Differential regulation of the attachment of Kaposi's sarcoma-associated herpesvirus (KSHV)-infected human B cells to extracellular matrix by KSHV-encoded gB and cellular alphaV integrins.

Kaposi's sarcoma-associated herpesvirus (KSHV) has two modes of replications: latent and lytic replications. Reactivation from latency is dictated, in part, by the cell cycle. Herein, we have attempted to delineate the importance of cell cycle in KSHV pathogenesis by exploring the expression pattern of cell-surface receptors during different phases of the cell cycle. alphaV integrin expression is augmented during S phase in fibroblasts, epithelial and KSHV-infected cells. Using a Matrigel system, we pioneer the concept that KSHV-infected primary effusion lymphoma cells can attach to extracellular matrix proteins. This attachment is mediated primarily via alphaV integrins or virally encoded gB, and occurs preferentially in cells from S phase or cells from S phase actively supporting a lytic infection respectively. Such an ability of infected B cells to attach to endothelial cells may also aid in the dissemination of infection. The keystone of this work is that for the first time, we describe the ability of KSHV-infected B cells to preferentially use cellular (alphaV) or viral (gB) receptors to specifically bind cells, depending upon the stage of the cell cycle and infection.

Sepsis in Special Populations.

Sepsis is recognized by the presence of physiologic and laboratory changes that reflect the inflammatory response to infection on cellular and systemic levels. Comorbid conditions, such as cirrhosis, end-stage renal disease, and obesity, alter patients' susceptibility to infection and their response to it once present. Baseline changes in vital signs and chronic medications often mask clues to the severity of illness. The physiologic, hematologic, and biochemical adjustments that accompany pregnancy and the puerperium introduce similar challenges. Emergency providers must remain vigilant for subtle alterations in the expected baseline for these conditions to arrive at appropriate management decisions.

Raf promotes human herpesvirus-8 (HHV-8/KSHV) infection.

Human herpesvirus-8 (HHV-8/KSHV) is etiologically associated with Kaposi's sarcoma (KS) and other tumors. Constitutive activation of the mitogen-activated protein kinase (MAPK) signaling pathway has been associated with a variety of tumors, including AIDS-related KS. The oncoprotein Raf is situated at a pivotal position in regulating the MAPK pathway. Hence, we analysed the effect of oncoprotein Raf on HHV-8 infectious entry into target cells. Here we report Raf expression to significantly enhance HHV-8 infection of target cells. These findings implicate a role for Raf not only in the infectious entry of HHV-8 but also in modulating KS pathogenesis.

Cigarette smoke concentrate inhibits Kaposi's sarcoma-associated herpesvirus infection.

Kaposi's sarcoma-associated herpesvirus (KSHV) is etiologically associated with Kaposi's sarcoma (KS), primary effusion lymphoma(PEL), multicentric Castleman disease, and other tumors. Progression of KS is dictated by an aberrant production of inflammatory cytokines and increase in KSHV infection of cells. In this study, we analyzed the effect of cigarette smoke concentrate (CSC) on KSHV infection of human foreskin fibroblasts (HFF) using real time quantitative RT-PCR. Our results demonstrated that the CSC-treated cells supported 50% lower infection of KSHV when compared to the untreated cells. Radiolabeled-binding assays indicated that CSC inhibited KSHV infection of cells at a post attachment stage of entry. Taken together, we report for the first time the ability of CSC to specifically inhibit KSHV infection of cells.

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.

Vascular endothelial growth factor augments human herpesvirus-8 (HHV-8/KSHV) infection.

