The adjuvant monophosphoryl lipid A increases the function of antigen-presenting cells

The induction of immune responses in vivo is typically performed with antigens administered in external adjuvants, like alum, complete Freund's adjuvant, LPS and, more recently, monophosphoryl lipid A (MPL). However, the role of the adjuvant is still poorly defined. The aim of this study was to test whether the MPL affects the function of antigen-presenting cells (APC) in vitro and in vivo. Antigen-pulsed APC [including macrophages, B cells and dendritic cells (DC)] were incubated or not with MPL, and their ability to sensitize naive T cells was tested in vitro and in vivo. The data show that MPL enhances the ability of macrophages and B cells to sensitize naive T cells, and confers to them the capacity to induce the development of T(h)1 and T(h)2. Administration of MPL i.v. in mice results in the redistribution of fully mature DC in the T cell area of the spleen. These observations suggest that MPL may induce an antigen-specific primary immune response by provoking the migration and maturation of DC that are the physiological adjuvant of the immune system.     

A complex of lactoferrin with monophosphoryl lipid A is an efficient adjuvant of the humoral and cellular immune response in mice

Our recent investigations demonstrated adjuvant properties of lactoferrin (LF). Other studies proved efficacy and safety of monophosphoryl lipid A (MPL) as an adjuvant in humans. In an attempt to construct more efficient and safer adjuvants, we evaluated the activity of LF-MPL complex, formed by incubation of LF and MPL from Hafnia alvei at 20:1 w/w ratio, and verified its characteristics by SDS-PAGE analysis. Binding kinetics was determined by surface plasmon resonance analysis using a BIAcore^TM 1000 biosensor system. The efficiency of the complex in enhancing the humoral and cellular immune responses was analyzed in BALB/c mice. The complex stimulated the humoral immune response to ovalbumin (OVA) and sheep red blood cells significantly stronger than both components separately, used at respective doses. In addition, the complex increased the serum levels of IgG, IgG2a and IgG1 OVA-specific antibodies as compared to the actions of LF or MPL alone. In the model of delayed type hypersensitivity (DTH) the strongest immune response was demonstrated with OVA administered subcutaneously, admixed with the complex. Administration of the complex in incomplete Freund’s adjuvant, together with a sensitizing dose of antigen, was similarly effective as immunization with complete Freund’s adjuvant. The complex also significantly enhanced the DTH response to orally administered Calmette-Guérin bacilli. In summary, the new type of adjuvant, the LF-MPL complex, was described. Its activity surpassed the adjuvant action of both constituents tested separately in the humoral and cellular immune responses in mice. The plausible mode of action of the new adjuvant is discussed.     

单磷酸脂质A佐剂对无细胞百日咳疫苗的免疫保护效果研究

目的 探讨单磷酸脂质A(MPLA)佐剂对无细胞百日咳疫苗(aP)的免疫保护效果影响.方法 aP中添加MPLA佐剂,在Balb/c小鼠上进行免疫以及感染保护实验.通过检测小鼠百日咳特异性IgG抗体及其分型抗体IgG1和IgG2a水平、感染后白细胞变化以及气管和肺组织细菌定植来进行免疫效果的评估.结果 aP+MPLA免疫的...     

Inactivation of suppressor T-cell activity by nontoxic monophosphoryl lipid A.

Treatment with nontoxic monophosphoryl lipid A (MPL), which was derived from a polysaccharide-deficient, heptoseless Re mutant of Salmonella typhimurium, was found to inactivate suppressor T-cell activity, as evidenced by a decrease in the degree of low-dose immunological paralysis expressed and an increase in the magnitude of the antibody response to type III pneumococcal polysaccharide. The effects produced, which could not be attributed to the polyclonal activation of immune B cells by MPL, were dependent upon the dose of MPL used, as well as the time when MPL was given relative to low-dose priming or immunization with type III pneumococcal polysaccharide. Neither amplifier nor helper T-cell activity was decreased by treatment with the same, or larger, doses of MPL. The significance of these findings to the use of MPL as an immunological adjuvant or an immunomodulating agent is discussed.     

