bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immunogenicity of
Bacillus anthracis
Protective Antigen Domains and Efficacy of Elicited Antibody Responses Depend on Host Genetic Background
Authors: Abboud Nareen , Casadevall Arturo 
Published: May 2008

ABSTRACT

Neutralizing antibodies to
Bacillus anthracis
protective antigen (PA), a component of anthrax toxin, mediate protection against anthrax. PA is antigenically complex and can elicit protective and nonprotective antibodies. Furthermore, vaccinated individuals demonstrate considerable variability in their antibody responses to PA. To explore the relationship between PA structure and antigenicity, we produced
Escherichia coli
strains expressing full-length PA (PA1-4), domains 2 to 4 (PA2-4), domain 1, (PA1), and domain 4 (PA4) and evaluated the immunogenicities and protective efficacies of the protein fractions in four mouse strains (strains A/J, BALB/c, C57BL/6, and Swiss Webster). Immunization with PA1-4 resulted in significantly higher lethal toxin-neutralizing antibody titers than immunization with any recombinant protein (rPA) fraction of PA. The magnitude and neutralizing capacity of the antibody response to full-length PA and its fragments varied depending on the mouse strain. We found no correlation between the antibody titer and the neutralizing antibody titer for A/J and Swiss Webster mice. In C57BL/6 mice, antibody titers and neutralization capacity correlated for two of four rPA domain proteins tested, while BALB/c mice displayed a similar correlation with only one rPA. By correlating the reactivity of immune sera with solvent-exposed linear peptide segments of PA, we tentatively assign the presence of four new linear B-cell epitopes in PA amino acids 121 to 150, 143 to 158, 339 to 359, and 421 to 440. We conclude that the genetic background of the host determines the relative efficacy of the antitoxin response. The results suggest that the variability observed in vaccination studies with PA-derived vaccines is a result of host heterogeneity and implies a need to develop other antigens as vaccine candidates.
PCR-Based Assay Using Occult Blood Detection Cards for Detection of Diarrheagenic
Escherichia coli
in Specimens from U.S. Travelers to Mexico with Acute Diarrhea
Authors: Grimes Kevin A. , Mohamed Jamal A. , DuPont Herbert L. , Padda Ranjit S. , Jiang Zhi-Dong , Flores Jose , Belkind-Gerson Jaime , Martinez-Sandoval Francisco G. , Okhuysen Pablo C. 
Published: May 2008

ABSTRACT

Large field studies of travelers' diarrhea for multiple destinations are limited by the need to perform stool cultures on site in a timely manner. A method for the collection, transport, and storage of fecal specimens that does not require immediate processing and refrigeration and that is stable for months would be advantageous. This study was designed to determine if enterotoxigenic
Escherichia coli
(ETEC) and enteroaggregative
E. coli
(EAEC) DNA could be identified from cards that were processed for the evaluation of fecal occult blood. U.S. students traveling to Mexico during 2005 to 2007 were monitored for the occurrence of diarrheal illness. When ill, students provided a stool specimen for culture and occult blood by the standard methods. Cards then were stored at room temperature prior to DNA extraction. Fecal PCR was performed to identify ETEC and EAEC in DNA extracted from stools and from occult blood cards. Significantly more EAEC cases were identified by PCR that was performed on DNA that was extracted from cards (49%) or from frozen feces (40%) than from culture methods that used HEp-2 adherence assays (13%) (
P
< 0.001). Similarly, more ETEC cases were detected from card DNA (38%) than from fecal DNA (30%) or by culture that was followed by hybridization (10%) (
P
< 0.001). The sensitivity and specificity of the card test were 75 and 62%, respectively, compared to those for EAEC by culture and were 50 and 63%, respectively, compared to those for ETEC. DNA extracted from fecal cards that was used for the detection of occult blood is of use in identifying diarrheagenic
E. coli
.
Prevention of Drug Carryover Effects in Studies Assessing Antimycobacterial Efficacy of TMC207
Authors: Lounis Nacer , Gevers Tom , Van Den Berg Joke , Verhaeghe Tom , van Heeswijk Rolf , Andries Koen 
Published: May 2008

