and 90% of viral clones were found to be cold sensitive. Complementation studies with different viral clones indicated that the cold-sensitive defect was probably associated with the same genetic function. Western blot analysis of the persistently infected cells indicated a significant diminution and expression of all measles-specific proteins at a nonpermissive temperature. Infection of NS20Y neuroblastoma cells with the cold-sensitive virus isolates resulted in the development of an immediate persistent infection, whereas infection of Vero or HeLa cells resulted in a characteristic lytic infection, suggesting that the cold-sensitive mutants may be selected or adapted for persistent infection in cells of neural origin.

Animals↗
PubMed1992

Identification and eradication of bovine viral diarrhea virus in a persistently infected dairy herd.

A milking herd consisting of 55 Holstein cows had experienced abortions in several cows, as well as congenital malformations in 1 newborn calf. Bovine viral diarrhea virus was isolated from blood mononuclear cell samples obtained from several cattle, documenting 1 acute infection and 8 persistently infected carriers identified by clinical appearance and laboratory testing. Initial suspicion of persistently infected status in some, but not all animals, was facilitated by poor growth rates in some calves. Virus isolation was performed on transtracheal wash fluid obtained from acutely and persistently infected cattle with respiratory tract infection. We describe the measures taken to identify and characterize the infecting virus strain, and the series of actions taken to identify and eliminate persistently infected carriers in a herd experiencing several related problems that were shown to be caused by bovine viral diarrhea virus.

Animals↗
PubMedDate not supplied

Persistent infection of humans with hepatitis B virus: mechanisms and consequences.

Although most infections of humans with hepatitis B virus are self-limited, up to 10% of individuals experiencing primary infection remain persistently infected. These individuals are usually asymptomatic but may suffer episodic or progressive liver injury that can result in cirrhosis and liver failure. In addition, chronic infection with hepatitis B virus is, in certain settings, associated with the late development of primary hepatocellular carcinoma. This review summarizes the biological characteristics of persistent viral infection, with particular emphasis on host and viral factors that affect the outcome of primary infection.

Adolescent↗
PubMed1988

Molecular analysis of viral RNAs in mice persistently infected with lymphocytic choriomeningitis virus.

Infection of newborn mice with lymphocytic choriomeningitis virus (LCMV) results in a lifelong persistent infection. Persistently infected animals continuously produce low levels of infectious virus and accumulate large amounts of intracellular viral nucleic acid (P. J. Southern, P. Blount, and M. B. A. Oldstone, Nature [London] 312:555-558, 1984). We have used gel electrophoresis and hybridization techniques to analyze viral RNAs that appear during the establishment and maintenance of a persistent LCMV infection in vivo to identify any role for defective and/or defective interfering RNAs. We have found a complex, heterogeneously sized population of viral RNAs in multiple independent tissues that is uniquely associated with persistent infections in vivo, but we have not yet established whether these RNAs have a causal or a consequential association with persistent infection by LCMV. Within the complex virus RNA population, full-length genomic L and S RNAs were readily detectable and represented the most abundant individual viral RNA species. RNAs apparently corresponding in size to the viral nucleoprotein and glycoprotein mRNAs could also be detected in these tissue RNA samples. The presence of glycoprotein mRNA indicates a potential mechanism of posttranscriptional regulation to account for the previously documented restriction in viral glycoprotein expression in persistently infected mice (M. B. A. Oldstone and M. J. Buchmeier, Nature (London) 300:360-362, 1982).

Animals↗
PubMed1987

Non-infectious morphologically altered nucleocapsids of measles virus from persistently infected cells.

Persistent measles virus infection of human HEp-2 or L-41 cells was accompanied by pronounced structural and functional changes of isolated intracellular viral nucleocapsids (NCs). The bulk of persistent NCs possessed altered conformation and a "string-of-beads" appearance, contained substantial amounts of subgenomic size RNAs, exhibited reduced transcriptase activity in vitro and lacked infectivity on transfection of susceptible cells. Immunogold staining revealed negligible binding of anti-P protein monoclonal antibodies to the "string-of-beads" type NCs, thus suggesting their non-functional state.

