Interferon alfacon-1 protects hamsters from lethal pichinde virus infection

Post-exposure intranasal IFNα suppresses replication and neuroinvasion of Venezuelan Equine Encephalitis virus within olfactory sensory neurons

BACKGROUND

Venezuelan Equine Encephalitis virus (VEEV) may enter the central nervous system (CNS) within olfactory sensory neurons (OSN) that originate in the nasal cavity after intranasal exposure. While it is known that VEEV has evolved several mechanisms to inhibit type I interferon (IFN) signaling within infected cells, whether this inhibits virologic control during neuroinvasion along OSN has not been studied.

METHODS

We utilized an established murine model of intranasal infection with VEEV and a repository of scRNAseq data from IFN-treated OSN to assess the cellular targets and IFN signaling responses after VEEV exposure.

RESULTS

We found that immature OSN, which express higher levels of the VEEV receptor LDLRAD3 than mature OSN, are the first cells infected by VEEV. Despite rapid VEEV neuroinvasion after intranasal exposure, olfactory neuroepithelium (ONE) and olfactory bulb (OB) IFN responses, as assessed by evaluation of expression of interferon signaling genes (ISG), are delayed for up to 48 h during VEEV neuroinvasion, representing a potential therapeutic window. Indeed, a single intranasal dose of recombinant IFNα triggers early ISG expression in both the nasal cavity and OB. When administered at the time of or early after infection, IFNα treatment delayed onset of sequelae associated with encephalitis and extended survival by several days. VEEV replication after IFN treatment was also transiently suppressed in the ONE, which inhibited subsequent invasion into the CNS.

CONCLUSIONS

Our results demonstrate a critical and promising first evaluation of intranasal IFNα for the treatment of human encephalitic alphavirus exposures.

Combating Lassa Fever in West African Sub-Region: Progress, Challenges, and Future Perspectives

Lassa fever (LF) is a rodent-borne disease that threatens human health in the sub-region of West Africa where the zoonotic host of Lassa virus (LASV) is predominant. Currently, treatment options for LF are limited and since no preventive vaccine is approved for its infectivity, there is a high mortality rate in endemic areas. This narrative review explores the transmission, pathogenicity of LASV, advances, and challenges of different treatment options. Our findings indicate that genetic diversity among the different strains of LASV and their ability to circumvent the immune system poses a critical challenge to the development of LASV vaccines/therapeutics. Thus, understanding the biochemistry, physiology and genetic polymorphism of LASV, mechanism of evading host immunity are essential for development of effective LASV vaccines/therapeutics to combat this lethal viral disease. The LASV nucleoprotein (NP) is a novel target for therapeutics as it functions significantly in several aspects of the viral life cycle. Consequently, LASV NP inhibitors could be employed as effective therapeutics as they will potentially inhibit LASV replication. Effective preventive control measures, vaccine development, target validation, and repurposing of existing drugs, such as ribavirin, using activity or in silico-based and computational bioinformatics, would aid in the development of novel drugs for LF management.

South American Hemorrhagic Fevers: A summary for clinicians

OBJECTIVES

This article is one of a series on acute, severe diseases of humans caused by emerging viruses for which there are no or limited licensed medical countermeasures. We approached this summary on South American Hemorrhagic Fevers (SAHF) from a clinical perspective that focuses on pathogenesis, clinical features, and diagnostics with an emphasis on therapies and vaccines that have demonstrated potential for use in an emergency situation through their evaluation in nonhuman primates (NHPs) and/or in humans.

METHODS

A standardized literature review was conducted on the clinical, pathological, vaccine, and treatment factors for SAHF as a group and for each individual virus/disease.

RESULTS

We identified 2 treatments and 1 vaccine platform that have demonstrated potential benefit for treating or preventing infection in humans and 4 other potential treatments currently under investigation.

CONCLUSION

We provide succinct summaries of these countermeasures to give the busy clinician a head start in reviewing the literature if faced with a patient with South American Hemorrhagic Fever. We also provide links to other authoritative sources of information.

