Enhanced specificity of truncated transmembrane protein for serologic confirmation of human T-cell lymphotropic virus type 1 (HTLV-1) and HTLV-2 infections by western blot (immunoblot) assay containing recombinant envelope glycoproteins

A novel high-performance rapid screening test for the detection of total HTLV-I and HTLV-II antibodies in HTLV-I/II infected patients

Rapid diagnosis of human T-cell lymphotropic virus (HTLV) type-I and -II infections are essential for timely and cost-effective disease interventions. MP Diagnostics ASSURE HTLV-I/II Rapid Test was developed for the rapid detection of anti-HTLV-I/II antibodies in patients' serum, plasma, and whole blood specimens. ASSURE HTLV-I/II Rapid Test employed MP Biomedicals' proprietary HTLV-I/II Trifusion recombinant antigen conjugated with gold nanoparticles and HTLV-I / HTLV-II recombinant antigens immobilized on the nitrocellulose membrane to detect total HTLV-I and HTLV-II antibodies. The overall performance of the ASSURE HTLV-I/II Rapid Test was found to be 99.42% sensitivity (95% Confidence Interval, 98.32-99.88%) and 100% specificity (95% Confidence Interval, 99.58-100.00%) in the tested clinical samples, including a total of 518 HTLV-I/II positive specimens (396 HTLV-I infection, 97 HTLV-II infection and 25 HTLV-I/II dual infection) and 872 HTLV negative clinical specimens consisting of 691 healthy donor samples, 116 potentially cross-reactive samples, and 65 samples with interfering substances. The ASSURE HTLV-I/II Rapid Test can effectively be deployed as a screening tool in any prevalence studies, blood banks or organ transplant centres.

Anti-Human T-Cell Leukemia Virus Type 1 (HTLV-1) Antibody Assays in Cerebrospinal Fluid for the Diagnosis of HTLV-1-Associated Myelopathy/Tropical Spastic Paraparesis

The anti-human T-cell leukemia virus type 1 (HTLV-1) antibody assay in common use has changed from the particle agglutination (PA) method to chemiluminescent immunoassay (CLIA) and chemiluminescent enzyme immunoassay (CLEIA). These assays were validated in serum but not in cerebrospinal fluid (CSF). However, anti-HTLV-1 antibody positivity in CSF is a requisite for diagnosing HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). We qualitatively compared the assays in CSF from 47 HAM/TSP patients diagnosed using PA, 15 HTLV-1 carriers (HCs), and 18 negative controls. In determining the positivity or negativity of CSF anti-HTLV-1 antibodies, we used serum cutoff points for CLIA and CLEIA because CSF cutoff points had not been decided. Truth table analysis revealed that the performance of CLIA was closer to that of PA and that CLEIA had low sensitivity. CSF antibodies from HAM/TSP patients were all positive by PA and CLIA but 83.0% positive by CLEIA. CSF antibodies from HCs were positive in 73.3%, 80.0%, and 6.7% by PA, CLIA, and CLEIA, respectively. Receiver operator characteristic curve analysis for CSF revealed that with the default cutoff point used for serum, CLIA and PA had comparable performances and CLEIA was less sensitive. The best performances of CLIA and CLEIA with adjusted cutoff points were 94.8% sensitivity and 95.5% specificity and 89.7% sensitivity and 95.5% specificity, respectively. We conclude that low-sensitivity CLEIA can underdiagnose HAM/TSP and that CLIA is a better alternative to PA in anti-HTLV-1 antibody assay for CSF with the current cutoff points.