Enhancement of humoral and cellular immune responses by monophosphoryl lipid A (MPLA) as an adjuvant to the rabies vaccine in BALB/c mice

The development of effective vaccines against the rabies virus could prevent infection with this fatal virus. However, the current rabies vaccine fails to provide a full range of protection because of its limited ability to elicit a cellular immune response and the requirement for repeat vaccination. Monophosphoryl lipid A (MPLA) is well known as a potent adjuvant to enhance immune responses against virus infection. Here we investigated the efficacy of MPLA as an adjuvant to improve the humoral and cellular immune responses to the rabies vaccine in BALB/c mice. Supplementation of the rabies vaccine with MPLA significantly accelerated the production of specific antibodies by 10 days compared to the original vaccines. Furthermore, MPLA promoted the induction of stronger cellular immune responses by the rabies vaccine, including the production of IL-4, IFN-γ and the activation of CD4⁺/CD8⁺ T cells, than those elicited without MPLA. Collectively, our findings indicated that MPLA enhances humoral and cellular immunity and is a promising adjuvant for the development of more effective rabies vaccines.     

Role of antigen-presenting cells in innate immune system

Activation of antigen-presenting cells (APC) and natural killer (NK) cells initiates the production of various proinflammatory cytokines including interleukin 12 (IL-12), interferon gamma (IFN-gamma) and nitric oxide (NO), which are important in the innate immune response for controlling infection by intracellular pathogens. In this review, we focus on these cytokines produced by APC and summarize the current understanding of how APC functions are regulated by cytokines in innate immunity.     

Mitogenicity of a spread film of monophosphoryl lipid A

When spread at the air-water interface, monophosphoryl lipid A (MPLA) forms stable insoluble monolayers that collapse at approximately 55 dyn/cm. At collapse, the exclusion area of each molecule is approximately 119 Angstrom(2), consistent with the cross-sectional area of the lipid's 6 acyl chains. The nominal thickness of such films is approximately 22 Angstrom, determined, presumably, by the length of the acyl chains. For biological modeling of MPLA films, a system was developed in which monolayers of the lipid are supported by monodisperse hydrophobic beads of microscopic dimensions. Beads coated with MPLA monolayers within which the nominal area of each molecule is approximately equivalent to the "take-off" area of the lipid at the air-water interface, 280 Angstrom(2), are mitogenic for spleen cells. Given the natural occurrence of lipid A in the bacterial cell wall as well as the inherent stability of lipid A films, it seems reasonable to assume that at least some of the biological activities attributed to the lipid derive from its presentation/operation at an interface, i.e., on a surface. We propose beads coated with adsorbed films of lipid A will prove useful tools for modeling the activities of the lipid both in vitro and in vivo, and for elucidating the surface dependency and structural requirements of those activities.     

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.     

Comparison of liposome-polycation-DNA(LPD) and monophosphoryl lipid A(MPL) adjuvant formulations in BALB/c mice models

It is of fundamental importance to use an appropriate adjuvant to generate a potent immune response for immunotherapy. In this study, we had a comparative investigation on the effectiveness of two adjuvant formulations, liposome-polycation-DNA (LPD) and monophosphoryl lipid A(MPL) in combination with a truncated peptide of bFGF(tbFGF) as antigen. LPD/tbFGF induced continuously increasing antibodies expression during the whole immunization period. In contrast, the level of antibodies was variable in MPL/tbFGF-immunized mice, MPL/tbFGF elicited potent antibodies response in the early-phase of immunization (during the first 3 immunizations), but the later immunizations did not produce a significant increase in the level of antibodies. Evaluation of IFN-γ and IL-4 responses revealed that both LPD/tbFGF and MPL/tbFGF demonstrated generation of higher level of IFN-γ, whereas no significant increase in IL-4 levels was detected in the two groups. In addition, histological analysis exhibited obvious germinal centers in the spleen tissues of LPD/tbFGF mice. The data suggested that LPD would be a promising long-effective adjuvant due to its potent and persistent immunostimulation and MPL could play an appropriate role in short-acting immunization.     

