Vaccine adjuvants: current state and future trends

New Insights on the Adjuvant Properties of the Leishmania infantum Eukaryotic Initiation Factor

Vaccination is the most effective tool against infectious diseases. Subunit vaccines are safer compared to live-attenuated vaccines but are less immunogenic and need to be delivered with an adjuvant. Adjuvants are essential for enhancing vaccine potency by improving humoral and cell-mediated immune responses. Only a limited number of adjuvants are licensed for human vaccines, and their mode of action is still not clear. Leishmania eukaryotic initiation factor (LeIF) has been described having a dual role, as a natural adjuvant and as an antigen that possesses advantageous immunomodulatory properties. In this study, we assessed the adjuvant properties of recombinant Leishmania infantum eukaryotic initiation factor (LieIF) through in vitro and in vivo assays. LieIF was intraperitoneally administered in combination with the protein antigen ovalbumin (OVA), and the widely used alum was used as a reference adjuvant. Our in vitro studies using J774A.1 macrophages showed that LieIF induced stimulatory effects as demonstrated by the enhanced surface expression of CD80 and CD86 co-stimulatory molecules and the induced production of the immune mediators NO and MIP-1α. Additionally, LieIF co-administration with OVA in an in vivo murine model induced a proinflammatory environment as demonstrated by the elevated expression of TNF-α, IL-1β, and NF-κB2 genes in peritoneal exudate cells (PEC). Furthermore, PEC derived from OVA-LieIF-immunized mice exhibited elevated expression of CD80 molecule and production of NO and MIP-1α in culture supernatants. Moreover, LieIF administration in the peritoneum of mice resulted in the recruitment of neutrophils and monocytes at 24 h post-injection. Also, we showed that this immunopotentiating effect of LieIF did not depend on the induction of uric acid danger signal. These findings suggest the potential use of LieIF as adjuvant in new vaccine formulations against different infectious diseases.

Safety and biocompatibility of injectable vaccine adjuvants composed of thermogelling block copolymer gels

Injectable thermogelling polymers have been recently investigated as novel adjuvants and delivery systems for next generation vaccines. As research into natural and synthetic biocompatible polymers progresses, the safety and biocompatibility of these compounds is of paramount importance. We have developed cationic pentablock copolymer (PBC) vaccine adjuvants based on Pluronic F127, a thermogelling triblock copolymer that has been approved by the FDA for multiple applications, and methacrylated poly(diethyl amino)ethyl methacrylate outer blocks. These novel materials have been demonstrated to effectively create an antigen depot, minimally impact antigen stability, and enhance the immune response to antigens (i.e., adjuvanticity) in mice. In this work, we investigated the safety and biocompatibility of the parent triblock Pluronic gels and the cationic PBC gels in mice. Histological analysis showed no injection site reactions and no damage to the liver or kidneys was observed upon administering the block copolymer formulations. However, the subcutaneous injection of a thermogelling Pluronic solution induced increased levels of lipids in the blood, with no further deleterious effects observed from the addition of the cationic outer blocks. This hyperlipidemia resolved within 30 days after the administration of the Pluronic formulation. To mitigate this adverse effect, the vaccine adjuvant formulations were modified by adding poly(vinyl alcohol), which allowed gelation, while reducing the amount of Pluronic in the formulation. This modified formulation abrogated the observed hyperlipidemia and no adverse effects were observed in the serum through biomarker analysis or at the injection site (i.e., inflammation) in comparison to the responses induced by administration of saline or incomplete Freund's adjuvant. These studies provide a foundation to developing these gels as adjuvants for next generation vaccines. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1754-1762, 2019.

Immunization of mice by the co-administration of codon-optimized HPV16 E7 and lL12 genes against HPV16-associated cervical cancer

BACKGROUND

Various promising procedures have been used to improve the potency of DNA vaccines for the treatment of human papillomavirus type 16 (HPV16) infections. Interleukin-12 (IL12) is a powerful adjuvant that can contribute to T cell-mediated protection against many pathogens, specifically viruses. Considering the important role of T cell-mediated immunity in tumor clearance, the induction of these responses can help control the progression of tumors in animal models. We have demonstrated that the co-administration of codon-optimized E7 (uE7) gene of HPV16 with interleukin-12 is effective in the development of antitumor responses.

OBJECTIVES

The present study examined the co-administration of codon-optimized HPV16 E7 gene with murine interleukin-12 gene (mIL-12) as a vaccine adjuvant in tumor mice model.

MATERIALS AND METHODS

C57BL/6 mice were studied for tumor progression after injection of recombinant DNA vaccines. Lactate dehydrogenase (LDH) and IFN-γ were measured to evaluate the activity of cytotoxic T lymphocytes (CTLs). Measurements of tumor volume and MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay were used for assessment of therapeutic antitumor effects of the vaccines.

RESULTS

Results showed that DNA vaccines, specifically codon-optimized E7/murine interleukin-12 (mIL-12), elicited significant differences in levels of IFN-γ and cytotoxic T lymphocyte (CTLs) responses compared to control groups. Furthermore, higher antitumor response and lower tumor size in the vaccine group was significantly evident compared to control group.

CONCLUSION

The co-administration of codon-optimized HPV16 E7 gene with IL12 significantly enhances the DNA vaccine potency against HPV16-associated cervical cancer.

Vaccination with a chikungunya virus-like particle vaccine exacerbates disease in aged mice

INTRODUCTION

Chikungunya virus (CHIKV) is a re-emerging pathogen responsible for causing outbreaks of febrile disease accompanied with debilitating joint pain. Symptoms typically persist for two weeks, but more severe and chronic chikungunya illnesses have been reported, especially in the elderly. Currently, there are no licensed vaccines or antivirals against CHIKV available. In this study, we combined a CHIK virus-like particle (VLP) vaccine with different adjuvants to enhance immunogenicity and protection in both, adult and aged mice.

METHODS

CHIK VLP-based vaccines were tested in 6-8-week-old (adult) and 18-24-month-old (aged) female C57BL/6J mice. Formulations contained CHIK VLP alone or adjuvants: QuilA, R848, or Imject Alum. Mice were vaccinated three times via intramuscular injections. CHIKV-specific antibody responses were characterized by IgG subclass using ELISA, and by microneutralization assays. In addition, CHIKV infections were characterized in vaccinated and non-vaccinated adult mice and compared to aged mice.

