Validation of a quantitative real-time PCR assay for HTLV-1 proviral load in peripheral blood mononuclear cells

CXCL-10 in Cerebrospinal Fluid Detects Neuroinflammation in HTLV-1-Associated Myelopathy with High Accuracy

BACKGROUND AND OBJECTIVES

HTLV-1-associated myelopathy (HAM) is a chronic progressive inflammatory disease of the spinal cord. This study assesses the diagnostic accuracy of the neuroinflammatory biomarkers neopterin and cysteine-X-cysteine motif chemokine ligand 10 (CXCL-10) in cerebrospinal fluid (CSF) for HAM.

METHODS

CSF samples from 75 patients with neurological disorders-33 with HAM (Group A), 19 HTLV-1-seronegative with other neuroinflammatory diseases (Group B), and 23 HTLV-1-seronegative with non-neuroinflammatory diseases (Group C)-were retrospectively evaluated. CSF examination included routine analysis, neopterin, and CXCL-10. The diagnostic potential of the biomarkers was evaluated using receiver operating characteristic curves.

RESULTS

Higher white cell counts and concentrations of protein, neopterin, and CXCL-10 in CSF were detected in group A (patients with HAM) and group B (p < 0.05). Neopterin showed good accuracy for HAM (A) (cut-off 15 nmol/L, 80% sensitivity, 74% specificity) and other neuroinflammation (group B) (cut-off 20 nmol/L, 79% sensitivity, 83% specificity). CXCL-10 demonstrated the highest accuracy in both groups, with Group A (cut-off 110 pg/mL, 97% sensitivity, 96% specificity) and Group B (cut-off 220 pg/mL, 100% sensitivity, 100% specificity).

CONCLUSIONS

Neopterin and CXCL-10 in CSF are accurate biomarkers for detecting neuroinflammation, including HAM. CXCL-10, in particular, is the superior biomarker for both chronic and acute neuroinflammatory diseases.

Development and Validation of Multiplex Quantitative Real-Time PCR Assays for Simultaneous Detection and Differentiation of HTLV-1 and HTLV-2, Using Different PCR Platforms and Reagent Brands

Brazil currently has the highest number of individuals infected with human T-lymphotropic virus 1- and 2- (HTLV-1 and HTLV-2) globally. At present, neither molecular protocols nor commercial assays are available for HTLV-1/-2 diagnosis or validated by the Brazilian Ministry of Health regulatory agency (ANVISA). We developed and validated two in-house multiplex quantitative real-time PCR for HTLV-1/-2 (mqPCR_HTLV) assays, targeting the pol and tax genes, for the simultaneous identification of HTLV-1, HTLV-2, and the albumin reference gene. The robustness of the assays was evaluated on two platforms using seven commercial master mix formulations. The reactions employed double plasmids (pHTLV1-Alb and pHTLV2-Alb) for the standard curve’s construction and for expressing the detection limit of the assays. They were able to detect 10 and 10 copies of HTLV-1 and 10 and 70 copies of HTLV-2 for the tax and pol targets, respectively. High efficiency was obtained using both the platforms and all the reagents evaluated and were successfully reproduced by other analysts. DNA samples from HTLV-1/-2-infected and non-infected patients and from HIV/HTLV-coinfected patients were evaluated to determine the feasibility of their use in routine diagnosis. The mqPCR_HTLV (pol and tax) assays demonstrated an overall specificity of 100% and a sensitivity of 97.4% when testing samples from patients without HIV infection, and sensitivities of 77.1% (pol) and 74.6% (tax) in samples from HIV/HTLV-coinfected patients. In addition, they resolved the issue of HTLV western blotting (WB) indeterminate and WB-untyped results in 45.5 and 66.7% of cases, respectively. The developed mqPCR_HTLV (pol and tax) assays indicated their feasibility for efficient and reliable HTLV diagnosis in various core facility laboratories under different conditions and supplies.

