Serological, epidemiological, and molecular differences between human T-cell lymphotropic virus Type 1 (HTLV-1)-seropositive healthy carriers and persons with HTLV-I Gag indeterminate Western blot patterns from the Caribbean

Geographic distribution, clinical epidemiology and genetic diversity of the human oncogenic retrovirus HTLV-1 in Africa, the world's largest endemic area

The African continent is considered the largest high endemic area for the oncogenic retrovirus HTLV-1 with an estimated two to five million infected individuals. However, data on epidemiological aspects, in particular prevalence, risk factors and geographical distribution, are still very limited for many regions: on the one hand, few large-scale and representative studies have been performed and, on the other hand, many studies do not include confirmatory tests, resulting in indeterminate serological results, and a likely overestimation of HTLV-1 seroprevalence. For this review, we included the most robust studies published since 1984 on the prevalence of HTLV-1 and the two major diseases associated with this infection in people living in Africa and the Indian Ocean islands: adult T-cell leukemia (ATL) and tropical spastic paraparesis or HTLV-1-associated myelopathy (HAM/TSP). We also considered most of the book chapters and abstracts published at the 20 international conferences on HTLV and related viruses held since 1985, as well as the results of recent meta-analyses regarding the status of HTLV-1 in West and sub-Saharan Africa. Based on this bibliography, it appears that HTLV-1 distribution is very heterogeneous in Africa: The highest prevalences of HTLV-1 are reported in western, central and southern Africa, while eastern and northern Africa show lower prevalences. In highly endemic areas, the HTLV-1 prevalence in the adult population ranges from 0.3 to 3%, increases with age, and is highest among women. In rural areas of Gabon and the Democratic Republic of the Congo (DRC), HTLV-1 prevalence can reach up to 10-25% in elder women. HTLV-1-associated diseases in African patients have rarely been reported in situ on hospital wards, by local physicians. With the exception of the Republic of South Africa, DRC and Senegal, most reports on ATL and HAM/TSP in African patients have been published by European and American clinicians and involve immigrants or medical returnees to Europe (France and the UK) and the United States. There is clearly a huge underreporting of these diseases on the African continent. The genetic diversity of HTLV-1 is greatest in Africa, where six distinct genotypes (a, b, d, e, f, g) have been identified. The most frequent genotype in central Africa is genotype b. The other genotypes found in central Africa (d, e, f and g) are very rare. The vast majority of HTLV-1 strains from West and North Africa belong to genotype a, the so-called 'Cosmopolitan' genotype. These strains form five clades roughly reflecting the geographic origin of the infected individuals. We have recently shown that some of these clades are the result of recombination between a-WA and a-NA strains. Almost all sequences from southern Africa belong to Transcontinental a-genotype subgroup.

Prevalence of Human T-Lymphotropic Virus Type 1 in Brain-Dead Organ Donors

Background: This study aimed to assess the prevalence of human T-lymphotropic virus type 1 (HTLV-1) among brain-dead organ donors at Masih Daneshvari Hospital in Tehran, Iran. Methods: By enzyme-linked immunosorbent assay (ELISA), 54 organ donors were screened for HTLV-1 virus in this descriptive cross-sectional study. Following that, Western blot confirmation was performed to confirm the HTLV-I infection. Results: Anti-HTLV-1 antibodies were detected in 2 (3.4%) cases out of 54 patients tested by ELISA. A western blot was performed in cases of positive results, but none of the subjects tested positive for HTLV-1 infection. Conclusions: The results of the present study indicated rare cases of HTLV-I infection in brain-dead organ donors. However, it is recommended that organ donors be investigated for the prevalence of this virus.

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

Background

Human T-Cell Lymphotropic Viruses (HTLV) type 1 and type 2 account for an estimated 5 to 10 million infections worldwide and are transmitted through breast feeding, sexual contacts and contaminated cellular blood components. HTLV-associated syndromes are considered as neglected diseases for which there are no vaccines or therapies available, making it particularly important to ensure the best possible diagnosis to enable proper counselling of infected persons and avoid secondary transmission. Although high quality antibody screening assays are available, currently available confirmatory tests are costly and have variable performance, with high rates of indeterminate and non-typable results reported in many regions of the world. The objective of this project was to develop and validate a new high-performance multiplex immunoassay for confirmation and discrimination of HTLV-1 and HTLV-2 strains.

Methodology/Principal findings

The multiplex platform was used first as a tool to identify suitable antigens and in a second step for assay development. With data generated on over 400 HTLV-positive blood donors sourced from USA and French blood banks, we developed and validated a high-precision interpretation algorithm. The Multi-HTLV assay demonstrated very high performance for confirmation and strain discrimination with 100% sensitivity, 98.1% specificity and 100% of typing accuracy in validation samples. The assay can be interpreted either visually or automatically with a colorimetric image reader and custom algorithm, providing highly reliable results.