ABSTRACT

The levels of TMC207 (R207910) that can be reached in mouse organs and the sputa of treated patients easily exceed the MIC of the compound and can therefore interfere with in vitro bacterial titrations. We studied the usefulness of protein-enriched media for the prevention of such drug carryover effects. The average MIC of
Mycobacterium tuberculosis
was determined on three different media: unsupplemented 7H11 agar (MIC = 0.03 μg/ml), 7H11 agar supplemented with 5% bovine serum albumin (BSA; MIC = 1 μg/ml), and Lowenstein-Jensen medium (MIC = 14.33 μg/ml). In a second stage of the study, the maximal noninhibitory concentrations (MNICs) of TMC207 were determined by adding TMC207 to the bacterial inoculum rather than to the culture medium. These MNICs were 0.97 μg/ml for 7H11 agar, 32.33 μg/ml for 7H11 agar with 5% BSA, and 96.33 μg/ml for Lowenstein-Jensen medium. Both protein-enriched media were able to prevent drug carryover effects, but the use of 7H11 medium supplemented with 5% BSA is preferred for practical reasons.
Severe Thrombocytopenia Associated with Acute Hepatitis E Virus Infection
Authors: Colson P. , Payraudeau E. , Leonnet C. , De Montigny S. , Villeneuve L. , Motte A. , Tamalet C. 
Published: May 2008

ABSTRACTWe describe here what is, to the best of our knowledge, the third reported case of severe thrombocytopenia associated with acute hepatitis E virus infection. The patient was a 72-year-old French woman. It seems likely that the cause of the thrombocytopenia was acute hepatitis E virus infection, possibly occurring via an immune mechanism. No complications were noted, in contrast to the two previous reports.
Monitoring Early Fusion Dynamics of Human Immunodeficiency Virus Type 1 at Single-Molecule Resolution
Authors: Dobrowsky Terrence M. , Zhou Yan , Sun Sean X. , Siliciano Robert F. , Wirtz Denis 
Published: May 2008

ABSTRACT

The fusion of human immunodeficiency virus type 1 (HIV-1) to host cells is a dynamic process governed by the interaction between glycoproteins on the viral envelope and the major receptor, CD4, and coreceptor on the surface of the cell. How these receptors organize at the virion-cell interface to promote a fusion-competent site is not well understood. Using single-molecule force spectroscopy, we map the tensile strengths, lifetimes, and energy barriers of individual intermolecular bonds between CCR5-tropic HIV-1 gp120 and its receptors CD4 and CCR5 or CXCR4 as a function of the interaction time with the cell. According to the Bell model, at short times of contact between cell and virion, the gp120-CD4 bond is able to withstand forces up to 35 pN and has an initial lifetime of 0.27 s and an intermolecular length of interaction of 0.34 nm. The initial bond also has an energy barrier of 6.7

k
B

T
(where

k
B

is Boltzmann's constant and
T
is absolute temperature). However, within 0.3 s, individual gp120-CD4 bonds undergo rapid destabilization accompanied by a shortened lifetime and a lowered tensile strength. This destabilization is significantly enhanced by the coreceptor CCR5, not by CXCR4 or fusion inhibitors, which suggests that it is directly related to a conformational change in the gp120-CD4 bond. These measurements highlight the instability and low tensile strength of gp120-receptor bonds, uncover a synergistic role for CCR5 in the progression of the gp120-CD4 bond, and suggest that the cell-virus adhesion complex is functionally arranged about a long-lived gp120-coreceptor bond.
Efficienttrans-Encapsidation of Hepatitis C Virus RNAs into Infectious Virus-Like Particles
Authors: Steinmann Eike , Brohm Christiane , Kallis Stephanie , Bartenschlager Ralf , Pietschmann Thomas 
Published: May 2008

ABSTRACTRecently, complete replication of hepatitis C virus (HCV) in tissue culture was established using the JFH1 isolate. To analyze determinants of HCV genome packaging and virion assembly, we developed a system that supports particle production based ontrans-packaging of subgenomic viral RNAs. Using JFH1 helper viruses, we show that subgenomic JFH1 replicons lacking the entire core to NS2 coding region are efficiently encapsidated into infectious virus-like particles. Similarly, chimeric helper viruses with heterologous structural proteinstrans-package subgenomic JFH1 replicons. Like authentic cell culture-produced HCV (HCVcc) particles, thesetrans-complemented HCV particles (HCVTCP) penetrate target cells in a CD81 receptor-dependent fashion. Since HCVTCPproduction was limited by competition between the helper and subgenomic RNA and to avoid contamination of HCVTCPstocks with helper viruses, we created HCV packaging cells. These cells encapsidate various HCV replicons with high efficiency, reaching infectivity titers up to 106tissue culture infectious doses 50 per milliliter. The produced particles display a buoyant density comparable to HCVcc particles and can be propagated in the packaging cell line but support only a single-round infection in naïve cells. Together, this work demonstrates that subgenomic HCV replicons are assembly competent, thus excludingcis-acting RNA elements in the core-to-NS2 genomic region essential for RNA packaging. The experimental system described here should be helpful to decipher the mechanisms of HCV assembly and to identify RNA elements and viral proteins involved in particle formation. Similar to other vector systems of plus-strand RNA viruses, HCVTCPmay prove valuable for gene delivery or vaccination approaches.
Differential Gene Regulation by Epstein-Barr Virus Type 1 and Type 2 EBNA2
Authors: Lucchesi Walter , Brady Gareth , Dittrich-Breiholz Oliver , Kracht Michael , Russ Rainer , Farrell Paul J. 
Published: May 2008

