Essay --

A. Specific Aims West Nile virus (WNV) was first identified in New York City in 1999 and quickly spread across the US to become the dominant mosquito-borne viral infection in humans in the country. Since its introduction to the US, WNV has been estimated to cause more than 3 million infections resulting in 37,000 confirmed cases of WNV disease in humans, 43% of which resulted in neuroinvasive diseases, and 1,100 deaths3. WNV has also been responsible for declines in certain US avian populations affecting over 100 different species. Avian species that are highly susceptible to severe WNV disease belong to the Corvidae family, including American crows (AMCRs) in which WNV infection is 100% lethal. This high mortality rate has led to the creation of a national surveillance program based on AMCRs in order to forecast WNV transmission to humans4. The genetic and pathological mechanisms to explain the interspecies variability in WNV susceptibility that have caused such large-scale declines in North American bird populations have not been determined. The objective of this proposal is to investigate: a) the antiviral response elicited in three avian species which contribute differentially to the amplification of WNV and have different disease outcomes following WNV infection, b) the differential antiviral induction potential in host cells and the sensitivity to antiviral host responses of three strains of WNV displaying a range of virulence capacities, and c) the role of cellular tropism in the elicitation of the host antiviral response and on WNV replication within host cells. I hypothesize that avian hosts susceptible to severe WNV disease do not mount an effective innate antiviral response that could control viral replication and diss... ...ent bird species. Based on data generated in Aim 1.1 genes identified to contribute to either susceptibility or resistant phenotypes in the type I interferon pathway will also be examined in this subaim. To identify the cell types critical for WNV amplification in each avian species, viral load will be quantified by qRT-PCR for each of the 8 time points. The mosquito cell targeted virus will serve as a control since replication will be unrestricted. Expected outcomes and potential pitfalls. It is anticipated that gene expression within the type I IFN pathway will be differentially expressed between the different inoculation groups and bird species. By limiting viral replication, we might also negatively impact the antiviral response in cell types that are major contributors to the type I IFN pathway thereby altering dissemination and viral replication potential.