Adjuvants In Human Vaccines Research Articles

Aluminum Hydroxide Influences Not Only the Extent but Also the Fine Specificity and Functional Activity of Antibody Responses to Tick-Borne Encephalitis Virus in Mice

Aluminum hydroxide is the most widely used adjuvant in human vaccines and serves as a potent enhancer of antibody production. Its stimulatory effect strongly depends on the adsorption of the antigen to the adjuvant, which may influence antigen presentation and, as a consequence, the fine specificity of antibody responses. Such variations can have functional consequences and can modulate the effectiveness of humoral immunity. Therefore, we investigated the influence of aluminum hydroxide on the fine specificity of antibody responses in a model study in mice using an inactivated purified virus particle, the flavivirus tick-borne encephalitis (TBE) virus, as an immunogen. To dissect and quantify the specificities of polyclonal antibodies in postimmunization sera, we established a platform of immunoassays using recombinant forms of the major target of neutralizing antibodies (protein E) as well as individual domains of E (DIII and the combination of DI and DII [DI+DII]). Our analyses revealed a higher proportion of neutralizing than virion binding (as detected by enzyme-linked immunosorbent assay) antibodies after immunization with aluminum hydroxide. Furthermore, the induction of antibodies to DIII, a known target of potently neutralizing antibodies, as well as their contributions to virus neutralization were significantly greater in mice immunized with adjuvant and correlated with a higher avidity of these antibodies. Thus, our data provide evidence that aluminum hydroxide can lead to functionally relevant modulations of antibody fine specificities in addition to its known overall immune enhancement effect.

Aluminium based adjuvants and their effects on mitochondria and lysosomes of phagocytosing cells

Aluminium oxyhydroxide, Al(OH)3 is one of few compounds approved as an adjuvant in human vaccines. However, the mechanism behind its immune stimulating properties is still poorly understood. In vitro co-culture of an aluminium adjuvant and the human monocytic cell line THP-1 resulted in reduced cell proliferation. Inhibition occurred at concentrations of adjuvant several times lower than would be found at the injection site using a vaccine formulation containing an aluminium adjuvant. Based on evaluation of the mitochondrial membrane potential, THP-1 cells showed no mitochondrial rupture after co-culture with the aluminium adjuvant, instead an increase in mitochondrial activity was seen. The THP-1 cells are phagocytosing cells and after co-culture with the aluminium adjuvant the phagosomal pathway was obstructed. Primary or early phagosomes mature into phagolysosomes with an internal pH of 4.5 – 5 and carry a wide variety of hydrolysing enzymes. Co-culture with the aluminium adjuvant yielded a reduced level of acidic vesicles and cathepsin L activity, a proteolytic enzyme of the phagolysosomes, was almost completely inhibited. THP-1 cells are an appropriate in vitro model in order to investigate the mechanism behind the induction of a phagocytosing antigen presenting cell into an inflammatory cell by aluminium adjuvants. Much information will be gained by investigating the phagosomal pathway and what occurs inside the phagosomes and to elucidate the ultimate fate of phagocytosed aluminium particles.

A physiologically-based pharmacokinetic (PBPK) model of squalene-containing adjuvant in human vaccines

Squalene is used in the oil phase of certain emulsion vaccine adjuvants, but its fate as a vaccine component following intramuscular (IM) injection in humans is unknown. In this study, we constructed a physiologically-based pharmacokinetic (PBPK) model for intramuscularly injected squalene-in-water (SQ/W) emulsion, in order to make a quantitative estimation of the tissue distribution of squalene following a single IM injection in humans. The PBPK model incorporates relevant physicochemical properties of squalene; estimates of the time course of cracking of a SQ/W emulsion; anatomical and physiological parameters at the injection site and beyond; and local, preferential lymphatic transport. The model predicts that a single dose of SQ/W emulsion will be removed from human deltoid muscle within six days following IM injection. The major proportion of the injected squalene will be distributed to draining lymph nodes and adipose tissues. The model indicates slow decay from the latter compartment most likely due to partitioning into neutral lipids and a low rate of squalene biotransformation there. Parallel pharmacokinetic modeling for mouse muscle suggests that the kinetics of SQ/W emulsion correspond to the immunodynamic time course of a commercial squalene-containing adjuvant reported in that species. In conclusion, this study makes important pharmacokinetic predictions of the fate of a squalene-containing emulsion in humans. The results of this study may be relevant for understanding the immunodynamics of this new class of vaccine adjuvants and may be useful in future quantitative risk analyses that incorporate mode-of-action data.

