Peptide vaccines incorporating a 'promiscuous' T-cell epitope bypass certain haplotype restricted immune responses and provide broad spectrum immunogenicity

Peptide immunization against the C-terminal of alpha-synuclein reduces locomotor activity in mice overexpressing alpha-synuclein

Abnormal accumulation of alpha-synuclein (αSyn) in the remaining nigra dopaminergic neurons is a common neuropathological feature found in patients with Parkinson's disease (PD). Antibody-based immunotherapy has been considered a potential approach for PD treatment. This study aims to investigate the effectiveness of active immunization against αSyn in a mouse model of PD. Adult mice were immunized with or without a synthetic peptide containing the C-terminal residues of human αSyn and activation epitopes, followed by an intranigral injection of adeno-associated virus vectors for overexpressing human αSyn. Upon the peptide injection, αSyn-specific antibodies were raised, accompanied by degeneration of dopaminergic neurons and motor deficits. Furthermore, the induction of neuroinflammation was postulated by the elevation of astroglial and microglial markers in the immunized mice. Instead of lessening αSyn toxicity, this peptide vaccine caused an increase in the pathogenic species of αSyn. Our data demonstrated the potential adverse effects of active immunization to raise antibodies against the C-terminal fragment of αSyn. This drawback highlights the need for further investigation to weigh the pros and cons of immunotherapy in PD. Applying the αSyn C-terminal peptide vaccine for PD treatment should be cautiously exercised. This study provides valuable insights into the intricate interplay among immune intervention, αSyn accumulation, and neurodegeneration.

Heterologous Expression of Recombinant Proteins and Their Derivatives Used as Carriers for Conjugate Vaccines

Carrier proteins that provide an effective and long-term immune response to weak antigens has become a real breakthrough in the disease prevention, making it available to a wider range of patients and making it possible to obtain reliable vaccines against a variety of pathogens. Currently, research is continuing both to identify new peptides, proteins, and their complexes potentially suitable for use as carriers, and to develop new methods for isolation, purification, and conjugation of already known and well-established proteins. The use of recombinant proteins has a number of advantages over isolation from natural sources, such as simpler cultivation of the host organism, the possibility of modifying genetic constructs, use of numerous promoter variants, signal sequences, and other regulatory elements. This review is devoted to the methods of obtaining both traditional and new recombinant proteins and their derivatives already being used or potentially suitable for use as carrier proteins in conjugate vaccines.

Plant-Produced Mouse-Specific Zona Pellucida 3 Peptide Induces Immune Responses in Mice

Contraceptive vaccines are designed to stimulate autoimmune responses to molecules involved in the reproductive process. A mouse-specific peptide from zona pellucida 3 (mZP3) has been proposed as a target epitope. Here, we employed a plant expression system for the production of glycosylated mZP3 and evaluated the immunogenicity of plant-produced mZP3-based antigens in a female BALB/c mouse model. In the mZP3-1 antigen, mZP3 fused with a T-cell epitope of tetanus toxoid, a histidine tag, and a SEKDEL sequence. A fusion antigen (GFP-mZP3-1) and a polypeptide antigen containing three repeats of mZP3 (mZP3-3) were also examined. Glycosylation of mZP3 should be achieved by targeting proteins to the endoplasmic reticulum. Agrobacterium-mediated transient expression of antigens resulted in successful production of mZP3 in Nicotiana benthamiana. Compared with mZP3-1, GFP-mZP3-1 and mZP3-3 increased the production of the mZP3 peptide by more than 20 and 25 times, respectively. The glycosylation of the proteins was indicated by their size and their binding to a carbohydrate-binding protein. Both plant-produced GFP-mZP3-1 and mZP3-3 antigens were immunogenic in mice; however, mZP3-3 generated significantly higher levels of serum antibodies against mZP3. Induced antibodies recognized native zona pellucida of wild mouse, and specific binding of antibodies to the oocytes was observed in immunohistochemical studies. Therefore, these preliminary results indicated that the plants can be an efficient system for the production of immunogenic mZP3 peptide, which may affect the fertility of wild mice.

Rotavirus spike protein ΔVP8* as a novel carrier protein for conjugate vaccine platform with demonstrated antigenic potential for use as bivalent vaccine

Conjugate vaccine platform is a promising strategy to overcome the poor immunogenicity of bacterial polysaccharide antigens in infants and children. A carrier protein in conjugate vaccines works not only as an immune stimulator to polysaccharide, but also as an immunogen; with the latter generally not considered as a measured outcome in real world. Here, we probed the potential of a conjugate vaccine platform to induce enhanced immunogenicity of a truncated rotavirus spike protein ΔVP8*. ΔVP8* was covalently conjugated to Vi capsular polysaccharide (Vi) of Salmonella Typhi to develop a bivalent vaccine, termed Vi-ΔVP8*. Our results demonstrated that the Vi-ΔVP8* vaccine can induce specific immune responses against both antigens in immunized mice. The conjugate vaccine elicits high antibody titers and functional antibodies against S. Typhi and Rotavirus (RV) when compared to immunization with a single antigen. Together, these results indicate that Vi-ΔVP8* is a potent and immunogenic vaccine candidate, thus strengthening the potential of conjugate vaccine platform with enhanced immune responses to carrier protein, including ΔVP8*.

Combining Well-Tempered Metadynamics Simulation and SPR Assays to Characterize the Binding Mechanism of the Universal T-Lymphocyte Tetanus Toxin Epitope TT830-843

Peptide TT830-843 from the tetanus toxin is a universal T-cell epitope. It helps in vaccination and induces T-cell activation. However, the fine molecular interaction between this antigen and the major histocompatibility complex (MHC) remains unknown. Molecular analysis of its interaction with murine MHC (H-2) was proposed to explore its immune response efficiency. Molecular dynamics simulations are important mechanisms for understanding the basis of protein-ligand interactions, and metadynamics is a useful technique for enhancing sampling in molecular dynamics. SPR (surface plasmon resonance) assays were used to validate whether the metadynamics results are in accordance with the experimental results. The peptide TT830-843 unbinding process was simulated, and the free energy surface reconstruction revealed a detailed conformational landscape. The simulation described the exiting path as a stepwise mechanism between progressive detachment states. We pointed out how the terminus regions act as anchors for binding and how the detachment mechanism includes the opening of α-helices to permit the peptide's central region dissociation. The results indicated the peptide/H-2 receptor encounter occurs within a distance lesser than 27.5 Å, and the encounter can evolve to form a stable complex. SPR assays confirmed the complex peptide/H-2 as a thermodynamically stable system, exhibiting enough free energy to interact with TCR on the antigen-presenting cell surface. Therefore, combining in silico and in vitro assays provided significant evidence to support the peptide/H-2 complex formation.

B-cell epitope peptide cancer vaccines: a new paradigm for combination immunotherapies with novel checkpoint peptide vaccine

In light of the numerous US FDA-approved humanized monoclonal antibodies (mAbs) for cancer immunotherapy, it is surprising that the advancement of B-cell epitope vaccines designed to elicit a natural humoral polyclonal antibody response has not gained traction in the immune-oncology landscape. Passive immunotherapy with humanized mAbs (Trastuzumab [Herceptin®]; Pertuzumab [Perjeta®]) has provided clinical benefit to breast cancer patients, albeit with significant shortcomings including toxicity problems and resistance, high costs, sophisticated therapeutic regimen and long half-life. The role of B-cell humoral immunity in cancer is under appreciated and underdeveloped. We have advanced the idea of active immunotherapy with chimeric B-cell epitope peptides incorporating a 'promiscuous' T-cell epitope that elicits a polyclonal antibody response, which provides safe, cost-effective therapeutic advantage over mAbs. We have created a portfolio of validated B-cell peptide epitopes against multiple receptor tyrosine kinases (HER-1, HER-3, IGF-1R and VEGF). We have successfully translated two HER-2 combination B-cell peptide vaccines in Phase I and II clinical trials. We have recently developed an effective novel PD-1 vaccine. In this article, I will review our approaches and strategies that focus on B-cell epitope cancer vaccines.