Conclusions/Significance

The newly developed Multi-HTLV is very competitive with currently used confirmatory assays and reduces considerably the number of indeterminate results. The multiparametric nature of the assay opens new avenues to study specific serological signatures of each patient, follow the evolution of infection, and explore utility for HTLV disease prognosis. Improving HTLV diagnostic testing will be critical to reduce transmission and to improve monitoring of seropositive patients.

HTLV viruses are responsible for more than 10 million cases of infection worldwide. The infection is considered as a neglected disease due to lack of vaccines and treatments. Accurate diagnosis is crucial for counselling infected persons and prevention of secondary transmissions. In spite of the development of excellent serological screening assays, many cases of indeterminate and untyped results are still regularly reported and their infection status remain uncertain. To address the need of more precise diagnosis, we have developed a new cutting-edge in-vitro diagnostic confirmation test, named Multi-HTLV, which has been validated on a large panel of HTLV samples. The test is a multiplex immunoassay allowing powerful detection of antibodies against HTLV through combination of a set of selective and validated virus-specific antigens in a blood sample. The Multi-HTLV assay increases the reliability of HTLV diagnostics and strain typing thanks to a high precision mathematical algorithm.

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

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.

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.

Performance of Commercially Available Serological Screening Tests for Human T-Cell Lymphotropic Virus Infection in Brazil

Serological screening for human T-cell lymphotropic virus type 1 (HTLV-1) is usually performed using enzyme-linked immunosorbent assay (ELISA), particle agglutination, or chemiluminescence assay kits. Due to an antigen matrix improvement entailing the use of new HTLV antigens and changes in the format of HTLV screening tests, as well as newly introduced chemiluminescence assays (CLIAs), a systematic evaluation of the accuracy of currently available commercial tests is warranted. We aimed to assess the performance of commercially available screening tests for HTLV infection diagnosis. A diagnostic accuracy study was conducted on a panel of 397 plasma samples: 200 HTLV-negative plasma samples, 170 HTLV-positive plasma samples, and 27 plasma samples indeterminate by Western blotting (WB). WB-indeterminate samples (i.e., those yielding no specific bands for HTLV-1 and/or HTLV-2) were assessed by PCR, and the results were used to compare agreement among the commercially available ELISA screening tests. For performance analysis, WB-indeterminate samples were excluded, resulting in a final study panel of 370 samples. Three ELISA kits (Murex HTLV-1/2 [Murex], anti-HTLV-1/2 SYM Solution [SYM Solution], and Gold ELISA HTLV-1/2 [Gold ELISA]) and one CLIA kit (Architect rHTLV-1/2) were evaluated. All screening tests demonstrated 100% sensitivity. Concerning the HTLV-negative samples, the SYM Solution and Gold ELISA kits had specificity values of >99.5%, while the Architect rHTLV-1/2 test presented 98.1% specificity, followed by Murex, which had a specificity of 92.0%. Regarding the 27 samples with WB-indeterminate results, after PCR confirmation, all ELISA kits showed 100% sensitivity but low specificity. Accuracy findings were corroborated by the use of Cohen's kappa value, which evidenced slight and fair agreement between PCR analysis and ELISAs for HTLV infection diagnosis. Based on the data, we believe that all evaluated tests can be safely used for HTLV infection screening.

Proviral Features of Human T Cell Leukemia Virus Type 1 in Carriers with Indeterminate Western Blot Analysis Results

Western blotting (WB) for human T cell leukemia virus type 1 (HTLV-1) is performed to confirm anti-HTLV-1 antibodies detected at the initial screening of blood donors and in pregnant women. However, the frequent occurrence of indeterminate results is a problem with this test. We therefore assessed the cause of indeterminate WB results by analyzing HTLV-1 provirus genomic sequences. A quantitative PCR assay measuring HTLV-1 provirus in WB-indeterminate samples revealed that the median proviral load was approximately 100-fold lower than that of WB-positive samples (0.01 versus 0.71 copy/100 cells). Phylogenic analysis of the complete HTLV-1 genomes of WB-indeterminate samples did not identify any specific phylogenetic groups. When we analyzed the nucleotide changes in 19 HTLV-1 isolates from WB-indeterminate samples, we identified 135 single nucleotide substitutions, composed of four types, G to A (29%), C to T (19%), T to C (19%), and A to G (16%). In the most frequent G-to-A substitution, 64% occurred at GG dinucleotides, indicating that APOBEC3G is responsible for mutagenesis in WB-indeterminate samples. Moreover, interestingly, five WB-indeterminate isolates had nonsense mutations in Pol and/or Tax, Env, p12, and p30. These findings suggest that WB-indeterminate carriers have low production of viral antigens because of a combination of a low proviral load and mutations in the provirus, which may interfere with host recognition of HTLV-1 antigens.

