Aluminum-containing Adjuvants Research Articles

Proanthocyanidins-based adjuvant for enhanced immune responses of SARS-CoV-2 subunit vaccine

Aluminum-containing adjuvants have been widely used in human vaccines, such as anti-COVID-19 vaccine, to enhance antigen-specific immune responses. However, a major limitation of aluminum adjuvants in clinical application is that they typically enhance humoral immune responses but have weaker effects on cellular immune responses. Therefore, there has been a continuous and active pursuit of novel adjuvants that can address the shortcomings of traditional adjuvants and improve vaccine efficacy. In this paper, we proposed a novel vaccine-adjuvant system utilizing the convenient physical mixing of natural proanthocyanidins (PCs) and its derivative with a recombinant RBD subunit vaccine, which induced comparable humoral immune responses compared to aluminum adjuvant. In the context of cellular immunity, PCs modified with 4-bromomethyl phenylboronic acid not only enhanced the maturation and migration of dendritic cells but also improved the antigen uptake and presentation capacity of monocytes, leading to robust activation of immune cells, particularly involving CD4+ and CD8+ T cells, thereby demonstrating a clear Th1/CTL response bias. In general, PCs andtheir derivatives could be potential innovative natural adjuvants which effectively balance the Th1/Th2 immune response to recompense for the deficiency of aluminum adjuvant, and our study also offers an approach to discovering safe and efficient natural adjuvants.

Neurotoxicity Profiling of Aluminum Salt-Based Nanoparticles as Adjuvants for Therapeutic Cancer Vaccine.

Therapeutic vaccines containing aluminum adjuvants have been widely used in the treatment of tumors due to their powerful immune-enhancing effects. However, the neurotoxicity of aluminum adjuvants with different physicochemical properties has not been completely elucidated. In this study, a library of engineered aluminum oxyhydroxide (EAO) and aluminum hydroxyphosphate (EAHP) nanoparticles was synthesized to determine their neurotoxicity in vitro. It was demonstrated that the surface charge of EAHPs and size of EAOs did not affect the cytotoxicity in N9, bEnd.3, and HT22 cells; however, soluble aluminum ions trigger the cytotoxicity in three different cell lines. Moreover, soluble aluminum ions induce apoptosis in N9 cells, and further mechanistic studies demonstrated that this apoptosis was mediated by mitochondrial reactive oxygen species generation and mitochondrial membrane potential loss. This study identifies the safety profile of aluminum-containing salts adjuvants in the nervous system during therapeutic vaccine use, and provides novel design strategies for their safer applications. SIGNIFICANCE STATEMENT: In this study, it was demonstrated that engineered aluminum oxyhydroxide and aluminum hydroxyphosphate nanoparticles did not induce cytotoxicity in N9, bEnd.3, and HT22 cells. In comparation, soluble aluminum ions triggered significant cytotoxicity in three different cell lines, indicating that the form in which aluminum is presenting may play a crucial role in its safety. Moreover, apoptosis induced by soluble aluminum ions was dependent on mitochondrial damage. This study confirms the safety of engineered aluminum adjuvants in vaccine formulations.

A Comparative Study of the Effects of Al(OH)3 and AlPO4 Adjuvants on the Production of Neutralizing Antibodies (NAbs) against Bovine parainfluenza Virus Type 3 (BPIV3) in Guinea Pigs.

Aluminum-containing adjuvants are extensively used in inactive human and animal vaccines owing to their favorable immunostimulatory and safe properties. Nonetheless, there is controversy over the effects of different aluminum salts as an adjuvant for the bovine parainfluenza virus type 3 (BPIV3) vaccine. In order to find a suitable adjuvant, we studied the effects of two adjuvants (i.e., aluminum hydroxide [Al(OH)3] and aluminum potassium sulfate [AlPO4]) on the production of neutralizing antibodies (NAbs) for an experimental BPIV3 vaccine. The animals under study (Guinea pigs) were randomly assigned to five groups of experimental vaccines containing Al(OH)3 (AH), AlPO4 (AP), Al(OH)3-AlPO4 mixture (MIX), commercial vaccine (COM), and control (NS). The treatment groups were immunized with two doses of vaccine 21 days apart (on days 0 and 21), and the control group received normal saline under the same conditions. The animals were monitored for 42 days, and blood samples were then taken. The results indicated that all vaccines were able to induce the production of NAbs at levels higher than the minimum protective titer (0.6). An increase in titer was observed throughout the monitoring period. Moreover, an increase in both the level and mean titer of NAbs obtained from the vaccine containing Al(OH)3 adjuvant was significantly higher than in the other studied groups (P≤0.005). The comparison of NAbs titer in other groups did not display a significant difference. Considering the speed of rising and the optimal titer of NAbs production in the experimental vaccine, the Al(OH)3 adjuvant is a suitable candidate for preparing a vaccine against BPIV3 for immunization.

