A novel antibody avidity methodology for rapid point-of-care serological diagnosis

β-Glucan as Trained Immunity-Based Adjuvants for Rabies Vaccines in Dogs

The mechanisms of trained immunity have been extensively described in vitro and the beneficial effects are starting to be deciphered in in vivo settings. Prototypical compounds inducing trained immunity, such as β-glucans, act through epigenetic reprogramming and metabolic changes of innate immune cells. The recent advances in this field have opened new areas for the development of Trained immunity-based adjuvants (TIbAs). In this study, we assessed in dogs the potential immune training effects of β-glucans as well as their capacity to enhance the adaptive immune response of an inactivated rabies vaccine (Rabisin®). Injection of β-glucan from Euglena gracilis was performed 1 month before vaccination with Rabisin® supplemented or not with the same β-glucan used as adjuvant. Trained innate immunity parameters were assessed during the first month of the trial. The second phase of the study was focused on the ability of β-glucan to enhance adaptive immune responses measured by multiple immunological parameters. B and T-cell specific responses were monitored to evaluate the immunogenicity of the rabies vaccine adjuvanted with β-glucan or not. Our preliminary results support that adjuvantation of Rabisin® vaccine with β-glucan elicit a higher B-lymphocyte immune response, the prevailing factor of protection against rabies. β-glucan also tend to stimulate the T cell response as shown by the cytokine secretion profile of PBMCs re-stimulated ex vivo. Our data are providing new insights on the impact of trained immunity on the adaptive immune response to vaccines in dogs. The administration of β-glucan, 1 month before or simultaneously to Rabisin® vaccination give promising results for the generation of new TIbA candidates and their potential to provide increased immunogenicity of specific vaccines.

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.

Comparative study of chikungunya Virus-Like Particles and Pseudotyped-Particles used for serological detection of specific immunoglobulin M

The incidence of chikungunya virus (CHIKV) infection has increased dramatically in recent decades. Effective diagnostic methods must be available to optimize patient management. IgM-capture Enzyme-Linked Immunosorbent Assay (MAC-ELISA) is routinely used for the detection of specific CHIKV IgM. This method requires inactivated CHIKV viral lysate (VL). The use of viral bioparticles such as Virus-Like Particles (VLPs) and Pseudotyped-Particles (PPs) could represent an alternative to VL. Bioparticles performances were established by MAC-ELISA; physico-chemical characterizations were performed by field-flow fractionation (HF5) and confirmed by electron microscopy. Non-purified PPs give a detection signal higher than for VL. Results suggested that the signal difference observed in MAC-ELISA was probably due to the intrinsic antigenic properties of particles. The use of CHIKV bioparticles such as VLPs and PPs represents an attractive alternative to VL. Compared to VL and VLPs, non-purified PPs have proven to be more powerful antigens for specific IgM capture.

Microbial identification from faces and urine in one step by two-photon excitation assay technique

Two-photon excitation fluorometry (TPX) is a separation-free bioaffinity assay technique which enables accurate diagnostic testing in microvolumes. The technology is currently commercially applied in an automated mariPOC® test system for rapid phenotypic multi-microbe detection of pathogen antigens. The first TPX applications for diagnostics were intended for respiratory infection testing from nasopharyngeal and oropharyngeal samples. Feces and urine are more complex sample matrices and contain substances that may interfere with immunoassay binding or fluorescence detection. Our objective was to study the suitability of these complex matrices in the TPX technique. As expected, feces and urine elevated fluorescence levels but the methodology has the unique property of compensating for matrix effects. Compensation allows reliable separation of specific fluorescence from the fluorescence caused by the matrix. The studied clinical samples did not contain immunoassay inhibitors. The results suggest that the methodology is robust and may provide reliable testing of feces and urine samples with high accuracy.

Multivariate analysis of the immune response to a vaccine as an alternative to the repetition of animal challenge studies for vaccines with demonstrated efficacy

The assessment of vaccine combinations, or the evaluation of the impact of minor modifications of one component in well-established vaccines, requires animal challenges in the absence of previously validated correlates of protection. As an alternative, we propose conducting a multivariate analysis of the specific immune response to the vaccine. This approach is consistent with the principles of the 3Rs (Refinement, Reduction and Replacement) and avoids repeating efficacy studies based on infectious challenges in vivo. To validate this approach, a set of nine immunological parameters was selected in order to characterize B and T lymphocyte responses against canine rabies virus and to evaluate the compatibility between two canine vaccines, an inactivated rabies vaccine (RABISIN^®) and a combined vaccine (EURICAN^® DAPPi-Lmulti) injected at two different sites in the same animals. The analysis was focused on the magnitude and quality of the immune response. The multi-dimensional picture given by this 'immune fingerprint' was used to assess the impact of the concomitant injection of the combined vaccine on the immunogenicity of the rabies vaccine. A principal component analysis fully discriminated the control group from the groups vaccinated with RABISIN^® alone or RABISIN^®+EURICAN^® DAPPi-Lmulti and confirmed the compatibility between the rabies vaccines. This study suggests that determining the immune fingerprint, combined with a multivariate statistical analysis, is a promising approach to characterizing the immunogenicity of a vaccine with an established record of efficacy. It may also avoid the need to repeat efficacy studies involving challenge infection in case of minor modifications of the vaccine or for compatibility studies.