PCR-in situ hybridization detection of human T-cell lymphotropic virus type 1 (HTLV-1) tax proviral DNA in peripheral blood lymphocytes of patients with HTLV-1-associated neurologic disease

Development of an IL-15-autocrine CD8 T-cell leukemia in IL-15-transgenic mice requires the cis expression of IL-15Rα

IL-15 has growth-promoting effects on select lymphoid subsets, including natural killer (NK) cells, NK T cells, intraepithelial lymphocytes (IELs), CD8 T cells, and γδ-T cells. Constitutive expression of murine IL-15 in IL-15-transgenic mice was reported to cause T-NK leukemia. We investigated whether IL-15 expression is sufficient for leukemic transformation using a human IL-15-transgenic (IL-15Tg) mouse model. We noted that 100% of the mice observed over a 2-year period (n > 150) developed fatal expansions of CD8 T cells with NK markers, and determined that these cells expressed IL-15 receptor alpha (IL-15Rα). The expression of IL-15Rα on CD8 T cells appears to be required for uncontrolled aggressive lymphoproliferation, because none of the IL-15Rα(-/-)-IL-15Tg mice that we followed for more than 2 years developed the fatal disease despite controlled expansion of CD8 T cells. In addition, in contrast to IL-15Tg mice, in which leukemia-like CD8 T cells expressed IL-15Rα persistently, acutely activated normal CD8 T cells only transiently expressed IL-15Rα. Inhibition of DNA methylation enabled sustained IL-15Rα expression induced by activation. We present a scenario for IL-15Tg mice in which CD8 T cells that acquire constitutive persistent IL-15Rα expression are at a selective advantage and become founder cells, outgrow other lymphocytes, and lead to the establishment of a leukemia-like condition.

Identification, localization, and function in steroidogenesis of PAP7: a peripheral-type benzodiazepine receptor- and PKA (RIalpha)-associated protein

Peptide hormones and cAMP acutely stimulate steroid biosynthesis by accelerating the transport of cholesterol into the mitochondria. The peripheral-type benzodiazepine receptor (PBR) has been shown to be an indispensable element of the cholesterol transport machinery. Using the yeast two-hybrid system and PBR as bait, we identified a protein that interacts with PBR, the PBR-associated protein PAP7. Using the regulatory subunit RIalpha of PKA as bait, we also isolated PAP7. Glutathione-S-transferase -PAP7 interacted with both the mitochondrial PBR and cytosolic PKA-RIalpha in MA-10 Leydig cells. PAP7 is a novel 52-kDa protein present in mouse, rat, and human tissues, and it has a major 3-kb mRNA transcript in all tissues examined. Immunohistochemical and in situ hybridization studies indicated that PAP7 is highly expressed in the gonads, adrenal, hippocampus, and distinct brain neuronal and glial populations. Overexpression of the full length PAP7 increased the hCG-induced steroid production. However, overexpression of a partial PAP7, which includes the PBR- and PKA-RIalpha-binding domains, inhibited the hormone-stimulated cholesterol transport and steroid synthesis. Treatment of MA-10 cells with oligonucleotides antisense to PAP7 also inhibited the hCG-stimulated steroid formation, suggesting that PAP7 is a functional element of the hormone-induced signal transduction cascade leading to steroidogenesis. PAP7 may function by targeting the PKA isoenzyme to organelles rich in PBR, i.e. mitochondria, where phosphorylation of specific protein substrates may induce the reorganization of PBR topography and function.

Strategies for signal amplification in nucleic acid detection

Many aspects of molecular genetics necessitate the detection of nucleic acid sequences. Current approaches involving target amplification (in situ PCR, Primed in situ Labeling, Self-Sustained Sequence Replication, Strand Displacement Amplification), probe amplification (Ligase Chain Reaction, Padlock Probes, Rolling Circle Amplification) and signal amplification (Tyramide Signal Amplification, Branched DNA Amplification) are summarized in the present review, together with their advantages and limitations.

Chromosomal positioning of human T-lymphotropic type 1 proviruses by fluorescence in situ hybridisation

Fluorescence in situ hybridisation (FISH) was employed to identify the chromosomal integration site of the human T-cell lymphotropic virus, type 1 (HTLV-1) present in T-cell clones derived from HTLV-1-infected individuals and a virally transformed cell line, C8166-45. Proviral sequences were detected in C8166-45 but not uninfected Jurkat cells. Integration sites were reliably detected in T-cell clones determined previously to be infected with HTLV-1. The results indicated that the transformed cell line and some of the T-cell clones possessed more than one proviral integration site. This hybridisation system is useful for determining the number of integration events and for localising proviruses to specific chromosomal regions.