Evaluation of cell viability dyes in antiviral assays with RNA viruses that exhibit different cytopathogenic properties

Studies were conducted to determine the performance of four dyes in assessing antiviral activities of compounds against three RNA viruses with differing cytopathogenic properties. Dyes included alamarBlue® measured by absorbance (ALB-A) and fluorescence (ALB-F), neutral red (NR), Viral ToxGlo™ (VTG), and WST-1. Viruses were chikungunya, dengue type 2, and Junin, which generally cause 100, 80-90, and 50% maximal cytopathic effect (CPE), respectively, in Vero or Vero 76 cells Compounds evaluated were 6-azauridine, BCX-4430, 3-deazaguanine, EICAR, favipiravir, infergen, mycophenolic acid (MPA), ribavirin, and tiazofurin. The 50% virus-inhibitory (EC50) values for each inhibitor and virus combination did not vary significantly based on the dye used. However, dyes varied in distinguishing the vitality of virus-infected cultures when not all cells were killed by virus infection. For example, VTG uptake into dengue-infected cells was nearly 50% when visual examination showed only 10-20% cell survival. ALB-A measured infected cell viability differently than ALB-F as follows: 16% versus 32% (dengue-infected), respectively, and 51% versus 72% (Junin-infected), respectively. Cytotoxicity (CC50) assays with dyes in uninfected proliferating cells produced similar CC50 values for EICAR (1.5-8.9μM) and MPA (0.8-2.5μM). 6-Azauridine toxicity was 6.1-17.5μM with NR, VTG, and WST-1, compared to 48-92μM with ALB-A and ALB-F (P<0.001). Curiously, the CC50 values for 3-deazaguanine were 83-93μM with ALB-F versus 2.4-7.0μM with all other dyes including ALB-A (P<0.001). Overall, ALB minimized the toxicities detected with these two inhibitors. Because the choice of dyes affected CC50 values, this impacted on the resulting in vitro selectivity indexes (calculated as CC50/EC50 ratio).

Development of real-time reverse transcriptase qPCR assays for the detection of Punta Toro virus and Pichinde virus

Background

Research with high biocontainment pathogens such as Rift Valley fever virus (RVFV) and Lassa virus (LASV) is expensive, potentially hazardous, and limited to select institutions. Surrogate pathogens such as Punta Toro virus (PTV) for RVFV infection and Pichinde virus (PICV) for LASV infection allow research to be performed under more permissive BSL-2 conditions. Although used as infection models, PTV and PICV have no standard real-time RT-qPCR assays to detect and quantify pathogenesis. PTV is also a human pathogen, making a standardized detection assay essential for biosurveillance. Here, we developed and characterized two real-time RT-qPCR assays for PICV and PTV by optimizing assay conditions and measuring the limit of detection (LOD) and performance in multiple clinical matrices.

Methods

Total nucleic acid from virus-infected Vero E6 cells was used to optimize TaqMan-minor groove binder (MGB) real-time RT-qPCR assays. A 10-fold dilution series of nucleic acid was used to perform analytical experiments with 60 replicates used to confirm assay LODs. Serum and whole blood spiked with 10-fold dilutions of PTV and PICV virus were assessed as matrices in a mock clinical context. The Cq, or cycle at which the fluoresce of each sample first crosses a threshold line, was determined using the second derivative method using Roche LightCycler 480 software version 1.5.1. Digital droplet PCR (ddPCR) was utilized to quantitatively determine RNA target counts/μl for PTV and PICV.

Results

Optimized PTV and PICV assays had LODs of 1000 PFU/ml and 100 PFU/ml, respectively, and this LOD was confirmed in 60/60 (PTV) and 58/60 (PICV) positive replicates. Preliminary mock clinical LODs remained consistent in serum and whole blood for PTV and PICV at 1000 PFU/ml and 100 PFU/ml. An exclusivity panel showed no cross reaction with near neighbors.

Conclusions

PTV and PICV Taq-man MGB based real-time RT-qPCR assays developed here showed relevant sensitivity and reproducibility in samples extracted from a variety of clinical matrices. These assays will be useful as a standard by researchers for future experiments utilizing PTV and PICV as infection models, offering the ability to track infection and viral replication kinetics during research studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-016-0509-3) contains supplementary material, which is available to authorized users.

