Aluminum adjuvants, commonly referred to as “alum,” are the most widespread immunostimulants in human vaccines. Although the mechanisms that promote humoral responses to alum-adsorbed antigens are still enigmatic, alum is thought to form antigen depots and induce inflammatory signals that, in turn, promote antibody production. It was recently noted that Imject® alum, a commercial aluminum-containing adjuvant commonly used in animal studies, is not the physicochemical equivalent of aluminum adjuvant present in human vaccines. This difference raises concerns about the use of Imject® alum in animal research as a model for approved aluminum adjuvants. Here, we compared the capacity of Imject® alum, Alhydrogel®, and a traditional alum-antigen precipitate to induce humoral responses in mice to the hapten-carrier antigen, NP-CGG [(4-hydroxy-3-nitrophenyl)acetyl-chicken γ-globulin]. The magnitude of humoral responses elicited by Alhydrogel® and precipitated alum was significantly greater than that induced by Imject® alum. The strength of the humoral responses elicited by different alum formulations was correlated with the quantity of pro-inflammatory cytokines induced and the numbers of inflammatory cells at the site of immunization. Moreover, Imject® exhibited a severely reduced capacity to adsorb protein antigens compared to Alhydrogel® and precipitated alum. These findings reveal substantial differences in the immunostimulatory properties of distinct alum preparations, an important point of consideration for the evaluation of novel adjuvants, the assessment of new alum-based vaccines, and in mechanistic studies of adjuvanticity.
alum; adjuvant; antibody; inflammation
Rationale: Chitin is a ubiquitous polysaccharide in fungi, insects, allergens, and parasites that is released at sites of infection. Its role in the generation of tissue inflammation, however, is not fully understood.
Objectives: We hypothesized that chitin is an important adjuvant for adaptive immunity.
Methods: Mice were injected with a solution of ovalbumin and chitin.
Measurements and Main Results: We used in vivo and ex vivo/in vitro approaches to characterize the ability of chitin fragments to foster adaptive immune responses against ovalbumin and compared these responses to those induced by aluminum hydroxide (alum). In vivo, ovalbumin challenge caused an eosinophil-rich pulmonary inflammatory response, Th2 cytokine elaboration, IgE induction, and mucus metaplasia in mice that had been sensitized with ovalbumin plus chitin or ovalbumin plus alum. Toll-like receptor-2, MyD88, and IL-17A played critical roles in the chitin-induced responses, and MyD88 and IL-17A played critical roles in the alum-induced responses. In vitro, CD4+ T cells from mice sensitized with ovalbumin plus chitin were incubated with ovalbumin-stimulated bone marrow–derived dendritic cells. In these experiments, CD4+ T-cell proliferation, IL-5, IL-13, IFN-γ, and IL-17A production were appreciated. Toll-like receptor-2, MyD88, and IL-17A played critical roles in these in vitro adjuvant properties of chitin. TLR-2 was required for cell proliferation, whereas IL-17 and TLR-2 were required for cytokine elaboration. IL-17A also inhibited the generation of adaptive Th1 responses.
Conclusions: These studies demonstrate that chitin is a potent multifaceted adjuvant that induces adaptive Th2, Th1, and Th17 immune responses. They also demonstrate that the adjuvant properties of chitin are mediated by a pathway(s) that involves and is regulated by TLR-2, MyD88, and IL-17A.
chitin; adjuvant; ovalbumin; aluminum hydroxide; alum
Vaccination of mice with yeast-secreted Plasmodium yoelii-derived 19-kilodalton merozoite surface protein 1 (yMSP119) has been shown to afford protection from challenge with a lethal strain of P. yoelii. Sterile immunity can be achieved when MSP119 is emulsified in Freund adjuvant but not when it is adsorbed to aluminum hydroxide gel (alum). Because complete Freund adjuvant is not an acceptable adjuvant for use in humans, alternative adjuvants must be identified for formulating MSP119 as a vaccine for use in humans. To determine whether oligodeoxynucleotides with CpG motifs (ODN), reported to be a powerful new class of adjuvants, could enhance the immunogenicity of yMSP119, C57BL/6 mice were vaccinated either with yMSP119 formulated with Freund adjuvant, with alum, or with ODN plus alum and challenged intravenously with P. yoelii 17XL asexual blood-stage parasites. Adsorption of immunogen and adjuvant to alum was optimized by adjusting buffer (phosphate versus acetate) and pH. We found that the adjuvant combination of ODN plus alum with yMSP119, injected intraperitoneally (i.p.), increased immunoglobulin G (IgG) yMSP119-specific antibody production 12-fold over Freund adjuvant given i.p., 3-fold over Freund adjuvant given subcutaneously (s.c.), 300-fold over alum given i.p., and 48-fold over alum given s.c. The predominant antibody isotype in the group receiving alum-ODN-yMSP119 was IgG1. Increased antibody levels correlated to protection from a challenge with P. yoelii 17XL. Supernatant cytokine levels of gamma interferon in yMSP119-stimulated splenocytes were dramatically elevated in the alum-ODN-yMSP119 group. Interleukin-10 (IL-10) levels were also elevated; however, no IL-5 was detected. The cytokine profile, as well as the predominant IgG1 antibody isotype, suggests the protective immune response was a mixed Th1/Th2 response.
