The development and use of vaccine adjuvants

Ordered mesoporous silicas for potential applications in solid vaccine formulations

In an effort to develop efficient vaccine formulations, the use of ordered mesoporous silica (SBA-15) as an antigen carrier has been investigated. SBA-15 has required properties such as high surface area and pore volume, including narrow pore size distribution to protect antigens inside its matrix. This study aimed to examine the impact of solvent removal methods, specifically freeze-drying and evaporation on the intrinsic properties of an immunogenic complex. The immunogenic complexes, synthesized and incorporated with BSA, were characterized by various physicochemical techniques. Small Angle X-ray Scattering measurements revealed the characteristic reflections associated to pure SBA-15, indicating the preservation of the silica mesostructured following BSA incorporation and the formation of BSA aggregates within the macropore region. Nitrogen Adsorption Isotherm measurements demonstrated a decrease in surface area and pore volume for all samples, indicating that the BSA was incorporated into the SBA-15 matrix. Fluorescence spectroscopy evidenced that the tryptophan residues in BSA inside SBA-15 or in solution displayed similar spectra, showing the preservation of the aromatic residues' environment. The Circular Dichroism spectra of BSA in both conditions suggest the preservation of its native secondary structure after the encapsulation process. The immunogenic analysis with the detection of anti-BSA IgG did not give any significant difference between the non-dried, freeze-dried or evaporated groups. However, all groups containing BSA and SBA-15 showed results almost three times higher than the groups with pure BSA (control group). These facts indicate that none of the BSA incorporation methods interfered with the immunogenicity of the complex. In particular, the freeze-dried process is regularly used in the pharmaceutical industry, therefore its adequacy to produce immunogenic complexes was proved Furthermore, the results showed that SBA-15 increased the immunogenic activity of BSA.

Gaston Ramon's Big Four

When immunology was still in its infancy, Gaston Ramon made several major contributions to humoral immunology [...].

Nucleic acid vaccination strategies for ovarian cancer

High grade serous carcinoma (HGSC) is one of the most lethal ovarian cancers that is characterised by asymptomatic tumour growth, insufficient knowledge of malignant cell origin and sub-optimal detection. HGSC has been recently shown to originate in the fallopian tube and not in the ovaries. Conventional treatments such as chemotherapy and surgery depend upon the stage of the disease and have resulted in higher rates of relapse. Hence, there is a need for alternative treatments. Differential antigen expression levels have been utilised for early detection of the cancer and could be employed in vaccination strategies using nucleic acids. In this review the different vaccination strategies in Ovarian cancer are discussed and reviewed. Nucleic acid vaccination strategies have been proven to produce a higher CD8+ CTL response alongside CD4+ T-cell response when compared to other vaccination strategies and thus provide a good arena for antitumour immune therapy. DNA and mRNA need to be delivered into the intracellular matrix. To overcome ineffective naked delivery of the nucleic acid cargo, a suitable delivery system is required. This review also considers the suitability of cell penetrating peptides as a tool for nucleic acid vaccine delivery in ovarian cancer.

Recent advances in the vaccine development for the prophylaxis of SARS Covid-19

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-caused Coronavirus Disease 2019 (COVID-19) is currently a global pandemic that has wreaked havoc on public health, lives, and the global economy. The present COVID-19 outbreak has put pressure on the scientific community to develop medications and vaccinations to combat COVID-19. However, according to highly optimistic forecasts, we could not have a COVID-19 vaccine until September 2020. This is due to the fact that a successful COVID-19 vaccine will necessitate a careful validation of effectiveness and adverse reactivity given that the target vaccine population includes high-risk people over 60, particularly those with severe co-morbid conditions, frontline healthcare professionals, and those involved in essential industrial sectors. For passive immunization, which is being considered for Covid-19, there are several platforms for vaccine development, each with its own advantages and disadvantages. The COVID-19 pandemic, which is arguably the deadliest in the last 100 years after the Spanish flu, necessitates a swift assessment of the various approaches for their ability to incite protective immunity and safety to prevent unintended immune potentiation, which is crucial to the pathogenesis of this virus. Considering the pandemic's high fatality rate and rapid spread, an efficient vaccination is critical for its management. As a result, academia, industry, and government are collaborating in unprecedented ways to create and test a wide range of vaccinations. In this review, we summarize the Covid-19 vaccine development initiatives, recent trends, difficulties, comparison between traditional vaccines development and Covid-19 vaccines development also listed the approved/authorized, phase-3 and pre-clinical trials Covid-19 vaccines in different countries.

