The ESCRT-0 Protein HRS Interacts with the Human T Cell Leukemia Virus Type 2 Antisense Protein APH-2 and Suppresses Viral Replication.

The divergent clinical outcomes of human T cell leukemia virus type 1 (HTLV-1) and HTLV-2 infections have been attributed to functional differences in their antisense proteins. In contrast to HTLV-1 bZIP factor (HBZ), the role of the antisense protein of HTLV-2 (APH-2) in HTLV-2 infection is poorly understood. In previous studies, we identified the endosomal sorting complex required for transport 0 (ESCRT-0) subunit HRS as a novel interaction partner of APH-2 but not HBZ. HRS is a master regulator of endosomal protein sorting for lysosomal degradation and is hijacked by many viruses to promote replication. However, no studies to date have shown a link between HTLVs and HRS. In this study, we sought to characterize the interaction between HRS and APH-2 and to investigate the impact of HRS on the life cycle of HTLV-2. We confirmed a direct specific interaction between APH-2 and HRS and showed that the CC2 domain of HRS and the N-terminal domain of APH-2 mediate their interaction. We demonstrated that HRS recruits APH-2 to early endosomes, possibly furnishing an entry route into the endosomal/lysosomal pathway. We demonstrated that inhibition of this pathway using either bafilomycin or HRS overexpression substantially extends the half-life of APH-2 and stabilizes Tax2B expression levels. We found that HRS enhances Tax2B-mediated long terminal repeat (LTR) activation, while depletion of HRS enhances HTLV-2 production and release, indicating that HRS may have a negative impact on HTLV-2 replication. Overall, our study provides important new insights into the role of the ESCRT-0 HRS protein, and by extension the ESCRT machinery and the endosomal/lysosomal pathway, in HTLV-2 infection.IMPORTANCE While APH-2 is the only viral protein consistently expressed in infected carriers, its role in HTLV-2 infection is poorly understood. In this study, we characterized the interaction between the ESCRT-0 component HRS and APH-2 and explored the role of HRS in HTLV-2 replication. HRS is a master regulator of protein sorting for lysosomal degradation, a feature that is manipulated by several viruses to promote replication. Unexpectedly, we found that HRS targets APH-2 and possibly Tax2B for lysosomal degradation and has an overall negative impact on HTLV-2 replication and release. The negative impact of interactions between HTLV-2 regulatory proteins and HRS, and by extension the ESCRT machinery, may represent an important strategy used by HTLV-2 to limit virus production and to promote persistence, features that may contribute to the limited pathogenic potential of this infection.

Transient increment of HTLV-2 proviral load in HIV-1-co-infected patients during treatment intensification with raltegravir.

BACKGROUND: Numerous studies have analyzed the effects of raltegravir intensification on HIV-1 viral replication in infected individuals receiving suppressive combined antiretroviral treatment (cART). Nevertheless, there are only two studies on the effect of raltegravir in HTLV-1 infection, and none in HTLV-2. OBJECTIVE: To study the effect of raltegravir on HTLV-2 infection in HIV-1-co-infected individuals. STUDY DESIGN: This retrospective longitudinal study included four HTLV-2-HIV-1-co-infected individuals who received raltegravir-based cART during 48 weeks and 11 HTLV-2-HIV-1-co-infected individuals under cART without raltegravir during 48 weeks. HTLV-2 proviral load, CD4 and CD8 count and frequency were analyzed. RESULTS: HTLV-2 proviral load significantly increased at week 24 compared to baseline among all the patients who received raltegravir (p=0.003), while no significant increases were found in the control group. No significant variation in either CD8 or CD4 counts was found during the follow up in both groups. CONCLUSIONS: Raltegravir induced a transient increment on total HTLV-2 DNA proviral load in HTLV-2/HIV-1-coinfected individuals on suppressive cART after 24 weeks.

Antiretroviral activity of thiosemicarbazone metal complexes.

Thiosemicarbazones display a wide antimicrobial activity by targeting bacteria, fungi, and viruses. Here, we report our studies on the antiviral activity of two thiosemicarbazone metal complexes, [bis(citronellalthiosemicarbazonato)nickel(II)] and [aqua(pyridoxalthiosemicarbazonato)copper(II)] chloride monohydrate, against the retroviruses HIV-1 and HTLV-1/-2. Both compounds exhibit antiviral properties against HIV but not against HTLVs . In particular, the copper complex shows the most potent anti-HIV activity by acting at the post-entry steps of the viral cycle.

In vitro photochemical inactivation of cell-associated human T-cell leukemia virus Type I and II in human platelet concentrates and plasma by use of amotosalen.

