Characterization of a variant erythrocyte surface antigen (VESA1) expressed by Babesia bovis during antigenic variation

Roberta M. O'Connor, Tamara J. Lane, Suzanne E. Stroup, David R. Allred

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57 Scopus citations

Abstract

Babesia bovis, an intraerythrocytic, protozoal parasite of cattle, undergoes clonal antigenic variation (Allred DR, Cinque RM, Lane TJ, Ahrens KP. Infect Immun 1994;62:91-98). This ability could provide a mechanism by which the parasite escapes host immune defenses to establish chronic infection. Previous work identified two parasite-derived antigens of M(r) 128 000 and 113 000 that were present on the surface of the infected erythrocyte and appeared to be associated with clonal antigenic variation (Allred DR, Cinque RM, Lane TJ, Ahrens KP. Infect Immun 1994;62:91-98). Two monoclonal antibodies (mAbs), 3F7.1H11 and 4D9.1G1, which recognize the variant erythrocyte surface antigen (VESA1) have been identified. These mAbs react only with the surface of erythrocytes infected with the B. bovis C9.1 clone in live-cell immunofluorescence assays. In both conventional and surface immunoprecipitations, the mAbs precipitate a variant antigen doublet that matches in mass the infected red blood cell (IRBC) surface antigens precipitated with bovine serum. In contrast, Western blot analysis revealed that only the M(r) 128 000 polypeptide is recognized by the mAbs. Neither mAb recognizes antigenically variant progenitor or progeny parasite clones in any of the immunoassays, confirming the involvement of this antigen in rapid clonal antigenic variation. Failure to label this antigen with [9,10(n)-3H]myristic acid, [9,10(n)-3H]palmitic acid or D-[6-3H]glucosamine indicates that these polypeptides are neither N-glycosylated nor fatty acylated. Identity of the variant antigen recognized by the mAbs with that putatively identified with immune serum was confirmed by comparison of partial proteolytic digestion products. Unambiguous identification of the VESA1 antigen as a component of antigenic variation will facilitate characterization of the events leading to antigenic variation on the B. bovis-infected erythrocyte surface and its significance to parasite survival during chronic infection.

Original languageEnglish (US)
Pages (from-to)259-270
Number of pages12
JournalMolecular and Biochemical Parasitology
Volume89
Issue number2
DOIs
StatePublished - Nov 1997
Externally publishedYes

Bibliographical note

Funding Information:
The excellent technical assistance of Brian Stephens, Katie Parsons, Greta Reutter, Ilene Serentill and Jennifer Long is gratefully acknowledged. We also wish to thank Dr Guy Palmer and Dr Charles Guy for the kind gifts of mAbs and Dr Roman Ganta for critically reviewing this manuscript. This work was supported by USDA grants #93-37204-9115 and #95-37204-2140.

Keywords

  • Antigenic variation
  • Babesia bovis
  • Erythrocyte membrane
  • Surface antigen

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