|Knowles, Donald - Don|
Submitted to: Infection and Immunity
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/15/2006
Publication Date: 6/9/2006
Citation: Noh, S.M., Brayton, K.A., Knowles Jr, D.P., Agnes, J.T., Dark, M.J., Brown, W.C., Baszler, T.V., Palmer, G.H. 2006. Differential Expression and Sequence Conservation of the Anaplasma marginale msp2 Gene Superfamily Outer Membrane Proteins. Infection and Immunity. 74(6):3471-3479. Interpretive Summary: Subsequent to obtaining the complete sequence of the genome of Anaplasma marginale (an economically important) blood disease of cattle we examined the genome to look for vaccine candidates. This report provides the characterization of new components of A. marginale, some of which were shown to be parts of the organism in red blood cells and a tick which transmits the disease. The components (proteins) are on the surface of the organism and part of a "superfamily". Some of these components (proteins) have already been shown to be important in immunity to this organism. Some of these components were only found in the red blood cell stage. The discovery of these proteins is an advancement in our research directed at the development of a safe and efficacious vaccine for anaplasmosis.
Technical Abstract: The genera Anaplasma and Ehrlichia include tick-transmitted pathogens of humans and animals. Successful transmission requires invasion and replication in both mammals and ticks, representing distinctly different host cell environments. These bacterial pathogens encode a protein superfamily, pfam01617, which includes the predominant outer membrane proteins of each species: MSP2 and MSP3 of Anaplasma marginale and A. ovis, A. phagocytophilum MSP2 (p44), Ehrlichia chaffeensis p28- OMP, E. canis p30, and E. ruminantium MAP1, and has been shown to be involved in both antigenic variation within the mammalian host and differential expression between the mammalian and arthropod hosts. Recently complete sequencing of the A. marginale genome has identified an expanded set of genes, designated omp1-14, encoding new members of this superfamily. Transcriptional analysis indicated that, with the exception of the three smallest ORFs, omp2, 3, and 6, these superfamily genes are transcribed in A. marginale infected erythrocytes, tick midgut and salivary gland, and IDE8 tick cell line. OMPs 1, 4, 7-9, and 11 were confirmed to be expressed as protein by A. marginale within infected erythrocytes with expression being either markedly lower (OMPs1, 4, 7-9) or absent (OMP11) in infected tick cells, which reflected regulation at the transcript level. Although the pfam01617 superfamily includes the antigenically variable MSP2 and MSP3 surface proteins, analysis of the omp1-14 sequences throughout a cycle of acute and persistent infection in the mammalian host and tick transmission reveals a high degree of conservation, an observation supported by sequence comparison between the St. Maries and Florida strain genomes.