Monitoring of HTLV-1-associated diseases by proviral load quantification using multiplex real-time PCR

Proviral load (PVL) is one of the determining factors for the pathogenesis and clinical progression of the human T-lymphotropic virus type I (HTLV-1) infection. In the present study, we optimized a sensitive multiplex real-time PCR for the simultaneous detection and quantification of HTLV-1 proviral load and beta-globin gene as endogenous control. The values obtained for HTLV-1 PVL were used to monitor the clinical evolution in HTLV-1-infected individuals. A vector containing cloned DNA targets of the real-time PCR for the beta-globin gene and the HTLV-1pol region was constructed. For the reaction validation, we compared the amplification efficiency of the constructed vector and MT-2 cell line containing HTLV-1. The analytical sensitivity of the reaction was evaluated by the application of a standard curve with a high order of magnitude. PVL assay was evaluated on DNA samples of HTLV-1 seropositive individuals. The construct showed adequate amplification for the beta-globin and HTLV-1 pol genes when evaluated as multiplex real-time PCR (slope = 3.23/3.26, Y-intercept = 40.18/40.73, correlation coefficient r² = 0.99/0.99, and efficiency = 103.98/102.78, respectively). The quantification of PVL using the MT-2 cell line was equivalent to the data obtained using the plasmidial curve (2.5 copies per cell). In HTLV-1-associatedmyelopathy/tropical spastic paraparesis patients, PVL was significantly higher (21315 ± 2154 copies/10⁵ PBMC) compared to asymptomatic individuals (1253 ± 691 copies/10⁵ PBMC). The obtained results indicate that the optimized HTLV-1 PVL assay using plasmidial curve can be applied for monitoring and follow-up of the progression of HTLV-1 disease. The use of a unique reference plasmid for both HTLV-1 and endogenous gene allows a robust and effective quantification of HTLV-1 PVL. In addition, the developed multiplex real-time PCR assay was efficient to be used as a tool to monitor HTLV-1-infected individuals.

qPrimerDB: A Powerful and User-Friendly Database for qPCR Primer Design

Real-time quantitative polymerase chain reaction (qPCR) is a powerful tool for analyzing and quantifying gene expression, and its primer design is the first and most important step. In order to improve the efficiency and effectiveness of primer design, we designed a database qPrimerDB, based on thermodynamics gene-specific for multispecies qPCR primers design.In this chapter, we explained the working principle of the database and detailed the step-by-step practical steps with examples. The valuable and time-saving qPrimerDB database is publicly accessible at http://biodb.swu.edu.cn/qprimerdb and will be routinely updated.

Laboratory diagnosis of human T-lymphotropic virus in Brazil: assays, flowcharts, challenges, and perspectives

INTRODUCTION

We present a data analysis and review of recent studies regarding the laboratory diagnosis of human T-lymphotropic virus 1 and 2 (HTLV-1/2) infections in Brazil.

METHODS

Target populations, available diagnostic serological assays (screening and complementary tests), molecular assays (in-house), causes of false-positive and false-negative results, and flowcharts were analyzed.

RESULTS

A table presents the target populations, two diagnostic flowcharts (depending on laboratory infrastructure and study population), and recent research that may improve how HTLV-1/2 is diagnosed in Brazil.

CONCLUSIONS

Our results support the implementation of public policies to reduce HTLV-1/2 transmission and its associated diseases.

Brazilian Protocol for Sexually Transmitted Infections 2020: human T-cell lymphotropic virus (HTLV) infection

This article addresses the Human T-lymphotropic virus (HTLV). This subject comprises the Clinical Protocol and Therapeutic Guidelines for Comprehensive Care for People with Sexually Transmitted Infections, published by the Brazilian Ministry of Health. HTLV-1/2 infection is a public health problem globally, and Brazil has the largest number of individuals living with the virus. HTLV-1 causes several clinical manifestations of neoplasm (adult T-cell leukemia/lymphoma) and inflammatory nature, such as HTLV-1-associated myelopathy and other manifestations such as uveitis, arthritis, and infective dermatitis. These pathologies have high morbidity and mortality and negatively impact the quality of life of infected individuals. This review includes relevant information for health authorities professionals regarding viral transmission, diagnosis, treatment, and monitoring of individuals living with HTLV-1 and 2 in Brazil. HTLV-1/2 transmission can occur through blood transfusion and derivatives, injectable drug use, organ transplantation, unprotected sexual intercourse, and vertical transmission.

