Towards development of T-cell vaccines

Lambda bacteriophage nanoparticles displaying GP2, a HER2/neu derived peptide, induce prophylactic and therapeutic activities against TUBO tumor model in mice

Generating a protective and long-lasting immune response is the primary goal in the expanding field of immunotherapeutic research. In current study we designed an immunogenic bacteriophage- based vaccine to induce a cytotoxic T lymphocyte activity against a mice tumor model over-expressing HER2/neu. Bacteriophage λ displaying a HER2/neu derived peptide GP2 was constructed and used as an anti-cancer vaccine in a BALB/c mouse xenograft tumor model. The results of our study indicated that phage nanoparticles displaying GP2 as a fused peptide to the gpD phage capsid protein induced a robust CTL response. Furthermore, the chimeric phage nanoparticles protected mice against HER2/neu-positive tumor challenge in both prophylactic and therapeutic settings. In conclusion, we propose that λ phage nanoparticles decorated with GP2 peptide merit further investigation for the development of peptide-based vaccines against HER2/neu overexpressing tumors.

On the emerging role of chemistry in the fashioning of biologics: synthesis of a bidomainal fucosyl GM1-based vaccine for the treatment of small cell lung cancer

The synthesis of the novel small cell lung cancer (SCLC) fucosyl GM1-based vaccine construct, featuring insertion of the HLA-DR binding 15 amino acid sequence derived from Plasmodium falciparum, is described. The resultant glycopeptide has been synthesized in an efficient manner. Finally, successful conjugation of the glycopeptide to the keyhole limpet hemocyanin (KLH) carrier protein completed the preparation of the vaccine.

A novel mimovirus vaccine containing survivin epitope with adjuvant IL-15 induces long-lasting cellular immunity and high antitumor efficiency

Numerous evidences have indicated that CD8+ cytotoxic T lymphocytes (CTLs) played a significant role in protecting host against tumors, thus CTLs have been involved as potentially relevant candidate targets of cancer immunotherapy. Moreover it is crucial to fully elucidate antigen-specific CTL response, especially high-avidity and long-lasting CTL response in vivo. In the present study, we reported a novel tumor vaccine (mimovirus), a viron-size particulate which consisted of a cell-penetrating peptide of Tat(49-57), a CTL epitope peptide survivin(85-93) and a plasmid encoding murine interleukin-15 (IL-15). We demonstrated that this tumor vaccine could effectively mediate the expression of the gene and presentation of the tumor antigen derived peptide ex vivo. Furthermore, the tumor vaccine supported a robust memory CTL-mediated long-term immunity in vivo, which could effectively protect BALB/c mice against fatal CT26 tumor challenge and improve their survival. These findings suggest that the tumor vaccine may provide an alternative therapeutic strategy for cancer patients.

Cytotoxic T lymphocyte response induced by an improved synthetic lipopeptide vaccine against cervical cancer

AIM

To explore cytotoxic T lymphocyte (CTL) response induced by the lipopeptide vaccine against cervical cancer.

METHODS

The immunological effect inducing CD8+ T cell-mediated cytotoxicity was investigated in human leukocyte antigen (HLA)-A2 transgenic mice and peripheral blood mononuclear cells (PBMC) of healthy HLA-A2.1+blood donor. The activity of specific CTL was measured by using a standard 4 h( 51)Cr release assay. The content of major histocompatibility complex (MHC) I on T2 cells and the expression of immune molecules on dendritic cells (DC) were detected by flow cytometry, and the concentrations of interleukin (IL)-12 and interferon-gamma were determined by ELISA.

RESULTS

The lipopeptide induced a strong epitope-specific CTL response both in vivo (transgenic mice) and in vitro (human PBMC). This CTL induction was critically dependent on the presence of the helper T lymphocyte epitope in transgenic mice, and the presence of a lipid tail bypassed the need for an adjuvant. The stability and persistence of the antigenic complex formed with the lipopeptide increased in comparison with the CTL parental peptide. The lipopeptide could induce the production of IL-12 in DC, but not the maturation of DC directly.