RESULTS

In adult mice, CHIKV infection of the right hind foot induced significant swelling, which peaked by day 7 post-infection at approximately 170% of initial size. Viral titers peaked at 2.53 × 1010 CCID50/ml on day 2 post-infection. Mice vaccinated with CHIK VLP-based vaccines developed robust anti-CHIKV-specific IgG antibody responses that were capable of neutralizing CHIKV in vitro. CHIK VLP alone or CHIK plus QuilA administered by IM injections protected 100% of mice against CHIKV. In contrast, the antibody responses elicited by the VLP-based vaccines were attenuated in aged mice, with negligible neutralizing antibody titers detected. Unvaccinated, aged mice were resistant to CHIKV infection, while vaccination with CHIKV VLPs exacerbated disease.

CONCLUSIONS

Unadjuvanted CHIK VLP vaccination elicits immune responses that protect 100% of adult mice against CHIKV infection. However, an improved vaccine/adjuvant combination is still necessary to enhance the protective immunity against CHIKV in the aged.

Cell wall fraction of Mycobacterium indicus pranii shows potential Th1 adjuvant activity

Very few adjuvants inducing Th1 immune response have been developed and are under clinical investigation. Hence, there is the need to find an adjuvant that elicits strong Th1 immune response which should be safe when injected in the host along with vaccines. Mycobacterium indicus pranii (MIP), a non-pathogenic vaccine candidate, has shown strong immunomodulatory activity in leprosy/tuberculosis/cancer and in genital warts patients where its administration shifted the host immune response towards Th1 type. These findings prompted us to study the components of MIP in detail for their Th1 inducing property. Since mycobacterial cell wall is very rich in immunostimulatory components and is known to play important role in immune modulation, we investigated the activity of MIP cell wall using Ovalbumin antigen (OVA) as model antigen. 'Whole cell wall' (CW) and 'aqueous soluble cell wall fractions' (ACW) induced significant Th1 immune response while 'cell wall skeleton' (CWS) induced strong Th2 type of immune response. Finally, functional activity of fractions having Th1 inducing activity was evaluated in mouse model of melanoma. CW demonstrated significant anti-tumor activity similar to whole MIP. Anti-tumor activity of CW could be correlated with enhanced tumor antigen specific Th1 immune response observed in tumor draining lymph nodes.

Promising Plant-Derived Adjuvants in the Development of Coccidial Vaccines

Coccidial parasites cause medical and veterinary diseases worldwide, frequently leading to severe illness and important economic losses. At present, drugs, chemotherapeutics and prophylactic vaccines are still missing for most of the coccidial infections. Moreover, the development and administration of drugs and chemotherapeutics against these diseases would not be adequate in livestock, since they may generate unacceptable residues in milk and meat that would avoid their commercialization. In this scenario, prophylactic vaccines emerge as the most suitable approach. Subunit vaccines have proven to be biologically safe and economically viable, allowing researchers to choose among the best antigens against each pathogen. However, they are generally poorly immunogenic and require the addition of adjuvant compounds to the vaccine formulation. During the last decades, research involving plant immunomodulatory compounds has become an important field of study based on their potential pharmaceutical applications. Some plant molecules such as saponins, polysaccharides, lectins and heat shock proteins are being explored as candidates for adjuvant/carriers formulations. Moreover, plant-derived immune stimulatory compounds open the possibility to attain the main goal in adjuvant research: a safe and non-toxic adjuvant capable of strongly boosting and directing immune responses that could be incorporated into different vaccine formulations, including mucosal vaccines. Here, we review the immunomodulatory properties of several plant molecules and discuss their application and future perspective as adjuvants in the development of vaccines against coccidial infections.

Comparison of immunoadjuvant activities of four bursal peptides combined with H9N2 avian influenza virus vaccine

The bursa of Fabricius (BF) is a central humoral immune organ unique to birds. Four bursal peptides (BP-I, BP-II, BP-III, and BP-IV) have been isolated and identified from the BF. In this study, the immunoadjuvant activities of BPs I to IV were examined in mice immunized with H9N2 avian influenza virus (AIV) vaccine. The results suggested that BP-I effectively enhanced cell-mediated immune responses, increased the secretion of Th1 (interferon gamma)- and Th2 (interleukin-4)-type cytokines, and induced an improved cytotoxic T-lymphocyte (CTL) response to the H9N2 virus. BP-II mainly elevated specific antibody production, especially neutralizing antibodies, and increased Th1- and Th2-type cytokine secretion. BP-III had no significant effect on antibody production or cell-mediated immune responses compared to those in the control group. A strong immune response at both the humoral and cellular levels was induced by BP-IV. Furthermore, a virus challenge experiment followed by H&E staining revealed that BP-I and BP-II promoted removal of the virus and conferred protection in mouse lungs. BP-IV significantly reduced viral titers and histopathological changes and contributed to protection against H9N2 AIV challenge in mouse lungs. This study further elucidated the immunoadjuvant activities of BPs I to IV, providing a novel insight into immunoadjuvants for use in vaccine design.

Stability of Vaccines

Vaccines are considered the most economical and effective preventive measure against most deadly infectious diseases. Vaccines help protect around three million lives every year, but hundreds of thousands of lives are lost due to the instability of vaccines. This review discusses the various types of instability observed, while manufacturing, storing, and distributing vaccines. It describes the specific stability problems associated with each type of vaccine. This review also discusses the various measures adopted to overcome these instability problems. Vaccines are classified based on their components, and this review discusses how these preventive measures relate to each type of vaccine. This review also includes certain case studies that illustrate various approaches to improve vaccine stability. Last, this review provides insight on prospective methods for developing more stable vaccines.

Biomaterials for vaccine-based cancer immunotherapy

The development of therapeutic cancer vaccines as a means to generate immune reactivity against tumors has been explored since the early discovery of tumor-specific antigens by Georg Klein in the 1960s. However, challenges including weak immunogenicity, systemic toxicity, and off-target effects of cancer vaccines remain as barriers to their broad clinical translation. Advances in the design and implementation of biomaterials are now enabling enhanced efficacy and reduced toxicity of cancer vaccines by controlling the presentation and release of vaccine components to immune cells and their microenvironment. Here, we discuss the rational design and clinical status of several classes of cancer vaccines (including DNA, mRNA, peptide/protein, and cell-based vaccines) along with novel biomaterial-based delivery technologies that improve their safety and efficacy. Further, strategies for designing new platforms for personalized cancer vaccines are also considered.

