The adjuvant monophosphoryl lipid A increases the function of antigen-presenting cells

Monophosphoryl Lipid A-Rhamnose Conjugates as a New Class of Vaccine Adjuvants

Adjuvant is an integral part of all vaccine formulations but only a few adjuvants with limited efficacies or application scopes are available. Thus, developing more robust and diverse adjuvants is necessary. To this end, a new class of adjuvants having α- and β-rhamnose (Rha) attached to the 1- and 6'-positions of monophosphoryl lipid A (MPLA) was designed, synthesized, and immunologically evaluated in mice. The results indicated a synergistic effect of MPLA and Rha, two immunostimulators that function via interacting with toll-like receptor 4 and recruiting endogenous anti-Rha antibodies, respectively. All the tested MPLA-Rha conjugates exhibited potent adjuvant activities to promote antibody production against both protein and carbohydrate antigens. Overall, MPLA-α-Rha exhibited better activities than MPLA-β-Rha, and 6'-linked conjugates were slightly better than 1-linked ones. Particularly, MPLA-1-α-Rha and MPLA-6'-α-Rha were the most effective adjuvants in promoting IgG antibody responses against protein antigen keyhole limpet hemocyanin and carbohydrate antigen sTn, respectively.

Controlled production of lipopolysaccharides increases immune activation in Salmonella treatments of cancer

Immunotherapies have revolutionized cancer treatment. These treatments rely on immune cell activation in tumours, which limits the number of patients that respond. Inflammatory molecules, like lipopolysaccharides (LPS), can activate innate immune cells, which convert tumour microenvironments from cold to hot, and increase therapeutic efficacy. However, systemic delivery of lipopolysaccharides (LPS) can induce cytokine storm. In this work, we developed immune-controlling Salmonella (ICS) that only produce LPS in tumours after colonization and systemic clearance. We tuned the expression of msbB, which controls production of immunogenic LPS, by optimizing its ribosomal binding sites and protein degradation tags. This genetic system induced a controllable inflammatory response and increased dendritic cell cross-presentation in vitro. The strong off state did not induce TNFα production and prevented adverse events when injected into mice. The accumulation of ICS in tumours after intravenous injection focused immune responses specifically to tumours. Tumour-specific expression of msbB increased infiltration of immune cells, activated monocytes and neutrophils, increased tumour levels of IL-6, and activated CD8 T cells in draining lymph nodes. These immune responses reduced tumour growth and increased mouse survival. By increasing the efficacy of bacterial anti-cancer therapy, localized production of LPS could provide increased options to patients with immune-resistant cancers.

Advances in Vaccine Adjuvants: Nanomaterials and Small Molecules

Adjuvants have been extensively and essentially formulated in subunits and certain inactivated vaccines for enhancing and prolonging protective immunity against infections and diseases. According to the types of infectious diseases and the required immunity, adjuvants with various acting mechanisms have been designed and applied in human vaccines. In this chapter, we introduce the advances in vaccine adjuvants based on nanomaterials and small molecules. By reviewing the immune mechanisms induced by adjuvants with different characteristics, we aim to establish structure-activity relationships between the physicochemical properties of adjuvants and their immunostimulating capability for the development of adjuvants for more effective preventative and therapeutic vaccines.

Glycovaccinology: The design and engineering of carbohydrate-based vaccine components

Vaccines remain one of the most important pillars in preventative medicine, providing protection against a wide array of diseases by inducing humoral and/or cellular immunity. Of the many possible candidate antigens for subunit vaccine development, carbohydrates are particularly appealing because of their ubiquitous presence on the surface of all living cells, viruses, and parasites as well as their known interactions with both innate and adaptive immune cells. Indeed, several licensed vaccines leverage bacterial cell-surface carbohydrates as antigens for inducing antigen-specific plasma cells secreting protective antibodies and the development of memory T and B cells. Carbohydrates have also garnered attention in other aspects of vaccine development, for example, as adjuvants that enhance the immune response by either activating innate immune responses or targeting specific immune cells. Additionally, carbohydrates can function as immunomodulators that dampen undesired humoral immune responses to entire protein antigens or specific, conserved regions on antigenic proteins. In this review, we highlight how the interplay between carbohydrates and the adaptive and innate arms of the immune response is guiding the development of glycans as vaccine components that act as antigens, adjuvants, and immunomodulators. We also discuss how advances in the field of synthetic glycobiology are enabling the design, engineering, and production of this new generation of carbohydrate-containing vaccine formulations with the potential to prevent infectious diseases, malignancies, and complex immune disorders.

A Glycolipidated-liposomal peptide vaccine confers long-term mucosal protection against Streptococcus pyogenes via IL-17, macrophages and neutrophils

Mucosally active subunit vaccines are an unmet clinical need due to lack of licensed immunostimulants suitable for vaccine antigens. Here, we show that intranasal administration of liposomes incorporating: the Streptococcus pyogenes peptide antigen, J8; diphtheria toxoid as a source of T cell help; and the immunostimulatory glycolipid, 3D(6-acyl) PHAD (PHAD), is able to induce long-lived humoral and cellular immunity. Mice genetically deficient in either mucosal antibodies or total antibodies are protected against S. pyogenes respiratory tract infection. Utilizing IL-17-deficient mice or depleting cellular subsets using antibodies, shows that the cellular responses encompassing, CD4+ T cells, IL-17, macrophages and neutrophils have important functions in vaccine-mediated mucosal immunity. Overall, these data demonstrate the utility of a mucosal vaccine platform to deliver multi-pronged protective responses against a highly virulent pathogen.

Applications and clinical trial landscape using Toll-like receptor agonists to reduce the toll of cancer

Toll-like receptors (TLRs), which serve as a bridge between innate and adaptive immunity, may be viable treatment targets. TLRs are the first line of defense against microbes and activate signaling cascades that induce immune and inflammatory responses. Patients with "hot" versus "cold" tumors may respond more favorably to immune checkpoint inhibition, and through their downstream effects, TLR agonists have the potential to convert "cold tumors" into "hot tumors" making TLRs in combination with immune checkpoint inhibitors, potential targets for cancer therapies. Imiquimod is a topical TLR7 agonist, approved by the FDA for antiviral and skin cancer treatments. Other TLR adjuvants are used in several vaccines including Nu Thrax, Heplisav, T-VEC, and Cervarix. Many TLR agonists are currently in development as both monotherapy and in combination with immune checkpoint inhibitors. In this review, we describe the TLR agonists that are being evaluated clinically as new therapies for solid tumors.

New-age vaccine adjuvants, their development, and future perspective

In the present scenario, immunization is of utmost importance as it keeps us safe and protects us from infectious agents. Despite the great success in the field of vaccinology, there is a need to not only develop safe and ideal vaccines to fight deadly infections but also improve the quality of existing vaccines in terms of partial or inconsistent protection. Generally, subunit vaccines are known to be safe in nature, but they are mostly found to be incapable of generating the optimum immune response. Hence, there is a great possibility of improving the potential of a vaccine in formulation with novel adjuvants, which can effectively impart superior immunity. The vaccine(s) in formulation with novel adjuvants may also be helpful in fighting pathogens of high antigenic diversity. However, due to the limitations of safety and toxicity, very few human-compatible adjuvants have been approved. In this review, we mainly focus on the need for new and improved vaccines; the definition of and the need for adjuvants; the characteristics and mechanisms of human-compatible adjuvants; the current status of vaccine adjuvants, mucosal vaccine adjuvants, and adjuvants in clinical development; and future directions.