Analysis of HTLV-1 proviral load (PVL) and antibody detected with various kinds of tests in Japanese blood donors to understand the relationship between PVL and antibody level and to gain insights toward better antibody testing

Adult T-cell leukemia/lymphoma (ATL) occurs in approximately 5% of individuals infected with human T-cell leukemia virus type 1 (HTLV-1). A high proviral load (PVL; more than four copies per 100 peripheral blood mononuclear cells (PBMCs) or 1.6 copies per 100 blood leukocytes) and being male are risk factors for ATL development. Whether anti-HTLV-1 antibody level is related to such risk is unknown. Here, PVL and antibody levels were examined using real-time PCR and other tests in 600 HTLV-1 positive screened Japanese blood donors to understand the relationship between PVL and antibody level in asymptomatic carriers and to gain insights toward better antibody testing for HTLV-1 infection. The 430 donors in whom proviral DNA was detected were considered as true positives for HTLV-1 infection. Among donors aged 40 years or older, more males than females had a PVL corresponding to more than 1.6% infected leukocytes, and an antibody titer below the median (P = 0.0018). In antibody tests using an HTLV-1 positive cell line or Env antigens there was a large discrepancy in antibody titer among 13 provirus-positive samples, probably suggesting that antibody-based screening tests should incorporate multiple HTLV-1 antigens, such as Gag and Env antigens.

Serological and Molecular Methods to Study Epidemiological Aspects of Human T-Cell Lymphotropic Virus Type 1 Infection

We estimated that at least 5-10 million individuals are infected with HTLV-1. Importantly, this number is based on the study of nearly 1.5 billion people living in known human T-cell lymphotropic virus type 1 (HTLV-1) endemic areas, for which reliable epidemiological data are available. However, for some highly populated regions including India, the Maghreb, East Africa, and some regions of China, no consistent data are yet available which prevents a more accurate estimation. Thus, the number of HTLV-1 infected people in the world is probably much higher. The prevalence of HTLV-1 prevalence varies depending on age, sex, and economic level in most HTLV-1 endemic areas. HTLV-1 seroprevalence gradually increases with age, especially in women. HTLV-1 has a simian origin and was originally acquired by humans through interspecies transmission from STLV-1 infected monkeys in the Old World. Three main modes of HTLV-1 transmission have been described; (1) from mother-to-child after prolonged breast-feeding lasting more than six months, (2) through sexual intercourse, which mainly, but not exclusively, occurs from male to female and lastly, (3) from contaminated blood products, which contain HTLV-1 infected lymphocytes. In specific areas, such as Central Africa, zoonotic transmission from STLV-1 infected monkeys to humans is still ongoing.The diagnostic methods used to study the epidemiological aspects of HTLV-1 infection mainly consist of serological assays for the detection of antibodies specifically directed against different HTLV-1 antigens. Screening tests are usually based on enzyme-linked immunoabsorbent assay (ELISA), chemiluminescence enzyme-linked immunoassay (CLEIA) or particle agglutination (PA). Confirmatory tests include mostly Western blots (WB)s or innogenetics line immunoassay (INNO-LIA™) and to a lesser extent immunofluorescence assay (IFA). The search for integrated provirus in the DNA from peripheral blood cells can be performed by qualitative and/or quantitative polymerase chain reaction (qPCR). qPCR is widely used in most diagnostic laboratories and quantification of proviral DNA is useful for the diagnosis and follow-up of HTLV-1 associated diseases such as adult T-cell leukemia (ATL) and tropical spastic paraparesis/HTLV-1 associated myelopathy (TSP/HAM). PCR also provides amplicons for further sequence analysis to determine the HTLV-1 genotype present in the infected person. The use of new generation sequencing methodologies to molecularly characterize full and/or partial HTLV-1 genomic regions is increasing. HTLV-1 genotyping generates valuable molecular epidemiological data to better understand the evolutionary history of this virus.

Low Proviral Load is Associated with Indeterminate Western Blot Patterns in Human T-Cell Lymphotropic Virus Type 1 Infected Individuals: Could Punctual Mutations be Related?

BACKGROUND

indeterminate Western blot (WB) patterns are a major concern for diagnosis of human T-cell lymphotropic virus type 1 (HTLV-1) infection, even in non-endemic areas.

OBJECTIVES

(a) to define the prevalence of indeterminate WB among different populations from Argentina; (b) to evaluate if low proviral load (PVL) is associated with indeterminate WB profiles; and (c) to describe mutations in LTR and tax sequence of these cases.

RESULTS

Among 2031 samples, 294 were reactive by screening. Of them, 48 (16.3%) were WB indeterminate and of those 15 (31.3%) were PCR+. Quantitative real-time PCR (qPCR) was performed to 52 HTLV-1+ samples, classified as Group 1 (G1): 25 WB+ samples from individuals with pathologies; Group 2 (G2): 18 WB+ samples from asymptomatic carriers (AC); and Group 3 (G3): 9 seroindeterminate samples from AC. Median PVL was 4.78, 2.38, and 0.15 HTLV-1 copies/100 PBMCs, respectively; a significant difference (p=0.003) was observed. Age and sex were associated with PVL in G1 and G2, respectively. Mutations in the distal and central regions of Tax Responsive Elements (TRE) 1 and 2 of G3 were observed, though not associated with PVL.The 8403A>G mutation of the distal region, previously related to high PVL, was absent in G3 but present in 50% of WB+ samples (p = 0.03).

