Mingqun Lin1, Qingming Xiong2, Matthew Chung3, Sean C Daugherty3, Sushma Nagaraj3, Naomi Sengamalay3, Sandra Ott3, Al Godinez3, Luke J Tallon3, Lisa Sadzewicz3, Claire Fraser3,4, Julie C Dunning Hotopp3,5,6, Yasuko Rikihisa7. 1. Department of Veterinary Biosciences, The Ohio State University, 1925 Coffey Road, Columbus, OH, 43210, USA. lin.427@osu.edu. 2. Department of Veterinary Biosciences, The Ohio State University, 1925 Coffey Road, Columbus, OH, 43210, USA. 3. Institute for Genome Sciences, University of Maryland School of Medicine, 801 W. Baltimore St, Baltimore, MD, 21201, USA. 4. Department of Medicine, University of Maryland School of Medicine, 801 W. Baltimore St, Baltimore, MD, 21201, USA. 5. Department of Microbiology and Immunology, University of Maryland School of Medicine, 801 W. Baltimore St, Baltimore, MD, 21201, USA. 6. Greenebaum Cancer Center, University of Maryland School of Medicine, 801 W. Baltimore St, Baltimore, MD, 21201, USA. 7. Department of Veterinary Biosciences, The Ohio State University, 1925 Coffey Road, Columbus, OH, 43210, USA. rikihisa.1@osu.edu.
Abstract
BACKGROUND: The genus Ehrlichia consists of tick-borne obligatory intracellular bacteria that can cause deadly diseases of medical and agricultural importance. Ehrlichia sp. HF, isolated from Ixodes ovatus ticks in Japan [also referred to as I. ovatus Ehrlichia (IOE) agent], causes acute fatal infection in laboratory mice that resembles acute fatal human monocytic ehrlichiosis caused by Ehrlichia chaffeensis. As there is no small laboratory animal model to study fatal human ehrlichiosis, Ehrlichia sp. HF provides a needed disease model. However, the inability to culture Ehrlichia sp. HF and the lack of genomic information have been a barrier to advance this animal model. In addition, Ehrlichia sp. HF has several designations in the literature as it lacks a taxonomically recognized name. RESULTS: We stably cultured Ehrlichia sp. HF in canine histiocytic leukemia DH82 cells from the HF strain-infected mice, and determined its complete genome sequence. Ehrlichia sp. HF has a single double-stranded circular chromosome of 1,148,904 bp, which encodes 866 proteins with a similar metabolic potential as E. chaffeensis. Ehrlichia sp. HF encodes homologs of all virulence factors identified in E. chaffeensis, including 23 paralogs of P28/OMP-1 family outer membrane proteins, type IV secretion system apparatus and effector proteins, two-component systems, ankyrin-repeat proteins, and tandem repeat proteins. Ehrlichia sp. HF is a novel species in the genus Ehrlichia, as demonstrated through whole genome comparisons with six representative Ehrlichia species, subspecies, and strains, using average nucleotide identity, digital DNA-DNA hybridization, and core genome alignment sequence identity. CONCLUSIONS: The genome of Ehrlichia sp. HF encodes all known virulence factors found in E. chaffeensis, substantiating it as a model Ehrlichia species to study fatal human ehrlichiosis. Comparisons between Ehrlichia sp. HF and E. chaffeensis will enable identification of in vivo virulence factors that are related to host specificity, disease severity, and host inflammatory responses. We propose to name Ehrlichia sp. HF as Ehrlichia japonica sp. nov. (type strain HF), to denote the geographic region where this bacterium was initially isolated.
BACKGROUND: The genus Ehrlichia consists of tick-borne obligatory intracellular bacteria that can cause deadly diseases of medical and agricultural importance. Ehrlichia sp. HF, isolated from Ixodes ovatus ticks in Japan [also referred to as I. ovatus Ehrlichia (IOE) agent], causes acute fatal infection in laboratory mice that resembles acute fatal human monocytic ehrlichiosis caused by Ehrlichia chaffeensis. As there is no small laboratory animal model to study fatal humanehrlichiosis, Ehrlichia sp. HF provides a needed disease model. However, the inability to culture Ehrlichia sp. HF and the lack of genomic information have been a barrier to advance this animal model. In addition, Ehrlichia sp. HF has several designations in the literature as it lacks a taxonomically recognized name. RESULTS: We stably cultured Ehrlichia sp. HF in caninehistiocytic leukemiaDH82 cells from the HF strain-infectedmice, and determined its complete genome sequence. Ehrlichia sp. HF has a single double-stranded circular chromosome of 1,148,904 bp, which encodes 866 proteins with a similar metabolic potential as E. chaffeensis. Ehrlichia sp. HF encodes homologs of all virulence factors identified in E. chaffeensis, including 23 paralogs of P28/OMP-1 family outer membrane proteins, type IV secretion system apparatus and effector proteins, two-component systems, ankyrin-repeat proteins, and tandem repeat proteins. Ehrlichia sp. HF is a novel species in the genus Ehrlichia, as demonstrated through whole genome comparisons with six representative Ehrlichia species, subspecies, and strains, using average nucleotide identity, digital DNA-DNA hybridization, and core genome alignment sequence identity. CONCLUSIONS: The genome of Ehrlichia sp. HF encodes all known virulence factors found in E. chaffeensis, substantiating it as a model Ehrlichia species to study fatal humanehrlichiosis. Comparisons between Ehrlichia sp. HF and E. chaffeensis will enable identification of in vivo virulence factors that are related to host specificity, disease severity, and host inflammatory responses. We propose to name Ehrlichia sp. HF as Ehrlichiajaponica sp. nov. (type strain HF), to denote the geographic region where this bacterium was initially isolated.
Authors: Joseph J Gillespie; Kelly A Brayton; Kelly P Williams; Marco A Quevedo Diaz; Wendy C Brown; Abdu F Azad; Bruno W Sobral Journal: Infect Immun Date: 2010-02-22 Impact factor: 3.441