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

Intranasal Self-Adjuvanted Lipopeptide Vaccines Elicit High Antibody Titers and Strong Cellular Responses against SARS-CoV-2

Despite concerted efforts to tackle the COVID-19 pandemic, the persistent transmission of SARS-CoV-2 demands continued research into novel vaccination strategies to combat the virus. In light of this, intranasally administered peptide vaccines, particularly those conjugated to an immune adjuvant to afford so-called "self-adjuvanted vaccines", remain underexplored. Here, we describe the synthesis and immunological evaluation of self-adjuvanting peptide vaccines derived from epitopes of the spike glycoprotein of SARS-CoV-2 covalently fused to the potent adjuvant, Pam2Cys, that targets toll-like receptor 2 (TLR2). When administered intranasally, these vaccines elicited a strong antigen-specific CD4+ and CD8+ T-cell response in the lungs as well as high titers of IgG and IgA specific to the native spike protein of SARS-CoV-2. Unfortunately, serum and lung fluid from mice immunized with these vaccines failed to inhibit viral entry in spike-expressing pseudovirus assays. Following this, we designed and synthesized fusion vaccines composed of the T-cell epitope discovered in this work, covalently fused to epitopes of the receptor-binding domain of the spike protein reported to be neutralizing. While antibodies elicited against these fusion vaccines were not neutralizing, the T-cell epitope retained its ability to stimulate strong antigen-specific CD4+ lymphocyte responses within the lungs. Given the Spike(883-909) region is still completely conserved in SARS-CoV-2 variants of concern and variants of interest, we envision the self-adjuvanting vaccine platform reported here may inform future vaccine efforts.

Assessment of the Impact of a Toll-like Receptor 2 Agonist Synthetic Lipopeptide on Macrophage Susceptibility and Responses to African Swine Fever Virus Infection

Toll-like receptor 2 (TLR2) ligands are attracting attention as prophylactic and immunopotentiator agents against pathogens, including viruses. We previously reported that a synthetic diacylated lipopeptide (Mag-Pam2Cys_P48) polarized porcine macrophages towards a proinflammatory antimicrobial phenotype. Here, we investigated its role in modulating monocyte-derived macrophage (moMΦ) responses against African swine fever virus (ASFV), the etiological agent of one of the greatest threats to the global pig industry. Two ASFV isolates were compared: the attenuated NH/P68 and the virulent 26544/OG10. No effect on virus infection nor the modulation of surface markers’ expression (MHC I, MHC II DR, CD14, CD16, and CD163) were observed when Mag-Pam2Cys_P48 treated moMΦ were infected using a multiplicity of infection (MOI) of 1. Mag-Pam2Cys_P48 treated moMΦ released higher levels of IL-1α, IL-1β, IL-1Ra, and IL-18 in response to infection with NH/P68 ASFV compared to 26544/OG10-infected and mock-infected controls. Surprisingly, when infected using a MOI of 0.01, the virulent ASFV 26544/OG10 isolate replicated even slightly more efficiently in Mag-Pam2Cys_P48 treated moMΦ. These effects also extended to the treatment of moMΦ with two other lipopeptides: Mag-Pam2Cys_P80 and Mag-Pam2Cys_Mag1000. Our data suggested limited applicability of TLR2 agonists as prophylactic or immunopotentiator agents against virulent ASFV but highlighted the ability of the virulent 26544/OG10 to impair macrophage defenses.

Signal sequence contributes to the immunogenicity of Pasteurella multocida lipoprotein E

Recombinant Pasterurella multocida lipoprotein E (PlpE) has been shown to protect against fowl cholera. This study aimed to determine if the signal sequence may contribute to the antigenicity and protective efficacy of recombinant PlpE. A small antigenic domain of PlpE (termed truncated PlpE, tPlpE) was constructed with (SP-tPlpE) or without (tPlpE) the signal sequence and evaluated in vitro and in vivo. In vitro, the HEK-Bule hTLR2 Cells were used to evaluate the activation of NF-kB in the test associated with the stimulation of the SP-tPlpE and tPlpE proteins. When chickens were immunized, compared to the tPlpE vaccine group, the SP-tPlpE group showed higher antibody levels and enhanced CD4⁺ T cell response. In a challenge test, the SP-tPlpE group showed a survival rate of 87.5% (n = 8), compared to 25% for the tPlpE group. It is confirmed that the inclusion of the native signal sequence enhanced protective efficacy against fowl cholera and may act as a vaccine adjuvant. The short SP-tPlpE construct is amenable to further vaccine engineering and has potential to be developed as a fowl cholera vaccine.

