Cellular gene expression altered by human cytomegalovirus: global monitoring with oligonucleotide arrays

Molecular genetics of Kaposi's sarcoma-associated herpesvirus (human herpesvirus-8) epidemiology and pathogenesis

Kaposi's sarcoma had been recognized as unique human cancer for a century before it manifested as an AIDS-defining illness with a suspected infectious etiology. The discovery of Kaposi's sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus-8, in 1994 by using representational difference analysis, a subtractive method previously employed for cloning differences in human genomic DNA, was a fitting harbinger for the powerful bioinformatic approaches since employed to understand its pathogenesis in KS. Indeed, the discovery of KSHV was rapidly followed by publication of its complete sequence, which revealed that the virus had coopted a wide armamentarium of human genes; in the short time since then, the functions of many of these viral gene variants in cell growth control, signaling apoptosis, angiogenesis, and immunomodulation have been characterized. This critical literature review explores the pathogenic potential of these genes within the framework of current knowledge of the basic herpesvirology of KSHV, including the relationships between viral genotypic variation and the four clinicoepidemiologic forms of Kaposi's sarcoma, current viral detection methods and their utility, primary infection by KSHV, tissue culture and animal models of latent- and lytic-cycle gene expression and pathogenesis, and viral reactivation from latency. Recent advances in models of de novo endothelial infection, microarray analyses of the host response to infection, receptor identification, and cloning of full-length, infectious KSHV genomic DNA promise to reveal key molecular mechanisms of the candidate pathogeneic genes when expressed in the context of viral infection.

The human cytomegalovirus

Human cytomegalovirus (HCMV), a betaherpesvirus, represents the major infectious cause of birth defects, as well as an important pathogen for immunocompromised individuals. The viral nucleocapsid containing a linear double-stranded DNA of 230 kb is surrounded by a proteinaceous tegument, which is itself enclosed by a loosely applied lipid bilayer. Expression of the HCMV genome is controlled by a cascade of transcriptional events that leads to the synthesis of three categories of viral proteins designated as immediate-early, early, and late. Clinical manifestations can be seen following primary infection, reinfection, or reactivation. About 10% of infants are infected by the age of 6 months following transmission from their mothers via the placenta, during delivery, or by breastfeeding. HCMV is a significant post-allograft pathogen and contributes to graft loss independently from graft rejection. Histopathologic examination of necropsy tissues demonstrates that the virus enters via the epithelium of the upper alimentary, respiratory, or genitourinary tracts. Hematogenous spreading is typically followed by infection of ductal epithelial cells. Infections are kept under control by the immune system. However, total HCMV clearance is rarely achieved, and the viral genome remains at selected sites in a latent state. Virological and molecular detection of HCMV, as well as serological demonstration of a specific immune response, are used for diagnosis. Treatment of HCMV infections is difficult because there are few options. The presently available drugs produced a significant clinical improvement, but suffer from poor oral bioavailability, low potency, development of resistance in clinical practice, and dose-limiting toxicities.

Gene expression changes in BVDV2-infected MDBK cells

Bovine viral diarrhoea virus (BVDV) is a ubiquitous viral pathogen of cattle. The virus exists as one of two biotypes, cytopathic and non-cytopathic, based on the ability to induce cytopathic effect in cell culture. The non-cytopathic biotypes are able to establish non-apparent, persistent infections in both cell culture and in bovine foetuses of fewer than 150 days gestation. The mechanism by which viral tolerance is established is unknown. To examine the changes in gene expression that occur following infection of host cells with BVDV, serial analysis of gene expression (SAGE), a global gene expression technology was used. SAGE, a sequence-based technology, allows quantification of virtually every transcript in a cell type without prior sequence information. Transcript expression levels and identities are determined by DNA sequencing of libraries composed of 14 base DNA fragments (tags) derived from the 3' end of each cellular mRNA transcript. Comparison of data obtained from non-infected and BVDV2-infected cell libraries revealed a number of changes in gene expression. Many of these transcriptional changes could be placed into distinct biochemical pathways or functions. Both alpha and beta tubulins were downregulated, indicating possible dysfunction in cell division and other functions where microtubules play a major role. Expression of several genes encoding proteins involved in energy metabolism were downregulated, indicating possible decreased ATP synthesis. Genes encoding proteins involved in protein translation and post-translational modifications were generally upregulated. These data indicate that following infection with BVDV, changes in gene expression occur that are beneficial for virus replication while placing the cell at a metabolic disadvantage.

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.

The ORF45 protein of Kaposi's sarcoma-associated herpesvirus is associated with purified virions

Kaposi's sarcoma-associated herpesvirus (KSHV) ORF45 is encoded by an immediate-early gene in the KSHV genome. This protein was recently shown to interact with interferon regulatory factor 7 and inhibit virus-mediated alpha/beta interferon induction (Zhu et al., Proc. Natl. Acad. Sci. USA 99:5573-5578, 2002). ORF45 was characterized as a phosphorylated protein, and it is localized in the cytoplasm of infected cells. In this report, we provide evidence that ORF45 is associated with KSHV virions. (i) ORF45 was detected in gradient-purified virions by Western blotting along with known structural proteins of KSHV including gB, K8.1, and major capsid protein. In contrast, ORF50/Rta, K8alpha, and ORF59/PF8 were not detected in the same virion preparation. (ii) ORF45 comigrates with KSHV virions in sucrose gradient ultracentrifugation. (iii) Virion-associated ORF45 was resistant to trypsin digestion but became sensitive after the virions were treated with detergent which destroys the viral envelope. (iv) ORF45 remained associated with tegument-nucleocapsid complex when virion-specific glycoproteins were removed after detergent treatment. (v) An ORF45 protein band was visualized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of extensively purified KSHV virions and identified by mass spectrometry. (vi) By immunoelectron microscopy, virus-like structures were specifically stained by anti-ORF45 antibody. Based on the evidence, we conclude that ORF45 is associated with purified KSHV virions and appears to be a tegument protein. The presence of ORF45 in KSHV virions raised the possibility that this protein may be delivered to host cells at the start of infection and therefore have the opportunity to act at the very early stage of the infection, suggesting an important role of ORF45 in KSHV primary infection.

Leaf vitamin C contents modulate plant defense transcripts and regulate genes that control development through hormone signaling

Vitamin C deficiency in the Arabidopsis mutant vtc1 causes slow growth and late flowering. This is not attributable to changes in photosynthesis or increased oxidative stress. We have used the vtc1 mutant to provide a molecular signature for vitamin C deficiency in plants. Using statistical analysis, we show that 171 genes are expressed differentially in vtc1 compared with the wild type. Many defense genes are activated, particularly those that encode pathogenesis-related proteins. Furthermore, transcript changes indicate that growth and development are constrained in vtc1 by the modulation of abscisic acid signaling. Abscisic acid contents are significantly higher in vtc1 than in the wild type. Key features of the molecular signature of ascorbate deficiency can be reversed by incubating vtc1 leaf discs in ascorbate. This finding provides evidence that many of the observed effects on transcript abundance in vtc1 result from ascorbate deficiency. Hence, through modifying gene expression, vitamin C contents not only act to regulate defense and survival but also act via phytohormones to modulate plant growth under optimal conditions.

