Animal models for Lassa virus infection

Lassa virus in novel hosts: insights into the epidemiology of lassa virus infections in southern Nigeria

Identification of the diverse animal hosts responsible for spill-over events from animals to humans is crucial for comprehending the transmission patterns of emerging infectious diseases, which pose significant public health risks. To better characterize potential animal hosts of Lassa virus (LASV), we assessed domestic and non-domestic animals from 2021-2022 in four locations in southern Nigeria with reported cases of Lassa fever (LF). Birds, lizards, and domestic mammals (dogs, pigs, cattle and goats) were screened using RT-qPCR, and whole genome sequencing was performed for lineage identification on selected LASV positive samples. Animals were also screened for exposure to LASV by enzyme-linked immunosorbent assay (ELISA). Among these animals, lizards had the highest positivity rate by PCR. Genomic sequencing of samples in most infected animals showed sub-lineage 2 g of LASV. Seropositivity was highest among cattle and lowest in pigs. Though the specific impact these additional hosts may have in the broader virus-host context are still unknown - specifically relating to pathogen diversity, evolution, and transmission - the detection of LASV in non-rodent hosts living in proximity to confirmed human LF cases suggests their involvement during transmission as potential reservoirs. Additional epidemiological data comparing viral genomes from humans and animals, as well as those circulating within the environment will be critical in understanding LASV transmission dynamics and will ultimately guide the development of countermeasures for this zoonotic health threat.

Preclinical Safety Assessment of the EBS-LASV Vaccine Candidate against Lassa Fever Virus

There are currently no prophylactic vaccines licensed to protect against Lassa fever caused by Lassa virus (LASV) infection. The Emergent BioSolutions (EBS) vaccine candidate, EBS-LASV, is being developed for the prevention of Lassa fever. EBS-LASV is a live-attenuated recombinant Vesicular Stomatitis Virus (rVSV)-vectored vaccine encoding the surface glycoprotein complex (GPC) from LASV and has two attenuating vector modifications: a gene shuffle of the VSV N gene and a deletion of the VSV G gene. Preclinical studies were performed to evaluate EBS-LASV's neurovirulence potential following intracranial (IC) injection and to determine the biodistribution and vector replication following intramuscular (IM) inoculation in mice. In addition, the potential EBS-LASV toxicity was assessed using repeated-dose IM EBS-LASV administration to rabbits. All mice receiving the IC injection of EBS-LASV survived, while mice administered the unattenuated control vector did not. The vaccine was only detected in the muscle at the injection site, draining lymph nodes, and the spleen over the first week following IM EBS-LASV injection in mice, with no detectable plasma viremia. No toxicity was observed in rabbits receiving a three-dose regimen of EBS-LASV. These studies demonstrate that EBS-LASV is safe when administered to animals and supported a first-in-human dose-escalation, safety, and immunogenicity clinical study.

Optimal reference genes for RNA tissue analysis in small animal models of hemorrhagic fever viruses

Reverse-transcription quantitative polymerase chain reaction assays are frequently used to evaluate gene expression in animal model studies. Data analyses depend on normalization using a suitable reference gene (RG) to minimize effects of variation due to sample collection, sample processing, or experimental set-up. Here, we investigated the suitability of nine potential RGs in laboratory animals commonly used to study viral hemorrhagic fever infection. Using tissues (liver, spleen, gonad [ovary or testis], kidney, heart, lung, eye, brain, and blood) collected from naïve animals and those infected with Crimean-Congo hemorrhagic fever (mice), Nipah (hamsters), or Lassa (guinea pigs) viruses, optimal species-specific RGs were identified based on five web-based algorithms to assess RG stability. Notably, the Ppia RG demonstrated stability across all rodent tissues tested. Optimal RG pairs that include Ppia were determined for each rodent species (Ppia and Gusb for mice; Ppia and Hrpt for hamsters; and Ppia and Gapdh for guinea pigs). These RG pair assays were multiplexed with viral targets to improve assay turnaround time and economize sample usage. Finally, a pan-rodent Ppia assay capable of detecting Ppia across multiple rodent species was developed and successfully used in ecological investigations of field-caught rodents, further supporting its pan-species utility.

[Recent advances in the development of vaccines against hemorrhagic fevers caused by arenaviruses]

Arenaviruses are a global threat, causing thousands of deaths each year in several countries around the world. Despite strong efforts in the development of vaccine candidates, vaccines against Lassa fever or Bolivian and Venezuelan hemorrhagic fevers are yet to be licensed for a use in humans. In this synthesis, we present the arenaviruses causing fatal diseases in humans and the main vaccine candidates that have been developed over the past decades with an emphasis on the measles-Lassa vaccine, the first Lassa vaccine ever tested in humans, and on the MOPEVAC platform that can potentially be used as a pan-arenavirus vaccine platform.

The Arenaviridae Family: Knowledge Gaps, Animal Models, Countermeasures, and Prototype Pathogens

Lassa virus (LASV), Junin virus (JUNV), and several other members of the Arenaviridae family are capable of zoonotic transfer to humans and induction of severe viral hemorrhagic fevers. Despite the importance of arenaviruses as potential pandemic pathogens, numerous gaps exist in scientific knowledge pertaining to this diverse family, including gaps in understanding replication, immunosuppression, receptor usage, and elicitation of neutralizing antibody responses, that in turn complicates development of medical countermeasures. A further challenge to the development of medical countermeasures for arenaviruses is the requirement for use of animal models at high levels of biocontainment, where each model has distinct advantages and limitations depending on, availability of space, animals species-specific reagents, and most importantly the ability of the model to faithfully recapitulate human disease. Designation of LASV and JUNV as prototype pathogens can facilitate progress in addressing the public health challenges posed by members of this important virus family.

