Novel SARS-CoV-2 variants induce higher toxicity in cardiovascular cells

Objective

SARS-CoV-2 causes the coronavirus disease 2019 (COVID-19) and has spawned a global health crisis. Virus infection can lead to elevated markers of cardiac injury and inflammation associated with a higher risk of mortality. However, it is so far unclear whether cardiovascular damage is caused by direct virus infection or is mainly secondary due to inflammation. Recently, additional novel SARS-CoV-2 variants have emerged accounting for more than 70% of all cases in Germany. To what extend these variants differ from the original strain in their pathology remains to be elucidated.

Here, we investigated the effect of the novel SARS-CoV-2 variants on cardiovascular cells.

Results

To study whether cardiovascular cells are permissive for SARS-CoV-2, we inoculated human iPS-derived cardiomyocytes and endothelial cells from five different origins, including umbilical vein endothelial cells, coronary artery endothelial cells (HCAEC), cardiac and lung microvascular endothelial cells, or pulmonary arterial cells, in vitro with SARS-CoV-2 isolates (G614 (original strain), B.1.1.7 (British variant), B.1.351 (South African variant) and P.1 (Brazilian variant)).

While the original virus strain infected iPS-cardiomyocytes and induced cell toxicity 96h post infection (290±10 cells vs. 130±10 cells; p=0.00045), preliminary data suggest a more severe infection by the novel variants. To what extend the response to the novel variants differ from the original strain is currently investigated by phosphoproteom analysis.

Of the five endothelial cells studied, only human coronary artery EC took up the original virus strain, without showing viral replication and cell toxicity. Spike protein was only detected in the perinuclear region and was co-localized with calnexin-positive endosomes, which was accompanied by elevated ER-stress marker genes, such as EDEM1 (1.5±0.2-fold change; p=0.04). Infection with the novel SARS-CoV-2 variants resulted in significant higher levels of viral spike compared to the current strain. Surprisingly, viral up-take was also seen in other endothelial cell types (e.g. HUVEC). Although no viral replication was observed (850±158 viral RNA copies at day 0 vs. 197±43 viral RNA copies at day 3; p=0.01), the British SARS-CoV-2 variant B.1.1.7 reduced endothelial cell numbers (0.63±0.03-fold change; p=0.0001).

Conclusion

Endothelial cells and cardiomyocytes showed a distinct response to SARS-CoV-2. Whereas cardiomyocytes were permissively infected, endothelial cells took up the virus, but were resistant to viral replication. However, both cell types showed signs of increased toxicity induced by the British SARS-CoV-2 variant. These data suggest that cardiac complications observed in COVID-19 patients might at least in part be based on direct infection of cardiovascular cells. The more severe cytotoxic effects of the novel variants implicate that patients infected with the new variants should be even more closely monitored.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): DFG and Willy-Pitzer Foundation

Detection and infectivity of SARS-CoV-2 in exhumated corpses

Postmortem detection of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) after the exhumation of a corpse can become important, e.g. in the case of subsequent medical malpractice allegations. To date, data on possible detection periods [e.g. by reverse transcription polymerase chain reaction (RT-PCR)] or on the potential infectivity of the virus after an exhumation are rare. In the present study, these parameters were examined in two cases with a time span of approximately 4 months between day of death and exhumation. Using SARS-CoV-2 RT-PCR on swabs of both lungs and the oropharynx detection was possible with cycle threshold (C_t) values of about 30 despite signs of beginning decay. RT-PCR testing of perioral and perinasal swabs and swabs collected from the inside of the body bag, taken to estimate the risk of infection of those involved in the exhumation, was negative. Cell culture-based infectivity testing was negative for both, lung and oropharyngeal swabs. In one case, RT-PCR testing at the day of death of an oropharyngeal swab showed almost identical C_t values as postmortem testing of an oropharyngeal swab, impressively demonstrating the stability of viral RNA in the intact corpse. However, favorable climatic conditions in the grave have to be taken into account, as it was wintertime with constant low temperatures. Nevertheless, it was possible to demonstrate successful postmortem detection of SARS-CoV-2 infection following exhumation even after months in an earth grave.

Infectivity of deceased COVID-19 patients

The duration of infectivity of SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) in living patients has been demarcated. In contrast, a possible SARS-CoV-2 infectivity of corpses and subsequently its duration under post mortem circumstances remain to be elucidated. The aim of this study was to investigate the infectivity and its duration of deceased COVID-19 (coronavirus disease) patients. Four SARS-CoV-2 infected deceased patients were subjected to medicolegal autopsy. Post mortem intervals (PMI) of 1, 4, 9 and 17 days, respectively, were documented. During autopsy, swabs and organ samples were taken and examined by RT-qPCR (real-time reverse transcription-polymerase chain reaction) for the detection of SARS-CoV-2 ribonucleic acid (RNA). Determination of infectivity was performed by means of virus isolation in cell culture. In two cases, virus isolation was successful for swabs and tissue samples of the respiratory tract (PMI 4 and 17 days). The two infectious cases showed a shorter duration of COVID-19 until death than the two non-infectious cases (2 and 11 days, respectively, compared to > 19 days), which correlates with studies of living patients, in which infectivity could be narrowed to about 6 days before to 12 days after symptom onset. Most notably, infectivity was still present in one of the COVID-19 corpses after a post-mortem interval of 17 days and despite already visible signs of decomposition. To prevent SARS-CoV-2 infections in all professional groups involved in the handling and examination of COVID-19 corpses, adequate personal safety standards (reducing or avoiding aerosol formation and wearing FFP3 [filtering face piece class 3] masks) have to be enforced for routine procedures.

Human Immunodeficiency Virus Resistance to AZT in MOLT4/8 Cells is Associated with a Lack of AZT Phosphorylation and is Bypassed by AZT-Monophosphate SATE Prodrugs

Human T lymphoid MOLT4/8 cells were grown continuously for more than 2 years in a medium containing 3′-azido-2′,3′-dideoxythymidine (zidovudine; AZT) at a concentration of 250 μM. These cells, designated MOLT-4/8rAZT250, were used to test the cytotoxic and antiviral activity of AZT. Intracellular accumulation of AZT, expression of the multidrug resistance 1 (MDR-1) gene, thymidine kinase (TK) gene and activity of the TK enzyme in cellular extracts were measured. The results showed that both the cytotoxic and antiviral activity of AZT were significantly lower in MOLT4/8rAZT250 than in MOLT4/8 cells; concentrations required to inhibit 50% production of the p24 human immunodeficiency virus type 1 (HIV-1) antigen of two laboratory strains were at least 100-fold higher in resistant cells. The MDR-1 gene was not expressed in the resistant cells. TK mRNA expression was significantly lower in the resistant than in the sensitive cells. TK enzymatic activity for deoxythymidine phosphorylation was impaired in MOLT4/8rAZT250 cells compared to the sensitive cells. AZT was phosphorylated only in the sensitive cells whereas no phosphorylation of AZT was found in the resistant cells. We tested whether several AZT-monophosphate triesters, which bypass cellular TK, could overcome resistance to the cytotoxic and antiviral activity of AZT. The bis( t-butylSATE) phosphotriester derivative of AZT showed comparable cytotoxic and antiviral activity in sensitive and resistant cells. The results demonstrated that MOLT4/8rAZT250 cells exert resistance to the anti-HIV activity of the drug mainly owing to the lack of AZT phosphorylation and that resistance may be bypassed by using AZT-monophosphate SATE prodrugs.

