Lipopeptide-based melanoma cancer vaccine induced a strong MART-27-35-cytotoxic T lymphocyte response in a preclinal study

Palmitoylated antigens for the induction of anti-tumor CD8+ T cells and enhanced tumor recognition

Induction of tumor-specific cytotoxic CD8⁺ T cells (CTLs) via immunization relies on the presentation of tumor-associated peptides in major histocompatibility complex (MHC) class I molecules by dendritic cells (DCs). To achieve presentation of exogenous peptides into MHC class I, cytosolic processing and cross-presentation are required. Vaccination strategies aiming to induce tumor-specific CD8⁺ T cells via this exogenous route therefore pose a challenge. In this study, we describe improved CD8⁺ T cell induction and in vivo tumor suppression of mono-palmitic acid-modified (C16:0) antigenic peptides, which can be attributed to their unique processing route, efficient receptor-independent integration within lipid bilayers, and continuous intracellular accumulation and presentation through MHC class I. We propose that this membrane-integrating feature of palmitoylated peptides can be exploited as a tool for quick and efficient antigen enrichment and MHC class I loading. Importantly, both DCs and non-professional antigen-presenting cells (APCs), similar to tumor cells, facilitate anti-tumor immunity by efficient CTL priming via DCs and effective recognition of tumors through enhanced presentation of antigens.

Palmitoylation of Membrane-Penetrating Magainin Derivatives Reinforces Necroptosis in A549 Cells Dependent on Peptide Conformational Propensities

Anticancer lipopeptides (ACLPs) are considered promising alternatives to combat resistant cancer cells, but the influence of peptide conformational propensity alone on their selectivity and mechanism remains obscure. In this study, we developed N-palmitoylated MK5E (P1MK5E) and MEK5 (P1MEK5) that have the same composition of 23 residues undergoing the pH-dependent structural alterations but differ in the conformational tendency of their amino acid composites. Nonlipidated peptides were readily accumulated in the A549 cell nucleus by the direct membrane translocation and the heparan sulfate-mediated endocytosis than the lipid-raft-dependent pathway. The increased hydrophobicity favored the amino acid-position-dependent folding of P1MK5E and P1MEK5, respectively, toward the α-helical coiled-coil nanofibrils and amyloidlike β-protofibrils. At the close concentrations (∼7.5 μM) to the toxic effects of doxorubicin (DOX), P1MK5E exhibited (i) an increased anticancer toxicity through a time-dependent S-phase arrest, (ii) enhanced plasma membrane permeability, and (iii) dose-dependent changes in the cell death characteristic features in the A549 cells relative to P1MEK5 that was almost inactive at ∼75 μM. These observations were in accordance with the TNF-α-mediated necroptotic signaling in the c-MYC/PARP1-overexpressed A549 cells exposed to P1MK5E and accompanied by the ultrastructure of plasma membrane protrusions, extensive endoplasmic reticulum (ER) membrane expansion, mitochondrial swelling, and the formation of distinct cytoplasmic vacuolation. The structural results and the bioactivity behaviors, herein, declared the significance of α-helical propensity in the peptide sequence and the nanostructure morphologies of self-assembling ACLPs upon the selectivity and enhanced anticancer effectiveness, which notably holds promise in the design and development of efficient therapeutics for cancer.

Optimization of peptide-based cancer vaccine compositions, by sequential screening, using versatile liposomal platform

Therapeutic cancer vaccines need thoughtful design to efficiently deliver appropriate antigens and adjuvants to the immune system. In the current study, we took advantage of the versatility of a liposomal platform to conceive and customize vaccines containing three elements needed for the induction of efficient antitumor immunity: i) a CD4 epitope peptide able to activate CD4⁺ T helper cells, ii) a CD8 tumor-specific epitope peptide recognized by CD8⁺ T cytotoxic cells and iii) Pattern Recognition Receptor (PRR) agonists which stand as adjuvants. Each type of component, conjugated to liposomes, was evaluated individually by comparing their vaccine efficacy after immunization of naïve mice. These screening steps resulted in the optimization of three liposomal constructs bearing a peptide from HA influenza virus protein as CD4 epitope, a peptide from HPV16 E7 oncoprotein as CD8 epitope and TLR4, TLR2/6 or NOD1 agonists as adjuvant, which displayed antitumor efficiency against a mouse model of disseminated tumors transformed by HPV16. Our results validated the interest of our customizable liposomal platform as delivery system for cancer vaccination. We also demonstrated its interest as tool for vaccine design allowing the strategical selection of components, and the evaluation of epitope-adjuvant association.