Localization of retrovirus in the central nervous system of a patient co-infected with HTLV-1 and HIV with HAM/TSP and HIV-associated dementia

Persons co-infected with HTLV-1 and HIV are at increased risk for neurologic disease. These patients may develop HAM/TSP and/or HIV-associated dementia. In this study, we localized cells infected with retrovirus in the central nervous system (CNS) of a patient with both HAM/TSP and HIV-associated dementia. HTLV-1 was localized to astrocytes and HIV to macrophage/microglia. There was no co-infection of a single cell phenotype in this patient. These data suggest that mechanisms other than co-infection of the same CNS cell may play a role in the development of neurologic disease in patients dual infected with HTLV-1 and HIV.

Development of a direct in situ RT-PCR method using labeled primers to detect cytokine mRNA inside cells

We have developed an original protocol of direct in situ RT-PCR with biotinylated labeled primers to detect cytokine mRNA inside cells. This label improved the specificity of the technique compared with the use of digoxigenin or fluorescein-labeled primers. We found a reliable correlation between the known expression of cytokine mRNA in a given cell and a positive signal with in situ RT-PCR. Nuclear counterstaining demonstrated that the positive signal obtained was distributed in the cytoplasm in accordance with mRNA localization. In addition, direct demonstration of the presence of the expected PCR product in cell extracts without non-specific parasitic DNA amplification provided strong support for the specificity of the method. Designing the primers in order to prevent DNA amplification, the use of recombinant Thermus thermophilus (rTth) DNA polymerase and a decreased duration of each cycle of PCR by combining the annealing and hybridization steps improved the reproducibility and reliability of the technique and morphological preservation of the cells. Experiments in which different proportions of cytokine mRNA positive and negative cells were mixed argue against significant diffusion of PCR product into initially cytokine mRNA negative cells, thereby leading to false-positive results. In comparison with the direct incorporation of labeled dNTP during amplification, our procedure appears to ensure greater specificity and does not need DNAse treatment which is often difficult to standardize. Detection of IL-2 and IFNgamma mRNA induction after T cell activation using this direct in situ RT-PCR method showed that the technique may be helpful for monitoring cytokine gene expression at a single cell level.

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.

Quantitative in situ PCR assay of HTLV-1 infected cells in peripheral blood lymphocytes of patients with ATL, HAM/TSP and asymptomatic carriers

We established an in situ PCR (IS-PCR) method that amplified the pX region of human T cell lymphotropic virus type 1 (HTLV-1) proviral DNA. The procedure was highly sensitive in accurately detecting the number of cells infected with HTLV-1. We estimated the number of HTLV-1 infected cells in peripheral blood lymphocytes (PBL) from patients with HAM/TSP, ATL and asymptomatic carriers. ATL patients (n = 5) had 8-93% IS-PCR positive cells for HTLV-1 and these percentages correlated with the clinical stages. Asymptomatic carriers (n = 3) had 0.8-3.8% (mean 1.1%, S.D. 1.7) positive cells. HAM/TSP patients (n = 10) had 3.1-8.5% (5.8% (5.8%, 2.7) positive cells. Patients with shorter duration of illness showed larger percentages compared with patients with longer duration. In one HAM/TSP patient, the number of IS-PCR positive cells decreased from 5.1% to 1.5% coincident with the times of lymphocytapheresis treatment. Our studies may suggest that an increased viral load initiates the pathogenic process of HAM/TSP and the estimation of HTLV-1 proviral load by IS-PCR method is useful to understand the clinical state of HAM/TSP.