Research Progress of Aluminum Phosphate Adjuvants and Their Action Mechanisms.

Although hundreds of different adjuvants have been tried, aluminum-containing adjuvants are by far the most widely used currently. It is worth mentioning that although aluminum-containing adjuvants have been commonly applied in vaccine production, their acting mechanism remains not completely clear. Thus far, researchers have proposed the following mechanisms: (1) depot effect, (2) phagocytosis, (3) activation of pro-inflammatory signaling pathway NLRP3, (4) host cell DNA release, and other mechanisms of action. Having an overview on recent studies to increase our comprehension on the mechanisms by which aluminum-containing adjuvants adsorb antigens and the effects of adsorption on antigen stability and immune response has become a mainstream research trend. Aluminum-containing adjuvants can enhance immune response through a variety of molecular pathways, but there are still significant challenges in designing effective immune-stimulating vaccine delivery systems with aluminum-containing adjuvants. At present, studies on the acting mechanism of aluminum-containing adjuvants mainly focus on aluminum hydroxide adjuvants. This review will take aluminum phosphate as a representative to discuss the immune stimulation mechanism of aluminum phosphate adjuvants and the differences between aluminum phosphate adjuvants and aluminum hydroxide adjuvants, as well as the research progress on the improvement of aluminum phosphate adjuvants (including the improvement of the adjuvant formula, nano-aluminum phosphate adjuvants and a first-grade composite adjuvant containing aluminum phosphate). Based on such related knowledge, determining optimal formulation to develop effective and safe aluminium-containing adjuvants for different vaccines will become more substantiated.

A Minimalist Binary Vaccine Carrier for Personalized Postoperative Cancer Vaccine Therapy.

In recent years, significant evolutions have been made in applying nanotechnologies for prophylactic and therapeutic cancer vaccine design. However, the clinical translation of nanovaccines is still limited owing to their complicated compositions and difficulties in the spatiotemporal coordination of antigen-presenting cell activation and antigen cross-presentation. Herein, a minimalist binary nanovaccine (BiVax) is designed that integrates innate stimulating activity into the carrier to elicit robust antitumor immunity. The authors started by making a series of azole molecules end-capped polyethylenimine (PEI-M), and weresurprised to find that over 60% of the PEI-M polymers have innate stimulating activity via activation of the stimulator of interferon genes pathway. PEI-4BImi, a PEI-M obtained from a series of polymers, elicits robust antitumor immune responses when used as a subcutaneously injected nanovaccine by simply mixing with ovalbumin antigens, and this BiVax system performs much better than the traditional ternary vaccine system, as well as, commercialized aluminum-containing adjuvants. This system also enables the fast preparation of personalized BiVax by compositing PEI-4BImi with autologous tumor cell membrane protein antigens, and a 60% postoperative cure rate is observed when combined with immune checkpoint inhibitors.

Experimental and molecular predictions of the adjuvanticity of snail mucin on hepatitis B vaccine in albino mice.

Although aluminum-containing adjuvants are widely used in human vaccination due to their excellent safety profile, they exhibit low effectiveness with many recombinant antigens. This study investigated the adjuvanticity of snail mucin with recombinant Hepatitis B Vaccine (rHBsAg). Twenty-five (25) female mice distributed unbiasedly into 5 groups were used in the study and were administered different rHBsAg/Mucin formulation at 7 days intervals. Blood samples were collected a day following the administration for analysis. The results of liver function and body weight analysis were indications that snail mucin had no adverse effect on the mice. The treatment group (administer mucin and rHBsAg) showed significantly (P<0.05) higher mean titres of anti-HBsAg antibodies when compared with the negative controls and the positive control administered with two doses of rHBsAg after the boost doses (day 28). Furthermore, a comparable immune response to positive control administered with three doses rHBaAG was recorded. In silico prediction, studies of the protein-protein interaction of a homology modelled snail mucus protein and HBsAg gave an indication of enhanced HBV antigen-antibody interaction. Therefore, this study has shown that snail mucin possesses some adjuvant properties and enhances immune response towards rHBsAg vaccine. However, there is a need for further molecular dynamics studies to understand its mechanism of action.