Correlation from undiluted vitreous cytokines of untreated central retinal vein occlusion with spectral domain optical coherence tomography

PURPOSE

To correlate inflammatory and proangiogenic key cytokines from undiluted vitreous of treatment-naïve central retinal vein occlusion (CRVO) patients with SD-OCT parameters.

METHODS

Thirty-five patients (age 71.1 years, 24 phakic, 30 nonischemic) underwent intravitreal combination therapy, including a single-site 23-gauge core vitrectomy. Twenty-eight samples from patients with idiopathic, non-uveitis floaterectomy served as controls. Interleukin 6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), and vascular endothelial growth factor (VEGF-A) levels were correlated with the visual acuity (logMar), category of CRVO (ischemic or nonischemic) and morphologic parameters, such as central macular thickness-CMT, thickness of neurosensory retina-TNeuro, extent of serous retinal detachment-SRT and disintegrity of the IS/OS and others.

RESULTS

The mean IL-6 was 64.7pg/ml (SD ± 115.8), MCP-1 1015.7 ( ± 970.1), and VEGF-A 278.4 ( ± 512.8), which was significantly higher than the control IL-6 6.2 ± 3.4pg/ml (P=0.06), MCP-1 253.2 ± 73.5 (P<0.0000001) and VEGF-A 7.0 ± 4.9 (P<0.0006). All cytokines correlated highly with one another (correlation coefficient r=0.82 for IL-6 and MCP-1; r=0.68 for Il-6 and VEGF-A; r=0.64 for MCP-1 and VEGF-A). IL-6 correlated significantly with CMT, TRT, SRT, dIS/OS, and dELM. MCP-1 correlated significantly with SRT, dIS/OS, and dELM. VEGF-A correlated not with changes in SD-OCT, while it had a trend to be higher in the ischemic versus the nonischemic CRVO group (P=0.09).

CONCLUSIONS

The inflammatory cytokines were more often correlated with morphologic changes assessed by SD-OCT, whereas VEGF-A did not correlate with CRVO-associated changes in SD-OCT. VEGF inhibition alone may not be sufficient in decreasing the inflammatory response in CRVO therapy.

Human neuroblastoma cells with acquired resistance to the p53 activator RITA retain functional p53 and sensitivity to other p53 activating agents

Adaptation of wild-type p53 expressing UKF-NB-3 cancer cells to the murine double minute 2 inhibitor nutlin-3 causes de novo p53 mutations at high frequency (13/20) and multi-drug resistance. Here, we show that the same cells respond very differently when adapted to RITA, a drug that, like nutlin-3, also disrupts the p53/Mdm2 interaction. All of the 11 UKF-NB-3 sub-lines adapted to RITA that we established retained functional wild-type p53 although RITA induced a substantial p53 response. Moreover, all RITA-adapted cell lines remained sensitive to nutlin-3, whereas only five out of 10 nutlin-3-adapted cell lines retained their sensitivity to RITA. In addition, repeated adaptation of the RITA-adapted sub-line UKF-NB-3^rRITA^10 μM to nutlin-3 resulted in p53 mutations. The RITA-adapted UKF-NB-3 sub-lines displayed no or less pronounced resistance to vincristine, cisplatin, and irradiation than nutlin-3-adapted UKF-NB-3 sub-lines. Furthermore, adaptation to RITA was associated with fewer changes at the expression level of antiapoptotic factors than observed with adaptation to nutlin-3. Transcriptomic analyses indicated the RITA-adapted sub-lines to be more similar at the gene expression level to the parental UKF-NB-3 cells than nutlin-3-adapted UKF-NB-3 sub-lines, which correlates with the observed chemotherapy and irradiation sensitivity phenotypes. In conclusion, RITA-adapted cells retain functional p53, remain sensitive to nutlin-3, and display a less pronounced resistance phenotype than nutlin-3-adapted cells.

Recent publications in medical microbiology and immunology: a retrospective

A look back is done to some clinical and basic research activities recently published in medical microbiology and immunology. The review covers clinical experiences and in vitro experiments to understand the emergency, pathogenicity, epidemic spread, and vaccine-based prevention of avian and swine-origin flu. Some new developments and concepts in diagnosis, (molecular) epidemiology, and therapy of AIDS, viral hepatitis C, and herpesvirus-associated diseases are outlined. Regulation of immune system has been discussed in a special issue 2010 including some aspects of CNS affections (measles). Mycobacterial infection and its prevention by modern recombinant vaccines have reached new interest, as well as new concepts of vaccination and prophylaxis against several other bacteria. Adaptation to host niches enables immune escape (example brucella) and determines virulence (example N. meningitidis). Chlamydia pneumoniae, previously considered to trigger atherosclerosis, is hypothetically associated to Alzheimer disease, while CMV, another putative trigger of atherosclerosis, gains evidence of oncomodulation in CNS tumor diseases. In terms of globalization, exotic virus infections are increasingly imported from southern countries.

Doxorubicin-induced cell death requires cathepsin B in HeLa cells

The cysteine protease cathepsin B acts as a key player in apoptosis. Cathepsin B-mediated cell death is induced by various stimuli such as ischemia, bile acids or TNFα. Whether cathepsin B can be influenced by anticancer drugs, however, has not been studied in detail. Here, we describe the modulation of doxorubicin-induced cell death by silencing of cathepsin B expression. Previously, it was shown that doxorubicin, in contrast to other drugs, selectively regulates expression and activity of cathepsin B. Selective silencing of cathepsin B by siRNA or the cathepsin B specific inhibitor CA074Me modified doxorubicin-mediated cell death in Hela tumor cells. Both Caspase 3 activation and PARP cleavage were significantly reduced in cells lacking cathepsin B. Moreover, mitochondrial membrane permeabilization as well as the release of cytochrome C and AIF from mitochondria into cytosol induced by doxorubicin were significantly diminished in cathepsin B suppressed cells. In addition, doxorubicin associated down-regulation of XIAP was not observed in cathepsin B silenced cells. Lack of cathepsin B significantly modified cell cycle regulatory proteins such as cdk1, Wee1 and p21 without significant changes in G(1), S or G(2)M cell cycle phases maybe indicating further cell cycle independent actions of these proteins. Consequently, cell viability following doxorubicin was significantly elevated in cells with cathepsin B silencing. In summary, our data strongly suggest a role of cathepsin B in doxorubicin-induced cell death. Therefore, increased expression of cathepsin B in various types of cancer can modify susceptibility towards doxorubicin.