CONCLUSION

The combination of CTL and the T helper epitope and lipid molecule can remarkably improve the immunogenicity of the CTL peptide, the mechanism of which is associated with an increase in the stability and persistence of the antigenic complex formed with the lipopeptide and in the production of IL-12 in DC induced by the lipopeptide. The lipopeptide can be considered a more effective vaccine type for human being.

Recent developments in veterinary vaccinology

Advancement in technology and science and our detailed knowledge of immunology, molecular biology, microbiology, and biochemistry among other basic science disciplines have defined new directions for vaccine development strategies. The applicability of genetic engineering and proteomics along with other new technologies have played pivotal roles in introducing novel ideas in vaccinology, and resulted in developing new vaccines and improving the quality of existing ones. Subunit vaccines, recombinant vaccines, DNA vaccines and vectored vaccines are rapidly gaining scientific and public acceptance as the new generation of vaccines and are seriously considered as alternatives to current conventional vaccines. The present review focuses on recent advances in veterinary vaccinology and addresses the effects and impact of modern microbiology, immunology, and molecular biology.

Pivotal molecules of MHC I pathway in human primary hepatocellular carcinoma

AIM: To investigate the expression of several important molecules involved in major histocompatibility complex (MHC) class I presentation pathway in primary hepatocellular carcinoma (HCC), and to determine whether cytotoxic T lymphocyte (CTL) vaccine therapy was suitable for HCC.

METHODS: Labeled streptavidin biotin (LSAB) method of immunohisto-chemistry was used to study 33 HCC tissue specimens.

RESULTS: Most HCC tissues and adjacent histological normal hepatocytes expressed HLA-I antigens,TAP, and B7, expression of B7 was especially strong, and there was no significant difference between them (P>0.05).

CONCLUSION: The MHC class I presentation pathway in primary hepatocellular carcinoma may not be abnormal or dysfunctional, and CTL could kill these tumor cells. Thus, it is suitable and practicable to design and construct CTL vaccine against HCC.

Induction of specific T-helper and cytolytic responses to epitopes displayed on a virus-like protein scaffold derived from the pyruvate dehydrogenase multienzyme complex

The icosahedral protein scaffold (1.5MDa) generated by self-assembly of the catalytic domains of the dihydrolipoyl acetyltransferase core of the pyruvate dehydrogenase multienzyme complex from Bacillus stearothermophilus has been engineered to display 60 copies of one or more peptide epitopes on a single molecule (E2DISP). An E2DISP scaffold displaying pep23, a 15-residue B- and T-helper epitope from the reverse transcriptase of HIV-1, was able to induce a pep23-specific T-helper response in cell lines in vitro. The same scaffold displaying both pep23 and peptide RT2, a nine-residue CTL epitope from HIV-1 reverse transcriptase, was able to prime an RT2-specific CD8(+) T-cell response in human cell lines in vitro and in HLA-A2 transgenic mice in vivo. This was accompanied by a humoral antibody response specific for E2DISP-presented epitopes. Thus, the icosahedral acetyltransferase core constitutes a simple and flexible scaffold for multiple epitope display with access to both cellular and humoral immune response pathways.

Processing of filamentous bacteriophage virions in antigen-presenting cells targets both HLA class I and class II peptide loading compartments

Virions of filamentous bacteriophage fd are capable of displaying multiple copies of peptide epitopes and generating powerful immune responses to them. To investigate the antigen processing mechanisms in human B cell lines used as antigen presenting cells, the major coat protein (pVIII) in intact virions was fluorescently labeled, and its localization in various intracellular compartments was followed using confocal microscopy. We show that the virions were taken up and processed to yield peptides that reach both the major histocompatibility complex (MHC) class II compartment and the endoplasmic reticulum. Moreover, when exposed to bacteriophages displaying a cytotoxic T lymphocyte (CTL) epitope from the reverse transcriptase of human immunodeficiency virus type-1 (HIV-1), B cells were lysed by specific cytotoxic lymphocytes. This confirms that filamentous bacteriophage virions are capable of being taken up and processed efficiently by MHC class I and class II pathways, even in nonprofessional antigen presenting cells. These remarkable features explain, at least in part, the unexpected ability of virions displaying foreign T-cell epitopes to prime strong T-helper-dependent CTL responses. These findings have important implications for the development of peptide-based vaccines, using filamentous bacteriophage virions as scaffolds.

