DNA or 2-deoxyguanosine reacts with hydroxyl free radical to form 8-hydroxy-deoxyguanosine (8-OH-dG). We found that 8-OH-dG can be effectively separated from deoxyguanosine by high pressure liquid chromatography and very sensitively detected using electrochemical detection. The sensitivity of electrochemical detection is about one-thousand fold enhanced over optical detection. Utilizing deoxyguanosine in bicarbonate buffer it was found that ferrous ion, but not ferric ion, was effective in forming 8-OH-dG. The hydroxyl free radical scavenging agents, thiourea and ethanol, were very effective in quenching Fe(11) mediated 8-OH-dG formation, but superoxide dismutase had very little effect.

We compared serial measurements of antibodies to mannan and to a cytoplasmic antigen (enzyme-linked immunosorbent assays), detection of mannan and an unidentified candidate antigen (latex agglutination), and assays of mannose and arabinitol (gas chromatographic assay of per-O-acetylated aldonitrile derivatives). In a high-inoculum intravascular-infection model, antimannan assays were consistently positive beginning on day 2 postinoculation, anti-cytoplasmic antigen assays followed the same time course but were less sensitive, mannan was detected in all samples beginning on day 2 postinoculation, and serum mannose concentrations peaked on day 3 postinoculation and were less sensitive than mannan detection. Other assays were not useful. In a lower-inoculum intravascular-infection model, the antibody assays became positive after a similar interval and remained positive for 28 days, with antimannan again being the more sensitive. Mannan and mannose tests were positive in week 1 postinoculation only, with mannan detection being the more sensitive. In a gastrointestinal-colonization model, antimannan assays became positive after 2 weeks of colonization, whereas anti-cytoplasmic antigen and mannan tests remained negative. In a model of gastrointestinal colonization followed by invasive infection produced by induction of neutropenia, only mannan detection was diagnostically useful. These data, comparing this panel of modern serodiagnostic techniques in controlled models of clinically relevant syndromes of candidiasis, enhance understanding of previous efforts in serodiagnosis of candidiasis and provide a foundation for further prospective studies in patients.

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