Effect of Phosphonated Carbocyclic 2′-Oxa-3′-Aza-Nucleoside on Human T-Cell Leukemia Virus Type 1 Infection In Vitro

Abstract

The human T-cell leukemia/lymphoma virus type 1 (HTLV-1) is an oncogenic retrovirus endemic in certain areas of the world including Japan and North and South America, where about 5% of the estimated 20 million HTLV-1-infected people develop HTLV-1-associated diseases (10,11,43), such as adult T-cell leukemia (ATL), human myelopathy/tropical spastic paraparesis (/TSP), or other minor inflammatory diseases. A number of studies have shown that HTLV-1 infects different types of cells (e.g., lymphocytes, monocytes, and fibroblasts) but preferentially T lymphocytes with a CD4 ϩ phenotype, which become immortalized following infection (26). In HTLV-1 infection viremia is essentially a "cytoviremia," since the virus is cell associated. In fact, cell-free virions are rarely infectious, and spreading of the virus in vivo does not require the extracellular release of viral particles. The spread of the virus within an individual host is most commonly recognized as being through the mitotic pathway, in which cell divisions and clonal expansion of infected cells ensure a constant level of viral load. However, recently it has been highlighted that the HTLV-1 viral load in vivo is also sustained by cell-tocell contact, involving intercellular viral spread. In particular, this "horizontal" spread allows the transfer of HTLV-1 infectious viral particles across the cell-cell junction by the generation of "virological synapses" between infected and uninfected cells (19,21). Transmission of HTLV-1 via cell-to-cell contact involves both integrin (3) and cytoskeleton proteins and participation of Env protein-cell receptor interactions (37). Either way, efficient transmission of HTLV-1 to noninfected cells implies reverse transcriptase (RT) dependency.In recent years, a number of strategies for therapeutic intervention have been pursued in the treatment of ATL or TSP, based on conventional chemotherapy or innovative approaches. However, until now, limited advances have been achieved in improving the therapy for HTLV-1-associated diseases. Therefore, symptomatic HTLV-1-infected patients still have inadequate treatment options with poor prognoses. Among the novel approaches for treating HTLV-1-related diseases, the use of topoisomerase 1 or 2 inhibitors in a pilot phase II study in refractory ATL did not provide satisfactory results (41). Similarly, treatments with the nucleoside analogue 2Ј deoxycoformycin (39) or inhibitors of AMP synthesis resulted in a limited response in ATL patients (42). Interestingly, studies based on a different strategy of chemotherapeutic intervention showed that ATL patients transiently responded to combined therapy with the nucleoside reverse transcriptase inhibitor (NRTI) azidothymidine (AZT) and interferon (IFN) (15) and that AZT treatment was beneficial to TSP patients (33), giving more encouraging results. In addition, a transient response to therapy with the NRTI lamivudine alone (38) or in combination with AZT (25) has been reported for human myelopathy/TSP. Moreover, IFN-␣ has been shown to have some ...

Truncated phosphonated C-1′-branched N,O-nucleosides: A new class of antiviral agents

“…HTLV-1 infection was carried out as previously shown. 26 Peripheral blood mononuclear cells were co-cultivated with a HTLV-1 chronically infected cell line and infection was evaluated as production of the viral core protein p19. HIV infection was carried on by using a stable T cell line (CEM) containing a plasmid encoding a green fluorescence protein (GFP) driven by the HIV-1 long terminal repeat.…”

Quantification of HTLV-1 reverse transcriptase activity in ATL patients treated with zidovudine and interferon-α

“…7 First, we tested the reliability of our HTLV-1 RT assay using serial dilution of MT2 supernatants mimicking conditions of those from ATL PBMC cultures. DNA extracted from cells harvested after 10 days in culture was used for HTLV-1 clonality analysis of samples collected before and after therapy for 1 representative responder patient and 1 nonresponder patient (details of the assays and of the preliminary tests are given in supplemental Methods).…”

“…Allogeneic stem cell transplantation can result in long-term disease control but few patients can be successfully transplanted. 3 Antiretrovirals with activity against HIV-1, such as zidovudine (39-azido-29,39-dideoxythymidine [AZT]) and tenofovir, and new phosphonated compounds, efficiently block HTLV-1 transmission in vitro, [4][5][6][7] whereas HTLV-1 was resistant to lamivudine. 8 Two preliminary phase 2 studies using the combination of AZT and interferon-a (IFN-a) reported an unexpectedly high response rate, particularly in previously untreated acute ATL patients.…”

Synthesis of N,O- homonucleosides with high conformational freedom

“…12 In this context we have tried to synthesize phosphonated N,O-homonucleosides 13c and 14c, starting from the phosphonated nitrone 12. However, in the cycloaddition reaction of 12 with compound 9 no significant amounts of cycloadducts were detected in the crude reaction mixture (entry 5) under traditional heating.…”