Animal models of highly pathogenic RNA viral infections: hemorrhagic fever viruses

The DNA-based Lassa vaccine INO-4500 confers durable protective efficacy in cynomolgus macaques against lethal Lassa fever

BACKGROUND

We have previously developed a DNA-based vaccine, INO-4500, encoding the Lassa lineage IV glycoprotein precursor. INO-4500, when delivered with electroporation, elicited humoral and cellular responses, and conferred 100% protection in cynomolgus non-human primates. Here, we expanded the characterization of INO-4500 assessing immunogenicity and protective efficacy of lower doses and single immunization, and the durability of immune responses.

METHODS

The study was divided into three arms evaluating INO-4500 vaccination: Arm 1 - Dosing regimen; Arm 2 - Single immunization; and Arm 3-Durability of immune responses and protective efficacy. Humoral and T cell responses were assessed by IgG binding ELISA, IFNγ ELISpot and flow cytometry-based T cell activation assays. NHPs were challenged with a lethal dose of Lassa lineage IV 8 weeks (Arms 1 and 2) or one year (Arm 3) after immunization. NHPs were assigned clinical scores and monitored for survival. Viremia, virus neutralization and release of soluble mediators were assessed post-challenge, as well as disease pathology following NHPs death or euthanasia.

RESULTS

INO-4500 induces dose-dependent immune responses and protective efficacy. Animals receiving two doses of 2 mg of INO-4500 show complete short- and long-term LASV protection. NHPs receiving 1 mg of INO-4500 are protected from LASV challenge one year after vaccination but are only partially protected 8 weeks post-vaccination. LASV-specific memory T cells are present in vaccinated NHPs one year after vaccination. INO-4500 vaccination prevents NHPs from developing severe disease.

CONCLUSIONS

These studies demonstrate that INO-4500 can provide short- and long-term protection in NHPs from lethal LASV challenge.

Emerging and reemerging infectious diseases: global trends and new strategies for their prevention and control

To adequately prepare for potential hazards caused by emerging and reemerging infectious diseases, the WHO has issued a list of high-priority pathogens that are likely to cause future outbreaks and for which research and development (R&D) efforts are dedicated, known as paramount R&D blueprints. Within R&D efforts, the goal is to obtain effective prophylactic and therapeutic approaches, which depends on a comprehensive knowledge of the etiology, epidemiology, and pathogenesis of these diseases. In this process, the accessibility of animal models is a priority bottleneck because it plays a key role in bridging the gap between in-depth understanding and control efforts for infectious diseases. Here, we reviewed preclinical animal models for high priority disease in terms of their ability to simulate human infections, including both natural susceptibility models, artificially engineered models, and surrogate models. In addition, we have thoroughly reviewed the current landscape of vaccines, antibodies, and small molecule drugs, particularly hopeful candidates in the advanced stages of these infectious diseases. More importantly, focusing on global trends and novel technologies, several aspects of the prevention and control of infectious disease were discussed in detail, including but not limited to gaps in currently available animal models and medical responses, better immune correlates of protection established in animal models and humans, further understanding of disease mechanisms, and the role of artificial intelligence in guiding or supplementing the development of animal models, vaccines, and drugs. Overall, this review described pioneering approaches and sophisticated techniques involved in the study of the epidemiology, pathogenesis, prevention, and clinical theatment of WHO high-priority pathogens and proposed potential directions. Technological advances in these aspects would consolidate the line of defense, thus ensuring a timely response to WHO high priority pathogens.

Mice with FVB-derived sequence on chromosome 17 succumb to disseminated virus infection due to aberrant NK cell and T cell responses

Zoonotic arenavirus infections can result in viral hemorrhagic disease, characterized by platelet loss, petechia, and multi-organ injury. The mechanisms governing these outcomes are likely impacted by virus strain and infection dose, as well as an individual's genetic background and immune constitution. To better understand the processes leading to severe pathogenesis, we compared two strains of inbred mice, C57BL/6J (B6) and FVB/NJ (FVB), that have diametrically opposed outcomes during disseminated lymphocytic choriomeningitis virus (LCMV) infection. Infection caused minimal pathogenesis in B6 mice, whereas FVB mice developed acute hepatitis and perished due, in part, to aberrant NK cell and T cell responses. Susceptible mice showed an outgrowth of cytolytic CD4+ T cells and loss of Treg cells. B6 congenic mice with the FVB allele at a 25Mb locus on chromosome 17 recapitulated FVB pathogenesis upon infection. A locus containing a limited number of variants in immune-related genes greatly impacts survival during infection.

An Outbred Guinea Pig Disease Model for Lassa Fever Using a Host-Adapted Clade III Nigerian Lassa Virus

Nigeria experiences annual outbreaks of Lassa fever (LF) with high case numbers. At least three clades of Lassa virus (LASV) have been documented in Nigeria, though recent outbreaks are most often associated with clade II or clade III viruses. Using a recently isolated clade III LASV from a case of LF in Nigeria in 2018, we developed and characterized a guinea pig adapted virus capable of causing lethal disease in commercially available Hartley guinea pigs. Uniform lethality was observed after four passages of the virus and was associated with only two dominant genomic changes. The adapted virus was highly virulent with a median lethal dose of 10 median tissue culture infectious doses. Disease was characterized by several hallmarks of LF in similar models including high fever, thrombocytopenia, coagulation disorders, and increased inflammatory immune mediators. High viral loads were noted in all solid organ specimens analyzed. Histological abnormalities were most striking in the lungs and livers of terminal animals and included interstitial inflammation, edema, and steatosis. Overall, this model represents a convenient small animal model for a clade III Nigeria LASV with which evaluation of specific prophylactic vaccines and medical countermeasures can be conducted.

Differential pathogenesis of closely related 2018 Nigerian outbreak clade III Lassa virus isolates

Nigeria continues to experience ever increasing annual outbreaks of Lassa fever (LF). The World Health Organization has recently declared Lassa virus (LASV) as a priority pathogen for accelerated research leading to a renewed international effort to develop relevant animal models of disease and effective countermeasures to reduce LF morbidity and mortality in endemic West African countries. A limiting factor in evaluating medical countermeasures against LF is a lack of well characterized animal models outside of those based on infection with LASV strain Josiah originating form Sierra Leone, circa 1976. Here we genetically characterize five recent LASV isolates collected from the 2018 outbreak in Nigeria. Three isolates were further evaluated in vivo and despite being closely related and from the same spatial / geographic region of Nigeria, only one of the three isolates proved lethal in strain 13 guinea pigs and non-human primates (NHP). Additionally, this isolate exhibited atypical pathogenesis characteristics in the NHP model, most notably respiratory failure, not commonly described in hemorrhagic cases of LF. These results suggest that there is considerable phenotypic heterogeneity in LASV infections in Nigeria, which leads to a multitude of pathogenesis characteristics that could account for differences between subclinical and lethal LF infections. Most importantly, the development of disease models using currently circulating LASV strains in West Africa are critical for the evaluation of potential vaccines and medical countermeasures.

Lassa fever is a severe viral hemorrhagic fever of humans caused by infection with Lassa virus, which is endemic in many countries in West Africa. Annually, an estimated 300,000–500,000 people are infected with Lassa virus, making it one of the most prominent agents responsible for hemorrhagic disease in humans. Despite this significant burden of disease, to date, no approved therapeutic or prophylactic vaccine exists for Lassa fever, due in part to a lack of characterized animal models for studying the disease. Here, we describe guinea pig and non-human primate models for Lassa fever using recently isolated viruses from a 2018 outbreak of Lassa fever in Nigeria. Despite similar collection locations and dates, the isolates obtained from human infections demonstrated a high degree of genotypic heterogeneity and phenotypic characteristics in animal models resulting in both lethal and non-lethal infections. Of interest, one isolate resulted in significant respiratory manifestations, an under-reported disease manifestation in humans. These models will provide comparative models to those already characterized and aid in elucidating disease characteristics of Lassa fever. In addition, they will serve the immediate purpose of evaluating known and novel medical countermeasures to treat and prevent disease in West Africa.