Lipopeptides for Vaccine Development

The development of lipopeptides (lipidated peptides) for vaccines is discussed, including their role as antigens and/or adjuvants. Distinct classes of lipopeptide architectures are covered including simple linear and ligated constructs and lipid core peptides. The design, synthesis, and immunological responses of the important class of glycerol-based Toll-like receptor agonist lipopeptides such as Pam₃CSK₄, which contains three palmitoyl chains and a CSK₄ hexapeptide sequence, and many derivatives of this model immunogenic compound are also reviewed. Self-assembled lipopeptide structures including spherical and worm-like micelles that have been shown to act as vaccine agents are also described. The work discussed includes examples of lipopeptides developed with model antigens, as well as for immunotherapies to treat many infectious diseases including malaria, influenza, hepatitis, COVID-19, and many others, as well as cancer immunotherapies. Some of these have proceeded to clinical development. The research discussed highlights the huge potential of, and diversity of roles for, lipopeptides in contemporary and future vaccine development.

Targeting Toll-Like Receptor 2: Polarization of Porcine Macrophages by a Mycoplasma-Derived Pam2cys Lipopeptide

Toll-like receptor 2 (TLR2) ligands are attracting increasing attention as prophylactic and immunotherapeutic agents against pathogens and tumors. We previously observed that a synthetic diacylated lipopeptide based on a surface protein of Mycoplasma agalactiae (Mag-Pam2Cys) strongly activated innate immune cells, including porcine monocyte-derived macrophages (moMΦ). In this study, we utilized confocal microscopy, flow cytometry, multiplex cytokine ELISA, and RT-qPCR to conduct a comprehensive analysis of the effects of scalar doses of Mag-Pam2Cys on porcine moMΦ. We observed enhanced expression of activation markers (MHC class I, MHC class II DR, CD25), increased phagocytotic activity, and release of IL-12 and proinflammatory cytokines. Mag-Pam2Cys also upregulated the gene expression of several IFN-α subtypes, p65, NOS2, and molecules with antimicrobial activities (CD14, beta defensin 1). Overall, our data showed that Mag-Pam2Cys polarized porcine macrophages towards a proinflammatory antimicrobial phenotype. However, Mag-Pam2Cys downregulated the expression of IFN-α3, six TLRs (TLR3, -4, -5, -7, -8, -9), and did not interfere with macrophage polarization induced by the immunosuppressive IL-10, suggesting that the inflammatory activity evoked by Mag-Pam2Cys could be regulated to avoid potentially harmful consequences. We hope that our in vitro results will lay the foundation for the further evaluation of this diacylated lipopeptide as an immunopotentiator in vivo.

Vaccine-Specific Immune Responses against Mycobacterium ulcerans Infection in a Low-Dose Murine Challenge Model

The neglected tropical disease Buruli ulcer (BU) is an infection of subcutaneous tissue with Mycobacterium ulcerans There is no effective vaccine. Here, we assessed an experimental prime-boost vaccine in a low-dose murine tail infection model. We used the enoyl reductase (ER) domain of the M. ulcerans mycolactone polyketide synthases electrostatically coupled with a previously described Toll-like receptor 2 (TLR-2) agonist-based lipopeptide adjuvant, R₄Pam₂Cys. Mice were vaccinated and then challenged via tail inoculation with 14 to 20 CFU of a bioluminescent strain of M. ulcerans Mice receiving either the experimental ER vaccine or Mycobacterium bovis bacillus Calmette-Guérin (BCG) were equally protected, with both groups faring significantly better than nonvaccinated animals (P < 0.05). To explore potential correlates of protection, a suite of 29 immune parameters were assessed in the mice at the end of the experimental period. Multivariate statistical approaches were used to interrogate the immune response data to develop disease-prognostic models. High levels of interleukin 2 (IL-2) and low gamma interferon (IFN-γ) produced in the spleen best predicted control of infection across all vaccine groups. Univariate logistic regression revealed vaccine-specific profiles of protection. High titers of ER-specific IgG serum antibodies together with IL-2 and IL-4 in the draining lymph node (DLN) were associated with protection induced by the ER vaccine. In contrast, high titers of IL-6, tumor necrosis factor alpha (TNF-α), IFN-γ, and IL-10 in the DLN and low IFN-γ titers in the spleen were associated with protection following BCG vaccination. This study suggests that an effective BU vaccine must induce localized, tissue-specific immune profiles with controlled inflammatory responses at the site of infection.