Evaluation of Microparticulate (S)-4,5-Dihydroxy-2,3-pentanedione (DPD) as a Potential Vaccine Adjuvant

Adjuvants potentiate the immune response against co-inoculated antigens in the vaccine formulation. Based on the mechanism of action, the adjuvants are classified as immunostimulatory adjuvants and vaccine delivery systems. (S)-4,5-Dihydroxy-2,3-pentanedione (DPD) is the precursor of bacterial quorum sensing molecule, autoinducer (AI)-2. We tested the immunogenicity and adjuvant potential of microparticulate formulation of (S)-DPD via in vitro evaluation. By formulating the microparticles of (S)-DPD, we consolidated the advantages of both the classes of adjuvants. The microparticulate (S)-DPD was tested for its immunogenicity and cytotoxicity. We further tested its adjuvant effect by combining it with particulate vaccines for measles and gonorrhea and compared the adjuvant effect observed with the microparticulate formulations of the FDA-approved adjuvants alum, MPL A®, and MF59®. Microparticulate (S)-DPD was found to be non-cytotoxic towards the antigen-presenting cells and had an adjuvant effect with microparticulate gonorrhea vaccine. Further studies with additional bacterial vaccines and the in vivo evaluation will confirm the potential of microparticulate (S)-DPD as a probable vaccine adjuvant candidate.

Asymmetric mesoporous silica nanoparticles as potent and safe immunoadjuvants provoke high immune responses

Asymmetric mesoporous silica nanoparticles with a head–tail structure are potent immunoadjuvants in delivering a peptide antigen, generating higher antibody immune response in mice compared to their symmetric counterparts.

Dendritic cells in the host response to implanted materials

The role of dendritic cells (DCs) and their targeted manipulation in the body's response to implanted materials is an important and developing area of investigation, and a large component of the emerging field of biomaterials-based immune engineering. The key position of DCs in the immune system, serving to bridge innate and adaptive immunity, is facilitated by rich diversity in type and function and places DCs as a critical mediator to biomaterials of both synthetic and natural origins. This review presents current views regarding DC biology and summarizes recent findings in DC responses to implanted biomaterials. Based on these findings, there is promise that the directed programming of application-specific DC responses to biomaterials can become a reality, enabling and enhancing applications almost as diverse as the larger field of biomaterials itself.

Ready-to-use colloidal adjuvant systems for intranasal immunization

Adjuvant systems based on oil-in-water (o/w) microemulsions (MEs) for vaccination via intranasal administration were prepared and evaluated. A ready-to-use blank ME system composed of mineral oil (oil), Labrasol (surfactant), Tween 80 (cosurfactant), and water was prepared and blended with antigen (Ag) solution prior to use. The o/w ME system developed exhibited nano-size droplets within the tested range of Ag concentrations and dilution factors. The maintenance of primary, secondary, and tertiary structural stability of ovalbumin (OVA) in ME, compared with OVA in solution, was demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism (CD), and fluorescence intensity measurements, respectively. The uptake efficiency in RAW 264.7 cells, evaluated by flow cytometry, of OVA in the ME group was significantly higher than that of the OVA solution group (p<0.05). In an intranasal immunization study with OVA ME in mice, elevated adjuvant effects in terms of mucosal immunization and Th1-dominant cell-mediated immune responses were identified. Given the convenience of use (simply mixing with Ag solution prior to use) and the adjuvant effects after intranasal immunization, the new o/w ME may be a practical and efficient adjuvant system for intranasal vaccination.

Schistosomiasis vaccine candidate Sm14/GLA-SE: Phase 1 safety and immunogenicity clinical trial in healthy, male adults

DESIGN

Safety and immunogenicity of a recombinant 14kDa, fatty acid-binding protein(FABP) from Schistosoma mansoni (rSm14) were evaluated through an open, non-placebo-controlled, dose-standardized trial, performed at a single research site. The vaccine was formulated with glucopyranosyl lipid A (GLA) adjuvant in an oil-in-water emulsion (SE) and investigated in 20 male volunteers from a non-endemic area for schistosomiasis in the state of Rio de Janeiro, Brazil. Fifty microgram rSm14 with 10 μg GLA-SE (rSm14/GLA-SE)/dose were given intramuscularly three times with 30-day intervals. Participants were assessed clinically, biochemically and immunologically for up to 120 days.

