Bivalent mucosal peptide vaccines administered using the LCP carrier system stimulate protective immune responses against Streptococcus pyogenes infection.

Despite the broad knowledge about the pathogenicity of Streptococcus pyogenes there is still a controversy about the correlate of protection in GAS infections. We aimed in further improving the immune responses stimulated against GAS comparing different vaccine formulations including bis-(3',5')-cyclic dimeric adenosine monophosphate (c-di-AMP) and BPPCysMPEG, a derivative of the macrophage-activating lipopeptide (MALP-2), as adjuvants, respectively, to be administered with and without the universal T helper cell epitope P25 along with the optimized B cell epitope J14 of the M protein and B and T cell epitopes of SfbI. Lipopeptide based nano carrier systems (LCP) were used for efficient antigen delivery across the mucosal barrier. The stimulated immune responses were efficient in protecting mice against a respiratory challenge with a lethal dose of a heterologous S. pyogenes strain. Moreover, combination of the LCP based peptide vaccine with c-di-AMP allowed reduction of antigen dose at the same time maintaining vaccine efficacy.

Pattern recognition receptors: sentinels in innate immunity and targets of new vaccine adjuvants.

The innate immune system plays an essential role in the host's first line of defense against microbial invasion, and involves the recognition of distinct pathogen-associated molecular patterns by pattern recognition receptors (PRRs). Activation of PRRs triggers cell signaling leading to the production of proinflammatory cytokines, chemokines and Type 1 interferons, and the induction of antimicrobial and inflammatory responses. These innate responses are also responsible for instructing the development of an appropriate pathogen-specific adaptive immune response. In this review, the focus is on different classes of PRRs that have been identified, including Toll-like receptors, nucleotide-binding oligomerization domain-like receptors, and the retinoic acid-inducible gene-I-like receptors, and their importance in host defense against infection. The role of PRR cooperation in generating optimal immune responses required for protective immunity and the potential of targeting PRRs in the development of a new generation of vaccine adjuvants is also discussed.

Immunological response to parenteral vaccination with recombinant hepatitis B virus surface antigen virus-like particles expressing Helicobacter pylori KatA epitopes in a murine H. pylori challenge model.

Virus-like particles (VLPs) based on the small envelope protein of hepatitis B virus (HBsAg-S) are immunogenic at the B- and T-cell level. In this study, we inserted overlapping sequences encoding the carboxy terminus of the Helicobacter pylori katA gene product into HBsAg-S. The HBsAg-S-KatA fusion proteins were able to assemble into secretion-competent VLPs (VLP-KatA). The VLP-KatA proteins were able to induce KatA-specific antibodies in immunized mice. The mean total IgG antibody titers 41 days post-primary immunization with VLP-KatA (2.3 × 10(3)) were significantly greater (P < 0.05) than those observed for vaccination with VLP alone (5.2 × 10(2)). Measurement of IgG isotypes revealed responses to both IgG1 and IgG2a (mean titers, 9.0 × 10(4) and 2.6 × 10(4), respectively), with the IgG2a response to vaccination with VLP-KatA being significantly higher than that for mice immunized with KatA alone (P < 0.05). Following challenge of mice with H. pylori, a significantly reduced bacterial load in the gastric mucosa was observed (P < 0.05). This is the first report describing the use of VLPs as a delivery vehicle for H. pylori antigens.

Toll-like receptor-mediated adjuvanticity and immunomodulation in dendritic cells: Implications for peptide vaccines.