Human βhsp90 as adjuvant in HCV Recombinant vaccine

There are more than 350 million individuals with hepatitis C in the world. One of the important problems in vaccine project is development of effective and suitable adjuvant in human vaccines. At present research we applied human βHsp90 protein as an adjuvant in recombinant HCV vaccine design. The thermal vector of pGP1-2 was used for human heat shock protein 90 expression. This protein injected to BalbC mice as an adjuvant together with recombinant protein of HCV core. The combination of these proteins was used and we evaluated the humoral and cellular immunity and the cytokine secretion of inguinal and popliteal lymph nodes lymphocytes were analyzed in vitro and ex vivo conditions. So the combination of Core protein together with hsp90 induced total IgG and IgG2a secretion. The spleen lymphocytes proliferation were increased equal to serum IgG2a level that was constant in second time bleeding with significant different to complexes with freund’s adjuvant. At first IL-4 and IL-5 cytokines were increased, after one week it decreased. Production of IL-4 showed there was no hypersensitivity reaction after vaccine injection.

Toll-like receptor-4 agonist in post-haemorrhage pneumonia: role of dendritic and natural killer cells

Haemorrhage-induced immunosuppression has been linked to nosocomial infections. We assessed the impact of monophosphoryl lipid A, a Toll/interleukin-1 receptor-domain-containing adaptor protein inducing interferon-biased Toll-like receptor-4 agonist currently used as a vaccine adjuvant in humans, on post-haemorrhage susceptibility to infection. We used a mouse model of post-haemorrhage pneumonia induced by methicillin-susceptible Staphylococcus aureus. Monophosphoryl lipid A was administered intravenously after haemorrhage and before pneumonia onset. Haemorrhage altered survival rate, increased lung damage (neutrophil accumulation, oedema and cytokine release) and altered the functions of dendritic and natural killer cells. Here, we show that monophosphoryl lipid A decreased systemic dissemination of S. aureus and dampened inflammatory lung lesions. Monophosphoryl lipid A partially restored the capacity for antigen presentation and the transcriptional activity in dendritic cells. Monophosphoryl lipid A did not restore the interferon-γ mRNA but prevented interleukin-10 mRNA overexpression in natural killer cells compared with untreated mice. Ex vivo monophosphoryl lipid A-stimulated dendritic cells or natural killer cells harvested from haemorrhaged animals were adoptively transferred into mice undergoing post-haemorrhage pneumonia. Stimulated dendritic cells (but not stimulated natural killer cells) improved the survival rate compared with mice left untreated. In vivo depletion of natural killer cells decreased survival rate of monophosphoryl lipid A-treated mice. Dendritic and natural killer cells are critically involved in the beneficial effects of monophosphoryl lipid A within post-haemorrhage pneumonia.

Alum Directly Modulates Murine B Lymphocytes to Produce IgG1 Isotype

Aluminum hydroxide (alum) is the most widely used adjuvant in human vaccines. Nevertheless, it is virtually unknown whether alum acts on B cells. In the present study, we explored the direct effect of alum on Ig expression by murine B cells in vitro. LPS-activated mouse spleen B cells were cultured with alum, and the level of isotype-specific Ig secretion, IgG1 secreting cell numbers, and Ig germ-line transcripts (GLT) were measured using ELISA, ELISPOT, and RT-PCR, respectively. Alum consistently enhanced total IgG1 production, numbers of IgG1 secreting cells, and GLTγ1 expression. These results demonstrate that alum can directly cause IgG1 isotype switching leading to IgG1 production.