Human immunodeficiency virus type-1 group M quasispecies evolution: diversity and divergence in patients co-infected with active tuberculosis

The evolution of intra-host human immunodeficiency virus type 1 (HIV-1) quasispecies prior and after treating active tuberculosis (TB) with chemotherapy in HIV-1/TB patients was assessed. Two time points HIV-1 quasispecies were evaluated by comparing HIV-1-infected patients with active tuberculosis (HIV-1/TB) and HIV-1-infected patients without tuberculosis (HIV-1/non-TB). Plasma samples were obtained from the Frankfurt HIV cohort, and HIV-1 RNA was isolated. C2V5 env was amplified by PCR and molecular cloning was performed. Eight to twenty-five clones were sequenced from each patient. Various phylogenetic analyses were performed. We found a significant increase in diversity and divergence in HIV-1/TB compared to the HIV-1/non-TB. For HIV-1/TB, the average rate of evolution of C2V5 env was higher than previous reports (2.4 × 10(-4) substitution/site/day). Two groups of HIV-1/TB were observed based on the rate of HIV-1 evolution and coreceptor usage: A fast evolving R5-tropic dominating group and a relatively slowly evolving X4 group. The results demonstrated that active TB has an impact on HIV-1 viral diversity and divergence over time. The influence of active TB on longitudinal evolution of HIV-1 may be predominant for R5 viruses.

Determination of serum antibodies against swine-origin influenza A virus H1N1/09 by immunofluorescence, haemagglutination inhibition, and by neutralization tests: how is the prevalence rate of protecting antibodies in humans?

In April 2009, a new variant of influenza A virus, subtype H1N1v emerged in Mexico and spread all over the world producing the H1N1 pandemic in mankind after 1918-1920 and 1978/1979. Obviously there was no herd immunity against this new virus variant. Mainly young people, but less elderly were affected and presented severe and even lethal courses of disease. Since virus-specific antibodies are commonly regarded as markers of partial or complete immunoprotection, we performed antibody determinations in serum samples obtained from people before and after the pandemic has arrived in our region (Frankfurt/M., Germany). The assays were done by indirect immunofluorescence, by neutralization test, and by a haemagglutination inhibition test (HI), which was established in a practical modification for general and easy use. Among 145 individuals, of whom serum specimens had been drawn before the onset of pandemic, 19 revealed humoral immunity, i.e. titres of H1N1v neutralizing antibodies (at least 1:64). Eleven were older than 60 years, one belonged to the age group 40-59 years, three to the age group 20-39 years, and two to the age group 15-19 years. After the onset of pandemic in Frankfurt, serum specimens drawn from n = 225 randomly selected patients of our local university hospital were investigated for antibodies against H1N1v by HI, which is generally recommended for routine check of immunity. Twenty-eight individuals revealed the protecting antibody titre of at least 1:40. The age distribution had moved to mean age groups. The results fit to the incidence of influenza A/H1N1(09) disease, as confirmed by RT-PCR in patients admitted to our hospital, peaking in the younger age groups up to 30 years (second affected group: 30-40 years). While commonly used solid-phase antibody tests (like immunofluorescence) are not suitable to diagnose passed H1N1(09) infection and acquired immunity, this can be easily done by HI. Expecting the next waves of influenza A/H1N1v infections, HI testing may avoid vaccinations under special risk of severe or hidden adverse reactions.

The impact of treatment with tumour necrosis factor-alpha antagonists on the course of chronic viral infections: a review of the literature

Biologics that antagonize the biological activity of tumour necrosis factor (TNF)-alpha, namely infliximab, etanercept and adalimumab, are increasingly used for treatment of immune-mediated inflammatory diseases, including psoriasis, worldwide. TNF-alpha antagonists are known to increase the risk of reactivation and infection, particularly of infections with intracellular bacteria such as Mycobacterium tuberculosis. More frequently these agents are given to patients with viral infections. Viral hepatitis and human immunodeficiency virus infections are often present in these patients, with a considerable geographical variation. Other concomitant viral infections such as herpes, cytomegalovirus and varicella zoster virus may occur much more frequently than tuberculosis or leprosy. General recommendations about the management related to possible problems associated with anti-TNF-alpha treatment and these viral infections are lacking. This short review will give an overview of the most recent data available on the effects of anti-TNF-alpha therapy on viral infections with a particular focus on patient management and screening recommendations.

Inhibition of murine AIDS by pro-glutathione (GSH) molecules

Antioxidant molecules can be used both to replenish the depletion of reduced glutathione (GSH) occurring during HIV infection, and to inhibit HIV replication. The purpose of this work was to assess the efficacy of two pro-GSH molecules able to cross the cell membrane more easily than GSH. We used an experimental animal model consisting of C57BL/6 mice infected with the LP-BM5 viral complex; the treatments were based on the intramuscular administration of I-152, a pro-drug of N-acetylcysteine and S-acetyl-beta-mercaptoethylamine, and S-acetylglutathione, an acetylated GSH derivative. The results show that I-152, at a concentration of 10.7 times lower than GSH, caused a reduction in lymph node and spleen weights of about 55% when compared to infected animals and an inhibition of about 66% in spleen and lymph node virus content. S-acetylglutathione, at half the concentration of GSH, caused a reduction in lymph node weight of about 17% and in spleen and lymph node virus content of about 70% and 30%, respectively. These results show that the administration of pro-GSH molecules may favorably substitute for the use of GSH as such.

Valproic acid inhibits adhesion of vincristine- and cisplatin-resistant neuroblastoma tumour cells to endothelium

Drug resistance to chemotherapy is often associated with increased malignancy in neuroblastoma (NB). In pursuit of alternative treatments for chemoresistant tumour cells, we tested the response of multidrug-resistant SKNSH and of vincristine (VCR)-, doxorubicin (DOX)-, or cisplatin (CDDP)-resistant UKF-NB-2, UKF-NB-3 or UKF-NB-6 NB tumour cell lines to valproic acid (VPA), a differentiation inducer currently in clinical trials. Drug resistance caused elevated NB adhesion (UKF-NB-2(VCR), UKF-NB-2(DOX), UKF-NB-2(CDDP), UKF-NB-3(VCR), UKF-NB-3(CDDP), UKF-NB-6(VCR), UKF-NB-6(CDDP)) to an endothelial cell monolayer, accompanied by downregulation of the adhesion receptor neural cell adhesion molecule (NCAM). Based on the UKF-NB-3 model, N-myc proteins were enhanced in UKF-NB-3(VCR) and UKF-NB-3(CDDP), compared to the drug naïve controls. p73 was diminished, whereas the p73 isoform deltaNp73 was upregulated in UKF-NB-3(VCR) and UKF-NB-3(CDDP). Valproic acid blocked adhesion of UKF-NB-3(VCR) and UKF-NB-3(CDDP), but not of UKF-NB-3(DOX), and induced the upregulation of NCAM surface expression, NCAM protein content and NCAM coding mRNA. Valproic acid diminished N-myc and enhanced p73 protein level, coupled with downregulation of deltaNp73 in UKF-NB-3(VCR) and UKF-NB-3(CDDP). Valproic acid also reverted enhanced adhesion properties of drug-resistant UKF-NB-2, UKF-NB-6 and SKNSH cells, and therefore may provide an alternative approach to the treatment of drug-resistant NB by blocking invasive processes.

