Adenovectored RSV Prefusion Glycoprotein + Soluble Glycoprotein Combination Immunization Establishes Persistent Opsonophagocytic Antibody Response through IgG3

Xin Tong^1*Ross Blanc^1,2Deniz Cizmeci¹Hadar Malca^1,2Jaewon Kang¹Christy Comeaux³Benoit Callendret³Arangassery Rosemary Bastian⁴Mehak Khan¹Galit Alter¹Daniel Lingwood¹Ryan McNamara^1,2*

• ¹Ragon Institute, Cambridge, Massachusetts, United States
• ²School of Public Health, Harvard University, Boston, United States
• ³Moderna Therapeutics, Cambridge, Maryland, United States
• ⁴BioNTech, Cambridge, United States

Respiratory syncytial virus (RSV) is a leading cause of severe respiratory diseases in vulnerable populations. A Phase IIb clinical trial revealed a combination vaccine of adenovirus-26-vectored RSV prefusion glycoprotein (Ad26.preF) and soluble RSV preF (SpreF) protein demonstrated 80.0% protectiveness against RSV-associated lower respiratory tract diseases with polyfunctional antibody responses. Here, we evaluated the durability of vaccine-induced humoral responses longitudinally with a second dose of Ad26.preF/SpreF protein combination vaccine including antibody subclasses, isotypes, Fcγ receptor binding, and Fc-effector functions. Our results indicate that the single-dose provided a durable, highly opsinophagocytic response through IgG3 against RSV-F A and B. Humoral networks revealed a strong Fc-gamma receptor (FcgR) engagement leveraged by IgG1, IgG2, and IgG3. Interestingly, this response appeared to be highly persistent as a booster dose one year after the primary vaccine yielded no discernable anamnestic responses or expansion of humoral breadth. The long-term effect of the durability of immune persistence of RSV combination vaccines merits further monitoring.This study explores the longitudinal immunological signatures associated with an innovative approach to immunizing against respiratory syncytial virus (RSV), a major cause of severe respiratory disease worldwide, particularly in vulnerable populations. The research focuses on a combination vaccine that includes an adenovirus-based vector and soluble RSV proteins. This combination stimulates a strong, long-lasting antibody response that engages multiple immune mechanisms, particularly those involving opsonophagocytic activity, which is crucial for clearing infections. Unlike traditional vaccines that primarily induce neutralizing antibodies, this study highlights how nonneutralizing antibodies and other immune pathways contribute to fighting RSV. The research found that while a single dose of the vaccine elicits a durable immune response, a second dose does not significantly enhance this effect, suggesting that the initial immunization may create a lasting immune "persistence". This finding could help shape future vaccine strategies, especially in vulnerable populations like older adults, where immune responses are often weakened. Overall, the study's contribution lies in deepening the understanding of how multi-functional antibodies can improve vaccine efficacy against RSV, advancing the development of more effective vaccines.