Mimovirus: a novel form of vaccine that induces hepatitis B virus-specific cytotoxic T-lymphocyte responses in vivo

CD8(+) cytotoxic T lymphocytes (CTLs) are now recognized as important mediators of immunity against intracellular pathogens, including human immunodeficiency virus and tumors. How to efficiently evoke antigen-specific CTL responses in vivo has become a crucial problem in the development of modern vaccines. Here, we developed a completely novel CTL vaccine-mimovirus, which is a kind of virus-size particulate antigen delivery system. It was formed by the self-assembly of a cationic peptide containing 18 lysines and a CTL-epitope peptide of HBsAg(28-39), with a plasmid encoding mouse interleukin-12 (IL-12) through electrostatic interactions. We examined the formation of mimovirus by DNA retardation assay, DNase I protection assay, and transmission electron microscopy and demonstrated that mimovirus could efficiently transfer the plasmid encoding IL-12 into mammalian cells such as P815 cells in vitro. Furthermore, it was proved that mimovirus could induce an HBsAg(28-39)-specific CTL response in vivo. Considering its effectiveness, flexibility, and defined composition, mimovirus is potentially a novel system for vaccination against intracellular pathogens and tumors.

Exogenous peptides delivered by ricin require processing by signal peptidase for transporter associated with antigen processing-independent MHC class I-restricted presentation

In this study we demonstrate that a disarmed version of the cytotoxin ricin can deliver exogenous CD8(+) T cell epitopes into the MHC class I-restricted pathway by a TAP-independent, signal peptidase-dependent pathway. Defined viral peptide epitopes genetically fused to the N terminus of an attenuated ricin A subunit (RTA) that was reassociated with its partner B subunit were able to reach the early secretory pathway of sensitive cells, including TAP-deficient cells. Successful processing and presentation by MHC class I proteins was not dependent on proteasome activity or on recycling of MHC class I proteins, but rather on a functional secretory pathway. Our results demonstrated a role for signal peptidase in the generation of peptide epitopes associated at the amino terminus of RTA. We showed, first, that potential signal peptide cleavage sites located toward the N terminus of RTA can be posttranslationally cleaved by signal peptidase and, second, that mutation of one of these sites led to a loss of peptide presentation. These results identify a novel MHC class I presentation pathway that exploits the ability of toxins to reach the lumen of the endoplasmic reticulum by retrograde transport, and suggest a role for endoplasmic reticulum signal peptidase in the processing and presentation of MHC class I peptides. Because TAP-negative cells can be sensitized for CTL killing following retrograde transport of toxin-linked peptides, application of these results has direct implications for the development of novel vaccination strategies.

Micellar-type complexes of tailor-made synthetic block copolymers containing the HIV-1 tat DNA for vaccine application

A novel class of cationic block copolymers constituted by a neutral hydrophilic poly(ethylene glycol) (PEG) block and a positively charged poly(dimethylamino)ethyl methacrylate block was prepared for delivery of DNA. These block copolymers spontaneously assemble with DNA to give in aqueous medium micellar-like structures. Five of these novel block copolymers (K1-5), differing in the length of both the PEG chain and the linear charge density of the poly(dimethylamino)ethyl methacrylate block, were prepared and analyzed for gene delivery, gene expression and safety. All five block copolymers protected DNA from DNAse I digestion and delivered the DNA into the cell. However, only three of them (K1, K2 and K5) released the DNA at level allowing efficient gene expression into cells. No toxic effects of both the copolymers alone or their DNA complexes were observed in vitro or in mice. In addition, copolymers were scarcely immunogenic. These results indicate that this novel class of cationic block copolymers is safe and possesses the biological characteristics required for DNA delivery, thus, representing promising vehicles for DNA vaccination.