Adjuvant activity of monophosphoryl lipid A for nasal and oral immunization with soluble or liposome-associated antigen

The effectiveness of monophosphoryl lipid A (MPL) as a mucosal adjuvant was investigated following oral or intranasal (i.n.) administration of an aqueous adjuvant formulation of MPL (MPL-AF) added to soluble antigen or liposomal antigen or incorporated into liposomal antigen membranes. Groups of BALB/c female mice were immunized with 50 to 100 microg of free or liposomal Streptococcus mutans crude glucosyltransferase (C-GTF) with or without MPL-AF added to the vaccine or incorporated into the liposomal membrane. Plasma, saliva, vaginal wash, and fecal extract samples were collected biweekly following immunization and assessed for antigen-specific antibody activity by enzyme-linked immunosorbent assay (ELISA). Mice immunized by the i.n. route had higher levels of salivary, plasma, and vaginal immunoglobulin A (IgA) anti-C-GTF responses and higher levels of plasma IgG anti-C-GTF than the orally immunized groups. A second administration of the vaccine 14 weeks after the initial immunization resulted in an anamnestic response to C-GTF resulting in 10- and 100-fold increases in saliva and plasma IgA and plasma IgG, respectively (in the i.n. immunized groups). Mice receiving a second i.n. immunization with liposomal antigen and MPL-AF had higher salivary IgA anti-C-GTF responses than mice immunized with antigen plus MPL-AF or liposomal antigen (P < 0.05). Plasma IgG anti-C-GTF activity was highest in mice immunized by the i.n. route with antigen formulations containing MPL-AF (P < 0.05). These results demonstrate the effectiveness of MPL-AF as an adjuvant for potentiating mucosal and systemic immune responses to liposomal C-GTF following i.n. immunization.     

Role of TIM-4 in innate or adaptive immune response

Human being living in constant contact with microbes and pathogen and in the process has developed a recognition pattern of pathogenic structure in the immune cells. The gut lumen has high density of microbes thus the immune response is slightly tolerable to certain microbes, known as commensal flora. These microbes along with other innocuous agents do not cause any inflammation response normally, and are considered as harmless by the immune cells. In immune hypersensitivity condition, such as colitis or food allergy, this mechanism is disturbed. T cell immunoglobulin and mucin domain (TIM)-4 is a phosphatidylserine receptor expressed in mature antigen presenting cells. It is shown that TIM-4 and its ligand TIM-1 are associated in intestinal immune response. However the characteristic of TIM-4 sometimes seems to be two-faced and there is a possibility that TIM-4 also bind to other ligands.     

A well-tolerated grass pollen-specific allergy vaccine containinga novel adjuvant, monophosphoryl lipid A, reduces allergic symptoms after only four preseasonal injections

BACKGROUND: We present data showing that a Th1-inducing adjuvant can reduce the number of injections required for allergy vaccination. Allergy vaccination is the only treatment for type 1 hypersensitivity that can alter the underlying disease process. A switch of specific T-cell activity from Th2 >Th1 to Th1 >Th2 is believed to be an important change seen after long-term vaccination therapy. An immunologic adjuvant that enhances such a switch could be used to reduce the number of injections required. This would improve compliance with the treatment and provide pharmacoeconomic advantages. Such an adjuvant is 3-deacylated monophosphoryl lipid A (MPL adjuvant, Corixa). METHODS: A multicentre, placebo-controlled, randomized, double-blind clinical study was performed with a new standardized allergy vaccine comprising a tyrosine-adsorbed glutaraldehyde-modified grass pollen extract containing MPL adjuvant. Four subcutaneous injections of the active product were given preseasonally to 81 grass pollen-sensitive subjects, and 60 received placebo injections (tyrosine alone). Diary cards were used to record symptoms and medication taken during approximately 30 days of the grass pollen season. RESULTS: There was a statistical advantage in favour of the active treatment for nasal (P = 0.016) and ocular (P = 0.003) symptoms and combined symptom and medication scores (P=0.013). Titrated skin prick testing revealed a significant reduction of skin sensitivity in the active group compared to placebo (P = 0.04). Grass-pollen-specific IgG antibody was raised by active treatment (P < 0.01). A rise in IgE antibody was seen in the placebo group during the season (P < 0.01). The first year's treatment rise of IgE was not seen in the active group, and no rise occurred during the pollen season. More local adverse events were seen in the active group. There was no difference in generalized adverse events. CONCLUSION: A new, well-tolerated allergy vaccine, incorporating a Th1-inducing adjuvant, MPL, was efficacious and after only four preseasonal injections produced antibody changes normally associated with long injection schedules. This may encourage wider application of allergy vaccination. The vaccine is now available in a number of countries as Pollinex Quattro.     