[Brazilian Protocol for Sexually Transmitted Infections 2020: human T cell lymphotropic virus (HTLV) infection]

This manuscript is related to the chapter about human T-cell lymphotropic virus (HTLV) that is part of the Clinical Protocol and Therapeutic Guidelines for Comprehensive Care for People with Sexually Transmitted Infections, published by the Brazilian Health Ministry. HTLV-1/2 infection is a worldwide public health problem and Brazil has the largest number of individuals living with the virus. HTLV-1 causes a variety of clinical manifestations of a neoplastic nature, such as adult leukemia/T-cell lymphoma, and also of an inflammatory nature, such as HTLV-1-associated myelopathy, as well as other manifestations such as uveitis, arthritis and infective dermatitis. These pathologies have high morbidity and mortality and negatively impact the quality of life of infected individuals. This review includes relevant information for health service managers and workers regarding virus transmission modes, diagnosis, treatment and monitoring of individuals living with HTLV-1 and 2 in Brazil.

Use of synthetic oligonucleotides for determination of HTLV-1 proviral load by real-time PCR: a helpful alternative approach in the clinical management

AIMS

To evaluate the potential use of synthetic oligonucleotides as a standard curve for proviral load (PVL) of human T-cell leukaemia virus type 1 (HTLV-1) quantification in peripheral blood mononuclear cells (PBMC) of HTLV-1-infected individuals by quantitative real-time polymerase chain reaction (qPCR) analysis.

METHODS AND RESULTS

Synthetic oligonucleotides based on HTLV-1 genome were customized to use as a standard curve. Twelve anti-HTLV-1-positive samples with known HTLV-1 PVL, previously quantified by qPCR assay using TARL-2 cells as a conventional standard curve, were submitted to the new protocol. The proviral quantification levels had a high concordance with qPCR results using a conventional standard curve. The results demonstrate that the conventional standard curve can be replaced by a synthetic standard curve due to its ability to quantification based on the linearity and qPCR efficiency and similar results with a validated qPCR assay using a conventional standard curve.

CONCLUSIONS

Synthetic oligonucleotides standard curves could be a very useful tool on HTLV-1 diagnosis and absolute HTLV-1 PVL quantification.

SIGNIFICANCE AND IMPACT OF THE STUDY

HTLV-1 PVL determination using synthetic oligonucleotides standard curve by qPCR could be a helpful alternative for the laboratories that monitor infected patients as an important prognostic factor in HTLV-1-associated diseases progression. Also, it can decrease costs and overcome the biological limitations of the plasmid curve.

Cytokine profile and proviral load among Japanese immigrants and non-Japanese infected with HTLV-1 in a non-endemic area of Brazil

The lifetime risk of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) development differs among ethnic groups. To better understand these differences, this prospective cohort study was conducted to investigate the cytokine profile and the HTLV-1 proviral load (PVL) in Japanese and non-Japanese populations with HAM/TSP and asymptomatic carriers (ACs). The serum IL-2, IL-4, IL-6, IL-10, IL-17, TNF-α, and IFN-γ levels were quantified using the Cytometric Bead Array in 40 HTLV-1-infected patients (11 HAM/TSP and 29 ACs) and 18 healthy controls (HCs) in Brazil. Among ACs, 15 were Japanese descendants and 14 were non-Japanese. Of 11 patients with HAM/TSP, only one was a Japanese descendant. The HTLV-1 PVL was quantified by real-time PCR. The HTLV-1 PVL was 2.7-fold higher in HAM/TSP patients than ACs. Regardless of the clinical outcome, the PVL was significantly higher in patients younger than 60 years than older patients. The HAM/TSP and ACs had higher IL-10 serum concentrations than that of HCs. The ACs also showed higher IL-6 serum levels than those of HCs. According to age, the IL-10 and IL-6 levels were higher in ACs non-Japanese patients older than 60 years. HAM/TSP patients showed a positive correlation between IL-6 and IL-17 and a negative correlation between the PVL and IL-17 and IFN-γ. In the all ACs, a significant positive correlation was observed between IL-2 and IL-17 and a negative correlation was detected between IL-10 and TNF-α. Only 6.25% of the Japanese patients were symptomatic carriers, compared with 41.67% of the non-Japanese patients. In conclusion, this study showed that high levels of HTLV-1 PVL was intrinsicaly associated with the development of HAM/TSP. A higher HTLV-1 PVL and IL10 levels found in non-Japanese ACs over 60 years old, which compared with the Japanese group depicts that the ethnic background may interfere in the host immune status. More researches also need to be undertaken regarding the host genetic background to better understand the low frequency of HAM/TSP in Japanese HTLV-1-infected individuals.