Construction and expression of Mycobacterium tuberculosis fusion protein AR2 and its immunogenicity in combination with various adjuvants to form vaccine

Tuberculosis (TB) is recognized as a highly infectious disease worldwide, and Bacille Calmette-Guerin (BCG) remains the only TB vaccine licensed for clinical use. As there is little evidence that BCG is effective in adults, there is an urgent need for a safe and effective vaccine to control TB in adults. In this study, we tested the immunomodulatory efficiency of the fusion protein AR2. whole blood IFN-γ release assay (WBIA) was used to detect antigen specificity. The immunogenicity of the vaccine was tested in C57BL/6 mice, and confirmed by enzyme-linked immunosorbent assay (ELISA), flow cytometry, and qRT-PCR. The fusion protein AR2 was successfully constructed and expressed. The level of IFN-γ in the peripheral blood of subjects stimulated by AR2 was significantly higher than in those induced by all subcomponent proteins. AR2-specific IgG and the Th1 cytokines IFN-γ, TNF-α, and iNOS were significantly increased in the group treated with the fusion protein and compound adjuvant (AR2+DMC). Likewise, the number of IFN-γ⁺ CD4⁺, IFN-γ⁺CD8⁺, and IL-4⁺ CD8⁺ T lymphocytes increased significantly. The combination of the fusion protein and the compound adjuvant (AR2+DMC) may be a suitable candidate for an enhanced TB vaccine. This study provides theoretical and experimental support for future research to enhance the effectiveness of TB vaccines and provides an experimental basis for evaluating the influence of different adjuvants on vaccine efficacy.

First-in-human assessment of safety and immunogenicity of low and high doses of Plasmodium falciparum malaria protein 013 (FMP013) administered intramuscularly with ALFQ adjuvant in healthy malaria-naïve adults

The global burden of malaria remains substantial. Circumsporozoite protein (CSP) has been demonstrated to be an effective target antigen, however, improvements that offer more efficacious and more durable protection are still needed. In support of research and development of next-generation malaria vaccines, Walter Reed Army Institute of Research (WRAIR) has developed a CSP-based antigen (FMP013) and a novel adjuvant ALFQ (Army Liposome Formulation containing QS-21). We present a single center, open-label, dose-escalation Phase 1 clinical trial to evaluate the safety and immunogenicity of the FMP013/ALFQ malaria vaccine candidate. In this first-in-human evaluation of both the antigen and adjuvant, we enrolled ten subjects; five received 20 μg FMP013 / 0.5 mL ALFQ (Low dose group), and five received 40 μg FMP013 / 1.0 mL ALFQ (High dose group) on study days 1, 29, and 57. Adverse events and immune responses were assessed during the study period. The clinical safety profile was acceptable and there were no serious adverse events. Both groups exhibited robust humoral and cellular immunological responses, and compared favorably with historical responses reported for RTS,S/AS01. Based on a lower reactogenicity profile, the 20 μg FMP013 / 0.5 mL ALFQ (Low dose) was selected for follow-on efficacy testing by controlled human malaria infection (CHMI) with a separate cohort. Trial Registration:Clinicaltrials.gov Identifier NCT04268420 (Registered February 13, 2020).

Expression of the Antimicrobial Peptide Piscidin 1 and Neuropeptides in Fish Gill and Skin: A Potential Participation in Neuro-Immune Interaction

Antimicrobial peptides (AMPs) are found widespread in nature and possess antimicrobial and immunomodulatory activities. Due to their multifunctional properties, these peptides are a focus of growing body of interest and have been characterized in several fish species. Due to their similarities in amino-acid composition and amphipathic design, it has been suggested that neuropeptides may be directly involved in the innate immune response against pathogen intruders. In this review, we report the molecular characterization of the fish-specific AMP piscidin1, the production of an antibody raised against this peptide and the immunohistochemical identification of this peptide and enkephalins in the neuroepithelial cells (NECs) in the gill of several teleost fish species living in different habitats. In spite of the abundant literature on Piscidin1, the biological role of this peptide in fish visceral organs remains poorly explored, as well as the role of the neuropeptides in neuroimmune interaction in fish. The NECs, by their role as sensors of hypoxia changes in the external environments, in combination with their endocrine nature and secretion of immunomodulatory substances would influence various types of immune cells that contain piscidin, such as mast cells and eosinophils, both showing interaction with the nervous system. The discovery of piscidins in the gill and skin, their diversity and their role in the regulation of immune response will lead to better selection of these immunomodulatory molecules as drug targets to retain antimicrobial barrier function and for aquaculture therapy in the future.

Vaccination of mice with hybrid protein containing Exotoxin S and PcrV with adjuvants alum and MPL protects Pseudomonas aeruginosa infections

Pseudomonas aeruginosa as a common pathogen causing urinary tract infections (UTIs) has been resistant to different antibiotics and developing an effective vaccine can be an alternative strategy. In the present study, the immunogenicity and protection efficacy of formulations composed of a hybrid protein composed of P. aeruginosa V-antigen (PcrV) and exoenzyme S (ExoS) with alum and MPL were evaluated. The hybrid protein could increase the specific systemic and mucosal immune responses, as well as cellular responses as compared with control groups. Combining of alum or MPL adjuvant with the hybrid protein significantly improved the levels of IgG1, serum IgA, mucosal IgG, and IL-17 as compared to the ExoS.PcrV alone. After bladder challenge with a P. aeruginosa strain, the bacterial loads of bladder and kidneys were significantly decreased in mice received ExoS.PcrV admixed with alum and ExoS.PcrV admixed with MPL than controls. The present study indicated that immunization of mice with a hybrid protein composed of ExoS and PcrV could induce multifactorial immune responses and opsonize the bacteria and decrease the viable bacterial cells. Because P. aeruginosa have caused therapeutic challenges worldwide, our study proposed ExoS.PcrV + alum and ExoS.PcrV + MPL as promising candidates for the prevention of infections caused by P. aeruginosa.

Monophosphoryl lipid A directly regulates Th1 cytokine production in human CD4+ T-cells through Toll-like receptor 2 and 4

BACKGROUND

The monophosphoryl lipid A (MPLA) is a detoxified LPS derivative and an emerging safe immune adjuvant in human vaccine development. The adjuvant MPLA promotes antigen-presenting cell (APC) function and preferentially induces a Th1 response following vaccination. However, the mechanism by which the MPLA detoxicates and exerts its adjuvants effect on T-cell, particualrly the Th1 response is unknown.

AIMS

We assessed the direct effects of MPLA on murine and human CD4+ T-cell proliferation and the profile of cytokine production ex vivo.

RESULTS

We report that CD4+ T-cells only express functional TLR2 and TLR4 when activated by TCR stimulation, in particularly in the presence of IFNα. The activated T cells thereafter can respond directly to MPLA. MPLA does not affect T-cell proliferation in human T cells, but can induce a balanced Th1 cytokine profile in CD4+ T-cells by reducing the production of Th1 cytokines and enhancing the production of the regulatory cytokine IL-10. The MPLA-mediated regulatory effect on activated CD4+ T-cells is TLR2 and TLR4 dependent and can be abolished by the lipid A blocker polymyxin B.

CONCLUSION

These data provide evidence, at least in part, for the safe induction of an appropriate level of Th1 response by adjuvant MPLA in human vaccine development.