Regulation of host cell transcriptional physiology by the avian pneumovirus provides key insights into host-pathogen interactions

Infection with a viral pathogen triggers several pathways in the host cell that are crucial to eliminating infection, as well as those that are used by the virus to enhance its replication and virulence. We have here used suppression subtractive hybridization and cDNA microarray analyses to characterize the host transcriptional response in an avian pneumovirus model of infection. The results of our investigations reveal a dynamic host response that includes the regulation of genes with roles in a vast array of cellular functions as well as those that have not been described previously. The results show a considerable upregulation in transcripts representing the interferon-activated family of genes, predicted to play a role in virus replication arrest. The analysis also identified transcripts for proinflammatory leukocyte chemoattractants, adhesion molecules, and complement that were upregulated and may account for the inflammatory pathology that is the hallmark of viral respiratory infection. Interestingly, alterations in the transcription of several genes in the ubiquitin and endosomal protein trafficking pathways were observed, suggesting a role for these pathways in virus maturation and budding. Taken together, the results of our investigations provide key insights into individual genes and pathways that constitute the host cell's response to avian pneumovirus infection, and they have enabled the development of resources and a model of host-pathogen interaction for an important avian respiratory tract pathogen.

The human cytomegalovirus UL82 gene product (pp71) accelerates progression through the G1 phase of the cell cycle

As viruses are reliant upon their host cell to serve as proper environments for their replication, many have evolved mechanisms to alter intracellular conditions to suit their own needs. For example, human cytomegalovirus induces quiescent cells to enter the cell cycle and then arrests them in late G(1), before they enter the S phase, a cell cycle compartment that is presumably favorable for viral replication. Here we show that the protein product of the human cytomegalovirus UL82 gene, pp71, can accelerate the movement of cells through the G(1) phase of the cell cycle. This activity would help infected cells reach the late G(1) arrest point sooner and thus may stimulate the infectious cycle. pp71 also induces DNA synthesis in quiescent cells, but a pp71 mutant protein that is unable to induce quiescent cells to enter the cell cycle still retains the ability to accelerate the G(1) phase. Thus, the mechanism through which pp71 accelerates G(1) cell cycle progression appears to be distinct from the one that it employs to induce quiescent cells to exit G(0) and subsequently enter the S phase.

HCMV glycoprotein US6 mediated inhibition of TAP does not affect HLA-E dependent protection of K-562 cells from NK cell lysis

Human cytomegalovirus has evolved multiple strategies to interfere with immune recognition by the host. A variety of mechanisms affect antigen presentation by major histocompatibility complex class I molecules resulting in a reduced class I cell-surface expression. This downregulation is expected to trigger natural killer (NK) cytotoxicity, requiring counteraction by the virus to establish long-term infection. Here we describe that the human cytomegalovirus gpUS6 protein, which has been demonstrated to downregulate the expression of human leukocyte antigen (HLA) class I and the presentation of cytotoxic T lymphocyte epitopes by blocking transporter associated with antigen presentation (TAP function), does not affect the ability of HLA-E to inhibit NK cell mediated lysis of K-562 cells by interaction with CD94/NKG2A expressed on NK cells. Cell surface expression and function of HLA-E is not altered although gpUS6 inhibits TAP-dependent peptide transport by 95%. Moreover, HLA-E molecules presenting HLA class I signal sequence-derived peptides are functionally detectable on transfected TAP-deficient RMA-S cells.

Human cytomegalovirus UL37 immediate early target minigene RNAs are accurately spliced and polyadenylated

The human cytomegalovirus (HCMV) UL36-38 immediate early (IE) locus encodes proteins required for virus growth. The UL37 IE promoter drives production of differentially spliced and unspliced RNAs. To study their post-transcriptional processing, we generated target minigenes encoding each UL37 RNA splicing substrate. Target 1 RNA, spanning UL37 exon 1 (x1) donor and 2 (x2) acceptor as well as adjacent intronic sequences, but not the UL38 gene, accurately reproduced UL37 x1/x2 RNA splicing in transfected permissive cells. Surprisingly, deletion of distal intronic sequences nt -82 to -143 from the UL37x2 acceptor resulted in aberrant splicing to an upstream non-consensus exonic donor. Target 1 RNAs carry the UL37x1 polyadenylation (PA) signal and site as well as a downstream SV40 early PA signal. Both the UL37x1 and SV40 PA signals are used in wild-type target 1 RNAs but inhibited in UL37x1 PA signal mutants. Alternative RNA splicing of UL37 exons 2 to 3 or 3A as well as exons 3 to 4, observed in HCMV mature UL37 and UL36 spliced RNAs, is accurately reproduced with target minigene RNAs carrying the corresponding UL37 exonic and intronic sequences. Moreover, alternative splicing using two novel UL37 exon 3 consensus splice donors (di and dii) was found in target and in HCMV-infected cell RNA. These results demonstrate that: (i) target minigene RNAs accurately recapitulate the processing of UL37 IE RNAs in the HCMV-infected cell; (ii) precise UL37x1 donor selection is modulated by 3'-distal UL37 intronic sequences; and (iii) UL37 exon 3 contains multiple alternative consensus splice donors.

Expression of interferon inducible genes following Hantaan virus infection as a mechanism of resistance in A549 cells

Hantaan virus (HTN) is a causative agent of hemorrhagic fever with renal syndrome (HFRS). Little is known of its pathogenesis or the molecular mechanisms underlying resistance to HTN infection. In the present study, DNA microarray technology was used to monitor changes in mRNA levels after HTN infection, to elucidate resistance mechanisms to viral infection by understanding virus-host interactions. We found that several interferon (IFN)-inducible genes were up-regulated in host cells infected with HTN. According to previous available data, IFNs have been reported to be inhibitory, but their mode of action has not been yet clear. In this study, the 2',5'-oligoadenylated synthetase (OAS) and Mx1 genes, not a double-stranded RNA-dependent protein kinase R (PKR), of the IFN response pathways are associated with antiviral activity during HTN infection. Furthermore, A549 cells treated with IFN-alpha were protected against HTN infection. Taken together, these results confirmed that IFN plays a role in cellular defenses against HTN infection at an early stage of the infection and revealed the resistance mechanism for HTN infection.

Strategies for the identification and analysis of viral immune-evasive genes--cytomegalovirus as an example

Co-evolution of herpesviruses with their hosts has resulted in multiple interactions between viral genes and cellular functions. Some interactions control genomic maintenance and replication in specific tissues, other affect the immune control at various stages. Few immunomodulatory functions of genes can be predicted by sequence homology. The majority of genes with immunomodulatory properties only become apparent in functional assays. This chapter reviews procedures which have been used for successful identification of immunomodulatory genes in the past and deals with recent methods which may be applicable for the identification of additional immunomodulatory functions unknown so far.

