bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Variability of Group A Human Respiratory Syncytial Virus Strains Circulating in Germany from 1998 to 2007
Authors: Reiche Janine , Schweiger Brunhilde
Published: April 2009

The variability between respiratory syncytial virus (RSV) strains is one of the features of RSV infections that might contribute to the ability of the virus to infect people repeatedly and cause yearly outbreaks. To study the molecular epidemiology of RSV, more than 1,400 RSV isolates from human nasopharyngeal aspirates or nasal or throat swabs from patients with respiratory illness were identified and differentiated by TaqMan reverse transcription-PCR into groups A and B. RSV group A was dominant in seven out of nine epidemic seasons. Phylogenetic analysis revealed that RSV group A genotypes GA2 and GA5 circulated from 1998 to 2007. Genotype GA7 was present in only two seasons (1999 to 2000 and 2002 to 2003). Comparison of the synonymous mutation/nonsynonymous mutation ratios showed greater evidence for selection pressure for genotype GA2 (1.18) than for GA5 (4.34). Partial protein sequences were predicted to encode G proteins of 298 amino acids in length and in a few cases of G proteins of 297 amino acids in length. Amino acid analysis also revealed genotype-specific amino acid substitutions: two substitutions for genotype GA2, seven for GA5, and three for GA7. Two to four putative, genotype-specific N-linked glycosylation sites were determined. Predicted O-glycosylation sites included 22 to 34 residues. This study provides for the first time data on the circulation pattern of RSV group A genotypes and their molecular characterization in Germany during nine consecutive epidemic seasons.
HLA Class I Subtype-Dependent Expansion of KIR3DS1
+
and KIR3DL1
+
NK Cells during Acute Human Immunodeficiency Virus Type 1 Infection
Authors: Alter Galit , Rihn Suzannah , Walter Katharine , Nolting Anne , Martin Maureen , Rosenberg Eric S. , Miller Jeffrey S. , Carrington Mary , Altfeld Marcus
Published: April 2009

NK cells are critical in the early containment of viral infections. Epidemiological and functional studies have shown an important role of NK cells expressing specific killer immunoglobulin-like receptors (KIRs) in the control of human immunodeficiency virus type 1 (HIV-1) infection, but little is known about the mechanisms that determine the expansion of these antiviral NK cell populations during acute HIV-1 infection. Here we demonstrate that NK cells expressing the activating receptor KIR3DS1
+
and, to a lesser extent, the inhibitory receptor KIR3DL1
+
specifically expand in acute HIV-1 infection in the presence of HLA-B Bw480I, the putative HLA class I ligand for KIR3DL1/3DS1. These data demonstrate for the first time the HLA class I subtype-dependent expansion of specific KIR
+
NK cells during an acute viral infection in humans.
Identification of Infected B-Cell Populations by Using a Recombinant Murine Gammaherpesvirus 68 Expressing a Fluorescent Protein
Authors: Collins Christopher M. , Boss Jeremy M. , Speck Samuel H.
Published: April 2009

Infection of inbred mice with murine gammaherpesvirus 68 (MHV68) has proven to be a powerful tool to study gammaherpesvirus pathogenesis. However, one of the limitations of this system has been the inability to directly detect infected cells harvested from infected animals. To address this issue, we generated a transgenic virus that expresses the enhanced yellow fluorescent protein (YFP), driven by the human cytomegalovirus immediate-early promoter and enhancer, from a neutral locus within the viral genome. This virus, MHV68-YFP, replicated and established latency as efficiently as did the wild-type virus. During the early phase of viral latency, MHV68-YFP efficiently marked latently infected cells in the spleen after intranasal inoculation. Staining splenocytes for expression of various surface markers demonstrated the presence of MHV68 in distinct populations of splenic B cells harboring MHV68. Notably, these analyses also revealed that markers used to discriminate between newly formed, follicular and marginal zone B cells may not be reliable for phenotyping B cells harboring MHV68 since virus infection appears to modulate cell surface expression levels of CD21 and CD23. However, as expected, we observed that the overwhelming majority of latently infected B cells at the peak of latency exhibited a germinal center phenotype. These analyses also demonstrated that a significant percentage of MHV68-infected splenocytes at the peak of viral latency are plasma cells (ca. 15% at day 14 and ca. 8% at day 18). Notably, the frequency of virus-infected plasma cells correlated well with the frequency of splenocytes that spontaneously reactivate virus upon explant. Finally, we observed that the efficiency of marking latently infected B cells with the MHV68-YFP recombinant virus declined at later times postinfection, likely due to shut down of transgene expression, and indicating that the utility of this marking strategy is currently limited to the early stages of virus infection.
Infection of HLA-DR1 Transgenic Mice with a Human Isolate of Influenza A Virus (H1N1) Primes a Diverse CD4 T-Cell Repertoire That Includes CD4 T Cells with Heterosubtypic Cross-Reactivity to Avian (H5N1) Influenza Virus
Authors: Richards Katherine A. , Chaves Francisco A. , Sant Andrea J.
Published: April 2009