In recent years one important trend of Allergen-specific immunotherapy is to investigate new adjuvants with immunomodulatory properties. The outer membrane vesicle or proteoliposome (PL) from Neisseria meningitidis serogroup B has been reported as a potent adjuvant inducing a Th1-skewed response. The aim of this work was to assess the immunogenicity of a novel anti-allergic vaccine candidate based on purified allergens from Dermatophagoides siboney mite and PL as adjuvant, both components adsorbed onto Aluminum hydroxide.
In a preventative experimental setting BALB/c mice were administered with 3 doses containing 5 μg of Der s 1 allergen at one week intervals by subcutaneous route. Further, mice were subjected to allergen challenge by aerosol inhalation. In another experiment, mice were administered first with 2 doses of PL + Alum and later with the whole vaccines formulation, including the allergen. The allergen-specific antibody response was assessed determining serum levels of IgE, IgG1, and IgG2a by ELISA. The local allergic inflammatory response was evaluated by measuring cytokine levels (IL-4, IL-5, IFNg and IL-10) in broncho-alveolar lavage (BAL) by ELISA.
The formulation consistently induced IgG2a, as well as IgG1 antibodies with a potential anti-IgE blocking effect. The induction of IgG2a was clearly PL dependent while IgG1 was dependent mostly of Alum. Prior administration of the proteoliposome with alum without allergen showed to enhance this allergen-specific immunogenic effect. The vaccine prevented the development of systemic (IgE) and local allergic response in mice subjected to allergen exposure by inhalant route. Vaccinated mice showed lower levels of serum IgE, Th2 cytokines (IL-4, IL-5) in BAL and lower eosinophil counting in blood as compared to controls. Histological examination of lungs showed also a diminished allergic inflammatory response in vaccinated mice in contrast with mice which were administered with the conventional formulation of Alum-adsorbed allergen.
The antiallergic protective effect was proven in a preventative setting, showing to decrease the inflammatory response in the lungs of mice exposed to allergen aerosol, as well as, a Th2-antagonistic immune response with few injections.
The development of an effective vaccine is critical for prevention of a Middle East respiratory syndrome coronavirus (MERS-CoV) pandemic. Some studies have indicated the receptor-binding domain (RBD) protein of MERS-CoV spike (S) is a good candidate antigen for a MERS-CoV subunit vaccine. However, highly purified proteins are typically not inherently immunogenic. We hypothesised that humoral and cell-mediated immunity would be improved with a modification of the vaccination regimen. Therefore, the immunogenicity of a novel MERS-CoV RBD-based subunit vaccine was tested in mice using different adjuvant formulations and delivery routes. Different vaccination regimens were compared in BALB/c mice immunized 3 times intramuscularly (i.m.) with a vaccine containing 10 µg of recombinant MERS-CoV RBD in combination with either aluminium hydroxide (alum) alone, alum and polyriboinosinic acid (poly I:C) or alum and cysteine-phosphate-guanine (CpG) oligodeoxynucleotides (ODN). The immune responses of mice vaccinated with RBD, incomplete Freund’s adjuvant (IFA) and CpG ODN by a subcutaneous (s.c.) route were also investigated. We evaluated the induction of RBD-specific humoral immunity (total IgG and neutralizing antibodies) and cellular immunity (ELISpot assay for IFN-γ spot-forming cells and splenocyte cytokine production). Our findings indicated that the combination of alum and CpG ODN optimized the development of RBD-specific humoral and cellular immunity following subunit vaccination. Interestingly, robust RBD-specific antibody and T-cell responses were induced in mice immunized with the rRBD protein in combination with IFA and CpG ODN, but low level of neutralizing antibodies were elicited. Our data suggest that murine immunity following subunit vaccination can be tailored using adjuvant combinations and delivery routes. The vaccination regimen used in this study is promising and could improve the protection offered by the MERS-CoV subunit vaccine by eliciting effective humoral and cellular immune responses.
Aluminum oxyhydroxide (alum) is a crystalline compound widely used as an immunological adjuvant of vaccines. Concerns linked to the use of alum particles emerged following recognition of their causative role in the so-called macrophagic myofasciitis (MMF) lesion detected in patients with myalgic encephalomyelitis/chronic fatigue/syndrome. MMF revealed an unexpectedly long-lasting biopersistence of alum within immune cells in presumably susceptible individuals, stressing the previous fundamental misconception of its biodisposition. We previously showed that poorly biodegradable aluminum-coated particles injected into muscle are promptly phagocytosed in muscle and the draining lymph nodes, and can disseminate within phagocytic cells throughout the body and slowly accumulate in brain. This strongly suggests that long-term adjuvant biopersistence within phagocytic cells is a prerequisite for slow brain translocation and delayed neurotoxicity. The understanding of basic mechanisms of particle biopersistence and brain translocation represents a major health challenge, since it could help to define susceptibility factors to develop chronic neurotoxic damage. Biopersistence of alum may be linked to its lysosome-destabilizing effect, which is likely due to direct crystal-induced rupture of phagolysosomal membranes. Macrophages that continuously perceive foreign particles in their cytosol will likely reiterate, with variable interindividual efficiency, a dedicated form of autophagy (xenophagy) until they dispose of alien materials. Successful compartmentalization of particles within double membrane autophagosomes and subsequent fusion with repaired and re-acidified lysosomes will expose alum to lysosomal acidic pH, the sole factor that can solubilize alum particles. Brain translocation of alum particles is linked to a Trojan horse mechanism previously described for infectious particles (HIV, HCV), that obeys to CCL2, signaling the major inflammatory monocyte chemoattractant.
alum; vaccine adjuvants; macrophagic myofasciitis; neurotoxicity; genetics; monocytes; CCL2; MCP1
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.
