Preparation of coated nanoparticles for a new mucosal vaccine delivery system

It has been found that the adsorption of antigens onto chitosan particles is an easy and unique mild loading process suitable to be used with vaccines. In order to increase the stability of this particles and to prevent an immediate desorption in gastrointestinal fluids, a coating process with sodium alginate was developed. One of the challenges of this developing process was to keep the particles in the nanosized range in order to be taken up by M-cells of the Peyer's patches. The observed inversion of the particles' zeta potential values after coating suggested the presence of an alginate coating layer. These results were confirmed by FTIR and DSC techniques. Additionally, in vitro release studies showed that the presence of the alginate layer around the particles was able to prevent a burst release of loaded ovalbumin and to improve the stability of the nanoparticles in simulated intestinal fluid at 37 °C. The optimisation of the coating process resulted in 35% (w/w) for the loading capacity of the coated particles. SEM investigations confirmed a suitable size of the coated nanoparticles for the uptake by M-cells.http://www.sciencedirect.com/science/article/B6T7W-4GJKTSJ-1/1/555d86da8f88d8d33ad90f6e41f68e2

Uptake studies in rat Peyer's patches, cytotoxicity and release studies of alginate coated chitosan nanoparticles for mucosal vaccination

The design of particulate vaccine delivery systems, particularly for mucosal surfaces, has been a focus of interest in recent years. In this context, we have previously described the development and the characterization of a new nanosized delivery system, consisting of a model antigen adsorbed to chitosan particles and coated with sodium alginate. In the present work the ovalbumin release profiles from these coated nanoparticles in different pH buffers were investigated and compared to those of the uncoated particles. Cytotoxicity of the polymers and nanoparticles was assessed using the MTT assay. Finally, particle uptake studies in rat Peyer's patches were performed. It was demonstrated that the coating of the nanoparticles with sodium alginate not only avoided a burst release observed with uncoated particles but also increased the stability of the particles at pH 6.8 and 7.4 at 37 °C. At neutral pH, the release was lower than 5% after 3.5 h incubation in a low ionic strength buffer. For both, chitosan and alginate polymers, and for the nanoparticles, comparable cell viability data close to 100%, were obtained. Additionally, based on confocal laser scanning microscopy observations, it was shown that alginate coated nanoparticles were able to be taken up by rat Peyer's patches, rendering them suitable carriers for intestinal mucosal vaccination.http://www.sciencedirect.com/science/article/B6T3D-4K6CHRP-1/1/a257a285900ecde6d4747e1df67e1a8

Different transmission patterns in the early stages of the influenza A(H1N1) v pandemic: A comparative analysis of 12 European countries

Following the emergence of a novel strain of influenza A(H1N1) in Mexico and the United States in April 2009, its epidemiology in Europe during the summer was limited to sporadic and localised outbreaks. Only the United Kingdom experienced widespread transmission declining with school holidays in late July. Using statistical modelling where applicable we explored the following causes that could explain this surprising difference in transmission dynamics: extinction by chance, differences in the susceptibility profile, age distribution of the imported cases, differences in contact patterns, mitigation strategies, school holidays and weather patterns. No single factor was able to explain the differences sufficiently. Hence an additive mixed model was used to model the country-specific weekly estimates of the effective reproductive number using the extinction probability, school holidays and weather patterns as explanatory variables. The average extinction probability, its trend and the trend in absolute humidity were found to be significantly negatively correlated with the effective reproduction number - although they could only explain about 3% of the variability in the model. By comparing the initial epidemiology of influenza A (H1N1) across different European countries, our analysis was able to uncover a possible role for the timing of importations (extinction probability), mixing patterns and the absolute humidity as underlying factors. However, much uncertainty remains. With better information on the role of these epidemiological factors, the control of influenza could be improved. (C) 2011 Elsevier B. V. All rights reserved