Search PubMed⌕ Search

Biomedical subjects

A Blauvelt

Publications and source records attributed to A Blauvelt.

At least 19 recordsLinked to original sources

Hypoxia induces lytic replication of Kaposi sarcoma-associated herpesvirus.

There is substantial evidence that Kaposi sarcoma-associated herpesvirus (KSHV) plays an important role in the pathogenesis of all forms of Kaposi sarcoma (KS). It has been noted that KS commonly occurs in locations, such as the feet, where tissue may be poorly oxygenated. On the basis of this observation, the potential role of hypoxia in the reactivation of KSHV replication was explored by studying 2 KSHV-infected primary effusion lymphoma B-cell lines (BC-3 and BCBL-1) latently infected with KSHV. Acute and chronic exposure of these cells to hypoxia (1% O(2)) induced KSHV lytic replication, as indicated by an increase in intracellular lytic protein expression and detection of virus in cell supernatants by Western immunoblotting. In addition, hypoxia increased the levels of secreted viral interleukin-6. Moreover, hypoxia enhanced the lytic replication initiated by the viral inducer 12-O-tetradecanoylphorbol-13-acetate. Desferoxamine and cobalt chloride, 2 compounds that increase the intracellular levels of hypoxia-inducible factor 1, were also able to induce KSHV lytic replication. These studies suggest that hypoxia is an inducer of KSHV replication. This process may play an important role in the pathogenesis of KS.

B-Lymphocytes↗

Targeted inhibition of calcineurin signaling blocks calcium-dependent reactivation of Kaposi sarcoma-associated herpesvirus.

Kaposi sarcoma-associated herpesvirus (KSHV) is associated with KS, primary effusion lymphoma (PEL), and multicentric Castleman disease. Reactivation of KSHV in latently infected cells and subsequent plasma viremia occur before the development of KS. Intracellular signaling pathways involved in KSHV reactivation were studied. In latently infected PEL cells (BCBL-1), KSHV reactivation in single cells was determined by quantitative flow cytometry. Viral particle production was determined by electron microscope analyses and detection of minor capsid protein in culture supernatants. Agents that mobilized intracellular calcium (ionomycin, thapsigargin) induced expression of KSHV lytic cycle-associated proteins and led to increased virus production. Calcium-mediated virus reactivation was blocked by specific inhibitors of calcineurin-dependent signal transduction (cyclosporine, FK506). Similarly, calcium-mediated virus reactivation in KSHV-infected dermal microvascular endothelial cells was blocked by cyclosporine. Furthermore, retroviral transduction with plasmid DNA encoding VIVIT, a peptide specifically blocking calcineurin-NFAT interactions, inhibited calcium-dependent KSHV reactivation. By contrast, chemical induction of lytic-phase infection by the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate was blocked by protein kinase C inhibitors, but not by calcineurin inhibitors. In summary, calcineurin-dependent signal transduction, an important signaling cascade in vivo, induces calcium-dependent KSHV replication, providing a possible target for the design of antiherpesvirus strategies in KSHV-infected patients.

Calcineurin↗

Low levels of productive HIV infection in Langerhans cell-like dendritic cells differentiated in the presence of TGF-beta1 and increased viral replication with CD40 ligand-induced maturation.

Langerhans cells (LC) represent dendritic cells (DC) within mucosal epithelium that are purported initial targets for HIV following sexual exposure to virus. Here, morphologic, phenotypic, functional and HIV infection experiments were performed using monocyte-derived DC cultured in the presence of GM-CSF, IL-4 and TGF-beta1 (G4T-DC), GM-CSF and IL-4 (G4-DC), and G4T-DC incubated for an additional 3 days with CD40 ligand (CD40L-DC). G4T-DC, which demonstrated characteristics of immature LC, could be productively infected by either R5- or X4-HIV strains. Infection levels, however, were markedly lower than those observed in immature G4-DC. Surprisingly, CD40L-DC, which demonstrated features of mature LC, could be productively infected with HIV at higher levels than immature G4T-DC. Productive HIV infection in these three DC populations correlated positively with cell surface expression of CD4, CCR5 and CXCR4. We suggest that low levels of HIV infection in LC-like G4T-DC indicate an inefficient mechanism by which HIV can initially infect individuals, perhaps explaining the relative difficulty in becoming infected during sexual exposure to virus. In addition, enhanced HIV infection in LC-like G4T-DC following CD40L treatment suggests a mechanism by which inflammatory CD40L(+) T cells, if present in mucosal tissue, could lead to increased HIV transmission rates.

