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PubMed1990

Interferon cures cells lytically and persistently infected with African swine fever virus in vitro.

Human interferon alpha (IFN-alpha) and interferon gamma (IFN-gamma) inhibit African swine fever (ASF) virus replication in Vero cells. IFN-alpha and IFN-gamma exert a synergistic inhibition. Human tumor necrosis factor (TNF) does not inhibit ASF virus replication in this cell line, but in combination with IFNs it has antiviral enhancing activity. Analysis of the mechanism of inhibition suggests that the action of these cytokines blocks a step that comes prior to DNA replication. The 2'-5' A synthetase activity is induced in Vero cells by treatment with these cytokines and is activated after ASF virus infection. More interesting is the finding that continuous treatment with IFN-alpha cures Vero cells from lytic and persistent infections with ASF virus. A potential application of IFN for the treatment of animals carrying the virus is suggested.

2',5'-Oligoadenylate Synthetase↗
PubMed1987

The astrocyte is a target cell in mice persistently infected with mouse hepatitis virus, strain JHM.

Mouse hepatitis virus, strain JHM (MHV-JHM), causes a late onset, clinically apparent, demyelinating encephalomyelitis in 40% of suckling C57BL/6 mice born to immunized dams. Suckling mice born to unimmunized dams rapidly succumb to an acute encephalomyelitis. MHV-JHM can be isolated from the brains and spinal cords of maternal antibody-protected mice when the late onset disease becomes clinically apparent, showing that the virus must be present in these mice when they are still asymptomatic. To determine which cells of the central nervous system (CNS) were potential reservoirs for the virus during the asymptomatic period, tissue sections were assayed simultaneously by immunoperoxidase and immunofluorescence staining for the presence of viral antigen and for glial fibrillary acidic protein (GFAP), a marker for astrocytes. The results indicate that 20% (range 0-52%) of the MHV-JHM infected cells in asymptomatic mice were astrocytes. In mice symptomatic with late onset hindlimb paralysis, a higher percentage of infected cells were astrocytes. These results indicate that astrocytes are a target cell in both symptomatic and asymptomatic mice persistently infected with MHV-JHM, and suggest that the astrocyte is a potential cellular reservoir for MHV-JHM in asymptomatic mice.

Acute Disease↗
PubMed2006

Leukocyte profile of cattle persistently infected with bovine viral diarrhea virus.

Animals acutely infected with bovine viral diarrhea virus (BVDV) exhibit transient immunosuppression as a result of the virus' predilection for cells that play critical roles in the host immune system. Acute BVDV infections have major effects on thymic and follicular T-lymphocytes, as well as follicular B-lymphocytes, often resulting in severe reduction in circulating numbers of lymphocytes and suppression of functional activities of these cells. Granulocytes and monocytes are equally susceptible to BVDV infections with reduction in numbers and suppression functions. However, there is limited information on the leukocyte profile of cattle persistently infected (PI) with BVDV. This study reports on phagocytic activities of granulocytes and monocytes as well as immunophenotyping by flow cytometric analysis of leukocytes isolated from healthy non-PI (NPI) and PI animals. No significant differences were found between the leukocyte profiles and the phagocytic activities of PI animals when compared to a group of healthy NPI animals.

Animals↗
PubMed2000

Persistent infection mechanism of GB virus C/hepatitis G virus differs from that of hepatitis C virus.

OBJECTIVE: Changes in the deduced amino acid sequence of the envelope 2 (E2) region of the GB virus C/hepatitis G virus (GBV-C/HGV) were analyzed to investigate whether or not the region contributes to persistent infection with the virus. METHODS: Eight patients with acute hepatitis C and 1 patient with acute hepatitis of unknown etiology were included in the study. GBV-C/HGV RNA was detected in 6 patients, including the patient with hepatitis of unknown origin. The nucleotide sequence of the E2 region of hepatitis C virus (HCV) and GBV-C/HGV was determined by direct sequencing of polymerase chain reaction products in 5 patients with HCV infection and in 6 patients with GBV-C/HGV infection twice during the period of early infection and several months or years later in each patient. RESULTS: The mean substitution rate of the deduced amino acid sequence in the E2 region was over 100 times lower (p < 0.001) in GBV-C/HGV (0.01 +/- 0.04/month/100 sites) than in HCV (2.4 +/- 1.7/month/100 sites). The amino acid sequence of the loop domain of GBV-C/HGV-E2 did not change in any of the 6 patients. On the other hand, the sequence of the hypervariable region of HCV-E2 changed remarkably (5.9 +/- 4.3/month/100 sites). No amino acid substitution in the loop domain was observed in 7 additional patients who showed persistent GBV-C/HGV viremia for more than 2 years. CONCLUSION: These results indicate that changes in the amino acid sequence of the E2 region are not involved in the mechanism of persistent GBV-C/HGV infection.