BACKGROUND: Human T-cell leukemia virus Types I and II (HTLV-I and HTLV-II), blood-borne retroviruses found worldwide, can cause leukemia, immunosuppression, and severe neurologic diseases. In most countries, HTLV-I and -II screening is not performed systematically for blood donations. A new photochemical treatment (PCT) with a synthetic psoralen was developed to inactivate most pathogens in platelet (PLT) concentrates or plasma and to improve the safety of blood donations. STUDY DESIGN AND METHODS: Cell-associated HTLV-I or -II (10(6)/mL) was inoculated in full-size fresh PLT concentrates or fresh frozen plasma and treated with 150 micromol per L amotosalen (S-59) and different doses of long-wavelength ultraviolet A (UVA) light. The residual viral titer in the treated samples was assessed by a cocultivation assay on indicator cells. RESULTS: The inactivation obtained at a 3.0 J per cm2 UVA dose was greater than 5.2 log foci-forming units (FFUs) per mL for HTLV-I and 4.6 log FFUs per mL for HTLV-II in presence of human PLT concentrates and greater than 4.5 log FFUs per mL for HTLV-I and 5.7 log FFUs per mL for HTLV-II in the presence of human plasma. The residual infectivity was very low and shown as the limit of detection of the cocultivation assay. CONCLUSION: In human plasma or PLT concentrates, the retroviruses HTLV-I and -II were strongly sensitive to the PCT with 150 micromol per L amotosalen (S-59) and a 3.0 J per cm2 UVA dose. This high efficiency for photoinactivation of these retroviruses opens a possibility of improving the safety of PLTs or plasma transfusion in the future.

In vivo and in vitro treatment of HTLV-1 and HTLV-2 infected cells with arsenic trioxide and interferon-alpha.

Adult T-cell leukemia/lymphoma (ATLL) is a malignant lymphoproliferation of mature activated T-cells, mostly CD4, which develops after a long period of latency following Human T cell Lymphotropic virus Type 1 infection. It is characterized by the clonal integration of one or more HTLV-1 proviruses in the tumor cells. There are 4 major subtypes of ATLL: a smoldering type, a chronic type, a lymphoma type and a leukemic/acute type. The survival rate of ATLL patients, especially those who develop the acute leukemic or lymphomas forms, is very poor and such a tumor remains one of the most severe lymphoproliferations. Treatment of ATLL patients using conventional chemotherapy has very limited benefit, since HTLV-1 transformed cells are resistant to most apoptosis-inducing agents. Recently, antiretroviral therapy using the combination of zidovudine (AZT) and interferon alpha (IFN-alpha) has been shown to induce a high complete remission rate and to prolong the survival of ATLL patients. Based on the current physiopathology, other drugs such as arsenic trioxide combined to IFN-alpha have also been demonstrated to synergize in vitro for inducing apoptosis in HTLV-1 infected T cells. Such drugs have now been used in vivo for treating ATLL patients. Both in vitro and in vivo data will be discussed.

Infection and cellular activation by human T-cell leukemia viruses, types I and II.

Resting peripheral blood mononuclear cells (PBMC) or purified T-cells can be induced to proliferate when cocultured in vitro with fixed HTLV-infected T-cells. This process of HTLV-dependent cellular activation and induction of proliferation has been considered distinctive because of an apparent independence from conventional T-cell costimulatory signals. We have examined several HTLV-infected cell lines and found that proliferation was readily induced in resting PBMC by T-cells that were productively-infected with HTLV. However, equivalent HTLV-productive infection in a B-cell line failed to induce proliferation in PBMC, suggesting that HTLV-dependent induction of proliferation in PBMC was, at least in part, dependent upon a T-cell-specific signal. Furthermore, the induction of proliferation in PBMC populations was found to overlap with, and actually require, transfer and establishment of HTLV infection within the T-cell compartment of the PBMC population. These findings suggest that virus-induced activation of target cells may be directly associated with transfer and spread of HTLV infection.

Fuchsin acid selectively inhibits human immunodeficiency virus (HIV) replication in vitro.

Fuchsin acid, an anionic dye, is a selective inhibitor of human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) in vitro. Its 50% effective dose for inhibition of HIV-1-induced cytopathogenicity in MT-4 cells and HIV-1 antigen expression in HUT-78 cells is 42 and 16 microM, respectively. These values are comparable to those of suramin, the first compound shown to be a selective inhibitor of HIV-1. However, fuchsin acid is less cytotoxic than suramin. The selectivity index of fuchsin acid, based on the ratio of the 50% cytotoxic dose to the 50% effective dose, is greater than 74 in MT-4 cells and greater than 39 in HUT-78 cells. Fuchsin acid is a much weaker inhibitor of HIV-1 reverse transcriptase than are suramin and aurintricarboxylic acid. Fuchsin acid does not interfere with the adsorption of HIV-1 particles to MT-4 cells even at concentrations that completely block HIV-1 replication in MT-4 cells. The mechanism of action of fuchsin acid remains subject of further study.