Considerable success has been made with many peptide antigen formulations and it appears that peptide-based vaccines are emerging as the next generation of prophylactic and remedial immunotherapy. However, peptides are typically poorly immunogenic and rely on delivery with potent immunostimulatory adjuvants that activate the innate and adaptive arms of the immune system. Our research aims to develop novel peptide antigen delivery systems that incorporate multiple pattern-recognition receptor (PRR) agonists and is focused on those designed to stimulate Toll-like receptors (TLRs) on dendritic cells (DCs). The cytokine (IL-4, IL-6, IL-10, IL-12 and IL-23) profiles of DCs induced by individual TLR agonists have been evaluated. From this data we predicted which TLR agonists may influence a particular T helper cell (Th) response. Using purified DCs that were derived from precursor cells in murine bone marrow and then stimulated simultaneously with multiple TLR agonists, we have shown synergy between various TLR agonist pairs leading to enhanced cytokine production. Using various mitogen-activated protein kinase (MAPK) inhibitors (c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and p38 MAPK) we have demonstrated the importance of p38 MAPK and ERK signaling pathways in IL-12p70 and IL-12p40 production in DCs induced by TLR stimulation, whereas the JNK pathway appeared to have a negative regulatory role on cytokine production in DCs stimulated with certain TLR agonists. An important role for nuclear factor-kappa B and phosphoinositol-3-kinase as positive regulators of TLR signaling in DCs leading to cytokine production was also demonstrated. The significance of this research lies not only in improving potency, but by understanding the immunological mechanisms of adjuvanticity, in being able to tailor peptide vaccines to generate specific types of Th responses required for immunity against various types of pathogens.

Dual stimulation of MyD88-dependent Toll-like receptors induces synergistically enhanced production of inflammatory cytokines in murine bone marrow-derived dendritic cells.

BACKGROUND: Triggering Toll-like receptors (TLRs) on dendritic cells (DCs) induces inflammatory cytokine production necessary for T helper type 1 immunity. The present study investigated whether simultaneous stimulation of two TLRs that signal through the same or different pathway(s) enhances cytokine production in DCs. METHODS: Fms-like tyrosine kinase-3 ligand-generated murine DCs were used in stimulation assays with TLR agonists with or without pharmacological inhibitors of cell signaling pathways. Cytokine levels were evaluated by enzyme-linked immunosorbent assay or cytometric bead array. RESULTS: There was synergistic enhancement of interleukin (IL)-6 and IL-12, which were significantly inhibited by inhibitors of nuclear factor-kappaB and phosphatidylinositol 3-kinase. IL-12p40 was significantly inhibited by both p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase inhibitors, whereas IL-12p70 was inhibited by p38 MAPK inhibitor alone. IL-6 was significantly inhibited by extracellular signal-regulated kinase and, variably, by p38 MAPK and c-Jun N-terminal kinase inhibitors. CONCLUSIONS: Production of cytokines in DCs after simultaneous stimulation of TLRs that signal through the same or different pathway(s) showed differential use of MAPK signaling pathways, yet both nuclear factor-kappaB and the phosphatidylinositol 3-kinase pathway as a positive regulator of TLR signaling were important. Our data suggest an important role for MyD88-dependent signaling pathways in TLR-mediated synergistic enhancement of inflammatory cytokine production in DCs.

Regulation of Toll-like receptor-induced chemokine production in murine dendritic cells by mitogen-activated protein kinases.

Production of chemokines in dendritic cells (DCs) may be crucial in modulating immune responses generated through Toll-like receptor (TLR)-mediated recognition of microbial products. We evaluated chemokine production in DCs induced by TLR agonists and investigated the role of signaling pathways. DCs were generated from mouse bone marrow cells cultured with Fms-like tyrosine kinase-3 ligand and stimulated with a wide array of individual TLR agonists or simultaneously with pairs of combinations. Production of monocyte chemoattractant protein-1 (MCP-1/CCL2), macrophage inflammatory protein-1 (MIP-1/CCL3) and regulated on activation, normal T cell expressed and secreted (RANTES/CCL5), were determined in cell culture supernatants by ELISA or cytokine cytometric bead array. Pharmacological inhibitors of p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), nuclear factor-kappaB (NF-kB) and phosphatidylinositol 3-kinase (PI3K), were used to investigate the role of signaling pathways. TLR agonists induced significantly elevated MCP-1, RANTES, and MIP-1. Production of RANTES and MIP-1 was particularly prominent after stimulation of DCs with TLR3 (Poly(I:C)), and TLR7/8 (R848) or TLR9 (CpG ODN) agonists, respectively. However, down-modulation of chemokine production was observed in simultaneously TLR-stimulated DCs. A positive role was identified for NF-kB, PI3K and ERK, whereas JNK had a negative regulatory effect on chemokine production in DCs. Positive and negative regulatory roles for the p38 MAPK pathway were observed. Thus, chemokine levels differed and most notably there was down-modulation of chemokines in DCs stimulated with combined TLR agonists. Furthermore, analysis of signaling pathways revealed a role for MAPKs in positive and negative regulation of chemokine production in DCs. The chemokine response of DCs induced by TLR agonists appears complex and could have important implications for vaccine design.

