104 Immunogenicity and Safety Aspects of Adeno-Associated Virus–Like Particles (AAVLPS) as Carriers for B-Cell Vaccines

BACKGROUND: Adeno-associated viruses (AAV) are non-human pathogenic and replication defective ssDNA viruses. The surface of AAV consists of 60 capsomers, which can be exploited for high density display of recombinant peptides. AAV-like particles (AAVLP) can be generated via assembly of the recombinant capsid protein VP3. The aim of this study was to evaluate the uptake mechanism, immunogenicity and safety aspects of an AAVLP-displayed B-cell epitope, taking ovalbumin (OVA) as a model antigen/allergen. METHODS: An OVA derived linear B-cell epitope and for control purposes OVA-non related peptide TP18 (cholesterol-ester transfer protein 18) were inserted into capsid protein VP3 of AAVLPs. RESULTS: Life cell microscopy indicated that AAVLP internalized into HeLa epithelial cells and remained in intracellular vesicles up to 18 hours. When we immunized BALB/c subcutaneously, sera of AAVLP-OVA immunized mice showed similar titres of OVA-specific IgG1 compared to mice immunized with OVA protein. However, in OVA immunized mice high OVA-specific IgE levels could be recorded, whereas immunizations with OVA-AAVLP rendered background IgE levels only. In accordance, sera of OVA mice which permitted mast cell degranulation upon OVA trigger in a specific β-hexosaminidase release assay, whereas sera of OVA-AAVLP mice did not contain anaphylactogenic antibodies. In an in vivo anaphylaxis experiment, upon intravenous OVA challenge OVA-immunized mice presented significant drop of body temperature, whereas AAVLP-OVA mice remained unaffected. CONCLUSIONS: Our study demonstrates the immunogenicity, safety and efficacy of AAVLP as display system of B-cell epitopes for vaccination.