Induction of hepatitis B virus-specific cytotoxic T lymphocytes response in vivo by filamentous phage display vaccine

The ability of inducing MHC class I restricted cytotoxic T lymphocytes response in vivo via recombinant filamentous phage was investigated. The recombinant filamentous phage particles that displayed the Hepatitis B virus epitope S(28--39) were injected into BALB/c (H-2d) mice without adjuvants. A MHC class I restricted HBs specific CTL response was found 8 days after injection. The potentiality of using the recombinant filamentous phage as anti-virus vaccine was discussed.

Induction of vigorous helper and cytotoxic T cell as well as B cell responses by dendritic cells expressing a modified antigen targeting receptor-mediated internalization pathway

Efficient Ag presentation is essential to induce effective cellular and humoral immune responses. Thus, one central goal of current immunotherapy and vaccine development is to enhance Ag presentation to induce potent and broad immune responses. Here, a novel Ag presentation strategy is developed by transducing dendritic cells (DCs) to produce an Ag for presentation as an exogenous Ag to efficiently induce both humoral and cellular immunity. The principle of this strategy is illustrated by genetically modifying DCs to secrete a model hepatitis B virus Ag fused with a cell-binding domain and to process the fusion Ag as an exogenous Ag after receptor-mediated internalization for MHC class I and II presentation. Vigorous Ag-specific CD4(+) helper and CD8(+) cytotoxic T cell, as well as B cell, responses were induced by the transduced DCs in mouse models. Thus, this novel strategy uses a receptor-mediated internalization process to efficiently induce all arms of the adaptive immunity and may provide a powerful means to develop potent vaccines and immunotherapies.

Induction of a polarized Th1 response by insertion of multiple copies of a viral T-cell epitope into adenylate cyclase of Bordetella pertussis

The adenylate cyclase (CyaA) of Bordetella pertussis delivers the N-terminal catalytic domain into the cytosol of a large number of eukaryotic cells, in particular, professional antigen-presenting cells. This allows the delivery of CD8(+) T-cell epitopes to the major histocompatibility complex class I presentation pathway. We have previously shown that immunization of mice with CyaA carrying a single CD8(+) T-cell epitope leads to antiviral protection as well as to protective and therapeutic antitumor immunity associated with the induction of specific cytotoxic T-lymphocyte (CTL) responses. Here, we evaluated the capacity of CyaA carrying one to four copies of the CD8(+) CD4(+) T-cell epitope from the nucleoprotein of the lymphocytic choriomeningitis virus to induce T-cell responses. Both CTL and Th1-like specific responses were detected in mice immunized with recombinant CyaA with or without adjuvant. Although the insertion of the larger peptides resulted in partial loss of the invasive capacity of recombinant CyaA, insertion of several copies of the same epitope led to a strong enhancement of Th1 responses and, to a lesser degree, CTL responses. These results underscore the potency of CyaA for vaccine design with a new impact on diseases in which the Th1 response has been described to have a beneficial effect.

Recombinant polioviruses expressing hepatitis B virus-specific cytotoxic T-lymphocyte epitopes

T-cell immune response to recombinant poliovirus expressing foreign antigens has not been elucidated well. In order to investigate the potential use of poliovirus as a T-cell vaccine vector, we constructed recombinant polioviruses expressing HBV-derived CTL epitopes, HBsAg(28-39) (L(d)-restricted; IPQSLDSWWTSL) and HBc(93-100) (K(b)-restricted; MGLKFRQL) at the junction between the P2 and P3 regions, designated V3CDs and V3CDc, respectively. The V3CDs and V3CDc recombinant viruses replicated efficiently in HeLa cells and showed a similar infection profile to that of the wild-type Mahoney strain in one-step growth kinetics. Genetic stability analysis showed that V3CDc retained the foreign insert over twelve successive passages examined, whereas V3CDs lost part of the foreign insert after four passages. Our results indicated that the stability of the inserted foreign sequences was rather affected by their nucleotide sequence than by their length when located between the P2 and P3 regions. The junction between these nonstructural protein-coding regions is a novel site for the construction of replication-competent recombinant poliovirus. Immunization of BALB/c (H-2(d)) and C57BL/6 mice (H-2(b)) with V3CDs and V3CDc, respectively, elicited significant antigen-specific CTL responses to HBsAg(28-39) but not to HBcAg(93-100).