Human herpesvirus-8 (HHV-8/KSHV) is etiologically associated with Kaposi's sarcoma (KS) and other tumors. The Raf oncoprotein enhances HHV-8 infection of target cells. In addition, we have previously demonstrated that Raf induces vascular endothelial growth factor (VEGF) expression. VEGF is a growth factor that has autocrine growth activity and has been implicated in the formation of the spindle shape cell morphology characteristic of Kaposi's sarcoma (KS). The aim of this study was to test the hypothesis that VEGF enhances infection of HHV-8. Herein, we demonstrate that the soluble VEGF enhanced green florescence protein encoding (GFP)-HHV-8 (rKSHV.152) infection of human foreskin fibroblasts (HFF) and not of 293 cells. We found this to be in part, due to the fact that HFF inherently produces significantly lower concentrations of VEGF when compared to 293 cells. Treating 293 cells (but not HFF) with a VEGF receptor (VEGFR) inhibitor significantly lowered infection. Furthermore, transfecting 293 cells with VEGF specific si-RNA did not alter the binding of HHV-8 to cells; but significantly lowered VEGF expression and thus GFP-HHV-8 infection. Interestingly, lowering VEGF expression in 293 cells wtih VEGF specific si-RNA did not completely inhibit GFP-HHV-8 infection. We conclude that VEGF is not a requirement for HHV-8 infection; but VEGF plays a major role in augmenting infection at a post binding stage of entry. These findings suggest that targeting VEGF/VEGFR may prove efficacious in controlling HHV-8 associated pathogenesis.

Role for Raf in the entry of viruses associated with AIDS (review).

The biology of acquired immune deficiency (AIDS) is yet to be completely understood partly because it is complicated by the manifestation of various viral infections and associated pathogenesis. Virus entry into target cells is a key step in the virus replication cycle which is characterized by intricate and complex interactions between virus and host cells. Analyses of virus entry are always hampered to some extent due to the inability to mimic in vivo conditions. Emphasis has been placed on understanding what the virus does during the entry process; for example the signaling it mediates during entry, or identifying the cellular receptors with which the virus interact. Often, the role of the cellular environment that is critical for the complex process of virus uptake has taken a back stage. Interestingly, most of the viruses associated with AIDS cause tumors. In a recently concluded study, we identified a role for intracellular oncogenic (Raf) signaling in human herpesvirus-8 (HHV-8/KSHV) infection of target cells. In this review we present an update on entry of various viruses commonly associated with AIDS and yet another novel way of analyzing virus entry.

B-Raf-dependent expression of vascular endothelial growth factor-A in Kaposi sarcoma-associated herpesvirus-infected human B cells.

Kaposi sarcoma-associated herpesvirus/human herpesvirus 8 (KSHV/HHV-8) is etiologically linked to Kaposi sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman disease. Vascular endothelial growth factor-A (VEGF-A) is one of the essential factors required in KSHV pathogenesis, mainly due to its ability to mediate angiogenesis. In this report we analyzed the relationship between Raf and VEGF-A expression in KSHV-infected hematopoietic cells. All of the KSHV-infected cell lines (derived from PEL) expressed higher levels of B-Raf and VEGF-A when compared with uninfected cells. Inhibition of Raf to mitogen-induced extracellular kinase (MEK) to extracellular signal-related kinase (ERK) signaling, either by the use of MEK inhibitor (PD98059) or by siRNA specific to B-Raf, significantly lowered VEGF-A expression. In addition, B-Raf-induced VEGF-A expression was demonstrated to be sufficient to enhance tubule formation in endothelial cells. Interestingly, we did not observe mutation in the B-Raf gene of the KSHV-infected PEL cell lines. Taken together, we report for the first time the ability of Raf-associated signaling to play a role in the expression of VEGF-A in KSHV-infected hematopoietic cells.

Raf-induced vascular endothelial growth factor augments Kaposi's sarcoma-associated herpesvirus infection.

Recombinant green fluorescent protein encoding Kaposi's sarcoma-associated herpesvirus (rKSHV.152) infection of beta-estradiol stimulated human foreskin fibroblasts (HFF) or HFF/DeltaB-Raf([FF]):ER (expressing a weaker form of B-Raf) could be enhanced to levels comparable to that of HFF/DeltaB-Raf([DD]):ER cells by pretreating cells with soluble vascular endothelial growth factor (VEGF). Conversely, VEGF expression and infection efficiency typically observed in beta-estradiol stimulated HFF/DeltaB-Raf([DD]):ER cells could be lowered significantly by treating with VEGF small interfering RNA. In addition, we observed enhancement of the KSHV infection in HFF cells transfected with human VEGF(121). These results confirm the ability of Raf-induced VEGF to augment KSHV infection of cells.