Advances in the design and delivery of peptide subunit vaccines with a focus on toll-like receptor agonists.

Considerable success has been made with many peptide antigen formulations, and peptide-based vaccines are emerging as the next generation of prophylactic and remedial immunotherapy. However, finding an optimal platform balancing all of the requirements for an effective, specific and safe immune response remains a major challenge for many infectious and chronic diseases. This review outlines how peptide immunogenicity is influenced by the way in which peptides are presented to the immune system, underscoring the need for multifunctional delivery systems that couple antigen and adjuvant into a single construct. Particular attention is given to the ability of Toll-like receptor agonists to act as adjuvants. A survey of recent approaches to developing peptide antigen delivery systems is given, many of which incorporate Toll-like receptor agonists into the design.

Oral vaccine delivery--new strategies and technologies.

Although most commercial vaccines are delivered by injection, there is an increasing interest in needle-free vaccine delivery for reasons including the ability to elicit immune responses at mucosal surfaces, ease of administration, and the ability to administer vaccines without the need for trained medical professionals. This review summarizes strategies and technologies that are being used to improve oral vaccine absorption. Peptides and proteins, which comprise important vaccine components, exhibit unfavorable physicochemical properties including degradation in the gastrointestinal tract, and poor transport across the intestinal wall, which hinder oral vaccine development. Approaches to overcome these obstacles aim to provide new vaccines and delivery systems that are capable of eliciting protective immune responses, and are making an impact on current vaccine development.

B- and T-cell responses in group a streptococcus M-protein- or Peptide-induced experimental carditis.

The etiology of rheumatic fever and rheumatic heart disease (RF/RHD) is believed to be autoimmune, involving immune responses initiated between streptococcal and host tissue proteins through a molecular mimicry mechanism(s). We sought to investigate the humoral and cellular responses elicited in a Lewis rat model of group A streptococcus M-protein- or peptide-induced experimental valvulitis/carditis, a recently developed animal model which may, in part, represent human rheumatic carditis. Recombinant streptococcal M5 protein elicited opsonic antibodies in Lewis rats, and anti-M5 antisera recognized epitopes within the B- and C-repeat regions of M5. One peptide from the streptococcal M5 protein B-repeat region (M5-B.6, amino acids 161 to 180) induced lymphocytes that responded to both recombinant M5 and cardiac myosin. Rats immunized with streptococcal M5 protein developed valvular lesions, distinguished by infiltration of CD3(+), CD4(+), and CD68(+) cells into valve tissue, consistent with human studies that suggest that RF/RHD are mediated by inflammatory CD4(+) T cells and CD68(+) macrophages. The current study provides additional information that supports the use of the rat autoimmune valvulitis model for investigating RF/RHD.

Expression of maturation markers on murine dendritic cells in response to group A streptococcal lipopeptide vaccines.

Bone marrow (BM)-FMS-like tyrosine kinase 3 (Flt3) ligand-murine dendritic cells (DC) in response to group A streptococcal (GAS) lipopeptide vaccines containing an analogue of a Toll-like receptor (TLR) 2 agonist showed significant up-regulation in expression of DC maturation markers CD40 and CD80 when compared to unstimulated controls. There were significant increases in MHC class II, CD40, CD80 and CD86 expression on classical DC and plasmacytoid DC after in vivo administration or in vitro stimulation of BM-granulocyte macrophage colony stimulating factor (GMCSF)-DC with lipopolysaccharide but not lipopeptide GAS vaccines. Our results indicate that an LCP-GAS vaccine induced phenotypic maturation of BM-Flt3-DC but not BM-GMCSF-DC.

Development of a liposaccharide-based delivery system and its application to the design of group A streptococcal vaccines.

