Self-Amplifying RNA Vaccines for Venezuelan Equine Encephalitis Virus Induce Robust Protective Immunogenicity in Mice

Abstract

Venezuelan equine encephalitis virus (VEEV) is a known biological defense threat. A live-attenuated investigational vaccine, TC-83, is available, but it has a high non-response rate and can also cause severe reactogenicity. We generated two novel VEE vaccine candidates using self-amplifying mRNA (SAM). LAV-CNE is a live-attenuated VEE SAM vaccine formulated with synthetic cationic nanoemulsion (CNE) and carrying the RNA genome of TC-83. IAV-CNE is an irreversibly-attenuated VEE SAM vaccine formulated with CNE, delivering a TC-83 genome lacking the capsid gene. LAV-CNE launches a TC-83 infection cycle in vaccinated subjects but eliminates the need for live-attenuated vaccine production and potentially reduces manufacturing time and complexity. IAV-CNE produces a single cycle of RNA amplification and antigen expression without generating infectious viruses in subjects, thereby creating a potentially safer alternative to live-attenuated vaccine. Here, we demonstrated that mice vaccinated with LAV-CNE elicited immune responses similar to those of TC-83, providing 100% protection against aerosol VEEV challenge. IAV-CNE was also immunogenic, resulting in significant protection against VEEV challenge. These studies demonstrate the proof of concept for using the SAM platform to streamline the development of effective attenuated vaccines against VEEV and closely related alphavirus pathogens such as western and eastern equine encephalitis and Chikungunya viruses.

mRNA Vaccine Era—Mechanisms, Drug Platform and Clinical Prospection

“…Against Venezuelan equine encephalitis virus (VEEV), two synthetic CNE-encapsulated Venezuelan equine encephalitis SAM vaccine candidates, LAV-CNE (carrying the RNA genome of TC-83, a live-attenuated investigational vaccine strain) and IAV-CNE (carrying TC-83 viral genome with the capsid gene deleted), were designed to be capable of offering immune protection [160]. In inoculated mice, both vaccines induced robust virus-specific neutralizing antibodies and provided protection from wild-type VEEV aerosol challenge [160].…”

“…Against Venezuelan equine encephalitis virus (VEEV), two synthetic CNE-encapsulated Venezuelan equine encephalitis SAM vaccine candidates, LAV-CNE (carrying the RNA genome of TC-83, a live-attenuated investigational vaccine strain) and IAV-CNE (carrying TC-83 viral genome with the capsid gene deleted), were designed to be capable of offering immune protection [160]. In inoculated mice, both vaccines induced robust virus-specific neutralizing antibodies and provided protection from wild-type VEEV aerosol challenge [160]. In addition, mRNA-based candidate vaccines have been developed and trialed against diverse viruses such as chikungunya virus, herpes simplex virus, human metapneumovirus and parainfluenza virus, all showing desirable development prospects [161][162][163].…”

A new generation of vaccines based on alphavirus self-amplifying RNA

“…pig Protection against lethal ZIKV challenge [ 33 •• ] Neutral LPP GFP/Luc/HA Mouse Specific and functional T cell responses [ 32 • ] CAFs/PEI Chlamydia ag. Immune responses, unaffected by TLR-agonists [ 36 ] pABOL HA Protection from influenza virus challenge [ 40 ] CNE VEEV TC-83 Full protection against VEEV challenge [ 30 •• ] cVEEV Viral ag. Rodents/NHP Specific T cell and antibody responses [ 24 ] HA Mouse/Ferret Protection against heterologous virus challenge [ 26 ] NP+GM-CSF Mouse Enhanced APC recruitment & virus protection [ 27 • ] Mannose-LNP IM/ID HA Enhanced APC uptake & immune responses [ 31 ] ...…”

“…In particular, evidence has been provided that HIV vaccination with a relatively low dose of saRNA (50 μg) was both safe and immunogenic in nonhuman primates [ 28 ]. The CNE system has even been employed to deliver a live-attenuated VEEV vaccine using the full-length RNA genome of VEEV TC-83 attenuated strain [ 30 •• ]. This vaccine induced immune responses similar to those of TC-83 VPs, providing 80% protection against VEEV challenge in mice.…”

Vaccine Advances against Venezuelan, Eastern, and Western Equine Encephalitis Viruses

“…Self-amplifying mRNA technology utilizes synthetic RNA derived from the viral genome, which is then encapsulated in lipid nanoparticles or cationic nanoemulsions [ 124 ]. This technology has produced an mRNA vaccine encoding the genome of VEEV strain TC-83 that shows enhanced safety with similar immunogenicity as an inoculation with the live TC-83 strain and 100% protection against an aerosol VEEV challenge [ 125 ].…”