Acute Disease↗
PubMed1990

Dextran sulfate and other polyanionic anti-HIV compounds specifically interact with the viral gp120 glycoprotein expressed by T-cells persistently infected with HIV-1.

Eighty to 100% of persistently HIV-1-infected HUT-78 cells express the viral glycoprotein gp120 as demonstrated with anti-gp 120 monoclonal antibody (mAb) and fluorescence-activated cell sorter (FACS) analysis. Several polyanionic anti-HIV compounds, i.e., dextran sulfate, pentosan polysulfate, heparin, aurintricarboxylic acid (ATA), suramin, and Evans blue, which are known to inhibit the adsorption of HIV particles to CD4+ cells, prevented the binding of anti-gp120 mAb to the persistently HIV-1 infected HUT-78 cells. This effect was dose-dependent and reversible. Except for ATA, the polyanionic compounds did not interfere with the binding of Leu3a/OKT4A mAB, indicating that they do not directly bind to the CD4 receptor. Thus, the inhibitory effect of dextran sulfate and its congeners on the interaction of the HIV gp120 with the cellular CD4 receptor can be ascribed to a specific binding ("shielding") of gp120.

Antibodies, Monoclonal↗
PubMed1996

Reduced precore transcription and enhanced core-pregenome transcription of hepatitis B virus DNA after replacement of the precore-core promoter with sequences associated with e antigen-seronegative persistent infections.

Hepatitis B virus variants harboring nucleotide alterations in the preC-C promoter have been detected in fulminant hepatitis B as well as in HBeAg-seronegative persistent infection. However, it has not been demonstrated that variants with nucleotide alterations in the preC-C promoter cause various disease states. We replaced the preC-C promoter region of a wild-type genome with the most frequent naturally occurring mutated form and introduced it into HepG2 cells. The mutant with coexisting A1762T and G1764A substitutions produced less than one-fifth of the wild-type level of HBeAg. Conversely, the mutant generated 2.4 times more core particle antigen and showed a high-replicator phenotype. RNase protection and quantitative 5' RACE showed a 16- to 32-fold reduction of preC transcripts and a 4-fold induction of C transcripts of the mutant compared to wild-type. The preC transcript of the mutant had a more heterogeneous 5' end than that of the wildtype. However, the mutations did not alter the initiation sites of C transcription. When the promoter region was cloned into CAT plasmids, the mutations had dual effects on preC and C promoter activities, decreasing and increasing them, respectively. These results suggest that these mutations are responsible for the reduced HBeAg production as well as the enhanced replication and core production. Analysis of revertants with either single point mutation showed that T at 1762 is critical for the mutant phenotype.

Amino Acid Sequence↗
PubMed2004

Increase in gammadelta T cells in the blood of cattle persistently infected with bovine leukemia virus following administration of recombinant bovine IFN-gamma.

To examine the effect of recombinant bovine interferon-gamma (rbIFN-gamma) on cattle persistently infected with bovine leukemia virus (BLV), BLV-infected cattle were inoculated intraperitoneally with IFN-gamma. All cattle were febrile after inoculation with IFN-gamma and then recovered within 48 h. Flow cytometric analysis showed that the numbers of CD4+ and CD8+ T cells were decreased for 2-3 days and then their numbers were recovered. The number of gammadelta T cells increased after the fever. In contrast, the number of IgM+ lymphocytes remained low for about 1 week. Moreover, the numbers of syncytia produced by peripheral blood lymphocytes decreased and remained low compared to that before IFN-gamma administration. These results suggest that IFN-gamma induces the up-regulation of gammadelta T cells, decreases the number of IgM+ lymphocytes and suppresses the growth of BLV in BLV-infected cattle in vivo.

Animals↗
PubMed2003

Response of calves persistently infected with noncytopathic bovine viral diarrhea virus (BVDV) subtype 1b after vaccination with heterologous BVDV strains in modified live virus vaccines and Mannheimia haemolytica bacterin-toxoid.