Novel Genetic Constructs for Production of Recombinant HTLV-1/2 Antigens and Evaluation of Their Reactivity to Plasma Samples from HTLV-1-Infected Patients

Human T-cell leukemia virus type 1 (HTLV-1) can cause life-threatening diseases for which there are no effective treatments. Prevention of HTLV-1 infection requires massive testing of pregnant women, blood for transfusion, and organs for transplantation, as well as safe sex. In this context, serological assays are widely used for monitoring HTLV-1 infections. Despite the necessity for recombinant antigens to compose serological tests, there is little information available on procedures to produce recombinant HTLV-1/2 antigens for serological diagnostic purposes. In this work, we tested a series of genetic constructions to select those more amenable for production in bacterial systems. To overcome the constraints in expressing sections of viral envelope proteins in bacteria, we have used the p24 segment of the gag protein as a scaffold to display the immunogenic regions of gp46 and gp21. Nine recombinant antigenic proteins derived from HTLV-1 and five derived from HTLV-2 were successfully purified. The HTLV-1 antigens showed high efficiency in discriminating HTLV-positive samples from HTLV-negative samples using enzyme-linked immunosorbent assays. Interestingly, HTLV-1-positive samples showed a high level of cross-reaction with HTLV-2 antigens. This finding is explained by the high sequence conservation between the structural proteins of these two highly related viruses. In summary, the results presented in this work provide a detailed description of the methods used to produce recombinant HTLV-1 and HTLV-2 antigens, and they demonstrate that the HTLV-1 antigens show strong potential for serological diagnosis of HTLV-1 infections.

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

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.

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.

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.

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.

The epidemiology of human retrovirus-associated illnesses

Human T-cell leukemia/lymphoma virus type 1 (HTLV-1) was the first oncogenic human retrovirus discovered in 1980. It is estimated that around 10-20 million people are infected with HTLV-1 worldwide. However, HTLV-1 is not a ubiquitous virus. Indeed, HTLV-1 is present throughout the world with clusters of high endemicity including mainly southern Japan, the Caribbean region, parts of South America and intertropical Africa, with foci in the Middle East and Australia. The origin of this puzzling geographical repartition is probably linked to a founder effect in certain human groups. In the high endemic areas, 0.5 to 50% of the people have antibodies against HTLV-1 antigens. HTLV-1 seroprevalence increases with age, especially in women. HTLV-1 has 3 modes of transmission: mother to child, mainly through prolonged breastfeeding (> 6 months); sexual, mainly but not exclusively occurring from male to female; and by blood products contaminated by infected lymphocytes. HTLV-1 is mainly the etiological agent of two very severe diseases: a malignant T CD4+ cell lymphoproliferation of very poor prognosis, named adult T-cell leukemia/lymphoma (ATLL), and a chronic neuro-myelopathy named tropical spastic paraparesis/HTLV-1-associated myelopathy (TSP/HAM). HTLV-1 is also associated with rare anterior uveitis, infective dermatitis and myositis in some high HTLV-1 endemic areas. The repartition of the different molecular subtypes or genotypes is mainly linked to the geographical origin of the infected persons but not to the associated pathology. HTLV-1 possesses a remarkable genetic stability probably linked to viral amplification via clonal expansion of infected cells rather than by reverse transcription. This stability can be used as a molecular tool to gain better insights into the origin, evolution and modes of dissemination of HTLV-1 and infected populations. HTLV-1 originated in humans through interspecies transmission from STLV-1, a very closely related retrovirus, highly endemic in several populations of apes and Old World monkeys.

Multiple retroviral infection by HTLV type 1, 2, 3 and simian foamy virus in a family of Pygmies from Cameroon

To better understand the origins and modes of transmission of HTLV-3 and to search for other retroviral infections (HTLV-1, HTLV-2, foamy viruses), we studied the family of a HTLV-3-infected individual (Pyl43), from Cameroon. Thirty-five persons were included. All adult men were still actively hunting nonhuman primates (NHP). All women were also butchering and cutting-up animals. Five persons reported a bite by an NHP. While HTLV-3 infection was only found in Pyl43, HTLV-1 and HTLV-2 infections were found, respectively, in 5 and 9 persons with one being co-infected by both retroviruses. Phylogenetic analysis suggested intra-familial transmission of HTLV-1 subtypes B and D and HTLV-2. One man was infected by a chimpanzee foamy virus, acquired probably 45 years ago, through a bite. Acquisition of retroviral infections still occurs in central Africa involving to various extent not only intra-familial transmission for HTLV-1/HTLV-2 but also direct interspecies transmission from NHP for foamy virus and possibly for HTLV-1 and HTLV-3.

