Inhibition of cyclooxygenase 2 blocks human cytomegalovirus replication

Development of new antivirals for herpesviruses

The long-term treatment of herpesvirus infections with current antivirals in immunocompromised hosts leads to the development of drug-resistant viruses. Because nearly all currently available antivirals finally target viral DNA polymerase, virus resistant to one drug often shows cross-resistance to other drugs. In addition, nearly all the antivirals show various kinds of side effects or poor bioavailability. This evidence highlights the need for developing new antivirals for herpesviruses that have the different viral targets. Recently, high-throughput screening of large compound collections for inhibiting specific viral enzymes, or in vitro cell culture assay, has identified several new antivirals that target different viral proteins. These include the inhibitors of helicase/primase complex, terminase complex, portal protein and UL97 protein kinase. In addition, non-nucleoside inhibitors for viral DNA polymerase have been also developed. This review will focus on these new compounds that directly inhibit viral replication.

Cytomegalovirus infection in symptomatic periapical pathosis

AIM

To compare the presence of human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV) infections in samples from 25 symptomatic and 19 asymptomatic periapical lesions.

METHODOLOGY

Periapical samples were collected by sterile curettes in conjunction with apicectomy. cDNA-based HCMV and EBV identification was performed on total mRNAs extracted from peripapical tissues, using primers for genes transcribed during the productive phase of the herpesvirus infection. Statistical analysis was performed using chi-squared test.

RESULTS

HCMV was detected in 100% of the symptomatic and in 37% of the asymptomatic study lesions. EBV was identified only in HCMV-infected periapical lesions. The difference in occurrence of HCMV and EBV between symptomatic and asymptomatic periapical lesions was statistically significant (P < 0.0001).

CONCLUSIONS

The noteworthy finding of this study was the ubiquitous occurrence of HCMV active infection in symptomatic periapical pathosis. EBV may contribute to periapical pathogenesis in a subset of symptomatic lesions. HCMV and EBV infections may cause periapical pathosis by inducing cytokine and chemokine release from inflammatory or connective tissue cells, or by impairing local host defences resulting in heightened virulence of resident bacterial pathogens. Knowledge about the role of herpesviruses in periapical pathosis seems important to fully delineate the pathogenesis of endodontic infectious diseases. HCMV and probably EBV should be added to the list of putative pathogenic agents in symptomatic periapical disease.

Human cytomegalovirus carries a cell-derived phospholipase A2 required for infectivity

Human cytomegalovirus (HCMV) is known to carry host cell-derived proteins and mRNAs whose role in cell infection is not understood. We have identified a phospholipase A2 (PLA2) activity borne by HCMV by using an assay based on the hydrolysis of fluorescent phosphatidylcholine. This activity was found in all virus strains analyzed and in purified strains. It was calcium dependent and was sensitive to inhibitors of cytosolic PLA2 (cPLA2) but not to inhibitors of soluble PLA2 or calcium-independent PLA2. No other phospholipase activity was detected in the virus. Purified virus was found to contain human cellular cPLA2alpha, as detected by monoclonal antibody. No homology with PLA2 was found in the genome of HCMV, indicating that HCMV does not code for a PLA2. Decreased de novo expression of immediate-early proteins 1 and 2 (IE1 and IE2), tegument phosphoprotein pp65, and virus production was observed when HCMV was treated with inhibitors of cPLA2. Cell entry of HCMV was not altered by those inhibitors, suggesting the action of cPLA2 was postentry. Together, our results indicate a selective sorting of a cell-derived cPLA2 during HCMV maturation, which is further required for infectivity.