Preparation, characterisation and maintenance of drug efficacy of doxorubicin-loaded human serum albumin (HSA) nanoparticles

Human serum albumin (HSA) nanoparticles represent promising drug carrier systems. Binding of cytostatics to HSA nanoparticles may diminish their toxicity, optimise their body distribution and/or may overcome multidrug resistance. In the present study, doxorubicin-loaded HSA nanoparticle preparations were prepared. Doxorubicin was loaded to the HSA nanoparticles either by adsorption to the nanoparticles' surfaces or by incorporation into the particle matrix. Both loading strategies resulted in HSA nanoparticles of a size range between 150nm and 500nm with a loading efficiency of 70-95%. The influence on cell viability of the resulting nanoparticles was investigated in two different neuroblastoma cell lines. The anti-cancer effects of the drug-loaded nanoparticles were increased in comparison to doxorubicin solution. Based on these result a standard protocol for the preparation of doxorubicin-loaded HSA nanoparticles for further antitumoural studies was established.

Pharmacology of intracellular cytosine-arabinoside-5'-triphosphate in malignant cells of pediatric patients with initial or relapsed leukemia and in normal lymphocytes

PURPOSE

The prodrug cytosinearabinoside (ara-C) is widely used in the treatment of acute leukemias. The active drug is the intracellular metabolite cytosine-arabinoside-5'-triphosphate (ara-CTP). The purpose of the present study was to investigate the relation between sensitivity and pharmacokinetic parameters Cmax, t1/2 and AUC of ara-CTP. The obtained results were compared to previous studies.

EXPERIMENTAL DESIGN

Cmax, t1/2 and AUC of ara-CTP were assessed in leukemic cells of 17 pediatric patients with acute lymphoblastic leukemia (ALL) and in 6 lymphoblastic cell lines and compared with normal lymphocytes of 9 healthy donors by high pressure liquid chromatography (HPLC). The sensitivity of the cells against ara-C was determined by the MTT assay.

RESULTS

The intracellular accumulation of ara-CTP was significantly lower in normal lymphocytes (Cmax 47.7-60.9 pmol/10(6) cells) compared to leukemic cell lines (Cmax 11-1128 pmol/10(6) cells) and leukemic cells of our patients (Cmax 85.9-631 pmol/10(6) cells). Similar results were found for the AUC. There was no significant difference between initial and relapsed leukemias in our small cohort. A correlation between sensitivity in terms of IC50 values and the intracellular ara-CTP accumulation was observed in cell lines, but not in leukemic cells and normal lymphocytes from healthy donors.

CONCLUSIONS

Pharmacokinetic parameters varied tremendously in leukemic cells in contrast to normal lymphocytes without a difference in sensitivity. It is worthwhile to compare literature data to assess an optimal dosage of ara-C in pediatric patients.

Will the next human influenza pandemic be caused by the virus of the avian flu A/H5N1? Arguments pro and counter

In 1997, the avian influenza A subtype H5N1 that caused big outbreaks of fowl pest in mass poultry farming had emerged in Hong Kong. Its spread throughout Eurasia had given rise to concerns in terms of the possible imminence of the next human influenza pandemic. In this article, epidemiological and virological arguments supporting or declining this fear are outlined and discussed with regard to viral infectivity and pathogenicity.

Antiviral and immunomodulatory properties of new pro-glutathione (GSH) molecules

Reduced glutathione (GSH) is present in millimolar concentrations in mammalian cells. It is involved in many cellular functions such as detoxification, amino acid transport, production of coenzymes, and the recycling of vitamins E and C. GSH acts as a redox buffer to preserve the reduced intracellular environment. Decreased glutathione levels have been found in numerous diseases such as cancer, viral infections, and immune dysfunctions. Many antioxidant molecules, such as GSH and N-acetylcysteine (NAC), have been demonstrated to inhibit in vitro and in vivo viral replication through different mechanisms of action. Accumulating evidence suggests that intracellular GSH levels in antigen-presenting cells such as macrophages, influence the Th1/Th2 cytokine response pattern, and more precisely, GSH depletion inhibits Th1-associated cytokine production and/or favours Th2 associated responses. It is known that GSH is not transported to most cells and tissues in a free form. Therefore, a number of different approaches have been developed in the last years to circumvent this problem. This review discusses the capacity of some new molecules with potent pro-GSH effects either to exert significant antiviral activity or to augment GSH intracellular content in macrophages to generate and maintain the appropriate Th1/Th2 balance. The observations reported herein show that pro-GSH molecules represent new therapeutic agents to treat antiviral infections and Th2-mediated diseases such as allergic disorders and AIDS.

Efficacy of various disinfectants against SARS coronavirus

The recent severe acute respiratory syndrome (SARS) epidemic in Asia and Northern America led to broad use of various types of disinfectant in order to control the public spread of the highly contagious virus. However, only limited data were available to demonstrate their efficacy against SARS coronavirus (SARS-CoV). We therefore investigated eight disinfectants for their activity against SARS-CoV according to prEN 14476. Four hand rubs were tested at 30s (Sterillium, based on 45% iso-propanol, 30% n-propanol and 0.2% mecetronium etilsulphate; Sterillium Rub, based on 80% ethanol; Sterillium Gel, based on 85% ethanol; Sterillium Virugard, based on 95% ethanol). Three surface disinfectants were investigated at 0.5% for 30 min and 60 min (Mikrobac forte, based on benzalkonium chloride and laurylamine; Kohrsolin FF, based on benzalkonium chloride, glutaraldehyde and didecyldimonium chloride; Dismozon pur, based on magnesium monoperphthalate), and one instrument disinfectant was investigated at 4% for 15 min, 3% for 30 min and 2% for 60 min [Korsolex basic, based on glutaraldehyde and (ethylenedioxy)dimethanol]. Three types of organic load were used: 0.3% albumin, 10% fetal calf serum, and 0.3% albumin with 0.3% sheep erythrocytes. Virus titres were determined by a quantitative test (endpoint titration) in 96-well microtitre plates. With all tested preparations, SARS-CoV was inactivated to below the limit of detection (reduction factor mostly > or =4), regardless of the type of organic load. In summary, SARS-CoV can be inactivated quite easily with many commonly used disinfectants.

Valproic acid induces extracellular signal-regulated kinase 1/2 activation and inhibits apoptosis in endothelial cells

The histone deacetylase (HDAC) inhibitor valproic acid (VPA) was recently shown to inhibit angiogenesis, but displays no toxicity in endothelial cells. Here, we demonstrate that VPA increases extracellular signal-regulated kinase 1/2 (ERK 1/2) phosphorylation in human umbilical vein endothelial cells (HUVEC). The investigation of structurally modified VPA derivatives revealed that the induction of ERK 1/2 phosphorylation is not correlated to HDAC inhibition. PD98059, a pharmacological inhibitor of the mitogen-activated protein kinase kinase 1/2, prevented the VPA-induced ERK 1/2 phosphorylation. In endothelial cells, ERK 1/2 phosphorylation is known to promote cell survival and angiogenesis. Our results showed that VPA-induced ERK 1/2 phosphorylation in turn causes phosphorylation of the antiapoptotic protein Bcl-2 and inhibits serum starvation-induced HUVEC apoptosis and cytochrome c release from the mitochondria. Moreover, the combination of VPA with PD98059 synergistically inhibited angiogenesis in vitro and in vivo.

