bluuebunny/crossref_metadata_2025_split huggingface dataset:
Increased Immunogenicity of Human Immunodeficiency Virus gp120 Engineered To Express Galα1-3Galβ1-4GlcNAc-R Epitopes
Authors: Abdel-Motal Ussama , Wang Shixia , Lu Shan , Wigglesworth Kim , Galili Uri 
Published: June 2006

ABSTRACTThe glycan shield comprised of multiple carbohydrate chains on the human immunodeficiency virus (HIV) envelope glycoprotein gp120 helps the virus to evade neutralizing antibodies. The present study describes a novel method for increasing immunogenicity of gp120 vaccine by enzymatic replacement of sialic acid on these carbohydrate chains with Galα1-3Galβ1-4GlcNAc-R (α-gal) epitopes. These epitopes are ligands for the natural anti-Gal antibody constituting ∼1% of immunoglobulin G in humans. We hypothesize that vaccination with gp120 expressing α-gal epitopes (gp120αgal) results in in vivo formation of immune complexes with anti-Gal, which targets vaccines for effective uptake by antigen-presenting cells (APC), due to interaction between the Fc portion of the antibody and Fcγ receptors on APC. This in turn results in effective transport of the vaccine to lymph nodes and effective processing and presentation of gp120 immunogenic peptides by APC for eliciting a strong anti-gp120 immune response. This hypothesis was tested in α-1,3-galactosyltransferase knockout mice, which produce anti-Gal. Mice immunized with gp120αgalproduced anti-gp120 antibodies in titers that were >100-fold higher than those measured in mice immunized with comparable amounts of gp120 and effectively neutralized HIV. T-cell response, measured by ELISPOT, was much higher in mice immunized with gp120αgalthan in mice immunized with gp120. It is suggested that gp120αgalcan serve as a platform for anti-Gal-mediated targeting of additional vaccinating HIV proteins fused to gp120αgal, thereby creating effective prophylactic vaccines.
Transmission of Simian Immunodeficiency Virus SIVcpz and the Evolution of Infection in the Presence and Absence of Concurrent Human Immunodeficiency Virus Type 1 Infection in Chimpanzees
Authors: Heeney Jonathan L. , Rutjens Erik , Verschoor Ernst J. , Niphuis Henk , ten Haaft Peter , Rouse Scott , McClure Hazel , Balla-Jhagjhoorsingh Sunita , Bogers Willy , Salas Mary , Cobb Kathy , Kestens Luc , Davis David , van der Groen Guido , Courgnaud Valerie , Peeters Martine , Murthy Krishna K. 
Published: June 2006

ABSTRACTCurrent data suggest that the human immunodeficiency virus type 1 (HIV-1) epidemic arose by transmission of simian immunodeficiency virus (SIV) SIVcpz from a subspecies of common chimpanzees (Pan troglodytes troglodytes) to humans. SIVcpz of chimpanzees is itself a molecular chimera of SIVs from two or more different monkey species, suggesting that recombination was made possible by coinfection of one individual animal with different lentiviruses. However, very little is known about SIVcpz transmission and the susceptibility to lentivirus coinfection of its natural host, the chimpanzee. Here, it is revealed that either infected plasma or peripheral blood mononuclear cells readily confer infection when exposure occurs by the intravenous or mucosal route. Importantly, the presence of preexisting HIV-1 infection did not modify the kinetics of SIVcpz infection once it was established by different routes. Although humoral responses appeared as early as 4 weeks postinfection, neutralization to SIVcpz-ANT varied markedly between animals. Analysis of the SIVcpzenvsequence over time revealed the emergence of genetic viral variants and persistent SIVcpz RNA levels of between 104and 105copies/ml plasma regardless of the presence or absence of concurrent HIV-1 infection. These unique data provide important insight into possible routes of transmission, the kinetics of acute SIVcpz infection, and how readily coinfection with SIVcpz and other lentiviruses may be established as necessary preconditions for potential recombination.
Regulation of Adeno-Associated Virus DNA Replication by the Cellular TAF-I/Set Complex
Authors: Pegoraro Gianluca , Marcello Alessandro , Myers Michael P. , Giacca Mauro 
Published: June 2006

