Efficient species C HAdV infectivity in plasmocytic cell lines using a clathrin-independent lipid raft/caveola endocytic route

MβCD inhibits SFTSV entry by disrupting lipid raft structure of the host cells

Severe fever with thrombocytopenia syndrome virus (SFTSV), recently named as Dabie bandavirus, belongs to the family Phenuiviridae of the order Bunyavirales, is a newly-identified bunyavirus with a case fatality rate of up to 30%, posing a serious threat to public health. Lipid rafts on plasm membranes are important for the entry of enveloped viruses; however, the role of lipid rafts in bunyavirus entry remains unclear. In this study, we found that methyl-beta-cyclodextrin (MβCD), a drug that disrupts cholesterol in lipid rafts of cell membranes, inhibits SFTSV infection. Additionally, there is a back-complementary effect of SFTSV infection upon the addition of cholesterol. Moreover, the concentration of SFTSV particles in lipid rafts during entry directly indicated the role of lipid rafts as a gateway, whereas MβCD could inhibit SFTSV entry by affecting the structure of lipid rafts. In an in vivo study, MβCD also reduced the susceptibility of mice to SFTSV infection. Our results suggest that SFTSV can interact with Talin1 proteins on lipid rafts to enter host cells by endocytosis of lipid rafts and reveal the potential therapeutic value of MβCD for SFTSV infection.

Human Adenovirus Entry and Early Events during Infection of Primary Murine Neurons: Immunofluorescence Studies In Vitro

Human adenovirus (HAdV) is a common pathogen, which can lead to various clinical symptoms and-in some cases-central nervous system (CNS) dysfunctions, such as encephalitis and meningitis. Although the initial events of virus entry have already been identified in various cell types, the mechanism of neuronal uptake of adenoviruses is relatively little understood. The aim of this study was to investigate early events during adenoviral infection, in particular to determine the connection between cellular coxsackievirus and adenovirus receptor (CAR), clathrin, caveolin, and early endosomal proteins (EEA1 and Rab5) with the entry of HAdVs into primary murine neurons in vitro. An immunofluorescence assay and confocal microscopy analysis were carried out to determine HAdV4, 5, and 7 correlation with CAR, clathrin, caveolin, and early endosomal proteins in neurons. The quantification of Pearson's coefficient between CAR and HAdVs indicated that the HAdV4 and HAdV5 types correlated with CAR and that the correlation was more substantial for HAdV5. Inhibition of clathrin-mediated endocytosis using chlorpromazine limited the infection with HAdV, whereas inhibition of caveolin-mediated endocytosis did not affect virus entry. Thus, the entry of tested HAdV types into neurons was most likely associated with clathrin but not caveolin. It was also demonstrated that HAdVs correlate with the Rab proteins (EEA1, Rab5) present in early vesicles, and the observed differences in the manner of correlation depended on the serotype of the virus. With our research, we strove to expand knowledge regarding the mechanism of HAdV entry into neurons, which may be beneficial for developing potential therapeutics in the future.

Human Adenovirus Type 26 Infection Mediated by αvβ3 Integrin Is Caveolin-1-Dependent

Human adenovirus type 26 (HAdV26) has been recognized as a promising platform for vaccine vector development, and very recently vaccine against COVID-19 based on HAdV26 was authorized for emergency use. Nevertheless, basic biology of this virus, namely, pathway which HAdV26 uses to enter the cell, is still insufficiently known. We have shown here that HAdV26 infection of human epithelial cells expressing low amount of αvβ3 integrin involves clathrin and is caveolin-1-independent, while HAdV26 infection of cells with high amount of αvβ3 integrin does not involve clathrin but is caveolin-1-dependent. Thus, this study demonstrates that caveolin-1 is limiting factor in αvβ3 integrin-mediated HAdV26 infection. Regardless of αvβ3 integrin expression, HAdV26 infection involves dynamin-2. Our data provide for the first-time description of HAdV26 cell entry pathway, hence increase our knowledge of HAdV26 infection. Knowing that functionality of adenovirus vector is influenced by its cell entry pathway and intracellular trafficking, our results will contribute to better understanding of HAdV26 immunogenicity and antigen presentation when used as vaccine vector.