Immunization of mice with chimeric antigens displaying selected epitopes confers protection against intestinal colonization and renal damage caused by Shiga toxin-producing Escherichia coli

Shiga toxin-producing Escherichia coli (STEC) cause diarrhea and dysentery, which may progress to hemolytic uremic syndrome (HUS). Vaccination has been proposed as a preventive approach against STEC infection; however, there is no vaccine for humans and those used in animals reduce but do not eliminate the intestinal colonization of STEC. The OmpT, Cah and Hes proteins are widely distributed among clinical STEC strains and are recognized by serum IgG and IgA in patients with HUS. Here, we develop a vaccine formulation based on two chimeric antigens containing epitopes of OmpT, Cah and Hes proteins against STEC strains. Intramuscular and intranasal immunization of mice with these chimeric antigens elicited systemic and local long-lasting humoral responses. However, the class of antibodies generated was dependent on the adjuvant and the route of administration. Moreover, while intramuscular immunization with the combination of the chimeric antigens conferred protection against colonization by STEC O157:H7, the intranasal conferred protection against renal damage caused by STEC O91:H21. This preclinical study supports the potential use of this formulation based on recombinant chimeric proteins as a preventive strategy against STEC infections.

Protective immunity following vaccination with a recombinant multiple-epitope protein of bovine herpesvirus type I in a rabbit model

Bovine herpesvirus type 1 (BoHV-1) causes considerable economic losses to the cow industry. Vaccination remains an effective strategy to control the diseases associated with BoHV-1. However, live vaccines present safety concerns, especially in pregnant cows; thus, nonreplicating vaccines have been developed to control the disease. The envelope glycoproteins of BoHV-1 induce a protective immune response. In this work, selected epitopes on glycoproteins gD, gC, and gB were constructed in triplicate with linker peptides. Vaccination of rabbits demonstrated that P2-gD/gC/gB with AAYAAY induced higher specific antibodies than that with GGGGS linker. P2-gD/gC/gB with AAYAAY linker was fused with bovine interleukin-6 (BoIL-6) or rabbit IL-6 (RaIL-6) and bacterially expressed. Rabbits were intramuscularly immunized with 100 μg of P2-gD/gC/gB-BoIL-6, P2-gD/gC/gB-RaIL-6, P2-gD/gC/gB, P2-gD/gC/gB plus BoIL-6, P2-(gD-a)3-BoIL-6, or P2-(gD-a)3 emulsified with ISA 206 adjuvant thrice at 3-week intervals. P2-gD/gC/gB-BoIL-6 generated a higher titer of BoHV-1-specific antibodies, neutralizing antibodies, interferon (IFN)-γ, and IL-4 compared with P2-gD/gC/gB plus BoIL-6, P2-gD/gC/gB-RaIL-6, or other formulation. P2-gD/gC/gB-BoIL-6 triggered similar levels of antibodies and significantly higher titer of IFN-γ and IL-4 compared with inactivated bovine viral diarrhea (BVD)-infectious bovine rhinotracheitis (IBR) vaccine. Rabbits vaccinated with P2-gD/gC/gB-BoIL-6 dramatically reduced viral shedding and tissue lesions in lungs and trachea after viral challenge and reactivation compared with those with P2-gD/gC/gB plus BoIL-6 or P2-gD/gC/gB-RaIL-6. P2-gD/gC/gB-BoIL-6 provided protective effects against viral shedding and tissue pathogenesis similar to those of the inactivated vaccine. The data confirmed the safety and immunogenicity of multiple-epitope recombinant protein and a potential vaccine candidate to control the disease, especially for pregnant cattle.

Immunoinformatics-Aided Design and Evaluation of a Potential Multi-Epitope Vaccine against Klebsiella Pneumoniae

Klebsiella pneumoniae is an opportunistic gram-negative bacterium that causes nosocomial infection in healthcare settings. Despite the high morbidity and mortality rate associated with these bacterial infections, no effective vaccine is available to counter the pathogen. In this study, the pangenome of a total of 222 available complete genomes of K. pneumoniae was explored to obtain the core proteome. A reverse vaccinology strategy was applied to the core proteins to identify four antigenic proteins. These proteins were then subjected to epitope mapping and prioritization steps to shortlist nine B-cell derived T-cell epitopes which were linked together using GPGPG linkers. An adjuvant (Cholera Toxin B) was also added at the N-terminal of the vaccine construct to improve its immunogenicity and a stabilized multi-epitope protein structure was obtained using molecular dynamics simulation. The designed vaccine exhibited sustainable and strong bonding interactions with Toll-like receptor 2 and Toll-like receptor 4. In silico reverse translation and codon optimization also confirmed its high expression in E. coli K12 strain. The computer-aided analyses performed in this study imply that the designed multi-epitope vaccine can elicit specific immune responses against K. pneumoniae. However, wet lab validation is necessary to further verify the effectiveness of this proposed vaccine candidate.

Immunogenicity of synthetic peptide constructs based on PvMSP9E795-A808, a linear B-cell epitope of the P. vivax Merozoite Surface Protein-9

Plasmodium vivax Merozoite Surface Protein-9 (PvMSP-9) is a malaria vaccine candidate naturally immunogenic in humans and able to induce high antibody titers in animals when delivered as a recombinant protein. Recently, we identified the sequence EAAPENAEPVHENA (PvMSP9_E795-A808) as the main linear B-cell epitope in naturally exposed individuals. However, the potential of PvMSP9_E795-A808 as an immunogen in experimental animal models remained unexplored. Here we assess the immunogenicity of PvMSP9_E795-A808 using synthetic peptides. The peptides tested in BALB/c mice include two repeats of the sequence EAAPENAEPVHENA tested alone (peptide RII), or linked to an autologous (PvMSP9 peptide pL; pLRII) or heterologous (p2 tetanus toxin universal T cell epitope; TTRII) T cell epitope. Immune responses were evaluated by ELISA, FLUOROSPOT, and indirect immunofluorescence. We show that all of the peptide constructs tested were immunogenic eliciting specific IgG antibodies at different levels, with a prevalence of IgG1 and IgG2. Animals immunized with synthetic peptides containing T cell epitopes (pLRII or TTRII) had more efficient antibody responses that resulted in higher antibody titers able to recognize the native protein by immunofluorescence. Relevantly, the frequency of IFN-γ secreting SFC elicited by immunization with TTRII synthetic peptide was comparable to that reported to the PvMSP9-Nt recombinant protein. Taken together, our study indicates that PvMSP9_E795-A808 is highly immunogenic in mice and further studies to evaluate its value as promising vaccine target are warranted. Moreover, our study supports the critical role of CD4 T cell epitopes to enhance humoral responses induced by subunit based vaccines.

PilVax - a novel peptide delivery platform for the development of mucosal vaccines

Peptide vaccines are an attractive strategy to engineer the induction of highly targeted immune responses and avoid potentially allergenic and/or reactogenic protein regions. However, peptides by themselves are often unstable and poorly immunogenic, necessitating the need for an adjuvant and a specialised delivery system. We have developed a novel peptide delivery platform (PilVax) that allows the presentation of a stabilised and highly amplified peptide as part of the group A streptococcus serotype M1 pilus structure (PilM1) on the surface of the non-pathogenic bacterium Lactococcus lactis. To show proof of concept, we have successfully inserted the model peptide Ova_324–339 into 3 different loop regions of the backbone protein Spy0128, which resulted in the assembly of the pilus containing large numbers of peptide on the surface of L. lactis. Intranasal immunisation of mice with L. lactis PilM1-Ova generated measurable Ova-specific systemic and mucosal responses (IgA and IgG). Furthermore, we show that multiple peptides can be inserted into the PilVax platform and that peptides can also be incorporated into structurally similar, but antigenically different pilus structures. PilVax may be useful as a cost-effective platform for the development of peptide vaccines against a variety of important human pathogens.

A paradigm shift: Cancer therapy with peptide-based B-cell epitopes and peptide immunotherapeutics targeting multiple solid tumor types: Emerging concepts and validation of combination immunotherapy

There is a recognizable and urgent need to speed the development and application of novel, more efficacious anti-cancer vaccine therapies that inhibit tumor progression and prevent acquisition of tumor resistance. We have created and established a portfolio of validated peptide epitopes against multiple receptor tyrosine kinases and we have identified the most biologically effective combinations of EGFR (HER-1), HER-2, HER-3, VEGF and IGF-1R peptide vaccines/mimics to selectively inhibit multiple receptors and signaling pathways. The strategy is based on the use of chimeric conformational B-cell epitope peptides incorporating "promiscuous" T-cell epitopes that afford the possibility of generating an enduring immune response, eliciting protein-reactive high-affinity anti-peptide antibodies as potential vaccines and peptide mimics that act as antagonists to receptor signaling that drive cancer metastasis. In this review we will summarize our ongoing studies based on the development of combinatorial immunotherapeutic strategies that act synergistically to enhance immune-mediated tumor killing aimed at addressing mechanisms of tumor resistance for several tumor types.