Functional genomics in virology and antiviral drug discovery

Virology research and antiviral drug discovery are poised to benefit from the post-genomic revolution for three main reasons. First, viruses need the host to replicate and are therefore vulnerable to inhibition of cellular pathways. Knowledge of complete genomic sequences of both virus and host now permits the study of this interplay on a global scale. Combining transcriptomics and proteomics with large-scale gene knockdown experiments will enable the identification of novel antiviral targets. Second, massive parallel assay systems, such as DNA microarrays, which define the post-genomic era, will facilitate viral diagnostics. Third, the combination of genetics with genomics will enable the analysis of viral mutants and strains on an unprecedented scale. The dramatic effects of viral infection on host cell transcriptional patterns have been well-documented and will be briefly highlighted. In addition, we discuss recent trends that apply functional genomics methods to the discovery of new targets and therapies for viral disease.

Human cytomegalovirus-induced host cell enlargement is iron dependent

A hallmark of human cytomegalovirus (HCMV) infection is the characteristic enlargement of the host cells (i.e., cytomegaly). Because iron (Fe) is required for cell growth and Fe chelators inhibit viral replication, we investigated the effects of HCMV infection on Fe homeostasis in MRC-5 fibroblasts. Using the metallosensitive fluorophore calcein and the Fe chelator salicylaldehyde isonicotinoyl hydrazone (SIH), the labile iron pool (LIP) in mock-infected cells was determined to be 1.04 +/- 0.05 microM. Twenty-four hours postinfection (hpi), the size of the LIP had nearly doubled. Because cytomegaly occurs between 24 and 96 hpi, access to this larger LIP could be expected to facilitate enlargement to approximately 375% of the initial cell size. The ability of Fe chelation by 100 microM SIH to limit enlargement to approximately 180% confirms that the LIP plays a major role in cytomegaly. The effect of SIH chelation on the mitochondrial membrane potential (DeltaPsi(M)) and morphology was studied using the mitochondrial voltage-sensitive dye JC-1. The mitochondria in mock-infected cells were heterogeneous with a broad distribution of DeltaPsi(M) and were threadlike. In contrast, the mitochondria of HCMV-infected cells had a more depolarized DeltaPsi(M) distributed over a narrow range and were grainlike in appearance. However, the HCMV-induced alteration in DeltaPsi(M) was not affected by SIH chelation. We conclude that the development of cytomegaly is inhibited by Fe chelation and may be facilitated by an HCMV-induced increase in the LIP.

The role and regulation of COX-2 during viral infection

Prostaglandins are lipid mediators, generated by cyclooxygenase (COX), that have been shown to participate in the regulation of virus replication and the modulation of inflammatory responses following infection. A number of studies support a role for PGE2 in the modulation of virus replication and virulence in a cell type and virus selective manner. Virus infection also stimulates the expression of a number of proinflammatory gene products, including COX-2, inducible nitric oxide synthase (iNOS) as well as proinflammatory cytokines. This review will focus on the mechanisms by which proinflammatory prostaglandin production regulates virus replication and virulence. In addition, the signaling pathways that are activated during a virus infection, and that regulate proinflammatory gene expression in macrophages will be reviewed. Specific attention will be placed on the ability of virus infection to activate multiple signaling cascades (such as PKR, MAPK, iPLA2, NF-kappaB) and how these pathways are integrated in the regulation of individual target gene expression.

Host gene induction and transcriptional reprogramming in Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8)-infected endothelial, fibroblast, and B cells: insights into modulation events early during infection

Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) is etiologically linked to the endothelial tumor Kaposi's sarcoma and with two lymphoproliferatve disorders, primary effusion lymphoma and multicentric Castleman's disease. HHV-8 infects a variety of target cells both in vivo and in vitro, binds to the in vitro target cells via cell surface heparan sulfate, and uses the alpha(3)beta(1) integrin as one of the entry receptors. Within minutes of infection, HHV-8 induced the integrin-mediated signaling pathways and morphological changes in the target cells (S. M. Akula et al., Cell, 108: 407-419, 2002; P. P. Naranatt et al., J. Virol., 77: 1524-1539, 2003). As an initial step toward understanding the role of host genes in HHV-8 infection and pathogenesis, modulation of host cell gene expression immediately after infection was examined. To reflect HHV-8's broad cellular tropism, mRNAs collected at 2 and 4 h after infection of primary human endothelial [human adult dermal microvascular endothelial cells (HMVECd)] and foreskin fibroblast [human foreskin fibroblast (HFF)] cells and human B cell line (BJAB) were analyzed by oligonucleotide array with approximately 22,000 human transcripts. With a criteria of >2-fold gene induction as significant, approximately 1.72% of the genes were differentially expressed, of which, 154 genes were shared by at least two cells and 33 genes shared by all three cells. HHV-8-induced transcriptional profiles in the endothelial and fibroblast cells were closely similar, with substantial differences in the B cells. In contrast to the antiapoptotic regulators induced in HMVECd and HFF cells, proapoptotic regulators were induced in the B cells. A robust increase in the expression of IFN-induced genes suggestive of innate immune response induction was observed in HMVECd and HFF cells, whereas there was a total lack of immunity related protein inductions in B cells. These striking cell type-specific behaviors suggest that HHV-8-induced host cell gene modulation events in B cells may be different compared with the adherent endothelial and fibroblast target cells. Functional clustering of modulated genes identified several host molecules hitherto unknown to HHV-8 infection. These results indicate that early during infection, HHV-8 reprograms the host transcriptional machinery regulating a variety of cellular processes including apoptosis, transcription, cell cycle regulation, signaling, inflammatory response, and angiogenesis, all of which may play important roles in the biology and pathogenesis of HHV-8.

Human cytomegalovirus (HCMV) IE1 plays role in resistance to apoptosis with etoposide in cancer cell line by Cdk2 accumulation

Human cytomegalovirus (HCMV) has many strategies to survive the attack of the host. HCMV infection of host cells induces cellular activation and disturbance of the cell cycle. It is possible that HCMV modulates the behavior of certain cancer cells that are susceptible to HCMV infection. This study was performed to identify the possible mechanism of resistance to apoptotic stimuli in some cancer cell lines by HCMV infection. HCMV-infected cancer cells showed resistance to apoptosis induced by the topoisomerase II inhibitor etoposide. UMG1-2, which constitutively expresses HCMV immediate-early protein-1 (IE1), had resistance to apoptosis induced by etoposide as compared with the parental cell line U373MG. Measurement of caspases activity with fluorogenic substrates in etoposide-treated U373MG and UMG1-2 cells and the direct activation of caspase-3 with peptides containing arginine-glycine-aspartate in U373MG and UMG1-2 cells revealed that the inhibition level of apoptosis by HCMV IE1 would be upstream of caspase-3 in the caspase cascade pathway. Cellular expression of Cdk2 was increased in UMG1- 2 after etoposide treatment while the expression of E2F-1 in UMG1-2 was decreased as compared with that in U373MG. The Cdk2 inhibitor, roscovitine, decreased the resistance to apoptosis on etoposide-treated UMG1-2. These results suggest that aberrant HCMV infection confers resistance to anticancer drugs on some cancer cells and protects cells from apoptosis, possibly due to the deregulation of cyclin-dependent kinase by HCMV immediate-early protein.

Effects of pharmacological cyclin-dependent kinase inhibitors on viral transcription and replication

