Accurate determination of adjuvant-associated protein or peptide by ninhydrin assay

Mucosal and systemic immune responses following mucosal immunisation of tetanus toxoid entrapped in lipid nanoparticles prepared by microwave reactor

In this study, the use of a microwave reactor, which allowed high input of energy into a pressurised system in a short period of time, was investigated for preparation of lipid nanoparticles (LNPs). The aim was to optimise the formulation process by reducing manufacturing time. Two types of LNPs were prepared; non-ionic surfactant vesicles (NISV) and bilosomes (modified NISV incorporating bile salts), with a model antigen (tetanus toxoid, TT) and the immune response induced after mucosal (nasal and oral, respectively) administration was assessed. The TT loaded LNPs were characterised in terms of particle size, size distribution, morphology, and entrapment efficiency. Immunisation was evaluated by lethal challenge with tetanus toxin in an animal model. The efficiency of vaccination was evaluated by measuring the anti-TT IgG antibody levels in the vaccinated animals. Bilosomes formed by this method showed an immunogen entrapment efficiency of ∼ 30% which was significantly (p<0.05) higher than entrapment efficiency in the NISV. The percentage of animals that survived when challenged with tetanus toxin correlated with the level of IgG determined in the serum of mice immunised with LNPs by the mucosal route. Moreover, there were significant (p<0.05) differences between orally and nasally immunised groups. Animal groups immunised bilosomes via the oral route showed the highest level of IgG (1.2±0.13) compared to the positive control, LN+Xn, and no immunised group. Similarly, groups immunised via the nasal route showed significantly (p<0.0001) higher titres compared with the control group. Mucosal TT was capable of inducing systemic specific IgG anti-TT responses that were higher than the parenteral vaccine.

How to define and study structural proteins as biopolymer materials

Structural proteins, including silk fibroins, play an important role in shaping the skeletons and structures of cells, tissues, and organisms. The amino acid sequences of structural proteins often show characteristic features, such as a repeating tandem motif, that are notably different from those of functional proteins such as enzymes and antibodies. In recent years, materials composed of or containing structural proteins have been studied and developed as biomedical, apparel, and structural materials. This review outlines the definition of structural proteins, methods for characterizing structural proteins as polymeric materials, and potential applications.

Recombinant baculovirus associated with bilosomes as an oral vaccine candidate against HEV71 infection in mice

BACKGROUND

Human enterovirus 71 (HEV71) is one of the major pathogen responsible for hand, foot and mouth disease (HFMD). Currently no effective vaccine or antiviral drugs are available. Like poliovirus, EV71 is transmitted mainly by the feco-oral route. To date the majority of the studied EV71 vaccine candidates are administered parenterally. Injectable vaccines induce good systemic immunity but mucosal responses are often unsatisfactory, whereas mucosal vaccines provide both systemic and mucosal immunity. Therefore, oral immunization appears to be an attractive alternative to parenteral immunization.

METHODOLOGY/PRINCIPAL FINDINGS

In this report, we studied the efficacy of an orally administered vaccine candidate developed using recombinant baculovirus displaying VP1 (Bac-VP1) in a murine model. Gastrointestinal delivery of Bac-VP1 significantly induced VP1-specific humoral (IgG) and mucosal (IgA) immune responses. Further, we studied the efficacy of the Bac-VP1 associated with bilosomes and observed that the Bac-VP1 associated with bilosomes elicited significantly higher immune responses compared to bilosomes non-associated with Bac-VP1. However, mice immunized subcutaneously with live Bac-VP1 had significantly enhanced VP1 specific serum IgG levels and higher neutralizing antibody titers compared with mice orally immunized with live Bac-VP1 alone or associated with bilosomes.

CONCLUSION

Bilosomes have been shown to possess inherent adjuvant properties when associated with antigen. Therefore Bac-VP1 with bilosomes could be a promising oral vaccine candidate against EV71 infections. Thus, Bac-VP1 loaded bilosomes may provide a needle free, painless approach for immunization against EV71, thereby increasing patient compliance and consequently increasing vaccination coverage.