Development of an epitope-based HIV-1 vaccine strategy from HIV-1 lipopeptide to dendritic-based vaccines

INTRODUCTION

Development of a safe, effective and globally affordable Human Immunodeficiency Virus strain 1 (HIV-1) vaccine offers the best hope for future control of the HIV-1 pandemic. However, with the exception of the recent RV144 trial, which elicited a modest level of protection against infection, no vaccine candidate has shown efficacy in preventing HIV-1 infection or in controlling virus replication in humans. There is also a great need for a successful immunotherapeutic vaccine since combination antiretroviral therapy (cART) does not eliminate the reservoir of HIV-infected cells. But to date, no vaccine candidate has proven to significantly alter the natural history of an individual with HIV-1 infection. Areas covered: For over 25 years, the ANRS (France Recherche Nord&Sud Sida-HIV hépatites) has been committed to an original program combining basic science and clinical research developing an epitope-based vaccine strategy to induce a multiepitopic cellular response against HIV-1. This review describes the evolution of concepts, based on strategies using HIV-1 lipopeptides towards the use of dendritic cell (DC) manipulation. Expert commentary: Understanding the crucial role of DCs in immune responses allowed moving from the non-specific administration of HIV-1 sequences with lipopeptides to DC-based vaccines. These DC-targeting strategies should improve HIV-1 vaccine efficacy.

Synthetic self-adjuvanting glycopeptide cancer vaccines

Due to changes in glycosyltransferase expression during oncogenesis, the glycoproteins of cancer cells often carry highly truncated carbohydrate chains compared to those on healthy cells. These glycans are known as tumor-associated carbohydrate antigens (TACAs), and are prime targets for use in vaccines for the prevention and treatment of cancer. Herein, we review the state-of-the-art in targeting the immune system toward tumor-associated glycopeptide antigens via synthetic self-adjuvanting vaccines, in which the antigenic and adjuvanting moieties of the vaccines are present in the same molecule. The majority of the self-adjuvanting glycopeptide cancer vaccines reported to date employ antigens from mucin 1, a protein which is highly over-expressed and aberrantly glycosylated in many forms of cancer. The adjuvants used in these vaccines predominantly include lipopeptide- or lipoamino acid-based TLR2 agonists, although studies investigating stimulation of TLR9 and TLR4 are also discussed. Many of these adjuvants are highly lipophilic, and, upon conjugation to antigenic peptides, provide amphiphilic vaccine molecules. The amphiphilic nature of these vaccine constructs can lead to the formation of higher-order structures by vaccines in solution, which are likely to be important for their efficacy in vivo.

Self-adjuvanting lipoimmunogens for therapeutic HPV vaccine development: potential clinical impact

The goal of therapeutic HPV vaccines is the induction of cytotoxic T lymphocyte immunity against HPV-associated cancers. Recombinant proteins and synthetic peptides have high safety profiles but low immunogenicity, which limits their efficacy when used in a vaccine. Self-adjuvanting lipid moieties have been conjugated to synthetic peptides or expressed as lipoproteins to enhance the immunogenicity of vaccine candidates. Mono-, di- and tri-palmitoylated peptides have been demonstrated to activate dendritic cells and induce robust cellular immunity against infectious diseases and cancer. Recently, a platform technology using the high-yield production of recombinant lipoproteins with Toll-like receptor 2 agonist activity was established for the development of novel subunit vaccines. This technology represents a novel strategy for the development of therapeutic HPV vaccines. In this review, we describe recent progress in the design of therapeutic HPV vaccines using lipoimmunogens.

