Gene array analysis reveals changes in peripheral nervous system gene expression following stimuli that result in reactivation of latent herpes simplex virus type 1: induction of transcription factor Bcl-3

How Rheumatoid Arthritis Can Result from Provocation of the Immune System by Microorganisms and Viruses

The pathogenesis of rheumatoid arthritis (RA), similar to development of a majority of inflammatory and autoimmune disorders, is largely due to an inappropriate or inadequate immune response to environmental challenges. Among these challenges, infectious agents are the undisputed leaders. Since the 1870s, an impressive list of microorganisms suspected of provoking RA has formed, and the list is still growing. Although a definite causative link between a specific infectious agent and the disease has not been established, several arguments support such a possibility. First, in the absence of a defined pathogen, the spectrum of triggering agents may include polymicrobial communities or the cumulative effect of several bacterial/viral factors. Second, the range of infectious episodes (i.e., clinical manifestations caused by pathogens) may vary in the process of RA development from preclinical to late-stage disease. Third, infectious agents might not trigger RA in all cases, but trigger it in a certain subset of the cases, or the disease onset may arise from an unfortunate combination of infections along with, for example, psychological stress and/or chronic joint tissue microtrauma. Fourth, genetic differences may have a role in the disease onset. In this review, two aspects of the problem of “microorganisms and RA” are debated. First, is there an acquired immune deficiency and, in turn, susceptibility to infections in RA patients due to the too frequent and too lengthy infections, which at last break the tolerance of self antigens? Or, second, is there a congenital deficiency in tolerance and inflammation control, which may occur even with ordinary infection frequency and duration?

Cellular transcription factors induced in trigeminal ganglia during dexamethasone-induced reactivation from latency stimulate bovine herpesvirus 1 productive infection and certain viral promoters

Bovine herpesvirus 1 (BHV-1), an alphaherpesvirinae subfamily member, establishes latency in sensory neurons. Elevated corticosteroid levels, due to stress, reproducibly triggers reactivation from latency in the field. A single intravenous injection of the synthetic corticosteroid dexamethasone (DEX) to latently infected calves consistently induces reactivation from latency. Lytic cycle viral gene expression is detected in sensory neurons within 6 h after DEX treatment of latently infected calves. These observations suggested that DEX stimulated expression of cellular genes leads to lytic cycle viral gene expression and productive infection. In this study, a commercially available assay-Bovine Gene Chip-was used to compare cellular gene expression in the trigeminal ganglia (TG) of calves latently infected with BHV-1 versus DEX-treated animals. Relative to TG prepared from latently infected calves, 11 cellular genes were induced more than 10-fold 3 h after DEX treatment. Pentraxin three, a regulator of innate immunity and neurodegeneration, was stimulated 35- to 63-fold after 3 or 6 h of DEX treatment. Two transcription factors, promyelocytic leukemia zinc finger (PLZF) and Slug were induced more than 15-fold 3 h after DEX treatment. PLZF or Slug stimulated productive infection 20- or 5-fold, respectively, and Slug stimulated the late glycoprotein C promoter more than 10-fold. Additional DEX-induced transcription factors also stimulated productive infection and certain viral promoters. These studies suggest that DEX-inducible cellular transcription factors and/or signaling pathways stimulate lytic cycle viral gene expression, which subsequently leads to successful reactivation from latency in a small subset of latently infected neurons.

A limited innate immune response is induced by a replication-defective herpes simplex virus vector following delivery to the murine central nervous system

Herpes simplex virus type 1 (HSV-1)-based vectors readily transduce neurons and have a large payload capacity, making them particularly amenable to gene therapy applications within the central nervous system (CNS). Because aspects of the host responses to HSV-1 vectors in the CNS are largely unknown, we compared the host response of a nonreplicating HSV-1 vector to that of a replication-competent HSV-1 virus using microarray analysis. In parallel, HSV-1 gene expression was tracked using HSV-specific oligonucleotide-based arrays in order to correlate viral gene expression with observed changes in host response. Microarray analysis was performed following stereotactic injection into the right hippocampal formation of mice with either a replication-competent HSV-1 or a nonreplicating recombinant of HSV-1, lacking the ICP4 gene (ICP4-). Genes that demonstrated a significant change (P < .001) in expression in response to the replicating HSV-1 outnumbered those that changed in response to mock or nonreplicating vector by approximately 3-fold. Pathway analysis revealed that both the replicating and nonreplicating vectors induced robust antigen presentation but only mild interferon, chemokine, and cytokine signaling responses. The ICP4- vector was restricted in several of the Toll-like receptor-signaling pathways, indicating reduced stimulation of the innate immune response. These array analyses suggest that although the nonreplicating vector induces detectable activation of immune response pathways, the number and magnitude of the induced response is dramatically restricted compared to the replicating vector, and with the exception of antigen presentation, host gene expression induced by the nonreplicating vector largely resembles mock infection.

