Intermolecular relationships of major surface proteins of Anaplasma marginale

Abstract

Immunization with Anaplasma marginale membranes containing major surface proteins (MSPs) induces protective immunity against clinical disease (N. Tebele, T. C. McGuire, and G. H. Palmer, Infect. Immun. 59:3199-3204, 1991). For use in design of a recombinant antigen subunit vaccine for A. marginak, intermolecular relationships of known A. marginale MSPs were analyzed. Under nonreducing conditions, MSP-2 and MSP-5 occur as multimers. A large (>300-kDa-molecular-mass), nonreduced protein complex contained MSP-la linked by disulfide bonds to MSP-lb and by noncovalent bonds to MSP-5. MSP-2 was also noncovalently bound to this complex. The nearest neighbor membrane proteins were identified by cross-linking reactions followed by immunoblotting with anti-MSP antibodies. A cross-linked aggregate retained in the stacking gel contained MSP-la, MSP-lb, MSP-2, MSP-3, MSP-4, and MSP-5. Collectively, the data indicate that MSP-2 and MSP-5 occur as monomers and disulfide-bonded multimers. The MSP-1 complex occurs as both disulfide-bonded and noncovalently associated MSP-la and MSP-lb, and MSP-2 and MSP-5 are noncovalently associated with MSP-1. Also, MSP-1, MSP-2, MSP-3, and MSP-4 are nearest neighbors, and MSP-5 is noncovalently associated with this cross-linked complex.

Expression ofAnaplasma marginaleMajor Surface Protein 2 Variants during Persistent Cyclic Rickettsemia

“…Expression of recurrent types together with new types may contribute to the formation of new epitopes that were not previously recognized by the immune response. Because MSP-2 dimerizes on the surface of A. marginale (35), simultaneous expression of variants within a single organism could result in formation of conformationally unique epitopes. If a few organisms expressing a unique combination of variant MSP-2 are able to escape immune clearance in one rickettsemic cycle, then a new population of A. marginale expressing the combination of a recurrent type and a newly generated variant MSP-2 may emerge in the subsequent cycle.…”

Anaplasmosis Control: Past, Present, and Future

“…MSP 1 through 5 have been identified and information on the gene sequences, recombinant protein analogs, monospecific and monoclonal antibodies, isolate variability, and potential value in diagnostic assays and vaccines are available. [28][29][30][31][32][33]19,[34][35][36][37][38][39][40][41][42] MSP1 has been shown to confer partial protection in immunized cattle against A. marginale challenge, and to contain an epitope recognized by monoclonal antibodies capable of in vitro neutralization of isolated rickettsia. 38 MSP1a varies in size among different geographic isolates, but the neutralization-sensitive epitope is conserved.…”

Identification and Functional Analysis of an Immunoreactive DsbA-Like Thio-Disulfide Oxidoreductase of Ehrlichia spp

“…(3). Intramolecular covalent disulfide bonds between major surface proteins of the related rickettsial pathogen Anaplasma marginale have also been described and suggest that disulfide linkages are important in ehrlichial outer membrane structure (16).…”

“…This is the first report of a thio-disulfide oxidoreductase in Ehrlichia, and it provides evidence that disulfide bond formation may occur, perhaps playing an important role in the ehrlichial life cycle and pathogenesis. Previous studies with the related agent A. marginale demonstrated the importance of intra-and intermolecular disulfide bonds in the supramolecular structure of the cell envelope (16). Disulfide bonds in chlamydiae are involved in the development of ultrastructural forms of the organism (3), which are similar in appearance to the Ehrlichia reticulate and dense-cored forms (12).…”