Disparate adjuvant properties among three formulations of “alum” (52.11)

Abstract Aluminum salts, commonly referred to as “alum,” are the most common adjuvants in human vaccines and serve as a benchmark in the development of novel adjuvants. Although the mechanisms that promote humoral responses to alum-adsorbed antigens are still enigmatic, alum is thought to induce inflammatory signals that, in turn, promote antibody production. It has been noted that some formulations of alum used in animal studies, notably Imject alum®, are not the chemical equivalents of the aluminum used in human vaccines, raising concerns where Imject serves as the comparator for novel adjuvants. Here, we compared the capacity of Imject alum, Alhydrogel®, and a traditional alum-antigen (Alum-Ag) precipitate to induce humoral responses in mice to the hapten-carrier NP-CGG. Primary humoral responses elicited by Alhydrogel and the Alum-Antigen precipitate were significantly greater than those induced by Imject alum. The three alum formulations elicited comparable responses in terms of acute eosinophil and monocyte infiltration at the immunization site, but neutrophil recruitment by Imject alum was signficantly reduced compared to Alum-Ag precipitate or Alhydrogel. These findings reveal substantial differences in the adjuvant properties and inflammatory effects of distinct alum preparations, an important consideration in the analysis of new adjuvants and mechanistic studies of alum’s adjuvanticity.

Human prophylactic vaccine adjuvants and their determinant role in new vaccine formulations

Adjuvants have been considered for a long time to be an accessory and empirical component of vaccine formulations. However, accumulating evidence of their crucial role in initiating and directing the immune response has increased our awareness of the importance of adjuvant research in the past decade. Nevertheless, the importance of adjuvants still is not fully realized by many researchers working in the vaccine field, who are involved mostly in the search for better target antigens. The choice of a proper adjuvant can be determinant for obtaining the best results for a given vaccine candidate, but it is restricted due to intellectual property and know-how issues. Consequently, in most cases the selected adjuvant continues to be the aluminum salt, which has a record of safety, but predominantly constitutes a delivery system (DS). Ideally, new strategies should combine immune potentiators (IP) and DS by mixing both compounds or by obtaining structures that contain both IP and DS. In addition, the term immune polarizer has been introduced as an essential concept in the vaccine design strategies. Here, we review the theme, with emphasis on the discussion of the few licensed new adjuvants, the need for safe mucosal adjuvants and the adjuvant/immunopotentiating activity of conjugation. A summary of toxicology and regulatory issues will also be discussed, and the Finlay Adjuvant Platform is briefly summarized.

The Importance of Adjuvant Formulation in the Development of a Tuberculosis Vaccine

An effective protein-based vaccine for tuberculosis will require a safe and effective adjuvant. There are few adjuvants in approved human vaccines, including alum and the oil-in-water-based emulsions MF59 (Novartis Vaccines and Diagnostics), AS03 and AS04 (GlaxoSmithKline Biologics), AF03 (Sanofi), and liposomes (Crucell). When used with pure, defined proteins, both alum and emulsion adjuvants are effective at inducing primarily humoral responses. One of the newest adjuvants in approved products is AS04, which combines monophosphoryl lipid A, a TLR-4 agonist, with alum. In this study, we compared two adjuvants: a stable oil-in-water emulsion (SE) and a stable oil-in-water emulsion incorporating glucopyranosyl lipid adjuvant, a synthetic TLR-4 agonist (GLA-SE), each together with a recombinant protein, ID93. Both the emulsion SE and GLA-SE adjuvants induce potent cellular responses in combination with ID93 in mice. ID93/SE induced Th2-biased immune responses, whereas ID93/GLA-SE induced multifunctional CD4(+) Th1 cell responses (IFN-γ, TNF-α, and IL-2). The ID93/GLA-SE vaccine candidate induced significant protection in mice and guinea pigs, whereas no protection was observed with ID93/SE, as assessed by reductions in bacterial burden, survival, and pathology. These results highlight the importance of properly formulating subunit vaccines with effective adjuvants for use against tuberculosis.

Macrophagic myofasciitis: characterization and pathophysiology

Aluminium oxyhydroxide (alum), a nanocrystalline compound forming agglomerates, has been used in vaccines for its immunological adjuvant effect since 1927. Alum is the most commonly used adjuvant in human and veterinary vaccines, but the mechanisms by which it stimulates immune responses remain 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 the site of previous intramuscular (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 the site of injection or diffuses and accumulates in distant organs. Animal experiments indicate that biopersistent nanomaterials taken up by monocyte-lineage cells in tissues, such as 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 the brain.