Functional genomic analysis of herpes simplex virus type 1 counteraction of the host innate response

Herpes simplex virus type 1 (HSV-1) mutants lacking the ICP34.5 gene are severely attenuated in mouse models and have a significant growth defect in confluent mouse embryo fibroblasts. Previously, ICP34.5 was demonstrated to have a crucial role in evading the innate immune response to infection by mediating the dephosphorylation of eIF2alpha, a translation initiation factor phosphorylated by PKR during the antiviral response. To further understand the role of ICP34.5 in evasion of the antiviral response, we used transcriptional profiling to examine host cell gene expression in both wild-type and ICP34.5-null virus-infected mouse embryo fibroblasts over a time course of infection. Our study revealed that cells responded to infection within 3 h through PKR-dependent eIF2alpha phosphorylation and that the majority of up-regulated genes at 3 h postinfection were involved in the antiviral response. HSV-1 counters this response through early expression of ICP34.5 and dephosphorylation of eIF2alpha. By 12 h postinfection, the differences between the number and functional classification of genes differentially up- and down-regulated between wild-type and ICP34.5-null virus-infected cells were maximal. Specifically, in wild-type virus-infected cells, the majority of changed genes were involved in metabolic and biosynthetic processes, while in ICP34.5-null virus-infected cells, mostly antiviral genes were up-regulated. Further, ICP34.5-null virus-infected cells produced greater amounts of beta interferon than wild-type virus-infected cells. These results indicate that ICP34.5 expression and function at early times postinfection have a pivotal role in the ability of HSV-1 to gain control of the host cell and maintain an environment for successful viral replication.

The cellular response to herpes simplex virus type 1 (HSV-1) during latency and reactivation

In order to learn more about the cellular response to viral gene activity during latency and reactivation of herpes simplex virus type 1 (HSV-1), the authors have employed microarray analysis. On an array of about 1200 cellular genes, approximately 56 genes were found to be differentially regulated in infected trigeminal ganglia of mice, compared to uninfected mice, during latency and reactivation. Of these genes, 10 were examined more closely using quantitative real-time polymerase chain reaction (PCR) to confirm the microarray results. Genes involved in interferon and other signaling pathways appeared to predominate in response to a latent or reactivating HSV infection. Interestingly, some genes found to be differentially regulated in latently infected ganglia are neuronal-specific genes (pro-opiomelanocortinin; zinc finger proteins of the cerebellum 1 and 2). During reactivation, the involvement of several cell signaling molecules that may be important for the initiation of an HSV infection was observed, including various receptors and molecules involved in cell-cell spread.

Viral and cellular gene transcription in fibroblasts infected with small plaque mutants of varicella-zoster virus

Varicella-zoster virus (VZV) is an alphaherpesvirus that causes varicella and herpes zoster. In these experiments, cDNA corresponding to 69 VZV open reading frames was added to 42K human cDNA microarrays and used to examine viral as well as cellular gene transcription concurrently in fibroblasts infected with two genetically distinct small plaque VZV mutants, rOka/ORF63rev[T171] and rOkaDeltagI. rOka/ORF63rev[T171] has a point mutation in ORF63, which encodes the immediate early regulatory protein, IE63, and rOkaDeltagI has a deletion of ORF67, encoding glycoprotein I (gI). rOka/ORF63rev[T171] was deficient in the transcription of several viral genes compared to the recombinant rOka control virus. Deletion of ORF67 had minimal effects on viral gene transcription. Effects of rOka/ORF63rev[T171] and rOkaDeltagI on host cell gene transcription were similar to the rOka control, but a few host cell genes were regulated differently in rOkaDeltagI-infected cells. Infection of fibroblasts with intact or small plaque VZV mutants was associated with down-regulation of NF-kappaB and interferon responsive genes, down-regulation of TGF-beta responsive genes accompanied by reduced amounts of fibrotic/wound healing response genes (e.g. collagens, follistatin) and activation of cellular proliferation genes, and alteration of neuronal growth markers, as well as cellular genes encoding proteins important in protein and vesicle trafficking. These observations suggest that replication of VZV small plaque mutant viruses and intact VZV have similar consequences for host cell gene transcription in infected cells, and that the small plaque phenotype in these mutants reflects deficiencies in viral gene expression.

