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PubMed2005

Measles virus superinfection immunity and receptor redistribution in persistently infected NT2 cells.

A recombinant measles virus (MV) expressing red fluorescent protein (MVDsRed1) was used to produce a persistently infected cell line (piNT2-MVDsRed1) from human neural precursor (NT2) cells. A similar cell line (piNT2-MVeGFP) was generated using a virus that expresses enhanced green fluorescent protein. Intracytoplasmic inclusions containing the viral nucleocapsid protein were evident in all cells and viral glycoproteins were present at the cell surface. Nevertheless, the cells did not release infectious virus nor did they fuse to generate syncytia. Uninfected NT2 cells express the MV receptor CD46 uniformly over their surface, whereas CD46 was present in cell surface aggregates in the piNT2 cells. There was no decrease in the overall amount of CD46 in piNT2 compared to NT2 cells. Cell-to-cell fusion was observed when piNT2 cells were overlaid onto confluent monolayers of MV receptor-positive cells, indicating that the viral glycoproteins were correctly folded and processed. Infectious virus was released from the underlying cells, indicating that persistence was not due to gross mutations in the virus genome. Persistently infected cells were superinfected with MV or canine distemper virus and cytopathic effects were not observed. However, mumps virus could readily infect the cells, indicating that superinfection immunity is not caused by general soluble antiviral factors. As MVeGFP and MVDsRed1 are antigenically indistinguishable but phenotypically distinct it was possible to use them to measure the degree of superinfection immunity in the absence of any cytopathic effect. Only small numbers of non-fusing green fluorescent piNT2-MVDsRed1 cells (1 : 300 000) were identified in which superinfecting MVeGFP entered, replicated and expressed its genes.

Antigens, CD↗

PubMed1975

Immune enhancement of the tumorigenicity of hamster brain tumor cells persistently infected with measles virus.

Studies were conducted on the tumorigenicity of a hamster brain tumor (HBT) cell line persistently infected with measles virus (MV). This cell population, termed HBT-M, exhibited decreased tumorigenicity in weanling hamsters when implanted intracutaneously. The lowered tumorigenicity of the HBT-M cells could be counteracted by concurrent hydrocortisone treatment restoring the tumor-producing capacity to levels comparable to those of the highly tumorigenic HBT cells. It was also determined that prior immunization of hamsters with MV resulted in enhancement of tumor formation from usually subtumorigenic doses of HBT-M cells. This increase in tumorigenicity appeared to correlate with high titers of MV antibody. Treatment of hamsters with cyclophosphamide resulted in a reduction of MV antibody titers and effected a decrease of HBT-M cell tumorigenicity to control levels. Preliminary studies with passive immunizations indicated that the enhancing factor could be transferred in the sera from hamsters hyperimmunized with MV. These data suggested that MV antibody may potentiate the development of neoplasia of cells persistently infected with MV in a manner similar to the enhancement of tumor growth by blocking antibody.

Animals↗

PubMed1985

Monoclonal antibodies against five structural components of measles virus. II. Characterization of five cell lines persistently infected with measles virus.

Groups of monoclonal antibodies against measles virus nucleoprotein (NP), phosphoprotein (P), matrix (M), hemagglutinin (H) and fusion (F) components were used for characterization of 5 persistently infected cell lines. In four of these lines (Lu106 carrier, MaSSPE, MaPi, HEpPi) all cells were infected but the cells mostly produced noninfectious virus products. The fifth line (HNT in vero cells) did not produce any infectious virus and only a fraction of the cells were infected in most passages. In agreement with earlier findings the virus strains showed marked variations in the M epitope pattern and also some variation in the H epitope pattern. In addition epitope variations were found in both NP and P protein, which contrasted with conserved antigen characteristics of these components in lytically replicating virus. Restriction of fusion in the persistent infections was studied further. HNT and Lu 106 cells showed selective quantitative restriction in F protein synthesis. Lu106 cells were found to contain distinct epitopic F species. In contrast MaSSPE cells produced readily detectable cleaved F protein and in addition extracellular virus products carried hemolytic activity. The fact that no cell fusion occurred was interpreted to be due to particular properties of the Ma 106 cells, a concept supported by the absence of fusion of these cells when infected with syncytiogenic measles virus. It is concluded that (a) under conditions of persistence of measles-virus without requirement for synthesis of complete virions a more pronounced variation in epitope characteristics of virus components is encountered than in lytic infections; and b) that persistence of measles virus shows individualistic characteristics which may reflect changes in the virus and/or innate properties of the host cells.