Protective efficacy of Hla-MntC-SACOL0723 fusion protein adjuvanted in alum and MPL against Staphylococcus aureus sepsis infection in mice

To develop a suitable and effective vaccine against Staphylococcus aureus (S. aureus), we selected the Hla-MntC-SACOL0723 (HMS) recombinant protein with two different formulations of alum and Monophosphoryl lipid A (MPL) adjuvants. In this study, we aimed to evaluate the potentials of alum and MPL adjuvants in stimulating the immune response of HMS vaccine candidate against S. aureus. To evaluate the type of induced immune response, anti-HMS total IgG, IgG1, IgG2a, and IFN-γ, IL-2, IL-4, and IL-17 cytokines were determined after vaccination of mice with HMS-alum, HMS-MPL candidates. Mice were challenged with Methicillin-resistant Staphylococcus aureus (MRSA) was isolated from pressure sores and evaluated for bacterial load in the kidney homogenates and survival rate. It was observed that total IgG and isotypes (IgG1 and IgG2a), IL-4, and IL-17 were significantly increased in the group that received HMS-alum vaccine compared with the group that received HMS-MPL formulation. On the other hand, the levels of IFN-γ and IL-2 cytokines in the group that received HMS-MPL were higher than the group that received HMS-alum formulation. Bacterial load in the mice who received HMS protein formulated with alum adjuvant was reduced more than the mice who received HMS protein formulated with MPL adjuvant. Histopathological analysis showed more pathological changes in kidney tissues of the group received of HMS-MPL compared with the HMS-alum formulation. The survival rate was equal in both groups of immunized with HMS-alum and HMS-MPL formulations. Finally, it could be concluded that both adjuvants of alum and MPL are suitable immune response enhancers to HMS vaccine candidate.

Innate cell microenvironments in lymph nodes shape the generation of T cell responses during type I inflammation

Microanatomical organization of innate immune cells within lymph nodes (LNs) is critical for the generation of adaptive responses. In particular, steady-state LN-resident dendritic cells (Res cDCs) are strategically localized to intercept lymph-draining antigens. Whether myeloid cell organization changes during inflammation and how that might affect the generation of immune responses are unknown. Here, we report that during type I, but not type II, inflammation after adjuvant immunization or viral infection, antigen-presenting Res cDCs undergo CCR7-dependent intranodal repositioning from the LN periphery into the T cell zone (TZ) to elicit T cell priming. Concurrently, inflammatory monocytes infiltrate the LNs via local blood vessels, enter the TZ, and cooperate with Res cDCs by providing polarizing cytokines to optimize T cell effector differentiation. Monocyte infiltration is nonuniform across LNs, generating distinct microenvironments with varied local innate cell composition. These spatial microdomains are associated with divergent early T cell effector programming, indicating that innate microenvironments within LNs play a critical role in regulating the quality and heterogeneity of T cell responses. Together, our findings reveal that dynamic modulation of innate cell microenvironments during type I inflammation leads to optimized generation of adaptive immune responses to vaccines and infections.

Natural and synthetic carbohydrate-based vaccine adjuvants and their mechanisms of action

Modern subunit vaccines based on homogeneous antigens offer more precise targeting and improved safety compared with traditional whole-pathogen vaccines. However, they are also less immunogenic and require an adjuvant to increase the immunogenicity of the antigen and potentiate the immune response. Unfortunately, few adjuvants have sufficient potency and low enough toxicity for clinical use, highlighting the urgent need for new, potent and safe adjuvants. Notably, a number of natural and synthetic carbohydrate structures have been used as adjuvants in clinical trials, and two have recently been approved in human vaccines. However, naturally derived carbohydrate adjuvants are heterogeneous, difficult to obtain and, in some cases, unstable. In addition, their molecular mechanisms of action are generally not fully understood, partly owing to the lack of tools to elucidate their immune-potentiating effects, thus hampering the rational development of optimized adjuvants. To address these challenges, modification of the natural product structure using synthetic chemistry emerges as an attractive approach to develop well-defined, improved carbohydrate-containing adjuvants and chemical probes for mechanistic investigation. This Review describes selected examples of natural and synthetic carbohydrate-based adjuvants and their application in synthetic self-adjuvanting vaccines, while also discussing current understanding of their molecular mechanisms of action.

Immunogenicity of Antigen Adjuvanted with AS04 and Its Deposition in the Upper Respiratory Tract after Intranasal Administration

Adjuvant system 04 (AS04) is in injectable human vaccines. AS04 contains two known adjuvants, 3-O-desacyl-4'-monophosphoryl lipid A (MPL) and insoluble aluminum salts. Data from previous studies showed that both MPL and insoluble aluminum salts have nasal mucosal vaccine adjuvant activity. The present study was designed to test the feasibility of using AS04 as an adjuvant to help nasally administered antigens to induce specific mucosal and systemic immunity as well as to evaluate the deposition of antigens in the upper respiratory tract when adjuvanted with AS04. Alhydrogel, an aluminum (oxy)hydroxide suspension, was mixed with MPL to form AS04, which was then mixed with ovalbumin (OVA) or 3× M2e-HA2, a synthetic influenza virus hemagglutinin fusion protein, as an antigen to prepare OVA/AS04 and 3× M2e-HA2/AS04 vaccines, respectively. In mice, AS04 enabled antigens, when given intranasally, to induce specific IgA response in nasal and lung mucosal secretions as well as specific IgG response in the serum samples of the immunized mice, whereas subcutaneous injection of the same vaccine induced specific antibody responses only in the serum samples but not in the mucosal secretions. Splenocytes isolated from mice intranasally immunized with the OVA/AS04 also proliferated and released cytokines (i.e., IL-4 and IFN-γ) after in vitro stimulation with the antigen. In the immunogenicity test, intranasal OVA/AS04 was not more effective than intranasal OVA/MPL at the dosing regimens tested. However, when compared to OVA/MPL, OVA/AS04 showed a different atomized droplet size distribution and more importantly a more favorable OVA deposition profile when atomized into a nasal cast that was 3-D printed based on the computer tomography scan of the nose of a child. It is concluded that AS04 has mucosal adjuvant activity when given intranasally. In addition, there is a reason to be optimistic about using AS04 as an adjuvant to target an antigen of interest to the right region of the nasal cavity in humans for immune response induction.

Nanotechnology-Based Vaccines for Allergen-Specific Immunotherapy: Potentials and Challenges of Conventional and Novel Adjuvants under Research

The increasing prevalence of allergic diseases demands efficient therapeutic strategies for their mitigation. Allergen-specific immunotherapy (AIT) is the only causal rather than symptomatic treatment method available for allergy. Currently, AIT is being administered using immune response modifiers or adjuvants. Adjuvants aid in the induction of a vigorous and long-lasting immune response, thereby improving the efficiency of AIT. The successful development of a novel adjuvant requires a thorough understanding of the conventional and novel adjuvants under development. Thus, this review discusses the potentials and challenges of these adjuvants and their mechanism of action. Vaccine development based on nanoparticles is a promising strategy for AIT, due to their inherent physicochemical properties, along with their ease of production and ability to stimulate innate immunity. Although nanoparticles have provided promising results as an adjuvant for AIT in in vivo studies, a deeper insight into the interaction of nanoparticle-allergen complexes with the immune system is necessary. This review focuses on the methods of harnessing the adjuvant effect of nanoparticles by detailing the molecular mechanisms underlying the immune response, which includes allergen uptake, processing, presentation, and induction of T cell differentiation.

Dendritic cell subsets in T cell programming: location dictates function

Dendritic cells (DCs) can be viewed as translators between innate and adaptive immunity. They integrate signals derived from tissue infection or damage and present processed antigen from these sites to naive T cells in secondary lymphoid organs while also providing multiple soluble and surface-bound signals that help to guide T cell differentiation. DC-mediated tailoring of the appropriate T cell programme ensures a proper cascade of immune responses that adequately targets the insult. Recent advances in our understanding of the different types of DC subsets along with the cellular organization and orchestration of DC and lymphocyte positioning in secondary lymphoid organs over time has led to a clearer understanding of how the nature of the T cell response is shaped. This Review discusses how geographical organization and ordered sequences of cellular interactions in lymph nodes and the spleen regulate immunity.

