Diseño de vacunas frente al virus de la fiebre aftosa basadas en la utilización de pseudopartículas virales quiméricas de RHDV

Abstract

Development of new vaccine strategies against infectious diseases is a major field of research for livestock industry. There is a real need to generate new cost-effective, safe vaccines adequate to serologically differentiate between vaccinated and infected animals (DIVA vaccines). In the past years, new antigens have been described (synthetic peptides and recombinant proteins) which are potentially protective against different diseases of interest in animal health. However, these types of antigens, afford only a limited level of protection in certain cases and it is widely accepted that they are weakly immunogenic by themselves. Therefore, strategies conceived to enhance the efficacy of subunit vaccines, such as their incorporation into VLP-based delivery systems, for multimeric display, are very relevant if field applications are considered. The VLPs derived from the calicivirus Rabbit Hemorrhagic Disease virus (RHDV) constitute an excellent vaccine vector. They have shown their ability to induce a protective antiviral immunity against the disease from which it is derived, as well as to induce specific cellular and humoral immune response against heterologous epitopes incorporated into its particle. The general objective of this doctoral thesis was the design of RHDV-based VLPs that may serve as vaccines against Foot-and-Mouth Disease (FMD). This is a disease of utmost relevance in animal health and its causative agent, the Foot-and-Mouth Disease Virus (FMDV) is a well characterized pathogen for which immunodominant epitopes for B and T cell activation have been widely defined. The specific objectives of this thesis included: Firstly, the generation of RHDV chimeric VLPs presenting FMDV B and T cell epitopes. Secondly, the in vivo evaluation of the immune response generated by RHDV-FMDV chimeric VLPs in murine and porcine models, as well as the evaluation of their ability to induce protective antiviral activity during a viral challenge in pigs. Thirdly, the study of the versatility of RHDV VLPs to allow the incorporation of different peptides in a single molecule and to evaluate the induction of multivalent immunogenicity. Finally, the generation of a recombinant adenovirus expressing the FMDV 3D protein, highly conserved between serotypes and described as a potent inducer of a cellular response was used as a strategy to further enhance virus specific T cell responses in vivo. The results presentedin this doctoral thesis show that the VLPs derived from RHDV constitute an effective platform for the presentation of heterologous epitopes and the induction of neutralizing responses to at least three different FMDV serotypes. Through in vivo vaccination and challenge tests, they have been shown to induce a neutralizing response comparable or superior to that obtained by conventional vaccination in pigs. In addition, the RHDV VLPs proved to be permissive for the incorporation of heterologous B epitopes in two different insertion sites simultaneously, thus generating a multivalent humoral response to FMDV serotypes O and A. Lastly, a recombinant adenovirus expressing FMDV 3D protein was able to induce a specific cellular response in vivo.