SARS-coronavirus (SARS-CoV) and the safety of a solvent/detergent (S/D) treated immunoglobulin preparation

SARS-coronavirus (SARS-CoV) is a newly emerged, highly pathogenic agent that caused over 8000 human infections with nearly 800 deaths between November 2002 and September 2003. While direct person-to-person transmission via respiratory droplets accounted for most cases, other modes have not been ruled out. SARS-CoV viraemia does not seem to reach high titres, however, it has to be excluded that virus transmission may occur via blood transfusion or application of therapeutic plasma products, e.g. fresh-frozen plasma or single components derived thereof. Manufacturing processes of all plasma derivatives are required to comprise dedicated virus inactivation/removal steps. Treatment with a mixture of solvent and detergent (SD) has successfully been applied to inactivate the most members of the transfusion-relevant viruses without affecting therapeutic properties of the products. The SD treatment irreversibly disrupts the lipid envelope of viruses such as HIV, HBV, HCV, HGV and CMV. In this study we evaluated the manufacturing process of an immunoglobulin preparation (OCTAGAM, manufactured by Octapharma Pharmazeutika Produktionsges.m.b.H., Vienna, Austria) for its capacity to inactivate the SARS-CoV. Our results demonstrate that SARS-CoV was completely inactivated below the limit of detection. This was found to occur within 1 min of SD treatment.

Characterization of drug-resistant neuroblastoma cell lines by comparative genomic hybridization

Three parental neuroblastoma cell lines and nine derived lines resistant to Vincristin, Doxorubicin and Cisplatin, respectively, using CGH were studied. CGH profiles of all three parental cell lines were obtained using DNA from a healthy volunteer as reference DNA. Labeled DNA from each of the drug resistant daughter cell lines and labeled DNA from their parental sensitive cell lines were hybridized to obtain a comparison of gains and losses that accompanied the development of resistance for that particular drug. All three parental cell lines were characterized by typical findings for high risk neuroblastoma: N-myc amplification, gain of 17q, and loss of 1p36.2-36.3. Acquired drug resistance in the neuroblastoma cell lines appeared to be accompanied by a large array of DNA sequence copy number changes. The regions frequently affected in chemo-resistant cell lines included gains of 13q14.1-32, and 7q11.2-31.3, 4 q. Amplifications were seen at 7q 21.1 consistent with MDR1 amplification in UKF-NB-2 VCR, UKF-NB-3 DOXO, UKF-NB-4 VCR, and UKF-NB-4 DOXO, but not in any Cisplatin resistant line. All Cisplatin and Doxorubicin and two Vincristin resistant line (UKF-NB-2 VCR and UKF-NB-4 VCR) had a deletion of part of 19q or the whole 19 chromosome. All lines resistant to Vincristin or Doxorubicin and two Cisplatin resistant lines (UKF-NB-2 CDDP and UKF-NB-4 CDDP) had a deletion of at least part of 17q, UKF-NB-4 DOXO had deletion of the whole chromosome 17. The loss of 17q may cause chemoresistance by deletion of topoisomerase IIalpha gene. Deletion of 19 q in all but one chemo-resistant lines may influence of cytochromes P450 genes which are located on 19q13.2. Also gains of 15q 22, which were detected in UKF-NB-4 VCR, UKF-NB-2 DOXO and UKF-NB-4 DO X O, may affect other cytochromes P450 genes.

Stability and inactivation of SARS coronavirus

The SARS-coronavirus (SARS-CoV) is a newly emerged, highly pathogenic agent that caused over 8,000 human infections with nearly 800 deaths between November 2002 and September 2003. While direct person-to-person transmission via respiratory droplets accounted for most cases, other modes have not been ruled out. Faecal shedding is common and prolonged and has caused an outbreak in Hong Kong. We studied the stability of SARS-CoV under different conditions, both in suspension and dried on surfaces, in comparison with other human-pathogenic viruses, including human coronavirus HCoV-229E. In suspension, HCoV-229E gradually lost its infectivity completely while SARS-CoV retained its infectivity for up to 9 days; in the dried state, survival times were 24 h versus 6 days. Thermal inactivation at 56 degrees C was highly effective in the absence of protein, reducing the virus titre to below detectability; however, the addition of 20% protein exerted a protective effect resulting in residual infectivity. If protein-containing solutions are to be inactivated, heat treatment at 60 degrees C for at least 30 min must be used. Different fixation procedures, e.g. for the preparation of immunofluorescence slides, as well as chemical means of virus inactivation commonly used in hospital and laboratory settings were generally found to be effective. Our investigations confirm that it is possible to care for SARS patients and to conduct laboratory scientific studies on SARS-CoV safely. Nevertheless, the agents tenacity is considerably higher than that of HCoV-229E, and should SARS re-emerge, increased efforts need to be devoted to questions of environmental hygiene.

Infection of cultured intestinal epithelial cells with severe acute respiratory syndrome coronavirus

To identify a model for the study of intestinal pathogenesis of severe acute respiratory syndrome (SARS) we tested the sensitivity of six human intestinal epithelial cell lines to infection with SARS coronavirus (SARS-CoV). In permissive cell lines, effects of SARS-CoV on cellular gene expression were analysed using high-density oligonucleotide arrays. Caco-2 and CL-14 cell lines were found to be highly permissive to SARS-CoV, due to the presence of angiotensin-converting enzyme 2 as a functional receptor. In both cell lines, SARS-CoV infection deregulated expression of cellular genes which may be important for the intestinal pathogenesis of SARS.

Cytomegalovirus infection blocks apoptosis in cancer cells

Recent pathological findings reveal a higher frequency of human cytomegalovirus (HCMV) in tumor cells from different tumors compared with surrounding tissues. Experimental investigations suggest possible supportive effects of HCMV for tumor development and progression. One HCMV effect on tumor cells is the inhibition of apoptosis, leading to the promotion of tumor cell survival. Decreased sensitivity to treatment-induced tumor cell death is a major reason for failure of anticancer chemotherapy. HCMV infection interferes with both the intrinsic and extrinsic cellular apoptosis pathways. HCMV promotes cell survival signaling influencing the tumor suppressor p53 and its relative p73, and stimulates the antiapoptotic Ras/Raf/MEK/Erk- and PI-3K-signaling pathways. Antiapoptotic effects mediated by HCMV are inhibited by antiviral treatment in cell culture. Therefore, a better understanding of the influence of HCMV infection on tumor cell apoptosis might translate into improved anti-cancer therapy.

