Pharmacokinetic Analyses of a Lipid Nanoparticle-Encapsulated mRNA-Encoded Antibody against Rift Valley Fever Virus.

Rift Valley fever virus (RVFV) could cause an emergency illness characterized by fever, muscle pain, and even death in humans or ruminants. However, there are no approved antiviral drugs that prevent or treat RVFV infection. While therapeutic antibodies have shown promising potential for prevention or treatment in several studies, many studies are ongoing, especially in the field of infectious diseases. Among these studies, the mRNA-LNP platform shows great potential for application, following the COVID-19 pandemic. Previously, we have obtained a neutralizing antibody against RVFV, which was named A38 protein and verified to have a high binding and neutralization ability. In this study, we aimed to identify an effectively optimized sequence and expressed the prioritized mRNA-encoded antibody in vitro. Notably, we effectively expressed mRNA-encoded protein and used the mRNA-LNP platform to generate A38-mRNA-LNP. Pharmacokinetic experiments were conducted in vivo and set up in two groups of mRNA-A38 group and A38 protein group, which were derived from mRNA-LNP and plasmid DNA-expressed proteins, respectively. A38-mRNA-LNPs were administrated by intramuscular injection, A38 proteins were administrated by intravenous administration, and their unique ability to maintain long-lasting protein concentrations by mRNA-encoded protein was demonstrated with the mRNA-encoded protein providing a longer circulating half-life compared to injection of the free A38 protein. These preclinical data on the mRNA-encoded antibody highlighted its potential to prevent infectious diseases in the future.

Efficacy of Coxiella burnetii and its chloroform-methanol residue (CMR) fraction against Rift Valley fever virus infection in mice.

Strains of Coxiella burnetii phase I and II whole cells (WC-I and WC-II) or whole cell fractions were assessed for their potential to induce long-lasting protection in endotoxin-non-responder C3H/HeJ or CD-1 mice against Rift Valley fever (RVF) virus challenge. Among the whole cell fractions, only the chloroform-methanol residue (CMR), administered as a single dose (100 micrograms per mouse) 24 h before viral challenge, effectively protected 100% of the mice from RVF virus; the CMR of the Ohio strain of C. burnetii was not protective. Most of the RVF virus-infected mice treated with other C. burnetii cell fractions died, although their times to death varied. Lipopolysaccharide (LPS) associated with CMR preparations used in these studies, did not protect against RVF virus challenge. A single dose of 100 micrograms of CMR given 24 h before viral challenge completely eradicated 4-5 logs of RVF virus in the serum, liver, spleen, and central nervous system. Compared to several other immunomodulators, CMR was an equally effective antiviral agent. Efficacy of CMR of both Henzerling and Ohio strains disappeared or was marginal when treatment was initiated 2-3 days before RVF viral challenge, even when a second or a third dose of CMR was administered after challenge. A single dose of liposome-encapsulated CMR to RVF virus-infected mice extended the range of therapeutic efficacy of this biologically active component of C. burnetii to 4 days before infection.

Protection against Rift Valley fever virus infection in mice upon administration of interferon-inducing RNA transcripts from the FMDV genome.

In this work we have addressed the effect of synthetic, non-infectious, RNA transcripts, mimicking structural domains of the non-coding regions (NCRs) of the foot-and-mouth disease virus (FMDV) genome on the infection of mice with Rift Valley fever virus (RVFV). Groups of 5 mice were inoculated intraperitoneally (i.p.) with 200 µg of synthetic RNA resembling the 5'-terminal S region, the internal ribosome entry site (IRES) or the 3'-NCR of the FMDV genome. RNA inoculation was performed 24h before (-24 h), 24 h after (+24 h) or simultaneously to the challenge with a lethal dose of RVFV. Administration of the IRES RNA afforded higher survival rates than administration of S or 3'NCR transcripts either at -24h or +24h after challenge. In contrast, when RNA inoculation and viral challenge were performed simultaneously, all mice survived in both IRES- and 3'NCR-inoculated groups, with an 80% survival in mice receiving the S RNA. Among survivors, a complete correlation between significant anti-RVFV circulating antibody titers and resistance to a second lethal challenge with the virus was observed, supporting a limited viral replication in the RNA-inoculated animals upon the first challenge. All three RNA transcripts were able to induce the production of systemic antiviral and pro-inflammatory cytokines. These data show that triggering of intracellular pathogen sensing pathways constitutes a promising approach towards development of novel RVF preventive or therapeutic strategies.

A replication-incompetent Rift Valley fever vaccine: chimeric virus-like particles protect mice and rats against lethal challenge.

Virus-like particles (VLPs) present viral antigens in a native conformation and are effectively recognized by the immune system and therefore are considered as suitable and safe vaccine candidates against many viral diseases. Here we demonstrate that chimeric VLPs containing Rift Valley fever virus (RVFV) glycoproteins G(N) and G(C), nucleoprotein N and the gag protein of Moloney murine leukemia virus represent an effective vaccine candidate against Rift Valley fever, a deadly disease in humans and livestock. Long-lasting humoral and cellular immune responses are demonstrated in a mouse model by the analysis of neutralizing antibody titers and cytokine secretion profiles. Vaccine efficacy studies were performed in mouse and rat lethal challenge models resulting in high protection rates. Taken together, these results demonstrate that replication-incompetent chimeric RVF VLPs are an efficient RVFV vaccine candidate.