Immunogenicity of H-2Kb-low affinity, high affinity, and covalently-bound peptides in anti-tumor vaccination

CTL induction by immunization with synthetic peptide epitopes has been shown to inhibit tumor growth and its metastatic spread. Ex vivo pulsing of peptides on MHC class I-bearing cells such as RMA-S cells or professional APCs elicits an effective CTL response. Since the stability of the MHC-peptide complex is strongly correlated with the overall immunogenecity, we compared the effect of immunization with low affinity, high affinity, and irreversibly bound MHC peptides in the context of immunotherapy of metastasis. MUT1, a tumor-associated antigen peptide that was isolated from 3LL Lewis lung carcinoma, is a low H-2Kb binder. MUT1 was modified into a high binder by changing positions 3, 5, and 8 to the favorable anchor residues. In addition, we introduced a photo-active chemical moiety, which can bind irreversibly to MHC upon illumination. These peptides, loaded onto RMA-S, were used to immunize mice against the 3LL tumor. Vaccination via the covalent conjugation of the low binder peptide was found to increase the CTL response measured against MUT1 loaded cells and against H-2Kb transfected D122 cells relative to the native MUT1 peptide. However, the photo cross-linking of the high affinity peptide to the MHC did not significantly improve the induction of specific CTL. The level of CTL activity was elevated to the same extent by either cross-linking the peptide to the MHC or by modifying it into a high-binder peptide. The protective capacity of all the peptide-based vaccines against D122 metastatic spread to the lungs was found to be comparable. These results indicate that augmentation of the affinity of a TAA peptide to the RMA-S surface MHC molecules, by conversion to a high-affinity mimotope or by photo-conjugation, can significantly enhance the immune response. There seems to be, however, a ceiling beyond which increase in the peptide-binding affinity does not lead to a corresponding enhancement of the overall immunogenicity of the peptide.

Phage-displayed T-cell epitope grafted into immunoglobulin heavy-chain complementarity-determining regions: an effective vaccine design tested in murine cysticercosis

A new type of immunogenic molecule was engineered by replacing all three complementarity-determining-region (CDR) loops of the human immunoglobulin (Ig) heavy-chain variable (V(H)) domain with the Taenia crassiceps epitope PT1 (PPPVDYLYQT) and by displaying this construct on the surfaces of M13 bacteriophage. When BALB/c mice were immunized with such phage particles (PIgphage), a strong protection against challenge infection in very susceptible female hosts was obtained. When specifically stimulated, the in vivo-primed CD4(+) and CD8(+) T cells isolated from mice immunized with PT1, both as a free peptide and as the PIgphage construct, proliferated in vitro, indicating efficient epitope presentation by both major histocompatibility complex class II and class I molecules in the specifically antigen-pulsed macrophages used as antigen-presenting cells. These data demonstrate the immunogenic potential of recombinant phage particles displaying CDR epitope-grafted Ig V(H) domains and establish an alternative approach to the design of an effective subunit vaccine for prevention of cysticercosis. The key advantage of this type of immunogen is that no adjuvant is required for its application. The proposed strategy for immunogen construction is potentially suitable for use in any host-pathogen interaction.

