Line Immunoassay for Confirmation and Discrimination of Human T-Cell Lymphotropic Virus Infections in Inconclusive Western Blot Serum Samples from Brazil.

Karoline R Campos,Thessika H A Araujo,Fred L N Santos,Bernardo Galvão-Castro,Noilson L S Gonçalves,Vanessa Da Silva Brito,Adele Caterino-De-Araujo,Yi-Wei Tang

doi:10.1128/jcm.01384-19

Abstract

Difficulties in confirming and discriminating human T-cell lymphotropic virus type 1 (HTLV-1) and HTLV-2 infections by serological Western blot (WB) assays (HTLV Blot 2.4; MP Biomedicals) have been reported in Brazil, mainly in HIV/AIDS patients, with a large number of WB-indeterminate and WB-positive but HTLV-untypeable results. Nonetheless, a line immunoassay (LIA) (INNO-LIA HTLV-I/II; Fujirebio) provided enhanced specificity and sensitivity for confirming HTLV-1/2 infections. To add information concerning the improved ability of the LIA in relation to WB when applied to samples of individuals from different risk groups from Brazil, we performed the present study. Three groups were analyzed: group 1 (G1), with 62 samples from HIV/AIDS patients from São Paulo, SP (48 WB indeterminate and 14 HTLV untypeable); group 2 (G2), with 24 samples from patients with hepatitis B or hepatitis C from São Paulo (21 WB indeterminate and 3 HTLV untypeable; 17 HIV seropositive); and group 3 (G3), with 25 samples from an HTLV outpatient clinic in Salvador, Bahia (16 WB indeterminate and 9 HTLV untypeable; all HIV seronegative). Overall, the LIA confirmed HTLV-1/2 infection (HTLV-1, HTLV-2, or HTLV) in 66.1% (G1), 83.3% (G2), and 76.0% (G3) of samples. Interestingly, the majority of WB-indeterminate results were confirmed by the LIA as being HTLV-2 positive in G1 and G2 but not in G3, in which the samples were defined as being HTLV-1 or HTLV positive. These results agree with the virus types that circulate in such patients of different regions in Brazil and emphasize that the LIA is the best serological test for confirming HTLV-1 and HTLV-2 infections, independently of being applied in HTLV-monoinfected or HTLV-coinfected individuals.

Highlights

Despite regional variations, Brazil is one of the largest areas of the world where human T-cell lymphotropic virus type 1 (HTLV-1) is endemic [1]
Another molecular assay, real-time PCR or quantitative PCR, was proposed as a confirmatory HTLV-1/2 molecular assay; low sensitivity was found when applied on HIV blood samples and on those from Brazilian patients infected with human T-cell lymphotropic virus type 2 (HTLV-2), which could be due to low HTLV-2 proviral loads [12,13,14,15]
More males were found among the hepatitis B virus (HBV)/hepatitis C virus (HCV)-infected patients in group 2 (G2), with significant differences in relation to HIV/AIDS patients in group 1 (G1) and HTLV patients in group 3 (G3) (P ϭ 0.0048)

Summary

Introduction

Brazil is one of the largest areas of the world where human T-cell lymphotropic virus type 1 (HTLV-1) is endemic [1]. In 1998, a new HTLV-1/2 serological confirmatory assay employed a line immunoassay (LIA) with a nylon membrane sensitized with the most relevant antigens, recombinant proteins, or synthetic peptides of HTLV-1 and HTLV-2 [16] This new immunoassay (INNO-LIA HTLV) demonstrated better results than WB, with improved sensitivity for the confirmation of HTLV-1 and HTLV-2 infections, thereby reducing numbers of WB-indeterminate results [16]. Few studies have compared the performances of LIA and WB in Brazil, one employing blood bank samples [17] and two using serum samples from HIV/AIDS patients [14, 15]. These studies indicated that the LIA was the best assay to confirm or rule out HTLV-1/2 infection. The present study aimed to evaluate the use of INNO-LIA for clarifying WB-indeterminate and WB-HTLV-untypeable serum samples

Methods

Results

Conclusion