Vaccine Candidates against Arenavirus Infections

The viral family Arenaviridae contains several members that cause severe, and often lethal, diseases in humans. Several highly pathogenic arenaviruses are classified as Risk Group 4 agents and must be handled in the highest biological containment facility, biosafety level-4 (BSL-4). Vaccines and treatments are very limited for these pathogens. The development of vaccines is crucial for the establishment of countermeasures against highly pathogenic arenavirus infections. While several vaccine candidates have been investigated, there are currently no approved vaccines for arenavirus infection except for Candid#1, a live-attenuated Junin virus vaccine only licensed in Argentina. Current platforms under investigation for use include live-attenuated vaccines, recombinant virus-based vaccines, and recombinant proteins. We summarize here the recent updates of vaccine candidates against arenavirus infections.

Virus-CKB 2.0: Viral-Associated Disease-Specific Chemogenomics Knowledgebase

Transmissible and infectious viruses can cause large-scale epidemics around the world. This is because the virus can constantly mutate and produce different variants and subvariants to counter existing treatments. Therefore, a variety of treatments are urgently needed to keep up with the mutation of the viruses. To facilitate the research of such treatment, we updated our Virus-CKB 1.0 to Virus-CKB 2.0, which contains 10 kinds of viruses, including enterovirus, dengue virus, hepatitis C virus, Zika virus, herpes simplex virus, Andes orthohantavirus, human immunodeficiency virus, Ebola virus, Lassa virus, influenza virus, coronavirus, and norovirus. To date, Virus-CKB 2.0 archived at least 65 antiviral drugs (such as remdesivir, telaprevir, acyclovir, boceprevir, and nelfinavir) in the market, 178 viral-related targets with 292 available 3D crystal or cryo-EM structures, and 3766 chemical agents reported for these target proteins. Virus-CKB 2.0 is integrated with established tools for target prediction and result visualization; these include HTDocking, TargetHunter, blood-brain barrier (BBB) predictor, Spider Plot, etc. The Virus-CKB 2.0 server is accessible at https://www.cbligand.org/g/virus-ckb. By using the established chemogenomic tools and algorithms and newly developed tools, we can screen FDA-approved drugs and chemical compounds that may bind to these proteins involved in viral-associated disease regulation. If the virus strain mutates and the vaccine loses its effect, we can still screen drugs that can be used to treat the mutated virus in a fleeting time. In some cases, we can even repurpose FDA-approved drugs through Virus-CKB 2.0.

Lassa Virus Treatment Options

Lassa fever causes an approximate 5000 to 10,000 deaths annually in West Africa and cases have been imported into Europe and the Americas, challenging public health. Although Lassa virus was first described over 5 decades ago in 1969, no treatments or vaccines have been approved to treat or prevent infection. In this review, we discuss current therapeutics in the development pipeline for the treatment of Lassa fever, focusing on those that have been evaluated in humans or animal models. Several treatments, including the antiviral favipiravir and a human monoclonal antibody cocktail, have shown efficacy in preclinical rodent and non-human primate animal models and have potential for use in clinical settings. Movement of the promising preclinical treatment options for Lassa fever into clinical trials is critical to continue addressing this neglected tropical disease.

Patent landscape of novel technologies for combating category-A Arenavirus infections

INTRODUCTION

Arenavirus are unique category-A pathogens that are also classified as Orphan diseases. Very few options exist currently for treating Viral Hemorrhagic Fever (VHF) caused by viruses belonging to the Arenaviridae family [1]. The current review provides detailed patent landscape and a description of selected technologies developed for combating category-A Arenavirus. Currently, Arenavirus infections are epidemic [2] but could cause widespread pandemics due to ease of dissemination and lack of immunity against these viruses.

AREAS COVERED

The key strings for selected Arenavirus VHF were run separately in MCPaIRS®, PatSeer, and Questel database. The search was limited to Title, Abstract and Claim fields; one member per patent family was considered for analysis.

EXPERT OPINION

Synthetic molecules dominate the patent landscape, while natural products have not been extensively claimed for the treatment of Arenavirus infection. The broad-spectrum activity has been highly desired for Arenavirus treatment, but few reports have experimentally tested it. With each year, a constant increase in number of patents published is seen, while the maximum number of applications was filed in 2017. The research in VHF is driven by public funds; the maximum numbers of patents were filed by publicly funded organizations.

An optimized five-color/seven-parameter flow cytometry panel for immunophenotyping guinea pig peripheral blood lymphocytes

Guinea pigs are an ideal animal model for the study of several infectious diseases, including tuberculosis, legionellosis, brucellosis, and spotted fever rickettsiosis. In comparison to the murine model, clinical signs in guinea pigs are more representative of disease in humans, the guinea pig immune system is more similar to that of the human, and their large size offers logistic advantages for sample collection while following disease progression. Unfortunately, the advantage of using guinea pigs in biomedical research, particularly in understanding the immune response to infectious agents, is limited in large part by the paucity of available reagents and lack of genetically manipulated strains. Here, we expand the utility of guinea pigs in biomedical research by establishing an optimized five-color/seven-parameter polychromatic flow cytometric assay for immunophenotyping lymphocytes. This assay fills a need for immunophenotyping peripheral blood lymphocytes and is an improvement over current published flow cytometry assays for guinea pigs. We anticipate that our approach will be an important starting point for developing new assays to evaluate the cellular immune response to infectious diseases in the guinea pig model. Importantly, we are currently using this assay for evaluating immunity to spotted fever rickettsiosis in a guinea pig-tick-Rickettsia system, where CD8+ T cells are a critical contributor to the immune response. Developing resources to utilize the guinea pig more effectively will enhance our ability to understand infectious diseases where the guinea pig would otherwise be the ideal model.