A self-amplifying RNA vaccine against COVID-19 with long-term room-temperature stability

Abstract

AbstractmRNA vaccines were the first to be authorized for use against SARS-CoV-2 and have since demonstrated high efficacy against serious illness and death. However, limitations in these vaccines have been recognized due to their requirement for cold storage, short durability of protection, and lack of access in low-resource regions. We have developed an easily-manufactured, potent self-amplifying RNA (saRNA) vaccine against SARS-CoV-2 that is stable at room temperature. This saRNA vaccine is formulated with a nanostructured lipid carrier (NLC), providing stability, ease of manufacturing, and protection against degradation. In preclinical studies, this saRNA/NLC vaccine induced strong humoral immunity, as demonstrated by high pseudovirus neutralization titers to the Alpha, Beta, and Delta variants of concern and induction of bone marrow-resident antibody-secreting cells. Robust Th1-biased T-cell responses were also observed after prime or homologous prime-boost in mice. Notably, the saRNA/NLC platform demonstrated thermostability when stored lyophilized at room temperature for at least 6 months and at refrigerated temperatures for at least 10 months. Taken together, this saRNA delivered by NLC represents a potential improvement in RNA technology that could allow wider access to RNA vaccines for the current COVID-19 and future pandemics.

Intranasal self-amplifying RNA SARS-CoV-2 vaccine produces protective respiratory and systemic immunity and prevents viral transmission

“…The SARS-CoV-2 vaccine saRNA contains a codon-optimized Wuhan-strain D614G SARS-CoV-2 spike protein sequence driven by a Venezuelan equine encephalitis virus (VEEV)-based replicon (Figure 1A) 24 . This saRNA is complexed to the exterior of AAHI’s proprietary NLC nanoparticle to create the final vaccine product AAHI-SC2 (Figure 1B).…”

“…The saRNA plasmid was designed and selected based on immunogenicity measures from i.m. immunization 24 . Briefly, the saRNA encodes a SARS-CoV-2 spike sequence based on a GenBank sequence (MT246667.1) containing the D614G mutation, a diproline at sites 987-988, and a QQAQ substitution for RRAR in the furin cleavage site (683-686).…”

“…The colloid mixture was then processed at 30,000 psi for 11 discrete microfluidization passes using an M-110P microfluidizer (Microfluidics). The NLC product was then filtered through a 0.22-μm polyethersulfone filter and stored at 2°C–8°C until use 24,30,72 .…”

“…This saRNA is complexed to the exterior of AAHI's proprietary NLC nanoparticle to create the final vaccine product AAHI-SC2 (Figure 1B). This construct is highly thermostable maintaining immunogenicity after storage at 25°C lyophilized for up to 2 months and at 4°C lyophilized for up to 10 months 24 The i.n. saRNA-NLC vaccine elicited high serum IgG and SARS-CoV-2 Wuhan-strain neutralization titers that would be predicted to be protective (>1000 IC50) 31,32 at all i.n.…”

“…We previously developed an i.m. administered nanostructured lipid carrier(NLC)-delivered self-amplifying RNA (saRNA) vaccine against SARS-CoV-2 23,24 , which induces both high serum neutralizing responses 25–27 and robust activation of CD4 + and CD8 + T cells, responses that may be critical to sustained potent immunity 26 . This saRNA-NLC vaccine platform additionally has unique thermostability relative to other mRNA delivery systems 24,28–30 , and may be readily lyophilized and stored at room temperature for months or under refrigeration likely for years 24,30 .…”