Encephalitis induced by bovine herpesvirus 5 and protection by prior vaccination or infection with bovine herpesvirus 1.
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Calves were intranasally challenged with bovine herpesvirus 5 (BHV5) and followed for the development of viral infection, clinical encephalitis, histologic lesions in the brain, and viral sequences in the trigeminal ganglia. Calves that were previously vaccinated with bovine herepesvirus 1 (BHV1, n = 4) or previously infected with BHV1 (n = 5) or that had not been exposed to either virus (n = 4) were compared. No calf developed signs of encephalitis, although all calves developed an infection as indicated by nasal secretion of BHV5 and seroconversion to the virus. Histologic lesions of encephalitis consisting of multifocal gliosis and perivascular cuffs of lymphocytes were observed in calves not previously exposed to BHV1. BHV5 sequences were amplified from the trigeminal ganglia of calves previously vaccinated and from calves not previously exposed to BHV1; calves sequentially challenged with BHV1 and later BHV5 had exclusively BHV1 sequences in their trigeminal ganglia. Administration of dexamethasone 28 days after BHV5 challenge did not influence clinical disease or histologic lesions in either previously unexposed calves (n = 2) or previously immunized calves (n = 2), although it did cause recrudescence of BHV5, as detected by nasal virus secretion. (+info)
Immunity to rotavirus infection in mice.
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Recent findings from our laboratory regarding the immune response of mice to rotavirus (a mucosal pathogen) show that although in most situations an acquired (T or B cell or both) response is necessary for elimination of primary rotavirus infection, unidentified innate mechanisms can also play a role in some mouse strains. Similar to what is seen with many other viruses, CD8+ T cells appear to provide the first but not the exclusive mechanism that mediates clearance of a primary rotavirus infection. Antibodies are the critical mediators of prevention against rotavirus reinfection. Nonneutralizing IgA monoclonal antibodies directed against VP6 (an internal structural rotavirus protein) can mediate immunity against rotaviruses in vivo. Rotavirus-specific CD8+ T cells can mediate their antiviral effect in the absence of perforin, fas, or interferon-gamma and are preferentially represented in the subset that expresses high levels of the enteric mucosal homing receptor alpha4beta7. (+info)
Events following the infections of enucleate cells with measles virus.
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The development of measles virus (Edmonston) and SSPE measles virus (Horta-Barbosa) has been examined in enucleate BSC 1 cells. New antigen synthesis in measles virus infected enucleate cells has been demonstrated by fluorescent antibody, by the formation of extensive syncytia from enucleate cells alone and by analysis of polypeptide formation by polyacrylamide gel electrophoresis. All polypeptides formed in nucleate cells were also present in enucleate cells but the amount synthesized was reduced to around 20% of that in nucleate cells. There was also a significant reduction in the amount of antigen detected by fluorescent antibody in enucleate as compared to nucleate preparations. Examination of RNA synthesis in infected enucleate cells revealed only a marginal increase in acid-insoluble material. Titration of the output of infectious virus from enucleate cells infected at both 37 and 31 degrees C indicated a consistent reduction of almost two log units compared to nucleate cells. That the enucleate cells were capable of replicating input genome at these times was demonstrated by the successful growth of respiratory syncytial virus, both at 37 and 31 degrees C. SSPE measles virus grew to higher yield in nucleate BSC 1 than measles virus but there was again a reduction of more than two log units in enucleate cells. All polypeptides synthesized in SSPE infected nucleate cells were apparent in enucleate cells. (+info)
Ortho- and paramyxoviruses from migrating feral ducks: characterization of a new group of influenza A viruses.
