Immunomodulation Through Beta-D-glucan in Chemically-induced Necrotizing Pancreatitis.

BACKGROUND: Although the ability of ß-D-glucan and monophosphoryl lipid A (MPLA) to modulate immune responses has been studied in human primary cells, their effect on sterile inflammation models such as necrotizing pancreatitis has never been investigated. MATERIALS AND METHODS: 85 male New Zealand rabbits were assigned into following groups: A: control, B: pretreatment with ß-D-glucan 3 d before pancreatitis, C: pretreatment with MPLA 3 d before pancreatitis, D: pretreatment with ß-D-glucan and laminarin 3 d before pancreatitis, E: treatment with ß-D-glucan 1 d after pancreatitis, and F: MPLA 1 d after pancreatitis. Pancreatitis was induced by sodium taurocholate injection into the pancreatic duct and parenchyma. Survival was recorded for 21 d. On days 1, 3, and 7, blood was collected for amylase measurement. Peripheral blood mononuclear cells were isolated and stimulated for tumor necrosis factor alpha and interleukin 10 production. Pancreatic necrosis and tissue bacterial load were assessed. RESULTS: 21-d survival was prolonged after pretreatment or treatment with ß-D-glucan; this benefit was lost with laminarin administration. At sacrifice, pancreatic inflammatory alterations were more prominent in the control group. Bacterial load was lower after pretreatment or treatment with ß-D-glucan and MPLA. Tumor necrosis factor alpha production from stimulated peripheral blood mononuclear cells was significantly decreased, whereas interleukin 10 production remained unaltered after pretreatment or treatment with ß-D- glucan. CONCLUSIONS: ß-D-glucan reduces mortality of experimental pancreatitis in vivo. This is mediated through attenuation of cytokine production and prevention of bacterial translocation.

A novel glycocluster molecule prevents timothy-induced allergic airway inflammation in mice.

BACKGROUND: Allergen-specific immunotherapy (SIT) effectively alleviates type I allergic diseases characterized by T helper (Th)2-type immunity. Our recent studies have shown that a synthetic trivalent glycocluster, triacedimannose (TADM), suppresses the Th2-type allergic inflammation. The aim of this study was to compare TADM with two well-known adjuvants, unmethylated cytosine-phosphate-guanine oligodeoxynucleotide (CpG) and monophosphoryl lipid A (MPLA) in a grass allergen-induced chronic allergic inflammation model in mice. METHODS: Female BALB/c mice were intranasally sensitized with 50 µL of timothy grass pollen extract (TE) twice a week for a period of 15 weeks. Therapeutic intranasal treatments were then performed once a week after the tenth intranasal TE instillation using TADM (10 or 25 µg/50 µL), CpG-ODN (20 µg/50 µL) or MPLA (2 µg/50 µL). Groups of 9-10 animals per treatment were killed 24 hours after the last timothy dosage. Blood, bronchoalveolar lavage (BAL) fluids and lung biopsies were taken for subsequent analysis. RESULTS: When mice were repeatedly exposed to TE for 15 weeks, the number of eosinophils and lymphocytes increased in the BAL fluids. The eosinophil and lymphocyte counts decreased dose-dependently and were practically abolished in the mice treated with TADM. Treatments with MPLA or CpG significantly increased the numbers of neutrophils, while CpG nonsignificantly decreased eosinophilia compared to timothy exposure. CONCLUSIONS: A novel synthetic glycocluster molecule inhibited the development of grass-induced eosinophilic pulmonary inflammation in mice when administrated in the airways. This compound could be a candidate to be used either as an adjuvant in SIT or as a topical anti-inflammatory treatment.

TLR4-Based Immunotherapeutics in Cancer: A Review of the Achievements and Shortcomings.

