Analysis of sequences and loci of p44 homologs expressed by Anaplasma phagocytophila in acutely infected patients.
Anaplasma phagocytophila is an obligatory intragranulocytic bacterium that causes human granulocytic ehrlichiosis. Immunodominant 44-kDa outer membrane proteins of A. phagocytophila are encoded by a p44 multigene family. In the present study, expression profiles of p44 genes in the blood of acutely infected patients in the year 2000 were characterized. A single p44 gene was predominantly expressed in peripheral blood leukocytes from one patient, while up to 17 different p44 genes were transcribed without a single majority in the other two patients. The cDNA sequences of the central hypervariable region of several p44 genes were identical among the isolates from the three patients and a 1995 A. phagocytophila isolate. A. phagocytophila was isolated by cell culture from all of the three 2000 patients. Genomic Southern blot analysis of the three 2000 and two 1995 A. phagocytophila isolates with probes specific to the most dominant p44 transcript in each patient showed that the p44 loci in the A. phagocytophila genome were conserved. Analysis of the predicted amino acid sequences of 43 different p44 genes including 19 new sequences found in the present study, revealed that five amino acids were absolutely conserved. The hypervariable region was subdivided into five domains, including three extremely hypervariable central domains. These results suggest that variations in the sequences of p44 are not random but are restricted. Furthermore, several p44 genes are not hypermutatable in nature, based on the conservation of gene sequences and loci among isolates obtained 5 years apart.
Lin
Quan
Q
Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus 43210, USA.
Zhi
Ning
N
Ohashi
Norio
N
Horowitz
Harold W
HW
Aguero-Rosenfeld
Maria E
ME
Raffalli
John
J
Wormser
Gary P
GP
Rikihisa
Yasuko
Y
D000208:Acute Disease; D000595:Amino Acid Sequence; D000709:Anaplasma / Q000235:genetics / Q000378:metabolism*; D000712:Anaplasmosis / Q000382:microbiology / Q000503:physiopathology; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D017124:Conserved Sequence; D016873:Ehrlichiosis / Q000382:microbiology* / Q000503:physiopathology; D014644:Genetic Variation; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D001425:Bacterial Outer Membrane Proteins; C450839:p44 protein, Anaplasma phagocytophila