IMPORTANCE In order to fulfill its role as a vector, adenovirus needs to successfully deliver its DNA genome to the host nucleus, a process highly influenced by adenovirus intracellular translocation. Thus, cell entry pathway and intracellular trafficking determine functionality of human adenovirus-based vectors. Endocytosis of HAdV26, currently extensively studied as a vaccine vector, has not been described so far. We present here that HAdV26 infection of human epithelial cells with high expression of αvβ3 integrin, one of the putative HAdV26 receptors, is caveolin-1- and partially dynamin-2-dependent. Since caveolin containing domains provide a unique environment for specific signaling events and participate in inflammatory signaling one can imagine that directing HAdV26 cell entry toward caveolin-1-mediate pathway might play role in immunogenicity of this virus. Therefore, our results contribute to better understanding of HAdV26 infection pathway, hence, can be helpful in explaining induction of immune response and antigen presentation by HAdV26-based vaccine vector.

Human adenovirus type 26 basic biology and its usage as vaccine vector

Due to their nature, adenoviruses have been recognised as promising candidates for vaccine vector development. Since they mimic natural infection, recombinant adenovirus vectors have been proven as ideal shuttles to deliver foreign transgenes aiming at inducing both humoral and cellular immune response. In addition, a potent adjuvant effect can be exerted due to the adenovirus inherent stimulation of various elements of innate and adaptive immunity. Due to its low seroprevalence in humans as well as induction of favourable immune response to inserted transgene, human adenovirus type 26 (HAdV-D26) has been recognised as a promising platform for vaccine vector development and is studied in number of completed or ongoing clinical studies. Very recently HAdV-D26 based Ebola and Covid-19 vaccines were approved for medical use. In this review, current state of the art regarding HAdV-D26 basic biology and its usage as vaccine vector will be discussed.

The Revolving Door of Adenovirus Cell Entry: Not All Pathways Are Equal

Adenoviruses represent exceptional candidates for wide-ranging therapeutic applications, from vectors for gene therapy to oncolytics for cancer treatments. The first ever commercial gene therapy medicine was based on a recombinant adenovirus vector, while most recently, adenoviral vectors have proven critical as vaccine platforms in effectively controlling the global coronavirus pandemic. Here, we discuss factors involved in adenovirus cell binding, entry, and trafficking; how they influence efficiency of adenovirus-based vectors; and how they can be manipulated to enhance efficacy of genetically modified adenoviral variants. We focus particularly on endocytosis and how different adenovirus serotypes employ different endocytic pathways to gain cell entry, and thus, have different intracellular trafficking pathways that subsequently trigger different host antiviral responses. In the context of gene therapy, the final goal of the adenovirus vector is to efficiently deliver therapeutic transgenes into the target cell nucleus, thus allowing its functional expression. Aberrant or inefficient endocytosis can impede this goal, therefore, it should be considered when designing and constructing adenovirus-based vectors.

Membrane Rafts: Portals for Viral Entry

Membrane rafts are dynamic, small (10-200 nm) domains enriched with cholesterol and sphingolipids that compartmentalize cellular processes. Rafts participate in roles essential to the lifecycle of different viral families including virus entry, assembly and/or budding events. Rafts seem to participate in virus attachment and recruitment to the cell surface, as well as the endocytic and non-endocytic mechanisms some viruses use to enter host cells. In this review, we will introduce the specific role of rafts in viral entry and define cellular factors implied in the choice of one entry pathway over the others. Finally, we will summarize the most relevant information about raft participation in the entry process of enveloped and non-enveloped viruses.