Toll-like Receptor 4 (TLR4) agonists have had a long journey in the field of cancer immunotherapy. Nevertheless, despite the remarkable number of the TLR4 ligands that have gone through various preclinical and clinical stages, only two (Bacillus Calmette-Guérin (BCG) and monophosphoryl lipid A (MPLA)) have hitherto obtained the FDA approval for clinical application in cancer treatment. This paper provides a comprehensive review of the TLR4 agonists' journey as cancer active immunotherapeutics. Following a brief discussion of the rationale behind the use of TLR ligands in cancer immunotherapy, we will initially focus on the forerunner of the TLR4 agonists, bacterial lipopolysaccharide (LPS). Within this context, the potentials and shortcomings of immunotherapy with this agent will be addressed, the strategies that have been devised to enhance the associated therapeutic outcome will be discussed, and the consequent achievements and shortcomings will be summarized. Subsequently, further and perhaps less well-known, molecular, bacterial, and viral TLR4 agonists with potential for cancer immunotherapy will be introduced, and if present, the outcome of the preclinical and clinical investigations of these agents will be reviewed. Finally, a look will be cast upon the promising souvenirs of the relatively new arena of nanotechnology, where TLR4 activating nanoparticulate systems will be proposed as potential candidates for the future development of this field.

The Impact on Allergy-Related Cells of a Birch Pollen Allergoid, with and without Monophosphoryl Lipid A, in Comparison with the Native Equivalent.

BACKGROUND: The clinical efficacy and safety of allergoid immunotherapy have been demonstrated in clinical trials. However, simultaneous monitoring of the immunological changes by allergoids versus allergens in the cells of the same individual has not been extensively performed, and the impact of concurrent Toll-like receptor 4 (TLR4) ligation has not been specified. METHODS: Three types of birch allergen were utilized: glutaraldehyde-treated allergoid (extract A), the same allergoid plus monophosphoryl lipid A (MPL), i.e., TLR4 ligand (extract A*), and native allergen (extract B). Antigen-specific responses after the in vitro stimulation of blood cells with the extracts were assessed by studying costimulatory receptors on the B cell surface by flow cytometry, cytokine responses by ELISA, and CD63 and CD203c upregulation (basophil activation test) in allergic versus nonallergic subjects. RESULTS: HLA-DR selectively increased upon allergen or allergoid treatment in the allergic group only. The extract types elicited similar cytokine responses, with IL-6 and IL-10 production detected only in certain atopic subjects. The allergoids revealed a strong reduction (100- to <10,000-fold) in basophil activation versus native allergen. Reactivity was undetectable in the basophils from nonallergic subjects. CONCLUSION: The allergenicity of the allergoid employed was sharply reduced when compared to the native allergen, while its immunogenicity was largely retained, especially in the presence of MPL. We also provide further evidence that allergic and nonallergic individuals show preexisting differences in their immune repertoires.

Toll-like receptor 4 stimulation with the detoxified ligand monophosphoryl lipid A improves Alzheimer's disease-related pathology.

Alzheimer's disease (AD) is the most common cause of dementia worldwide. The pathogenesis of this neurodegenerative disease, currently without curative treatment, is associated with the accumulation of amyloid ß (Aß) in brain parenchyma and cerebral vasculature. AD patients are unable to clear this toxic peptide, leading to Aß accumulation in their brains and, presumably, the pathology associated with this devastating disease. Compounds that stimulate the immune system to clear Aß may therefore have great therapeutic potential in AD patients. Monophosphoryl lipid A (MPL) is an LPS-derived Toll-like receptor 4 agonist that exhibits unique immunomodulatory properties at doses that are nonpyrogenic. We show here that repeated systemic injections of MPL, but not LPS, significantly improved AD-related pathology in APP(swe)/PS1 mice. MPL treatment led to a significant reduction in Aß load in the brain of these mice, as well as enhanced cognitive function. MPL induced a potent phagocytic response by microglia while triggering a moderate inflammatory reaction. Our data suggest that the Toll-like receptor 4 agonist MPL may be a treatment for AD.

Efficacy of a short course of specific immunotherapy in patients with allergic rhinoconjunctivitis to ragweed pollen.