Neuronal molecular mimicry in immune-mediated neurologic disease

Molecular mimicry is implicated in the pathogenesis of autoimmune diseases such as diabetes mellitus, rheumatoid arthritis, and multiple sclerosis (MS). Cellular and antibody-mediated immune responses to shared viral-host antigens have been associated with the development of disease in these patients. Patients infected with human T-lymphotropic virus type I (HTLV-I) develop HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP), an immune-mediated disorder of the central nervous system (CNS) that resembles some forms of MS. Damage to neuronal processes in the CNS of HAM/TSP patients is associated with an activated cellular and antibody-mediated immune response. In this study, IgG isolated from HAM/TSP patients was immunoreactive with uninfected neurons and this reactivity was HTLV-I specific. HAM/TSP IgG stained uninfected neurons in human CNS and cell lines but not nonneuronal cells. Neuronal western blots showed IgG reactivity with a single 33-kd band in all HAM/TSP patients tested. By contrast, no neuron-specific IgG reactivity could be demonstrated from HTLV-I seronegative controls and, more important, from HTLV-I seropositive, neurologically asymptomatic individuals. Both immunocytochemical staining and western blot reactivity were abolished by preincubating HAM/TSP IgG with HTLV-I protein lysate but not by control proteins. Staining of CNS tissue by a monoclonal antibody to HTLV-I tax (an immunodominant HTLV-I antigen) mimicked HAM/TSP IgG immunoreactivity. There was no staining by control antibodies. Absorption of HAM/TSP IgG with recombinant HTLV-I tax protein or preincubation of CNS tissue with the monoclonal antibody to HTLV-I tax abrogated the immunocytochemical and western blot reactivity of HAM/TSP IgG. Furthermore, in situ human IgG localized to neurons in HAM/TSP brain but not in normal brain. These data indicate that HAM/TSP patients develop an antibody response that targets uninfected neurons, yet reactivity is blocked by HTLV-I, suggesting viral-specific autoimmune reactivity to the CNS, the damaged target organ in HAM/TSP.

HTLV-I and HTLV-II virus expression increase with HIV-1 coinfection

Coinfections with HIV-1 and HTLV-I or HTLV-II have been associated with unique immunophenotypes and an increased risk for development of neurodegenerative conditions. These findings may result from an increased HTLV-I or II viral burden in dually infected individuals. To investigate this possibility, HTLV-I/II tax/rex messenger RNA and viral antigen expression in peripheral blood mononuclear cells (PBMCs) were measured in 37 HTLV-I- or HTLV-II-infected subjects with or without HIV-1 coinfection. Tax/rex messenger RNA was detected in 14 of 24 PBMC samples from dually infected subjects, compared with only 1 of 13 PBMC samples from singly infected subjects (58% versus 7%; p < .003). The reverse transcription-polymerase chain reaction (RT-PCR) assay correlated with HTLV-I/II viral antigen detection in PBMC cultures but not with HIV-1 viral load levels in plasma. These findings may provide clues regarding the pathophysiologic consequences of HIV/HTLV-I and HIV/HTLV-II coinfections.

Detection of HTLV-1 by polymerase chain reaction in situ hybridization in adult T-cell leukemia/lymphoma

A method for nonradioactive polymerase chain reaction in situ hybridization was developed and used to determine the distribution of human T-lymphotropic virus type I (HTLV-I) proviral DNA in paraffin-embedded surgical specimens of adult T-cell leukemia/lymphoma (ATLL). As controls, we used biopsy samples of five cases of mycosis fungoides, cells of an HTLV-I-infected cell line (MT2), as well as HTLV-1-negative cells (YAS). We successfully detected the amplicon of the HTLV-1 tax sequence in the nuclei of the cutaneous infiltrating lymphoid cells in 90% (9/10) of ATLL cases. Studies also revealed the existence of HTLV-1 provirus DNA in nuclei of sweat gland epithelial cells and vascular endothelial cells as well as lymphoid cells in ATLL patients. Mycosis fungoides and YAS cells were negative for the HTLV-I tax sequence, but MT2 cells were strongly positive. The results indicated that this technique was more sensitive in detecting intracellular amplicons than was the previous in situ hybridization method. Through its use, we were able to easily determine the distribution of HTLV-I-positive cells among the various cells and tissues of paraffin-embedded archival materials.

Detection of HTLV-I in Peripheral Blood Lymphocytes from Patients with Chronic HTLV-I-Associated Myelopathy/Tropical Spastic Paraparesis and Asymptomatic Carriers by PCR-in situ Hybridization

Less than 5% of people infected with human T-lymphotropic virus type I (HTLV-I) develop HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a chronic progressive neurologic disease. A number of factors have been implicated in the development of HAM/TSP including heterogeneity of viral sequences, host-genetic background, viral-specific cellular immune responses and viral load. This study examined the presence of HTLV-1 tax DNA in peripheral blood lymphocytes (PBL) from 2 chronic HAM/TSP patients and 2 asymptomatic HTLV-I carriers by using PCR-in situ hybridization (PCR-ISH) for the in situ presence of proviral HTLV-I tax DNA. By this technique, rare PBL from these HTLV-I-infected individuals contained HTLV-I DNA. PCR-ISH did not detect any difference in the number of infected cells between HAM/TSP patients and asymptomatic carriers. Copyright 1997 S. Karger AG, Basel