A novel SARS-CoV-2 Beta RBD DNA vaccine directly targeted to antigen-presenting cells induces strong humoral and T cell responses

Throughout the COVID-19 pandemic, several variants of concern (VoC) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have evolved, affecting the efficacy of the approved COVID-19 vaccines. To address the need for vaccines that induce strong and persistent cross-reactive neutralizing antibodies and T cell responses, we developed a prophylactic SARS-CoV-2 vaccine candidate based on our easily and rapidly adaptable plasmid DNA vaccine platform. The vaccine candidate, referred to here as VB2129, encodes a protein homodimer consisting of the receptor binding domain (RBD) from lineage B.1.351 (Beta) of SARS-CoV-2, a VoC with a severe immune profile, linked to a targeting unit (human LD78β/CCL3L1) that binds chemokine receptors on antigen-presenting cells (APCs) and a dimerization unit (derived from the hinge and CH3 exons of human IgG3). Immunogenicity studies in mice demonstrated that the APC-targeted vaccine induced strong antibody responses to both homologous Beta RBD and heterologous RBDs derived from Wuhan, Alpha, Gamma, Delta, and Omicron BA.1 variants, as well as cross-neutralizing antibodies against these VoC. Overall, preclinical data justify the exploration of VB2129 as a potential booster vaccine that induces broader antibody- and T cell-based protection against current and future SARS-CoV-2 VoC.

Abstract 3558: A novel and versatile cytokine empowered DNA vaccine platform with superior immune activating potential

Immunotherapy, in particular Immune Checkpoint Blockade (ICB) has been regarded as the next standard of care for many solid tumor indications. Yet, a significant proportion of patients do not respond to therapy. More specifically, failure of ICB has been linked to the absence of an anti-tumor immune response that can be boosted or revitalized. Cancer vaccines that are designed to elicit such response by educating the host immune system to recognize tumor antigens, are therefore considered a key next generation therapeutic modality for the treatment of human cancers.

Various vaccine platforms have been developed over the years, but recent advances in delivery technologies combined with the intrinsic qualities of the DNA matrix have positioned DNA vaccines as a safe and flexible alternative to other types of vaccine technologies. Vaccibody is developing DNA vaccines that allows specific targeting of tumors antigens to Antigen Presenting Cells (APCs), thus maximizing the elicited immune response.

Here we present a second-generation version of our DNA platform in which our vaccibody molecule can be co-expressed with immune-stimulatory proteins from one plasmid using a multicistronic design. Compared to the vaccibody molecule alone the simultaneous expression of selected immune stimulatory cytokines was shown to boost the overall immune response almost 3-fold to drive a potent anti-tumor response.

These data demonstrate the flexibility and potential of DNA vaccines as well as the advantages of combining an APC targeted delivery of tumor specific antigens together with a local production of immune stimulatory proteins.

Citation Format: Audun Beraas, Pierre Dillard, Judith Jing Wong, Christian Winther Wold, Eirik Solbakken, Linn Guro Oslen, Joel Benjamin Heim, Stalin Chellappa, Agnete Fredriksen, Mikkel Wandahl Pedersen, Stine Granum. A novel and versatile cytokine empowered DNA vaccine platform with superior immune activating potential [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3558.

Towards new cholera prophylactics and treatment: Crystal structures of bacterial enterotoxins in complex with GM1 mimics

Cholera is a life-threatening disease in many countries, and new drugs are clearly needed. C-glycosidic antagonists may serve such a purpose. Here we report atomic-resolution crystal structures of three such compounds in complexes with the cholera toxin. The structures give unprecedented atomic details of the molecular interactions and show how the inhibitors efficiently block the GM1 binding site. These molecules are well suited for development into low-cost prophylactic drugs, due to their relatively easy synthesis and their resistance to glycolytic enzymes. One of the compounds links two toxin B-pentamers in the crystal structure, which may yield improved inhibition through the formation of toxin aggregates. These structures can spark the improved design of GM1 mimics, either alone or as multivalent inhibitors connecting multiple GM1-binding sites. Future developments may further include compounds that link the primary and secondary binding sites. Serving as decoys, receptor mimics may lessen symptoms while avoiding the use of antibiotics.