Human immunodeficiency virus type 1 enters primary human brain microvascular endothelial cells by a mechanism involving cell surface proteoglycans independent of lipid rafts

Neuropathies and neurological dysfunction induced by coronaviruses

During the recent years, viral epidemic due to coronaviruses, such as SARS (Severe Acute Respiratory Syndrome), Middle East Respiratory Coronavirus Syndrome (MERS), and COVID-19 (coronavirus disese-19), has become a global problem. In addition to causing cardiovascular and respiratory lethal dysfunction, these viruses can cause neurodegeneration leading to neurological disorders. Review of the current scientific literature reveals the multiple neuropathies and neuronal dysfunction associated with these viruses. Here, we review the major findings of these studies and discuss the main neurological sequels and outcomes of coronavirus infections with SARS, MERS, and COVID-19. This article analyzes and discusses the main mechanisms of coronavirus-induced neurodegeneration according to the current experimental and clinical studies. Coronaviruses can damage the nerves directly through endovascular dysfunctions thereby affecting nerve structures and synaptic connections. Coronaviruses can also induce neural cell degeneration indirectly via mitochondrial dysfunction inducing oxidative stress, inflammation, and apoptosis. Thus, coronaviruses can cause neurological disorders by inducing neurovascular dysfunction affecting nerve structures and synaptic connections, and by inducing inflammation, oxidative stress, and apoptosis. While some of these mechanisms are similar to other RNA viruses, the neurotoxic mechanisms of COVID-19, MERS, and SARS-CoV viruses are unknown and need detailed clinical and experimental studies.

Innate Immune Sensing of Viruses and Its Consequences for the Central Nervous System

Viral infections remain a global public health concern and cause a severe societal and economic burden. At the organismal level, the innate immune system is essential for the detection of viruses and constitutes the first line of defense. Viral components are sensed by host pattern recognition receptors (PRRs). PRRs can be further classified based on their localization into Toll-like receptors (TLRs), C-type lectin receptors (CLR), retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), NOD-like receptors (NLRs) and cytosolic DNA sensors (CDS). TLR and RLR signaling results in production of type I interferons (IFNα and -β) and pro-inflammatory cytokines in a cell-specific manner, whereas NLR signaling leads to the production of interleukin-1 family proteins. On the other hand, CLRs are capable of sensing glycans present in viral pathogens, which can induce phagocytic, endocytic, antimicrobial, and pro- inflammatory responses. Peripheral immune sensing of viruses and the ensuing cytokine response can significantly affect the central nervous system (CNS). But viruses can also directly enter the CNS via a multitude of routes, such as the nasal epithelium, along nerve fibers connecting to the periphery and as cargo of infiltrating infected cells passing through the blood brain barrier, triggering innate immune sensing and cytokine responses directly in the CNS. Here, we review mechanisms of viral immune sensing and currently recognized consequences for the CNS of innate immune responses to viruses.

Heparan sulfate proteoglycan-mediated dynamin-dependent transport of neural stem cell exosomes in an in vitro blood-brain barrier model

Drug delivery to the brain is greatly hampered by the presence of the blood–brain barrier (BBB) which tightly regulates the passage of molecules from blood to brain and vice versa. Nanocarriers, in which drugs can be encapsulated, can move across the blood–brain barrier (BBB) via the process of transcytosis, thus showing promise to improve drug delivery to the brain. Here, we demonstrate the use of natural nanovesicles, that is, exosomes, derived from C17.2 neural stem cells (NSCs) to efficiently carry a protein cargo across an in vitro BBB model consisting of human brain microvascular endothelial cells. We show that the exosomes are primarily taken up in brain endothelial cells via endocytosis, while heparan sulfate proteoglycans (HSPGs) act as receptors. Taken together, our data support the view that NSC exosomes may act as biological nanocarriers for efficient passage across the BBB. Nanomedicines that target HSPGs may improve their binding to brain endothelial cells and, possibly, show subsequent transcytosis across the BBB.

The Paradox of HIV Blood-Brain Barrier Penetrance and Antiretroviral Drug Delivery Deficiencies

HIV attacks the body's immune cells, frequently compromises the integrity of the blood-brain barrier (BBB), and infects the CNS in the early stages of infection. Dysfunction of the BBB further potentiates viral replication within the CNS, which can lead to HIV-associated neuropathology. Antiretroviral therapy (ART) significantly improves HIV patient outcomes and reduces mortality rates. However, there has been limited progress in targeting latent viral reservoirs within the CNS, which may eventually lead to rebound viremia. While ART drugs are shown to be effective in attenuating HIV replication in the periphery, the protection of the brain by the BBB offers an isolated sanctuary to harbor HIV and maintains chronic and persistent replication within the CNS. In this review, we elucidate the pathology of the BBB, its ability to potentiate viral replication, as well as current therapies and insufficiencies in treating HIV-infected individuals.

Protein LY6E as a candidate for mediating transport of adeno-associated virus across the human blood-brain barrier

The blood-brain barrier (BBB) is a major obstacle for the treatment of central nervous system (CNS) disorders. Significant progress has been made in developing adeno-associated virus (AAV) variants with increased ability to cross the BBB in mice. However, these variants are not efficacious in non-human primates. Herein, we employed various bioinformatic techniques to identify lymphocyte antigen-6E (LY6E) as a candidate for mediating transport of AAV across the human BBB based on the previously determined mechanism of transport in mice. Our results provide insight into future discovery and optimization of AAV variants for CNS gene delivery in humans.

Molecular Signatures of HIV-1 Envelope Associated with HIV-Associated Neurocognitive Disorders

PURPOSE OF REVIEW

The HIV-1 envelope gene (env) has been an intense focus of investigation in the search for genetic determinants of viral entry and persistence in the central nervous system (CNS).

RECENT FINDINGS

Molecular signatures of CNS-derived HIV-1 env reflect the immune characteristics and cellular constraints of the CNS compartment. Although more readily found in those with advanced HIV-1 and HIV-associated neurocognitive disorders (HAND), molecular signatures distinguishing CNS-derived quasispecies can be identified early in HIV-1 infection, in the presence or absence of combination antiretroviral therapy (cART), and are dynamic. Amino acid signatures of CNS-compartmentalization and HAND have been identified across populations. While some significant overlap exists, none are universal. Detailed analyses of CNS-derived HIV-1 env have allowed researchers to identify a number of molecular determinants associated with neuroadaptation. Future investigations using comprehensive cohorts and longitudinal databases have the greatest potential for the identification of robust, validated signatures of HAND in the cART era.