Understanding CD8+ T-cell responses toward the native and alternate HLA-A*02:01-restricted WT1 epitope

The Wilms' tumor 1 (WT1) antigen is expressed in solid and hematological malignancies, but not healthy tissues, making it a promising target for cancer immunotherapies. Immunodominant WT1 epitopes, the native HLA-A2/WT1_126-134 (RMFPNAPYL) (HLA-A2/RMFPNAPYL epitope (WT1A)) and its modified variant YMFPNAPYL (HLA-A2/YMFPNAPYL epitope (WT1B)), can induce WT1-specific CD8⁺ T cells, although WT1B is more stably bound to HLA-A*02:01. Here, to further determine the benefits of those two targets, we assessed the naive precursor frequencies; immunogenicity and cross-reactivity of CD8⁺ T cells directed toward these two WT1 epitopes. Ex vivo naive WT1A- and WT1B-specific CD8⁺ T cells were detected in healthy HLA-A*02:01⁺ individuals with comparable precursor frequencies (1 in 10⁵–10⁶) to other naive CD8⁺ T-cell pools (for example, A2/HIV-Gag_77-85), but as expected, ~100 × lower than those found in memory populations (influenza, A2/M1_58-66; EBV, A2/BMLF1_280-288). Importantly, only WT1A-specific naive precursors were detected in HLA-A2.1 mice. To further assess the immunogenicity and recruitment of CD8⁺ T cells responding to WT1A and WT1B, we immunized HLA-A2.1 mice with either peptide. WT1A immunization elicited numerically higher CD8⁺ T-cell responses to the native tumor epitope following re-stimulation, although both regimens produced functionally similar responses toward WT1A via cytokine analysis and CD107a expression. Interestingly, however, WT1B immunization generated cross-reactive CD8⁺ T-cell responses to WT1A and could be further expanded by WT1A peptide revealing two distinct populations of single- and cross-reactive WT1A⁺CD8⁺ T cells with unique T-cell receptor-αβ gene signatures. Therefore, although both epitopes are immunogenic, the clinical benefits of WT1B vaccination remains debatable and perhaps both peptides may have separate clinical benefits as treatment targets.

Biotechnology approaches to produce potent, self-adjuvanting antigen-adjuvant fusion protein subunit vaccines

Traditional vaccination approaches (e.g. live attenuated or killed microorganisms) are among the most effective means to prevent the spread of infectious diseases. These approaches, nevertheless, have failed to yield successful vaccines against many important pathogens. To overcome this problem, methods have been developed to identify microbial components, against which protective immune responses can be elicited. Subunit antigens identified by these approaches enable the production of defined vaccines, with improved safety profiles. However, they are generally poorly immunogenic, necessitating their administration with potent immunostimulatory adjuvants. Since few safe and effective adjuvants are currently used in vaccines approved for human use, with those available displaying poor potency, or an inability to stimulate the types of immune responses required for vaccines against specific diseases (e.g. cytotoxic lymphocytes (CTLs) to treat cancers), the development of new vaccines will be aided by the availability of characterized platforms of new adjuvants, improving our capacity to rationally select adjuvants for different applications. One such approach, involves the addition of microbial components (pathogen-associated molecular patterns; PAMPs), that can stimulate strong immune responses, into subunit vaccine formulations. The conjugation of PAMPs to subunit antigens provides a means to greatly increase vaccine potency, by targeting immunostimulation and antigen to the same antigen presenting cell. Thus, methods that enable the efficient, and inexpensive production of antigen-adjuvant fusions represent an exciting mean to improve immunity towards subunit antigens. Herein we review four protein-based adjuvants (flagellin, bacterial lipoproteins, the extra domain A of fibronectin (EDA), and heat shock proteins (Hsps)), which can be genetically fused to antigens to enable recombinant production of antigen-adjuvant fusion proteins, with a focus on their mechanisms of action, structural or sequence requirements for activity, sequence modifications to enhance their activity or simplify production, adverse effects, and examples of vaccines in preclinical or human clinical trials.