Adjuvant; Vaccine; Inulin; Complement; Cellular; Immune; Th1; Th2
Many new vaccines under development consist of rationally designed recombinant proteins that are relatively poor immunogens unless combined with potent adjuvants. There is only one adjuvant in common use in the U.S., aluminum phosphate or hydroxide (e.g. alum). This adjuvant, however, has significant limitations, particularly regarding the generation of strong cell-mediated (T cell) immune responses. A novel adjuvant, JVRS-100, composed of cationic liposome-DNA complexes (CLDC) has been evaluated for immune enhancing activity. The JVRS-100 adjuvant has been shown to elicit robust immune responses compared to CpG oligonucleotides, alum, and MPL adjuvants, and efficiently enhances both humoral and cellular immune responses. Safety has been evaluated in preclinical studies, and the adjuvant is now in early-stage clinical development. One application of this novel adjuvant is to augment the immune responses to recombinant subunit antigens, which are often poorly immunogenic. The JVRS-100 adjuvant, when combined with a recombinant influenza hemagglutinin (H1), elicited increased specific antibody and T-cell responses in mice. Single-dose vaccination and prime/boost vaccinations with JVRS-100-H1 were both shown to be protective (i.e., survival, reduced weight loss) following H1N1 (PR/8/34) virus challenge. Enhanced immunological responses could be critically important for improved efficacy and dose-sparing of a recombinant influenza vaccine.
Adjuvant; vaccine; influenza
A liposome-encapsulated cloned protein (R32tet32) containing sequences from the tetrapeptide repeat region of the circumsporozoite protein of Plasmodium falciparum sporozoites was examined for immunogenicity with rabbits and monkeys. Effects of adjuvants were tested by encapsulation of the antigen in liposomes either lacking or containing lipid A and adsorption with aluminum hydroxide (ALUM). When rabbits were immunized with R32tet32 alone, a primary antibody response was not seen and a secondary response did not appear until 32 to 36 weeks after boosting. Immunization with ALUM-adsorbed R32tet32 resulted in a minimal primary antibody response. A moderate secondary antibody response was detected within 2 weeks after boosting, but antibody levels decreased to preimmunization levels 8 weeks after boosting. When R32tet32 was encapsulated in liposomes containing lipid A, strong primary and secondary antibody responses were observed. Strong primary and secondary responses also were obtained when R32tet32 was encapsulated in liposomes either containing or lacking lipid A and the liposomes were adsorbed with ALUM. The strongest antibody response was obtained by immunization with ALUM-adsorbed liposomes containing lipid A and R32tet32, suggesting that the adjuvant effects of liposomes, lipid A, and ALUM were additive or synergistic.
Long-term biodistribution of nanomaterials used in medicine is largely unknown. This is the case for alum, the most widely used vaccine adjuvant, which is a nanocrystalline compound spontaneously forming micron/submicron-sized agglomerates. Although generally well tolerated, alum is occasionally detected within monocyte-lineage cells long after immunization in presumably susceptible individuals with systemic/neurologic manifestations or autoimmune (inflammatory) syndrome induced by adjuvants (ASIA).
On the grounds of preliminary investigations in 252 patients with alum-associated ASIA showing both a selective increase of circulating CCL2, the major monocyte chemoattractant, and a variation in the CCL2 gene, we designed mouse experiments to assess biodistribution of vaccine-derived aluminum and of alum-particle fluorescent surrogates injected in muscle. Aluminum was detected in tissues by Morin stain and particle induced X-ray emission) (PIXE) Both 500 nm fluorescent latex beads and vaccine alum agglomerates-sized nanohybrids (Al-Rho) were used.
Intramuscular injection of alum-containing vaccine was associated with the appearance of aluminum deposits in distant organs, such as spleen and brain where they were still detected one year after injection. Both fluorescent materials injected into muscle translocated to draining lymph nodes (DLNs) and thereafter were detected associated with phagocytes in blood and spleen. Particles linearly accumulated in the brain up to the six-month endpoint; they were first found in perivascular CD11b+ cells and then in microglia and other neural cells. DLN ablation dramatically reduced the biodistribution. Cerebral translocation was not observed after direct intravenous injection, but significantly increased in mice with chronically altered blood-brain-barrier. Loss/gain-of-function experiments consistently implicated CCL2 in systemic diffusion of Al-Rho particles captured by monocyte-lineage cells and in their subsequent neurodelivery. Stereotactic particle injection pointed out brain retention as a factor of progressive particle accumulation.
Nanomaterials can be transported by monocyte-lineage cells to DLNs, blood and spleen, and, similarly to HIV, may use CCL2-dependent mechanisms to penetrate the brain. This occurs at a very low rate in normal conditions explaining good overall tolerance of alum despite its strong neurotoxic potential. However, continuously escalating doses of this poorly biodegradable adjuvant in the population may become insidiously unsafe, especially in the case of overimmunization or immature/altered blood brain barrier or high constitutive CCL-2 production.
