Biomedical subjects

Jason Rice

Publications and source records attributed to Jason Rice.

11 recordsLinked to original sources

PubMed2006

Priming protective CD8 T cell immunity by DNA vaccines encoding chimeric, stress protein-capturing tumor-associated antigen.

DNA vaccines encoding heat shock protein (hsp)-capturing, chimeric peptides containing antigenic determinants of the tumor-associated Ag (TAA) gp70 (an envelope protein of endogenous retrovirus) primed stable, specific, and tumor-protective CD8 T cell immunity. Expression of gp70 transcripts was detectable in most normal tissues but was particularly striking in some (but not all) tumor cell lines tested (including the adenocarcinoma cell line CT26). An approximately 200 residue gp70 fragment or its L(d)-binding antigenic AH1 peptide cloned in-frame behind an hsp-capturing (cT(272)) or noncapturing (T(60)) N-terminal large SV40 tumor Ag sequence was expressed as either hsp-binding or -nonbinding chimeric Ags. Only hsp-capturing, chimeric fusion proteins were expressed efficiently in transfected cell lines and primed TAA-specific CD8 T cell immunity. This immunity mediated protection in the CT26 and mKSA models. A vaccination strategy based on delivering antigenic, hsp-associated TAA fragments can thus prime protective CD8 T cell immunity even if these TAA are of low intrinsic immunogenicity.

Adenocarcinoma↗

PubMed2006

DNA fusion vaccines induce epitope-specific cytotoxic CD8(+) T cells against human leukemia-associated minor histocompatibility antigens.

The graft-versus-leukemia effect of allogeneic stem-cell transplantation is believed to be mediated by T-cell recognition of minor histocompatibility antigens on recipient cells. For minor histocompatibility antigens HA-1 and HA-2, normal cell expression is restricted to hemopoietic cells, and boosting the immune response to these antigens may potentiate graft-versus-leukemia effect without accompanying graft-versus-host disease. To increase efficacy, expansion of HA-1- or HA-2-specific CTL before transplantation is desirable. However, primary HA-1- or HA-2-specific CTL expanded in vitro are often of low avidity. An alternative approach is to prime specific CTL responses in vivo by vaccination. Clearly, donor vaccination must be safe and specific. We have developed DNA fusion vaccines able to induce high levels of epitope-specific CTL using linked CD4(+) T-cell help. The vaccines incorporate a domain of tetanus toxin (DOM) fused to a sequence encoding a candidate MHC class I binding peptide. This design generates antitumor CD8(+) T-cell responses and protective immunity in preclinical models. For clinical application, we constructed vaccines encoding HLA-A*0201-restricted peptides from human HA-1 and HA-2, which were fused to DOM, and tested their performance in HLA-A*0201-transgenic mice. Priming induced epitope-specific, IFNgamma-producing CD8(+) T cells with cytotoxic function boosted to high levels with electroporation. Strikingly, these mouse T cells efficiently killed human lymphoblastoid cell lines expressing endogenous HA-1 or HA-2. High avidity is indicated by the independence of cytolysis from CD8/MHC class I interaction. These safe epitope-specific vaccines offer a potential strategy to prime HA-1- or HA-2-specific CTL in transplant donors before adoptive transfer.

Amino Acid Sequence↗

PubMed2006

Optimizing cancer immunotherapy trials: back to basics.

Attempts to raise effective immunity against cancer are benefiting from information on the nature of the immunity involved and its regulation and, perhaps, now it is time to step back and define our approach in molecular terms prior to clinical testing. Although there are immunological differences between mice and patients, results from murine studies are encouraging early 'translation' of concepts to the clinic and it is vital to take immunological principles emerging from mice into clinical vaccine design. One is the requirement to break tolerance against over-expressed self-antigens, a potentially risky procedure but necessary for several cancer targets. A study in this issue of the European Journal of Immunology attempts to do this by using xenogeneic antigens, albeit with variable outcome. The unstated goal is to activate T-cell help but this can be achieved more effectively by harnessing a predictable anti-microbial repertoire. The second issue lies in the delivery of antigen. One strategy is "prime/boost" using DNA priming and boosting with a viral vector; however, this induces blocking immunity against viral proteins, and must be used judiciously. There are other physical methods to increase immunity such as electroporation, which can itself be used in 'prime/boost' sequence. These twin problems of engagement of T-cell help and delivery of adequate antigen can now be addressed by applying immunological logic to cancer vaccines.

Antigens, Neoplasm↗

PubMed2005

Electroporation as a "prime/boost" strategy for naked DNA vaccination against a tumor antigen.