HER-3 peptide vaccines/mimics: Combined therapy with IGF-1R, HER-2, and HER-1 peptides induces synergistic antitumor effects against breast and pancreatic cancer cells

The human epidermal growth factor receptor 3 (HER-3/ErbB3) is a unique member of the human epidermal growth factor family of receptors, because it lacks intrinsic kinase activity and ability to heterodimerize with other members. HER-3 is frequently upregulated in cancers with epidermal growth factor receptor (EGFR/HER-1/ErbB1) or human epidermal growth factor receptor 2 (HER-2/ErBB2) overexpression, and targeting HER-3 may provide a route for overcoming resistance to agents that target EGFR or HER-2. We have previously developed vaccines and peptide mimics for HER-1, HER-2 and vascular endothelial growth factor (VEGF). In this study, we extend our studies by identifying and evaluating novel HER-3 peptide epitopes encompassing residues 99-122, 140-162, 237-269 and 461-479 of the HER-3 extracellular domain as putative B-cell epitopes for active immunotherapy against HER-3 positive cancers. We show that the HER-3 vaccine antibodies and HER-3 peptide mimics induced antitumor responses: inhibition of cancer cell proliferation, inhibition of receptor phosphorylation, induction of apoptosis and antibody dependent cellular cytotoxicity (ADCC). Two of the HER-3 epitopes 237-269 (domain II) and 461-479 (domain III) significantly inhibited growth of xenografts originating from both pancreatic (BxPC3) and breast (JIMT-1) cancers. Combined therapy of HER-3 (461-471) epitope with HER-2 (266-296), HER-2 (597-626), HER-1 (418-435) and insulin-like growth factor receptor type I (IGF-1R) (56-81) vaccine antibodies and peptide mimics show enhanced antitumor effects in breast and pancreatic cancer cells. This study establishes the hypothesis that combination immunotherapy targeting different signal transduction pathways can provide effective antitumor immunity and long-term control of HER-1 and HER-2 overexpressing cancers.

Inclusion of a universal tetanus toxoid CD4(+) T cell epitope P2 significantly enhanced the immunogenicity of recombinant rotavirus ΔVP8* subunit parenteral vaccines

Currently available live oral rotavirus vaccines, Rotarix(®) and RotaTeq(®), are highly efficacious in developed countries. However, the immunogenicity and efficacy of such vaccines in some developing countries are low. We reported previously that bacterially-expressed rotavirus ΔVP8* subunit vaccine candidates with P[8], P[4] or P[6] specificity elicited high-titer virus neutralizing antibodies in animals immunized intramuscularly. Of note was the finding that antibodies induced with the P[8]ΔVP8* vaccine neutralized both homotypic P[8] and heterotypic P[4] rotavirus strains to high titer. To further improve its vaccine potential, a tetanus toxoid universal CD4(+) T cell epitope P2 was introduced into P[8] or P[6]ΔVP8* construct. The resulting recombinant fusion proteins expressed in Escherichia coli were of high solubility and were produced with high yield. Two doses (10 or 20 μg/dose) of the P2-P[8]ΔVP8* vaccine or P2-P[6]ΔVP8* vaccine with aluminum phosphate adjuvant elicited significantly higher geometric mean homologous neutralizing antibody titers than the vaccines without P2 in intramuscularly immunized guinea pigs. Interestingly, high levels of neutralizing antibody responses induced in guinea pigs with 3 doses of the P2-P[8]ΔVP8* vaccine persisted for at least 6 months. Furthermore, in the gnotobiotic piglet challenge study, three intramuscular doses (50 μg/dose) of the P2-P[8]ΔVP8* vaccine with aluminum phosphate adjuvant significantly delayed the onset of diarrhea and significantly reduced the duration of diarrhea and the cumulative diarrhea score after oral challenge with virulent human rotavirus Wa (G1P[8]) strain. The P2-P[8]ΔVP8* vaccine induced serum virus neutralizing antibody and VP4-specific IgG antibody production prechallenge, and primed the pigs for higher antibody and intestinal and systemic virus-specific IFN-γ producing CD4(+) T cell responses postchallenge. These two subunit vaccines could be used at a minimum singly or preferably in bivalent formulation to provide antigenic coverage of most of the G types of global importance.

A multi-epitope vaccine based on Chlamydia trachomatis major outer membrane protein induces specific immunity in mice

We evaluated the immunogenicity and efficacy of a candidate vaccine comprising the major outer membrane protein (MOMP) multi-epitope of Chlamydia trachomatis. A short gene of multi-epitope derived from MOMP containing multiple T- and B-cell epitopes was artificially synthesized. The recombinant plasmid pET32a(+) containing codon optimized MOMP multi-epitope gene was constructed. Expression of the fusion protein Trx-His-MOMP multi-epitope in Escherichia coli was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blot analysis. Balb/c mice were inoculated with the purified fusion protein subcutaneously three times with 2-week intervals. Results showed that the MOMP multi-epitope elicited not only strong humoral immune responses to C. trachomatis by generating significantly high levels of specific antibodies (IgG1 and IgG2a), but also a cellular immune response by inducing robust cytotoxic T lymphocyte responses in mice. Furthermore, the MOMP multi-epitope substantially primed secretion of IFN-γ, revealing that this vaccine could induce a strong Th1 response. Finally, the mice vaccinated with the MOMP multi-epitope displayed a reduction of C. trachomatis shedding upon a chlamydial challenge and an accelerated clearance of the infected C. trachomatis. In conclusion, the MOMP multi-epitope vaccine may have the potentiality for the development of effective prophylactic and therapeutic vaccines against the C. trachomatis infection.

T-cell epitope-dependent immune response in inbred (C57BL/6J, SJL/J, and C3H/HeN) and transgenic P301S and Tg2576 mice

Alzheimer's disease is characterized by two pathological hallmarks, the intracellular deposition of hyperphosphorylated Tau protein and the extracellular deposition of Aβ1-40/42 , both being targets for immunotherapy. This study evaluates the immunogenic properties of three AD-specific B-cell epitopes (Tau229-237 [pT231/pS235], pyroGluAβ3-8 , and Aβ37/38-42/43 ) linked to five foreign T-cell epitopes (MVFP, TT, TBC Ag85B, PvT19, and PvT53) by immunizing inbred C57BL/6J (H-2(b) ), SJL/J (H-2(s2) ), and C3H/HeN (H-2(k) ) mice. Two promising candidates with respect to MHC II restriction were selected, and two transgenic mouse models of AD, P301S (H-2(b/) (k) ) and Tg2576 (H-2(b/) (s) ) animals, were immunized with one B-cell epitope in combination with two T-cell epitopes. Responders displayed an enhanced immune response compared with wild-type animals, which supports the vaccine design and the vaccination strategy. The immune response was also characterized by specific IgG subtype titers, which revealed a strong polarization toward the humoral pathway for immunization of phospho-Tau, whereas for both Aβ vaccines, a mixed cellular/humoral pathway response was observed. Despite the diversity and unpredictability of the immunogenicity of the peptide vaccines, all three peptide vaccine formulations appear to be promising constructs for future evaluation of their therapeutic properties.

Peptide vaccines and peptidomimetics of EGFR (HER-1) ligand binding domain inhibit cancer cell growth in vitro and in vivo

Epidermal growth factor receptor (EGFR) is a validated target for several cancers including lung, colorectal, and certain subtypes of breast cancer. Cetuximab targets ligand binding of EGFR, but major problems like high cost, short t1/2, toxicity, and emergence of resistance are associated with the drug. Immunization with EGFR B cell epitopes will train the immune system to produce specific Abs that can kill cancer cells. Also, therapy with stable, less-expensive, and nontoxic EGFR peptide mimics will block EGFR signaling and inhibit cancer growth. We designed three peptides based on the contact sites between EGF and EGFR. The B cell epitopes were synthesized alone and also linked with the measles virus T cell epitope to produce a chimeric peptide vaccine. The peptide vaccines were immunogenic in both mice and rabbits and Abs raised against the vaccine specifically bound EGFR-expressing cells and recombinant human EGFR protein. The peptide mimics and the anti-peptide Abs were able to inhibit EGFR signaling pathways. Immunization with the peptide vaccine or treatment with the B cell epitopes significantly reduced tumor growth in both transplantable breast and lung cancer models. Immunohistochemical analysis also showed significant reductions in microvascular density and actively dividing cells in the tumor sections after treatment in the FVB/n breast cancer model. The 418-435 B cell epitope was the best candidate both as a vaccine or peptide mimic because it caused significant inhibition in the two mouse models. Our results show that this novel EGFR B cell epitope has great potential to be used as a vaccine or treatment option for EGFR-expressing cancers.

