A single ultra-low dose self-amplifying RNA rabies vaccine confers rapid and complete protection in mice

Rabies is a fatal zoonotic disease caused by the Rabies virus (RABV), resulting in approximately 59,000 deaths globally each year. Of these fatalities, 95 % occur in impoverished regions across Asia and Africa where medical resources are scarce, with children accounting for as much as 40 % of the total cases. To address the logistical challenges of current inactivated rabies vaccines-such as the complexities of multi-dose regimens and manufacturing constraints-this study aimed to develop a rabies vaccine based on a self-amplifying mRNA (saRNA) platform, which offers potential advantages in rapid protection, scalable production, and dose-sparing capacity.

An optimized saRNA encoding the rabies glycoprotein was constructed. In SPF BALB/c mice, immunogenicity and protective efficacy against 100 LD₅₀ intracranial CTN-1 challenge were evaluated after single-dose (0.0008-1 μg) or two-dose regimens, with particular attention to early protection at days 7 and 14 post-immunization.

A single administration of 0.1 μg saRNA vaccine delivered 100 % survival upon challenge at day 14 (62.5 % at day 7), accompanied by high-titer neutralizing antibodies and robust T-cell activation. This effective dose is 15-fold lower than previously reported values. A two-dose schedule between day 0 and day 7 further reduced the dose required for 100 % protection by 80 %, from 0.1 μg to 0.02 μg.

The optimized saRNA rabies vaccine achieves complete protection within 14 days after a single microgram-level dose, or after two ultra-low doses, outperforming traditional inactivated vaccines and offering an efficient regimen for simplified post-exposure prophylaxis.