Group A streptococcus (GAS) is associated with many human diseases, ranging in severity from benign to life-threatening. A promising strategy for developing vaccines against GAS involves the use of carbohydrates as carriers for peptide antigens. This study describes the optimized synthesis of d-glucose and d-galactose derived carriers, bearing an adipate linker and four tert-butoxycarbonyl protected aminopropyl groups. Prophylactic GAS vaccine candidates were synthesized by conjugating multiple copies of a single GAS M protein derived peptide antigen (either J8 or J14) onto the carbohydrate carriers. These antigens contain peptide sequences, which are highly conserved and offer the potential to prevent infections caused by up to 70% of GAS strains. Lipophilic amino acids were also conjugated to the d-glucose anomeric carbon to produce a self-adjuvanting liposaccharide vaccine. High serum IgG antibody titers against each of the incorporated peptide epitopes were detected following subcutaneous immunization of B10.BR (H-2 (k)) mice with the liposaccharide vaccine candidates.

Toward the development of prophylactic and therapeutic human papillomavirus type-16 lipopeptide vaccines.

Four lipid-core peptide systems were synthesized using stepwise solid-phase peptide synthesis, incorporating a sequence from the human papillomavirus type-16 (HPV-16) E7 protein (E744-62), for the purpose of developing vaccines against HPV-16 associated cervical cancer. d-Mannose was conjugated to the vaccine in order to investigate whether the targeting of dendritic cell mannose receptors would improve vaccine efficacy. The ability of the vaccines to clear or reduce the size of HPV-16 associated tumors was assessed in C57BL/6 (H-2b) mice using the TC-1 HPV-16 tumor model. Overall, significant reductions in the size of TC-1 tumors were observed in the mouse model, with the conjugation of mannose to these vaccines demonstrated to clear or reduce the size of TC-1 tumors to a greater extent than non-mannose-containing vaccines (37 out of 40 versus 21 out of 30 tumors cleared, respectively).

Progress in M-protein-based subunit vaccines to prevent rheumatic fever and rheumatic heart disease.

Infection with the human bacterial pathogen group A Streptococcus (GAS) is estimated to cause over 500,000 deaths per year, the majority of which are related to rheumatic fever (RF) and rheumatic heart disease (RHD). While GAS is an important cause of morbidity and mortality globally, the burden of GAS-associated diseases is greater in less developed countries and in indigenous populations of developed countries. The antiphagocytic bacterial surface M protein is a major candidate antigen in the development of a vaccine to prevent GAS infection and RF/RHD. A major obstacle, however, in the development of an M-protein-based vaccine is the widespread diversity of circulating GAS strains and M protein types. Added to this is the possibility of inducing autoimmunity following vaccination as a result of molecular mimicry between the M protein and host tissue proteins. Research has been aimed at the development of a safe GAS vaccine that is able to induce broad-coverage protective immunity. The development of subunit vaccine approaches targeting the M protein using various vaccine delivery technologies is the focus of this review.

Advances in potential M-protein peptide-based vaccines for preventing rheumatic fever and rheumatic heart disease.

Rheumatic fever (RF) and rheumatic heart disease (RHD) are postinfectious complications of an infection (or repeated infection) with the Gram-positive bacterium, Streptococcus pyogenes (also known as group A streptococcus, GAS). RF and RHD are global problems and affect many indigenous populations of developed countries and many developing countries. However, RF and RHD are only part of a larger spectrum of diseases caused by this organism. The development of a vaccine against GAS has primarily targeted the abundant cell-surface protein called the M-protein. This review focuses on different M-protein-based-subunit vaccine approaches and the different delivery technologies used to administer these vaccine candidates in preclinical studies.

Method for the synthesis of highly pure vaccines using the lipid core peptide system.