Immunostimulants in respiratory diseases: focus on Pidotimod

Usefulness of Pidotimod and its role as immunostimulant, has been discussed, we know, for several decades. Nevertheless, there is still much to know. Understanding its mechanisms and its potential usefulness in airway infections and its prevention, asthma both Th2 and non Th2 type, bronchiectasis, as adjuvant in vaccination and in allergen immunotherapy still remains to clearly unveil. The aim of this paper was to provide a useful updated review of the role of the main available immunostimulants, giving particular focus on Pidotimod use and its potentials utility in respiratory diseases. Pidotimod showed its usefulness in reducing need for antibiotics in airway infections, increasing the level of immunoglobulins (IgA, IgM, IgG) and T-lymphocyte subsets (CD3+, CD4+) endowed with immunomodulatory activity that affect both innate and adaptive immune responses. Higher expression of TLR2 and of HLA-DR molecules, induction of dendritic cell maturation and release of pro-inflammatory molecules, stimulation of T lymphocyte proliferation and differentiation toward a Th1 phenotype, as well as an increase of the phagocytosis have been demonstrated to be associated with Pidotimod in in vitro studies. All these activities are potentially useful for several respiratory conditions such as asthma, COPD, and recurrent respiratory tract infections.

Combining Monophosphoryl Lipid A (MPL), CpG Oligodeoxynucleotide (ODN), and QS-21 Adjuvants Induces Strong and Persistent Functional Antibodies and T Cell Responses against Cell-Traversal Protein for Ookinetes and Sporozoites (CelTOS) of Plasmodium falciparum in BALB/c Mice

Plasmodium falciparum cell-traversal protein for ookinetes and sporozoites (PfCelTOS) is an advanced vaccine candidate that has a crucial role in the traversal of the malaria parasite in both mosquito and mammalian hosts. As recombinant purified proteins are normally poor immunogens, they require to be admixed with an adjuvant(s); therefore, the objective of the present study was to evaluate the capacity of different vaccine adjuvants, monophosphoryl lipid A (MPL), CpG, and Quillaja saponaria Molina fraction 21 (QS-21), alone or in combination (MCQ [MPL/CpG/QS-21]), to enhance the immunogenicity of Escherichia coli-expressed PfCelTOS in BALB/c mice. This goal was achieved by the assessment of anti-PfCelTOS IgG antibodies (level, titer, IgG isotype profile, avidity, and persistence) and extracellular Th1 cytokines using an enzyme-linked immunosorbent assay (ELISA) on postimmunized BALB/c mouse sera and PfCelTOS-stimulated splenocytes, respectively. Also, an assessment of the transmission-reducing activity (TRA) of anti-PfCelTOS obtained from different vaccine groups was carried out in female Anopheles stephensi mosquitoes by using a standard membrane feeding assay (SMFA). In comparison to PfCelTOS alone, administration of PfCelTOS with three distinct potent Th1 adjuvants in vaccine mouse groups showed enhancement and improvement of PfCelTOS immunogenicity that generated more bias toward a Th1 response with significantly enhanced titers and avidity of the anti-PfCelTOS responses that could impair ookinete development in A. stephensi However, immunization of mice with PfCelTOS with MCQ mixture adjuvants resulted in the highest levels of induction of antibody titers, avidity, and inhibitory antibodies in oocyst development (88%/26.7% reductions in intensity/prevalence) in A. stephensi It could be suggested that adjuvant combinations with different mechanisms stimulate better functional antibody responses than adjuvants individually against challenging diseases such as malaria.

Compartmentalization of dendritic cell and T-cell interactions in the lymph node: Anatomy of T-cell fate decisions

Upon receiving cognate and co-stimulatory priming signals from antigen (Ag)-presenting dendritic cells (DCs) in secondary lymphoid tissues, naïve CD4+ T cells differentiate into distinct effector and memory populations. These alternate cell fate decisions, which ultimately control the T-cell functional attributes, are dictated by programming signals provided by Ag-bearing DCs and by other cells that are present in the microenvironment in which T-cell priming occurs. We know that DCs can be subdivided into multiple populations and that the various DC subsets exhibit differential capacities to initiate development of the different CD4+ T-helper populations. What is less well understood is why different subanatomic regions of secondary lymphoid tissues are colonized by distinct populations of Ag-presenting DCs and how the location of these DCs influences the type of T-cell response that will be generated. Here we review how chemokine receptors and their ligands, which position allergen and nematode-activated DCs within different microdomains of secondary lymphoid tissues, contribute to the establishment of IL-4 committed follicular helper T and type 2 helper cell responses.

IL-33 enhances the kinetics and quality of the antibody response to a DNA and protein-based HIV-1 Env vaccine

Induction of a sustained and broad antibody (Ab) response is a major goal in developing a protective HIV-1 vaccine. DNA priming alone shows reduced levels of immunogenicity; however, when combined with protein boosting is an attractive vaccination strategy for induction of humoral responses. Using the VC10014 DNA and protein-based vaccine consisting of HIV-1 envelope (Env) gp160 plasmids and trimeric gp140 proteins derived from an HIV-1 clade B infected subject who developed broadly neutralizing serum Abs, and which has been previously demonstrated to induce Tier 2 heterologous neutralizing Abs in rhesus macaques, we evaluated whether MPLA and IL-33 when administered during the DNA priming phase enhances the humoral response in mice. The addition of IL-33 during the gp160 DNA priming phase resulted in high titer gp120-specific plasma IgG after the first immunization. The IL-33 treated mice had higher plasma IgG Ab avidity, breadth, and durability after DNA and protein co-immunization with alum adjuvant as compared to MPLA and alum only treated mice. IL-33 was also associated with a significant IgM Env-specific response and expansion of peritoneal and splenic B-1b B cells. These results indicate that DNA priming in the presence of exogenous IL-33 qualitatively alters the HIV-1 Env-specific humoral response, improving the kinetics and breadth of potentially protective Ab.

Preparation of nanoliposomes linked to HER2/neu-derived (P5) peptide containing MPL adjuvant as vaccine against breast cancer

The study was aimed at evaluating antitumor and immunomodulatory effects of liposomal vaccine composed of P5 human epidermal growth factor receptor 2 (HER2)/neu-derived peptide coupled to the surface of high-temperature nanoliposomes containing distearoylphosphocholine:distearoylphosphoglycerol:Chol:dioleoylphosphatidylethanolamine (DOPE) comprising monophosphoryl lipid A (MPL) adjuvant in HER2/neu overexpressing the breast cancer model. BALB/c mice bearing TUBO carcinoma were subcutaneously immunized with formulations containing 10 µg P5 peptide and 25 µg MPL three times with 2-week intervals. To determine immuno responses in immunized mice, the amount of released interferon-γ and IL-4 were measured by the enzyme-linked immunospot method and the flow cytometric analysis on the isolated splenocytes. The results demonstrated that tumor-bearing mice immunized with Lip/DOPE/MPL/P5 formulation had the most released interferon-γ and the highest cytotoxic T lymphocyte responses that led to the lowest tumor size and the longest survival time than those of other formulations. The results achieved by Lip/DOPE/MPL/P5 formulation could make it a suitable candidate to induce effective antigen-specific tumor immunity against breast cancer.

Comparative study of adjuvants for allergen-specific immunotherapy in a murine model

AIM

To compare the immunological and clinical changes induced by allergen-specific immunotherapy (AIT) using different adjuvants.

