Infection Of Hematopoietic Cells Research Articles

Host-encoded CTCF regulates human cytomegalovirus latency via chromatin looping

Human cytomegalovirus (HCMV) is a prevalent pathogen that establishes life-long latent infection in hematopoietic cells. While this infection is usually asymptomatic, immune dysregulation leads to viral reactivation, which can cause significant morbidity and mortality. However, the mechanisms underpinning reactivation remain incompletely understood. The HCMV major immediate early promoter (MIEP)/enhancer is a key factor in this process, as its transactivation from a repressed to active state helps drive viral gene transcription necessary for reactivation from latency. Numerous host transcription factors bind the MIE locus and recruit repressive chromatin modifiers, thus impeding virus reactivation. One such factor is CCCTC-binding protein (CTCF), a highly conserved host zinc finger protein that mediates chromatin conformation and nuclear architecture. However, the mechanisms by which CTCF contributes to HCMV latency were previously unexplored. Here, we confirm that CTCF binds two convergent sites within the MIE locus during latency in primary CD14+ monocytes, and following cellular differentiation, CTCF association is lost as the virus reactivates. While mutation of the MIE enhancer CTCF binding site does not impact viral lytic growth in fibroblasts, this mutant virus fails to maintain latency in myeloid cells. Furthermore, we show the two convergent CTCF binding sites allow looping to occur across the MIEP, supporting transcriptional repression during latency. Indeed, looping between the two sites diminishes during virus reactivation, concurrent with activation of MIE transcription. Taken together, our data reveal that three-dimensional chromatin looping aids in the regulation of HCMV latency and provides insight into promoter/enhancer regulation that may prove broadly applicable across biological systems.

In silico interrogation of the miRNAome of infected hematopoietic cells to predict processes important for human cytomegalovirus latent infection

Human cytomegalovirus (HCMV) latency in CD34+ progenitor cells is the outcome of a complex and continued interaction of virus and host that is initiated during very early stages of infection and reflects pro- and anti-viral activity. We hypothesized that a key event during early infection could involve changes to host miRNAs, allowing for rapid modulation of the host proteome. Here, we identify 72 significantly upregulated miRNAs and three that were downregulated by 6hpi of infection of CD34+ cells which were then subject to multiple in silico analyses to identify potential genes and pathways important for viral infection. The analyses focused on the upregulated miRNAs and were used to predict potential gene hubs or common mRNA targets of multiple miRNAs. Constitutive deletion of one target, the transcriptional regulator JDP2, resulted in a defect in latent infection of myeloid cells; interestingly, transient knockdown in differentiated dendritic cells resulted in increased viral lytic IE gene expression, arguing for subtle differences in the role of JDP2 during latency establishment and reactivation of HCMV. Finally, in silico predictions identified clusters of genes with related functions (such as calcium signaling, ubiquitination, and chromatin modification), suggesting potential importance in latency and reactivation. Consistent with this hypothesis, we demonstrate that viral IE gene expression is sensitive to calcium channel inhibition in reactivating dendritic cells. In conclusion, we demonstrate HCMV alters the miRNAome rapidly upon infection and that in silico interrogation of these changes reveals new insight into mechanisms controlling viral gene expression during HCMV latency and, intriguingly, reactivation.

Design of a US28 ORF Deletion Virus in a Temperature-Sensitive Cytomegalovirus Strain Fails to Promote Lytic Replication in Hematopoietic Cells.

Human cytomegalovirus (CMV) is a ubiquitous pathogen that latently resides in hematopoietic cells. Latently infected individuals with dysfunctional immune systems often experience CMV reactivation, which can cause devastating disease and mortality. While factors dictating the balance between latency and reactivation are not completely understood, CMV US28 is required for maintaining latent infection, and viral mutants that alter US28 function result in a lytic-like, rather than latent, infection in hematopoietic cells. In turn, viral lytic factors alter the host cell, making it challenging to characterize the US28-specific changes in the cellular milieu. To circumvent this, we generated a temperature-sensitive TB40/E recombinant virus, TB40/EgfpC510G (tsC510G), into which we engineered an amino acid change at position 510 (C510G) of IE2, as previously described in the CMV Towne strain. Using tsC510G, we then deleted the US28 ORF, termed tsC510G-US28Δ. Consistent with previous findings, tsC510G-US28Δ fails to undergo latency in Kasumi-3 cells at the permissive temperature. However, parallel cultures maintained at the non-permissive temperature showed a significant reduction in infectious center frequency, as measured by limiting dilution assay. Thus, we generated a new US28 mutant virus for use as a tool to study US28-specific changes in latently infected hematopoietic cells in the absence of induced lytic replication.