Sulfotransferase and Heparanase: Remodeling Engines in Promoting Virus Infection and Disease Development

An extraordinary binding site generated in heparan sulfate (HS) structures, during its biosynthesis, provides a unique opportunity to interact with multiple protein ligands including viral proteins, and therefore adds tremendous value to this master molecule. An example of such a moiety is the sulfation at the C3 position of glucosamine residues in HS chain via 3-O sulfotransferase (3-OST) enzymes, which generates a unique virus-cell fusion receptor during herpes simplex virus (HSV) entry and spread. Emerging evidence now suggests that the unique patterns in HS sulfation assist multiple viruses in invading host cells at various steps of their life cycles. In addition, sulfated-HS structures are known to assist in invading host defense mechanisms and initiating multiple inflammatory processes; a critical event in the disease development. All these processes are detrimental for the host and therefore raise the question of how HS-sulfation is regulated. Epigenetic modulations have been shown to be implicated in these reactions during HSV infection as well as in HS modifying enzyme sulfotransferases, and therefore pose a critical component in answering it. Interestingly, heparanase (HPSE) activity is shown to be upregulated during virus infection and multiple other diseases assisting in virus replication to promote cell and tissue damage. These phenomena suggest that sulfotransferases and HPSE serve as key players in extracellular matrix remodeling and possibly generating unique signatures in a given disease. Therefore, identifying the epigenetic regulation of OST genes, and HPSE resulting in altered yet specific sulfation patterns in HS chain during virus infection, will be a significant a step toward developing potential diagnostic markers and designing novel therapies.

HIV-associated synaptic degeneration

Human immunodeficiency virus (HIV) infection induces neuronal injuries, with almost 50% of infected individuals developing HIV-associated neurocognitive disorders (HAND). Although highly activate antiretroviral therapy (HAART) has significantly reduced the incidence of severe dementia, the overall prevalence of HAND remains high. Synaptic degeneration is emerging as one of the most relevant neuropathologies associate with HAND. Previous studies have reported critical roles of viral proteins and inflammatory responses in this pathogenesis. Infected cells, including macrophages, microglia and astrocytes, may release viral proteins and other neurotoxins to stimulate neurons and cause excessive calcium influx, overproduction of free radicals and disruption of neurotransmitter hemostasis. The dysregulation of neural circuits likely leads to synaptic damage and loss. Identification of the specific mechanism of the synaptic degeneration may facilitate the development of effective therapeutic approaches to treat HAND.

Genome-Wide Screening Uncovers the Significance of N-Sulfation of Heparan Sulfate as a Host Cell Factor for Chikungunya Virus Infection

The molecular mechanisms underlying chikungunya virus (CHIKV) infection are poorly characterized. In this study, we analyzed the host factors involved in CHIKV infection using genome-wide screening. Human haploid HAP1 cells, into which an exon-trapping vector was introduced, were challenged with a vesicular stomatitis virus pseudotype bearing the CHIKV E3 to E1 envelope proteins. Analysis of genes enriched in the cells resistant to the pseudotyped virus infection unveiled a critical role of N-sulfation of heparan sulfate (HS) for the infectivity of the clinically isolated CHIKV Thai#16856 strain to HAP1 cells. Knockout of NDST1 that catalyzes N-sulfation of HS greatly decreased the binding and infectivity of CHIKV Thai#16856 strain but not infectivity of Japanese encephalitis virus (JEV) and yellow fever virus (YFV). While glycosaminoglycans were commonly required for the efficient infectivity of CHIKV, JEV, and YFV, as shown by using B3GAT3 knockout cells, the tropism for N-sulfate was specific to CHIKV. Expression of chondroitin sulfate (CS) in NDST1-knockout HAP1 cells did not restore the binding of CHIKV Thai#16856 strain and the infectivity of its pseudotype but restored the infectivity of authentic CHIKV Thai#16856, suggesting that CS functions at later steps after CHIKV binding. Among the genes enriched in this screening, we found that TM9SF2 is critical for N-sulfation of HS and therefore for CHIKV infection because it is involved in the proper localization and stability of NDST1. Determination of the significance of and the relevant proteins to N-sulfation of HS may contribute to understanding mechanisms of CHIKV propagation, cell tropism, and pathogenesis.IMPORTANCE Recent outbreaks of chikungunya fever have increased its clinical importance. Chikungunya virus (CHIKV) utilizes host glycosaminoglycans to bind efficiently to its target cells. However, the substructure in glycosaminoglycans required for CHIKV infection have not been characterized. Here, we unveil that N-sulfate in heparan sulfate is essential for the efficient infection of a clinical CHIKV strain to HAP1 cells and that chondroitin sulfate does not help the CHIKV binding but does play roles at the later steps in HAP1 cells. We show, by comparing previous reports using Chinese hamster ovary cells, along with another observation that enhanced infectivity of CHIKV bearing Arg82 in envelope E2 does not depend on glycosaminoglycans in HAP1 cells, that the infection manner of CHIKV varies among host cells. We also show that TM9SF2 is required for CHIKV infection to HAP1 cells because it is involved in the N-sulfation of heparan sulfate through ensuring NDST1 activity.

Exosomes contribute to the transmission of anti-HIV activity from TLR3-activated brain microvascular endothelial cells to macrophages

Human brain microvascular endothelial cells (HBMECs), the major cell type in the blood-brain barrier (BBB), play a key role in maintaining brain homeostasis. However, their role in the BBB innate immunity against HIV invasion of the central nervous system (CNS) remains to be determined. Our early work showed that TLR3 signaling of HBMECs could produce the antiviral factors that inhibit HIV replication in macrophages. The present study examined whether exosomes from TLR3-activated HBMECs mediate the intercellular transfer of antiviral factors to macrophages. Primary human macrophages could take up exosomes from TLR3-activated HBMECs. HBMECs-derived exosomes contained multiple antiviral factors, including several key IFN-stimulated genes (ISGs; ISG15, ISG56, and Mx2) at mRNA and protein levels. The depletion of exosomes from TLR3-activated HBMECs culture supernatant diminished HBMECs-mediated anti-HIV activity in macrophages. In conclusion, we demonstrate that exosomes shed by HBMECs are able to transport the antiviral molecules to macrophages. This finding suggests the possibility that HIV nonpermissive BBB cells (HBMECs) can help to restore the antiviral state in HIV-infected macrophages, which may be a defense mechanism against HIV neuroinvasion.

Glycosaminoglycans and infection

Glycosaminoglycans (GAGs) are complex linear polysaccharides expressed in intracellular compartments, at the cell surface, and in the extracellular environment where they interact with various molecules to regulate many cellular processes implicated in health and disease. Subversion of GAGs is a pathogenic strategy shared by a wide variety of microbial pathogens, including viruses, bacteria, parasites, and fungi. Pathogens use GAGs at virtually every major portals of entry to promote their attachment and invasion of host cells, movement from one cell to another, and to protect themselves from immune attack. Pathogens co-opt fundamental activities of GAGs to accomplish these tasks. This ingenious strategy to subvert essential activities of GAGs likely prevented host organisms from deleting or inactivating these mechanisms during their evolution. The goal of this review is to provide a mechanistic overview of our current understanding of how microbes subvert GAGs at major steps of pathogenesis, using select GAG-pathogen interactions as representative examples.

Dendrimeric based microbicides against sexual transmitted infections associated to heparan sulfate

Cell surface heparan sulfate (HS) represents a common link that many sexually transmitted infections (STIs) require for infection.

