ISCOMs/MPLA-Adjuvanted SDAD Protein Nanoparticles Induce Improved Mucosal Immune Responses and Cross-Protection in Mice.

The epidemics caused by the influenza virus are a serious threat to public health and the economy. Adding appropriate adjuvants to improve immunogenicity and finding effective mucosal vaccines to combat respiratory infection at the portal of virus entry are important strategies to boost protection. In this study, a novel type of core/shell protein nanoparticle consisting of influenza nucleoprotein (NP) as the core and NA1-M2e or NA2-M2e fusion proteins as the coating antigens by SDAD hetero-bifunctional crosslinking is exploited. Immune-stimulating complexes (ISCOMs)/monophosphoryl lipid A (MPLA) adjuvants further boost the NP/NA-M2e SDAD protein nanoparticle-induced immune responses when administered intramuscularly. The ISCOMs/MPLA-adjuvanted protein nanoparticles are delivered through the intranasal route to validate the application as mucosal vaccines. ISCOMs/MPLA-adjuvanted nanoparticles induce significantly strengthened antigen-specific antibody responses, cytokine-secreting splenocytes in the systemic compartment, and higher levels of antigen-specific IgA and IgG in the local mucosa. Meanwhile, significantly expanded lung resident memory (RM) T and B cells (TRM /BRM ) and alveolar macrophages population are observed in ISCOMs/MPLA-adjuvanted nanoparticle-immunized mice with a 100% survival rate after homogeneous and heterogeneous H3N2 viral challenges. Taken together, ISCOMs/MPLA-adjuvanted protein nanoparticles could improve strong systemic and mucosal immune responses conferring protection in different immunization routes.

A COVID-19 vaccine candidate based on SARS-CoV-2 spike protein and immune-stimulating complexes.

Spike protein from SARS-CoV-2, the etiologic agent of the COVID-19 pandemic disease, constitutes a structural protein that proved to be the main responsible for neutralizing antibody production. Thus, its sequence is highly considered for the design of candidate vaccines. Animal cell culture represents the best option for the production of subunit vaccines based on recombinant proteins since they introduce post-translational modifications that are important to mimic the natural antigenic epitopes. Particularly, the human cell line HEK293T has been explored and used for the production of biotherapeutics since the products derived from them present human-like post-translational modifications that are important for the protein's activity and immunogenicity. The aim of this study was to produce and characterize a potential vaccine for COVID-19 based on the spike ectodomain (S-ED) of SARS-CoV-2 and two different adjuvants: aluminum hydroxide (AH) and immune-stimulating complexes (ISCOMs). The S-ED was produced in sHEK293T cells using a 1-L stirred tank bioreactor operated in perfusion mode and purified. S-ED characterization revealed the expected size and morphology. High N-glycan content was confirmed. S-ED-specific binding with the hACE2 (human angiotensin-converting enzyme 2) receptor was verified. The immunogenicity of S-ED was evaluated using AH and ISCOMs. Both formulations demonstrated the presence of anti-RBD antibodies in the plasma of immunized mice, being significantly higher for the latter adjuvant. Also, higher levels of IFN-γ and IL-4 were detected after the ex vivo immune stimulation of spleen-derived MNCs from ISCOMs immunized mice. Further analysis confirmed that S-ED/ISCOMs elicit neutralizing antibodies against SARS-CoV-2. KEY POINTS: Trimeric SARS-CoV-2 S-ED was produced in stable recombinant sHEK cells in serum-free medium. A novel S-ED vaccine formulation induced potent humoral and cellular immunity. S-ED formulated with ISCOMs adjuvant elicited a highly neutralizing antibody titer.

Dual-action of colloidal ISCOMs: an optimized approach using Box-Behnken design for the management of breast cancer.

