title: Antigenic variation of Ehrlichia chaffeensis resulting from differential expression of the 28-kilodalton protein gene family.
abstract: The transcriptional activity and allele variation of the 28-kDa outer membrane protein gene (p28) of Ehrlichia chaffeensis were analyzed to determine the mechanism of the antigenic variation of the 28-kDa outer membrane proteins. Reverse transcriptase PCR amplification of mRNA indicated that 16 of the 22 members of the p28 multigene family were transcribed. Amino acid sequence analysis indicated that the p28-19 protein was produced in vitro in the Arkansas strain. The p28-19 gene and its promoter region were sequenced and compared in 12 clinical isolates of E. chaffeensis to determine allele variation. The variation of the p28-19 gene among the isolates is limited to three types represented by strains Arkansas, 91HE17, and Sapulpa, respectively. These results indicate that the majority of the p28 genes are active genes and that antigenic variation of the E. chaffeensis 28-kDa proteins may result from differential expression of the p28 gene family members rather than gene conversion.
authors.affiliation: Department of Pathology and WHO Collaborating Center for Tropical Diseases, University of Texas Medical Branch, Galveston, Texas 77555-0609, USA.
authors.forename: S Wesley
authors.initials: SW
authors.lastname: Long
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Zhang
authors.forename: Hai
authors.initials: H
authors.lastname: Qi
authors.forename: Steven
authors.initials: S
authors.lastname: Standaert
authors.forename: David H
authors.initials: DH
authors.lastname: Walker
authors.forename: Xue-Jie
authors.initials: XJ
authors.lastname: Yu
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D018469:Ehrlichia chaffeensis / Q000235:genetics / Q000276:immunology*; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D005810:Multigene Family; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
chemical_list: D001425:Bacterial Outer Membrane Proteins