Effect of human immunodeficiency virus on blood-brain barrier integrity and function: an update

The blood-brain barrier (BBB) is a diffusion barrier that has an important role in maintaining a precisely regulated microenvironment protecting the neural tissue from infectious agents and toxins in the circulating system. Compromised BBB integrity plays a major role in the pathogenesis of retroviral associated neurological diseases. Human Immunodeficiency Virus (HIV) infection in the Central Nervous System (CNS) is an early event even before the serodiagnosis for HIV positivity or the initiation of antiretroviral therapy (ART), resulting in neurological complications in many of the infected patients. Macrophages, microglia and astrocytes (in low levels) are the most productively/latently infected cell types within the CNS. In this brief review, we have discussed about the effect of HIV infection and viral proteins on the integrity and function of BBB, which may contribute to the progression of HIV associated neurocognitive disorders.

Heme oxygenase-1 dysregulation in the brain: implications for HIV-associated neurocognitive disorders

Heme oxygenase-1 (HO-1) is a highly inducible and ubiquitous cellular enzyme that subserves cytoprotective responses to toxic insults, including inflammation and oxidative stress. In neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease and multiple sclerosis, HO-1 expression is increased, presumably reflecting an endogenous neuroprotective response against ongoing cellular injury. In contrast, we have found that in human immunodeficiency virus (HIV) infection of the brain, which is also associated with inflammation, oxidative stress and neurodegeneration, HO-1 expression is decreased, likely reflecting a unique role for HO-1 deficiency in neurodegeneration pathways activated by HIV infection. We have also shown that HO-1 expression is significantly suppressed by HIV replication in cultured macrophages which represent the primary cellular reservoir for HIV in the brain. HO-1 deficiency is associated with release of neurotoxic levels of glutamate from both HIV-infected and immune-activated macrophages; this glutamate-mediated neurotoxicity is suppressed by pharmacological induction of HO-1 expression in the macrophages. Thus, HO-1 induction could be a therapeutic strategy for neuroprotection against HIV infection and other neuroinflammatory brain diseases. Here, we review various stimuli and signaling pathways regulating HO-1 expression in macrophages, which could promote neuronal survival through HO-1-modulation of endogenous antioxidant and immune modulatory pathways, thus limiting the oxidative stress that can promote HIV disease progression in the CNS. The use of pharmacological inducers of endogenous HO-1 expression as potential adjunctive neuroprotective therapeutics in HIV infection is also discussed.

Chondroitin Sulfate is the Primary Receptor for a Peptide-Modified AAV That Targets Brain Vascular Endothelium In Vivo

Recently, we described a peptide-modified AAV2 vector (AAV-GMN) containing a capsid-displayed peptide that directs in vivo brain vascular targeting and transduction when delivered intravenously. In this study, we sought to identify the receptor that mediates transduction by AAV-GMN. We found that AAV-GMN, but not AAV2, readily transduces the murine brain endothelial cell line bEnd.3, a result that mirrors previously observed in vivo transduction profiles of brain vasculature. Studies in vitro revealed that the glycosaminoglycan, chondroitin sulfate C, acts as the primary receptor for AAV-GMN. Unlike AAV2, chondroitin sulfate expression is required for cell transduction by AAV-GMN, and soluble chondroitin sulfate C can robustly inhibit AAV-GMN transduction of brain endothelial cells. Interestingly, AAV-GMN retains heparin-binding properties, though in contrast to AAV2, it poorly transduces cells that express heparan sulfate but not chondroitin sulfate, indicating that the peptide insertion negatively impacts heparan-mediated transduction. Lastly, when delivered directly, this modified virus can transduce multiple brain regions, indicating that the potential of AAV-GMN as a therapeutic gene delivery vector for central nervous system disorders is not restricted to brain vascular endothelium.

TRIM5α and TRIM22 are differentially regulated according to HIV-1 infection phase and compartment

The antiviral role of TRIM E3 ligases in vivo is not fully understood. To test the hypothesis that TRIM5α and TRIM22 have differential transcriptional regulation and distinct anti-HIV roles according to infection phase and compartment, we measured TRIM5α, TRIM22, and type I interferon (IFN-I)-inducible myxovirus resistance protein A (MxA) levels in peripheral blood mononuclear cells (PBMCs) during primary and chronic HIV-1 infection, with chronic infection samples being matched PBMCs and central nervous system (CNS)-derived cells. Associations with biomarkers of disease progression were explored. The impact of IFN-I, select proinflammatory cytokines, and HIV on TRIM E3 ligase-specific expression was investigated. PBMCs from individuals with primary and chronic HIV-1 infection had significantly higher levels of MxA and TRIM22 than did PBMCs from HIV-1-negative individuals (P < 0.05 for all comparisons). PBMCs from chronic infection had lower levels of TRIM5α than did PBMCs from primary infection or HIV-1-uninfected PBMCs (P = 0.0001 for both). In matched CNS-derived samples and PBMCs, higher levels of MxA (P = 0.001) and TRIM5α (P = 0.0001) in the CNS were noted. There was a negative correlation between TRIM22 levels in PBMCs and plasma viral load (r = -0.40; P = 0.04). In vitro, IFN-I and, rarely, proinflammatory cytokines induced TRIM5α and TRIM22 in a cell type-dependent manner, and the knockdown of either protein in CD4(+) lymphocytes resulted in increased HIV-1 infection. These data suggest that there are infection-phase-specific and anatomically compartmentalized differences in TRIM5α and TRIM22 regulation involving primarily IFN-I and specific cell types and indicate subtle differences in the antiviral roles and transcriptional regulation of TRIM E3 ligases in vivo.

IMPORTANCE

Type I interferon-inducible TRIM E3 ligases are a family of intracellular proteins with potent antiviral activities mediated through diverse mechanisms. However, little is known about the contribution of these proteins to antiviral immunity in vivo and how their expression is regulated. We show here that TRIM5α and TRIM22, two prominent members of the family, have different expression patterns in vivo and that the expression pattern depends on HIV-1 infection status and phase. Furthermore, expression differs in peripheral blood versus central nervous system anatomical sites of infection. Only TRIM22 expression correlated negatively with HIV-1 viral load, but gene silencing of both proteins enhances HIV-1 infection of target cells. We report subtle differences in TRIM5α and TRIM22 gene induction by IFN-I and proinflammatory cytokines in CD4(+) lymphocytes, monocytes, and neuronal cells. This study enhances our understanding of antiviral immunity by intrinsic antiviral factors and how their expression is determined.