Neuropeptide Y (NPY) occurs in G-protein-coupled receptors and offers targeted effects at the active sites for therapeutic action in various conditions like depression, stress, obesity and cancer. Immune stimulating complexes (ISCOMs) associate peptides with the lipid systems for enhancing antigen targeting to provide site-specific action and B-cell response. The present study focused on the encapsulation of NPY in ISCOMs to comprise dual action in the form of immunity modulation and management of breast cancer by arresting G0/G1 phase. The colloidal ISCOMs were prepared by coupling method and further optimized by Box-Behnken design of Design of Experiment (DoE) software. The NPY-loaded ISCOMs (formulation ISCN) were characterized by various parameters with higher % encapsulation efficiency of 87.99 ± 1.87% and in-vitro release of 84.16±3.2% of NPY for 24 h. The study of MTT assay on MCF-7 cell line for formulation ISCN exhibited a significant decrease in the cell growth of 66.41±4.7% at 10 µg/mL compared to plain NPY (52.21±0.04%). The MCF-7 cells showed a significant reduction in cytokine levels in the presence of formulation ISCN wherein TH1(TNF-α) and TH2(IL-10) levels were found to be 25.12±3.11 pg/mL and 35.76±4.23 pg/mL, respectively. The cell cycle study demonstrated that significant cells were blocked in the G0/G1 phase with 57.8±3.02% of cell apoptosis using formulation ISCN. The formulation ISCN was found to prolong t1/2 and increase AUC than plain NPY via intravenous administration due to complex formation with phospholipid. Hence, ISCOMs-based NPY system will be a promising approach for dual action as immunomodulation and anticancer effects by controlling the release of NPY.

Saponins from Quillaja saponaria and Quillaja brasiliensis: Particular Chemical Characteristics and Biological Activities.

Quillaja saponaria Molina represents the main source of saponins for industrial applications. Q. saponaria triterpenoids have been studied for more than four decades and their relevance is due to their biological activities, especially as a vaccine adjuvant and immunostimulant, which have led to important research in the field of vaccine development. These saponins, alone or incorporated into immunostimulating complexes (ISCOMs), are able to modulate immunity by increasing antigen uptake, stimulating cytotoxic T lymphocyte production (Th1) and cytokines (Th2) in response to different antigens. Furthermore, antiviral, antifungal, antibacterial, antiparasitic, and antitumor activities are also reported as important biological properties of Quillaja triterpenoids. Recently, other saponins from Q. brasiliensis (A. St.-Hill. & Tul.) Mart. were successfully tested and showed similar chemical and biological properties to those of Q. saponaria barks. The aim of this manuscript is to summarize the current advances in phytochemical and pharmacological knowledge of saponins from Quillaja plants, including the particular chemical characteristics of these triterpenoids. The potential applications of Quillaja saponins to stimulate further drug discovery research will be provided.

Saponin Interactions with Model Membrane Systems - Langmuir Monolayer Studies, Hemolysis and Formation of ISCOMs.

Saponins are used in medicine due to their pharmacological and immunological effects. To better understand interactions of saponins with model membranes and natural membranes of, for example, erythrocytes, Langmuir film balance experiments are well established. For most saponins, a strong interaction with cholesterol was demonstrated in dependence of both the aglycone part and the sugar moieties and is suggested to be correlated with a strong hemolytic activity, high toxicity, and high surface activity, as was demonstrated for the steroid saponin digitonin. In general, changes in the sugar chain or in substituents of the aglycone result in a modification of the saponin properties. A promising saponin with regard to fairly low hemolytic activity and high adjuvant effect is α-tomatine, which still shows a high affinity for cholesterol. An interaction with cholesterol and lipids has also been proven for the Quillaja saponin from the bark of Quillaja saponaria Molina. This triterpene saponin was approved in marketed vaccines as an adjuvant due to the formation of immunostimulating complexes. Immunostimulating complexes consist of a Quillaja saponin, cholesterol, phospholipids, and a corresponding antigen. Recently, another saponin from Quillaja brasiliensis was successfully tested in immunostimulating complexes, too. Based on the results of interaction studies, the formation of drug delivery systems such as immunostimulating complexes or similar self-assembled colloids is postulated for a variety of saponins.