The immunosuppressive drug mycophenolate mofetil impairs the adhesion capacity of gastrointestinal tumour cells

Immunosuppression correlates with the development and recurrence of cancer. Mycophenolate mofetil (MMF) has been shown to reduce adhesion molecule expression and leucocyte recruitment into the donor organ. We have hypothesized that MMF might also prevent receptor-dependent tumour dissemination. Therefore, we have investigated the effects of MMF on tumour cell adhesion to human umbilical vein endothelial cells (HUVEC) and compared them with the effects on T cell-endothelial cell interactions. Influence of MMF on cellular adhesion to HUVEC was analysed using isolated CD4+ and CD8+ T cells, or WiDr colon adenocarcinoma cells as the model tumour. HUVEC receptors ICAM-1, VCAM-1, E-selectin and P-selectin were detected by flow cytometry, Western blot or Northern blot analysis. Binding activity of T cells or WiDr cells in the presence of MMF were measured using immobilized receptor globulin chimeras. MMF potently blocked both T cell and WiDr cell binding to endothelium by 80%. Surface expression of the endothelial cell receptors was reduced by MMF in a dose-dependent manner. E-selectin mRNA was concurrently reduced with a maximum effect at 1 microm. Interestingly, MMF acted differently on T cells and WiDr cells. Maximum efficacy of MMF was reached at 10 and 1 microm, respectively. Furthermore, MMF specifically suppressed T cell attachment to ICAM-1, VCAM-1 and P-selectin. In contrast, MMF prevented WiDr cell attachment to E-selectin. In conclusion, our data reveal distinct effects of MMF on both T cell adhesion and tumour cell adhesion to endothelial cells. This suggests that MMF not only interferes with the invasion of alloactivated T cells, but might also be of value in managing post-transplantation malignancy.

Glycyrrhizin, an active component of liquorice roots, and replication of SARS-associated coronavirus

The outbreak of SARS warrants the search for antiviral compounds to treat the disease. At present, no specific treatment has been identified for SARS-associated coronavirus infection. We assessed the antiviral potential of ribavirin, 6-azauridine, pyrazofurin, mycophenolic acid, and glycyrrhizin against two clinical isolates of coronavirus (FFM-1 and FFM-2) from patients with SARS admitted to the clinical centre of Frankfurt University, Germany. Of all the compounds, glycyrrhizin was the most active in inhibiting replication of the SARS-associated virus. Our findings suggest that glycyrrhizin should be assessed for treatment of SARS.

Prions and orthopedic surgery

Prions are a novel class of infectious agents that cause subacute encephalopathy in man and animals as human Creutzfeldt-Jakob disease (CJD), sheep scrapie and bovine spongiform encephalopathy (BSE). Previously, prions were shown to be transmitted by neuro- and ophthalmosurgical measures and by application of brain-derived therapeutic hormones. Recently, prions have been detected in blood specimens of experimentally infected monkeys indicating a principal threat to transfusion medicine, furthermore in human or bovine materials used in reconstructive surgery. In this article the risk of prion transmission from the surgeon to the patient or vice versa during (orthopedic) surgery is reevaluated including the issues of blood transfusion. This is accomplished based on recent epidemiologic findings and biometric calculations on the spread of prions in animals and humans as well as in terms of experimental data on artificially contaminated medical materials and devices. The overall risk of prion transmission in orthopedic surgery is considered very low if adequately prepared and sterilized materials and devices are used.

Cross-talk between human herpesvirus 8 and the transactivator protein in the pathogenesis of Kaposi's sarcoma in HIV-infected patients

AIDS-associated Kaposi's sarcoma (AKS) is particularly aggressive and it is one of the principal neoplasms in regions of Africa affected by both high endemic HHV8 and epidemic HIV infection. In this study, serum samples from 18 patients with Kaposi's sarcoma from Tanzania, mostly males (n = 15 vs 3), were subjected to analysis with respect to HHV8-DNA load and antibody spectrum against the HIV-1 tat protein. Of the 18 patients, 14 were HIV-1-positive. The median HHV8 virus load in the HIV-1-positive group was 2075 DNA copies/ml, compared to 450 copies/ml in the HIV-1-negative group. In the HIV-1-positive group, the males had a higher HHV8-DNA virus load as compared to females (median: 4600 vs 1400 genome copies per ml). Since tat can promote AKS development (4-6) by intercellular signalling pathways, and these signals can be abolished by anti-tat IgG (7-9), we have examined the anti-tat IgG spectrum in this study. It would be expected that the levels of serum HHV8-DNA are higher in KS patients who have low anti-tat IgG titer, or who are anti-tat IgG-negative. In the present study, seven out of fifteen AKS patients were positive for anti-tat IgG. Although, we have not seen a strict quantitative relationship between serum anti-tat IgG and HHV8-DNA levels, our data appear to suggest a correlation between the two parameters. In view of these observations and the published data, we suggest that cross-signalling pathways between the tat protein and HHV8-DNA are involved in the complexity of pathogenesis of Kaposi's sarcoma.

Increase of fetal hemoglobin synthesis indicating differentiation induction in children receiving valproic acid

Differentiation induction is a distinct concept in the treatment of malignant diseases, considering that malignant cells share many features with immature progenitor cells that are capable of terminal differentiation. Treatment of tumor cells with short-chain fatty acid treatment of erythroid progenitors in vitro and in vivo induces cellular differentiation resulting in gamma-globin, i.e., fetal hemoglobin synthesis. Valproic acid (VPA) is a branched-chain fatty acid that is able to inhibit growth of human and rodent tumor cells and to induce a mature phenotype. The antitumoral effects observed in preclinical studies were reached at concentrations that are readily achieved in patients treated with VPA for epilepsy. Hypothesizing that anticonvulsive VPA levels may be used for antitumoral differentiation induction therapy of pediatric malignant tumors, the authors studied fetal hemoglobin-inducing capacity of VPA in children treated with VPA for epilepsy. Fetal hemoglobin was significantly increased in 30 children with epilepsy treated with VPA monotherapy for at least 3 months when compared to untreated control patients. Furthermore, fetal hemoglobin levels correlated with VPA serum levels. The study confirms the dose-dependent stimulating effect of VPA on fetal hemoglobin synthesis at anticonvulsive doses. The results suggest that nontoxic VPA levels reached in pediatric epilepsy patients should be capable of inducing cellular differentiation of pediatric malignant tumors for therapeutic purposes. Broad clinical experience with VPA and its low toxicity further encourage the evaluation of VPA in pediatric oncology for differentiation induction therapy.