Human immunodeficiency virus and heparan sulfate: from attachment to entry inhibition

By targeting cells that provide protection against infection, HIV-1 causes acquired immunodeficiency syndrome. Infection starts when gp120, the viral envelope glycoprotein, binds to CD4 and to a chemokine receptor usually CCR5 or CXCR4. As many microorganisms, HIV-1 also interacts with heparan sulfate (HS), a complex group of cell surface associated anionic polysaccharides. It has been thought that this binding, occurring at a step prior to CD4 recognition, increases infectivity by pre-concentrating the virion particles at the cell surface. Early work, dating from before the identification of CCR5 and CXCR4, showed that a variety of HS mimetics bind to the gp120 V3 loop through electrostatic interactions, compete with cell surface associated HS to bind the virus and consequently, neutralize the infectivity of a number of T-cell line-adapted HIV-1 strains. However, progress made to better understand HIV-1 attachment and entry, coupled with the recent identification of additional gp120 regions mediating HS recognition, have considerably modified this view. Firstly, the V3 loop from CXCR4-using viruses is much more positively charged compared to those using CCR5. HS inhibition of cell attachment is thus restricted to CXCR4-using viruses (such as T-cell line-adapted HIV-1). Secondly, studies aiming at characterizing the gp120/HS complex revealed that HS binding was far more complex than previously thought: in addition to the V3 loop of CXCR4 tropic gp120, HS interacts with several other cryptic areas of the protein, which can be induced upon CD4 binding, and are conserved amongst CCR5 and CXCR4 viruses. In view of these data, this review will detail the present knowledge on HS binding to HIV-1, with regards to attachment and entry processes. It will discuss the perspective of targeting the gp120 co-receptor binding site with HS mimetic compounds, a strategy that recently gave rise to entry inhibitors that work in the low nanomolar range, independently of co-receptor usage.

Peptide-derivatized SB105-A10 dendrimer inhibits the infectivity of R5 and X4 HIV-1 strains in primary PBMCs and cervicovaginal histocultures

Peptide dendrimers are a class of molecules that exhibit a large array of biological effects including antiviral activity. In this report, we analyzed the antiviral activity of the peptide-derivatized SB105-A10 dendrimer, which is a tetra-branched dendrimer synthetized on a lysine core, in activated peripheral blood mononuclear cells (PBMCs) that were challenged with reference and wild-type human immunodeficiency virus type 1 (HIV-1) strains. SB105-A10 inhibited infections by HIV-1 X4 and R5 strains, interfering with the early phases of the viral replication cycle. SB105-A10 targets heparan sulfate proteoglycans (HSPGs) and, importantly, the surface plasmon resonance (SPR) assay revealed that SB105-A10 strongly binds gp41 and gp120, most likely preventing HIV-1 attachment/entry through multiple mechanisms. Interestingly, the antiviral activity of SB105-A10 was also detectable in an organ-like structure of human cervicovaginal tissue, in which SB105-A10 inhibited the HIV-1ada R5 strain infection without altering the tissue viability. These results demonstrated the strong antiviral activity of SB105-A10 and suggest a potential microbicide use of this dendrimer to prevent the heterosexual transmission of HIV-1.

When human immunodeficiency virus meets chemokines and microglia: neuroprotection or neurodegeneration?

Chemokines are chemotactic cytokines that were originally discovered as promoters of leukocyte proliferation and mobility. In recent years, however, evidence has demonstrated constitutive expression of chemokines and chemokine receptors in a variety of cells in the central and peripheral nervous system and has proposed a role for chemokines in neurodegenerative diseases characterized by inflammation and microglia proliferation. In addition, chemokine receptors, and in particular CXCR4 and CCR5, mediate human immunodeficiency virus type 1 (HIV) infection of immunocompetent cells as well as microglia. Subsequently, HIV, through a variety of mechanisms, promotes synapto-dendritic alterations and neuronal loss that ultimately lead to motor and cognitive impairments. These events are accompanied by microglia activation. Nevertheless, a microglia-mediated mechanism of neuronal degeneration alone cannot fully explain some of the pathological features of HIV infected brain such as synaptic simplification. In this article, we present evidence that some of the microglia responses to HIV are beneficial and neuroprotective. These include the ability of microglia to release anti-inflammatory cytokines, to remove dying cells and to promote axonal sprouting.

Role of heparan sulfate in sexually transmitted infections

Cell surface heparan sulfate (HS), a polysaccharide composed of alternating uronic acid and glucosamine residues, represents a common link that many sexually transmitted infections (STIs) require for infection. Variable modifications within the monomeric units of HS chains together with their unique structural conformations generate heterogeneity, which expands the ability of HS to bind a diverse array of host and microbial proteins. Recent advances made in the field of glycobiology have critically enhanced our understanding of HS and its interactions with microbes and their significance in important human diseases. The role of HS has been elaborated for several STIs to include those caused by herpes simplex virus, human immunodeficiency virus, human papillomavirus, and Chlamydia. In addition, gonorrhea, syphilis, and yeast infections are also dependent on the presence of HS on human target cells. Critical steps such as pathogen adhesion or binding to host cells followed by internalization to enhance intracellular survival and possible spread to other cells are mediated by HS. In addition, HS guided cell signaling plays a role in the development of angiogenesis and inflammation associated with many STIs. Past and ongoing investigations are providing new push for the development of HS-mimetics and analogs as novel prevention strategies against many different STIs. This review article summarizes the significance of HS in STIs and describes how emerging new products that target HS can be used to control the spread of STIs.

Accelerated diabetic retinopathy and late human immunodeficiency virus diagnosis

PURPOSE

To describe a case of rapidly progressive diabetic retinopathy in a patient who is human immunodeficiency virus positive.

METHODS

This is an observational case report.

RESULTS

Fundus examination shows worsening of diabetic retinopathy with new vessels and vitreous hemorrhage in both eyes despite intense pan retinal photocoagulation.

CONCLUSION

For patients with diabetes, additional diagnosis of human immunodeficiency virus increases the challenge of managing diabetic retinopathy as proliferation can appear rapidly and tends to worsen in these patients.

Function of membrane rafts in viral lifecycles and host cellular response

Membrane rafts are small (10–200 nm) sterol- and sphingolipid-enriched domains that compartmentalize cellular processes. Membrane rafts play an important role in viral infection cycles and viral virulence. Viruses are divided into four main classes, enveloped DNA virus, enveloped RNA virus, nonenveloped DNA virus, and nonenveloped RNA virus. General virus infection cycle is also classified into two sections, the early stage (entry process) and the late stage (assembly, budding, and release processes of virus particles). In the viral cycle, membrane rafts act as a scaffold of many cellular signal transductions, which are associated with symptoms caused by viral infections. In this paper, we describe the functions of membrane rafts in viral lifecycles and host cellular response according to each virus classification, each stage of the virus lifecycle, and each virus-induced signal transduction.

Molecular functions of syndecan-1 in disease

Syndecan-1 is a cell surface heparan sulfate proteoglycan that binds to many mediators of disease pathogenesis. Through these molecular interactions, syndecan-1 can modulate leukocyte recruitment, cancer cell proliferation and invasion, angiogenesis, microbial attachment and entry, host defense mechanisms, and matrix remodeling. The significance of syndecan-1 interactions in disease is underscored by the striking pathological phenotypes seen in the syndecan-1 null mice when they are challenged with disease-instigating agents or conditions. This review discusses the key molecular functions of syndecan-1 in modulating the onset, progression, and resolution of inflammatory diseases, cancer, and infection.