Traditional vaccines consisting of whole attenuated microorganisms, killed microorganisms, or microbial components, administered with an adjuvant (e.g. alum), have been proved to be extremely successful. However, to develop new vaccines, or to improve upon current vaccines, new vaccine development techniques are required. Peptide vaccines offer the capacity to administer only the minimal microbial components necessary to elicit appropriate immune responses, minimizing the risk of vaccination associated adverse effects, and focusing the immune response toward important antigens. Peptide vaccines, however, are generally poorly immunogenic, necessitating administration with powerful, and potentially toxic adjuvants. The attachment of lipids to peptide antigens has been demonstrated as a potentially safe method for adjuvanting peptide epitopes. The lipid core peptide (LCP) system, which incorporates a lipidic adjuvant, carrier, and peptide epitopes into a single molecular entity, has been demonstrated to boost immunogenicity of attached peptide epitopes without the need for additional adjuvants. The synthesis of LCP systems normally yields a product that cannot be purified to homogeneity. The current study describes the development of methods for the synthesis of highly pure LCP analogs using native chemical ligation. Because of the highly lipophilic nature of the LCP lipid adjuvant, difficulties (e.g. poor solubility) were experienced with the ligation reactions. The addition of organic solvents to the ligation buffer solubilized lipidic species, but did not result in successful ligation reactions. In comparison, the addition of approximately 1% (w/v) sodium dodecyl sulfate (SDS) proved successful, enabling the synthesis of two highly pure, tri-epitopic Streptococcus pyogenes LCP analogs. Subcutaneous immunization of B10.BR (H-2(k)) mice with one of these vaccines, without the addition of any adjuvant, elicited high levels of systemic IgG antibodies against each of the incorporated peptides.

Synthesis of a highly pure lipid core peptide based self-adjuvanting triepitopic group A streptococcal vaccine, and subsequent immunological evaluation.

We have developed a highly pure, self-adjuvanting, triepitopic Group A Streptococcal vaccine based on the lipid core peptide system, a vaccine delivery system incorporating lipidic adjuvant, carrier, and peptide epitopes into a single molecular entity. Vaccine synthesis was performed using native chemical ligation. Due to the attachment of a highly lipophilic adjuvant, addition of 1% (w/v) sodium dodecyl sulfate was necessary to enhance peptide solubility in order to enable ligation. The vaccine was synthesized in three steps to yield a highly pure product (97.7% purity) with an excellent overall yield. Subcutaneous immunization of B10.BR (H-2(k)) mice with the synthesized vaccine, with or without the addition of complete Freund's adjuvant, elicited high serum IgG antibody titers against each of the incorporated peptide epitopes.

Bactericidal activity of M protein conserved region antibodies against group A streptococcal isolates from the Northern Thai population.

BACKGROUND: Most group A streptococcal (GAS) vaccine strategies have focused on the surface M protein, a major virulence factor of GAS. The amino-terminus of the M protein elicits antibodies, that are both opsonic and protective, but which are type specific. J14, a chimeric peptide that contains 14 amino acids from the M protein conserved C-region at the carboxy-terminus, offers the possibility of a vaccine which will elicit protective opsonic antibodies against multiple different GAS strains. In this study, we searched for J14 and J14-like sequences and the number of their repeats in the C-region of the M protein from GAS strains isolated from the Northern Thai population. Then, we examined the bactericidal activity of J14, J14.1, J14-R1 and J14-R2 antisera against multiple Thai GAS strains. RESULTS: The emm genes of GAS isolates were sequenced and grouped as 14 different J14-types. The most diversity of J14-types was found in the C1-repeat. The J14.1 type was the major sequence in the C2 and C3-repeats. We have shown that antisera raised against the M protein conserved C-repeat region peptides, J14, J14.1, J14-R1 and J14-R2, commonly found in GAS isolates from the Northern Thai population, are able to kill GAS of multiple different emm types derived from an endemic area. The mean percent of bactericidal activities for all J14 and J14-like peptide antisera against GAS isolates were more than 70%. The mean percent of bactericidal activity was highest for J14 antisera followed by J14-R2, J14.1 and J14-R1 antisera. CONCLUSION: Our study demonstrated that antisera raised against the M protein conserved C-repeat region are able to kill multiple different strains of GAS isolated from the Northern Thai population. Therefore, the four conserved "J14" peptides have the potential to be used as GAS vaccine candidates to prevent streptococcal infections in an endemic area.