Multifaceted Functions of Host Cell Caveolae/Caveolin-1 in Virus Infections

Virus infection has drawn extensive attention since it causes serious or even deadly diseases, consequently inducing a series of social and public health problems. Caveolin-1 is the most important structural protein of caveolae, a membrane invagination widely known for its role in endocytosis and subsequent cytoplasmic transportation. Caveolae/caveolin-1 is tightly associated with a wide range of biological processes, including cholesterol homeostasis, cell mechano-sensing, tumorigenesis, and signal transduction. Intriguingly, the versatile roles of caveolae/caveolin-1 in virus infections have increasingly been appreciated. Over the past few decades, more and more viruses have been identified to invade host cells via caveolae-mediated endocytosis, although other known pathways have been explored. The subsequent post-entry events, including trafficking, replication, assembly, and egress of a large number of viruses, are caveolae/caveolin-1-dependent. Deprivation of caveolae/caveolin-1 by drug application or gene editing leads to abnormalities in viral uptake, viral protein expression, or virion release, whereas the underlying mechanisms remain elusive and must be explored holistically to provide potential novel antiviral targets and strategies. This review recapitulates our current knowledge on how caveolae/caveolin-1 functions in every step of the viral infection cycle and various relevant signaling pathways, hoping to provide a new perspective for future viral cell biology research.

Adenoviral vector-based strategies against infectious disease and cancer

Adenoviral vectors are widely employed against infectious diseases or cancers, as they can elicit specific antibody responses and T cell responses when they are armed with foreign genes as vaccine carriers, and induce apoptosis of the cancer cells when they are genetically modified for cancer therapy. In this review, we summarize the biological characteristics of adenovirus (Ad) and the latest development of Ad vector-based strategies for the prevention and control of emerging infectious diseases or cancers. Strategies to circumvent the pre-existing neutralizing antibodies which dampen the immunogenicity of Ad-based vaccines are also discussed.

Adenovirus-based vaccines for fighting infectious diseases and cancer: progress in the field

The field of adenovirology is undergoing rapid change in response to increasing appreciation of the potential advantages of adenoviruses as the basis for new vaccines and as vectors for gene and cancer therapy. Substantial knowledge and understanding of adenoviruses at a molecular level has made their manipulation for use as vaccines and therapeutics relatively straightforward in comparison with other viral vectors. In this review we summarize the structure and life cycle of the adenovirus and focus on the use of adenovirus-based vectors in vaccines against infectious diseases and cancers. Strategies to overcome the problem of preexisting antiadenovirus immunity, which can hamper the immunogenicity of adenovirus-based vaccines, are discussed. When armed with tumor-associated antigens, replication-deficient and oncolytic adenoviruses can efficiently activate an antitumor immune response. We present concepts on how to use adenoviruses as therapeutic cancer vaccines and consider some of the strategies used to further improve antitumor immune responses. Studies that explore the prospect of adenoviruses as vaccines against infectious diseases and cancer are underway, and here we give an overview of the latest developments.

Caveolin-1 associated adenovirus entry into human corneal cells

The cellular entry of viruses represents a critical area of study, not only for viral tropism, but also because viral entry dictates the nature of the immune response elicited upon infection. Epidemic keratoconjunctivitis (EKC), caused by viruses within human adenovirus species D (HAdV-D), is a severe, ocular surface infection associated with corneal inflammation. Clathrin-mediated endocytosis has previously been shown to play a critical role in entry of other HAdV species into many host cell types. However, HAdV-D endocytosis into corneal cells has not been extensively studied. Herein, we show an essential role for cholesterol rich, lipid raft microdomains and caveolin-1, in the entry of HAdV-D37 into primary human corneal fibroblasts. Cholesterol depletion using methyl-β-cyclodextrin (MβCD) profoundly reduced viral infection. When replenished with soluble cholesterol, the effect of MβCD was reversed, allowing productive viral infection. HAdV-D37 DNA was identified in caveolin-1 rich endosomal fractions after infection. Src kinase activity was also increased in caveolin-1 rich endosomal fractions after infection, and Src phosphorylation and CXCL1 induction were both decreased in caveolin-1-/- mice corneas compared to wild type mice. siRNA knock down of caveolin-1 in corneal cells reduced chemokine induction upon viral infection, and caveolin-1-/- mouse corneas showed reduced cellular entry of HAdV-D37. As a control, HAdV-C2, a non-corneal pathogen, appeared to utilize the caveolar pathway for entry into A549 cells, but failed to infect corneal cells entirely, indicating virus and cell specific tropism. Immuno-electron microscopy confirmed the presence of caveolin-1 in HAdV-D37-containing vesicles during the earliest stages of viral entry. Collectively, these experiments indicate for the first time that HAdV-D37 uses a lipid raft mediated caveolin-1 associated pathway for entry into corneal cells, and connects the processes of viral entry with downstream proinflammatory cell signaling.

