Flow cytometric analysis of peripheral blood lymphocyte immunophenotypes in persons infected with Treponema pallidum.

To characterize the human immune response to syphilis, we determined the effect of infection with Treponema pallidum on the percentage of the various lymphocyte subpopulations in the peripheral blood of infected and uninfected persons. Monoclonal antibodies labeled with either fluorescein isothiocyanate or phycoerythrin were used to perform dual color analysis on a FACScan with the following markers: CD3 for total T cells, CD4 for T helper cells, CD8 for T suppressor cells, CD19 for B cells, and CD16 plus CD56 for natural killer cells. Lymphocyte immunophenotype results were analyzed by the stage of untreated syphilis and by gender. Although they were within the ranges of the normal distribution of immunophenotypes, the percentages of CD4+ cells were significantly lower (P < 0.001) and those of CD8+ cells were higher (P = 0.03) in patients with syphilis than in the uninfected population. For infected versus uninfected subjects, both women and men, the differences in the mean percentages of CD3+ and CD4+ cells were significant (P < or = 0.05). Significant differences were noted between the sexes in secondary syphilis only in the mean percentages of cells positive for CD3, CD4, CD8, and CD16 plus CD56. Gender had no effect on lymphocyte subpopulations in subjects with primary or latent syphilis. In the control population, significant differences due to gender were observed in the percentages of cells positive for CD3, CD4, and CD16 plus CD56.

Interlaboratory comparison of the toluidine red unheated serum test antigen preparation.

The toluidine red unheated serum test (TRUST) antigen, a macroscopic flocculation test antigen developed by Pettit et al. (J. Clin. Microbiol. 18:1141-1145, 1983) by modifying the color-coded antigen of Kasatiya and Lambert (Appl. Microbiol. 28:317-318, 1974), was compared with the Venereal Disease Research Laboratory (VDRL) slide and rapid plasma reagin (RPR) 18-mm circle card tests for sensitivity, specificity, and reproducibility. Two lots of TRUST antigen were prepared by two laboratories in the Centers for Disease Control. Both laboratories performed the TRUST and VDRL slide test on serum samples from 1,102 patients attending the DeKalb County, Georgia, Sexually Transmitted Disease Clinic. In addition, one laboratory performed the RPR card test. Reactive sera were quantitated in the three nontreponemal tests and confirmed with the fluorescent treponemal antibody absorption test. The sensitivity in untreated syphilis for all nontreponemal tests involved was 98.4%. The specificity for these tests was 98.6%. The qualitative reproducibility among the four lots of TRUST antigen, VDRL slide, and RPR card tests was 98.2%. Only 20 sera showed discrepant results. Intralaboratory reproducibility of the two TRUST antigens was 100% for one laboratory and 99.6% for the other. Interlaboratory reproducibility for the four lots of TRUST and the VDRL slide test was 99%. Quantitative agreement +/- 1 dilution between the TRUST and RPR card test was 92.3%, and quantitative agreement +/- 1 dilution for the TRUST and RPR card test versus the VDRL slide test averaged 50%. The TRUST appeared to be comparable to the RPR card test in all parameters compared.

Toluidine red unheated serum test, a nontreponemal test for syphilis.

We have shown that a modification of the color-coded antigen developed by Kasatiya and Lambert (Appl. Microbiol. 28:317-318, 1974) can be used as a substitute for other nontreponemal antigens used in screening tests for syphilis. The antigen is based on the Venereal Disease Research Laboratory antigen, with EDTA, choline chloride, and toluidine red toner added. Performance of the toluidine red unheated serum test (TRUST) is identical to that of the rapid plasma reagin 18-mm circle card test (U.S. Department of Health, Education, and Welfare, Public Health Service Publication no. 411). In a series of preliminary evaluations, the TRUST antigen was found to be stable over a period of 6 months at 4 degrees C. In a comparison of TRUST with the rapid plasma reagin card test, the qualitative agreement was 100%, whereas agreement between these two tests and the Venereal Disease Research Laboratory slide test was 99.7%. The quantitative agreement +/- 1 twofold dilution between TRUST and the rapid plasma reagin card test was 100%; between TRUST and the Venereal Disease Research Laboratory slide test it was 75.0%; and between the rapid plasma reagin card and Venereal Disease Research Laboratory slide tests it was 60.0%.