Acute myelitis as presenting symptom of HIV-HTLV-1 co-infection

A 21-year-old woman presented with acute-onset spastic paraparesis. The MRI spinal scan revealed a contrast-enhanced T2 hyperintensity between C5-T2. The most common neurotropic pathogens were excluded by first level tests. Under suspicion of an acute immune-mediated myelitis, a corticosteroid therapy was administered. However, a seropositivity for both human immunodeficiency virus (HIV) type 1 and human T-lymphotropic virus (HTLV) subsequently emerged. An antiretroviral therapy was started while steroids discontinued. Patient's clinical conditions remained unchanged. HIV-HTLV-1 co-infection should be included in the differential diagnosis of any acute myelitis, even in patients with a preserved immune status and no risk factors.

Design of primers and probes for quantitative real-time PCR methods

Design of primers and probes is one of the most crucial factors affecting the success and quality of quantitative real-time PCR (qPCR) analyses, since an accurate and reliable quantification depends on using efficient primers and probes. Design of primers and probes should meet several criteria to find potential primers and probes for specific qPCR assays. The formation of primer-dimers and other non-specific products should be avoided or reduced. This factor is especially important when designing primers for SYBR(®) Green protocols but also in designing probes to ensure specificity of the developed qPCR protocol. To design primers and probes for qPCR, multiple software programs and websites are available being numerous of them free. These tools often consider the default requirements for primers and probes, although new research advances in primer and probe design should be progressively added to different algorithm programs. After a proper design, a precise validation of the primers and probes is necessary. Specific consideration should be taken into account when designing primers and probes for multiplex qPCR and reverse transcription qPCR (RT-qPCR). This chapter provides guidelines for the design of suitable primers and probes and their subsequent validation through the development of singlex qPCR, multiplex qPCR, and RT-qPCR protocols.

HTLV-1 ORF-I Encoded Proteins and the Regulation of Host Immune Response: Viral Induced Dysregulation of Intracellular Signaling

The human T-cell lymphotropic virus type 1 (HTLV-1) is a retrovirus associated with both proliferative and inflammatory disorders. This virus causes a persistent infection, mainly in CD4+ T lymphocyte. The ability to persist in the host is associated with the virus capacity to evade the immune response and to induce infected T-cell proliferation, once the HTLV-1 maintains the infection mainly by clonal expansion of infected cells. There are several evidences that ORF-I encoded proteins, such as p12 and p8, play an important role in this context. The present study will review the molecular mechanisms that HTLV-1 ORF-I encoded proteins have to induce dysregulation of intracellular signaling, in order to escape from immune response and to increase the infected T-cell proliferation rate. The work will also address the impact of ORF-I mutations on the human host and perspectives in this study field.

Relevance of retrovirus quantification in cerebrospinal fluid for neurologic diagnosis

Different human retroviruses, such as Human Immunodeficiency Virus (HIV) and Human T-cell Lymphotropic Virus (HTLV), can cause neurologic infection. However, a definitive diagnosis may be hampered by several factors. Quantification of the viral or proviral load in cerebrospinal fluid (CSF) may be helpful in the diagnosis of nervous system disorders due to retroviral infection and may influence the treatment approach. The present work discusses retrovirus infection and neurologic impairment, as well as the usefulness of the determination of the HIV and HTLV proviral or viral load in cerebrospinal fluid in cases of neurologic disorder, in light of recent advances in this field. This study also discusses the different molecular techniques for quantifying the proviral load (real-time quantitative PCR, droplet digital PCR, and semi-nested real-time reverse transcription PCR) that are currently available.