METHODS

Participants were screened for inclusion by physical examination, haematology and blood chemistry; then followed to assess adverse events and immunogenicity. Sera were tested for IgG (total and isotypes) and IgE. T cell induction of cytokines IL-2, IL-5, IL-10, IFNγ and TNFα was assessed by Milliplex kit and flow cytometry.

RESULTS

The investigational product showed high tolerability; some self-limited, mild adverse events were observed during and after vaccine administration. Significant increases in Sm14-specific total IgG, IgG1 and IgG3 were observed 30 days after the first vaccination with specific IgG2 and IgG4 after 60 days. An increase in IgE antibodies was not observed at any time point. The IgG response was augmented after the second dose and 88% of all vaccinated subjects had developed high anti-Sm14 IgG titres 90 days after the first injection. From day 60 and onwards, there was an increase in CD4(+) T cells producing single cytokines, particularly TNFα and IL-2, with no significant increase of multi-functional TH1 cells.

CONCLUSION

Clinical trial data on tolerability and specific immune responses after vaccination of adult, male volunteers in a non-endemic area for schistosomiasis with rSm14/GLA-SE, support this product as a safe, strongly immunogenic vaccine against schistosomiasis paving the way for follow-up Phase 2 trials. Study registration ID: NCT01154049 at http://www.clinicaltrials.gov.

The mechanisms of action of vaccines containing aluminum adjuvants: an in vitro vs in vivo paradigm

Adjuvants such as the aluminum compounds (alum) have been dominantly used in many vaccines due to their immunopotentiation and safety records since 1920s. However, how these mineral agents influence the immune response to vaccination remains elusive. Many hypotheses exist as to the mode of action of these adjuvants, such as depot formation, antigen (Ag) targeting, and the induction of inflammation. These hypotheses are based on many in vitro and few in vivo studies. Understanding how cells interact with adjuvants in vivo will be crucial to fully understanding the mechanisms of action of these adjuvants. Interestingly, how alum influences the target cell at both the cellular and molecular level, and the consequent innate and adaptive responses, will be critical in the rational design of effective vaccines against many diseases. Thus, in this review, mechanisms of action of alum have been discussed based on available in vitro vs in vivo evidences to date.

Applications of immunochemistry in human health: advances in vaccinology and antibody design (IUPAC Technical Report)

This report discusses the history and mechanisms of vaccination of humans as well as the engineering of therapeutic antibodies. Deeper understanding of the molecular interactions involved in both acquired and innate immunity is allowing sophistication in design of modified and even synthetic vaccines. Recombinant DNA technologies are facilitating development of DNA-based vaccines, for example, with the recognition that unmethylated CpG sequences in plasmid DNA will target Toll-like receptors on antigen-presenting cells. Formulations of DNA vaccines with increased immunogenicity include engineering into plasmids with “genetic adjuvant” capability, incorporation into polymeric or magnetic nanoparticles, and formulation with cationic polymers and other polymeric and non-polymeric coatings. Newer methods of delivery, such as particle bombardment, DNA tattooing, electroporation, and magnetic delivery, are also improving the effectiveness of DNA vaccines. RNA-based vaccines and reverse vaccinology based on gene sequencing and bioinformatic approaches are also considered. Structural vaccinology is an approach in which the detailed molecular structure of viral epitopes is used to design synthetic antigenic peptides. Virus-like particles are being designed for vaccine deliveries that are based on structures of viral capsid proteins and other synthetic lipopeptide building blocks. A new generation of adjuvants is being developed to further enhance immunogenicity, based on squalene and other oil–water emulsions, saponins, muramyl dipeptide, immunostimulatory oligonucleotides, Toll-like receptor ligands, and lymphotoxins. Finally, current trends in engineering of therapeutic antibodies including improvements of antigen-binding properties, pharmacokinetic and pharmaceutical properties, and reduction of immunogenicity are discussed. Taken together, understanding the chemistry of vaccine design, delivery and immunostimulation, and knowledge of the techniques of antibody design are allowing targeted development for the treatment of chronic disorders characterized by continuing activation of the immune system, such as autoimmune disorders, cancer, or allergies that have long been refractory to conventional approaches.