Animal Models for the Study of Rodent-Borne Hemorrhagic Fever Viruses: Arenaviruses and Hantaviruses

Human pathogenic hantaviruses and arenaviruses are maintained in nature by persistent infection of rodent carrier populations. Several members of these virus groups can cause significant disease in humans that is generically termed viral hemorrhagic fever (HF) and is characterized as a febrile illness with an increased propensity to cause acute inflammation. Human interaction with rodent carrier populations leads to infection. Arenaviruses are also viewed as potential biological weapons threat agents. There is an increased interest in studying these viruses in animal models to gain a deeper understating not only of viral pathogenesis, but also for the evaluation of medical countermeasures (MCM) to mitigate disease threats. In this review, we examine current knowledge regarding animal models employed in the study of these viruses. We include analysis of infection models in natural reservoirs and also discuss the impact of strain heterogeneity on the susceptibility of animals to infection. This information should provide a comprehensive reference for those interested in the study of arenaviruses and hantaviruses not only for MCM development but also in the study of viral pathogenesis and the biology of these viruses in their natural reservoirs.

Viral microRNA effects on pathogenesis of polyomavirus SV40 infections in syrian golden hamsters

Effects of polyomavirus SV40 microRNA on pathogenesis of viral infections in vivo are not known. Syrian golden hamsters are the small animal model for studies of SV40. We report here effects of SV40 microRNA and influence of the structure of the regulatory region on dynamics of SV40 DNA levels in vivo. Outbred young adult hamsters were inoculated by the intracardiac route with 1×10⁷ plaque-forming units of four different variants of SV40. Infected animals were sacrificed from 3 to 270 days postinfection and viral DNA loads in different tissues determined by quantitative real-time polymerase chain reaction assays. All SV40 strains displayed frequent establishment of persistent infections and slow viral clearance. SV40 had a broad tissue tropism, with infected tissues including liver, kidney, spleen, lung, and brain. Liver and kidney contained higher viral DNA loads than other tissues; kidneys were the preferred site for long-term persistent infection although detectable virus was also retained in livers. Expression of SV40 microRNA was demonstrated in wild-type SV40-infected tissues. MicroRNA-negative mutant viruses consistently produced higher viral DNA loads than wild-type SV40 in both liver and kidney. Viruses with complex regulatory regions displayed modestly higher viral DNA loads in the kidney than those with simple regulatory regions. Early viral transcripts were detected at higher levels than late transcripts in liver and kidney. Infectious virus was detected infrequently. There was limited evidence of increased clearance of microRNA-deficient viruses. Wild-type and microRNA-negative mutants of SV40 showed similar rates of transformation of mouse cells in vitro and tumor induction in weanling hamsters in vivo. This report identified broad tissue tropism for SV40 in vivo in hamsters and provides the first evidence of expression and function of SV40 microRNA in vivo. Viral microRNA dampened viral DNA levels in tissues infected by SV40 strains with simple or complex regulatory regions.

The recent discovery of virally encoded microRNAs (miRNAs) raises the possibility of additional regulatory processes being involved in viral replication, immune recognition, and host cell survival. In this study, we sought to characterize the effect of SV40-encoded miRNAs and the structure of the viral regulatory region on infections in outbred Syrian golden hamsters. Results revealed that SV40 has a wide tissue tropism, including liver, kidney, spleen, lung, and brain, with kidney the preferred site for long-term persistent infection. Significant increases in tissue-associated viral DNA loads were observed with miRNA-negative mutant strains, whereas the presence of SV40 miRNAs had no effect on tumor induction and little effect on viral clearance. Our results provide the first evidence for SV40 miRNA expression and function in an in vivo animal model and highlight the complexity of regulation of SV40 viral replication and persistent infections.

Current drug discovery strategies against arenavirus infections

Arenaviruses are a large group of emerging viruses including several causative agents of severe hemorrhagic fevers with high mortality in man. Considering the number of people affected and the currently limited therapeutic options, novel efficacious therapeutics against arenaviruses are urgently needed. Over the past decade, significant advances in knowledge about the basic virology of arenaviruses have been accompanied by the development of novel therapeutics targeting different steps of the arenaviral life cycle. High-throughput, small-molecule screens identified potent and broadly active inhibitors of arenavirus entry that were instrumental for the dissection of unique features of arenavirus fusion. Novel inhibitors of arenavirus replication have been successfully tested in animal models and hold promise for application in humans. Late in the arenavirus life cycle, the proteolytic processing of the arenavirus envelope glycoprotein precursor and cellular factors critically involved virion assembly and budding provide further promising 'druggable' targets for novel therapeutics to combat human arenavirus infection.

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.

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.

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.

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.

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.