Generation of a universal CD4 memory T cell recall peptide effective in humans, mice and non-human primates

CD4T cells play a key role in humoral immunity by providing help to B cells, enabling effective antibody class switching and affinity maturation. Some vaccines may generate a poor response due to a lack of effective MHC class II epitopes, resulting in ineffective helper T cell activation and recall and consequently poor humoral immunity. It may be beneficial to provide a CD4T cell helper peptide with a vaccine particularly in the case of a poorly immunogenic antigen. Such a T cell helper peptide must be promiscuous in its ability to bind a broad range of MHC class II alleles due to broad allelic variation in the human population. We designed a chimeric MHC class II peptide (TpD) with epitopes from tetanus toxoid and diphtheria toxoid, separated by an internal cathepsin cleavage site. TpD was capable of inducing a memory recall response in peripheral blood mononuclear cells from 20/20 human donors. T cells responding to TpD showed a central memory phenotype. Immunization of mice with a synthetic nicotine nanoparticle vaccine containing TpD showed that the peptide was required for robust antibody production and resulted in a long term CD4 memory T cell recall response. As a pre-clinical model two non-human primate species, rhesus macaques and cynomolgus monkeys, were immunized with a nicotine nanoparticle vaccine and evaluated for an anti-nicotine antibody response and TpD specific memory T cells. We found that 4/4 rhesus monkeys had both sustained antibody production and TpD memory T cells for the duration of the experiment (119 days). In addition 30/30 cynomolgus monkeys dosed with nicotine vaccine nanoparticles showed dose-dependent antibody generation and T cell recall response compared to saline injected controls. In summary we have developed a potent universal memory T cell helper peptide (TpD) that is active in vitro in human PBMCs and in vivo in mice and non-human primates.

Retargeting NK-92 for anti-melanoma activity by a TCR-like single-domain antibody

The efficacy of immunotherapy based on natural killer (NK) cells is hampered by intrinsic non-specific cytotoxicity and insufficient activation of NK cells. Here, we confer the T-cell receptor-like (TCR-like) specificity on NK cells, taking advantage of both the innate and adaptive immune arms of the immune response to generate enhanced anti-melanoma activity. The TCR-like antibody (Ab) GPA7 was selected against melanoma-associated gp100/human leukocyte antigen (HLA)-A2 complex and then fused to intracellular domain of CD3-ζ chain. This fusion construct was incorporated into NK-92MI cell line and expressed as a chimeric antigen receptor on the surface of the cell. The anti-tumour activity of the transgenic NK-92MI-GPA7-ζ cell line was assessed against melanoma in vitro and in vivo. The engineered NK-92MI-GPA7-ζ cells could recognize melanoma cells in the context of HLA-A2 and showed enhanced killing of both melanoma cell lines and primary melanoma. Furthermore, adoptively transferred NK-92MI-GPA7-ζ cells significantly suppressed the growth of human melanoma in a xenograft model in mice. Collectively, these results demonstrate that the TCR-like Ab, GPA7, could redirect NK cells to target the intracellular antigen gp100 and enhance anti-melanoma activity, providing a promising immunotherapeutic strategy to prevent and treat melanoma.

Whole protein and defined CD8(+) and CD4(+) peptides linked to penetratin targets both MHC class I and II antigen presentation pathways

Cytoplasmic delivery and cross-presentation of proteins and peptides is necessary for processing and presentation of antigens for the generation of cytotoxic T cells. We previously described the use of the 16 amino acid peptide penetratin from the Drosophila Antennapedia homeodomain (penetratin, Antp) to transport cytotoxic T lymphocyte epitopes derived from ovalbumin (OVA) or the Mucin-1 tumor-associated antigen into cells. We have now shown that penetratin covalently conjugated to OVA protein and linked in tandem to CD4(+) and/or CD8(+) T-cell epitopes from OVA-stimulated T cells in vitro (B3Z T-cell hybridoma and OT-I and OT-II T cells). The induction of these responses was directly mediated by the penetratin peptide as linking a nonspecific 16-mer peptide to OVA or mixing did not induce CD8(+) or CD4(+) T-cell responses in vitro. Furthermore, interferon (IFN)-γ-secreting CD4(+) and CD8(+) T cells were induced which suppressed B16.OVA tumor growth in C57BL/6 mice. Tumor protection was mediated by a CD8(+) T-cell-dependent mechanism and did not require CD4(+) help to protect mice 7 days after a boost immunization. Alternatively, 40 days after a boost immunization, the presence of CD4(+) help enhanced antigen-specific IFN-γ-secreting CD8(+) T cells and tumor protection in mice challenged with B16.OVA. Long-term CD8 responses were equally enhanced by antigen-specific and universal CD4 help. In addition, immunization with AntpOVA significantly delayed growth of B16.OVA tumors in mice in a tumor therapy model.