We have developed novel DNA fusion vaccines encoding tumor Ags fused to pathogen-derived sequences. This strategy activates linked T cell help and, using fragment C of tetanus toxin, amplification of anti-tumor Ab, CD4(+), and CD8(+) T cell responses is achievable in mice. However, there is concern that simple DNA vaccine injection may produce inadequate responses in larger humans. To overcome this, we tested electroporation as a method to increase the transfection efficiency and immune responses by these tumor vaccines in vivo in mice. Using a DNA vaccine expressing the CTL epitope AH1 from colon carcinoma CT26, we confirmed that effective priming and tumor protection in mice are highly dependent on vaccine dose and volume. However, suboptimal vaccination was rendered effective by electroporation, priming higher levels of AH1-specific CD8(+) T cells able to protect mice from tumor growth. Electroporation during priming with our optimal vaccination protocol did not improve CD8(+) T cell responses. In contrast, electroporation during boosting strikingly improved vaccine performance. The prime/boost strategy was also effective if electroporation was used at both priming and boosting. For Ab induction, DNA vaccination is generally less effective than protein. However, prime/boost with naked DNA followed by electroporation dramatically increased Ab levels. Thus, the priming qualities of DNA fusion vaccines, integrated with the improved Ag expression offered by electroporation, can be combined in a novel homologous prime/boost approach, to generate superior antitumor immune responses. Therefore, boosting may not require viral vectors, but simply a physical change in delivery, facilitating application to the cancer clinic.

Adjuvants, Immunologic↗

PubMed2004

DNA fusion vaccines induce targeted epitope-specific CTLs against minor histocompatibility antigens from a normal or tolerized repertoire.

We have designed DNA fusion vaccines able to induce high levels of epitope-specific CD8(+) T cells, using linked CD4(+) T cell help. Such vaccines can activate effective immunity against tumor Ags. To model performance against minor histocompatibility (H) Ags important in allogeneic hemopoietic stem cell transplantation, responses against the H2D(b)-restricted Uty and Smcy male HY epitopes have been investigated. Vaccination of females induced high levels of tetramer-specific, IFN-gamma-producing CD8(+) T cells against each epitope. Vaccines incorporating a single epitope primed effector CTL able to kill male splenocytes in vitro and in vivo, and HY(Db)Uty-specific vaccination accelerated rejection of syngeneic male skin grafts. Priming against either epitope established long-term memory, expandable by injection of male cells. Expanded CD8(+) T cells remained specific for the priming HY epitope, with responses to the second suppressed. To investigate vaccine performance in a tolerized repertoire, male mice were vaccinated with the fusion constructs. Strikingly, this also generated epitope-specific IFN-gamma-producing CD8(+) T cells with cytotoxic function. However, numbers and avidity were lower than in vaccinated females, and vaccinated males failed to reject CFSE-labeled male splenocytes in vivo. Nevertheless, these findings indicate that DNA fusion vaccines can mobilize CD8(+) T cells against endogenous minor H Ags, even from a profoundly tolerized repertoire. In the transplantation setting, vaccination of donors could prime and expand specific T cells for in vivo transfer. For patients, vaccination could activate a potentially less tolerized repertoire against similar Ags that may be overexpressed by tumor cells, for focused immune attack.

Animals↗

PubMed2004

DNA vaccines to attack cancer.

Delivery of antigens by injection of the encoding DNA allows access to multiple antigen-presenting pathways. Knowledge of immunological processes can therefore be used to modify construct design to induce selected effector functions. Expression can be directed to specific intracellular sites, and additional genes can be fused or codelivered to amplify responses. Therapeutic vaccination against cancer adds a requirement to overcome tolerance and to activate a weakened immune repertoire. Induction of CD4(+) T helper cells is critical for both antibody and T cell effector responses. To activate immunity against tumor antigens, we fused the tumor-derived sequences to genes encoding microbial proteins. This strategy engages T helper cells from the large antimicrobial repertoire for linked help for inducing antibody against cell-surface tumor antigens. The principle of linked T cell help also holds for induction of epitope-specific antitumor CD8(+) T cells, but the microbial sequence has to be minimized to avoid competition with tumor antigens. Epitope-specific DNA vaccination leads to powerful antitumor attack and can activate immunity from a profoundly tolerized repertoire. Vaccine designs validated in preclinical models are now in clinical trial with immune responses detected against both tumor antigens and fused microbial antigens. DNA priming is highly efficient, but boosting may benefit from increased antigen expression. Physical methods including electroporation provide increased expression without introducing additional competing antigens. A wide range of cancers can be targeted, and objective assays of response will determine efficacy.

Animals↗

PubMed2004

Tumor vaccines.

Explore the source record for details and available documents.

Animals↗

PubMed2004

DNA fusion gene vaccines against cancer: from the laboratory to the clinic.