The Toll-Like Receptor 4 Agonist Monophosphoryl Lipid A Augments Innate Host Resistance to Systemic Bacterial Infection

Monophosphoryl lipid A (MPLA) is a Toll-like receptor 4 (TLR4) agonist that is currently used as a vaccine adjuvant in humans. In this study, we evaluated the effect of MPLA treatment on the innate immune response to systemic bacterial infections in mice. Mice treated with MPLA after burn injury showed improved survival and less local and systemic dissemination of bacteria in a model of Pseudomonas aeruginosa burn wound infection. Prophylactic treatment with MPLA significantly enhanced bacterial clearance at the site of infection and reduced systemic dissemination of bacteria despite causing attenuation of proinflammatory cytokine production during acute intra-abdominal infection caused by cecal ligation and puncture. Administration of MPLA at 1 h after CLP also improved bacterial clearance but did not alter cytokine production. MPLA treatment increased the numbers of granulocytes, double-positive myeloid cells, and macrophages at sites of infection and increased the percentage and total numbers of myeloid cells mediating phagocytosis of bacteria. Depletion of Ly6G(+) neutrophils, but not macrophages, eliminated the ability of MPLA treatment to improve bacterial clearance. The immunomodulatory effects of MPLA were absent in TLR4-deficient mice. In conclusion, these studies show that MPLA treatment significantly augments the innate immune response to bacterial infection by enhancing bacterial clearance despite the attenuation of proinflammatory cytokine production. The enhanced bacterial clearance is mediated, in part, by increased numbers of myeloid cells with effective phagocytic functions at sites of infection and is TLR4 dependent.

KSAC, the First Defined Polyprotein Vaccine Candidate for Visceral Leishmaniasis

A subunit vaccine using a defined antigen(s) may be one effective solution for controlling leishmaniasis. Because of genetic diversity in target populations, including both dogs and humans, a multiple-antigen vaccine will likely be essential. However, the cost of a vaccine to be used in developing countries must be considered. We describe herein a multiantigen vaccine candidate comprised of antigens known to be protective in animal models, including dogs, and to be recognized by humans immune to visceral leishmaniasis. The polyprotein (KSAC) formulated with monophosphoryl lipid A, a widely used adjuvant in human vaccines, was found to be immunogenic and capable of inducing protection against Leishmania infantum, responsible for human and canine visceral leishmaniasis, and against L. major, responsible for cutaneous leishmaniasis. The results demonstrate the feasibility of producing a practical, cost-effective leishmaniasis vaccine capable of protecting both humans and dogs against multiple Leishmania species.

Carbohydrate-based immune adjuvants

The role for adjuvants in human vaccines has been a matter of vigorous scientific debate, with the field hindered by the fact that for over 80 years, aluminum salts were the only adjuvants approved for human use. To this day, alum-based adjuvants, alone or combined with additional immune activators, remain the only adjuvants approved for use in the USA. This situation has not been helped by the fact that the mechanism of action of most adjuvants has been poorly understood. A relative lack of resources and funding for adjuvant development has only helped to maintain alum’s relative monopoly. To seriously challenge alum’s supremacy a new adjuvant has many major hurdles to overcome, not least being alum’s simplicity, tolerability, safety record and minimal cost. Carbohydrate structures play critical roles in immune system function and carbohydrates also have the virtue of a strong safety and tolerability record. A number of carbohydrate compounds from plant, bacterial, yeast and synthetic sources have emerged as promising vaccine adjuvant candidates. Carbohydrates are readily biodegradable and therefore unlikely to cause problems of long-term tissue deposits seen with alum adjuvants. Above all, the Holy Grail of human adjuvant development is to identify a compound that combines potent vaccine enhancement with maximum tolerability and safety. This has proved to be a tough challenge for many adjuvant contenders. Nevertheless, carbohydrate-based compounds have many favorable properties that could place them in a unique position to challenge alum’s monopoly over human vaccine usage.