Alum; Vaccine adverse effect; Vaccine adjuvant; Nanomaterial biodistribution; Nanomaterial neurodelivery; Macrophages; Macrophagic myofasciitis; CCL-2; Single nucleotide polymorphisms (SNPs)
Alum (aluminiun hydroxide) is the most widely used adjuvant in human vaccines, but the immune mechanisms that are activated by alum remain poorly understood. Alum has been recently shown to promote caspase-1 activation and IL-1β secretion but the cellular pathways involved remain elusive. Here we report that the release of IL-1β triggered by alum is abrogated in macrophages deficient in Nlrp3 and Asc but not Nlrc4. The requirement of the Nlrp3 inflammasome was specific for IL-1β in that secretion of TNF-α was independent of Nlrp3 or Asc. Consistently, processing of pro-caspase-1 induced by alum was abolished in macrophages lacking Nlrp3 or Asc. Unlike caspase-1 processing and IL-1β secretion triggered by LPS, alum-mediated activation of the inflammasome did not require exogenous ATP. Importantly, induction of IgG production against human serum albumin by alum was unimpaired in mice deficient in Nlrp3. These results indicate that alum induces IL-1β via the Nlrp3 inflammasome but this activity is dispensable for alum-mediated adjuvant activity.
Adjuvant; Alum; caspase-1; NLR
Type 1 diabetes (T1DM) is an autoimmune disease leading to destruction of insulin producing beta cells and life-long requirement for insulin therapy. Glutamic acid decarboxylase (GAD) is a major target of this immune response. Studies in animal models of autoimmunity have shown that treatment with a target antigen can modulate aggressive autoimmunity. We evaluated immunization with GAD formulated in aluminum hydroxide (alum) as an adjuvant in recent onset T1DM.
In this multicentre, double-masked, randomised controlled trial, 145 subjects (ages 3-45) with T1DM for less than 3 months received 3 injections of 20 μg GAD-alum (48 subjects), 2 injections of GAD-alum and one of alum alone (49 subjects) or 3 injections of alum (48 subjects) subcutaneously at baseline, 4 weeks later and 8 weeks after the second injection. Primary outcome was baseline-adjusted geometric mean 2-hour area under the curve (AUC) serum C-peptide following a mixed meal tolerance test at one year. Secondary outcomes included changes in HbA1c and insulin dose, and safety. This trial is registered in ClinicalTrials.gov (NCT00529399).
The ratio (experimental to control) of the adjusted population mean of C-peptide for the GAD-alum ×3 and GAD-alum ×2/alum ×1 groups is 0.998 (95% CI: [0.779, 1.22], p = 0.98) and 0.926 (95% CI: [0.720, 1.13], p = 0.50), respectively. HbA1c and insulin use did not differ between groups. There was no difference in rate or severity of adverse events between groups.
Antigen-based immunotherapy therapy using GAD-alum given subcutaneously in two or three doses over 4 to 12 weeks does not alter the course of loss of insulin secretion over one year in subjects with recently diagnosed T1DM. While antigen-based therapy is a highly desireable treatment and is effective in animal models, translation to human autoimmune disease remains a challenge.
National Institutes of Health.
glutamic acid decarboxylase; type 1 diabetes; antigen specific therapy; immune modulation; children
Deposition of uric acid crystals in joints causes the acute and chronic inflammatory disease known as gout and prolonged airway exposure to silica crystals leads to the development of silicosis, an irreversible fibrotic pulmonary disease. Aluminum salt (Alum) crystals are frequently used as vaccine adjuvant. The mechanisms by which crystals activate innate immunity through the Nlrp3 inflammasome are not well understood. Here, we show that uric acid, silica and Alum crystals trigger the extracellular delivery of endogenous ATP, which just precedes the secretion of mature interleukin-1β (IL-1β) by macrophages, both events depending on purinergic receptors and connexin/pannexin channels. Interestingly, not only ATP but also ADP and UTP are involved in IL-1β production upon these Nlrp3 inflammasome activators through multiple purinergic receptor signaling. These findings support a pivotal role for nucleotides as danger signals and provide a new molecular mechanism to explain how chemically and structurally diverse stimuli can activate the Nlrp3 inflammasome.
ATP; danger signal; inflammasome; P2R; NLR
Adjuvants based on aluminum salts (Alum) are commonly used in vaccines to boost the immune response against infectious agents. However, the detailed mechanism of how Alum enhances adaptive immunity and exerts its adjuvant immune effect remains unclear. Other than being comprised of micron-sized aggregates that include nanoscale particulates, Alum lacks specific physicochemical properties to explain activation of the innate immune system, including the mechanism by which aluminum-based adjuvants engage the NLRP3 inflammasome and IL-1β production. This is putatively one of the major mechanisms required for an adjuvant effect. Because we know that long aspect ratio nanomaterials trigger the NLRP3 inflammasome, we synthesized a library of aluminum oxyhydroxide (AlOOH) nanorods to determine whether control of the material shape and crystalline properties could be used to quantitatively assess NLRP3 inflammasome activation and linkage of the cellular response to the material’s adjuvant activities in vivo. Using comparison to commercial Alum, we demonstrate that the crystallinity and surface hydroxyl group display of AlOOH nanoparticles quantitatively impact the activation of the NLRP3 inflammasome in human THP-1 myeloid cells or murine bone marrow-derived dendritic cells (BMDCs). Moreover, these in vitro effects were correlated with the immunopotentiation capabilities of the AlOOH nanorods in a murine OVA immunization model. These results demonstrate that shape, crystallinity and hydroxyl content play an important role in NLRP3 inflammasome activation and are therefore useful for quantitative boosting of antigen-specific immune responses. These results show that the engineered design of aluminum-based adjuvants in combination with dendritic cell property-activity analysis can be used to design more potent aluminum-based adjuvants.
