Pre- and post-exposure protection against Western equine encephalitis virus after single inoculation with adenovirus vector expressing interferon alpha

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.

Elevated Levels of Interferon-α Act Directly on B Cells to Breach Multiple Tolerance Mechanisms Promoting Autoantibody Production

OBJECTIVE

Elevated levels of serum interferon-α (IFNα) and the disruption of B cell tolerance are central to systemic lupus erythematosus (SLE) immunopathogenesis; however, the relationship between these 2 processes remains unclear. The purpose of this study was to investigate the impact of elevated IFNα levels on B cell tolerance mechanisms in vivo and determine whether any changes observed were due to the direct effect of IFNα on B cells.

METHODS

Two classical mouse models of B cell tolerance were used in conjunction with an adenoviral vector encoding IFNα to mimic the sustained elevations of IFNα seen in SLE. The role of B cell IFNα signaling, T cells, and Myd88 signaling was determined using B cell-specific IFNα receptor-knockout, CD4+ T cell-depleted, or Myd88-knockout mice, respectively. Flow cytometry, enzyme-linked immunosorbent assay, real-time quantitative polymerase chain reaction, and cell cultures were used to study the effects of elevated IFNα on the immunologic phenotype.

RESULTS

Elevation of serum IFNα disrupts multiple B cell tolerance mechanisms and leads to autoantibody production. This disruption was dependent upon B cell expression of IFNα receptor. Many of the IFNα-mediated alterations also required the presence of CD4+ T cells as well as Myd88, suggesting that IFNα acts directly on B cells to modify their response to Myd88 signaling and their ability to interact with T cells.

CONCLUSION

The results provide evidence that elevated IFNα levels act directly on B cells to facilitate autoantibody production and further highlight the importance of IFN signaling as a potential therapeutic target in SLE.

Reprogramming viral immune evasion for a rational design of next-generation vaccines for RNA viruses

Type I interferons (IFNs-α/β) are antiviral cytokines that constitute the innate immunity of hosts to fight against viral infections. Recent studies, however, have revealed the pleiotropic functions of IFNs, in addition to their antiviral activities, for the priming of activation and maturation of adaptive immunity. In turn, many viruses have developed various strategies to counteract the IFN response and to evade the host immune system for their benefits. The inefficient innate immunity and delayed adaptive response fail to clear of invading viruses and negatively affect the efficacy of vaccines. A better understanding of evasion strategies will provide opportunities to revert the viral IFN antagonism. Furthermore, IFN antagonism-deficient viruses can be generated by reverse genetics technology. Such viruses can potentially serve as next-generation vaccines that can induce effective and broad-spectrum responses for both innate and adaptive immunities for various pathogens. This review describes the recent advances in developing IFN antagonism-deficient viruses, their immune evasion and attenuated phenotypes in natural host animal species, and future potential as veterinary vaccines.

Antiviral activity of canine interferon lambda 3 expressed using a recombinant adenovirus against canine coronavirus, canine parvovirus, and canine distemper virus

Canine coronavirus (CCoV), canine parvovirus (CPV), and canine distemper virus (CDV) are highly contagious canine pathogens; dogs with these diseases are difficult to treat. In a previous study, we developed a recombinant adenovirus expressing canine interferon lambda 3 (Ad-caIFNλ3) in canine epithelial cells. In this study, we aimed to investigate the antiviral activity of Ad-caIFNλ3 against CCoV, CPV, and CDV in two canine cell lines, A72 and MDCK. Ad-caIFNλ3 transduction suppressed replication of these viruses without cytotoxicity. Our results suggest that Ad-caIFNλ3 may be a therapeutic candidate for canine viral diseases.

Alphaviruses: Host pathogenesis, immune response, and vaccine & treatment updates

Human pathogens belonging to the Alphavirus genus, in the Togaviridae family, are transmitted primarily by mosquitoes. The signs and symptoms associated with these viruses include fever and polyarthralgia, defined as joint pain and inflammation, as well as encephalitis. In the last decade, our understanding of the interactions between members of the alphavirus genus and the human host has increased due to the re-appearance of the chikungunya virus (CHIKV) in Asia and Europe, as well as its emergence in the Americas. Alphaviruses affect host immunity through cytokines and the interferon response. Understanding alphavirus interactions with both the innate immune system as well as the various cells in the adaptive immune systems is critical to developing effective therapeutics. In this review, we summarize the latest research on alphavirus-host cell interactions, underlying infection mechanisms, and possible treatments.