Development of a novel oil-in-water emulsion and evaluation of its potential adjuvant function in a swine influenza vaccine in mice

Background

Vaccination is the principal strategy for prevention and control of diseases, and adjuvant use is an effective strategy to enhance vaccine efficacy. Traditional mineral oil-based adjuvants have been reported with post-immunization reactions. Developing new adjuvant formulations with improved potency and safety will be of great value.

Results

In the study reported herein, a novel oil-in-water (O/W) Emulsion Adjuvant containing Squalane (termed EAS) was developed, characterized and investigated for swine influenza virus immunization. The data show that EAS is a homogeneous nanoemulsion with small particle size (~ 105 nm), low viscosity (2.04 ± 0.24 cP at 20 °C), excellent stability (at least 24 months at 4 °C) and low toxicity. EAS-adjuvanted H3N2 swine influenza vaccine was administrated in mice subcutaneously to assess the adjuvant potency of EAS. The results demonstrated that in mice EAS-adjuvanted vaccine induced significantly higher titers of hemagglutination inhibition (HI) and IgG antibodies than water-in-oil (W/O) vaccines or antigen alone, respectively, at day 42 post vaccination (dpv) (P < 0.05). EAS-adjuvanted vaccine elicited significantly stronger IgG1 and IgG2a antibodies and higher concentrations of Th1 (IFN-γ and IL-2) cytokines compared to the W/O vaccine or antigen alone. Mice immunized with EAS-adjuvanted influenza vaccine conferred potent protection after homologous challenge.

Conclusion

The O/W emulsion EAS developed in the present work induced potent humoral and cellular immune responses against inactivated swine influenza virus, conferred effective protection after homologous virus challenge and showed low toxicity in mice, indicating that EAS is as good as the commercial adjuvant MF59. The superiority of EAS to the conventional W/O formulation in adjuvant activity, safety and stability will make it a potential veterinary adjuvant.

The Modified Vaccination Technique

In addition to active and passive immunizations, there is a third method of immunization, the modified vaccination technique, which is based on injecting a combination of target antigens and antibodies against this antigen. The vaccine is essentially comprised of immune complexes with pre-determined immune-inducing components. When such an immune complex (target antigen × antibody against the target antigen) with a slight antigen excess is administered, it evokes a corrective immune response by the production of the same antibody with the same specificity against the target antigen that is present in the immune complex (pre-determined immune response).

Adjuvant activity of ethanol extract of Hippophae rhamnoides leaves with inactivated rabies virus antigen

CONTEXT

Hippophae rhamnoides L. (Elaeagnaceae), commonly known as seabuckthorn (SBT), is known for its medicinal and nutritional properties.

OBJECTIVE

Evaluation of in vivo adjuvant activity of SBT leaf extract (SBTE) with inactivated rabies virus antigen (Rb).

MATERIALS AND METHODS

Swiss albino mice were immunized with aqueous-alcoholic SBTE (100 mg/kg body weight) or algel (aluminium hydroxide gel) with or without Rb (5% v/v). After priming, booster was administered on day 14. Rabies virus neutralizing antibody (RVNA) titers were estimated by rapid fluorescent focus inhibition test in sera samples collected on days 7, 14, 21, 28 and 35. Effect of adjuvant administration on cytotoxic T lymphocytes (CTLs), memory T cells, plasma and CD11c⁺ cells was studied by flow cytometry. In vitro hemolysis was assayed in human RBC.

RESULTS

RVNA titers were significantly enhanced (p < 0.05) after booster administration in mice immunized with SBTE + Rb as compared to the controls. In combination, SBTE, algel and Rb, enhanced the RVNA titers. CTLs significantly increased (p < 0.05) in SBTE + Rb immunized mice. Memory T cells and plasma cells were 27.9 and 15.9%, respectively, in SBTE + Rb immunized mice as compared to that of 20.3 and 11.3%, respectively, in Rb immunized group. SBTE + Rb enhanced peritoneal CD11c⁺ cells (25.8%) as compared to 9.4% cells in Rb immunized mice, showed 3.2-fold increment in LPS induced IL-1β. No RBC hemolysis was observed with SBTE.

CONCLUSIONS

This study demonstrates the potential adjuvant activity of SBTE with Rb by increasing RVNA titers and CTL response.

Fingolimod can act as a facilitator to establish the primary T-cell response with reduced need of adjuvants

The CD8⁺ T-cell response is an essential part of the adaptive immunity. Adjuvants are routinely required for priming of T cells against antigens encountered in lymph nodes (LNs) to generate antigen-specific immunity but may concomitantly trigger unexpected inflammatory responses. Sphingosine-1-phosphate (S1P) induces transient desensitization of S1P receptors on LN T cells and temporarily blocks their egress, leading to prolonged intranodal retention that allows effective immunosurveillance and increases the chance of priming. In light of the regulatory role of S1P in T-cell migration, we here develop a strategic approach to the T-cell priming with protein vaccine containing low-dose TLR-based adjuvants (LDAV) to induce antigen-specific CD8⁺ T cell responses as efficiently as using regular dose adjuvants in vaccine (RDAV). We found that when combined with one low dose of the S1P analog fingolimod administered into the same vaccination site posteriorly at a specific time, LDAV can elicit a primary response that reaches the level of that induced by RDAV with respect to the response magnitude and functionality. Time-course studies indicate that LDAV and fingolimod in combination act to mimic the expansion kinetics of RDAV-primed antigen-specific CD8⁺ T cells. Further, intranodal accumulation of cDC1 is markedly enhanced in mice receiving the combination vaccination despite the decrease in adjuvant use. Of particular note is the marginal cutaneous inflammation at the injection site, indicating an added benefit of using fingolimod. Therefore, fingolimod as a nonadjuvant agent essentially facilitates antigen-specific T-cell priming with reduced need of adjuvants and minimized adverse reactions.

Oral co-administration of a bacterial protease inhibitor in the vaccine formulation increases antigen delivery at the intestinal epithelial barrier

The study of capture and processing of antigens (Ags) by intestinal epithelial cells is very important for development of new oral administration systems. Efficient oral Ag delivery systems must resist enzymatic degradation by gastric and intestinal proteases and deliver the Ag across biological barriers. The recombinant unlipidated outer membrane protein from Brucella spp. (U-Omp19) is a protease inhibitor with immunostimulatory properties used as adjuvant in oral vaccine formulations. In the present work we further characterized its mechanism of action and studied the interaction and effect of U-Omp19 on the intestinal epithelium. We found that U-Omp19 inhibited protease activity from murine intestinal brush-border membranes and cysteine proteases from human intestinal epithelial cells (IECs) promoting co-administered Ag accumulation within lysosomal compartments of IECs. In addition, we have shown that co-administration of U-Omp19 facilitated the transcellular passage of Ag through epithelial cell monolayers in vitro and in vivo while did not affect epithelial cell barrier permeability. Finally, oral co-delivery of U-Omp19 in mice induced the production of Ag-specific IgA in feces and the increment of CD103⁺ CD11b⁻ CD8α⁺ dendritic cells subset at Peyer's patches. Taken together, these data describe a new mechanism of action of a mucosal adjuvant and support the use of this rationale/strategy in new oral delivery systems for vaccines.

