Subunit intranasal vaccines offer the prospect of inducing combined systemic-mucosal immunity against mucosally transmitted infections such as human immunodeficiency virus. However, although human studies have demonstrated the induction of active immunity, secretory immunoglobulin A (sIgA) responses are variable, and no study has demonstrated protection by accepted vaccine-licensing criteria as measured by direct toxin-neutralizing activity. Using the genetically inactivated mutant diphtheria toxoid CRM197 in a bioadhesive polycationic polysaccharide chitosan delivery system, we found that a single nasal immunization was well tolerated and boosted antitoxin neutralizing activity in healthy volunteers, which could be further boosted by a second immunization. The neutralizing activity far exceeded accepted protective levels and was equivalent to that induced by standard intramuscular vaccine and significantly greater than intranasal immunization with CRM197 in the absence of chitosan. A striking but unexpected observation was that although unilateral intranasal immunization induced circulating antitoxin antibody-secreting cells, a nasal antitoxin sIgA response was seen only after the second immunization and only in the vaccinated nostril. If these data are reproduced in larger studies, an intranasal diphtheria vaccine based on CRM197-chitosan could be rapidly licensed for human use. However, a restricted sIgA response suggests that care must be taken in the priming-boosting strategy and clinical sampling techniques when evaluating such vaccines for the induction of local mucosal immunity.

Respiratory syncytial virus (RSV), an important pathogen of the lower respiratory tract, is responsible for severe illness both in new born and young children and in elderly people. Due to complications associated with the use of the early developed vaccines, there is still a need for an effective vaccine against RSV. Most pathogens enter the body via mucosal surfaces and therefore vaccine delivery via routes such as the nasal, may well prove to be superior in inducing protective immune responses against respiratory viruses, since both local and systemic immunity can be induced by nasal immunisation. Previously we have shown that intradermal immunisation of a plasmid DNA encoding the CTL epitope from the M2 protein of RSV induced protective CTL responses. In the present study, the mucosal delivery of plasmid DNA formulated with chitosan has been investigated. Chitosan is a polysachharide consisting of copolymers of N-acetylglucosamine and glucosamine that is derived from chitin, a material found in the shells of crustacea. Intranasal immunisation with plasmid DNA formulated with chitosan induced peptide- and virus-specific CTL responses in BALB/c mice that were comparable to those induced via intradermal immunisation. Following RSV challenge of chitosan/DNA immunised mice, a significant reduction (P<0.001) in the virus load was observed in the lungs of immunised mice compared to that in the control group. These results indicate the potential of immunisation with chitosan-formulated epitope-based vaccines via the intranasal route.

Surface-modified albumin nanoparticles were prepared from two poly(ethylene glycol)–human serum albumin conjugates: poly(thioetheramido acid)–poly(ethylene glycol) copolymer-grafted HSA (HSA–PTAAC–PEG) and methoxy poly(ethylene glycol)-grafted HSA (HSA–mPEG). Rose bengal (RB) was used as a model drug for encapsulation into the nanoparticles either during the particle production or by adsorption post particle preparation. The drug incorporation and release was affected by the different production methods and the different polymer compositions. When RB was loaded in HSA and HSA/HSA–PTAAC–PEG nanoparticles, up to 5% (w/w) drug content was achieved. The drug loading in HSA–mPEG nanoparticles was much lower and the results from the microcalorimetry study indicated that the low loading efficiency was due to less drug–protein binding sites available in the HSA–mPEG molecule as compared to the HSA molecule. The release of RB from the albumin nanoparticles was very slow in PBS and dramatically accelerated in the presence of trypsin. Compared with unmodified nanoparticles, the slower release of RB from the surface-modified HSA nanoparticles in the presence of the enzyme suggested that the existence of a steric hydrophilic barrier on the surface of the nanoparticles made digestion of the nanoparticles more difficult.

In recent years microspheres or microparticles produced from biodegradable polymers such as poly(D,L-lactide) (PLA) and poly(D, L-lactide-co-glycolide) (PLGA) containing encapsulated vaccine antigens have been investigated for administration via parenteral, oral, and intranasal routes. These microparticles allow the controlled release of vaccines with an aim to reduce the number of doses for primary immunisation or to develop single dose vaccines. The polymer materials have been widely regarded as being of minimal toxicity. Evaluation of candidate systems in animal studies have shown antibody levels and cell responses similar to or greater than those observed with adjuvants such as alum. However, there are concerns regarding the integrity and immunogenicity of the antigen during the encapsulation process when the antigen is exposed to organic solvents, high shear stresses and the exposure of antigen to low pH which is caused by polymer degradation. An alternative approach would be to adsorb antigens to the surface of biodegradable polymer particles. Polymeric lamellar substrate particles (PLSP), produced by a simple precipitation of PLA, are suitable for this purpose. The adsorption of antigens onto these particles is a simple procedure. It avoids pH changes due to bulk polymer degradation and the use of solvents and therefore will be less damaging to the vaccine. Moreover, such systems will be much easier to scale up for a clinical study and eventual manufacture. The aim of this article is to discuss the preparation and physical characteristics of PLSP, antigen adsorption, in vivo efficacy of PLSP antigen systems and to consider the potential of PLSP as controlled release adjuvants for protein, peptide or viral vaccines.

