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Biomedical subjects

A Suhrbier

Publications and source records attributed to A Suhrbier.

At least 19 recordsLinked to original sources
PubMed2001

Asymptomatic primary Epstein-Barr virus infection occurs in the absence of blood T-cell repertoire perturbations despite high levels of systemic viral load.

Primary infection with the human herpesvirus, Epstein-Barr virus (EBV), may result in subclinical seroconversion or may appear as infectious mononucleosis (IM), a lymphoproliferative disease of variable severity. Why primary infection manifests differently between patients is unknown, and, given the difficulties in identifying donors undergoing silent seroconversion, little information has been reported. However, a longstanding assumption has been held that IM represents an exaggerated form of the virologic and immunologic events of asymptomatic infection. T-cell receptor (TCR) repertoires of a unique cohort of subclinically infected patients undergoing silent infection were studied, and the results highlight a fundamental difference between the 2 forms of infection. In contrast to the massive T-cell expansions mobilized during the acute symptomatic phase of IM, asymptomatic donors largely maintain homeostatic T-cell control and peripheral blood repertoire diversity. This disparity cannot simply be linked to severity or spread of the infection because high levels of EBV DNA were found in the blood from both types of acute infection. The results suggest that large expansions of T cells within the blood during IM may not always be associated with the control of primary EBV infection and that they may represent an overreaction that exacerbates disease.

Antibodies, Viral↗
PubMed2001

Delayed emergence of bovine leukemia virus after vaccination with a protective cytotoxic T cell-based vaccine.

In a previous study eight MHC class I-matched sheep were vaccinated with a minimal cytotoxic T lymphocyte (CTL) peptide epitope vaccine and were challenged with the retrovirus, bovine leukemia virus (BLV). Half the vaccinated animals remained PCR negative after challenge, whereas the remaining half and the placebo group became PCR positive within 4 weeks postchallenge (Hislop AD, Good MF, Mateo L, Gardner J, Gatei MH, Daniel RCW, Meyers BV, Lavin MF, and Suhrbier A: Nat Med 1998;4:1193). Here we show that neither epitope mutations nor processing differences explained why half the peptide-vaccinated animals failed to resist the BLV challenge. However, in these animals the development of BLV-induced lymphosarcomas was significantly delayed compared with the placebo group, suggesting a role for CTLs in preventing retrovirus-induced cancers. Importantly, two of the initially protected animals become PCR positive after approximately 1.5 years, indicating extended suppression but not elimination of challenge virus by vaccine-induced CTLs. The late emergence of virus could not be explained by epitope escape mutations or the loss of memory CTL responses. We speculate that high levels of effector CTL may be needed to protect animals from a postchallenge viremia and maintenance of such effector CTLs, rather than memory CTLs, may be required to prevent subsequent emergence of virus from latent pools.

Animals↗
PubMed2001

Cytotoxic T cell polyepitope vaccines delivered by ISCOMs.

CD8 alphabeta cytotoxic T lymphocyte (CTL) polyepitope or polytope vaccines have traditionally been delivered using recombinant vector or DNA based delivery modalities. Here we show the delivery of polytope vaccines in the form of either synthetic polypeptides or recombinant polytope proteins by ImmunoStimulatory COMplexes (ISCOMs(R)). Induction of multiple protective CTL responses by these polytope-ISCOM formulations were comparable to viral vector or DNA based delivery modalities as assessed by IFNgamma ELISpot, chromium release and viral challenge assays. Measurement of CTL responses specific for the different epitopes revealed immunodominance patterns, which were largely independent of the vaccine vector or the order of the epitopes in the polytope. ISCOMs thus emerge as a viable human delivery modality for protein-based polytope vaccines.

Amino Acid Sequence↗
PubMed2001

Immune responses to ISCOM formulations in animal and primate models.

ISCOMs are typically 40 nm cage-like structures comprising antigen, saponin, cholesterol and phospholipid. ISCOMs have been shown to induce antibody responses and activate T helper cells and cytolytic T lymphocytes in a number of animal species, including non-human primates. Recent clinical studies have demonstrated that ISCOMs are also able to induce antibody and cellular immune responses in humans. This review describes the current understanding of the ability of ISCOMs to induce immune responses and the mechanisms underlying this property. Recent progress in the characterisation and manufacture of ISCOMs will also be discussed.

Animals↗
PubMed2001

Design of a polyepitope construct for the induction of HLA-A0201-restricted HIV 1-specific CTL responses using HLA-A*0201 transgenic, H-2 class I KO mice.