Manganese salts function as potent adjuvants

Aluminum-containing adjuvants have been used for nearly 100 years to enhance immune responses in billions of doses of vaccines. To date, only a few adjuvants have been approved for use in humans, among which aluminum-containing adjuvants are the only ones widely used. However, the medical need for potent and safe adjuvants is currently continuously increasing, especially those triggering cellular immune responses for cytotoxic T lymphocyte activation, which are urgently needed for the development of efficient virus and cancer vaccines. Manganese is an essential micronutrient required for diverse biological activities, but its functions in immunity remain undefined. We previously reported that Mn2+ is important in the host defense against cytosolic dsDNA by facilitating cGAS-STING activation and that Mn2+ alone directly activates cGAS independent of dsDNA, leading to an unconventional catalytic synthesis of 2′3′-cGAMP. Herein, we found that Mn2+ strongly promoted immune responses by facilitating antigen uptake, presentation, and germinal center formation via both cGAS-STING and NLRP3 activation. Accordingly, a colloidal manganese salt (Mn jelly, MnJ) was formulated to act not only as an immune potentiator but also as a delivery system to stimulate humoral and cellular immune responses, inducing antibody production and CD4+/CD8+ T-cell proliferation and activation by either intramuscular or intranasal immunization. When administered intranasally, MnJ also worked as a mucosal adjuvant, inducing high levels of secretory IgA. MnJ showed good adjuvant effects for all tested antigens, including T cell-dependent and T cell-independent antigens, such as bacterial capsular polysaccharides, thus indicating that it is a promising adjuvant candidate.

Aluminiodun txerto-laguntzaileen eraginaren azterketa sistemen biologiaren bidez

Hamarkadak dira aluminio konposatuak txertoen laguntzaile gisa erabiltzen direla albaitaritzan eta giza txertoetan. Laguntzaile horien erabilera oso hedatua egon arren, ez da ongi ezagutzen zein mekanismoren bidez eragiten dituzten ondorio onuragarriak eta, aldizka, kontrako erreakzioak eragin ditzakete. Sistemen biologiako tekniken bidez laguntzaile hauen sinadura molekularra ikertu da, gizakietan zein etxabereetan. Hainbat eragin-mekanismo proposatu dira aluminioaren sistema immunea pizteko ahalmena azaltzeko eta analisi transkriptomikoetan erlazionatutako geneak aurkitu dira. Batzuetan emaitzak kontraesanezkoak dira, aktibatzen den erantzun immunea desberdina izan daitekeelako egoeraren arabera. Aluminiogatzen tamainak, formak, propietate fisiko-kimikoek eta antigenoen absortzioak eragina dutela ematen du era berean. Laguntzaile hauek ez dira antigeno-garraiatzaile soilak, sistema immunea kitzikatzen duten arrisku-seinale endogenoak pizten baitituzte. Argitzeke dago oraindik haien eragin-mekanismo zehatza eta epe luzeko aktibazio immunitarioak sistema immunitarioaren gainestimulazioa eragin dezakeen.

Dendritic Mesoporous Silica Nanoparticle Adjuvants Modified with Binuclear Aluminum Complex: Coordination Chemistry Dictates Adjuvanticity.

Aluminum-containing adjuvants used in vaccine formulations suffer from low cellular immunity, severe aggregation, and accumulation in the brain. Conventional aluminosilicates widely used in the chemical industry focus mainly on acidic sites for catalytic applications, but they are rarely used as adjuvants. Reported here is an innovative "ligand-assisted steric hindrance" strategy to create a high density of six-coordinate VI Al-OH groups with basicity on dendritic mesoporous silica nanoparticles as new nanoadjuvants. Compared to four-coordinate IV Al-modified counterparts, VI Al-OH-rich aluminosilicate nanoadjuvants enhance cellular delivery of antigens and provoke stronger cellular immunity. Moreover, the aluminum accumulation in the brain is more reduced than that with a commercial adjuvant. These results show that coordination chemistry can be used to control the adjuvanticity, providing new understanding in the development of next-generation vaccine adjuvants.