NLRP3 Inflammasome; IL-1β; Aluminum Oxyhydroxide; Oxidative Stress; Vaccine Adjuvant; Humoral and Cellular Immune Responses; Alum
Advances in nanotechnology and nanomaterials have facilitated the development of silicon dioxide, or Silica, particles as a promising immunological adjuvant for the generation of novel prophylactic and therapeutic vaccines. In the present study, we have compared the adjuvanting potential of commercially available Silica nanoparticles (initial particles size of 10–20 nm) with that of aluminium hydroxide, or Alum, as well as that of complete and incomplete Freund's adjuvants for the immunisation of BALB/c mice with virus-like particles (VLPs) formed by recombinant full-length Hepatitis B virus core (HBc) protein. The induction of B-cell and T-cell responses was studied after immunisation. Silica nanoparticles were able to adsorb maximally 40% of the added HBc, whereas the adsorption capacity of Alum exceeded 90% at the same VLPs/adjuvant ratio. Both Silica and Alum formed large complexes with HBc VLPs that sedimented rapidly after formulation, as detected by dynamic light scattering, spectrophotometry, and electron microscopy. Both Silica and Alum augmented the humoral response against HBc VLPs to the high anti-HBc level in the case of intraperitoneal immunisation, whereas in subcutaneous immunisation, the Silica-adjuvanted anti-HBc level even exceeded the level adjuvanted by Alum. The adjuvanting of HBc VLPs by Silica resulted in the same typical IgG2a/IgG1 ratios as in the case of the adjuvanting by Alum. The combination of Silica with monophosphoryl lipid A (MPL) led to the same enhancement of the HBc-specific T-cell induction as in the case of the Alum and MPL combination. These findings demonstrate that Silica is not a weaker putative adjuvant than Alum for induction of B-cell and T-cell responses against recombinant HBc VLPs. This finding may have an essential impact on the development of the set of Silica-adjuvanted vaccines based on a long list of HBc-derived virus-like particles as the biological component.
To investigate the enhancement of humoral immunity when CpG ODN (cytidine phosphate guanosine oligodeoxynucleotides) and aluminium adjuvants are complexed with the HCV (Hepatitis C virus) recombinant immunogen in mice.
After immunizing Balb/c mice with the recombination HCV antigen adjuvanted with pUCpGs10 and/or aluminium(antigen+CpG+alum, antigen+CpG, antigen+alum, antigen+PBS), enzyme-linked immunosorbent assay (ELISA) was used to measure the specific serum antibody titers of IgG, to determine the neutralization response to various peptide genotypes, and to determine the concentration of IL-6 and IL-10 in supernatants of in vitro cultured splenic lymphocytes. Enzyme-linked immunospot assay (ELISPOT) was used to quantify the non-specific and specific splenic antibody-secreting cells (ASCs), and flow cytometry (FCM) determined the ratio of different splenic lymphocytes. The serum of rabbits immunized with the recombinant pBVGST/HVR1 antigen immunoprecipitated the HCV isolated from 12 patients' serum.
The sera antibody titers were 1:51200, 1:9051, 1:18102, 1:6400 respectively after the final immunization and demonstrated good neutralization responses to the six gene peptide containing 1a, 1b, 2a, 3a, 4a and 6a. The aluminum adjuvant increased the population of both specific ASCs (P < 0.01) and total ASCs(P < 0.05), with a proportional rise in concentrations of CD19+CD27+ (P < 0.05), as well as levels of IL-6, IL-10 (P < 0.05) in splenic lymphocytes. The results clearly indicated a significantly higher number of CD19+CD38+ splenic lymphocytes with the aluminum and pUCpGs10 adjuvant present compared to the control group(P < 0.05). Anti-HVR1 antibody in induced mice can cross-reactively capture HCV particles (10/12).
1. The aluminum adjuvant induces a potent Th2-biased immune response by increasing both the populations of specific and total ASCs and the ratio of CD19+CD27+ cells. 2. The pUCpGs10 complexed with the aluminum adjuvant boosts the population of plasma cells and increase the efficiency of the immune response. 3. The two adjuvants have synergistic effects on humoral immunity. 4. The recombinant HVR1 protein has the possibility of generating broadly reactive anti-HVR1 antibody.
