Evaluation of a new HTLV-I/II polymerase chain reaction

Detection of HTLV-I and -II in Scottish blood donor samples and archive donations

BACKGROUND AND OBJECTIVES

Positive samples identified during routine serological screening for HCV (hepatitis C virus), HBV (hepatitis B virus) and HIV (human immunodeficiency virus) are confirmed by nucleic acid testing in the SNBTS (Scottish National Blood Transfusion Service) PCR Reference laboratory. Serological screening for HTLV-I (human T-cell lymphotropic virus type I) and -II was implemented in Scotland in November 2002, at which time a PCR assay was not available for confirmation. Our aim was to develop a real-time PCR assay that could be used for the confirmation of samples showing HTLV-I serological positive or indeterminate reactivity and to investigate whether a serologically silent carrier status exists ('Tax' only) in the Scottish donor population.

MATERIALS AND METHODS

A real-time HTLV PCR was devised using a lymphoblastoid cell line which has HTLV-I sequence integrated in the genome (C8166 cells). These were spiked into peripheral blood mononuclear cells. The assay was evaluated on archived serologically confirmed HTLV-positive samples and new positives identified since implementation of screening.

RESULTS

HTLV-I and -II were detected in cells and plasma from stored donations and a serological positive donation identified in routine screening. HTLV DNA can also be amplified from the plasma obtained from plasma preparation tubes. There was no evidence of a carrier status ('Tax' only) in 100 serologically negative blood donors tested. The PCR assay developed is reliable and sensitive, capable of identifying one copy of HTLV-I.

CONCLUSIONS

The HTLV PCR is a useful addition for HTLV confirmation, especially in serologically indeterminate samples and for look-back studies. HTLV PCR confirmation will provide additional useful information for donor medical staff for counselling donors.

Strategies for diagnosis of HTLV-I and -II

BACKGROUND

No gold standard exists for diagnosis of HTLV infection. The aim of thus study was to compare the accuracy of a combination of two sensitive ELISAs with Western blot (WB), a line immunoassay, and PCR for diagnosis of HTLV infection.

STUDY DESIGN AND METHODS

Nine hundred eighty-five specimens were tested for the presence of HTLV antibodies by HTLV-I and/or HTLV-II EIAs (Murex and Ortho), WB (Diagnostic Biotechnology), line immunoassay (INNO-LIA, Innogenetics), and/or presence of HTLV DNA by PCR. The results were compared with the probable HTLV infection status of each subject, as determined by detailed review of all available laboratory, clinical, and epidemiologic data.

RESULTS

The sensitivity for diagnosis of HTLV-I infection was high for all assays evaluated, but both PCR and WB had a lower sensitivity rate (approx., 80%) for confirmation of HTLV-II. INNO-LIA detected 94 percent of the HTLV-II-positive samples. However, Murex EIA in combination with Ortho EIA was 100-percent sensitive for the detection of both HTLV-I and HTLV-II antibodies. Furthermore, the number of samples giving indeterminate results in the ELISA combination was much lower as compared with WB (2.5% vs. 50%).

CONCLUSION

Based on these findings, a new, more sensitive and specific test strategy for HTLV diagnosis than the current algorithm, which includes WB, is proposed. Thereby, both the direct and indirect costs can be substantially reduced.

The effect of antiretroviral therapy on HTLV infection

No effective treatment for TSP/HAM has been described so far. Interventions with corticosteroids, plasmapheresis, interferon and, more recently, with antiretroviral drugs have been tried with poor results. The main HTLV replication mechanism is thought to be through clonal expansion of HTLV-infected cells, which excludes the involvement of the reverse transcriptase (RT) enzyme. However, a virological and clinical improvement has been noticed in HTLV-I carriers suffering from TSP/HAM receiving zidovudine or lamivudine. Herein, we describe the virological and clinical outcome in two TSP/HAM patients infected with HTLV-I treated with zidovudine plus lamivudine, and in two HTLV-II/HIV-1 co-infected patients receiving triple combinations including lamivudine. While, one TSP/HAM patient experienced a 2 log decrease in HTLV-I proviral load, an increase of 1 log was observed in another patient after several months of treatment with zidovudine plus lamivudine. The two HTLV-II/HIV-1 co-infected patients showed an initial increase in HTLV-II proviral load after beginning HAART followed by a slight decline a few months later. Plasma HIV-1 RNA fell to <50 copies/ml in both patients after beginning therapy. None of the four HTLV positive patients developed genetic changes at the conserved YMDD domain within their respective RT genes, which could be related to lamivudine resistance. No clinical improvement was observed in one TSP/HAM patient after more than 1 year on treatment with nucleoside analogues. The inhibition of the HTLV RT along with the cytostatic effect of some nucleoside analogues, including zidovudine, could reduce HTLV replication, and therefore reduce HTLV proviral load. The clinical consequences of this effect need to be further examined.

Prevalence of HTLV infection in pregnant women in Spain

OBJECTIVE

To estimate the prevalence of HTLV infection among pregnant women in Spain.

METHODS

A commercial ELISA incorporating HTLV-I and HTLV-II antigens was used for HTLV antibody screening. Repeatedly reactive samples were further examined by western blot. Moreover, confirmation with PCR was performed when cells were available.