Epitope-specific immune recognition of the nontypeable Haemophilus influenzae outer membrane protein 26

Previous studies using rodent respiratory infection models of nontypeable Haemophilus influenzae (NTHi) infection have established the 26-kDa outer membrane protein of the bacterium, OMP26, as a potential vaccine antigen for NTHi. This study undertook a comprehensive immunological identification of OMP26 T- and B-cell epitopes. A series of OMP26 peptides were constructed and regions of the OMP26 antigen involved in recognition by lymphocyte receptors and induction of acquired immune responses were identified. The dominant T-cell epitopes for OMP26 were located toward the C-terminus between amino acid residues 95 and 197 (T3+T4 region) as mapped using antigen-specific lymphocyte proliferation assays. The newly identified T-cell epitopes exhibited strong capacity for efficient T-cell activation, suggesting that, compared with other OMP26 regions; epitopes within the T3+T4 region have the highest affinity for binding to major histocompatibility complex molecules. In contrast, the predominant B-cell epitopes of OMP26 were located more centrally within the molecule between amino acid residues 45 and 145 (T2+T3 region) as determined using enzyme-linked immunosorbent assay and surface plasmon resonance assays. The T2+T3 region was immunodominant in several species including chinchilla, mice and rats when assessed using both mucosal and parenteral immunization regimes. In addition, the antibodies directed against the T2+T3 region bound to intact NTHi cell surface, according to flow cytometry. Collectively, these results specifically locate the amino acid sequences containing the OMP26 T- and B-cell epitopes, which, as newly mapped antigenic epitopes for lymphocyte recognition, will be useful to improve existing NTHi vaccine strategies. Comprehensive definition of the minimum epitope length required for optimal B- and T-cell responses requires further study.

Peptide vaccines and targeting HER and VEGF proteins may offer a potentially new paradigm in cancer immunotherapy

The ErbB family (HER-1, HER-2, HER-3 and HER-4) of receptor tyrosine kinases has been the focus of cancer immunotherapeutic strategies while antiangiogenic therapies have focused on VEGF and its receptors VEGFR-1 and VEGFR-2. Agents targeting receptor tyrosine kinases in oncology include therapeutic antibodies to receptor tyrosine kinase ligands or the receptors themselves, and small-molecule inhibitors. Many of the US FDA-approved therapies targeting HER-2 and VEGF exhibit unacceptable toxicities, and show problems of efficacy, development of resistance and unacceptable safety profiles that continue to hamper their clinical progress. The combination of different peptide vaccines and peptidomimetics targeting specific molecular pathways that are dysregulated in tumors may potentiate anticancer immune responses, bypass immune tolerance and circumvent resistance mechanisms. The focus of this review is to discuss efforts in our laboratory spanning two decades of rationally developing peptide vaccines and therapeutics for breast cancer. This review highlights the prospective benefit of a new, untapped category of therapies biologically targeted to EGF receptor (HER-1), HER-2 and VEGF with potential peptide 'blockbusters' that could lay the foundation of a new paradigm in cancer immunotherapy by creating clinical breakthroughs for safe and efficacious cancer cures.

Evaluation of the potency of the anti-idiotypic antibody Ab2/3H6 mimicking gp41 as an HIV-1 vaccine in a rabbit prime/boost study

The HIV-1 envelope protein harbors several conserved epitopes that are recognized by broadly neutralizing antibodies. One of these neutralizing sites, the MPER region of gp41, is targeted by one of the most potent and broadly neutralizing monoclonal antibody, 2F5. Different vaccination strategies and a lot of efforts have been undertaken to induce MPER neutralizing antibodies but little success has been achieved so far. We tried to consider the alternative anti-idiotypic vaccination approach for induction of 2F5-like antibodies. The previously developed and characterized anti-idiotypic antibody Ab2/3H6 was expressed as antibody fragment fusion protein with C-terminally attached immune-modulators and used for immunization of rabbits to induce antibodies specific for HIV-1. Only those rabbits immunized with immunogens fused with the immune-modulators developed HIV-1 specific antibodies. Anti-anti-idiotypic antibodies were affinity purified using a two-step affinity purification protocol which revealed that only little amount of the total rabbit IgG fraction contained HIV-1 specific antibodies. The characterization of the induced anti-anti-idiotypic antibodies showed specificity for the linear epitope of 2F5 GGGELDKWASL and the HIV-1 envelope protein gp140. Despite specificity for the linear epitope and the truncated HIV-1 envelope protein these antibodies were not able to exhibit virus neutralization activities. These results suggest that Ab2/3H6 alone might not be suitable as a vaccine.

Engineered conformation-dependent VEGF peptide mimics are effective in inhibiting VEGF signaling pathways

Angiogenesis, or formation of new blood vessels, is crucial to cancer tumor growth. Tumor growth, progression, and metastasis are critically influenced by the production of the pro-angiogenic vascular endothelial growth factor (VEGF). Promising anti-angiogenic drugs are currently available; however, their susceptibilities to drug resistance and long term toxicity are serious impediments to their use, thus requiring the development of new therapeutic approaches for safe and effective angiogenic inhibitors. In this work, peptides were designed to mimic the VEGF-binding site to its receptor VEGFR-2. The VEGF conformational peptide mimic, VEGF-P3(CYC), included two artificial cysteine residues, which upon cyclization constrained the peptide in a loop native-like conformation to better mimic the anti-parallel structure of VEGF. The engineered cyclic VEGF mimic peptide demonstrated the highest affinity to VEGFR-2 by surface plasmon resonance assay. The VEGF peptide mimics were evaluated as inhibitors in several in vitro assays in which VEGF-dependent signaling pathways were observed. All VEGF mimics inhibited VEGFR-2 phosphorylation with VEGF-P3(CYC) showing the highest inhibitory effects when compared with unstructured peptides. Additionally, we show in several angiogenic in vitro assays that all the VEGF mimics inhibited endothelial cell proliferation, migration, and network formation with the conformational VEGF-P3 (CYC) being the best. The VEGF-P3(CYC) also caused a significant delay in tumor development in a transgenic model of VEGF(+/-)Neu2-5(+/-). These results indicate that the structure-based design is important for the development of this peptidomimetic and for its anti-angiogenic effects.

Immunogenic comparison for two different recombinant chimeric peptides (CP12 and CP22) containing one or two copies of three linear B cell epitopes from β-hCG subunit

To develop a superior chimeric peptide (CP) vaccine of human chorionic gonadotropin (hCG), two CP antigens (named CP12 and CP22) encoding one or two copies of three linear B cell epitopes from the β-hCG subunit and six foreign T cell epitopes, including two promiscuous TCEs from hepatitis B surface antigen and tetanus toxoid, were constructed and biosynthesized. The hCG CP12 and CP22 of 21 or 23 kDa, respectively, were expressed in Escherichia coli at the level of ~1% of total cell proteins when inserted into thermo-inducible pBV221 expression vector. The purified CP12 and CP22 proteins with >95% relative homogeneity are immunogenic, and elicited antibodies against the β5, β9 and β8 BCEs of β-hCG in both rabbits and three different inbred strains of mice. A mouse uterine weight study in Balb/c mice demonstrated that the CP12 and CP22 antigens with an additional β5 neutralizing epitope enhanced the in vivo bio-neutralization capacity of the induced antibodies compared to the C-terminal immunogen of β-hCG. We propose that the biosynthesized CP22, possessing with two copies of three BCEs, represents a novel candidate antigen for an hCG contraceptive or tumor therapeutic vaccine.

Immunization with synthetic VEGF peptides in ovarian cancer

OBJECTIVE

To assess the role of active immunotherapy targeting VEGF with a peptide vaccine as a potential treatment for ovarian cancer.

