EHRLICHIA CHAFFEENSIS TANDEM REPEAT PROTEIN INVOLVED IN A COMPLEX NETWORK OF HOST CELL INTERACTIONS

Abdul Wakeel, Ph.D., J.A. Kuriakose, M.S., and J.W. McBride, Ph.D.

Department of Pathology, UTMB

Background: Ehrlichia chaffeensis, an obligately intracellular gram-negative bacterium infects mononuclear phagocytes and replicates within cytoplasmic membrane-bound vacuoles called morula; this bacterium is the etiologic agent of human monocytotropic ehrlichiosis (HME). E. chaffeensis exploits the host cell by modulating a variety of cellular processes, but the ehrlichial effector proteins involved are unknown. Objective: To determine the role of secreted, differentially expressed, tandem repeat containing protein, p47, in host pathobiology. Methods: Yeast-two hybrid assay, coimmunoprecipitation, and confocal microscopy. Results: Yeast-two hybrid experiments and coimmunoprecipitation assays revealed that p47 interacts with polycomb group ring finger 5 (PCGF5) protein, Src protein-tyrosine kinase Fyn (FYN), protein tyrosine phosphatase, non-receptor type 2 (PTPN2), adenylate cyclase-associated protein 1 (CAP1), and immunoglobulin lambda-like polypeptide 1 (IGLL1). Confocal microscopy of E. chaffeensis infected THP-1 cells demonstrated that anti-p47 antibodies reacted differentially to morulae containing the dense-cored ehrlichiae, which also colocalized with PCGF5, FYN, PTPN2, and CAP1. Conclusions: p47 is involved in complex interactions with host cell molecules involved in signaling and regulating transcription in the infected host cell, thus facilitating ehrlichial survival. (Supported by the NIH AI 071145.)