The Thrombopoietin Receptor Agonist Eltrombopag Inhibits Human Cytomegalovirus Replication Via Iron Chelation.

The thrombopoietin receptor agonist eltrombopag was successfully used against human cytomegalovirus (HCMV)-associated thrombocytopenia refractory to immunomodulatory and antiviral drugs. These effects were ascribed to the effects of eltrombopag on megakaryocytes. Here, we tested whether eltrombopag may also exert direct antiviral effects. Therapeutic eltrombopag concentrations inhibited HCMV replication in human fibroblasts and adult mesenchymal stem cells infected with six different virus strains and drug-resistant clinical isolates. Eltrombopag also synergistically increased the anti-HCMV activity of the mainstay drug ganciclovir. Time-of-addition experiments suggested that eltrombopag interfered with HCMV replication after virus entry. Eltrombopag was effective in thrombopoietin receptor-negative cells, and the addition of Fe3+ prevented the anti-HCMV effects, indicating that it inhibits HCMV replication via iron chelation. This may be of particular interest for the treatment of cytopenias after hematopoietic stem cell transplantation, as HCMV reactivation is a major reason for transplantation failure. Since therapeutic eltrombopag concentrations are effective against drug-resistant viruses, and synergistically increase the effects of ganciclovir, eltrombopag is also a drug-repurposing candidate for the treatment of therapy-refractory HCMV disease.

Role of human cytomegalovirus genotype polymorphisms in AIDS patients with cytomegalovirus retinitis.

Although several host factors have been identified to influence the course of HCMV infection, it still remains unclear why in AIDS patients without highly active antiretroviral therapy human cytomegalovirus (HCMV) retinitis is one of the most common opportunistic infections, whereas in other immunosuppressed individuals it has a low incidence. It was suggested that HCMV glycoprotein B strains may be suitable as marker for virulence and HCMV retinitis. Moreover, UL144 ORF, a member of the TNF-α receptor superfamily, may play a crucial role in innate defences and adaptive immune response of HCMV infection. Furthermore, sequence analyses of HCMV genes UL128, UL130, and UL131A as major determinants of virus entry and replication in epithelial and other cell types were performed. To evaluate the association of sequence variability of depicted viral genes with HCMV retinitis and in vitro growth properties in retinal pigment epithelial cells (RPE) and human foreskin fibroblasts (HFF), we compared 14 HCMV isolates obtained from vitreous fluid and urine of AIDS patients with clinically proven HCMV retinitis. Isolates were analyzed by PCR cycle sequencing and phylogenetic analysis. In addition, sequences of HCMV strains AF1, U8, U11, VR1814, and its cell culture adapted derivates were included. Sequence analysis of gB yielded three genetic subtypes (gB type 1 (5 isolates), gB type 2 (12 isolates), and gB type 3 (5 Isolates)), whereas sequence analysis of UL144 showed a greater diversity (7 isolates type 1A, 2 isolates type 1C, 7 isolates type 2, and 3 isolates type 3). In contrast, the UL128, UL130, and UL131A genes of all low-passage isolates were highly conserved and showed no preferential clustering. Moreover, in HFF and RPE cells, all of our HCMV isolates replicated efficiently independently of their genetic subtype. In conclusion, beside a possible link between the gB subtype 2 and HCMV retinitis, our study found no direct evidence for a connection between UL144/UL128/UL130/UL131A genotypes and the incidence of HCMV retinitis in AIDS patients.

The human eye (retina): a site of persistent HCMV infection?

BACKGROUND: Human cytomegalovirus (HCMV) retinitis frequently occurs in severely naturally and iatrogenically immunocompromised patients. It has been shown that the immune-privileged retina is a major site of HCMV infection in AIDS patients. It is conceivable either that during the immunosuppression HCMV infection reactivates in various other organs viremically affecting the retina or that HCMV persisting in the retina may locally reactivate and result in HCMV retinitis. METHODS: As there is still controversy about the sites of HCMV latency and persistence we investigated 75 eyes of HIV-seronegative patients undergoing enucleation due to a variety of malignant and non-viral benign ophthalmic disorders for the retinal presence of HCMV antigen and DNA. RESULTS: None of the analyzed patients had symptoms of HCMV retinitis. Immunohistologic staining as well as Taq Man DNA PCR analysis showed all samples to be free of HCMV. CONCLUSIONS: Our data suggest that the human eye is rather unlikely to be a site of productive or latent HCMV persistence.

Impact of persistent cytomegalovirus infection on human neuroblastoma cell gene expression.