Seronegative persistently infected (PI) calves with bovine viral diarrhea virus (BVDV) subtype 1b were vaccinated with each of four modified live virus (MLV) BVDV vaccines and a Mannheimia haemolytica bacterin-toxoid. Nasal swabs and peripheral blood leukocytes (PBL) were collected for virus isolation and serums were collected after vaccination and tested for BVDV1a, BVDV1b, BVDV2, bovine herpesvirus-1 (BHV-1), bovine parainfluenza-3 virus (PI-3V), and bovine respiratory syncytial virus (BRSV) antibodies. M. haemolytica and Pasteurella multocida antibodies were detected using ELISA procedures. None of the PI calves developed mucosal disease (MD) after MLV vaccination. None of the BVDV PI calves seroconverted to BVDV1b after MLV vaccination. Calves receiving MLV vaccines seroconverted to the respective type/subtype in the vaccine. Calves receiving a MLV vaccine with noncytopathic (NCP) BVDV1 (subtype not designated) did not seroconvert to BVDV1a, BVDV1b, or BVDV2. The PI calves were positive for BVDV subtype 1b, in the PBL and nasal swabs throughout the study. Calves receiving each of three vaccines with known BVDV1a strains had BVDV1a positive samples after vaccination, in some but not all calves, up to Day 28. The PI BVDV1b calves did not respond with increased M. haemolytica antibodies after vaccination compared to BVDV negative calves receiving the same M. haemolytica vaccine.

Animals↗
PubMed1966

Persistent infection of a rat kidney cell line with Rauscher murine leukemia virus.

Duc-Nguyen, Huu (National Cancer Institute, Bethesda, Md.), Edith N. Rosenblum, and Robert F. Zeigel. Persistent infection of a rat kidney cell line with Rauscher murine leukemia virus. J. Bacteriol. 92:1133-1140. 1966.-The propagation of a murine leukemia virus (Rauscher) in a kidney cell line, derived from a rat with lymphoid leukemia, was studied. A complement-fixing (CF) antigen reacting with Rauscher immune sera was detected at various passage levels, which correlated with the visualization by use of electron microscopy of viral buds and viral particles in different stages of maturation in all passages. Five-month-old monolayers continued to shed virus and to yield high CF antigen titers. The cell-free supernatant fluid from cultures of the 14th passage was shown to be infectious for a normal rat kidney cell line, as evidenced by the appearance of the CF antigen in this line. Interferon production was not demonstrated in infected cultures. The overall data indicated that rat kidney cells could be used to propagate Rauscher virus in a carrier state.

Animals↗
PubMed1987

Dominance of temperature-sensitive phenotypes. II. Vesicular stomatitis virus mutants from a persistent infection interfere with shut-off of host protein synthesis by wild-type virus.

The dominance of a mutant (VSV-PI) isolated from a long-term persistent infection over wild-type vesicular stomatitis virus (wt-VSV) is reported. This dominance has some important differences from and similarities to the dominance of conventional ts mutants studied previously (J. S. Youngner, D. W. Frielle, and P. Whitaker-Dowling, 1986, Virology 155, 225-235). Unlike the ts mutants representing complementation groups I and IV, coinfection with VSV-PI does not reduce the yield of infectious wt-VSV at either the permissive (37 degrees) or nonpermissive (39.5 degrees) temperatures. However, in double infections with wt-VSV and VSV-PI at 37 degrees, viral RNA synthesis patterns were converted to those of the RNA synthesis phenotype of VSV-PI: reduced mRNA transcription and enhanced replication of genomic RNA. In addition, VSV-PI which shuts off host protein synthesis very inefficiently was able to interfere in double infections with the ability of wt-VSV to rapidly shut off host protein synthesis. This finding suggests that the mutant virus is not just missing the factor(s) responsible for the inhibition of host protein synthesis but has a dominant activity which works in trans to interfere with the shut-off function of wt-VSV. Ultraviolet irradiation of VSV-PI was used to determine the target size of the interference function. The calculated value for the uv target size is equal to that of the viral genome. This suggests that either viral replication or the expression of the last gene on the viral genome (encoding the L protein) is required for interference by VSV-PI with the shut-off of host cell protein synthesis by wt-VSV.

Animals↗
PubMed1994

Border disease virus antigens in lymphocyte subpopulations in the peripheral blood of persistently infected sheep.

Biotinylated virus-specific antibodies were used to detect Border disease virus antigen by flow cytometry in the mononuclear cells of the peripheral blood of 15 sheep persistently infected with Border disease virus. The viral antigen was present in 12.86 +/- 4.65% (mean +/- SD) of mononuclear cells (MNC). The percentage of MNC that contained viral antigen was higher in lambs than in adult sheep, with mean rates of 22.68 +/- 5.02% and 11.65 +/- 4.39%, respectively. Depletion methods were used to estimate the distribution of viral antigen in peripheral blood lymphocyte subsets. The viral antigen was present in T-cells (OvCD5+), B-cells (LCAp220+) and non-T- and non-B-cells. Depletion studies revealed that 5.39 +/- 2.47% of the cells expressing the LCAp220 epitope (B-cells), 23.38 +/- 11.38% of those expressing the OvCD5 epitope (T-cells) and 55.07 +/- 10.93% of those which were neither B- nor T-cells were positive for viral antigen. Most (57.18 +/- 5.41%) of the T-cells containing viral antigen were cytotoxic/suppressor (OvCD8), 25.63 +/- 2.97% were helper (OvCD4) cells and 12.24 +/- 3.21% expressed the gamma/delta (OvWC1) epitope.