Cyclin-dependent kinases (CDKs) are required for replication of adeno-, papilloma- and other viruses that replicate only in dividing cells. Surprisingly, CDKs are also required for replication of HIV-1, HSV-1, and other viruses that can replicate in non-dividing cells. Since two low-molecular weight pharmacological CDK inhibitors (PCIs), flavopiridol (Flavo) and roscovitine (Rosco), appear to be non-toxic in human clinical trials against cancer, these drugs have been proposed as potential antiviral drugs. Rosco preferentially inhibits CDKs involved in cell cycle regulation (CDK1, 2, and 7) or neuronal functions (CDK5), whereas Flavo preferentially inhibits CDKs involved in cell cycle (CDK1, 2, 4, 7) or transcription (CDK7, and 9). As potential antivirals, PCIs display several advantages: (i) they are active against many different viruses, including drug-resistant strains of HIV-1 and HSV-1; (ii) PCI-resistant mutants of HIV-1 or HSV-1 have not been identified; and (iii) the antiviral effects of PCIs and conventional antivirals appear to be additive (as expected from drugs that target independent pathways). Moreover, PCIs target both the etiological agents (i.e., the virus) and the pathogenic mechanisms (i.e., unrestricted cell division) of the many diseases that include both a CDK-requiring virus and unrestricted cell division (e.g., Kaposi's sarcoma, cervical carcinoma, HIV-associated nephropathy-HIVAN). This is nicely illustrated in a recent study which demonstrated the efficacy of Flavo in a mouse model of HIVAN. Herein, we will review the involvement of CDKs in viral replication and the antiviral properties of the most extensively characterized PCIs, with special emphasis on the mechanisms of inhibition of viral transcription.

Renal Cyclooxygenase-2 (Cox-2)

BACKGROUND/AIMS

The role of COX-2 for renal function during renal development, for physiology and pathophysiology of renal diseases and the side effects of available COX-2 inhibitors, has gained increasing interest. We aimed therefore to review the respective role of renal COX-2.

METHODS

Review of relevant recent publications in the field, and in addition of in part unpublished data obtained in our laboratories.

RESULTS

COX-2 is 'constitutively' localized in the kidney i.e. in macula densa, TALH, interstitial cells, and is of utmost importance for normal renal development. Renal COX-2 is regulated by for example sodium and volume intake, angiotensin II, glucocorticoids often involving specific COX-2 promotor response elements. COX-2 derived prostanoids are required for preservation of renal blood flow and glomerular filtration especially in states of fluid deficit, they promote natriuresis, and furthermore may stimulate renin secretion during low-sodium intake/loop diuretic use. Conversely, COX-2 inhibitors decrease glomerular filtration, and renal perfusion, sometimes even causing acute renal failure. In addition, COX-2 inhibitors cause sodium retention, edema formation, cardiac failure and hypertension. The role of COX-2 derived prostanoids in renal inflammation or failure including diabetic nephropathy and renal transplantation remains at present controversial.

CONCLUSION

COX-2 is one of the major players in renal physiology and pathophysiology. One focus of future work should be placed on COX-2 in primary renal diseases.

COX-2 induction during murine gammaherpesvirus 68 infection leads to enhancement of viral gene expression

The murine gammaherpesvirus 68 (MHV-68 or gammaHV-68) model provides many advantages for studying virus-host interactions involved in gammaherpesvirus replication, including the role of cellular responses to infection. We examined the effects of cellular cyclooxygenase-2 (COX-2) and its by-product prostaglandin E(2) (PGE(2)) on MHV-68 gene expression and protein production following de novo infection of cultured cells. Western blot analyses revealed an induction of COX-2 protein in MHV-68-infected cells but not in cells infected with UV-irradiated MHV-68. Luciferase reporter assays demonstrated activation of the COX-2 promoter during MHV-68 replication. Two nonsteroidal anti-inflammatory drugs, a COX-2-specific inhibitor (NS-398) and a COX-1-COX-2 inhibitor (indomethacin), substantially reduced MHV-68 protein production in infected cells. Inhibition of viral protein expression and virion production by NS-398 was reversed in the presence of exogenous PGE(2). Global gene expression analysis using an MHV-68 DNA array showed that PGE(2) increased production of multiple viral gene products, and NS-398 inhibited production of many of the same genes. These studies suggest that COX-2 activity and PGE(2) production may play significant roles during MHV-68 de novo infection.