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The bacterial protease inhibitor U-Omp19 limits antigens proteolysis by enterocytes.

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Oral co-administration of U-Omp19 increases antigen half-life inside enterocytes.

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U-Omp19 oral administration does not affect epithelial cell barrier permeability.

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Oral co-delivery of U-Omp19 increases frequency of dendritic cells bearing antigen.

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U-Omp19 increases the half-life and immunogenicity of cholera toxin subunit B antigen.

Applications of Immunomodulatory Immune Synergies to Adjuvant Discovery and Vaccine Development

Pathogens comprise a diverse set of immunostimulatory molecules that activate the innate immune system during infection. The immune system recognizes distinct combinations of pathogenic molecules leading to multiple immune activation events that cooperate to produce enhanced immune responses, known as 'immune synergies'. Effective immune synergies are essential for the clearance of pathogens, thus inspiring novel adjuvant design to improve vaccines. We highlight current vaccine adjuvants and the importance of immune synergies to adjuvant and vaccine design. The focus is on new technologies used to study and apply immune synergies to adjuvant and vaccine development. Finally, we discuss how recent findings can be applied to the future design and characterization of synergistic adjuvants and vaccines.

Physical activation of innate immunity by spiky particles

Microbial biochemicals have been indicated as the primary stimulators of innate immunity, the first line of the body's defence against infections. However, the influence of topological features on a microbe's surface on immune responses remains largely unknown. Here we demonstrate the ability of TiO₂ microparticles decorated with nanospikes (spiky particles) to activate and amplify the immune response in vitro and in vivo. The nanospikes exert mechanical stress on the cells, which results in potassium efflux and inflammasome activation in macrophages and dendritic cells during phagocytosis. The spiky particles augment antigen-specific humoral and cellular immune responses in the presence of monophosphoryl lipid A and elicit protective immunity against tumour growth and influenza viral infection. The study offers insights into how surface physical cues can tune the activation of innate immunity and provides a basis for engineering particles with increased immunogenicity and adjuvanticity.

A TLR4-derived non-cytotoxic, self-assembling peptide functions as a vaccine adjuvant in mice

Vaccination is devised/formulated to stimulate specific and prolonged immune responses for long-term protection against infection or disease. A vaccine component, namely adjuvant, enhances antigen recognition by the host immune system and thereby stimulates its cellular and adaptive responses. Especially synthetic Toll-like receptor (TLR) agonists having self-assembling properties are considered as good candidates for adjuvant development. Here, a human TLR4-derived 20-residue peptide (TR-433), present in the dimerization interface of the TLR4-myeloid differentiation protein-2 (MD2) complex, displayed self-assembly and adopted a nanostructure. Both in vitro studies and in vivo experiments in mice indicated that TR-433 is nontoxic. TR-433 induced pro-inflammatory responses in THP-1 monocytes and HEK293T cells that were transiently transfected with TLR4/CD14/MD2 and also in BALB/c mice. In light of the self-assembly and pro-inflammatory properties of TR-433, we immunized with a mixture of TR-433 and either ovalbumin or filarial antigen trehalose-6-phosphate phosphatase (TPP). A significant amount of IgG titers was produced, suggesting adjuvanting capability of TR-433 that was comparable with that of Freund's complete adjuvant (FCA) and appreciably higher than that of alum. We found that TR-433 preferentially activates type 1 helper T cell (T_h1) response rather than type 2 helper T cell (T_h2) response. To our knowledge, this is the first report on the identification of a short TLR4-derived peptide that possesses both self-assembling and pro-inflammatory properties and has significant efficacy as an adjuvant, capable of activating cellular responses in mice. These results indicate that TR-433 possesses significant potential for development as a new adjuvant in therapeutic application.

Synthetic Toll-like receptor agonists for the development of powerful malaria vaccines: a patent review

INTRODUCTION

Currently, there is no efficient vaccine available against clinical malaria. However, continuous efforts have been committed to develop powerful antimalarial vaccine by discovery of novel antigens with in-depth understanding of its nature, immunogenicity, and presentation (delivery adjuvants). Moreover, another important part of vaccine development includes discovery of better immunostimulatory formulation components (immunostimulants). A protective vaccine against malaria requires antigen-specific B and T helper cell responses as well as cytotoxic T lymphocyte (CTL) responses. A long-lasting B and T memory cell production is also required for effective malaria vaccine. Since activation of Toll-like receptors (TLRs) promotes both innate inflammatory responses as well as the induction of adaptive immunity, several initiatives have been mounted during the last few years for the use of TLR agonists as malaria vaccine adjuvants.

AREAS COVERED

The review summarizes reports related to the use and development of TLR agonists as malaria vaccine adjuvants and describes various strategies involved for the selection of specific antigens and TLR agonists.

EXPERT OPINION

TLR agonists are promising adjuvants for the development of effective malaria vaccine, allowing for both innate inflammatory responses as well as the induction of adaptive immunity.

Topical Application of a Vitamin A Derivative and Its Combination With Non-ablative Fractional Laser Potentiates Cutaneous Influenza Vaccination

Skin contains a large number of antigen presenting cells, making intradermal (ID) injection one of the most effective ways for vaccine administration. However, although current adjuvants may cause severe local reactions and inflammations in the skin, no adjuvant has been approved for ID vaccination so far. Here, we report that topical application of all-trans retinoic acid (ATRA), a vitamin A derivative produced in the human body, augmented cutaneous influenza vaccination. The adjuvant effects were evaluated in a murine vaccination/challenge model by using A/California/07/2009 pandemic vaccine (09V) or a seasonal influenza vaccine (SIV). ATRA drove a Th2-biased immune response, as demonstrated by profoundly elevated IgG1 titer rather than IgG2 titer. Combining ATRA with a non-ablative fractional laser (NAFL), which represents a new category of vaccine adjuvant utilizing physical stimuli to induce self-immune stimulators, further enhanced the efficacy of influenza vaccines with a more balanced Th1/Th2 immune response. The dual adjuvant strengthened cross-reactive immune responses against both homogenous and heterogeneous influenza viral strains. Analysis of gene expression profile showed that ATRA/NAFL stimulated upregulation of cytosolic nucleic acid sensors and their downstream factors, leading to a synergistic elevation of type I interferon expression. Consistent with this finding, knocking out IRF3 or IRF7, two key downstream regulatory factors in most nucleic acid sensing pathways, resulted in a significant decrease in the adjuvant effect of ATRA/NAFL. Thus, our study demonstrates that the self molecule ATRA could boost cutaneous influenza vaccination either alone or ideally in combination with NAFL.