Distinct role for CD8 T cells toward cutaneous tumors and visceral metastases

The growth of immunogenic tumors in immunocompetent individuals is one of the oldest conundrums in tumor immunology. Although the ability of mouse CD8+ T cells to control transplanted tumors is well documented, little is known about their impact on autochthonous tumors. To gain insight into the role of CD8+ T cells during the course of cancer development, we produced a novel model of spontaneous melanoma. The metallothionein (MT)-ret/AAD mouse is transgenic for the RET oncogene and the chimeric MHC molecule AAD (alpha1-alpha2 domains of HLA-A2 linked to alpha3 domain of H2-Dd). This model recapitulates the natural history of human melanoma, and expression of the AAD molecule makes it suitable for analyzing CD8+ T cell responses directed against peptide Ags that have been previously identified in HLA-A2+ melanoma patients. We found that, as tumors grow, mice develop a broad melanoma-specific CD8+ T cell response. Occurrence of cutaneous nodules is not affected by CD8+ T cell depletion, showing that although CD8+ T cells are functional, they have no effect on established cutaneous tumors. However, depleted mice die from visceral disease much earlier than controls, showing that CD8+ T cells control metastasis spreading and disease progression. Antigenic modulation is observed in visceral metastases, suggesting that visceral nodules may be subject to immunoediting. Our data demonstrate that growth of melanoma in the MT-ret/AAD model involves several tolerance mechanisms sequentially. They also reveal a different role for CD8+ T cells toward early stage of cutaneous tumors and late visceral metastatic stage of the disease.

New T cell epitopes identified from an anti-idiotypic antibody mimicking ovarian cancer associated antigen

Anti-idiotype (Id) antibodies can be used to induce specific cellular immune responses against tumor antigens, but the mechanism of antigenicity is not always clear. We previously reported an anti-Id antibody, 6B11, which mimics human ovarian cancer associated antigen OC166-9. To explore the molecular basis of cellular immune response induced by 6B11, a panel of peptides derived from complementarity determining region (CDR) of 6B11 were synthesized. After a series of immunologic experiments, we found that the light chain CDR3 peptide and heavy chain CDR3 peptide were the MHC class I and class II epitopes of 6B11, respectively. The combination of MHC class I and class II epitopes is more effective than 6B11 in inducing specific cellular immune response against ovarian cancer. Our study provided the structural basis of antigenicity of 6B11. The identification of antigen-specific T cell eptitopes in 6B11 should facilitate the design of epitope-based vaccine against human ovarian cancer.

[From fundamental immunology to development of vaccinology]

In the last ten years research in vaccinology has been developed in the world to conceive new vaccine approaches against infections like HIV/AIDS. Jean-Gérard Guillet is a pioneer in the development of new vaccine strategies. From the first results he obtained in the late 80's on the presentation of antigenic peptides to T cells, he axed his work on the study of induction mechanisms of T cell mediated immune responses. The selection of antigenic peptides and the search to enhance antigen immunogenicity led him to elaborate lipopeptides as new vaccine formulae. The efficacy of these preparations was tested in animal models (mouse, macaque) and, thereafter, in humans with clinical trials promoted by the French National Agency for AIDS and viral hepatitis (ANRS). The study of T-cell induced responses in vaccinated volunteers was implemented following the creation of two facilities, an immuno-monitoring platform and the Clinical Investigation Centre Cochin-Pasteur, a structure specialized in vaccinology.

Synthesis of toll-like receptor-2 targeting lipopeptides as self-adjuvanting vaccines

Effective Th1- and Th2-type immune responses that result in protective immunity against pathogens can be induced by self-adjuvanting lipopeptides containing the lipid moiety dipalmitoyl-S-glyceryl cysteine (Pam2Cys). The potent immunogenicity of these lipopeptides is due to their ability to activate dendritic cells by targeting and signaling through Toll-like receptor-2 (TLR-2). In addition, the simplicity and flexibility in their design as well as their ease of chemical definition and characterisation makes them highly attractive vaccine candidates for humans and animals. We describe in this chapter the techniques involved in the synthesis of an immunocontraceptive lipopeptide vaccine as well as the experimental assays carried out to evaluate its efficiency.