Animals↗

PubMed1999

In vivo disturbance of hematopoiesis in mice persistently infected with murine cytomegalovirus: impairment of stromal cell function.

Although the pathogenic effects of a primary cytomegalovirus (CMV) infection on hematopoiesis has been largely investigated so far, the effects of a persistent or latent infection have yet to be elucidated. The effects of persistent CMV infection on hematopoiesis thus were examined using BALB/c mice at 4 weeks postinfection with 0. 2 LD50 of murine CMV (MCMV) infection as a persistent infection model. The parameters of constitutive hematopoiesis of MCMV persistently infected mice were completely identical to those of the control. However, the inductive hematopoiesis, examined by the autologous marrow reconstitution after 5-fluorouracil administration, was significantly impaired in the MCMV persistently infected mice (P < 0.05). In a colony-forming unit-spleen assay and a long-term bone marrow culture system, a decreased capacity of bone marrow stromal cells to support hematopoiesis was observed in the MCMV-infected mice in comparison with the controls. The existence of MCMV DNA in the adherent cells of long-term bone marrow culture from the MCMV-infected mice were confirmed by a polymerase chain reaction but not in the nonadherent cells. Furthermore, the increased expression level of tumor necrosis factor-alpha by stromal cells was also observed by semiquantitative reverse transcriptase-polymerase chain reaction. These results therefore strongly suggest that MCMV remains to infect the stromal cells while also inhibiting inductive hematopoiesis through the impairment of the stromal cell functions in the MCMV persistently infected mice.

Animals↗

PubMed2005

Viral infection in internally structured hosts. I. Conditions for persistent infection.

For a virus population within its host, two important levels of structure can be considered: multiple cell types which can be infected, and tissue types or body compartments which may be coupled via movement. We develop a model with both types of structure. Migration between compartments can create "sources" and "sinks" within the virus population, where realized viral growth rate and abundance is lowered in some compartments compared to what would be observed in isolation. Using both analytical and numerical methods, we investigate how this within-host spatial structure affects the conditions for persistent viral infection. We find that migration between compartments makes the establishment of infection more difficult than it would be in the absence of migration, implying that within-host spatial structure combined with viral movement decreases the likelihood of viral establishment. If migration is symmetrical and compartments are heterogeneous, an increase in migration rates between compartments generally makes establishment less likely. This may help to explain the tissue specificity observed for many viruses. There are, however, important exceptions to this result. These include circumstances where the virus initially invades a compartment that is unfavorable to population growth and migration is necessary to infect other parts of the host body. Stochastic aspects of viral establishment may also favor increased migration as it tends to dampen the amplitude of fluctuations in population size during the initial transient phase of establishment.

Animals↗

PubMed1995

Detection of immunodeficiencies and persistent infections by urinary neopterin measurement.

We evaluated the clinical significance of measurement of urinary neopterin levels in primary immunodeficiencies and persistent infections exclusively at afebrile or asymptomatic periods. Despite the examinations at afebrile or asymptomatic periods, urinary neopterin levels were elevated in some patients with primary immunodeficiencies and in patients with persistent infections of human immunodeficiency virus (HIV) or Epstein-Barr virus (EBV). Therefore, urinary neopterin measurement at afebrile periods will be useful as one of the screening tests in the detection of such disorders among children with occasional episodes of infections.

Adolescent↗

PubMed1998

Viability and gene expression in Chlamydia trachomatis during persistent infection of cultured human monocytes.