Sstr2A: a relevant target for the delivery of genes into human glioblastoma cells using fiber-modified adenoviral vectors

Glioblastomas are the most aggressive of the brain tumors occurring in adults and children. Currently available chemotherapy prolongs the median survival time of patients by only 4 months. The low efficiency of current treatments is partly owing to the blood-brain barrier, which restricts the penetration of most drugs into the central nervous system. Locoregional treatment strategies thus become mandatory. In this context, viral tools are of great interest for the selective delivery of genes into tumoral cells. Gliomas express high levels of type 2 somatostatin receptors (sstr2A), pinpointing them as suitable targets for the improvement of transduction efficiency in these tumors. We designed a new adenoviral vector based on the introduction of the full-length somatostatin (SRIF (somatotropin release-inhibiting factor)) sequence into the HI loop of the HAdV fiber protein. We demonstrate that (i) HAdV-5-SRIF uptake into cells is mediated by sstr2A, (ii) our vector drives high levels of gene expression in cells expressing endogenous sstr2A, with up to 65-fold enhancement and (iii) low doses of HAdV-5-SRIF are sufficient to infect high-grade human primary glioblastoma cells. Adenoviral vectors targeting SRIF receptors might thus represent a promising therapeutic approach to brain tumors.

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.

An adenovirus traffic update: from receptor engagement to the nuclear pore

Adenoviruses have a bipolar nature: they are ubiquitous pathogens that occasionally cause life-threatening diseases or they can be engineered into powerful gene transfer vectors. The goal of this article is to summarize the most recent advances in adenovirus receptor engagement, internalization, endosomal maturation, endosomal escape and trafficking to the nuclear pore. A better understanding of this initial part of the adenovirus lifecycle may identify new mechanistic-based treatments for adenovirus-induced diseases and help in the engineering of more efficient vectors.

Cell entry and trafficking of human adenovirus bound to blood factor X is determined by the fiber serotype and not hexon:heparan sulfate interaction

Human adenovirus serotype 5 (HAdV5)-based vectors administered intravenously accumulate in the liver as the result of their direct binding to blood coagulation factor X (FX) and subsequent interaction of the FX-HAdV5 complex with heparan sulfate proteoglycan (HSPG) at the surface of liver cells. Intriguingly, the serotype 35 fiber-pseudotyped vector HAdV5F35 has liver transduction efficiencies 4-logs lower than HAdV5, even though both vectors carry the same hexon capsomeres. In order to reconcile this apparent paradox, we investigated the possible role of other viral capsid proteins on the FX/HSPG-mediated cellular uptake of HAdV5-based vectors. Using CAR- and CD46-negative CHO cells varying in HSPG expression, we confirmed that FX bound to serotype 5 hexon protein and to HAdV5 and HAdV5F35 virions via its Gla-domain, and enhanced the binding of both vectors to surface-immobilized hypersulfated heparin and cellular HSPG. Using penton mutants, we found that the positive effect of FX on HAdV5 binding to HSPG and cell transduction did not depend on the penton base RGD and fiber shaft KKTK motifs. However, we found that FX had no enhancing effect on the HAdV5F35-mediated cell transduction, but a negative effect which did not involve the cell attachment or endocytic step, but the intracellular trafficking and nuclear import of the FX-HAdV5F35 complex. By cellular imaging, HAdV5F35 particles were observed to accumulate in the late endosomal compartment, and were released in significant amounts into the extracellular medium via exocytosis. We showed that the stability of serotype 5 hexon:FX interaction was higher at low pH compared to neutral pH, which could account for the retention of FX-HAdV5F35 complexes in the late endosomes. Our results suggested that, despite the high affinity interaction of hexon capsomeres to FX and cell surface HSPG, the adenoviral fiber acted as the dominant determinant of the internalization and trafficking pathway of HAdV5-based vectors.