Capsid↗
PubMed1997

A computer simulation of the transmission dynamics and the effects of duration of immunity and survival of persistently infected animals on the spread of bovine viral diarrhoea virus in dairy cattle.

This paper describes a computer model that mimics the spread of bovine viral diarrhoea virus (BVDV) infection through a closed herd. The model is able to simulate the spread of infection when a persistently infected (PI) animal is introduced into an infection-free herd, and it is used to investigate the role of persistently infected animals, seroconverting animals, loss of PI calves and duration of immunity on the level of infection within the herd. Under typical management conditions one persistently infected animal poses a real threat to a herd, and the prospect of the herd becoming infection free in a 10-year period without intervention is remote. Seroconverting animals are found to be an important source of infection in herds with few immune animals. The increased loss of PI calves is likely to restrict the numbers of PI animals in a herd, and loss of immunity is important since it increases the possibility of a PI calf being born.

Animals↗
PubMed1985

Influence of interferon on persistent infection caused by Borna disease virus in vitro.

The effect of interferon (IFN) on infection and maintenance of persistent infection of Borna disease (BD) virus in cell cultures was investigated. Acutely BD virus-infected primary rabbit brain and rat lung cells produced significant levels of interferon detectable 3 days post-infection in the culture supernatants. Rat brain and rat lung cells persistently infected with BD virus produced only moderate levels of IFN over a long period. In contrast, persistently infected Madin-Darby canine kidney (MDCK) cells did not produce detectable amounts of IFN. Exogenous homologous IFN completely inhibited the expression of BD virus antigen in acutely infected rabbit brain cells, when added during the first 24 h after infection. IFN added later (2 to 6 days post-infection) reduced virus titres to different degrees depending on the onset of treatment. However, IFN added to persistently infected rat lung cells did not appear to influence the degree or quality of BD virus antigen expression or the intracellular amount of infectious virus. Two facts indicate that IFN is not involved in the establishment or maintenance of persistent BD virus infection in vitro. Thus, MDCK cells, which could not be induced to produce IFN, can be readily persistently infected with BD virus in vitro, and exogenous IFN did not appear to influence persistent BD virus infection.

Animals↗
PubMed1979

[Nature and significance of persistent infections (author's transl)].

The "persistent" viral infections, besides "subclinical" infections, pertain to the vast group of "clinically inapparent" infections. They differ from subclinical infections by a temporally unlimited "co-existence" with the pathogen. Pathogenetically, three forms of development are possible: 1. latent infections, 2. tolerated infections, 3. occult infections. Persistent viral infections are the inexhaustible reservoir for many viruses. To the organism affected they may be of benefit (infection immunity, interference, paraimmunity) or of disadvantage (activation of the infection with conversion into a disease, cause of many chronic, slowly developing disease processes, immunopathogenic consequences), the disadvantages prevailing. To the environment, persistent infections are invisible sources of danger as they produce carriers and chronic carriers.

Carrier State↗
PubMed1990

Characterization of human parainfluenza virus type 3 persistent infection in cell culture.

Three cell lines persistently infected with human parainfluenza virus type 3 were characterized on a molecular level in this study. All six structural protein genes were transcribed into monocistronic RNAs in the persistently infected cells. In both acutely and persistently infected cells, polycistronic transcripts were abundant, although the ratio of polycistronic to monocistronic transcripts was reduced in the persistently infected cells. Each of the persistently infected cell lines contained a distinct subgenomic RNA species. The subgenomic RNAs were present in purified nucleocapsid cores, indicating that they represent viral genome RNA, were far more abundant than full-length RNA, and were stably maintained through at least 36 cell passages. Nucleotide sequence analysis of the subgenomic RNAs from two of the persistently infected cell lines revealed that the 5' ends are identical to that of the standard genome. Hybridization experiments with oligonucleotide probes showed that both fragments retain sequences from the 5' end of the standard genome and contain approximately 1,200 nucleotides (cell line 1) and 1,500 nucleotides (cell line 2) of the polymerase gene sequence. The demonstration of several alterations in viral gene expression in persistently infected cells offers insight into the factors associated with persistence of parainfluenza virus 3.

Animals↗