Project Number: 5410-32000-015-00
Project Type: Appropriated

Start Date: Feb 01, 2007
End Date: Jan 31, 2012

Objective:
1. Determine the vector competence of North American mosquitoes to virulent and marked Rift Valley fever virus (RVFV) vaccine strains, including amplification and vertical transmission. 2. Develop expression and delivery systems to advance the discovery of diagnostics and vaccines specifically designed for the control and eradication of RVF. 3. Develop direct and indirect diagnostic tests for the early detection of RVFV, including the differentiation of infected from vaccinated animals.

Approach:
The approach to determine the vector competence of North American mosquito species for RVFV will be to focus on key mosquito species that feed on RVFV susceptible livestock and will include genetic studies of mosquito vector competence for RVFV. Differences in vector competence among populations of the same species throughout the U.S. will be examined using virulent RVFV and candidate RVF marked vaccine virus strains. The potential for RVFV to reassort with indigenous Bunyaviruses will be assessed. This project will provide scientific information critical for assessing the risk of RVFV spreading via endemic mosquito species if it is introduced into the U.S. The approach to develop expression and delivery systems to advance diagnostic and vaccine technology will be to develop alphavirus replicon vectors expressing the RVFV glycoproteins, leading to vaccines that elicit high levels of neutralizing anti-RVFV antibody, which prevent the amplification of wild type RVFV in susceptible ruminant hosts. The development of transmission blocking vaccines that target virus development in the insect vector will be explored. In addition, the immunogenic characteristics of RVFV proteins will be evaluated to support the development of companion diagnostic tests that can support control strategies. The approach to development of early detection technology for RVFV will be the discovery and transfer of quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR) technology to the National Animal Health Laboratory Network. The research will also focus on the development of antibody-based diagnostic tests using non-infectious expressed antigens that will enable early detection and differentiate infected from vaccinated animals.