BACKGROUND: Specific immunotherapy acts to modify the underlying cause of allergic rhinoconjunctivitis. Addition of adjuvants, such as monophosphoryl lipid A (MPL), might allow for efficacious and safe treatment with only 4 injections administered preseasonally, which is in contrast to most available schedules requiring long injection courses. OBJECTIVE: The primary objective was to assess the clinical efficacy of Ragweed MATA MPL (short ragweed pollen allergoid adsorbed to L-Tyrosine + MPL) versus placebo in reducing allergic rhinoconjunctivitis symptoms caused by ragweed pollen in an environmental exposure chamber (EEC) 3 weeks after treatment. METHODS: This was a randomized, double-blind, placebo-controlled phase IIb study to evaluate the clinical efficacy and safety of Ragweed MATA MPL compared with placebo by using controlled ragweed pollen exposure in an EEC. Two hundred twenty-eight patients with a history of ragweed allergy and positive skin prick test responses to ragweed were randomized and received 4 weekly injections of active treatment or placebo. Total nasal and nonnasal symptom scores were obtained in the EEC before and after treatment. RESULTS: Mean improvement in total symptom scores in the Ragweed MATA MPL group was statistically significantly greater than in the placebo group (relative mean improvement of active vs placebo, 48%; P < .05; median improvement, 82%). The majority of adverse events (AEs) experienced by subjects were mild injection-site reactions. No severe systemic AEs or serious AEs occurred during the study. CONCLUSION: This study demonstrated that an ultrashort course of Ragweed MATA MPL is efficacious in reducing allergy symptoms in patients with seasonal allergic rhinitis and that it is well tolerated.

Adjuvant cationic liposomes presenting MPL and IL-12 induce cell death, suppress tumor growth, and alter the cellular phenotype of tumors in a murine model of breast cancer.

Dendritic cells (DC) process and present antigens to T lymphocytes, inducing potent immune responses when encountered in association with activating signals, such as pathogen-associated molecular patterns. Using the 4T1 murine model of breast cancer, cationic liposomes containing monophosphoryl lipid A (MPL) and interleukin (IL)-12 were administered by intratumoral injection. Combination multivalent presentation of the Toll-like receptor-4 ligand MPL and cytotoxic 1,2-dioleoyl-3-trmethylammonium-propane lipids induced cell death, decreased cellular proliferation, and increased serum levels of IL-1ß and tumor necrosis factor (TNF)-α. The addition of recombinant IL-12 further suppressed tumor growth and increased expression of IL-1ß, TNF-α, and interferon-γ. IL-12 also increased the percentage of cytolytic T cells, DC, and F4/80(+) macrophages in the tumor. While single agent therapy elevated levels of nitric oxide synthase 3-fold above basal levels in the tumor, combination therapy with MPL cationic liposomes and IL-12 stimulated a 7-fold increase, supporting the observed cell cycle arrest (loss of Ki-67 expression) and apoptosis (TUNEL positive). In mice bearing dual tumors, the growth of distal, untreated tumors mirrored that of liposome-treated tumors, supporting the presence of a systemic immune response.

TLR4 inhibition impairs bacterial clearance in a therapeutic setting in murine abdominal sepsis.

OBJECTIVE AND DESIGN: To investigate the therapeutic effect of E5564 (a clinically used TLR4 inhibitor) in murine abdominal sepsis elicited by intraperitoneal infection with a highly virulent Escherichia coli in the context of concurrent antibiotic therapy. METHODS: Mice were infected with different doses (~2 × 10(4)-2 × 10(6) CFU) of E. coli O18:K1 and treated after 8 h with ceftriaxone 20 mg/kg i.p. combined with either E5564 10 mg/kg i.v. or vehicle. For survival studies this treatment was repeated every 12 h. Bacterial loads and inflammatory parameters were determined after 20 h in peritoneal lavage fluid, blood, liver and lung tissue. Plasma creatinin, AST, ALT and LDH were determined to assess organ injury. RESULTS: E5564 impaired bacterial clearance under the antibiotic regime after infection with a low dose E. coli (1.7 × 10(4) CFU) while renal function was slightly preserved. No differences were observed in bacterial load and organ damage after infection with a tenfold higher (1.7 × 10(5) E. coli) bacterial dose. While treatment with E5564 slightly attenuated inflammatory markers provoked by the sublethal doses of 104-105 E. coli under the antibiotic regime, it did not affect lethality evoked by infection with 1.7 × 106 E. coli. CONCLUSIONS: The impact of TLR4 inhibition during abdominal sepsis by virulent E. coli bacteria is only beneficial at low infection grade at cost of bactericidal activity.