ABSTRACTA transfection assay with a lymphoblastoid cell line infected with Epstein-Barr virus was used to compare the abilities of type 1 and type 2 EBNA2 to sustain cell proliferation. The reduced proliferation in cells expressing type 2 EBNA2 correlated with loss of expression of some cell genes that are known to be targets of type 1 EBNA2. Microarray analysis of EBNA2 target genes identified a small number of genes that are more strongly induced by type 1 than by type 2 EBNA2, and one of these genes (CXCR7) was shown to be required for proliferation of lymphoblastoid cell lines. The Epstein-Barr virus LMP1 gene was also more strongly induced by type 1 EBNA2 than by type 2, but this effect was transient. Type 1 and type 2 EBNA2 were equally effective at arresting cell proliferation of Burkitt's lymphoma cell lines lacking Epstein-Barr virus and were also shown to cause apoptosis in these cells. The results indicate that differential gene regulation by Epstein-Barr virus type 1 and type 2 EBNA2 may be the basis for the much weaker B-cell transformation activity of type 2 Epstein-Barr virus strains compared to type 1 strains.
Rhesus Macaque
TRIM5
Alleles Have Divergent Antiretroviral Specificities
Authors: Wilson Sam J. , Webb Benjamin L. J. , Maplanka Charlotte , Newman Ruchi M. , Verschoor Ernst J. , Heeney Jonathan L. , Towers Greg J. 
Published: May 2008

ABSTRACT

TRIM5α is a potent barrier to cross-species retroviral transmission, and TRIM5αs from different species have divergent antiretroviral specificities. Multiple
TRIM5
alleles circulate within rhesus macaque populations. Here we show that they too have different antiretroviral specificities, highlighting how
TRIM5
genotypes contribute to protection in an individual or a population.
A Bovine Herpesvirus Type 1 Mutant Virus Specifying a Carboxyl-Terminal Truncation of Glycoprotein E Is Defective in Anterograde Neuronal Transport in Rabbits and Calves
Authors: Liu Z. F. , Brum M. C. S. , Doster A. , Jones C. , Chowdhury S. I. 
Published: May 2008

ABSTRACTBovine herpesvirus type 1 (BHV-1) is an important component of the bovine respiratory disease complex (BRDC) in cattle. The ability of BHV-1 to transport anterogradely from neuronal cell bodies in trigeminal ganglia (TG) to nerve ending in the noses and corneas of infected cattle following reactivation from latency plays a significant role in the pathogenesis of BRDC and maintenance of BHV-1 in the cattle population. We have constructed a BHV-1 bacterial artificial chromosome (BAC) clone by inserting an excisable BAC plasmid sequence in the long intergenic region between the glycoprotein B (gB) and UL26 genes. A BAC-excised, reconstituted BHV-1 containing only the 34-bp loxP sequence within the gB-UL26 intergenic region was highly infectious in calves, retained wild-type virulence properties, and reactivated from latency following treatment with dexamethasone. Using a two-step Red-mediated mutagenesis system inEscherichia coli, we constructed a gE cytoplasmic tail-truncated BHV-1 and a gE-rescued BHV-1. Following primary infection, the gE cytoplasmic tail-truncated virus was efficiently transported retrogradely from the nerve endings in the nose and eye to cell bodies in the TG of calves and rabbits. However, following dexamethasone-induced reactivation from latency, the gE mutant virus was not isolated from nasal and ocular sheddings. Reverse transcriptase PCR assays detected VP5 transcription in the TG of rabbits infected with gE-rescued and gE cytoplasmic tail-truncated viruses during primary infection and after dexamethasone treatment but not during latency. Therefore, the BHV-1gE cytoplasmic tail-truncated virus reactivated in the TG; however, it had defective anterograde transport from TG to nose and eye in calves and rabbits.
The Cytoplasmic Terminus of Kaposi's Sarcoma-Associated Herpesvirus Glycoprotein B Is Not Essential for Virion Egress and Infectivity
Authors: Subramanian R. , D'Auvergne O. , Kong Haixia , Kousoulas K. G. 
Published: May 2008