Evaluation of recombinant Mycoplasma hyopneumoniae P97/P102 paralogs formulated with selected adjuvants as vaccines against mycoplasmal pneumonia in pigs

Pig responses to recombinant subunit vaccines containing fragments of eight multifunctional adhesins of the Mycoplasma hyopneumoniae (Mhp) P97/P102 paralog family formulated with Alhydrogel(®) or Montanide™ Gel01 were compared with a commercial bacterin following experimental challenge. Pigs, vaccinated intramuscularly at 9, 12 and 15 weeks of age with either of the recombinant formulations (n=10 per group) or Suvaxyn(®) M. hyo (n=12), were challenged with Mhp strain Hillcrest at 17 weeks of age. Unvaccinated, challenged pigs (n=12) served as a control group. Coughing was assessed daily. Antigen-specific antibody responses were monitored by ELISA in serum and tracheobronchial lavage fluid (TBLF), while TBLF was also assayed for cytokine responses (ELISA) and bacterial load (qPCR). At slaughter, gross and histopathology of lungs were quantified and damage to epithelial cilia in the porcine trachea was evaluated by scanning electron microscopy. Suvaxyn(®) M. hyo administration induced significant serological responses against Mhp strain 232 whole cell lysates (wcl) and recombinant antigen F3P216, but not against the remaining vaccine subunit antigens. Alhydrogel(®) and Montanide™ Gel01-adjuvanted antigen induced significant antigen-specific IgG responses, with the latter adjuvant eliciting comparable Mhp strain 232 wcl specific IgG responses to Suvaxyn(®) M. hyo. No significant post-vaccination antigen-specific mucosal responses were detected with the recombinant vaccinates. Suvaxyn(®) M. hyo was superior in reducing clinical signs, lung lesion severity and bacterial load but the recombinant formulations offered comparable protection against cilial damage. Lower IL-1β, TNF-α and IL-6 responses after challenge were associated with reduced lung lesion severity in Suvaxyn(®) M. hyo vaccinates, while elevated pathology scores in recombinant vaccinates corresponded to cytokine levels that were similarly elevated as in unvaccinated pigs. This study highlights the need for continued research into protective antigens and vaccination strategies that will prevent Mhp colonisation and establishment of infection.

Ginsenoside Re as an adjuvant to enhance the immune response to the inactivated rabies virus vaccine in mice

The inactivated rabies virus vaccine (RV) is a relatively expensive vaccine, prone to failure in some cases. Ginsenoside Re (Re) is a saponin isolated from Panax ginseng, and has an adjuvant property. Here the adjuvant effect of Re to improve the immune response to the RV is evaluated in mice. ICR mice were immunized with saline, 2.50mg/kg Re, 20μl RV, 100μl RV, or 20μl of RV adjuvanted with Re (1.25, 2.50 or 5.00mg/kg). Different time points after boosting, we measured serum antibodies in blood samples and separated splenocytes to detect lymphocyte proliferation and the production of IL-4, IL-10, IL-12, and IFN-γ in vitro. We also compared immunizations containing 20μl RV and 20μl RV adjuvanted with Re (5.00mg/kg) for the expression of CD4(+) and CD8(+) T-cell subsets at different time points. Results indicated that co-administration of Re significantly enhanced serum antibody titers, increased the CD4(+):CD8(+) ratio, and enhanced both proliferation responses and IL-4, IL-10, IL-12 and IFN-γ secretions. Both Th1 and Th2 immune responses were activated. The supplementation of the Re (5.00mg/kg) to 20μl of RV significantly amplified serum antibody responses and Th1/Th2 responses inducing similar protection as did 100μl of RV. This suggests that Re could be used to reduce the dose, and therefore the cost, of the RV to achieve the same effective protection. Re merits further studies for use with vaccines of mixed Th1/Th2 immune responses.

Characterization of chemically defined poly-N-isopropylacrylamide based copolymeric adjuvants

PNiPAAm is a thermo-responsive polymer with an adjuvant activity. To identify the minimal chemical structure present within PNiPAAm responsible for its adjuvant property, three different constituent polymers with specific functional groups were synthesized through free radical reaction and tested their adjuvant potential along with PNiPAAm. Among them, polymer with isopropyl attached to an amide showed maximal adjuvant activity in rodents followed by polymer with amide or ketone functional groups. However, secondary amine containing polymer did not show any adjuvant activity. In addition, to improve the adjuvant properties of PNiPAAm, we incorporated an affinity ligand, boronate. At first, we synthesized and characterized the dual responsive copolymers PNiPAAm-co-VPBA and PNiPAAm-co-VPBA-co-DMAEMA. Biocompatibility of these copolymers was confirmed both in vitro and in vivo. Mice injected with these copolymers mixed with collagen (CII) developed significant levels of anti-CII antibodies comprising of all the major IgG subclasses and an increased T cell activation. At the injection site, massive infiltration of immune cells was observed. However, only PNiPAAm-co-VPBA-co-DMAEMA-CII induced arthritis in mice after injection of 0.5M fructose confirming the importance of effective release of CII from the polymer for its adjuvant activity. Thus, a fine balance of hydrophobicity and hydrophilicity promotes adjuvant properties and continuous release of antigen, in this case CII, from polymer is essential for its adjuvant activity.

