Publication Database

AAV-vector based vaccines for pandemic viruses: Evaluation of broadly reactive responses against influenza A viruses and SARS-CoV-2 (2024)

Art

Hochschulschrift

Autor

Stelzer, Sandra (WE 12)

Quelle

Berlin, 2024 — XII, 193 Seiten

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/43341

Kontakt

Institut für Tierpathologie

Robert-von-Ostertag-Str. 15
14163 Berlin
+49 30 838 62450
pathologie@vetmed.fu-berlin.de

Abstract / Zusammenfassung

Influenza A viruses and SARS-CoV-2 continue to pose a severe threat to public health. Both are zoonotic pathogens, having arisen from the close human-animal interface. For both viruses vaccines are available, however their continuous evolution leads to immune escape so that the vaccines need to be continuously evaluated, updated and re-administered. For influenza viruses, immunity is mainly directed against the head of the viral surface protein HA, which is continuously changing due to drift processes, resulting in strain-specific responses. For SARS-CoV-2, the spike glycoprotein on the surface, which facilitates receptor-binding is the target of current vaccines. For both viruses, the interest lies in the development of broadly reactive vaccines which can protect against current and future variants. A concept that has gained interest in the development of vaccines is the induction of non-neutralizing antibodies that can activate cellular effector-functions, like ADCC. Another important aspect is the induction of mucosal antibodies, in regard to the infection route of both viruses. New delivery platforms have also been evaluated and gained momentum during the SARS-CoV-2 pandemic, for example vector vaccines (e.g. Vakzevria®), or mRNA-based vaccines (e.g. Comirnaty®). New vaccine candidates are also continuously developed and evaluated, for example the nucleoprotein-based vaccine by Leroux-Roels et al. (2023), which is currently in clinical trials. The AAV-vectors used in this thesis have shown to be safe for the use in humans and have already been successfully evaluated for the use as vaccine vectors. Intriguingly, they can be repeatedly administered via the respiratory tract, following the natural infection route. For IAV, this thesis aimed to assess a possible synergistic effect of an AAV-vector vaccine combining the HA and NP antigens of the influenza virus A/California/7/2009pdm. Furthermore, it was hypothesized that, opposed to WIV vaccination, the AAV-vaccine could induce broadly reactive responses. Additionally, an AAV-vector vaccine carrying the HA of the group 2 virus A/Aichi/2/68 (H3N2) was assessed regarding the hypothesis of the induction of a broadened immune response in combination with the group 1 HA of A/California/7/2009pdm. Furthermore, the induction of a mucosal immune response along the route of application in the respiratory tract was evaluated. To measure these responses, humoral, i.e. neutralizing, broadly reactive, and FcγR-activating responses were evaluated in the sera of immunized C57BL/6 mice, mucosal responses were assessed in nasal washes and lung samples, and T-cells were measured in spleens. The protective efficiency was assessed by an experimental challenge of mice with homologous, heterologous and heterosubtypic virus. Here, it was shown that a bivalent AAV-HA/NP vaccine was superior to WIV immunization. In the serum of mice immunized with AAV-HA/NP, broadly reactive antibodies and FcγR-activating responses could be detected, while in nasal washes and lung samples mucosal antibodies were present. After a prime-boost i.n. application the vaccine was also capable of protecting mice from viral challenge of homologous, heterologous and heterosubtypic virus, which WIV did not. An AAV-vector vaccine containing a group 2 HA (H3) was evaluated for the first time in vivo and proved to be successful in inducing strain-specific antibodies and protecting against homologous challenge but did not induce broadly reactive antibodies. Another aim of this thesis was the design and evaluation of an AAV-vector vaccine against SARS-CoV-2, because earlier studies evaluating a similar AAV-vector vaccine against SARS-CoV showed promising results. In the course of this thesis, the vaccine was further adapted to the emerging VOCs. In addition to the overall immunogenicity, the hypothesized cross-reactivity and broadly reactive responses induced by the AAV-vaccines against the wildtype virus and the different VOCs were evaluated. The AAV-S-RBD vaccine was initially evaluated in mammalian cell culture models before the in vivo analyses were conducted. Initially, different mouse strains were evaluated, and for subsequent analyses BALB/c and NMRI mice were used. Sera, nasal washes, lung samples and spleens were analysed as mentioned for the mice in the IAV experiment. No viral challenge was conducted. For this part, an induction of variant-specific antibodies by the designed AAV-S-RBD vector could be shown, but it wasn’t robust. Interestingly, non-neutralizing antibodies induced by the AAV-S-RBD BA.2 vector could be shown to induce FcγR-activating responses. Overall, in this thesis AAV-vectors have been demonstrated to be promising vaccine candidates for the induction of broadly reactive immune responses against influenza viruses and SARS-CoV-2.