Double conjugation strategy to incorporate lipid adjuvants into multiantigenic vaccines

Conjugation of multiple peptides by their N-termini is a promising technique to produce branched multiantigenic vaccines.

Conjugation of multiple peptides by their N-termini is a promising technique to produce branched multiantigenic vaccines. We established a double conjugation strategy that combines a mercapto-acryloyl Michael addition and a copper-catalysed alkyne-azide 1,3-dipolar cycloaddition (CuAAC) reaction to synthesise self-adjuvanting branched multiantigenic vaccine candidates. These vaccine candidates aim to treat cervical cancer and include two HPV-16 derived epitopes and a novel self-adjuvanting moiety. This is the first report of mercapto-acryloyl conjugation applied to the hetero conjugation of two unprotected peptides by their N-termini followed by a CuAAC reaction to conjugate a novel synthetic lipoalkyne self-adjuvanting moiety. In vivo experiments showed that the most promising vaccine candidate completely eradicated tumours in 46% of the mice (6 out of 13 mice).

Progress in vaccine development

Vaccination has a proven record as one of the most effective medical approaches to prevent the spread of infectious diseases. Traditional vaccine approaches involve the administration of whole killed or weakened microorganisms to stimulate protective immune responses. Such approaches deliver many microbial components, some of which contribute to protective immunity, and assist in guiding the type of immune response that is elicited. Despite their impeccable record, these approaches have failed to yield vaccines for many important infectious organisms. This has prompted a move towards more defined vaccines ('subunit vaccines'), where individual protective components are administered. This unit provides an overview of the components that are used for the development of modern vaccines including: an introduction to different vaccine types (whole organism, protein/peptide, polysaccharide, conjugate, and DNA vaccines); techniques for identifying subunit antigens; vaccine delivery systems; and immunostimulatory agents ('adjuvants'), which are fundamental for the development of effective subunit vaccines.

TLR Agonists as Modulators of the Innate Immune Response and Their Potential as Agents Against Infectious Disease

Immunotherapies that can either activate or suppress innate immune responses are being investigated as treatments against infectious diseases and the pathology they can cause. The objective of these therapies is to elicit protective immune responses thereby limiting the harm inflicted by the pathogen. The Toll-like receptor (TLR) signaling pathway plays critical roles in numerous host immune defenses and has been identified as an immunotherapeutic target against the consequences of infectious challenge. This review focuses on some of the recent advances being made in the development of TLR-ligands as potential prophylactic and/or therapeutic agents.

Modern subunit vaccines: development, components, and research opportunities

Traditional vaccines, based on the administration of killed or attenuated microorganisms, have proven to be among the most effective methods for disease prevention. Safety issues related to administering these complex mixtures, however, prevent their universal application. Through identification of the microbial components responsible for protective immunity, vaccine formulations can be simplified, enabling molecular-level vaccine characterization, improved safety profiles, prospects to develop new high-priority vaccines (e.g. for HIV, tuberculosis, and malaria), and the opportunity for extensive vaccine component optimization. This subunit approach, however, comes at the expense of decreased immunity, requiring the addition of immunostimulatory agents (adjuvants). As few adjuvants are currently used in licensed vaccines, adjuvant development represents an exciting area for medicinal chemists to play a role in the future of vaccine development. In addition, immune responses can be further customized though optimization of delivery systems, tuning the size of particulate vaccines, targeting specific cells of the immune system (e.g. dendritic cells), and adding components to aid vaccine efficacy in whole immunized populations (e.g. promiscuous T-helper epitopes). Herein we review the current state of the art and future direction in subunit vaccine development, with a focus on the described components and their potential to steer the immune response toward a desired response.

Toll-like receptors in autoimmunity with special reference to systemic lupus erythematosus

The Toll-like receptor (TLR) family plays a fundamental role in host innate immunity by mounting a rapid and potent inflammatory response to pathogen infection. TLRs recognize distinct microbial components and activate intracellular signaling pathways that induce expression of host inflammatory genes. Several studies have indicated that TLRs are implicated in many inflammatory and immune disorders. Extensive research in the past decade to understand TLR-mediated mechanisms of innate immunity has enabled pharmaceutical companies to begin to develop novel therapeutics for the purpose of controlling an inflammatory disease. The roles of TLRs in the development of autoimmune diseases have been studied. TLR7 and TLR9 have key roles in production of autoantibodies and/or in development of systemic autoimmune disease. It remains to be determined their role in apoptosis, in the pathogenesis of RNA containing immune complexes, differential expression of TLRs by T regulatory cells.