Cellular immune responses induced with dose-sparing intradermal administration of HIV vaccine to HIV-uninfected volunteers in the ANRS VAC16 trial

OBJECTIVE

The objective was to compare the safety and cellular immunogenicity of intradermal versus intramuscular immunization with an HIV-lipopeptide candidate vaccine (LIPO-4) in healthy volunteers.

METHODOLOGY

A randomized, open-label trial with 24 weeks of follow-up was conducted in France at six HIV-vaccine trial sites. Sixty-eight healthy 21- to 55-year-old HIV-uninfected subjects were randomized to receive the LIPO-4 vaccine (four HIV lipopeptides linked to a T-helper-stimulating epitope of tetanus-toxin protein) at weeks 0, 4 and 12, either intradermally (0.1 ml, 100 microg of each peptide) or intramuscularly (0.5 ml, 500 microg of each peptide). Comparative safety of both routes was evaluated. CD8+ T-cell immune responses to HIV epitopes (ELISpot interferon-gamma assay) and tetanus toxin-specific CD4+ T-cell responses (lymphoproliferation) were assessed at baseline, two weeks after each injection, and at week 24.

RESULTS AND CONCLUSION

No severe, serious or life-threatening adverse events were observed. Local pain was significantly more frequent after intramuscular injection, but local inflammatory reactions were more frequent after intradermal immunization. At weeks 2, 6, 14 and 24, the respective cumulative percentages of induced CD8+ T-cell responses to at least one HIV peptide were 9, 33, 39 and 52 (intradermal group) or 14, 20, 26 and 37 (intramuscular group), and induced tetanus toxin-specific CD4+ T-cell responses were 6, 27, 33 and 39 (intradermal), or 9, 46, 54 and 63 (intramuscular). In conclusion, intradermal LIPO-4 immunization was well tolerated, required one-fifth of the intramuscular dose, and induced similar HIV-specific CD8+ T-cell responses. Moreover, the immunization route influenced which antigen-specific T-cells (CD4+ or CD8+) were induced.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00121121.

Comparison of lipopeptide-based immunocontraceptive vaccines containing different lipid groups

We have previously shown that incorporating the lipid moiety dipalmitoyl-S-glyceryl cysteine (Pam2Cys) into peptide structures effectively adjuvants otherwise weak immunogens. In this study lipopeptides based on luteinising hormone releasing hormone (LHRH) as a B cell epitope, [B], were synthesised in tandem with a 17-residue T-helper epitope, [T], derived from the fusion protein of the morbillivirus canine distemper virus. In this way vaccine candidates with the structure [T]-[B] were produced. These peptides were then lipidated with different diacylated moieties. The acyl moieties used were: palmitic acid (C16) to give Pam2Cys, stearic acid (C18) to give Ste2Cys, lauric acid (C12) to give Lau2Cys and octanoic acid (C8) to give Oct2Cys. We compared the immunogenicities of these simple lipopeptides in BALB/c mice by measuring their ability to induce anti-LHRH antibodies and found that immunogenicity was dependent on the length of the alkane chains of the incorporated lipid moieties with the hierarchy C16=C18>C12>C8. The antibody levels elicited by the lipopeptides also correlated with their ability to inhibit the reproductive capability of female mice in fertility trials. Furthermore, the C16 lipopeptide was the most effective in activating dendritic cells, measured by up regulation of surface MHC Class II molecules, and also in activating NF-kappaB in a Toll-like receptor-2 (TLR2)-dependent manner.

Encapsulation of lipopeptides within liposomes: Effect of number of lipid chains, chain length and method of liposome preparation

The purpose of this study was to systematically investigate the effect of lipid chain length and number of lipid chains present on lipopeptides on their ability to be incorporated within liposomes. The peptide KAVYNFATM was synthesized and conjugated to lipoamino acids having acyl chain lengths of C8, C12 and C16. The C12 construct was also prepared in the monomeric, dimeric and trimeric form. Liposomes were prepared by two techniques: hydration of dried lipid films (Bangham method) and hydration of freeze-dried monophase systems. Encapsulation of lipopeptide within liposomes prepared by hydration of dried lipid films was incomplete in all cases ranging from an entrapment efficiency of 70% for monomeric lipoamino acids at a 5% (w/w) loading to less than 20% for di- and trimeric forms at loadings of 20% (w/w). The incomplete entrapment of lipopeptides within liposomes appeared to be a result of the different solubilities of the lipopeptide and the phospholipids in the solvent used for the preparation of the lipid film. In contrast, encapsulation of lipopeptide within liposomes prepared by hydration of freeze-dried monophase systems was high, even up to a loading of 20% (w/w) and was much less affected by the acyl chain length and number than when liposomes were prepared by hydration of dried lipid films. Freeze drying of monophase systems is better at maintaining a molecular dispersion of the lipopeptide within the solid phospholipid matrix compared to preparation of lipid film by evaporation, particularly if the solubility of the lipopeptide in solvents is markedly different from that of the polar lipids used for liposome preparation. Consequently, upon hydration, the lipopeptide is more efficiently intercalated within the phospholipid bilayers.