Animals↗
PubMed1990

An ELISA for detecting pestivirus antigen in the blood of sheep persistently infected with border disease virus.

A monoclonal antibody capture enzyme-linked immunosorbent assay (ELISA) has been developed to detect a pestivirus-specific antigen in leucocytes of sheep persistently infected with border disease virus. A blind trial was conducted to compare the specificity of the ELISA with conventional tissue culture virus isolation on blood samples from 58 sheep, aged 3 to 48 months. There was total agreement between the two tests; 27 sheep were shown to be BDV-infected. The ELISA OD values of the positive samples ranged from 0.12 to 0.86 and were not related to age, strain of virus with which they were infected or presence of serum neutralising antibody. Negative samples had OD values between 0 and 0.02.

Animals↗
PubMed2003

Detection of carrier cattle and sheep persistently infected with foot-and-mouth disease virus by a rapid real-time RT-PCR assay.

The detection of foot-and-mouth disease virus (FMDV) in persistently infected carriers among exposed ruminants is of great importance in disease control. For this purpose, a real time, fluorogenic reverse transcription polymerase chain reaction (real-time RT-PCR) assay was evaluated for the identification of FMDV carrier animals. The results indicate that this real time RT-PCR assay may be suitable for detection of FMDV carrier animals.

Animals↗
PubMed2001

Infectivity, persistence and serological response of nine Trichinella genotypes in rats.

Domestic and sylvatic Trichinella genotypes were evaluated for infectivity, muscle larvae persistence, and host antibody responses in rats. Groups of rats were inoculated with T. spiralis, T. nativa, T. britovi, three genotypes of T. pseudospiralis (from USSR, USA, and Australia), T. murrelli, Trichinella T6, and T. nelsoni, respectively. The muscle larvae intensity (larvae per gram), total larval burden (lpg x rat weight), and the antibody levels were determined at necropsy 5, 10, 20, and 40 weeks post inoculation. All Trichinella genotypes were established in the rats, but infectivity and persistence differed significantly: T. spiralis established and persisted in high numbers, the three T. pseudospiralis genotypes were also highly infective but differed significantly in persistence, T. britovi and T. nativa had limited infectivity and persistence, Trichinella T6 had low infectivity and very low persistence, and T. murrelli and T. nelsoni were almost non-infective. Except for T. spiralis, initial total muscle larval burdens declined significantly for other genotypes during the experiment. A high initial serological response was detected for all genotypes, but the antibody levels decreased rapidly in relation to decreasing larval burdens. After 20 w.p.i. the antibody levels remained high only in T. spiralis and T. pseudospiralis infected rats. The high infectivity and persistence of T. pseudospiralis in rats, suggests that in addition to T. spiralis, this species might be of significant importance in the domestic cycle of trichinellosis.

Animals↗
PubMed1995

Persistent infection of rhesus macaques with T-cell-line-tropic and macrophage-tropic clones of simian/human immunodeficiency viruses (SHIV).

To elucidate the functions of human immunodeficiency virus type 1 (HIV-1) genes in a nonhuman primate model, we have constructed infectious recombinant viruses (chimeras) between the pathogenic molecular clone of simian immunodeficiency virus (SIV) SIVmac239 and molecular clones of HIV-1 that differ in phenotypic properties controlled by the env gene. HIV-1SF33 is a T-cell-line-tropic virus which induces syncytia, and HIV-1SF162 is a macrophage-tropic virus that does not induce syncytia. A DNA fragment encoding tat, rev, and env (gp160) of SIVmac239 has been replaced with the counterpart genetic region of HIV-1SF33 and HIV-1SF162 to derive chimeric recombinant simian/human immunodeficiency virus (SHIV) strains SHIVSF33 and SHIVSF162, respectively. In the acute infection stage, macaques inoculated with SHIVSF33 had levels of viremia similar to macaques infected with SIVmac239, whereas virus loads were 1/10th to 1/100th those in macaques infected with SHIVSF162. Of note is the relatively small amount of virus detected in lymph nodes of SHIVSF162-infected macaques. In the chronic infection stage, macaques infected with SHIVSF33 also showed higher virus loads than macaques infected with SHIVSF162. Virus persists for over 1 year, as demonstrated by PCR for amplification of viral DNA in all animals and by virus isolation in some animals. Antiviral antibodies, including antibodies to the HIV-1 env glycoprotein (gp160), were detected; titers of antiviral antibodies were higher in macaques infected with SHIVSF33 than in macaques infected with SHIVSF162. Although virus has persisted for over 1 year after inoculation, these animals have remained healthy with no signs of immunodeficiency. These findings demonstrate the utility of the SHIV/macaque model for analyzing HIV-1 env gene functions and for evaluating vaccines based on HIV-1 env antigens.