Hematopoietic cell-mediated dissemination of murine cytomegalovirus is regulated by NK cells and immune evasion.

Cytomegalovirus (CMV) causes clinically important diseases in immune compromised and immune immature individuals. Based largely on work in the mouse model of murine (M)CMV, there is a consensus that myeloid cells are important for disseminating CMV from the site of infection. In theory, such dissemination should expose CMV to cell-mediated immunity and thus necessitate evasion of T cells and NK cells. However, this hypothesis remains untested. We constructed a recombinant MCMV encoding target sites for the hematopoietic specific miRNA miR-142-3p in the essential viral gene IE3. This virus disseminated poorly to the salivary gland following intranasal or footpad infections but not following intraperitoneal infection in C57BL/6 mice, demonstrating that dissemination by hematopoietic cells is essential for specific routes of infection. Remarkably, depletion of NK cells or T cells restored dissemination of this virus in C57BL/6 mice after intranasal infection, while dissemination occurred normally in BALB/c mice, which lack strong NK cell control of MCMV. These data show that cell-mediated immunity is responsible for restricting MCMV to hematopoietic cell-mediated dissemination. Infected hematopoietic cells avoided cell-mediated immunity via three immune evasion genes that modulate class I MHC and NKG2D ligands (m04, m06 and m152). MCMV lacking these 3 genes spread poorly to the salivary gland unless NK cells were depleted, but also failed to replicate persistently in either the nasal mucosa or salivary gland unless CD8+ T cells were depleted. Surprisingly, CD8+ T cells primed after intranasal infection required CD4+ T cell help to expand and become functional. Together, our data suggest that MCMV can use both hematopoietic cell-dependent and -independent means of dissemination after intranasal infection and that cell mediated immune responses restrict dissemination to infected hematopoietic cells, which are protected from NK cells during dissemination by viral immune evasion. In contrast, viral replication within mucosal tissues depends on evasion of T cells.

Regulation of the MIE Locus During HCMV Latency and Reactivation.

Human cytomegalovirus (HCMV) is a ubiquitous herpesviral pathogen that results in life-long infection. HCMV maintains a latent or quiescent infection in hematopoietic cells, which is broadly defined by transcriptional silencing and the absence of de novo virion production. However, upon cell differentiation coupled with immune dysfunction, the virus can reactivate, which leads to lytic replication in a variety of cell and tissue types. One of the mechanisms controlling the balance between latency and reactivation/lytic replication is the regulation of the major immediate-early (MIE) locus. This enhancer/promoter region is complex, and it is regulated by chromatinization and associated factors, as well as a variety of transcription factors. Herein, we discuss these factors and how they influence the MIE locus, which ultimately impacts the phase of HCMV infection.

Antigenic Fingerprinting of Respiratory Syncytial Virus (RSV)-A-Infected Hematopoietic Cell Transplant Recipients Reveals Importance of Mucosal Anti-RSV G Antibodies in Control of RSV Infection in Humans.

Respiratory syncytial virus (RSV) infection causes significant morbidity in hematopoietic cell transplant (HCT) recipients. However, antibody responses that correlate with recovery from RSV disease are not fully understood. In this study, antibody repertoire in paired serum and nasal wash samples from acutely RSV-A-infected HCT recipients who recovered early (<14 days of RSV shedding) were compared with late-recovered patients (≥14 days of shedding) using gene fragment phage display libraries and surface plasmon resonance. Anti-F serum responses were similar between these 2 groups for antibody repertoires, neutralization titers, anti-F binding antibodies (prefusion and postfusion proteins), antibody avidity, and binding to specific antigenic sites. In contrast, nasal washes from early-recovered individuals demonstrated higher binding to F peptide containing p27. While the serum RSV G antibody repertoires in the 2 groups were similar, the strongest difference between early-recovered and late-recovered patients was observed in the titers of nasal wash antibodies, especially binding to the central conserved domain. Most importantly, a significantly higher antibody affinity to RSV G was observed in nasal washes from early-recovered individuals compared with late-recovered HCT recipients. These findings highlight the importance of mucosal antibodies in resolution of RSV-A infection in the upper respiratory tract.

