Lymphocyte alveolitis in HAM/TSP patients. Preliminary report

Direct detection of diverse metabolic changes in virally transformed and tax-expressing cells by mass spectrometry

Background

Viral transformation of a cell starts at the genetic level, followed by changes in the proteome and the metabolome of the host. There is limited information on the broad metabolic changes in HTLV transformed cells.

Methods and Principal Findings

Here, we report the detection of key changes in metabolites and lipids directly from human T-lymphotropic virus type 1 and type 3 (HTLV1 and HTLV3) transformed, as well as Tax1 and Tax3 expressing cell lines by laser ablation electrospray ionization (LAESI) mass spectrometry (MS). Comparing LAESI-MS spectra of non-HTLV1 transformed and HTLV1 transformed cells revealed that glycerophosphocholine (PC) lipid components were dominant in the non-HTLV1 transformed cells, and PC(O-32∶1) and PC(O-34∶1) plasmalogens were displaced by PC(30∶0) and PC(32∶0) species in the HTLV1 transformed cells. In HTLV1 transformed cells, choline, phosphocholine, spermine and glutathione, among others, were downregulated, whereas creatine, dopamine, arginine and AMP were present at higher levels. When comparing metabolite levels between HTLV3 and Tax3 transfected 293T cells, there were a number of common changes observed, including decreased choline, phosphocholine, spermine, homovanillic acid, and glycerophosphocholine and increased spermidine and N-acetyl aspartic acid. These results indicate that the lipid metabolism pathway as well as the creatine and polyamine biosynthesis pathways are commonly deregulated after expression of HTLV3 and Tax3, indicating that the noted changes are likely due to Tax3 expression. N-acetyl aspartic acid is a novel metabolite that is upregulated in all cell types and all conditions tested.

Conclusions and Significance

We demonstrate the high throughput in situ metabolite profiling of HTLV transformed and Tax expressing cells, which facilitates the identification of virus-induced perturbations in the biochemical processes of the host cells. We found virus type-specific (HTLV1 vs. HTLV3), expression-specific (Tax1 vs. Tax3) and cell-type–specific (T lymphocytes vs. kidney epithelial cells) changes in the metabolite profiles. The new insight on the affected metabolic pathways can be used to better understand the molecular mechanisms of HTLV induced transformation, which in turn can result in new treatment strategies.

Molecular and cellular aspects of HTLV-1 associated leukemogenesis in vivo

Most cancers and leukemias are preceded by a prolonged period of clinical latency during which cellular, chromosomal and molecular aberrations help move normal cell towards the malignant phenotype. The problem is that premalignant cells are usually indistinguishable from their normal counterparts, thereby ruling out the possibility to investigate the events that govern early leukemogenesis in vivo. Adult T cell leukemia/lymphoma (ATLL) is a T cell malignancy that occurs after a 40-60-year period of clinical latency in about 3-5% of HTLV-1-infected individuals. ATLL cells are monoclonally expanded and harbor an integrated provirus. A persistent oligo/polyclonal expansion of HTLV-1-bearing cells has been shown to precede ATLL, supporting the fact that in ATLL tumor cells arise from a clonally expanding non-malignant cell. It is possible to isolate infected, ie preleukemic, cells during the premalignant asymptomatic phase of the infection, thus providing an exceptional system to study the mechanisms underlying human cancers. Here we review some of the consequences of HTLV-1 on its host cell in vivo, at different stages of infection.

[Clinical and immunological consequences of the association between HTLV-1 and strongyloidiasis]

Strongyloidiasis is one of most important forms of helminthiasis in tropical countries and epidemiologic studies have shown the association of this parasitic disease with HTLV. It has been observed in regions where both these agents are endemic and coinfection may result in an increase in the disseminated forms of strongyloidiasis as well as recurrent strongyloidiasis. While HTLV-1 is related to a high production of IFN-gamma; and deviation of the immune response towards a Th1 response, the protection against helminths is associated with Th2 like immune response. Individuals infected with HTLV and S. stercoralis have a reduction in the production of IL-4, IL-5, IL-13 and parasitic IgE response, all of which are factors participating in the defense mechanism against S. stercoralis. These abnormalities are the basis for the occurrence of an increase in the severe forms of strongyloidiasis among patients infected with HTLV-1.

Somatic mutation in human T-cell leukemia virus type 1 provirus and flanking cellular sequences during clonal expansion in vivo

BACKGROUND

Human T-cell leukemia virus type 1 (HTLV-1), the causative agent of adult T-cell leukemia/lymphoma, shows intrapatient genetic variability. Although HTLV-1 can replicate via the reverse transcription of virion RNA to a double-stranded DNA provirus (the conventional manner for retroviruses), its predominant mode of replication is via the clonal expansion (mitosis) of the infected cell. This expansion is achieved by the viral oncoprotein Tax, which keeps the infected CD4 T lymphocyte cycling. Because Tax also interferes with cellular DNA repair pathways, we investigated whether somatic mutations of the provirus that occur during the division of infected cells could account for HTLV-1 genetic variability.

