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United States Department of Agriculture

Agricultural Research Service

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2010 Annual Report

1a. Objectives (from AD-416)
To assess the pathogenicity and infectivity of influenza vaccine reassortants and their respective parental wild type viruses for chickens. This includes: 1) determining in vivo pathotype of wild type and reassortant vaccine candidate strains in chickens, and 2) assess in vivo infectivity and pathogenicity in chickens using simulated natural route of exposure (intranasal).

1b. Approach (from AD-416)
The challenge studies will be conducted in BSL-3 Enhanced facilities. Four vaccine candidates will be tested per year using the below study design: 1) conducting in vivo pathotype of virus strains by intravenous testing in chickens using intravenous pathogenicity index, and 2) conducting in vivo infectivity and pathogenicity testing by intranasal inoculation of chickens and determining the ability for the virus to grow as evident by virus shedding for oropharynx and cloaca, and ability to cause disease by assessing clinical features, serological reaction and histopathological changes to various organs.

3. Progress Report
This research relates to inhouse objective 4: Use molecular epidemiologic techniques and viral genomics to understand virus transmission and spread of AI outbreaks in poultry and wild birds. As part of U.S. pandemic plan, the Cooperator developed low pathogenic strains for potential vaccines through use of reverse genetics. This agreement tests such strains for possible virulence as a regulatory requirement and conducts research in poultry with such viruses. During 2010, ARS tested a reverse genetic pandemic H5 vaccine strain (A/Egypt/3300-N3/2008(H5N1)PR8-IDCDC-RG13) and its parent virus (A/Egypt/3300-N3/2008 [H5N1]), in 4-wk-old chickens by intranasal infectivity and pathogenesis testing and in official intravenous pathogenicity tests. The parent virus was highly lethal to chickens, causing a severe systemic viral infection and was uniformly lethal. The vaccine strain was not pathogenic in chickens, failing to make any chickens sick on intravenous pathogenicity index (IVPI) test, and on intranasal test, the virus did not infect chickens. These studies indicate the human pandemic vaccine strain is safe and of low risk for producing adverse effects in poultry systems. Progress was monitored via email and telephone conversations with the cooperator.

4. Accomplishments

Last Modified: 06/27/2017
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