Herpesvirus quiescence in neuronal cells. V: forskolin-responsiveness of the herpes simplex virus type 1 alpha0 promoter and contribution of the putative cAMP response element

The herpes simplex virus (HSV)-1 alpha0 promoter contains a putative cAMP response element (CRE) located at positions -68 to -60 with respect to the initiation of transcription. In this report, the authors examined the functionality of this element using (1) luciferase reporter gene assays in nerve growth factor-differentiated (ND)-PC12 cells and (2) virus-induced activation from quiescently infected (QIF)-PC12 cells. The putative alpha0 CRE was completely eliminated by digestion with the restriction enzyme Tsp45I followed by mung bean nuclease treatment. The mutated region was verified by DNA sequencing and was inserted into the alpha0-luciferase reporter plasmid (pRDalpha0-LUC) creating (pRDalpha0deltaCRE-LUC), and into the HSV-1 genome of strain 17(+)(alpha0deltaCRE). Insertion into both copies of the alpha0 promoter was verified by Southern blot analysis. ND-PC12 cells transfected with pRDalpha0-LUC and pRDalpha0deltaCRE-LUC plasmids responded similarly to forskolin (50 microM), with approximately 250% increases in luciferase activity compared to mock-treated cultures as measured 3 days following treatment. When QIF-PC12 cultures established with HSV-1 strain 17(+) and alpha0deltaCRE were treated with forskolin (50 microM) 17 days post infection, virus was detected in 9/24 (37.5%) and 13/24 (54.2%) of induced cultures by day 8 post treatment, respectively. In contrast, virus was detected in 0/23 and 1/24 (4.2%) of mock-treated cultures by day 8 post treatment for wild-type and mutant viruses, respectively. These findings indicate that the alpha0 promoter is forskolin responsive, the purported CRE of the alpha0 promoter does not confer forskolin responsiveness in ND-PC12 cells, and this element is not required for reactivation of HSV-1 from QIF-PC12 cells.

Gene expression profiling in the HSV-1 latently infected mouse trigeminal ganglia following hyperthermic stress

PURPOSE

To assess gene expression in herpes simplex virus type 1 (HSV-1) latent mouse trigeminal ganglia (TG) at 6 and 24 hours after hyperthermic stress.

METHODS

Uninfected and HSV-1 latently infected mice were heat stressed (43 degrees C, 10 min). TG from six groups of mice were studied: 1) uninfected, not stressed, 2) uninfected, heat-stressed, sacrificed at 6 hours after hyperthermia, 3) uninfected, heat-stressed, sacrificed at 24 hours after hyperthermia, 4) latently infected, not stressed, 5) latently infected, heat-stressed, sacrificed at 6 hours after hyperthermia, 6) latently infected, heat-stressed, sacrificed at 24 hours after hyperthermia. Poly A(+) mRNA from the TG of each group of mice was reverse transcribed, labeled with (32)P, and incubated on a nylon gene array membrane. The genes showing the largest signal-to-control changes (varying by a factor of at least 1.27-fold) were considered to have undergone significant change in expression.

RESULTS

Six hours after heat stress the genes whose expression was altered included the FK506-binding protein gene (decreased), the T-complex protein 1 alpha subunit gene (increased), and the 94-kDa glucose-regulated protein gene (increased in uninfected TG, decreased in infected TG). Heat stress increased expression of the DNA excision repair protein ERCC5 gene 24 hours after the treatment. Genes previously reported to exhibit increased transcription 1 hour after stress did not continue to show significant transcriptional activation at 6 or 24 hours.

CONCLUSION

Altered gene expression at 6 and 24 hours after heat stress was different from previously reported changes in gene expression 1 hour after hyperthermia in HSV-1 latently infected mice.

Changes in gene expression in latent HSV-1-infected rabbit trigeminal ganglia following epinephrine iontophoresis

PURPOSE

The aim of the present study was to identify the genes that express in the nervous system when herpes simplex virus type 1 (HSV-1) reactivates from latency by using subtraction cloning following epinephrine iontophoresis.

METHODS

The corneas of New Zealand White rabbits (2 to 2.5 kg) were topically inoculated with 5 x 10(5) PFU of plaque-purified HSV-1 strain McKrae. Corneal infection was monitored by slit lamp examination (SLE) on days 3-7 after infection. At 30 d post-infection, eyes were assessed for infectious virus by ocular swabs. Disappearance of virus in ocular swabs signified latency for HSV-1. Latently-infected rabbits were subjected to transcorneal iontophoresis. The messenger RNA (mRNA) was isolated from the trigeminal ganglia and used for subtraction cloning and subtraction library synthesis.