CONCLUSIONS

indeterminate WB results confirmed later as HTLV-1 positive may be associated with low PVL levels. Mutations in LTR and tax are described; their functional relevance remains to be determined.

Human T-lymphotropic virus-1 serology in the Northern Territory: 2008-2011

A retrospective observational study of human T-lymphotropic virus-1 (HTLV-1) serology requests made to the Northern Territory Government Pathology Service (NTGPS) between 2008 and 2011, was undertaken to review aspects of HTLV-1 sero-epidemiology and performance of the assays. A total of 5686 HTLV-1 serology requests, representing 3555 individual patients, were received during the study period; 368 HTLV-1 confirmed positive serology results were identified from the 3555 individual patients included in the sample. There was a distinct difference in the performance of the two antibody assays in use during this period, with the Serodia particle agglutination having a 5.7% indeterminate positivity rate compared to 18.1% indeterminate positivity rate of the Abbott HTLV 1/2 assay. We believe this is partially a serological anomaly related to current Australian western blot positive interpretative criteria, rather than false positive screening assay results.The majority (99.7%) of positive results occurred in Indigenous patients. The HTLV-1 positive rate varied geographically from a regional high of 51.7%, and falling inversely with distance from Central Australia. Patients with positive serology had a mean age of 49.9 (±13.9) years, with positivity occurring equally in males and females.

No Evidence of HTLV-II Infection Among Immonoblot Indeterminate Samples Using Nested PCR in Mashhad, Northeast of Iran

OBJECTIVE(S)

Although HTLV-I infection is endemic in different geographical parts of the world including Northeast of Iran, there have been no documents of HTLV-II infection in this region. It is reported that one possible reason for seroindeterminate state in HTLV western blot is HTLV-II virus. This study aimed to investigate the presence of HTLV-II among blood donors with seroindeterminate western blot results.

MATERIALS AND METHODS

Three ml whole blood obtained from 50 blood donors referring to Mashhad Blood Transfusion Organization who had reactive Elisa for HTLV-I and seroindeterminate HTLV western blot state. A conventional PCR was applied to detect HTLV-I provirus using specific primers while a nested PCR was designed with specific external and internal primers for the detection of HTLV-II.

RESULTS

The average age of participants, 39 males and 11 females, was 37.12± 14.36 years. The average OD of the Elisa assay was 1.767± 1.195. The most common indeterminate patterns were Rgp46-II alone (n=12, 27.3%), Rgp46-I alone (n=7, 15.9%), and Rgp46-I with GD21 (n=7, 15.9%).After introducing the DNA to the PCR tests, results revealed 10 (20%) HTLV-I PCR positive samples while no HTLV-II positive sample was detected by nested PCR. There were no significant age, blood group, Optical Density of the Elisa assay, and western blot indeterminate pattern differences between HTLV-I PCR positive and negative samples. Conclusion : No HTLV-II positive sample was detected in this study which confirms the absence of HTLV-II infection in this region. However, high frequency of HTLV-I PCR positive samples among the seroindeterminate cases implies on the important role of molecular techniques for further confirmation of the infection.

A new and frequent human T-cell leukemia virus indeterminate Western blot pattern: epidemiological determinants and PCR results in central African inhabitants

Human T-cell leukemia virus (HTLV) indeterminate Western blot (WB) serological patterns are frequently observed in plasma/serum from persons living in intertropical areas. In the framework of ongoing projects on HTLV-1/2 and related viruses in Central Africa, we systematically analyzed plasma from villagers living in South Cameroon by WB. The group included 1,968 individuals (mean age, 44 years; age range, 5 to 90 years; 978 women/990 men), both Bantus (1,165) and Pygmies (803). Plasma samples were tested by WB analysis (MPD HTLV Blot 2.4) and interpreted according to the manufacturer's instructions. Only clear bands were considered in the analysis. Among the 1,968 plasma samples, 38 (1.93%) were HTLV-1, 13 (0.66%) were HTLV-2, and 6 (0.3%) were HTLV WB seropositive. Furthermore, 1,292 (65.65%) samples were WB sero-indeterminate, including 104 (5.28%) with an HTLV-1 Gag-indeterminate pattern (HGIP) and 68 (3.45%) with a peculiar yet unreported pattern exhibiting mostly a strong shifted GD21 and a p28. The other 619 (31.45%) samples were either WB negative or exhibited other patterns, mostly with unique p19 or p24 bands. DNA, extracted from peripheral blood buffy coat, was subjected to PCR using several primer pairs known to detect HTLV-1/2/3/4. Most DNAs from HTLV-1- and HTLV-seropositive individuals were PCR positive. In contrast, all the others, from persons with HTLV-2, HGIP, new WB, and other indeterminate patterns, were PCR negative. Epidemiological determinant analysis of the persons with this new peculiar WB pattern revealed that seroprevalence was independent from age, sex, or ethnicity, thus resembling the indeterminate profile HGIP rather than HTLV-1. Moreover, this new pattern persists over time.

