Protection against lymphocytic choriomeningitis virus infection induced by a reduced peptide bond analogue of the H-2Db-restricted CD8(+) T cell epitope GP33.
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Recent investigations have suggested that pseudopeptides containing modified peptide bonds might advantageously replace natural peptides in therapeutic strategies. We have generated eight reduced peptide bond Psi(CH2-NH) analogues corresponding to the H-2Db-restricted CD8(+) T cell epitope (called GP33) of the glycoprotein of the lymphocytic choriomeningitis virus. One of these pseudopeptides, containing a reduced peptide bond between residues 6 and 7 (Psi(6-7)), displayed very similar properties of binding to major histocompatibility complex (MHC) and recognition by T cell receptor transgenic T cells specific for GP33 when compared with the parent peptide. We assessed in vitro and in vivo the proteolytic resistance of GP33 and Psi(6-7) and analyzed its contribution to the priming properties of these peptides. The Psi(6-7) analogue exhibited a dramatically increased proteolytic resistance when compared with GP33, and we show for the first time that MHC-peptide complexes formed in vivo with a pseudopeptide display a sustained half-life compared with the complexes formed with the natural peptide. Furthermore, in contrast to immunizations with GP33, three injections of Psi(6-7) in saline induced significant antiviral protection in mice. The enhanced ability of Psi(6-7) to induce antiviral protection may result from the higher stability of the analogue and/or of the MHC-analogue complexes. (+info)
TRANCE, a tumor necrosis factor family member critical for CD40 ligand-independent T helper cell activation.
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CD40 ligand (CD40L), a tumor necrosis factor (TNF) family member, plays a critical role in antigen-specific T cell responses in vivo. CD40L expressed on activated CD4(+) T cells stimulates antigen-presenting cells such as dendritic cells, resulting in the upregulation of costimulatory molecules and the production of various inflammatory cytokines required for CD4(+) T cell priming in vivo. However, CD40L- or CD40-deficient mice challenged with viruses mount protective CD4(+) T cell responses that produce normal levels of interferon gamma, suggesting a CD40L/CD40-independent mechanism of CD4(+) T cell priming that to date has not been elucidated. Here we show that CD4(+) T cell responses to viral infection were greatly diminished in CD40-deficient mice by administration of a soluble form of TNF-related activation-induced cytokine receptor (TRANCE-R) to inhibit the function of another TNF family member, TRANCE. Thus, the TRANCE/TRANCE-R interaction provides costimulation required for efficient CD4(+) T cell priming during viral infection in the absence of CD40L/CD40. These results also indicate that not even the potent inflammatory microenvironment induced by viral infections is sufficient to elicit efficient CD4(+) T cell priming without proper costimulation provided by the TNF family (CD40L or TRANCE). Moreover, the data suggest that TRANCE/TRANCE-R may be a novel and important target for immune intervention. (+info)
Use of a high-affinity peptide that aborts MHC-restricted cytotoxic T lymphocyte activity against multiple viruses in vitro and virus-induced immunopathologic disease in vivo.
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Binding of a specific peptide(s) from a viral protein to major histocompatibility complex (MHC) class I molecules is a critical step in the activation of CD8(+) cytotoxic T lymphocytes (CTLs). Once activated, CTLs can cause lethal disease in an infected host, for example, by killing virus-containing ependymal and ventricular cells in the central nervous system or viral protein-expressing beta cells in the pancreatic islets of Langerhans. Here we describe the usage of a designed (not natural) high-affinity peptide to compete with viral peptide(s)-MHC binding. This peptide blocks virus-induced CTL-mediated disease both in the CNS and in the pancreatic islets in vivo. Further, the blocking peptide aborts MHC-restricted killing of target cells by CTLs generated to three separate viruses: lymphocytic choriomeningitis virus, influenza virus, and simian virus 40. (+info)
CpG-containing oligonucleotides are efficient adjuvants for induction of protective antiviral immune responses with T-cell peptide vaccines.
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Synthetic nonmethylated oligonucleotides containing CpG dinucleotides (CpG-ODNs) have been shown to exhibit immunostimulatory activity. CpG-ODNs have the capacity to directly activate B cells, macrophages, and dendritic cells, and we show here that this is reflected by cell surface binding of oligonucleotides to these cell subsets. However, T cells are not directly activated by CpG-ODNs, which correlates with the failure to bind to the T-cell surface. Efficient competition for CpG-induced B-cell activation by non-CpG-containing oligonucleotides suggests that oligonucleotides might bind to an as yet undefined sequence-nonspecific receptor prior to cellular activation. Induction of protective T-cell responses against challenge infection with lymphocytic choriomeningitis virus (LCMV) or with recombinant vaccinia virus expressing the LCMV glycoprotein was achieved by immunizing mice with the immunodominant major histocompatibility complex class I-binding LCMV glycoprotein-derived peptide gp33 together with CpG-ODNs. In these experiments, B cells, potentially serving as CpG-ODN-activated antigen-presenting cells (APCs), were not required for induction of protective immunity since CpG-ODN-gp33-immunized B-cell-deficient mice were equally protected against challenge infection with both viruses. This finding suggested that macrophages and/or dendritic cells were sufficiently activated in vivo by CpG-ODNs to serve as potent APCs for the induction of naive T cells. Furthermore, treatment with CpG-ODN alone induced protection against infection with Listeria monocytogenes via antigen-independent activation of macrophages. These data suggest that CpG activation of macrophages and dendritic cells may provide a critical step in CpG-ODN adjuvant activity. (+info)
In vivo selection of neutralization-resistant virus variants but no evidence of B cell tolerance in lymphocytic choriomeningitis virus carrier mice expressing a transgenic virus-neutralizing antibody.