Exposition à l’aluminium vaccinal en France en 2018

Aluminum-containing vaccine adjuvants stimulate an adequate immune response to vaccination. The safety and rapid elimination of these molecules, a guarantee of their safe use for several decades, have been challenged by a growing number of studies over the last 20 years. Evaluation of exposure to aluminum adjuvants of an individual is thus essential. The current review answers the following questions: what is the exposure of aluminum adjuvants of an individual vaccinated in France? What are the factors of variation? To evaluate the immunization exposure to aluminum for a vaccinee in France, we used the 2018 vaccination schedule and the Social Security database for vaccines reimbursed that year. French mandatory and recommended vaccines for an individual who does not travel abroad and has no particular professional obligations have been taken into account. Our results show that an individual following the vaccination requirements and recommendations of 2018 receives between 2545 and 7735μg of Al3+ during his lifetime, and at least 50% before the age of 1year. Exposure varies with age, weight, sex, and choice of administered vaccines. Vaccines with higher doses of aluminum are mainly injected at the beginning of life. Women receive a proportionately larger dose than men. The most reimbursed vaccines are often those with the highest amount of aluminum salts.

Post-vaccination subcutaneous aluminum granuloma.

Vaccination is a successful and cost-effective public health intervention. Aluminum-containing adjuvants are used worldwide to improve the immune response of vaccines. Side effects of aluminum-containing adjuvants in skin and subcutis are usually accompanied by persistent itch, and it may be challenging to diagnose asymptomatic cases. Here we present a case of a 1-year-old girl with asymptomatic subcutaneous nodules. Magnetic resonance imaging (MRI) revealed subcutaneous lesions: 16 mm on the upper right and 4 mm on the upper left arms. Histological examination revealed a granulomatous reaction with lymphoid follicle-like structures in the subcutis, accompanied by a considerable number of macrophages with PAS-positive granular cytoplasm. Moreover, the granules stained positive with aluminon staining, which revealed the existence of aluminum. These findings indicate post-vaccination aluminum granuloma. Due to the benign nature of aluminum granuloma and the benefit of routine vaccination, we decided to recommend that the patient continue taking the routine vaccination.

Structural characterization of a protein adsorbed on aluminum hydroxide adjuvant in vaccine formulation

The heterogeneous composition of vaccine formulations and the relatively low concentration make the characterization of the protein antigens extremely challenging. Aluminum-containing adjuvants have been used to enhance the immune response of several antigens over the last 90 years and still remain the most commonly used. Here, we show that solid-state NMR and isotope labeling methods can be used to characterize the structural features of the protein antigen component of vaccines and to investigate the preservation of the folding state of proteins adsorbed on Alum hydroxide matrix, providing the way to identify the regions of the protein that are mainly affected by the presence of the inorganic matrix. l-Asparaginase from E. coli has been used as a pilot model of protein antigen. This methodology can find application in several steps of the vaccine development pipeline, from the antigen optimization, through the design of vaccine formulation, up to stability studies and manufacturing process.

Konvencionalni i napredni adjuvansi u formulacijama vakcina - mineralni adsorbenti, nanočestični nosači i sistemi tipa mikroigala

In the era of modern vaccinology, limited immunogenicity of the most commonly used antigens has enforced the use of various adjuvants in vaccine formulations to achieve desired immune response. Aluminum-containing adjuvants have been, historically, the most widely used mineral immunostimulants, generally regarded as safe to use in human vaccines. The great academic progress in inorganic (nano)materials synthesis, structure control and functionalization design has led to a growing interest in innovative adjuvants such as clays, mesoporous silica nanoparticles, zinc oxide, iron oxide and iron hydroxide nanoparticles, etc. On the other hand, there has been an intention to use specific nanoparticulated antigen delivery systems, such as nanoemulsions, in order to protect antigens from premature proteolytic degradation and/or to improve antigen immunogenicity by facilitating antigen uptake and processing by antigen presenting cells. Simultaneously, numerous research efforts have been focused on the development of innovative technologies for antigen delivery into the skin (such as microneedles), with the aim to improve vaccine efficacy alongside with enhanced patient adherence, particularly in children population (noninvasive or minimally invasive administration). Therefore, this review deals with each of these approaches in more detail, with the special emphasis on examples of their use in vaccine formulations as well as on the factors influencing their efficacy and safety.

Molecular Signature of Aluminum Hydroxide Adjuvant in Ovine PBMCs by Integrated mRNA and microRNA Transcriptome Sequencing.