Induction of protection in mice against a respiratory challenge by a vaccine formulated with the Chlamydia major outer membrane protein adjuvanted with IC31 ®

IC31 ®, a novel adjuvant, has been shown to be effective by increasing the levels of IFN-γ in animal models when delivered with several antigens. Here, we tested the ability of IC31 ®, to enhance the protective ability of the Chlamydia trachomatis native major outer membrane protein (nMOMP). BALB/c mice were immunized by the intramuscular (i.m.) and subcutaneous (s.c.) routes with nMOMP + IC31 ®. Another group of animals was immunized with nMOMP + Alum and as a negative control mice were immunized with ovalbumin (Ova) + IC31 ®. Animals immunized with nMOMP + IC31 ® developed high Chlamydia-specific IgG titers. The serum levels of IgG1 were higher than those of the IgG2a. T cells, from the spleens of mice immunized with IC31 ®-adjuvanted nMOMP demonstrated a strong lymphoproliferative reaction to Chlamydia elementary bodies (EB) compared with the groups immunized with nMOMP + Alum or Ova + IC31 ®. A similar comparison between these groups of mice revealed that the levels of IFN-γ in the supernatants from stimulated T-cells were significantly higher in animals immunized with nMOMP + IC31 ®. Following an intranasal challenge with C. trachomatis, the mice immunized with IC31 ®-adjuvanted nMOMP showed significant protection. The change in body weight, an indication of the severity of the infection, was significantly less reduced in mice immunized with nMOMP + IC31 ®. Furthermore, the weight of the lungs, as well as the pulmonary Chlamydia burden, was significantly lower in the animals immunized with nMOMP + IC31 ® when compared with the groups immunized with nMOMP + Alum or with Ova + IC31 ®. In conclusion, these results provide the rationale for further preclinical testing of IC31 ® using other chlamydial antigens, and support the potential evaluation of this adjuvant in human vaccines against Chlamydia.

Immunomodulatory properties of E. coli enterotoxins

Event Abstract Back to Event Immunomodulatory properties of E. coli enterotoxins George Hajishengallis1* 1 University of Louisville, Departement of Microbiology and Immunology, United States Most infectious diseases occur, or are initiated, at mucosal surfaces. This is because the vast majority of pathogens colonize or invade the mucosae via oral, respiratory, or urogenital routes. However, purified vaccine proteins generally do not stimulate immune responses, in large part because they fail to induce appropriate activation signals in antigen-presenting cells, such as dendritic cells. An effective vaccine, therefore, would need to induce immunostimulatory signals without concomitant toxicity. This can be accomplished through the use of safe and effective adjuvants in vaccine formulations. Heat-labile enterotoxins are potent mucosal and systemic adjuvants but their intrinsic enterotoxicity precludes their use as adjuvants for human vaccines. In common to the Type I heat-labile enterotoxins from Vibrio cholerae or Escherichia coli, the Type II enterotoxins of E. coli (LT-II) display AB5 oligomeric structure, in which an enzymatically toxic A subunit is linked to a pentameric ganglioside-binding (B5) subunit. Studies by our group have succeeded to dissociate useful adjuvant properties from the toxicity of LT-IIa and LT-IIb. Specifically, the recombinantly expressed B pentameric subunits of LT-IIa and LT-IIb (LT-IIa-B5 and LT-IIb-B5, respectively) not only lack enterotoxicity but, strikingly, can activate the Toll-like receptor (TLR)-2/TLR1 signaling complex and stimulate antibody responses to co-administered vaccine proteins. Moreover, certain engineered point-substitution mutations in the TLR2-interactive region of LT-II-B5 molecules enhance the ability of the adjuvants to interact with TLR2/TLR1. Additional studies showed that the immunomodulatory properties of LT-II-B5 molecules are regulated, at least in part, by their capacity to enhance antigen uptake, migration, and antigen presentation by dendritic cells in a strictly TLR2-dependent manner. Hitherto, the adjuvant effects of heat-labile enterotoxins have been considered to depend on their ganglioside-binding and catalytic-toxic activities, and arguably on certain catalytic-independent activities of their A subunits. Our findings show that the B pentameric subunits of Type II enterotoxins are immunostimulatory by a novel mechanism that involves TLR2 signaling. Keywords: adjuvans, B5 subunits, concomitant toxicity, immunostimulatory signals, TLR2 signaling Conference: ECMIS - E. coli and the Mucosal Immune System : Interaction, Modulation and Vaccination, Ghent, Belgium, 2 Jul - 5 Jul, 2011. Presentation Type: Oral Presentation Topic: Virulence factors and influence on innate and/or adaptive immunity Citation: Hajishengallis G (2011). Immunomodulatory properties of E. coli enterotoxins. Front. Immunol. Conference Abstract: ECMIS - E. coli and the Mucosal Immune System : Interaction, Modulation and Vaccination. doi: 10.3389/conf.fimmu.2011.01.00006 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 22 Sep 2011; Published Online: 26 Sep 2011. * Correspondence: Prof. George Hajishengallis, University of Louisville, Departement of Microbiology and Immunology, Louisville, United States, g0haji01@louisville.eu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers George Hajishengallis Google George Hajishengallis Google Scholar George Hajishengallis PubMed George Hajishengallis Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Delta inulin: a novel, immunologically active, stable packing structure comprising -D-[2 -> 1] poly(fructo-furanosyl) -D-glucose polymers

