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Michael A Chattergoon

Publications and source records attributed to Michael A Chattergoon.

9 recordsLinked to original sources
PubMed2005

Coimmunization with an optimized IL-15 plasmid results in enhanced function and longevity of CD8 T cells that are partially independent of CD4 T cell help.

DNA vaccines are a promising technology for the induction of Ag-specific immune responses, and much recent attention has gone into improving their immune potency. In this study we test the feasibility of delivering a plasmid encoding IL-15 as a DNA vaccine adjuvant for the induction of improved Ag-specific CD8(+) T cellular immune responses. Because native IL-15 is poorly expressed, we used PCR-based strategies to develop an optimized construct that expresses 80-fold higher than the native IL-15 construct. Using a DNA vaccination model, we determined that immunization with optimized IL-15 in combination with HIV-1gag DNA constructs resulted in a significant enhancement of Ag-specific CD8(+) T cell proliferation and IFN-gamma secretion, and strong induction of long-lived CD8(+) T cell responses. In an influenza DNA vaccine model, coimmunization with plasmid expressing influenza A PR8/34 hemagglutinin with the optimized IL-15 plasmid generated improved long term CD8(+) T cellular immunity and protected the mice against a lethal mucosal challenge with influenza virus. Because we observed that IL-15 appeared to mostly adjuvant CD8(+) T cell function, we show that in the partial, but not total, absence of CD4(+) T cell help, plasmid-delivered IL-15 could restore CD8 secondary immune responses to an antigenic DNA plasmid, supporting the idea that the effects of IL-15 on CD8(+) T cell expansion require the presence of low levels of CD4 T cells. These data suggest a role for enhanced plasmid IL-15 as a candidate adjuvant for vaccine or immunotherapeutic studies.

AIDS Vaccines↗
PubMed2004

Co-immunization with plasmid IL-12 generates a strong T-cell memory response in mice.

Plasmid encoded exogenous IL-12 delivered as a DNA vaccine adjuvant has been shown to improve vaccine-induced immunity. In particular, pIL-12 greatly improves antigen (Ag)-specific cytotoxic tlymphocyte (CTL) activity in immunized mice. The longevity of this response has not previously been studied in detail. We have studied the effect of co-immunization with pIL-12 on HIV gp160 and Influenza A Hemeagglutinnin-specific memory immune responses. Mice co-immunized with pIL-12 and plasmid encoded antigens maintained a greater memory response than those immunized with the plasmid antigen alone which could be measured at least 6 months after vaccination. Further, this translated to an improved outcome after challenge of long term rested mice that were previously immunized. The strength of the immune response as well as the number of Ag-specific T-cells is proportional to the number of Ag-specific cells primed by the vaccination regimen.

AIDS Vaccines↗
PubMed2003

Costimulatory molecule immune enhancement in a plasmid vaccine model is regulated in part through the Ig constant-like domain of CD80/86.

There is great interest in understanding the role of costimulatory molecules in immune activation. In both the influenza and HIV DNA immunization models, several groups have reported that coimmunization of mice with plasmids encoding immunogen and CD86, but not CD80, effectively boosts Ag-specific T cell activation. This difference in immune priming provided an opportunity to examine the functional importance of different regions of the B.7 molecules in immune activation. To examine this issue, we developed a series of chimeric CD80 and CD86 constructs as well as deletion mutants, and examined their immune activating potential in the DNA vaccine model. We demonstrate that the lack of an Ig constant-like region in the CD80 molecule is critically important to the enhanced immune activation observed. CD80 C-domain deletion mutants induce a highly inflammatory Ag-specific cellular response when administered as part of a plasmid vaccine. The data suggest that the constant-like domains, likely through intermolecular interactions, are critically important for immune regulation during costimulation and that engineered CD80/86 molecules represent more potent costimulatory molecules and may improve vaccine adjuvant efficacy.

Adjuvants, Immunologic↗
PubMed2003

Mechanism of HIV-1 viral protein R-induced apoptosis.

The paradigm of HIV-1 infection includes the diminution of CD4(+) T cells, loss of immune function, and eventual progression to AIDS. However, the mechanisms that drive host T cell depletion remain elusive. One HIV protein thought to participate in this destructive cascade is the Vpr gene product. Accordingly, we review the biology of the HIV-1 viral protein R (Vpr) an apoptogenic HIV-1 accessory protein that is packaged into the virus particle. In this review we focus specifically on Vpr's ability to induce host cell apoptosis. Recent evidence suggests that Vpr implements a unique mechanism to drive host cell apoptosis, by directly depolarizing the mitochondria membrane potential. Vpr's attack on the mitochondria results in release of cytochrome c resulting in activation of the caspase 9 pathway culminating in the activation of caspase 3 and the downstream events of apoptosis. Vpr may interact with the adenine nucleotide translocator (ANT) to prompt this cascade. The role of Vpr-induced apoptosis in HIV pathogenesis is considered.