MATERIALS & METHODS

Olea europaea pollen-sensitized mice were treated with olea plus aluminum hydroxide, calcium phosphate, monophosphoryl lipid A (MPL) or immunostimulatory sequences (ISS).

RESULTS

Aluminum hydroxide seems to drive initially to a Th2-type response. Bacteria-derived adjuvants (MPL and ISS) skew the immune response toward Th1 and Treg pathways. Specific-IgE production was lower after AIT with MPL and ISS. Moreover, IgG2a production significantly increased in ISS-treated mice. Bacteria-derived adjuvants also improved the Th1 cytokine response due to IFN-γ higher secretion. In addition, they improved bronchial hyper-reactivity and lung inflammation.

CONCLUSION

Bacteria-derived adjuvants may enhance the efficacy of AIT.

Modifying Dendritic Cell Activation with Plasmonic Nano Vectors

Dendritic cells (DCs) can acquire, process, and present antigens to T-cells to induce an immune response. For this reason, targeting cancer antigens to DCs in order to cause an immune response against cancer is an emerging area of nanomedicine that has the potential to redefine the way certain cancers are treated. The use of plasmonically active silver-coated gold nanorods (henceforth referred to as plasmonic nano vectors (PNVs)) as potential carriers for DC tumor vaccines has not been presented before. Effective carriers must be able to be phagocytized by DCs, present low toxicity, and induce the maturation of DCs—an early indication of an immune response. When we treated DCs with the PNVs, we found that the cell viability of DCs was unaffected, up to 200 μg/ml. Additionally, the PNVs associated with the DCs as they were phagocytized and they were found to reside within intracellular compartments such as endosomes. More importantly, the PNVs were able to induce expression of surface markers indicative of DC activation and maturation, i.e. CD40, CD86, and MHC class II. These results provide the first evidence that PNVs are promising carriers for DC-based vaccines and warrant further investigating for clinical use.

Distinct oxysterol requirements for positioning naïve and activated dendritic cells in the spleen

Correct positioning of dendritic cells (DCs) is critical for efficient pathogen encounter and antigen presentation. Epstein-Barr virus-induced gene 2 (EBI2) has been identified as a chemoattractant receptor required for naïve CD4⁺DCIR2⁺ DC positioning in response to 7α,25-hydroxycholesterol (7α,25-HC). We now provide evidence that a second EBI2 ligand, 7α,27-HC, is involved in splenic DCIR2⁺ DC positioning and homeostasis. Cyp27a1, the enzyme uniquely required for 7α,27-HC synthesis, is expressed by stromal cells in the region of naïve DC localization. After activation, DCIR2⁺ DCs move into the T cell zone. We find that EBI2 is rapidly up-regulated in DCIR2⁺ DCs under certain activation conditions, and positioning at the B-T zone interface depends on EBI2. Under conditions of type I interferon induction, EBI2 ligand levels are elevated, causing activated DCIR2⁺ DCs to disperse throughout the T zone. Last, we provide evidence that oxysterol metabolism by Batf3-dependent DCs is important for EBI2-dependent positioning of activated DCIR2⁺ DCs. This work indicates that 7α,27-HC functions as a guidance cue in vivo and reveals a multitiered role for EBI2 in DC positioning. Deficiency in this organizing system results in defective CD4⁺ T cell responses.

Rationalized design of a mucosal vaccine protects against Mycobacterium tuberculosis challenge in mice

Pulmonary tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) is a leading cause of global morbidity and mortality. The only licensed TB vaccine, Mycobacterium bovis bacillus Calmette-Guerin (BCG), has variable efficacy in protecting against pulmonary TB. Thus, the development of more effective TB vaccines is critical to control the TB epidemic. Specifically, vaccines delivered through the mucosal route are known to induce Th17 responses and provide superior protection against Mtb infection. However, already tested Th17-inducing mucosal adjuvants, such as heat-labile enterotoxins and cholera toxins, are not considered safe for use in humans. In the current study, we rationally screened adjuvants for their ability to induce Th17-polarizing cytokines in dendritic cells (DCs) and determined whether they could be used in a protective mucosal TB vaccine. Our new studies show that monophosphoryl lipid A (MPL), when used in combination with chitosan, potently induces Th17-polarizing cytokines in DCs and downstream Th17/Th1 mucosal responses and confers significant protection in mice challenged with a clinical Mtb strain. Additionally, we show that both TLRs and the inflammasome pathways are activated in DCs by MPL-chitosan to mediate induction of Th17-polarizing cytokines. Together, our studies put forward the potential of a new, protective mucosal TB vaccine candidate, which incorporates safe adjuvants already approved for use in humans.

Identification of BALB/c Immune Markers Correlated with a Partial Protection to Leishmania infantum after Vaccination with a Rationally Designed Multi-epitope Cysteine Protease A Peptide-Based Nanovaccine

BACKGROUND

Through their increased potential to be engaged and processed by dendritic cells (DCs), nanovaccines consisting of Poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) loaded with both antigenic moieties and adjuvants are attractive candidates for triggering specific defense mechanisms against intracellular pathogens. The aim of the present study was to evaluate the immunogenicity and prophylactic potential of a rationally designed multi-epitope peptide of Leishmania Cysteine Protease A (CPA160-189) co-encapsulated with Monophosphoryl lipid A (MPLA) in PLGA NPs against L. infantum in BALB/c mice and identify immune markers correlated with protective responses.

METHODOLOGY/PRINCIPAL FINDINGS

The DCs phenotypic and functional features exposed to soluble (CPA160-189, CPA160-189+MPLA) or encapsulated in PLGA NPs forms of peptide and adjuvant (PLGA-MPLA, PLGA-CPA160-189, PLGA-CPA160-189+MPLA) was firstly determined using BALB/c bone marrow-derived DCs. The most potent signatures of DCs maturation were obtained with the PLGA-CPA160-189+MPLA NPs. Subcutaneous administration of PLGA-CPA160-189+MPLA NPs in BALB/c mice induced specific anti-CPA160-189 cellular and humoral immune responses characterized by T cells producing high amounts of IL-2, IFN-γ and TNFα and IgG1/IgG2a antibodies. When these mice were challenged with 2x107 stationary phase L. infantum promastigotes, they displayed significant reduced hepatic (48%) and splenic (90%) parasite load at 1 month post-challenge. This protective phenotype was accompanied by a strong spleen lymphoproliferative response and high levels of IL-2, IFN-γ and TNFα versus low IL-4 and IL-10 secretion. Although, at 4 months post-challenge, the reduced parasite load was preserved in the liver (61%), an increase was detected in the spleen (30%), indicating a partial vaccine-induced protection.

CONCLUSIONS/SIGNIFICANCE

This study provide a basis for the development of peptide-based nanovaccines against leishmaniasis, since it reveals that vaccination with well-defined Leishmania MHC-restricted epitopes extracted from various immunogenic proteins co-encapsulated with the proper adjuvant or/and phlebotomine fly saliva multi-epitope peptides into clinically compatible PLGA NPs could be a promising approach for the induction of a strong and sustainable protective immunity.

