Lin Quan, Rikihisa Yasuko, Felek Suleyman, Wang Xueqi, Massung Robert F, Woldehiwet Zerai
Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, 1925 Coffey Road, Columbus, OH 43210-1093, USA.
Infect Immun. 2004 Jul;72(7):3883-9. doi: 10.1128/IAI.72.7.3883-3889.2004.
The msp2 and p44 genes encode polymorphic major outer membrane proteins that are considered unique to the intraerythrocytic agent of Anaplasma marginale and the intragranulocytic agent of Anaplasma phagocytophilum, respectively. In the present study, however, we found an msp2 gene in A. phagocytophilum that was remarkably conserved among A. phagocytophilum strains from human granulocytic anaplasmosis (HGA) patients, ticks, and a horse from various regions in the United States, but the gene was different in a sheep isolate from the United Kingdom. The msp2 gene in the A. phagocytophilum strain HZ genome was a single-copy gene and was located downstream of two Ehrlichia chaffeensis omp-1 homologs and a decarboxylase gene (ubiD). The msp2 gene was expressed by A. phagocytophilum in the blood from HGA patients NY36 and NY37 and by A. phagocytophilum isolates from these patients cultured in HL-60 cells at 37 degrees C. The msp2 gene was also expressed in a DBA/2 mouse infected by attaching ticks infected with strain NTN-1 and in a horse experimentally infected by attaching strain HZ-infected ticks. However, the transcript of the msp2 gene was undetectable in A. phagocytophilum strain HZ in SCID mice and Ixodes scapularis ticks infected with strain NTN-1. These results indicate that msp2 is functional in various strains of A. phagocytophilum, and relative expression ratios of msp2 to p44 vary in different infected hosts. These findings may be important in understanding roles that Msp2 proteins play in granulocytic ehrlichia infection and evolution of the polymorphic major outer membrane protein gene families in Anaplasma species.
msp2和p44基因分别编码多态性主要外膜蛋白，它们被认为是边缘无形体的红细胞内病原体和嗜吞噬细胞无形体的粒细胞内病原体所特有的。然而，在本研究中，我们在嗜吞噬细胞无形体中发现了一个msp2基因，该基因在来自美国不同地区的人类粒细胞无形体病（HGA）患者、蜱虫和一匹马的嗜吞噬细胞无形体菌株中显著保守，但在来自英国的一株绵羊分离株中该基因有所不同。嗜吞噬细胞无形体菌株HZ基因组中的msp2基因是单拷贝基因，位于两个恰菲埃立克体omp - 1同源基因和一个脱羧酶基因（ubiD）的下游。msp2基因在HGA患者NY36和NY37的血液中的嗜吞噬细胞无形体以及在HL-6０细胞中于37℃培养的这些患者的嗜吞噬细胞无形体分离株中表达。msp2基因也在通过附着感染NTN-1菌株的蜱虫而感染的DBA/2小鼠以及通过附着感染HZ菌株的蜱虫而实验感染的一匹马中表达。然而，在SCID小鼠和感染NTN-1菌株的肩突硬蜱中的嗜吞噬细胞无形体菌株HZ中未检测到msp2基因的转录本。这些结果表明msp2在嗜吞噬细胞无形体的各种菌株中具有功能，并且msp2与p44的相对表达比率在不同的感染宿主中有所不同。这些发现对于理解Msp2蛋白在粒细胞埃立克体感染中的作用以及无形体物种中多态性主要外膜蛋白基因家族的进化可能具有重要意义。