We report a novel isoform of β-D-[2 → 1] poly(fructo-furanosyl) α-D-glucose termed delta inulin (DI), comparing it with previously described alpha (AI), beta (BI) and gamma (GI) isoforms. In vitro, DI is the most immunologically active weight/weight in human complement activation and in binding to monocytes and regulating their chemokine production and cell surface protein expression. In vivo, this translates into potent immune adjuvant activity, enhancing humoral and cellular responses against co-administered antigens. As a biocompatible polysaccharide particle, DI is safe and well tolerated by subcutaneous or intramuscular injection. Physico-chemically, DI forms as an insoluble precipitate from an aqueous solution of suitable AI, BI or GI held at 37-48°C, whereas the precipitate from the same solution at lower temperatures has the properties of AI or GI. DI can also be produced by heat conversion of GI suspensions at 56°C, whereas GI is converted from AI at 45°C. DI is distinguished from GI by its higher temperature of solution in dilute aqueous suspension and by its lower solubility in dimethyl sulfoxide, both consistent with greater hydrogen bonding in DI's polymer packing structure. DI suspensions can be dissolved by heat, re-precipitated by cooling as AI and finally re-converted back to DI by repeated heat treatment. Thus, DI, like the previously described inulin isoforms, reflects the formation of a distinct polymer aggregate packing structure via reversible noncovalent bonding. DI forms the basis for a potent new human vaccine adjuvant and further swells the growing family of carbohydrate structures with immunological activity.

Alphavirus replicon-based enhancement of mucosal and systemic immunity is linked to the innate response generated by primary immunization

Venezuelan equine encephalitis virus replicon particles (VRP) function as an effective systemic, cellular and mucosal adjuvant when codelivered with antigen, and show promise for use as a component in new and existing human vaccine formulations. We show here that VRP are effective at low dose and by intramuscular delivery, two useful features for implementation of VRP as a vaccine adjuvant. In mice receiving a prime and boost with antigen, we found that VRP are required in prime only to produce a full adjuvant effect. This outcome indicates that the events triggered during prime with VRP are sufficient to establish the nature and magnitude of the immune response to a second exposure to antigen. Events induced by VRP in the draining lymph node after prime include robust secretion of many inflammatory cytokines, upregulation of CD69 on leukocytes, and increased cellularity, with a disproportionate increase of a cell population expressing CD11c, CD11b, and F4/80. We show that antigen delivered 24h after administration of VRP does not benefit from an adjuvant effect, indicating that the events which are critical to VRP-mediated adjuvant activity occur within the first 24h. Further studies of the events induced by VRP will help elucidate the mechanism of VRP adjuvant activity and will advance the safe implementation of this adjuvant in human vaccines.

Effect of Granulocyte/Macrophage Colony-Stimulating Factor on Circulating CD8+ and CD4+ T-Cell Responses to a Multipeptide Melanoma Vaccine: Outcome of a Multicenter Randomized Trial