Pre-erythrocytic malaria vaccines: identifying the targets

Pre-erythrocytic malaria vaccines target Plasmodium during its sporozoite and liver stages, and can prevent progression to blood-stage disease, which causes a million deaths each year. Whole organism sporozoite vaccines induce sterile immunity in animals and humans and guide subunit vaccine development. A recombinant protein-in-adjuvant pre-erythrocytic vaccine called RTS,S reduces clinical malaria without preventing infection in field studies and additional antigens may be required to achieve sterile immunity. Although few vaccine antigens have progressed to human testing, new insights into parasite biology, expression profiles and immunobiology have offered new targets for intervention. Future advances require human trials of additional antigens, as well as platforms to induce the durable antibody and cellular responses including CD8(+) T cells that contribute to sterile protection.

Multiparameter telemetry as a sensitive screening method to detect vaccine reactogenicity in mice

Refined vaccines and adjuvants are urgently needed to advance immunization against global infectious challenges such as HIV, hepatitis C, tuberculosis and malaria. Large-scale screening efforts are ongoing to identify adjuvants with improved efficacy profiles. Reactogenicity often represents a major hurdle to the clinical use of new substances. Yet, irrespective of its importance, this parameter has remained difficult to screen for, owing to a lack of sensitive small animal models with a capacity for high throughput testing. Here we report that continuous telemetric measurements of heart rate, heart rate variability, body core temperature and locomotor activity in laboratory mice readily unmasked systemic side-effects of vaccination, which went undetected by conventional observational assessment and clinical scoring. Even minor aberrations in homeostasis were readily detected, ranging from sympathetic activation over transient pyrogenic effects to reduced physical activity and apathy. Results in real-time combined with the potential of scalability and partial automation in the industrial context suggest multiparameter telemetry in laboratory mice as a first-line screen for vaccine reactogenicity. This may accelerate vaccine discovery in general and may further the success of vaccines in combating infectious disease and cancer.

Adjuvant properties of a biocompatible thermo-responsive polymer of N-isopropylacrylamide in autoimmunity and arthritis

To evaluate the thermo-responsive poly(N-isopropylacrylamide) (PNiPAAm) polymer as an adjuvant, we synthesized PNiPAAm through free radical polymerization and characterized it both in vitro and in vivo. The polymer when mixed with collagen type II (CII) induced antigen-specific autoimmunity and arthritis. Mice immunized with PNiPAAm-CII developed significant levels of CII-specific IgG response comprising major IgG subclasses. Antigen-specific cellular recall response was also enhanced in these mice, while negligible level of IFN-γ was detected in splenocyte cultures, in vitro. PNiPAAm-CII-immunized arthritic mouse paws showed massive infiltration of immune cells and extensive damage to cartilage and bone. As determined by immunostaining, most of the CII protein retained its native configuration after injecting it with PNiPAAm in naive mice. Physical adsorption of CII and the high-molecular-weight form of moderately hydrophobic PNiPAAm induced a significant anti-CII antibody response. Similar to CII, mice immunized with PNiPAAm and ovalbumin (PNiPAAm-Ova) induced significant anti-ovalbumin antibody response. Comparable levels of serum IFN-γ, IL-1β and IL-17 were observed in ovalbumin-immunized mice with complete Freund, incomplete Freund (CFA and IFA) or PNiPAAm adjuvants. However, serum IL-4 levels were significantly higher in PNiPAAm-Ova and CFA-Ova groups compared with the IFA-Ova group. Thus, we show for the first time, biocompatible and biodegradable thermo-responsive PNiPAAm can be used as an adjuvant in several immunological applications as well as in better understanding of the autoimmune responses against self-proteins.