METHODS

A peptide vaccine targeting antigenic B-cell epitopes of VEGF were identified and linked to a promiscuous T-cell epitope. Elicited antibodies were assessed for their ability to recognize the VEGF protein, inhibit angiogenesis, inhibit the interaction of VEGF with its receptor, and inhibit cancer growth in mice.

RESULTS

Following immunization, high-titered elicited antibodies were shown to be specific for the full-length VEGF protein by ELISA and Western blot. Anti-VEGF peptide antibodies inhibited cellular migration, proliferation, invasion, tube formation, and growth of aortic ring cultures. These antibodies inhibited the interaction between VEGF and its receptor (VEGFR2) in a concentration-dependent manner. Confirmation of this mechanism was demonstrated through inhibition of VEGFR2 phosphorylation following culture of human endothelial vein endothelial cells with anti-VEGF peptide antibodies. These antibodies were shown to inhibit ovarian cancer xenograft growth in a nude mouse model following intraperitoneal passive immunization. Active immunization with the VEGF peptide vaccine inhibited VEGF-dependent pancreatic islet cell tumor growth in RIP1-Tag2 transgenic mice and was associated with decreased vasculogenesis in these tumors compared with animals vaccinated with an irrelevant peptide. Active immunization also inhibited growth of tumors from a VEGF overexpressing ovarian cancer cell line, resulting in decreased tumor size and tumor vessel density compared with control mice.

CONCLUSIONS

Active immunization with VEGF peptides elicits antibodies that inhibit tumor growth by blocking VEGF-dependent angiogenesis.

High throughput T epitope mapping and vaccine development

Mapping of antigenic peptide sequences from proteins of relevant pathogens recognized by T helper (Th) and by cytolytic T lymphocytes (CTL) is crucial for vaccine development. In fact, mapping of T-cell epitopes provides useful information for the design of peptide-based vaccines and of peptide libraries to monitor specific cellular immunity in protected individuals, patients and vaccinees. Nevertheless, epitope mapping is a challenging task. In fact, large panels of overlapping peptides need to be tested with lymphocytes to identify the sequences that induce a T-cell response. Since numerous peptide panels from antigenic proteins are to be screened, lymphocytes available from human subjects are a limiting factor. To overcome this limitation, high throughput (HTP) approaches based on miniaturization and automation of T-cell assays are needed. Here we consider the most recent applications of the HTP approach to T epitope mapping. The alternative or complementary use of in silico prediction and experimental epitope definition is discussed in the context of the recent literature. The currently used methods are described with special reference to the possibility of applying the HTP concept to make epitope mapping an easier procedure in terms of time, workload, reagents, cells and overall cost.

Mimotope vaccination--from allergy to cancer

BACKGROUND

Mimotopes are peptides mimicking protein, carbohydrates or lipid epitopes and can be generated by phage display technology. When selected by antibodies, they represent exclusively B-cell epitopes and are devoid of antigen/allergen-specific T-cell epitopes. Coupled to carriers or presented in a multiple antigenic peptide form mimotopes achieve immunogenicity and induce epitope-specific antibody responses upon vaccination.

OBJECTIVE/METHODS

In allergy IgG antibodies may block IgE binding to allergens, whereas other IgG antibody specificities enhance this and support the anaphylactic reaction. In cancer, inhibitory antibody specificities prevent growth signals derived from overexpressed oncogenes, whereas growth-promoting specificities enhance signalling and proliferation. Therefore, the mimotope concept is applicable to both fields for epitope-specific vaccination and analysis of conformational B-cell epitopes for the allergen/antigen.

RESULTS/CONCLUSIONS

Mimotope technology is a relatively young theme in allergology and oncology. Still, proof of concept studies testing allergen and tumour mimotope vaccines suggest that mimotopes are ready for clinical trials.

Priming with SARS CoV S DNA and boosting with SARS CoV S epitopes specific for CD4+ and CD8+ T cells promote cellular immune responses

Cellular immune response plays an important role in antiviral immunity. In our previous study, immunization of mice with severe acute respiratory syndrome coronavirus (SARS CoV) spike (S) DNA vaccine could induce both humoral and cellular immunity in response to a pool of entire overlapping S peptides. Identification of functional dominant epitopes in SARS CoV S protein for T cells is crucial for further understanding of cellular immune responses elicited by SARS CoV S DNA vaccine. In present study, mice were immunized with SARS CoV S DNA vaccine. Subsequently, a pool of 17–19 mers overlapped SARS CoV S peptides, which served as immunogens, were scanned to identify the specific epitopes for T cells. Two H-2^d restricted CD4⁺ T epitopes, N60 (S435–444) and P152 (S1111–1127), and two H-2^d restricted CD8⁺ T cell epitopes, N50 (S365–374) and P141 (S1031–1047) were identified by three different methods, enzyme-linked immunosorbent assay (ELISA), enzyme linked immunospot assay (ELISPOT) and fluorescence activated cell sorter (FACS). The dominant CD4⁺ T cell epitope (N60) and CD8⁺ T cell epitope (N50) located in the receptor-binding domain (RBD) of SARS CoV S protein, which mediated virus combining and fusing to susceptible cells. Importantly, our novel finding is that mice primed with SARS S DNA vaccine and boosted with T cell epitopes (N50 and N60) could promote antigen specific CD4⁺ and CD8⁺ T cell immune responses. Our study provides valuable information for the design of vaccine for SARS study.

Injectable polymer microspheres enhance immunogenicity of a contraceptive peptide vaccine

Advanced contraceptive peptide vaccines suffer from the unavailability of adjuvants capable of enhancing the antibody response with acceptable safety. We sought to overcome this limitation by employing two novel poly(lactic-co-glycolic acid) (PLGA) microsphere formulations to deliver a synthetic human chorionic gonadotropin (hCG) peptide antigen co-synthesized with a T-cell epitope from tetanus toxoid (TT), C-TT2-CTP35: surface-conjugated immunogen to induce phagocytosis; and encapsulated peptide to provide a depot effect, with MgCO(3) co-encapsulated in the polymer to neutralize acidity from the biodegrading PLGA polyester. A single immunization of encapsulated peptide in rabbits elicited a stronger antibody response with equivalent duration relative to a positive control--three injections of the peptide administered in a squalene-based water-in-oil emulsion. Surface-conjugated peptide was less effective but enhanced antibody levels at 1/5 the dose, relative to soluble antigen. Most remarkable and unexpected was the finding that co-encapsulation of base was essential to attain the powerful adjuvant effect of the PLGA-MgCO(3) system, as the MgCO(3)-free microspheres were completely ineffective. A promising contraceptive hCG peptide vaccine with acceptable side effects (i.e., local tissue reactions) was achieved by minimizing PLGA and MgCO(3) doses, without significantly affecting antibody response.

Tandem copies of a human rotavirus VP8 epitope can induce specific neutralizing antibodies in BALB/c mice

The VP8 subunit protein of human rotavirus (HRV) plays an important role in viral infectivity and neutralization. Recombinant peptide antigens displaying the amino acid sequence M(1)ASLIYRQLL(10), a linear neutralization epitope on the VP8 protein, were constructed and examined for their ability to generate anti-peptide antibodies and HRV-neutralizing antibodies in BALB/c mice. Peptide antigen constructs were expressed in E. coli as fusion proteins with thioredoxin and a universal tetanus toxin T-cell epitope (P2), in order to enhance the anti-peptide immune response. The peptide antigen containing three tandem copies of the VP8 epitope induced significantly higher levels of anti-peptide antibody than only a single copy of the epitope, or the peptide co-administered with the carrier protein and T-cell epitope. Furthermore, the peptide antigen containing three copies of the peptide produced significantly higher virus-neutralization titres, higher than VP8, indicating that a peptide antigen displaying repeating copies of the amino acid region 1-10 of VP8 is a more potent inducer of HRV-neutralizing antibodies than VP8 alone, and may be useful for the production of specific neutralizing antibodies for passive immunotherapy of HRV infection.