The prevalence and significance of HTLV-I/II seroindeterminate Western blot patterns

Human T-lymphotropic virus type I (HTLV-I) infects an estimated 15–20 million persons worldwide. A number of diseases have been associated with the virus including adult T-cell leukemia (ATL), HTLV-associated myelopathy/tropical spastic paraparesis (HAM/TSP), HTLV-I uveitis, and HTLV-I-associated infective dermatitis. Once it was shown that there is an increased risk for developing HAM/TSP associated with blood transfusion, screening for HTLV-1 among blood banks was implemented in Japan, United States, France, and the Netherlands. This process includes detection by an enzyme immunoassay (EIA) followed by a confirmatory Western blot (WB) in which recombinant proteins specific for HTLV-I Env glycoproteins are incorporated into WB strips. HTLV-I seropositive results are defined by the presence of antibodies against either gp46 or gp62/68 (both Env protein bands) and either p19, p24, or p53 (one of the gag bands). HTLV-II seropositivity is confirmed by the presence of rgp46-II. However, numerous cases have been documented in which serum samples are reactive by EIA, but an incomplete banding pattern is displayed by subsequent confirmatory WB. Although the significance of these HTLV-I/II seroindeterminates is unclear, it may suggest a much higher incidence of exposure to HTLV-I/II than previously estimated.

Molecular analysis of human T cell lymphotropic virus type 1 and 2 (HTLV-1/2) seroindeterminate blood donors from Northeast Iran: evidence of proviral tax, env, and gag sequences

Human T cell lymphotropic virus type 1 and 2 (HTLV-1/2) Western blot indeterminate results are a problem for blood banks in endemic areas. To determine the prevalence of HTLV-1/2 infection among indeterminate donors, we analyzed 130 cases from Mashhad, an HTLV-1/2 endemic area in Northeast Iran. The most frequent Western blot bands were GD21 alone (37.2%) followed by rgp46-2 alone (32.1%). We further tested 40 available DNA samples of these cases by PCR for viral sequences, tax, gag, and pol, and found five cases (12.5%) to be positive for two or three HTLV-1 genes. There were no significant age, sex, and blood group differences between PCR-positive and PCR-negative cases. Among PCR-positive individuals, the most prevalent Western blot bands were variable combinations of rgp46-1, GD21, and gp21. The mean of the optical density (OD) of the enzyme-linked immunosorbent assay (ELISA) test was significantly higher in PCR-positive individuals. The frequency of the rgp46-1 band was also significantly higher in PCR-positive cases compared to PCR-negative ones. In conclusion, the majority of HTLV-indeterminate donors lack the HTLV provirus and therefore are not considered infected. However, in some cases with higher ODs in the ELISA test and seroreactivity to env proteins, rgp46-1 and GD21 in particular may be indicative of infection and need further evaluation by molecular methods.

Long-term serological follow-up of blood donors with an HTLV-indeterminate western blot: antibody profile of seroconverters and individuals with false reactions

The high proportion of indeterminate results of the screening test for human T-lymphotropic virus (HTLV) infection has been a challenge worldwide. In this study, 60 persons with seroindeterminate results for HTLV were followed until their serological status was defined. At least two independent serological tests (EIA and WB) from sequential samples were performed at an average interval of 4.4 years, totaling 141 serum samples tested. Seroconversion occurred in 12 individuals (reactive by EIA, positive by WB and PCR), and 48 were classified as false reactions (non-reactive EIA and negative PCR, but indeterminate WB). The seroconverter group had epidemiological features similar to those seen in HTLV-1 carriers, and the average time of follow-up for seroconversion was 4 years. In the group with false reactions, the most frequent indeterminate WB pattern in the samples was the presence of p24 alone. This pattern was absent in the seroconverter group, suggesting that p24 alone is an indicator of false reactivity. In contrast, the presence of p19 and p24 seems to be an indicator of true reactivity, since this pattern was frequent (66.7%) among the seroconverters and much less common (10.4% of the first samples) among the individuals with false reactions (P = 0.0001). Thus, HTLV infection may be suspected when reactivity to p19 and p24 is observed. Individuals with an indeterminate WB pattern should be followed-up and retested. The improvement of the HTLV algorithm screening of blood donors has been necessary to reduce inconclusive results and to avoid unnecessary follow-up to define the status of infection.

Anti-Tax antibody levels in asymptomatic carriers, oligosymptomatic carriers, patients with rheumatologic disease or with HAM/TSP do not correlate with HTLV-1 proviral load

BACKGROUND

HTLV-1 infects millions of people around the world and induces myelopathy (HAM/TSP), adult T-cell leukemia (ATL) or other inflammatory or rheumatologic diseases. The host-virus interaction causes asymptomatic carriers to develop HAM/TSP. Biomarkers are needed to predict patients who are at risk for HAM/TSP. Tax is highly immunogenic and is a major target protein recognized by cytotoxic T lymphocytes. Anti-Tax antibodies are involved in HAM/TSP pathogenesis.

OBJECTIVES

To assess anti-Tax IgG reactivity with a flow cytometry assay (FCA) using an infection/transfection system with Vaccinia virus and pLW44/Tax-expressing Tax and to correlate the anti-Tax response and the HTLV-1 proviral load.