METHODS

An inverse polymerase chain reaction strategy was designed to distinguish somatic mutations from reverse transcription-associated substitutions. This strategy allows the proviral sequences to be isolated together with flanking cellular sequences. Using this method, we sequenced 208 HTLV-1 provirus 3' segments, together with their integration sites, belonging to 29 distinct circulating cellular clones from infected individuals.

RESULTS

For 60% of the clones, 8%-80% of infected cells harbored a mutated HTLV-1 provirus, without evidence of reverse transcription-associated mutations. Mutations within flanking cellular sequences were also identified at a frequency of 2.8 x 10(-4) substitution per base pair. Some of these clones carried multiple discrete substitutions or deletions, indicating progressive accumulation of mutations during clonal expansion. The overall frequency of somatic mutations increased with the degree of proliferation of infected T cells.

CONCLUSIONS

These data indicate that, in vivo, HTLV-1 variation results mainly from postintegration events that consist of somatic mutations of the proviral sequence occurring during clonal expansion. The finding of substitutions in flanking sequences suggests that somatic mutations occurring after integration, presumably coupled with selection, help move the cellular clones toward a transformed phenotype, of which adult T-cell leukemia/lymphoma is the end point.

Two-step nature of human T-cell leukemia virus type 1 replication in experimentally infected squirrel monkeys (Saimiri sciureus)

After experimental infection of squirrel monkeys (Saimiri sciureus) with human T-cell leukemia virus type 1 (HTLV-1)-infected cells, the virus is transcribed only transiently in circulating blood, spleen, and lymph nodes. Stable disappearance of viral expression occurs at 2 to 3 weeks after inoculation. This coincides with the development of the anti-HTLV-1 immune response and persistent detection of the provirus in peripheral blood mononuclear cells (PBMCs). In this study, the HTLV-1 replication pattern was analyzed over time in PBMCs and various organs from two HTLV-1-infected squirrel monkeys. Real-time quantitative PCR confirmed that PBMCs and lymphoid organs constitute the major reservoirs for HTLV-1. The PCR amplification of HTLV-1 flanking sequences from PBMCs evidenced a pattern of clonal expansion of infected cells identical to that observed in humans. Dissemination of the virus in body compartments appeared to result from cellular transport of the integrated provirus. The circulating proviral burden increased as a function of time in one animal studied over a period of 4 years. The high proviral loads observed in the last samples resulted from the accumulation of infected cells via the extensive proliferation of a restricted number of persistent clones on a background of polyclonally expanded HTLV-1-positive cells. Therefore, HTLV-1 primary infection in squirrel monkeys is a two-step process involving a transient phase of reverse transcription followed by persistent multiplication of infected cells. This suggests that the choice of the target for blocking HTLV-1 replication might depend on the stage of infection.

High circulating proviral load with oligoclonal expansion of HTLV-1 bearing T cells in HTLV-1 carriers with strongyloidiasis

Adult T cell leukemia (ATLL) develops in 3 - 5% of HTLV-1 carriers after a long period of latency during which a persistent polyclonal expansion of HTLV-1 infected lymphocytes is observed in all individuals. This incubation period is significantly shortened in HTLV-1 carrier with Strongyloides stercoralis (Ss) infection, suggesting that Ss could be a cofactor of ATLL. As an increased T cell proliferation at the asymptomatic stage of HTLV-1 infection could increase the risk of malignant transformation, the effect of Ss infection on infected T lymphocytes was assessed in vivo in HTLV-1 asymptomatic carriers. After real-time quantitative PCR, the mean circulating HTLV-1 proviral load was more than five times higher in HTLV-1 carriers with strongyloidiasis than in HTLV-1+ individuals without Ss infection (P<0.009). This increased proviral load was found to result from the extensive proliferation of a restricted number of infected clones, i.e. from oligoclonal expansion, as evidenced by the semiquantitative amplification of HTLV-1 flanking sequences. The positive effect of Ss on clonal expansion was reversible under effective treatment of strongyloidiasis in one patient with parasitological cure whereas no significant modification of the HTLV-1 replication pattern was observed in an additional case with strongyloidiasis treatment failure. Therefore, Ss stimulates the oligoclonal proliferation of HTLV-1 infected cells in HTLV-1 asymptomatic carriers in vivo. This is thought to account for the shortened period of latency observed in ATLL patients with strongyloidiasis. Oncogene (2000) 19, 4954 - 4960

Adult T-cell leukemia-lymphoma in a patient with HTLV-I/II associated myelopathy

Chronic myelopathy associated with T-lymphotropic virus type I (HAM) has been described as an endemic disease in several areas of the world, meanwhile there are few papers describing the association between HAM and adult T cell leukemia-lymphoma. We report the case of a man that, after four years of progressive spastic paraparesis and neurogenic bladder, developed a clinical picture of a lymphoproliferative disorder characterized by dermal and systemic involvement, mimicking mycosis fungoides/Sézary syndrome.