Adult↗

Skin diseases associated with human herpesvirus 6, 7, and 8 infection.

Relatively recently, the discovery and analysis of three new human herpesviruses, human herpesvirus (HHV)-6, HHV-7, and Kaposi's sarcoma-associated herpesvirus (KSHV), also known as HHV-8, has contributed greatly to our understanding of the pathogenesis of several common dermatoses. HHV-6 and HHV-7 are closely related beta-herpesviruses that have been linked with roseola (mostly HHV-6), severe drug eruptions (HHV-6), and pityriasis rosea (mostly HHV-7). KSHV is a gamma-herpesvirus that is now believed to be the long sought after etiologic agent of Kaposi's sarcoma. The evidence for these skin disease associations and key findings from recent basic science investigations on viral pathogenesis are discussed in this review. In addition, possible therapeutic implications of these research studies are explored.

Herpesvirus 6, Human↗

Candidate microbicides block HIV-1 infection of human immature Langerhans cells within epithelial tissue explants.

Initial biologic events that underlie sexual transmission of HIV-1 are poorly understood. To model these events, we exposed human immature Langerhans cells (LCs) within epithelial tissue explants to two primary and two laboratory-adapted HIV-1 isolates. We detected HIV-1(Ba-L) infection in single LCs that spontaneously emigrated from explants by flow cytometry (median of infected LCs = 0.52%, range = 0.08-4.77%). HIV-1-infected LCs downregulated surface CD4 and CD83, whereas MHC class II, CD80, and CD86 were unchanged. For all HIV-1 strains tested, emigrated LCs were critical in establishing high levels of infection (0.1-1 microg HIV-1 p24 per milliliter) in cocultured autologous or allogeneic T cells. HIV-1(Ba-L) (an R5 HIV-1 strain) more efficiently infected LC-T cell cocultures when compared with HIV-1(IIIB) (an X4 HIV-1 strain). Interestingly, pretreatment of explants with either aminooxypentane-RANTES (regulated upon activation, normal T cell expressed and secreted) or cellulose acetate phthalate (potential microbicides) blocked HIV-1 infection of LCs and subsequent T cell infection in a dose-dependent manner. In summary, we document HIV-1 infection in single LCs after exposure to virus within epithelial tissue, demonstrate that relatively low numbers of these cells are capable of inducing high levels of infection in cocultured T cells, and provide a useful explant model for testing of agents designed to block sexual transmission of HIV-1.

Anti-HIV Agents↗

An IL6 promoter polymorphism is associated with a lifetime risk of development of Kaposi sarcoma in men infected with human immunodeficiency virus.

Kaposi sarcoma (KS) is an angioproliferative inflammatory condition that occurs commonly in patients infected with human immunodeficiency virus (HIV). Inflammatory cytokines and growth factors promote the development of KS. Because physiologically important cytokine polymorphisms modulate host inflammatory responses, we investigated the association between KS and common regulatory polymorphisms in 5 proinflammatory cytokine genes encoding interleukin (IL) IL-1alpha, IL-1beta, tumor necrosis factor (TNF) alpha, TNF-beta, and IL-6 and in the IL-1 receptor antagonist (IL1RN). We also examined the contribution of stromal-derived factor 1 and chemokine receptor 5 (Delta32) polymorphisms to KS development. The population consisted of 115 HIV-infected men with KS and 126 deceased HIV-infected men without KS. The only strong association was observed between an IL6 promoter polymorphism (G-174C) and susceptibility to KS in HIV-infected men (P =.0035). Homozygotes for IL6 allele G, associated with increased IL6 production, were overrepresented among patients with KS (P =.0046), whereas allele C homozygotes were underrepresented (P =.0062). Substantial in vitro evidence indicates that IL-6 contributes to the pathogenesis of KS. Our results show that IL6 promoter genotypes associated with altered gene expression are risk factors for development of KS. Identification of a genetic risk factor for development of KS has important clinical implications for prevention and therapy.