The specificity of the CD4 T-cell immune response to influenza virus is influenced by the genetic complexity of the virus and periodic encounters with variant subtypes and strains. In order to understand what controls CD4 T-cell reactivity to influenza virus proteins and how the influenza virus-specific memory compartment is shaped over time, it is first necessary to understand the diversity of the primary CD4 T-cell response. In the study reported here, we have used an unbiased approach to evaluate the peptide specificity of CD4 T cells elicited after live influenza virus infection. We have focused on four viral proteins that have distinct intracellular distributions in infected cells, hemagglutinin (HA), neuraminidase (NA), nucleoprotein, and the NS1 protein, which is expressed in infected cells but excluded from virion particles. Our studies revealed an extensive diversity of influenza virus-specific CD4 T cells that includes T cells for each viral protein and for the unexpected immunogenicity of the NS1 protein. Due to the recent concern about pandemic avian influenza virus and because CD4 T cells specific for HA and NA may be particularly useful for promoting the production of neutralizing antibody to influenza virus, we have also evaluated the ability of HA- and NA-specific CD4 T cells elicited by a circulating H1N1 strain to cross-react with related sequences found in an avian H5N1 virus and find substantial cross-reactivity, suggesting that seasonal vaccines may help promote protection against avian influenza virus.
A Point Mutation, E95D, in the Mumps Virus V Protein Disengages STAT3 Targeting from STAT1 Targeting
Authors: Puri Mamta , Lemon Ken , Duprex W. Paul , Rima Bertus K. , Horvath Curt M.
Published: April 2009

Mumps virus, like other paramyxoviruses in the
Rubulavirus
genus, encodes a V protein that can assemble a ubiquitin ligase complex from cellular components, leading to the destruction of cellular signal transducer and activator of transcription (STAT) proteins. While many V proteins target the interferon-activated STAT1 or STAT2 protein, mumps virus V protein is unique in its ability to also target STAT3 for ubiquitin modification and proteasome-mediated degradation. Here we report that a single amino acid substitution in the mumps virus V protein, E95D, results in defective STAT3 targeting while maintaining the ability to target STAT1. Results indicate that the E95D mutation disrupts the ability of the V protein to associate with STAT3. A recombinant mumps virus carrying the E95D mutation in its P and V proteins replicates normally in cultured cells but fails to induce targeting of STAT3. Infection with the recombinant virus results in the differential regulation of a number of cellular genes compared to wild-type mumps virus and increases cell death in infected cells, producing a large-plaque phenotype.
Human Papillomavirus Type 16 (HPV-16) Virus-Like Particle L1-Specific CD8
+
Cytotoxic T Lymphocytes (CTLs) Are Equally Effective as E7-Specific CD8
+
CTLs in Killing Autologous HPV-16-Positive Tumor Cells in Cervical Cancer Patients: Implications for L1 Dendritic Cell-Based Therapeutic Vaccines
Authors: Bellone Stefania , El-Sahwi Karim , Cocco Emiliano , Casagrande Francesca , Cargnelutti Marilisa , Palmieri Michela , Bignotti Eliana , Romani Chiara , Silasi Dan-Arin , Azodi Masoud , Schwartz Peter E. , Rutherford Thomas J. , Pecorelli Sergio , Santin Alessandro D.
Published: April 2009

Papillomavirus-like particles (VLPs) based on L1 capsid protein represent a promising prophylactic vaccine against human papillomavirus (HPV) infections. However, cell-mediated immune responses against this antigen are believed to be of limited therapeutic value in established HPV-infected cervical lesions and, for this reason, have not been intensively investigated in cervical cancer patients. In this study we analyzed and quantified by real-time PCR (RT-PCR) the RNA expression levels of E6, E7, and L1 genes in flash-frozen HPV-16 cervical carcinomas. In addition, the kinetics of expression of E6, E7, and L1 in HPV-16-infected primary cell lines established as long-term cultures in vitro was also evaluated at RNA and protein levels. Finally, in order to evaluate the therapeutic potential of L1-specific CD4
+
and CD8
+
T lymphocytes responses in cervical cancer patients, L1 VLP-loaded dendritic cells (DCs) were used to stimulate peripheral blood lymphocytes from cervical cancer patients and such responses were compared to those elicited by the E7 oncoprotein. We show that 22 of 22 (100%) flash-frozen cervical biopsy samples collected from HPV-16-positive cervical cancer patients harbor L1, in addition to E6 and E7 RNA, as detected by RT-PCR. E7 RNA copy number (mean, 176.2) was significantly higher in HPV-16-positive cervical cancers compared to the E6 RNA copy number (mean, 47.3) and the L1 copy number (mean, 58.3) (
P
< 0.0001 and
P
< 0.001, respectively). However, no significant differences in expression levels between E6 and L1 were found. Kinetic studies of E6, E7, and L1 RNA and protein expression levels in primary tumors showed a sharp reduction in L1 expression after multiple in vitro passages compared to E6 and E7. Autologous DCs pulsed with HPV-16 VLPs or recombinant full-length E7 elicited strong type 1 L1- and E7-specific responses in CD4
+
and CD8
+
T cells from cervical cancer patients. Importantly, L1 VLP-specific CD8
+
T lymphocytes expressed strong cytolytic activity against autologous tumor cells and were as effective as E7-specific cytotoxic T lymphocytes in lysing naturally HPV-16-infected autologous tumor cells. Taken together, these data demonstrate a consistent expression of L1 in primary cervical tumors and the possibility of inducing effective L1/tumor-specific CD4
+
and CD8
+
T-lymphocyte responses in patients harboring HPV-infected cervical cancer. These results may have important implications for the treatment of patients harboring established HPV-infected lesions with L1 VLPs or combined E7/L1 DC-based vaccinations.
Herpesvirus Capsid Association with the Nuclear Pore Complex and Viral DNA Release Involve the Nucleoporin CAN/Nup214 and the Capsid Protein pUL25
Authors: Pasdeloup David , Blondel Danielle , Isidro Anabela L. , Rixon Frazer J.
Published: April 2009