HIV-related neurocognitive impairment--a review

Neurocognitive impairments following central nervous system opportunistic infections and HIV-associated dementia (HAD) were common clinical features of HIV infection prior to anti-retroviral therapy. As HIV infection has evolved from an invariably fatal disease with a poor prognosis to a condition requiring long-term management, HIV-related neurocognitive disorders have been the subject of increasing research. This review will examine the recent changes in the understanding of the HIV-associated neurocognitive disorders (HAND) including the changing epidemiology, risk factors associated with its development, methods for screening for the disorders and evolving treatment options.

Advances in our understanding of the pathogenesis of HIV-1 associated nephropathy in children

Childhood HIV-1 associated nephropathy (HIVAN) is a clinical and renal histological disease characterized by heavy proteinuria associated with focal and segmental glomerular sclerosis and/or mesangial hyperplasia in combination with microcystic tubular dilatation. These lesions lead to renal enlargement and rapid progression to kidney failure. Children of African ancestry have a unique susceptibility to developing HIVAN. It is estimated that approximately 300,000 HIV-infected children living in the sub-Saharan Africa could develop HIVAN if they do not receive appropriate antiretroviral therapy. This article discusses recent developments and controversies related to the pathogenesis of childhood HIVAN. The role of host genetic factors, including the newly identified variants in the APOL1 gene, is discussed in the context of previous studies that established the pathological paradigm for HIVAN, and our current understanding of the functional genomics analysis. Hopefully, these advances will provide new research opportunities to generate better treatments for children with HIVAN.

Membrane raft redox signalosomes in endothelial cells

Membrane rafts (MRs) are specialized microdomains in the cell membrane with an altered lipid composition. Upon various stimulations, MRs can be clustered to aggregate or recruit NADPH oxidase sub-units and related proteins to form MR redox signalosomes in the membrane of cells like vascular endothelial cells (ECs). Multiple protein complexes, like MR redox signalosomes, are now considered to play a crucial role in the regulation of cell function and in the development of different cell dysfunctions. To form such redox signalosomes, ceramide will be generated from the hydrolysis of sphingomyelin by lysosomal acid sphingomyelinase that has been translocated via lysosome fusion to the MR area. In this brief review, current information is provided to help understand the occurrence and function of MR redox signalosomes. This may increase enthusiasm of the scientific community for further studies on the molecular mechanisms and the functional significance of forming such MR redox signalosomes.

Primate gammaretroviruses require an ancillary factor not required for murine gammaretroviruses to infect BHK cells

BHK cells remain resistant to xenotropic murine retrovirus-related virus (XMRV) or gibbon ape leukemia virus (GALV) infection, even when their respective receptors, Xpr1 or PiT1, are expressed. We set out to determine the stage at which viral infection is blocked and whether this block is mediated by a dominant-negative factor or the absence of a requisite ancillary factor. BHK cells bind neither XMRV nor GALV envelope proteins. BHK cells expressing the appropriate receptors bind XMRV or GALV envelope proteins. BHK cells can be infected by NZB-XMV(New Zealand Black mouse xenotropic murine virus)-enveloped vectors, expressing an envelope derived from a xenotropic retrovirus that, like XMRV, employs Xpr1 as a receptor, and also by vectors bearing the envelope of 10A1 murine leukemia virus (MLV), a murine retrovirus that can use PiT1 as a receptor. The retroviral vectors used in these analyses differ solely in their viral envelope proteins, suggesting that the block to XMRV and GALV infection is mediated at the level of envelope-receptor interactions. N-linked glycosylation of the receptors was not found to mediate resistance of receptor-expressing BHK cells to GALV or XMRV, as shown by tunicamycin treatment and mutation of the specific glycosylation site of the PiT1 receptor. Hybrid cells produced by fusing BHKXpr1 or BHKPiT1 to XMRV- or GALV-resistant cells, respectively, can mediate efficient XMRV or GALV infection. These findings indicate that BHK cells lack a factor that is required for infection by primate xenotropic viruses. This factor is not required for viruses that use the same receptors but were directly isolated from mice.

Properties of HTLV-I transformed CD8+ T-cells in response to HIV-1 infection

HIV-1 infection studies of primary CD8(+) T-cells are hampered by difficulty in obtaining a significant number of targets for infection and low levels of productive infection. Further, there exists a paucity of CD8-expressing T-cell lines to address questions pertaining to the study of CD8(+) T-cells in the context of HIV-1 infection. In this study, a set of CD8(+) T-cell clones were originated through HTLV-I transformation in vitro, and the properties of these cells were examined. The clones were susceptible to T-cell tropic strains of the virus and exhibited HIV-1 production 20-fold greater than primary CD4(+) T-cells. Productive infection resulted in a decrease in expression of CD8 and CXCR4 molecules on the surface of the CD8(+) T-cell clones and antibodies to these molecules abrogated viral binding and replication. These transformed cells provide an important tool in the study of CD8(+) T-cells and may provide important insights into the mechanism(s) behind HIV-1 induced CD8(+) T-cell dysfunction.

The proteoglycan bamacan is a host cellular ligand of vaccinia virus neurovirulence factor N1L

Neurovirulence is one of the pathological complications associated with vaccinia virus (VV) infection/vaccination. Although the viral N1L protein has been identified as the neurovirulence factor, none of the host N1L-interacting factors have been identified so far. In the present study, we identified N1L-interacting proteins by screening a human brain cDNA expression library with N1L as a bait protein in a yeast two-hybrid analysis. The analysis revealed that N1L interacts with human brain-originated cellular basement membrane-associated chondroitin sulfate proteoglycan (bamacan). The N1L-binding domain of bamacan was mapped to its C-terminal 227 amino acids. The N1L-bamacan interaction was further confirmed in both VV-infected and N1L-transfected mammalian cells. Following the confirmation of the protein interactions by coimmunoprecipitation experiments, confocal microscopic analysis revealed that N1L colocalizes with bamacan both in VV-infected B-SC-1 cells as well as in mice neuronal tissue. Furthermore, a human neural cell line, which expresses bamacan to moderately elevated levels relative to a non-neural cell line, supported enhanced viral growth. Overall, these studies clearly suggest that bamacan interacts with the VV-N1L and such interactions seem to play a positive role in promoting the viral growth and perhaps contribute to the virulence of VV in neural cells.

Novel mechanisms of central nervous system damage in HIV infection

Human immunodeficiency virus-1 infection of the central nervous system is an early event after primary infection, resulting in motor and cognitive defects in a significant number of individuals despite successful antiretroviral therapy. The pathology of the infected brain is characterized by enhanced leukocyte infiltration, microglial activation and nodules, aberrant expression of inflammatory factors, neuronal dysregulation and loss, and blood–brain barrier disruption. Months to years following the primary infection, these central nervous system insults result in a spectrum of motor and cognitive dysfunction, ranging from mild impairment to frank dementia. The mechanisms that mediate impairment are still not fully defined. In this review we discuss the cellular and molecular mechanisms that facilitate impairment and new data that implicate intercellular communication systems, gap junctions and tunneling nanotubes, as mediators of human immunodeficiency virus-1 toxicity and infection within the central nervous system. These data suggest potential targets for novel therapeutics.