There have been few in vivo studies on the effect of aluminum hydroxide adjuvant and its influence on the immune response to vaccination. In this study, lambs received a parallel subcutaneous treatment with either commercial vaccines containing aluminum hydroxide or an equivalent dose of this compound only with the aim of identifying the activated molecular signature. Blood samples were taken from each animal at the beginning and at the end of the experiment and PBMCs isolated. Total RNA and miRNA libraries were prepared and sequenced. After alignment to the Oar3.1 reference genome and differential expression with 3 programs, gene enrichment modeling was performed. For miRNAs, miRBase and RNAcentral databases were used for detection and characterization. Three expression comparisons were made: vaccinated animals at the beginning and at the end of the treatment, adjuvanted animals at the same times, and animals of both treatments at the end of the experiment. After exposure to both treatments, a total of 2,473; 2,980 and 429 differentially expressed genes were identified in vaccinated animals, adjuvanted animals and animals at the end of both treatments, respectively. In both adjuvant and vaccine treated animals the NF-κB signaling pathway was enriched. On the other hand, it can be observed a downregulation of cytokines and cytokine receptors in the adjuvanted group compared to the vaccinated group at the final time, suggesting a milder induction of the immune response when the adjuvant is alone. As for the miRNA analysis, 95 miRNAs were detected: 64 previously annotated in Ovis aries, 11 annotated in Bos taurus and 20 newly described. Interestingly, 6 miRNAs were differentially expressed in adjuvant treated animals, and 3 and 1 in the other two comparisons. Lastly, an integrated miRNA-mRNA expression profile was developed, in which a miRNA-mediated regulation of genes related to DNA damage stimulus was observed. In brief, it seems that aluminum-containing adjuvants are not simple delivery vehicles for antigens, but also induce endogenous danger signals that can stimulate the immune system. Whether this contributes to long-lasting immune activation or to the overstimulation of the immune system remains to be elucidated.

Evidence Refuting the Existence of Autoimmune/Autoinflammatory Syndrome Induced by Adjuvants (ASIA)

Autoimmune/autoinflammatory syndrome induced by adjuvants (ASIA) was described in 2011. Over time the condition and its triggers have broadened to include several autoimmune disorders, the macrophagic myofasciitis syndrome, the Gulf war syndrome, the sick building syndrome, siliconosis, and the chronic fatigue syndrome. The aluminum-containing adjuvants in the hepatitis B vaccine and the human papillomavirus vaccine in particular have been stated to be the major causes of the disorder. Here, we review the specificity of the diagnostic criteria for ASIA. We also examine relevant human data, pertaining to causation, particularly from patients undergoing allergen-specific immunotherapy (IT). Patients undergoing allergen-specific IT receive 100 to 500 times more injected aluminum over 3 to 5 years, compared with hepatitis B and human papillomavirus vaccine recipients. In a large pharmacoepidemiological study, in contrast to case series of ASIA, patients receiving aluminum-containing allergen IT preparations were shown to have a lower incidence of autoimmune disease. In another clinical trial, there were no increases in exacerbations in a cohort of patients with systemic lupus erythematosus immunized with the hepatitis B vaccine. Current data do not support the causation of ASIA by vaccine adjuvants containing aluminum, which should be of reassurance to patients undergoing routine immunizations as well as to those undergoing allergen-specific IT.

CpG-ODN Shapes Alum Adjuvant Activity Signaling via MyD88 and IL-10

Aluminum-containing adjuvants usually referred as Alum are considered as T helper type-2 (Th2) adjuvants, while agonists of toll-like receptors (TLRs) are viewed as adjuvants that favor Th1/Th17 immunity. Alum has been used in numerous vaccine formulations; however, its undesired pro-Th2 adjuvant activity constitutes a caveat for Alum-based vaccines. Combining Alum with TLR-dependent, pro-Th1/Th17 adjuvants might dampen the pro-Th2 activity and improve the effectiveness of vaccine formulations. Here, using the ovalbumin (OVA) model of allergic lung inflammation, we found that sensitization with the synthetic TLR9 agonist, which is composed of oligodeoxynucleotides containing CpG motifs adsorbed to Alum, inhibited the development of OVA-induced lung allergic Th2 responses without shifting toward a Th1 pattern. The conversion of T cell immunity from the polarized allergic Th2 response to a non-polarized form by sensitization with OVA/Alum/CpG was dependent on MyD88 signaling in myeloid cells. Notably, sensitization of IL-10-deficient mice with OVA/Alum/CpG resulted in the development of neutrophilic lung inflammation associated with IFNγ production. However, in IL-10/IL-12-deficient mice, it resulted in neutrophilic inflammation dominated by IL-17 production. We conclude that OVA/Alum/CpG sensitization signaling via MyD88 and IL-10 molecules results in non-polarized immunity. Conversely, OVA/Alum/CpG sensitization in presence of MyD88 but absence of IL-10 or IL-10/IL-12 molecules results, respectively, in neutrophilic inflammation associated with IFNγ or IL-17 production. Our work provides novel OVA models of lung inflammation and suggests that Alum/CpG-based formulations might be of potential use in anti-allergic or anti-infectious processes.

