Chitosan based delivery systems for mucosal immunization against bovine herpesvirus 1 (BHV-1)

Bovine herpesvirus 1 (BHV-1), is a major pathogen of cattle which causes serious infections, including infectious bovine rhinotracheitis (IBR)/infectious pustular vulvovaginitis (IPV). At present, BHV-1 is still a serious threat to animal health and productivity in Turkey, hence to develop a more efficient and economical vaccine system against BHV-1 is certainly an important necessity. A mucosal vaccination strategy would provide both mucosal and systemic immune responses to protect disease progression and transmission. However, vaccination through mucosal membranes requires adjuvants/delivery systems in order to enhance the immunogenicity of the antigens. Chitosan, which is a biodegradable, biocompatible and bioadhesive natural polysaccharide, has been shown to be promising both as a delivery system and an adjuvant for mucosal vaccination. In this study, microparticles with appropriate size (<10 μm), positive surface charge and high loading efficiency (∼95%) were prepared for mucosal delivery of BHV-1, using various types of chitosan with different molecular weight and solubility. Particles were shown to be taken up by the cells, mostly around the nucleus, whereas with aggregates which were bigger in size were adsorbed at the surface. Furthermore, gel formulations with a suitable viscosity which would provide easy application and remain on the mucosa for extended period of time were also developed with a high zeta potential indicating a stable system. Both the BHV-1 loaded microparticle and gel formulations were shown to maintain cell viability and antigen integrity. Chitosan-based formulations are suggested as promising adjuvant/delivery systems for mucosal immunization against BHV-1.