The principal host cell for persistently infecting synovial Chlamydia trachomatis is the macrophage. During infection of human monocytes/macrophages in culture this bacterium displays aberrant morphology and produces no new elementary bodies, reflecting the situation in synovium. Here we investigate the metabolic status of C. trachomatis (serovar K) during an extended infection of human peripheral monocytes in vitro. Using reverse transcription-polymerase chain reaction assays, we have shown that primary transcripts from the chlamydial rRNA operons are present throughout a 10-day course of infection. Other assays targeting mRNAs from chlamydial genes encoding r-proteins S5 and L5, the glycyl-tRNA synthetase, the 60-kDa cysteine-rich outer membrane protein, and the KDO transferase indicate that these messengers are also present throughout the entire 10-day period. The gene encoding the 57-kDa heat-shock protein (hsp60) is expressed by the bacterium throughout the 10-day infection of cultured monocytes, but transcript levels from the gene encoding the major outer membrane protein (omp1) appear to be attenuated. Western analyses targeting these latter proteins confirm the presence of the hsp60 gene product, and the virtual absence of major outer membrane protein, in chlamydia-infected cultured human monocytes. Thus, during extended infection of human monocytes in vitro, chlamydia are non-productive but transcriptionally active; the pattern of transcriptional activity reflects that known for persistent C. trachomatis infection in vivo in synovial tissue.

Antibodies, Monoclonal↗

PubMed1989

Lymphocyte subpopulations in the blood of sheep persistently infected with border disease virus.

The surface phenotypes of peripheral blood lymphocytes in groups of lambs and adult sheep persistently infected with Border disease virus (P-I BD) were compared with those of healthy controls. The proportion and number of lymphocytes bearing surface immunoglobulin (sIg+) and expressing class II MHC antigen (B cells) were significantly increased. A significant increase in CD1+ lymphocytes was also evident. Conversely, the proportion of T lymphocytes in P-I BD lambs was reduced. A marked reduction in the proportion of circulating lymphocytes expressing class I MHC antigen was also observed. These findings were not affected by differences in the strain of the virus responsible for the persistent infection.

Aging↗

PubMed1998

Experimental induction of mucosal disease: consequences of superinfection of persistently infected cattle with different strains of cytopathogenic bovine viral diarrhea virus.

Mucosal disease (MD) can be induced in cattle persistently infected with noncytopathogenic bovine viral diarrhea virus (ncp BVD virus) by superinfecting them with antigenically related cytopathogenic (cp) BVD virus strains. While some of these animals succumb to early onset MD after 2 to 3 weeks post infectionem (p.i.), others only react by producing neutralizing antibodies against the cp BVD virus strain and may develop late onset MD after longer incubation periods. The aim of this study was to determine if an increasing degree of antigenic homology between the ncp and the superinfecting cp BVD virus strains as determined by their comparative reactivity with E2 glycoprotein specific monoclonal antibodies (mabs) increases the probability of inducing early or late onset MD, respectively. For this, each two of eight clinically healthy animals from the same herd and persistently infected with the same ncp BVD viruses were superinfected with four different cp BVD virus strains. As only two of these animals developed late onset MD, one animal from a different herd that developed early onset MD was included in the study. Besides clinical observation and testing for antibody production, virus isolation and characterization of the cp BVD virus isolates were performed. The results indicate that antigenic similarity as determined by comparative mab analysis alone is not sufficient to allow prediction of the outcome of the disease.

Amino Acid Sequence↗

PubMed1981

Persistent infection with mouse hepatitis virus, JHM strain in DBT cell culture.

After inoculation with JHM strain into DBT cell monolayers, a persistently infected DBT cell culture was established without producing typical cytopathic changes after about 15th passages. By immunofluorescence virus specific antigen was demonstrated in 10 to 15% DBT cells. This persistently infected culture (JHM-CC) was resistant to superinfection with parental JHM, but such resistance was not shown against vesicular stomatitis virus. JHM-CC virus produced small plaques on DBT cell monolayers. Temperature sensitive (TS) mutant, defective interfering (DI) particle or interferon was not detected in the JHM-CC. To intracerebral inoculation with JHM-CC virus, cortisone treated ICR mice survived without showing clinical signs, however, demyelinating lesions were produced in the brain and spinal cord of them.

Animals↗

PubMed1983

Decreased colony forming ability of human cells persistently infected with baboon endogenous virus. Brief report.