Animals↗
PubMed1993

Analysis of 3' terminals of human immunodeficiency virus type 1 transcripts in persistently infected cells.

To examine the 3' terminal processing of human immunodeficiency virus type 1 (HIV-1) transcripts and the effects of phorbol ester (TPA) on this processing, cellular RNAs from persistently infected T cells (MOLT-4) or promonocytes (U937), with or without TPA treatment, were analyzed. To map the 3' terminals of viral transcripts, the RNA samples were examined by RNase-protection assay with an HIV-1 long terminal repeat (LTR) antisense riboprobe. Without TPA treatment, the viral transcripts initiated at the cap site in 5' LTR and polyadenylated at poly(A) site in 3' LTR were dominantly detected in both types of cells. This analysis demonstrated that some occlusion mechanism inactivating the poly(A) site in 5' LTR might exist in these infected cells. After TPA treatment, we found a dramatic shift in the protected patterns of viral transcripts in MOLT-4 cells, while the shift in U937 cells was less dramatic. These results suggested that the primary factor(s) involved in the observed effect of TPA might be cellular. We also demonstrated that the shift in the protected patterns of viral transcripts was associated with increased steady-state levels of viral transcripts. These results indicated that the factors involved in the TPA-induced shift might have some relation to the trans-activation of HIV-1 by similar substances.

Base Sequence↗
PubMed2002

Pestivirus in cattle: experimentally induced persistent infection in calves.

Twenty-two heifers were infected intranasally with non-cytopathic bovine viral diarrhoea virus (BVDV) between days 74 and 82 of pregnancy. All animals had developed serum antibodies against BVDV 5 weeks later. No clinical effects were seen in the heifers, and they all delivered a live calf. The newborn calves were generally small, appeared unthrifty as typical 'poor doers', and some developed secondary infections with diarrhoea and signs of respiratory disease. Eighteen of the 22 calves were born without antibodies against BVDV and were persistently infected (PI) with the virus. One was weak at birth and died the following day. Four calves were born with serum antibodies against BVDV and with no detectable virus. Three of these showed signs and/or pathological changes indicating disease in the central nervous system. Otherwise, there were no obvious clinical differences between these calves and the PI calves, nor were there any apparent significant differences in blood parameters between these groups. In general, the calves showed low gamma-globulin values and thrombocytopaenia, but moderately increased fibrinogen values and relatively normal lymphocyte numbers.

Animals↗
PubMed1981

Influence of anti-mouse interferon serum on the growth and metastasis of tumor cells persistently infected with virus and of human prostatic tumors in athymic nude mice.

Baby hamster kidney or HeLa cells form tumors in 100% of athymic nude mice. When such cells are persistently infected (PI) with RNA viruses, such as mumps or measles virus, the tumor cells either fail to grow or form circumscribed benign nodules. Neither the parental nor the virus PI tumor cells form invasive or metastatic lesions in nude mice. Previous studies have indicated a correlation between the susceptibility of virus-PI tumor cells in vitro and the cytolytic activity of natural killer (NK) cells and their failure to grow in vivo. Because interferon (IF) is the principal regulatory molecule governing the differentiation of NK cells, it was possible to test the relevance of the IF-NK cell system in vivo to restriction of tumor growth by treatment of nude mice with anti-IF globulin. This treatment was shown to reduce both IF production and NK activity in spleen cells. Both parental and virus-PI tumor cells grew and formed larger tumors in nude mice treated with anti-IF globulin than in control nude mice. The viral-PI tumor cells and the uninfected parental cells formed tumors in treated mice that were highly invasive and often metastatic. Some human tumor types have been notoriously difficult to establish as tumor lines in nude mice (e.g., primary human prostatic carcinomas). When transplanted into nude mice treated either with anti-IF globulin or anti-lymphocyte serum, two prostatic carcinomas grew and produced neoplasms with local invasiveness and some metastases. The results are consistent with the view that interferon may be important in restricting the growth, invasiveness, and metastases of tumor cells by acting indirectly through components of the immune system, such as NK cells.

Animals↗