Granulocyte/macrophage colony-stimulating factor (GM-CSF) administered locally together with vaccines can augment T-cell responses in animal models. Human experience has been limited to small and uncontrolled trials. Thus, a multicenter randomized phase II trial was done to determine whether local administration of GM-CSF augments immunogenicity of a multipeptide vaccine. It also assessed immunogenicity of administration in one versus two vaccine sites. One hundred twenty-one eligible patients with resected stage IIB to IV melanoma were vaccinated with 12 MHC class I-restricted melanoma peptides to stimulate CD8+ T cells plus a HLA-DR-restricted tetanus helper peptide to stimulate CD4+ T cells, emulsified in incomplete Freund's adjuvant, with or without 110 microg GM-CSF. Among 119 evaluable patients, T-cell responses were assessed by IFN-gamma ELIspot assay and tetramer analysis. Clinical outcomes were recorded. CD8+ T-cell response rates to the 12 MHC class I-restricted melanoma peptides (by day 50) with or without GM-CSF were 34% and 73%, respectively (P < 0.001), by direct ELIspot assay. Tetramer analyses corroborated the functional data. CD4+ T-cell responses to tetanus helper peptide were higher without GM-CSF (95% versus 77%; P = 0.005). There was no significant difference by number of vaccine sites. Three-year overall and disease-free survival estimates (95% confidence interval) were 76% (67-83%) and 52% (43-61%), respectively, with too few events to assess differences by study group. High immune response rates for this multipeptide vaccine were achieved, but CD8+ and CD4+ T-cell responses were lower when administered with GM-CSF. These data challenge the value of local GM-CSF as a vaccine adjuvant in humans.

Effect of granulocyte-macrophage colony stimulating factor (GM-CSF) administered with a multipeptide vaccine on circulating CD8+ and CD4+ T-cell responses: Outcome of a multicenter randomized trial

3008 Background: GM-CSF administered locally with vaccines can augment T-cell responses in animal models. Human experience with GM-CSF has mostly occurred in uncontrolled or nonrandomized trials. Thus, a multicenter prospective randomized phase II trial was performed to determine whether local administration of GM-CSF augments immunogenicity of a multipeptide vaccine administered in an emulsion with an incomplete Freund's adjuvant (IFA). A second component of the trial was designed to assess whether the vaccine administered in two sites is more immunogenic than in a single site. Methods: 121 eligible and evaluable patients with resected stage IIB-IV melanoma were administered a sequence of multipeptide vaccines, each consisting of 12 MHC Class I-restricted melanoma peptides (12MP) to stimulate CD8+ T cells, plus an HLA-DR restricted tetanus helper peptide to stimulate CD4+ T cells. Peptides were emulsified with IFA, with or without GM-CSF. T cell responses were assessed by IFN-gamma ELIspot assay and tetramer analysis, weekly x 8. Clinical outcome was evaluated for all patients. Results: Vaccination was well-tolerated, and each peptide was immunogenic. Overall CD8+ T-cell response rates to the 12MP (days 1–50), for patients vaccinated with or without GM-CSF were 43% and 75%, respectively (p &lt; 0.001), and response magnitude was almost twice as high in patients without GM-CSF. Class I MHC tetramer analyses corroborated the functional data. There was also a greater CD4+ T-cell response to the tetanus helper peptide without GM-CSF than with it (95% and 77%, respectively, p = 0.005). There was no significant difference in immune response rates by the number of vaccine sites. For the entire patient group, 3-year overall and disease-free survival estimates [95% CI] were 76% [67, 83%] and 52% [43, 61%], respectively. There have been too few events to assess differences in clinical outcome by study arm. Conclusions: High immune response rates were achieved with this multipeptide vaccine, but CD8+ and CD4+ T-cell responses appear to be partially suppressed with addition of GM-CSF. These data challenge the value of local GM-CSF as a vaccine adjuvant in humans. [Table: see text]

Mechanism of action of licensed vaccine adjuvants

Despite the fact that alum and oil-in-water emulsions have been used for decades as human vaccine adjuvants in a large number of individuals, their mechanism of action is not completely understood. It has been reported that these particulate adjuvants act by increasing antigen availability and uptake by immune cells. However, recent work on alum and on the squalene-based emulsion MF59, has demonstrated that besides antigen delivery functions, these classes of adjuvants can also activate innate immunity pathways in vivo, generating an immunocompetent environment at injection site. Interestingly, it has been demonstrated that alum adjuvanticity depends on the activation of a protein complex called NLPR3/inflammasome, which is required for the correct processing of a number of pro-inflammatory cytokines, including IL1β. More work needs to be performed to investigate if the inflammasome is also required for the activity of MF59 and of other particulate vaccine adjuvants.