Evaluation of a new third-generation ARCHITECT rHTLV-I/II assay for blood screening and diagnosis

In comparison to current on-market assays, the ARCHITECT rHTLV-I/II assay is the first fully automated assay that simultaneously detects human T-cell lymphotropic virus type I (HTLV-I) and type II (HTLV-II) in human serum and plasma. Specificity was assessed on 5646 blood donors and 692 clinical specimens. For sensitivity determination, 301 HTLV-I-positive and 105 HTLV-II-positive specimens were tested. Precision was between 3.98% and 4.31% coefficient of variation (CV) for specimens with 1 to 6 sample to cutoff. Specificity was 99.95% and 99.86% on specimens from blood donors and hospitalized patients, respectively. Sensitivity evaluation showed 100% detection on 301 HTLV-I and 105 HTLV-II specimens. HTLV-I and HTLV-II viruses are still circulating among general populations even in the low prevalence areas. To control the further spread of these retroviruses, we need to know that it is important to continue screening of blood. The performance evaluation data from this study demonstrate that the high throughput and fully automated ARCHITECT rHTLV-I/II chemiluminescence immunoassay effectively serves this purpose.

Evaluation of a new, fully automated immunoassay for detection of HTLV-I and HTLV-II antibodies

Screening blood donations for human T-lymphotropic virus types I and II (HTLV-I/II) continues to be important in protecting the safety of blood products and controlling the global spread of these retroviruses. We have developed a fully automated, third generation chemiluminescent immunoassay, ARCHITECT rHTLV-I/II, for detection of antibodies to HTLV-I/II. The assay utilizes recombinant proteins and synthetic peptides and is configured in a double antigen sandwich assay format. Specificity of the assay was 99.98% (9,254/9,256, 95% CI = 99.92-100%) with the negative specimens from the general population including blood donors, hospital patients and pregnant women from the US, Japan and Nicaragua. The assay demonstrated 100% sensitivity by detecting 498 specimens from individuals infected with HTLV-I (n = 385) and HTLV-II (n = 113). ARCHITECT rHTLV-I/II results were in complete agreement with the Murex HTLV-I/II reference assay and 99.7% agreement with the Genelabs HTLV Blot 2.4 confirmatory assay. Analytical sensitivity of the assay was equivalent to Murex HTLV-I/II assay based on end point dilutions. Furthermore, using a panel of 397 specimens from Japan, the ARCHITECT rHTLV-I/II assay exhibited distinct discrimination between the antibody negative (Delta Value = -7.6) and positive (Delta Value = 7.6) populations. Based on the excellent specificity and sensitivity, the new ARCHITECT rHTLV-I/II assay should be an effective test for the diagnosis of HTLV-I/II infection and also for blood donor screening.

New insights into the pathogenesis, diagnosis and treatment of human T-cell leukemia virus type 1-induced disease

It has been over 25 years since the discovery of human T-cell leukemia virus type 1 (HTLV-1); however, the exact sequence of events that occur during primary infection, clinical latency or the development of disease remains unresolved. The advances in molecular virology and neuroimmunology have contributed significantly to our understanding of HTLV-1 pathogenesis, but also uncovered the complexity of the virus–host interaction both in the peripheral blood and the CNS. Here, we overview the general pathologic features of HTLV-1, molecular mechanisms of oncogenic transformation and characteristics of the host immune response during the associated neuroinflammatory process. We also discuss both current and new approaches in the diagnosis and therapy of HTLV-1 associated diseases – adult T-cell leukemia and HTLV-1-associated myelopathy/tropical spastic paraparesis. Finally, potentially important emerging areas of research that may have an impact on our understanding of the pathogenic mechanism have been briefly introduced.