In a model of human neuroblastoma (NB) cell lines persistently infected with human cytomegalovirus (HCMV) we previously showed that persistent HCMV infection is associated with an increased malignant phenotype, enhanced drug resistance, and invasive properties. To gain insights into the mechanisms of increased malignancy we analyzed the global changes in cellular gene expression induced by persistent HCMV infection of human neuroblastoma cells by use of high-density oligonucleotide microarrays (HG-U133A, Affymetrix) and RT-PCR. Comparing the gene expression of different NB cell lines with persistently infected cell sub-lines revealed 11 host cell genes regulated in a similar manner throughout all infected samples. Nine of these 11 genes may contribute to the previously observed changes in malignant phenotype of persistently HCMV infected NB cells by influencing invasive growth, apoptosis, angiogenesis, and proliferation. Thus, this work provides the basis for further functional studies.

Effects of S-acetylglutathione in cell and animal model of herpes simplex virus type 1 infection.

Intracellular glutathione (GSH) plays an important regulatory role in the host response to viral infections. Replenishment of intracellular GSH is a desirable yet challenging goal, since systemic GSH supplementation is rather inefficient due to a short half-life of GSH in blood plasma. Further, GSH is not taken up by cells directly, but needs to be broken down into amino acids and resynthesized to GSH intracellularly, this process often being impaired during viral infections. These obstacles may be overcome by a novel glutathione derivative S-acetylglutathione (S-GSH), which is more stable in plasma and taken up directly by cells with subsequent conversion to GSH. In the present study, in vitro effects of supplementation with S-GSH or GSH on intracellular GSH levels, cell survival and replication of human herpes simplex virus type 1 (HSV-1) were studied in human foreskin fibroblasts. In addition, in vivo effects of supplementation with S-GSH or GSH on HSV-1-induced mortality were studied in hr/hr mice. In cell culture, viral infection resulted in a significant decrease of intracellular GSH levels. S-GSH efficiently and dose-dependently (5 and 10 mM tested) restored intracellular GSH, and this replenishment was more efficient than with GSH supplementation. In mice, S-GSH, but not GSH, significantly decreased HSV-1-induced mortality ( P<0.05). The data suggest that S-GSH is a suitable antiviral agent against HSV-1 both in vitro and in vivo, indicating that this drug may be of benefit in the adjunctive therapy of HSV-1 infections.

Oncomodulatory signals by regulatory proteins encoded by human cytomegalovirus: a novel role for viral infection in tumor progression.

A high frequency of human cytomegalovirus (HCMV) genome and antigens in tumor samples of patients with different malignancies is now well documented, although the causative role for HCMV in the development of the neoplasias remains to be established. HCMV infection can modulate multiple cellular regulatory and signalling pathways in a manner similar to that of oncoproteins of small DNA tumor viruses such as human papilloma virus or adenoviruses. However, in contrast to these DNA tumor viruses, HCMV infection fails to transform susceptible normal human cells. There is now growing evidence that tumor cells with disrupted regulatory and signalling pathways enable HCMV to modulate their properties including stimulation of cell proliferation, survival, invasion, production of angiogenic factors, and immunogenic properties. In contrast to previously suggested "hit and run" transformation we suggest that persistence in tumor cells is essential for HCMV to fully express its oncomodulatory effects. These effects are observed particularly in persistent HCMV infection and are mediated mainly by activity of HCMV regulatory proteins. In persistently HCMV-infected tumor cell lines - a selection of novel, slowly growing virus variants with changes in coding sequences for virus regulatory proteins takes place. As a result, oncomodulatory effects of HCMV infection may lead to a shift to more malignant phenotype of tumor cells contributing to tumor progression.

Thrombin stimulates IL-6 and IL-8 expression in cytomegalovirus-infected human retinal pigment epithelial cells.

Recently, we reported that thrombin specifically stimulates protease-activated receptor-1 (PAR-1) signaling in RPE entailing inhibition of Sp1 dependent HCMV replication. We now studied whether thrombin modulates the expression of the proinflammatory cytokine/chemokines IL-6 and IL-8 in mock- and cytomegalovirus-infected human retinal pigment epithelial cells (RPE). Our data show that thrombin/PAR-1 stimulates IL-6 and IL-8 gene transcription and protein secretion in both mock- and HCMV-infected RPE. Thrombin/PAR-1-mediated signaling stimulated PKC and NF-kappaB-dependent IL-6 and IL-8 gene expression via phosphoinositide 3-kinase and further downstream via p42/44 and p38 MAPKs. Thus, thrombin/PAR-1-mediated IL-6/IL-8 gene expression is uncoupled from Sp1 inhibition and may support proinflammatory pathomechanisms probably involved in hemorrhage/HCMV retinitis progression.

Thrombin induces Sp1-mediated antiviral effects in cytomegalovirus-infected human retinal pigment epithelial cells.

