High prevalence of false-negative anti-HTLV type I/II enzyme-linked immunosorbent assay results in HIV type 1-positive patients

Neither molecular diversity of the envelope, immunosuppression status, nor proviral load causes indeterminate HTLV western blot profiles in samples from human T-cell lymphotropic virus type 2 (HTLV-2)-infected individuals

Although human T-cell lymphotropic virus type 2 (HTLV-2) is considered of low pathogenicity, serological diagnosis is important for counseling and monitoring. The confirmatory tests most used are Western blot (WB) and PCR. However, in high-risk populations, about 50% of the indeterminate WB were HTLV-2 positives by PCR. The insensitivity of the WB might be due to the use of recombinant proteins of strains that do not circulate in our country. Another possibility may be a high level of immunosuppression, which could lead to low production of virus, resulting in low stimulation of antibody. We found one mutation, proline to serine in the envelope region in the position 184, presented at least 1/3 of the samples, independent the indeterminate WB profile. In conclusion, we found no correlation of immune state, HTLV-2 proviral load, or env diversity in the K55 region and WB indeterminate results. We believe that the only WB kit available in the market is probably more accurate to detect HTLV-1 antibodies, and some improvement for HTLV-2 detection should be done in the future, especially among high-risk population.

Evaluation of the use of real-time PCR for human T cell lymphotropic virus 1 and 2 as a confirmatory test in screening for blood donors

INTRODUCTION: HTLV-1/2 screening among blood donors commonly utilizes an enzyme-linked immunosorbent assay (EIA), followed by a confirmatory method such as Western blot (WB) if the EIA is positive. However, this algorithm yields a high rate of inconclusive results, and is expensive. METHODS: Two qualitative real-time PCR assays were developed to detect HTLV-1 and 2, and a total of 318 samples were tested (152 blood donors, 108 asymptomatic carriers, 26 HAM/TSP patients and 30 seronegative individuals). RESULTS: The sensitivity and specificity of PCR in comparison with WB results were 99.4% and 98.5%, respectively. PCR tests were more efficient for identifying the virus type, detecting HTLV-2 infection and defining inconclusive cases. CONCLUSIONS: Because real-time PCR is sensitive and practical and costs much less than WB, this technique can be used as a confirmatory test for HTLV in blood banks, as a replacement for WB.

Performances of HTLV serological tests in diagnosing HTLV infection in high-risk population of São Paulo, Brazil

Testing problems in diagnosing human T-lymphotropic virus (HTLV) infection, mostly HTLV-II, have been documented in HIV/AIDS patients. Since December 1998, the Immunology Department of Instituto Adolfo Lutz (IAL) offers HTLV-I/II serology to Public Health Units that attend HTLV high-risk individuals. Two thousand, three hundred and twelve serum samples: 1,393 from AIDS Reference Centers (Group I), and 919 from HTLV out-patient clinics (Group II) were sent to IAL for HTLV-I/II antibodies detection. The majority of them were screened by two enzyme immunoassays (EIAs), and confirmed by Western Blot (WB 2.4, Genelabs). Seven different EIA kits were employed during the period, and according to WB results, the best performance was obtained by EIAs that contain HTLV-I and HTLV-II viral lysates and rgp21 as antigens. Neither 1st and 2nd, nor 3rd generation EIA kits were 100% sensitive in detecting truly HTLV-I/II reactive samples. HTLV-I and HTLV-II prevalence rates of 3.3% and 2.5% were detected in Group I, and of 9.6% and 3.6% in Group II, respectively. High percentages of HTLV-seroindeterminate WB sera were detected in both Groups. The algorithm testing to be employed in HTLV high-risk population from São Paulo, Brazil, needs the use of two EIA kits of different formats and compounds as screening, and because of high seroindeterminate WB, may be another confirmatory assay.

Phylogeny of human T cell lymphotropic virus type 1 in Peru: a high degree of evolutionary relatedness with South African isolates

We investigated the prevalence and molecular epidemiology of human T cell lymphotropic virus type 1 in Peruvian HIV-1-positive subjects, and found a 10.1% prevalence in a consecutive series of 318 HIV-1-positive patients living in Lima. Phylogenetic analysis of the long terminal repeat of 10 patient isolates showed that all of them belonged to the HTLV-1aA (Transcontinental) subgroup. Although the majority of the Peruvian sequences included in the analysis formed a clade with other Latin American sequences, the isolates of three patients clustered significantly with South African strains. These data show a high prevalence of HTLV-1 infection in HIV-1-positive subjects living in Lima and confirm the presence in Latin America of HTLV-1 strains probably arising from South Africa.

Can the level of immunosuppression in human immunodeficiency virus-infected patients affect the reliability of human T-cell lymphotropic virus type 2 serological diagnosis?

