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 10 6 to 10 8 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.

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.

Ebola virus is one of the most virulent human pathogens, and infection with the Zaire ebolavirus (EBOV) species results in up to 90% mortality (1). Ebola outbreaks are mostly concentrated in remote areas of sub-Saharan Africa (2), but evidence of prior Ebola infection of swine in the Philippines (3), the presence of Ebola virus antibodies among orangutans in Indonesia (4) and bats in China (5), and the existence of an Ebola virus-like filovirus among European insectivorous bats (6) indicates that Ebola virus may be more widespread than previously thought. Since pigs have been established as a new intermediate host for Ebola (3), with effective transmission to nonhuman primates (NHPs) (7), there is the potential for Ebola to overwhelm larger populations should the virus be introduced in more-populous areas. Therefore, preventative and therapeutic strategies need to be developed to protect the population at large.While several prophylactic vaccine candidates against EBOV have shown preclinical promise in NHPs (8), the options for postexposure intervention are limited. A major reason is that EBOV typically kills its host within 6 to 10 days after the onset of symptoms (8), thereby providing a very small window for intervention before death from multiple organ failure. A recent promising treatment is a combination of three Ebola virus glycoprotein-specific murine monoclonal antibodies (MAbs), 1H3, 2G4, and 4G7, that protects 100% and 50% of NHPs when administered 24 and 48 h, respectively, after lethal EBOV infection (9-11). Another combination of chimeric humanized MAbs produced in plants was also able to save lethally infected NHPs, with 2 of 3 infected animals surviving when the MAbs were administered either 24 or 48 h after EBOV challenge (12). These findings constitute a substantial improvement in the length of the therapeutic window over previous postexposure strategies, which required administration within 60 min of exposure to EBOV in order to result in at least partial survival of NHPs. Ideally, an optimized treatment would be capable of saving infected individuals even when given hours before death.DEF201 is a replication-defective recombinant human adenovirus of serotype 5 (AdHu5) expressing consensus human alpha interferon (IFN-␣) (13). It was previously investigated as a broadspectrum antiviral and shown to be effective against several viral pathogens (14-18). While IFN-␣ treatment has been associated with various amounts of toxicity in the past, these adverse effects are mostly due to the short half-life of the protein, thereby necessitating extremely high doses in order to have a biologically relevant impact. Adenovirus-vectored administration of the IFN-␣ gene allows for steady delivery of the protein, which avoids the bolus dose effect of recombinant IFN-␣. Safety and toxicity studies on DEF201 in rodents indicate tolerability meeting regulatory requirements. Furthermore, combination studies to increase the effectiveness of an adenovirus-based EBOV vaccine showed that DEF201 was superior to all othe...

There are no FDA licensed vaccines or therapeutics for Venezuelan equine encephalitis virus (VEEV) which causes a debilitating acute febrile illness in humans that can progress to encephalitis. Previous studies demonstrated that murine and macaque monoclonal antibodies (mAbs) provide prophylactic and therapeutic efficacy against VEEV peripheral and aerosol challenge in mice. Additionally, humanized versions of two neutralizing mAbs specific for the E2 glycoprotein, 1A3B-7 and 1A4A-1, administered singly protected mice against aerosolized VEEV. However, no studies have demonstrated protection in nonhuman primate (NHP) models of VEEV infection. Here, we evaluated a chimeric antibody 1A3B-7 (c1A3B-7) containing mouse variable regions on a human IgG framework and a humanized antibody 1A4A-1 containing a serum half-life extension modification (Hu-1A4A-1-YTE) for their post-exposure efficacy in NHPs exposed to aerosolized VEEV. Approximately 24 hours after exposure, NHPs were administered a single bolus intravenous mAb. Control NHPs had typical biomarkers of VEEV infection including measurable viremia, fever, and lymphopenia. In contrast, c1A3B-7 treated NHPs had significant reductions in viremia and lymphopenia and on average approximately 50% reduction in fever. Although not statistically significant, Hu-1A4A-1-YTE administration did result in reductions in viremia and fever duration. Delay of treatment with c1A3B-7 to 48 hours post-exposure still provided NHPs protection from severe VEE disease through reductions in viremia and fever. These results demonstrate that post-exposure administration of c1A3B-7 protected macaques from development of severe VEE disease even when administered 48 hours following aerosol exposure and describe the first evaluations of VEEV-specific mAbs for post-exposure prophylactic use in NHPs. Viral mutations were identified in one NHP after c1A3B-7 treatment administered 24 hrs after virus exposure. This suggests that a cocktail-based therapy, or an alternative mAb against an epitope that cannot mutate without resulting in loss of viral fitness may be necessary for a highly effective therapeutic.

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.