STUDY DESIGN

: We enrolled 81 individuals: 9 HTLV-1 seronegative (NP) and 72 HTLV-1 positive (23 HTLV-1 asymptomatic carriers (AC), 12 oligosymptomatic patients (OL), 7 with rheumatologic diseases (DR) and 30 with HAM/TSP (HT)). Anti-Tax reactivity was assessed by FCA, and HTLV-1 proviral load was measured with real time PCR.

RESULTS

The HT and DR groups showed greater anti-Tax IgG reactivity (p<0.001 and p<0.05 comparing HT to the OL and AC group, respectively; p<0.05 comparing DR to the OL group), and the reactivity in the DR+HT group was significantly different when compared to the AC group (p<0.05) and to the OL group (p<0.001). The proviral load was higher in the HT group compared to the OL (p<0.001) and in the HT+DR group compared to OL (p<0.001). There was no correlation between anti-Tax IgG reactivity and proviral load in any of the HTLV-1-infected groups.

CONCLUSION

These findings suggest that although anti-Tax IgG reactivity and the HTLV-1 proviral load are important markers of the development of HTLV-1-associated diseases, their levels are not correlated.

Performance of IgG and IgG1 anti-HTLV-1 reactivity by an indirect immunofluorescence flow cytometric assay for the identification of persons infected with HTLV-1, asymptomatic carriers and patients with myelopathy

In this study, the performance of IgG and IgG1 anti-HTLV-1 reactivity obtained by a flow cytometric assay was evaluated to verify its applicability for the diagnosis of persons infected with HTLV-1, including asymptomatic carriers and patients with myelopathy. The ability to identify patients with myelopathy among persons infected with HTLV-1 was also examined. Western blot assays were performed to assess the reactivity profiles of sera from asymptomatic carriers and patients with myelopathy against viral proteins. The data showed that IgG1 detected by flow cytometric assay is effective for the diagnosis of persons infected with HTLV-1 with 97% sensitivity and 100% specificity. IgG and IgG1 exhibited high performance in distinguishing patients with myelopathy from asymptomatic carriers. Using serum dilutions and cut-off points established previously a second HTLV-1 carrier group was tested using flow cytometric assay to detect IgG and IgG1. The data demonstrated sensitivity of 93% and 98%, respectively, confirming the high reactivity of persons infected with HTLV-1 detected by this method. Western blot assays confirmed the high specificity of MT-2 cells as a reliable source of viral antigen since only sera from persons infected with HTLV-1 recognised MT-2 proteins. Furthermore, a high reactivity to Gag and Env proteins was observed, especially among patients with myelopathy. These data suggest that flow cytometric detection of IgG1 is a valuable, non-conventional serological method to diagnose HTLV-1 infection and for research purposes.

Molecular evidence of human T-cell lymphotropic virus types 1 and 2 (HTLV-1 and HTLV-2) infections in HTLV seroindeterminate individuals from São Paulo, Brazil

BACKGROUND

Using enzyme immunoassays and Western blot (Wb) tests, HTLV serodiagnosis yields indeterminate results in a significant number of cases.

OBJECTIVE

To determine the prevalence of HTLV infection among HTLV-seroindeterminate individuals.

STUDY DESIGN

We studied peripheral blood mononuclear cells from 65 anti-HTLV Wb-seroindeterminate individuals by attempting to amplify proviral DNA sequences (tax and pol) to identify HTLV-1 and HTLV-2 infections.

RESULTS

These 65 specimens exhibited predominantly (43%) anti-HTLV antibodies to gag-coded antigens in the absence of anti-p24 on Wb analysis. Tax proviral sequences were detected in 6 (9.2%) samples. According to restricted fragment polymorphism analysis (RFLP), we identified HTLV-1 proviral DNA in 4 samples, HTLV-2 in one and sequences from both in another. Nested PCR for the pol region was positive in 3 (4.6%) specimens, which were also positive for tax sequences. After hybridization HTLV-1 infection was confirmed in 2 samples (3.1%) and HTLV-2 in another (1.5%). Detection of a single HTLV DNA sequence may be due to infection by defective provirus, but its significance remains undefined. In this cohort, no Wb reactivity pattern was predictive of proviral detection. HTLV-1 infection was demonstrated in an individual who had Wb reactivity to gag-coded antigens only.

CONCLUSIONS

This emphasizes the importance of clinical and laboratory follow-up of HTLV-seroindeterminate individuals from endemic areas.

Human T-lymphotropic virus type 1 (HTLV-1) prevalence and quantitative detection of DNA proviral load in individuals with indeterminate/positive serological results

BACKGROUND

HTLV-1 infection is currently restricted to endemic areas. To define the prevalence of HTLV-1 infection in patients living in Italy, we first carried out a retrospective serological analysis in a group of people originating from African countries referred to our hospital from January 2003 to February 2005. We subsequently applied a real time PCR on peripheral blood mononuclear cells from subjects with positive or indeterminate serological results.