Definition of anti-tyrosinase MAb T311 linear determinant by proteome-based similarity analysis

Using non-self discrimination as a driving force in generating peptide immunogenicity, we have developed a computer-assisted proteomic analysis in order to identify the protein antigenic regions that have evoked humoral response. The purpose of this study was to further validate the computational analysis for melanoma-associated antigens and, at the same time, to assess the efficacy of the methodology in defining antigenic regions of autoantigens associated to autoimmune diseases. To achieve this two-fold objective, we have examined the enzyme tyrosinase, a protein that represents an important autoantigen in patients with vitiligo or melanoma. Here, we report that the antigenic linear determinant of the monoclonal antibody (Mab) T311 raised against the melanoma/vitiligo tyrosinase autoantigen is located in the low similarity 15-mer amino acid sequence tyrosinase 233-247 IPYWDWRDAEKCDIC, within the fragment 237-247. These data confirm non-similarity to the host proteome as a factor that participates in shaping peptide immune reactivity and may be a first step towards designing tyrosinase antigenic peptides to be used for (i) direct neutralization of harmful melanocytes-attacking autoantibodies in vitiligo, or (ii) production of antibodies against tyrosinase-positive melanomas. Moreover tyrosinase peptide antigens might be used as key tools in studying the boundaries between self-tolerance and autoimmunity phenomena.

Lipopeptide epitopes extended by an N?-palmitoyl-lysine moiety increase uptake and maturation of dendritic cells through a Toll-like receptor-2 pathway and trigger a Th1-dependent protective immunity

Lipopeptides, a form of peptide immunogens, are currently under intense investigation as human vaccines for many infectious pathogens and cancers. However, the cellular and molecular mechanisms of lipopeptide immunogenicity are only partially understood. We have investigated the influence of the lipid content on the immunogenicity of lipopeptides using the herpes simplex virus type 1 (HSV-1) gD(1-23) peptide as a model antigen. Totally synthetic lipopeptides were constructed by covalent attachment to the peptide backbone of either Nepsilon-palmitoyl-lysine (palmitoyl-lipidated peptide, palmitoyl-LP) or cholesterol-lysine (cholesterol-lipidated peptide, cholesterol-LP). Immunization of mice with the palmitoyl-LP, but not with its cholesterol-LP analog, induced a strong T cell-dependent protective immunity against lethal HSV-1 infection. Analysis of cytokine profiles and IgG2a/IgG1 ratios revealed that a dominant Th1-type immune response was stimulated by the palmitoyl-LP, as opposed to a Th2 response generated by its cholesterol-LP analog. The palmitoyl-LP was efficiently taken up in vitro by immature dendritic cells (DC) in a time- and dose-dependent manner, and induced phenotypic maturation and production of pro-inflammatory cytokines by DC. Finally, DC stimulated with the palmitoyl-LP induced antigen-specific T cell responses through the Toll-like receptor-2 pathway. These findings have important implications for the development of effective lipopeptide immunization strategies against infectious pathogens.

Epitope-based vaccines: an update on epitope identification, vaccine design and delivery

The basic premise of the epitope-based approach to vaccine development is that, in certain cases, the responses induced by the natural immunogen are not optimal, and can be improved upon by isolation or optimization of specific components of the response. For example, immunodominance is a key factor limiting the type and breadth of adaptive immunity. Recent advances in understanding the mechanisms of immunodominance thus represent an opportunity to further develop the epitope-based approach.

