Self-Amplifying Replicon RNA Delivery to Dendritic Cells by Cationic Lipids

Abstract

Advances in RNA technology during the past two decades have led to the construction of replication-competent RNA, termed replicons, RepRNA, or self-amplifying mRNA, with high potential for vaccine applications. Cytosolic delivery is essential for their translation and self-replication, without infectious progeny generation, providing high levels of antigen expression for inducing humoral and cellular immunity. Synthetic nanoparticle-based delivery vehicles can both protect the RNA molecules and facilitate targeting of dendritic cells—critical for immune defense development. Several cationic lipids were assessed, with RepRNA generated from classical swine fever virus encoding nucleoprotein genes of influenza A virus. The non-cytopathogenic nature of the RNA allowed targeting to dendritic cells without destroying the cells—important for prolonged antigen production and presentation. Certain lipids were more effective at delivery and at promoting translation of RepRNA than others. Selection of particular lipids provided delivery to dendritic cells that resulted in translation, demonstrating that delivery efficiency could not guarantee translation. The observed translation in vitro was reproduced in vivo by inducing immune responses against the encoded influenza virus antigens. Cationic lipid-mediated delivery shows potential for promoting RepRNA vaccine delivery to dendritic cells, particularly when combined with additional delivery elements.

mRNA as a Transformative Technology for Vaccine Development to Control Infectious Diseases

“…injection in mice. Englezou et al144 explored and optimized cationic lipids and lipoplex formation to increase the uptake, release in the cytoplasm, and translation of a self-amplifying mRNA molecule in DCs. The lipoplex, optimized for increased in vitro translation in DCs, elicited pro-inflammatory cytokines, humoral responses, and T cellular responses against the self-amplifying mRNA-encoded influenza NP antigen after s.c. vaccination in mice and in an adoptive transfer model.…”

Self-Amplifying RNA Viruses as RNA Vaccines

“…One area of interest has been the targeting of DCs as described for SFV-IL-18 transduced DCs in mice with B16 xenografts [ 80 ] and VEE-neu transduced DCs in a mouse tumor model for breast cancer [ 86 ]. Furthermore, RNA replicons of CSFV expressing influenza virus NP complexed with liposomes for delivery to DCs, elicited immune responses both in vitro and in vivo [ 65 ]. Another approach relates to combination therapy of self-amplifying RNA virus vectors with drugs and irradiation ( Table 2 ), including tumor eradication with SFV-HPV E6,7 particles, sunitinib and low-dose irradiation [ 95 ] or enhanced immune responses of VSV and ruxolitinib co-administration [ 120 ].…”

“…Immunization of neonatal BALB/c mice elicited strong innate immune responses demonstrating significantly higher and sustained influenza virus-specific IgG antibodies compared to mice immunized with antigen only. Recently, liposome-encapsulation of RNA replicons of the flavivirus classical swine fever virus (CSFV) expressing influenza virus NP elicited immune responses both in vitro and in vivo [ 65 ].…”

The Potential of Self-amplifying RNA Vaccines for Infectious Diseases and COVID-19

“…Expression of interleukin-2 (IL-2) resulted in 5.5-fold increase in intratumoral IL-2 levels and 2.1fold increase in infiltrating CD8+ T cells in a B16F10 melanoma model, leading to significantly slower tumor growth. In addition to liposome-and polymer-based delivery strategies to provide improved delivery, protection against degradation and recognition by the host immune system [15,69,70,79,98,99] attention has also been paid to delivery safety including engineering of vectors providing the highest safety standards. For instance, point mutations introduced into the SFV p62 precursor sequence prevented the cleavage of p62 into E2 and E3 proteins, which resulted in conditionally infectious particles and reduction of production of replication competent SFV particles [120].…”