A whole genome association study of mother-to-child transmission of HIV in Malawi

BACKGROUND

More than 300,000 children are newly infected with HIV each year, predominantly through mother-to-child transmission (HIV MTCT). Identification of host genetic traits associated with transmission may more clearly explain the mechanisms of HIV MTCT and further the development of a vaccine to protect infants from infection. Associations between transmission and a selection of genes or single nucleotide polymorphisms (SNP)s may give an incomplete picture of HIV MTCT etiology. Thus, this study employed a genome-wide association approach to identify novel variants associated with HIV MTCT.

METHODS

We conducted a nested case-control study of HIV MTCT using infants of HIV(+) mothers, drawn from a cohort study of malaria and HIV in pregnancy in Blantyre, Malawi. Whole genome scans (650,000 SNPs genotyped using Illumina genotyping assays) were obtained for each infant. Logistic regression was used to evaluate the association between each SNP and HIV MTCT.

RESULTS

Genotype results were available for 100 HIV(+) infants (at birth, 6, or 12 weeks) and 126 HIV(-) infants (at birth, 6, and 12 weeks). We identified 9 SNPs within 6 genes with a P-value < 5 × 10(-5) associated with the risk of transmission, in either unadjusted or adjusted by maternal HIV viral load analyses. Carriers of the rs8069770 variant allele were associated with a lower risk of HIV MTCT (odds ratio = 0.27, 95% confidence interval = 0.14, 0.51), where rs8069770 is located within HS3ST3A1, a gene involved in heparan sulfate biosynthesis. Interesting associations for SNPs located within or near genes involved in pregnancy and development, innate immunological response, or HIV protein interactions were also observed.

CONCLUSIONS

This study used a genome-wide approach to identify novel variants associated with the risk of HIV MTCT in order to gain new insights into HIV MTCT etiology. Replication of this work using a larger sample size will help us to differentiate true positive findings.

Genome-wide identification of susceptibility alleles for viral infections through a population genetics approach

Viruses have exerted a constant and potent selective pressure on human genes throughout evolution. We utilized the marks left by selection on allele frequency to identify viral infection-associated allelic variants. Virus diversity (the number of different viruses in a geographic region) was used to measure virus-driven selective pressure. Results showed an excess of variants correlated with virus diversity in genes involved in immune response and in the biosynthesis of glycan structures functioning as viral receptors; a significantly higher than expected number of variants was also seen in genes encoding proteins that directly interact with viral components. Genome-wide analyses identified 441 variants significantly associated with virus-diversity; these are more frequently located within gene regions than expected, and they map to 139 human genes. Analysis of functional relationships among genes subjected to virus-driven selective pressure identified a complex network enriched in viral products-interacting proteins. The novel approach to the study of infectious disease epidemiology presented herein may represent an alternative to classic genome-wide association studies and provides a large set of candidate susceptibility variants for viral infections.

Viruses have represented a constant threat to human communities throughout their history, therefore, human genes involved in anti-viral response can be thought of as targets of virus-driven selective pressure. Here we utilized the marks left by selection to identify viral infection-associated allelic variants. We analyzed more than 660,000 single nucleotide polymorphisms (SNPs) genotyped in 52 human populations, and we used virus diversity (the number of different viruses in a geographic region) to measure virus-driven selective pressure. Results showed that genes involved in immune response and in the biosynthesis of glycan structures functioning as viral receptors display more variants associated with virus diversity than expected by chance. The same holds true for genes encoding proteins that directly interact with viral components. Genome-wide analysis identified 441 variants, mapping to 139 human genes, significantly associated with virus-diversity. We analyzed the functional relationships among genes subjected to virus-driven selective pressure and identified a complex interaction network enriched in viral products-interacting proteins. Therefore, we describe a novel approach for the identification of gene variants that may be involved in the susceptibility to viral infections.

Regulation of CCR5 expression in human placenta: insights from a study of mother-to-child transmission of HIV in Malawi

Background

Human promoter polymorphisms in the chemokine co-receptor 5 gene (CCR5) have been noted for association with mother-to-child transmission of HIV (HIV MTCT) as well as reduced receptor expression in vitro, but have not been clearly associated with CCR5 expression in vivo. Placental expression of CCR5 may be influenced by such polymorphisms as well as other in vivo regulatory factors.

Methodology/Principal Findings

We evaluated the associations between infant CCR5 polymorphisms, measures of maternal infection, and placental expression of CCR5 among mother-infant pairs in Blantyre, Malawi. RNA was extracted from placental tissue and used in multiplex real-time PCR to quantify gene expression. Through linear regression, we observed that CCR5-2554T (β = −0.67, 95% CI = −1.23, −0.11) and -2132T (β = −0.75, 95% CI = −0.131, −0.18) were significantly associated with reduced placental expression of CCR5. An incremental increase in CCR5 expression was observed for incremental increases in expression of two heparan sulfate genes involved in viral infection, HS3ST3A1 (β = 0.27, 95% CI = 0.18, 0.35) and HS3ST3B1 (β = 0.11, 95% CI = 0.06, 0.18). Among HIV infected mothers, an incremental increase in maternal HIV viral load was also associated with higher CCR5 expression (β = 0.76, 95% CI = 0.12, 1.39). Maternal HIV status had no overall effect (β = 0.072, 95% CI = −0.57, −0.72). Higher CCR5 expression was observed for mothers with malaria but was not statistically significant (β = 0.37, 95% CI = −0.43, 1.18).

Conclusions/Significance

These results provide in vivo evidence for genetic and environmental factors involved in the regulation of CCR5 expression in the placenta. Our findings also suggest that the measurement of placental expression of CCR5 alone is not an adequate indicator of the risk of mother-to-child transmission of HIV.

Proteoglycans in host-pathogen interactions: molecular mechanisms and therapeutic implications

Many microbial pathogens subvert proteoglycans for their adhesion to host tissues, invasion of host cells, infection of neighbouring cells, dissemination into the systemic circulation, and evasion of host defence mechanisms. Where studied, specific virulence factors mediate these proteoglycan-pathogen interactions, which are thus thought to affect the onset, progression and outcome of infection. Proteoglycans are composites of glycosaminoglycan (GAG) chains attached covalently to specific core proteins. Proteoglycans are expressed ubiquitously on the cell surface, in intracellular compartments, and in the extracellular matrix. GAGs mediate the majority of ligand-binding activities of proteoglycans, and many microbial pathogens elaborate cell-surface and secreted factors that interact with GAGs. Some pathogens also modulate the expression and function of proteoglycans through known virulence factors. Several GAG-binding pathogens can no longer attach to and invade host cells whose GAG expression has been reduced by mutagenesis or enzymatic treatment. Furthermore, GAG antagonists have been shown to inhibit microbial attachment and host cell entry in vitro and reduce virulence in vivo. Together, these observations underscore the biological significance of proteoglycan-pathogen interactions in infectious diseases.