The Integration of Human and Veterinary Studies for Better Understanding and Management of Crimean-Congo Haemorrhagic Fever

Outbreaks that occur as a result of zoonotic spillover from an animal reservoir continue to highlight the importance of studying the disease interface between species. One Health approaches recognise the interdependence of human and animal health and the environmental interplay. Improving the understanding and prevention of zoonotic diseases may be achieved through greater consideration of these relationships, potentially leading to better health outcomes across species. In this review, special emphasis is given on the emerging and outbreak pathogen Crimean-Congo Haemorrhagic Fever virus (CCHFV) that can cause severe disease in humans. We discuss the efforts undertaken to better understand CCHF and the importance of integrating veterinary and human research for this pathogen. Furthermore, we consider the use of closely related nairoviruses to model human disease caused by CCHFV. We discuss intervention approaches with potential application for managing CCHFV spread, and how this concept may benefit both animal and human health.

Antivirals in medical biodefense

The viruses historically implicated or currently considered as candidates for misuse in bioterrorist events are poxviruses, filoviruses, bunyaviruses, orthomyxoviruses, paramyxoviruses and a number of arboviruses causing encephalitis, including alpha- and flaviviruses. All these viruses are of concern for public health services when they occur in natural outbreaks or emerge in unvaccinated populations. Recent events and intelligence reports point to a growing risk of dangerous biological agents being used for nefarious purposes. Public health responses effective in natural outbreaks of infectious disease may not be sufficient to deal with the severe consequences of a deliberate release of such agents. One important aspect of countermeasures against viral biothreat agents are the antiviral treatment options available for use in post-exposure prophylaxis. These issues were adressed by the organizers of the 16th Medical Biodefense Conference, held in Munich in 2018, in a special session on the development of drugs to treat infections with viruses currently perceived as a threat to societies or associated with a potential for misuse as biothreat agents. This review will outline the state-of-the-art methods in antivirals research discussed and provide an overview of antiviral compounds in the pipeline that are already approved for use or still under development.

A recombinant vesicular stomatitis-based Lassa fever vaccine elicits rapid and long-term protection from lethal Lassa virus infection in guinea pigs

The World Health Organization has identified Lassa virus (LASV) as one of the top five pathogens to cause a severe outbreak in the near future. This study assesses the ability of a leading vaccine candidate, recombinant Vesicular stomatitis virus expressing LASV glycoprotein (VSVΔG/LASVGPC), and its ability to induce rapid and long-term immunity to lethal guinea pig-adapted LASV (GPA-LASV). Outbred guinea pigs were vaccinated with a single dose of VSVΔG/LASVGPC followed by a lethal challenge of GPA-LASV at 7, 14, 25, 189, and 355 days post-vaccination. Statistically significant rapid and long-term protection was achieved at all time points with 100% protection at days 7 and 14 post-vaccination. While 83 and 87% protection were achieved at 25 days and 6 months post-vaccination, respectively. When guinea pigs were challenged one year after vaccination 71% protection was achieved. Notable infectious virus was isolated from the serum and tissues of some but not all animals. Total LASVGPC-specific IgG titers were also measured on a monthly basis leading up to LASV challenge however, it is unclear if antibody alone correlates with short and long term survival. These studies confirm that a single dose of VSVΔG/LASVGPC can induce rapid and long-term protection from LASV infection in an aggressive outbred model of infection, and supports further development in non-human primates.

Lassa virus (LASV) is an emerging pathogen that can be associated with high case fatality but for which no clinically-approved vaccine currently exists. David Safronetz and colleagues at the Public Health Agency of Canada and the University of Manitoba investigate the efficacy of a single dose of a recombinant vaccine of LASV glycoproteins vectorized into vesicular stomatitis virus (VSVΔG/LASVGPC). Using guinea pigs lethally challenged with LASV, the protective efficacy of VSVΔG/LASVGPC and LASV-specific IgG is assessed at a number of time points out to approximately one year after vaccination. VSVΔG/LASVGPC elicits stable LASV glycoprotein-specific antibody production and durable protection from lethal LASV challenge, with 71% of animals surviving even at one year following vaccination and complete protection being afforded at earlier (weeks) time points. This pre-clinical model demonstrates the stable protection that can be established by a single dose of VSVΔG/LASVGPC.

Involvement of Pro-Inflammatory Macrophages in Liver Pathology of Pirital Virus-Infected Syrian Hamsters

New World arenaviruses cause fatal hemorrhagic disease in South America. Pirital virus (PIRV), a mammarenavirus hosted by Alston’s cotton rat (Sigmodon alstoni), causes a disease in Syrian golden hamsters (Mesocricetus auratus) (biosafety level-3, BSL-3) that has many pathologic similarities to the South American hemorrhagic fevers (BSL-4) and, thus, is considered among the best small-animal models for human arenavirus disease. Here, we extend in greater detail previously described clinical and pathological findings in Syrian hamsters and provide evidence for a pro-inflammatory macrophage response during PIRV infection. The liver was the principal target organ of the disease, and signs of Kupffer cell involvement were identified in mortally infected hamster histopathology data. Differential expression analysis of liver mRNA revealed signatures of the pro-inflammatory response, hematologic dysregulation, interferon pathway and other host response pathways, including 17 key transcripts that were also reported in two non-human primate (NHP) arenavirus liver-infection models, representing both Old and New World mammarenavirus infections. Although antigen presentation may differ among rodent and NHP species, key hemostatic and innate immune-response components showed expression parallels. Signatures of pro-inflammatory macrophage involvement in PIRV-infected livers included enrichment of Ifng, Nfkb2, Stat1, Irf1, Klf6, Il1b, Cxcl10, and Cxcl11 transcripts. Together, these data indicate that pro-inflammatory macrophage M1 responses likely contribute to the pathogenesis of acute PIRV infection.

Zika Virus Infection in Syrian Golden Hamsters and Strain 13 Guinea Pigs

To evaluate potential immunocompetent small animal models of Zika virus (ZIKV) infection, we inoculated Syrian golden hamsters (subcutaneously or intraperitoneally) and strain 13 guinea pigs (intraperitoneally) with Senegalese ZIKV strain ArD 41525 or Philippines ZIKV strain CPC-0740. We did not detect viremia in hamsters inoculated subcutaneously with either virus strain, although some hamsters developed virus neutralizing antibodies. However, we detected statistically significant higher viremias (P = 0.0285) and a higher median neutralization titer (P = 0.0163) in hamsters inoculated intraperitoneally with strain ArD 41525 compared with strain CPC-0740. Furthermore, some hamsters inoculated with strain ArD 41525 displayed mild signs of disease. By contrast, strain 13 guinea pigs inoculated intraperitoneally with either strain did not have detectable viremias and less than half developed virus neutralizing antibodies. Our results support the use of the Syrian golden hamster intraperitoneal model to explore phenotypic variation between ZIKV strains.

Exploring the Immunopathogenesis of Viral Hemorrhagic Fever in Mice with a Humanized Immune System

Viral hemorrhagic fever (VHF) as a disease entity was first codified in the 1930s by soviet scientists investigating patients suffering from hantavirus infection. The group of hemorrhagic fever viruses (HFVs) has since expanded to include members from at least four different virus families: Arenaviridae, Bunyaviridae, Filoviridae, and Flaviviridae, all enveloped single-stranded RNA viruses. After infection, the natural hosts of HFVs do not develop symptoms, whereas humans can be severely affected. This observation and other evidence from experimental data suggest that the human immune system plays a crucial role in VHF pathogenesis. For this reason mice with a human immune system, referred to here as humanized mice (humice), are valuable tools that provide insight into disease mechanisms and allow for preclinical testing of novel vaccinations approaches as well as antiviral agents. In this article, we review the impact of humice in VHF research.

