Poster abstracts
Poster number 2 submitted by Mariella Mestres-Villanueva
Ehrlichia sp. HF outer membrane proteins as vaccine candidates in a fatal human monocytic ehrlichiosis mouse model
Mariella A. Mestres-Villanueva (Molecular, Cellular, and Developmental Biology MCDB), Khem Budachetri (Department of Veterinary Biosciences), Tsian Zhang (Department of Veterinary Biosciences), Wenqing Zhang (Department of Veterinary Biosciences), Mingqun Lin (Department of Veterinary Biosciences)
Abstract:
Ehrlichia chaffeensis is an obligatory intracellular bacterium that causes the emerging tick-borne disease, human monocytic ehrlichiosis (HME), a severe, influenza-like illness. The only treatment for HME is the broad-spectrum antibiotic Doxycycline and there is no vaccine available. Ehrlichia spp. lack conventional pathogen-associated molecular patterns, but surface proteins and virulence factors have been identified and their roles in transmission and disease have been studied. Entry-triggering protein of Ehrlichia (EtpE) is an invasin required for bacterial entry into human cells; the C-terminal (EtpE-C) binds DNase-X to induce receptor-mediated endocytosis. Outer membrane proteins OMP-1B and P28 are immunodominant major surface proteins and porins expressed by bacteria in ticks and mammals, respectively. Ehrlichia spp. possess Type IV secretion system (T4SS) and VirB2 proteins function as major pilus subunits, thus playing an important role in binding of the host cell membrane and secretion of T4SS effectors into the host cell cytoplasm. The objective of this study is to determine the vaccine potential of four Ehrlichia surface proteins in the mouse model of acute fatal HME, using Ehrlichia sp. HF (EHF). The genes encoding each protein were cloned into a protein expression vector, followed by expression and purification of the recombinant proteins. Five groups of immunocompetent mice were immunized with rEtpE-C, rOMP-1B, rP28, rVirB2-4 or sham-immunized with ISCOM alone and will be challenged with EHF in tick cells and infected ticks. At euthanasia, blood, spleen, and liver will be collected for analysis of bacterial load and cytokine expression levels via qPCR and RT-qPCR, respectively. The immune cell population in spleen will be analyzed by flow cytometry. This project will lead to a more thorough understanding of the pathogenicity and immunological response in fatal ehrlichiosis patients and on the potential of these antigens for vaccination strategies.
Keywords: Ehrlichia, Immunization, ISCOM