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Principal Investigator: Dr. Nikolaus Osterrieder
Contact Information: E-mail: no34@cornell.edu - Phone: 607-253-4045
Sponsor: Harry M. Zweig Memorial Fund for Equine Research
Grant Number: N/A
Title: Equine Herpesvirus Type 1 Virulence and Vaccine Efficacy
Annual Direct Cost: $74,353
Project Period: 01/01/06-12/31/07
Description (provided by applicant): The broad objectives of this proposal are to determine the roles of two secreted glycoproteins, gp2 and gG, in equine herpesvims type 1 (EHV-1) cellular tropism, immune evasion, virulence and vaccine protection. We hypothesize that gp2 and gG thwart the horse's immune response and/or influence cell tropism. We will test the in vivo and in vitro properties of mutant EHV-1 harboring various forms of gp2 and/or are devoid of gG. Mutant viruses will be generated from a recently isolated, highly pathogenic and neurovirulent isolate, termed NY05. The influence of gp2 and gG on the degree and duration of immune protection will also be tested.
1) To construct mutant viruses from NY05. The New York 2005 (NY05) isolate of EHV-1 was isolated from a lethal neurological case of EHV-1 infection. The isolate was tested in horses and the induction.of neurological signs under experimental conditions, was achieved. NY05 was cloned as a bacterial artificial chromosome (BAC), and we will abrogate or modify gp2 and/or gG expression by applying a newly established mutagenesis method that allows markerless modification of cloned viral genomes in Escherichia coli.
2) To test growth of gp2 variants and gG-negative rNY05 in vitro and in vivo. Recent studies in our laboratory have shown that EHV-1 is able to infect T cells, but predominantly targets B lymphocytes after addition to peripheral blood mononuclear cells (PBMC). Susceptibility of equine B cells to EHV-1 has not been reported. Using fluorescent viruses that express mRFP1 attached to the small capsid protein, we shall investigate whether recombinant viruses lacking the major attachment protein gp2 and/or gG exhibit different cellular tropisms in vitro. Freshly prepared PBMC as well as primary endothelial cells will be used for these assays. In addition, growth properties and tropisms of selected mutant viruses in horses will be assessed.
3) To test the role of gp2 and gG in immune protection. Thwarting of the host immune response by gp2 and gG may be at least, partially responsible for the weak and short-lived immunity against EHV-1. Mutant viruses from vaccine strain RacH will be generated that express various forms of gp2 and/or are devoid of gG. Horses will be vaccinated with mutant viruses and challenge infection with the NY05 vires will follow. The clinical outcome and the quantity and quality, of the immune response after challenge infection will be assessed. Levels of secretory IgA and circulating Ig isotypes (IgGa, IgGb, and IgG(T)) will be determined, because recent data indicates that effective immune protection is reflected by a low EHV-1-specific IgG(T) to IgGa/b ratio.
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