[Current status and future prospects in HMGB1 and receptor researches].

High mobility group box protein1 (HMGB1), a ubiquitous chromatin component, is released by necrotic cells, apoptotic cells, and cells in profound distress. HMGB1 plays a critical role as a proinflammatory mediator. HMGB1 represents an important new target for drug development in a variety of inflammatory disorders, including stroke, brain injury, arteriosclerosis, and cancer. The antibodies against HMGB1 and its receptors ar hopeful candidates for immunotherapeutic strategy for treating patients with these diseases. HMGB1 forms immunostimulatory complexes by interaction with cytokines and other endogenous or exogenous factors. The HMGB1-partner molecule complexes can enhance the immune response induced by the ligand alone. The current status of HMGB1 works is summarized and future prospects will be provided in this review.

Coadministration of polyinosinic:polycytidylic acid and immunostimulatory complexes modifies antigen processing in dendritic cell subsets and enhances HIV gag-specific T cell immunity.

Currently approved adjuvants induce protective Ab responses but are more limited for generating cellular immunity. In this study, we assessed the effect of combining two adjuvants with distinct mechanisms of action on their ability to prime T cells: the TLR3 ligand, polyinosinic:polycytidylic acid (poly I:C), and immunostimulatory complexes (ISCOMs). Each adjuvant was administered alone or together with HIV Gag protein (Gag), and the magnitude, quality, and phenotype of Gag-specific T cell responses were assessed. For CD8 T cells, all adjuvants induced a comparable response magnitude, but combining poly I:C with ISCOMs induced a high frequency of CD127(+), IL-2-producing cells with decreased expression of Tbet compared with either adjuvant alone. For CD4 T cells, combining poly I:C and ISCOMs increased the frequency of multifunctional cells, producing IFN-γ, IL-2, and TNF, and the total magnitude of the response compared with either adjuvant alone. CD8 or CD4 T cell responses induced by both adjuvants mediated protection against Gag-expressing Listeria monocytogenes or vaccinia viral infections. Poly I:C and ISCOMs can alter Ag uptake and/or processing, and we therefore used fluorescently labeled HIV Gag and DQ-OVA to assess these mechanisms, respectively, in multiple dendritic cell subsets. Poly I:C promoted uptake and retention of Ag, whereas ISCOMs enhanced Ag degradation. Combining poly I:C and ISCOMs caused substantial death of dendritic cells but persistence of degraded Ag. These data illustrate how combining adjuvants, such as poly I:C and ISCOMs, that modulate Ag processing and have potent innate activity, can enhance the magnitude, quality, and phenotype of T cell immunity.

Phenotypic analysis of ovine antigen presenting cells loaded with nanoparticles migrating from the site of vaccination.

Virus-sized particulate adjuvants such as ISCOMs, polystyrene nanoparticles and virus-like particles have been shown to target dendritic cells, resulting in the activation of T and B cells in vivo. Using an ovine pseudo-afferent lymph cannulation model to capture APC that traffic from the site of injection to the local lymph node, we show that 40-50 nm nanoparticles are taken up at the site of injection by dendritic cells (DCs) migrating to the draining lymph node. These DCs can express CD11c, CD1b, CD5, MHC class II and CD8. Nanoparticles transported by DCs migrating from the site of injection to the local lymph node therefore needs to be considered as a new mechanism underlying the immunogenicity of virus-sized vaccine delivery systems.

T-helper 1 cells elicited by H5N1 vaccination predict seroprotection.