The association between rLiHyp1 protein plus adjuvant and amphotericin B is an effective immunotherapy against visceral leishmaniasis in mice.

Treatment of visceral leishmaniasis (VL) is compromised by drug toxicity, high cost and/or the emergence of resistant strains. Though canine vaccines are available, there are no licensed prophylactic human vaccines. One strategy to improve clinical outcome for infected patients is immunotherapy, which associates a chemotherapy that acts directly to reduce parasitism and the administration of an immunogen-adjuvant that activates the host protective Th1-type immune response. In this study, we evaluated an immunotherapy protocol in a murine model by combining recombinant (r)LiHyp1 (a hypothetical amastigote-specific Leishmania protein protective against Leishmania infantum infection), with monophosphoryl-lipid A (MPLA) as adjuvant and amphotericin B (AmpB) as reference antileishmanial drug. We used this protocol to treat L. infantum infected-BALB/c mice, and parasitological, immunological and toxicological evaluations were performed at 1 and 30 days after treatment. Results showed that mice treated with rLiHyp1/MPLA/AmpB presented the lowest parasite burden in all organs evaluated, when both a limiting dilution technique and qPCR were used. In addition, these animals produced higher levels of IFN-γ and IL-12 cytokines and IgG2a isotype antibody, which were associated with lower production of IL-4 and IL-10 and IgG1 isotype. Furthermore, low levels of renal and hepatic damage markers were found in animals treated with rLiHyp1/MPLA/AmpB possibly reflecting the lower parasite load, as compared to the other groups. We conclude that the rLiHyp1/MPLA/AmpB combination could be considered in future studies as an immunotherapy protocol to treat against VL.

Modulation of soluble and particulate antigen transport in afferent lymph by monophosphoryl lipid A.

Vaccine adjuvants stimulate the innate immune system and determine the outcome of the immune response induced. A better understanding of their action is therefore crucial to the development of new and safer vaccines. Monophosphoryl lipid A (MPL), a 'detoxified' version of lipolysaccharide, is a promising new adjuvant component in human vaccines. The present study uses an ovine lymphatic cannulation model to study cell recruitment and antigen transport from the injection site into the afferent lymph, and how this is modulated by co-injection with MPL. Compared with saline, MPL injections caused only minor variations in lymph flow and no difference in cell number migrating into the lymph. MPL did, however, cause a significantly increased recruitment of neutrophils and monocytes, but not dendritic cells (DC) into the lymph for the first 12 h. Soluble ovalbumin (OVA) antigen flowed freely into the lymph over a 24-h period and was slightly reduced at 6-9 h in the MPL-injected sites. OVA-coated fluorescent 1-µ beads were initially transported predominantly by neutrophils and, from 24 to 72 h, by DC. MPL induced an increased and more sustained transport of beads by neutrophils and monocytes although it did not increase the phagocytic capacity of these cells. In contrast to aluminium adjuvant, MPL did not increase bead transport by DC at the later time point. These studies provide important new insights in the in vivo action of different adjuvants and the initial events that set up an immune response after vaccination.

Assessment of specific immunotherapy efficacy using a novel placebo score-based method.

BACKGROUND: In trials of allergen immunotherapy, allergen exposure is typically assessed by pollen counts, but these may misrepresent exposure if performed remotely from multiple study centers. OBJECTIVE: To assess whether symptomatology in placebo-treated patients is a better measure of local allergen burden at individual centers in such trials. METHODS: Data from a multicenter, placebo-controlled trial of preseasonal grass pollen immunotherapy were reanalyzed to identify the 4 weeks at each center in which the placebo-treated subjects had the highest combined symptom/medication scores (CSMS). The difference in CSMS between active and placebo groups was compared during the 4 peak placebo score weeks (PlSW) and the 4 peak pollen count weeks (PoCW). RESULTS: The benefit of immunotherapy over placebo in the PlSW analysis (18.5%) was greater than in the PoCW analysis (13.6%), with increased statistical significance (P = .0001, .0038, respectively). Similar improved discrimination was observed when analyzing benefits in subgroups of patients with severe symptoms, a high disease burden, and in different geographical locations. CONCLUSION: This novel PlSW analysis results in better discrimination of the effects of allergen immunotherapy compared with placebo and may be widely applicable in similar studies, both prospectively and retrospectively.