Alleles↗

HIV-infected human Langerhans cells transmit infection to human lymphoid tissue ex vivo.

OBJECTIVES: To create a novel ex vivo model for early biologic events involved in sexual transmission of HIV and to demonstrate that Langerhans cells (LC), the purported initial mucosal target cells for HIV, play a critical role in this process. METHODS: Epidermal cells containing LC were isolated from normal-appearing skin of healthy volunteers and exposed to a panel of primary and laboratory-adapted R5- and X4-HIV isolates, washed and applied to the surfaces of allogeneic tonsil tissue blocks. Viral replication was followed by measuring HIV p24 protein in culture supernatants by ELISA. RESULTS: Both R5- and X4-HIV isolates could be transmitted by LC and established high levels of infection in lymphoid tissue (p24 > 10 ng/ml). Depletion of LC within epidermal cell suspensions abrogated the ability of HIV-exposed suspensions to transmit virus to tonsil histocultures. CONCLUSIONS: Using a novel ex vivo model, human LC are shown for the first time to be the major epidermal cell type that is involved in transmission of HIV infection to human lymphoid tissue. Importantly, this system could prove useful in further understanding LC trafficking and other early biological events involved in primary HIV infection.

Cells, Cultured↗

Variant genotypes of FcgammaRIIIA influence the development of Kaposi's sarcoma in HIV-infected men.

Disturbances in inflammatory cytokine production and immune regulation coupled with human herpesvirus-8 (HHV-8) infection underlie the current understanding of the pathogenesis of Kaposi's sarcoma (KS), the most common HIV-associated malignancy. The low affinity Fc gamma receptors (FcgammaR) for IgG link humoral and cellular immunity by mediating interaction between antibodies and effector cells, such as phagocytes and natural killer cells. We examined the frequency of polymorphic forms of the low affinity FcgammaRs, FcgammaRIIA, FcgammaRIIIA, and FcgammaRIIIB in 2 cohorts of HIV-infected men with KS and found that the FcgammaRIIIA genotype exerts a significant influence on susceptibility to or protection from KS. The FF genotype was underrepresented in patients with KS, whereas the VF genotype was associated with development of KS. A similar association was observed between FcgammaRIIIA genotypes and HHV-8 seropositivity. These observations suggest a possible role for FcgammaRIIIA in the development of KS during HIV infection.

Acquired Immunodeficiency Syndrome↗

Human skin Langerhans cells are targets of dengue virus infection.

Dengue virus (DV), an arthropod-borne flavivirus, causes a febrile illness for which there is no antiviral treatment and no vaccine. Macrophages are important in dengue pathogenesis; however, the initial target cell for DV infection remains unknown. As DV is introduced into human skin by mosquitoes of the genus Aedes, we undertook experiments to determine whether human dendritic cells (DCs) were permissive for the growth of DV. Initial experiments demonstrated that blood-derived DCs were 10-fold more permissive for DV infection than were monocytes or macrophages. We confirmed this with human skin DCs (Langerhans cells and dermal/interstitial DCs). Using cadaveric human skin explants, we exposed skin DCs to DV ex vivo. Of the human leukocyte antigen DR-positive DCs that migrated from the skin, emigrants from both dermis and epidermis, 60-80% expressed DV antigens. These observations were supported by histologic findings from the skin rash of a human subject who received an attenuated tetravalent dengue vaccine. Immunohistochemistry of the skin showed CD1a-positive DCs double-labeled with an antibody against DV envelope glycoprotein. These data demonstrate that human skin DCs are permissive for DV infection, and provide a potential mechanism for the transmission of DV into human skin.

Blood Cells↗

Widespread cutaneous vascular papules associated with peripheral blood eosinophilia and prominent inguinal lymphadenopathy.