Role of CD8(+) T-cell immunity in influenza infection: potential use in future vaccine development

Continued circulation of the highly pathogenic avian H5N1 influenza A virus has many people worried that an influenza pandemic is imminent. Compounding this is the realization that H5N1 vaccines based on current influenza vaccine technology (designed to generate protective antibody responses) may be suboptimal at providing protection. As a consequence, there is recent interest in vaccine strategies that elicit cellular immunity, particularly the cytotoxic T lymphocyte response, in an effort to provide protection against a potential pandemic. A major issue is the lack of information about the precise role that these 'hitmen' of the immune system have in protecting against both pandemic and seasonal influenza. We need to know more about how the induction and maintenance of cytotoxic T lymphocytes after influenza infection can impact protection from further infection. The challenge is then to use this information in the design of vaccines that will protect against pandemic influenza and will help optimize CD8(+) killer T-cell responses in other infections.

Lipidated promiscuous peptides vaccine for tuberculosis-endemic regions

Despite nine decades of Bacillus Calmette--Guérin (BCG) vaccination, tuberculosis continues to be a major global health challenge. Clinical trials worldwide have proved the inadequacy of the BCG vaccine in preventing the manifestation of pulmonary tuberculosis in adults. Ironically, the efficacy of BCG is poorest in tuberculosis endemic areas. Factors such as nontuberculous or environmental mycobacteria and helminth infestation have been suggested to limit the efficacy of BCG. Hence, in high TB-burden countries, radically novel strategies of vaccination are urgently required. Here we showcase the properties of lipidated promiscuous peptide vaccines that target and activate cells of the innate and adaptive immune systems by employing a Toll-like receptor-2 agonist, S-[2,3-bis(palmitoyloxy)propyl]cysteine (Pam2Cys). Such a strategy elicits robust protection and enduring memory responses by type 1 T helper cells (Th1). Consequently, lipidated peptides may yield a better vaccine than BCG.

Affinity thresholds for naive CD8+ CTL activation by peptides and engineered influenza A viruses

High-avidity interactions between TCRs and peptide + class I MHC (pMHCI) epitopes drive CTL activation and expansion. Intriguing questions remain concerning the constraints determining optimal TCR/pMHCI binding. The present analysis uses the TCR transgenic OT-I model to assess how varying profiles of TCR/pMHCI avidity influence naive CTL proliferation and the acquisition of effector function following exposure to the cognate H-2K(b)/OVA(257-264) (SIINFEKL) epitope and to mutants provided as peptide or in engineered influenza A viruses. Stimulating naive OT-I CD8(+) T cells in vitro with SIINFEKL induced full CTL proliferation and differentiation that was largely independent of any need for costimulation. By contrast, in vitro activation with the low-affinity EIINFEKL or SIIGFEKL ligands depended on the provision of IL-2 and other costimulatory signals. Importantly, although they did generate potent endogenous responses, infection of mice with influenza A viruses expressing these same OVA(257) variants failed to induce the activation of adoptively transferred naive OT-I CTLps, an effect that was only partially overcome by priming with a lipopeptide vaccine. Subsequent structural and biophysical analysis of H2-K(b)OVA(257), H2-K(b)E1, and H2-K(b)G4 established that these variations introduce small changes at the pMHCI interface and decrease epitope stability in ways that would likely impact cell surface presentation and recognition. Overall, it seems that there is an activation threshold for naive CTLps, that minimal alterations in peptide sequence can have profound effects, and that the antigenic requirements for the in vitro and in vivo induction of CTL proliferation and effector function differ substantially.