BACKGROUND: Vaccination is the best measure to protect the population against a potential influenza H5N1 pandemic, but 2 doses of vaccine are needed to elicit protective immune responses. An immunological marker for H5N1 vaccine effectiveness is needed for early identification of the best vaccine candidate. METHODS: We conducted a phase I clinical trial of a virosomal H5N1 vaccine adjuvanted with Matrix M. Sixty adult volunteers were vaccinated intramuscularly with 2 doses of either 30 µg hemagglutinin (HA) alone or with 1.5, 7.5, or 30 µg HA and Matrix M adjuvant (50 µg). The humoral response was measured by the hemagglutination inhibition (HI), microneutralization (MN), and single radial hemolysis (SRH) assays, and the CD4(+) T-helper 1 (Th1)-cell response was measured by intracellular staining for the cytokines interleukin 2, interferon γ, and tumor necrosis factor α. RESULTS: The adjuvanted vaccine effectively induced CD4(+) Th1-cell responses, and the frequency of influenza-specific Th1 cells after the first vaccine dose predicted subsequent HI, MN, and SRH seroprotective responses after the second vaccination. CONCLUSIONS: These results support early identification of Th1-cell responses as a predictive biomarker for an efficient vaccine response, which could have great implications for early identification of persons with low or no response to vaccine when evaluating future pandemic influenza vaccines.

Immunogenicity of a spike protein subunit-based COVID-19 vaccine with broad protection against various SARS-CoV-2 variants in animal studies.

SARS-CoV-2 pandemic has profound impacts on human life and global economy since the outbreak in 2019. With the new variants continue to emerge with greater immune escaping capability, the protectivity of the available vaccines is compromised. Therefore, development a vaccine that is capable of inducing immunity against variants including omicron strains is in urgent need. In this study, we developed a protein-based vaccine BCVax that is consisted of antigen delta strain spike protein and QS21-based adjuvant AB801 in nanoparticle immune stimulation complex format (AB801-ISCOM). Results from animal studies showed that high level of anti-S protein IgG was induced after two doses of BCVax and the IgG was capable of neutralizing multiple variants of pseudovirus including omicron BA.1 or BA.2 strains. In addition, strong Th1 response was stimulated after BCVax immunization. Furthermore, BCvax with AB801-ISCOM as the adjuvant showed significant stronger immunity compared with the vaccine using aluminum hydroxide plus CpG 1018 as the adjuvant. BCVax was also evaluated as a booster after two prior vaccinations, the IgG titers and pseudovirus neutralization activities against BA.2 or BA.4/BA.5 were further enhanced suggesting BCVax is a promising candidate as booster. Taken together, the pre-clinical data warrant BCVax for further development in clinic.

Structure of immune stimulating complex matrices and immune stimulating complexes in suspension determined by small-angle x-ray scattering.

Immune stimulating complex (ISCOM) particles consisting of a mixture of Quil-A, cholesterol, and phospholipids were structurally characterized by small-angle x-ray scattering (SAXS). The ISCOM particles are perforated vesicles of very well-defined structures. We developed and implemented a novel (to our knowledge) modeling method based on Monte Carlo simulation integrations to describe the SAXS data. This approach is similar to the traditional modeling of SAXS data, in which a structure is assumed, the scattering intensity is calculated, and structural parameters are optimized by weighted least-squares methods when the model scattering intensity is fitted to the experimental data. SAXS data from plain ISCOM matrix particles in aqueous suspension, as well as those from complete ISCOMs (i.e., with an antigen (tetanus toxoid) incorporated) can be modeled as a polydisperse distribution of perforated bilayer vesicles with icosahedral, football, or tennis ball structures. The dominating structure is the tennis ball structure, with an outer diameter of 40 nm and with 20 holes 5-6 nm in diameter. The lipid bilayer membrane is 4.6 nm thick, with a low-electron-density, 2.0-nm-thick hydrocarbon core. Surprisingly, in the ISCOMs, the tetanus toxoid is located just below the membrane inside the particles.

[Enhancing the immunogenic activity of influvac vaccine in the use of adjuvant TI complexes modified by echinochrome A].