Block in entry of enteric adenovirus type 41 in HEK293 cells

Human species F adenoviruses, HAdV-40 and HAdV-41, display characteristic gut tropism in vivo as well as poor infectivity in cell culture. To address the hypothesis that poor infectivity of HAdV-40/41 reflects a partial block prior to genome delivery, the internalization and trafficking of HAdV-41, HAdV-5 (species C) and HAdV-35 (species B) were compared in 293 (human embryonic kidney) cells, which complement E1B function in HAdV-40/41, and in A549 (lung epithelial) cells. Unlike fluorescently labeled HAdV-5 virions which were transported towards the nucleus and HAdV-35 virions which colocalized with LAMP-1, HAdV-41 virions appeared to be scattered throughout the cytoplasm but did not colocalize with markers of late endosomes/lysosomes (cathepsin B, LAMP-1) or with caveolin 1. Fluorescent dextran was released from vesicles in only 10% of HAd41-infected cells that took up dextran, compared to 70% of HAdV-5-infected cells, suggesting inefficient disruption of endosomes by HAdV-41 or uptake of HAdV-41 virions into a different compartment than HAdV-5 virions. Quantitative transmission electron microscopy, which showed greater binding of HAdV-41 virions to 293 cells than to A549 cells, identified a major block in uptake of HAdV-41 virions from the surface of both cell lines. More than 80% of virions remained on the surface 60 min p.i. and as late as 4h p.i. In contrast to HAdV-5 and HAdV-35 virions, which associated mostly with clathrin-coated pits, HAdV-41 virions associated mostly with caveolar-like invaginations and, to a lesser extent, with larger non-clathrin-coated pits, suggesting internalization by pathways other than clathrin-mediated endocytosis.

Cell-Penetrating Penta-Peptides (CPP5s): Measurement of Cell Entry and Protein-Transduction Activity

Previously, we developed cell-penetrating penta-peptides (CPP5s). In the present study, VPTLK and KLPVM, two representative CPP5s, were used to characterize the cell-penetration and protein-transduction activities of these small molecules. Various inhibitors of endocytosis and pinocytosis (chlorpromazine, cytochalasin D, Filipin III, amiloride, methyl-β-cyclodextrin, and nocodazole) were tested. Only cytochalasin D showed suppression of CPP5 entry, though the effect was partial. In addition, CPP5s were able to enter a proteoglycan-deficient CHO cell line. These results suggest that pinocytosis and endocytosis may play only a minor role in the cell entry of CPP5s. By mass spectrometry, we determined that the intracellular concentration of VPTLK ranged from 20 nM to 6.0 μM when the cells were cultured in medium containing 1 μM - 1.6 mM VPTLK. To determine the protein-transduction activity of CPP5s, the Tex-LoxP EG cell line, which has a Cre-inducible green fluorescent protein (GFP) gene, was used. VPTLK and KLPVM were added to the N-terminus of Cre, and these fusion proteins were added to the culture medium of Tex-LoxP EG cells. Both VPTLK-Cre and KLPVM-Cre were able to turn on GFP expression in these cells, suggesting that CPP5s have protein-transduction activity. Since CPP5s have very low cytotoxic activity, even at a concentration of 1.6 mM in the medium, CPP5s could be utilized as a new tool for drug delivery into cells.

Adenovirus 5 and chimeric adenovirus 5/F35 employ distinct B-lymphocyte intracellular trafficking routes that are independent of their cognate cell surface receptor

Gene transfer applications with adenovirus (Ad) type 5 are limited by its native tropism, hampering their use in several cell types. To address this limitation, several Ad vectors bearing chimeric fiber have been produced to take advantage of the different cellular receptors used by other subgroups of Ads. In this study, we have compared the transduction efficiency of Ad5 and the chimeric Ad5/F35 in primary human B lymphocytes and B-cell lines as a function of the developmental stage. We found that transduction efficiencies of the two Ads differ independently of their targeted cellular receptor but are related to the intracellular localization of the virus. In efficiently transduced cells, Ads were localized in early endosomes or cytosol, whereas in poorly transduced cells they were localized within late endosomes/lysosomes. Finally, we demonstrate that treatment of cells with phosphatase inhibitors known to redirect endocytosis towards caveolae, increased Ad5/F35 transduction efficiency.