(36/10399)
Ortho- and parainfluenza viruses isolated from the cloacas of migrating feral ducks shot on the Mississippi flyway included three strains of influenza. A virus (Hav6 Nav1, Hav6 Nl, Hav7 Neq2) as well as Newcastle disease virus. One influenza virus, A/duck/Memphis/546/74, possessed Hav3 haemagglutinin, but the neuraminidase was not inhibited by any of the known influenza reference antisera. The neuraminidase on this virus was related to the neuraminidases on A/duck/GDR/72 (H2 N?), A/turkey/Ontario/7732/66 (Hav 5 N?), A/duck/Ukraine/1/60 (Hav3 N?) and A/turkey/Wisconsin/68. We therefore propose that the neuraminidase on this group of influenza viruses be designated Nav6. The A/duck/Memphis/546/74 influenza virus caused an ocular discharge in 1 of 5 ducks and was shed in faeces for 10 days; it was stable in faecal samples for up to 3 days at 20 degrees C. These results suggest that ecological studies on influenza in avian species should include attempts to isolate virus from faeces. Faecal-oral transmission is an attractive explanation for the spread of influenza virus from feral birds to other animals. (+info)
Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) can regulate dendritic cell-induced activation and cytotoxicity of CD8(+) T cells independently of CD4(+) T cell help.
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The mechanisms that regulate the strength and duration of CD8(+) cytotoxic T cell activity determine the effectiveness of an antitumor immune response. To better understand the antitumor effects of anti-cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) antibody treatment, we analyzed the effect of CTLA-4 signaling on CD8(+) T cells in vitro and in vivo. In vitro, cross-linking of CTLA-4 on purified CD8(+) T cells caused decreased proliferative responses to anti-CD3 stimulation and rapid loss of activation marker expression. In vivo, blockade of CTLA-4 by neutralizing anti-CTLA-4 mAb greatly enhanced the accumulation, activation, and cytotoxic activity of CD8(+) T cells induced by immunization with Ag on dendritic cells (DC). This enhanced response did not require the expression of MHC class II molecules on DC or the presence of CD4(+) T cells. These results demonstrate that CTLA-4 blockade is able to directly enhance the proliferation and activation of specific CD8(+) T cells, indicating its potential for tumor immunotherapy even in situations in which CD4(+) T cell help is limited or absent. (+info)
Immunogenicity of herpes simplex virus type 1 mutants containing deletions in one or more alpha-genes: ICP4, ICP27, ICP22, and ICP0.
(38/10399)
Replication defective mutants of HSV have been proposed both as vaccine candidates and as vehicles for gene therapy because of their inability to produce infectious progeny. The immunogenicity of these HSV replication mutants, at both qualitative and quantitative levels, will directly determine their effectiveness for either of these applications. We have previously reported (Brehm et al., J. Virol., 71, 3534, 1997) that a replication defective mutant of HSV-1, which expresses a substantial level of viral genes without producing virus particles, is as efficient as wild-type HSV-1 in eliciting an HSV-specific cytotoxic T-lymphocyte (CTL) response. In this report, we have further evaluated the immunogenic potential of HSV-1-derived replication defective mutants by examining the generation of HSV-specific CTL following immunization with viruses that are severely restricted in viral gene expression due to mutations in one or more HSV alpha genes (ICP4, ICP27, ICP22, and ICP0). To measure the CTL responses induced by the HSV alpha-mutants, we have targeted two H-2Kb-restricted CTL epitopes: an epitope in a virion protein, gB (498-505), and an epitope in a nonvirion protein, ribonucleotide reductase (RR1 822-829). The HSV mutants used in this study are impaired in their ability to express gB while a majority of them still express RR1. Our findings demonstrate that a single immunization with these mutants is able to generate a strong CTL response not only to RR1 822-829, but also to gB498-505 despite their inability to express wild-type levels of gB. Furthermore, a single immunization with any individual mutant can also provide immune protection against HSV challenge. These results suggest that mutants which are restricted in gene expression may be used as effective immunogens in vivo. (+info)
Long-lasting protection by live attenuated simian immunodeficiency virus in cynomolgus monkeys: no detection of reactivation after stimulation with a recall antigen.
