Zika Vaccine Development Using Self-Amplifying Messenger RNA

Despite the waning epidemiology, the development of a vaccine for Zika virus (ZIKV) infection remains a public health priority to protect against congenital ZIKV infection in future outbreaks. 

A new study published on August 7, 2020, describes the preclinical selection and development of a potent ZIKV vaccine from 9 constructs using SAM technology expressing various forms of the ZIKV prM-E antigen. 

This study identified one ZIKV SAM vaccine candidate, VRC5283, that provided complete protection from ZIKV challenge in both mice and NHPs.

This study demonstrated that 75 μg of SAM vaccine-elicited similar neutralizing activity and protection as 4 mg of DNA vaccine expressing the same protein sequence.

This is the first time that a SAM vaccine has been demonstrated to be protective in the NHP model. 

And they used a CNE formulation as a delivery vehicle of the VRC5283 DNA vaccine.

The VRC5283 DNA vaccine has previously been shown to protect NHPs from ZIKV infection and is currently in phase 2 clinical trials.

This technology has been well characterized and is known to generate a rapid immune response when administered. These properties make SAM CNE particularly suitable for rapid response to emerging outbreaks.

And, the synthetic delivery component of this technology also has the advantage of circumventing antibody responses to vector structural proteins commonly seen with viral vectors, while still eliciting antigen-specific immune responses with similar magnitude and composition.

These findings demonstrate the importance of evaluating multiple vaccine candidates in vivo even when only subtle differences can be detected in vitro.

The data shown demonstrates that a ZIKV SAM vaccine delivered by CNE is remarkably effective in animals, including NHPs. Future clinical studies will determine whether this preclinical result can translate to efficacy in humans and whether the SAM vaccine approach can protect women of child-bearing age, and in turn fetuses, during a ZIKV outbreak.

ZikaNews publishes release-based Zika disease news.