MicroRNA expression profiling of primary sheep testicular cells in response to bluetongue virus infection

Bluetongue virus (BTV) is a member of the genus Orbivirus within the family Reoviridae and causes a non-contagious, insect-transmitted disease in domestic and wild ruminants, mainly in sheep and occasionally in cattle and some species of deer. Virus infection can trigger the changes of the cellular microRNA (miRNA) expression profile, which play important post-transcriptional regulatory roles in gene expression and can greatly influence viral replication and pathogenesis. Here, we employed deep sequencing technology to determine which cellular miRNAs were differentially expressed in primary sheep testicular (ST) cells infected with BTV. A total of 25 known miRNAs and 240 novel miRNA candidates that were differentially expressed in BTV-infected and uninfected ST cells were identified, and 251 and 8428 predicted target genes were annotated, respectively. Nine differentially expressed miRNAs and their mRNA targets were validated by quantitative reverse transcription-polymerase chain reaction. Targets prediction and functional analysis of these regulated miRNAs revealed significant enrichment for several signaling pathways including MAPK, PI3K-Akt, endocytosis, Hippo, NF-kB, viral carcinogenesis, FoxO, and JAK-STAT signaling pathways. This study provides a valuable basis for further investigation on the roles of miRNAs in BTV replication and pathogenesis.

Syrian Hamsters as a Small Animal Model for Emerging Infectious Diseases: Advances in Immunologic Methods

The use of small animal models for the study of infectious disease is critical for understanding disease progression and for developing prophylactic and therapeutic treatment options. For many diseases, Syrian golden hamsters have emerged as an ideal animal model due to their low cost, small size, ease of handling, and ability to accurately reflect disease progression in humans. Despite the increasing use and popularity of hamsters, there remains a lack of available reagents for studying hamster immune responses. Without suitable reagents for assessing immune responses, researchers are left to examine clinical signs and disease pathology. This becomes an issue for the development of vaccine and treatment options where characterizing the type of immune response generated is critical for understanding protection from disease. Despite the relative lack of reagents for use in hamsters, significant advances have been made recently with several hamster specific immunologic methods being developed. Here we discuss the progress of this development, with focus on classical methods used as well as more recent molecular methods. We outline what methods are currently available for use in hamsters and what is readily used as well as what limitations still exist and future perspectives of reagent and assay development for hamsters. This will provide valuable information to researchers who are deciding whether to use hamsters as an animal model.

Incorporation of GM-CSF or CD40L Enhances the Immunogenicity of Hantaan Virus-Like Particles

A safe and effective Hantaan virus (HTNV) vaccine is highly desirable because HTNV causes an acute and often fatal disease (hemorrhagic fever with renal syndrome, HFRS). Since the immunity of the inactivated vaccine is weak and the safety is poor, HTNV virus-like particles (VLPs) offer an attractive and safe alternative. These particles lack the viral genome but are perceived by the immune system as virus particles. We hypothesized that adding immunostimulatory signals to VLPs would enhance their efficacy. To accomplish this enhancement, we generated chimeric HTNV VLPs containing glycosylphosphatidylinositol (GPI)-anchored granulocyte macrophage colony-stimulating factor (GM-CSF) or CD40 ligand (CD40L) and investigated their biological activity in vitro. The immunization of mice with chimeric HTNV VLPs containing GM-CSF or CD40L induced stronger humoral immune responses and cellular immune responses compared to the HTNV VLPs and Chinese commercial inactivated hantavirus vaccine. Chimeric HTNV VLPs containing GM-CSF or CD40L also protected mice from an HTNV challenge. Altogether, our results suggest that anchoring immunostimulatory molecules into HTNV VLPs can be a potential approach for the control and prevention of HFRS.

Prediction of promiscuous T-cell epitopes in the Zika virus polyprotein: An in silico approach

OBJECTIVE

To predict immunogenic promiscuous T cell epitopes from the polyprotein of the Zika virus using a range of bioinformatics tools. To date, no epitope data are available for the Zika virus in the IEDB database.

METHODS

We retrieved nearly 54 full length polyprotein sequences of the Zika virus from the NCBI database belonging to different outbreaks. A consensus sequence was then used to predict the promiscuous T cell epitopes that bind MHC 1 and MHC II alleles using PorPred1 and ProPred immunoinformatic algorithms respectively. The antigenicity predicted score was also calculated for each predicted epitope using the VaxiJen 2.0 tool.

RESULTS

By using ProPred1, 23 antigenic epitopes for HLA class I and 48 antigenic epitopes for HLA class II were predicted from the consensus polyprotein sequence of Zika virus. The greatest number of MHC class I binding epitopes were projected within the NS5 (21%), followed by Envelope (17%). For MHC class II, greatest number of predicted epitopes were in NS5 (19%) followed by the Envelope, NS1 and NS2 (17% each). A variety of epitopes with good binding affinity, promiscuity and antigenicity were predicted for both the HLA classes.

CONCLUSION

The predicted conserved promiscuous T-cell epitopes examined in this study were reported for the first time and will contribute to the imminent design of Zika virus vaccine candidates, which will be able to induce a broad range of immune responses in a heterogeneous HLA population. However, our results can be verified and employed in future efficacious vaccine formulations only after successful experimental studies.

Novel strategies for development of hemorrhagic fever arenavirus live-attenuated vaccines

INTRODUCTION

Several arenaviruses, chiefly Lassa virus (LASV), cause hemorrhagic fever (HF) disease in humans and pose significant public health problems in their endemic regions. Moreover, HF arenaviruses represent credible biodefense threats. There are not FDA-approved arenavirus vaccines and current anti-arenaviral therapy is limited to an off-label use of ribavirin that is only partially effective.

AREAS COVERED

Live-attenuated vaccines (LAV) represent the most feasible approach to control HF arenaviruses within their endemic regions. Different platforms, including recombinant viral vectors expressing LASV antigens, and the use of attenuated reassortant arenaviruses, have been used to develop LAV candidates against LASV with promising results in animal models of LASV infection, but none of them has entered a clinical trial. These vaccine efforts have been the subject of recent reviews and will not be examined in this review, which is focused on new avenues for the development of safe and effective LAV to combat HF arenaviruses. Expert commentary: The development of arenavirus reverse genetics has provided investigators with a novel powerful approach to manipulate the genomes of HF arenaviruses, which has opened new avenues for the rapid development of safe and effective LAV to combat these human pathogens.

Proteomic analysis of sheep primary testicular cells infected with bluetongue virus

Bluetongue virus (BTV) causes a non‐contagious, arthropod‐transmitted disease in wild and domestic ruminants, such as sheep. In this study, we used iTRAQ labeling coupled with LC‐MS/MS for quantitative identification of differentially expressed proteins in BTV‐infected sheep testicular (ST) cells. Relative quantitative data were obtained for 4455 proteins in BTV‐ and mock‐infected ST cells, among which 101 and 479 proteins were differentially expressed at 24 and 48 h post‐infection, respectively, indicating further proteomic changes during the later stages of infection. Ten corresponding genes of differentially expressed proteins were validated via real‐time RT‐PCR. Expression levels of three representative proteins, eIF4a1, STAT1 and HSP27, were further confirmed via western blot analysis. Bioinformatics analysis disclosed that the differentially expressed proteins are primarily involved in biological processes related to innate immune response, signal transduction, nucleocytoplasmic transport, transcription and apoptosis. Several upregulated proteins were associated with the RIG‐I‐like receptor signaling pathway and endocytosis. To our knowledge, this study represents the first attempt to investigate proteome‐wide dysregulation in BTV‐infected cells with the aid of quantitative proteomics. Our collective results not only enhance understanding of the host response to BTV infection but also highlight multiple potential targets for the development of antiviral agents.

