Re-evaluation of anti-HTLV-I Western blot assay using HTLV-I and HTLV-II serum panels

Abstract

Background: Western blot assay is accepted to be a confirmatory test of anti-HTLV-I antibodies, and several WB criteria have been proposed for confirming HTLV-I seropositivity. There is a necessity for comprehensive study on the criteria. Objectives: This study was performed to evaluate anti-HTLV-I WB kits and feasibility of the WB criteria. Study design: We tested 3 commercially available WB kits: PROBLOT HTLV-I, Eitest ATL-WB and HTLV BLOT 2.2, by a standard HTLV-I serum panel which had been established in our previous study. Sensitivity and specificity to detect each component of HTLV-I antigens were evaluated by the correlation coefficient, R-value. Specificity of the anti-HTLV-I WB kits and HTLV BLOT 2.3 was further evaluated by a standard HTLV-II serum panel established from the HTLV-I II epidemiological surveillance of Colombian natives. Results: PROBLOT HTLV-I showed high R-values (⩾0.980) for p28, p53 and gp46, but low R-values (<0.900) for p19 and p24. Eitest ATL-WB showed a high R-value for p19, but low R-values for p53, gp46 and rgp21. HTLV BLOT 2.2 showed high R-values for p28 and recombinant gp46-I, but low R-values for p53 and gp46. The HTLV-II serum panel showed positive reactions with p24 and p19 of HTLV-I but a little if any reactions with p28 and gp46 of HTLV-I. Although these reactions could not define HTLV-II-specific WB patterns in anti-HTLV-I WB, HTLV-I- and HTLV-II-specific recombinant gp46 in HTLV BLOT 2.3 were useful to distinguish anti-HTLV-II antibodies. Conclusions: The currently available anti-HTLV-I WB kits are sufficient for confirmatory testing of anti-HTLV-I antibodies with WHO criteria using one gag and one env positivity, but they are inadequate for anti-HTLV-II confirmatory testing.