Intranasal infection by MCMV reveals key roles for viral evasion of MHC-I to enable viral spreading and CD4 T cell help to promote functional CD8 T cell responses

Abstract Natural Cytomegalovirus (CMV) infection occurs primarily through the oral/nasal mucosa. Recent evidence from murine (M)CMV infection suggested that MCMV is spread to salivary gland (SG) by dendritic cells after intranasal (i.n.) inoculation. In agreement with this, a recombinant MCMV, which cannot replicate in hematopoietic cells, could not spread to SG after i.n. infection. However, the mechanisms by which infected cells evade immune control while spreading the virus are unclear. In fact, previous work suggested that deleting all three genes blocking MHC-I antigen presentation results in only a subtle defect in total latent viral loads and SG replication in vivo. Surprisingly, we found that viral evasion of MHC-I antigen presentation was critical for MCMV to replicate persistently in nasal mucosa and spread to SG after i.n. inoculation, in contrast to intraperitoneal (i.p.) infection. Remarkably, depletion of CD4 T cells reversed this immune restriction on viral spreading, enabling even MCMV lacking all evasion genes to replicate in nasal mucosa and spread to SG after i.n. infection. This was not due to a direct anti-viral effect of CD4 T cells as delaying CD4 T cell depletion until day 7 post infection restored immune control of MCMV at later times. Instead, priming and expansion of functional CD8 T cells was impaired by lack of CD4 T cells after i.n. infection, in contrast to i.p. infection. Thus, intranasal inoculation revealed a critical role for CD4 T cell help in the promotion of protective CD8 T cell responses. Moreover, our data suggest since MCMV spreads only in infected hematopoietic cells after i.n. infection, viral evasion of MHC-I is necessary to protect CD8 T cells from killing infected cells carrying MCMV.

Transcriptome-wide characterization of human cytomegalovirus in natural infection and experimental latency

The transcriptional program associated with herpesvirus latency and the viral genes regulating entry into and exit from latency are poorly understood and controversial. Here, we developed and validated a targeted enrichment platform and conducted large-scale transcriptome analyses of human cytomegalovirus (HCMV) infection. We used both an experimental hematopoietic cell model of latency and cells from naturally infected, healthy human subjects (clinical) to define the breadth of viral genes expressed. The viral transcriptome derived from experimental infection was highly correlated with that from clinical infection, validating our experimental latency model. These transcriptomes revealed a broader profile of gene expression during infection in hematopoietic cells than previously appreciated. Further, using recombinant viruses that establish a nonreactivating, latent-like or a replicative infection in CD34+ hematopoietic progenitor cells, we defined classes of low to moderately expressed genes that are differentially regulated in latent vs. replicative states of infection. Most of these genes have yet to be studied in depth. By contrast, genes that were highly expressed, were expressed similarly in both latent and replicative infection. From these findings, a model emerges whereby low or moderately expressed genes may have the greatest impact on regulating the switch between viral latency and replication. The core set of viral genes expressed in natural infection and differentially regulated depending on the pattern of infection provides insight into the HCMV transcriptome associated with latency in the host and a resource for investigating virus-host interactions underlying persistence.

Tetherin Inhibits Cell-Free Virus Dissemination and Retards Murine Leukemia Virus Pathogenesis.