Animal Models

Full evaluation of the interactions between a virus and host during infection and clearance requires a living organism. A live animal is also necessary for development of vaccines requiring evaluation of immunogenicity and an immune response that protects from challenge. Study of the natural host for the virus is ideal, but often not possible. Mice have emerged over the last 60 years as the most popular animal model for studying viral pathogenesis due to extensive genetic and immunologic characterization, wide availability of reagents, inbred and transgenic strains, and small size. However, responses in mice are not always predictive of those in the natural host. Other species commonly used include guinea pigs, ferrets, chickens, and nonhuman primates. When choosing an animal model for a study, factors to be considered include host susceptibility to the infection, animal size, cost, availability of housing and reagents, potential confounding coinfections, and ethical restrictions.

Development and utilization of a custom PCR array workflow: analysis of gene expression in mycoplasma genitalium and guinea pig (Cavia porcellus)

Transcriptome analysis is a powerful tool for evaluating molecular pathways central to maturation of specific biological processes and disease states. Recently, PCR-based arrays have supplemented microarray and RNA-seq methodologies for studying changes in gene expression levels. PCR arrays are a more cost efficient alternative, however commercially available assemblies are generally limited to only a few more widely researched species (e.g., rat, human, and mouse). Consequently, the investigation of emerging or under-studied species is hindered until such assays are created. To address this need, we present data documenting the success of a developed workflow with enhanced potential to create and validate novel RT-PCR arrays for underrepresented species with whole or partial genome annotation. Utilizing this enhanced workflow, we have achieved a success rate of 80 % for first-round designs for over 400 primer pairs. Of these, ~160 distinct targets were sequence confirmed. Proof of concept studies using two unique arrays, one targeting the pathogenic bacterium Mycoplasma genitalium and the other specific for the guinea pig (Cavia porcellus), allowed us to identify significant (P < 0.05) changes in mRNA expression validated by subsequent qPCR. This flexible and adaptable platform provides a valuable and cost-effective alternative for gene expression analysis.

Transcriptome sequencing and development of an expression microarray platform for liver infection in adenovirus type 5-infected Syrian golden hamsters

The Syrian golden hamster is an attractive animal for research on infectious diseases and other diseases. We report here the sequencing, assembly, and annotation of the Syrian hamster transcriptome. We include transcripts from ten pooled tissues from a naïve hamster and one stimulated with lipopolysaccharide. Our data set identified 42,707 non-redundant transcripts, representing 34,191 unique genes. Based on the transcriptome data, we generated a custom microarray and used this new platform to investigate the transcriptional response in the Syrian hamster liver following intravenous adenovirus type 5 (Ad5) infection. We found that Ad5 infection caused a massive change in regulation of liver transcripts, with robust up-regulation of genes involved in the antiviral response, indicating that the innate immune response functions in the host defense against Ad5 infection of the liver. The data and novel platforms developed in this study will facilitate further development of this important animal model.

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Syrian hamster transcriptome; 42,707 transcripts representing 34,191 unique genes

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Syrian hamster custom expression microarray platform

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Ad5 intravenous infection of the Syrian hamster liver

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Ad5 upregulation of hamster liver genes involved in innate antiviral response.

Development of Small-Molecule Antivirals for Ebola

Ebola hemorrhagic fever is a deadly disease caused by infection with one of the Ebola virus species. Although a significant progress has recently been made in understanding of Ebola virus biology and pathogenesis, development of effective anti-Ebola treatments has not been very productive, compared to other areas of antiviral research (e.g., HIV and HCV infections). No approved vaccine or medicine is available for Ebola but several are currently under development. This review summarises attempts in identification, evaluation, and development of small-molecule candidates for treatment of Ebola viral disease, including the most promising experimental drugs brincidofovir (CMX001), BCX4430, and favipiravir (T-705).

Evaluation of Ebola Virus Inhibitors for Drug Repurposing

A systematic screen of FDA-approved drugs was performed to identify compounds with in vitro antiviral activities against Ebola virus (EBOV). Compounds active (>50% viral inhibition and <30% cellular toxicity) at a single concentration were tested in dose-response assays to quantitate the antiviral activities in replication and viral entry assays as well as cytotoxicity in the Vero cell line used to conduct these assays. On the basis of the approved human dosing, toxicity/tolerability, and pharmacokinetic data, seven of these in vitro hits from different pharmacological classes (chloroquine (CQ), amiodarone, prochlorperazine, benztropine, azithromycin, chlortetracycline, and clomiphene) were evaluated for their in vivo efficacy at a single dose and were administered via either intraperitoneal (ip) or oral route. Initially, azithromycin (100 mg/kg, twice daily, ip), CQ (90 mg/kg, twice daily, ip), and amiodarone (60 mg/kg, twice daily, ip) demonstrated significant increases in survival in the mouse model. After repeat evaluation, only CQ was found to reproducibly give significant efficacy in the mouse model with this dosing regimen. Azithromycin and CQ were also tested in a guinea pig model of EBOV infection over a range of doses, but none of the doses increased survival, and drug-related toxicity was observed at lower doses than in the mouse. These results show the benefits and specific challenges associated with drug repurposing and highlight the need for careful evaluation of approved drugs as rapidly deployable countermeasures against future pandemics.

Animal models for viral haemorrhagic fever

Viral haemorrhagic fever can be caused by one of a diverse group of viruses that come from four different families of RNA viruses. Disease severity can vary from mild self-limiting febrile illness to severe disease characterized by high fever, high-level viraemia, increased vascular permeability that can progress to shock, multi-organ failure and death. Despite the urgent need, effective treatments and preventative vaccines are currently lacking for the majority of these viruses. A number of factors preclude the effective study of these diseases in humans including the high virulence of the agents involved, the sporadic nature of outbreaks of these viruses, which are typically in geographically isolated areas with underserviced diagnostic capabilities, and the requirements for high level bio-containment. As a result, animal models that accurately mimic human disease are essential for advancing our understanding of the pathogenesis of viral haemorrhagic fevers. Moreover, animal models for viral haemorrhagic fevers are necessary to test vaccines and therapeutic intervention strategies. Here, we present an overview of the animal models that have been established for each of the haemorrhagic fever viruses and identify which aspects of human disease are modelled. Furthermore, we discuss how experimental design considerations, such as choice of species and virus strain as well as route and dose of inoculation, have an influence on animal model development. We also bring attention to some of the pitfalls that need to be avoided when extrapolating results from animal models.

Rift Valley fever virus infection in golden Syrian hamsters

Rift Valley fever virus (RVFV) is a formidable pathogen that causes severe disease and abortion in a variety of livestock species and a range of disease in humans that includes hemorrhagic fever, fulminant hepatitis, encephalitis and blindness. The natural transmission cycle involves mosquito vectors, but exposure can also occur through contact with infected fluids and tissues. The lack of approved antiviral therapies and vaccines for human use underlies the importance of small animal models for proof-of-concept efficacy studies. Several mouse and rat models of RVFV infection have been well characterized and provide useful systems for the study of certain aspects of pathogenesis, as well as antiviral drug and vaccine development. However, certain host-directed therapeutics may not act on mouse or rat pathways. Here, we describe the natural history of disease in golden Syrian hamsters challenged subcutaneously with the pathogenic ZH501 strain of RVFV. Peracute disease resulted in rapid lethality within 2 to 3 days of RVFV challenge. High titer viremia and substantial viral loads were observed in most tissues examined; however, histopathology and immunostaining for RVFV antigen were largely restricted to the liver. Acute hepatocellular necrosis associated with a strong presence of viral antigen in the hepatocytes indicates that fulminant hepatitis is the likely cause of mortality. Further studies to assess the susceptibility and disease progression following respiratory route exposure are warranted. The use of the hamsters to model RVFV infection is suitable for early stage antiviral drug and vaccine development studies.

