A genetically engineered prime-boost vaccination strategy for oculonasal delivery with poly(d,l-lactic-co-glycolic acid) microparticles against infection of turkeys with avian Metapneumovirus.

摘要

In this study we demonstrated the use of an oculonasally delivered poly(d,l-lactic-co-glycolic acid) microparticle (PLGA-MP)-based and genetically engineered vaccination strategy in the avian system. An avian Metapneumovirus (aMPV) fusion (F) protein-encoding plasmid vaccine and the corresponding recombinant protein vaccine were produced and bound to or encapsulated by PLGA-MP, respectively. The PLGA-MP as the controlled release system was shown in vitro to not induce any cytopathic effects and to efficiently deliver the F protein-based aMPV-vaccines to avian cells for further processing. Vaccination of turkeys was carried out by priming with an MP-bound F protein-encoding plasmid vaccine and a booster-vaccination with an MP-encapsulated recombinant F protein. Besides the prime-boost F-specific vaccinated birds, negative control birds inoculated with a mock-MP prime-boost regimen as well as non-vaccinated birds and live vaccinated positive control birds were included in the study. The MP-based immunization of turkeys via the oculonasal route induced systemic humoral immune reactions as well as local and systemic cellular immune reactions, and had no adverse effects on the upper respiratory tract. The F protein-specific prime-boost strategy induced partial protection. After challenge the F protein-specific MP-vaccinated birds showed less clinical signs and histopathological lesions than control birds of mock MP-vaccinated and non-vaccinated groups did. The vaccination improved viral clearance and induced accumulation of local and systemic CD4+ T cells when compared to the mock MP-vaccination. It also induced systemic aMPV-neutralizing antibodies. The comparison of mock- and F protein-specific MP-vaccinated birds to non-vaccinated control birds suggests that aMPV-specific effects as well as adjuvant effects mediated by MP may have contributed to the overall protective effect.