Molecular characterization of human T-cell lymphotropic virus type 2 (HTLV-II) from people living in urban areas of Sao Paulo city: Evidence of multiple subtypes circulation

BACKGROUND

In Brazil, human T-cell lymphotropic virus type I and type II (HTLV-I and HTLV-II) are co-circulating and possess approximately 65% homology, which results in high cross-reactivity in serological tests. Based on the detection of EIA and Western blot (WB) tests, HTLV serodiagnosis yields indeterminate results in high-risk population, with the true determination of HTLV-II prevalence requiring a combined serological and molecular analysis. Molecular analysis of HTLV-II isolates has shown the existence of four distinct subtypes: IIa, IIb, IIc, and IId. The aim of this study was to evaluate the routine EIA and WB used in Sao Paulo city, as well as molecular methods for confirmation of infection and HTLV-II subtype distribution.

RESULTS

Two hundred ninety-three individuals, who were enrolled in the HTLV out-clinic in Sao Paulo city, Brazil, between July 1997 and May 2003, were tested by EIAs, and positive sera 232 (79%) reactive by one of the tests. When these sera were tested by WB revealed 134 were HTLV-I, 28 HTLV-II, 4 HTLV-I/II, and 48 were indeterminate. Polymerase chain reaction (PCR) on the indeterminate group showed that 20 (42%) were HTLV-II and 28 were negative. From a total of 48 HTLV-II subjects with DNA available, restriction fragment length polymorphism (RFLP) of the env region revealed 47 HTLV-IIa and 1 HTLV-IIb. The phylogenetic analysis was performed on 23 samples, which identified 19 as subtype a, Brazilian subcluster, and 4 as subtype b. This is the first time HTLV-II subtype b has been described in Brazil. However, further studies, such as a complete nucleotide DNA sequencing, need to be done to confirm these findings.

Seroprevalence of Human T Cell Leukemia Virus in HIV Antibody-Negative Populations in Rural Cameroon

Seven hundred forty-seven serum samples collected from humans in 4 separate rural village areas in Cameroon were examined for antibody to human T cell leukemia viruses (HTLVs) by use of an enzyme immunoassay followed by a Western blot assay. Of the 88 serum samples that the enzyme immunoassay found to be repeatedly reactive, the HTLV status of 49 samples was confirmed by Western blot assay to be HTLV type I, and the status of 6 samples was confirmed to be HTLV type II.

Discovery of a new human T-cell lymphotropic virus (HTLV-3) in Central Africa

Human T-cell Leukemia virus type 1 (HTLV-1) and type 2 (HTLV-2) are pathogenic retroviruses that infect humans and cause severe hematological and neurological diseases. Both viruses have simian counterparts (STLV-1 and STLV-2). STLV-3 belongs to a third group of lymphotropic viruses which infect numerous African monkeys species. Among 240 Cameroonian plasma tested for the presence of HTLV-1 and/or HTLV-2 antibodies, 48 scored positive by immunofluorescence. Among those, 27 had indeterminate western-blot pattern. PCR amplification of pol and tax regions, using HTLV-1, -2 and STLV-3 highly conserved primers, demonstrated the presence of a new human retrovirus in one DNA sample. tax (180 bp) and pol (318 bp) phylogenetic analyses demonstrated the strong relationships between the novel human strain (Pyl43) and STLV-3 isolates from Cameroon. The virus, that we tentatively named HTLV-3, originated from a 62 years old Bakola Pygmy living in a remote settlement in the rain forest of Southern Cameroon. The plasma was reactive on MT2 cells but was negative on C19 cells. The HTLV 2.4 western-blot exhibited a strong reactivity to p19 and a faint one to MTA-1. On the INNO-LIA strip, it reacted faintly with the generic p19 (I/II), but strongly to the generic gp46 (I/II) and to the specific HTLV-2 gp46. The molecular relationships between Pyl43 and STLV-3 are thus not paralleled by the serological results, as most of the STLV-3 infected monkeys have an "HTLV-2 like" WB pattern. In the context of the multiple interspecies transmissions which occurred in the past, and led to the present-day distribution of the PTLV-1, it is thus very tempting to speculate that this newly discovered human retrovirus HTLV-3 might be widespread, at least in the African continent.