After penetrating the host cell, the herpesvirus capsid is transported to the nucleus along the microtubule network and docks to the nuclear pore complex before releasing the viral DNA into the nucleus. The viral and cellular interactions involved in the docking process are poorly characterized. However, the minor capsid protein pUL25 has recently been reported to be involved in viral DNA uncoating. Here we show that herpes simplex virus type 1 (HSV-1) capsids interact with the nucleoporin CAN/Nup214 in infected cells and that RNA silencing of CAN/Nup214 delays the onset of viral DNA replication in the nucleus. We also show that pUL25 interacts with CAN/Nup214 and another nucleoporin, hCG1, and binds to the pUL36 and pUL6 proteins, two other components of the herpesvirus particle that are known to be important for the initiation of infection and viral DNA release. These results identify CAN/Nup214 as being a nuclear receptor for the herpesvirus capsid and pUL25 as being an interface between incoming capsids and the nuclear pore complex and as being a triggering element for viral DNA release into the nucleus.
Identification of Varicella-Zoster Virus-Specific CD8 T Cells in Patients after T-Cell-Depleted Allogeneic Stem Cell Transplantation
Authors: van der Heiden Pim L. J. , de Boer Renate , van der Steen Dirk M. , Kester Michel G. D. , van der Hoorn Menno W. A. G. , Haarman Wilmy M. E. , Barnby-Porritt Helen E. , Fry Jeremy W. , Napper C. E. , Marijt Erik W. A. , Willemze Roel , Falkenburg J. H. Frederik , Heemskerk Mirjam H. M.
Published: April 2009

To study the role of CD8 T cells in the control of varicella-zoster virus (VZV) reactivation, we developed multimeric major histocompatibility complexes to identify VZV-specific CD8 T cells. Potential HLA-A2 binding peptides from the putative immediate-early 62 protein (IE62) of VZV were tested for binding, and peptides with sufficient binding capacity were used to generate pentamers. Patients with VZV reactivation following stem cell transplantation were screened with these pentamers, leading to the identification of the first validated class I-restricted epitope of VZV. In 42% of HLA-A2 patients following VZV reactivation, these IE62-ALW-A2 T cells could be detected ex vivo.
Hepatitis B Virus Core Gene Mutations Which Block Nucleocapsid Envelopment
Authors: Koschel Matthias , Oed Daniela , Gerelsaikhan Tudevdagwa , Thomssen Reiner , Bruss Volker
Published: April 2009

Recently we generated a panel of hepatitis B virus core gene mutants carrying single insertions or deletions which allowed efficient expression of the core protein in bacteria and self-assembly of capsids. Eleven of these mutations were introduced into a eukaryotic core gene expression vector and characterized by
trans
complementation of a core-negative HBV genome in cotransfected human hepatoma HuH7 cells. Surprisingly, four mutants (two insertions [EFGA downstream of A11 and LDTASALYR downstream of R39] and two deletions [Y38-R39-E40 and L42]) produced no detectable capsids. The other seven mutants supported capsid formation and pregenome packaging/viral minus- and plus-strand-DNA synthesis but to different levels. Four of these seven mutants (two insertions [GA downstream of A11 and EHCSP downstream of P50] and two deletions [S44 and A80]) allowed virion morphogenesis and secretion. The mutant carrying a deletion of A80 at the tip of the spike protruding from the capsid was hepatitis B virus core antigen negative but wild type with respect to virion formation, indicating that this site might not be crucial for capsid-surface protein interactions during morphogenesis. The other three nucleocapsid-forming mutants (one insertion [LS downstream of S141] and two deletions [T12 and P134]) were strongly blocked in virion formation. The corresponding sites are located in the part of the protein forming the body of the capsid and not in the spike. These mutations may alter sites on the particle which contact surface proteins during envelopment, or they may block the appearance of a signal for the transport or the maturation of the capsid which is linked to viral DNA synthesis and required for envelopment.
RNA Dimerization Defect in a Rous Sarcoma Virus Matrix Mutant
Authors: Parent Leslie J. , Cairns Tina M. , Albert Jessica A. , Wilson Carol B. , Wills John W. , Craven Rebecca C.
Published: April 2009

The retrovirus matrix (MA) sequence of the Gag polyprotein has been shown to contain functions required for membrane targeting and binding during particle assembly and budding. Additional functions for MA have been proposed based on the existence of MA mutants in Rous sarcoma virus (RSV), murine leukemia virus, human immunodeficiency virus type 1, and human T-cell leukemia virus type 1 that lack infectivity even though they release particles of normal composition. Here we describe an RSV MA mutant with a surprising and previously unreported phenotype. In the mutant known as Myr1E, the small membrane-binding domain of the Src oncoprotein has been added as an N-terminal extension of Gag. While Myr1E is not infectious, full infectivity can be reestablished by a single amino acid substitution in the Src sequence (G2E), which eliminates the addition of myristic acid and the membrane-binding capacity of this foreign sequence. The presence of myristic acid at the N terminus of the Myr1E Gag protein does not explain its replication defect, because other myristylated derivatives of RSV Gag are fully infectious (e.g., Myr2 [C. R. Erdie and J. W. Wills, J. Virol. 64:5204–5208, 1990]). Biochemical analyses of Myr1E particles reveal that they contain wild-type levels of the Gag cleavage products, Env glycoproteins, and reverse transcriptase activity when measured on an exogenous template. Genomic RNA incorporation appears to be mildly reduced compared to the wild-type level. Unexpectedly, RNA isolated from Myr1E particles is monomeric when analyzed on nondenaturing Northern blots. Importantly, the insertional mutation does not lie within previously identified dimer linkage sites. In spite of the dimerization defect, the genomic RNA from Myr1E particles serves efficiently as a template for reverse transcription as measured by an endogenous reverse transcriptase assay. In marked contrast, after infection of avian cells, the products of reverse transcription are nearly undetectable. These findings might be explained either by the loss of a normal function of MA needed in the formation or stabilization of RNA dimers or by the interference in such events by the mutant MA molecules. It is possible that Myr1E viruses package a single copy of viral RNA.
B7 Costimulation Is Critical for Antibody Class Switching and CD8+Cytotoxic T-Lymphocyte Generation in the Host Response to Vesicular Stomatitis Virus
Authors: McAdam Alexander J. , Farkash Evan A. , Gewurz Benjamin E. , Sharpe Arlene H.
Published: April 2009