Adenovirus-driven overexpression of proteinases in organ-cultured normal human corneas leads to diabetic-like changes

Our previous data suggested the involvement of matrix metalloproteinase-10 (MMP-10) and cathepsin F (CTSF) in the basement membrane and integrin changes occurring in diabetic corneas. These markers were now examined in normal human organ-cultured corneas upon recombinant adenovirus (rAV)-driven transduction of MMP-10 and CTSF genes. Fifteen pairs of normal autopsy human corneas were used. One cornea of each pair was transduced with rAV expressing either CTSF or MMP-10 genes. 1-2 x 10(8) plaque forming units of rAV per cornea were added to cultures for 48 h with or without sildenafil citrate. The fellow cornea of each pair received control rAV with vector alone. After 6-10 days additional incubation without rAV, corneas were analyzed by Western blot or immunohistochemistry, or tested for healing of 5-mm circular epithelial wounds caused by topical application of n-heptanol. Sildenafil significantly increased epithelial transduction efficiency, apparently by stimulation of rAV endocytosis through caveolae. Corneas transduced with CTSF or MMP-10 genes or their combination had increased epithelial immunostaining of respective proteins compared to fellow control corneas. Staining for diabetic markers integrin alpha(3)beta(1), nidogen-1, nidogen-2, and laminin gamma2 chain became weaker and irregular upon proteinase transduction. Expression of phosphorylated Akt was decreased in proteinase-transduced corneas. Joint overexpression of both proteinases led to significantly slower corneal wound healing that became similar to that observed in diabetic corneas. The data suggest that MMP-10 and CTSF may be responsible for abnormal marker patterns and impaired wound healing in diabetic corneas. Inhibition of these proteinases in diabetic corneas may alleviate diabetic keratopathy symptoms.

Infectious entry of equine herpesvirus-1 into host cells through different endocytic pathways

We investigated the mechanism by which equine herpesvirus-1 (EHV-1) enters primary cultured equine brain microvascular endothelial cells (EBMECs) and equine dermis (E. Derm) cells. EHV-1 colocalized with caveolin in EBMECs and the infection was greatly reduced by the expression of a dominant negative form of equine caveolin-1 (ecavY14F), suggesting that EHV-1 enters EBMECs via caveolar endocytosis. EHV-1 entry into E. Derm cells was significantly reduced by ATP depletion and treatments with lysosomotropic agents. Enveloped virions were detected from E. Derm cells by infectious virus recovery assay after viral internalization, suggesting that EHV-1 enters E. Derm cells via energy- and pH-dependent endocytosis. These results suggest that EHV-1 utilizes multiple endocytic pathways in different cell types to establish productive infection.

Lipids and membrane microdomains in HIV-1 replication

Several critical steps in the replication cycle of human immunodeficiency virus type 1 (HIV-1) - entry, assembly and budding - are complex processes that take place at the plasma membrane of the host cell. A growing body of data indicates that these early and late steps in HIV-1 replication take place in specialized plasma membrane microdomains, and that many of the viral and cellular components required for entry, assembly, and budding are concentrated in these microdomains. In particular, a number of studies have shown that cholesterol- and sphingolipid-enriched microdomains known as lipid rafts play important roles in multiple steps in the virus replication cycle. In this review, we provide an overview of what is currently known about the involvement of lipids and membrane microdomains in HIV-1 replication.

Intracellular trafficking of a fiber-modified adenovirus using lipid raft/caveolae endocytosis

Most adenoviral vectors (HAdvs) elaborated for gene therapy are derived from serotype 5 viruses that use clathrin-coated vesicle endocytosis for cell entry. However, it appears that adenoviral vectors are able to take advantage of lipid raft/caveolae endocytosis to infect cells. In vivo targeting of a therapeutic gene to specific cells by vector engineering has become a major focus of gene therapy research. Yet, modification of adenoviral tropism, especially fiber gene engineering, can induce deficient intracellular trafficking of the viral particle, with a shift in subcellular localization resulting in extensive exocytosis. In this study we demonstrate that uptake of a fiber-modified adenovirus using lipid raft/caveolae endocytosis leads to non-altered intracellular trafficking without endosomal retention. Moreover, activation of lipid raft structures by this vector leads to the formation of "mega-caveosomes". These results demonstrate that, by forcing adenoviruses to take advantage of a non-clathrin, non-classical endocytic pathway, it is possible to compensate for the deficiency in endosomolysis that is associated with the use of some of the fiber-modified adenoviral constructs. Moreover, it renders such vectors ideal candidates for infecting human coxsackie and adenoviruses receptor (hCAR) negative cells.