Development of a new tacaribe arenavirus infection model and its use to explore antiviral activity of a novel aristeromycin analog

Background

A growing number of arenaviruses can cause a devastating viral hemorrhagic fever (VHF) syndrome. They pose a public health threat as emerging viruses and because of their potential use as bioterror agents. All of the highly pathogenic New World arenaviruses (NWA) phylogenetically segregate into clade B and require maximum biosafety containment facilities for their study. Tacaribe virus (TCRV) is a nonpathogenic member of clade B that is closely related to the VHF arenaviruses at the amino acid level. Despite this relatedness, TCRV lacks the ability to antagonize the host interferon (IFN) response, which likely contributes to its inability to cause disease in animals other than newborn mice.

Methodology/Principal Findings

Here we describe a new mouse model based on TCRV challenge of AG129 IFN-α/β and -γ receptor-deficient mice. Titration of the virus by intraperitoneal (i.p.) challenge of AG129 mice resulted in an LD₅₀ of ∼100 fifty percent cell culture infectious doses. Virus replication was evident in the serum, liver, lung, spleen, and brain 4–8 days after inoculation. MY-24, an aristeromycin derivative active against TCRV in cell culture at 0.9 µM, administered i.p. once daily for 7 days, offered highly significant (P<0.001) protection against mortality in the AG129 mouse TCRV infection model, without appreciably reducing viral burden. In contrast, in a hamster model of arenaviral hemorrhagic fever based on challenge with clade A Pichinde arenavirus, MY-24 did not offer significant protection against mortality.

Conclusions/Significance

MY-24 is believed to act as an inhibitor of S-adenosyl-L-homocysteine hydrolase, but our findings suggest that it may ameliorate disease by blunting the effects of the host response that play a role in disease pathogenesis. The new AG129 mouse TCRV infection model provides a safe and cost-effective means to conduct early-stage pre-clinical evaluations of candidate antiviral therapies that target clade B arenaviruses.

Therapies for coronaviruses. Part 2: Inhibitors of intracellular life cycle

BACKGROUND

Severe acute respiratory syndrome (SARS) coronavirus emerged from an animal reservoir in 2002 and has the potential to reemerge, as shown by the occurrence of non-laboratory-associated new cases in the winter of 2003. In the absence of a vaccine, broad spectrum anticoronaviral medications are needed.

OBJECTIVE

Anticoronavirals targeting viral entry were reviewed in part I. Here we review anticoronaviral therapies directed against the intracellular life cycle, with an emphasis on allowed patents and pending patents.

METHOD

The published literature, in particular, patent publications is searched for relevant documents. The information is organized and critiqued.

RESULTS/CONCLUSION

Many promising anticoronaviral strategies are identified. Monoclonal antibodies, protease inhibitors, interferon-based drugs and nucleic-acid based antivirals are most advanced, each having its own advantages and disadvantages. A multi-pronged approach, keeping all venues open, is advocated.

Viral regulatory region effects on vertical transmission of polyomavirus SV40 in hamsters

Viral strain differences influence the oncogenic potential of polyomavirus simian virus 40 (SV40). We hypothesized that viral strain differences might also affect vertical transmission of SV40 in susceptible hosts. Pregnant Syrian golden hamsters were inoculated intraperitoneally with 10(7) plaque-forming units of SV40 and offspring were sacrificed post-delivery (1-21 days, 6 months). Organ extracts were analyzed for SV40 DNA by polymerase chain reaction assay. Transmission of SV40 from mother to offspring was detected in over half of litters. Most placentas were virus-positive. Mothers inoculated with SV40 strains containing complex regulatory regions transmitted virus more frequently than those infected with simple enhancer viruses (p<0.001). Virus was detected more often in progeny brain than in spleen (p<0.05). Several progeny were virus-positive at 6 months of age, suggesting viral persistence. Maternal animals retained virus in several tissues through day 21 and developed T-antigen antibodies. These results indicate that SV40 replicates in hamsters, vertical transmission of SV40 can occur, and the viral regulatory region influences transmission.