Variation in blood microbial lipopolysaccharide (LPS) contributes to immune reconstitution in response to suppressive antiretroviral therapy in HIV.

BACKGROUND: In HIV infection, even under long-term antiretroviral therapy (ART), up to 20% of HIV-infected individuals fail to restore CD4+ T cell counts to the levels similar to those of healthy controls. The mechanisms of poor CD4+ T cell reconstitution on suppressive ART are not fully understood. METHODS: Here, we tested the hypothesis that lipopolysaccharide (LPS) from bacteria enriched in the plasma from immune non-responders (INRs) contributes to blunted CD4+ T cell recovery on suppressive ART in HIV. We characterized plasma microbiome in HIV INRs (aviremic, CD4+ T cell counts < 350 cells/µl), immune responders (IRs, CD4+ T cell counts > 500 cells/µl), and healthy controls. Next, we analyzed the structure of the lipid A domain of three bacterial species identified by mass spectrometry (MS) and evaluated the LPS function through LPS induced proinflammatory responses and CD4+ T cell apoptosis in PBMCs. In comparison, we also evaluated plasma levels of proinflammatory cytokine and chemokine patterns in these three groups. At last, to study the causality of microbiome-blunted CD4+ T cell recovery in HIV, B6 mice were intraperitoneally (i.p.) injected with heat-killed Burkholderia fungorum, Serratia marcescens, or Phyllobacterium myrsinacearum, twice per week for total of eight weeks. FINDINGS: INRs exhibited elevated plasma levels of total microbial translocation compared to the IRs and healthy controls. The most enriched bacteria were Burkholderia and Serratia in INRs and were Phyllobacterium in IRs. Further, unlike P. myrsinacearum LPS, B. fungorum and S. marcescens LPS induced proinflammatory responses and CD4+ T cell apoptosis in PBMCs, and gene profiles of bacteria-mediated cell activation pathways in THP-1 cells in vitro. Notably, LPS structural analysis by mass spectrometry revealed that lipid A from P. myrsinacearum exhibited a divergent structure consistent with weak toll-like receptor (TLR) 4 agonism, similar to the biological profile of probiotic bacteria. In contrast, lipid A from B. fungorum and S. marcescens showed structures more consistent with canonical TLR4 agonists stemming from proinflammatory bacterial strains. Finally, intraperitoneal (i.p.) injection of inactivated B. fungorum and S. marcescens but not P. myrsinacearum resulted in cell apoptosis in mesenteric lymph nodes of C57BL/6 mice in vivo. INTERPRETATION: These results suggest that the microbial products are causally associated with INR phenotype. In summary, variation in blood microbial LPS immunogenicity may contribute to immune reconstitution in response to suppressive ART. Collectively, this work is consistent with immunologically silencing microbiome being causal and targetable with therapy in HIV. FUNDING: This work was supported by the National Institute of Allergy and Infectious Diseases (NIAID; R01 AI128864, Jiang) (NIAID; P30 AI027767, Saag/Health), the Medical Research Service at the Ralph H. Johnson VA Medical Center (merit grant VA CSRD MERIT I01 CX-002422, Jiang), and the National Institute of Aging (R21 AG074331, Scott). The SCOPE cohort was supported by the UCSF/Gladstone Institute of Virology & Immunology CFAR (P30 AI027763, Gandhi) and the CFAR Network of Integrated Clinical Systems (R24 AI067039, Saag). The National Center for Advancing Translational Sciences of the National Institutes of Health under Award Number UL1TR001450 (the pilot grant, Jiang). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Structural differences in bacterial lipopolysaccharides determine atherosclerotic plaque progression by regulating the accumulation of neutrophils.

