Safety Profile of a Virus-Like Particle-Based Vaccine Targeting Self-Protein Interleukin-5 in Horses

• Main Authors: Sigridur Jonsdottir, Victoria Fettelschoss, Florian Olomski, Stephanie C. Talker, Jelena Mirkovitch, Tanya Rhiner, Katharina Birkmann, Franziska Thoms, Bettina Wagner, Martin F. Bachmann, Thomas M. Kündig, Eliane Marti, Antonia Fettelschoss-Gabriel
• Format: Article
• Language: English
• Published: MDPI AG 2020-05-01
• Series: Vaccines
• Subjects: therapeutic vaccine; self-protein; safety
• Online Access: https://www.mdpi.com/2076-393X/8/2/213

：<i>Background:</i><b> </b>Insect bite hypersensitivity (IBH) is an eosinophilic allergic dermatitis of horses caused by type I/IVb reactions against mainly <i>Culicoides</i> bites. The vaccination of IBH-affected horses with equine IL-5 coupled to the Cucumber mosaic virus-like particle (eIL-5-CuMV_TT) induces IL-5-specific auto-antibodies, resulting in a significant reduction in eosinophil levels in blood and clinical signs. <i>Objective:</i> the preclinical and clinical safety of the eIL-5-CuMV_TT vaccine.<b> </b><i>Methods</i><i>:</i> The<b> </b>B cell responses were assessed by longitudinal measurement of IL-5- and CuMV_TT-specific IgG in the serum and plasma of vaccinated and unvaccinated horses. Further, peripheral blood mononuclear cells (PBMCs) from the same horses were re-stimulated in vitro for the proliferation and IFN-γ production of specific T cells. In addition, we evaluated longitudinal kidney and liver parameters and the general blood status. An endogenous protein challenge was performed in murine IL-5-vaccinated mice.<b> </b>Results: The vaccine was well tolerated as assessed by serum and cellular biomarkers and also induced reversible and neutralizing antibody titers in horses and mice. Endogenous IL-5 stimulation was unable to re-induce anti-IL-5 production. The CD4⁺ T cells of vaccinated horses produced significantly more IFN-γ and showed a stronger proliferation following stimulation with CuMV_TT as compared to the unvaccinated controls. Re-stimulation using <i>E.</i><i> </i><i>coli</i>-derived proteins induced low levels of IFNγ⁺CD4⁺ cells in vaccinated horses; however, no IFN-γ and proliferation were induced following the HEK-eIL-5 re-stimulation.<b> </b><i>Conclusions:</i> Vaccination using eIL-5-CuMV_TT induces a strong B-cell as well as CuMV_TT-specific T cell response without the induction of IL-5-specific T cell responses. Hence, B-cell unresponsiveness against self-IL-5 can be bypassed by inducing CuMV_TT carrier-specific T cells, making the vaccine a safe therapeutic option for IBH-affected horses.