Treatment of late stage disease in a model of arenaviral hemorrhagic fever: T-705 efficacy and reduced toxicity suggests an alternative to ribavirin

A growing number of arenaviruses are known to cause viral hemorrhagic fever (HF), a severe and life-threatening syndrome characterized by fever, malaise, and increased vascular permeability. Ribavirin, the only licensed antiviral indicated for the treatment of certain arenaviral HFs, has had mixed success and significant toxicity. Since severe arenaviral infections initially do not present with distinguishing symptoms and are difficult to clinically diagnose at early stages, it is of utmost importance to identify antiviral therapies effective at later stages of infection. We have previously reported that T-705, a substituted pyrazine derivative currently under development as an anti-influenza drug, is highly active in hamsters infected with Pichinde virus when the drug is administered orally early during the course of infection. Here we demonstrate that T-705 offers significant protection against this lethal arenaviral infection in hamsters when treatment is begun after the animals are ill and the day before the animals begin to succumb to disease. Importantly, this coincides with the time when peak viral loads are present in most organs and considerable tissue damage is evident. We also show that T-705 is as effective as, and less toxic than, ribavirin, as infected T-705-treated hamsters on average maintain their weight better and recover more rapidly than animals treated with ribavirin. Further, there was no added benefit to combination therapy with T-705 and ribavirin. Finally, pharmacokinetic data indicate that plasma T-705 levels following oral administration are markedly reduced during the latter stages of disease, and may contribute to the reduced efficacy seen when treatment is withheld until day 7 of infection. Our findings support further pre-clinical development of T-705 for the treatment of severe arenaviral infections.

Cytokine patterns in a comparative model of arenavirus haemorrhagic fever in guinea pigs

Arenaviruses such as Lassa virus cause a spectrum of disease in humans ranging from mild febrile illness to lethal haemorrhagic fever. The contributions of innate immunity to protection or pathogenicity are unknown. We compared patterns of expression of cytokines of innate immunity in mild versus severe arenavirus disease using an established guinea pig model based on the macrophage-tropic arenavirus Pichinde virus (PICV). Cytokine transcripts were measured by using real-time RT-PCR in target organs and blood during mild infection (caused by PICV, P2 variant) and lethal haemorrhagic fever (caused by PICV, P18 variant). In the initial peritoneal target cells, virulent P18 infection was associated with significantly increased gamma interferon (IFN-gamma) and monocyte chemoattractant protein-1 (MCP-1, CCL2) mRNA levels relative to P2 infection. Peritoneal cells from P18-infected animals had decreased tumour necrosis factor alpha (TNF-alpha), interleukin (IL)-8 (CXCL-8) and IL-12p40 transcripts relative to mock-infected animals. Late in infection, P18-infected peripheral blood leukocytes (PBL) had decreased TNF-alpha, IFN-gamma, and regulated upon activation, normal T cell expressed and secreted (RANTES, CCL-5) cytokine transcripts relative to P2-infected PBL. We conclude that, in severe arenavirus disease, patterns of cytokine expression in the initially infected cells favour recruitment of additional target monocytes, while inhibiting some of their pro-inflammatory responses. Suppression rather than overexpression of pro-inflammatory cytokines accompanied the terminal shock in this model of arenavirus haemorrhagic fever.

Exploring kinase inhibitors as therapies for human arenavirus infections

Arenaviruses are rodent-borne RNA viruses, and some have the capacity to cause hemorrhagic fever and death in infected individuals and thus have been identified as a potential bioterrorism threat. Ribavirin and supportive care are currently the approved therapeutic options for individuals suffering from arenavirus-induced hemorrhagic fever. However, new research has suggested that immune plasma treatment or kinase inhibitors may provide a therapeutic option for treating arenavirus infections in humans. This article puts forth a perspective as to the potential use of kinase inhibitors as an antiviral therapeutic for arenavirus infections.

Prophylactic and therapeutic intervention of Punta Toro virus (Phlebovirus, Bunyaviridae) infection in hamsters with interferon alfacon-1

Punta Toro virus (PTV) is a member of the Bunyaviridae family, genus Phlebovirus, related to the highly pathogenic Rift Valley fever virus (RVFV). It produces a disease in hamsters that models severe Rift Valley fever (RVF) in humans. The recent outbreak of RVF in Kenya stresses the need to identify prophylactic and therapeutic measures for preventing and treating severe forms of disease. To this end, interferon (IFN) alfacon-1 (consensus IFN-alpha) was evaluated in cell culture against RVFV and PTV, and in the hamster PTV infection model. Survival outcome following treatment initiated pre- and post-virus challenge and the suppression of viral burden and liver disease in infected hamsters was determined. Pre-treatment of cell cultures with IFN alfacon-1 induced marked antiviral activity against both viruses. Intraperitoneal treatment of hamsters initiated 4 h prior to infection with PTV was highly protective and greatly limited liver disease and systemic and liver viral burden. Complete protection from a highly lethal challenge dose was afforded by treatment initiated 36 h following viral inoculation. Although efficacy was much reduced, IFN alfacon-1 therapy was still beneficial when started as late as 3-5 days post-virus exposure. These studies suggest that IFN alfacon-1 may be an effective treatment for early intervention following infection with RVFV.