Prospects on the Use of Schizochytrium sp. to Develop Oral Vaccines

Although oral subunit vaccines are highly relevant in the fight against widespread diseases, their high cost, safety and proper immunogenicity are attributes that have yet to be addressed in many cases and thus these limitations should be considered in the development of new oral vaccines. Prominent examples of new platforms proposed to address these limitations are plant cells and microalgae. Schizochytrium sp. constitutes an attractive expression host for vaccine production because of its high biosynthetic capacity, fast growth in low cost culture media, and the availability of processes for industrial scale production. In addition, whole Schizochytrium sp. cells may serve as delivery vectors; especially for oral vaccines since Schizochytrium sp. is safe for oral consumption, produces immunomodulatory compounds, and may provide bioencapsulation to the antigen, thus increasing its bioavailability. Remarkably, Schizochytrium sp. was recently used for the production of a highly immunoprotective influenza vaccine. Moreover, an efficient method for transient expression of antigens based on viral vectors and Schizochytrium sp. as host has been recently developed. In this review, the potential of Schizochytrium sp. in vaccinology is placed in perspective, with emphasis on its use as an attractive oral vaccination vehicle.

Osmolytes in vaccine production, flocculation and storage: a critical review

Small molecule osmolytes, responsible for protecting stresses have long been known to rescue proteins and enzymes from loss of function. In addition to protecting macromolecules integrity, many osmolytes also act as potential antioxidant and also help to prevent protein aggregation, amyloid formation or misfolding, and therefore are considered promising molecules for neurodegenerative and many other genetic diseases. Osmolytes are also known to be involved in the regulation of several key immunological processes. In the present review we discuss in detail the effect of these compounds on important aspects of vaccines i.e., increasing the efficiency, production and purification steps. The present review therefore will help researchers to make a better strategy in vaccine production to formulation by incorporating specific and appropriate osmolytes in the processes.

Application of a novel nanoemulsion adjuvant for rabies vaccine which stabilizes a Krebs cycle intermediate (SDH) in an animal model

Rabies is the most lethal zoonotic, vaccine-preventable viral disease in the world. Its treatment is complicated by insufficient vaccine supply and the requirement for four to five repeated injections, as commercially available inactivated rabies lack adjuvant and have low immunogenicity. In this study, we focused on the role of a Krebs cycle intermediate, succinate dehydrogenase (SDH), in the innate immune response to cytokine production. We formulated a novel nanoemulsion adjuvant, Golden03, which stabilizes mouse SDH activity and contains more coenzyme Q10 and succinic acid than the classic MF59 adjuvant. Mice were immunized on days 1, 3, and 7, with seroconversion rate results suggesting that Golden03 significantly enhanced vaccine-stimulated antibody production against the rabies virus. Neutralizing antibody concentration testing by RFFIT indicated that treatment with Golden03 could result in antibody levels of up to 0.74 IU/mL 5 days post infection (DPI). ELISPOT for IFN-γ in mouse spleen cells showed that Golden03 enhanced immune responses at 14 DPI, inducing a rapid and powerful cellular response compared to the control group. Furthermore, the Vaccine-Golden03 group displayed no obvious weight loss or death after intracranial injection with CVS-11. An additional advantage is that Golden03 allowed for a three-quarter reduction in dose, while maintaining its efficacy and rapid stimulation effect. We suggest that Golden03 could be developed as a potential adjuvant for use in human rabies vaccine.

The effect of exercise on local and systemic adverse reactions after vaccinations - Outcomes of two randomized controlled trials

INTRODUCTION

An adverse reaction associated with vaccination is considered to be a key barrier to vaccinate, yet little attention has been given to interventions to reduce their occurrence. Exercise is a behavioural adjuvant which may also influence adverse reactions. Here, two randomized controlled trials are reported, examining the effects of exercise on self-reported adverse reactions following vaccination in adolescents and young adults.

METHODS

Study one; 116 adolescents receiving the HPV vaccine were randomly allocated to either Control (n = 56) or Pre-vaccine Exercise (n = 60) group (2015-2016). Exercise consisted of 15-minutes upper body exercise. Study two; 78 young adults receiving the influenza vaccine were randomly allocated to either Control (n = 19), or one of 3 exercise groups: Pre-vaccine Arm (n = 19), Pre-vaccine Leg (n = 20) or Post-vaccine Arm (n = 20) (2017). Exercise included 15-minutes of arm or leg exercises prior to or after vaccination. All participants in both studies completed an adverse events diary for seven-days post-vaccination.

RESULTS

Study one; Reported days of tenderness in female adolescents that exercised were significantly lower than control (p = 0.032), with a similar trend in reported days of pain (p = 0.050). Furthermore, days of feeling ill (p = 0.070) and reduced appetite (p = 0.067) were found to be lower with exercise, although not significant. Overall, female adolescents reported significantly more days of pain (p = 0.003), tenderness (p < 0.001), swelling (p = 0.011), and feeling ill (p = 0.0040). Study two; Exercise groups reported reduced days of swelling (p = 0.018), fever (p = 0.013), and lowered appetite (p = 0.011) across both genders. Furthermore, females reported reduced days of medication use with exercise (p = 0.034), and a trend toward reduced days of swelling (p = 0.052).

DISCUSSION

In two separate trials, a short bout of exercise reduced reported adverse reactions after vaccinations for local and systemic adverse reactions. Gender differences in reported local and systemic adverse reactions were more evident among adolescents than young adults. These findings support the need for further work to examine the potential benefit of exercise in improving vaccination procedures.