A peptide carrier with a built-in vaccine adjuvant: construction of immunogenic conjugates

A multifunctional carrier combining B/T cell epitopes (i), a built-in vaccine adjuvant (ii), and a universal T cell epitope (iii) for the construction of potent and specific immunogenic conjugates is presented. The IL-1beta(163-171) fragment known to reproduce the immunostimulatory and adjuvant effects of the whole IL-1beta without possessing any of the pro-inflammatory properties of IL-1beta was covalently anchored to the N-terminus of the Sequential Oligopeptide Carrier, SOC(n), formed by the repeating tripeptide unit Lys-Aib-Gly. A promiscuous T cell epitope derived from the tetanus toxin, TT(593-599), was also positioned in the carboxy terminus of SOC(n) as a universal immunogen to provide broad immunogenicity. Selected B/T cell epitopes from the Sm and La/SSB autoantigens, against which is directed the humoral autoimmunity in patients with systemic lupus erythematosus and Sjögren's Syndrome, respectively, were coupled to the Lys-N(epsilon)H2 groups of the carrier, and the formulated constructs were administered in animals following the conventional immunization protocol of complete/incomplete Freund's adjuvant. The induced immune responses were compared with that produced when the Sm- and La/SSB-reconstituted immunogenic conjugates were injected alone. High titers of specific antibodies recognizing the priming construct, as well as the cognate autoantigen, were obtained when administered alone without the assistance of Freund's adjuvant. It is concluded that our approach provides the conceptual and experimental framework for the development of multifunctional immunogenic conjugates eliciting enhanced, specific, and prolonged humoral response for usage as human vaccine candidates.

Structural and immunogenicity analysis of chimeric B-cell epitope constructs derived from the gp46 and gp21 subunits of the envelope glycoproteins of HTLV-1

B-cell epitopes were selected from the gp21 and gp46 subunits of the envelope glycoprotein of human T-cell lymphotropic virus type 1 (HTLV-1) by computer-aided analyses of protein antigenicity. Molecular modeling was used to design and synthesize the epitopes as chimeric constructs with promiscuous T-helper epitopes derived either from the tetanus toxoid (amino acids 947-967) or measles virus fusion protein (amino acids 288-302). Circular dichroism measurements revealed that the peptides had a secondary structure that correlated well with the crystal structure data or predicted structure. The chimeric peptides were then evaluated for their immunogenicity in rabbits or mice. Antibodies against one of the epitopes derived from the gp21 subunit were found to be neutralizing in its ability to inhibit the formation of virus-induced syncytia. These studies underscore the importance of the gp21 transmembrane region for the development of vaccine candidates. The applicability of a chimeric approach is discussed in the context of recent findings regarding the role of gp21 transmembrane region in the viral fusion process.

A chimeric multi-human epidermal growth factor receptor-2 B cell epitope peptide vaccine mediates superior antitumor responses

Immunotherapeutic approaches to cancer should focus on novel undertakings that modulate immune responses by synergistic enhancement of antitumor immunological parameters. Cancer vaccines should preferably be composed of multiple defined tumor Ag-specific B and T cell epitopes. To develop a multiepitope vaccine, 12 high ranking B cell epitopes were identified from the extracellular domain of the human epidermal growth factor receptor-2 (HER-2) oncoprotein by computer-aided analysis. Four novel HER-2 B cell epitopes were synthesized as chimeras with a promiscuous T cell epitope (aa 288-302) from the measles virus fusion protein (MVF). Two chimeric peptide vaccines, MVF HER-2(316-339) and MVF HER-2(485-503) induced high levels of Abs in outbred rabbits, which inhibited tumor cell growth. In addition, Abs induced by a combination of two vaccines, MVF HER-2(316-339) and MVF HER-2(628-647) down-modulated receptor expression and activated IFN-gamma release better than the individual vaccines. Furthermore, this multiepitope vaccine in combination with IL-12 caused a significant reduction (p = 0.004) in the number of pulmonary metastases induced by challenge with syngeneic tumor cells overexpressing HER-2. Peptide Abs targeting specific sites in the extracellular domain may be used for exploring the oncoprotein's functions. The multiepitope vaccine may have potential application in the treatment of HER-2-associated cancers.

Synthetic peptides as cancer vaccines

Effective cancer therapy or prevention has been the dream of physicians and scientists for many years. Although we are still very far from our ultimate goal of cancer prevention, significant milestones have been realized in terms of our knowledge base and understanding of the pathogenesis of cancerous cells and the involvement of the immune system against both self- and virus-associated tumor antigens. Immunotherapeutic strategies are now accepted to being superior in terms of the exquisite specificity that they offer in targeting only tumor cells as opposed to the existent chemotherapy or radiation therapy that is more general and invasive with many associated side effects. There are several immunotherapeutic strategies that are currently under investigation. This review primarily focuses on the significant advances made in the use of synthetic peptides in the development of subunit cancer vaccines. We have attempted to highlight some of the fundamental issues regarding antigen processing and presentation, Major Histocompatibility Complex (MHC) restriction, T-cell help, structural determinants in antibody recognition, and the use of these concepts in the rational design and delivery of peptide vaccines to elicit protective humoral and cell mediated immune responses. The recent use of costimulatory molecules and cytokines to augment immune responses also has been discussed along with the contributions of our laboratory to the field of synthetic peptide vaccine development.

Immunization of female cynomolgus macaques with a synthetic epitope of sperm-specific lactate dehydrogenase results in high antibody titers but does not reduce fertility

Previous studies have reported reduced fertility in female baboons immunized with a synthetic peptide derived from the sperm-specific isozyme of lactate dehydrogenase (LDH-C). In this study, a similar approach was used to immunize female cynomolgus macaques with the same peptide sequence (bC5-19) conjugated to a T-cell epitope from tetanus toxin (TT). Twelve female monkeys were immunized with bC5-19:TT delivered with Ribi MPL adjuvant vehicle, and 10 control female monkeys were injected with the adjuvant vehicle only. All 12 females in the treatment group developed LDH-C-specific serum antibodies as measured by ELISA, but anti-LDH-C antibodies were not detected in vaginal fluids of the immunized animals. After 4 months of timed mating immediately following the immunizations, five of the ten immunized females became pregnant, as did six of the ten control females. Anti-sera from both pregnant and nonpregnant bC5-19:TT-immunized females recognize a single band at 35 kDa on Western blots of whole sperm extracts, and purified Igs from the same sera localize along the principle piece of the flagellum of permeabilized sperm.

A new helicoid-type sequential oligopeptide carrier (SOC(n)) for developing potent antigens and immunogens

A new class of sequential oligopeptide carriers (SOC(n)) for anchoring antigenic/immunogenic peptides has been constructed. The carrier, formed by the repetitive Lys-Aib-Gly moiety, is designed to display a predetermined 3D structure, so that the attached peptides would obtain a defined spatial orientation. Conformational analysis showed that SOC(n) adopt a distorted 3(10)-helical structure, while the coupled peptides preserve their original 'active' structure. Coupling to the carrier may also result to the enhancement of one conformer of the anchored peptide. It is concluded that the structure of SOC(n) offers an optimal presentation of the attached peptides, so that potent antigens or immunogens are generated.

Peptide carriers: A helicoid-type sequential oligopeptide carrier (SOC(n)) for multiple anchoring of antigenic/immunogenic peptides

A new peptide carrier with three-dimensional predetermined structural motif has been constructed by the repetitive Lys-Aib-Gly moiety. The sequential oligopeptide carrier (SOC(n)), (Lys-Aib-Gly)(n), adopts a distorted 3(10)-helical conformation and the Lys-N(epsilon)H(2) anchoring groups exhibit defined spatial orientations. Conformational analysis of the SOC(n) conjugates showed that the coupled peptides retain their initial "active" structure, while prevalence of one conformer was also observed. It is concluded that the beneficial structural elements of SOC(n) induce a favorable arrangement of the conjugated peptides, so that potent antigens and immunogens are generated.

Protection against development of otitis media induced by nontypeable Haemophilus influenzae by both active and passive immunization in a chinchilla model of virus-bacterium superinfection

Three separate studies, two involving active-immunization regimens and one involving a passive-transfer protocol, were conducted to initially screen and ultimately more fully assess several nontypeable Haemophilus influenzae outer membrane proteins or their derivatives for their relative protective efficacy in chinchilla models of otitis media. Initial screening of these antigens (P5-fimbrin, lipoprotein D, and P6), delivered singly or in combination with either Freund's adjuvant or alum, indicated that augmented bacterial clearance from the nasopharynx, the middle ears, or both anatomical sites could be induced by parenteral immunization with P5-fimbrin combined with lipoprotein D, lipoprotein D alone, or the synthetic chimeric peptide LB1 (derived from P5-fimbrin), respectively. Data from a second study, wherein chinchillas were immunized with LB1 or lipoprotein D, each delivered with alum, again indicated that clearance of nontypeable H. influenzae could be augmented by immunization with either of these immunogens; however, when this adjuvant was used, both antibody titers in serum and efficacy were reduced. A third study was performed to investigate passive delivery of antisera directed against either LB1, lipoprotein D, nonacylated lipoprotein D, or a unique recombinant peptide designated LPD-LB1(f)2,1,3. The last three antiserum pools were generated by using the combined adjuvant of alum plus monophosphoryl lipid A. Passive transfer of sera specific for LB1 or LPD-LB1(f)2,1,3 to adenovirus-compromised chinchillas, prior to intranasal challenge with nontypeable H. influenzae, significantly reduced the severity of signs and incidence of otitis media which developed (P </= 0.001). Collectively, these data indicate the continued merit of further developing LB1 and LPD-LB1(f)2,1,3 as components of vaccines for otitis media.