Complete sequence and genomic analysis of rhesus cytomegalovirus

The complete DNA sequence of rhesus cytomegalovirus (RhCMV) strain 68-1 was determined with the whole-genome shotgun approach on virion DNA. The RhCMV genome is 221,459 bp in length and possesses a 49% G+C base composition. The genome contains 230 potential open reading frames (ORFs) of 100 or more codons that are arranged colinearly with counterparts of previously sequenced betaherpesviruses such as human cytomegalovirus (HCMV). Of the 230 RhCMV ORFs, 138 (60%) are homologous to known HCMV proteins. The conserved ORFs include the structural, replicative, and transcriptional regulatory proteins, immune evasion elements, G protein-coupled receptors, and immunoglobulin homologues. Interestingly, the RhCMV genome also contains sequences with homology to cyclooxygenase-2, an enzyme associated with inflammatory processes. Closer examination identified a series of candidate exons with the capacity to encode a full-length cyclooxygenase-2 protein. Counterparts of cyclooxygenase-2 have not been found in other sequenced herpesviruses. The availability of the complete RhCMV sequence along with the ability to grow RhCMV in vitro will facilitate the construction of recombinant viral strains for identifying viral determinants of CMV pathogenicity in the experimentally infected rhesus macaque and to the development of CMV as a vaccine vector.

Aspirin-induced asthma: advances in pathogenesis, diagnosis, and management

In some asthmatic individuals, aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) that inhibit cyclooxygen-ase 1 (COX-1) exacerbate the condition. This distinct clinical syndrome, called aspirin-induced asthma (AIA), is characterized by an eosinophilic rhinosinusitis, nasal polyposis, aspirin sensitivity, and asthma. There is no in vitro test for the disorder, and diagnosis can be established only by provocation challenges with aspirin or NSAIDs. Recent major advances in the molecular biology of eicosanoids, exemplified by the cloning of 2 cysteinyl leukotriene receptors and the discovery of a whole family of cyclooxygenase enzymes, offer new insights into mechanisms operating in AIA. The disease runs a protracted course even if COX-1 inhibitors are avoided, and the course is often severe, many patients requiring systemic corticosteroids to control their sinusitis and asthma. Aspirin and NSAIDs should be avoided, but highly specific COX-2 inhibitors, known as coxibs, are well tolerated and can be safely used. Aspirin desensitization, followed by daily aspirin treatment, is a valuable therapeutic option in most patients with AIA, particularly those with recurrent nasal polyposis or overdependence on systemic corticosteroids.

Antiherpesvirus drugs: a promising spectrum of new drugs and drug targets

In the absence of effective vaccines to control herpesvirus infections, nucleosidic antiviral drugs have been the mainstay of clinical treatment since their development in the late 1970s. However, given the drawbacks of these drugs, including the increasing emergence of drug-resistant clinical isolates, new strategies for treating herpesvirus infections are warranted. A range of promising new drugs with novel molecular targets has been developed, but will they cure latent infections?

Human cytomegalovirus activates inflammatory cytokine responses via CD14 and Toll-like receptor 2

Human cytomegalovirus (CMV) is a ubiquitous opportunistic pathogen that causes significant morbidity and mortality in immunocompromised people. An understanding of how CMV induces and circumvents host immunity is of critical importance in efforts to design effective therapeutics. It was recently discovered that mere cell contact by CMV particles leads to profound modulation of cellular gene expression, including induction of inflammatory cytokines and interferon-stimulated genes characteristic of innate immune detection. These findings suggest that a membrane receptor recognizes a CMV envelope protein(s), leading to innate immune activation. Here, we show that the pattern recognition receptors Toll-like receptor 2 (TLR2) and CD14 recognize CMV virions and trigger inflammatory cytokine production. Induction of inflammatory cytokines is mediated via TLR2-dependent activation of NF-kappa B. Since many of the pathological processes associated with CMV disease are facilitated or directly mediated by inflammatory cytokines, identification of the host membrane detection machinery may ultimately lead to improved therapeutics.