Induction of specific humoral and cellular immune responses in a mouse model following gene fusion of HSP70C and Hantaan virus Gn and S0.7 in an adenoviral vector

Heat shock proteins (HSPs) display adjuvant functions when given as fusion proteins to enhance vaccination efficiency. To evaluate enhanced potency of Hantaan virus (HTNV) glycoprotein (GP) and nucleocapsid protein (NP) immunogenicity by heat shock protein 70 (HSP70), a recombinant adenovirus rAd-GnS0.7-pCAG-HSP70C expression vector was developed by genetically linking the HSP70 C-terminal gene (HSP70 359-610 aa, HSP70C) to the Gn and 0.7 kb fragment of the NP (aa1-274-S0.7). C57BL/6 mice were immunized with these recombinant adenoviral vectors. A series of immunological assays determined the immunogenicity of the recombinant adenoviral vectors. The results showed that rAd-GnS0.7-pCAG-HSP70C induced a stronger humoral and cellular immune response than other recombinant adenoviruses (rAd-GnS0.7-pCAG and rAd-GnS0.7) and the HFRS vaccine control. Animal protection experiments showed that rAd-GnS0.7-pCAG-HSP70C was effective at protecting C57BL/6 mice from HTNV infection. The results of the immunological experiments showed that HSP70C lead to enhanced vaccine potency, and suggested significant potential in the development of genetically engineered vaccines against HTNV.

Dendritic cell subtypes from lymph nodes and blood show contrasted gene expression programs upon Bluetongue virus infection

Human and animal hemorrhagic viruses initially target dendritic cells (DCs). It has been proposed, but not documented, that both plasmacytoid DCs (pDCs) and conventional DCs (cDCs) may participate in the cytokine storm encountered in these infections. In order to evaluate the contribution of DCs in hemorrhagic virus pathogenesis, we performed a genome-wide expression analysis during infection by Bluetongue virus (BTV), a double-stranded RNA virus that induces hemorrhagic fever in sheep and initially infects cDCs. Both pDCs and cDCs accumulated in regional lymph nodes and spleen during BTV infection. The gene response profiles were performed at the onset of the disease and markedly differed with the DC subtypes and their lymphoid organ location. An integrative knowledge-based analysis revealed that blood pDCs displayed a gene signature related to activation of systemic inflammation and permeability of vasculature. In contrast, the gene profile of pDCs and cDCs in lymph nodes was oriented to inhibition of inflammation, whereas spleen cDCs did not show a clear functional orientation. These analyses indicate that tissue location and DC subtype affect the functional gene expression program induced by BTV and suggest the involvement of blood pDCs in the inflammation and plasma leakage/hemorrhage during BTV infection in the real natural host of the virus. These findings open the avenue to target DCs for therapeutic interventions in viral hemorrhagic diseases.

The search for animal models for Lassa fever vaccine development

Lassa virus (LASV) is the most prevalent arenavirus in West Africa and is responsible for several hundred thousand infections and thousands of deaths annually. The sizeable disease burden, numerous imported cases of Lassa fever (LF) and the possibility that LASV can be used as an agent of biological warfare make a strong case for vaccine development. Currently there is no licensed LF vaccine and research and devlopment is hampered by the high cost of nonhuman primate animal models and by biocontainment requirements (BSL-4). In addition, a successful LF vaccine has to induce a strong cell-mediated cross-protective immunity against different LASV lineages. All of these challenges will be addressed in this review in the context of available and novel animal models recently described for evaluation of LF vaccine candidates.

A recently isolated Lassa virus from Mali demonstrates atypical clinical disease manifestations and decreased virulence in cynomolgus macaques

The virulence of Soromba-R, a Lassa virus strain recently isolated from southern Mali, was assessed in 2 animal models of Lassa fever: inbred strain 13 guinea pigs and cynomolgus macaques. In both models, the Malian isolate demonstrated tissue tropism and viral titers similar to those of historical Lassa virus isolates from Sierra Leone (Josiah) and Liberia (Z-132); however, the Soromba-R isolate was found to be less pathogenic, as determined by decreased mortality and prolonged time to euthanasia in macaques. Interestingly, in addition to the classic indicators of Lassa fever, Soromba-R infection presented with moderate to severe pulmonary manifestations in the macaque model. Analysis of host responses demonstrated increased immune activation in Soromba-R-infected macaques, particularly in neutrophil-activating or -potentiating proinflammatory cytokines or growth factors, including tumor necrosis factor α, macrophage inflammatory protein 1α, interleukin 1β, and granulocyte colony-stimulating factor, as well as interleukin 5, which may be responsible for the decreased lethality and uncharacteristic clinical presentation. These results suggest that the strain of Lassa virus circulating in Mali might be less pathogenic than strains circulating in the historical region of endemicity and may result in an atypical presentation for Lassa fever, which could complicate clinical diagnosis.

Animal Models of Human Viral Diseases

As the threat of exposure to emerging and reemerging viruses within a naive population increases, it is vital that the basic mechanisms of pathogenesis and immune response be thoroughly investigated. By using animal models in this endeavor, the response to viruses can be studied in a more natural context to identify novel drug targets, and assess the efficacy and safety of new products. This is especially true in the advent of the Food and Drug Administration's animal rule. Although no one animal model is able to recapitulate all the aspects of human disease, understanding the current limitations allows for a more targeted experimental design. Important facets to be considered before an animal study are the route of challenge, species of animals, biomarkers of disease, and a humane endpoint. This chapter covers the current animal models for medically important human viruses, and demonstrates where the gaps in knowledge exist.

Lymphocytic choriomeningitis virus infection in FVB mouse produces hemorrhagic disease

The viral family Arenaviridae includes a number of viruses that can cause hemorrhagic fever in humans. Arenavirus infection often involves multiple organs and can lead to capillary instability, impaired hemostasis, and death. Preclinical testing for development of antiviral or therapeutics is in part hampered due to a lack of an immunologically well-defined rodent model that exhibits similar acute hemorrhagic illness or sequelae compared to the human disease. We have identified the FVB mouse strain, which succumbs to a hemorrhagic fever-like illness when infected with lymphocytic choriomeningitis virus (LCMV). FVB mice infected with LCMV demonstrate high mortality associated with thrombocytopenia, hepatocellular and splenic necrosis, and cutaneous hemorrhage. Investigation of inflammatory mediators revealed increased IFN-γ, IL-6 and IL-17, along with increased chemokine production, at early times after LCMV infection, which suggests that a viral-induced host immune response is the cause of the pathology. Depletion of T cells at time of infection prevented mortality in all treated animals. Antisense-targeted reduction of IL-17 cytokine responsiveness provided significant protection from hemorrhagic pathology. F1 mice derived from FVB×C57BL/6 mating exhibit disease signs and mortality concomitant with the FVB challenged mice, extending this model to more widely available immunological tools. This report offers a novel animal model for arenavirus research and pre-clinical therapeutic testing.

