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Infection and Immunity, February 2000, p. 584-593, Vol. 68, No. 2
Department of Microbiology and Immunology,
Medical College of Ohio, Toledo, Ohio 43614,1
and Medical Service, Tucson Veterans Affairs Medical
Center,2 and Department of Medicine,
University of Arizona,3 Tucson, Arizona
85723
Received 19 July 1999/Returned for modification 2 September
1999/Accepted 30 October 1999
Multinucleate parasitic cells (spherules) of Coccidioides
immitis isolates produce a membranous outer wall component (SOW) in vitro which has been reported to be reactive with antibody from
patients with coccidioidal infection, elicits a potent proliferative response of murine immune T cells, and has immunoprotective capacity in
a murine model of coccidioidomycosis. To identify the antigenic components of SOW, the crude wall material was first subjected to
Triton X-114 extraction, and a water-soluble fraction derived from this
treatment was examined for protein composition and reactivity in
humoral and cellular immunoassays. Protein electrophoresis revealed
that the aqueous fraction of three different isolates of C. immitis each contained one or two major glycoproteins (SOWgps), distinguished by their molecular sizes, which ranged from 58 to 82 kDa.
The SOWgps, however, showed identical N-terminal amino acid sequences,
and each was recognized by sera from patients with C. immitis infection. Antibody raised against the purified 58-kDa
glycoprotein (SOWgp58) of the Silveira isolate was used for Western
blot and immunolocalization analyses. Expression of SOWgp was shown to
be parasitic phase specific, and the antigen was localized to the
membranous SOW. The water-soluble fraction of SOW and the purified
SOWgp58 were tested for the ability to stimulate proliferation of human
peripheral monocytic cells (PBMC). The latter were obtained from
healthy volunteers with positive skin test reaction to spherulin, a
parasitic-phase antigen of C. immitis, and from volunteers
who showed no skin test reaction to the same antigen. The SOW
preparations stimulated proliferation of PBMC from skin test-positive
but not skin test-negative donors, and the activated cells secreted
gamma interferon, which is indicative of a T helper 1 pathway of immune
response. Results of this study suggest that SOWgp is a major parasitic
cell surface-expressed antigen that elicits both humoral and
cellular immune responses in patients with coccidioidal infection.
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Copyright © 2000, American Society for Microbiology. All rights reserved.
A Major Cell Surface Antigen of Coccidioides
immitis Which Elicits Both Humoral and Cellular Immune
Responses
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, Medical College of Ohio, 3055 Arlington Ave., Toledo, OH 43614. Phone: (419) 383-5423. Fax: (419) 383-3002. E-mail: gtcole{at}mco.edu.
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