Partial delipidation improves the T-cell antigenicity of hepatitis B virus surface antigen

Hepatitis B virus surface antigen (HBsAg) is a complex macromolecular particle composed of glycoproteins and lipids. The latter, representing 25% of the particle mass, are of host origin and determine the solubility, stability, and, indirectly, B-cell immunogenicity of HBsAg. HBsAg is a T-cell-dependent immunogen that does not elicit a detectable humoral immune response in 5% of HBsAg vaccine recipients and in most subjects suffering from chronic hepatitis B. We investigated the influence of the lipid content on the antigenicity of the particle. Lipids were partially removed from HBsAg by treatment with beta-D-octyl glucoside and density centrifugation. Sham treatment consisted of density centrifugation of HBsAg only. We compared the in vitro proliferative responses of established T-cell lines and nonfractionated peripheral blood mononuclear cells (PBMC) from HBsAg vaccinees and chronic HBV patients when stimulated with partially delipidated HBsAg, untreated HBsAg, or sham-treated HBsAg. In all experiments, delipidated HBsAg turned out to be 10 to 100 times more antigenic than its untreated or sham-treated counterpart. Remarkably, PBMC from vaccine nonresponders or chronic HBV patients displayed a proliferative response towards delipidated HBsAg, whereas native HBsAg never induced a response. A series of control experiments demonstrated that this enhancement of T-cell antigenicity was HBsAg specific and directly linked to lipid extraction. Nonspecific adjuvant effects of any kind could be ruled out. In vivo evaluation in mice demonstrated that delipidated particles lose most of their B-cell antigenicity. However, when native and delipidated particles were mixed, these mixtures induced equal or slightly superior anti-HBs responses to those induced by the same quantity of native HBsAg alone. In conclusion, our data show that partial delipidation of HBsAg strikingly increases the T-cell antigenicity of this unique viral antigen.

Oral delivery of tetanus toxoid using vesicles containing bile salts (bilosomes) induces significant systemic and mucosal immunity

Protein antigens administered via the oral route are exposed to a hostile environment in the gastrointestinal tract, consisting of digestive enzymes and a range of pH (1-7.5). Using a delivery system can afford protection to entrapped components against degradation and permit delivery of antigen to the cells responsible for generating local and systemic immune responses. In this comparative study, mice were immunised orally with tetanus toxoid (40 or 200 microg dose/mouse, four doses in total) entrapped in non-ionic surfactant vesicles formulated with bile salts (bilosomes). The higher entrapped dose (BV-TT, 200 microg) induced IgG1 by study week 3 to similar levels to those observed with subcutaneous un-entrapped TT at the lower (<50 microg) dose. However, both bilosome formulations (BV-TT, low, and high doses), though not un-entrapped TT, caused a rise in the numbers of IgA positive plasma cells observed in the small intestine, primarily in the first 15 cm of the small intestine.

Optimisation of a lipid based oral delivery system containing A/Panama influenza haemagglutinin

Vaccine antigens administered by the oral route are often degraded by gastric secretions during gastrointestinal transit. This necessitates larger and more frequent doses of antigen for vaccination. A delivery system, which overcomes this, is a lipid vesicle containing bile salts (bilosome), which prevents antigen degradation and enhances mucosal penetration. The effect of bilosome formulation modification on vaccine transit efficacy across the mucosa was determined. Specific antibody levels were assessed by end-point titre ELISA and the subclasses determined. Significant IgG1 titres were induced when the protein loading was doubled from 15 to 30 microg (P=0.009) and was equivalent to antigen administration by the subcutaneous route. No IgG2a was induced, indicating the generation of a TH2 response. Significant mucosal IgA levels were also observed with this treatment group (P=0.05).

Analysis of the role of vaccine adjuvants in modulating dendritic cell activation and antigen presentation in vitro

We have studied the effects of adjuvant formulations on the activation and antigen-presenting functions of bone marrow-derived dendritic cells (DCs). While LPS could induce high-level expression of MHC Class II and co-stimulator molecules on DCs, it did not enhance antigen presentation to co-stimulation independent DO11.GFP T hybridoma cells. In contrast, alum, NISV and PLGA formulations failed to activate DCs, but NISV and PLGA could enhance antigen-presentation efficiency by 10-100-fold. Irrespective of the previously described antigen release characteristics of each adjuvant, antigen presentation peaked at 6h and waned thereafter for all formulations. Given the importance of DCs in the activation of nai;ve T cell responses, these studies suggest that as yet undefined pathways of DC activation in vivo may underlie the activity of alum, PLGA and NISV adjuvants. Furthermore, as NISV and PLGA do not appear to act as slow-release systems in DCs, the ability of these particulate systems to induce high levels of antigen presentation by DCs probably has a more significant role in their adjuvant activity.