Advanced vaccine candidates for Lassa fever

Lassa virus (LASV) is the most prominent human pathogen of the Arenaviridae. The virus is transmitted to humans by a rodent reservoir, Mastomys natalensis, and is capable of causing lethal Lassa Fever (LF). LASV has the highest human impact of any of the viral hemorrhagic fevers (with the exception of Dengue Fever) with an estimated several hundred thousand infections annually, resulting in thousands of deaths in Western Africa. The sizeable disease burden, numerous imported cases of LF in non-endemic countries, and the possibility that LASV can be used as an agent of biological warfare make a strong case for vaccine development. Presently there is no licensed vaccine against LF or approved treatment. Recently, several promising vaccine candidates have been developed which can potentially target different groups at risk. The purpose of this manuscript is to review the LASV pathogenesis and immune mechanisms involved in protection. The current status of pre-clinical development of the advanced vaccine candidates that have been tested in non-human primates will be discussed. Major scientific, manufacturing, and regulatory challenges will also be considered.

Animal models, prophylaxis, and therapeutics for arenavirus infections

Arenaviruses are enveloped, bipartite negative single-stranded RNA viruses that can cause a wide spectrum of disease in humans and experimental animals including hemorrhagic fever. The majority of these viruses are rodent-borne and the arenavirus family can be divided into two groups: the Lassa-Lymphocytic choriomeningitis serocomplex and the Tacaribe serocomplex. Arenavirus-induced disease may include characteristic symptoms ranging from fever, malaise, body aches, petechiae, dehydration, hemorrhage, organ failure, shock, and in severe cases death. Currently, there are few prophylactic and therapeutic treatments available for arenavirus-induced symptoms. Supportive care and ribavirin remain the predominant strategies for treating most of the arenavirus-induced diseases. Therefore, efficacy testing of novel therapeutic and prophylactic strategies in relevant animal models is necessary. Because of the potential for person-to-person spread, the ability to cause lethal or debilitating disease in humans, limited treatment options, and potential as a bio-weapon, the development of prophylactics and therapeutics is essential. This article reviews the current arenavirus animal models and prophylactic and therapeutic strategies under development to treat arenavirus infection.

The Syrian hamster model of hantavirus pulmonary syndrome

Hantavirus pulmonary syndrome (HPS) is a relatively rare, but frequently fatal disease associated with New World hantaviruses, most commonly Sin Nombre and Andes viruses in North and South America, respectively. It is characterized by fever and the sudden, rapid onset of severe respiratory distress and cardiogenic shock, which can be fatal in up to 50% of cases. Currently there are no approved antiviral therapies or vaccines for the treatment or prevention of HPS. A major obstacle in the development of effective medical countermeasures against highly pathogenic agents like the hantaviruses is recapitulating the human disease as closely as possible in an appropriate and reliable animal model. To date, the only animal model that resembles HPS in humans is the Syrian hamster model. Following infection with Andes virus, hamsters develop HPS-like disease which faithfully mimics the human condition with respect to incubation period and pathophysiology of disease. Perhaps most importantly, the sudden and rapid onset of severe respiratory distress observed in humans also occurs in hamsters. The last several years has seen an increase in studies utilizing the Andes virus hamster model which have provided unique insight into HPS pathogenesis as well as potential therapeutic and vaccine strategies to treat and prevent HPS. The purpose of this article is to review the current understanding of HPS disease progression in Syrian hamsters and discuss the suitability of utilizing this model to evaluate potential medical countermeasures against HPS.

Severe hemorrhagic fever in strain 13/N guinea pigs infected with Lujo virus

Lujo virus (LUJV) is a novel member of the Arenaviridae family that was first identified in 2008 after an outbreak of severe hemorrhagic fever (HF). In what was a small but rapidly progressing outbreak, this previously unknown virus was transmitted from the critically ill index patient to 4 attending healthcare workers. Four persons died during this outbreak, for a total case fatality of 80% (4/5). The suspected rodent source of the initial exposure to LUJV remains a mystery. Because of the ease of transmission, high case fatality, and novel nature of LUJV, we sought to establish an animal model of LUJV HF. Initial attempts in mice failed, but infection of inbred strain 13/N guinea pigs resulted in lethal disease. A total of 41 adult strain 13/N guinea pigs were infected with either wild-type LUJV or a full-length recombinant LUJV. Results demonstrated that strain 13/N guinea pigs provide an excellent model of severe and lethal LUJV HF that closely resembles what is known of the human disease. All infected animals experienced consistent weight loss (3–5% per day) and clinical illness characterized by ocular discharge, ruffled fur, hunched posture, and lethargy. Uniform lethality occurred by 11–16 days post-infection. All animals developed disseminated LUJV infection in various organs (liver, spleen, lung, and kidney), and leukopenia, lymphopenia, thrombocytopenia, coagulopathy, and elevated transaminase levels. Serial euthanasia studies revealed a temporal pattern of virus dissemination and increasing severity of disease, primarily targeting the liver, spleen, lungs, and lower gastrointestinal tract. Establishing an animal LUJV model is an important first step towards understanding the high pathogenicity of LUJV and developing vaccines and antiviral therapeutic drugs for this highly transmissible and lethal emerging pathogen.

The pathogenic arenaviruses are a diverse group of human pathogens capable of causing a wide range of human illness ranging from encephalitis to severe hemorrhagic fever throughout the New and Old World. In 2008, a previously unknown virus (now named Lujo virus) caused a high case fatality outbreak (80%) in southern Africa. Limited data available from these patients indicated that LUJV HF was characterized by thrombocytopenia, elevated liver transaminases, coagulopathy, viral antigen in multiple tissues, neurological symptoms in some cases, and eventual death. The source of exposure of the index patient remains unknown. Due to the unusually high lethality and rapid human to human spread, we sought to develop an animal model of Lujo hemorrhagic fever. We report here that after infection with Lujo virus, Strain 13/N guinea pigs develop a hemorrhagic fever syndrome similar to the disease observed in human patients. This animal model of severe Lujo hemorrhagic fever is a critical first step to increase our understanding of this highly pathogenic virus, and to develop anti-viral therapeutics or experimental vaccines for this new and unique threat to human health.

Extended protection against phlebovirus infection conferred by recombinant adenovirus expressing consensus interferon (DEF201)

Punta Toro virus (PTV; Bunyaviridae, Phlebovirus) is related to Rift Valley fever virus (RVFV), a pathogenic agent which causes severe disease in humans and livestock primarily in the sub-Saharan region of Africa. The recent range expansion of RVFV and the potential for its intentional release into naïve populations pose a significant threat to public health and agriculture. Studies modeling disease in rodents and nonhuman primates have shown that PTV and RVFV are highly sensitive to the antiviral effects of alpha interferon (IFN-α), an important component of the innate antiviral host response. While recombinant IFN-α has high therapeutic value, its utility for the treatment of neglected tropical diseases is hindered by its short in vivo half-life and costly production of longer-lasting pegylated IFNs. Here, we demonstrate extended preexposure protection against lethal PTV challenge following a single intranasal administration of DEF201, which is a replication-deficient human adenovirus type 5 vector engineered to constitutively express consensus IFN-α (cIFN-α) from transduced host cells. DEF201 was also efficacious when administered within 24 h as a postexposure countermeasure. Serum concentrations of cIFN-α could be detected as early as 8 h following treatment and persisted for more than 1 week. The prolonged antiphlebovirus prophylactic effect, low production costs, and ease of administration make DEF201 a promising agent for intervention during natural disease outbreaks and for countering possible bioterrorist acts.

Platelets support a protective immune response to LCMV by preventing splenic necrosis

Severe arenaviral infections in humans are characterized by clinical findings common to other viral hemorrhagic fevers (VHFs), including thrombocytopenia, leukopenia, skin and internal organ hemorrhages, high viral replication, splenic necrosis, and death. Host responses, rather than direct damage by the arenaviral replication, account for most of the observed pathology, but it is not known what protective roles platelets may have in each of the manifestations. To address this issue in an animal model, we compared nondepleted (100%), partially depleted (15%), and profoundly (< 2.5%) platelet depleted mice infected with the mouse arenavirus lymphocytic choriomeningitis virus (LCMV). Here, we describe that systemic bleedings and death were seen only in those animals receiving the stronger depletion treatment. Furthermore, we showed that the nonhemorrhagic but partially platelet-depleted mice were unable to control the viral replication because of generalized splenic necrosis, affecting innate and adaptive immune cells.These data suggest that, by their supportive roles in hemostasis, platelets may be preventing the severe pathology observed in human arenaviral infections.