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.

Complete sequence of a novel highly divergent simian T-cell lymphotropic virus from wild-caught red-capped mangabeys (Cercocebus torquatus) from Cameroon: a new primate T-lymphotropic virus type 3 subtype

Among 65 samples obtained from a primate rescue center located in Cameroon, two female adult red-capped mangabeys (Cercocebus torquatus) (CTO-602 and CTO-604), of wild-caught origin, had a peculiar human T-cell lymphotropic virus type 2 (HTLV-2)-like Western blot seroreactivity (p24, RGD21, +/-K55). Analyses of the simian T-cell lymphotropic virus type 3 (STLV-3)/CTO-604 complete proviral sequence (8,919 bp) indicated that this novel strain was highly divergent from HTLV-1 (60% nucleotide similarity), HTLV-2 (62%), or STLV-2 (62%) prototypes. It was, however, related to STLV-3/PH-969 (87%), a divergent STLV strain previously isolated from an Eritrean baboon. The STLV-3/CTO-604 sequence possesses the major open reading frames corresponding to the structural, enzymatic, and regulatory proteins. However, its long terminal repeat is shorter, with only two 21-bp repeats. Furthermore, as demonstrated by reverse transcriptase PCR, this new STLV exhibits significant differences from STLV-3/PH-969 at the mRNA splice junction position level. In all phylogenetic analyses, STLV-3/CTO-604 and STLV-3/PH-969 clustered in a highly supported single clade, indicating an evolutionary lineage independent from primate T-lymphotropic virus type 1 (PTLV-1) and PTLV-2. Nevertheless, the nucleotide divergence between STLV-3/PH-969 and STLV-3/CTO-604 is equivalent to or higher than the divergence observed between the different HTLV-1 or HTLV-2 subtypes. Thus, the STLV-3/CTO-604 strain can be considered the prototype of a second subtype in the PTLV-3 type. The presence of two related viruses in evolutionarily distantly related African monkeys species, living in two opposite ecosystems (rain forest versus desert), reinforces the possible African origin of PTLV and opens new avenues regarding the search for a possible human counterpart of these viruses in individuals exhibiting such HTLV-2-like seroreactivities.

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

To investigate the significance of serological human T-cell lymphotropic virus type 1 (HLTV-1) Gag indeterminate Western blot (WB) patterns in the Caribbean, a 6-year (1993 to 1998) cross-sectional study was conducted with 37,724 blood donors from Guadeloupe (French West Indies), whose sera were routinely screened by enzyme immunoassay (EIA) for the presence of HTLV-1 and -2 antibodies. By using stringent WB criteria, 77 donors (0.20%) were confirmed HTLV-1 seropositive, whereas 150 (0.40%; P < 0.001) were considered HTLV seroindeterminate. Among them, 41.3% (62) exhibited a typical HTLV-1 Gag indeterminate profile (HGIP). Furthermore 76 (50.7%) out of the 150 HTLV-seroindeterminate subjects were sequentially retested, with a mean duration of follow-up of 18.3 months (range, 1 to 70 months). Of these, 55 (72.4%) were still EIA positive and maintained the same WB profile whereas the others became EIA negative. This follow-up survey included 33 persons with an HGIP. Twenty-three of them (69.7%) had profiles that did not evolve over time. Moreover, no case of HTLV-1 seroconversion could be documented over time by studying such sequential samples. HTLV-1 seroprevalence was characterized by an age-dependent curve, a uniform excess in females, a significant relation with hepatitis B core (HBc) antibodies, and a microcluster distribution along the Atlantic coast of Guadeloupe. In contrast, the persons with an HGIP were significantly younger, had a 1:1 sex ratio, did not present any association with HBc antibodies, and were not clustered along the Atlantic façade. These divergent epidemiological features, together with discordant serological screening test results for subjects with HGIP and with the lack of HTLV-1 proviral sequences detected by PCR in their peripheral blood mononuclear cell DNA, strongly suggest that an HGIP does not reflect true HTLV-1 infection. In regard to these data, healthy blood donors with HGIP should be reassured that they are unlikely to be infected with HTLV-1 or HTLV-2.