Human cytomegalovirus gene expression during infection of primary hematopoietic progenitor cells: a model for latency

Human cytomegalovirus (HCMV) resides latently in hematopoietic cells of the bone marrow. Although viral genomes can be found in CD14+ monocytes and CD34+ progenitor cells, the primary reservoir for latent cytomegalovirus is unknown. We analyzed human hematopoietic subpopulations infected in vitro with a recombinant virus that expresses a green fluorescent protein marker gene. Although many hematopoietic cell subsets were infected in vitro, CD14+ monocytes and various CD34+ subpopulations were infected with the greatest efficiency. We have developed an in vitro system in which to study HCMV infection and latency in CD34+ cells cultured with irradiated stromal cells. Marker gene expression was substantially reduced by 4 days postinfection, and infectious virus was not made during the culture period. However, viral DNA sequences were maintained in infected CD34+ cells for >20 days in culture, and, importantly, virus replication could be reactivated by coculture with human fibroblasts. Using an HCMV gene array, we examined HCMV gene expression in CD34+ cells. The pattern of viral gene expression was distinct from that observed during productive or nonproductive infections. Some of these expressed viral genes may function in latency and are targets for further analysis. Altered gene expression in hematopoietic progenitors may be indicative of the nature and outcome of HCMV infection.

Cell cycle arrest by human cytomegalovirus 86-kDa IE2 protein resembles premature senescence

Primary human embryo lung fibroblasts and adult diploid fibroblasts infected by the human cytomegalovirus (HCMV) display beta-galactosidase (beta-Gal) activity at neutral pH (senescence-associated beta-Gal [SA-beta-Gal] activity) and overexpression of the plasminogen activator inhibitor type 1 (PAI-1) gene, two widely recognized markers of the process designated premature cell senescence. This activity is higher when cells are serum starved for 48 h before infection, a process that speeds and facilitates HCMV infection but that is insufficient by itself to induce senescence. Fibroblasts infected by HCMV do not incorporate bromodeoxyuridine, a prerequisite for the formal definition of senescence. At the molecular level, cells infected by HCMV, beside the accumulation of large amounts of the cell cycle regulators p53 and pRb, the latter in its hyperphosphorylated form, display a strong induction of the cyclin-dependent kinase inhibitor (cdki) p16(INK4a), a direct effector of the senescence phenotype in fibroblasts, and a decrease of the cdki p21(CIP1/WAF). Finally, a replicative senescence state in the early phases of infection significantly increased the number of cells permissive to virus infection and enhanced HCMV replication. HCMV infection assays carried out in the presence of phosphonoformic acid, which inhibits the virus DNA polymerase and the expression of downstream genes, indicated that immediate-early and/or early (alpha) genes are sufficient for the induction of SA-beta-Gal activity. When baculovirus vectors expressing HCMV IE1-72 or IE2-86 proteins were inoculated into fibroblasts, the increase of p16(INK4a) (observed predominantly with IE2-86) was similar to that observed with the whole virus, as was the induction of SA-beta-Gal activity, suggesting that the viral IE2 gene leads infected cells into senescence. Altogether our results demonstrate for the first time that HCMV, after arresting the cell cycle and inhibiting apoptosis, triggers the cellular senescence program, probably through the p16(INK4a) and p53 pathways.

Genetic determinants of coxsackievirus B3 pathogenesis

The development of high throughput genomic and bioinformatic analysis tools, coupled with established molecular techniques, has allowed new insights into the pathogenesis of infectious diseases. In humans, coxasackievirus B3 (CVB3) is the primary etiological agent of viral myocarditis, an inflammatory disease process involving the heart muscle. Early host cellular survival and apoptotic mechanisms during viral infections, as well as immune events, affect myocarditis progression and outcome. Therefore, our laboratory has been keenly interested in infectomics, defined here as the transcriptional events of both virus and host. We first elucidated up- or downregulated transcriptional activities in CVB3-infected hearts by mRNA differential display. Further characterization of these regulated genes including Nip21, IP10, and IGTPase, and study of their role in CVB3-infection are underway. In further dissection of the stages of myocarditis-peak viremia, inflammatory infiltration and tissue repair-we used cDNA microarrays to probe differential gene expression in the myocardium following virus infection. Following virus infection, there are global decreases in metabolic and mitochondrial genes, increases in signaling genes and distinctive patterns in other functional groups. To establish early gene expression profiles in infected cells by themselves, we also used oligonucleotide arrays in an in vitro model of CVB3 infection. Notably, we have found increased expression of transcription factors c-fos and c-jun down-stream of extracellular signal-related kinase, a pathway which is crucial for virus replication and pathogenesis. Our investigations based on gene profiling following CVB3 infection have thus far been fruitful in providing new experimental leads. High throughput genetic analysis has allowed us to simultaneously try on greater than 12,000 potential genetic "glass slippers." Our in vitro experimental plan has enabled us to chart prominent patterns of gene expression, analyzed by novel bioinformatic approaches, and to separate varied and potentially significant gene expression events.

General and specific alterations in programming of global viral gene expression during infection by VP16 activation-deficient mutants of herpes simplex virus type 1

During productive infection by herpes simplex virus 1 (HSV-1), viral gene expression occurs in a temporally regulated cascade in which transcription of the viral immediate-early (IE) genes is strongly stimulated by the virion protein VP16. We have employed an oligonucleotide microarray to examine the effect of VP16 mutations on the overall pattern of viral gene expression following infection of HeLa cells. This microarray detects essentially all HSV-1 transcripts with relative and absolute levels correlating well with known kinetics of expression. This analysis revealed that deletion of the VP16 activation domain sharply reduced overall viral gene expression; moreover, the pattern of this reduced expression varied greatly from the pattern of a wild-type (wt) infection. However, when this mutant virus was delivered at a high multiplicity of infection or in the presence of the cellular stress inducer hexamethylene bisacetamide, expression was largely restored to the wt levels and pattern. Infection with virions that deliver wt VP16 protein at the start of infection but synthesize only truncated VP16 resulted in a normal kinetic cascade. This suggests that newly synthesized VP16 does not play a significant role in the expression of later classes of transcripts. The VP16 activation domain comprises two subregions. Deletion of the C-terminal subregion resulted in minimal changes in the level and profile of gene expression compared to a normal (wt) cascade. In contrast, deletion of the N-terminal subregion reduced the overall expression levels and skewed the relative levels of IE transcripts but did not significantly alter the kinetic pattern of early and late transcript expression. We conclude that the general activation of IE gene transcription by VP16, but not the specific ratios of IE transcripts, is necessary for the subsequent ordered expression of viral genes. Moreover, this report establishes the feasibility of microarray analysis for globally assessing viral gene expression programs as a function of the conditions of infection.

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.