Human cytomegalovirus (HCMV) retinitis causing retinal detachment and destruction of the blood-retina barrier is closely related to retinal hemorrhage/coagulation. However, the effects of procoagulants on HCMV (re)activation in retinal cells have not been investigated yet. Therefore, we studied whether thrombin modulates the expression of HCMV immediate early (IE) and late (L) genes in cultured human retinal pigment epithelial cells (RPE). Thrombin specifically stimulated the protease-activated receptor-1 (PAR-1) on RPE and, surprisingly, inhibited basal and 12,0-tetradecanoylphorbol 13-acetate-stimulated HCMV IE gene expression in infected RPE. On the other hand, HCMV strongly induced Sp1 DNA binding activity, which was prevented by thrombin/PAR1-mediated Sp1 hyperphosphorylation. Our data suggest that thrombin/PAR-1 may inhibit Sp1-dependent HCMV replication, which might be an important regulatory mechanism for HCMV persistence and replication in RPE.

Multimutated herpes simplex virus g207 is a potent inhibitor of angiogenesis.

The mode of the antitumoral activity of multimutated oncolytic herpes simplex virus type 1 G207 has not been fully elucidated yet. Because the antitumoral activity of many drugs involves the inhibition of tumor blood vessel formation, we determined if G207 had an influence on angiogenesis. Monolayers of human umbilical vein endothelial cells and human dermal microvascular endothelial cells, but not human dermal fibroblasts, bronchial epithelial cells, and retinal glial cells, were highly sensitive to the replicative and cytotoxic effects of G207. Moreover, G207 infection caused the destruction of endothelial cell tubes in vitro. In the in vivo Matrigel plug assay in mice, G207 suppressed the formation of perfused vessels. Intratumoral treatment of established human rhabdomyosarcoma xenografts with G207 led to the destruction of tumor vessels and tumor regression. Ultrastructural investigations revealed the presence of viral particles in both tumor and endothelial cells of G207-treated xenografts, but not in adjacent normal tissues. These findings show that G207 may suppress tumor growth, in part, due to inhibition of angiogenesis.

Potent oncolytic activity of multimutated herpes simplex virus G207 in combination with vincristine against human rhabdomyosarcoma.

Replication restricted oncolytic viruses such as multimutated herpes simplex virus type 1 (HSV-1) G207 represent a novel and attractive approach for cancer therapy, including pediatric solid tumors. Rhabdomyosarcoma is the most common soft-tissue sarcoma of childhood and is often diagnosed already as an advanced disseminated disease. Despite aggressive therapeutic approaches, the prognosis for patients with metastatic rhabdomyosarcoma remains grim. Therefore, there is a need for novel effective drugs with superior safety and efficacy profile. In this study, we showed marked in vitro activity of HSV-1 G207 against embryonal and alveolar rhabdomyosarcoma cells. All human embryonal (KF-RMS-1, RD, and CCA) and alveolar RMS (KFR, Rh28, Rh30, and Rh41) cell lines were highly sensitive to cytotoxic and replicative effects of G207 even at a multiplicity of infection of 0.01, except embryonal Rh1 rhabdomyosarcoma cells, which were efficiently killed only upon multiplicity of infection of 1.0. i.v. G207 treatment of xenotransplanted KFR and KF-RMS-1 tumors in mice led to significant tumor growth inhibition of both tumor entities, whereas intraneoplastic G207 treatment additionally resulted in complete tumor disappearance in 25% of animals. No difference has been found between alveolar and embryonal types of rhabdomyosarcoma. Combination treatment of both cell lines with G207 and vincristine led to strongly enhanced in vitro cytotoxicity without affecting infection efficiency and replication of G207 in KFR as well as in KF-RMS-1 cells. In vivo combination treatment using i.v. G207 and vincristine resulted in complete regression of alveolar rhabdomyosarcoma in five of eight animals and significant growth inhibition of embryonal rhabdomyosarcoma. Taking into consideration the proven safety of G207 in humans, we suggest that G207 alone and in combination with vincristine should be additionally evaluated as a potential agent against human rhabdomyosarcoma.

Development of resistance to vincristine and doxorubicin in neuroblastoma alters malignant properties and induces additional karyotype changes: a preclinical model.