RESULTS

Our results indicate 18 genes with increased expression and 6 genes with decreased levels. Northern blot analysis revealed that genes for OX-40 ligand, MHC class II HLA-DR-alpha and beta-microglobulin showed predominant increase followed by tyrosine 3'-monooxygenase, proteolipid protein, tyrosine beta, and apolipoprotein D. Genes that underwent reduced expression included cytochrome c oxidase subunit I, ATP synthase isoform, cytochrome b, ATPase 9, and at least one unidentified gene.

CONCLUSIONS

Our results, particularly the increased detection of OX-40 ligand and MHC class II-alpha and beta-2 microglobulin, support the finding that lymphocytes persist in latently-infected trigeminal ganglia (TGs). These results also suggest a role of the immune system in HSV-1 recurrences. In addition, we have detected genes associated with neuronal disorders, OX-40L, proteolipid protein, and apolipoprotein D.

Transcription factor binding and histone modifications on the integrated proviral promoter in human T-cell leukemia virus-I-infected T-cells

The human T-cell leukemia virus (HTLV-I)-encoded Tax protein is a potent transcriptional activator that stimulates expression of the integrated provirus. Biochemical studies indicate that Tax, together with cellular transcription factors, interacts with viral cAMP-response element enhancer elements to recruit the pleiotropic coactivators CREB-binding protein and p300. Histone acetylation by these coactivators has been shown to play a major role in activating HTLV-I transcription from chromatin templates in vitro. However, the extent of histone modification and the precise identity of the cellular regulatory proteins bound at the HTLV-I promoter in vivo is not known. Chromatin immunoprecipitation analysis was used to investigate factor binding and histone modification at the integrated HTLV-I provirus in infected T-cells (SLB-1). These studies reveal the presence of Tax, a variety of ATF/CREB and AP-1 family members (CREB, CREB-2, ATF-1, ATF-2, c-Fos, and c-Jun), and both p300 and CREB-binding protein at the HTLV-I promoter. Consistent with the binding of these coactivators, we observed histone H3 and H4 acetylation at three regions within the proviral genome. Histone deacetylases were also present at the viral promoter and, following their inhibition, we observe an increase in histone H4 acetylation on the HTLV-I promoter and a concomitant increase in viral RNA. Together, these results suggest that a variety of transcriptional activators, coactivators, and histone deacetylases participate in the regulation of HTLV-I transcription in infected T-cells.

Explant-induced reactivation of herpes simplex virus occurs in neurons expressing nuclear cdk2 and cdk4

Herpes simplex virus (HSV) establishes productive (lytic) infections in nonneuronal cells and nonproductive (latent) infections in neurons. It has been proposed that HSV establishes latency because quiescent neurons lack cellular factors required for productive infection. It has been further proposed that these putative factors are induced following neuronal stress, as a requirement for HSV reactivation. To date, the identity of these putative cellular factors remains unknown. We have demonstrated that cyclin-dependent kinase (cdk) 1, 2, or 7 is required for HSV replication in nonneuronal cells. Interestingly, cdks 1 and 2 are not expressed in quiescent neurons but can be induced in stressed neurons. Thus, cdks may be among the cellular proteins required for HSV reactivation whose neuronal expression is differentially regulated during stress. Herein, we determined that neuronal expression of nuclear cdk2, cdk4, and cyclins E and D2 (which activate cdks 2 and 4, respectively) was induced following explant cultivation, a stressful stimulus that induces HSV reactivation. In contrast, neuronal expression of cdk7 and cytoplasmic cdk4 decreased during explant cultivation, whereas cdk3 was detected in the same small percentage of neurons before and after explant cultivation and cdks 1, 5, and 6 were not detected in neuronal cell bodies. HSV-1 reactivated specifically in neurons expressing nuclear cdk2 and cdk4, and an inhibitor specific for cdk2 inhibited HSV-1 reactivation. We conclude that neuronal levels of cdk2 are among the factors that determine the outcome of HSV infections of neurons.

Herpes simplex virus evolved to use the human defense mechanisms to establish a lifelong infection in neurons--a review and hypothesis

The review of recent studies using DNA microarrays shed new light on herpes simplex virus (HSV) replicative cycle, the response of immature dendritic cells (DCs) to pathogens and the response of neurons in trigeminal ganglia to virus reactivation. These studies provided a better understanding of the molecular biology of HSV during infection, latency and reactivation. The research on the sensory trigeminal neurons and the neuronal axons (type C fibers) that transverse the skin basal membrane, enter the skin epidermis and interact with the cell membrane of the skin resident immature DCs provided an insight on the connection between the nervous system and the host immune system. Based on these studies a hypothesis is presented suggesting that HSV evolved to use the human host defense systems (pain signals, the immune system cells and sensory neurons) to ensure its entry from the skin epithelium into the sensory neurons. Reactivated HSV in the neurons utilizes the same host defense systems to return to the skin epithelium.