HLA-A*0201 transgenic, H-2D(b)/mouse beta2-microglobulin double-knockout mice were used to compare and optimize the immunogenic potential of 17HIV 1-derived,HLA-A0201-restricted epitopic peptides. A tyrosine substitution in position 1 of the epitopic peptides, which increases both their affinity for and their HLA-A0201 molecule stabilizing capacity, was introduced in a significant proportion, having verified that such modifications enhance their immunogenicity in respect of their natural antigenicity. Based on these results, a 13-polyepitope construct was inserted in the pre-S2 segment of the hepatitis B middle glycoprotein and used for DNA immunization. Long-lasting CTL responses against most of the inserted epitopes could be elicited simultaneously in a single animal with cross-recognition in several cases of their most common natural variants.

AIDS Vaccines↗
PubMed2001

Arbovirus of marine mammals: a new alphavirus isolated from the elephant seal louse, Lepidophthirus macrorhini.

A novel alphavirus was isolated from the louse Lepidophthirus macrorhini, collected from southern elephant seals, Mirounga leonina, on Macquarie Island, Australia. The virus displayed classic alphavirus ultrastructure and appeared to be serologically different from known Australasian alphaviruses. Nearly all Macquarie Island elephant seals tested had neutralizing antibodies against the virus, but no virus-associated pathology has been identified. Antarctic Division personnel who have worked extensively with elephant seals showed no serological evidence of exposure to the virus. Sequence analysis illustrated that the southern elephant seal (SES) virus segregates with the Semliki Forest group of Australasian alphaviruses. Phylogenetic analysis of known alphaviruses suggests that alphaviruses might be grouped according to their enzootic vertebrate host class. The SES virus represents the first arbovirus of marine mammals and illustrates that alphaviruses can inhabit Antarctica and that alphaviruses can be transmitted by lice.

Alphavirus↗
PubMed2000

Effect of pre-existing cytotoxic T lymphocytes on therapeutic vaccines.

Therapeutic vaccines which aim to induce CD8(+) cytotoxic T lymphocyte (CTL) responses will often be required to perform in the presence of pre-existing CTL which recognize epitopes within the vaccine. Here we explore the ability of a viral vaccine vector presenting several co-dominant CTL epitopes to prime CTL responses in animals that have a pre-existing CTL response to one of the epitopes in the vaccine. The vaccine was usually capable of inducing multiple new responses, suggesting that immunodomination effects of pre-existing CTL may generally be minimal following vaccination. However, when large numbers of pre-existing CTL were present, a novel type of immune modulation was observed whereby (1) the vaccine failed to prime efficiently new CTL responses that were restricted by the same MHC gene as the pre-existing responses, and (2) vaccine-induced CTL responses restricted by other MHC genes were enhanced. These results may have implications for therapeutic multi-epitope vaccines for diseases like HIV and melanoma, which aim to broaden CTL responses.

Adoptive Transfer↗
PubMed2000

An arthrogenic alphavirus induces monocyte chemoattractant protein-1 and interleukin-8.

Cytokines and chemokines play important roles in both autoimmune and infectious arthritides. Here we describe the cytokines and chemokines induced by Ross River (RR) virus infection of synovial fibroblasts and macrophages in vitro. RR virus is the aetiological agent of epidemic polyarthritis (EPA), a principally acute and chronic rheumatic disease affecting up to 7,000 Australians annually. Infected fibroblasts increased expression of mRNA coding for monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8), and granulocyte-macrophage colony-stimulating factor. MCP-1, IL-8, macrophage inflammatory protein-2, and to a lesser extent interferon gamma-induced protein-10 mRNA were upregulated in infected macrophages. Expression of MCP-1 is consistent with the predominantly monocytic effusion found in EPA synovia.

Alphavirus Infections↗
PubMed1999

An HLA-A2 polyepitope vaccine for melanoma immunotherapy.

Epitope-based vaccination strategies designed to induce tumor-specific CD8 CTL are being widely considered for cancer immunotherapy. Here we describe a recombinant poxvirus vaccine that codes for ten HLA-A2-restricted epitopes derived from five melanoma Ags conjoined in an artificial polyepitope or polytope construct. Target cells infected with the melanoma polytope vaccinia were recognized by three different epitope-specific CTL lines derived from HLA-A2 melanoma patients, and CTL responses to seven of the epitopes were generated in at least one of six HLA-A2-transgenic mice immunized with the construct. CTL lines derived from vaccinated transgenic mice were also able to kill melanoma cells in vitro. Multiple epitopes within the polytope construct were therefore shown to be individually immunogenic, illustrating the feasibility of the polytope approach for melanoma immunotherapy. Tumor escape from CTL surveillance, through down regulation of individual tumor Ags and MHC alleles, might be overcome by polytope vaccines, which simultaneously target multiple cancer Ags.