ABSTRACTThe relative contributions of cell-free virion circulation and direct cell-to-cell transmission to retroviral dissemination and pathogenesis are unknown. Tetherin/Bst2 is an antiviral protein that blocks enveloped virion release into the extracellular milieu but may not inhibit cell-to-cell virus transmission. We developed live-cell imaging assays which show that tetherin does not affect Moloney murine leukemia virus (MoMLV) spread, and only minimally affects vesicular stomatitis virus (VSV) spread, to adjacent cells in a monolayer. Conversely, cell-free MLV and VSV virion yields and VSV spread to distal cells were dramatically reduced by tetherin. To elucidate the roles of tetherin and cell-free virions during in vivo viral dissemination and pathogenesis, we developed mice carrying an inducible human tetherin (hTetherin) transgene. While ubiquitous hTetherin expression was detrimental to the growth and survival of mice, restriction of hTetherin expression to hematopoietic cells gave apparently healthy mice. The expression of hTetherin in hematopoietic cells had little or no effect on the number of MoMLV-infected splenocytes and thymocytes. However, hTetherin expression significantly reduced cell-free plasma viremia and also delayed MoMLV-induced disease. Overall, these results suggest that MoMLV spread within hematopoietic tissues and cell monolayers involves cell-to-cell transmission that is resistant to tetherin but that virion dissemination via plasma is inhibited by tetherin and is required for full MoMLV pathogenesis.IMPORTANCE Retroviruses are thought to spread primarily via direct cell-to-cell transmission, yet many have evolved to counteract an antiviral protein called tetherin, which may selectively inhibit cell-free virus release. We generated a mouse model with an inducible tetherin transgene in order to study how tetherin affects retroviral dissemination and on which cell types its expression is required to do so. We first developed a novel in vitro live-cell imaging assay to demonstrate that while tetherin does indeed dramatically reduce cell-free virus spreading, it has little to no effect on direct cell-to-cell transmission of either vesicular stomatitis virus (VSV) or the retrovirus MoMLV. Using our transgenic mouse model, we found that tetherin expression on hematopoietic cells resulted in the specific reduction of MoMLV cell-free plasma viremia but not the number of infected hematopoietic cells. The delay in disease associated with this scenario suggests a role for cell-free virus in retroviral disease progression.

Development of Novel Bioanalytical Methods to Determine the Effective Concentrations of Phosphorodiamidate Morpholino Oligomers in Tissues and Cells

Phosphorodiamidate morpholino oligomers (PMO) are neutrally charged, sequence-specific antisense agents that interfere with targeted gene expression. PMO have been shown to be highly specific and potent therapies after cellular uptake, yet methods to detect PMO in tissue and inside the cell are limited. We offer in this report novel methods for the detection of cellular resident PMO using flow cytometry-fluorescence in situ hybridization (flow FISH) and a sandwich hybridization technique to quickly and sensitively quantify tissue resident PMO. These methods rely on oligonucleotide probes complementary to a PMO to specifically detect and quantify cell-associated and tissue resident PMO after in vitro or in vivo administration. Using the sandwich hybridization technique, we show that intranasally delivered PMO demonstrates zero-order clearance kinetics from the lung. Furthermore, PMO was detected in nonhematopoietic and hematopoietic cells of the lung regardless of influenza virus infection, although an increase in PMO uptake in infected hematopoietic cells was observed. Coincident measurement of target knock-down to cell-associated influenza A PMO concentration allowed for the calculation of an EC50.

A bioanalytical method for detection of phosphorodiamidate morpholino oligomers in cells. (65.44)

Abstract Phosphorodiamidate morpholino oligomers (PMOs) are neutrally charged antisense agents that interfere with target gene expression by inhibition of translation or by altering splicing of pre-mRNA. PMOs have been shown to be highly specific and potent therapies after cellular uptake, yet a method to detect PMO inside the cell has not been developed. We offer in this report a novel method for the detection of cellular resident PMO using flow cytometry-fluorescence in situ hybridization (flow FISH) which takes advantage of locked nucleic acid (LNA) oligonucleotides as probes. A biotinylated LNA probe complementary to an Influenza A specific PMO (IA-PMO) was used to specifically detect and quantify intracellular IA-PMO after in vitro or in vivo administration with or without Influenza A infection. While IA-PMO was detected in non-hematopoietic and hematopoietic cells of the lung regardless of influenza virus infection, it was detected at higher levels in influenza infected hematopoietic lung cells as compared to uninfected cells. Coincident measurement of target knock down to intracellular IA-PMO concentration allowed for the calculation of an EC50. Furthermore, it was observed that an increase in IA-PMO uptake occurs in infected hematopoietic cells.

