The Trypanosoma lewisi immunofluorescence test: a new simple technique for simultaneous determination of total antinuclear antibodies and the detection of antibodies to double-stranded DNA.

An indirect immunofluorescence technique was developed for the detection of antibodies to dsDNA and the simultaneous assessment of antinuclear antibodies 'in toto' (ANA). This assay was based upon the use as substrate of smears of peripheral blood derived from rats infected with Trypanosoma lewisi. T. lewisi possesses a giant kinetoplast posteriorly to the nucleus. Enzyme digestion and absorption experiments provided strong evidence that T. lewisi kinetoplast contains dsDNA uncontaminated by other nuclear antigens. The T. lewisi immunofluorescent test was evaluated on a total of 130 sera (30 from patients with SLE) and compared with radioimmunoassays for antibodies to dsDNA ([125I]dsDNA-RIA) and antibodies to ssDNA ([125I]ssDNA-RIA). Excellent correlation was found between kinetoplast immunofluorescence and [125I]dsDNA-RIA, whereas no non-SLE sera showing significant ssDNA binding activity gave kinetoplast staining. With a single exception, only SLE sera reacted with T.lewisi kinetoplast. Sera containing autoantibodies other than ANA did not induce fluorescence of any part of the parasite, including the flagellum and its base. These results indicate that the T. lewisi immunofluorescence test is specific and reliable, and combines the advantages of Crithidia luciliae with those of Trypanosoma gambiense. It may be used routinely for evaluation of total ANA and simultaneous detection of antibodies against dsDNA.