Amino Acid Sequence↗
PubMed1999

Peptide based cytotoxic T-cell vaccines; delivery of multiple epitopes, help, memory and problems.

Synthetic CD8+ cytotoxic T-lymphocyte (CTL) peptide epitope based vaccines are being developed against a number of human diseases. Here we describe extensive preclinical testing of peptide epitope vaccines formulated with a protein as a source of CD4 help and Montanide ISA 720, an adjuvant currently in human clinical trials. Such water-in-oil formulations could effectively co-deliver several peptide epitopes and simultaneously induce multiple independent CTL responses. The efficiency of CTL induction by some peptides was, however, dependent on the aqueous buffer conditions, with poor performance correlating with non-covalent peptide oligomerisation. Any of a number of proteins currently used in human vaccines could supply CD4 help and no difference in CTL induction was obtained if the CD4 response was amnestic or a primary. Peptide immunisation was found to induce long term CTL memory and the recall of protective responses did not depend on an amnestic CD4 response. Slow pyroglutamic acid formation and rapid oxidation of methionine residues was observed in water-in-oil formulations, however, the latter had no effect on CTL induction. These data highlight the need to monitor for potential deleterious chemical events and interpeptide interactions, but illustrate that peptide based vaccination can effectively deliver multiple epitopes, in conjunction with any protein, and induce protective memory.

Adjuvants, Immunologic↗
PubMed1999

H-2 class I knockout, HLA-A2.1-transgenic mice: a versatile animal model for preclinical evaluation of antitumor immunotherapeutic strategies.

H-2 class I-negative, HLA-A2.1-transgenic HHD mice were used for a comparative evaluation of the immunogenicity of HLA-A2.1-restricted human tumor-associated cytotoxic T lymphocyte (CTL) epitopes. A hierarchy was established among these peptides injected into mice in incomplete Freund's adjuvant which correlates globally with their capacity to bind and stabilize HLA-A2.1 molecules. Co-injection of a helper peptide enhanced most CTL responses. In contrast, classical HLA class I-transgenic mice which still express their own class I molecules did not, in most cases, develop HLA-A2.1-restricted CTL responses under the same experimental conditions. Different monoepitope immunization strategies of acceptable clinical usage were compared in HHD mice. Recombinant Ty-virus-like particles, or DNA encoding epitopes fused to the hepatitis B virus middle envelope protein gave the best results. Using this latter approach and a melanoma-based polyepitope construct, CTL responses against five distinct epitopes could be elicited simultaneously in a single animal. Thus, HHD mice provide a versatile animal model for preclinical evaluation of peptide-based cancer immunotherapy.

Amino Acid Sequence↗
PubMed1999

Genetic vaccination strategies for enhanced cellular, humoral and mucosal immunity.

In this article, we describe several novel genetic vaccination strategies designed to facilitate the development of different types of immune responses. These include: i) the consecutive use of DNA and fowlpoxvirus vectors in "prime-boost" strategies which induce greatly enhanced and sustained levels of both cell-mediated immunity and humoral immunity, including mucosal responses; ii) the co-expression of genes encoding cytokines and cell-surface receptors, and the use of immunogenic carrier molecules, for immune modulation and/or improved targeting of vector-expressed vaccine antigens; and iii) the expression of minimal immunogenic amino acid sequences, particularly cytotoxic CD8+ T-cell determinants, in "polytope" vector vaccines. The capacity to modulate and enhance specific immune responses by the use of approaches such as these may underpin the development of vaccines against diseases for which no effective strategies are currently available.

Animals↗
PubMed1999

Immunogenicity of a human immunodeficiency virus (HIV) polytope vaccine containing multiple HLA A2 HIV CD8(+) cytotoxic T-cell epitopes.

Compelling evidence now suggests that alphabeta CD8 cytotoxic T lymphocytes (CTL) have an important role in preventing human immunodeficiency virus (HIV) infection and/or slowing progression to AIDS. Here, we describe an HIV type 1 CTL polyepitope, or polytope, vaccine comprising seven contiguous minimal HLA A2-restricted CD8 CTL epitopes conjoined in a single artificial construct. Epitope-specific CTL lines derived from HIV-infected individuals were able to recognize every epitope within the construct, and HLA A2-transgenic mice immunized with a recombinant virus vaccine coding for the HIV polytope also generated CTL specific for different epitopes. Each epitope in the polytope construct was therefore processed and presented, illustrating the feasibility of the polytope approach for HIV vaccine design. By simultaneously inducing CTL specific for different epitopes, an HIV polytope vaccine might generate activity against multiple challenge isolates and/or preempt the formation of CTL escape mutants.