HCV; humoral immunity; adjuvant; ELISPOT; FCM
Porcine small intestinal submucosa (SIS) of Cook Biotech is licensed and widely used for tissue remodeling in humans. SIS was shown to be highly effective as an adjuvant in model studies with prostate and ovarian cancer vaccines. However, SIS adjuvanticity relative to alum, another important human-licensed adjuvant, has not yet been delineated in terms of activation of innate immunity via inflammasomes and boosting of antibody responses to soluble proteins and hapten-protein conjugates. We used ovalbumin, and a hapten-protein conjugate, phthalate-keyhole limpet hemocyanin. The evaluation of SIS was conducted in BALB/c and C57BL/6 mice using both intraperitoneal and subcutaneous routes. Inflammatory responses were studied by microarray profiling of chemokines and cytokines and by qPCR of inflammasomes-related genes. Results showed that SIS affected cytokine and chemokines microenvironments such as up-regulation of IL-4 and CD30-ligand and activation of chemotactic factors LIX and KC (neutrophil chemotactic factors), MCP-1 (monocytes chemotactic factors), MIP 1-α (macrophage chemotactic factor) and lymphotactin, as well as, growth factors like M-CSF. SIS also promoted gene expression of Nod-like receptors (NLR) and associated downstream effectors. However, in contrast to alum, SIS had no effects on pro-inflammatory cytokines (IL-6, IL-1β, TNF-α) or NLRP3, but it appeared to promote both Th1 and Th2 responses under different conditions. Lastly, it was as effective as alum in engendering a lasting and specific antibody response, primarily of IgG1 type.
Aluminium oxyhydroxide (alum), a nano-crystaline compound forming agglomerates, has been introduced in vaccine for its immunologic adjuvant effect in 1927. Alum is the most commonly used adjuvant in human and veterinary vaccines but mechanisms by which it stimulates immune responses remains incompletely understood. Although generally well tolerated, alum may occasionally cause disabling health problems in presumably susceptible individuals. A small proportion of vaccinated people present with delayed onset of diffuse myalgia, chronic fatigue and cognitive dysfunction, and exhibit very long-term persistence of alum-loaded macrophages at site of previous intra-muscular (i.m.) immunization, forming a granulomatous lesion called macrophagic myofasciitis (MMF). Clinical symptoms associated with MMF are paradigmatic of the recently delineated “autoimmune/inflammatory syndrome induced by adjuvants” (ASIA). The stereotyped cognitive dysfunction is reminiscent of cognitive deficits described in foundry workers exposed to inhaled Al particles. Alum safety concerns will largely depend on whether the compound remains localized at site of injection or may diffuse and accumulate in distant organs. Animal experiments indicate that biopersistent nanomaterials taken-up by monocytes-lineage cells in tissues, e.g. fluorescent alum surrogates, can first translocate to draining lymph nodes, and thereafter circulate in blood within phagocytes and reach the spleen, and, eventually, slowly accumulate in brain.
Adjuvants, Immunologic; adverse effects; Alum Compounds; adverse effects; Animals; Fasciitis; chemically induced; immunology; pathology; physiopathology; Humans; Myositis; chemically induced; immunology; pathology; physiopathology; Nanostructures; Phagocytes; metabolism; Syndrome
Since the pandemic (H1N1) 2009 virus has been a seasonal flu which still poses great human health concerns worldwide, vaccination would be considered as the most effective strategy to control the influenza virus spreading. Here, we assessed adjuvant efficacy of modified outer membrane vesicle (mOMV) towards the pandemic H1N1 split antigen.
Materials and Methods
For this study, mice were vaccinated twice with various amount of antigen (0.05, 0.1, and 0.5 µg/dose hemagglutinin [HA]) that were mixed with mOMV, aluminum hydroxide (alum), and MF59, as well as the combined adjuvant comprising the mOMV plus alum.
We found that all the adjuvanted vaccines of A/California/04/09 (CA04, H1N1) containing HA antigen more than 0.1 µg/dose protected effectively from lethal challenge (maCA04, H1N1) virus, compared to the antigen only group. Furthermore, vaccinated mice received as low as 0.05 µg/dose of the split vaccine containing the combined adjuvant (10 µg of mOMV plus alum) showed a full protection against lethal challenge with H1N1 virus. Taken together, these results suggest that mOMV can exert not only the self-adjuvanticity but also a synergy effect for the vaccine efficacy when combined with alum.
Our results indicate that mOMV could be a promising vaccine adjuvant by itself and it could be used as a vaccine platform for development of various vaccine formulations to prepare future influenza pandemic.