Evaluation of carcinogenic potential of two nitro-musk derivatives, musk xylene and musk tibetene in a host-mediated in vivo/in vitro assay system

We have developed a host-mediated assay system for detection of the transforming activity of chemical carcinogens on peritoneal macrophages. Directly, as well as indirectly acting carcinogenic substances, administered intraperitoneally to NMRI mice, could be examined in this way. Resident macrophages were recovered by peritoneal lavage from treated and untreated mice and cultured in soft agar. After 5-6 days the normal and transformed cells could be distinguished. Statistical analysis comparing cells from musk xylene- or musk tibetene-treated animals with those from control mice proved that the test is positive. Musk xylene and musk tibetene revealed a cell-transforming potential that showed a dose-dependent response in our host-mediated assay system. We have succeeded in establishing permanent cell lines from mice treated with musk xylene, or musk tibetene. The oncogenicity of these cell lines was tested in athymic nu/nu mice. Animals injected subcutaneously with these cells (1 x 10(6) cells at each side of the neck) developed tumors at the injection sites within 3 weeks of treatment. The experimental data reported here lead to the conclusion that musk xylene, as well as musk tibetene, have carcinogenic activity. In contrast to the negative results for mutagenicity and genotoxicity, a non-genotoxic mechanism for the carcinogenicity of musk xylene and musk tibetene must be considered.

Antiviral and immunomodulatory activity of the metal chelator ethylenediaminedisuccinic acid against cytomegalovirus in vitro and in vivo

Antiviral activity of the metal chelator ethylenediaminedisuccinic acid (EDDS) was examined in vitro against human cytomegalovirus (HCMV) wild type strains and strains that are resistant against ganciclovir (GCV) and cidofovir (HPMPC). EDDS inhibited the replication of wild-type as well as GCV- and HPMPC-resistant strains with a 50% effective concentration of 7.4-12 microg/ml. At concentrations of 100 microg/ml EDDS, unlike GCV or HPMPC, suppressed HCMV-induced up-regulation of intercellular adhesion molecule-1 (ICAM-1) and reduced T-cell adhesion to HCMV-infected cells in a monolayer adhesion model. In vitro EDDS inhibited murine cytomegalovirus (MCMV) replication (EC50 8.6 microg/ml) and caused in mice some protection against MCMV induced mortality at a non-toxic dose. Since immunopathological factors may play a significant role in HCMV disease it will be of interest to further study whether EDDS is effective in terms of modulation of inflammatory responses to HCMV infections.

S-acyl-2-thioethyl (SATE) pronucleotides are potent inhibitors of HIV-1 replication in T-lymphoid cells cross-resistant to deoxycytidine and thymidine analogs

The biological evaluation of mononucleotide prodrugs (pronucleotides) of various nucleoside reverse transcriptase inhibitors (NRTIs) such as zidovudine (AZT), zalcitabine (ddC) and lamivudine (3TC) was reported in human T-lymphoid MOLT-4/8 cells which were grown continuously for more than 1 year in a medium containing cytarabine (Ara-C). In this cell line, expression of deoxycytidine kinase (dCK) and thymidine kinase 1 (TK1) was decreased in comparison to parental cells (3.8 and 2.9-fold, respectively). The lower mRNA level of TK1 correlated significantly with lower enzyme activity, whereas no dCK activity was detectable. In Ara-C-resistant cells, anti-HIV-1 effects of ddC, 3TC and AZT were more than 100-fold lower compared with parental cells. In contrast, the corresponding mononucleoside phosphotriesters bearing S-acyl-2-thioethyl (SATE) groups as biolabile phosphate protection retained anti-HIV-1 activity due to their ability to bypass the first monophosphorylation step catalyzed by dCK or TK1. The results demonstrate that in vitro selection of T-lymphoid cells in the presence of Ara-C results in cross-resistance to deoxycytidine (ddC, 3TC) and thymidine (AZT) analogs and that these cellular resistance mechanisms can be bypassed by the use of bis(SATE) pronucleotides.

Human cytomegalovirus circumvents NF-kappa B dependence in retinal pigment epithelial cells

The human CMV (HCMV) is a persistent virus that may cause severe inflammatory responses especially in immunocompromised hosts. In different cell types, HCMV infection leads to the activation of the pleiotropic transcription factor, NF-kappaB, which triggers virus replication but also propagates cell-mediated inflammatory mechanisms that largely depend on PG synthesis. We investigated the interactions of HCMV and the NF-kappaB-dependent PG synthesis pathway in cultures of retinal pigment epithelial (RPE) cells that are known to be infected in HCMV retinitis patients. Unlike in other cell types, HCMV increased neither NF-kappaB activity nor p65 and p105/50 mRNA levels in RPE cells. Both TNF-alpha and phorbol ester 12,0-tetradecanoylphorbol 13-acetate (TPA) enhanced NF-kappaB activity but only TPA increased HCMV replication. Cyclooxygenase-2 expression and PGE2 release was increased by TPA and TNF-alpha but not by HCMV infection. Stimulatory activity of TPA on HCMV replication was suppressed by protein kinase C inhibitors and inhibitors of p42/44 and p38 mitogen-activated protein kinases but not by NF-kappaB inhibitors. In conclusion, HCMV circumvents the NF-kappaB route in favor of the protein kinase C-dependent mitogen-activated protein kinase pathway in RPE cells. This virus/host cell interaction might be a mechanism that promotes HCMV persistence in immune-privileged organs such as the eye.

Treatment of drug-resistant human neuroblastoma cells with cyclodextrin inclusion complexes of aphidicolin

Treatment failure in most neuroblastoma (NB) patients is related to primary and/or acquired resistance to conventional chemotherapeutic agents. Aphidicolin (APH), a tetracyclic diterpene, exhibits specific cytotoxic action against NB cells. The purpose of this study was to compare antitumoral efficacy of APH in parental NB cell lines and cell subclones that exhibit drug resistance to vincristine (VCR), doxorubicin (DOX) and cisplatin. Due to poor solubility of APH in water, gamma-cyclodextrin (gamma-CD) inclusion complexes of APH were used for systemic treatment of xenotransplanted parental and VCR-resistant UKF-NB-3 tumours. APH and its gamma-CD inclusion complexes inhibited growth of parental and drug-resistant NB cells at equimolar doses in vitro. Growth of VCR-sensitive and -resistant NB tumors was inhibited at equal doses in a dose-dependent fashion in vivo. These results indicate that the specific cytotoxic activity of APH against NB cells in vitro and in vivo is independent of cellular mechanisms facilitating drug resistance to conventional chemotherapeutic drugs. Hence, taking into account our previous findings that APH acts synergistically with VCR and DOX, APH might be an additive tool for the therapy of NB and is suitable for evaluation in clinical studies of NB treatment protocols.

Antisense oligonucleotide ISIS 2922 targets IE-expression and prevents HCMV-IE-induced suppression of TSP-1 and TSP-2 expression

ISIS 2922, but not ganciclovir (GCV), inhibits HCMV immediate early protein (IE) expression in different infected cell lines and prevents down-modulation of extracellular matrix proteins thrombospondin-1 and -2 induced by IE proteins. While action of ISIS 2922 is mainly due to specific inhibition of IE 2 mRNA, there is also evidence for unspecific effects in terms of inhibition of virus adhesion and penetration.