Human cytomegalovirus retinitis: pathogenicity, immune evasion and persistence

Human cytomegalovirus (HCMV) retinitis frequently occurs in severely naturally and iatrogenically immunocompromised patients. It has been shown that the immune-privileged retinal pigment epithelium (RPE) is a major site of persistent HCMV. Recently, evidence has accumulated to show that HCMV immediate early (IE) gene expression in RPE cells deviates ocular antiviral inflammation via FasL. Moreover, unlike in other cell types, the HCMV major IE1/2 enhancer promoter (MIEP) resists activation by proinflammatory stimuli mediated by the transcription factor NF-kappaB. However, tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) found at elevated levels in transplant recipients and AIDS patients with retinitis sensitize RPE cells and other retinal cells to FasL-mediated apoptosis, thus contributing to retina destruction and necrosis rather than inflammation. These specific features of RPE cells in conjunction with deregulated immune responses of immunocompromised patients seem to contribute to virus persistence and pathogenesis within the immune-privileged ocular retina.

Regulation of cyclooxygenase-2 expression by macrophages in response to double-stranded RNA and viral infection

In this study the regulation of macrophage expression of cyclooxygenase-2 (COX-2) in response to dsRNA and virus infection was examined. Treatment of RAW 264.7 macrophages with dsRNA results in COX-2 mRNA accumulation and protein expression and the production of PGE(2). Similar to dsRNA, encephalomyocarditis virus (EMCV) infection of RAW 264.7 cells stimulates COX-2 expression and PGE(2) accumulation. The dsRNA-dependent protein kinase (PKR), which has been shown to participate in the regulation of gene expression in response to dsRNA and virus infection, does not appear to participate in the regulation of COX-2 expression by macrophages. Expression of dominant negative mutants of PKR in RAW 264.7 cells fails to attenuate dsRNA- and EMCV-induced COX-2 expression or PGE(2) production. Furthermore, dsRNA and EMCV stimulate COX-2 expression and PGE(2) accumulation to similar levels in macrophages isolated from wild-type and PKR-deficient mice. Recently, a novel PKR-independent role for the calcium-independent phospholipase A(2) (iPLA(2)) in the regulation of inducible NO synthase expression by macrophages in response to virus infection has been identified. The selective iPLA(2) suicide substrate inhibitor bromoenol lactone prevents dsRNA- and EMCV-stimulated inducible NO synthase expression; however, bromoenol lactone does not attenuate dsRNA- or EMCV-induced COX-2 expression by macrophages. In contrast, inhibition of NF-kappaB activation prevents dsRNA-stimulated COX-2 expression and PGE(2) accumulation by macrophages. These findings indicate that virus infection and treatment with dsRNA stimulate COX-2 expression by a mechanism that requires the activation of NF-kappaB and that is independent of PKR or iPLA(2) activation.

Regulation of Ido-Mediated Bacteriostasis In Macrophages: Role of Antibiotics And Anti-Inflammatory Agents

Induction of IDO is also under strict control by the immune system and we have previously shown that there are a number of cytokines involved in the down-regulation of IDO induction. In clinical practice anti-inflammatory substances and antibiotics are commonly used and may influence the outcome of bacterial infection. We analysed the IFNgamma-dependant IDO induction and bacteriostasis of Staphylococcus aureus and Group A Streptococcus (GAS) in monocyte-derived-macrophages (MDM) from cord blood and peripheral blood of healthy adult donors with attention to the effect of down-regulatory cytokines and of two commonly used anti-inflammatory agents, hydrocortisone and indomethacin, on both IDO activity and bacterial growth. In addition to this we were interested in the effect of sub-inhibitory concentrations of the antibiotic ampicillin on this IDO-mediated effect, the premise being that for a substantial period of antibiotic therapy the infection site is exposed to sub-inhibitory concentrations of antibiotic. We found that after stimulation with IFNgamma, MDM inhibited streptococcal growth. This was due to IFNgamma-induced IDO activity as demonstrated by reconstitution of growth by supplemental tryptophan. This IDO-mediated bacteriostasis was inhibited by the cytokines IL-10, IL-4 and TGFbeta. Furthermore, addition of indomethacin to IFNgamma stimulated MDM also resulted in the abrogation of the IDO-induced bacteriostasis, a result of the inhibition of IDO induction. Surprisingly, co-stimulation with hydrocortisone and IFNgamma apparently increased the IDO activity in cord blood MDM, but had no effect on the IDO-activity of adult peripheral blood MDM. Bacteriostasis in cord blood MDM, on the other hand, was not affected by co-stimulation with hydrocortisone. Ampicillin, in sub-inhibitory concentrations had no effect on the IDO activity itself but did have a synergistic effect on the IDO-induced bacteriostasis in MDM cultures. We conclude that therapy with indomethacin may increase the risk of clinically important bacterial infection due to the inhibition of the IDO-induced bacteriostasis. In addition sub-inhibitory concentrations of ampicillin may play a role in the area of infection where IFNgamma stimulated macrophages are to be found in abundance.

