No abstract

Full-length nucleoproteins from Ebola and Marburg viruses were expressed as His-tagged recombinant proteins in Escherichia coli and nucleoprotein-based enzyme-linked immunosorbent assays (ELISAs) were established for the detection of antibodies specific to Ebola and Marburg viruses. The ELISAs were evaluated by testing antisera collected from rabbit immunized with Ebola and Marburg virus nucleoproteins. Although little cross-reactivity of antibodies was observed in anti-Ebola virus nucleoprotein rabbit antisera, the highest reactions to immunoglobulin G (IgG) were uniformly detected against the nucleoprotein antigens of homologous viruses. We further evaluated the ELISA's ability to detect antibodies to Ebola and Marburg viruses using human sera samples collected from individuals passing through the Guangdong port of entry. With a threshold set at the mean plus three standard deviations of average optical densities of sera tested, the ELISA systems using these two recombinant nucleoproteins have good sensitivity and specificity. These results demonstrate the usefulness of ELISA for diagnostics as well as ecological and serosurvey studies of Ebola and Marburg virus infection.

We undertook an investigation to assess the utility of a recombinant Coccidioides immitis complement-fixing (CF) antigen for detecting CF antibody in sera from patients with coccidioidomycosis. Enzyme-linked immunosorbent assays established that recombinant CF antigen and, for comparison, a commercially available coccidioidin were reactive with 19 of 19 sera from patients with active coccidioidomycosis. The recombinant antigen was significantly more sensitive than coccidioidin. The median titer obtained when patients' sera were assayed against recombinant CF antigen was 1:51,200 compared to 1:25,600 with coccidioidin (P < 0.027). The recombinant antigen was also more effective in distinguishing the antibody levels in sera from patients with pulmonary coccidioidomycosis than in sera from those with disseminated disease. Whereas patients with pulmonary disease showed a median antibody titer of 1:25,600, those with multifocal disease showed a median titer of 1:102,400 (P < 0.028). The recombinant CF antigen was found, however, to express an epitope(s) that reacted with sera from 6 of 12 patients with histoplasmosis and 2 of 12 patients with blastomycosis. Coccidioidomycosis is a mycotic disease endemic in the semiarid regions of the southwestern United States, Mexico, and Central and South American (4). The etiologic agent, Coccidioides immitis, is a dimorphic fungus which propagates in the soil in a mycelial form that gives rise to infectious arthroconidia. Primary infection is acquired via inhalation of the arthroconidia, which convert in host tissue into endosporulating spherules. The disease has protean manifestations, which range from a primary, asymptomatic or benign pulmonary infection to a progressive pulmonary or extrapulmonary disease involving the skin, bones and/or joints, central nervous system, and other organ systems (5). There has been a significant increase in the incidence of coccidioidomycosis in recent years (1, 14, 16). The number of newly diagnosed cases not only among persons who are immunologically compromised but also among otherwise healthy persons who are exposed to arthroconidia has surged (1, 4, 5, 19). A definitive diagnosis of coccidioidomycosis is made by demonstrating C. immitis in tissue or by culture. In the absence of positive findings, physicians often make a presumptive diagnosis on the basis of a positive complement-fixing (CF) assay for antibody to coccidioidin (CDN). Despite the immense value of detecting the CF antibody, as both a diagnostic and prognostic aid, only two procedures, the CF assay (15) and an immunodiffusion assay for CF antibody (IDCF) (8), both of which utilize crude culture filtrates of C. immitis, are available for detecting this antibody. The CF assay is more sensitive than the IDCF but lacks specificity (10, 12, 15, 16). The IDCF is specific, but because of its lower level of sensitivity test specimens may need to be concentrated prior to the IDCF (12). Attempts to purify the CF antigen from C. immitis mycelial or spherule-phase extracts for use in the de...