Oral immunisation with peptide and protein antigens by formulation in lipid vesicles incorporating bile salts (bilosomes)

The ability of non-ionic surfactant vesicles to induce systemic immune responses in mice following oral immunisation was studied using a standard antigen (bovine serum albumin), a synthetic measles peptide and an influenza sub-unit vaccine. The effectiveness of this formulation was significantly increased by incorporating bile salts (in particular deoxycholate) into the formulation. We have named the resulting vesicles bilosomes. We found that the most effective immunisation protocol was to give two doses of vaccine three days apart and then repeat this protocol two weeks later. Following this method, preparation of measles peptide in bilosomes produced a specific cell mediated response, as measured by splenocyte proliferation and IL-2 production. Of particular significance, these studies demonstrate that oral administration of bilosomes incorporating the influenza sub-unit vaccine could induce as potent an antibody response as the parenterally administered vaccine containing the same quantity of antigen. In addition, the Th1/Th2 balance, as measured by antibody subclasses, was similar whether animals were immunised by the oral or the parenteral vaccine route. As bilosomes are prepared from naturally occurring lipids and have no apparent toxicity associated with their use, they represent a useful modification of conventional lipid vesicle based systems for the oral delivery of proteins and peptides.

Lipid Vesicle Size Determines the Th1 or Th2 Response to Entrapped Antigen

Understanding the factors that control the differential induction of Th1 and Th2 responses is a key immunologic objective with profound implications for vaccination and immunotherapy of infectious and autoimmune diseases. Using Ag formulated in lipid vesicles prepared from nonionic surfactants, we describe a novel mechanism influencing the balance of the Th1 or Th2 response. Our results indicate that inoculation of BALB/c mice with vesicles with a mean diameter ≥225 nm preferentially induces Th1 responses, as characterized by increased titers of IgG2a in plasma and elevated IFN-γ production by lymph node cells. However, preparation of the same quantity of Ag in vesicles with mean diameter of ≤155 nm induces a Th2 response, as identified by IgG1 in the absence of IgG2a production and increased lymph node IL-5 production. Although large (≥225 nm) vesicles could induce IL-12 production, smaller vesicles (≤155 nm) could not. However, small vesicles did induce higher levels of IL-1β production by macrophages than larger vesicles. The role of IL-12 in this response was confirmed in IL-12-deficient mice, whose spleen cells failed to produce IFN-γ following in vivo priming with Ag prepared in large vesicles. Our results therefore indicate that macrophages respond to endocytosis of large or small vesicles by producing different patterns of cytokines that can subsequently direct the immune response toward a Th1 or a Th2 phenotype.

Investigation into suitable carrier molecules for use in an anti-gonadotrophin releasing hormone vaccine

Gonadal function can be controlled through immunoneutralisation of gonadotrophin releasing hormone (GnRH), with an analogue, GnRH-glycys, linked to a carrier molecule and an appropriate adjuvant. In this study, four different types of carrier molecule were investigated: (a) single and branched amino acid polymers--[poly-(D-glu, D-lys) and poly-(phe, glu)-poly(DL-ala)-poly(lys)]; (b) bacterial toxoids--diphtheria (DT) and tetanus (TT); (c) synthetic T-helper epitopes--derived from malarial circumsporozite protein (CS) and measles virus fusion protein (MVF); and (d) thyroglobulin (Thy)--a large protein. The effect of non-ionic surfactant vesicles (NISV) and an aluminum hydroxide based adjuvant (alum), was also examined. Although good antibody responses were achieved with GnRH-glycys-DT, GnRH-glycys-TT and GnRH-glycys-Thy, adsorbed onto alum and the dimerised synthetic T-helper epitope constructs, incorporated into NISV, a critical antibody titre was necessary to result in morphological changes in the gonads and complete suppression of spermatogenesis. This was only achieved with tetanus toxoid and the dimerised T-helper epitopes.

Lipid vesicle-entrapped influenza A antigen modulates the influenza A-specific human antibody response in immune reconstituted SCID-human mice

This study was designed to investigate the capacity of purified influenza antigen in the presence and absence of adjuvant to induce human antibody responses in human-PBL-SCID mice. Non-ionic surfactant vesicles (NISV) were used as adjuvant as they have been shown to promote the development of Th1 responses in mouse studies. Human peripheral blood lymphocyte-SCID mice were inoculated with either purified influenza antigen (A/Texas, H3N2) or influenza antigen entrapped in NISV. Both vaccinated groups produced significantly higher plasma levels of influenza-specific human IgG when individually compared with non-vaccinated controls. However, similar comparisons revealed that specific IgM levels were significantly higher only in the group challenged with purified antigen. Further analysis of IgG subclasses also demonstrated an adjuvant-dependent dichotomy in the responses of the vaccine groups when compared with non-vaccinated controls. Thus, only influenza-specific IgG1 antibodies (associated with Th1 responses in humans) were significantly increased above control levels using antigen with adjuvant, while both this subclass and antigen-specific IgG4 (Th2 associated) were significantly increased with antigen alone. These results illustrate the suitability of this model for use in human vaccination studies and demonstrates that influenza antigen applied with NISV selectively promotes only Th1 responses, unlike free antigen which also promotes Th2 responses in vivo.