Toxoplasma gondii HLA-B*0702-restricted GRA7(20-28) peptide with adjuvants and a universal helper T cell epitope elicits CD8(+) T cells producing interferon-γ and reduces parasite burden in HLA-B*0702 mice

The ability of CD8(+) T cells to act as cytolytic effectors and produce interferon-γ (IFN-γ) was demonstrated to mediate resistance to Toxoplasma gondii in murine models because of the recognition of peptides restricted by murine major histocompatibility complex (MHC) class I molecules. However, no T gondii-specific HLA-B07-restricted peptides were proven protective against T gondii. Recently, 2 T gondii-specific HLA-B*0702-restricted T cell epitopes, GRA7(20-28) (LPQFATAAT) and GRA3(27-35) (VPFVVFLVA), displayed high-affinity binding to HLA-B*0702 and elicited IFN-γ from peripheral blood mononuclear cells of seropositive HLA-B*07 persons. Herein, these peptides were evaluated to determine whether they could elicit IFN-γ in splenocytes of HLA-B*0702 transgenic mice when administered with adjuvants and protect against subsequent challenge. Peptide-specific IFN-γ-producing T cells were identified by enzyme-linked immunosorbent spot and proliferation assays utilizing splenic T lymphocytes from human lymphocyte antigen (HLA) transgenic mice. When HLA-B*0702 mice were immunized with one of the identified epitopes, GRA7(20-28) in conjunction with a universal CD4(+) T cell epitope (PADRE) and adjuvants (CD4(+) T cell adjuvant, GLA-SE, and TLR2 stimulatory Pam(2)Cys for CD8(+) T cells), this immunization induced CD8(+) T cells to produce IFN-γ and protected mice against high parasite burden when challenged with T gondii. This work demonstrates the feasibility of bioinformatics followed by an empiric approach based on HLA binding to test this biologic activity for identifying protective HLA-B*0702-restricted T gondii peptides and adjuvants that elicit protective immune responses in HLA-B*0702 mice.

Lipid motif of a bacterial antigen mediates immune responses via TLR2 signaling

The cross-talk between the innate and the adaptive immune system is facilitated by the initial interaction of antigen with dendritic cells. As DCs express a large array of TLRs, evidence has accumulated that engagement of these molecules contributes to the activation of adaptive immunity. We have evaluated the immunostimulatory role of the highly-conserved outer membrane lipoprotein P6 from non-typeable Haemophilus influenzae (NTHI) to determine whether the presence of the lipid motif plays a critical role on its immunogenicity. We undertook a systematic analysis of the role that the lipid motif plays in the activation of DCs and the subsequent stimulation of antigen-specific T and B cells. To facilitate our studies, recombinant P6 protein that lacked the lipid motif was generated. Mice immunized with non-lipidated rP6 were unable to elicit high titers of anti-P6 Ig. Expression of the lipid motif on P6 was also required for proliferation and cytokine secretion by antigen-specific T cells. Upregulation of T cell costimulatory molecules was abrogated in DCs exposed to non-lipidated rP6 and in TLR2^−/− DCs exposed to native P6, thereby resulting in diminished adaptive immune responses. Absence of either the lipid motif on the antigen or TLR2 expression resulted in diminished cytokine production from stimulated DCs. Collectively; our data suggest that the lipid motif of the lipoprotein antigen is essential for triggering TLR2 signaling and effective stimulation of APCs. Our studies establish the pivotal role of a bacterial lipid motif on activating both innate and adaptive immune responses to an otherwise poorly immunogenic protein antigen.

Human immunome, bioinformatic analyses using HLA supermotifs and the parasite genome, binding assays, studies of human T cell responses, and immunization of HLA-A*1101 transgenic mice including novel adjuvants provide a foundation for HLA-A03 restricted CD8+T cell epitope based, adjuvanted vaccine protective against Toxoplasma gondii

Background

Toxoplasmosis causes loss of life, cognitive and motor function, and sight. A vaccine is greatly needed to prevent this disease. The purpose of this study was to use an immmunosense approach to develop a foundation for development of vaccines to protect humans with the HLA-A03 supertype. Three peptides had been identified with high binding scores for HLA-A03 supertypes using bioinformatic algorhythms, high measured binding affinity for HLA-A03 supertype molecules, and ability to elicit IFN-γ production by human HLA-A03 supertype peripheral blood CD8⁺ T cells from seropositive but not seronegative persons.