Canine interferon lambda 3 expressed using an adenoviral vector effectively induces antiviral activity against canine influenza virus

Interferon-lambda (IFN-λ) is a type-III IFN and is considered a candidate of antiviral therapeutics. Although the antiviral effects of IFN-λ have been investigated in several studies, it has not been clinically approved as an antiviral agent. In this study, an adenoviral vector expression system employing a tetracycline-operator system was developed to control the expression of canine IFN-λ3. The antiviral effects of canine IFN-λ3 were determined in Madin-Darby canine kidney cells and canine tracheal epithelial cells. After transducing each cell line with recombinant adenovirus containing canine interferon lambda3 gene (Ad-caIFNλ3), the mRNA-expression of interferon-stimulated genes Mx1, ISG15, and OAS1 increased significantly (P < 0.05). The replication of canine influenza virus (CIV) was significantly suppressed in Ad-caIFNλ3-infected cells. These results indicate that the newly constructed adenoviral vector system could express canine IFN-λ3, which could subsequently inhibit CIV replication in two canine cell lines. These data imply that the recombinant Ad-caIFNλ3 can potentially be used to treat canine influenza and other viral diseases.

Adenovirus vectored IFN-α protects mice from lethal challenge of Chikungunya virus infection

Chikungunya virus (CHIKV) is a mosquito-borne pathogen that is responsible for numerous large and geographical epidemics, causing millions of cases. However, there is no vaccine or therapeutics against CHIKV infection available. Interferon-alpha (IFN-α) has been shown to produce potent antiviral responses during viral infection. Herein we demonstrated the use of an adenovirus-vectored expressed mouse IFN-α (mDEF201) as a prophylactic and therapeutic treatment against CHIKV in vivo. 6-day-old BALB/c mice were pre- or post-treated intranasally with single dose of mDEF201 at 5 x 106 PFU per mouse and challenged with lethal dose of CHIKV. Complete survival protection was observed in mice upon a single dose of mDEF201 administration 1 days prior to virus challenge. Viral load in the serum and multiple organs were significantly reduced upon mDEF201 administration in a dose dependent manner as compare with adenovirus 5 vector placebo set. Histological analysis of the mice tissue revealed that mDEF201 could significantly reduce the tissue morphological abnormities, mainly infiltration of immune cells and muscle fibre necrosis caused by CHIKV infection. In addition, administration of mDEF201 at 6 hours post CHIKV challenge also showed promising inhibitory effect against viral replication and dissemination. In conclusion, single-dose of intranasal administration with mDEF201 as a prophylactic or therapeutic agent within 6 hours post CHIKV infection is highly protective against a lethal challenge of CHIKV in the murine model.

Effect of exogenous expression of IFN-γ on the new world alphavirus replication and infection

Aim: IFN-γ plays an important role in control of the old world alphavirus infection. However, the role of IFN-γ in the infection by the new world alphaviruses is not well characterized. Materials & methods: Ad5-mIFN-γ, a recombinant, replication-deficient human adenovirus, was constructed to express mouse IFN-γ (mIFN-γ) and a mouse, lethal challenge model of the new world alphavirus western equine encephalitis virus (WEEV) was used. Results: A single-dose injection of Ad5-mIFN-γ produced a high level of mIFN-γ in mice. Cells inoculated with Ad5-mIFN-γ restricted the replication of WEEV. A single-dose injection of Ad5-mIFN-γ delayed the WEEV infection and extended the survival time in mice. Conclusion: IFN-γ restricts the WEEV infection.

Post-exposure treatment of non-human primates lethally infected with Ebola virus with EBOTAb, a purified ovine IgG product

Despite sporadic outbreaks of Ebola virus (EBOV) over the last 4 decades and the recent public health emergency in West Africa, there are still no approved vaccines or therapeutics for the treatment of acute EBOV disease (EVD). In response to the 2014 outbreak, an ovine immunoglobulin therapy was developed, termed EBOTAb. After promising results in the guinea pig model of EBOV infection, EBOTAb was tested in the cynomolgus macaque non-human primate model of lethal EBOV infection. To ensure stringent therapeutic testing conditions to replicate likely clinical usage, EBOTAb was first delivered 1, 2 or 3 days post-challenge with a lethal dose of EBOV. Results showed a protective effect of EBOTAb given post-exposurally, with survival rates decreasing with increasing time after challenge. Viremia results demonstrated that EBOTAb resulted in a decreased circulation of EBOV in the bloodstream. Additionally, assay of liver enzymes and histology analysis of local tissues identified differences between EBOTAb-treated and untreated groups. The results presented demonstrate that EBOTAb conferred protection against EBOV when given post-exposure and should be explored and developed further as a potential intervention strategy for future outbreaks, which are likely to occur.