HTLV-1 and HTLV-2 infections in HIV-infected individuals from Santos, Brazil: seroprevalence and risk factors

Because HTLV-I, HTLV-2, and HIV share identical modes of transmission, simultaneous or subsequent infections with these retroviruses are to be expected. The population of Santos, the largest port in Latin America, includes large numbers of female commercial sex workers and intravenous drug users, presumably having been exposed to retroviral infection. To evaluate the seroprevalence of HTLV infection and their associated risk factors, a cross-sectional survey was carried out in 499 HIV-infected individuals from Santos, Brazil. HTLV testing consisted of enzyme immunoassays for serologic screening and confirmatory Western blot testing. Overall HTLV-I and HTLV-2 seroprevalences were 6.0% (95% confidence interval [CI], 3.9-8.1) and 7.4% (95% CI, 5.1-9.7), respectively. Multivariate logistic regression for statistical analysis revealed HTLV-I infection to be independently associated with: intravenous drug use (IDU) (odds ratio [OR]. 2.99; 95% CI, 1.09-8.20), seropositivity to hepatitis C virus (HCV) (OR, 3.03; 95% CI, 1.02-9.01) and < 3 years of education (OR, 4.73; 95% CI, 1.56-14.41). HTLV-2 infection was associated with: IDU (OR, 3.22; 95% CI, 1.33-7.84), HCV seropositivity (OR, 5.40; 95% CI, 1.86-15.66) and nonwhite race (OR, 3.32; 95% CI, 1.58-7.00). Results indicate that HIV-infected individuals living in Santos are at similarly high risk of being exposed to HTLV-1 and HTLV-2. IDU constitutes the main risk factor for HTLV acquisition in this population, and there is no significant risk associated with sexual practice.

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.

Retroviral sequences in rheumatoid arthritis synovium

There are several relationships between retroviruses and cellular transformation, as well as retroviruses being involved in the development of autoimmune diseases. Retroviruses have been discussed as etiologic agents modulating or triggering certain pathways in the pathogenesis of rheumatoid arthritis (RA). However, none of the currently known retroviruses has been identified as specific for RA. Due to the unique properties of retroviruses, distinct experimental approaches can be used to detect retroviral activity in cells and tissues. Current research in RA using state-of-the-art molecular biology techniques includes both the search for exogenous and endogenous retroviral gene sequences in synovium of patients with RA.

Large granular lymphocyte leukaemia occurring after renal transplantation

Post-transplantation lymphoproliferative disorders (PTLD) are a clinicopathologically heterogeneous group of lymphoid proliferations. The majority are of B-cell origin and associated with Epstein-Barr virus (EBV) infection. In contrast, the development of T-cell PTLD is much less common and EBV does not appear to be involved in pathogenesis. In this report we describe three patients who developed large granular lymphocyte (LGL) leukaemia after renal transplantation. These patients had clonal expansion of CD3+, CD8+, CD57+, CD56- LGL. We were unable to detect CMV antigen or find evidence for EBV or human T-cell leukaemia/lymphoma virus genome in the LGL from these patients. These data show that LGL leukaemia should be included as one of the types of T-cell proliferations which can occur post transplant.