In vitro immunization with a recombinant antigen carrying the HIV-1 RT248-262 determinant inserted at different locations results in altered TCRVB region usage

Immunodominance or cripticity of a peptide-borne determinant may be influenced by the protein context in which the epitope is embedded. In this frame, we previously showed that certain human T cell clones, derived from different donors, may differentially recognize the RT248-262 helper determinant depending on whether it is provided to the presenting cells as a synthetic peptide or as a recombinant carrier protein to which the sequence of interest is fused. We now report that, upon in vitro immunization of human PBL with autologous APC, the epitope-specific TCRVB repertoire obtained when selection is applied by pulsing the APC with the cognate synthetic peptide is different from that found when a recombinant protein is used in which the antigenic sequence is placed at either a N-terminal or C-terminal location of the GST carrier. As the TCRVB distribution is not a function of the APC used, we propose that processing of different recombinant molecules containing the same epitope may generate MHC/peptide complexes which, being antigenically diverse, may recruit distinct TCR specificities. These findings may be relevant for evaluating and predicting the immunogenic potential of subunit vaccines based on synthetic peptides or on recombinant proteins as compared to the native antigen.

Human tumor antigens for cancer vaccine development

The adoptive transfer of tumor-infiltrating lymphocytes (TIL) along with interleukin (IL)-2 into autologous patients with cancer resulted in the objective regression of tumor, indicating that T cells play an important role in tumor regression. In the last few years, efforts have been made towards understanding the molecular basis of T-cell-mediated antitumor immunity and elucidating the molecular nature of tumor antigens recognized by T cells. Tumor antigens identified thus far could be classified into several categories: tissue-specific differentiation antigens, tumor-specific shared antigens and tumor-specific unique antigens. CD4+ T cells play a central role in orchestrating the host immune response against cancer, infectious diseases and autoimmune diseases, and we thus have attempted to identify major histocompatibility complex (MHC) class II-restricted tumor antigens as well. The identification of tumor rejection antigens provides new opportunities for the development of therapeutic strategies against cancer. This review will summarize the current status of MHC class I- and class II-restricted human tumor antigens, and their potential application to cancer treatment.

Antigen-specific in vitro activation of T-lymphocyte subsets of cattle immunized with a modified live bovine herpesvirus 1 vaccine

Bovine peripheral blood mononuclear cells from cattle immunized with a modified live virus bovine herpesvirus 1 (BHV1) vaccine and from BHV1-negative cattle were incubated in vitro with inactivated BHV1 for 6 days. Activation of T-lymphocyte subsets was measured by two-color flow cytometric analysis of T-cell phenotype and surface expression of CD25, the alpha-subunit of the high-affinity interleukin-2 receptor. Vaccinated animals, but not unvaccinated animals, had CD3+, CD4+, and gamma-delta T cells that significantly (p < 0.05) increased expression of CD25 when incubated with BHV1. CD8+ T cells from vaccinated animals did not consistently increase CD25 expression when incubated with inactivated BHV1.

Identification of a novel major histocompatibility complex class II-restricted tumor antigen resulting from a chromosomal rearrangement recognized by CD4(+) T cells

CD4(+) T cells play an important role in antitumor immune responses and autoimmune and infectious diseases. Although many major histocompatibility complex (MHC) class I-restricted tumor antigens have been identified in the last few years, little is known about MHC class II- restricted human tumor antigens recognized by CD4(+) T cells. Here, we describe the identification of a novel melanoma antigen recognized by an human histocompatibility leukocyte antigen (HLA)-DR1-restricted CD4(+) tumor-infiltrating lymphocyte (TIL)1363 using a genetic cloning approach. DNA sequencing analysis indicated that this was a fusion gene generated by a low density lipid receptor (LDLR) gene in the 5' end fused to a GDP-L-fucose:beta-D-galactoside 2-alpha-L-fucosyltransferase (FUT) in an antisense orientation in the 3' end. The fusion gene encoded the first five ligand binding repeats of LDLR in the NH2 terminus followed by a new polypeptide translated in frame with LDLR from the FUT gene in an antisense direction. Southern blot analysis showed that chromosomal DNA rearrangements occurred in the 1363mel cell line. Northern blot analysis detected two fusion RNA transcripts present only in the autologous 1363mel, but not in other cell lines or normal tissues tested. Two minimal peptides were identified from the COOH terminus of the fusion protein. This represents the first demonstration that a fusion protein resulting from a chromosomal rearrangement in tumor cells serves as an immune target recognized by CD4(+) T cells.