Cytotoxic drug treatment of neuroblastoma often leads to the development of drug resistance and may be associated with increased malignancy. To study the effects of long-term cytotoxic treatment on malignant properties of tumor cells, we established 2 neuroblastoma cell sublines resistant to vincristine (VCR) and doxorubicin (DOX). Both established cell lines (UKF-NB-2(r)VCR(20) and UKF-NB-2(r)DOX(100)) were highly resistant to VCR, DOX and vice-versa but retained their sensitivity to cisplatin. UKF-NB-2(r)VCR(20) and UKF-NB-2(r)DOX(100) expressed significant amounts of P-glycoprotein, while parental cells were P-glycoprotein negative. GD2 expression was upregulated, whereas NCAM expression was decreased in both resistant cells. Spectral karyotype (SKY) analysis revealed complex aberrant karyotypes in all cell lines and additional acquired karyotype changes in both resistant cells. All cell lines harbored high levels of N-myc amplification. Compared to parental cells, UKF-NB-2(r)VCR(20) and UKF-NB-2(r)DOX(100) exhibited more than 2-fold increase in clonal growth in vitro, accelerated adhesion and transendothelial penetration and higher tumorigenicity in vivo. We conclude that development of drug resistance and acquisition of certain karyotypic alterations is associated with an increase of additional malignant properties that may contribute to the poor prognosis in advanced forms of NB. The 2 novel neuroblastoma cell sublines also provide useful models for the study of drug resistance in aggressive forms of neuroblastoma.

In vitro antiviral activity of aphidicolin and its derivates. Synergistic effects of aphidicolin with other antiviral drugs.

Twenty derivatives of aphidicolin were tested against HSV (herpes simplex virus), HCMV (human cytomegalovirus) and adenovirus in vitro. In addition, the antiviral activity of aphidicolin (CAS 38966-21-1) in combination with aciclovir (CAS 59277-89-3) or cidofovir (CAS 113852-37-2) against HSV was determined. The antiviral effects were evaluated using plaque reduction assay in Vero cells or human Foreskin Fibroblasts (HFF) for HSV and HCMV, respectively. Combination indexes were calculated using the method of Chou and Talalay. Two derivatives (K14254 and K14266) that are considered to be prodrugs of aphidicolin were shown to inhibit HCMV and HSV replication comparably to aphidicolin. None of the tested substances inhibited adenovirus replication. Aphidicolin acted synergistically with aciclovir in a 1:1 molar ratio and with cidofovir in different ratios. Aphidicolin and its two antiviral active derivatives might represent useful additional tools for antiviral therapy of HSV and HCMV infections, especially in combination with clinically used drugs.

Induction of differentiation and suppression of malignant phenotype of human neuroblastoma BE(2)-C cells by valproic acid: enhancement by combination with interferon-alpha.

Valproic acid (VPA) has been shown to induce growth-arrest and differentiation of human neuroectodermal tumors similarly to several other fatty acids. In the present study, we show that continuous VPA treatment together with Interferon-alpha (INF-alpha) synergistically inhibited cell growth of a well-established model of neuroblastoma (NB) differentiation using the human N-myc amplified cell line BE(2)-C. Suppression of tumor growth was accompanied by morphological features of neuronal differentiation and inhibition of histone deacetylase activity. Furthermore, induction of differentiation was concomitant with altered expression of genes related to malignant phenotype such as down-regulation of N-myc, induction of bcl-2 and neural cell adhesion molecule. Production of inhibitors of angiogenesis like thrombospondin-1 and activin A was up-regulated in differentiated NB cells. Treatment with VPA alone decreased the ability of BE(2)-C cells to adhere to and penetrate human endothelium. All these effects of VPA were significantly enhanced when combined with INF-alpha which on its own had little or no effect. These results suggest that combination of VPA and INF-alpha may provide a novel therapeutic strategy for NB due to enhanced inhibition of tumor cell growth, induction of tumor differentiation and suppression of malignant biology by reduced angiogenic and decreased metastatic potentials.

Expression level of neural cell adhesion molecule (NCAM) inversely correlates with the ability of neuroblastoma cells to adhere to endothelium in vitro.

The precise function of cell adhesion molecules in the hematogenous phase of neuroblastoma metastasis is poorly understood. The aim of this study was to investigate whether neural cell adhesion molecule (NCAM) modulates neuroblastoma cell (NB) adhesion and transendothelial penetration in a coculture model. Our data, assessed on 11 NB cell lines, demonstrate an inverse correlation between NCAM expression and NB cell adhesion. Transfection of the NB cell line UKF-NB-4 with a cDNA encoding the human NCAM-140 kD isoform enhanced NCAM expression and the amount of tumor cell aggregates, reduced the amount of single tumor cells, and diminished initial NB cell adhesion to an endothelial cell monolayer. Treatment of UKF-NB-4 with NCAM antisense oligonucleotides reduced NCAM surface level, increased the number of single tumor cells, and induced up-regulation of NB cell adhesion to endothelium. Modulation of NCAM expression had no effect on transendothelial penetration. Fluorescence analysis revealed a down-regulation of NCAM in single tumor cells, prior to NB adhesion. The data support the view that low levels of NCAM are necessary for NB cells to leave a tumor cell aggregate and adhere to endothelial cells.