ABSTRACT
Kaposi's sarcoma-associated herpesvirus (KSHV)-encoded glycoprotein B (gB) is an important determinant of viral infectivity and virion egress. A small interfering RNA (siRNA)-based strategy was devised to inhibit KSHV gB gene expression. Transient cotransfection of plasmids constitutively expressing gB and anti-gB siRNAs in 293 cells substantially inhibited gB mRNA levels and protein production. Similarly, transient expression of siRNAs into the primary effusion lymphoma cell line BCBL-1 caused a substantial reduction of gB transcripts and protein synthesis. TaqMan real-time PCR assays against the lytic KSHV gene ORF59 and infectivity assays on 293 cells were employed to assess the effect of inhibiting gB synthesis on virion egress from BCBL-1 cells and infectivity on 293 cells, respectively. These experiments showed that gB was essential for virion egress and infectivity. Transfection of a codon-optimized gB gene with the first 540 nucleotides altered, and therefore not recognized by anti-gB siRNAs that target the native but not the codon-optimized sequence, efficiently rescued virion egress and infectivity in BCBL-1 cells in the presence of siRNAs inhibiting wild-type gB expression. To assess the role of the cytoplasmic domain of gB in virion egress, mutant gB genes were generated specifying carboxyl terminal truncations of 25 and 58 amino acids disrupting two prominent predicted α-helical domains associated with virus-induced cell fusion. A third truncation removed the entire predicted cytoplasmic terminus of 84 amino acids, while a fourth truncation removed 110 amino acids, including the terminal most hydrophobic, intramembrane anchoring sequence. Virion egress experiments revealed that all truncated gBs facilitated virion egress from BCBL-1 cells, with the exception of the largest 110-amino-acid truncation, which removed the gB anchoring sequence. Importantly, the gB truncation that removed the entire predicted cytoplasmic domain increased virion egress, suggesting the presence of a egress regulation domain located proximal to the intramembrane sequence within the cytoplasmic domain of gB. All supernatant virions were infectious on 293 cells, indicating that the carboxyl terminus of gB is not essential for either virion egress or virus infectivity.
The Immune Response to Herpes Simplex Virus Type 1 Infection in Susceptible Mice Is a Major Cause of Central Nervous System Pathology Resulting in Fatal Encephalitis
Authors: Lundberg Patric , Ramakrishna Chandran , Brown Jeffrey , Tyszka J. Michael , Hamamura Mark , Hinton David R. , Kovats Susan , Nalcioglu Orhan , Weinberg Kenneth , Openshaw Harry , Cantin Edouard M. 
Published: May 2008

ABSTRACTThis study was undertaken to investigate possible immune mechanisms in fatal herpes simplex virus type 1 (HSV-1) encephalitis (HSE) after HSV-1 corneal inoculation. Susceptible 129S6 (129) but not resistant C57BL/6 (B6) mice developed intense focal inflammatory brain stem lesions of primarily F4/80+macrophages and Gr-1+neutrophils detectable by magnetic resonance imaging as early as day 6 postinfection (p.i.). Depletion of macrophages and neutrophils significantly enhanced the survival of infected 129 mice. Immunodeficient B6 (IL-7R−/−Kitw41/w41) mice lacking adaptive cells (B6-E mice) and transplanted with 129 bone marrow showed significantly accelerated fatal HSE compared to B6-E mice transplanted with B6 marrow or control nontransplanted B6-E mice. In contrast, there was no difference in ocular viral shedding in B6-E mice transplanted with 129 or B6 bone marrow. Acyclovir treatment of 129 mice beginning on day 4 p.i. (24 h after HSV-1 first reaches the brain stem) reduced nervous system viral titers to undetectable levels but did not alter brain stem inflammation or mortality. We conclude that fatal HSE in 129 mice results from widespread damage in the brain stem caused by destructive inflammatory responses initiated early in infection by massive infiltration of innate cells.
Identification of Closely Spaced but Distinct Transcription Initiation Sites for the Murine Gammaherpesvirus 68 Latency-Associated M2 Gene
Authors: DeZalia Mark , Speck Samuel H. 
Published: May 2008