Age-dependent resistance to lethal alphavirus encephalitis in mice: analysis of gene expression in the central nervous system and identification of a novel interferon-inducible protective gene, mouse ISG12

Several different mammalian neurotropic viruses produce an age-dependent encephalitis characterized by more severe disease in younger hosts. To elucidate potential factors that contribute to age-dependent resistance to lethal viral encephalitis, we compared central nervous system (CNS) gene expression in neonatal and weanling mice that were either mock infected or infected intracerebrally with a recombinant strain, dsTE12Q, of the prototype alphavirus Sindbis virus. In 1-day-old mice, infection with dsTE12Q resulted in rapidly fatal disease associated with high CNS viral titers and extensive CNS apoptosis, whereas in 4-week-old mice, dsTE12Q infection resulted in asymptomatic infection with lower CNS virus titers and undetectable CNS apoptosis. GeneChip expression comparisons of mock-infected neonatal and weanling mouse brains revealed developmental regulation of the mRNA expression of numerous genes, including some apoptosis regulatory genes, such as the proapoptotic molecules caspase-3 and TRAF4, which are downregulated during development, and the neuroprotective chemokine, fractalkine, which is upregulated during postnatal development. In parallel with increased neurovirulence and increased viral replication, Sindbis virus infection in 1-day-old mice resulted in both a greater number of host inflammatory genes with altered expression and greater changes in levels of host inflammatory gene expression than infection in 4-week-old mice. Only one inflammatory response gene, an expressed sequence tag similar to human ISG12, increased by a greater magnitude in infected 4-week-old mouse brains than in infected 1-day-old mouse brains. Furthermore, we found that enforced neuronal ISG12 expression results in a significant delay in Sindbis virus-induced death in neonatal mice. Together, our data identify genes that are developmentally regulated in the CNS and genes that are differentially regulated in the brains of different aged mice in response to Sindbis virus infection.

Expression profiling confirms the role of endocytic receptor megalin in renal vitamin D3 metabolism

BACKGROUND

The endocytic receptor megalin constitutes the major pathway for clearance of low-molecular weight plasma proteins from the glomerular filtrate into the renal proximal tubules. Furthermore, the receptor has been implicated in a number of other functions in the kidney including uptake and activation of 25-(OH) vitamin D3, calcium and sodium reabsorption as well as signal transduction.

METHODS

We used genome-wide expression profiling by microarray technology to detect changes in the gene expression pattern in megalin knockout mouse kidneys and to uncover some of the renal pathways affected by megalin deficiency.

RESULTS

Alterations were identified in several (patho)physiologic processes in megalin-deficient kidneys including the renal vitamin D metabolism, transforming growth factor (TGF)-beta1 signal transduction, lipid transport and heavy metal detoxification. Most importantly, changes were detected in the mRNA levels of 25-(OH) vitamin D-24-hydroxylase and 25-(OH) vitamin D-1alpha-hydroxylase as well as strong up-regulation of TGF-beta1 target genes. Both findings indicate plasma vitamin D deficiency and lack of vitamin D signaling in renal tissues.

CONCLUSIONS

Expression profiling confirms a crucial role for megalin in renal vitamin D metabolism.

Activation and inhibition of virus and interferon: the herpesvirus story

Viral infection of a host leads to induction of an immune system attack against the virus along with a counterattack by the virus against the host. Interferons are highly upregulated upon viral infection and function as key regulators of the host innate defense system. Whereas many RNA viruses are sensitive to the effects of interferon, several of the large DNA viruses are relatively resistant, given their capacity to encode proteins that disarms the host response. The herpesvirus family is a large and diverse family of viruses that infects vertebrates and invertebrates and possesses the ability to remain latent in their host for life. This paper summarizes the relationship between herpesviruses and interferon, including the ability of herpesviruses to induce interferon production, mechanisms by which interferon decreases herpesvirus replication, and strategies of herpesviruses to counteract these mechanisms.

IRF3 mediates a TLR3/TLR4-specific antiviral gene program

We have identified a subset of genes that is specifically induced by stimulation of TLR3 or TLR4 but not by TLR2 or TLR9. Further gene expression analyses established that upregulation of several primary response genes was dependent on NF-kappaB, commonly activated by several TLRs, and interferon regulatory factor 3 (IRF3), which was found to confer TLR3/TLR4 specificity. Also identified was a group of secondary response genes which are part of an autocrine/paracrine loop activated by the primary response gene product, interferon beta (IFNbeta). Selective activation of the TLR3/TLR4-IRF3 pathway potently inhibited viral replication. These results suggest that TLR3 and TLR4 have evolutionarily diverged from other TLRs to activate IRF3, which mediates a specific gene program responsible for innate antiviral responses.

Survey of transcript expression in rainbow trout leukocytes reveals a major contribution of interferon-responsive genes in the early response to a rhabdovirus infection

Virus infections induce changes in the expression of host cell genes. A global knowledge of these modifications should help to better understand the virus/host cell interactions. To obtain a more comprehensive view of the rainbow trout response to a viral infection, we used the subtractive suppressive hybridization methodology in the viral hemorrhagic septicemia model of infection. We infected rainbow trout leukocytes with viral hemorrhagic septicemia virus (VHSV), and total RNA from infected and mock-infected cells was compared at 40 h postinfection. Twenty-four virus-induced genes were ultimately retrieved from the subtracted cDNA library, and their differential expression was further confirmed by semiquantitative reverse transcription-PCR and Northern blot analysis. Among these sequences, three were already described as VHSV-induced genes. Eight sequences with known homologs were extended to full-length cDNA using 5' and 3' rapid amplification of cDNA ends, and they were subsequently divided into three functional subsets. Four genes were homologous to mammalian interferon responsive genes, three were similar to chemo-attractant molecules (CXC chemokine, galectin), and two had nucleic acid binding domains. All of the virus-induced genes were also induced by rainbow trout interferon, indicating that the interferon pathway is the predominant component of the anti-VHSV response. They were also expressed in vivo in experimentally infected fish, indicating their biological relevance in natural infection.

[GeneChip system from a bioinformatical point of view]

GeneChip (Affymetrix, Inc., USA) employs a specific method for spotting DNA probes on chips, which is different from any other DNA chips, and can complete the whole process from sample preparation to data construction and analysis. The GeneChip system can be applied to both gene expression analysis and genomic mutation analysis, which would play an important role in human genome analysis in the future. Techniques for data construction ("wet" experimental techniques), which are the major components in the GeneChip system, are generally established as routine work in the first screening process in most laboratories worldwide. The most important point would be how we exchange experimental data produced by researchers and gene/genome information available both on the public and the commercial bases so that we reduce useful information on gene expression. Recently, the center of the research has been shifting to computing technology for data processing ("bioinformatics"). This article separately deals with gene expression analysis and genomic analysis, with emphasis on bioinformatics. We describe the data on gene expression screening, the gene targeting process, the analysis of genomic DNA mutations using the P53 probe array, and the HuSNP mapping assays, by presenting our experimental examples.

Epstein-Barr virus reactivation after superinfection of the BJAB-B1 and P3HR-1 cell lines with cytomegalovirus

BACKGROUND

Studies examining herpesvirus-herpesvirus (cytomegalovirus (CMV)-Epstein-Barr virus (EBV)) interactions are limited, and many of the studies have been clinical observations suggesting such an interaction exists. This report aims to examine the in vitro susceptibilities of BJAB-B1 and P3HR-1 cells (EBV positive Burkitt's lymphoma B-cell lines) to a CMV superinfection; and show that EBV reactivation occurs after CMV superinfects these cell lines.