A new section entitled "Dermatology Grand Rounds at the NIH" appears this month. The idea behind it is to provide a unique look at instructive dermatologic cases being presented at the weekly Dermatology Branch Grand Rounds at the National Cancer Institute, National Institutes of Health (NIH), Bethesda, Maryland. Patients seen at the NIH Clinical Center (which includes the NIH inpatient wards and outpatient clinics) are indeed unusual. To be evaluated here, they must be referred by an outside physician and must be placed in a research protocol. In other words, by this criterion, all NIH patients are considered research subjects. The diseases studied at the NIH range from the common to the obscure. Similarly, the dermatologic manifestations of these diseases are equally as diverse. Thus the purpose of this new section is to share some of these fascinating cases with the dermatologic community at large, as well as to provide a glimpse of exciting translational research that has relevance to clinical dermatologists. The format will be simple. Cases will be presented as unknowns, including relevant results from the history, physical examination, and histopathologic analyses. This will be done to challenge the clinicopathologic skills of the readers; authors will make every attempt to make the color clinical and pathologic photographs of the highest quality possible to assist readers in making the correct diagnoses. The discussion will be brief, focusing on the key teaching points of each case. These teaching points will vary from cases to case, covering clinical and histologic information, treatment issues, and/or novel laboratory advances with clinical relevance. Authors will emphasize brevity and clarity in all subsections of the case report, which I hope will promote a good learning experience for dermatology residents and busy practitioners alike. This section will initially be published 4 times annually. Finally, because the section is new to the JAAD, I welcome comments and suggestions to improve the quality of the articles.-Andrew Blauvelt, MD Feature Editor

Aged↗

Phosphorylation of the invariant chain by protein kinase C regulates MHC class II trafficking to antigen-processing compartments.

The invariant chain (Ii) plays a critical role in the transport of newly synthesized class II molecules to endosomal Ag-processing compartments. Of the two major isoforms of human Ii, only Ii-p35 is phosphorylated in vivo, and inhibiting Ii phosphorylation inhibits the trafficking of newly synthesized class II molecules to Ag-processing compartments. We now report that a member of the protein kinase C family of serine/threonine kinases is responsible for the constitutive phosphorylation of 50% of the total cellular pool of Ii-p35 in a wide variety of APCs, including B lymphocytes, PBMC, immature dendritic cells, and mature dendritic cells. Stimulation of protein kinase C activity in APCs significantly enhanced the kinetics of degradation of class II-associated Ii in Ag-processing compartments and the binding of antigenic peptides to these class II molecules. In cells expressing an Ii-phosphorylation mutant, trafficking of class II molecules to endosomes was impaired and Ii proteolysis was inhibited, demonstrating a direct effect of Ii phosphorylation on MHC class II trafficking. These results demonstrate that phosphorylation of Ii in APCs alters the kinetics of trafficking of newly synthesized class II molecules to lysosomal Ag-processing compartments.

Antigen Presentation↗

Normal immune function of monocyte-derived dendritic cells from HIV-infected individuals: implications for immunotherapy.

Dendritic cells (DC) are the most potent cells involved in the generation of primary and secondary immune responses. To assess the feasibility of using autologous DC as immunotherapy for HIV disease, we analyzed a variety of immune parameters using DC isolated from HIV-infected (HIV+) individuals, as well as DC obtained from HIV-uninfected (HIV-) individuals infected in vitro with HIV. After stimulation with recombinant CD40 ligand (CD40LT), cytokine and beta-chemokine production were similar by DC from HIV- donors infected in vitro with the CCR5-using HIV Ba-L strain (n = 8) compared with uninfected DC from the same donors. Production of beta-chemokines, but not of cytokines, was increased by a CXCR4-using IIIB strain-infected DC (n = 7). Stimulation of HIV-infected DC with CD40LT decreased infection in Ba-L-infected DC, but had no effect on IIIB-infected DC. Consistent with this finding, CD40LT down-regulated CCR5 and up-regulated CXCR4 expression on DC. Monocyte-derived DC were also propagated from 15 HIV+ and 13 HIV- donors. They exhibited similar expression of costimulatory molecules and produced similar amounts of IL-12, IL-10, and beta-chemokines, following stimulation. By contrast, stimulated PBMC from HIV+ patients exhibited decreased IL-12 and increased IL-10 production. In summary, phenotype, cytokine secretion, and beta-chemokine production by DC from HIV+ individuals were normal. These cells may prove useful in boosting cellular immune responses in HIV+ individuals.

Adoptive Transfer↗

Fractalkine, a CX3C chemokine, is expressed by dendritic cells and is up-regulated upon dendritic cell maturation.

