Biomedical subjects

Brian Livingston

Publications and source records attributed to Brian Livingston.

6 recordsLinked to original sources

PubMed2005

A CD8+ T cell heptaepitope minigene vaccine induces protective immunity against Chlamydia pneumoniae.

An intact T cell compartment and IFN-gamma signaling are required for protective immunity against Chlamydia. In the mouse model of Chlamydia pneumoniae (Cpn) infection, this immunity is critically dependent on CD8(+) T cells. Recently we reported that Cpn-infected mice generate an MHC class I-restricted CD8(+) Tc1 response against various Cpn Ags, and that CD8(+) CTL to multiple epitopes inhibit Cpn growth in vitro. Here, we engineered a DNA minigene encoding seven H-2(b)-restricted Cpn CTL epitopes, the universal pan-DR epitope Th epitope, and an endoplasmic reticulum-translocating signal sequence. Immunization of C57BL/6 mice with this construct primed IFN-gamma-producing CD8(+) CTL against all seven CTL epitopes. CD8(+) T cell lines generated to minigene-encoded CTL epitopes secreted IFN-gamma and TNF-alpha and exhibited CTL activity upon recognition of Cpn-infected macrophages. Following intranasal challenge with Cpn, a 3.6 log reduction in mean lung bacterial numbers compared with control animals was obtained. Using a 20-fold increase in the Cpn challenging dose, minigene-vaccinated mice had a 60-fold reduction in lung bacterial loads, compared with controls. Immunization and challenge studies with beta(2)-microglobulin(-/-) mice indicated that the reduction of lung Cpn burdens was mediated by the MHC class I-dependent CD8(+) T cells to minigene-included Cpn CTL epitopes, rather than by pan-DR epitope-specific CD4(+) T cells. This constitutes the first demonstration of significant protection achieved by immunization with a CD8(+) T cell epitope-based DNA construct in a bacterial system and provides the basis for the optimal design of multicomponent anti-Cpn vaccines for humans.

Amino Acid Sequence↗

PubMed2004

Cellular immune responses to the hepatitis B virus polymerase.

CD4 T cells play an important role in hepatitis B virus (HBV) infection by secretion of Th1 cytokines that down-regulate HBV replication, and by promoting CD8 T cell and B cell responses. We have identified and characterized 10 CD4 T cell epitopes within polymerase and used them to analyze the immunological effects of long-term antiviral therapy as compared with spontaneous recovery from HBV infection. Candidate epitopes were tested for binding to 14 HLA-DR molecules and in IFN-gamma ELISPOT and cytotoxicity assays using peripheral blood lymphocytes from 66 HBV-infected patients and 16 uninfected controls. All 10 epitopes bound with high affinity to the most prevalent HLA-DR Ags, were conserved among HBV genomes, and induced IFN-gamma responses from HBV-specific CD4+ T cells. Several epitopes contained nested MHC class I motifs and stimulated HBV-specific IFN-gamma production and cytotoxicity of CD8+ T cells. HBV polymerase-specific responses were more frequent during acute, self-limited hepatitis and after recovery (12 of 18; 67%) than during chronic hepatitis (16 of 48 (33%); p=0.02). Antiviral therapy of chronic patients restored HBV polymerase and core-specific T cell responses during the first year of treatment, but thereafter, responses decreased and, after 3 years, were no more frequent than in untreated patients. Decreased T cell responsiveness during prolonged therapy was associated with increased prevalence of lamivudine-resistant HBV mutants and increased HBV titers. The data provide a rationale for the combination of antiviral and immunostimulatory therapy. These newly described HBV polymerase epitopes could be a valuable component of a therapeutic vaccine for a large and ethnically diverse patient population.

Adult↗

PubMed2003

Diverse repertoire of HIV-1 p24-specific, IFN-gamma-producing CD4+ T cell clones following immune reconstitution on highly active antiretroviral therapy.