BACKGROUND AND AIMS: Gut microbial lipopolysaccharide (LPS) induces endotoxemia, an independent risk factor for cardiovascular disease (CVD). However, no studies have demonstrated how structural differences in each bacterial LPS contribute to endotoxemia. Here, we investigated the effects of different acyl chains in the lipid A moiety of LPS on endotoxemia and the subsequent immune response and atherosclerotic plaque formation. METHODS: Apoe-/- mice were intraperitoneally administered 2 mg/kg of Escherichia coli-derived LPS (E. LPS, as a representative of hexa-acylated lipid A), Bacteroides-derived LPS (B. LPS, as a representative of penta- or tetra-acylated lipid A), or saline (control) once a week, six times. An immunohistological assessment was performed on plaque sections. RESULTS: E. LPS administration induced endotoxemia, but B. LPS and saline did not. In E. LPS-treated mice, total plaque areas in the aortic root were significantly increased, and neutrophil accumulation and increased formation of neutrophil extracellular traps (NETs) were observed at the plaque lesions, but not in B. LPS-treated mice. A single dose of E. LPS significantly increased the accumulation of neutrophils in plaque lesions on day 3, and NET formation on day 7. E. LPS also increased interleukin-1 beta (IL-1ß) production in plaque lesions on day 7. Furthermore, NET formation and IL-1ß production were also observed in human coronary plaques. CONCLUSIONS: We identified a previously unknown link between structural differences in LPS and atherosclerosis. Lowering microbial LPS activity may reduce NET formation in plaques and prevent CVD progression.

Manufacturing-dependent change in biological activity of the TLR4 agonist GSK1795091 and implications for lipid A analog development.

A phase I trial (NCT03447314; 204686) evaluated the safety and efficacy of GSK1795091, a Toll-like receptor 4 (TLR4) agonist, in combination with immunotherapy (GSK3174998 [anti-OX40 monoclonal antibody], GSK3359609 [anti-ICOS monoclonal antibody], or pembrolizumab) in patients with solid tumors. The primary endpoint was safety; other endpoints included efficacy, pharmacokinetics, and pharmacodynamics (PD). Manufacturing of GSK1795091 formulation was modified during the trial to streamline production and administration, resulting in reduced PD (cytokine) activity. Fifty-four patients received GSK1795091 with a combination partner; 32 received only the modified GSK1795091 formulation, 15 received only the original formulation, and seven switched mid-study from the original to the modified formulation. Despite the modified formulation demonstrating higher systemic GSK1795091 exposure compared with the original formulation, the transient, dose-dependent elevations in cytokine and chemokine concentrations were no longer observed (e.g., IP-10, IL10, IL1-RA). Most patients (51/54; 94%) experienced ≥1 treatment-emergent adverse event (TEAE) during the study. Safety profiles were similar between formulations, but a higher incidence of TEAEs associated with immune responses (chills, fatigue, pyrexia, nausea, and vomiting) were observed with the original formulation. No conclusions can be made regarding GSK1795091 anti-tumor activity due to the limited data collected. Manufacturing changes were hypothesized to have caused the change in biological activity in this study. Structural characterization revealed GSK1795091 aggregate size in the modified formulation to be twice that in the original formulation, suggesting a negative correlation between GSK1795091 aggregate size and PD activity. This may have important clinical implications for future development of structurally similar compounds.

Anti-HBs antibody persistence following primary vaccination with an investigational AS02(v)-adjuvanted hepatitis B vaccine in patients with renal insufficiency.

BACKGROUND: Three doses of the investigational AS02(v)-adjuvanted hepatitis B virus (HBV) vaccine HB-AS02 have been shown to induce more rapid seroprotection and higher anti-HBs antibody concentrations in patients with renal insufficiency than four doses of FENDrix™ (HB-AS04), an adjuvanted HBV vaccine licensed in Europe for use in this population. This study evaluated persistence of immune response up to 36 months after primary vaccination. METHODS: In this open, international, Phase III follow-up study, 151 pre-dialysis, peritoneal dialysis and hemodialysis patients ≥15 years of age received HB-AS02 at 0, 1, 6 months and 149 received HB-AS04 at 0, 1, 2, 6 months. Of these, 99 and 80 returned at Month 36, 76 and 62 of whom were eligible for inclusion in the Long-Term According-To-Protocol (LT-ATP) cohort for descriptive analysis of antibody persistence (mean age: 65.6 years). RESULTS: At Month 36, 89.5% of subjects in the HB-AS02 group and 72.6% of those in the HB-AS04 group had anti-HBs antibody concentrations ≥10 mIU/ml. Anti-HBs antibody concentrations were ≥100 mIU/ml in 82.9% and 35.5% of subjects, respectively. Anti-HBs geometric mean antibody concentrations were higher in the HB-AS02 group over the 36 months of follow-up. An exploratory "time to boost" analysis confirmed that subjects who received HB-AS02 were 2.54 times more likely than those who received HB-AS04 to have anti-HBs antibody concentrations ≥10 mIU/ml at Month 36 (p=0.013 [95% CI: 1.22, 5.31]). CONCLUSION: HB-AS02 candidate vaccine induces high and persistent anti-HBs antibody levels in pre-dialysis, peritoneal dialysis and hemodialysis patients, potentially reducing the need for booster doses in this population.