Lipid and carbohydrate based adjuvant/carriers in immunology

This review discusses various issues regarding vaccines; what are they and how they work, safety aspects, the role of adjuvants and carriers in vaccination, synthetic peptides as immunogens, and new technologies for vaccine development and delivery including the identification of novel adjuvants for mucosal vaccine delivery. There has been a recent increase of interest in the use of lipids and carbohydrates as adjuvants, and so a particular emphasis is placed on adjuvants derived from lipids or carbohydrates, or from both.

The immunodominant influenza matrix T cell epitope recognized in human induces influenza protection in HLA-A2/K(b) transgenic mice

The protective efficacy of the influenza matrix protein epitope 58-66 (called M1), recognized in the context of human HLA-A2 molecules, was evaluated in a HLA-A2/K(b) transgenic mouse model of lethal influenza infection. Repeated subcutaneous immunizations with M1 increased the percentage of survival. This effect was mediated by T cells since protection was abolished following in vivo depletion of all T lymphocytes, CD8(+), or CD4(+) T cells. The survival correlated with the detection of memory CD8(+) splenocytes able to proliferate in vitro upon stimulation with M1 and to bind M1-loaded HLA-A2 dimers, as well as with M1-specific T cells in the lungs, which were directly cytotoxic to influenza-infected cells following influenza challenge. These results demonstrated for the first time that HLA-A2-restricted cytotoxic T cells specific for the major immunodominant influenza matrix epitope are protective against the infection. They encourage further in vivo evaluation of T cell epitopes recognized in the context of human MHC molecules.

Strategies in cancer vaccines development

The recent definition of tumour-specific immunity in cancer patients and the identification of tumour-associated antigens have generated renewed enthusiasm for the application of immune-based therapies for the treatment of malignancies. Recent developments in cancer vaccines have also been based on an improved understanding of the cellular interactions required to induce a specific anti-tumour immune response. Consequently, a number of cancer vaccines have entered clinical trials. Targeting broad-spectrum tumour-associated antigens has emerged as a strategy to lower the risk of tumour escape due to the loss of specific nominal antigen. Amongst the most challenging of tumour-associated antigens to which to target in active specific immunotherapy applications are carbohydrate antigens. As carbohydrates are intrinsically T-cell-independent antigens, more novel approaches are perhaps needed to drive specific-T-cell-dependent immune responses to carbohydrate antigens. In this context peptide mimetics of core structures of tumour-associated carbohydrate antigens might be developed to augment immune responses to these broad-spectrum antigens.

Update on cancer vaccines

The development of vaccines to induce tumor-specific immunity in patients with cancer has as emerged as a major area of investigation. The identification of antigens uniquely expressed by tumor cells and a heightened understanding of tumor immunology have resulted in efforts to activate host immunity to recognize and reject tumor cells. Tumor-associated antigens and peptides, genes encoding tumor antigens, and modified whole tumor cells have been used in preclinical studies with provocative results. Potent antigen-presenting cells, known as dendritic cells, have also been modified using peptides, genetic material, or whole tumor cells to present tumor antigens in the context of co-stimulation to overcome tolerance and induce tumor-specific cell killing. Promising data generated from the preclinical evaluation of cancer vaccines have resulted in the initiation of clinical trials to define the associated toxicity profile, immunologic response, and clinical impact of this treatment approach. We summarize the preclinical and clinical experience in this expanding area of investigation. Cancer vaccines hold much promise; however, many unresolved questions remain in the effort to generate a clinically meaningful treatment strategy.

Emerging strategies in tumor vaccines

Reports of novel developments in tumor vaccines that have appeared in the year ending May 1, 2002 are reviewed here. Antigenic moieties were revealed for tumors previously considered nonimmunogenic. The use of peptides spanning mutations detected exclusively in tumor tissue avoids the common concern for autoimmune responses. Carbohydrate biology is revealing novel antigenic moieties. The search for helper epitopes from tumor antigens has come into full swing. Humoral immunity is regaining terrain, particularly through the development of antiidiotypic antibodies. Major steps forward have been made in optimizing modes and routes of antigen delivery and in the use of immune adjuvants. In the clinic, phase I/II trials support the notion that tumor vaccines are safe. Because these trials are conducted in patients in whom tumor remission is not a realistic endpoint, patient responses were established by immune monitoring strategies to detect subtle changes in antitumor reactivity. Both clinical and laboratory data stress the vast potential of tumor vaccines for the treatment of cancer.