A Strategy for Screening and Confirmation of HTLV-1/2 Infections in Low-Endemic Areas

Abstract

Serological tests have been widely used for detecting human T-cell lymphotropic virus type 1/2 (HTLV-1/2) antibodies in the endemic areas, but their performance in low-risk populations is rarely reported. The aim of this study was to evaluate the performance of four HTLV-1/2 screening assays and to discuss a strategy for diagnosis of HTLV-1/2 infection in a non-endemic area. At the present study, 1546 specimens repeatedly reactive (RR) by one screening ELISA were collected from blood centers/banks from January 2016 to April 2019. Avioq-ELISA, Murex-ELISA, Roche-ECLIA and Fujirebio-CLIA were independently performed on each plasma sample and compared to WB and LIA confirmatory tests. Positive or indeterminate specimens with blood available were quantified by qPCR. The results showed that 48 samples were finally confirmed as HTLV-1 positive, 13 were HTLV positive, 151 were indeterminate, and 387 were negative. All the WB-positive samples were also LIA-positive. Roche-ECLIA showed the highest sensitivity that was able to detect 91.8% positives and combined with the Murex-ELISA would significantly increase the positive detection rate (98.4%). In addition, LIA yield more indeterminate and HTLV-untyped results than WB (152 vs. 27), but was able to resolve infection status of some individuals with an indeterminate WB. Besides, 3 WB indeterminate and 1 LIA-untyped samples were confirmed as HTLV-1 positive by qPCR. Based on these findings, we put forward a proper test strategy for HTLV-1/2 diagnosis in low-prevalence areas. If possible, the Roche-ECLIA with the highest sensitivity is suggested as a second screening assay in primary labs. If not, all RR specimens are recommended to be firstly retested by Roche-ECLIA and Murex-ELISA in the reference lab. Secondly, samples reactive to any one of the two tests were quantified by qPCR, and then the NAT-negatives were furtherly submitted to LIA for confirmation. Thereby, the cost can be reduced and the diagnostic accuracy would be improved.

Human T-Lymphotropic Virus-1/2 Infection in Central Brazil Prisons: A Multicenter Study

“…One sample (ID-573) was HTLV indeterminate in the western blot test, but anti-HTLV was detected by ELISA method and the presence of HTLV proviral DNA was detected by amplification of the HTLV Tax gene through nested-PCR. The finding of indeterminate results in the WB for HTLV and positive by PCR has already been reported in other studies (Broutet et al, 1996;Osti et al, 1998;Ji et al, 2020;Halbrook et al, 2021). About this phenomenon, one hypothesis that we can consider is a longer time for seroconversion that can be associated with low antigenic stimulation due to the defective proviruses (Cánepa et al, 2015;Kuramitsu et al, 2017;Gomes et al, 2020).…”

Seroprevalence of human T-lymphotropic virus infection among blood donors in China: a first nationwide survey

“…Two assays based on the ELISA method (R1 and R2) showed unsatisfied positive detection rates using confirmed positive samples. Furthermore, our previous study showed remarkable different PPVs of these four assays, varying from 21.0% (R3) to 91.7% (R1) [ 25 ]. Therefore, a special strategy should be applied to screen samples from non-epidemic areas to avoid both false negatives and false positives results.…”

A novel high performing multiplex immunoassay Multi-HTLV for serological confirmation and typing of HTLV infections

“…For instance during seroconversion, antibodies to GP21 appear earlier than those to P24 and P19 [42]. One follow-up study examined indeterminate patient profiles with an isolated GP21-I/II band and found that some patients became HTLV-positive over time suggesting that some patients were in the seroconversion phase at the time of testing [26].…”

“…HTLV-2/HIV co-infection) due to proviral load reduction [24]. Therefore PCR should not be used alone for confirmation but rather in combination with WB or for investigation of inconclusive results [25,26]. The INNO-LIA immunoassay, widely used in Europe, is currently considered to be excellent for serological confirmation [20,27,28].…”

“…The INNO-LIA immunoassay, widely used in Europe, is currently considered to be excellent for serological confirmation [20,27,28]. The test is superior to WB, due to clearer interpretation criteria directly linked to a decreased number of antigens, and readability and improved performance by eliminating uncertain and false positive results [20,26,29]. However, the test is costly, making it difficult to use in routine diagnostics, especially in resource limited areas such as South America [20].…”