Vaccination against target antigens expressed by cancer cells has now become a realistic goal. DNA vaccines provide a direct link between identification of genetic markers in tumors and vaccine formulation. Simplicity of manufacture facilitates construction of vaccines against disease subsets or even for individual patients. To engage an immune system that exists to fight pathogens, we have developed fusion gene vaccines encoding tumor antigens fused to pathogen-derived sequences. This strategy activates high levels of T-cell help, the key to induction and maintenance of effective immunity. We have dissected the immunogenic tetanus toxin to obtain specific sequences able to activate antibody, CD4+, or CD8+ T cells to attack selected fused tumor antigens. Principles established in preclinical models are now being tested in patients. So far, objective immune responses against idiotypic antigen of neoplastic B cells have been observed in patients with B-cell malignancies and in normal transplant donors. These responses provide a platform for testing physical methods to improve DNA delivery and strategies to boost responses. For cancer, demands are high, because vaccines have to activate powerful immunity against weak antigens, often in a setting of immune damage or tolerance. Vaccination strategies against cancer and against microbes are sharing knowledge and technology for mutual benefit.

Antigens, Neoplasm↗

PubMed2002

Critical components of a DNA fusion vaccine able to induce protective cytotoxic T cells against a single epitope of a tumor antigen.

DNA vaccines can activate immunity against tumor Ags expressed as MHC class I-associated peptides. However, priming of CD8(+) CTL against weak tumor Ags may require adjuvant molecules. We have used a pathogen-derived sequence from tetanus toxin (fragment C (FrC)) fused to tumor Ag sequences to promote Ab and CD4(+) T cell responses. For induction of CD8(+) T cell responses, the FrC sequence has been engineered to remove potentially competitive MHC class I-binding epitopes and to improve presentation of tumor epitopes. The colon carcinoma CT26 expresses an endogenous retroviral gene product, gp70, containing a known H2-L(d)-restricted epitope (AH1). A DNA vaccine encoding gp70 alone was a poor inducer of CTL, and performance was not significantly improved by fusion of full-length FrC. However, use of a minimized domain of FrC, with the AH1 sequence fused to the 3' position, led to rapid induction of high levels of CTL. IFN-gamma-producing epitope-specific CTL were detectable ex vivo and these killed CT26 targets in vitro. The single epitope vaccine was more effective than GM-CSF-transfected CT26 tumor cells in inducing an AH1-specific CTL response and equally effective in providing protection against tumor challenge. Levels of AH1-specific CTL in vivo were increased following injection of tumor cells, and CTL expanded in vitro were able to kill CT26 cells in tumor bearers. Pre-existing immunity to tetanus toxoid had no effect on the induction of AH1-specific CTL. These data demonstrate the power of epitope-specific CTL against tumor cells and illustrate a strategy for priming immunity via a dual component DNA vaccine.

Animals↗

PubMed2002

A gamma-herpesvirus immune evasion gene allows tumor cells in vivo to escape attack by cytotoxic T cells specific for a tumor epitope.

DNA vaccines induce CTL attack on target tumor epitopes, but tumor elimination in vivo also requires sufficient effector CTL to enter the site, guided by inflammatory chemokines. Many herpesviruses contain genes for chemokine and chemokine receptor-like proteins to protect infected cells from immune attack. To assess if this evasion strategy could protect tumor cells, we used a model where CTL specific for a single epitope were the only effectors. Following DNA vaccination, CTL eliminated tumor cells from a subcutaneous site. However, introducing a viral gene encoding a secreted broad-spectrum chemokine-binding protein (M3) into tumor cells completely blocked CTL attack. Transduced tumor cells also protected neighboring non-transduced tumor. These findings confirm the importance of chemokines for migration of CTL to a non-lymphoid site. They may have relevance for escape of human virus-associated malignancies, and raise the question of whether analogous molecules might contribute to the failure of CTL to eliminate tumors.

Animals↗

PubMed1997

Fluorescent oligonucleotide rDNA probes that specifically bind to a common nanoflagellate, Paraphysomonas vestita.

Nanoflagellates are ecologically important, but morphological identification requires techniques which are not practicable for use in quantitative studies of populations; alternative methods of accurate recognition of nanoflagellate species in mixed populations are therefore desirable. Fluorescent oligonucleotide probes which hybridize with unique sequences of the small subunit (SSU) rRNA have been exploited as 'phylogenetic stains' in the identification of bacteria. In this paper we describe the preparation and application of probes which specifically hybridize with a common nanoflagellate species, Paraphysomonas vestita. The sequence of nucleotides in the SSU rRNA gene of this flagellate was determined and compared with those of related species to select unique P. vestita sequences 18-21 nucleotides in length. Five sequences in different parts of the SSU rRNA gene were used to design 5'-fluorescently labelled oligonucleotide probes. Published sequences were used to make probes that hybridized with all eukaryotes (EUK) or any cellular organism (UNI), and probes were designed not to hybridize with rRNA (CON). Optimum conditions for hybridization were determined. In all cases, UNI probes hybridized with the cells, but CON probes were only bound to a limited extent. All five probes targeted to P. vestita proved to be species-specific; they hybridized well with this species, but not with three other species of the same genus, nor with three more distantly related flagellate species, nor with a ciliate, nor with bacteria. These probes provide a means of quantitatively measuring the proportion of P. vestita cells in samples of mixed protists.

Animals↗