Adjuvanted Immunotherapy Approaches for Peanut Allergy

Food allergies are a growing public health concern with an estimated 8% of US children affected. Peanut allergies are also on the rise and often do not spontaneously resolve, leaving individuals at-risk for potentially life-threatening anaphylaxis throughout their lifetime. Currently, two forms of peanut immunotherapy, oral immunotherapy (OIT) and epicutaneous immunotherapy (EPIT), are in Phase III clinical trials and have shown promise to induce desensitization in many subjects. However, there are several limitations with OIT and EPIT, such as allergic side effects, daily dosing requirements, and the infrequent outcome of long-term tolerance. Next-generation therapies for peanut allergy should aim to overcome these limitations, which may be achievable with adjuvanted immunotherapy. An adjuvant can be defined as anything that enhances, accelerates, or modifies an immune response to a particular antigen. Adjuvants may allow for lower doses of antigen to be given leading to decreased side effects; may only need to be administered every few weeks or months rather than daily exposures; and may induce a long-lasting protective effect. In this review article, we highlight examples of adjuvants and formulations that have shown pre-clinical efficacy in treating peanut allergy.

Size-dependent neutralizing activity of gold nanoparticle-based subunit vaccine against dengue virus

Dengue results in substantial human morbidity and significant socio-economic impacts, but a specific dengue therapeutic is not available. The currently available dengue vaccine has low efficacy and high rate of adverse effects, necessitating different strategies for the development of a safer and more efficient vaccine against dengue virus. We describe here a hybrid combination of different-sized gold nanoparticles (AuNPs) and domain III of envelope glycoprotein derived from serotype 2 of dengue virus (EDIII) as dengue subunit vaccine. The efficacy of the EDIII-functionalized AuNPs (AuNP-E) to induce neutralizing antibody in BALB/c mice is evaluated. Obtained results show that AuNP-E induced a high level of antibody which mediates serotype-specific neutralization of dengue virus. More importantly, the level of antibody is dependent on both the size of AuNPs and the concentration of AuNP-E, implicating the possibility to modulate it through adjusting these parameters. These results represent an important step towards the development of tetravalent AuNP-based subunit dengue vaccine.

STATEMENT OF SIGNIFICANCE

This research presents a novel subunit vaccine against dengue virus using a hybrid comprising gold nanoparticles (AuNPs) and domain III of envelop protein (EDIII). We proved the neutralizing activity of anti-EDIII antibody induced in immunized mice on Dengue virus serotype 2 in an AuNP core size and concentration dependent manner. The hybrid concept behind this work could also be adopted for the development of a tetravalent vaccine against four serotypes of Dengue virus.

Vaccination against Toxoplasma gondii using rhoptry antigens: a systematic review

Toxoplasma gondii is an obligate intracellular parasitic protozoan that infects a wide variety of vertebrates as intermediate hosts. The aim of the current systematic review study is to clarify the latest status of studies in the literature regarding rhoptry-associated recombinant proteins or rhoptry-associated recombinant DNAs as potential vaccines against toxoplasmosis. The search was performed systematically in 8 databases, four in English and four in Persian, up to February 2017. Overall, ROP2 was the most commonly used ROPs in DNA vaccines (27.27%) and protein vaccines (6.81%). Furthermore, regarding the type of adjuvants, route and dose of vaccination, animal models, challenge methods, and measurement of immune responses has been discussed in the text. It is hoped that this article help researchers to conduct more effective studies in the field of immunization against T. gondii.

Augmentation of vaccine-induced humoral and cellular immunity by a physical radiofrequency adjuvant

Protein/subunit vaccines often require external adjuvants to induce protective immunity. Due to the safety concern of chemical adjuvants, physical adjuvants were recently explored to boost vaccination. Physical adjuvants use physical energies rather than chemicals to stimulate tissue stress and endogenous danger signal release to boost vaccination. Here we present the safety and potency of non-invasive radiofrequency treatment to boost intradermal vaccination in murine models. We show non-invasive radiofrequency can increase protein antigen-induced humoral and cellular immune responses with adjuvant effects comparable to widely used chemical adjuvants. Radiofrequency adjuvant can also safely boost pandemic 2009 H1N1 influenza vaccination with adjuvant effects comparable to MF59-like AddaVax adjuvant. We find radiofrequency adjuvant induces heat shock protein 70 (HSP70) release and activates MyD88 to mediate the adjuvant effects. Physical radiofrequency can potentially be a safe and potent adjuvant to augment protein/subunit vaccine-induced humoral and cellular immune responses.

Design and testing of a highly conserved human rotavirus VP8* immunogenic peptide with potential for vaccine development

Rotavirus infection of young children particularly below five years of age resulting in severe diarhoea, is the cause of a large number of infant deaths all over the world, more so in developing countries like India. Vaccines developed against this infection in the last two decades have shown mixed results with some of them leading to complications. Oral vaccines have not been very effective in India. Significant diversity has been found in circulating virus strains in India. Development of a vaccine against diverse genetic variants of the different strains would go a long way in reducing the incidence of infection in developing countries. Success of such a vaccine would depend to a large extent on the antigenic peptide to be used in antibody production. The non-glycosylated protein VP4 on the surface capsid of the virus is important in rota viral immunogenicity and the major antigenic site(s) responsible for neutralization of the virus via VP4 is in the VP8* subunit of VP4. It is necessary that the peptide should be very specific and a peptide sequence which would stimulate both the T and B immunogenic cells would provide maximum protection against the virus. Advanced computational techniques and existing databases of sequences of the VP4 protein of rotavirus help in identification of such specific sequences. Using an in silico approach we have identified a highly conserved VP8* subunit of the VP4 surface protein of rotavirus which shows both T and B cell processivity and is also non-allergenic. This sub-unit could be used in in vivo models for induction of antibodies.

Cationic lipids as one-component vaccine adjuvants: A promising alternative to alum

Effective vaccine formulations consist of several components: an antigen carrier, the antigen, a stimulator of cellular immunity such as a Toll-like Receptors (TLRs) ligand, and a stimulator of humoral response such as an inflammasome activator. Here, we investigated the immunostimulatory and adjuvant properties of lipopolyamines, cationic lipids used as gene carriers. We identified new lipopolyamines able to activate both TLR2 and TLR4 and showed that lipopolyamines interact with TLRs via a mechanism different from the one used by bacterial ligands, activating a strong type-I IFN response, pro-inflammatory cytokines and IL-1β secretion. The TLR and inflammasome stimulations, together with the antigen carrier properties of lipopolyamines, resulted in both humoral and cellular immunity in mice vaccinated against OVA and make lipopolyamines promising one-component vaccine adjuvants.