The self-assembly of marine macrophyte glycolipids, holothurian saponin, and cholesterol gave rise to nanoscale morphological structures called tubular immunostimulating (TI) complexes. Whether the latter could be used on the basis of vaccine preparations containing the influenza virus subunit antigens was studied. There was an obvious increase in the immunogenicity of influenza virus hemagglutinin when the experimental animals were immunized with this antigen as part of TI complexes. It was shown that the adjuvant activity of the TI complex to influenza virus hemagglutinin could be enhanced by adding the known antioxidant echinochrome A from a sand-dollar (Echinarachnius parma) to the matrix of the TI complex.

Formulation of IMXQB: Nanoparticles Based on Quillaja brasiliensis Saponins to be Used as Vaccine Adjuvants.

Adjuvants are essential components of subunit, recombinant, nonreplicating and killed vaccines, as they are substances that boost, shape, and/or enhance the immune response triggered by vaccination. Saponins obtained from the Chilean Q. saponaria tree are used as vaccine adjuvants in commercial vaccines, although they are scarce and difficult to obtain. In addition, tree felling is needed during its extraction, which has ecological impact. Q. brasiliensis leaf-extracted saponins arise as a more sustainable alternative, although its use is still limited to preclinical studies. Despite the remarkable immunostimulating properties of saponins, they are toxic to mammalian cells, due to their intrinsic characteristics. For these reasons they are mostly used in veterinary vaccines, although recently the Q. saponaria purified saponin QS-21 has been included in adjuvant systems for human vaccines, such as Mosquirix and Shingrix (GSK). In order to abrogate the toxicity of the saponins fractions, they can be formulated as immunostimulating complexes (ISCOMs). ISCOM-matrices are cage-like nanoparticles of approximately 40 nm, formulated combining saponins and lipids, without antigen, and are great adjuvants able to promote Th1-biased immune responses in a safe manner. Herein we describe how to formulate ISCOM-matrices nanoparticles using Q. brasiliensis purified saponin fractions (IMXQB) by the dialysis method. In addition, we indicate how to verify the appropriate size and homogeneity of the formulated nanoparticles.

Immunogenicity of a recombinant hemagglutinin neuraminidase-Porcine rubulavirus produced by Escherichia coli of Porcine rubulavirus gives protective immunity of litter after challenge.

Porcine rubulavirus (PRV) is a contagious virus that affects the Mexican swine industry. This work aimed to evaluate the immunogenicity of an recombinant hemagglutinin neuraminidase-Porcine rubulavirus (rHN-PorPV) candidate vaccine on pregnant sows, and the protective efficacy afforded to their 7-day-old suckling piglets against PRV lethal challenge. Three sows were immunized with rHN-PorPV formulated with immune-stimulating complex (ISCOMs) and two sows with rHN-PorPV protein alone as well as a mock-immunized pregnant sow (negative control). Quantitative ELISA detected a high concentration of anti-rHN-PorPV Immunoglobulin G (IgG) antibodies in sow sera after the second dose of vaccine administered on day 14 until farrowing, showing viral-neutralizing and cross-neutralization activity against different variants of PRV. Sera samples from piglets of immunized sows (with or without adjuvant), showed high concentrations of IgG antibodies. As expected, piglets from the negative control sow (n=5), exhibited severe signs of disease and 100% of mortality after PRV challenge study. Conversely, 75% and 87.5% of the piglets born from the rHN-PorPV and the rHN-PorPV-ISCOMs-immunized sows (n=8), survived, respectively, showing milder PRV clinical signs. Our data indicate that rHN-PorPV candidate vaccine produced in Escherichia coli induces efficient humoral response in pregnant sows and that the maternally derived immunity provides high protection to suckling piglets against PRV lethal challenge.

Investigation of the interaction between modified ISCOMs and stratum corneum lipid model systems.