Zidovudine (AZT) resistance in H9 cells due to decreased TK expression is associated with hypermethylation of TK gene

AZT resistant human T-lymphoid H9 cells, deficient in TK gene expression, re-expressed TK mRNA and regained the ability to metabolize AZT by exposure to the demethylation agent azacytidine (AzaCd). Cytotoxic and anti-HIV-1 effects of AZT were increased in H9 AZT resistant cells treated with AzaCd when compared to untreated cells. This leads to the assumption that drug induced DNA hypermethylation was involved in the TK gene-silencing mechanism. Our results suggest approaches using modulation of gene methylation for increasing antiviral efficiency of drugs.

Cytarabine treatment of human T-lymphoid cells induces decreased HIV-1 receptor expression and reduced HIV-1 susceptibility

Continuous cultivation of T-lymphoid C8166 cells in the presence of pharmacological relevant concentration of cytarabine (Ara-C) results in significantly decreased expression of CD4 and CXCR4 molecules, the major cellular receptor and co-receptor of T-lymphotropic HIV-1 isolates. This change in receptor expression leads to decreased susceptibility of Ara-C resistant cells to HIV-1 infection demonstrated by reduced binding and penetration of HI-virus.

Treatment of cytomegalovirus diseases

This review summarizes current strategies for the treatment of human cytomegalovirus (CMV) infection/diseases in high-risk patients such as transplant recipients and AIDS patients. Since the major drugs ganciclovir (Cytovene), foscarnet (Foscavir) and cidofovir (Vistide) are frequently associated with severe side effects and the formation of viral resistance, it should be endeavored to develop better strategies in anti-CMV treatment. Moreover, blocking of the viral replication does not always resolve the manifestations which are often linked with CMV-associated immunopathomechanisms. Thus, the efficacy of the available drugs is also discussed in the light of their ability to modulate inflammatory components of the cell-mediated immune system.

Viral and cellular factors for resistance against antiretroviral agents

Long-term treatment of HIV-1-infected patients with antiretroviral agents may result in failure of therapy, due to the rapid emergence of resistant virus mutants with decreased susceptibility to therapeutic agents. However, in addition to viral resistance other factors, i.e. cellular factors, may contribute to the waning efficiency of chemotherapy. It has been shown in vitro that continuous treatment of cell lines with nucleoside reverse transcriptase inhibitors, such as 3'-azido-2',3'-dideoxythymidine (zidovudine, AZT), may induce decreased activity of cellular thymidine kinase (TK). Measurements of TK activity in ex vivo stimulated peripheral blood mononuclear cells of HIV-1-infected patients who undergo AZT long-term monotherapy as well as combination therapy provide evidence that diminished cellular TK activity may develop. This leads to the assumption that due to long-term treatment with nucleoside analogs, altered drug metabolism in host cells may contribute to inefficient activation of chemotherapeutic agents in HIV-1 patients. Thus, intracellular subtherapeutic levels of the active compounds may develop. In this intracellular environment, selection of resistant virus populations may be promoted. Due to the expanding number of antiretroviral compounds and the requirement for lifelong treatment of HIV-1-infected persons with antiretroviral agents, both viral and cellular resistance mechanisms must be considered in the context of failing chemotherapy.

Modulatory effects of human cytomegalovirus infection on malignant properties of cancer cells

Although there is no definitive evidence of the association of human cytomegalovirus (HCMV) infection with human cancers, the oncogenic potential of HCMV has been well established by in vitro studies demonstrating the ability of UV-irradiated or infectious virus to transform a variety of cells. After prolonged passaging the transformed cell type was maintained while HCMV DNA sequences were no more detectable. Three morphological transforming regions (mtr) of HCMV have been identified. The effects of HCMV on cellular functions which may be associated with the malignant phenotype include the expression of oncogenes and transcriptional activation of growth factors and interleukin synthesis. In infected cells, HCMV induces cytoskeletal alterations and changes in expression of cell surface receptors for extracellular matrix proteins which could result in increased motility and dissemination of cancer cells. Several human neuroblastoma cell lines undergo maturation in different neural crest derived cell types upon treatment with oncogenic potential agents, i.e. retinoic acid. The persistent HCMV infection of neuroblastoma cells (> 1 year) is accompanied by the increased expression of oncoproteins (i.e. N-myc) and decreased expression of tyrosine hydroxylase and dopamine-beta-hydroxylase. The activation of the cellular metabolism is due to HCMV binding to cellular receptors (prior to virus gene expression) and to the activity of HCMV immediate early (IE) gene products. IE proteins act directly as transcriptional activators or their activity is mediated by a variety of cellular transcription factors. HCMV infection may result in activation of promoters of cellular genes coding for cytokines, replication enzymes, proto-oncogenes and viral promoters. Recently it has been demonstrated that HCMV IE proteins block apoptosis probably by suppressing the ability of the antioncogene p53 to activate a reporter gene. The interactions of HCMV with tumor suppressor proteins such as p53 or retinoblastoma (pRb) susceptibility protein are reminiscent of those mediated by the oncoproteins of DNA tumor viruses. The acquisition of a fully malignant phenotype by normal cells is thought to require several mutations in a number of cellular genes. In this connection, HCMV may play the role of a nonobligate either direct or indirect cofactor for tumor genesis, e.g. by blocking apoptosis, which may be an essential requirement for tumor progression. Due to the stimulation of growth factors and/or inhibition of antioncogenes by its gene products, HCMV may modulate the malignant potential for tumor cells.

Increased efficacy of aphidicolin killing of human neuroblastoma cells in vitro by encapsulation in liposomes

Aphidicolin is a tetracyclic diterpene antibiotic which kills human neuroblastoma cells (NB) in vitro while it has no significant effect on the viability of different human cell types including normal embryonal cells. In the present study, we tested whether aphidicolin encapsulated in liposomes kills NB cells with the efficacy superior to that of unencapsulated aphidicolin. The drug was entrapped in vesicles composed of phosphatidylcholine, phosphatidylserine and cholesterol in a molar ratio of 83:5:12. The treatment with encapsulated aphidicolin at a concentration of 200 nmol for 5 days killed all cells of three human NB cell lines. In contrast, at least 30% of the cells survived 5 days of treatment with 200 nmol unencapsulated aphidicolin. The results showed that aphidicolin killing of human NB cells may be increased by encapsulation in liposomes.

Inhibition of cytomegalovirus immediate early gene expression: a therapeutic option?

The replication cycle of the human cytomegalovirus (HCMV) is characterized by the expression of immediate early (IE), early (E), and late (L) gene regions. Current antiviral strategies are directed against the viral DNA polymerase expressed during the early phase of infection. The regulation of the IE-1 and IE-2 gene expression is the key to latency and active replication due to their transactivating and repressing functions. There is growing evidence that the pathogenic features of HCMV are largely due to the abilities of IE-1 and IE-2 to transactivate cellular genes. Consequently, current drugs used to inhibit HCMV infection would have no impact on IE-1 and IE-2-induced effects that are produced before the early phase. Moreover, when HCMV DNA replication is inhibited, IE gene products accumulate in infected cells causing disturbances of host cell functions. This review summarizes the biological functions of HCMV-IE gene expression, their relevance in pathogenesis, as well as efforts to develop novel treatment strategies directed against HCMV-IE expression.