Polysaccharides as vaccine adjuvants

Adjuvant is a substance added to vaccine to improve the immunogenicity of antigens, and it can induce stronger immune responses and reduce the dosage and production cost of vaccine in populations responding poorly to vaccination. Adjuvants in development or in use mainly include aluminum salts, oil emulsions, saponins, immune-stimulating complexes, liposomes, microparticles, nonionic block copolymers, polysaccharides, cytokines and bacterial derivatives. Polysaccharide adjuvants have attracted much attention in the preparation of nano vaccines and nano drugs because natural polysaccharides have the characteristics of intrinsic immunomodulating, biocompatibility, biodegradability, low toxicity and safety. Moreover, it has been proved that a variety of natural polysaccharides possess better immune promoting effects, and they can enhance the effects of humoral, cellular and mucosal immunities. In the present study, we systematically reviewed the recent studies on polysaccharides with vaccine adjuvant activities, including chitosan-based nanoparticles (NPs), glucan, mannose, inulin polysaccharide and Chinese medicinal herb polysaccharide. The application and future perspectives of polysaccharides as adjuvants were also discussed. These findings lay a foundation for the further development of polysaccharide adjuvants. Collectively, more and more polysaccharide adjuvants will be developed and widely used in clinical practice with more in-depth investigations of polysaccharide adjuvants.

The Use of Chitosan-Coated Membrane Vesicles for Immunization Against Salmonid Rickettsial Septicemia in an Adult Zebrafish Model

The introduction of fish vaccination has had a tremendous impact on the aquaculture industry by providing an important measurement in regard to disease control. Infectious diseases caused by intracellular pathogens do, however, remain an unsolved problem for the industry. This is in many cases directly connected to the inability of vaccines to evoke a cellular immunity needed for long-term protection. Thus, there is a need for new and improved vaccines and adjuvants able to induce a strong humoral and cellular immune response. We have previously shown that membrane vesicles (MVs) from the intracellular fish pathogen Piscirickettsia salmonis are able to induce a protective response in adult zebrafish, but the incorporation of an adjuvant has not been evaluated. In this study, we report the use of chitosan as an adjuvant in combination with the P. salmonis-derived MVs for improved immunization against P. salmonis. Both free chitosan and chitosan-coated MVs (cMVs) were injected into adult zebrafish and their efficacy evaluated. The cMVs provided a significant protection (p < 0.05), while a small but nonsignificant reduction in mortalities was registered for fish injected with free chitosan. Both free chitosan and the cMVs were shown to induce an increased immune gene expression of CD 4, CD 8, MHC I, Mpeg1.1, TNFα, IL-1β, IL-10, and IL-6, but to a higher degree in the cMV group. Taken together, the results indicate a potential use of chitosan-coated MVs for vaccination, and that zebrafish is a promising model for aquaculture-relevant studies.

Adjuvants for allergy immunotherapeutics

Allergic diseases are reaching epidemic proportions in developed countries. In particular, food allergy is increasing in prevalence and severity, thus becoming an important socioeconomic burden. Numerous cell types and cell populations, which form an intricate and balanced network, are involved in an immune response. This balance is occasionally disturbed, leading to the onset of different diseases, such as allergic diseases. Antihistamines and corticosteroids provide some degree of relief from the symptoms of allergic conditions. However, the only treatment that can revert the disease is immunotherapy. Nevertheless, specific immunotherapy has at least 2 major drawbacks: it is time-consuming, and it can produce local and even systemic allergic side effects. Immunotherapy's potential goes beyond our current knowledge of the immune response; nevertheless, we can still design strategies to reach a safer immune modulation for treating allergies. This review deals with the use of adjuvants to reduce the undesirable side effects associated with specific allergen immunotherapy. For example, nanoparticles used as immunoadjuvants are offering promising results in preclinical assays.

Intranasal inoculate of influenza virus vaccine against lethal virus challenge

Vaccine adjuvants are essential for enhancing immune responses during vaccination. However, only a limited number of safe and effective adjuvants, especially mucosal adjuvants, are available for use in vaccines. The development of a practically applicable mucosal adjuvant is therefore urgently needed. Here, we showed that the non-toxic CTA1-DD adjuvant, which combined the full enzymatic activity of the A1 subunit of cholera toxin (CT) with two immunoglobulin-binding domains of Staphylococcus aureus protein A (SpA), promoted mucosal and systemic humoral and cell-mediated immune responses following intranasal administration with H1N1 split vaccine in mice. We demonstrated that CTA1-DD-adjuvant vaccine provided 100% protection against mortality and greatly reduced morbidity in a mouse model. We also showed that addition of CTA1-DD to the vaccine elicited significantly higher hemagglutination inhibition titers and IgG antibodies in sera than alum adjuvant. Furthermore, CTA1-DD significantly promoted the production of mucosal secretory IgA in lung lavages and vaginal lavages. We also showed that CTA1-DD could be used as a mucosal adjuvant to enhance T cell responses. Our results clearly indicated that CTA1-DD contributed to the elicitation of a protective cell-mediated immune response required for efficacious vaccination against influenza virus, which suggested that this adjuvant could be explored further as a clinically safe mucosal vaccine adjuvant for respiratory diseases and other mucosal diseases.

Evaluation of alum-based adjuvant on the immunogenicity of salmonella enterica serovar typhi conjugates vaccines

The function of adjuvant in maintaining the long-term immune response to Typhoid conjugate vaccine (TCV) was evaluated in. Two TCV products, Vi-DT and Vi-TT, were formulated in either aluminum phosphate (AlPO₄) or aluminum hydroxide (AlOH) as adjuvants and TCV formulated in phosphate buffer saline were used as controls. In each case, a group of Balb/c mice was injected intramuscularly with two doses of the formulated vaccine at two-week intervals. The anti-Vi IgG responses were monitored by Enzyme-Linked Immunosorbent Assay and the levels of CD4⁺ T-cells expressing cytokine were characterized using intracellular cytokine staining. All mice immunized by TCV formulated in adjuvant elicited anti-Vi response to a higher level than the group receiving TCV formulated in PBS. The extent of adsorption of TCV in AlOH was greater than that in AlPO₄, and this finding correlated well with the observation that the mice immunized with two doses of Vi-DT(AlOH) elicited anti-Vi IgG to a level higher than that seen with Vi-DT(AlPO₄). The mice primed with Vi-TT(AlOH) produced lower anti-Vi IgG (25.901 GM) compared to those receiving Vi-TT(AlPO₄) (49.219 GM). However, after the second injection, the former raised the antibody level significantly to 137.008 GM while the latter provided a value of only 104.966 GM. The groups of mice vaccinated by TCV formulated in AlOH expressed IL4 at higher levels than the other groups, which correlated positively with the high Anti-Vi IgG in these animals. In conclusion, AlOH could be recommended as an effective adjuvant for TCV to provide a long-term immune response.