Results

Herein, when these peptides were administered with the universal CD4⁺T cell epitope PADRE (AKFVAAWTLKAAA) and formulated as lipopeptides, or administered with GLA-SE either alone, or with Pam₂Cys added, we found we successfully created preparations that induced IFN-γ and reduced parasite burden in HLA-A*1101(an HLA-A03 supertype allele) transgenic mice. GLA-SE is a novel emulsified synthetic TLR4 ligand that is known to facilitate development of T Helper 1 cell (TH1) responses. Then, so our peptides would include those expressed in tachyzoites, bradyzoites and sporozoites from both Type I and II parasites, we used our approaches which had identified the initial peptides. We identified additional peptides using bioinformatics, binding affinity assays, and study of responses of HLA-A03 human cells. Lastly, we found that immunization of HLA-A*1101 transgenic mice with all the pooled peptides administered with PADRE, GLA-SE, and Pam₂Cys is an effective way to elicit IFN-γ producing CD8⁺ splenic T cells and protection. Immunizations included the following peptides together: KSFKDILPK (SAG1_224-232); AMLTAFFLR (GRA6_164-172); RSFKDLLKK (GRA7_134-142); STFWPCLLR (SAG2C_13-21); SSAYVFSVK(_SPA250-258); and AVVSLLRLLK(SPA_89-98). This immunization elicited robust protection, measured as reduced parasite burden using a luciferase transfected parasite, luciferin, this novel, HLA transgenic mouse model, and imaging with a Xenogen camera.

Conclusions

Toxoplasma gondii peptides elicit HLA-A03 restricted, IFN-γ producing, CD8⁺ T cells in humans and mice. These peptides administered with adjuvants reduce parasite burden in HLA-A*1101 transgenic mice. This work provides a foundation for immunosense based vaccines. It also defines novel adjuvants for newly identified peptides for vaccines to prevent toxoplasmosis in those with HLA-A03 supertype alleles.

Neoepitope antibodies against MMP-cleaved and aggrecanase-cleaved aggrecan

Neoepitope antibodies recognize the newly created N or C terminus of protein degradation products but fail to recognize the same sequence of amino acids present in intact or undigested protein. Aggrecan neoepitope antibodies have been pivotal in studies determining the contribution of matrix metalloproteinases (MMPs) and aggrecanases to aggrecanolysis. In particular, an antibody to the A(374)RGSV N terminus was instrumental in the landmark discovery of the aggrecanases, ADAMTS-4 and ADAMTS-5. Antibodies to neoepitopes at the major MMP cleavage site DIPEN(341)/(342)FFGVG helped to distinguish MMP-driven aggrecan loss from aggrecanase-driven aggrecan loss and identified a role for MMPs in late-stage disease. More recently, neoepitope antibodies that recognize cleavage sites in the chondroitin sulphate-rich region of aggrecan have been used to show that aggrecanase cleavage proceeds in a defined manner, beginning at the C terminus and proceeding to the signature cleavage at NITEGE(373)/(374)ARGSV in the interglobular domain. Work with the C-terminal neoepitope antibodies has underscored the need to use a suite of neoepitope antibodies to fully describe aggrecanolysis in vitro. In this chapter, we describe the production of two aggrecan neoepitope antibodies as examples: the monoclonal anti-FFGVG antibody (AF-28) and the polyclonal anti-DIPEN antisera.

Toll-like receptor 2 dependent immunogenicity of glycoconjugate vaccines containing chemically derived zwitterionic polysaccharides

Group B Streptococcus (GBS) causes serious infection in neonates and is an important target of vaccine development. Zwitterionic polysaccharides (ZPS), obtained through chemical introduction of positive charges into anionic polysaccharides (PS) from GBS, have the ability to activate human and mouse antigen presenting cells (APCs) through toll-like receptor 2 (TLR2). To generate a polysaccharide vaccine with antigen (Ag) and adjuvant properties in one molecule, we have conjugated ZPS with a carrier protein. ZPS-glycoconjugates induce higher T-cell and Ab responses to carrier and PS, respectively, compared to control PS-glycoconjugates made with the native polysaccharide form. The increased immunogenicity of ZPS-conjugates correlates with their ability to activate dendritic cells (DCs). Moreover, protection of mothers or neonate offspring from lethal GBS challenge is better when mothers are immunized with ZPS-conjugates compared to immunization with PS-conjugates. In TLR2 knockout mice, ZPS-conjugates lose both their increased immunogenicity and protective effect after vaccination. When ZPS are coadministered as adjuvants with unconjugated tetanus toxoid (TT), they have the ability to increase the TT-specific antibody titer. In conclusion, glycoconjugates containing ZPS are potent vaccines. They target Ag to TLR2-expressing APCs and activate these APCs, leading to better T-cell priming and ultimately to higher protective Ab titers. Thus, rational chemical design can generate potent PS-adjuvants with wide application, including glycoconjugates and coadministration with unrelated protein Ags.