Epitope mapping of HTLV envelope seroreactivity in LGL leukaemia

Sera from approximately 50% of patients with large granular lymphocyte (LGL) leukaemia react with a recombinant human T-cell leukaemia/lymphoma virus (HTLV) transmembrane envelope protein, p21e. Two immunodominant epitopes within env p21e have been defined by reactivity against recombinant proteins GD21 and BA21. In this study sera from 41 patients with LGL leukaemia were examined for reactivity against these recombinant HTLV env proteins. Overall, 21/41 (51%) sera reacted to p21e. Only two sera reacted to GD21. The predominant immunoreactivity against p21e was directed against the BA21 epitope, with 19/41 (46%) sera being BA21 positive. Seroconversion to BA21 protein was also documented. PCR analyses confirmed the low incidence of protypical HTLV sequences (2/41, 5%). These data document an association between BA21 seroreactivity and LGL leukaemia. This finding raises the possibility that such BA21 seroreactivity could be due to cross-reactivity to a cellular or retroviral antigen sharing some amino acid homology with the transmembrane glycoprotein of HTLV.

Sensitivity of two enzyme-linked immunosorbent assay tests in relation to western blot in detecting human T-cell lymphotropic virus types I and II infection among HIV-1 infected patients from São Paulo, Brazil

We investigated the presence of human T-cell lymphotropic virus types I and II (HTLV-I and HTLV-II) infections, first searching for specific antibodies in 553 serum samples obtained from HIV-1-infected patients from São Paulo, Brazil. Sera were screened using two enzyme-linked immunosorbent assays (ELISAs): the ELISA-EM (ELISA HTLV-I/II, EMBRABIO, BR), which contains HTLV-I and HTLV-II lysates, and the ELISA-DB [ELISA HTLV-I/II, Diagnostic Biotechnology (DB), Singapore], which contains HTLV-I lysate, and HTLV-I and HTLV-II recombinant env proteins (MTA-1 and K55, respectively). Serum samples showing two positive and/or borderline results were confirmed by Western blot (WB 2.3, DB), which discriminates HTLV-I from HTLV-II. WB analyses disclosed 22 cases (4.0%) of HTLV-I and 34 (6.1%) of HTLV-II seroreactivity; 24 sera had indeterminate antibody profile (4.3%) and 2 specimens showed reactivity to both MTA-1 and K55 env proteins. Using stringent WB criteria and analyzing the population according to risk factors, the prevalence rates of HTLV-I and HTLV-II infections were 11.2% and 16.8% in i.v. drug users, 3.4% and 5.5% in heterosexual individuals, and 1.4% and 2.2% in homosexual/bisexual men, respectively. A comparison of ELISA and WB results disclosed that both ELISAs were highly sensitive in detecting HTLV-I antibodies, whereas the ELISA-DB showed 82% sensitivity and the ELISA-EM 100% sensitivity in detecting HTLV-II antibodies. PCR analyses conducted on 37 representative cells samples confirmed the presence of HTLV proviral DNA in the majority of concordant serological cases, except in one, which was HTLV-I infected and seroreacted with K55 protein of HTLV-II. Indeed, after PCR, one case of HTLV-I infection and HTLV-II coinfection, and 30% of WB-seroindeterminate or inconclusive cases infected with HTLV-II could be detected. Our data stress high prevalences of both HTLV-I and HTLV-II infections in HIV-1 coinfected i.v. drug users from São Paulo, and suggests that ELISA kits containing only K55 protein as the HTLV-II-specific antigen, may not have the appropriate sensitivity for the detection of HTLV-II infection in this geographic region, pointing out the need of improved screening tests to be used in Brazil.