RESULTS

The BJAB-B1 and P3HR-1 cells were observed to be susceptible to a CMV superinfection by detecting the major immediate early (MIE) viral transcript and protein (p52) expression. The BZLF1 transcript was observed in both cell lines superinfected with CMV, indicating EBV reactivation. BZLF1 protein was observed in the BJAB-B1 cells. Antigen detection was not performed in the P3HR-1 cells.

CONCLUSION

The results from the in vitro superinfections support the in vivo studies suggesting a CMV infection is related to an EBV reactivation and suggests that CMV may be important as a co-factor in EBV pathogenesis in the immunocompromised patient.

Identification of NF-kappaB-dependent gene networks in respiratory syncytial virus-infected cells

Respiratory syncytial virus (RSV) is a mucosa-restricted virus that is a leading cause of epidemic respiratory tract infections in children. In epithelial cells, RSV replication activates nuclear translocation of the inducible transcription factor nuclear factor kappaB (NF-kappaB) through proteolysis of its cytoplasmic inhibitor, IkappaB. In spite of a putative role in mediating virus-inducible gene expression, the spectrum of NF-kappaB-dependent genes induced by RSV infection has not yet been determined. To address this, we developed a tightly regulated cell system expressing a nondegradable, epitope-tagged IkappaBalpha isoform (Flag-IkappaBalpha Mut) whose expression could be controlled by exogenous addition of nontoxic concentrations of doxycycline. Flag-IkappaBalpha Mut expression potently inhibited IkappaBalpha proteolysis, NF-kappaB binding, and NF-kappaB-dependent gene transcription in cells stimulated with the prototypical NF-kappaB-activating cytokine tumor necrosis factor alpha (TNF-alpha) and in response to RSV infection. High-density oligonucleotide microarrays were then used to profile constitutive and RSV-induced gene expression in the absence or presence of Flag-IkappaBalpha Mut. Comparison of these profiles revealed 380 genes whose expression was significantly changed by the dominant-negative NF-kappaB. Of these, 236 genes were constitutive (not RSV regulated), and surprisingly, only 144 genes were RSV regulated, representing numerically approximately 10% of the total population of RSV-inducible genes at this time point. Hierarchical clustering of the 144 RSV- and Flag-IkappaBalpha Mut-regulated genes identified two discrete gene clusters. The first group had high constitutive expression, and its expression levels fell in response to RSV infection. In this group, constitutive mRNA expression was increased by Flag-IkappaBalpha Mut expression, and the RSV-induced decrease in expression was partly inhibited. In the second group, constitutive expression was very low (or undetectable) and, after RSV infection, expression levels strongly increased. In this group, NF-kappaB was required for RSV-inducible expression because Flag-IkappaBalpha Mut expression blocked their induction by RSV. This latter cluster includes chemokines, transcriptional regulators, intracellular proteins regulating translation and proteolysis, and secreted proteins (complement components and growth factor regulators). These data suggest that NF-kappaB action induces global cellular responses after viral infection.

Viruses and the type I interferon antiviral system: induction and evasion

The type I interferon (IFN) system responds to viral infection and induces an "antiviral state" in cells, providing an important first line of defense against virus infection. Interaction of type I IFNs (IFN alpha and IFN beta) with their receptor induces hundreds of cellular genes. Of the proteins induced by IFN, the antiviral function of only a few is known, and their mechanisms of action are only partly understood. Additionally, although viral-encoded mechanisms that counteract specific components of the type I IFN response have been known for some time, it has recently become clear that many (if not most) viruses encode some form of IFN-antagonist. Understanding the interplay between viral-encoded IFN antagonists and the interferon response will be essential if the therapeutic potential of IFNs is to be fully exploited.

Transcriptional profiling of interferon regulatory factor 3 target genes: direct involvement in the regulation of interferon-stimulated genes

Ubiquitously expressed interferon regulatory factor 3 (IRF-3) is directly activated after virus infection and functions as a key activator of the immediate-early alpha/beta interferon (IFN) genes, as well as the RANTES chemokine gene. In the present study, a tetracycline-inducible expression system expressing a constitutively active form of IRF-3 (IRF-3 5D) was combined with DNA microarray analysis to identify target genes regulated by IRF-3. Changes in mRNA expression profiles of 8,556 genes were monitored after Tet-inducible expression of IRF-3 5D. Among the genes upregulated by IRF-3 were transcripts for several known IFN-stimulated genes (ISGs). Subsequent analysis revealed that IRF-3 directly induced the expression of ISG56 in an IFN-independent manner through the IFN-stimulated responsive elements (ISREs) of the ISG56 promoter. These results demonstrate that, in addition to its role in the formation of a functional immediate-early IFN-beta enhanceosome, IRF-3 is able to discriminate among ISRE-containing genes involved in the establishment of the antiviral state as a direct response to virus infection.

Infection of cells with human cytomegalovirus during S phase results in a blockade to immediate-early gene expression that can be overcome by inhibition of the proteasome

Cells infected with human cytomegalovirus (HCMV) after commencing DNA replication do not initiate viral immediate-early (IE) gene expression and divide before arresting. To determine the nature of this blockade, we examined cells that were infected 24 h after release from G(0) using immunofluorescence, laser scanning cytometry, and fluorescence-activated cell sorting (FACS) analysis. Approximately 40 to 50% of the cells had 2N DNA content, became IE(+) in the first 12 h, and arrested. Most but not all of the cells with >2N DNA content did not express IE antigens until after mitosis. To define the small population of IE(+) cells that gradually accumulated within the S and G(2)/M compartments, cells were pulsed with bromodeoxyuridine (BrdU) just prior to S-phase infection and analyzed at 12 h postinfection for IE gene expression, BrdU positivity, and cell cycle position. Most of the BrdU(+) cells were IE(-) and had progressed into G(2)/M or back to G(1). The majority of the IE(+) cells in S and G(2)/M were BrdU(-). Only a few cells were IE(+) BrdU(+), and they resided in G(2)/M. Multipoint BrdU pulse-labeling revealed that, compared to cells actively synthesizing DNA at the beginning of the infection, a greater percentage of the cells that initiated DNA replication 4 h later could express IE antigens and proceed into S. Synchronization of the cells with aphidicolin also indicated that the blockade to the activation of IE gene expression was established in cells soon after initiation of DNA replication. It appears that a short-lived protein in S-phase cells may be required for IE gene expression, as it is partially restored by treatment with the proteasome inhibitor MG132.