Receptors for the Anaphylatoxin C5a (CD88) on Human Mesangial Cells

In these studies, we determined whether there are receptors for the anaphylatoxin C5a (C5aR, CD88) on human mesangial cells (HMC). To prepare Abs to C5aR, we first synthesized an immunogenic peptide spanning residues 8–32 of the molecule, and this peptide was used to immunize rabbits. Anti-C5aR antiserum, but not preimmune serum, stained fixed and unfixed HMC in culture. By Western blotting anti-C5aR, Abs identified a 49.6-kDa protein in HMC. By reverse-transcription PCR, a cDNA product of 558 bp was amplified corresponding to the expected size of C5aR cDNA. A cDNA of the same size was amplified simultaneously from human PBL. Restriction mapping of the products amplified from HMC and from PBL gave restriction fragments of the same size. Incubation of HMC with increasing doses of C5a caused a progressive increase in the levels of the transcription factors activator protein-1 (AP-1) and cAMP response element binding protein (CREB), but C5a had no effect on the level of nuclear factor-κB (NF-κB). The effects of C5a on AP-1 were concentration and time dependent and peaked after 60 min. In contrast, the C5a metabolite C5adesArg had no significant effect on AP-1 levels. Preincubation of HMC with rabbit anti-C5aR antiserum inhibited partially the effect of C5a on AP-1. However, anti-C5aR Abs alone had no appreciable effects on AP-1. C5a caused a significant up-regulation of mRNA for the early response genes c-jun and c-fos on HMC. These results provide evidence for the presence of C5aR in adult HMC in culture and indicate that, after binding to C5aR, the anaphylatoxin C5a causes significant up-regulation of certain transcription factors and early response genes.

Preliminary studies with recombinant chorionic gonadotropin beta-subunit produced in Escherichia coli for use as an antigen in a birth control vaccine

PROBLEM

Prototype human chorionic gonadotropin (hCG) vaccines based on natural sources are unsuitable for widespread applications due to their complex manufacturing procedures, cost, and carrier-mediated immune suppression.

METHOD OF STUDY

Wistar rats were immunized with alum-adsorbed CG beta (recombinant), CG beta-TT, and nCG beta (native CG beta)-TT, whereas Bonnet monkeys were immunized with only CG beta. The anti-hCG antibody titre in the sera obtained at different time points were quantified by radioimmunoassay. The sera of Wistar rats were characterized in terms of their affinity to hCG, bioneutralization capacity (by inhibition of hCG-induced testosterone production in Leydig cells), and cross-reactivity with human luteinizing hormone, human follicle-stimulating hormone, and human thyroid-stimulating hormone (by direct binding assays).

RESULTS

Antigen-binding capacities of sera obtained upon immunization with CG beta were 3,080 +/- 943 ng/ml (n = 6) and 3,993 +/- 1,292 ng/ml (n = 4), respectively, in rats and monkeys. The analysis of data revealed that immunization of rats with CG beta produced antibodies comparable to that of CG beta-TT and nCG beta-TT.

CONCLUSION

The study opens up the possibility of producing pure and highly immunogenic CG beta by a recombinant DNA route, as a consistent source of antigen for birth control vaccine.

Colinear synthesis of an antigen-specific B-cell epitope with a 'promiscuous' tetanus toxin T-cell epitope: a synthetic peptide immunocontraceptive

Carrier conjugation is commonly used to provide T-cell help for small, linear peptides containing antigen-specific B-cell epitopes. However, carrier conjugation is expensive, variable and often results in adverse side effects if the conjugate is administered repeatedly. To eliminate the need for carrier conjugation, we examined two synthetic peptides for their ability to elicit sustained antibody titres in female rabbits and baboons. One peptide (hC1-20) was based on the sequence of the sperm-specific isozyme of human lactate dehydrogenase (LDH-C4). This peptide stimulates helper T-cell responses. The other peptide (bC5-19:TT) was a chimera between an LDH-C4 B-cell epitope and a 'promiscuous' T-cell epitope from tetanus toxin which has been shown to bind to and stimulate many different major histocompatibility complex alleles. Both peptides were immunogenic in rabbits and baboons. The chimera elicited consistently high antibody titres and was immunogenic in 19/19 wild-caught female baboons. When 14 bC5-19:TT immunized baboons were mated, their fertility was reduced by 62% compared with controls (P < 0.02). This carrier-free construct can be incorporated into biodegradable microspheres which may provide long-term protection from pregnancy with a single dose.

Tandem repeats of T helper epitopes enhance immunogenicity of fusion proteins by promoting processing and presentation

Empirical findings have shown that recombinant chimeric proteins may be made more immunogenic if T helper epitopes are incorporated as tandem repeats. In the present study we investigated the mechanisms responsible for the enhanced immunogenicity of fusion proteins composed of the heat-stable enterotoxin of enterotoxigenic E. coli (STa) linked to multiple copies of the ovalbumin323-339 T helper epitope (ova) and a connecting dimer of an Ig-binding region of Staphylococcus aureus protein A (ZZ), which were previously shown to stimulate strong anti-STa titres in mice. We used B cell and macrophage cell lines as APC and IL-2 production by ova-specific T cells as our read-out system. Fusion proteins containing four repeated T helper epitopes were found to be the most immunogenic and resulted in 50-fold higher IL-2 production than constructs with a single T helper epitope. Under limiting APC conditions the construct with four epitopes was the best inducer of IL-2, indicating that this construct was most effectively processed by the APC. Analysis of IL-2R alpha expression by flow cytometry confirmed that four copies gave the highest frequency of activated T cells in culture, indicating a direct correlation between ability to activate T cells and IL-2 production in culture. Also in vivo, the fusion protein with four epitopes exhibited the strongest T cell priming effect. Moreover, both in vitro and in vivo, the ZZ construct was found to serve as an efficient means for targeting of the fusion proteins to B cells, thereby allowing access to the Ig receptor uptake pathway for Ag. The present study provides direct evidence that fusion proteins can be constructed to optimize processing in the individual APC and enhance activation of clonal T cells.

Relative immunogenicity and efficacy of two synthetic chimeric peptides of fimbrin as vaccinogens against nasopharyngeal colonization by nontypeable Haemophilus influenzae in the chinchilla

The OMP P5-homologous fimbriae of nontypeable Haemophilus influenzae (NTHi) are an adhesin and a virulence factor for otitis media in chinchilla models. We synthesized two peptides (LB1 and LB2) which incorporate determinants of the fimbrial subunit co-linearly synthesized with a "promiscuous" T-cell epitope from the fusion protein of measles virus. Sera obtained from immunized rabbits and chinchillas demonstrated significant reciprocal titers against both the homologous peptide and isolated fimbrial protein. Antisera also immunolabeled native fimbriae of whole unfixed NTHi. Immunization with LB1 or fimbrin resulted in elimination of NTHi from the chinchilla nasopharynx 2-3 weeks earlier than controls, respectively.