Role of heterogeneous cell population on modulation of dendritic cell phenotype and activation of CD8 T cells for use in cell-based immunotherapies

Dendritic cell (DC)-based immunotherapies have much utility in their ability to prime antigen-specific adaptive immune responses. However, there does not yet exist a consensus standard to how DCs should be primed. In this study, we aimed to determine the role of heterogeneous co-cultures, composed of both CD11c+ (DCs) and CD11c- cells, in combination with monophosphoryl lipid A (MPLA) stimulation on DC phenotype and function. Upon DC priming in different co-culture ratios, we observed reduced expression of MHCII and CD86 and increased antigen uptake among CD11c+ cells in a CD11c- dependent manner. DCs from all culture conditions were induced to mature by MPLA treatment, as determined by secretion of pro-inflammatory cytokines IL-12 and TNF-α. Antigen-specific stimulation of CD4+ T cells was not modulated by co-culture composition, in terms of proliferation nor levels of IFN-γ. However, the presence of CD11c- cells enhanced cross-presentation to CD8+ T cells compared to purified CD11c+ cells, resulting in increased cell proliferation along with higher IFN-γ production. These findings demonstrate the impact of cell populations present during DC priming, and point to the use of heterogeneous cultures of DCs and innate immune cells to enhance cell-mediated immunity.

Thermostabilization, Expression, Purification, and Crystallization of the Human Serotonin Transporter Bound to S-citalopram

The serotonin transporter is a sodium and chloride-coupled transporter that "pumps" extracellular serotonin into cells. S-citalopram is a drug used to treat depression and anxiety by binding to the serotonin transporter with high-affinity, blocking serotonin reuptake. Here we report an efficient procedure and a set of tools to stabilize, express, purify, and crystallize serotonin transporter-antibody complexes bound to S-citalopram and other antidepressants. Mutations which stabilize the serotonin transporter were identified using an S-citalopram binding assay. Serotonin transporter expressed in baculovirus-transduced HEK293S GnTI^- cells, was reconstituted into proteoliposomes and used to raise high-affinity antibodies. We have developed a strategy to discover antibodies that are useful for structural studies. A straightforward approach for the expression of antibody fragments in Sf9 cells has also been established. Transporter-antibody complexes purified using this procedure are well-behaved and readily crystallize, producing complexes with S-citalopram that diffract X-rays to 3-4 Å resolution. The strategies developed here can be utilized to determine the structure of other challenging membrane proteins.

STAT4 is required for the generation of Th1 and Th2, but not Th17 immune responses during monophosphoryl lipid A adjuvant activity

STAT4 is critical for the production of IFN-γ during the generation of T_h1 immune responses. We investigated the role of STAT4 in mediating T_h1-inducing activity of a vaccine adjuvant monophosphoryl lipid A (MPL-A) using the standard antigen ovalbumin (OVA) in STAT4KO mice. Our results show that splenocytes from STAT4KO mice displayed lower OVA-specific T-cell proliferation and IL-2 production compared with wild-type (WT) mice. Further, IFN-γ production was diminished in STAT4KO-derived splenocytes but the levels of IL-12 and TNF-α were similar compared with WT mice. Interestingly, STAT4 deficiency also led to a decrease in IL-10 and T_h2 cytokines such as IL-4 and IL-13 upon MPL-A immunization, although IL-17 production was similar between WT- and STAT4KO-derived splenocytes. Our observations for defective T_h1 and T_h2 responses in STAT4KO mice were further supported by the low levels of T_h1-associated IgG2a and T_h2-associated IgG1 in the sera of these mice. Taken together, our results show that STAT4 plays a critical role in mediating both T_h1 and T_h2 responses upon immunization with MPL-A. Our study provides a better understanding of how MPL-A mediates T-cell activation which will be critical for future vaccine development.

MPLA-coated hepatitis B virus surface antigen (HBsAg) nanocapsules induce vigorous T cell responses in cord blood derived human T cells

Chronic hepatitis B virus (HBV) infection is the most prevalent serious liver infection in the world. A frequent route of infection represents mother-to-child transmission. Efficient control of HBV replication depends on antigen-specific cellular immune response mediated by dendritic cells (DCs). Aim of the present study was to evaluate optimized adjuvant combinations, efficiently maturing monocyte-derived neonatal and adult dendritic cells (moDCs). In addition, the potential of polymeric HBsAg-nanocapsules (HBsAg-NCs) was investigated regarding up-take by moDCs and the subsequent induction of specific T cell responses in a human co-culture model. Simultaneous stimulation of moDCs with MPLA and IFNγ induced up-regulation of CD80 and HLA-DR along with vigorous secretion of IL-12p70. MPLA-coating of HBsAg-NCs promoted NCs-uptake by moDCs. Finally, MPLA-HBsAg-NCs-pulsed moDCs with IFNγ increased T cell proliferation and induced antigen-specific IFNγ release by T cells. The herein presented vaccine approach provides a rational for neonatal and therapeutic immunization strategies against HBV.

The role of MyD88- and TRIF-dependent signaling in monophosphoryl lipid A-induced expansion and recruitment of innate immunocytes

Treatment with the TLR4 agonist MPLA augments innate resistance to common bacterial pathogens. However, the cellular and molecular mechanisms by which MPLA augments innate immunocyte functions are not well characterized. This study examined the importance of MyD88- and TRIF-dependent signaling for leukocyte mobilization, recruitment, and activation following administration of MPLA. MPLA potently induced MyD88- and TRIF-dependent signaling. A single injection of MPLA caused rapid mobilization and recruitment of neutrophils, a response that was largely mediated by the chemokines CXCL1 and -2 and the hemopoietic factor G-CSF. Rapid neutrophil recruitment and chemokine production were regulated by both pathways although the MyD88-dependent pathway showed some predominance. In further studies, multiple injections of MPLA potently induced mobilization and recruitment of neutrophils and monocytes. Neutrophil recruitment after multiple injections of MPLA was reliant on MyD88-dependent signaling, but effective monocyte recruitment required activation of both pathways. MPLA treatment induced expansion of myeloid progenitors in bone marrow and upregulation of CD11b and shedding of L-selectin by neutrophils, all of which were attenuated in MyD88- and TRIF-deficient mice. These results show that MPLA-induced neutrophil and monocyte recruitment, expansion of bone marrow progenitors and augmentation of neutrophil adhesion molecule expression are regulated by both the MyD88- and TRIF-dependent pathways.

Toll-Like Receptor 4 Agonistic Antibody Promotes Host Defense against Chronic Pseudomonas aeruginosa Lung Infection in Mice

Chronic lower respiratory tract infection with Pseudomonas aeruginosa is difficult to treat due to enhanced antibiotic resistance and decreased efficacy of drug delivery to destroyed lung tissue. To determine the potential for restorative immunomodulation therapies, we evaluated the effect of Toll-like receptor 4 (TLR4) stimulation on the host immune response to Pseudomonas infection in mice. We implanted sterile plastic tubes precoated with P. aeruginosa in the bronchi of mice, administered the TLR4/MD2 agonistic monoclonal antibody UT12 intraperitoneally every week, and subsequently analyzed the numbers of viable bacteria and inflammatory cells and the levels of cytokines. We also performed flow cytometry-based phagocytosis and opsonophagocytic killing assays in vitro using UT12-treated murine peritoneal neutrophils. UT12-treated mice showed significantly enhanced bacterial clearance, increased numbers of Ly6G(+) neutrophils, and increased concentrations of macrophage inflammatory protein 2 (MIP-2) in the lungs (P < 0.05). Depletion of CD4(+) T cells eliminated the ability of the UT12 treatment to improve bacterial clearance and promote neutrophil recruitment and MIP-2 production. Additionally, UT12-pretreated peritoneal neutrophils exhibited increased opsonophagocytic killing activity via activation of the serine protease pathway, specifically neutrophil elastase activity, in a TLR4-dependent manner. These data indicated that UT12 administration significantly augmented the innate immune response against chronic bacterial infection, in part by promoting neutrophil recruitment and bactericidal function.

