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Journal of Clinical Microbiology, 09 1995, 2405-2410, Vol 33, No. 9
AH van Vliet, BA van der Zeijst, E Camus, SM Mahan, D Martinez and F Jongejan
Currently available serological tests for cowdriosis (Cowdria ruminantium
infection) in domestic ruminants are hampered by their low specificities
because of cross-reactivity with Ehrlichia spp. The use of recombinant
major antigenic protein (MAP1) of C. ruminantium for serodiagnosis was
investigated. Overlapping fragments of the MAP1 protein were expressed in
Escherichia coli and were reacted with sera from sheep infected with either
C. ruminantium or Ehrlichia ovina. Two immunogenic regions on the MAP1
protein, designated MAP1-A and MAP1-B, were identified. MAP1-A was reactive
with C. ruminantium antisera, E. ovina antisera, and three MAP1-specific
monoclonal antibodies, whereas MAP1-B reacted only with C. ruminantium
antisera. An indirect enzyme- linked immunosorbent assay (ELISA) based on
MAP1-B was further developed and validated with sera from animals
experimentally infected with C. ruminantium or several Ehrlichia spp.
Antibodies raised in sheep, cattle, and goats against nine isolates of C.
ruminantium reacted with MAP1-B. Cross-reactivity with MAP1-B was limited
to Ehrlichia canis and Ehrlichia chaffeensis, two rickettsias which do not
infect ruminants. Antibodies to Ehrlichia spp. which do infect ruminants
(E. bovis, E. ovina, and E. phagocytophila) did not react with MAP1-B.
Antibody titers to C. ruminantium in sera from experimentally infected
cattle, goats, and sheep were detectable for 50 to 200 days postinfection.
Further validation of the recombinant MAP1-B- based ELISA was done with
sera obtained from sheep raised in heartwater- free areas in Zimbabwe and
from several Caribbean islands. A total of 159 of 169 samples which were
considered to be false positive by immunoblotting or indirect ELISA did not
react with MAP1-B.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Use of a specific immunogenic region on the Cowdria ruminantium MAP1 protein in a serological assay
Department of Bacteriology, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
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