Treatment of Argentine hemorrhagic fever

Argentine hemorrhagic fever (AHF) is a rodent-borne illness caused by the arenavirus Junin that is endemic to the humid pampas of Argentina. AHF has had significant morbidity since its emergence in the 1950s, with a case-fatality rate of the illness without treatment between 15% and 30%. The use of a live attenuated vaccine has markedly reduced the incidence of AHF. Present specific therapy involves the transfusion of immune plasma in defined doses of neutralizing antibodies during the prodromal phase of illness. However, alternative forms of treatment are called for due to current difficulties in early detection of AHF, related to its decrease in incidence, troubles in maintaining adequate stocks of immune plasma, and the absence of effective therapies for severely ill patients that progress to a neurologic–hemorrhagic phase. Ribavirin might be a substitute for immune plasma, provided that the supply is guaranteed. Immune immunoglobulin or monoclonal antibodies should also be considered. New therapeutic options such as those being developed for systemic inflammatory syndromes should also be valuated in severe forms of AHF.

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

A diverse group of highly pathogenic RNA viruses cause a severe multisystemic illness in humans commonly referred to as viral hemorrhagic fever (VHF). Although they can vary widely in clinical presentation, all VHFs share certain features that include intense fever, malaise, bleeding and shock. Effective antiviral therapies for most of the VHFs are lacking. Complicating development of intervention strategies is the relative infrequency and unpredictability of VHF outbreaks making human clinical trials extremely challenging or unfeasible. Therefore, animal models that can recapitulate human disease are essential to the development of effective antivirals and vaccines. In general, a good animal model of VHF will demonstrate systemic dispersion of the virus through infection of mononuclear phagocytes and dendritic cells, which induces the release of inflammatory mediators that increase vascular permeability and facilitate coagulation. The culmination of this process leads to significant loss of plasma volume and terminal hypovolemic shock. Although it is clear that nonhuman primate models are the most faithful to human disease, the more accessible and less costly rodent models, including those based on infection with related surrogate viruses, can reproduce certain components of VHF and can serve as suitable preclinical models for initial development of effective countermeasures. Such models are sufficient for testing of drugs that directly block viral replication, but may be inadequate for evaluating therapies that depend for their success on the activation or inhibition of host responses.

In vitro and in vivo activities of T-705 against arenavirus and bunyavirus infections

There is a need for the development of effective antivirals for the treatment of severe viral diseases caused by members of the virus families Bunyaviridae and Arenaviridae. The pyrazine derivative T-705 (6-fluoro-3-hydroxy-2-pyrazinecarboxamide) has demonstrated remarkable antiviral activity against influenza virus and, to a lesser degree, against some other RNA viruses (Y. Furuta, K. Takahashi, Y. Fukuda, M. Kuno, T. Kamiyama, K. Kozaki, N. Nomura, H. Egawa, S. Minami, Y. Watanabe, H. Narita, and K. Shiraki, Antimicrob. Agents Chemother., 46:977-981, 2002). Here, we report that T-705 is highly active against a panel of bunyaviruses (La Crosse, Punta Toro, Rift Valley fever, and sandfly fever viruses) and arenaviruses (Junin, Pichinde, and Tacaribe viruses) by cytopathic effect and virus yield reduction cell-based assays. The 50% effective concentrations for T-705 ranged from 5 to 30 microg/ml and 0.7 to 1.2 microg/ml against the bunyaviruses and arenaviruses examined, respectively. We also demonstrate that orally administered T-705 is efficacious in treating Punta Toro virus in the mouse and hamster infection models, as well as Pichinde virus infection in hamsters. When administered twice daily for 5 to 6 days, beginning 4 h pre- or 24 h post-Punta Toro virus challenge, a 30-mg/kg of body weight/day dose provided complete protection from death and limited viral burden and liver disease. A dose of 50 mg/kg/day was found to be optimal for treating Pichinde infection and limiting viral replication and disease severity. In general, T-705 was found to be more active than ribavirin in cell-based assays and in vivo, as reflected by substantially greater therapeutic indexes. Our results suggest that T-705 may be a viable alternative for the treatment of life-threatening bunyaviral and arenaviral infections.