Development and characterization of synthetic glucopyranosyl lipid adjuvant system as a vaccine adjuvant

Innate immune responses to vaccine adjuvants based on lipopolysaccharide (LPS), a component of gram-negative bacterial cell walls, are driven by Toll-like receptor (TLR) 4 and adaptor proteins including MyD88 and TRIF, leading to the production of inflammatory cytokines, type I interferons, and chemokines. We report here on the characterization of a synthetic hexaacylated lipid A derivative, denoted as glucopyranosyl lipid adjuvant (GLA). We assessed the effects of GLA on murine and human dendritic cells (DC) by combining microarray, mRNA and protein multiplex assays and flow cytometry analyses. We demonstrate that GLA has multifunctional immunomodulatory activity similar to naturally-derived monophosphory lipid A (MPL) on murine DC, including the production of inflammatory cytokines, chemokines, DC maturation and antigen-presenting functions. In contrast, hexaacylated GLA was overall more potent on a molar basis than heterogeneous MPL when tested on human DC and peripheral blood mononuclear cells (PBMC). When administered in vivo, GLA enhanced the immunogenicity of co-administered recombinant antigens, producing strong cell-mediated immunity and a qualitative T(H)1 response. We conclude that the GLA adjuvant stimulates and directs innate and adaptive immune responses by inducing DC maturation and the concomitant release of pro-inflammatory cytokines and chemokines associated with immune cell trafficking, activities which have important implications for the development of future vaccine adjuvants.

Adjuvant effects on antibody titre

Antibody titre is a measure of the presence and amount of antibodies specific to an antigen that are present in the blood. In particular, the titre of an antibody sample is a measure of the antibody concentration determined under a defined set of conditions, with the antibody concentration being commonly established by enzyme-linked immunosorbent assay, also called ELISA, or a variation of this technology.Enzyme-linked immunosorbent assay, also called ELISA, enzyme immunoassay or EIA, is a biochemical technique used to detect the presence of an antibody or an antigen in a sample. The ELISA/EIA approach is an extremely robust technology and readily amenable to validation and quality control if adherence to ISO quality standards is required. This chapter describes in detail a specific ELISA protocol which has potential generic application.

Adjuvants for malaria vaccines

There is a renewed enthusiasm about subunit vaccines for malaria coincident with the formation of new alliances and partnerships raising international public awareness, attracting increased resources and the re-focusing of research programs on adjuvant development for infectious disease vaccines. It is generally accepted that subunit vaccines for malaria will require adjuvants to induce protective immune responses, and availability of suitable adjuvants has in the past been a barrier to the development of malaria vaccines. Several novel adjuvants are now in licensed products or in late stage clinical development, while several others are in the earlier development pipeline. Successful vaccine development requires knowing which adjuvants to use and knowing how to formulate adjuvants and antigens to achieve stable, safe, and immunogenic vaccines. For the majority of vaccine researchers this information is not readily available, nor is access to well-characterized adjuvants. In this minireview, we outline the current state of adjuvant research and development as it pertains to effective malaria vaccines.

New horizons in adjuvants for vaccine development

Over the last decade, there has been a flurry of research on adjuvants for vaccines, and several novel adjuvants are now in licensed products or in late stage clinical development. The success of adjuvants in enhancing the immune response to recombinant antigens has led many researchers to re-focus their vaccine development programs. Successful vaccine development requires knowing which adjuvants to use and knowing how to formulate adjuvants and antigens to achieve stable, safe and immunogenic vaccines. For the majority of vaccine researchers this information is not readily available, nor is access to well-characterized adjuvants. In this review, we outline the current state of adjuvant research and development and how formulation parameters can influence the effectiveness of adjuvants.

A new vaccine adjuvant (BOS 2000) a potent enhancer mixed Th1/Th2 immune responses in mice immunized with HBsAg

Adjuvants in vaccines are immune stimulants that play an important role in the induction of effective and appropriate immune responses to vaccine component. In search of a potent vaccine adjuvant, the water-soluble biopolymeric fraction BOS 2000 from Boswellia serrata was evaluated for desired activity. We investigated the ability of BOS 2000 to enhance HBsAg specific immune responses. The effect was determined in the form of protective anti-HBsAg titers, neutralizing antibodies (IgG1 and IgG2a), spleen cell lymphocyte proliferation by using MTT assay, Th1 (IFN-gamma and TNF-alpha) and Th2 (IL-4) cytokines as well as T-lymphocyte subsets (CD4/CD8) and intracellular cytokines (IFN-gamma/IL-4), these responses were highest in BOS 2000 immunized mice. Alum induced only a modest enhancement of antibody responses. Reducing the dose of adjuvant by 18.1-fold in comparison to alum, total IgG and its subtypes (IgG1 and IgG2a) antibodies titer in serum was significantly enhanced. Analysis of HBsAg specific cytokines revealed that alum was associated with a predominantly IL-4 response. In contrast, BOS 2000 was associated with production of both IFN-gamma and IL-4. We conclude that BOS 2000 is a potent enhancer of antigen-specific Th1 and Th2 immune responses in comparison to alum with Th2 limitation and is a promising adjuvant for vaccine applications.