Single dose of an adenovirus vectored mouse interferon-α protects mice from lethal EV71 challenge

Enterovirus 71 (EV71) causes hand-foot-and-mouth diseases as well as neurological complications in young children. Interferon (IFN) can inhibit the replication of many viruses with low cytotoxic effects. Previously, an adenovirus vectored mouse interferon-α (DEF201), subtype 5, was generated by Wu et al, 2007. In this study, the antiviral effects of DEF201 against EV71 were evaluated in a murine model. 6-day-old BALB/c mice were administered a single dose of DEF201 before or after infection with lethal dose of EV71. The survival rate, clinical symptoms, tissue viral loads and histology pathogenesis were evaluated. IFN gene expression following a single dose of DEF201 maintained high concentrations of 100-9000 pg/mL for more than 7 days in mice serum. Pre-infection administration of a single dose of 10⁶ PFU of DEF201 offered full protection of the mice against EV71 infection compared with the empty Ad5 vector control. In addition, virus load in DEF201-treated mice muscle tissue was significantly decreased as compared with empty vector control. Histopathology analysis revealed that DEF201 significantly prevented the development of severe tissue damage with reduction of viral antigen in the murine muscle tissue. Post-infection treatment at 6 h offered full protection and partial protection at 12 h, indicating that DEF201 could be used as an anti-EV71 therapeutic agent in early stage of EV71 infection. In addition, our study showed that DEF201 enhanced the neutralization ability of serum in EV71-vaccinated mice, implying that DEF201 could promote the production of specific anti-EV71 antibodies. In conclusion, single dose of DEF201 is highly efficacious as a prophylactic agent against EV71 infection in vivo.

Addressing Therapeutic Options for Ebola Virus Infection in Current and Future Outbreaks

Ebola virus can cause severe hemorrhagic disease with high fatality rates. Currently, no specific therapeutic agent or vaccine has been approved for treatment and prevention of Ebola virus infection of humans. Although the number of Ebola cases has fallen in the last few weeks, multiple outbreaks of Ebola virus infection and the likelihood of future exposure highlight the need for development and rapid evaluation of pre- and postexposure treatments. Here, we briefly review the existing and future options for anti-Ebola therapy, based on the data coming from rare clinical reports, studies on animals, and results from in vitro models. We also project the mechanistic hypotheses of several potential drugs against Ebola virus, including small-molecule-based drugs, which are under development and being tested in animal models or in vitro using various cell types. Our paper discusses strategies toward identifying and testing anti-Ebola virus properties of known and medically approved drugs, especially those that can limit the pathological inflammatory response in Ebola patients and thereby provide protection from mortality. We underline the importance of developing combinational therapy for better treatment outcomes for Ebola patients.

Virulence determinants of New World alphaviruses and broad-acting therapeutic strategies

ABSTRACT 

New World alphaviruses of eastern equine encephalitis virus (EEEV), western equine encephalitis virus (WEEV) and Venezuelan equine encephalitis virus (VEEV) are endemic in North and South America, and infect humans and equine through mosquitoes. In addition, these viruses are highly infectious when aerosolized, making them potential biowarfare and bioterrorism agents. Currently, no approved vaccines or drugs are available for prevention and treatment. Extensive studies have been carried out to understand molecular mechanisms of virulence among New World alphaviruses. This review will focus on virus-encoded, interferon antagonizing proteins which play major role in determination of virulence of New World alphaviruses. Understanding of molecular mechanism of these proteins will shed light on development of broad-acting antivirals against New World alphaviruses.

mAbs and Ad-vectored IFN-α therapy rescue Ebola-infected nonhuman primates when administered after the detection of viremia and symptoms

ZMAb is a promising treatment against Ebola virus (EBOV) disease that has been shown to protect 50% (two of four) of nonhuman primates (NHPs) when administered 2 days post-infection (dpi). To extend the treatment window and improve protection, we combined ZMAb with adenovirus-vectored interferon-α (Ad-IFN) and evaluated efficacy in EBOV-infected NHPs. Seventy-five percent (three of four) and 100% (four of four) of cynomolgus and rhesus macaques survived, respectively, when treatment was initiated after detection of viremia at 3 dpi. Fifty percent (two of four) of the cynomolgus macaques survived when Ad-IFN was given at 1 dpi, followed by ZMAb starting at 4 dpi, after positive diagnosis. The treatment was able to suppress viremia reaching ~10(5) TCID50 (median tissue culture infectious dose) per milliliter, leading to survival and robust specific immune responses. This study describes conditions capable of saving 100% of EBOV-infected NHPs when initiated after the presence of detectable viremia along with symptoms.

An update on the use of antibodies against the filoviruses

Multiple recent, independent studies have confirmed that passively administered antibodies can provide effective postexposure therapy in nonhuman primates after exposure to an otherwise lethal dose of Ebola virus or Marburg virus. In this article, we review composition and performance of the antibody cocktails tested thus far, what is known about antibody epitopes on the viral glycoprotein target and ongoing research questions in further development of such cocktails for pre-exposure or emergency postexposure use.