Hepatitis-associated aplastic anemia during a primary infection of genotype 1a torque teno virus

A 12-year-old Japanese boy suffered from severe acute hepatitis and pancytopenia. The patient underwent successful bone marrow transplantation from an HLA-identical sister. Torque teno virus (TTV) DNA of genotype 1a and IgM-class antibody against the virus were detected in sera at the onset of hepatitis. TTV/1a DNA and anti-TTV/1a IgM antibody levels were undetectable on the 16th and 46th days after the onset of illness, respectively. Anti-TTV/1a IgG antibody was positive throughout the observation period. Sequential viral load and anti-TTV/1a IgM antibody suggested a primary infection of TTV/1a. Genomic sequence of the virus coincided with that of the original strain first isolated from human. TTV DNA was quantified at 130 copies in 10(5) bone marrow mononuclear cells, which suggested that infection of hematopoietic cells might be the cause of aplasia. This is the first report of TTV hepatitis-associated aplastic anemia assessed by the anti-TTV antibodies and viral load in peripheral blood and bone marrow.

Characterization of a Novel Golgi Apparatus-Localized Latency Determinant Encoded by Human Cytomegalovirus

Human cytomegalovirus (HCMV) exists indefinitely in infected individuals by a yet poorly characterized latent infection in hematopoietic cells. We previously demonstrated a requirement for the putative UL138 open reading frame (ORF) in promoting a latent infection in CD34(+) hematopoietic progenitor cells (HPCs) infected in vitro. In our present study, we have identified two coterminal transcripts of 2.7 and 3.6 kb and a 21-kilodalton (kDa) protein (pUL138) that are derived from the UL138 locus with early-late gene kinetics during productive infection. The UL138 transcripts and protein are detected in both fibroblasts and HPCs. A recombinant virus, FIX-UL138(STOP), that synthesizes the UL138 transcripts but not the protein exhibited a partial loss-of-latency phenotype in HPCs, similar to the phenotype observed for the UL138-null recombinant virus. This finding suggests that the UL138 protein is required for latency, but it does not exclude the possibility that the UL138 transcripts or other ORFs also contribute to latency. The mechanisms by which pUL138 contributes to latency remain unknown. While the 86- and 72-kDa immediate-early proteins were not detected in HPCs infected with HCMV in vitro, pUL138 did not function directly to suppress expression from the major immediate-early promoter in reporter assays. Interestingly, pUL138 localizes to the Golgi apparatus in infected cells but is not incorporated into virus particles. The localization of pUL138 to the Golgi apparatus suggests that pUL138 contributes to HCMV latency by a novel mechanism. pUL138 is the first HCMV protein demonstrated to promote an infection with the hallmarks of latency in CD34(+) HPCs.

Impaired Immune Reconstitution after HLA-Mismatched Transplantation Due to Antigen Specific T-Cell Recognition Restricted by the Disparate Haplotype

The applicability of HLA matched hematopoietic stem cell transplantation (SCT) is limited by the lack of HLA matched donors. In contrast, an HLA haploidentical donor can be found for almost all patients. Posttransplantation immunodeficiency leading to high morbidity and mortality from viral infections is a major barrier to the broader application of haploidentical SCT. In HLA mismatched SCT profound T cell depletion is necessary to prevent GVHD, but also leads to slower T-cell reconstitution. Vigorous T-cell depletion, however, does not fully explain the increased immunodeficiency. Despite a gradual normalization of absolute T-cell and total lymphocyte number after haploidentical SCT, the immunodeficiency may persist for years. Additionally, an increase in the number of mismatched HLA alleles between patient and donor leads to more profound post transplantation immunodeficiency. We hypothesized that another explanation for the long lasting immunodeficiency is T-cell antigen recognition via the haplotype disparate between patient and donor. T-cells recognizing viral epitopes in the donor non-shared HLA molecule will attack virus infected hematopoietic cells of donor origin but not virus infected non-hematopoietic cells of patient origin. To investigate the role of T-cell disparate haplotype restriction in posttransplantation immunodeficiency, we characterized the immune responses against CMV in two patients at various time points after haploidentical and mismatched SCT. The first patient was HLA-A2 negative and transplanted with SCT of an HLA-A2 positive haploidentical donor. After the SCT he suffered from life threatening CMV reactivations for almost two years. Using tetramers composed of the HLA-A2 molecule and CMV-pp65-NLV epitope, we determined that in this patient CMV specific T-cells restricted to the donor HLA-A2 were present from 6 months after the SCT and remained present during the two year period of recurrent CMV infections. Since the HLA-A2 allele was not shared between patient and donor, these results indicate that T cells restricted by non-shared donor-HLA were unable to protect against infections. The second patient transplanted with an HLA mismatched SCT, suffered from CMV reactivations only in the first 6 months after SCT. Already 3 months after SCT CMV specific T cells restricted to the shared HLA-B8 allele were present in high concentrations, whereas the CMV specific T-cells restricted to the non-shared donor HLA-A1 allele disappeared in time. Our results suggest that for an effective immune response the T cells need to recognize viral epitopes restricted to the HLA shared between patient and donor and that impaired immune reconstitution after haploidentical SCT is, in part, the result of antigen specific T cell responses restricted to the disparate haplotype.