Antibody and cytotoxic T-lymphocyte (CTL) responses have critical roles in eliminating many viral infections. In addition to stimulation of the T-cell receptor, T cells require costimulatory signals to respond optimally. We evaluated the role of B7 costimulatory molecules (B7-1 and B7-2) in the immune response to viral infection using vesicular stomatitis virus (VSV) and mice lacking either B7-1 or B7-2 or both molecules. Mice lacking both B7-1 and B7-2 had essentially no anti-VSV immunoglobulin G1 (IgG1) response, decreased IgG2a responses, and normal IgM responses, while mice lacking either B7-1 or B7-2 had unaltered anti-VSV antibody responses compared to wild-type mice. Depletion of CD4+cells further reduced the IgG2a response in mice lacking both B7 molecules, suggesting that CD4−cells may supply help for IgG2a in the absence of B7 costimulation. The absence of both B7 molecules profoundly reduced generation of both primary and secondary VSV-specific class I major histocompatibility complex (MHC)-restricted CTL, whereas VSV-specific CTL responses in mice lacking either B7-1 or B7-2 were similar to those of wild-type animals. Class I MHC-restricted CTL in wild-type mice were not dependent on CD4+cells, suggesting that the failure of CTL in the absence of B7s is due to a lack of B7 costimulation directly to the CD8+CTL. These data demonstrate that B7-1 and B7-2 have critical, overlapping functions in the antibody and CTL responses to this viral infection.
A Comprehensive Approach to Mapping the Interacting Surfaces of Murine Amphotropic and Feline Subgroup B Leukemia Viruses with Their Cell Surface Receptors
Authors: Tailor Chetankumar S. , Nouri Ali , Kabat David
Published: April 2009

Because mutations in envelope glycoproteins of retroviruses or in their cell surface receptors can eliminate function by multiple mechanisms, it has been difficult to unambiguously identify sites for their interactions by site-directed mutagenesis. Recently, we developed a gain-of-function approach to overcome this problem. Our strategy relies on the fact that feline leukemia virus subgroup B (FeLV-B) and amphotropic murine leukemia virus (A-MLV) have closely related gp70 surface envelope glycoproteins and use related Na
+
-dependent phosphate symporters, Pit1 and Pit2, respectively, as their receptors. We previously observed that FeLV-B/A-MLV envelope glycoprotein chimeras spliced between the variable regions VRA and VRB were unable to use Pit1 or Pit2 as a receptor but could efficiently use specific Pit1/Pit2 chimeras. The latter study suggested that the VRA of A-MLV and FeLV-B functionally interact with the presumptive extracellular loops 4 and 5 (ECL4 and -5) of their respective receptors, whereas VRB interacts with ECL2. We also found that FeLV-B gp70 residues F60 and P61 and A-MLV residues Y60 and V61 in the first disulfide-bonded loop of VRA were important for functional interaction with the receptor's ECL4 or -5. We have now extended this approach to identify additional VRA and VRB residues that are involved in receptor recognition. Our studies imply that FeLV-B VRA residues F60 and P61 interact with the Pit1 ECL5 region, whereas VRA residues 66 to 78 interact with Pit1 ECL4. Correspondingly, A-MLV VRA residues Y60 and V61 interact with the Pit2 ECL5 region, whereas residues 66 to 78 interact with Pit2 ECL4. Similar studies that focused on the gp70 VRB implicated residues 129 to 139 as contributing to specific interactions with the receptor ECL2. These results identify three regions of gp70 that interact in a specific manner with distinct portions of their receptors, thereby providing a map of the functionally interacting surfaces.
Identification of a Short, Hydrophilic Amino Acid Sequence Critical for Origin Recognition by the Bovine Papillomavirus E1 Protein
Authors: Gonzalez Annika , Bazaldua-Hernandez Cynthia , West Michael , Woytek Kelly , Wilson Van G.
Published: April 2009