Yeast Shells Encapsulating Adjuvant AS04 as an Antigen Delivery System for a Novel Vaccine against Toxoplasma Gondii.

Toxoplasma gondii (T. gondii) infection causes severe zoonotic toxoplasmosis, which threatens the safety of almost one-third of the human population globally. However, there is no effective protective vaccine against human toxoplasmosis. This necessitates anti-T. gondii vaccine development, which is a main priority of public health. In this study, we optimized the adjuvant system 04 (AS04), a vaccine adjuvant constituted by 3-O-desacyl-4'-monophosphoryl lipid A (a TLR4 agonist) and aluminum salts, by packing it within natural extracts of ß-glucan particles (GPs) from Saccharomyces cerevisiae to form a GP-AS04 hybrid adjuvant system. Through a simple mixing procedure, we loaded GP-AS04 particles with the total extract (TE) of T. gondii lysate, forming a novel anti-T. gondii vaccine GP-AS04-TE. Results indicated that the hybrid adjuvant can efficiently and stably load antigens, mediate antigen delivery, facilitate the dendritic uptake of antigens, boost dendritic cell maturation and stimulation, and increase the secretion of pro-inflammatory cytokines. In the mouse inoculation model, GP-AS04-TE significantly stimulated the function of dendritic cells, induced a very strong TE-specific humoral and cellular immune response, and finally showed a strong and effective protection against toxoplasma chronic and acute infections. This work proves the potential of GP-AS04 for exploitation as a vaccine against a range of pathogens.

Monophosphoryl lipid A (MPL) as an adjuvant for anti-cancer vaccines: clinical results.

As technological advances allow for the identification of tumor-associated antigens (TAAs) against which adaptive immune responses can be raised, efforts to develop vaccines for the treatment of cancer continue to gain momentum. Some of these vaccines target differentiation antigens that are expressed by tumors derived from one particular tissue (e. g., Melan-A/ MART-1, tyrosinase, gp 100). Some target antigens are specifically expressed in tumors of different types but not in normal tissues (e. g., MAGE-3), while other possible targets are antigens that are expressed at low level in normal tissues and are over-expressed in tumors of different types (e. g., HER2, Muc 1). Oncogenes (HER2/neu, Ras, E7 HPV 16), tumor suppressor genes (pS3) or tumor-specific post-translational modified proteins (under glycosylated Muc 1) can also be used as cancer vaccine candidates. In either case, these antigens tend to be poorly inmmunogenic by themselves and vaccines containing them generally require the inclusion of potent immunological adjuvants in order to generate robust anti-tumor immune responses in humans. Many adjuvants currently under evaluation for use in cancer vaccines activate relevant antigen presenting cells, such as dendritic cells and macrophages, via toll-like receptors (TLRs) and promote effective uptake, processing and presentation of antigen to T-cells in draining lymph nodes.Lipid A, the biologically active portion of the gram-negative bacterial cell wall constituent lipopolysaccharide (LPS), is known to possess strong immunostimulatory properties and has been evaluated for more than two decades as an adjuvant for promoting immune responses to minimally immunogenic antigens, including TAAs. The relatively recent discovery of TLRs and the identification of TLR4 as the signaling receptor for lipid A have allowed for a better understanding of how this immunostimulant functions with regard to induction of innate and adaptive immune responses.Although several lipid A species, including LPS and synthetic analogs, have been developed and tested as monotherapeutics for the treatment of cancer,1-8 only 3-O-desacyl-4'-monophosphoryl lipid A (MPL) has been evaluated as a cancer vaccine adjuvant in published human clinical trials. MPL comprises the lipid A portion of Salmonella minnesota LPS from which the (R)-3-hydroxytetrade canoyl group and the l-phosphare have been removed by successive acid and base hydrolysis.9 LPS and MPL induce similar cytokine profiles, but MPLis at least 1OO-fold less toxic.9,10 lOMPL has been administered to more than 300, 000 human subjects in studies of next-generation vaccines.11 In this chapter, published clinical trials conducted to evaluate the safety and/or efficacy of various cancer vaccines containing MPL, either alone or combined with other immunostimulants, Such as cell wall skeleton (CWS) of Mycobacterium phlei in the adjuvant Detox; Biomira, Inc.), the saponin QS-21 (in the adjuvants AS01B and AS02B; GSK Biologicals) or with QS-21 and CpG oligonucleotides (in the adjuvant AS15; GSK Biologicals) will be summarized. Combining MPL with other immunostimulants has been demonstrated to be advantageous in many cases and may be required to elicit the full complement of activities necessary to achieve an effective immune response and overcome the ability of tumors to evade attack by the immune system. In this chapter, information relating to vaccines targeting specific cancers will be presented in the first section, while information relating to vaccines targeting multiple tumor types by the induction of immune responses to shared TAAs is presented in the second section.