Human cytomegalovirus latent infection of myeloid cells directs monocyte migration by up-regulating monocyte chemotactic protein-1.

Following primary infection, human cytomegalovirus (HCMV) establishes a latent infection in hematopoietic cells from which it reactivates to cause serious disease in immunosuppressed patients such as allograft recipients. HCMV is a common cause of disease in newborns and transplant patients and has also been linked with vascular diseases such as primary and post-transplant arteriosclerosis. A major factor in the pathogenesis of vascular disease is the CC chemokine MCP-1. In this study, we demonstrate that granulocyte macrophage progenitors (GMPs) latently infected with HCMV significantly increased expression of MCP-1 and that this phenotype was dependent on infection with viable virus. Inhibitors of a subset of G(alpha) proteins and PI3K inhibited the up-regulation of MCP-1 in latently infected cultures, suggesting that the mechanism underlying this phenotype involves signaling through a G-protein coupled receptor. In GMPs infected with the low passage viral strain Toledo, up-regulated MCP-1 was restricted to a subset of myeloid progenitor cells expressing CD33, HLA-DR, and CD14 but not CD1a, CD15, or CD16, and the increase in MCP-1 was sufficient to enhance migration of CD14(+) monocytes to latently infected cells. Latent HCMV-mediated up-regulation of MCP-1 provides a mechanism by which HCMV may contribute to vascular disease during the latent phase of infection or facilitate dissemination of virus upon reactivation from latency.

Tat-regulated expression of RNA interference: Triggers for the treatment of HIV infection

HIV infection is a lifelong problem requiring continual medication for suppressing viral replication. Current strategies of antiretroviral drug combinations have proven effective in prolonging the time from infection to the symptoms of AIDS. Nevertheless, chemotherapy is not without its problems, which include toxicities and eventual emergence of virus mutants that are resistant to current antiretrovirals. Gene therapy refers to the introduction of effector oligonucleotides to transiently or stably alter gene expression or the delivery and expression of an exogenous gene within a specific target cell. A number of studies have demonstrated effective silencing/inhibition of HIV-1 replication by using RNA-based effector oligonucleotides for RNA interference. In this study, we have taken advantage of lentiviral vector-mediated delivery of anti-HIV short hairpin RNA for the treatment of HIV infection in hematopoietic cells.

Immunomodulatory Properties of a Viral Homolog of Human Interleukin-10 Expressed by Human Cytomegalovirus during the Latent Phase of Infection

Human cytomegalovirus (HCMV) establishes a latent infection in hematopoietic cells, from which it can reactivate to cause significant disease in immunocompromised individuals. HCMV expresses a functional homolog of the immunosuppressive cytokine interleukin-10 (termed cmvIL-10), and alternate splicing of the cmvIL-10 transcript results in expression of a latency-associated cmvIL-10 transcript (LAcmvIL-10). To determine whether LAcmvIL-10 encodes immunosuppressive functions, recombinant LAcmvIL-10 protein was generated, and its impact on major histocompatibility complex class II (MHC-II) expression was examined on granulocyte macrophage progenitor cells (GM-Ps) and monocytes. LAcmvIL-10 (and cmvIL-10) downregulated MHC-II on the surfaces of both cell types. This downregulation was associated with a decrease in total MHC-II protein and transcription of components of the MHC-II biosynthesis pathway. Unlike cmvIL-10, LAcmvIL-10 did not trigger phosphorylation of Stat3, and its ability to downregulate MHC-II was not blocked by neutralizing antibodies to the human IL-10 receptor, suggesting that LAcmvIL-10 either does not engage the cellular IL-10 receptor or utilizes it in a different manner from cmvIL-10. The impact of LAcmvIL-10 on dendritic cell (DC) maturation was also assessed. In contrast to cmvIL-10, LAcmvIL-10 did not inhibit the expression of costimulatory molecules CD40, CD80, and CD86 and the maturation marker CD83 on DCs, nor did it inhibit proinflammatory cytokines (IL-1alpha, IL-1beta, IL-6 and tumor necrosis factor alpha). Thus, LAcmvIL-10 retains some, but not all, of the immunosuppressive functions of cmvIL-10. As GM-Ps and monocytes support latent infection, expression of LAcmvIL-10 may enable HCMV to avoid immune recognition and clearance during latency.

