Safety, immunogenicity, and efficacy of the ML29 reassortant vaccine for Lassa fever in small non-human primates

Self Cite

The attenuated Lassa vaccine candidate ML29 is a laboratory-produced reassortant between Lassa and Mopeia viruses, two Old World arenaviruses that differ by 40% in nucleic acid sequence. In our previous studies, ML29 elicited sterilizing immunity against Lassa virus challenge in guinea pigs and marmosets and virus-specific cell-mediated immunity in both simian immunodeficiency virus (SIV)-infected and uninfected rhesus macaques. Here, we show that ML29 is stable after 12 passages in vitro without losing its plaque morphology or its attenuated phenotype in suckling mice. Additionally, we used deep sequencing to characterize the viral population comprising the original stock of ML29, the stock of ML29 after 12 passages in Vero cells, and the ML29 isolates obtained from vaccinated animals. Twenty-seven isolates bore approximately 77 mutations that exceeded 20% of the single-nucleotide polymorphism (SNP) changes at any single locus. Of these 77 mutations, 5 appeared to be host specific, for example, appearing in mice but not in primates. None of these mutations were reversions of ML29 to the sequences of the parental Lassa and Mopeia viruses. The host-specific mutations indicate viral adaptations to virus-host interactions, and such interactions make reasonable targets for antiviral approaches. Variants capable of chronic infection did not emerge from any of the primate infections, even in immune-deficient animals, indicating that the ML29 reassortant is reasonably stable in vivo. In conclusion, the preclinical studies of ML29 as a Lassa virus vaccine candidate have been advanced, showing high levels of protection in nonhuman primates and acceptable stability both in vitro and in vivo.

Section: Discussionmentioning

confidence: 99%

Genetic Variation In Vitro and In Vivo of an Attenuated Lassa Vaccine Candidate

Zapata

Goicochea

Nadai

et al. 2014

Self Cite

“…However, epidemiological studies strongly support the argument that development of a live attenuated vaccine would be the most feasible and attractive approach to control LASV, as well as other potentially emerging human-pathogenic arenaviruses, as such vaccines induce robust and long-term cellular and humoral immune protective responses following a single-dose immunization without the use of adjuvants (3,31,32). In this regard, the Mopeia virus (MOPV)/ LASV ML29 reassortant is a LASV live attenuated candidate vaccine that has been shown to provide post-exposure protection and to be safe and immunogenic in guinea pigs and small nonhuman primates (33)(34)(35). However, the mechanisms of ML29 attenuation remain poorly understood and additional mutations in ML29 or reassortments between ML29 and circulating virulent strains of LASV could result in viruses with enhanced virulence (36).…”

mentioning

confidence: 99%

Arenavirus Genome Rearrangement for the Development of Live Attenuated Vaccines

Cheng

Ortiz-Riaño

Torre

et al. 2015

100

Several members of the Arenaviridae family cause hemorrhagic fever disease in humans and pose serious public health problems in their geographic regions of endemicity as well as a credible biodefense threat. To date, there have been no FDA-approved arenavirus vaccines, and current antiarenaviral therapy is limited to an off-label use of ribavirin that is only partially effective. Arenaviruses are enveloped viruses with a bisegmented negative-stranded RNA genome. Each genome segment uses an ambisense coding strategy to direct the synthesis of two viral polypeptides in opposite orientations, separated by a noncoding intergenic region. Here we have used minigenome-based approaches to evaluate expression levels of reporter genes from the nucleoprotein (NP) and glycoprotein precursor (GPC) loci within the S segment of the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV). We found that reporter genes are expressed to higher levels from the NP than from the GPC locus. Differences in reporter gene expression levels from the NP and GPC loci were confirmed with recombinant trisegmented LCM viruses. We then used reverse genetics to rescue a recombinant LCMV ( A renaviruses are enveloped viruses with a bisegmented negative-strand (NS) RNA genome that cause chronic infections of rodents across the world (1). Zoonotic transmission through either direct contact with contaminated material or inhalation of aerosolized particles can result in severe infection in humans (1). Several arenaviruses, mainly, Lassa virus (LASV), the agent responsible for Lassa fever (LF) in western Africa, and Junín virus (JUNV), the causative agent of Argentine hemorrhagic fever (AHF) in the Argentinean Pampas, cause severe HF diseases in humans that are associated with high morbidity and significant mortality, posing important health problems in their regions of endemicity (1-3). Importantly, increased travel has resulted in the importation of LF into nonendemic metropolitan regions around the globe, including the United States (4, 5), Europe (6), and Japan (7). Moreover, similarly to the situation recently illustrated with the 2014 Ebola virus outbreak in western Africa (8, 9), evidence indicates that regions of LASV endemicity are expanding. In addition, the recent identification of two novel HF-causing arenaviruses, Chapare virus in Bolivia (10) and Lujo virus in South Africa (11), has further reinforced concerns about the emergence of novel HF-causing arenaviruses. Additionally, evidence indicates that the lymphocytic choriomeningitis virus (LCMV) prototypic arenavirus, distributed worldwide, is a neglected human pathogen of clinical significance (12-15). Besides their impact in human public health, arenaviruses pose also a credible biodefense threat, and six of them, including LCMV, LASV, and JUNV, are classified as NIAID category A agents (2, 16). Threats posed by humanpathogenic arenaviruses are further aggravated by the lack of FDA-approved vaccines (1) and by current antiarenaviral therapy