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The infection of cynomolgus monkeys with an attenuated simian immunodeficiency virus (SIV) (C8) carrying a deletion in the nef gene results in a persistent infection associated with an extremely low viral burden in peripheral blood mononuclear cells. The aim of this study was to determine (1) the breadth of the protection after repeated challenges of monkeys with SIV homologous strains of different pathogenicity, (2) the genotypic stability of the live virus vaccine, (3) whether the protection might depend on cellular resistance to superinfection, and (4) whether immunogenic stimuli such as recall antigens could reactivate the replication of the C8 virus. To address these goals, the monkeys were challenged at 40 weeks after C8 infection with 50 MID50 of cloned SIVmac251, BK28 grown on macaque cells. They were protected as indicated by several criteria, including virus isolation, anamnestic serological responses, and viral diagnostic PCR. At 92 weeks after the first challenge, unfractionated peripheral blood mononuclear cells from protected monkeys were susceptible to the in vitro infection with SIVmac32H, spl. At 143 weeks after C8 infection, the four protected monkeys were rechallenged with 50 MID50 of the pathogenic SIVmac32H, spl grown on macaque cells. Once again, they were protected. The C8 virus remained genotypically stable, and depletion of CD4(+) cells was not observed during approximately 3 years of follow-up. In contrast, it was found that the infection with SIVmac32H, spl induced CD4(+) cell depletion in three of three control monkeys. Of importance, stimulation with tetanus toxoid, although capable of inducing specific humoral and T cell proliferative responses, failed to induce a detectable reactivation of C8 virus. (+info)
Comparison of human sera reactivities in immunoblots with recombinant human herpesvirus (HHV)-8 proteins associated with the latent (ORF73) and lytic (ORFs 65, K8.1A, and K8.1B) replicative cycles and in immunofluorescence assays with HHV-8-infected BCBL-1 cells.
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The development of reliable, sensitive, and specific serological methods for the detection of human herpesvirus-8 (HHV-8) antibodies is critical for a thorough understanding of HHV-8 prevalence and pathogenesis. To evaluate the potential usefulness of HHV-8 proteins in measuring the responses against both latent and lytic antigens, we selected 1 latent [open reading frame (ORF) 73] antigen and 3 HHV-8 lytic antigens (ORFs 65, K8.1A, and K8.1B) previously identified as immunogenic [Virology (1998) 243, 208-217]. Full-length genomic ORF 73 and full-length ORFs 65, K8.1A, and K8.1B from the cDNA clones were cloned, expressed in bacterial and baculovirus-insect cell expression systems, and purified as GST fusion proteins. These recombinant proteins were used in Western blot reactions to test sera from 104 human immunodeficiency virus (HIV)+/Kaposi's sarcoma (KS)+ homosexual men, 77 HIV+/KS- homosexual men, and 84 age-matched HIV-/KS- men. These sera were also tested in immunofluorescence assays (IFAs) with uninduced and 12-O-tetradecanoylphorbol-13-acetate-induced B cell lymphoma-1 cells to detect antibodies against latency-associated nuclear antigens (LANA) and antibodies against lytic antigens (cytoplasmic fluorescence). These sera exhibited differential reactivities reflecting different titers of antibodies against HHV-8 proteins, and variable reactivities were seen more commonly with the sera from HIV-/KS- adult men. In the Western blot assay, 89% (93 of 104) of HIV+/KS + sera, 60% (46 of 77) of HIV+/KS- sera, and 7% (6 of 84) HIV+/KS- sera were reactive with both latent and lytic recombinant antigens. Western blot reactions with ORF 73 protein were more sensitive than LANA-IFA results. The lytic IFA and lytic Western blot (ORFs 65 and K8.1A) assays were more sensitive than the ORF 73 Western blots and LANA-IFA. With an exception of 2 sera from the HIV-/KS- group, all sera positive for lytic IFA antibodies and ORF 65 and K8.1A antibodies were also positive for latent antibodies. With few exceptions, sera positive for ORF 65 antibodies were also positive for K8.1A antibodies, and sera recognized the K8.1A protein more often than the K8.1B protein. There is a high degree of concordance between IFA and Western blot reactions, suggesting that this panel of HHV-8 recombinant proteins could detect a majority of the HHV-8-seropositive individuals. These results suggest that IFA followed by confirmation with the Western blot reactions with a panel of latent and lytic immunogenic antigens would provide a reliable, sensitive, and specific method for the detection of HHV-8 antibodies. (+info)