Status presens of antiviral drugs and strategies: Part II: RNA VIRUSES (EXCEPT RETROVIRUSES)

More than 40 compounds have been formally licensed for clinical use as antiviral drugs, and half of these are used for the treatment of HIV infections. The others have been approved for the therapy of herpesvirus (HSV, VZV, CMV), hepadnavirus (HBV), hepacivirus (HCV) and myxovirus (influenza, RSV) infections. New compounds are in clinical development or under preclinical evaluation, and, again, half of these are targeting HIV infections. Yet, quite a number of important viral pathogens (i.e. HPV, HCV, hemorrhagic fever viruses) remain in need of effective and/or improved antiviral therapies.

Viruses and Viral Diseases

More than 40 compounds have been formally licensed for clinical use as antiviral drugs, and half of these are used for the treatment of human immunodeficiency virus (HIV) infections. The others have been approved for the therapy of herpesvirus (herpes simplex virus (HSV), varicella-zoster virus (VZV), cytomegalovirus (CMV)), hepadnavirus (hepatitis B virus (HBV)), hepacivirus (hepatitis C virus (HCV)), and myxovirus (influenza, respiratory synctural virus (RSV)) infections. New compounds are in clinical development or under preclinical evaluation, and, again, half of these target HIV infections. Yet, quite a number of important viral pathogens (i.e., human papilloma virus (HPV), HCV, hemorrhagic fever viruses) remain in need of effective and/or improved antiviral therapies.

Combinatorial ribavirin and interferon alfacon-1 therapy of acute arenaviral disease in hamsters

Several arenaviruses endemic to South America (Junin, Machupo, and Guanarito) and Africa (Lassa) are known to cause frequently fatal haemorrhagic fever. With the exception of ribavirin, which has demonstrated efficacy in cases of Lassa fever, there is no other effective therapeutic for the treatment of arenaviral haemorrhagic fever. We have recently reported that consensus interferon-a (IFN alfacon-1) can protect hamsters from lethal Pichinde virus (PCV) infection, which serves as a model for acute arenaviral disease in humans. Here we demonstrate highly effective therapy through the combined use of ribavirin with IFN alfacon-1 for the treatment of PCV infection in hamsters. Ribavirin was given orally, twice per day for 7 days, and IFN alfacon-1 was administered intraperitoneally once per day for 10 days. Treatments were initiated 1-5 days post-virus challenge using various dose combinations, many of which were less than optimal when the drugs were given independently. Combining suboptimal doses of ribavirin (5-10 mg/kg/day) with IFN alfacon-1 (5-10 microg/kg/day), we were able to demonstrate increased protection from mortality, reduced viral burden and liver disease, and greatly extended survival times as compared to treatments where drugs were administered alone. Our data indicate that combination therapy results in synergistic activity that may slow down the progression of the disease and decrease fatality rates associated with severe arenaviral infections in humans. Further, combination therapy reduces the effective dosage of ribavirin, which would serve to limit its toxicity.

Prophylactic treatment with recombinant Eimeria protein, alone or in combination with an agonist cocktail, protects mice from Banzi virus infection

A recombinant Eimeria protozoan protein antigen (rEA) has been shown to have antitumor and antiviral activity. The purpose of this study was to determine the effect of rEA treatment alone or in combination with an agonist cocktail consisting of granulocyte macrophage colony stimulating factor (GM-CSF), interferon gamma (IFN-gamma), interleukin 4 (IL-4), and anti CD-40 antibody, in the treatment of Banzi virus (BV) disease in BALB/c mice. Treatment with rEA resulted in a significant increase in survival, weight gain, and mean day to death in BV-infected mice and resulted in a significant decrease in brain virus titer. Treatment with rEA, in combination with a 4-agonist cocktail, improved disease parameters to a greater degree than rEA treatment alone. The effect of treatment with a reduced concentration of agonist cocktail or fewer components of the agonist cocktail, in combination with rEA, on disease outcome in BV-infected mice was also investigated. Treatment with rEA, alone or in combination with agonist cocktail, 24h after virus challenge did not improve disease. Treatment with rEA, alone or in combination with an agonist cocktail, is efficacious for the prophylaxis of BV infection in mice.