Standardization of allergen-specific immunotherapy vaccines

In the 1970s and 1980s, scientific methods were introduced in the standardization of allergen vaccines and, in combination with improved documentation of the clinical benefits obtained using standardized vaccines, specific allergy treatment as a scientifically based, reproducible, and safe treatment for allergic disease was established. This article describes important issues in the control of source materials and vaccine preparation as part of the European standardization of allergen vaccines, and also includes a discussion of vaccines that are based on recombinant allergens, which may appear on the market in the near future.

Novel human polysaccharide adjuvants with dual Th1 and Th2 potentiating activity

Pure soluble, recombinant and synthetic antigens, despite their better tolerability, are unfortunately often much less immunogenic than live or killed whole organism vaccines. Thus, the move towards the development of safer subunit vaccines has created a major need for more potent adjuvants. In particular, there is an urgent need for adjuvants capable of boosting cellular (Th1) immunity but without unacceptable toxicity. The adjuvant activity of aluminium compounds (aluminium phosphate or hydroxide) was first described by Glenny and colleagues in 1926. Surprisingly, despite the description of over one hundred adjuvants in the scientific literature, alum remains the only adjuvant approved for human use in the USA. Unfortunately, alum has no effect on cellular immunity and is faced with increasing concerns regarding potential for cumulative aluminium toxicity. Why then has alum not been replaced in human vaccines? Despite the enormous number of candidates, potency has invariably been associated with increased toxicity, and this more than anything else has precluded their use, particularly in prophylactic vaccines where safety issues are paramount. Hence, there is a major unmet need for a safe efficacious adjuvant capable of boosting cellular plus humoral immunity. The extensive data on inulin-based adjuvants indicate that these are excellent candidates to replace alum as the adjuvant of choice for many vaccines. Particular advantages offered by inulin-based adjuvants is that they induce cellular in addition to humoral immunity and offer excellent safety, tolerability, ease of manufacture and formulation. Thus, adjuvants based on inulin have enormous potential for use in vaccines against both pathogens and cancer.

Separation and quantification of a novel two-component vaccine adjuvant

Two reversed-phase HPLC methods were developed for the quantitative determination of the two components of the novel vaccine adjuvant IC31. The adjuvant consists of a mixture of a synthetic oligodeoxynucleotide (ODN) and an 11-mer cationic peptide. The negatively charged oligodeoxynucleotide and the positively charged peptide form a complex that has to be quantitatively dissociated for analysis. Dissociation of the complex was achieved with a basic heparin solution (1000 IU/ml) when analyzing the ODN, whereas 30% acetic acid was used for the determination of the peptide. Both methods are suitable for identification and quantification but also for stability indicating investigations.

Non-clinical safety evaluation of novel vaccines and adjuvants: new products, new strategies

Advances in molecular biology and biotechnology, coupled with an increased understanding of disease processes and mechanisms of protective immunity have facilitated the development of new rationally-designed vaccines utilising recombinant proteins, naked DNA, live vectors, genetically-modified toxins and whole dendritic and tumour cells for both prophylaxis and therapy of a wide range of indications. These new vaccine technologies coupled with novel adjuvants, delivery systems, formulations, dosing routes and regimes present many unique and difficult challenges in demonstrating product safety and efficacy to support clinical testing. This paper aims to review these novel vaccine and adjuvant technologies and to highlight the key safety issues potentially associated with them. Approaches taken to demonstrate vaccine safety by assessing systemic and local toxicity, biodistribution and persistence, immunogenicity and immunotoxicity, reproductive toxicology, safety pharmacology and genotoxicity within the current regulatory framework are presented.