METHODS

All the sera were first analysed by serological methods (ELISA and/or Western Blotting) and then the peripheral blood mononuclear cells from subjects with positive or inconclusive serological results were analyzed for the presence of proviral DNA by a sensitive SYBR Green real time PCR. In addition, twenty HTLV-I ELISA negative samples were assayed by real time PCR approach as negative controls.

RESULTS

Serological results disclosed serum reactivity by ELISA (absorbance values equal or greater than the cut-off value) in 9 out of 3408 individuals attending the Sexually Transmitted Diseases Clinic and/or Oncology Department, and 2 out 534 blood donors enrolled as a control population. Irrespective of positive or inconclusive serological results, all these subjects were analyzed for the presence of proviral DNA in peripheral blood mononuclear cells by SYBR real time PCR. A clear-cut positive result for the presence of HTLV-1 DNA was obtained in two subjects from endemic areas.

CONCLUSION

SYBR real time PCR cut short inconclusive serological results. This rapid and inexpensive assay showed an excellent linear dynamic range, specificity and reproducibility readily revealing and quantifying the presence of virus in PBMCs. Our results highlight the need to monitor the presence of HTLV-1 in countries which have seen a large influx of immigrants in recent years. Epidemiological surveillance and correct diagnosis are recommended to verify the prevalence and incidence of a new undesirable phenomenon.

Human T-cell lymphotropic virus types I and II (HTLV-I and -II) infection among seroindeterminate cases in Argentina

Human T-cell lymphotropic virus (HTLV) seroindeterminate cases have been reported among blood donors (BD) and in at-risk populations worldwide, including Argentina. The objective of the present work was to study the presence of HTLV-I/II infection and its association to specific Western blot (WB) patterns among healthy BD and at-risk populations in Argentina. We analyzed 83 HTLV-I/II seroindeterminate WB cases diagnosed among BD (n = 49) and in different at-risk populations (n = 34) for human retroviruses infections. Multiple indeterminate WB patterns were observed. Out of the total, 13.2% (11/83) of the cases were found to be HTLV-I/II positive by nested-PCR (n-PCR), including 13.2% (11/83) HTLV-I and 2.4% (2/83) presenting HTLV-I and -II co-infection. Most of their serological profiles showed reactivity to gag or env codified proteins. Two samples amplified only one of the six analyzed genes (1 HTLV-I pol gene and 1 HTLV-II tax gene). There was no association between the presence of Trypanosoma cruzi infection and an HTLV-I/II indeterminate WB pattern (only 3 of the 83 samples were positive for T. cruzi antibodies). In conclusion, the majority of HTLV-seroindeterminate WB donors lacked HTLV provirus and was thus considered uninfected. However, when seroreactivity to Env and Gag proteins are observed on the WB and especially in at-risk populations, HTLV infection should be suspected; such individuals should be followed-up and retested.

False positive antibody results against human T-cell lymphotropic virus in patients with severe acute respiratory syndrome

Taiwan suffered from the outbreak of severe acute respiratory syndrome (SARS) in 2003. Our laboratory performed a series of virology and serology tests for SARS patients admitted to our hospital. Cross‐reactivity was found when testing for antibody against human T‐cell lymphotropic virus (HTLV) in one patient with SARS. Therefore, antibodies against HTLV were examined in paired‐sera from 26 SARS patients. ELISA and a neutralization test were used to measure anti‐SARS antibodies. Seroconversion for antibody against SARS‐CoV was observed in all patients. Surprisingly, with the use of ELISA for HTLV, sera for 13 patients were positive for HTLV (50%), and seroconversion for HTLV was also observed in 10 patients (38.5%). Western blot for HTLV on those 26 paired‐sera from 13 HTLV‐positive patients displayed 5 positive results for HTLV‐I, 7 positive results for HTLV‐II, 1 positive result for both HTLV‐I and II, 9 negative results for either HTLV‐I or HTLV‐II, and 4 “indeterminate” results. The findings that antibody to HTLV can be detected in blood samples collected from SARS patients provide important information for safe handling of blood products. Without such knowledge, blood products can be discarded mistakenly even though they contain anti‐SARS‐CoV antibodies that may be potentially valuable for SARS therapy. J. Med. Virol. 77:331–336, 2005. © 2005 Wiley‐Liss, inc.

Can we improve the management of blood donors with nonspecific reactivity in viral screening and confirmatory assays?

Donors with nonspecific reactivity in viral screening or confirmatory assays are problematic for blood services because of donor management issues and product loss. Considerable experience has now accumulated in the use of screening and confirmatory assays; therefore, it is timely to examine the ways in which donors with nonspecific reactivity are managed. In this review, we summarize the causes and characteristics of nonspecific reactivity in blood donors and approaches for reducing the number of nonspecific reactive results and we offer some suggestions for improving the management of these donors.