Buggy Creek virus (Togaviridae: Alphavirus) upregulates expression of pattern recognition receptors and interferons in House Sparrows (Passer domesticus)

Birds serve as reservoirs for at least 10 arthropod-borne viruses, yet specific immune responses of birds to arboviral infections are relatively unknown. Here, adult House Sparrows were inoculated with an arboviral alphavirus, Buggy Creek virus (BCRV), or saline, and euthanized between 1 and 3 days postinoculation. Virological dynamics and gene expression dynamics were investigated. Birds did not develop viremia postinoculation, but cytopathic virus was found in the skeletal muscle and spleen of birds 1 and 3 days postinoculation (DPI). Viral RNA was detected in the blood of BCRV-infected birds 1 and 2 DPI, in oral swabs 1-3 DPI, and in brain, heart, skeletal muscle, and spleen 1-3 DPI. Multiple genes were significantly upregulated following BCRV infection, including pattern recognition receptors (TLR7, TLR15, RIG-1), type I interferon (IFN-α), and type II interferon (IFN-γ). This is the first study to report avian immunological gene expression profiles following an arboviral infection.

Protection against Chikungunya virus induced arthralgia following prophylactic treatment with adenovirus vectored interferon (mDEF201)

Recent outbreaks of Chikungunya virus (CHIKV) infection have resulted in millions of cases of disease with significant morbidity. No approved antiviral treatments exist for the prevention or treatment of this viral disease. Infection with CHIKV results in a high rate of symptomatic disease that primarily includes a debilitating arthralgia. To model this cardinal disease manifestation, adult DBA/1J mice were challenged with CHIKV by footpad injection. Viremia and hind limb virus titers increased ∼100-fold while spleen virus increased >1000-fold within 1day post-virus infection (dpi). Footpad swelling was measured over a 10-day period, with peak swelling observed between 6 and 7dpi. Histology of the hind leg at the site of virus challenge showed evidence of myositis and synovitis starting on 5dpi. Cytokine profiling of the hind limb at the site of inoculation revealed a biphasic inflammatory response represented by an increase in IL-6, MCP-1, IFN-γ, MIP-1α, RANTES, and IL-17. To investigate the prophylactic capacity of IFN, mice were treated with mDEF201, an adenovirus-vectored IFN-α. Intranasal administration of a single 10(7)pfu/ml dose of mDEF201 administered 21days to 24h prior to infection, significantly reduced footpad swelling, virus titers in the hind leg and spleen, and several inflammatory cytokines. Efficacy was not observed when treatment was initiated 24h after virus challenge. This arthralgia model of CHIKV recapitulates relevant disease features commonly observed in human disease making it applicable to preclinical testing of therapies that target both viral replication and the associated joint disease.

Post-exposure therapy of filovirus infections

Filovirus infections cause fatal hemorrhagic fever characterized by the initial onset of general symptoms before rapid progression to severe disease; the most virulent species can cause death to susceptible hosts within 10 days after the appearance of symptoms. Before the advent of monoclonal antibody (mAb) therapy, infection of nonhuman primates (NHPs) with the most virulent filovirus species was fatal if interventions were not administered within minutes. A novel nucleoside analogue, BCX4430, has since been shown to also demonstrate protective efficacy with a delayed treatment start. This review summarizes and evaluates the potential of current experimental candidates for treating filovirus disease with regard to their feasibility and use in the clinic, and assesses the most promising strategies towards the future development of a pan-filovirus medical countermeasure.

Type 1 interferon gene transfer enhances host defense against pulmonary Streptococcus pneumoniae infection via activating innate leukocytes

Pneumococcal infections are the leading cause of community-acquired pneumonia. Although the type 1 interferon-α (IFN-α) is a well-known antiviral cytokine, the role of IFN-α in antipneumococcal host defense and its therapeutic potential remain poorly understood. We have investigated these issues by using a murine transgene expression model. We found that in control animals, Streptococcus pneumoniae infection caused severe weight loss and excessive lung inflammation, associated with rapid bacterial outgrowth. In contrast, the animals that received a single dose of an adenoviral vector expressing IFN-α prior to pneumococcal infection demonstrated rapid and effective control of bacterial replication and lung inflammation and improved clinical outcome. Enhanced protection by IFN-α was due to increased activation of neutrophils and macrophages with increased release of reactive oxygen and nitrogen species and bacterial killing. Furthermore, we found that raised levels of IFN-α in the lung remained immune protective even when the gene transfer vector was given at a time postpneumococcal infection. Our study thus shows that the classically antiviral type 1 IFN can be exploited for enhancing immunity against pneumococcal infection via its activating effects on innate immune cells. Our findings hold implications for the therapeutic use of IFN-α gene transfer strategies to combat pneumococcal infections.