Apoptosis↗
PubMed2003

Engineering cross-presentation in vivo.

Apoptotic bodies deliver antigens (Ags) to the cross-presentation pathways of dendritic cells (DCs), where their presentation has been associated with both the maintenance of tolerance as well as the induction of protective immunity. The manner in which apoptotic bodies are generated, their abundance in relation to local DCs, and the milieu in which they are generated appear to be the major factors determining whether apoptotic bodies will induce CD8(+) T cell activation or anergy. These observations have been extended to the field of vaccination, where the engineered apoptosis of Ag-bearing/loaded cells in vivo has been used to prime strong CD8(+) T cell immunity. This review will examine Ag capture and cross-presentation by DCs, with particular emphasis on the manipulation of apoptotic bodies in vivo for the purpose of vaccination.

Animals↗
PubMed2002

Adenovirus encoding HIV-1 Vpr activates caspase 9 and induces apoptotic cell death in both p53 positive and negative human tumor cell lines.

The targeted delivery of genes whose products arrest the cell cycle and/or induce apoptosis represent an important tool for the understanding and controlling forms of unregulated cell growth. The vpr gene product of HIV-1 has been reported to interfere with cell growth and induce apoptosis, but the mechanism of its action is not clearly understood. In order to study these important properties of Vpr, we created a recombinant adenovirus H5.010CMV-vpr (adCMV-vpr) as a tool to deliver the vpr gene to various cell lines to examine its biology. Vpr protein expression was confirmed by Western blot analysis in adCMV-vpr infected cells. We tested the effects of adCMV-vpr on cell growth of several tumor cell lines. Infection of both p53 positive and p53 deficient tumor cell lines with adCMV-vpr resulted in dramatic induction of cell death in short-term assays. We observed that apoptosis was induced through the mitochondrial pathway as we observed changes in the cytochrome c content accompanied by caspase 9 activation. As Bcl-2 is reported to interfere with apoptosis through the mitochondrial pathway, we examined the effect of adCMV-vpr in Bcl-2 over expressing cell lines. We observed that Bcl-2 overexpression does not inhibit adCMV-vpr induced apoptosis. The properties of adCMV-vpr inducing apoptosis through caspase 9 in a p53 pathway independent manner suggest that this is an important reagent. Such a vector may give insight into approaches designed to limit the growth of pathogenic human cells.

Adenoviridae↗
PubMed2002

Identification of crucial residues for the antibacterial activity of the proline-rich peptide, pyrrhocoricin.

Members of the proline-rich antibacterial peptide family, pyrrhocoricin, apidaecin and drosocin appear to kill responsive bacterial species by binding to the multihelical lid region of the bacterial DnaK protein. Pyrrhocoricin, the most potent among these peptides, is nontoxic to healthy mice, and can protect these animals from bacterial challenge. A structure-antibacterial activity study of pyrrhocoricin against Escherichia coli and Agrobacterium tumefaciens identified the N-terminal half, residues 2-10, the region responsible for inhibition of the ATPase activity, as the fragment that contains the active segment. While fluorescein-labeled versions of the native peptides entered E. coli cells, deletion of the C-terminal half of pyrrhocoricin significantly reduced the peptide's ability to enter bacterial or mammalian cells. These findings highlighted pyrrhocoricin's suitability for combating intracellular pathogens and raised the possibility that the proline-rich antibacterial peptides can deliver drug leads into mammalian cells. By observing strong relationships between the binding to a synthetic fragment of the target protein and antibacterial activities of pyrrhocoricin analogs modified at strategic positions, we further verified that DnaK was the bacterial target macromolecule. Inaddition, the antimicrobial activity spectrum of native pyrrhocoricin against 11 bacterial and fungal strains and the binding of labeled pyrrhocoricin to synthetic DnaK D-E helix fragments of the appropriate species could be correlated. Mutational analysis on a synthetic E. coli DnaK fragment identified a possible binding surface for pyrrhocoricin.

Agrobacterium tumefaciens↗
PubMed2002

Plasmid immunization primes unique DTH responses to HIV-1MN envelope epitopes as compared to recombinant protein vaccination.

Current evidence suggests that the induction of cell-mediated immunity is required for a successful HIV-1 vaccine. Delayed type hypersensitivity (DTH) and cellular cytotoxicity are closely linked elements of the cellular immune response, both are favored by immunizations that result in a T-helper (Th)-1 response. The classical experimental animal for the study of DTH is the guinea pig. Here we report that guinea pigs can readily be sensitized for DTH skin reactions to envelope protein with a plasmid expressing HIV-1(MN) (subtype B) envelope, as well as with the recombinant HIV-1 envelope protein. Further, utilizing peptide probes that in aggregate represent the entire gp120 molecule, common and unique dominant epitopes induced by each method of immunization were identified.

AIDS Vaccines↗