The lone CX3C chemokine, fractalkine (FK), is expressed in a membrane-bound form on activated endothelial cells and mediates attachment and firm adhesion of T cells, monocytes and NK cells. We now show that FK is associated with dendritic cells (DC) in epidermis and lymphoid organs. In normal human skin, dual-color fluorescence microscopy co-localized FK expression with Langerhans cells expressing CD1a. In tonsil, FK-positive DC expressed CD83, a marker for mature DC. Human and murine cultured DC up-regulated FK mRNA expression with maturation. Furthermore, CD40 ligation, but not TNF-alpha or lipopolysaccharide treatment, of activated, migratory DC that had migrated from skin explants resulted in a 2.5-fold increase of surface expression of FK without significant alterations of expression of CD80, CD86, CD54 or MHC class II. Since FK mediates adhesion of T cells to activated endothelial cells, the increased expression of FK during DC maturation (and particularly by CD40 ligation) may play a role in the ability of T cells and mature DC to form conjugates and engage in cell-cell communication.

Animals↗

Human herpesvirus 6 infects dendritic cells and suppresses human immunodeficiency virus type 1 replication in coinfected cultures.

Human herpesvirus 6 (HHV-6) has been implicated as a cofactor in the progressive loss of CD4(+) T cells observed in AIDS patients. Because dendritic cells (DC) play an important role in the immunopathogenesis of human immunodeficiency virus (HIV) disease, we studied the infection of DC by HHV-6 and coinfection of DC by HHV-6 and HIV. Purified immature DC (derived from adherent peripheral blood mononuclear cells in the presence of granulocyte-macrophage colony-stimulating factor and interleukin-4) could be infected with HHV-6, as determined by PCR analyses, intracellular monoclonal antibody staining, and presence of virus in culture supernatants. However, HHV-6-infected DC demonstrated neither cytopathic changes nor functional defects. Interestingly, HHV-6 markedly suppressed HIV replication and syncytium formation in coinfected DC cultures. This HHV-6-mediated anti-HIV effect was DC specific, occurred when HHV-6 was added either before or after HIV, and was not due to decreased surface expression or function of CD4, CXCR4, or CCR5. Conversely, HIV had no demonstrable effect on HHV-6 replication. These findings suggest that HHV-6 may protect DC from HIV-induced cytopathicity in AIDS patients. We also demonstrate that interactions between HIV and herpesviruses are complex and that the observable outcome of dual infection is dependent on the target cell type.

Cell Survival↗

Identification and rapid quantification of early- and late-lytic human herpesvirus 8 infection in single cells by flow cytometric analysis: characterization of antiherpesvirus agents.

Human herpesvirus 8 (HHV-8) infection is associated with Kaposi's sarcoma, primary effusion lymphoma (PEL), and multicentric Castleman's disease. In this study, we used monoclonal antibodies (MAbs) directed against HHV-8 lytic cycle-associated proteins encoded by open reading frame (ORF) 59 (nuclear PF-8 protein) and ORF K8.1 (viral envelope glycoprotein K8.1 [gpK8.1]) to investigate HHV-8 lytic infection in single cells. Lytically infected cells were labeled with MAbs, stained with fluorescently conjugated secondary Abs, and analyzed by flow cytometry. A 3-day stimulation of HHV-8-positive PEL cell lines (BCBL-1 and BC-3) with 12-O-tetradecanoylphorbol-13-acetate (30 nM) or n-butyric acid (0.3 mM) maximized the expression of lytic-phase viral proteins and minimized cell toxicity. The absolute number of expressing cells was inducer and cell line dependent. Expression of PF-8 occurred earlier and more frequently (in up to 20% of cells) than did expression of gpK8.1. A subset of PF-8 positive cells (25%) co-expressed gpK8.1, representing the majority of gpK8.1 expressing cells. Acyclovir, foscarnet, cidofovir, and PMEA reduced the number of cells expressing gpK8.1, but not the number expressing the nonstructural early lytic gene product PF-8. By contrast, alpha interferon (IFN-alpha) and IFN-beta reduced expression of both PF-8 and gpK8.1, implying an overall inhibitory effect on viral gene transcription or translation. In summary, we have characterized and quantified HHV-8 lytic infection in single cells by dual measurement of early- and late-lytic-cycle HHV-8 protein expression. This technique should prove useful for screening of possible antiherpesvirus agents and for detailed phenotypic characterization of HHV-8-infected cells in vitro and in patients with HHV-8-associated diseases.