RESULTS

20,366 pregnant women in 12 different Spanish cities were tested in a 3 year period (July 1996 to August 1999). 32 samples were repeatedly reactive by ELISA, and 10 of them were confirmed as positive by western blot (eight for HTLV-II and two for HTLV-I). In addition, three of 13 women who had an indeterminate western blot pattern yielded positive results for HTLV-II by PCR. All 11 HTLV-II infected women had been born in Spain, and all but one were former drug users. Seven of them were coinfected with HIV-1. One HTLV-I infected woman was from Peru, where HTLV is endemic and where she most probably was infected during sexual intercourse.

CONCLUSION

The overall prevalence of HTLV infection among pregnant women in Spain is 0.064% (13/20,366), and HTLV-II instead of HTLV-I is the most commonly found variant. A strong relation was found among HTLV-II infection and specific epidemiological features, such as Spanish nationality and injecting drug use. Although HTLV-II can be vertically transmitted, mainly through breast feeding, both the low prevalence of infection and its lack of pathogenicity would not support the introduction of HTLV antenatal screening in Spain.

In vivo fluctuation of HTLV-I and HTLV-II proviral load in patients receiving antiretroviral drugs

HTLV-I and HTLV-II infect T lymphocytes. A high HTLV-I proviral load in peripheral blood mononuclear cells (PBMCs) has been associated with a higher risk of neurologic disease. For HTLV-II, large numbers of infected lymphocytes might contribute to accelerate the immunodeficiency and increase the risk of neuropathy in HTLV-II/HIV-1 coinfected people. We have examined the impact of antiretroviral drugs on HTLV proviral load, testing longitudinal samples collected from 1 HTLV-I infected patient suffering HTLV-I-associated myelopathy (HAM), and two HTLV-II/ HIV-1 coinfected subjects. The HAM patient showed a reduction greater than 2 log in the peripheral proviral load after being treated with zidovudine and lamivudine. In contrast, potent antiretroviral treatment in HIV-1/HTLV-II coinfected carriers produced an initial increase in the HTLV proviral load, which was followed by a reduction greater than 1 log thereafter. In conclusion, antiretroviral drugs seem to reduce HTLV proviral load, although in HIV-1 coinfected persons a transient increase in HTLV proviral load could reflect the rapid blocking of HIV-1 replication occurring in response to therapy, thus causing an increase in the number of circulating T lymphocytes carrying HTLV proviral DNA.

Evaluation of the INNO-LIA HTLV I/II assay for confirmation of human T-cell leukemia virus-reactive sera in blood bank donations

We have evaluated a new serological confirmatory test (INNO-LIA HTLV I/II Ab [INNO-LIA]) for human T-cell leukemia virus (HTLV) using a large collection of samples from Brazilian blood donors (São Paulo region) and compared the results with those obtained by Western blotting (WB) tests (WB2.3 and WB2.4). Blood donations were initially screened by enzyme-linked immunosorbent assays (ELISAs) based on viral lysates, and repeatedly reactive samples were further tested by WB2.3. When available, samples were also tested by PCR, two additional ELISAs based on recombinant antigens (recombinant ELISAs), a new-generation WB assay (WB2.4), and the INNO-LIA. Of the 18,169 samples tested, 292 (1.61%) were repeatedly reactive in the ELISAs (viral lysate based) and were further tested by WB2.3; 97 were positive (19 that were typed as HTLV type I [HTLV-I], 12 that were typed as HTLV type II [HTLV-II], and 66 that were nontypeable), 17 were negative, and 178 had indeterminate results. Of the samples with indeterminate results, 172 were tested by INNO-LIA, which could resolve 153 samples as negative. Regarding the positive samples, WB2. 3 and INNO-LIA produced concordant results for all HTLV-I-positive samples, whereas for HTLV-II they agreed for 10 of 12 samples; the 2 samples with discordant results were considered to be positive for HTLV-II by WB with WB2.3 but negative for HTLV-II by INNO-LIA and the two recombinant ELISAs. Furthermore, of the 66 nontypeable samples, 60 underwent testing by INNO-LIA; 54 turned out to be negative by the latter test as well as by recombinant ELISAs. In conclusion, the new serological confirmatory assay for HTLV (INNO-LIA HTLV I/II Ab) resolved the results for the majority of the indeterminate and positive-untypeable samples frequently observed by WB assays.

Assessment of a new immunoassay for serological confirmation and discrimination of human T-cell lymphotropic virus infections

The present study evaluated a new confirmatory assay for antibodies to human T-cell lymphotropic virus type 1 and 2 (HTLV-1 and HTLV-2) proteins performed with serum samples from various commercial sources. The new test is a line immunoassay (LIA) with a nylon membrane sensitized with the most relevant antigens of HTLVs: the envelope gp46 and gp21 as well as the gag p24 and p19 antigens, represented by either recombinant proteins or synthetic peptides. A total of 176 serum or plasma samples were tested, of which 66 were HTLV-1 positive, 72 were HTLV-2 positive, and 38 were HTLV negative; of the 38 HTLV-negative samples 23 were indeterminate by Western blotting (WB). Serially diluted samples (n = 33) from HTLV-1- and HTLV-2-infected patients were also analyzed to determine the sensitivity of the new assay. The new confirmatory assay (INNO-LIA HTLV) performed markedly better than WB assays for those samples reactive by screening. Accurate confirmation of the presence of HTLV-1 and HTLV-2 antibodies and accurate discrimination of HTLV-1 and HTLV-2 antibodies were obtained for all the HTLV-seropositive samples. Due to its enhanced specificity and sensitivity, the new assay not only improves the ability to confirm and discriminate HTLV infections but also eliminates the vast majority of WB-indeterminate and false-positive specimens.