The Cryptococcus neoformans gene DHA1 encodes an antigen that elicits a delayed-type hypersensitivity reaction in immune mice.
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.
Mandel
M A
MA
Department of Plant Pathology, College of Agriculture, University of Arizona, Tucson, USA.
Grace
G G
GG
Orsborn
K I
KI
Schafer
F
F
Murphy
J W
JW
Orbach
M J
MJ
Galgiani
J N
JN
D000595:Amino Acid Sequence; D000818:Animals; D000946:Antigens, Fungal / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D001483:Base Sequence; D003001:Cloning, Molecular; D003455:Cryptococcus neoformans / Q000235:genetics / Q000276:immunology*; D005800:Genes, Fungal; D006968:Hypersensitivity, Delayed / Q000209:etiology*; D007114:Immunization; D051379:Mice; D008808:Mice, Inbred CBA; D008969:Molecular Sequence Data; D008970:Molecular Weight
D000946:Antigens, Fungal