Detection of keratinocyte growth factor (KGF) messenger ribonucleic acid and immunolocalization of KGF in the canine testis

Keratinocyte growth factor (KGF) was originally discovered in human embryonic lung fibroblasts and is a member of the fibroblast growth factor (FGF) family. Members of the FGF family have been shown to regulate testicular function. However, the recently discovered KGF has not been studied in the testis. KGF has been detected in many other tissues, including the prostate, an organ whose development and function have been associated with presence of the testis. In this study, KGF mRNA was detected in the whole testis using reverse transcription polymerase chain reaction (RT-PCR). The 575-bp KGF-specific product was detected along with a 594-bp β-actin-specific product. To identify the cell types in which KGF mRNA was predominantly expressed, interstitial cells were physically separated from seminiferous tubules. The interstitial cells were then sorted on a discontinuous Percoll gradient and total cellular mRNAs isolated. Using RT-PCR and Southern hybridization with specific cDNA probes, the KGF mRNA was detected in interstitial cells. KGF expression levels were then evaluated semiquantitatively with a competitive RT-PCR assay. KGF expression levels were highest in interstitial cells that equilibrated between 20 and 30% Percoll. Enriched Leydig cells and seminiferous tubules expressed low levels of KGF. Finally, immunohistochemical analysis was performed on canine testes using a rabbit anti-KGF polyclonal antibody. The KGF protein was localized predominantly to peritubular cells of the canine testis. These results suggest that KGF is synthesized in the canine testis.

Analysis of the interaction between a synthetic peptide of influenza virus hemagglutinin and monoclonal antibodies using an optical biosensor

The interaction between two monoclonal antibodies and their corresponding Fab' fragments with a synthetic peptide, corresponding to the C-terminal 23 residues of the HA1 chain of influenza virus hemagglutinin against which they were generated, has been examined using an optical biosensor employing the detection principal of surface plasmon resonance (Pharmacia BIAcore). The data obtained has been analysed in detail by linear transformation of the primary data and nonlinear regression analysis, as well as by analysis of equilibrium binding data. The 2/1 antibodies and their Fab' fragments displayed higher affinity than the corresponding 1/1 proteins. The IgGs were found to have equilibrium association constants (KA) 10-20-fold higher than the corresponding Fab' fragments. This appears largely to be due to differences in the dissociation rate constant (kd) and probably reflects increased avidity due to bivalent binding.

Keratinocyte growth factor (KGF/FGF-7) has a paracrine role in canine prostate: molecular cloning of mRNA encoding canine KGF

cDNA encoding the canine keratinocyte growth factor (KGF) was cloned from normal canine prostate tissue. The authentic canine KGF cDNA sequence, 686 bp in length, spans the protein-coding region and 88 bp of the 5' and 19 bp of the 3' untranslated regions of canine KGF. The predicted amino acid sequence of canine KGF is composed of 194 amino acid residues. Canine KGF exhibits highest homology with the human KGF cDNA and amino acid sequences (95.8% and 97.4%, respectively), while it demonstrates the lowest homology with the rat sequences at 88.0% and 92.3%, respectively. The degrees of homology with mouse cDNA and amino acid sequences are 91.8% and 95.9%, respectively. By using RNase protection assay, KGF was shown to be expressed in normal prostate tissues of both mature and young (5-month-old) dogs. In vitro, the recombinant canine KGF has mitogenic activity on cultured canine epithelial cells, whereas it has no effect on cultured canine prostatic stromal cells. This novel canine KGF cDNA may be a valuable tool in the study of human benign prostatic hyperplasia using the canine prostatic as a model.

Progress in the development of human chorionic gonadotropin antifertility vaccines

Prototype human chorionic gonadotropin (hCG) vaccines have demonstrated the feasibility of effectively eliciting antibodies in women and inhibiting fertility in both humans and nonhuman primates. Also, no serious side-effects due to immunization against self antigens have been revealed to date. However, the formulations so far tested in clinical trials are not suitable for widespread applications due to problems associated with complexities in production, burdensome application procedures, the need for frequent booster immunizations or cost of manufacture. Current research efforts involve the development of delivery systems to permit annual or biannual intervals between immunizations for protection from pregnancy, procedures for mucosal immunizations, methods to reduce hypersensitivity and local reactions, and procedures for reducing the cost of production. Recent progress in understanding the crystalline structure of the hCG molecule has stimulated further studies to define immunological epitope sequences that might constitute immunogens in future vaccines. The incorporation of vaccine components into biodegradable microspheres has resulted in formulations that elicit elevated antibody levels in rabbits for more than one year. Preclinical and clinical studies with such formulations are planned. Studies using totally synthetic peptide immunogens constituting hCG B-cell epitopes and "promiscuous" T-cell epitopes from bacterial or viral proteins have been shown to be equally immunogenic as conjugates of hCG peptides with macromolecular carriers. Still other peptide immunogens have been developed that can elicit antibody production without detectable proliferation of helper T cells. Some of these peptides can induce systemic immunity from oral immunization or systemic injections. Alternative vehicles for administering vaccine components with reduced local reactivity show promise for new vaccine formulations.

Human T-lymphotropic virus type 1 peptides in chimeric and multivalent constructs with promiscuous T-cell epitopes enhance immunogenicity and overcome genetic restriction

Conventional strategies of viral peptide immunizations often elicit low-affinity antibody responses and have limited ability to elicit immune responses in outbred animals of diverse major histocompatibility (MHC) haplotypes. This genetically restricted T-cell-stimulatory activity of peptides is a serious obstacle to vaccine design. However, the use of promiscuous T-cell epitopes may circumvent this problem. Promiscuous T-cell epitopes from tetanus toxin (amino acids [aa] 580 to 599) and the measles virus F protein (aa 288 to 302) that bind to several isotypic and allotypic forms of human MHC class II molecules have been identified and have been used in highly immunogenic constructs to overcome haplotype-restricted immune responses. Chimeric and beta-template peptide constructs incorporating known human T-lymphotropic virus type 1 (HTLV-1) B- and T-cell epitopes from the surface envelope protein gp46 (SP2 [aa 86 to 107] and SP4a [aa 190 to 209]) and promiscuous T-cell peptides were synthesized, and their immunogenicities were evaluated in both rabbits and mouse strains of divergent haplotypes (C3H/HeJ [H-2k], C57BL/6 [H-2b], and BALB/c [H-2d]). In addition, peptide preparations were structurally characterized by analytical high-performance liquid chromatography, mass spectrometry, and circular dichroism. In contrast to their linear forms, the chimeric constructs of both the SP2 and SP4a epitopes displayed alpha-helical secondary structures. Immunogenicity of the peptide constructs was evaluated by direct and competitive enzyme-linked immunosorbant assay (ELISA), as well as by radioimmunoprecipitation, syncytium inhibition, and antigen-induced lymphocyte proliferation assays. Immunization with the SP4a peptide without conjugation to a carrier protein produced antibodies specific for SP4a in two mouse strains (C3H/HeJ and C57BL/6). However, BALB/c mice failed to respond to the peptide, indicating that the T-cell epitope of the SP4a sequence is MHC restricted. In contrast, the chimeric constructs MVF-SP2 and SP4a-measles virus F protein were highly immunogenic, producing elevated ELISA titers after only two immunizations. Elicited antibodies recognized native forms of gp46 in ELISAs and radioimmunoprecipitation assays, as well as inhibited HTLV-1-mediated syncytium formation. In addition, chimeric constructs were effective at induction of lymphocyte proliferation to the T-cell epitope, SP4a, in each strain of immunized mice. Our data demonstrate that the antibody response to retroviral peptides is enhanced by promiscuous peptide constructs, in part because of the ability of such constructs to promote appropriate secondary structural forms of viral epitopes. In addition, these constructs promote virus-specific helper T-cell responses, thereby overcoming genetically restricted immune responses to the synthetic peptides.

Generation and characterization of monoclonal antibodies specific for members of the mammalian 70-kDa heat shock protein family

The 70-kDa heat shock proteins (hsp70) are a highly conserved, abundant, and ubiquitous family of proteins expressed by all organisms from bacteria to humans. It is well established that hsp70 family members function as molecular chaperones and aid in the intracellular folding of newly synthesized or denatured proteins. Current evidence suggests an emerging role for hsp70 family members in immune responses and in clinically important responses to stress and tissue damage. Here we report the generation and characterization of several MAbs to hsp70 family members. Immune responses to this highly conserved family were induced in mice by immunization with synthetic peptides that contain regions of the mouse mitochondrial hsp70 coupled to a potent helper T cell epitope derived from tetanus toxoid. The resulting MAbs include ones specific for the human and mouse mitochondrial hsp70 and others that show cross-reactivity among the family members and recognize the mitochondrial hsp70, the endoplasmic reticulum resident hsp70, Bip/grp78, the constitutively expressed cytosolic hsp70, hsc70, and the heat-induced member, hsp70. Significantly, these MAbs are effective in Western blotting, in immunoprecipitation, and in immunofluorescence, and thus should find applications in the purification and detection of members of this important family.