HIV-1 Ag-specific CD4(+) T cell proliferative responses in human subjects with advanced, untreated HIV-1 disease are often weak or undetectable. Conversely, HIV-1-specific CD4(+) T cell proliferation is occasionally detected following suppression of HIV-1 replication with highly active antiretroviral therapy (HAART). These observations suggest that unchecked HIV-1 replication may lead to depletion or dysfunction of HIV-1-specific CD4(+) T cells, and that these defects may be partially corrected by viral suppression and subsequent immune reconstitution. However, the impact of this immune reconstitution on the repertoire of HIV-1-specific CD4(+) T cells has not been thoroughly evaluated. To examine the HIV-1-specific CD4(+) T cell repertoire in this clinical setting, we established HIV-1 p24-specific CD4(+) T cell clones from a successfully HAART-treated subject whose pretreatment peripheral CD4 count was 0 cells/ micro l. Eleven different p24-specific CD4(+) T cell clonotypes were distinguished among 13 clones obtained. Most clones produced both IFN-gamma and IL-4 upon Ag stimulation. Clones targeted eight distinct epitopes that varied in their conservancy among HIV-1 strains, and responses were restricted by one of three MHC II molecules. Clones showed a range of functional avidities for both protein and peptide Ags. Additional studies confirmed that multiple HIV-1 p24-derived epitopes were targeted by IFN-gamma-producing CD4(+) cells from subjects first treated with HAART during advanced HIV-1 disease (median, 4.5 peptides/subject; range, 3-6). These results suggest that in HAART-treated subjects whose peripheral CD4(+) T cell pools were once severely depleted, the HIV-1-specific CD4(+) T cell repertoire may include a diverse array of clonotypes targeting multiple HIV-1 epitopes.

Alleles↗

PubMed2002

T-lymphocyte epitope identification and their use in vaccine development for HIV-1.

Cellular immune responses mediated by CD8+ cytotoxic T-lymphocytes (CTL) and CD4+ helper T-lymphocytes (HTL) are needed to effectively control and clear many viral pathogens, including HIV-1. Thus, vaccines for HIV-1 capable of inducing CTL and HTL responses are now the focus of multiple academic and industry-based research and development programs. The use of defined, minimal CTL and HTL epitopes in vaccines has several potential advantages. Firstly, it is possible to use epitopes that are conserved thus targeting the majority of viral variants within a given clade or across clades. Secondly, epitopes from multiple viral structural or accessory gene products can be included in vaccines, which supports the induction cellular immune responses with significant breadth. Finally, dominance relationships between epitopes can be altered to increase immune recognition of subdominant epitopes. HTL and CTL epitopes from HIV-1 have recently been identified and characterized in numbers that are large enough to support their use in experimental vaccines. Initial studies with prototype DNA vaccines encoding epitopes indicate the need to include intracellular targeting sequences, to direct the encoded gene products to different cellular compartments, and amino acid spacer sequences between epitopes to optimize the processing, and subsequent presentation, of individual epitopes. Vaccines composed of CTL or HTL epitopes are now being developed for clinical testing.

AIDS Vaccines↗

PubMed2002

A rational strategy to design multiepitope immunogens based on multiple Th lymphocyte epitopes.

Four HLA-DR-restricted HIV-derived Th lymphocyte (HTL) epitopes cross-reactive with the murine I-A(b) class II molecule were used to evaluate different vaccine design strategies to simultaneously induce multiple HTL responses. All four epitopes were immunogenic in H-2(b) mice, demonstrating the feasibility of murine models to evaluate epitope-based vaccines destined for human use. Immunization with a pool of peptides induced responses against all four epitopes; illustrating immunodominance does not prevent the induction of balanced multispecific responses. When different delivery systems were evaluated, a multiple Ag peptide construct was found to be less efficient than a linear polypeptide encompassing all four epitopes. Further characterization of linear polypeptide revealed that the sequential arrangement of the epitopes created a junctional epitope with high affinity class II binding. Disruption of this junctional epitope through the introduction of a GPGPG spacer restored the immunogenicity against all four epitopes. Finally, we demonstrate that a GPGPG spacer construct can be used to induce HTL responses by either polypeptide or DNA immunization, highlighting the flexibility of the approach.

Amino Acid Sequence↗

PubMed2002

Epitope identification and vaccine design for cancer immunotherapy.

The development of processes for engineering multi-epitope vaccines based on the identification and selection of epitope packages, along with vaccine design optimization using epitope placements and spacers to optimize processing efficacy, are reviewed. The Epimmune Inc epitope identification process has been applied to numerous cancer types, but also applies to infectious diseases. Epitope-analog efforts in novel vaccine design have also been explored and their uses in prophylactic and therapeutic applications are eagerly anticipated.

Animals↗