ABSTRACT
The Rep proteins of the adeno-associated virus (AAV) are required for viral replication in the presence of adenovirus helper functions and as yet poorly characterized cellular factors. In an attempt to identify such factors, we purified Flag-Rep68-interacting proteins from human cell lysates. Several polypeptides were identified by mass spectrometry, among which was ANP32B, a member of the acidic nuclear protein 32 family which takes part in the formation of the template-activating factor I/Set oncoprotein (TAF-I/Set) complex. The N terminus of Rep was found to specifically bind the acidic domain of ANP32B; through this interaction, Rep was also able to recruit other members of the TAF-I/Set complex, including the ANP32A protein and the histone chaperone TAF-I/Set. Further experiments revealed that silencing of ANP32A and ANP32B inhibited AAV replication, while overexpression of all of the components of the TAF-I/Set complex increased de novo AAV DNA synthesis in permissive cells. Besides being the first indication that the TAF-I/Set complex participates in wild-type AAV replication, these findings have important implications for the generation of recombinant AAV vectors since overexpression of the TAF-I/Set components was found to markedly increase viral vector production.
Rapid Pathogenesis Induced by a Vesicular Stomatitis Virus Matrix Protein Mutant: Viral Pathogenesis Is Linked to Induction of Tumor Necrosis Factor Alpha
Authors: Publicover Jean , Ramsburg Elizabeth , Robek Michael , Rose John K. 
Published: June 2006

ABSTRACT
Vesicular stomatitis virus (VSV) matrix (M) protein blocks host mRNA export from the nucleus and thereby inhibits interferon induction in infected cells. M mutants with mutations of methionine 51 (M51) lack this shutoff function. We examined pathogenesis of a VSV M mutant with a deletion of M51 (VSVΔM51) after intranasal infection of BALB/c mice and found an unexpected phenotype. Mice that received VSVΔM51 experienced a more rapid but overall less severe weight loss than mice that received the recombinant wild-type VSV (rwtVSV). Rapid weight loss was not explained by faster initial replication because VSVΔM51 replication was controlled faster than rwtVSV replication in the lungs and did not spread systemically like rwtVSV. This faster control of VSVΔM51 correlated with a more rapid induction of interferon in the lung. Because tumor necrosis factor alpha (TNF-α) is associated with weight loss, we examined TNF-α induction in mice infected with rwtVSV or VSVΔM51. We found more-rapid induction of TNF-α by the mutant at early times after infection, while rwtVSV induced more TNF-α later in infection. This result suggested that TNF-α induction might explain both the rapid weight loss caused by the mutant and the overall greater weight loss caused by the rwtVSV. Using TNF-α knockout mice (C57BL/6 background), we showed that weight loss following rwtVSV infection was greatly reduced in the absence of TNF-α. Although the rapid weight loss caused by VSVΔM51 was less pronounced in C57BL/6 mice, it was eliminated in the absence of TNF-α. These results indicate a role for TNF-α in the pathogenesis of VSV.
PKR and RNase L Contribute to Protection against Lethal West Nile Virus Infection by Controlling Early Viral Spread in the Periphery and Replication in Neurons
Authors: Samuel Melanie A. , Whitby Kevin , Keller Brian C. , Marri Anantha , Barchet Winfried , Williams Bryan R. G. , Silverman Robert H. , Gale Michael , Diamond Michael S. 
Published: June 2006

ABSTRACTWest Nile virus (WNV) is a neurotropic, mosquito-borne flavivirus that can cause lethal meningoencephalitis. Type I interferon (IFN) plays a critical role in controlling WNV replication, spread, and tropism. In this study, we begin to examine the effector mechanisms by which type I IFN inhibits WNV infection. Mice lacking both the interferon-induced, double-stranded-RNA-activated protein kinase (PKR) and the endoribonuclease of the 2′,5′-oligoadenylate synthetase-RNase L system (PKR−/−× RL−/−) were highly susceptible to subcutaneous WNV infection, with a 90% mortality rate compared to the 30% mortality rate observed in congenic wild-type mice. PKR−/−× RL−/−mice had increased viral loads in their draining lymph nodes, sera, and spleens, which led to early viral entry into the central nervous system (CNS) and higher viral burden in neuronal tissues. Although mice lacking RNase L showed a higher CNS viral burden and an increased mortality, they were less susceptible than the PKR−/−× RL−/−mice; thus, we also infer an antiviral role for PKR in the control of WNV infection. Notably, a deficiency in both PKR and RNase L resulted in a decreased ability of type I IFN to inhibit WNV in primary macrophages and cortical neurons. In contrast, the peripheral neurons of the superior cervical ganglia of PKR−/−× RL−/−mice showed no deficiency in the IFN-mediated inhibition of WNV. Our data suggest that PKR and RNase L contribute to IFN-mediated protection in a cell-restricted manner and control WNV infection in peripheral tissues and some neuronal subtypes.
Processing of Human Cytomegalovirus UL37 Mutant Glycoproteins in the Endoplasmic Reticulum Lumen prior to Mitochondrial Importation
Authors: Mavinakere Manohara S. , Williamson Chad D. , Goldmacher Victor S. , Colberg-Poley Anamaris M. 
Published: June 2006