Enhanced protective immunity of the chimeric vector-based vaccine rAdV-SFV-E2 against classical swine fever in pigs by a Salmonella bacterial ghost adjuvant

Classical swine fever (CSF) is a highly contagious swine disease caused by classical swine fever virus (CSFV). Previously, we demonstrated that rAdV-SFV-E2, an adenovirus-delivered, Semliki Forest virus replicon-vectored marker vaccine against CSF, is able to protect pigs against lethal CSFV challenge. From an economical point of view, it will be beneficial to reduce the minimum effective dose of the vaccine. This study was designed to test the adjuvant effects of Salmonella enteritidis-derived bacterial ghosts (BG) to enhance the protective immunity of rAdV-SFV-E2 in pigs. Groups of 5-week-old pigs (n = 4) were immunized intramuscularly twice with 10⁵ median tissue culture infective doses (TCID₅₀) rAdV-SFV-E2 combined with 10¹⁰ colony forming units (CFU) BG, 10⁶ or 10⁵ TCID₅₀ rAdV-SFV-E2 alone or 10¹⁰ CFU BG alone at an interval of 3 weeks, and challenged with the highly virulent CSFV Shimen strain at 1 week post-booster immunization. The results show that the pigs inoculated with 10⁵ TCID₅₀ rAdV-SFV-E2 plus BG or 10⁶ TCID₅₀ rAdV-SFV-E2 alone were completely protected from lethal CSFV challenge, in contrast with the pigs vaccinated with 10⁵ TCID₅₀ rAdV-SFV-E2 or BG alone, which displayed partial or no protection following virulent challenge. The data indicate that BG are a promising adjuvant to enhance the efficacy of rAdV-SFV-E2 and possibly other vaccines.

A Novel Prime and Boost Regimen of HIV Virus-Like Particles with TLR4 Adjuvant MPLA Induces Th1 Oriented Immune Responses against HIV

HIV virus-like particles (VLPs) present the HIV envelope protein in its native conformation, providing an ideal vaccine antigen. To enhance the immunogenicity of the VLP vaccine, we sought to improve upon two components; the route of administration and the additional adjuvant. Using HIV VLPs, we evaluated sub-cheek as a novel route of vaccine administration when combined with other conventional routes of immunization. Of five combinations of distinct prime and boost sequences, which included sub-cheek, intranasal, and intradermal routes of administration, intranasal prime and sub-cheek boost (IN+SC) resulted in the highest HIV-specific IgG titers among the groups tested. Using the IN+SC regimen we tested the adjuvant VesiVax Conjugatable Adjuvant Lipid Vesicles (CALV) + monophosphoryl lipid A (MPLA) at MPLA concentrations of 0, 7.5, 12.5, and 25 μg/dose in combination with our VLPs. Mice that received 12.5 or 25 μg/dose MPLA had the highest concentrations of Env-specific IgG2c (20.7 and 18.4 μg/ml respectively), which represents a Th1 type of immune response in C57BL/6 mice. This was in sharp contrast to mice which received 0 or 7.5 μg MPLA adjuvant (6.05 and 5.68 μg/ml of IgG2c respectively). In contrast to IgG2c, MPLA had minor effects on Env-specific IgG1; therefore, 12.5 and 25 μg/dose of MPLA induced the optimal IgG1/IgG2c ratio of 1.3. Additionally, the percentage of germinal center B cells increased significantly from 15.4% in the control group to 31.9% in the CALV + 25 μg MPLA group. These mice also had significantly more IL-2 and less IL-4 Env-specific CD8⁺ T cells than controls, correlating with an increased percentage of Env-specific central memory CD4⁺ and CD8⁺ T cells. Our study shows the strong potential of IN+SC as an efficacious route of administration and the effectiveness of VLPs combined with MPLA adjuvant to induce Env specific Th1-oriented HIV-specific immune responses.

Evaluation of the effect of MPL and delivery route on immunogenicity and protectivity of different formulations of FimH and MrpH from uropathogenic Escherichia coli and Proteus mirabilis in a UTI mouse model

Urinary tract infections (UTIs) caused by Escherichia coli and Proteus mirabilis are an important cause of morbidity and with the high rate of relapse and spread of multi-drug resistant pathogens, pose a significant public health challenge worldwide. Lack of an efficacious commercial vaccine targeting both uropathogens makes development of a combined vaccine highly desirable. In this study the immunogenicity and protective efficacy of different formulations of FimH of UPEC, MrpH of P. mirabilis and their fusion protein (MrpH.FimH) subcutaneously administered with and without Monophosphoryl lipid A (MPL) adjuvant were evaluated. Our data showed that the subcutaneously administered proteins induced both serum and mucosal IgG, which MPL significantly improved developing a mixed Th1 and Th2 immune response. However, the preparations induced a higher systemic and mucosal IgG and IL-2 levels by this route compared to the intranasal. Immunization of mice with MrpH.FimH fusion with MPL or a mixture of FimH, MrpH and MPL conferred the highest protection of the bladder and kidneys when challenged with UPEC and P. mirabilis in a UTI mouse model. Therefore considering these results MrpH.FimH fusion with MPL administered subcutaneously or intranasally could be a promising vaccine candidate for elimination of UTIs caused by UPEC and P. mirabilis.

Enhanced humoral response in pregnant mice immunized with liposome encapsulated recombinant neutralizing epitope protein of Hepatitis- E virus

BACKGROUND

Pregnant women from developing countries are at high-risk of hepatitis E-associated high mortality and constitute priority population for vaccination. So far, candidate vaccines have not been evaluated during pregnancy. We evaluated our vaccine candidate, recombinant Neutralizing Epitope protein (rNEp) encapsulated in liposomes, in pregnant mice.

METHODS

A single dose (10 μg) of the formulation was administered intramuscularly on day 7 of pregnancy. Titres of serum IgG antibodies to hepatitis E virus (IgG-anti-HEV), levels of cytokines and biochemical parameters were determined. Spleens were harvested from pregnant and non-pregnant mice for immunophenotyping (flow cytometry), cytokines (cytometric bead array, CBA) and gene expression of immune response genes (Taqman low density array, TLDA). Histopathology studies of spleen, liver, kidneys, brain and muscle was carried out.

RESULTS

The vaccine was well-tolerated during pregnancy as evidenced by histopathology and serum biochemical parameters. Anti-HEV titres were significantly higher in the pregnant balb/c and C57BL/6 mice (3592 ± 802 and 1016 ± 138 respectively, than in non-pregnant groups (634 ± 191 and 320 ± 55 respectively, p < 0.001 for both) suggesting that the higher antibody response in pregnant mice was independent of the genetic makeup of the host but immunogen-driven. Pups receiving vertically transferred antibodies developed lower anti-HEV antibodies (p < 0.05) when immunized with the formulation after seronegativity than in the age-matched mice without such antibodies. In non-pregnant mice, a Th1 response and discordance between splenic and serum cytokines was evident while in pregnancy, a Th2 bias was observed irrespective of immunization. Increased CD19 levels correlated with higher anti-HEV titres in pregnant mice.

CONCLUSION

The single dose of the vaccine was safe and highly immunogenic in pregnant mice. Degree and type of immune response to vaccination during pregnancy is immunogen-driven. In-depth studies are needed to understand the underlying immunologic mechanism(s). These encouraging results for a vaccine intended for use in pregnant women should be confirmed in higher animals.

