Multivariate analysis of the immune response to different rabies vaccines.

In a previous study, we proposed as an alternative to the use of animals in infectious challenge studies, a new approach describing the vaccine-induced immune response through the multivariate analysis of a defined set of immune parameters characterizing the B and T immune responses. This multivariate analysis, i.e. immune fingerprint, was evaluated first to assess the impact of minor changes in well characterized vaccines. The approach showed promising results in the assessment of the compatibility between two licensed vaccines. In the present study, the immune fingerprint was used to compare adjuvants with the various immunological parameters of the immune fingerprint as well as to assess the ability of this approach to discriminate different Rabies vaccine formulations in dogs. RABISIN® was the reference vaccine, adjuvanted with aluminum hydroxide. An exploratory factor analysis was used to analyse the covariance structure of the immunological data. Significant differences were observed between groups. RABISIN and a linear polyacrylate (SPA09) adjuvanted vaccine performed better than chitosan adjuvanted ones, both for humoral and cell immune responses. This study showed that the immune fingerprint approach can be used to screen vaccine formulations. It provides additional information compared to classical vaccination and infectious challenge efficacy study.

Comprehensive two-dimensional gas chromatography for biogas and biomethane analysis.

The gas industry is going to be revolutionized by being able to generate bioenergy from biomass. The production of biomethane - a green substitute of natural gas - is growing in Europe and the United-States of America. Biomethane can be injected into the gas grid or used as fuel for vehicles after compression. Due to various biomass inputs (e.g. agricultural wastes, sludges from sewage treatment plants, etc.), production processes (e.g. anaerobic digestion, municipal solid waste (MSW) landfills), seasonal effects and purification processes (e.g. gas scrubbers, pressure swing adsorption, membranes for biogas upgrading), the composition and quality of biogas and biomethane produced is difficult to assess. All previous publications dealing with biogas analysis reported that hundreds of chemicals from ten chemical families do exist in trace amounts in biogas. However, to the best of our knowledge, no study reported a detailed analysis or the implementation of comprehensive two-dimensional gas chromatography (GC×GC) for biogas matrices. This is the reason why the benefit of implementing two-dimensional gas chromatography for the characterization of biogas and biomethane samples was evaluated. In a first step, a standard mixture of 89 compounds belonging to 10 chemical families, representative of those likely to be found, was used to optimize the analytical method. A set consisting of a non-polar and a polar columns, respectively in the first and the second dimension, was used with a modulation period of six seconds. Applied to ten samples of raw biogas, treated biogas and biomethane collected on 4 industrial sites (two MSW landfills, one anaerobic digester on a wastewater treatment plant and one agricultural biogas plant), this analytical method provided a "fingerprint" of the gases composition at the molecular level in all biogas and biomethane samples. Estimated limits of detection (far below the µgNm-3) coupled with the resolution of GC×GC allowed the comparison of the real samples considered. This first implementation of GC×GC for the analysis of biogas and biomethane demonstrated unambiguously that it is a promising tool to provide a "fingerprint" of samples, and to monitor trace compounds by families.