ABSTRACTThe human cytomegalovirus (HCMV) UL37 glycoprotein (gpUL37) is internally cleaved and its products divergently traffic to mitochondria or are retained in the secretory pathway. To define the requirements for gpUL37 cleavage, residues −1 and −3 of the consensus endoplasmic reticulum (ER) signal peptidase I site within exon 3 (UL37x3) were replaced by bulky tyrosines (gpUL37 cleavage site mutant I). Internal cleavage of this UL37x3 mutant was inhibited, verifying usage of the consensus site at amino acids (aa) 193/194. The full-length mitochondrial species of gpUL37 cleavage site mutant I was N glycosylated and endoglycosidase H sensitive, indicating that ER translocation and processing took place prior to its mitochondrial importation. Moreover, these results suggest that internal cleavage of gpUL37 is not necessary for its N glycosylation. Partial deletion or disruption of the UL37 hydrophobic core immediately upstream of the cleavage site resulted in decreased protein abundance, suggesting that the UL37x3 hydrophobic α-helix contributes to either correct folding or stability of gpUL37. Insertion of the UL37x3 hydrophobic core and cleavage site into pUL37M, a splice variant of gpUL37 which lacks these sequences and is neither proteolytically cleaved nor N glycosylated, resulted in its internal cleavage and N glycosylation. Its NH2-terminal fragment, pUL37M-NH2, was detected more abundantly in mitochondria, while its N-glycosylated C-terminal fragment, gpUL37M-COOH, was detected predominantly in the ER in a manner analogous to that of gpUL37 cleavage products. These results indicate that UL37x3 aa 178 to 205 are prerequisite for gpUL37 internal cleavage and alter UL37 protein topology allowing N glycosylation of its C-terminal sequences. In contrast, the NH2-terminal UL37x1 hydrophobic leader, present in pUL37x1, pUL37M, and gpUL37, is not cleaved from mature UL37 protein, retaining a membrane anchor for UL37 isoforms during trafficking. Taken together, these results suggest that HCMV gpUL37 undergoes sequential trafficking, during which it is ER translocated, processed, and then mitochondrially imported.
Epstein-Barr Virus Shed in Saliva Is High in B-Cell-Tropic Glycoprotein gp42
Authors: Jiang R. , Scott R. S. , Hutt-Fletcher L. M. 
Published: June 2006

ABSTRACTEpstein-Barr virus is an orally transmitted human herpesvirus that infects epithelial cells and establishes latency in memory B lymphocytes. Movement of virus between the two cell types is facilitated by changes in amounts of an envelope glycoprotein, gp42, which are effected by interaction of gp42 with HLA class II in a B cell. Here we used the differential ability of virus to bind to CD21-positive B cells and CD21-negative epithelial cells, which is also influenced by levels of gp42, to determine that the majority of virus shed in saliva is derived from an HLA class II-negative cell.
Comparative Analysis of 22 Coronavirus HKU1 Genomes Reveals a Novel Genotype and Evidence of Natural Recombination in Coronavirus HKU1
Authors: Woo Patrick C. Y. , Lau Susanna K. P. , Yip Cyril C. Y. , Huang Yi , Tsoi Hoi-Wah , Chan Kwok-Hung , Yuen Kwok-Yung 
Published: June 2006

