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Infection and Immunity, November 2000, p. 6196-6201, Vol. 68, No. 11
Medical and Research Services, Veterans
Affairs Medical Center,2 and Department
of Medicine, College of Medicine,3 and
Department of Plant Pathology, College of
Agriculture,1 University of Arizona, Tucson
Arizona, and Department of Microbiology, University of
Oklahoma, Oklahoma City, Oklahoma4
Received 28 June 2000/Accepted 25 July 2000
When mice are vaccinated with a culture filtrate from
Cryptococcus neoformans (CneF), they mount a protective
cell-mediated immune response as detected by dermal delayed-type
hypersensitivity (DTH) to CneF. We have identified a gene
(DHA1) whose product accounts at least in part for the DTH
reactivity. Using an acapsular mutant (Cap-67) of C. neoformans strain B3501, we prepared a culture filtrate
(CneF-Cap67) similar to that used for preparing the commonly used skin
test antigen made with C. neoformans 184A (CneF-184A). CneF-Cap67 elicited DTH in mice immunized with CneF-184A.
Deglycosylation of CneF-Cap67 did not diminish its DTH activity.
Furthermore, size separation by either chromatography or differential
centrifugation identified the major DTH activity of CneF-Cap67 to be
present in fractions that contained proteins of approximately 19 to 20 kDa. Using N-terminal and internal amino acid sequences derived from
the 20-kDa band, oligonucleotide primers were designed, two of which
produced a 776-bp amplimer by reverse transcription-PCR (RT-PCR) using
RNA from Cap-67 to prepare cDNA for the template. The amplimer was used
as a probe to isolate clones containing the full-length
DHA1 gene from a phage genomic library prepared from strain
B3501. The full-length cDNA was obtained by 5' rapid amplification of
cDNA ends and RT-PCR. Analysis of DHA1 revealed a
similarity between the deduced open reading frame and that of a
developmentally regulated gene from Lentinus edodes
(shiitake mushroom) associated with fruiting-body formation. Also, the
gene product contained several amino acid sequences identical to those determined biochemically from the purified 20-kDa peptide encoded by
DHA1. Recombinant DHA1 protein expressed in
Escherichia coli was shown to elicit DTH reactions similar
to those elicited by CneF-Cap67 in mice immunized against C. neoformans. Thus, DHA1 is the first gene to be cloned
from C. neoformans whose product has been shown to possess
immunologic activity.
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Copyright © 2000, American Society for Microbiology. All rights reserved.
The Cryptococcus neoformans Gene
DHA1 Encodes an Antigen That Elicits a Delayed-Type
Hypersensitivity Reaction in Immune Mice
*
Corresponding author. Mailing address: Valley Fever
Center for Excellence (1-111), 3601 South Sixth Ave., Tucson, AZ 85723. Phone: (520) 792-1450 ext. 6793. Fax: (520) 629-4738. E-mail: spherule{at}u.arizona.edu.
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