Pathogenic Old World arenaviruses inhibit TLR2/Mal-dependent proinflammatory cytokines in vitro

Lymphocytic choriomeningitis virus (LCMV), the prototype arenavirus, and Lassa virus (LASV), the causative agent of Lassa fever (LF), have extensive strain diversity and significant variations in pathogenicity for humans and experimental animals. The WE strain of LCMV (LCMV-WE), but not the Armstrong (Arm) strain, induces a fatal LF-like disease in rhesus macaques. We also demonstrated that LASV infection of human macrophages and endothelial cells resulted in reduced levels of proinflammatory cytokines. Here we have shown that cells infected with LASV or with LCMV-WE suppressed Toll-like receptor 2 (TLR2)-dependent proinflammatory cytokine responses. The persisting isolate LCMV clone 13 (CL13) also failed to stimulate interleukin-6 (IL-6) in macrophages. In contrast, nonpathogenic Mopeia virus, which is a genetic relative of LASV and LCMV-Arm induced robust responses that were TLR2/Mal dependent, required virus replication, and were enhanced by CD14. Superinfection experiments demonstrated that the WE strain of LCMV inhibited the Arm-mediated IL-8 response during the early stage of infection. In cells transfected with the NF-κB-luciferase reporter, infection with LCMV-Arm resulted in the induction of NF-κB, but cells infected with LCMV-WE and CL13 did not. These results suggest that pathogenic arenaviruses suppress NF-κB-mediated proinflammatory cytokine responses in infected cells.

Progress in the experimental therapy of severe arenaviral infections

A number of viruses in the family Arenaviridae cause severe illness in humans. Lassa virus in West Africa and a number of agents in South America produce hemorrhagic fever in persons exposed to aerosolized excretions of the pathogens' rodent hosts. Because arenaviruses are not transmitted by arthropods, and person-to-person spread is rare, human infections occur singly and sporadically, and are usually not diagnosed until the patient is severely ill. Because the arenaviruses are naturally transmitted by the airborne route, they also pose a potential threat as aerosolized bioterror weapons. The broad-spectrum antiviral drug ribavirin was shown to reduce mortality from Lassa fever, and has been tested against Argentine hemorrhagic fever, but it is not an approved treatment for either disease. Human immune convalescent plasma was proven to be effective for Argentine hemorrhagic fever in a controlled trial. New treatments are needed to block viral replication without causing toxicity and to prevent the increased vascular permeability that is responsible for hypotension and shock. In this paper, we review current developments in the experimental therapy of severe arenaviral infections, focusing on drugs that have been tested in animal models, and provide a perspective on future research.

An antibody recognizing the apical domain of human transferrin receptor 1 efficiently inhibits the entry of all new world hemorrhagic Fever arenaviruses

Five New World (NW) arenaviruses cause human hemorrhagic fevers. Four of these arenaviruses are known to enter cells by binding human transferrin receptor 1 (hTfR1). Here we show that the fifth arenavirus, Chapare virus, similarly uses hTfR1. We also identify an anti-hTfR1 antibody, ch128.1, which efficiently inhibits entry mediated by the glycoproteins of all five viruses, as well as replication of infectious Junín virus. Our data indicate that all NW hemorrhagic fever arenaviruses utilize a common hTfR1 apical-domain epitope and suggest that therapeutic agents targeting this epitope, including ch128.1 itself, can be broadly effective in treating South American hemorrhagic fevers.

Evaluation of Lassa virus vaccine immunogenicity in a CBA/J-ML29 mouse model

Lassa fever (LF) is one of the most prevalent viral hemorrhagic fevers in West Africa responsible for thousands of deaths annually. The BSL-4 containment requirement and lack of small animal model to evaluate Lassa virus (LASV)-specific cell-mediated immunity (CMI) complicate development of effective LF vaccines. Here we have described a CBA/J-ML29 model allowing evaluation of LASV-specific CMI responses in mice. This model is based on Mopeia virus reassortant clone ML29, an attractive immunogenic surrogate for LASV. A single intraperitoneal (i.p.) immunization of CBA/J mice with ML29 protected animals against a lethal homologous intracerebral (i.c.) challenge with 588 LD(50). The ML29-immunized mice displayed negligible levels of LASV-specific antibody titers, but LASV-specific CMI responses were detectable early and peaked on day 8-10 after immunization. A T cell cytotoxicity assay in vivo showed a correlation between LASV-specific cytotoxicity and the timing of protection induced by the ML29 immunization. Notably, CBA/J mice that received CD8+ T cell-depleted splenocytes from ML29-immunized donors all succumbed to a lethal i.c. challenge, demonstrating that CD8+ T cells are critical in protection. The CBA/J-ML29 model can be useful immunological tool for the preliminary evaluation of immunogenicity and efficacy of vaccine candidates against LASV outside of BSL-4 containment facilities.

Crimean-Congo hemorrhagic fever virus-infected hepatocytes induce ER-stress and apoptosis crosstalk

Crimean-Congo hemorrhagic fever virus (CCHFV) is a widely distributed tick-borne member of the Nairovirus genus (Bunyaviridae) with a high mortality rate in humans. CCHFV induces a severe disease in infected patients that includes, among other symptoms, massive liver necrosis and failure. The interaction between liver cells and CCHFV is therefore important for understanding the pathogenesis of this disease. Here, we described the in vitro CCHFV-infection and -replication in the hepatocyte cell line, Huh7, and the induced cellular and molecular response modulation. We found that CCHFV was able to infect and replicate to high titres and to induce a cytopathic effect (CPE). We also observed by flow cytometry and real time quantitative RT-PCR evidence of apoptosis, with the participation of the mitochondrial pathway. On the other hand, we showed that the replication of CCHFV in hepatocytes was able to interfere with the death receptor pathway of apoptosis. Furthermore, we found in CCHFV-infected cells the over-expression of PUMA, Noxa and CHOP suggesting the crosstalk between the ER-stress and mitochondrial apoptosis. By ELISA, we observed an increase of IL-8 in response to viral replication; however apoptosis was shown to be independent from IL-8 secretion. When we compared the induced cellular response between CCHFV and DUGV, a mild or non-pathogenic Nairovirus for humans, we found that the most striking difference was the absence of CPE and apoptosis. Despite the XBP1 splicing and PERK gene expression induced by DUGV, no ER-stress and apoptosis crosstalk was observed. Overall, these results suggest that CCHFV is able to induce ER-stress, activate inflammatory mediators and modulate both mitochondrial and death receptor pathways of apoptosis in hepatocyte cells, which may, in part, explain the role of the liver in the pathogenesis of CCHFV.

The LANL hemorrhagic fever virus database, a new platform for analyzing biothreat viruses

Hemorrhagic fever viruses (HFVs) are a diverse set of over 80 viral species, found in 10 different genera comprising five different families: arena-, bunya-, flavi-, filo- and togaviridae. All these viruses are highly variable and evolve rapidly, making them elusive targets for the immune system and for vaccine and drug design. About 55 000 HFV sequences exist in the public domain today. A central website that provides annotated sequences and analysis tools will be helpful to HFV researchers worldwide. The HFV sequence database collects and stores sequence data and provides a user-friendly search interface and a large number of sequence analysis tools, following the model of the highly regarded and widely used Los Alamos HIV database [Kuiken, C., B. Korber, and R.W. Shafer, HIV sequence databases. AIDS Rev, 2003. 5: p. 52–61]. The database uses an algorithm that aligns each sequence to a species-wide reference sequence. The NCBI RefSeq database [Sayers et al. (2011) Database resources of the National Center for Biotechnology Information. Nucleic Acids Res., 39, D38–D51.] is used for this; if a reference sequence is not available, a Blast search finds the best candidate. Using this method, sequences in each genus can be retrieved pre-aligned. The HFV website can be accessed via http://hfv.lanl.gov.