Acyclovir↗

The role of human herpesvirus 8 in the pathogenesis of Kaposi's sarcoma.

Human herpesvirus 8 is a novel gamma-herpesvirus that has been linked with all clinical types of KS through both DNA and serologic studies. By electron microscopic, in situ hybridization, and in situ PCR studies, virus is found in tumor spindle cells, in normal-appearing endothelial cells within lesions, and in tumor-infiltrating leukocytes. The fact that most tumor cells are latently, as opposed to lytically, infected with HHV8 makes the possibility of treating KS patients with antiherpesviral medications unlikely. Human herpesvirus 8 infection is also associated with BCBL and CD and has recently been reported in patients with multiple myeloma and sarcoidosis (although these latter associations have not been substantiated). Interestingly, the HHV8 genome contains many genes that could be involved in evading normal immune surveillance. Importantly, B-cell lines derived from patients with BCBL have been extremely useful in elucidating the virologic and biological properties of HHV8. In summary, both HHV8 gene analyses and clinico-epidemiologic studies generated by many research teams throughout the world support the concept that HHV8 is the etiologic agent of KS. Future research will focus on developing in vitro model systems to study KS, delineating the expression pattern and function of HHV8-encoded proteins in vivo, determining factors that lead to the development of KS in HHV8-infected individuals, and devising novel therapeutic strategies for KS based on these advances in basic science.

AIDS-Related Opportunistic Infections↗

Cytokines regulate expression and function of the HIV coreceptor CXCR4 on human mature dendritic cells.

HIV-infected dendritic cells (DC) efficiently transmit infection to CD4+ T cells during the process of T cell activation. To further understand interactions between DC and HIV, cytokine regulation of HIV coreceptors on cultured Langerhans cells (cLC, as prototypes of mature DC) was studied. Expression of cell surface CXCR4 on cLC was up-regulated by IL-4 and TGF-beta1 and inhibited by IFN-alpha, IFN-beta, and IFN-gamma, whereas cytokines did not appreciably regulate CCR5. Changes in cell surface CXCR4 expression on cLC correlated with T cell-tropic (X4)-HIV envelope-mediated syncytium formation and X4-HIV infection levels. A relative increase in the ratio of type 2/type 1 cytokine production, which can occur in HIV disease, may up-regulate CXCR4 expression on mature DC and promote infection by X4 viruses. Importantly, these findings suggest that cytokine dysregulation may be linked to the emergence of X4-HIV strains as HIV-infected individuals progress to AIDS.

CD4 Antigens↗

No evidence of human herpesvirus 8 infection in patients with paraneoplastic pemphigus, pemphigus vulgaris, or pemphigus foliaceus.

Paraneoplastic pemphigus has been associated with both malignancies and multicentric Castleman's disease; the latter is a rare angiolymphoproliferative disorder that has also been linked with human herpesvirus 8 (HHV8) infection. Other diseases definitively associated with HHV8 include Kaposi's sarcoma and primary effusion lymphoma. In a search for additional HHV8-associated diseases, patients with paraneoplastic pemphigus, as well as patients with pemphigus vulgaris and pemphigus foliaceus, were studied. Using an immunofluorescence assay able to specifically detect antibodies directed against lytically induced HHV8 antigens, HHV8 antibodies were not detected in sera from 24 patients with paraneoplastic pemphigus (including 10 with concomitant Castleman's disease) nor from 19 patients with pemphigus vulgaris. Sera from patients with Kaposi's sarcoma and from healthy U.S. blood donors were positive (25 of 26) and negative (none of 20), respectively. In addition, HHV8 DNA was not found in frozen lesional skin of five patients with pemphigus vulgaris and five patients with pemphigus foliaceus by nested polymerase chain reaction (lower limit of detection = 10 copies viral DNA per microg total cellular DNA). Finally, tissue sections of lesional skin from 10 patients with pemphigus vulgaris were negative for HHV8 by in situ hybridization, using probes able to detect both latently and lytically expressed HHV8 genes in Kaposi's sarcoma tissue. In summary, no evidence of HHV8 infection was found in all types of pemphigus using a variety of methods. These findings do not support a general role for HHV8 in skin diseases associated with immunosuppression.

Castleman Disease↗