Ehrlichia chaffeensis 28 kDa outer membrane protein multigene family

摘要

The 28-kDa outer membrane proteins (P28) of Ehrlichia chaffeensis are encoded by a multigene family consisting of 21 members located in a 23-kb DNA fragment in the genome of E. chaffeensis. Fifteen of these proteins are claimed herein as novel sequences. The amino acid sequence identity of the various P28 proteins was 20-83%. Six of 10 tested p28 genes were actively transcribed in cell culture grown E. chaffeensis. RT-PCR also indicated that each of the p28 genes was monocistronic. These results suggest that the p28 genes are active genes and encode polymorphic forms of the P28 proteins. The P28s were also divergent among different isolates of E. chaffeensis. The large repertoire of the p28 genes in a single ehrlichial organism and antigenic diversity of the P28 among the isolates of E. chaffeensis suggest that the P28s may be involved in immune avoidance.