Analysis of Aluminium in Rat Following Administration of Allergen Immunotherapy Using Either Aluminium or Microcrystalline-Tyrosine-Based Adjuvants

Investigation into the absorption, distribution and elimination of aluminium in rat after subcutaneous aluminium adjuvant formulation administration using ICP-MS is described. Assays were verified under the principles of a tiered approach. There was no evidence of systemic exposure of aluminium, in brain or in kidney. Extensive and persistent retention of aluminium at the dose site was observed for at least 180 days after administration. This is the first published work that has quantified aluminium adjuvant retention based on the quantity of aluminium delivered in a typical allergy immunotherapy course. The results indicate that the repeated administration of aluminium-containing adjuvants will likely contribute directly and significantly to an individual's body burden of aluminium.

Patterns of binding of aluminum-containing adjuvants to Haemophilus influenzae type b and meningococcal group C conjugate vaccines and components

The basis of Haemophilus influenzae type b (Hib) and Neisseria meningitidis serogroup C (MenC) glycoconjugates binding to aluminum-containing adjuvants was studied. By measuring the amount of polysaccharide and protein in the non-adsorbed supernatant, the adjuvant, aluminum phosphate, AlPO4, was found to be less efficient than aluminum hydroxide, Al(OH)3 at binding to the conjugates, at concentrations relevant to licensed vaccine formulations and when equimolar. At neutral pH, binding of TT conjugates to AlPO4 was facilitated through the carrier protein, with only weak binding of AlPO4 to CRM197 being observed. There was slightly higher binding of either adjuvant to tetanus toxoid conjugates, than to CRM197 conjugates. This was verified in AlPO4 formulations containing DTwP–Hib, where the adsorption of TT-conjugated Hib was higher than CRM197-conjugated Hib. At neutral pH, the anionic Hib and MenC polysaccharides did not appreciably bind to AlPO4, but did bind to Al(OH)3, due to electrostatic interactions. Phosphate ions reduced the binding of the conjugates to the adjuvants. These patterns of adjuvant adsorption can form the basis for future formulation studies with individual and combination vaccines containing saccharide-protein conjugates.

The LALF32-51 peptide as component of HPV therapeutic vaccine circumvents the alum-mediated inhibition of IL-12 and promotes a Th1 response

Aluminum-containing adjuvants (alum) continue to be the most widely used adjuvants. It is common knowledge that these adjuvants predominantly induce humoral immunity, but some reports also describe their role combined with IL-12 in the induction of a Th1 immune response. In this study we want to investigate if alum could be an adjuvant to be used as a component of a therapeutic vaccine that require the generation of cell-mediated immunity. To demonstrate this concept we selected the human papillomavirus (HPV) 16-transformed mouse TC-1 cells as model and the fusion protein LALF32-51-E7 as antigen. Our results suggest that LALF32-51-E7 combined with aluminum hydroxide adjuvant promotes a Th1 immune response and consequently an anti-tumor response in the TC-1 tumor model. These results could have important application in future clinical trials in women with low grade squamous intraepithelial neoplasia.

Development of a High-Throughput Screening Platform to Study the Adsorption of Antigens onto Aluminum-Containing Adjuvants

Aluminum-containing salts are important adjuvants in the formulations of many licensed human vaccines. However, in the early stage of the design of a new vaccine, a thorough understanding of the adsorption mechanisms of an antigen onto an aluminum salt is required. Therefore, we have developed a robust, rapid, and reproducible high-throughput screening (HTS) platform to study the adsorption capacity of aluminum-containing vaccines. The adsorption isotherms on aluminum hydroxide and aluminum phosphate of two model proteins, β-casein, and bovine serum albumin, were evaluated using a liquid handling system, which permitted rapid sample preparation in a small volume without nonspecific adsorption. Highly reproducible adsorption capacities and adsorptive coefficients were estimated based on the Langmuir model. To demonstrate the potential of this HTS platform, we evaluated the adsorption isotherms for two antigens, hepatitis B surface antigen and a pneumococcal serotype polysaccharide conjugated to a protein-D carrier, onto aluminum-containing vaccines at either a constant protein or a constant aluminum concentration. The automated assay enabled the rapid quantification of antigen adsorption with a significant reduction in operator workload and reagent use. This platform should accelerate data acquisition during the development of a new vaccine.