Long-term protective potency of AAV vector-based SARS-CoV-2 prophylaxis in mice and non-human primates.

INTRODUCTION

Recombinant adeno-associated virus (rAAV)-mediated delivery of neutralizing antibodies is a promising strategy for rapid and durable prophylaxis against SARS-CoV-2.

METHODS

We evaluated the long-term expression, pharmacokinetics, immunogenicity, biodistribution, and protective efficacy of an rAAV vector of serotype DJ encoding the single-domain antibody P2C5 fused to a human Fc fragment (P2C5-Fc) in mice and common marmosets (Callithrix jacchus). Animals received a single intramuscular administration of rAAV-P2C5-Fc at a dose of 1 × 10¹³ vector genome copies per kg.

RESULTS

Rapid antibody detection in serum was observed, reaching peak concentrations (Cmax) by approximately 120 days and remaining at protective levels for >480 days in mice and up to 1,120 days in marmosets. Neutralizing titers closely paralleled serum P2C5-Fc concentrations and provided complete protection against lethal intranasal challenge with SARS-CoV-2 variants B.1.1.1 (Wuhan D614G) and BA.5 (Omicron) even at late time points (216 and 460 days post-administration in mice). Biodistribution analysis showed predominant localization of rAAV at the injection site and regional lymph nodes with minimal off-target spread. Moderate anti-AAV capsid antibody responses were detected, while anti-drug antibodies against P2C5-Fc remained undetectable in both species.

DISCUSSION: These findings demonstrate that a single intramuscular injection of rAAV-P2C5-Fc results in rapid onset, sustained expression, and long-term protective efficacy against SARS-CoV-2 variants in two preclinical models, supporting the potential of this platform for durable vectored immunoprophylaxis.