The modified ISCOMs, so-called Posintro nanoparticles, provide an opportunity for altering the surface charge of the particles, which influences their affinity for the negatively charged antigen sites, cell membranes and lipids in the skin. Hypothetically, this increases the passage of the ISCOMs (or their components) and their load through the stratum corneum. The subsequent increase in the uptake by the antigen-presenting cells results in enhanced transcutaneous immunization. To understand the nature of penetration of Posintro nanoparticles into the intercorneocyte space of the stratum corneum, the interaction between the nanoparticles and lipid model systems in form of liposomes and/or supported lipid bilayer was studied. As a lipid model we used Stratum Corneum Lipid (SCL), a mixture similar in composition to the lipids of the intercorneocyte space. By Förster Resonance Energy Transfer (FRET), Atomic Force Microscopy (AFM), Electrochemical Impedance Spectroscopy (EIS) and cryo-Transmission Electron Microscopy (cryo-TEM) it was shown that application of nanoparticles to the SCL bilayers results in lipid disturbance. Investigation of this interaction by means of Isothermal Titration Calorimetry (ITC) confirmed existence of an enthalpically unfavorable reaction. All these methods demonstrated that the strength of electrostatic repulsion between the negatively charged SCL and the nanoparticles affected their interaction, as decreasing the negative charge of the Posintro nanoparticles leads to enhanced disruption of lipid organization.

Incorporation of antigens from Mannheimia haemolytica culture supernatant, and recombinant bovine C3d into ISCOM matrix using neutravidin-biotin interaction.

The aim of this study was to incorporate antigens from Mannheimia haemolytica culture supernatant, and an immune modulatory molecule, recombinant bovine C3d (rBoC3d), into immune stimulating complexes (ISCOMs) using neutravidin-biotin interaction. Biotinylated ISCOM matrix was generated using a commercial kit. The biotinylated ISCOM matrix was incubated with neutravidin and then centrifuged in a sucrose density gradient. The rBoC3d was expressed as an in vivo biotinylated protein and with a c-Myc tag (EQKLISEEDL) engineered to facilitate detection. The neutravidin-coated ISCOM matrix was incubated with biotinylated antigens from M. haemolytica culture supernatants and rBoC3d. To test the association among the neutravidin-coated ISCOM matrix, biotinylated antigens and rBoC3d, an analytical sucrose density gradient (10-40%, w/w) was performed. The experimental formulations were run in SDS-PAGE gels under reducing conditions. For Western immunoblot analysis, polyclonal bovine antiavidin, monoclonal anti-c-Myc, monoclonal antileukotoxin, and anti-GS60 antibodies were used to detect the presence of neutravidin, rBoC3d, leukotoxin, and GS60 antigens, respectively. By taking advantage of the biotin-neutravidin interaction, not only leukotoxin but also the recombinant immunomodulatory molecule, rBoC3d, was incorporated into ISCOM particles.

Tubular immunostimulating complex based on cucumarioside A2-2 and monogalactosyldiacylglycerol from marine macrophytes.

BACKGROUND: There is an urgent need to develop safe and effective adjuvants for the new generation of subunit vaccines. We developed the tubular immunostimulating complex (TI-complex) as a new nanoparticulate antigen delivery system. The morphology and composition of TI-complexes principally differ from the known vesicular immunostimulating complexes (ISCOMs). However, methodology for the preparation of TI-complexes has suffered a number of shortcomings. The aim of the present work was to obtain an antigen carrier consisting of triterpene glycosides from Cucumaria japonica, cholesterol, and monogalactosyldiacylglycerol from marine macrophytes with reproducible properties and high adjuvant activity. RESULTS: The cucumarioside A2-2 - cholesterol - MGalDG ratio of 6:2:4 (by weight) was found to provide the most effective formation of TI-complexes and the minimum hemolytic activity in vitro. Tubules of TI-complexes have an outer diameter of about 16 nm, an inner diameter of 6 nm, and a length of 500 nm. A significant dilution by the buffer gradually destroyed the tubular nanoparticles. The TI-complex was able to increase the immunogenicity of the protein antigens from Yersinia pseudotuberculosis by three to four times. CONCLUSIONS: We propose an optimized methodology for the preparation of homogeneous TI-complexes containing only tubular particles, which would achieve reproducible immunization results. We suggest that the elaborated TI-complexes apply as a universal delivery system for different subunit antigens within anti-infectious vaccines and enhance their economic efficacy and safety.