Human-like antibodies neutralizing Western equine encephalitis virus

This study describes the development of the first neutralizing antibodies against Western equine encephalitis virus (WEEV), a member of the genus Alphavirus. WEEV is transmitted by mosquitoes and can spread to the human central nervous system, causing symptoms ranging from mild febrile reactions to life-threatening encephalitis. WEEV has been classified as a biological warfare agent by the US Centers for Disease Control and Prevention. No anti-WEEV drugs are currently commercially available. Neutralizing antibodies are useful for the pre- and post-exposure treatment of WEEV infections. In this study, two immune antibody gene libraries were constructed from two macaques immunized with inactivated WEEV. Four antibodies were selected from these libraries and recloned as scFv-Fc, with a human Fc part. These antibodies bound WEEV specifically in ELISA with little or no cross-reaction with other alphaviruses. They were further analyzed by immunohistochemistry. All binders were suitable for the intracellular detection of WEEV particles. Neutralizing activity was determined in vitro. Three of the four antibodies were found to be neutralizing; about 1 ng/mL of the best antibody (ToR69–3A2) neutralized 50% of 5x10⁴ TCID₅₀/mL. Due to its human-like nature with a germinality index of 89% (VH) and 91% (VL), the ToR69–3A2 antibody is a promising candidate for future passive vaccine development.

Sustained protection against Ebola virus infection following treatment of infected nonhuman primates with ZMAb

Ebola virus (EBOV) is one of the most lethal filoviruses, with mortality rates of up to 90% in humans. Previously, we demonstrated 100% and 50% survival of EBOV-infected cynomologus macaques with a combination of 3 EBOV-GP-specific monoclonal antibodies (ZMAb) administered at 24 or 48 hours post-exposure, respectively. The survivors demonstrated EBOV-GP–specific humoral and cell-mediated immune responses. In order to evaluate whether the immune response induced in NHPs during the ZMAb treatment and EBOV challenge is sufficient to protect survivors against a subsequent exposure, animals that survived the initial challenge were rechallenged at 10 or 13 weeks after the initial challenge. The animals rechallenged at 10 weeks all survived whereas 4 of 6 animals survived a rechallenge at 13 weeks. The data indicate that a robust immune response was generated during the successful treatment of EBOV-infected NHPs with EBOV, which resulted in sustained protection against a second lethal exposure.

Effects of nasal or pulmonary delivered treatments with an adenovirus vectored interferon (mDEF201) on respiratory and systemic infections in mice caused by cowpox and vaccinia viruses

An adenovirus 5 vector encoding for mouse interferon alpha, subtype 5 (mDEF201) was evaluated for efficacy against lethal cowpox (Brighton strain) and vaccinia (WR strain) virus respiratory and systemic infections in mice. Two routes of mDEF201 administration were used, nasal sinus (5-µl) and pulmonary (50-µl), to compare differences in efficacy, since the preferred treatment of humans would be in a relatively small volume delivered intranasally. Lower respiratory infections (LRI), upper respiratory infections (URI), and systemic infections were induced by 50-µl intranasal, 10-µl intranasal, and 100-µl intraperitoneal virus challenges, respectively. mDEF201 treatments were given prophylactically either 24 h (short term) or 56d (long-term) prior to virus challenge. Single nasal sinus treatments of 10(6) and 10(7) PFU/mouse of mDEF201 protected all mice from vaccinia-induced LRI mortality (comparable to published studies with pulmonary delivered mDEF201). Systemic vaccinia infections responded significantly better to nasal sinus delivered mDEF201 than to pulmonary treatments. Cowpox LRI infections responded to 10(7) mDEF201 treatments, but a 10(6) dose was only weakly protective. Cowpox URI infections were equally treatable by nasal sinus and pulmonary delivered mDEF201 at 10(7) PFU/mouse. Dose-responsive prophylaxis with mDEF201, given one time only 56 d prior to initiating a vaccinia virus LRI infection, was 100% protective from 10(5) to 10(7) PFU/mouse. Improvements in lung hemorrhage score and lung weight were evident, as were decreases in liver, lung, and spleen virus titers. Thus, mDEF201 was able to treat different vaccinia and cowpox virus infections using both nasal sinus and pulmonary treatment regimens, supporting its development for humans.

Vaccines and therapeutics for the encephalitic alphaviruses

This article is a review of vaccines and therapeutics in development for the encephalitic alphaviruses, which includes eastern equine encephalitis virus, western equine encephalitis virus and Venezuelan equine encephalitis virus. The encephalitic alphaviruses are endemic within regions in North and South America. Hosts are normally exposed after being bitten by infectious mosquitoes, and infection can develop into encephalitis in equines and humans with severe rates of morbidity and mortality. These viruses are also potential biological threat agents, being highly infectious via an aerosol route of exposure. In humans, equine encephalitis virus and western equine encephalitis virus are neurotropic viruses targeting the CNS and causing encephalitis. Mortality rates are 50 and 10%, respectively, for these viruses. On the other hand, Venezuelan equine encephalitis virus produces a systemic influenza-like illness with pathogenesis in the lungs and lymphoid tissue in adults and older children. The incidence of encephalitis is less than 5% in younger children with a case–mortality rate of 1%. The host response to virus infectivity is briefly discussed, along with a number of promising therapeutic and prophylactic approaches. These approaches can be broadly classified as: virus-specific, including vaccines, antibody therapy and gene-silencing oligonucleotides; or broad-spectrum, including interferon and activation of the host‘s innate immunity.

