Elena Campbell, University of Guelph

Elena S. B. Campbell (1)*, Wenguang Cao (2), Harper L. Griffin (1), Arielle N. Gillies (1), Yanlong Pei (1), Jordyn A. Lopes (1), Amira Rghei (1), Leonardo Susta (1), Khalil Karimi (1), Logan Banadyga (2), (3) and Sarah K. Wootton (1) 1. Department of Pathobiology, University of Guelph, Guelph, ON Canada 2. National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada 3. Department of Medical Microbiology and Infectious Disease, University of Manitoba, Winnipeg, MB, Canada

Suppressing & Conquering

Filoviruses, including Ebola virus (EBOV) and Marburg virus (MARV), are highly pathogenic and cause hemorrhagic fever in humans. Although EBOV vaccines and monoclonal antibody (mAb) therapies exist, durable, broad protection against other filoviruses is still lacking. Classical vaccines may underperform in immunocompromised or aging populations, and recombinant mAbs provide only short-lived protection, requiring repeat doses. Vectored immunoprophylaxis (VIP) offers an alternative strategy by leveraging the host as a "bioreactor," enabling sustained in vivo production of pathogen-specific mAbs following gene delivery. Adeno-associated virus (AAV) is used for VIP (AAV-VIP) due to its strong safety profile, and stable long-term expression following intramuscular (IM) administration. Using our muscle-tropic AAV6.2FF capsid, we have previously showed rapid, robust expression of anti-EBOV and anti-MARV human IgG1 antibodies with protective efficacy in small animal models. Herein, we engineered bispecific human IgG1 antibodies combining the pan-ebolavirus mAb FVM04 with MARV-specific mAb MR191 in two orientations (FVM04–MR191 and MR191–FVM04) to enable cross-genus targeting of filovirus glycoproteins. In lethal mouse-adapted EBOV and MARV challenge models, serum mAb levels rose dose‑dependently and continued increasing for 70 days post‑AAV delivery, achieving peak mean levels of 126–191 µg/mL (FVM04–MR191) and 87–134 µg/mL (MR191–FVM04). Vectored delivery conferred dose-dependent protection, with FVM04–MR191 achieving 100% survival against EBOV and 87.5% against MARV, while MR191–FVM04 demonstrated enhanced protection against MARV (up to 100%) but reduced EBOV efficacy. These findings show that AAV-delivered bispecific antibodies provide durable cross‑filovirus protection and that antibody orientation is key to determining protection in vivo.