ABSTRACT

We sequenced and compared the complete genomes of 22 strains of coronavirus HKU1 (CoV HKU1) obtained from nasopharyngeal aspirates of patients with respiratory tract infections over a 2-year period. Phylogenetic analysis of 24 putative proteins and polypeptides showed that the 22 CoV HKU1 strains fell into three clusters (genotype A, 13 strains; genotype B, 3 strains and genotype C, 6 strains). However, different phylogenetic relationships among the three clusters were observed in different regions of their genomes. From nsp4 to nsp6, the genotype A strains were clustered with the genotype B strains. For nsp7 and nsp8 and from nsp10 to nsp16, the genotype A strains were clustered with the genotype C strains. From hemagglutinin esterase (HE) to nucleocapsid (N), the genotype B strains were clustered closely with the genotype C strains. Bootscan analysis showed possible recombination between genotypes B and C from nucleotide positions 11500 to 13000, corresponding to the nsp6-nsp7 junction, giving rise to genotype A, and between genotypes A and B from nucleotide positions 21500 to 22500, corresponding to the nsp16-HE junction, giving rise to genotype C. Multiple alignments further narrowed the sites of crossover to a 143-bp region between nucleotide positions 11750 and 11892 and a 29-bp region between nucleotide positions 21502 and 21530. Genome analysis also revealed various numbers of tandem copies of a perfect 30-base acidic tandem repeat (ATR) which encodes NDDEDVVTGD and various numbers and sequences of imperfect repeats in the N terminus of nsp3 inside the acidic domain upstream of papain-like protease 1 among the 22 genomes. All 10 CoV HKU1 strains with incomplete imperfect repeats (1.4 and 4.4) belonged to genotype A. The present study represents the first evidence for natural recombination in coronavirus associated with human infection. Analysis of a single gene is not sufficient for the genotyping of CoV HKU1 strains but requires amplification and sequencing of at least two gene loci, one from nsp10 to nsp16 (e.g.,
pol
or helicase) and another from HE to N (e.g., spike or N). Further studies will delineate whether the ATR is useful for the molecular typing of CoV HKU1.
Activation of Triggering Receptor Expressed on Myeloid Cells-1 on Human Neutrophils by Marburg and Ebola Viruses
Authors: Mohamadzadeh Mansour , Coberley Sadie S. , Olinger Gene G. , Kalina Warren V. , Ruthel Gordon , Fuller Claudette L. , Swenson Dana L. , Pratt William D. , Kuhns Douglas B. , Schmaljohn Alan L. 
Published: June 2006

ABSTRACTMarburg virus (MARV) and Ebola virus (EBOV), members of the viral familyFiloviridae, cause fatal hemorrhagic fevers in humans and nonhuman primates. High viral burden is coincident with inadequate adaptive immune responses and robust inflammatory responses, and virus-mediated dysregulation of early host defenses has been proposed. Recently, a novel class of innate receptors called the triggering receptors expressed in myeloid cells (TREM) has been discovered and shown to play an important role in innate inflammatory responses and sepsis. Here, we report that MARV and EBOV activate TREM-1 on human neutrophils, resulting in DAP12 phosphorylation, TREM-1 shedding, mobilization of intracellular calcium, secretion of proinflammatory cytokines, and phenotypic changes. A peptide specific to TREM-1 diminished the release of tumor necrosis factor alpha by filovirus-activated human neutrophils in vitro, and a soluble recombinant TREM-1 competitively inhibited the loss of cell surface TREM-1 that otherwise occurred on neutrophils exposed to filoviruses. These data imply direct activation of TREM-1 by filoviruses and also indicate that neutrophils may play a prominent role in the immune and inflammatory responses to filovirus infections.
Analyses of Phosphorylation Events in the Rubella Virus Capsid Protein: Role in Early Replication Events
Authors: Law LokMan J. , Ilkow Carolina S. , Tzeng Wen-Pin , Rawluk Matthew , Stuart David T. , Frey Teryl K. , Hobman Tom C. 
Published: June 2006

ABSTRACT
The Rubella virus capsid protein is phosphorylated prior to virus assembly. Our previous data are consistent with a model in which dynamic phosphorylation of the capsid regulates its RNA binding activity and, in turn, nucleocapsid assembly. In the present study, the process of capsid phosphorylation was examined in further detail. We show that phosphorylation of serine 46 in the RNA binding region of the capsid is required to trigger phosphorylation of additional amino acid residues that include threonine 47. This residue likely plays a direct role in regulating the binding of genomic RNA to the capsid. We also provide evidence which suggests that the capsid is dephosphorylated prior to or during virus budding. Finally, whereas the phosphorylation state of the capsid does not directly influence the rate of synthesis of viral RNA and proteins or the assembly and secretion of virions, the presence of phosphate on the capsid is critical for early events in virus replication, most likely the uncoating of virions and/or disassembly of nucleocapsids.
Optimal Long-Term Humoral Responses to Replication-Defective Herpes Simplex Virus Require CD21/CD35 Complement Receptor Expression on Stromal Cells
Authors: Brockman Mark A. , Verschoor Admar , Zhu Jia , Carroll Michael C. , Knipe David M. 
Published: June 2006