Monoclonal antibodies combined with adenovirus-vectored interferon significantly extend the treatment window in Ebola virus-infected guinea pigs

Monoclonal antibodies (MAbs) are currently a promising treatment strategy against Ebola virus infection. This study combined MAbs with an adenovirus-vectored interferon (DEF201) to evaluate the efficacy in guinea pigs and extend the treatment window obtained with MAbs alone. Initiating the combination therapy at 3 days postinfection (d.p.i.) provided 100% survival, a significant improvement over survival with either treatment alone. The administration of DEF201 within 2 d.p.i. permits later MAb use, with protective efficacy observed up to 8 d.p.i.

Immune parameters correlate with protection against ebola virus infection in rodents and nonhuman primates

Ebola virus causes severe hemorrhagic fever in susceptible hosts. Currently, no licensed vaccines or treatments are available; however, several experimental vaccines have been successful in protecting rodents and nonhuman primates (NHPs) from the lethal Zaire ebolavirus (ZEBOV) infection. The objective of this study was to evaluate immune responses correlating with survival in these animals after lethal challenge with ZEBOV. Knockout mice with impaired ability to generate normal T and/or B cell responses were vaccinated and challenged with ZEBOV. Vaccine-induced protection in mice was mainly mediated by B cells and CD4(+) T cells. Vaccinated, outbred guinea pigs and NHPs demonstrated the highest correlation between survival and levels of total immunoglobulin G (IgG) specific to the ZEBOV glycoprotein (ZGP). These results highlight the relevance of total ZGP-specific IgG levels as a meaningful correlate of protection against ZEBOV exposure.

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.

Therapy and long-term prophylaxis of vaccinia virus respiratory infections in mice with an adenovirus-vectored interferon alpha (mDEF201)

An adenovirus 5 vector encoding for mouse interferon alpha, subtype 5 (mDEF201) was evaluated for efficacy against lethal vaccinia virus (WR strain) respiratory infections in mice. mDEF201 was administered as a single intranasal treatment either prophylactically or therapeutically at doses of 10⁶ to 10⁸ plaque forming units/mouse. When the prophylactic treatment was given at 56 days prior to infection, it protected 90% of animals from death (100% protection for treatments given between 1–49 days pre-infection), with minimal weight loss occurring during infection. Surviving animals re-challenged with virus 22 days after the primary infection were protected from death, indicating that mDEF201 did not compromise the immune response against the initial infection. Post-exposure therapy was given between 6–24 h after vaccinia virus exposure and protection was afforded by a 10⁸ dose of mDEF201 given at 24 h, whereas a 10⁷ dose was effective up to 12 h. Comparisons were made of the ability of mDEF201, given either 28 or 1 day prior to infection, to inhibit tissue virus titers and lung infection parameters. Lung, liver, and spleen virus titers were inhibited to nearly the same extent by either treatment, as were lung weights and lung hemorrhage scores (indicators of pneumonitis). Lung virus titers were significantly (>100-fold) lower than in the placebo group, and the other infection parameters in mDEF201 treated mice were nearly at baseline. In contrast, viral titers and lung infection parameters were high in the placebo group on day 5 of the infection. These results demonstrate the long-acting prophylactic and treatment capacity of mDEF201 to combat vaccinia virus infections.

Recent developments in anti-severe acute respiratory syndrome coronavirus chemotherapy

Severe acute respiratory syndrome coronavirus (SARS-CoV) emerged in early 2003 to cause a very severe acute respiratory syndrome, which eventually resulted in a 10% case-fatality rate. Owing to excellent public health measures that isolated focus cases and their contacts, and the use of supportive therapies, the epidemic was suppressed to the point that further cases have not appeared since 2005. However, despite intensive research since then (over 3500 publications), it remains an untreatable disease. The potential for re-emergence of the SARS-CoV or a similar virus with unknown but potentially serious consequences remains high. This is due in part to the extreme genetic variability of RNA viruses such as the coronaviruses, the many animal reservoirs that seem to be able host the SARS-CoV in which reassortment or recombination events could occur and the ability coronaviruses have to transmit relatively rapidly from species to species in a short period of time. Thus, it seems prudent to continue to explore and develop antiviral chemotherapies to treat SARS-CoV infections. To this end, the various efficacious anti-SARS-CoV therapies recently published from 2007 to 2010 are reviewed in this article. In addition, compounds that have been tested in various animal models and were found to reduce virus lung titers and/or were protective against death in lethal models of disease, or otherwise have been shown to ameliorate the effects of viral infection, are also reported.