The E1 protein of bovine papillomavirus (BPV) is a site-specific DNA binding protein that recognizes an 18-bp inverted repeat element in the viral origin of replication. Sequence-specific DNA binding function maps to the region from approximately amino acids 140 to 300, and isolated polypeptides containing this region have been shown to retain origin binding in vitro. To investigate the sequence and structural characteristics which contribute to sequence-specific binding, the primary sequence of this region was examined for conserved features. The BPV E1 DNA binding domain (E1DBD) contains three major hydrophilic domains (HR1, amino acids 179–191; HR2, amino acids 218 to 230; and HR3, amino acids 241 to 252), of which only HR1 and HR3 are conserved among papillomavirus E1 proteins. E1DBD proteins with lysine-to-alanine mutations in HR1 and HR3 were severely impaired for DNA binding function in vitro, while a lysine-to-alanine mutation in HR2 had a minimal effect on DNA binding. Mutation of adjacent threonine residues in HR1 (T187 and T188) revealed that these two amino acids made drastically different contributions to DNA binding, with the T187 mutant being severely defective for origin binding whereas the T188 mutant was only mildly affected. Helical wheel projections of HR1 predict that T187 is on the same helical face as the critical lysine residues whereas T188 is on the opposing face, which is consistent with their respective contributions to DNA binding activity. To examine E1 binding in vivo, a yeast one-hybrid system was developed. Both full-length E1 and the E1DBD polypeptide were capable of specifically interacting with the E1 binding site in the context of the yeast genome, and HR1 was also critical for this in vivo interaction. Overall, our results indicate that HR1 is essential for origin binding by E1, and the features and properties of HR1 suggest that it may be part of a recognition sequence that mediates specific E1-nucleotide contacts.
Simplified Strategy for Detection of Recombinant Human Immunodeficiency Virus Type 1 Group M Isolates by
gag/env
Heteroduplex Mobility Assay
Authors: Heyndrickx Leo , Janssens Wouter , Zekeng Léopold , Musonda Rosemary , Anagonou Séverin , Van der Auwera Gert , Coppens Sandra , Vereecken Katleen , De Witte Ko , Van Rampelbergh Rian , Kahindo Maina , Morison Linda , McCutchan Francine E. , Carr Jean K. , Albert Jan , Essex Max , Goudsmit Jaap , Asjö Birgitta , Salminen Mika , Buvé Anne ,   Study Group on Heterogeneity of HIV Epidemics in African Cities, van der Groen Guido
Published: April 2009

We developed a heteroduplex mobility assay in the
gag
gene (
gag
HMA) for the identification of group M subtypes A to H. The assay covers the region coding for amino acid 132 of p24 to amino acid 20 of p7 (according to human immunodeficiency virus type 1 [HIV-1] ELI, 460 bp). The
gag
HMA was compared with sequencing and phylogenetic analysis of an evaluation panel of 79 HIV-1 group M isolates isolated from infected individuals from different geographic regions. Application of
gag
HMA in combination with
env
HMA on 252 HIV-1- positive plasma samples from Bénin, Cameroon, Kenya, and Zambia revealed a high prevalence of a variety of intersubtype recombinants in Yaoundé, Cameroon (53.8%); Kisumu, Kenya (26.8%); and Cotonou, Bénin (41%); no recombinants were identified among the samples from Ndola, Zambia. The AG
IbNG
circulating recombinant form, as determined by
gag
HMA, was found to be the most common intersubtype recombinant in Yaoundé (39.4%) and Cotonou (38.5%). Using a one-tube reverse transcriptase PCR protocol, this
gag
HMA in combination with
env
HMA is a useful tool for rapidly monitoring the prevalence of the various genetic subtypes as well as of recombinants of HIV-1. Moreover, this technology can easily be applied in laboratories in developing countries.
Canine Adenovirus Vectors: an Alternative for Adenovirus-Mediated Gene Transfer
Authors: Kremer Eric J. , Boutin Sylvie , Chillon Miguel , Danos Olivier
Published: April 2009

Preclinical studies have shown that gene transfer following readministration of viral vectors is often inefficient due to the presence of neutralizing antibodies. Vectors derived from ubiquitous human adenoviruses may have limited clinical use because preexisting humoral and cellular immunity is found in 90% of the population. Furthermore, risks associated with the use of human adenovirus vectors, such as the need to immunosuppress or tolerize patients to a potentially debilitating virus, are avoidable if efficient nonhuman adenovirus vectors are feasible. Plasmids containing recombinant canine adenovirus (CAV) vectors from which the E1 region had been deleted were generated and transfected into a CAV E1-transcomplementing cell line. Vector stocks, with titers greater than or equal to those obtained with human adenovirus vectors, were free of detectable levels of replication-competent CAV and had a low particle-to-transduction unit ratio. CAV vectors were replication defective in all cell lines tested, transduced human-derived cells at an efficiency similar to that of a comparable human adenovirus type 5 vector, and are amenable to in vivo use. Importantly, 49 of 50 serum samples from healthy individuals did not contain detectable levels of neutralizing CAV antibodies.
Plasmid-Driven Formation of Influenza Virus-Like Particles
Authors: Neumann Gabriele , Watanabe Tokiko , Kawaoka Yoshihiro
Published: April 2009

We established a plasmid-based system for generating infectious influenza virus-like particles entirely from cloned cDNAs. Human embryonic kidney cells (293T) were transfected with plasmids encoding the influenza A virus structural proteins and with a plasmid encoding an influenza virus-like viral RNA (vRNA) which contained an antisense copy of the cDNA for green fluorescence protein (GFP) flanked by an RNA polymerase I promoter and terminator. Intracellular transcription of the latter construct by RNA polymerase I generated GFP vRNA that was packaged into influenza virus-like particles. This system, which produced more than 10
4
infectious particles per ml of supernatant, would be useful in studies of influenza virus replication and particle formation. It might also benefit efforts in vaccine production and in the development of improved gene therapy vectors.
Immune Complexes Containing Human Immunodeficiency Virus Type 1 Primary Isolates Bind to Lymphoid Tissue B Lymphocytes and Are Infectious for T Lymphocytes
Authors: Jakubik Jocelyn J. , Saifuddin Mohammed , Takefman Daniel M. , Spear Gregory T.
Published: April 2009