Adenovirus infection triggers a rapid, MyD88-regulated transcriptome response critical to acute-phase and adaptive immune responses in vivo

Nearly 50 years ago, the discovery of interferon prompted the notion that host cells innately respond to viral invasion. Since that time, technological advances have allowed this response to be extensively characterized and dissected in vitro. However, these advances have only recently been applied to highly complex, in vivo biological systems. To this end, we exploited high-titer adenovirus (Ad) vectors to globally investigate the innate immune response to nonenveloped viral infection in vivo. Our results indicated a potent cellular transcriptome response shortly after infection, with global assessments revealing significant dysregulation in approximately 15% of the measured transcripts derived from Ad vector-transduced tissue. Bioinformatics-based transcriptome analysis revealed a complex innate response to Ad infection, with induction of proinflammatory responses (and suppression of metabolism and mitochondrial genes) akin to those observed when mice are challenged with lipopolysaccharide. Despite this commonality, there were many unique aspects of the Ad-dependent transcriptome response, including the upregulation of several RNA regulatory mechanisms and apoptosis-related pathways, accompanied by the suppression of lysosomal and endocytic genes. Our results also implicated the Toll-like receptors (TLRs) in these responses, prompting specific investigations into this pathway. By using MyD88KO mice, our results confirmed that Ad-induced dysregulation of five functionally related gene clusters are significantly dependent on this TLR adaptor gene. MyD88 deficiency also resulted in significantly diminished, although not abolished, adaptive and acute-phase immune responses to Ad, confirming the transcriptome data, as well as specifically identifying MyD88 as a significant Ad immunity amplifier and regulator in vivo.

Virus infection and lipid rafts

Virus entry, assembly, and budding are important processes in the replication cycle of a virus. Viruses are dependent on host living cells for their replication. Viruses use the proliferative mechanism of host cells for replication of viral components. Lipid rafts, specific membrane microdomains play a critical role in virus replication because localizing and concentrating viral components in the microdomains for entry, assembly, and budding of various types of virus. In this review, we describe the involvement of membrane lipid rafts in the virus replication cycle with our current findings for understanding the role of membrane lipid rafts in virus infection.

Caveolin-1 and -2 in airway epithelium: expression and in situ association as detected by FRET-CLSM

BACKGROUND

Caveolae are involved in diverse cellular functions such as signal transduction, cholesterol homeostasis, endo- and transcytosis, and also may serve as entry sites for microorganisms. Hence, their occurrence in epithelium of the airways might be expected but, nonetheless, has not yet been examined.

METHODS

Western blotting, real-time quantitative PCR analysis of abraded tracheal epithelium and laser-assisted microdissection combined with subsequent mRNA analysis were used to examine the expression of cav-1 and cav-2, two major caveolar coat proteins, in rat tracheal epithelium. Fluorescence immunohistochemistry was performed to locate caveolae and cav-1 and -2 in the airway epithelium of rats, mice and humans. Electron-microscopic analysis was used for the identification of caveolae. CLSM-FRET analysis determined the interaction of cav-1alpha and cav-2 in situ.

RESULTS

Western blotting and laser-assisted microdissection identified protein and transcripts, respectively, of cav-1 and cav-2 in airway epithelium. Real-time quantitative RT-PCR analysis of abraded tracheal epithelium revealed a higher expression of cav-2 than of cav-1. Immunoreactivities for cav-1 and for cav-2 were co-localized in the cell membrane of the basal cells and basolaterally in the ciliated epithelial cells of large airways of rat and human. However, no labeling for cav-1 or cav-2 was observed in the epithelial cells of small bronchi. Using conventional double-labeling indirect immunofluorescence combined with CLSM-FRET analysis, we detected an association of cav-1alpha and -2 in epithelial cells. The presence of caveolae was confirmed by electron microscopy. In contrast to human and rat, cav-1-immunoreactivity and caveolae were confined to basal cells in mice. Epithelial caveolae were absent in cav-1-deficient mice, implicating a requirement of this caveolar protein in epithelial caveolae formation.