Human T lymphotropic virus types I and II proviral sequences in Argentinian blood donors with indeterminate Western blot patterns

Human T-cell lymphotropic virus (HTLV) seroindeterminate blood donors have been reported worldwide including Argentina. To investigate the significance of HTLV-I/II seroindeterminate Western blot (WB) patterns, we conducted an 8-year cross-sectional study. Of 86,238 Argentinian blood donors, 146 sera were reactive by screening tests. The WB results indicated that 20% were HTLV-I reactive, 8% HTLV-II reactive, 61% indeterminate, and 11% negative. The overall seroprevalence was 0.034% for HTLV-I, 0.014% for HTLV-II, and 0.103% for indeterminate. In 57 reactive specimens, HTLV-I/II provirus could be examined by type specific PCR for tax, pol, and env regions. When at least two gene fragments were amplified HTLV-I/II infection was considered confirmed. PCR results confirmed all WB seropositive samples for HTLV-I (n = 15), and HTLV-II (n = 7), and the only WB negative case was also PCR negative, showing a complete concordance between PCR and WB. However, of 34 WB seroindeterminate sera studied by PCR, in 5 was proviral DNA amplified. According to our criteria PCR confirmed one to be HTLV-I, and one HTLV-II, 3 remained indeterminate since only tax sequences were amplified. Among WB indeterminate samples tested by PCR, most of their serological profile showed reactivity to gag codified proteins but lacked env reactivities (70%). One sample with a WB gag pattern showed proviral tax sequences, but of the four samples with reactivity to env proteins GD21 (n = 3) or rgp46II (n = 1) PCR results indicated that one was HTLV-I, one was HTLV-II, and two were indeterminate (only tax sequences). In conclusion, the majority of HTLV-seroindeterminate WB donors exhibited a gag indeterminate profile lacking HTLV provirus, and were thus considered uninfected. However, seroreactivity to env proteins, in particular to GD21, may indicate infection and a follow-up study of each seroreactive blood donor should be considered.

Detection of human T-lymphotropic virus (HTLV) tax sequences in New York City blood donors seronegative for HTLV types 1 and 2

A potential public health concern is the reported detection of the human T-lymphotropic virus (HTLV) tax gene in the lymphocytes of up to 11% of a low-risk group of New York City blood donors (NYBD). This study aimed to independently confirm the prevalence of HTLV tax sequences in 293 NYBD. All NYBD tested negative for antibodies to HTLV types 1 and 2 and HTLV Tax. HTLV tax sequences were not detected in the NYBD lymphocytes. These data demonstrate the lack of HTLV-1 tax in this group of NYBD at low risk for HTLV infection.

Seroindeterminate HTLV-1 prevalence and characteristics in blood donors in Taiwan

Human T-cell leukemia virus type 1 (HTLV-1) is commonly accepted as the cause of adult T-cell leukemia and tropical spastic paraparesis/HTLV-1-associated myelopathy. Screening of blood donors for HTLV-1 and HTLV-2 was implemented in Taiwan in February 1996. From February 1996 to December 1998, we investigated the seroprevalence of HTLV-1 in all unpaid blood donors in Taiwan. Of 2,578,238 donors in all 6 blood centers, 1793 (0.06%) were seropositive for HTLV-1, and 605 (0.023%) were indeterminate for HTLV-1. Among these indeterminate donors, 359 (59.3%) were male. The most common HTLV-1-indeterminate pattern by Western blot in our study was GD21 alone (34.6%) followed by p24 alone (7.8%), p53 alone (6.5%), and gp46 + GD21 (6.0%). That GD21 pattern was found in 59.6% of indeterminate results in this study suggested that the majority of nonspecific enzyme immunoassay reactions were probably precipitated by viral envelop glycoprotein GD21.

A case-control study of risk factors associated with human T-cell lymphotrophic virus type-I seropositivity in blood donors from Guadeloupe, French West Indies

BACKGROUND AND OBJECTIVES

An age- and gender-specific distribution characterizes human T-cell lymphotrophic virus type-I (HTLV-I) seropositivity in Guadeloupe (French West Indies). Further epidemiological studies are required to identify other possible risk factors associated with this retroviral infection.

MATERIALS AND METHODS

A nested case-control study was conducted between 1997 and 1999 among blood donors. A total of 102 HTLV-I-positive subjects were matched (at a ratio of 1 : 3) by gender, age (+/-5 years) and donor status (new or regular) to 306 HTLV-I-negative controls. Information was obtained through a questionnaire assessing both environmental and behavioural variables.

RESULTS

Factors independently associated with HTLV-I infection included a low level of education [odds ratio (OR) 6.61, confidence interval (CI) 2.89-15.15], black ethnicity (OR 3.28, CI 1.01-10.65), two or more sex partners in the previous 3 years (OR 2.43, CI 1.16-5.10), early age at first sexual intercourse (0.84 risk reduction per additional year, CI 0.76-0.93), a history of sexually transmitted diseases (OR 2.29, CI 1.0-5.34) and positive Chlamydia serology (OR 1.95, CI 1.03-3.68).

CONCLUSION

These data provide a wide spectrum of features associated with HTLV-I seropositivity, especially sexual risk factors. It strongly suggests that heterosexual intercourse is an important route of HTLV-I transmission in Guadeloupe, even among low-risk populations such as blood donors.