Effect of exogenous interferon and an interferon inducer on western equine encephalitis virus disease in a hamster model

Mice are used as models for western equine encephalitis virus (WEEV) infection, but high mortality is generally only seen with intracranial or intranasal challenge, while peripheral inoculation results in approximately 50% mortality and is not dose-dependent. Hamsters were therefore studied as a model for WEEV infection. Hamsters were highly sensitive to intraperitoneal (i.p.) infection with WEEV. Disease progression was rapid, and virus titers in serum, brain, liver, and kidney of infected hamsters peaked between 2 and 4 days post-virus inoculation (dpi). Foci of virus infection were detected in neurons of the cerebral cortex and midbrain. Pre-treatment i.p. with either interferon alfacon-1 (5 microg/kg/day) or with Ampligen (3.2 mg/kg/day) resulted in complete survival, reduced brain titers, and improved weight gain. This model of WEEV infection in hamsters appears to serve as a suitable model for the evaluation of potential therapeutic agents for the treatment of WEE disease.

Comparison of the inhibitory effects of interferon alfacon-1 and ribavirin on yellow fever virus infection in a hamster model

Antiviral compounds were evaluated for efficacy against yellow fever virus (YFV) in a hamster model of YFV-induced liver disease. Challenge with a 10(2) 50% cell culture infectious doses of YFV resulted in a 50-80% mortality rate in female hamsters. Virus was detected by quantitative real-time RT-PCR (QRT-PCR) in liver, kidney, spleen and serum with peak titers on 4-6 days post-viral challenge (dpi). Serum levels of alkaline phosphatase, alanine aminotransferase (ALT), bilirubin, blood urea nitrogen, potassium and creatinine were significantly elevated, while serum levels of albumin, amylase, glucose, calcium, globulin, phosphorus, sodium and total protein were significantly reduced. Packed cell volume and white blood cell count were significantly elevated during the course of the infection. Intraperitoneal treatment of hamsters with 0.5-5 microg/kg/day interferon (IFN) alfacon-1, 100mg/kg/day viramidine or 50 mg/kg/day ribavirin, initiated 4h prior to YFV challenge, resulted in significant improvement in survival and serum ALT levels. Treatment with IFN alfacon-1 or ribavirin starting 2dpi, also significantly improved survival and serum ALT levels in hamsters challenged with YFV. Pre- and post-virus exposure treatment with IFN alfacon-1 was efficacious in improving disease in YFV-infected hamsters.

Recombinant Eimeria protozoan protein elicits resistance to acute phlebovirus infection in mice but not hamsters

A protein antigen from an Eimeria protozoan has recently been reported to induce antitumor activity in mice. This activity most likely results from the strong induction of interkeukin-12 (IL-12) and gamma interferon (IFN-gamma), which are also essential factors in the establishment of protective immunity against viral infection. We evaluated recombinant Eimeria antigen (rEA) as a potential immunotherapeutic agent in mouse and hamster models of acute phleboviral disease. Punta Toro virus (PTV) was highly sensitive to a single dose of nanogram quantities of rEA in the mouse infection model. Intraperitoneal treatment with rEA also reduced virus load and liver damage associated with PTV infection. IL-12 was elicited following exposure of uninfected mice to quantities of rEA of 10 ng or greater, and the levels peaked at between 3 and 8 h postexposure. IFN-gamma release was induced more slowly and required less rEA (1 ng) to produce a significant rise in systemic levels. The induction of IL-12 and IFN-gamma involved in the coordination of innate and adaptive immune responses to microbial pathogens required myeloid differentiation factor 88, a signaling adaptor shared by most members of the Toll-like receptor (TLR) family. Despite encouraging results in the murine system, rEA failed to protect hamsters challenged with PTV. Our findings suggest that hamsters may lack functional TLR11, which has recently been shown to recognize a profilin-like protein homologous to rEA from the protozoan Toxoplasma gondii. Further investigation into the immunostimulatory capacity of rEA in other mammalian systems is necessary.

A guided tour through the antiviral drug field

Approximately 40 compounds have been formally licensed for clinical use as antiviral drugs, with half of these in use for the treatment of HIV infections. The remaining have been approved for use in the therapy of herpes virus (herpes simplex virus, varicella zoster virus and cytomegalovirus), hepadnavirus, hepacivirus and myxovirus (influenza and respiratory syncytial virus) infections. New compounds are in clinical development or under preclinical evaluation, and again, half of these are intended to target HIV infections. However, quite a number of important viral pathogens (i.e., human papillomavirus, hepatitis C virus and hemorrhagic fever viruses) remain in need of effective and/or improved antiviral therapies.