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Molecular Basis for Surface Antigen Size Polymorphisms and Conservation of a Neutralization-Sensitive Epitope in Anaplasma marginale
David R. Allred, Travis C. McGuire, Guy H. Palmer, Steve R. Leib, Teresa M. Harkins, Terry F. McElwain and Anthony F. Barbet
Proceedings of the National Academy of Sciences of the United States of America
Vol. 87, No. 8 (Apr., 1990), pp. 3220-3224
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/2354132
Page Count: 5
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Anaplasmosis is one of several tick-borne diseases severely constraining cattle production and usage in many parts of the world. Cattle can be protected from anaplasmosis by immunization with major surface protein 1, a surface protein of Anaplasma marginale carrying a neutralization-sensitive epitope. Marked size polymorphisms exist among different isolates of A. marginale in the AmF105 subunit of major surface protein 1, yet all isolates still contain the neutralization-sensitive epitope. To clarify the basis for these observations, the msp1α gene encoding AmF105 was cloned from four isolates and sequenced. The encoded polypeptides share a high degree of overall homology between isolates but contain a domain with various numbers of tandemly repeated sequences and three regions of clustered amino acid substitutions outside the repeat domain. The polypeptide size differences are completely explained by the variations in the numbers of tandem repeat units. We have mapped the neutralization-sensitive epitope to a sequence that is present within each repeat unit. These results identify a basis for size polymorphisms of the surface polypeptide antigen concomitant with B-cell epitope conservation in rickettsiae.
Proceedings of the National Academy of Sciences of the United States of America © 1990 National Academy of Sciences