[Immunogenic and protective properties of nanosized constructs based on tubular immunostimulating complexes and pore forming protein of Yersinia pseudotuberculosis].

AIM: Evaluation of immunogenic and protective properties of constructs based on subunit porin antigen from Yersinia pseudotuberculosis, immunostimulating complexes (ISCOM) and tubular immunostimulating (TI) complexes. MATERIALS AND METHODS: Porin antibodies and blood serum cytokines were determined by using EIA. Porin-specific cell immunity was evaluated by DTH reaction inflammation index. Protective activity of porin formulations was determined by measuring specific gravity of animals surviving Yersinia pseudotuberculosis lethal challenge. RESULTS: Porin in TI complexes develops higher immunogenicity when compared with individual protein or protein with complete Freunds adjuvant. Porin in TI complexes develops higher protective activity, inhibits interferon synthesis in mice. Incorporation of porin into TI complexes results in neutralization of porin suppressive activity against DTH mechanisms and interferon system. CONCLUSION: TI complexes may be used as perspective carriers for bacterial antigens. TI complexes have adjuvant properties and can provide protective properties to porin vaccine constructs.

Zika Virus Envelope Domain III Recombinant Protein Delivered With Saponin-Based Nanoadjuvant From Quillaja brasiliensis Enhances Anti-Zika Immune Responses, Including Neutralizing Antibodies and Splenocyte Proliferation.

Nanoadjuvants that combine immunostimulatory properties and delivery systems reportedly bestow major improvements on the efficacy of recombinant, protein-based vaccines. Among these, self-assembled micellar formulations named ISCOMs (immune stimulating complexes) show a great ability to trigger powerful immunological responses against infectious pathogens. Here, a nanoadjuvant preparation, based on saponins from Quillaja brasiliensis, was evaluated together with an experimental Zika virus (ZIKV) vaccine (IQB80-zEDIII) and compared to an equivalent vaccine with alum as the standard adjuvant. The preparations were administered to mice in two doses (on days zero and 14) and immune responses were evaluated on day 28 post-priming. Serum levels of anti-Zika virus IgG, IgG1, IgG2b, IgG2c, IgG3 were significantly increased by the nanoadjuvant vaccine, compared to the mice that received the alum-adjuvanted vaccine or the unadjuvanted vaccine. In addition, a robust production of neutralizing antibodies and in vitro splenocyte proliferative responses were observed in mice immunized with IQB80-zEDIII nanoformulated vaccine. Therefore, the IQB80-zEDIII recombinant preparation seems to be a suitable candidate vaccine for ZIKV. Overall, this study identified saponin-based delivery systems as an adequate adjuvant for recombinant ZIKV vaccines and has important implications for recombinant protein-based vaccine formulations against other flaviviruses and possibly enveloped viruses.

Adjuvants for pandemic influenza vaccines.

The use of adjuvants is being explored as a means of improving vaccine immunogenicity. This is particularly important for the development of vaccines against potential pandemic influenza virus strains. Adjuvants act by prolonging the exposure time of antigen to the immune system, enhancing the delivery of antigen to antigen-presenting cells, or providing immunostimulatory signals that potentiate the immune response. Aluminum salts are the only licensed adjuvant in the United States, but the combination of these salts with inactivated influenza A/H5N1 antigens has had little effect on seroresponses. Several oil-in-water adjuvants, including MF59 and AS03, have significantly enhanced immune responses in healthy adult vaccine recipients to inactivated influenza A/H5N1. Additional studies are needed in vulnerable populations (younger and elderly persons, pregnant women, and immunocompromised patients) to confirm the safety and enhanced immunogenicity of these promising formulations. A number of other adjuvants are under investigation to evaluate their ability to improve the immunogenicity of inactivated vaccines targeting influenza A/H5N1.