ABSTRACT
Murine gammaherpesvirus 68 (MHV68) infection of mice provides a tractable small-animal system for assessing viral requirements for establishment of and reactivation from latency. The M2 gene product has no homology to any known proteins but has been shown to play a role in both the establishment of MHV68 latency and reactivation from latency. Furthermore, we have recently shown that M2 expression in primary murine B cells leads to enhanced proliferation, survival, and differentiation toward a preplasma memory B-cell phenotype (A. M. Siegel, J. H. Herskowitz, and S. H. Speck, PLoS Pathog. 4:e1000039, 2008). Previous studies have characterized the structure of the M2 transcript, but to date there has been no characterization of the M2 promoter, additional open reading frames (ORFs) in the M2 region, or identified splice acceptor and splice donor sites present in the previously characterized M2 gene transcript. Here we report (i) the identification and disruption of a novel transcript that encodes a short, previously unreported ORF (M2b) located in the intron between exon 1 and exon 2 of the M2 transcript; (ii) the identification of clustered but distinct M2 gene transcription initiation sites suggesting the presence of multiple promoters involved in regulating M2 gene transcription; (iii) the characterization in vivo of recombinant MHV68 harboring deletions within the identified M2 promoter region; and (iv) the in vivo analysis of recombinant MHV68 harboring mutations that ablate either the identified M2 splice acceptor or splice donor site. Finally, our 5′ rapid amplification of cDNA ends in conjunction with splice acceptor mutation analyses confirmed that all detected M2 gene transcripts expressed during MHV68 infection in mice splice into the M2 ORF downstream of the first AUG codon, providing strong evidence that initiation of the M2 gene product arises from the second AUG codon located at residue 8 in the M2 ORF. This initial detailed analysis of M2 gene transcription in vivo will aid future studies on regulation of M2 gene expression.
Identification of Mutated Cyclization Sequences That Permit Efficient Replication of West Nile Virus Genomes: Use in Safer Propagation of a Novel Vaccine Candidate
Authors: Suzuki Ryosuke , Fayzulin Rafik , Frolov Ilya , Mason Peter W. 
Published: May 2008

ABSTRACT
Existing live-attenuated flavivirus vaccines (LAV) could be improved by reducing their potential to recombine with naturally circulating viruses in the field. Since the highly conserved cyclization sequences (CS) found in the termini of flavivirus genomes must be complementary to each other to support genome replication, we set out to identify paired mutant CS that could support the efficient replication of LAV but would be unable to support replication in recombinant viruses harboring one wild-type (WT) CS. By systematic evaluation of paired mutated CS encoded in West Nile virus (WNV) replicons, we identified variants having single and double mutations in the 5′- and 3′-CS components that could support genome replication at WT levels. Replicons containing only the double-mutated CS in the 5′ or the 3′ ends of the genome were incapable of replication, indicating that mutated CS could be useful for constructing safer LAV. Despite the identity of the central portion of the CS in all mosquito-borne flaviviruses, viruses carrying complementary the double mutations in both the 5′- and the 3′-CS were indistinguishable from WT WNV in their replication in insect and mammalian cell lines. In addition to the utility of our novel CS pair in constructing safer LAV, we demonstrated that introduction of these mutated CS into one component of a recently described two-component genome system (A. V. Shustov, P. W. Mason, and I. Frolov, J. Virol. 81:11737-11748, 2007) enabled us to engineer a safer single-cycle WNV vaccine candidate with reduced potential for recombination during its propagation.
Differences in Hepatitis C Virus (HCV)-Specific CD8 T-Cell Phenotype during Pegylated Alpha Interferon and Ribavirin Treatment Are Related to Response to Antiviral Therapy in Patients Chronically Infected with HCV
Authors: Caetano Joana , Martinho António , Paiva Artur , Pais Beatriz , Valente Cristina , Luxo Cristina 
Published: May 2008

ABSTRACTCD8 T cells play a major role in antiviral immune responses. Their importance for progression to chronic hepatitis C and response to treatment are still unclear. To address these issues, hepatitis C virus (HCV)-specific CD8 T-cell responses were monitored, at the single-cell level, using HLA class I pentamers specific for HCV core and HCV NS3 epitopes, in 23 chronically infected patients during treatment with pegylated alpha interferon and ribavirin. Patients who presented a sustained-response to therapy had stronger HCV-specific CD8 T-cell responses at all time points studied. Moreover, there were clear differences in the phenotypes of these cells during therapy: in responder patients, terminally differentiated effector cells increased more rapidly, and their frequency was always higher than in nonresponder patients. Sustained-responder patients also showed a higher frequency of HCV-specific CD8 T cells producing cytotoxic factors. Overall, a late and inefficient differentiation process of HCV-specific CD8 T cells might be associated with lack of response to treatment. A better knowledge of the mechanisms underlying this impairment may be important for the development of new therapeutic strategies to maintain, restore, or increase CD8 T-cell effectiveness in chronic HCV infection.