Gammaherpesvirus lytic gene expression as characterized by DNA array

Gammaherpesviruses are associated with a number of diseases including lymphomas and other malignancies. Murine gammaherpesvirus 68 (MHV-68) constitutes the most amenable animal model for this family of pathogens. However experimental characterization of gammaherpesvirus gene expression, at either the protein or RNA level, lags behind that of other, better-studied alpha- and beta-herpesviruses. We have developed a cDNA array to globally characterize MHV-68 gene expression profiles, thus providing an experimental supplement to a genome that is chiefly annotated by homology. Viral genes started to be transcribed as early as 3 h postinfection (p.i.), and this was followed by a rapid escalation of gene expression that could be seen at 5 h p.i. Individual genes showed their own transcription profiles, and most genes were still being expressed at 18 h p.i. Open reading frames (ORFs) M3 (chemokine-binding protein), 52, and M9 (capsid protein) were particularly noticeable due to their very high levels of expression. Hierarchical cluster analysis of transcription profiles revealed four main groups of genes and allowed functional predictions to be made by comparing expression profiles of uncharacterized genes to those of genes of known function. Each gene was also categorized according to kinetic class by blocking de novo protein synthesis and viral DNA replication in vitro. One gene, ORF 73, was found to be expressed with alpha-kinetics, 30 genes were found to be expressed with beta-kinetics, and 42 genes were found to be expressed with gamma-kinetics. This fundamental characterization furthers the development of this model and provides an experimental basis for continued investigation of gammaherpesvirus pathology.

Potential applications of DNA microarrays in biodefense-related diagnostics

Recent years have witnessed a logarithmic growth in the number of applications involving DNA microarrays. Extrapolation of their use for infectious diagnostics and biodefense-related diagnostics seems obvious. Nevertheless, the application of DNA microarrays to biodefense-related diagnostics will depend on solving a set of substantial, yet approachable, technical and logistical problems that encompass diverse topics from amplification efficiency to bioinformatics.

UL40-mediated NK evasion during productive infection with human cytomegalovirus

Human cytomegalovirus (HCMV) exploits a range of strategies to evade and modulate the immune response. Its capacity to down-regulate MHC I expression was anticipated to render infected cells vulnerable to natural killer (NK) attack. Kinetic analysis revealed that during productive infection, HCMV strain AD169 first enhanced and then inhibited lysis of primary skin fibroblasts by a CD94/NKG2A(+)NKG2D(+)ILT2(+) NK line. The inhibition of cytotoxicity against strain AD169-infected fibroblasts was abolished by prior treatment of targets or effectors with anti-MHC I and anti-CD94 monoclonal antibodies, respectively, implying a CD94/HLA-E-dependent mechanism. An HCMV strain AD169, UL40 deletion mutant could not inhibit CD94/NKG2A(+) NK killing against skin fibroblasts. The contribution of UL40 to evasion of primary NK cells then was tested in a system where targets and effectors were MHC-matched. Primary NK cells activated with IFNalpha as well as cultured primary NK cell lines showed increased killing against DeltaUL40-infected fibroblasts compared with AD169-infected targets. This effect was abrogated by depletion of CD94(+) cells. These findings demonstrate that HCMV encodes a mechanism of evasion specifically targeted against a proportion of CD94(+) NK cells and show that this system functions during a productive infection.

Complementation of vaccinia virus lacking the double-stranded RNA-binding protein gene E3L by human cytomegalovirus

The cellular response to viral infection often includes activation of pathways that shut off protein synthesis and thereby inhibit viral replication. In order to enable efficient replication, many viruses carry genes such as the E3L gene of vaccinia virus that counteract these host antiviral pathways. Vaccinia virus from which the E3L gene has been deleted (VVDeltaE3L) is highly sensitive to interferon and exhibits a restricted host range, replicating very inefficiently in many cell types, including human fibroblast and U373MG cells. To determine whether human cytomegalovirus (CMV) has a mechanism for preventing translational shutoff, we evaluated the ability of CMV to complement the deficiencies in replication and protein synthesis associated with VVDeltaE3L. CMV, but not UV-inactivated CMV, rescued VVDeltaE3L late gene expression and replication. Thus, complementation of the VVDeltaE3L defect appears to depend on de novo CMV gene expression and is not likely a result of CMV binding to the cell receptor or of a virion structural protein. CMV rescued VVDeltaE3L late gene expression even in the presence of ganciclovir, indicating that CMV late gene expression is not required for complementation of VVDeltaE3L. The striking decrease in overall translation after infection with VVDeltaE3L was prevented by prior infection with CMV. Finally, CMV blocked both the induction of eukaryotic initiation factor 2alpha (eIF2alpha) phosphorylation and activation of RNase L by VVDeltaE3L. These results suggest that CMV has one or more immediate-early or early genes that ensure maintenance of a high protein synthetic capacity during infection by preventing activation of the PKR/eIF2alpha phosphorylation and 2-5A oligoadenylate synthetase/RNase L pathways.

Gene expression pattern in Caco-2 cells following rotavirus infection

Rotaviruses are recognized as the leading cause of severe dehydrating diarrhea in infants and young children worldwide. Preventive and therapeutic strategies are urgently needed to fight this pathogen. In tissue culture and in vivo, rotavirus induces structural and functional alterations in the host cell. In order to better understand the molecular mechanisms involved in the events after rotavirus infection, we identified host cellular genes whose mRNA levels changed after infection. For this analysis, we used microarrays containing more than 38,000 human cDNAs to study the transcriptional response of the human intestinal cell line Caco-2 to rotavirus infection. We found that 508 genes were differentially regulated >2-fold at 16 h after rotavirus infection, and only one gene was similarly regulated at 1 h postinfection. Of these transcriptional changes, 73% corresponded to the upregulation of genes, with the majority of them occurring late, at 12 or more hours postinfection. Some of the regulated genes were classified according to known biological function and included genes encoding integral membrane proteins, interferon-regulated genes, transcriptional and translational regulators, and calcium metabolism-related genes. A new picture of global transcriptional regulation in the infected cell is presented and families of genes which may be involved in viral pathogenesis are discussed.

Mechanisms of inhibition of the host interferon alpha/beta-mediated antiviral responses by viruses

Complex multicellular organisms have evolved sophisticated mechanisms to prevent and control infection by pathogens. Among these mechanisms, the type I interferon or interferon alpha/beta system represents one of the first lines of defense against viral infections. Typically, viral infection induces the synthesis and secretion of interferon alpha/beta by the infected cell, which in turn activates signaling pathways leading to an antiviral state. As a counter measure, many viruses have developed intriguing mechanisms to evade the interferon alpha/beta system of the host. In this review, we will summarize recent research developments in this interesting field of virus-host cell interactions.

Feature extraction and normalization algorithms for high-density oligonucleotide gene expression array data

Algorithms for performing feature extraction and normalization on high-density oligonucleotide gene expression arrays, have not been fully explored, and the impact these algorithms have on the downstream analysis is not well understood. Advances in such low-level analysis methods are essential to increase the sensitivity and specificity of detecting whether genes are present and/or differentially expressed. We have developed and implemented a number of algorithms for the analysis of expression array data in a software application, the DNA-Chip Analyzer (dChip). In this report, we describe the algorithms for feature extraction and normalization, and present validation data and comparison results with some of the algorithms currently in use.