Influenza A virus; A/California/04/09 (CA04, H1N1); Adjuvant; mOMV
Recently, we have shown that a vaccine consisting of a purified preparation of the Chlamydia trachomatis mouse pneumonitis (MoPn) major outer membrane protein (MOMP) and Freund's adjuvant can protect mice against a genital challenge. Here, we wanted to determine if CpG motifs could be used as an immune modulator to the MOMP to induce protection in mice against an intranasal (i.n.) challenge. One-week-old BALB/c mice were immunized intramuscularly and subcutaneously either once or three times at 2-week intervals with MOMP and CpG suspended in aluminum hydroxide (alum). Negative controls received ovalbumin, CpG, and alum. Positive controls were immunized i.n. with C. trachomatis MoPn elementary bodies (EB). Six weeks after the last immunization, mice were challenged i.n. with 104 inclusion-forming units (IFU) of the C. trachomatis MoPn serovar. Mice that received MOMP, CpG, and alum had a strong immune response, as shown by a high titer of serum antibodies to Chlamydia and significant lymphoproliferation of T-cells following stimulation with C. trachomatis EB. After the i.n. challenge mice immunized with MOMP, CpG, and alum showed significantly less body weight loss than the corresponding control mice immunized with ovalbumin, CpG, and alum. Ten days after the challenge the animals were euthanized, their lungs were weighed, and the numbers of IFU in the lungs were determined. The average weight of the lungs of the mice immunized with MOMP, CpG, and alum was significantly less than average weight of the lungs of the mice immunized with ovalbumin, CpG, and alum. Also, the average number of IFU recovered per mouse immunized with MOMP, CpG, and alum was significantly less than the average number of IFU per mouse detected in the mice inoculated with ovalbumin, CpG, and alum. In conclusion, our data show that CpG sequences can be used as an effective adjuvant with the C. trachomatis MoPn MOMP to elicit a protective immune response in mice against a chlamydial respiratory challenge.
Certain CpG motifs found in bacterial DNA enhance immune responses through Toll-like receptor 9 (TLR-9) and may also demonstrate adjuvant properties. Our objective was to determine if DNA from bacteria associated with periodontal disease could affect the immune response to other bacterial antigens in the oral cavity. Streptococcus sobrinus glucosyltransferase (GTF), an enzyme involved in dental caries pathogenesis, was used as a test antigen. Rowett rats were injected with aluminum hydroxide (alum) with buffer, alum-GTF, or alum-GTF together with either Escherichia coli DNA, Fusobacterium nucleatum DNA, or Porphyromonas gingivalis DNA. Contrary to expectation, animals receiving alum-GTF plus bacterial DNA (P. gingivalis in particular) demonstrated significantly reduced serum immunoglobulin G (IgG) antibody, salivary IgA antibody, and T-cell proliferation to GTF compared to animals immunized with alum-GTF alone. A diminished antibody response was also observed after administration of alum-GTF with the P. gingivalis DNA either together or separately, indicating that physical complexing of antigen and DNA was not responsible for the reduction in antibody. Since TLR triggering by DNA induces synthesis of prospective suppressive factors (e.g., suppressor of cytokine signaling [SOCS]), the effects of P. gingivalis DNA and GTF exposure on rat splenocyte production of SOCS family molecules and inflammatory cytokines were investigated in vitro. P. gingivalis DNA significantly up-regulated SOCS1 and SOCS5 expression and down-regulated interleukin-10 expression by cultured splenocytes. These results suggested that DNA from periodontal disease-associated bacteria did not enhance, but in fact suppressed, the immune response to a protein antigen from cariogenic streptococci, potentially through suppressive SOCS components triggered by innate mechanisms.
Toll-like receptor (TLR)4 agonists are known potent immunostimulatory compounds. These compounds can be formulated as part of novel adjuvants to enhance vaccine medicated immune responses. However, the contribution of the formulation to the innate in vivo activity of TLR4 agonist compounds is not well understood.
Methodology and Principal Findings
We evaluated synthetic TLR4 agonist Glucopyranosyl Lipid A (GLA) for its effects on molecular and cellular innate immune responses in the murine model. Microarray techniques were used to compare the responses to GLA in an aqueous formulation or in an oil-in-water Stable Emulsion formulation (GLA-SE) versus either SE alone or the mineral salt aluminum hydroxide (alum) at the muscle injection site over multiple timepoints. In contrast to the minimal gene upregulation induced by SE and alum, both GLA and GLA-SE triggered MyD88- and TRIF-dependent gene expression. Genes for chemokines, cytokine receptors, signaling molecules, complement, and antigen presentation were also strongly upregulated by GLA and GLA-SE. These included chemokines for TH1-type T cells (CXCL9 and CXCL10) and mononuclear leukocytes (CCL2, CCL3) among others. GLA-SE induced stronger and more sustained gene upregulation than GLA in the muscle; GLA-SE induced genes were also detected in local draining lymph nodes and at lower levels in peripheral blood. Both GLA and GLA-SE resulted in increased cellular trafficking to the draining lymph nodes and upregulated MHC molecules and ICAM1 on local dendritic cells. GLA and GLA-SE transiently upregulated circulating MCP-1, TNFα, IFNγ and IP-10 in blood.
While GLA and GLA-SE activate a large number of shared innate genes and proteins, GLA-SE induces a quantitatively and qualitatively stronger response than GLA, SE or alum. The genes and proteins upregulated could be used to facilitate selection of appropriate adjuvant doses in vaccine formulations.
Vaccines have profoundly impacted global health although concerns persist about their potential role in autoimmune or other adverse reactions. To address these concerns, vaccine components like immunogens and adjuvants require critical evaluation not only in healthy subjects but also in those genetically averse to vaccine constituents. Evaluation in autoimmune-prone animal models of adjuvants is therefore important in vaccine development. The objective here was to assess the effectiveness of experimental adjuvants: two phytol-derived immunostimulants PHIS-01 (phytanol) and PHIS-03 (phytanyl mannose), and a new commercial adjuvant from porcine small intestinal submucosa (SIS-H), relative to a standard adjuvant alum. Phytol derivatives are hydrophobic, oil-in water diterpenoids, while alum is hydrophilic, and SIS is essentially a biodegradable and collagenous protein cocktail derived from extracellular matrices.