Tropical spastic paraparesis/HTLV-I-associated myelopathy in Brazil

Brazil, the largest Latin American country, is highly heterogeneous, both demographically and socioeconomically. The overall human T-cell lymphotropic virus type I (HTLV-I) seroprevalence among blood donors is approximately 0.45%. These rates are highly variable, from 0 to 1.8%. Since 1989, many series of tropical spastic paraparesis/HTLV-I-associated myelopathy (TSP/HAM) cases have appeared in the literature, with high variation in the prevalence of HTLV-I among TSP patients (14.7-57%). The main clinical features of Brazilian TSP/HAM are similar to those in other endemic countries, but sensory signs are more frequent. Recently, the presence of peripheral nerve and muscular involvement has been characterized. The first nationwide study on the disease has been recently completed: it enrolled 163 patients and concluded that TSP/HAM is common in Brazil, mainly in the northeast and southeast regions; it predominates among women and whites; the most important risk factors for infection are sexual promiscuity and blood transfusion; and, although a remarkably uniform disease throughout the country, some statistically significant differences were detected, such as a higher proportion of females over males in the northeast region, a higher proportion of whites the southeast and the south and mulattos in the northeast, and, finally, a high rate of venereal diseases in the southeast region and of intravenous drug use in the south. Brazil seems to be a perfect setting for future epidemiologic, clinical, basic, and therapeutic studies on TSP/HAM.

Pulmonary involvement in patients with HTLV-I associated myelopathy

Pulmonary involvement in HTLV-I patients has been identified by several authors in Africa, Japan and Brazil. The objective of this controlled study is to establish an association between HAM and lymphocytosis in the bronchoalveolar fluid (BAL). Thirty-five adult patients with non-traumatic and non-tumoral myelopathy filled out a detailed historical survey and underwent a neurological examination, a thoracic radiological evaluation and a CSF examination. Of the patients in this sample, 22 were diagnosed with HTLV-I associated myelopathy and 13 had myelopathies with other etiologies. Lymphocytosis in the BAL fluid was detected in 18 (82%) of the HAM patients and in 2 (15%) of non-HAM patients. We concluded that the lung represents an important organ in the pathogenesis of HAM.

HTLV-I associated myelopathy/tropical spastic paraparesis. Report of the first cases in Rio Grande do Sul, Brazil

The HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP), a myelopathy with predominant involvement of the pyramidal tract with minimal sensory loss and associated with HTLV-I infection, endemic in tropical areas, has been identified in four patients in Porto Alegre (RS, Brazil), a temperate zone.

Lymphomatous meningoencephalitis in a patient with HAM/TSP

A case of lymphomatous meningoencephalitis in a 23 year old Brazilian patient with HTLV-I/II associated myelopathy is reported. The patient was admitted to the hospital with a clinical picture of decreased consciousness level, stiffness of the neck and previous diagnosis of myeloneuropathy. CSF examination showed lymphocytosis with blastic cells and antibodies against HTLV-I/II.

Brazilian studies on tropical spastic paraparesis. A meta-analysis

Tropical spastic paraparesis (TSP) is a chronic progressive myelopathy and in most of the cases has a retroviral (HTLV-1) etiology, when it is denominated HTLV-1 associated-mielopathy (HAM/TSP). Around 433 cases of TSP have been described in Northeast and Southeast Brazil. Among these cases, 157 (36.2%) are HTLV-1 positive and 276 (63.7%) are negative. Their mean age is 43.8 years with a slight predominance of females and mulattoes, although white patients are also numerous. Clinically all patients exhibit a spastic paraparesis with variable sphincter and sensory disturbance. Pain and autonomic symptoms seem to be expressive in the HTLV-1 positive HAM/TSP Brazilian patients.

[HTLV-1 associated myelopathies in the city of Salvador, Bahia]

Chronic myelopathy associated with human T-lymphotropic virus type I (HTLV-I) has been described in several endemic areas in Brazil. In Salvador, 102 patients with myelopathy were screened for HTLV-I/II by ELISA and Western blot assays. We found 36 patients with HTLV-I/II associated myelopathy confirming the high prevalence of HAM in Salvador. The initial complaint of our patients were urinary urgency, back pain and progressive unsteadiness on walking. On examination all of them had a spastic paraparesis, variable degrees of lower motor neuron syndrome, deep and superficial sensitive syndrome. MRI analysis revealed lesions in the periventricular white matter in addition to atrophy of the thoracic spinal cord. Clinical and magnetic resonance findings reveal that the inflammatory lesions of HAM involve not only the spinal cord but also the brain and peripheral nervous system.

[HTLV-I-associated myelopathy: a systemic disease]

Chronic myelopathy associated with T-lymphotropic virus type I (HAM) has been described as an endemic disease in several areas of the world mainly in Asia, Africa and Latin America. The involvement of the central and the peripheral nervous system by HTLV-I observed in South America and Africa points out that this disease is a leukoencephalomyeloneuropathy. Several authors reported involvement outside the nervous system (as uveitis, lymphocytic alveolitis and arthritis, among others) in patients with HAM. In this paper we emphasize that HAM is a systemic disease whose cofactors determine the clinical picture in each patient.