Measles virus-induced modulation of host-cell gene expression

The influence of measles virus (MV) infection on gene expression by human peripheral blood mononuclear cells (PBMCs) was examined with cDNA microarrays. The mRNA levels of more than 3000 cellular genes were compared between uninfected PBMCs and cells infected with either the Edmonston MV strain or a wild-type MV isolate. The MV-induced upregulation of individual genes identified by microarray analyses was confirmed by RT-PCR. In the present study, a total of 17 genes was found to be upregulated by MV infection. The Edmonston strain grew better in the PBMC cultures than the wild-type MV, and the Edmonston strain was a stronger inducer of the upregulated host cell genes than the wild-type virus. The anti-apoptotic B cell lymphoma 3 (Bcl-3) protein and the transcription factor NF-kappaB p52 subunit were upregulated in infected PBMCs both at the mRNA and at the protein level. Several genes of the interferon system including that for interferon regulatory factor 7 were upregulated by MV. The genes for a number of chaperones, transcription factors and other proteins of the endoplasmic reticulum stress response were also upregulated. These included the gene for the pro-apoptotic and growth arrest-inducing CHOP/GADD153 protein. Thus, the present study demonstrated the activation by MV of cellular mechanisms and pathways that may play a role in the pathogenesis of measles.

The use of DNA array technology in studies of ocular viral pathogenesis

DNA arrays can be used to simultaneously analyze the expression of hundreds of genes and permit systematic approaches to biological discovery with a potentially profound impact on genomics, pharmacogenomics, and proteomics. Microarrays have been used to study host-pathogen interactions, and recently this technology has been applied to investigate host-virus interactions. DNA arrays are used to monitor host alterations in several virus-induced cancers and upon infection with wild-type or modified viruses, or viral gene products. Alternatively, viral chips are used to characterize the transcriptional program of pathogenic viruses and in antiviral drug screening and drug resistance. With an aim to extend the use of this technology to ocular research, and specifically to study changes in host cell transcription in ocular adenovirus infection, we used a commercial array to compare adenovirus-infected human corneal cells to mock-infected cells. Of the 1176 genes analyzed, 72 genes associated with cell cycle regulation, apoptosis, oncogenesis, transcription, signaling, and inflammation were differentially regulated. In this review we summarize the use of DNA arrays in the study of viral infections and suggest potential uses of the technology in ocular viral pathogenesis research.

Altered patterns of cellular gene expression in dermal microvascular endothelial cells infected with Kaposi's sarcoma-associated herpesvirus

Kaposi's sarcoma (KS)-associated herpesvirus (KSHV; also called human herpesvirus 8) is believed to be the etiologic agent of Kaposi's sarcoma, multicentric Castleman's disease, and AIDS-associated primary effusion lymphoma. KSHV infection of human dermal microvascular endothelial cells (DMVEC) in culture results in the conversion of cobblestone-shaped cells to spindle-shaped cells, a characteristic morphological feature of cells in KS lesions. All spindle-shaped cells in KSHV-infected DMVEC cultures express the latency-associated nuclear protein LANA1, and a subfraction of these cells undergo spontaneous lytic cycle induction that can be enhanced by tetradecanoyl phorbol acetate (TPA) treatment. To study the cellular response to infection by KSHV, we used two different gene array screening systems to examine the expression profile of either 2,350 or 9,180 human genes in infected compared to uninfected DMVEC cultures in both the presence and absence of TPA. In both cases, between 1.4 and 2.5% of the genes tested were found to be significantly upregulated or downregulated. Further analysis by both standard and real-time reverse transcription-PCR procedures directly confirmed these results for 14 of the most highly upregulated and 13 of the most highly downregulated genes out of a total of 37 that were selected for testing. These included strong upregulation of interferon-responsive genes such as interferon response factor 7 (IRF7) and myxovirus resistance protein R1, plus upregulation of exodus 2 beta-chemokine, RDC1 alpha-chemokine receptor, and transforming growth factor beta3, together with strong downregulation of cell adhesion factors alpha(4)-integrin and fibronectin plus downregulation of bone morphogenesis protein 4, matrix metalloproteinase 2, endothelial plasminogen activator inhibitor 1, connective tissue growth factor, and interleukin-8. Significant dysregulation of several other cytokine-related genes or receptors, as well as endothelial cell and macrophage markers, and various other genes associated with angiogenesis or transformation was also detected. Western immunoblot and immunohistochemical analyses confirmed that the cellular IRF7 protein levels were strongly upregulated during the early lytic cycle both in KSHV-infected DMVEC and in the body cavity-based lymphoma BCBL1 PEL cell line.

Inhibition of cyclooxygenase 2 blocks human cytomegalovirus replication

Cyclooxygenase 2 (COX-2) mRNA, protein, and activity are transiently induced after infection of human fibroblasts with human cytomegalovirus. Prostaglandin E(2), the product of COX-2 activity, is transiently increased by a factor of >50 in cultures of virus-infected fibroblasts. Both specific (BMS-279652, 279654, and 279655) and nonspecific (indomethacin) COX-2 inhibitors can abrogate the virus-mediated induction of prostaglandin E(2) accumulation. Levels of COX-2 inhibitors that completely block the induction of COX-2 activity, but do not compromise cell viability, reduce the yield of human cytomegalovirus in human fibroblasts by a factor of >100. Importantly, the yield of infectious virus can be substantially restored by the addition of prostaglandin E(2) together with the inhibitory drug. This finding argues that elevated levels of prostaglandin E(2) are required for efficient replication of human cytomegalovirus in fibroblasts. COX-2 inhibitors block the accumulation of immediate-early 2 mRNA and protein, but have little effect on the levels of immediate-early 1 mRNA and protein. Viral DNA replication and the accumulation of some, but not all, early and late mRNAs are substantially blocked by COX-2 inhibitors. Elevated levels of prostaglandin E(2) apparently facilitate the production of immediate-early 2 protein. The failure to produce normal levels of this critical viral regulatory protein in the presence of COX-2 inhibitors might block normal progression beyond the immediate-early phase of human cytomegalovirus infection.

Tumor control in a model of bone marrow transplantation and acute liver-infiltrating B-cell lymphoma: an unpredicted novel function of cytomegalovirus

Tumor relapse and cytomegalovirus (CMV) infection are major concerns in the therapy of hematopoietic malignancies by bone marrow transplantation (BMT). Little attention so far has been given to a possible pathogenetic interplay between CMV and lymphomas. CMV inhibits stem cell engraftment and hematopoietic reconstitution. Thus, by causing maintenance of bone marrow aplasia and immunodeficiency, CMV could promote tumor relapse. Alternatively, CMV could aid tumor remission. One might think of cytopathogenic infection of tumor cells, induction of apoptosis or inhibitory cytokines, interference with tumor cell extravasation or tumor vascularization, or bystander stimulation of an antitumoral immune response. To approach these questions, the established model of experimental BMT and murine CMV infection was extended by the introduction of liver-infiltrating, highly tumorigenic variant clone E12E of BALB/c-derived B-cell lymphoma A20. We document a remarkable retardation of lymphoma progression. First-guess explanations were ruled out: (i) lymphoma cells were not infected; (ii) lymphoma cells located next to infected hepatocytes did not express executioner caspase 3 but were viable and proliferated; (iii) an inhibitory effect of virus on the formation of tumor nodules in the liver became apparent by day 7 after BMT, long before the reconstitution of immune cells; and (iv) recombinant tumor necrosis factor alpha (TNF-alpha) did not substitute for virus; accordingly anti-TNF-alpha did not prevent the inhibition. Notably, while the antitumoral effect required replicative virus, prevention of cytopathogenic infection of the liver by antiviral CD8 T cells did not abolish lymphoma control. These findings are paradigmatic for a novel virus-associated antitumoral mechanism distinct from oncolysis.