Spectroscopic analysis of Kaposi's sarcoma-associated herpesvirus infected cells by Raman tweezers

Kaposi's sarcoma-associated herpesvirus (KSHV), also referred to as human herpesvirus-8 (HHV-8), is a tumor causing virus. KSHV is the cause of several disease conditions known as Kaposi's sarcoma, multicentric Castleman disease, and primary effusion lymphoma. Cell culture supernatants from KSHV infected hematopoietic cells induced angiogenic tubule formation to a significantly greater extent than uninfected hematopoietic cells. Raman spectrum profiles were generated to differentiate the uninfected from KSHV infected cells. In general, profiles from all the hematopoietic cells shared similar peaks; however, the relative abundance of specific components varied significantly between the cells. Subsequent use of the multivariate analysis of the Raman spectra revealed significant differences between the uninfected and the KSHV infected cells. Taken together, this study reports the use of Raman tweezers to distinguish and analyze the biological relevance of KSHV infected cell signaling.

Human Cytomegalovirus Infection of Primitive Hematopoietic Progenitor Cells: A Model for Latency.

Human cytomegalovirus (CMV) is beta-herpesvirus that infects the majority of the population worldwide and establishes a lifelong relationship with its host by way of a latent infection. Although, CMV is of little consequence to healthy individuals, reactivation of CMV from latency can cause life-threatening disease in immunocompromised individuals such as bone marrow transplant recipients and AIDS patients. CMV establishes a latent infection in cells of the hematopoietic system. The focus of our work is to elucidate the mechanisms governing a latent infection and reactivation from latency. It is likely that both viral and cellular mechanisms govern the latent program. We have developed a novel in vitro model for CMV latency using primary human hematopoietic progenitors. Using this model to compare CMV infection in CD34+ hematopoietic subpopulations, the outcome of CMV infection was found to depend on the nature of the subpopulation of cells infected. Only primitive CD34+/CD38− progenitor cells harboured an infection with the hallmarks of latency. This subpopulation transiently expressed a unique subset of CMV genes in the absence of viral replication. Importantly, viral replication could be reactivated from this subpopulation. Other primitive (CD34+/c-kit+) and more mature (CD34+/CD38+ and CD34+/c-kit−) subpopulations resulted in an apparently abortive infection. Strikingly, a CD34+ subpopulation expressing a stem cell phenotype supported a productive infection. These results indicate that cellular determinants contribute to the outcome of HCMV infection in hematopoietic cells. Further, we have also demonstrated that viral determinants play a role in establishing a latent infection using our in vitro model. Comparing the clinical Toledo and FIX strains and the laboratory-adapted AD169 strain of CMV, only the clinical strains were able to establish an infection consistent with latency. AD169, by contrast, replicated productively. Genetic sequences unique to clinical strains have been identified and may contribute to its ability to establish a latent infection in vitro. These studies indicate that both viral and cellular determinants contribute to the establishment of CMV latency. Furthermore, these determinants may serve as targets for CMV disease prophylaxis following bone marrow transplantation or in AIDS patients.

Human Parvovirus Infections

The B19 strain of parvovirus causes several distinct and important clinical diseases in humans. Aplastic crisis in patients with chronic hemolytic anemia, persistent bone marrow depression in immunocompromised individuals, and hydrops fetalis all result from direct infection of hematopoietic cells by the virus. Erythema infectiosum, arthritis, and purpuric vasculitis are postinfectious manifestations of B19 parvovirus infection.