细胞外信号调节激酶介导单磷酰脂A的心脏保护作用

目的:探讨单磷酰脂A(MLA)的心脏保护作用及其细胞分子机制。方法:在猪心脏缺血再灌注(I/R)模型上,观察MLA预处理对于心肌梗塞面积的影响。并采用Westernblot的方法,检测MAL预处理后猪心肌组织内细胞外信调节激酶(ERKs)与HSP86含量的变化。结果:MAL预处理明显缩小猪心脏I/R所致心肌梗塞的范围,并使心肌组织内HSP86和ERKs蛋白水平发生上调。结论:MLA预处理可以减轻猪心脏I/R所造成的损伤,其机制涉及ERKs介导的HSP86蛋白合成的上调。     

Early-phase endotoxin tolerance: induction by a detoxified lipid A derivative, monophosphoryl lipid A.

After a sublethal exposure to lipopolysaccharide (LPS) or to lipid A, which is that portion of the LPS molecule associated with endotoxicity, a transient period ensues during which a normally responsive individual is rendered hyporesponsive to LPS-induced toxicity. This period has been defined as early-phase endotoxin tolerance. Recently, a nontoxic derivative of lipid A from Salmonella typhimurium, monophosphoryl lipid A (MPL), was isolated and purified. In this study, we assessed the ability of MPL to induce early endotoxin tolerance. Initial injection of MPL resulted in a dose-dependent stimulation of both serum colony-stimulating factor and serum interferon, indicators of in vivo LPS responsiveness. In contrast, MPL failed to induce the symptoms of endotoxicity which are normally seen after injection of even sublethal amounts of intact endotoxin or lipid A preparations. Injection of MPL on day 0 reduced significantly the amount of LPS-induced serum colony-stimulating factor and interferon produced upon challenge with Escherichia coli LPS 3 days later and also mitigated toxic manifestations, as evidenced by a marked increase in the 50% lethal dose. Like the early tolerance induced by wild-type (toxic) LPS, MPL-induced tolerance was characterized by an accompanying elevation in the number of bone marrow-derived macrophage progenitor cells and by an alteration in bone marrow cell sizing profiles. These results indicate that MPL is effective in inducing a state of LPS-hyporesponsiveness without the toxic side effects of endotoxin and that the structural component(s) necessary for induction of early-phase endotoxin tolerance is contained within MPL.     

Differential sensitivity of CD8+ suppressor and cytotoxic T lymphocyte activity to bacterial monophosphoryl lipid A.

Treatment with a preparation of monophosphoryl lipid A, known to be capable of abolishing the expression of CD8+ suppressor T cell activity generated during the antibody response to type III pneumococcal polysaccharide (SSS-III), was found to have no adverse effect upon either induction or expression of CD8+ cytotoxic T lymphocyte activity specific for influenza A virus antigens. This suggests that suppressor T cells and cytotoxic T lymphocytes represent functionally distinct subsets of CD8+ T cells which can be differentiated on the basis of their sensitivities to inactivation by monophosphoryl lipid A.     

Ability of monophosphoryl lipid A to augment the antibody response of young mice.

Treatment with nontoxic monophosphoryl lipid A increased the magnitude of the immunoglobulin M (IgM) antibody response to type III pneumococcal polysaccharide in young (2- to 4-week-old) mice. This was accompanied by the appearance of significant numbers of IgG1- and IgG3- secreting antibody-forming cells in 4-week-old mice. These findings indicate that monophosphoryl lipid A can be used as an adjuvant to improve the immunogenicity of poorly immunogenic antigens in young, immunologically immature animals.     

Effect of monophosphoryl lipid A on host resistance to bacterial infection.

The ability of monophosphoryl lipid A (MPLA) to enhance nonspecific host resistance to bacterial infections was studied. Mice were treated with MPLA prior to intraperitoneal challenge with Escherichia coli or Staphylococcus epidermidis. Animals received additional MPLA for 2 days postinfection, and survival rates were determined. Ten micrograms of MPLA per mouse significantly improved the survival of animals infected with either bacterial species. Dose-response studies showed significant MPLA-induced protection at doses of 6 micrograms/kg against E. coli challenge and 60 micrograms/kg against S. epidermidis challenge.