Viral encephalitis is a compelling bioterror disease target. Most of the causative agents, such as Nipah (NV), West Nile (WNV), Japanese encephalitis (JE) and Rabies viruses are accessible in nature, can infect via aerosol delivery, a means suitable for weaponization, and cause a lethal outcome in at least some infected individuals. The clinical course of these RNA virus infections is usually non-specific such that diagnosis is often delayed until after virus reaches the CNS and existing therapies are no longer effective. The most lethal viral encephalitis is rabies, with few documented survivors of the disease until recently. While rabies virus is a Category C bioterror agent due to the availability of vaccines that are protective either prior to, or in the first days following exposure, the current reagents fail to clear the virus from the CNS. We have recently constructed a live-attenuated rabies vaccine virus, designated TriGAS, that has a unique safety profile and the capacity to clear an existing wild-type rabies virus from the CNS in mice. The primary objective of this project is translational, to determine if TriGAS administration, with or without passively administered rabies virus neutralizing antibodies, is likely to trigger non- cytolytic clearance of rabies virus from the human CNS. TriGAS therapy will be optimized in mice, validated in dogs, and preclinically correlated with biomarkers of protective immunity in TriGAS-infected human brain tissues in vitro. Cerebrospinal fluid and serum samples from patients who either died of or recovered from CNS rabies infection will be studied to determine whether aspects critical to the development of a protective immune response differ between humans and the animal models. If so, TriGAS will be engineered to mitigate the difference, for example by expressing a chemokine or cytokine. TriGAS will be engineered to express glycoproteins from other viruses capable of causing encephalitis, potentially to serve as a vaccine vector for the clearance of multiple viruses from the CNS. The secondary objective of the project is therefore to determine if TriGAS expressing NV, WNV, and JE glycoproteins have similar safety profiles and evidence of efficacy as the parent virus, the goal being to develop a single vaccine that can safely clear several types of encephalitis viruses from CNS tissues.
Virus infections of the brain are a major health concern, particularly with respect to bioterrorism, because there is no specific treatment of established infections. Rabies is a classic example. This project will examine whether a new vaccine that shows potential for clearing rabies virus from the nervous system is likely to be safe and effective in humans and can be modified for use in other epidemic virus infections of the brain.
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