ABSTRACTReplication-defective herpes simplex virus (HSV) strains elicit durable immune responses and protect against virulent HSV challenge in mice, despite being unable to establish latent infection in neuronal cells. Mechanisms for generating long-lived immunity in the absence of viral persistence remain uncertain. In animals immunized with replication-defective HSV, durable serum immunoglobulin G (IgG) responses were elicited. Surprisingly, Western blot analyses revealed that the specificities of antiviral IgG changed over time, and antibody reactivity to some viral proteins was detected only very late. Thus, some of the durable IgG activity appeared to be contributed by either new or significantly enhanced antibody responses at late times. Following immunization, radiation bone marrow-chimeric mice lacking complement receptors CD21 and CD35 on stromal cells elicited only short-lived serum IgG and failed to mount recall responses to subsequent HSV exposure. Our results suggest that complement-mediated retention of viral antigens by stromal cells, such as follicular dendritic cells, is critical for optimal maintenance of antibody responses and B-cell memory following vaccination with replication-defective HSV.
Activation of NF-κB by the Latent vFLIP Gene of Kaposi's Sarcoma-Associated Herpesvirus Is Required for the Spindle Shape of Virus-Infected Endothelial Cells and Contributes to Their Proinflammatory Phenotype
Authors: Grossmann Claudia , Podgrabinska Simona , Skobe Mihaela , Ganem Don 
Published: June 2006

ABSTRACTKaposi's sarcoma (KS) is an inflammatory angioproliferative lesion induced by the infection of endothelial cells with the KS-associated herpesvirus (KSHV). Infected endothelial cells assume an elongated (spindle) shape that is one of the histologic signatures of KS. In vitro, latent viral infection of primary endothelial cells (but no other cell type) strikingly recapitulates these morphological findings. Here we report that the spindling phenotype involves major rearrangement of the actin cytoskeleton and can be attributed to the expression of a single viral protein, vFLIP, a known activator of NF-κB. Consistent with this, the inhibition of NF-κB activation blocks vFLIP-induced spindling in cultured endothelial cells. vFLIP expression in spindle cells also induces the production of a variety of proinflammatory cytokines and cell surface adhesion proteins that likely contribute to the inflammatory component of KS lesions.
Role of Invariant Thr80 in Human Immunodeficiency Virus Type 1 Protease Structure, Function, and Viral Infectivity
Authors: Foulkes Jennifer E. , Prabu-Jeyabalan Moses , Cooper Deyna , Henderson Gavin J. , Harris Janera , Swanstrom Ronald , Schiffer Celia A. 
Published: June 2006

ABSTRACT
Sequence variability associated with human immunodeficiency virus type 1 (HIV-1) is useful for inferring structural and/or functional constraints at specific residues within the viral protease. Positions that are invariant even in the presence of drug selection define critically important residues for protease function. While the importance of conserved active-site residues is easily understood, the role of other invariant residues is not. This work focuses on invariant Thr80 at the apex of the P1 loop of HIV-1, HIV-2, and simian immunodeficiency virus protease. In a previous study, we postulated, on the basis of a molecular dynamics simulation of the unliganded protease, that Thr80 may play a role in the mobility of the flaps of protease. In the present study, both experimental and computational methods were used to study the role of Thr80 in HIV protease. Three protease variants (T80V, T80N, and T80S) were examined for changes in structure, dynamics, enzymatic activity, affinity for protease inhibitors, and viral infectivity. While all three variants were structurally similar to the wild type, only T80S was functionally similar. Both T80V and T80N had decreased the affinity for saquinavir. T80V significantly decreased the ability of the enzyme to cleave a peptide substrate but maintained infectivity, while T80N abolished both activity and viral infectivity. Additionally, T80N decreased the conformational flexibility of the flap region, as observed by simulations of molecular dynamics. Taken together, these data indicate that HIV-1 protease functions best when residue 80 is a small polar residue and that mutations to other amino acids significantly impair enzyme function, possibly by affecting the flexibility of the flap domain.