Lipid A-mediated tolerance and cancer therapy.

The term "tolerance" from an immunological perspective, broadly encompasses a number of phenomena, but generally refers to a diminished responsiveness to LPS and/or other microbial products. With the discovery that many of the immunological, physiological and/or pathophysiological effects of LPS can be attributed to the lipid A moiety of the LPS molecule, a number of different lipid A analogs were synthesized with the goal of developing a drug that could be used clinically to treat cancer. In many instances, the development of tolerance to the lipid A congeners confounded the utility of these analogs as cancer therapeutics. In certain circumstances, however, the development of tolerance in patients has been utilized therapeutically to protect immunosuppressed patients from sepsis. Although numerous studies have been designed to investigate the development of tolerance, the underlying molecular mechanism remains unclear. This may be due, in part, to differences in the experimental models used, the sources and types of microbes and microbial products studied, kinetics of responses, and/or other experimental conditions. Nonetheless, a number of different signaling pathways have been identified as potentially modulating and/or triggering the development of tolerance. Though complex and incompletely understood, the capacity of tolerance to impact lipid A-based therapeutics, either positively or negatively, is inarguable, thus underscoring the necessity for further investigation toward elucidating the mechanisms contributing to the development of tolerance to lipid A and its analogs.

Antitumoral effects of lipids A, clinical studies.

Cancer remains the second leading cause of death, after cardiovascular diseases, in industrialized countries. The first goal to achieve is to prevent cancer occurrence or to diagnose it at an early and curable stage. Some screening strategies have been developed, with controversies across countries, for several cancer type; colorectal, breasts or prostate cancer for example.Treatment of cancer is generally based on surgery and radiotherapy for localized and attainable tumors, associated, in some cases, with adjuvant chemotherapy. Chemotherapy can also be used as first line treatment for disseminated diseases.The formulation of therapeutic strategies to enhance immune-mediated tumor destruction is a central goal of cancer immunology. Substantive progress toward delineating the mechanisms involved in innate and adaptive tumor immunity has improved the prospects for crafting efficacious treatments LPS and their active component lipid A, have been used in tumor therapy since the 19th century.Studies in animal models have shown promising results on different models of cancer but data from human trial are scarce. The published Phase-1 cancer studies have shown that lipid A analogues are usually well tolerated, most of the side effects being likely related to immune response, i. e., fever, chills and rigor. The administration of several lipids A analogues was shown to result in a significant increase in circulating levels of several cytokines but no objective antitumor responses were observed. Therefore clinical activity of such molecules deserves further experiments, likely in conjunction with chemotherapy.