A total of 175 human immunodeficiency virus (HIV)-positive intravenous drug users (IDU) with CD4 cell counts of <200 cells/microl were matched with 175 HIV-positive IDU with CD4 cell counts of >500 cells/microl. Enzyme immunoassay (EIA) reactivity and human T-cell lymphotropic virus type 2 (HTLV-2) Western blot (WB) positivity were more frequently observed in subjects with CD4 cell counts of >500 cells/microl. Most of the subjects with low CD4 cell counts and EIA reactivity carried HTLV-2 infection (WB positive and/or PCR positive). No subjects with low CD4 cell counts and a lack of reactive EIA were PCR positive for HTLV-2. Therefore, a negative EIA result can confidently discharge HTLV-2 infection in HIV-infected patients with severe immunosuppression, whereas PCR should be performed for subjects with a reactive HTLV EIA which is not further confirmed by WB.

High prevalence of human T-lymphotropic virus type 1 (HTLV-1) in immigrant male-to-female transsexual sex workers with HIV-1 infection

Human T-lymphotropic virus type 1 and 2 (HTLV-1 and HTLV-2) infections in Europe are limited to intravenous drug users and migrants coming from areas in which they are endemic. A survey was undertaken of HTLV-1 and HTLV-2 infections in 393 recent immigrants: 167 HIV-1 positive subjects (including 52 male-to-female transsexual sex workers) and 226 pregnant HIV-1 negative women. The prevalence of HTLV-1 was 3.6% in the HIV-1 positive group and 0.9% in the HIV-1 negative group. The highest HTLV-1 prevalence in both groups was found in persons from Latin America, particularly those born in Peru (up to 26% in the HIV-1 positive group). All of the HIV-1/HTLV-1 co-infected individuals were male-to-female transsexual sex workers in whom the overall prevalence of HTLV-1 infection was 11.5%. HTLV-2 was only found in the HIV-1 positive group (prevalence 1.2%); all of the infected subjects were transsexual sex workers from Brazil (overall prevalence 6.4%). Phylogenetic analysis showed that all of the HTLV-1 isolates were of the cosmopolitan type, clustering with other strains circulating in the patients' birthplaces; the HTLV-2 isolates were of subtype 2a, and clustered significantly with other Brazilian strains. These results suggest the independent origin of each infection in the patient's birthplace. The data raise concerns about the further spread of HTLV infections mainly through the sexual route.

Modulation of infection and type 1 cytokine expression parameters by morphine during in vitro coinfection with human T-cell leukemia virus type I and HIV-1

Infection of injection drug users (IDUs) with the human T-cell leukemia viruses (HTLVs) or HIV is considerably higher than in the non-IDU population. Also, coinfection with HIV-1 and HTLV type I (HTLV-I) occurs more frequently. There is little or no information on the effects of opiates (i.e., morphine) on HTLV infection alone or on coinfection of HTLV-I-infected cells with HIV-1. Therefore, in this report, we analyzed the in vitro effects of morphine on HIV or HTLV infection alone as well as on dual infection with HTLV-I and HIV-1. Morphine decreased the in vitro levels of interferon-gamma (IFN gamma) and IL-2 during single infections, and this effect was reversed by the addition of the opioid antagonist naloxone. In contrast, treatment with morphine resulted in a 31% and 36% increase in IFN gamma and IL-2 levels, respectively, during dual infection. In addition, naloxone had an apparent additive effect on the morphine-associated enhancement of IFN gamma and IL-2 expression in the dual-infection model. Despite the high levels of IFN gamma expression, the viability of the coinfected cells in the presence of morphine was maintained. Importantly, morphine treatment was associated with augmented viral reverse transcription activity in dually infected cultures, apparently to the benefit of HTLV-I. If a similar putative morphine-induced advantage for HTLV-I production also occurs during in vivo coinfection, opiates such as morphine could contribute to the observed increased rate of HIV-1/HTLV-I infection in the IDU population in a more direct fashion than was previously believed.

Increased risk of developing peripheral neuropathy in patients coinfected with HIV-1 and HTLV-2

One thousand one hundred fifty-two HIV-1-positive patients were screened for HTLV-2 infection, and the AIDS-free coinfected individuals were consecutively included in a longitudinal study with the aim of investigating the role of HTLV-2 in the progression to AIDS and the development of specific neurologic diseases. Two matched HIV-1-positive/HTLV-2-negative controls for each coinfected individual were also enrolled in the study. HTLV-2 infection was found in 95 (8.2%) of the HIV-1-positive patients, 30 of whom were followed up for a median of 28.5 months. No significant differences were observed between them and the patients infected with HIV-1 alone in terms of the rate of decline in CD4 cell counts, progression to AIDS, or AIDS mortality, but they had an increased risk of developing peripheral neuropathy (hazard ratio, 3.3; 95% confidence interval, 1.3-8.0; p =.009). One coinfected patient developed myelopathy during the follow-up. In the second part of the study, aimed at preliminarily assessing the effect of highly active antiretroviral therapy (HAART) on the incidence of peripheral neuropathy, we extended our observations to two groups of coinfected and singly infected individuals receiving HAART. An 80% decrease in incidence of peripheral neuropathy was observed among both groups without any significant difference between them. These results support the hypothesis that HTLV-2 plays a role in the development of neurologic abnormalities in HIV-1-infected patients and suggest that the immune reconstitution due to HAART may limit the activity of HTLV-2 as an opportunistic agent.