“…However, the Mopeia virus (MOPV)/LASV reassortant ML29 has shown promising safety and efficacy profiles in animal models, including nonhuman primates (21)(22)(23), but limited knowledge about the mechanisms of ML29 attenuation has raised the concern that additional ML29 mutations, or reassortants between ML29 and circulating LASV strains, could result in viruses with enhanced virulence. Likewise, a replication-competent attenuated recombinant vesicular stomatitis virus (VSV) expressing LASV glycoprotein has been reported to elicit protective immune responses in nonhuman primates against a lethal LASV challenge (24).…”

mentioning

confidence: 99%

Development of Live-Attenuated Arenavirus Vaccines Based on Codon Deoptimization

Cheng

Ortiz-Riaño

Nogales

et al. 2015

Arenaviruses have a significant impact on public health and pose a credible biodefense threat, but the development of safe and effective arenavirus vaccines has remained elusive, and currently, no Food and Drug Administration (FDA)-licensed arenavirus vaccines are available. Here, we explored the use of a codon deoptimization (CD)-based approach as a novel strategy to develop live-attenuated arenavirus vaccines. We recoded the nucleoprotein (NP) of the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) with the least frequently used codons in mammalian cells, which caused lower LCMV NP expression levels in transfected cells that correlated with decreased NP activity in cell-based functional assays. We used reverse-genetics approaches to rescue a battery of recombinant LCMVs (rLCMVs) encoding CD NPs (rLCMV/NP CD ) that showed attenuated growth kinetics in vitro. Moreover, experiments using the well-characterized mouse model of LCMV infection revealed that rLCMV/NP CD1 and rLCMV/NP CD2 were highly attenuated in vivo but, upon a single immunization, conferred complete protection against a subsequent lethal challenge with wild-type (WT) recombinant LCMV (rLCMV/WT). Both rLCMV/NP CD1 and rLCMV/NP CD2 were genetically and phenotypically stable during serial passages in FDA vaccine-approved Vero cells. These results provide proof of concept of the safety, efficacy, and stability of a CD-based approach for developing live-attenuated vaccine candidates against human-pathogenic arenaviruses. IMPORTANCESeveral arenaviruses cause severe hemorrhagic fever in humans and pose a credible bioterrorism threat. Currently, no FDA-licensed vaccines are available to combat arenavirus infections, while antiarenaviral therapy is limited to the off-label use of ribavirin, which is only partially effective and is associated with side effects. Here, we describe the generation of recombinant versions of the prototypic arenavirus LCMV encoding codon-deoptimized viral nucleoproteins (rLCMV/NP CD ). We identified rLCMV/NP CD1 and rLCMV/ NP CD2 to be highly attenuated in vivo but able to confer protection against a subsequent lethal challenge with wild-type LCMV. These viruses displayed an attenuated phenotype during serial amplification passages in cultured cells. Our findings support the use of this approach for the development of safe, stable, and protective live-attenuated arenavirus vaccines.A renaviruses cause chronic infections of rodents across the world, and human infections occur through mucosal exposure to aerosols or by direct contact of abraded skin with infectious materials (1). Several arenaviruses, chiefly Lassa virus (LASV), the causative agent of Lassa fever (LF) in West Africa, and Junín virus (JUNV), the causative agent of Argentine hemorrhagic fever (AHF) in Argentina, cause hemorrhagic fever (HF) disease in humans that is associated with high morbidity and significant mortality and pose important public health problems in their areas of endemicity (1-3). Notably, increased travel has led to the import...