Diverse functions of glycosaminoglycans in infectious diseases

Glycosaminoglycans (GAGs) are complex carbohydrates that are expressed ubiquitously and abundantly on the cell surface and in the extracellular matrix (ECM). The extraordinary structural diversity of GAGs enables them to interact with a wide variety of biological molecules. Through these interactions, GAGs modulate various biological processes, such as cell adhesion, proliferation and migration, ECM assembly, tissue repair, coagulation, and immune responses, among many others. Studies during the last several decades have indicated that GAGs also interact with microbial pathogens. GAG-pathogen interactions affect most, if not all, the key steps of microbial pathogenesis, including host cell attachment and invasion, cell-cell transmission, systemic dissemination and infection of secondary organs, and evasion of host defense mechanisms. These observations indicate that GAG-pathogen interactions serve diverse functions that affect the pathogenesis of infectious diseases.

Evidence for predilection of macrophage infiltration patterns in the deeper midline and mesial temporal structures of the brain uniquely in patients with HIV-associated dementia

Background

HIV-1 penetrates the central nervous system, which is vital for HIV-associated dementia (HAD). But the role of cellular infiltration and activation together with HIV in the development of HAD is poorly understood.

Methods

To study activation and infiltration patterns of macrophages, CD8+ T cells in relation to HIV in diverse CNS areas of patients with and without dementia. 46 brain regions from two rapidly progressing severely demented patients and 53 regions from 4 HIV+ non-dementia patients were analyzed. Macrophage and CD8+ T cell infiltration of the CNS in relation to HIV was assessed using immuno-histochemical analysis with anti-HIV (P24), anti-CD8 and anti-CD68, anti-S-100A8 and granzyme B antibodies (cellular activation). Statistical analysis was performed with SPSS 12.0 with Student's t test and ANOVA.

Results

Overall, the patterns of infiltration of macrophages and CD8+ T cells were indiscernible between patients with and without dementia, but the co-localization of macrophages and CD8+ T cells along with HIV P24 antigen in the deeper midline and mesial temporal structures of the brain segregated the two groups. This predilection of infected macrophages and CD8+ T cells to the middle part of the brain was unique to both HAD patients, along with unique nature of provirus gag gene sequences derived from macrophages in the midline and mesial temporal structures.

Conclusion

Strong predilection of infected macrophages and CD8+ T cells was typical of the deeper midline and mesial temporal structures uniquely in HAD patients, which has some influence on neurocognitive impairment during HIV infection.

Therapeutic approaches using host defence peptides to tackle herpes virus infections

One of the most common viral infections in humans is caused by herpes simplex virus (HSV). It can easily be treated with nucleoside analogues (e.g., acyclovir), but resistant strains are on the rise. Naturally occurring antimicrobial peptides have been demonstrated to possess antiviral activity against HSV. New evidence has also indicated that these host defence peptides are able to selectively stimulate the innate immune system to fight of infections. This review will focus on the anti-HSV activity of such peptides (both natural and synthetic), describe their mode of action and their clinical potential.

Spermatozoa capture HIV-1 through heparan sulfate and efficiently transmit the virus to dendritic cells

Semen is the main vector for HIV-1 dissemination worldwide. It contains three major sources of infectious virus: free virions, infected leukocytes, and spermatozoa-associated virions. We focused on the interaction of HIV-1 with human spermatozoa and dendritic cells (DCs). We report that heparan sulfate is expressed in spermatozoa and plays an important role in the capture of HIV-1. Spermatozoa-attached virus is efficiently transmitted to DCs, macrophages, and T cells. Interaction of spermatozoa with DCs not only leads to the transmission of HIV-1 and the internalization of the spermatozoa but also results in the phenotypic maturation of DCs and the production of IL-10 but not IL-12p70. At low values of extracellular pH (∼6.5 pH units), similar to those found in the vaginal mucosa after sexual intercourse, the binding of HIV-1 to the spermatozoa and the consequent transmission of HIV-1 to DCs were strongly enhanced. Our observations support the notion that far from being a passive carrier, spermatozoa acting in concert with DCs might affect the early course of sexual transmission of HIV-1 infection.

TSLP production by epithelial cells exposed to immunodeficiency virus triggers DC-mediated mucosal infection of CD4+ T cells

Mucosal dendritic cells have been implicated in the capture, storage, and transmission of HIV to CD4(+) T cells as well as in the promotion of HIV replication in activated CD4(+) T cells during the cognate T-cell and DC interaction. We report that HIV induces human genital mucosal epithelial cells to produce thymic stromal lymphopoietin (TSLP) via activation of the NFkappaB signaling pathway. The TSLP secreted by HIV exposed epithelial cells activated DC, which promoted proliferation and HIV-1 replication of co-cultured autologous CD4(+) T cells. In rhesus macaques, we observed dramatic increases in TSLP expression concurrent with an increase in viral replication in the vaginal tissues within the first 2 weeks after vaginal SIV exposure. These data suggest that HIV-mediated TSLP production by mucosal epithelial cells is a critical trigger for DC-mediated amplification of HIV-infection in activated CD4(+) T cells. The cross talk between mucosal epithelial cells and DC, mediated by HIV-induced TSLP, may be an important mechanism for the high rate of HIV infection in women through the vaginal mucosa.

A synthetic CD4-heparan sulfate glycoconjugate inhibits CCR5 and CXCR4 HIV-1 attachment and entry

The HIV-1 envelope, gp120, which features the binding determinants for both CD4 and coreceptor recognition, is key for virus entry and represents an attractive pharmacological target. However, critical domains for entry (coreceptor and CD4 binding sites) are either cryptic or located in partially occluded cavities. Here we developed a chemical approach to synthesize a CD4-mimetic peptide linked to a heparan sulfate dodecasaccharide. This molecule binds to gp120, induces the exposure of the coreceptor binding domain and renders it available for interaction with the oligosaccharide. The linkage between the CD4 mimetic and the heparan sulfate derivative provides strong cooperative effects, resulting in low-nanomolar antiviral activity toward both CCR5- and CXCR4-tropic HIV-1 strains. This compound, which has the unique ability to simultaneously target two critical and highly conserved regions of gp120, establishes a new type of inhibitor and suggests a general concept for the inhibition of numerous other biological systems.