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.

Resistance to Fas-mediated apoptosis of human T-cell lines expressing human T-lymphotropic virus type-2 (HTLV-2) Tax protein

The susceptibility to Fas-mediated apoptosis was evaluated in seven T-cell lines (two infected with HTLV-2, one with HTLV-1, and four HTLV-free) as well as in Jurkat cells transfected with a Tax-2 expressing vector. Fas-mediated apoptosis was significantly reduced in the HTLV-1- and HTLV-2-infected lines in comparison with the HTLV-free lines regardless of the surface expression of Fas antigen (which was no different in the infected and uninfected cells). Fas-mediated apoptosis was also significantly inhibited in Jurkat cells transfected with the Tax-2 expressing vector without any modification in Fas expression. There was significantly more antiapoptotic Bcl-x(L) mRNA and protein in the transfected than in the untransfected Jurkat T cells. In conclusion, our results suggest that HTLV-2 is capable of inhibiting Fas-mediated apoptosis by means of a mechanism involving the tax-2 gene and probably the expression of bcl-x(L) messenger and protein.

The discovery of two new divergent STLVs has implications for the evolution and epidemiology of HTLVs

We have isolated and characterised two divergent simian T-lymphotropic viruses (STLV), not belonging to the established human and simian T-lymphotropic virus lineages HTLV-1/STLV-1 and HTLV-2. STLV-L, from an Eritrean sacred baboon (Papio hamadryas), has been typed as a third type of simian T-lymphotropic virus, distinct from HTLV-1/STLV-1 and HTLV-2. The other virus, isolated from Congolese bonobos (Pan paniscus), is a distinct member of the HTLV-2 clade and has been designated STLV-2. The isolation of these two simian viruses shows that the spectrum of HTLVs/STLVs is larger than previously expected. Our data indicate that the two lineages STLV-L and HTLV-2/STLV-2 are of African origin, while the HTLV-1/STLV-1 lineage has been shown to be of Asian origin. These data, together with our phylogenetic analyses, suggest an African origin of the HTLV/STLV ancestor, which provides new clues about virus dissemination. Furthermore, the atypical serological profiles exhibited by STLV-L or STLV-2 infected animals in western blot, raise questions about the efficiency of current screening methods to type highly divergent HTLVs/STLVs. Considering the growing interest in xenotransplantations, more epidemiological and biological knowledge of simian and human T-lymphotropic viruses is necessary to estimate the risk of interspecies transmissions.

Development of internal controls for probe-based nucleic acid diagnostic assays

A method is described for the design, evaluation, and application of internal control targets and probes for use in probe-based nucleic acid diagnostic assays (i.e., PCR-ELISA). The technique is a modified version of oligonucleotide-directed mutagenesis in conjunction with PCR amplification to develop a novel probe-annealing sequence in a cloned IS1111a gene fragment of Coxiella burnetii. The internal control probe-recognition site with its complementary probe was identical to the wild-type-specific probe in length, base composition, location, and annealing temperature. Neither the internal control nor the wild-type probes annealed to the recognition sequence of the other. As both of the amplified nucleic acid fragments, internal control and wild type, were identical in length and base composition, the amplification conditions for the diagnostic assay were not affected. This allowed small copy numbers of the internal control clone to be loaded into a diagnostic assay without negatively affecting it. In a single reaction we were able to differentiate between an assay reporting a true or false-negative signal. A negative signal is defined as the absence of detectable pathogen genetic material (true) or inhibition/failure of the reaction (false).

Human T-lymphotropic virus type 2 (HTLV-2) provirus in circulating cells of the monocyte/macrophage lineage in patients dually infected with human immunodeficiency virus type 1 and HTLV-2 and having predominantly sensory polyneuropathy

We investigated the presence of human T-lymphotropic virus type 2 (HTLV-2) DNA in the peripheral blood mononuclear cell subsets obtained from 18 patients coinfected with human immunodeficiency virus type 1 and HTLV-2, 6 of whom also had predominantly sensory polyneuropathy (PSP). HTLV-2 DNA and RNA were found in CD8- and CD19-positive cells, and, for patients with PSP, in CD14-positive cells as well. Furthermore, the patients with PSP had higher proviral loads than those without PSP.