Surface modified human serum albumin (HSA) nanoparticles with a size of approximately 150 nm in diameter were prepared from a PEG-HSA conjugate, methoxy-polyethylene glycol modified human serum albumin (HSA-mPEG) using a coacervation method and crosslinked with glutaraldehyde. The zeta-potential of the surface modified nanoparticles was significantly lower than that of unmodified HSA nanoparticles. The existence of a hydrated steric barrier surrounding the nanoparticles was confirmed by electrolyte and pH induced flocculation tests. The surface modified nanoparticles showed a reduced plasma protein adsorption on the particle surface compared with unmodified particles.

The development of biomaterials to treat, repair, or reconstruct the human body is an increasingly important component of materials research. Collaboration between materials researchers and their industrial and clinical partners is essential for the development of this complex field. To demonstrate the importance of these interactions, two articles in this issue focus on advances in biomaterials relating to the use of colloidal systems for transport, drug delivery, and other medical applications. These articles were coordinated by Dominique Muster (Université Louis Pasteur, Strasbourg) and Franz Burny (Hôpital Erasme, Brussels). The following is the second of these two articles.

Surface-modified human serum albumin (HSA) nanospheres with a size of around 100 nm in diameter were prepared from poly(amidoamine)—poly(ethylene glycol) copolymer grafted human serum albumin (HSA-PAA-PEG) and poly(thioetheramido acid)—poly(ethylene glycol) copolymer grafted human serum albumin (HSA-PTAAC-PEG). The nanospheres were produced using a pH—coacervation method and cross-linked with glutaraldehyde. The cross-linking efficiency was affected by the type of albumin conjugate used. The zeta potential of the surface-modified nanospheres was significantly lower than that of unmodified particles. The existence of a hydrated steric barrier surrounding the nanospheres was confirmed by electrolyte- and pH-induced flocculation tests. The surface-modified nanospheres showed a reduced plasma protein adsorption on the particle surface compared with unmodified particles.

Human serum albumin (HSA) microspheres have been produced in the size range of 200 nm to 10 microns by the controlled addition of acetone to an aqueous solution of HSA, followed by stabilization of the formed microspheres at an elevated temperature. Microspheres produced by this acetone-heat denaturation method could be stabilized at relatively low temperatures (75 degrees C) over a short time period (15-30 min). The acetone-heat denaturation method is different from the traditional oil/water technique for preparation of HSA microspheres, both in terms of production method and the avoidance of high temperatures (> 100 degrees C) and extended heating times (> 30 min) for stabilization. This paper describes the influence of process conditions, such as volumes of acetone and HSA concentration, on the formation of the microspheres and their morphological characteristics. A loading efficiency of 8 per cent was achieved for the HSA microspheres when using rose bengal as a model compound. The release of rose bengal from the microspheres in phosphate buffered saline at 37 degrees C was dependent on the presence of the surfactant Tween 80, and varied from a 5 per cent release in 14 days in the absence of surfactant to a 50 per cent release in 8 h in the presence of surfactant.

Human serum albumin (HSA) nanospheres with a size less than 200 nm in diameter were prepared using a modified coacervation method and crosslinking with methyl polyethylene glycol modified oxidized Dextram (Dextranox-MPEG) which created a sterically stabilizing polyethylene oxide surface layer surrounding the nanospheres. The crosslinking efficiency and the surface characteristics of glutaraldehyde and Dextranox-MPEG crosslinked HSA nanospheres were determined and compared. The zeta potential of the Dextranox-MPEG crosslinked particles was significantly lower than that of glutaraldehyde stabilized particles. The existence of a hydrated steric barrier surrounding the nanospheres was confirmed by an electrolyte and pH induced flocculation test. The Dextranox-MPEG crosslinked nanospheres showed a significantly reduced plasma protein adsorption on the particle surface compared with glutaraldehyde crosslinked nanospheres.

Human serum albumin (HSA) nanospheres of about 100 nm diameter were prepared using a pH-coacervation method whereby acetone was added to an HSA solution (pH 9.0). The particles obtained were cross-linked by glutaraldehyde. Increasing the pH of the HSA solution resulted in a gradual rise in the particle size of the resultant nanospheres. A higher cross-linking efficiency was obtained with increased glutaraldehyde concentration and cross-linking time. No significant differences in surface properties, as determined by zeta potential measurements, were recorded between particles prepared from HSA solutions with different pH. The nanospheres were quite stable over 4 days in both phosphate buffer saline (PBS) solution (pH 7.4) and rat serum, but degraded rapidly over 6 hours when incubated in PBS solution containing trypsin.