Application of genome-wide gene expression profiling by high-density DNA arrays to the treatment and study of inflammatory bowel disease

Identification of factors involved in the initiation, amplification, and perpetuation of the chronic immune response and the identification of markers for the characterization of patient subgroups remain critical objectives for ongoing research in inflammatory bowel disease (IBD). The Human Genome Project and the development of the expressed sequence tag (EST) clone collection and database have made possible a new revolution in gene expression analysis. Instead of measuring one or a few genes, parallel DNA microarrays are capable of simultaneously measuring expression of thousands of genes, providing a glimpse into the logic and functional grouping of gene programs encoded by our genome. Applied to clinical specimens from affected and normal individuals, this methodology has the potential to provide a new level of information about disease pathogenesis not previously possible. Two dominant platforms for the construction of high-density microarrays have emerged: cDNA arrays and GeneChips. The first involves robotic spotting of DNA molecules, often derived from EST clone collections, onto a suitable solid phase matrix such as a glass slide. The second involves direct in situ synthesis of sets of gene-specific oligonucleotides on a silicon wafer by an eloquent derivative of the photolithography process. Both cDNA and oligonucleotide arrays are interrogated by hybridization with a fluorescent-labeled cDNA or cRNA representation of the original tissue mRNA. This enables measurement of the expression levels for thousands of mucosal genes in a single experiment. These technologies have recently become less expensive and more widely accessible to all researchers. This review details the principles and methods behind DNA array technology, data analysis and mining, and potential application to research and treatment of IBD.

The human cytomegalovirus UL35 gene encodes two proteins with different functions

The human cytomegalovirus (HCMV) virion is a complex structure that contains at least 30 proteins, many of which have been identified. We determined that the HCMV UL35 gene encodes two proteins, including a previously unidentified virion protein. A 22-kDa phosphoprotein (ppUL35(A)) was translated from a 1.2-kb UL35 transcript by 4 h postinfection; a second phosphoprotein of 75 kDa (ppUL35) was translated from a 2.2-kb transcript predominantly late in infection. The 22-kDa protein localized to the nucleus, while the 75-kDa protein localized to the juxtanuclear compartment and was packaged into virion particles. The 22-kDa protein was identical to the COOH-terminal end of the 75-kDa protein but was not found in virions, thus defining the NH(2)-terminal portion of the 75-kDa protein as essential for packaging. Expression of the 22-kDa protein inhibited activation of the major immediate-early promoter by ppUL82 (pp71), suggesting that the UL35 22-kDa protein may modulate expression of the major immediate-early gene.

Impact of viral infection on the gene expression profiles of proliferating normal human peripheral blood mononuclear cells infected with HIV type 1 RF

Exploiting the power of high-density gene arrays, the simultaneous expression analysis of 5600 cellular genes was executed on proliferating peripheral blood mononuclear cells (PBMCs) from three normal human donors that were infected in vitro with the T cell tropic laboratory strain of HIV-1, RF. Profiles of expressed genes were assessed at 1, 12, 24, 48, and 72 hr postinfection and compared with those of matched uninfected PBMCs. Viral infection resulted in an overall increase in the number of genes expressed with peaks of expression at 1, 12, and 48 hr postinfection. Functional clustering of genes whose expression level in infected PBMCs varied by 2-fold or greater from levels in the controls indicated that cellular activation markers, proteins associated with immune cell function and with transcription and translation, exhibited increased expression subsequent to viral infection. Gene families exhibiting a decline in gene expression were confined to the 72 hr time point and included genes associated with catabolism and a subset of genes involved with cell signaling and synthetic pathways. Self-organizing map (SOM) cluster analysis identified temporal patterns of coordinated gene expression in infected PBMCs including genes associated with the immune response, the cytoskeleton, and ribosomal subunit structural proteins required for protein synthesis.

Novel vacuolar H+-ATPase complexes resulting from overproduction of Vma5p and Vma13p

The vacuolar H(+)-ATPase (V-ATPase) is a multisubunit complex composed of two sectors: V(1), a peripheral membrane sector responsible for ATP hydrolysis, and V(0), an integral membrane sector that forms a proton pore. Vma5p and Vma13p are V(1) sector subunits that have been implicated in the structural and functional coupling of the V-ATPase. Cells overexpressing Vma5p and Vma13p demonstrate a classic Vma(-) growth phenotype. Closer biochemical examination of Vma13p-overproducing strains revealed a functionally uncoupled V-ATPase in vacuolar vesicles. The ATP hydrolysis rate was 72% of the wild-type rate; but there was no proton translocation, and two V(1) subunits (Vma4p and Vma8p) were present at lower levels. Vma5p overproduction moderately affected both V-ATPase activity and proton translocation without affecting enzyme assembly. High level overexpression of Vma5p and Vma13p was lethal even in wild-type cells. In the absence of an intact V(0) sector, overproduction of Vma5p and Vma13p had a more detrimental effect on growth than their deletion. Overproduced Vma5p associated with cytosolic V(1) complexes; this association may cause the lethality.

Immediate/early response to Trypanosoma cruzi infection involves minimal modulation of host cell transcription

Host cell infection by the intracellular pathogen, Trypanosoma cruzi, involves activation of signaling pathways, cytoskeletal reorganization, and targeted recruitment of host cell lysosomes. To determine the consequences of T. cruzi invasion on host cell gene expression, high density microarrays consisting of approximately 27,000 human cDNAs were hybridized with fluorescent probes generated from T. cruzi-infected human fibroblasts (HFF) at early time points following infection (2-24 h). Surprisingly, no genes were induced > or =2-fold in HFF between 2 and 6 h post-infection (hpi) in repeated experiments while immediate repression of six host cell transcripts was observed. A significant increase in transcript abundance for 106 host cell genes was observed at 24 hpi. Among the most highly induced is a set of interferon-stimulated genes, indicative of a type I interferon (IFN) response to T. cruzi. In support of this, T. cruzi-infected fibroblasts begin to secrete IFNbeta at 18 hpi following the induction of IFNbeta transcripts. As compared with global transcriptional responses evoked by other intracellular pathogens, T. cruzi is a stealth parasite that elicits few changes in host cell transcription during the initiation of infection.