Adeno-Associated Virus-Like Particles as New Carriers for B-Cell Vaccines: Testing Immunogenicity and Safety in BALB/c Mice

Abstract

Adeno-associated viruses (AAVs) are established vectors for gene therapy of different human diseases. AAVs are assembled of 60 capsomers, which can be genetically modified, allowing high-density display of short peptide sequences at their surface. The aim of our study was to evaluate the immunogenicity and safety of an adeno-associated virus-like particle (AAVLP)-displayed B-cell peptide epitope taking ovalbumin (OVA) as a model antigen or allergen from egg, respectively. An OVA-derived B-cell epitope was expressed as fusion protein with the AAV-2 capsid protein of VP3 (AAVLP-OVA) and for control, with the nonrelated peptide TP18 (AAVLP-TP18). Cellular internalization studies revealed an impaired uptake of AAVLP-OVA by mouse BMDC, macrophages, and human HeLa cells. Nevertheless, BALB/c mice immunized subcutaneously with AAVLP-OVA formed similarly high titers of OVA-specific IgG1 compared to mice immunized with the native OVA. The extent of the immune response was independent whether aluminum hydroxide or water in oil emulsion was used as adjuvant. Furthermore, in mice immunized with native OVA, high OVA-specific IgE levels were observed, which permitted OVA-specific mast-cell degranulation in a b-hexosaminidase release assay, whereas immunizations with AAVLP-OVA rendered background IgE levels only. Accordingly, OVAimmunized mice, but not AAVLP-OVA immunized mice, displayed an anaphylactic reaction with a significant drop of body temperature upon intravenous OVA challenge. From this mouse model, we conclude that AAVLPs that display B-cell epitope peptides on their surface are suitable vaccine candidates, especially in the field of allergy.

Recent advances in the use of nanoparticles for allergen‐specific immunotherapy

“…Immunization of mice with adeno‐associated VLPs expressing an OVA‐derived B‐cell epitope also led to a reduction of allergen‐specific IgE compared to treatment with soluble OVA, while OVA‐specific IgG1 titers were elevated. No anaphylactic reaction was observed for VLP‐treated mice upon OVA challenge …”

Anaphylaxis Imaging: Non-Invasive Measurement of Surface Body Temperature and Physical Activity in Small Animals

“…In the third experiment, previously published data from the positive and negative control mouse groups of a therapeutic egg-allergy mouse model [ 22 ] were extracted. When the positive control group immunized with alum-OVA was challenged with OVA, a rapid drop of body surface temperature from mean 31.46±0.68 to 28.12±0.68°C was observed ( Fig 4A ) and ref.…”

“…We investigated previously the safety of a therapeutic egg allergy vaccine based on Adeno-associated virus-like particles (AAVLPs) [ 22 ]. Female BALB/c mice (n = 5/group) were injected subcutaneously (s.c.) with alum-adsorbed ovalbumin (OVA) (positive control “alum-OVA”) three times in biweekly intervals, or were left untreated (“naïve”), and on day 41 challenged i.v.…”

“…by 50μg OVA in 50μl 0.9% NaCl. Even though the temperature and horizontal movement results of the positive and negative groups were presented in [ 22 ], they are included here for direct comparison of the technical data. Data of physical activity were also collected by a blinded observer ( Fig 1D ), published in [ 22 ].…”

“…In parallel to surface body temperature monitoring the images are further processed by a software that calculates the horizontally moved distance following the centre of heat points in the images, and the variations of vertical mouse movements based on the frequency of changes of mouse cross sectional image areas. The proof of principle is demonstrated using data from three independent anaphylaxis mouse models, immunized either with milk allergen casein [ 12 ], peanut allergen Ara h 2 [ 15 ] or egg allergen ovalbumin [ 22 ].…”