Structural analysis of a p44/msp2 expression site of Anaplasma phagocytophilum in naturally infected ticks in Japan

1 Laboratory of Microbiology, Department of Food and Nutritional Sciences, Graduate School of Nutritional and Environmental Sciences, University of Shizuoka and Global COE Program, Shizuoka 422-8526, Japan 2 Department of Microbiology, Shizuoka Institute of Environment and Hygiene, Shizuoka, Japan 3 Laboratory of Microbiology and Immunology, Faculty of Pharmacy, Chiba Institute of Science, Choshi 288-0025, Japan 4 Ohara Research Laboratory, Ohara General Hospital, Fukushima 960-0195, Japan Correspondence Norio Ohashi ohashi{at}u-shizuoka-ken.ac.jp Received April 9, 2009 Accepted August 20, 2009 Anaplasma phagocytophilum , an agent of human granulocytic anaplasmosis, infects neutrophils and causes an emerging tickborne febrile disease. The genome of this bacterium contains a large number of p44 / msp2 -related genes encoding 44 kDa major outer-membrane proteins, and it is known that a specific p44 / msp2 gene is predominantly transcribed from a single expression locus. This study successfully characterized the genomic expression site for p44 / msp2 (3.8 kb) in uncultured A. phagocytophilum from Ixodes persulcatus ticks inhabiting a northern part of Japan. Comparative analysis of the sequences revealed that the structures of the expression sites in Japanese A. phagocytophilum were similar to those of US strains from human patients and European strains from a dog and sheep, but omp-1N (upstream from p44 / msp2 ) and a truncated recA (downstream from p44 / msp2 ) in the p44 / msp2 expression site seemed to share similarities with those of US and European strains. The central hypervariable region sequences of Japanese p44 / msp2 were found to be quite diverse (24.4–100 % amino acid similarities) and distinct from their closest relatives from US human patients or animal host origins (56.3–97.6 % amino acid similarities) with some exceptions. Thus, this study provides significant information about the molecular characteristics of A. phagocytophilum in East Asia, as well as the global diversity of p44 / msp2 . The GenBank/EMBL/DDBJ accession numbers for the A. phagocytophilum p44 / msp2 gene sequences determined in this study are FJ600552 –FJ600615. The sequences of p44 / msp2 expression sites in Tick-162-18ES-Iwate-IP and Tick-176-5ES-Iwate-IP are FJ600595 and FJ600601 , respectively.