Improved vaccine-induced immune responses via a ROS-triggered nanoparticle-based antigen delivery system

Subunit vaccines that are designed based on recombinant antigens or peptides have shown promising potential as viable substitutes for traditional vaccines due to their better safety and specificity. However, the induction of adequate in vivo immune responses with appropriate effectiveness remains a major challenge for vaccine development. More recently, the implementation of a nanoparticle-based antigen delivery system has been considered a promising approach to improve the in vivo efficacy for subunit vaccine development. Thus, we have designed and prepared a nanoparticle-based antigen delivery system composed of three-armed PLGA, which is conjugated to PEG via the peroxalate ester bond (3s-PLGA-PO-PEG) and PEI as a cationic adjuvant (PPO NPs). It is known that during a foreign pathogen attack, NADPH, an oxidase, of the host organism is activated and generates an elevated level of reactive oxygen species, hydrogen peroxide (H2O2) primarily, as a defensive mechanism. Considering the sensitivity of the peroxalate ester bond to H2O2 and the cationic property of PEI for the induction of immune responses, this 3s-PLGA-PO-PEG/PEI antigen delivery system is expected to be both ROS responsive and facilitative in antigen uptake without severe toxicity that has been reported with cationic adjuvants. Indeed, our results demonstrated excellent loading capacity and in vitro stability of the PPO NPs encapsulated with the model antigen, ovalbumin (OVA). Co-culturing of bone marrow dendritic cells with the PPO NPs also led to enhanced dendritic cell maturation, antigen uptake, enhanced lysosomal escape, antigen cross-presentation and in vitro CD8+ T cell activation. In vivo experiments using mice further revealed that the administration of the PPO nanovaccine induced robust OVA-specific antibody production, upregulation of splenic CD4+ and CD8+ T cell proportions as well as an increase in memory T cell generation. In summary, we report here a ROS-triggered nanoparticle-based antigen delivery system that could be employed to promote the in vivo efficacy of vaccine-induced immune responses.

Outer Membrane Vesicles: Current Status and Future Direction of These Novel Vaccine Adjuvants

Adjuvants have been of great interest to vaccine formulation as immune-stimulators. Prior to the recent research in the field of immune stimulation, conventional adjuvants utilized for aluminum-based vaccinations dominated the adjuvant market. However, these conventional adjuvants have demonstrated obvious defects, including poor protective efficiency and potential side effects, which hindered their widespread circulation. Outer membrane vesicles (OMVs) naturally exist in gram-negative bacteria and are capable of engaging innate and adaptive immunity and possess intrinsic adjuvant capacity. They have shown tremendous potential for adjuvant application and have recently been successfully applied in various vaccine platforms. Adjuvants could be highly effective with the introduction of OMVs, providing complete immunity and with the benefits of low toxicity; further, OMVs might also be designed as an advanced mucosal delivery vehicle for use as a vaccine carrier. In this review, we discuss adjuvant development, and provide an overview of novel OMV adjuvants and delivery vehicles. We also suggest future directions for adjuvant research. Overall, we believe that OMV adjuvants would find high value in vaccine formulation in the future.

Antivenom Production against Bothrops jararaca and Bothrops erythromelas Snake Venoms Using Cross-Linked Chitosan Nanoparticles as an Immunoadjuvant

In Brazil, envenomation by snakes of the genus Bothrops is clinically relevant, particularly for the species Bothrops jararaca and B. erythromelas. The most effective treatment for envenomation by snakes is the administration of antivenoms associated with adjuvants. Novel adjuvants are required to reduce side effects and maximize the efficiency of conventional serum and vaccine formulations. The polymer chitosan has been shown to have immunoadjuvant properties, and it has been used as a platform for delivery systems. In this context, we evaluated the potential immunoadjuvant properties of chitosan nanoparticles (CNPs) loaded with B. jararaca and B. erythromelas venoms in the production of sera against these venoms. Stable CNPs were obtained by ionic gelation, and mice were immunized subcutaneously for 6 weeks with 100 µL of each snake venom at concentrations of 5.0 or 10.0% (w/w), encapsulated in CNPs or associated with aluminium hydroxide (AH). The evaluation of protein interactions with the CNPs revealed their ability to induce antibody levels equivalent to those of AH, even with smaller doses of antigen. In addition, the CNPs were less inflammatory due to their modified release of proteins. CNPs provide a promising approach for peptide/protein delivery from snake venom and will be useful for new vaccines.

Fabrication and characterization of DDAB/PLA-alginate composite microcapsules as single-shot vaccine

The most effective method to reduce chronic hepatitis B virus infection is the universal implementation of vaccination. The commercial aluminum-based vaccines need multiple-injection protocols for complete protection resulting in poor compliance in developing countries. It is necessary to develop single-shot vaccine formulations. In this study, novel antigen-loaded DDAB/PLA (didodecyldimethylammonium bromide/poly(lactic acid)) nanoparticles (NPs)-alginate composite microcapsules were developed as a single-shot vaccine. The hepatitis B surface antigen (HBsAg)-loaded DDAB/PLA NPs were successfully encapsulated into alginate microcapsules by a modified spray-solidification technique. The response surface method was applied to optimize the preparation parameters employing encapsulation efficiency of HBsAg and particle size of microcapsules as response variables. The antigen-loaded DDAB/PLA NPs-alginate composite microcapsules were prepared under these optimal conditions: the size of composite microcapsules was 24.25 μm, the Span value was 1.627, and the encapsulation efficiency of HBsAg was 68.4%. The obtained microcapsules were spherical gel microparticles with excellent dispersity and narrow size distributions. In vitro release profile indicated a slow release rate of encapsulated HBsAg especially in phosphate buffered saline solution. The microcapsules showed little toxicity in vivo. This vaccine delivery system could induce stronger immune responses by a single shot, which exhibited much higher cytokine secretion levels closely related to cellular immunity and comparable IgG titers to the traditional aluminum-adjuvanted vaccine with three shots.

A bioconjugate leveraging xenoreactive antibodies to alleviate cocaine-induced behavior

A method for potentiating the response to an anti-cocaine vaccine by leveraging xenoreactive antibodies against the carbohydrate epitope Galα1,3-Gal (GAL) was found to result in a highly specific anti-cocaine response that was able to significantly attenuate cocaine-induced locomotion at 20 mg kg^-1 with superior efficacy compared to a standard conjugate.