We studied phthalate -specific and cross-reactive anti-DNA antibody responses, and parameters associated with the onset of autoimmune disorders. We determined antibody isotype and cytokine/chemokine milieu induced by the above experimental adjuvants relative to alum. Our results indicated that the phytol-derived adjuvant PHIS-01 exceeded alum in enhancing anti-phthalate antibody without much cross reactivity with ds-DNA. Relatively, SIS and PHIS-03 proved less robust, but they were also less inflammatory. Interestingly, these adjuvants facilitated isotype switching of anti-hapten, but not of anti-DNA response. The current study reaffirms our earlier reports on adjuvanticity of phytol compounds and SIS-H in non autoimmune-prone BALB/c and C57BL/6 mice. These adjuvants are as effective as alum also in autoimmune-prone NZB/WF1 mice, and they have little deleterious effects.
Although all adjuvants tested impacted cytokine/chemokine milieu in favor of Th1/Th2 balance, the phytol compounds fared better in reducing the onset of autoimmune syndromes. However, SIS is least inflammatory among the adjuvants evaluated.
β-Glucan particles (GPs) are purified Saccharomyces cerevisiae cell walls treated so that they are primarily β1,3-d-glucans and free of mannans and proteins. GPs are phagocytosed by dendritic cells (DCs) via the Dectin-1 receptor, and this interaction stimulates proinflammatory cytokine secretion by DCs. As the hollow, porous GP structure allows for high antigen loading, we hypothesized that antigen-loaded GPs could be exploited as a receptor-targeted vaccine delivery system. Ovalbumin (OVA) was electrostatically complexed inside the hollow GP shells (GP-OVA). Incubation of C57BL/6J mouse bone marrow-derived DCs with GP-OVA resulted in phagocytosis, upregulation of maturation markers, and rapid proteolysis of OVA. Compared with free OVA, GP-OVA was >100-fold more potent at stimulating the proliferation of OVA-reactive transgenic CD8+ OT-I and CD4+ OT-II T cells, as measured by in vitro [3H]thymidine incorporation using DCs as antigen-presenting cells. Next, immune responses in C57BL/6J mice following subcutaneous immunizations with GP-OVA were compared with those in C57BL/6J mice following subcutaneous immunizations with OVA absorbed onto the adjuvant alum (Alum/OVA). Vaccination with GP-OVA stimulated substantially higher antigen-specific CD4+ T-cell lymphoproliferative and enzyme-linked immunospot (ELISPOT) responses than that with Alum/OVA. Moreover, the T-cell responses induced by GP-OVA were Th1 biased (determined by gamma interferon [IFN-γ] ELISPOT assay) and Th17 biased (determined by interleukin-17a [IL-17a] ELISPOT assay). Finally, both the GP-OVA and Alum/OVA formulations induced strong secretions of IgG1 subclass anti-OVA antibodies, although only GP-OVA induced secretion of Th1-associated IgG2c antibodies. Thus, the GP-based vaccine platform combines adjuvanticity and antigen delivery to induce strong humoral and Th1- and Th17-biased CD4+ T-cell responses.
Most licensed vaccines work by promoting protective antibody responses. However, for many infectious diseases, antibody-mediated protection appears to play a relatively minor role, and vaccination has met with limited success. While live-attenuated organisms generally elicit T-cell responses, their use in vaccines is limited by the potential for causing disease. Thus, there is an urgent need for new vaccine platforms that deliver antigens in such a manner as to promote strong T-cell-mediated responses. Here we designed a novel vaccine platform consisting of yeast-derived β-glucan particles (GPs) that combines antigen delivery and adjuvant activity. GPs loaded with the model antigen ovalbumin (OVA) stimulated robust humoral and T-cell responses in mice. In addition, the cellular response was Th1 and Th17 biased. This work has implications for the design of vaccines that stimulate biased T-cell responses as well as for understanding how immunity to fungal pathogens develops.
The combined adjuvant effect of ginsenoside Rg1 and aluminum hydroxide (alum) on immune responses to ovalbumin (OVA) in mice was investigated. BALB/c mice were subcutaneously (s.c.) inoculated twice with OVA alone or in combination with Rg1, alum, or Rg1 plus alum. Samples were collected 2 weeks after the boosting for the measurement of anti-OVA immunoglobulin G (IgG) isotypes in sera and gamma interferon (IFN-γ) and interleukin-5 (IL-5) produced in singular splenocyte cultures. Delayed-type hypersensitivity (DTH) responses were measured in mice immunized as described above. After 10 days, the mice were injected s.c. with OVA at the footpads. Thereafter, the thickness of the footpads was measured once daily for 5 days. The results indicated that alum enhanced mainly Th2 (IgG1 and IL-5) responses (P < 0.05), while Rg1 enhanced both Th1 (IgG1 and IL-5) and Th2 (IgG2a, IFN-γ, and DTH) responses (P < 0.05). The highest immune responses were found in the mice injected with OVA solution containing both alum and Rg1. In addition, the hemolytic activity of Rg1 was much lower than that of Quil A. Therefore, Rg1 deserves further studies in order to tailor desired immune responses when a mixed Th1/Th2 immune response is needed.