This study investigated the interaction of tonsil B lymphocytes with immune complexes containing human immunodeficiency virus (HIV IC) primary isolates and the infectivity of the B cell-bound HIV IC. Treatment of virus with a source of antibody and complement increased HIV IC binding to B cells by 5.6-fold. Most of the HIV IC that bound to B cells were not internalized but remained on the cell surface and were gradually released over 72 h. Cell-bound HIV IC were highly infectious for T cells while virus released by cultured B cells was only slightly infectious. Removal of HIV IC from the B-cell surface by protease treatment reduced the infection of T cells to near-background levels, indicating that infectious virus remained on the B-cell surface. These studies show that B lymphocytes can carry and transfer infectious HIV IC to T cells and thus suggest a novel mode of infection of T cells in lymphoid tissue that could be important for pathogenesis during HIV infection.
The effects of litter displacement on riverbank vegetation
Authors: Nilsson Christer , Grelsson Gunnel
Published: April 2009

The hypotheses that litter deposition on riverbanks would depend on riverbank features and that litter mass would affect riverbank vegetation were tested by sampling vegetation, litter, and soil along a seventh-order stretch of the unregulated Vindel River in northern Sweden. Sampling was carried out within a horizontal litter gradient at the top of the riverbank where most of the litter deposition occurs. The amount of leaf litter left on the riverbank after flooding was significantly correlated (P < 0.05) with soil organic matter. In contrast, wood litter mass and total litter mass were not correlated (P > 0.05) with riverbank features such as soil organic matter, riverbank slope, or stem density. Species richness, species diversity, and the proportions of stemmed and nonstemmed species showed quadratic relationships (P < 0.05) with leaf litter mass, whereas ground vegetation cover decreased monotonically (P < 0.05) with increasing leaf litter mass. Tall, stemmed species were most frequent at eroded sites with low amounts of leaf litter and at sites where leaf litter had accumulated. In contrast, the highest proportion of low-growing species was found at sites with intermediate leaf litter masses. Community characteristics such as species richness, species diversity, and the proportions of stemmed and nonstemmed species (but not ground vegetation cover) were less strongly correlated with wood litter mass and total litter mass. Linear equations explained about half of the variation in ground vegetation cover along gradients of wood and total litter masses. Density and richness of seeds increased with increasing litter mass. We discuss the litter effects in terms of productivity and disturbance and conclude that flooding in pristine rivers may exert a considerable influence on riverbank vegetation as a result of litter displacement.
The life cycle of Lagena radicicola, an oomycetous parasite of wheat roots
Authors: Barr D. J. S. , Désaulniers N. L.
Published: April 2009

Lagena radicicola Vanterpool & Ledingham is an obligate parasite inside root hairs and epidermal cells. It was cultured in a unifungal state on wheat in pots. The life cycle was examined by both light and transmission electron microscopy. The thallus developed inside a single host cell and formed either a single sporangium or one to four resting spores. Zoospore cleavage was completed in vesicles outside the root. The resting spores were similar to oospores in their development and cytology, but there was no evidence of cell fusion and sexuality. Virus-like particles were seen in 3- to 12-month-old cultures, and infected cells became degenerate. Key words: Oomycetes, ultrastructure, virus-like particles, biocontrol.
Variation in acid phosphatase activity among progeny from controlled crosses in the ectomycorrhizal fungus Laccaria bicolor
Authors: Kropp Bradley R.
Published: April 2009

The variation in acid phosphatase activity among the monokaryotic F1 progeny from two different synthesized dikaryotic cultures of the ectomycorrhizal basidiomycete Laccaria bicolor was examined. The progeny of one of the dikaryons showed variation in acid phosphatase activity up to 10 times that of the lowest value. The progeny of the other dikaryon were much less variable, showing differences of up to 5 times the lowest value. Both sets of monokaryotic progeny showed distributions indicative of polygenic inheritance for acid phosphatase activity in this fungus. Key words: ectomycorrhizae, genetics, monokaryon, acid phosphatase, Laccaria bicolor.
A comparison of seed storage proteins in subspecies and cultivars of Medicago sativa
Authors: Krochko Joan E. , Charbonneau Marc R. , Coulter Kelsye M. , Bowley Stephen R. , Bewley J. Derek
Published: April 2009

Seeds of alfalfa contain two storage globulins: alfin, a 7S vicilinlike protein, and medicagin, an 1IS leguminlike globulin. Alfin is easily solubilized and is found predominantly in the initial low salt soluble extract. Repeated extractions with this buffer (0.2 M NaCl, pH 7.0) fail to solubilize the medicagin protein. However, if the concentration of salt in the second extraction buffer is increased (0.4 to 1.0 M NaCl), there is a progressive increase in the amount of medicagin protein solubilized. The requirement for salt for solubilization is partially offset if the buffering pH is raised to 9.0. Buffers containing 2% SDS are no more efficient than 1.0 M NaCl in extracting medicagin, and the addition of 10 mM dithiothreitol is ineffective in increasing protein yields. Seed storage proteins of members of the Medicago sativa L. species complex were analyzed using one- and two-dimensional electrophoretic techniques. In total, 29 varieties were examined, including five subspecies, eight landraces, and a diploid and tetraploid isogenic line. For all of the samples examined, the polypeptide profiles for alfin and medicagin were very similar; the major differences between taxa were quantitative rather than qualitative. When medicagin was examined using two-dimensional techniques, minor variations in the polypeptide profile became apparent, In general, the variability was almost exclusively in the acidic polypeptides (size and number) rather than the basic polypeptides.
Limited Entry Policy and the Bristol Bay, Alaska Salmon Fishermen
Authors: Koslow J. Anthony
Published: April 2009

