Fluorescent Treponemal Antibody Test. Modification Based on Quantitation (FTA-200)

Abstract

The Fluorescent Treponemal Antibody (FTA) test described previously( 1) was critically appraised through participation in the Serology Evaluation and Research Assembly (SERA) Study conducted in 1956-57 ( 2 ) , and shown to produce highly sensitive and specific results. However, since completion of the SERA Study, a new chemical compound, fluorescein isothiocyanate, has been introduced (3) and is employed to produce labeled antiserums of increased potency ( 4 ) . Since fluorescein labeled antihuman globulin is the treponemal antibody detector system of the FTA test, an improvement in this reagent is reflected in an apparent increase in test. reactivity. This means that although the original I' TA test had a desirable level of reactivity, the procedure as performed( 5 ) with pressently available reagents has not been so measured. In this study, quantitation of the FTA test was undertaken to determine the present sensitivity and specificity olf the test as related to new and improved reagents and to ascertain any changes in qualitative procedure which might be employed to obtain a more satisfactolry result.Materials and methods. Test serums were obtained from the Serum Bank, USPHS Serologic Evaluation Study, and TPI Testing Service, all Venereal Disease Research ILab. Serums from the Serum Bank and TPI Testing service had been preserved by freezing at -20°C. SERA Study serums were selected for testing on basis of categories and availability. Qualitative FTA tests were performed by employing a test serum dilution of 1:s as described earlier ( 5 ) and a t dilution of 1 : 200 (FTA-200). Test serums demonstrating Reactive ( R) or Weakly Reactive ( W R ) results a t the 1 : 5 dilution were retested by preparing serial dilutions and determining a 2+ Reactive endpoint. Results obtained by the experimental qualitative procedure ( FTA-200) are expressed in terms of Nonreactive ( N ) or Reactive ( R ) . Weakly Reactive (WR I + )findings as designated for the FTA test are recorded as Nonreactive (N) in the FTA-200 procedure. Fluorescein labeled horse antihuman-globulin" was used as the treponemal antibody indicator in all tests. T h e conjugate was diluted a t 1:80 (optimal dilution for this particular lot) in phosphate buffered saline, p H 7.2 containing 2% Tween 80. Lyophilized Treponema pallidum antigen was employed for smear preparations. Two smears were prepared for each slide/test serum dilution. Of the 2 smears, the most satisfactory in terms of microscopic appearance (numbers and distributioin of T . pallida) was used folr reading and determining final reactions.

The use of the indirect fluorescent antibody technique in avian spirochaetosis1

“…However, this method would prove laborious and time-consuming when used for the detection of antibodies. Thus, the use of the indirect fluorescent antibody technique, which has been extensively investigated for detecting antibodies to Trepunema pallidum (Deacon et al, 1957;Deacon et al, 1960;Deacon and Hunter, 1962;Eng et al, 1963), was examined in this study. Marked differences in antibody titres to B. anserina were found in sera from immune, convalescent and healthy chickens.…”

“…Gross and Ball (1964) used the direct fluorescent antibody technique for the detection of Borrelia anserina in tissues and blood of chickens. Fluorescent antibody techniques have also been widely applied in the study of diseases caused by spirochaetal agents, such as Leptospira (Dacres, 1961 ;Dacres, 1963;Hirschberg and Vaughn, 1973;Hodges andEkdahl, 1973;Maestrone, 1963;Sundham and White, 1972), and Treponema (Deacon et al, 1957;Deacon et al, 1960;Deacon and Hunter, 1962;Eng et al, 1963;Kellog and Deacon, 1964).…”

Sensibilité et spécificité des tests tréponémiques – en particulier des tests d’immobilisation des tréponèmes et d’immuno-fluorescence

“…Deacon, Freem an et H arris [69] o n t proposé il y a peu de tem p s une m odification de la te c h n iq u e ; a y a n t co n sta té , depuis leurs prem iers tra v a u x u n e a u g m e n ta tio n de la sensibilité de la réactio n (due à l'in tro d u c tio n de l'iso th io c y a n a te à la p lace de l'iso c y a n a te de fluorescé ine, à l'usage de séru m s conjuguées de plus h a u ts titre s e t à l'in cor p o ra tio n de T w een 80 qui facilite la liaison an tig èn e-an tico rp s) ces a u te u rs e stim e n t q u e c e tte a u g m e n tatio n de sensibilité te n d à d im in u er la spécificité de la ré a c tio n ; ils p ro p o sen t donc de faire dis p a ra ître les réactio n s fa ib le m e n t positives, q u i se ra ie n t h a b itu elle m e n t non spécifiques en d ilu a n t les sérum s à ex am in er non plus à l/ 5 ou l/10, m ais à , / 20o (d 'où le nom FTA -200 test).…”

Reactions of extracts of Reiter treponeme with syphilitic and non-syphilitic human sera in the single radial haemolysis technique

“…Techniques utilising Treponema pallidum antigens include the Treponema pallidum immobilisation test (TPI) (Nelson and Mayer, 1949), the fluorescent treponemal antibody test (FTA) (Deacon, Freeman and Harris, 1960), the improved FTA (FTA-ABS) (Hunter, Deacon and Meyer, 1964) and the Treponema pallidum haemagglutination test (TPHA) (Rathlev, 1967). The TPI test is technically difficult (Wilkinson and Johnston, 1959) and is now rarely used.…”