Seroreactivity to an Envelope Protein of Human T-Cell Leukemia/Lymphoma Virus in Patients With CD3− (Natural Killer) Lymphoproliferative Disease of Granular Lymphocytes

Natural killer (NK) cells are CD3− large granular lymphocytes (LGL) responsible for immunity against viral infections. A chronic lymphoproliferative disorder of NK cells has been described in which the expanded NK cells display a restricted phenotype and cytotoxic activity. These data raise the hypothesis that proliferating LGL in these patients result from discrete expansions of NK cells responding to an unknown, perhaps viral, antigen. Recently, it was found that mice transgenic for the tax gene of human T-cell leukemia/lymphoma virus (HTLV) develop NK leukemia. Therefore, we studied 15 patients with chronic NK lymphoproliferative disorder for evidence of HTLV infection. Sera were tested using an HTLV-I/II-enzyme linked immunosorbent assay and a modified Western blot assay containing recombinant env proteins. None of the sera met conventional criteria for HTLV seroreactivity. However, sera from 11 patients (73%) reacted with the recombinant HTLV env protein p21E. The anti-p21E reactivity of these sera was then mapped employing the recombinant proteins GD21 and BA21. No reactivity to the immunodominant HTLV epitope GD21 was observed, suggesting that prototypical HTLV infection is unlikely in these patients. This was confirmed by finding no evidence for HTLV nucleic acids by PCR analyses employing primers specific for conserved regions in the env, pol, and pX genes. In contrast, 10 of the 15 sera reacted with the epitope BA21, documenting for the first time an association between a unique seroreactivity and disease. The high incidence of BA21 seroreactivity in these patients suggests that exposure to a protein containing homology to BA21 may be important in the pathogenesis of this lymphoproliferative disorder.

Neutralizing human monoclonal antibodies to conformational epitopes of human T-cell lymphotropic virus type 1 and 2 gp46

Ten human monoclonal antibodies derived from peripheral B cells of a patient with human T-cell lymphotropic virus (HTLV)-associated myelopathy are described. One monoclonal antibody recognized a linear epitope within the carboxy-terminal 43 amino acids of HTLV gp21, and two monoclonal antibodies recognized linear epitopes within HTLV type 1 (HTLV-1) gp46. The remaining seven monoclonal antibodies recognized denaturation-sensitive epitopes within HTLV-1 gp46 that were expressed on the surfaces of infected cells. Two of these antibodies also bound to viable HTLV-2 infected cells and immunoprecipitated HTLV-2 gp46. Virus neutralization was determined by syncytium inhibition assays. Eight monoclonal antibodies, including all seven that recognized denaturation-sensitive epitopes within HTLV-1 gp46, possessed significant virus neutralization activity. By competitive inhibition analysis it was determined that these antibodies recognized at least four distinct conformational epitopes within HTLV-1 gp46. These findings indicate the importance of conformational epitopes within HTLV-1 gp46 in mediating a neutralizing antibody response to HTLV infection.

Delineation of immunodominant epitopes of human T-lymphotropic virus types I and II and their usefulness in developing serologic assays for detection of antibodies to HTLV-I and HTLV-II

Several immunodominant B-cell epitopes have been mapped in the structural (gag, env) and regulatory (tax, rex) proteins of human T-lymphotropic virus type I (HTLV-I) and HTLV-II. Identification of these immunogenic epitopes not only has allowed the development of sensitive and specific serologic assays, but also has provided a tool to study correlates of host pathogenesis, viral transmission, and protection. The major immunogenic epitopes for HTLV-I are located at the C terminus of p19gag, the central and carboxyl terminus of gp46env, the central region of transmembrane envelope glycoprotein (p21e), and the carboxyl terminus of p40tax. Similarly, HTLV-II epitopes are located at the amino terminus and central region of gp46env, the central region of p21e, and the carboxyl terminus of p40tax. The transmembrane epitopes of HTLV-I and HTLV-II share extensive homologies and represent a highly cross-reactive region, while the remaining regions represent HTLV type-specific epitopes. The transmembrane epitope has been commonly used for detecting antibodies in both HTLV-I and HTLV-II-infected persons, whereas central envelope epitopes have been exploited for serologic differentiation between HTLV-I and HTLV-II. This detailed analysis at the epitope level has resulted in the development of highly sensitive and specific screening and confirmation assays for detection of antibodies to HTLVs.