The impact of limited entry was examined upon the diverse groups engaged in the Bristol Bay, Alaska salmon fishery. Whereas limited entry was intended to enhance the state's rural fishing economies, the system has in fact significantly diminished access of the local population to the fishery, the region's primary economic activity. A significant proportion of local fishermen were intially denied entry permits due to entry criteria in which the implicit definition of a legitimate fisherman was based largely upon a nonrural model, development of an application poorly designed for use by the rural Alaskan population, and administration of the program by a bureaucracy that appears insensitive to the needs of the rural communities. The salability of the permits, combined with the poorer fishing earnings of local fishermen and the generally impoverished local economy, led to a further drain of permits from local areas. Unless the system is substantially altered, local fishing communities can be expected to suffer significant further impoverishment because the fishery is now effectively closed to their burgeoning youthful population. However, the present system substantially benefits urban Alaskan fishermen (as well as non-Alaskan fishermen), who are more effective politically than their rural counterparts, so no substantial change in the present system can be expected. Limited entry programs clearly must be based upon a better understanding of the socioeconomic and cultural characteristics of targeted fishing communities if such highly inappropriate consequences are to be avoided.Key words: limited entry, Bristol Bay, salmon fishery, socioeconomic, Oncorhynchus nerka, fishery management
Influence of Time and Size at Release of Juvenile Coho Salmon (Oncorhynchus kisutch) on Returns at Maturity
Authors: Bilton H. T. , Alderdice D. F. , Schnute J. T.
Published: April 2009

Juvenile coho salmon (Oncorhynchus kisutch) were raised in six ponds at Rosewall Creek, Vancouver Island, British Columbia, from which releases were made at four times: April 14, May 12, June 10 and July 8, 1975. Prior to each release a portion of the juveniles in each pond were graded into three size groups (small, medium, large) based on size distributions in each pond. The juveniles were nose-tagged according to size group, pond, and release date, and marked by adipose fin removal. A total of 57 groups were released. Returns of adults and precocious males (jacks) to the weir and to the fishery (commercial, sport) were subjected to response surface analysis. Maximum adult returns of 43.5%, to the weir and fishery, were predicted for release of 25.1-g coho juveniles on the 173rd (Julian) day from January 1 (June 22, 1975). A significant interaction was noted between release time and size: maximum returns from early (April 14) releases would be expected from release of 16- to 17-g juveniles. Returns of jacks from the six ponds ranged from 0.0 to 4.65%. Predicted returns of jacks would be maximized from early release of large juveniles (> ~20 g in April). The benefit–cost ratio at the center of the time and size of release surface for maximum adult returns was estimated as 12.2:1. Maximum benefit–cost ratios were calculated for release of smaller juveniles between June 17 and 22, 1975. Benefit–costs associated with releases on the path of joint optimality between the two response centers rose from 12.2:1 (maximum adult returns) to a calculated 16.5:1 for release of 7.5-g juveniles on June 17, 1975. Size and time at juvenile release and success of adult returns are viewed as initial and final aspects of a biological system whose central components as yet are imperfectly understood. Some parts of the system are discussed in relation to possible ways of increasing the efficiency and cost–effectiveness of salmonid hatchery technology, as well as in predicting the success of returns in relation to conditions influencing survival and growth of juvenile migrants from natural stocks.Key words: coho salmon, juvenile salmon, release time and size, response surface analysis and optimization, survival, biomass, benefit–costs
LASER INDUCED METAL INSULATOR TRANSITION THROUGH EXCITON MECHANISM IN QUANTUM WELL SYSTEMS
Authors: RAJASHABALA S. , KANMANI S. S. , NAVANEETHAKRISHNAN K.
Published: April 2009

Within the effective mass approximation, the binding energies of a Wannier exciton in a GaAs-Ga 1-x Al x As quantum well in an electric field are investigated using a variational method. The binding energiesare obtained upon illlumination by laser radiation. The binding energy decreases as the well size increases when the size of the well is beyond 50 Å. The above behavior is for a quantum well of finite confinement. We have investigated the metal-insulator transition in such a system and report the values of critical concentrations of excitons at which metal-insulator transition occurs for different well dimensions. The calculated diamagnetic susceptibility shows the catastrophic behavior at the critical concentration.
STATISTICS OF INTERATOMIC Ni–Ni BONDS IN Ni-BASED TERNARY SOLID SOLUTIONS WITH NON-MAGNETIC ELEMENTS AND THEIR MAGNETIC BEHAVIOR
Authors: COSMA I. , CULEA E. , FECHETE R. , NICOARǍ S.
Published: April 2009

The drop of ferromagnetic moment in the ternary solid solutions Ni 1-x-y Cu x D y, (D = Zn, Si, Au, Al ) is analyzed in terms of the statistical model of the environment-dependent moments. This probabilistic model shows that the disappearing of one Ni atom ferromagnetic moment can be assigned to the replacement of at least four Ni – Ni bindings, out of twelve, in pure nickel. This paper aims at discussing all these features that, from the point of view of macroscopic equilibrium states, are related to the distribution of local bonds, provided by the peripheral electrons of the substitute atoms dissolved in the Ni matrix.
COLLECTIVE ELECTRONIC EXCITATIONS IN SYSTEMS EXHIBITING QUANTUM WELL STATES
Authors: POLITANO ANTONIO , CHIARELLO GENNARO
Published: April 2009