Specific localisation of human cytomegalovirus nucleic acids and proteins in human colorectal cancer

BACKGROUND

Colorectal cancer is the second most frequent cause of death from cancer in the USA, and most tumours arise sporadically with no clear cause or genetic predisposition. Human cytomegalovirus is a beta-herpesvirus that is endemic in the human population and can cause life-threatening disease in immunosuppressed adults. In vitro, human cytomegalovirus can transform cells and dysregulate many cellular pathways relevant to colon adenocarcinoma pathogenesis, especially those affecting the cell cycle, mutagenesis, apoptosis, angiogenesis, and cyclo-oxygenase-2 (COX-2) expression. We aimed to assess whether gene products of human cytomegalovirus could be detected in colorectal cancers.

METHODS

We obtained formalin-fixed, paraffin-embedded pathological specimens of colorectal polyps, adenocarcinomas, and adjacent normal mucosa from 29 patients. To detect human cytomegalovirus proteins and nucleic acids, we used immunohistochemistry with two different monoclonal antibodies, in-situ hybridisation, and PCR with DNA sequencing.

FINDINGS

Human cytomegalovirus proteins IE1-72 and pp65 were detected in a tumour cell-specific pattern in 14 (82%) of 17 and seven (78%) of nine colorectal polyps, respectively, and 12 (80%) of 15 and 11 (92%) of 12 adenocarcinomas, respectively, but not in adjacent non-neoplastic colon biopsy samples from the same patients (none of seven and none of two, respectively). Human cytomegalovirus infection of colon-cancer cells (Caco-2) in vitro resulted in specific induction of Bcl-2 and cyclo-oxygenase-2 proteins, both of which are thought to contribute to progression of colon cancer.

INTERPRETATION

Human cytomegalovirus nucleic acids and proteins can be found that specifically localise to neoplastic cells in human colorectal polyps and adenocarcinomas, and virus infection can induce important oncogenic pathways in colon-cancer cells.

Activation of monocyte cyclooxygenase-2 gene expression by human herpesvirus 6. Role for cyclic AMP-responsive element-binding protein and activator protein-1

Prostaglandin E(2) (PGE(2)) is an arachidonic acid metabolite mainly produced by activated monocytes/macrophages (Mo/Mphi) that display broad immunomodulatory activities. Several viruses capable of infecting Mo/Mphi modulate PGE(2) synthesis in a way that favors the infection processes and the spread of virions. In the present work, we studied the effect of human herpesvirus 6 (HHV-6) infection of Mo/Mphi on PGE(2) synthesis. Our results indicate that HHV-6 induces COX-2 gene expression and PGE(2) synthesis within a few hours of infection. We mapped the different promoter elements associated with COX-2 gene activation by HHV-6 to two cis-acting elements: a cyclic AMP-responsive element and an activator protein-1 element. HHV-6 immediate-early protein 2 was identified as a modulator of COX-2 gene expression in Mo/Mphi. Finally, addition of PGE(2) to HHV-6-infected peripheral blood mononuclear cells cultures was found to increase significantly viral replication. Overall, these results further contribute to the immunomodulatory properties of HHV-6 and highlight a potential role for eicosanoids in the replication process of this virus.