Plating efficiency (PE), i.e. colony forming ability, of primary human embryonic lung fibroblasts persistently infected with baboon endogenous virus (BaEV) decreased to less than 10 per cent of that of the uninfected cells. A line of human amnion (FL) cells showed a 55 per cent reduction of PE after the establishment of BaEV carrier state. No decrease of PE did occur as a result of BaEV persistent infection in a rhabdomyosarcoma cell line (A204) and in fibroblasts derived from adult human skin. This characteristic reduction of PE in the infected primary embryonic fibroblasts was completely abolished by cultivation of the cells with conditioned medium from confluent either virus-infected or uninfected culture.

Adult↗

PubMed1994

Elements in the long terminal repeat of HIV-1 that interact with nuclear extracts from Jurkat cells persistently infected with vaccinia virus.

Previous reports showed transactivation of the long terminal repeat (LTR) of HIV-1 in Jurkat cells persistently infected with vaccinia virus. In this communication, electrophoretic mobility shift assays were used to characterize the elements in HIV-1 LTR which might be responsible for the mechanism of transactivation. The results indicated that two elements, those for binding NF-kB and NFAT-1, were able to interact with nuclear extracts derived from Jurkat cells persistently infected with vaccinia virus, suggesting that they may play a role in the transactivation of HIV-1 LTR.

Base Sequence↗

PubMed1988

Virus-lymphocyte interactions. III. Biologic parameters of a virus variant that fails to generate CTL and establishes persistent infection in immunocompetent hosts.

Viruses that cause in vivo persistent infections avoid the host's immunologic surveillance machinery. A major component of that armamentarium is virus-specific MHC-restricted cytotoxic T lymphocyte (CTL) response of the host. Studies with lymphocytic choriomeningitis virus (LCMV) have uncovered a parental virus (CTL+) that in immuno-competent adults induces CTL and terminates acute infection and a variant (CTL-) that fails to elicit CTL responses and establishes a persistent state (R. Ahmed et al. (1984) J. Exp. Med. 160, 521-540). The biologic properties, similarities, and differences between CTL+ and CTL- viruses as regards their interactions with lymphocytes of newborn and adult mice is recorded here. CTL+ and CTL- viruses persist in lymphocytes of newborn inoculated mice, primarily within the T helper subset. Approximately 2% of lymphocytes express viral nucleic acid sequences while only 0.04% score as infectious centers suggesting incomplete viral replication. These levels were maintained over the course of infectious. In contrast, CTL- virus but not CTL+ persists in lymphocytes of mice inoculated when adults. Lymphocytes easily scored as infecting centers but rarely displayed nucleic acid sequences suggesting a different balance of incomplete to complete virion replication. Further, infectious centers decreased by 10-fold from the 3rd to 68th day of infection and the total numbers of T lymphocytes in the circulation decreased suggesting CTL- may replicate in and destroy lymphocytes of adult mice. In the following paper the primary nucleotide structure of the LCMV small RNA segment, the segment responsible for generation of CTL and encoding the proteins recognized by CTL, for CTL+ and CTL- viruses is reported.

Animals↗

PubMed1987

Frequency of association of noncytopathic bovine viral diarrhea virus with mononuclear leukocytes from persistently infected cattle.

All mononuclear leukocytes and T lymphocyte-enriched and B lymphocyte-enriched subpopulations of mononuclear leukocytes collected from 8 cows persistently infected with 1 of 3 isolates of noncytopathic bovine viral diarrhea virus were tested for association with virus. For all persistently infected cows, approximately 4.4% of all mononuclear leukocytes, 5.4% of T lymphocyte-enriched, and 2.1% of B lymphocyte-enriched subpopulations of mononuclear leukocytes were associated with virus. Differences between leukocyte populations in percentages of leukocytes associated with virus were real (P less than 0.05). Among virus isolates, significant differences in percentages of leukocytes associated with virus were not detected.

Animals↗

PubMed1990

Persistent infection of K562 cells by encephalomyocarditis virus.