Treatment of yellow fever virus with an adenovirus-vectored interferon, DEF201, in a hamster model

Interferon (IFN) is an innate immune response protein that is involved in the antiviral response during viral infection. Treatment of acute viral infections with exogenous interferon may be effective but is generally not feasible for clinical use due to many factors, including cost, stability, and availability. To overcome these limitations, an adenovirus type 5-vectored consensus alpha IFN, termed DEF201, was constructed as a potential way to deliver sustained therapeutic levels of systemic IFN. To demonstrate the efficacy of DEF201 against acute flaviviral disease, various concentrations of the construct were administered as a single intranasal dose prior to virus infection, which resulted in a dose-responsive, protective effect in a hamster model of yellow fever virus (YFV) disease. A DEF201 dose of 5×10(7) PFU/animal administered intranasally just prior to YFV challenge protected 100% of the animals, while a 10-fold lower DEF201 dose exhibited lower, although significant, levels of protection. Virus titers in the liver and serum and levels of serum alanine aminotransferase were all significantly reduced as a result of DEF201 administration at all doses tested. No toxicity, as indicated by weight loss or gross morbidity, was observed in non-YFV-infected animals treated with DEF201. Protection of YFV-infected animals was observed when DEF201 was delivered as early as 7 days prior to virus challenge and as late as 2 days after virus challenge, demonstrating effective prophylaxis and therapy in a hamster model of disease. Overall, it appears that DEF201 is effective in the treatment of YFV in a hamster model.

Evaluation of Different Strategies for Post-Exposure Treatment of Ebola Virus Infection in Rodents

Zaire Ebola virus (ZEBOV) is a pathogen that causes severe hemorrhagic fever in humans and non-human primates. There are currently no licensed vaccines or approved treatments available against ZEBOV infections. The goal of this work was to evaluate different treatment strategies in conjunction with a replication deficient, recombinant human adenovirus serotype 5-based vaccine expressing the Zaire Ebola virus glycoprotein (Ad-CAGoptZGP) in Ebola infected mice and guinea pigs.Guinea pigs were treated with Ad-CAGoptZGP in combination with different treatment strategies after challenge with guinea pig adapted-ZEBOV (GA-ZEBOV). B10.BR mice were used to further characterize efficacy and immune responses following co-administration of Ad-CAGoptZGP with the most effective treatment: AdHu5 expressing recombinant IFN-α (hereafter termed DEF201) after challenge with a lethal dose of mouse adapted-ZEBOV (MA-ZEBOV).In mice, DEF201 treatment was able to elicit full protection against a lethal dose of MA-ZEBOV when administered 30 minutes after infection. In guinea pigs the Ad-CAGoptZGP and DEF201 combination therapy elicited full protection when treated 30 minutes post-exposure and were a superior treatment to Ad-CAGoptZGP supplemented with recombinant IFN-α protein. Further analysis of the immune response revealed that addition of DEF201 to Ad-CAGoptZGP enhances the resulting adaptive immune response against ZGP. The results highlight the importance of the innate immune response in the prevention of ZEBOV pathogenesis and support further development of the Ad-CAGoptZGP with DEF201 treatment combination for post-exposure therapy against ZEBOV infection.

Principles of antidote pharmacology: an update on prophylaxis, post-exposure treatment recommendations and research initiatives for biological agents

The use of biological agents has generally been confined to military-led conflicts. However, there has been an increase in non-state-based terrorism, including the use of asymmetric warfare, such as biological agents in the past few decades. Thus, it is becoming increasingly important to consider strategies for preventing and preparing for attacks by insurgents, such as the development of pre- and post-exposure medical countermeasures. There are a wide range of prophylactics and treatments being investigated to combat the effects of biological agents. These include antibiotics (for both conventional and unconventional use), antibodies, anti-virals, immunomodulators, nucleic acids (analogues, antisense, ribozymes and DNAzymes), bacteriophage therapy and micro-encapsulation. While vaccines are commercially available for the prevention of anthrax, cholera, plague, Q fever and smallpox, there are no licensed vaccines available for use in the case of botulinum toxins, viral encephalitis, melioidosis or ricin. Antibiotics are still recommended as the mainstay treatment following exposure to anthrax, plague, Q fever and melioidosis. Anti-toxin therapy and anti-virals may be used in the case of botulinum toxins or smallpox respectively. However, supportive care is the only, or mainstay, post-exposure treatment for cholera, viral encephalitis and ricin - a recommendation that has not changed in decades. Indeed, with the difficulty that antibiotic resistance poses, the development and further evaluation of techniques and atypical pharmaceuticals are fundamental to the development of prophylaxis and post-exposure treatment options. The aim of this review is to present an update on prophylaxis and post-exposure treatment recommendations and research initiatives for biological agents in the open literature from 2007 to 2009.

