Use of a recombinant Coccidioides immitis complement fixation antigen- chitinase in conventional serological assays

Suzanne M. Johnson, C. Roger Zimmermann, Demosthenes Pappagianis

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The coccidioidal complement fixation (CF) antigen has been cloned previously, and the fusion protein has been expressed in Escherichia coli. The recombinant CF (rCF) antigen was affinity purified by adsorption- desorption to chitin, and its reactivity was studied by using sera containing coccidioidal antibodies. The affinity-purified rCF antigen formed a line of identity with an immunodiffusion (ID) CF reference antigen (coccidioidin) derived from mycelial-phase Coccidioides immitis and was reactive with human, canine, and equine sera containing coccidioidal antibody. The affinity- purified rCF antigen yielded no detectable reaction with Blastomyces or Histoplasma antiserum by ID. The affinity-purified rCF antigen fixed complement with positive human sera and, even when used at lower concentrations, yielded titers comparable to those obtained with the coccidioidin. The reactivity of the affinity-purified rCF antigen was further evaluated by enzyme immunoassay, in which it manifested good sensitivity (96.9%) and specificity (100%) when evaluated with 43 human patients' sera. Thus, the affinity-purified rCF antigen has yielded reactions comparable to those of crude coccidioidal antigens in conventional CF, IDCF, and enzyme immunoassay.

Original languageEnglish (US)
Pages (from-to)3160-3164
Number of pages5
JournalJournal of Clinical Microbiology
Issue number12
StatePublished - Dec 1996


ASJC Scopus subject areas

  • Microbiology (medical)
  • Microbiology

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