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B cell tolerance is maintained by active deletion and functional anergy of self-reactive B cells depending on the time, amount, and site of the self-antigen expression. To study B cell tolerance toward a transplacentally transmitted viral Ag, we crossed transgenic mice expressing the mu heavy and the kappa light chain of the lymphocytic choriomeningitis virus (LCMV)-neutralizing mAb KL25 (HL25-transgenic mice) with persistently infected LCMV carrier mice. Although HL25-transgenic LCMV carrier mice exhibited the same high virus titers as nontransgenic LCMV carrier mice, no evidence for B cell tolerance was found. In contrast, enhanced LCMV-neutralizing Ab titers were measured that, however, did not clear the virus. Instead, LCMV isolates from different tissues turned out to be neutralization resistant Ab escape variants expressing different substitutions of amino acid Asn119 of the LCMV-glycoprotein 1 that displays the neutralizing B cell epitope. Virus variants with the same mutations were also selected in vitro in the presence of the transgenic mAb KL25 confirming that substitutions of Asn119 have been selected by LCMV-neutralizing Abs. Thus, despite abundant expression of viral neo-self-antigen in HL25-transgenic LCMV carrier mice, transgenic B cells expressing LCMV-neutralizing Abs were rather stimulated than tolerized and neutralization resistant Ab escape variants were selected in vivo. (+info)
Identification of MaTu-MX agent as a new strain of lymphocytic choriomeningitis virus (LCMV) and serological indication of horizontal spread of LCMV in human population.
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In this study we elucidated the molecular character of MaTu-MX, previously described as an unusual transmissible agent. Amino acid sequencing of peptides generated from a 58-kDa MX-related protein purified from MaTu human carcinoma cells allowed us to identify it as a nucleoprotein (NP) of lymphocytic choriomeningitis virus (LCMV). Northern blot analysis detected LCMV-specific RNAs in MaTu cells. Comparative immunoprecipitations showed cross-reactivity between NP of LCMV strain WE and MX NP. Using RT-PCR, we have cloned MX NP cDNA. According to sequence comparison, MX LCMV is as closely related to both LCMV strains WE and Armstrong as these strains are to one another. Based on this finding we propose that MX is a new strain of LCMV. We also showed that the stability of MX NP in MaTu cells is very high and that the virus is transmissible by cell-to-cell contact or by cell-free extract to human HeLa and monkey Vero cells, but not to human AGS, canine MDCK, mouse NIH 3T3, and hamster CHO cells. Finally, employing MX LCMV NP in immunoprecipitation and solid-phase radioimmunoassay, we found 37.5% prevalence of anti-LCMV antibodies in human sera, suggesting possible horizontal spread of the virus in the human population. (+info)
Two roads diverged: interferon alpha/beta- and interleukin 12-mediated pathways in promoting T cell interferon gamma responses during viral infection.
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Viral infections induce CD8 T cell expansion and interferon (IFN)-gamma production for defense, but the innate cytokines shaping these responses have not been identified. Although interleukin (IL)-12 has the potential to contribute, IL-12-dependent T cell IFN-gamma has not been detected during viral infections. Moreover, certain viruses fail to induce IL-12, and elicit high levels of IFN-alpha/beta to negatively regulate it. The endogenous factors promoting virus-induced T cell IFN-gamma production were defined in studies evaluating CD8 T cell responses during lymphocytic choriomeningitis virus infections of mice. Two divergent supporting pathways were characterized. Under normal conditions of infections, the CD8 T cell IFN-gamma response was dependent on endogenous IFN-alpha/beta effects, but was IL-12 independent. In contrast, in the absence of IFN-alpha/beta functions, an IL-12 response was revealed and substituted an alternative pathway to IFN-gamma. IFN-alpha/beta-mediated effects resulted in enhanced, but the alternative pathway also promoted, resistance to infection. These observations define uniquely important IFN-alpha/beta-controlled pathways shaping T cell responses during viral infections, and demonstrate plasticity of immune responses in accessing divergent innate mechanisms to achieve similar ultimate goals. (+info)
A novel approach to visualize polyclonal virus-specific CD8 T cells in vivo.
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Recent technical breakthroughs in generating soluble MHC class I-peptide tetramers now allow the direct visualization of virus-specific CD8 T cells after infection in vivo. However, this technique requires the knowledge of the immunodominant viral epitopes recognized by T cells. Here, we describe an alternative approach to visualize polyclonal virus-specific CD8 T cells in vivo using a simple adoptive transfer system. In our approach, C57BL/6 (Thy1.2) mice were infected with lymphocytic choriomeningitis virus, vesicular stomatitis virus, or vaccinia virus to induce virus-specific memory T cells. Tracer T cells (2 x 106) from these virus-immune mice were adoptively transferred into nonirradiated (C57BL/6 x B6.PL-Thy-1a)F1 mice. After infection of the F1-recipient mice with the appropriate virus, the transferred cells expanded vigorously, and on day 8 postinfection 60-80% of total CD8 T cells were of donor T cell origin. Under the same conditions memory CD4 T cells gave rise to at least 10 times less cell numbers than memory CD8 T cells. The transfer system described here not only allows to visualize effector and memory CD8 T cells in vivo but also to isolate them for further in vitro characterization without knowing the epitopes recognized by these Ag-specific CD8 T cells. (+info)