Infection of human erythroleukemic K562 cells by encephalomyocarditis virus readily resulted in establishment of persistently infected cultures. In contrast to the usual typical lytic infection by encephalomyocarditis virus, in which trypan blue staining of cells reaches close to 100% by about 15 h postinfection, K562 cell cultures required 3 to 4 days postinfection to reach a maximum of about 80 to 90% cell staining. The proportion of K562 cells taking up stain gradually decreased to about 10% of those present by about 13 days postinfection; during this time, virus yield per day measured by either plaque or hemagglutination titration fell about 10-fold. The decrease in percent staining was followed by waves of increased staining accompanied by increased virus production. Virus-producing cultures were maintained for over 3 months. Evolution of both virus and cells accompanied establishment of persistence in that plaque size changed from about 7 mm in diameter for the original virus to less than 1.5 mm by day 20 postinfection and most of the cells cloned from persistently infected cultures were resistant to superinfection with the original virus. Resistance was due, at least in part, to reduced virus attachment in that binding of 3H-labeled virus to cloned resistant cells was about 2% of that to uninfected cells.

Animals↗

PubMed1996

Maintenance of pluripotency in mouse embryonic stem cells persistently infected with murine coronavirus.

A persistently coronavirus-infected embryonic stem (ES) cell line A3/MHV was established by infecting an ES cell line, A3-1, with mouse hepatitis virus type-2. Although almost all A3/MHV cells were found infected, both A3/MHV and A3-1 cells expressed comparable levels of cell surface differentiation markers. In addition, A3/MHV cells retained the ability to form embryoid bodies. These results suggest that persistent coronavirus infection does not affect the differentiation of ES cells.

Animals↗

PubMed1996

Analysis of La Crosse virus S-segment RNA and its positive-sense transcripts in persistently infected mosquito tissues.

La Crosse (LAC) virus is an important cause of pediatric arboviral encephalitis in the United States. LAC virus is biologically transmitted by the mosquito Aedes triseriatus, and, like other arthropod-borne viruses, it establishes a persistent, nonpathogenic infection in its vector following oral infection. To investigate LAC virus persistent infection of mosquitoes, a reverse transcription-PCR assay was developed for the amplification of LAC virus negative-sense small (S) genome RNA segment, its full-length complement, and its mRNA transcript for qualitative analysis of transcription and replication in persistently infected mosquito tissues. RNAs were assayed from midguts removed at predetermined times after infection with a LAC virus-containing blood meal. LAC virus genome was detected almost uniformly in midguts at days 3 to 28 postinfection (p.i.) and, as the time p.i. progressed, in more of the samples than either mRNA or viral cRNA (vcRNA). Thus, persistent LAC virus infection of A. triseriatus midguts was correlated with a reduction in detectable viral mRNA and vcRNA. The assay was also used for analysis of virus-specified RNA in both quiescent and biosynthetically active mosquito ovaries. Viral replication decreased, as indicated by the absence of viral mRNA and vcRNA, in the ovaries of mosquitoes that did not receive further blood meals after their original oral infection. Viral replication increased in ovaries of mosquitoes that took an additional blood meal 30 days p.i. and was continuous in mosquitoes that took multiple meals to stimulate oogenesis. Thus, virus replication in persistently infected mosquito ovaries was dependent on host cell biosynthetic status.

Aedes↗

PubMed2001

Reduced expression of surface glycoproteins in mouse fibroblasts persistently infected with human respiratory syncytial virus (HRSV).

BCH4 cells, persistently infected with Human Respiratory Syncytial Virus (HRSV), were obtained by Fernie et al. [12] after infection of a BALB/c mouse embryo cell line with the Long strain of HRSV. To understand the basis of HRSV persistence, the expression of HRSV RNAs and proteins was evaluated in BCH4 cells and infected parental BALB/c and fully permissive HEp-2 cells. Production of viral mRNAs was severely impaired in BCH4 cells. In addition, the expression level of the surface glycoproteins F and G was markedly reduced relative to internal viral proteins. However, virus recovered from BCH4 cells could lytically infect HEp-2 cells and expressed normal levels of surface glycoproteins. No evidence of defective genomes or interfering particles was found in BCH4 cells. Taken together, these data indicate that reduction of both viral mRNA accumulation and surface glycoprotein biosynthesis are at the basis of HRSV persistence in BCH4 cells.

Animals↗