CONCLUSION

These results show that caveolae and caveolins are integral membrane components in basal and ciliated epithelial cells, indicating a crucial role in these cell types. In addition to their physiological role, they may be involved in airway infection.

PS80 interferes with the antiallergic effect of Cry-consensus peptide, a novel recombinant peptide for immunotherapy of Japanese cedar pollinosis, at very low concentration through modulation of Th1/Th2 balance

Polysorbate 80 (PS80 or Tween-80) is often used as an additive to promote the rapid solubilization of pharmaceuticals in aqueous solutions. We investigated whether coinjection of a minimal amount of PS80 had a modulatory effect on the immunotherapeutic effects of Cry (Cryptomeria)-consensus peptide, a novel peptide developed for the therapeutic management of Japanese cedar pollinosis, using a Cry j 1-sensitized mouse model with experimental allergic rhinitis. Subcutaneous challenge with Cry-consensus peptide plus 50 microg/ml of PS80 did not affect the antigen-specific proliferation of splenocytes, but decreased the potency of Cry-consensus peptide to inhibit antigen-specific interleukin (IL)-5 production by the cells significantly in comparison with challenge with Cry-consensus peptide alone. However, there was no significant difference between the effect of Cry-consensus peptide administration on interferon (IFN)-gamma production in the presence and absence of PS80, indicating that PS80 interfered with the T helper 1 (Th1)-dominant T helper balance induced by Cry-consensus peptide challenge. Moreover, the increase in the level of antigen-specific immunoglobulin G2a (IgG2a) induced by Cry-consensus peptide challenge was inhibited slightly but unambiguously by PS80 coinjection. These in vitro experiments indicated that PS80 induces Th2-type differentiation of T helper cells through preferential inhibition of IFN-gamma expression relative to IL-5 expression in splenocytes in a concentration-dependent manner. In naïve mice, sensitization by Cry-consensus peptide with PS80 induced antigen-specific IL-5 production more potently than sensitization by Cry-consensus peptide alone, and when PS80 was added to bone marrow-derived dendritic cells, the endocytosis of fluorescence-labelled Cry-consensus peptide was dramatically inhibited in a concentration-dependent manner. Therefore, we conclude that PS80 has an immunomodulatory effect on the antigen-specific response resulting in a shift towards Th2 predominance with respect to the antigen recognition stage. Taken together, our findings suggest that PS80 might decrease the efficacy of Cry-consensus peptide through modulation of the efficiency of antigen endocytosis and/or of the direction of successive T helper cell differentiation.

Improved gene delivery to B lymphocytes using a modified adenovirus vector targeting CD21

Gene transfer by adenoviruses, which are widely used for gene therapy, may provide an alternative approach to treatment of several hematopoietic malignancies. However, a major limitation of adenovirus 5-based gene therapy lies in the natural tropism of the virus for the widely expressed hCAR receptor. The efficacy of adenoviral vectors could be improved if viral vectors that exhibit tissue-specific gene delivery were developed. For efficient gene transfer it is essential that every step from binding of virus to target cells to transgene expression is successfully accomplished. We developed a specific vector targeting the CD21 receptor, by inserting a CD21 binding sequence, derived from the EBV GP350/220 protein, into the HI loop of the HAdV5 fiber protein. This vector, HAdV5-CD21HIloop, binds specifically to CD21-positive cells and results in enhanced expression of the transgene in these cells and reduced expression in CD21-negative cells. Viral infection is highly correlated with the presence of CD21 receptors. Taken together, these results demonstrate that HAdV5-CD21HIloop is able to transduce CD21-positive cells specifically with reduced infection of nontarget cells. This is the result of the maintenance of the intracellular trafficking of the genetically modified adenovirus without vesicular retention, leading to enhanced nuclear transfer.