Use of recombinant adenovirus vectored consensus IFN-α to avert severe arenavirus infection

Several arenaviruses can cause viral hemorrhagic fever, a severe disease with case-fatality rates in hospitalized individuals ranging from 15-30%. Because of limited prophylaxis and treatment options, new medical countermeasures are needed for these viruses classified by the National Institutes of Allergy and Infectious Diseases (NIAID) as top priority biodefense Category A pathogens. Recombinant consensus interferon alpha (cIFN-α) is a licensed protein with broad clinical appeal. However, while cIFN-α has great therapeutic value, its utility for biodefense applications is hindered by its short in vivo half-life, mode and frequency of administration, and costly production. To address these limitations, we describe the use of DEF201, a replication-deficient adenovirus vector that drives the expression of cIFN-α, for pre- and post-exposure prophylaxis of acute arenaviral infection modeled in hamsters. Intranasal administration of DEF201 24 h prior to challenge with Pichindé virus (PICV) was highly effective at protecting animals from mortality and preventing viral replication and liver-associated disease. A significant protective effect was still observed with a single dosing of DEF201 given two weeks prior to PICV challenge. DEF201 was also efficacious when administered as a treatment 24 to 48 h post-virus exposure. The protective effect of DEF201 was largely attributed to the expression of cIFN-α, as dosing with a control empty vector adenovirus did not protect hamsters from lethal PICV challenge. Effective countermeasures that are highly stable, easily administered, and elicit long lasting protective immunity are much needed for arena and other viral infections. The DEF201 technology has the potential to address all of these issues and may serve as a broad-spectrum antiviral to enhance host defense against a number of viral pathogens.

Effective oral favipiravir (T-705) therapy initiated after the onset of clinical disease in a model of arenavirus hemorrhagic Fever

Background

Lassa and Junín viruses are the most prominent members of the Arenaviridae family of viruses that cause viral hemorrhagic fever syndromes Lassa fever and Argentine hemorrhagic fever, respectively. At present, ribavirin is the only antiviral drug indicated for use in treatment of these diseases, but because of its limited efficacy in advanced cases of disease and its toxicity, safer and more effective antivirals are needed.

Methodology/Principal Findings

Here, we used a model of acute arenaviral infection in outbred guinea pigs based on challenge with an adapted strain of Pichindé virus (PICV) to further preclinical development of T-705 (Favipiravir), a promising broad-spectrum inhibitor of RNA virus infections. The guinea pig-adapted passage 19 PICV was uniformly lethal with an LD₅₀ of ∼5 plaque-forming units and disease was associated with fever, weight loss, thrombocytopenia, coagulation defects, increases in serum aspartate aminotransferase (AST) concentrations, and pantropic viral infection. Favipiravir (300 mg/kg/day, twice daily orally for 14 days) was highly effective, as all animals recovered fully from PICV-induced disease even when therapy was initiated one week after virus challenge when animals were already significantly ill with marked fevers and thrombocytopenia. Antiviral activity and reduced disease severity was evidenced by dramatic reductions in peak serum virus titers and AST concentrations in favipiravir-treated animals. Moreover, a sharp decrease in body temperature was observed shortly after the start of treatment. Oral ribavirin was also evaluated, and although effective, the slower rate of recovery may be a sign of the drug's known toxicity.

Conclusions/Significance

Our findings support further development of favipiravir for the treatment of severe arenaviral infections. The optimization of the experimental favipiravir treatment regimen in the PICV guinea pig model will inform critical future studies in the same species based on challenge with highly pathogenic arenaviruses such as Lassa and Junín.

Several viruses in the Arenaviridae family cause severe life-threatening hemorrhagic fever syndromes, which are considered neglected tropical diseases in endemic areas of Africa and South America. Ribavirin, the only licensed antiviral indicated for use has limited efficacy when treating advanced cases of disease and is associated with toxicity. In the present study, we use a model of acute arenaviral disease in guinea pigs based on infection with an adapted strain of the Pichindé arenavirus (PICV) to further preclinical development of a promising broad-spectrum antiviral drug candidate, favipiravir. Oral favipiravir was highly effective in the treatment of sick animals with marked fevers, as all recovered fully from lethal PICV infection even when therapy was initiated one week after virus challenge. Antiviral activity and reduced disease severity was evidenced by dramatic reductions in serum virus loads and serum aspartate aminotransferase, an enzyme released into the bloodstream following tissue damage and a marker for severe arenaviral infections. Moreover, a sharp decrease in fever was observed shortly after the onset of treatment. Our findings support further development of favipiravir for the treatment of severe arenaviral infections, for which there are presently no safe and effective therapies for treating advanced cases of disease.

Lymphocytic choriomeningitis virus (LCMV) infection of macaques: a model for Lassa fever

Arenaviruses such as Lassa fever virus (LASV) and lymphocytic choriomeningitis virus (LCMV) are benign in their natural reservoir hosts, and can occasionally cause severe viral hemorrhagic fever (VHF) in non-human primates and in human beings. LCMV is considerably more benign for human beings than Lassa virus, however certain strains, like the LCMV-WE strain, can cause severe disease when the virus is delivered as a high-dose inoculum. Here we describe a rhesus macaque model for Lassa fever that employs a virulent strain of LCMV. Since LASV must be studied within Biosafety Level-4 (BSL-4) facilities, the LCMV-infected macaque model has the advantage that it can be used at BSL-3. LCMV-induced disease is rarely as severe as other VHF, but it is similar in cases where vascular leakage leads to lethal systemic failure. The LCMV-infected macaque has been valuable for describing the course of disease with differing viral strains, doses and routes of infection. By monitoring system-wide changes in physiology and gene expression in a controlled experimental setting, it is possible to identify events that are pathognomonic for developing VHF and potential treatment targets.

Evidence of disseminated intravascular coagulation in a hemorrhagic fever with renal syndrome-scoring models and severe illness

BACKGROUND

Viral hemorrhagic fevers (VHF) are considered to be a serious threat to public health worldwide with up to 100 million cases annually. The general hypothesis is that disseminated intravascular coagulation (DIC) is an important part of the pathogenesis. The study objectives were to study the variability of DIC in consecutive patients with acute hemorrhagic fever with renal syndrome (HFRS), and to evaluate if different established DIC-scores can be used as a prognostic marker for a more severe illness.

METHOD AND FINDINGS

In a prospective study 2006-2008, data from 106 patients with confirmed HFRS were analyzed and scored for the presence of DIC according to six different templates based on criteria from the International Society on Thrombosis and Haemostasis (ISTH). The DIC-scoring templates with a fibrinogen/CRP-ratio were most predictive, with predictions for moderate/severe illness (p<0.01) and bleeding of moderate/major importance (p<0.05). With these templates, 18.9-28.3% of the patients were diagnosed with DIC.

CONCLUSIONS

DIC was found in about one fourth of the patients and correlated with a more severe disease. This supports that DIC is an important part of the pathogenesis in HFRS. ISTH-scores including fibrinogen/CRP-ratio outperform models without. The high negative predictive value could be a valuable tool for the clinician. We also believe that our findings could be relevant for other VHFs.