We present high-resolution electron energy loss spectroscopy (HREELS) measurements on surface plasmon (SP) dispersion in systems exhibiting quantum well states (QWS), i.e. Na / Cu (111), Ag / Cu (111), and Ag / Ni (111). Our results demonstrate that the dominant coefficient of SP dispersion for thin and layer-by-layer Ag films presenting QWS is quadratic even at small q||, in contrast with previous measurements on Ag semi-infinite media and Ag thin films deposited on Si (111). We suggest that this behavior is due to screening effects enhanced by the presence of QWS shifting the position of the centroid of the induced charge less inside the geometrical surface compared with Ag surfaces and Ag / Si (111). For ultrathin Ag films, i.e. two layers, the dispersion was found to be not positive, as theoretically predicted. Annealing of the Ag film caused an enhancement of the free-electron character of the QWS, thus inducing a negative linear term of the dispersion curve of the SP. Moreover, we report the first experimental evidence of chemical interface damping in thin films for K / Ag / Ni (111). As regards Na / Cu (111), we found a different dispersion curve compared with thick Na films, thus confirming the enhanced screening by Na QWS.

Results reported here should shed light on the influence of QWS on dynamical screening phenomena in thin films.
Mo–Si–B ALLOYS OXIDATION PROTECTIVE COATING FOR SiC-COATED CARBON/CARBON COMPOSITES
Authors: FENG TAO , LI HE-JUN , FU QIAN-GANG , SHI XIAO-HONG , LI KE-ZHI
Published: April 2009

A novel Mo – Si – B double-layer coating was prepared for the carbon/carbon ( C / C ) composites by pack cementation in an argon atmosphere. The structures of the double-layer coatings were characterized by XRD and SEM. The as-received coating shows an excellent oxidation resistance at high and intermediate temperature. It could effectively protect C / C composites from oxidation for 30 h with a weight loss of 0.9% in air at 1873 K, and for 25 h with a weight loss of l.7% at 1173 K. The oxidation protective coating was principally due to producing eutectic glass film for decreasing oxygen diffusing through the penetrable cracks in the coating.
INFLUENCE OF DISPERSION ON COATING EFFECT OFZrB2@Al(OH)3–Y(OH)3CORE-SHELL COMPOSITE PARTICLES
Authors: SONG JIE-GUANG , LI YANG-LIANG , JI GANG-CHANG , DU DA-MING , XU MING-HAN , ZHANG LIAN-MENG
Published: April 2009

ZrB2are widely applied because of some excellent performances; however, ZrB2is easily oxidized in the high-temperature air. To reach better Al ( OH )3– Y ( OH )3composite shell and higher coating ratio on the ZrB2particles surfaces, ZrB2particles must be adequately dispersed in the ZrB2suspension during the coating process. The dispersion of ZrB2particles and the influence of dispersion on coating effect of ZrB2@ Al ( OH )3– Y ( OH )3core-shell composite particles were investigated. The dispersion of ZrB2suspension adding the polyelectrolyte dispersant is better than that of ZrB2suspension adding the nonionic dispersant; the dispersant content is 2 vol% of ZrB2suspension to reach the best dispersion. The best dispersion is obtained by the ultrasonic dispersion for 10 min. ZrB2particles are coated using the dispersant and the ultrasonic dispersion in the ZrB2suspension to obtain the better coating effect. The dispersion of ZrB2particles is increased with increasing the coating content.
Chronic hypoxia increases pressure-dependent myogenic tone of the uterine artery in pregnant sheep: role of ERK/PKC pathway
Authors: Chang Katherine , Xiao Daliao , Huang Xiaohui , Longo Lawrence D. , Zhang Lubo
Published: April 2009

Chronic hypoxia during pregnancy has profound effects on uterine artery (UA) contractility and attenuates uterine blood flow. The present study tested the hypothesis that chronic hypoxia inhibits the pregnancy-induced reduction in pressure-dependent myogenic tone of resistance-sized UAs. UAs were isolated from nonpregnant ewes (NPUAs) and near-term pregnant ewes (PUAs) that had been maintained at sea level (∼300 m) or at high altitude (3,801 m) for 110 days. In normoxic animals, the pressure-dependent myogenic response was significantly attenuated in PUAs compared with NPUAs. Hypoxia significantly increased myogenic tone in PUAs and abolished its difference between PUAs and NPUAs. Consistently, there was a significant increase in PKC-mediated baseline Ca2+sensitivity of PUAs in hypoxic animals. Hypoxia significantly increased phorbol 12,13-dibutyrate (PDBu)-induced contractions in PUAs but not in NPUAs. Whereas the inhibition of ERK1/2 by PD-98059 potentiated PDBu-mediated contractions of PUAs in normoxic animals, it failed to do so in hypoxic animals. Hypoxia decreased ERK1/2 expression in PUAs. PDBu induced membrane translocation of PKC-α and PKC-ε. Whereas there were no significant differences in PKC-α translocation among all groups, the translocation of PKC-ε was significantly enhanced in NPUAs compared with PUAs in normoxic animals, and hypoxia significantly increased PKC-ε translocation in PUAs. In the presence of PD-98059, there were no significant differences in PDBu-induced PKC-ε translocation among all groups. Treatment of PUAs isolated from normoxic animals with 10.5% O2for 48 h ex vivo significantly increased PDBu-induced contractions and eliminated its difference between PUAs and NPUAs. The results suggest that hypoxia upregulates pressure-dependent myogenic tone through its direct effect in suppressing ERK1/2 activity and increasing the PKC signal pathway, leading to an increase in the Ca2+sensitivity of the myogenic mechanism in the UA during pregnancy.