Applying biodegradable particles to enhance cancer vaccine efficacy

One of the primary goals of our group and our collaborators here at the University of Iowa is to develop therapeutic cancer vaccines using biodegradable and biocompatible polymer-based vectors. A major advantage of using discretely packaged immunogenic cargo over non-encapsulated vaccines is that they promote enhanced cellular immunity, a key requirement in achieving antitumor activity. We discuss the importance of co-encapsulation of tumor antigen and adjuvant, with specific focus on the synthetic oligonucleotide adjuvant, cytosine-phosphate-guanine oligodeoxynucleotides. We also discuss our research using a variety of polymers including poly(α-hydroxy acids) and polyanhydrides, with the aim of determining the effect that parameters, such as size and polymer type, can have on prophylactic and therapeutic tumor vaccine formulation efficacy. Aside from their role as vaccine vectors per se, we also address the research currently underway in our group that utilizes more novel applications of biodegradable polymer-based particles in facilitating other types of immune-based therapies.

Intranasal immunization with fusion protein MrpH·FimH and MPL adjuvant confers protection against urinary tract infections caused by uropathogenic Escherichia coli and Proteus mirabilis

Urinary tract infections (UTIs) caused by Uropathogenic Escherichia coli (UPEC) and Proteus mirabilis are among the most common infections in the world. Currently there are no vaccines available to confer protection against UTI in humans. In this study, the immune responses and protection of FimH of UPEC with MrpH antigen of P. mirabilis in different vaccine formulations with and without MPL adjuvant were assessed. Mice intranasally immunized with the novel fusion protein MrpH·FimH induced a significant increase in IgG and IgA in serum, nasal wash, vaginal wash, and urine samples. Mice immunized with fusion MrpH·FimH also showed a significant boost in cellular immunity. Addition of MPL as the adjuvant enhanced FimH and MrpH specific humoral and cellular responses in both systemic and mucosal samples. Vaccination with MrpH·FimH alone or in combination with MPL showed the highest efficiency in clearing bladder and kidney infections in mice challenged with UPEC and P. mirabilis. These findings may indicate that the protection observed correlates with the systemic, mucosal and cellular immune responses induced by vaccination with these preparations. Our data suggest MrpH·FimH fusion protein with or without MPL as adjuvant could be potential vaccine candidates for elimination of UPEC and P. mirabilis. These data altogether are promising and these formulations are good candidates for elimination of UPEC and P. mirabilis.

Enhancement of adaptive immunity by the human vaccine adjuvant AS01 depends on activated dendritic cells

Adjuvant System AS01 is a liposome-based vaccine adjuvant containing 3-O-desacyl-4'-monophosphoryl lipid A and the saponin QS-21. AS01 has been selected for the clinical development of several candidate vaccines including the RTS,S malaria vaccine and the subunit glycoprotein E varicella zoster vaccine (both currently in phase III). Given the known immunostimulatory properties of MPL and QS-21, the objective of this study was to describe the early immune response parameters after immunization with an AS01-adjuvanted vaccine and to identify relationships with the vaccine-specific adaptive immune response. Cytokine production and innate immune cell recruitment occurred rapidly and transiently at the muscle injection site and draining lymph node postinjection, consistent with the rapid drainage of the vaccine components to the draining lymph node. The induction of Ag-specific Ab and T cell responses was dependent on the Ag being injected at the same time or within 24 h after AS01, suggesting that the early events occurring postinjection were required for these elevated adaptive responses. In the draining lymph node, after 24 h, the numbers of activated and Ag-loaded monocytes and MHCII(high) dendritic cells were higher after the injection of the AS01-adjuvanted vaccine than after Ag alone. However, only MHCII(high) dendritic cells appeared efficient at and necessary for direct Ag presentation to T cells. These data suggest that the ability of AS01 to improve adaptive immune responses, as has been demonstrated in clinical trials, is linked to a transient stimulation of the innate immune system leading to the generation of high number of efficient Ag-presenting dendritic cells.

Enhancement of humoral and cellular immune responses by monophosphoryl lipid A (MPLA) as an adjuvant to the rabies vaccine in BALB/c mice

The development of effective vaccines against the rabies virus could prevent infection with this fatal virus. However, the current rabies vaccine fails to provide a full range of protection because of its limited ability to elicit a cellular immune response and the requirement for repeat vaccination. Monophosphoryl lipid A (MPLA) is well known as a potent adjuvant to enhance immune responses against virus infection. Here we investigated the efficacy of MPLA as an adjuvant to improve the humoral and cellular immune responses to the rabies vaccine in BALB/c mice. Supplementation of the rabies vaccine with MPLA significantly accelerated the production of specific antibodies by 10 days compared to the original vaccines. Furthermore, MPLA promoted the induction of stronger cellular immune responses by the rabies vaccine, including the production of IL-4, IFN-γ and the activation of CD4⁺/CD8⁺ T cells, than those elicited without MPLA. Collectively, our findings indicated that MPLA enhances humoral and cellular immunity and is a promising adjuvant for the development of more effective rabies vaccines.

A short protocol using dexamethasone and monophosphoryl lipid A generates tolerogenic dendritic cells that display a potent migratory capacity to lymphoid chemokines

Background

Generation of tolerogenic dendritic cells (TolDCs) for therapy is challenging due to its implications for the design of protocols suitable for clinical applications, which means not only using safe products, but also working at defining specific biomarkers for TolDCs identification, developing shorter DCs differentiation methods and obtaining TolDCs with a stable phenotype. We describe here, a short-term protocol for TolDCs generation, which are characterized in terms of phenotypic markers, cytokines secretion profile, CD4+ T cell-stimulatory ability and migratory capacity.

Methods

TolDCs from healthy donors were generated by modulation with dexamethasone plus monophosphoryl lipid A (MPLA-tDCs). We performed an analysis of MPLA-tDCs in terms of yield, viability, morphology, phenotypic markers, cytokines secretion profile, stability, allogeneic and antigen-specific CD4+ T-cell stimulatory ability and migration capacity.

Results

After a 5-day culture, MPLA-tDCs displayed reduced expression of costimulatory and maturation molecules together to an anti-inflammatory cytokines secretion profile, being able to maintain these tolerogenic features even after the engagement of CD40 by its cognate ligand. In addition, MPLA-tDCs exhibited reduced capabilities to stimulate allogeneic and antigen-specific CD4+ T cell proliferation, and induced an anti-inflammatory cytokine secretion pattern. Among potential tolerogenic markers studied, only TLR-2 was highly expressed in MPLA-tDCs when compared to mature and immature DCs. Remarkable, like mature DCs, MPLA-tDCs displayed a high CCR7 and CXCR4 expression, both chemokine receptors involved in migration to secondary lymphoid organs, and even more, in an in vitro assay they exhibited a high migration response towards CCL19 and CXCL12.

Conclusion

We describe a short-term protocol for TolDC generation, which confers them a stable phenotype and migratory capacity to lymphoid chemokines, essential features for TolDCs to be used as therapeutics for autoimmunity and prevention of graft rejection.

Mechanisms of action of adjuvants

Adjuvants are used in many vaccines, but their mechanisms of action are not fully understood. Studies from the past decade on adjuvant mechanisms are slowly revealing the secrets of adjuvant activity. In this review, we have summarized the recent progress in our understanding of the mechanisms of action of adjuvants. Adjuvants may act by a combination of various mechanisms including formation of depot, induction of cytokines and chemokines, recruitment of immune cells, enhancement of antigen uptake and presentation, and promoting antigen transport to draining lymph nodes. It appears that adjuvants activate innate immune responses to create a local immuno-competent environment at the injection site. Depending on the type of innate responses activated, adjuvants can alter the quality and quantity of adaptive immune responses. Understanding the mechanisms of action of adjuvants will provide critical information on how innate immunity influences the development of adaptive immunity, help in rational design of vaccines against various diseases, and can inform on adjuvant safety.