Single-dose intranasal administration with mDEF201 (adenovirus vectored mouse interferon-alpha) confers protection from mortality in a lethal SARS-CoV BALB/c mouse model

Interferons (IFNs) are a first line of defense against viral infection. Herein we describe the use of an adenovirus vectored mouse IFN alpha gene (mDEF201) as a prophylactic and treatment countermeasure in a SARS-CoV-infected BALB/c mouse model. Complete survival protection was observed in mice given a single dose of mDEF201 administered intranasally 1, 3, 5, 7, or 14 days prior to lethal SARS-CoV challenge (p < 0.001), and body weights of these treated mice were unaffected by the challenge. In addition, low doses of mDEF201 protected lungs in a dose dependent manner as measured by a reduction in gross pathology. Intranasal treatment with mDEF201 ranging from 10⁶ to 10⁸ PFU significantly protected mice against a lethal SARS-CoV infection in a dose dependent manner up to 12 h post infection (p < 0.001). The data suggest that mDEF201 is a new class of antiviral agent further development as treatment for SARS-CoV infections.

Chikungunya virus arthritis in adult wild-type mice

Chikungunya virus is a mosquito-borne arthrogenic alphavirus that has recently reemerged to produce the largest epidemic ever documented for this virus. Here we describe a new adult wild-type mouse model of chikungunya virus arthritis, which recapitulates the self-limiting arthritis, tenosynovitis, and myositis seen in humans. Rheumatic disease was associated with a prolific infiltrate of monocytes, macrophages, and NK cells and the production of monocyte chemoattractant protein 1 (MCP-1), tumor necrosis factor alpha (TNF-alpha), and gamma interferon (IFN-gamma). Infection with a virus isolate from the recent Reunion Island epidemic induced significantly more mononuclear infiltrates, proinflammatory mediators, and foot swelling than did an Asian isolate from the 1960s. Primary mouse macrophages were shown to be productively infected with chikungunya virus; however, the depletion of macrophages ameliorated rheumatic disease and prolonged the viremia. Only 1 microg of an unadjuvanted, inactivated, whole-virus vaccine derived from the Asian isolate completely protected against viremia and arthritis induced by the Reunion Island isolate, illustrating that protection is not strain specific and that low levels of immunity are sufficient to mediate protection. IFN-alpha treatment was able to prevent arthritis only if given before infection, suggesting that IFN-alpha is not a viable therapy. Prior infection with Ross River virus, a related arthrogenic alphavirus, and anti-Ross River virus antibodies protected mice against chikungunya virus disease, suggesting that individuals previously exposed to Ross River virus should be protected from chikungunya virus disease. This new mouse model of chikungunya virus disease thus provides insights into pathogenesis and a simple and convenient system to test potential new interventions.

Encephalitic alphaviruses

This review will cover zoonotic, encephalitic alphaviruses in the family Togaviridae. Encephalitic alphaviruses, i.e. Western- (WEEV), Eastern- (EEEV), Venezuelan equine encephalitis virus (VEEV) and, more rarely, Ross River virus, Chikungunya virus and Highlands J virus (HJV), are neuroinvasive and may cause neurological symptoms ranging from mild (e.g., febrile illness) to severe (e.g., encephalitis) in humans and equines. Among the naturally occurring alphaviruses, WEEV, EEEV and VEEV have widespread distributions in North, Central and South America. WEEV has found spanning the U.S. from the mid-West (Michigan and Illinois) to the West coast and extending to Canada with human cases reported in 21 states. EEEV is found along the Gulf (Texas to Florida) and Atlantic Coast (Georgia to New Hampshire), as well as in the mid-West (Wisconsin, Illinois and Michigan) and in Canada, with human cases reported in 19 states. In contrast, transmission of VEEV occurs predominantly in Central and South America. As with their geographical distribution, equine encephalitis viruses differ in their main mosquito vector species and their zoonotic potential.

Alpha interferon as an adenovirus-vectored vaccine adjuvant and antiviral in Venezuelan equine encephalitis virus infection

There are no widely available vaccines or antiviral drugs capable of protecting against infection with Venezuelan equine encephalitis virus (VEEV), although an adenovirus vector expressing VEEV structural proteins protects mice from challenge with VEEV and is potentially a vaccine suitable for human use. This work examines whether alpha interferon (IFN-α) could act as an adjuvant for the adenovirus-based vaccine. IFN-α was either expressed by a plasmid linked to the adenovirus vaccine or encoded by a separate adenovirus vector administered as a mixture with the vaccine. In contrast to previous reports with other vaccines, the presence of IFN-α reduced the antibody response to VEEV. When IFN-α was encoded by adenovirus, the lack of a VEEV-specific response was accompanied by an increase in the immune response to the adenovirus vector. IFN-α also plays a direct role in defence against virus infection, inducing the expression of a large number of antiviral proteins. Adenovirus-delivered IFN-α protected mice from VEEV disease when administered 24 h prior to challenge, but not when administered 6 h post-challenge, suggesting that up to 24 h is required for the development of the IFN-mediated antiviral response.