Project Number: 5348-32000-033-00
Project Type: Appropriated

Start Date: Oct 20, 2011
End Date: Oct 19, 2016

Objective:
Objective 1: Identify the molecular determinants of efficient tick-borne transmission of Anaplasma marginale through comparison of pathogen strains with distinctly different transmission phenotypes. Subobjective 1.A: Compare the tick colonization and transmission efficiency phenotypes of A. marginale subsp. centrale before and after tick selection. Subobjective 1.B: Identify genetic markers that are predictive of the tick transmission phenotype of A. marginale field strains. Objective 2: Identify the molecular determinants of vector competence with the goal of blocking tick transmission of Anaplasma marginale. Subobjective 2.A: Define the proteome of the A. marginale-containing vacuole in cultured tick cells. Subobjective 2.B: Identify tick proteins that are required for A. marginale replication in tick cell culture. Subobjective 2.C: Identify tick-specific genes that are required for A. marginale transmission. Objective 3: Assess the capacity to induce protective immunity to challenge by identifying and testing subdominant Anaplasma marginale antigens with the goal of developing a crossprotective vaccine. Subobjective 3.A: Identify the widely conserved outer membrane proteins that induce broadly cross-reactive antibody. Subobjective 3.B: Test the ability of the proteins identified in subobjective 3.A to induce protection to homologous and heterologous A. marginale challenge.

Approach:
Anaplasma marginale, the causative agent of anaplasmosis, is the most prevalent tick-borne pathogen of livestock worldwide. This bacterial pathogen causes a significant disease burden to cattle in the United States and is a barrier to trade. The tools currently available to control this disease are limited and rely on treatment of clinically affected animals and tick control. The work proposed here is designed to fill knowledge gaps required for development of more effective control strategies. In the proposed experiments we target two points of control, one aimed at preventing infection of the bovine host, and the other aimed at preventing tick transmission. Using a comparative approach, we will identify genetic markers of highly efficient tick transmission in A. marginale, thus allowing for the development of a vaccine targeting potential outbreak strains. Concurrently, we will identify and test conserved subdominant antigens for the ability to induce protection against homologous and heterologous challenge in cattle. Together these data will guide the development of an effective vaccine. Using a proteomics approach followed by RNAi experiments to knock-down specific gene function, we will identify the molecules unique to the tick that are required for A. marginale transmission. Identification of these molecules will lay the foundation for development of novel methods to block transmission of A. marginale at the level of the tick vector. Replacing 5348-32000-027-00D (October 2011).