AIDS Vaccines↗
PubMed1999

Picornavirus receptor down-regulation by plasminogen activator inhibitor type 2.

Therapeutic interference with virus-cell surface receptor interactions represents a viable antiviral strategy. Here we demonstrate that cytoplasmic expression of the serine protease inhibitor (serpin), plasminogen activator inhibitor type 2 (PAI-2), affords a high level of protection from lytic infection by multiple human picornaviruses. The antiviral action of PAI-2 was mediated primarily through transcriptional down-regulation of the following virus receptors: intercellular adhesion molecule 1 (ICAM-1, a cellular receptor for the major group of rhinoviruses), decay-accelerating factor (a cellular receptor for echoviruses and coxsackieviruses), and to a lesser extent the coxsackie-adenovirus receptor protein (a cellular receptor for group B coxsackieviruses and group C adenoviruses). Expression of related cell surface receptors, including membrane cofactor protein and the poliovirus receptor, remained unaffected. These findings suggest that PAI-2 and/or related serpins may form the basis of novel antiviral strategies against picornavirus infections and also therapeutic interventions against ICAM-1-mediated respiratory inflammation.

CD55 Antigens↗
PubMed1998

The serine proteinase inhibitor (serpin) plasminogen activation inhibitor type 2 protects against viral cytopathic effects by constitutive interferon alpha/beta priming.

The serine proteinase inhibitor (serpin) plasminogen activator inhibitor type 2 (PAI-2) is well characterized as an inhibitor of extracellular urokinase-type plasminogen activator. Here we show that intracellular, but not extracellular, PAI-2 protected cells from the rapid cytopathic effects of alphavirus infection. This protection did not appear to be related to an effect on apoptosis but was associated with a PAI-2-mediated induction of constitutive low-level interferon (IFN)-alpha/beta production and IFN-stimulated gene factor 3 (ISGF3) activation, which primed the cells for rapid induction of antiviral genes. This primed phenotype was associated with a rapid development of resistance to infection by the PAI-2 transfected cells and the establishment of a persistent productive infection. PAI-2 was also induced in macrophages in response to viral RNA suggesting that PAI-2 is a virus response gene. These observations, together with the recently demonstrated PAI-2-mediated inhibition of tumor necrosis factor-alpha induced apoptosis, (a) illustrate that PAI-2 has an additional and distinct function as an intracellular regulator of signal transduction pathway(s) and (b) demonstrate a novel activity for a eukaryotic serpin.

Adenoviruses, Human↗
PubMed1998

Delivery of multiple CD8 cytotoxic T cell epitopes by DNA vaccination.

Development of CD8 alphabeta CTL epitope-based vaccines requires an effective strategy capable of co-delivering large numbers of CTL epitopes. Here we describe a DNA plasmid encoding a polyepitope or "polytope" protein, which contained multiple contiguous minimal murine CTL epitopes. Mice vaccinated with this plasmid made MHC-restricted CTL responses to each of the epitopes, and protective CTL were demonstrated in recombinant vaccinia virus, influenza virus, and tumor challenge models. CTL responses generated by polytope DNA plasmid vaccination lasted for 1 yr, could be enhanced by co-delivering a gene for granulocyte-macrophage CSF, and appeared to be induced in the absence of CD4 T cell-mediated help. The ability to deliver large numbers of CTL epitopes using relatively small polytope constructs and DNA vaccination technology should find application in the design of human epitope-based CTL vaccines, in particular in vaccines against EBV, HIV, and certain cancers.

Amino Acid Sequence↗
PubMed1998

Vaccine-induced cytotoxic T lymphocytes protect against retroviral challenge.

The development of prophylactic vaccines against retroviral diseases has been impeded by the lack of obvious immune correlates for protection. Cytotoxic T-lymphocyte (CTL), CD4-lymphocyteS, chemokine and/or antibody responses have all been associated with protection against HIV and AIDS; however, effective and safe vaccination strategies remain elusive. Here we show that vaccination with a minimal ovine CTL peptide epitope identified within gp51 of the retrovirus bovine leukemia virus (BLV), consistently induced peptide-specific CTLs. Only sheep whose CTLs were also capable of recognizing retrovirus-infected cells were fully protected when challenged with BLV. This retrovirus displays limited sequence variation; thus, in the relative absence of confounding CTL escape variants, virus-specific CTLs targeting a single epitope were able to prevent the establishment of a latent retroviral infection.

Animals↗