Potent enhancement of cellular and humoral immune responses against recombinant hepatitis B antigens using AS02A adjuvant in healthy adults

Recombinant subunit protein vaccines generally elicit good humoral immune responses, weak helper T cell responses and no cytotoxic T cell responses. Certain adjuvants are known to enhance humoral and cellular immune responses. This study evaluated the humoral, CD4+ T helper and CTL responses induced by the recombinant SL* protein adjuvanted with AS02A in comparison with non-adjuvanted SL* in PBS in two groups of 15 healthy adult volunteers. The AS02A adjuvant contains monophosphoryl lipid A (MPL), QS21 and an oil in water emulsion. The adjuvanted vaccine induced fast and vigorous humoral and helper T cell responses of the Th1 type. Using a pool of overlapping 20mer peptides a cytotoxic response was detected in 6 out of 14 HLA-A2-positive (+) and HLA-A2-negative (-) recipients of the adjuvanted vaccine. All HLA-A2-positive subjects in the adjuvanted group and up to 30% of the subjects in the SL* PBS group displayed a CTL response against selected HLA-A2-restricted CD8+ T cell epitopes. The non-adjuvanted vaccine induced a very weak antibody response and no helper T cell responses. Local and general reactions were more frequently reported by AS02A recipients than in the non-adjuvanted group but the safety profile was considered acceptable. AS02A can be considered as a useful adjuvant that strongly enhances the cellular and humoral responses of subunit protein vaccines.

Degradation of the tumor antigen epitope gp100280–288 by fibroblast-associated enzymes abolishes specific immunorecognition

Degradation of the tumor antigen epitope gp100(280-288) (YLEPGPVTA) was investigated in the presence of cultured human fibroblasts, and acellular supernatants obtained from these cells; the possible effect of substrate degradation on in vitro immunorecognition was also addressed. In the presence of fibroblasts, gp100(280-288) was degraded to free amino acids with a half-life of less than 4 min; hydrolysis data support the hypothesis that substrate degradation was mainly caused by the activity of cell-expressed amino- and carboxypeptidases. Gp100(280-288) was also degraded in the presence of acellular supernatants: under these conditions, the hydrolysis pattern was similar to that observed in the presence of whole cells, but degradation kinetics was slower. As a result of these phenomena, immunorecognition of gp100(280-288)-specific cytotoxic T lymphocyte (CTL) clones was severely hampered, and was totally suppressed after 90 min. In conclusion, the high activity of fibroblast-expressed proteases, and the presence of wide-scope soluble enzymes, may explain, at least in part, the low activity of peptide-based antineoplastic vaccines, as well as the transient effectiveness of subcutaneously administered peptides in general.

Immunological Foundations to the Quest for New Vaccine Adjuvants

Developing efficient adjuvants for human vaccines that elicit broad and sustained immune responses at systemic or mucosal levels remains a formidable challenge for the vaccine industry. Conventional approaches in the past have been largely empirical and--at best--partially successful. Importantly, recent advances in our understanding of the immune system, most particularly with respect to early proinflammatory signals, are leading to the identification of new biological targets for vaccine adjuvants. This review covers both the current status of adjuvant testing in humans, the residual needs for vaccines in development, and the emerging immunological foundations for adjuvant design. A better understanding of the biology of toll-like receptors, non-conventional T cell subpopulations, T and B cell memory, regulatory T cells, and mucosal immunity has profound implications for a modern approach to adjuvant screening and development. The future lies in the high throughput screening of synthetic chemical entities targeting well-characterized biological molecules. Used alone or in combination, such synthetic adjuvants will allow stimulation or modulation in a safe and efficient manner of strong effector, regulatory and memory immune mechanisms.

Survey of human-use adjuvants

Although there are only four adjuvants used in licensed vaccines for humans, a wealth of information on novel vaccine adjuvants has become available in both animal models and clinical studies over the past decade. Many vaccine candidates require immunopotentiation to achieve a satisfactory immune response, which is driving the search for new and safer approaches. In this review, we take a brief look at what is known of the mechanisms of action, consider some of the elements of product development, then survey several of the classes of adjuvants within the context of human trials.

New technology platforms in the development of vaccines for the future

The desire for improved quality of life in both industrialised and under-developed nations has led to the quest for greater understanding and subsequent prevention and treatment of diseases. Here we discuss some of the latest of modern medicine's approaches to vaccination and disease treatment. Our main subject of discussion being the novel antigen delivery systems termed immunopotentiating reconstituted influenza virosomes (IRIVs) and their use as vaccines. Particular attention is paid to the currently licensed Epaxal and Inflexal V, good examples of the improvements being made in vaccinology. Alternative uses of virosomes such as peptide delivery, cytosolic drug delivery and gene delivery are also considered, highlighting the flexibility of the IRIV formulation and method of action. The paper concludes with consideration of alternative novel approaches to vaccinology including bacterial carriers for DNA vaccines, recombinant MV vaccines and polysaccharide-protein conjugates.