The HIV-1 envelope glycoprotein gp120 features four heparan sulfate binding domains, including the co-receptor binding site

It is well established that the human immunodeficiency virus-1 envelope glycoprotein surface unit, gp120, binds to cell-associated heparan sulfate (HS). Virus infectivity is increased by such interaction, and a variety of soluble polyanions efficiently neutralize immunodeficiency virus-1 in vitro. This interaction has been mainly attributed to the gp120 V3 loop. However, although evidence suggested that this particular domain does not fully recapitulate the binding activity of the protein, the ability of HS to bind to other regions of gp120 has not been completely addressed, and the exact localizations of the polysaccharide binding sites are not known. To investigate in more detail the structural basis of the HS-gp120 interaction, we used a mapping strategy and compared the heparin binding activity of wild type and mutant gp120 using surface plasmon resonance-based binding assays. Four heparin binding domains (1-4) were identified in the V2 and V3 loops, in the C-terminal domain, and within the CD4-induced bridging sheet. Interestingly, three of them were found in domains of the protein that undergo structural changes upon binding to CD4 and are involved in co-receptor recognition. In particular, Arg(419), Lys(421), and Lys(432), which directly interact with the co-receptor, are targeted by heparin. This study provides a complete account of the gp120 residues involved in heparin binding and identified several binding surfaces that constitute potential target for viral entry inhibition.

Heparin enhances the furin cleavage of HIV-1 gp160 peptides

Infectious HIV-1 requires gp160 cleavage by furin at the REKR511 downward arrow motif (site1) into the gp120/gp41 complex, whereas the KAKR503 (site2) sequence remains uncleaved. We synthesized 41mer and 51mer peptides, comprising site1 and site2, to study their conformation and in vitro furin processing. We found that, while the previously reported 19mer and 13mer analogues represent excellent in vitro furin substrates, the present extended sequences require heparin for optimal processing. Our data support the hypothesis of a direct binding of heparin with site1 and site2, allowing selective exposure/accessibility of the REKR sequence, which is only then optimally cleaved by furin.

The interferon-induced expression of APOBEC3G in human blood-brain barrier exerts a potent intrinsic immunity to block HIV-1 entry to central nervous system

In the human genome, the APOBEC3 gene has expanded into a tandem array of genes termed APOBEC3A-H. Several members of this family have potent anti-HIV-1 activity. Here we demonstrate that APOBEC-3B/3C/3F and -3G are expressed in all major cellular components of the CNS. Moreover, we show that both interferon-alpha (IFN-alpha) and IFN-gamma significantly enhance the expression of APOBEC-3G/3F and drastically inhibit HIV-1 replication in primary human brain microvascular endothelial cells (BMVECs), the major component of blood-brain barrier (BBB). As the viral inhibition can be neutralized by APOBEC3G-specific siRNA, APOBEC3G plays a key role to mediate the anti-HIV-1 activity of IFN-alpha and/or IFN-gamma. Our findings suggest that, in addition to the restriction at viral entry level, the restriction from APOBEC3 family could account for the low-level replication of HIV-1 in BMVECs. The manipulation of IFN-APOBEC3 signaling pathway could be a potent therapeutic strategy to prevent HIV invasion to central nervous system (CNS).

Lipid rafts of primary endothelial cells are essential for Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8-induced phosphatidylinositol 3-kinase and RhoA-GTPases critical for microtubule dynamics and nuclear delivery of viral DNA but dispensable for binding and entry

Early during de novo infection of human microvascular dermal endothelial (HMVEC-d) cells, Kaposi's sarcoma-associated herpesvirus (KSHV) (human herpesvirus 8 [HHV-8]) induces the host cell's preexisting FAK, Src, phosphatidylinositol 3-kinase (PI3-K), Rho-GTPases, Diaphanous-2 (Dia-2), Ezrin, protein kinase C-zeta, extracellular signal-regulated kinase 1/2 (ERK1/2), and NF-kappaB signal pathways that are critical for virus entry, nuclear delivery of viral DNA, and initiation of viral gene expression. Since several of these signal molecules are known to be associated with lipid raft (LR) domains, we investigated the role of LR during KSHV infection of HMVEC-d cells. Pretreatment of cells with LR-disrupting agents methyl beta-cyclo dextrin (MbetaCD) or nystatin significantly inhibited the expression of viral latent (ORF73) and lytic (ORF50) genes. LR disruption did not affect KSHV binding but increased viral DNA internalization. In contrast, association of internalized viral capsids with microtubules (MTs) and the quantity of infected nucleus-associated viral DNA were significantly reduced. Disorganized and disrupted MTs and thick rounded plasma membranes were observed in MbetaCD-treated cells. LR disruption did not affect KSHV-induced FAK and ERK1/2 phosphorylation; in contrast, it increased the phosphorylation of Src, significantly reduced the KSHV-induced PI3-K and RhoA-GTPase and NF-kappaB activation, and reduced the colocalizations of PI3-K and RhoA-GTPase with LRs. Biochemical characterization demonstrated the association of activated PI3-K with LR fractions which was inhibited by MbetaCD treatment. RhoA-GTPase activation was inhibited by PI3-K inhibitors, demonstrating that PI3-K is upstream to RhoA-GTPase. In addition, colocalization of Dia-2, a RhoA-GTPase activated molecule involved in MT activation, with LR was reduced. KSHV-RhoA-GTPase mediated acetylation and aggregation of MTs were also reduced. Taken together, these studies suggest that LRs of endothelial cells play critical roles in KSHV infection and gene expression, probably due to their roles in modulating KSHV-induced PI3-K, RhoA-GTPase, and Dia-2 molecules essential for postbinding and entry stages of infection such as modulation of microtubular dynamics, movement of virus in the cytoplasm, and nuclear delivery of viral DNA.

Polyomavirus JC infects human brain microvascular endothelial cells independent of serotonin receptor 2A

Although human polyomavirus JC (JCV) is known to cause progressive multifocal leukoencephalopathy (PML) in immunocompromised individuals, the mechanism by which JCV crosses the blood-brain barrier (BBB) remains unclear. To test our hypothesis that cell-free JCV gains entry into the brain by infecting endothelial cells, we inoculated human brain microvascular endothelial (HBMVE) cells with 50 HAU (1.33+/-0.27 x 10(7) genome copies) of JCV(Mad1) and analyzed the expression of early and late viral genes and proteins by immunocytochemistry, quantitative real-time PCR (qPCR), quantitative real-time reverse transcriptase PCR (qRT-PCR) and immunoprecipitation followed by Western blotting. JCV infected and replicated efficiently in HBMVE cells and produced infectious virions several hundred fold higher than the infecting inoculum. HBMVE cells in vitro did not express serotonin receptor 2A (5HT(2A)R), and 5HT(2A)R blockers did not prevent JCV infection of HBMVE cells. Collectively, our data indicate that the productive in vitro infection of HBMVE cells by JCV is independent of 5HT(2A)R.

Endothelial cell infection and hemostasis

As an important component of the vasculature, endothelial cell lining covers the inner surface of blood vessels and provides an active barrier interface between the vascular and perivascular compartments. In addition to maintaining vasomotor equilibrium and organ homeostasis and communicating with circulating blood cells, the vascular endothelium also serves as the preferred target for a number of infectious agents. This review article focuses on the roles of interactions between vascular endothelial cells and invading pathogens and resultant endothelial activation in the pathogenesis of important human diseases with viral and bacterial etiologies. In this perspective, the signal transduction events that regulate vascular inflammation and basis for endothelial cell tropism exhibited by certain specific viruses and pathogenic bacteria are also discussed.