bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immune Suppression Uncovers Endogenous Cytopathic Effects of the Hepatitis B Virus
Authors: Meuleman Philip , Libbrecht Louis , Wieland Stefan , De Vos Rita , Habib Nagy , Kramvis Anna , Roskams Tania , Leroux-Roels Geert 
Published: February 2006

ABSTRACTIt is generally accepted that the host's immune response rather than the virus itself is causing the hepatocellular damage seen in acute and chronic hepatitis B virus (HBV) infections. However, in situations of severe immune suppression, chronic HBV patients may develop a considerable degree of liver disease. To examine whether HBV has direct cytopathic effects in severely immune compromised hosts, we have infected severe combined immune deficient mice (uPA-SCID), harboring human liver cells, with HBV. Serologic analysis of the plasma of HBV-infected animals revealed the presence of extremely high amounts of viral genomes and proteins. Histological analysis of the livers of uPA-SCID chimeras infected with HBV for more than 2 months showed that the majority of human hepatocytes had a ground-glass appearance, stained intensely for viral proteins, and showed signs of considerable damage and cell death. This histopathologic pattern closely resembles the picture observed in the livers of immunosuppressed HBV patients. These lesions were not observed in animals infected with HBV for less than 1 month. Ultrastructural analysis of long-term-infected hepatocytes showed a highly increased presence of cylindrical HBsAg structures, core particles, and Dane particles compared to short-term-infected hepatocytes. These long-term-infected hepatocytes also contained elevated amounts of HBV cccDNA. In conclusion, HBV causes dramatic intracellular changes and hepatocellular damage in the human hepatocytes that reside in a severely immune deficient mouse. These lesions show much resemblance to the ones encountered in immunosuppressed chronic HBV patients. Our observations indicate that HBV may be directly cytopathic in conditions of severe immune suppression.
Cyclophilin A and TRIM5α Independently Regulate Human Immunodeficiency Virus Type 1 Infectivity in Human Cells
Authors: Sokolskaja Elena , Berthoux Lionel , Luban Jeremy 
Published: February 2006

ABSTRACT
Cyclophilin A (CypA), a cytoplasmic, human immunodeficiency virus type 1 (HIV-1) CA-binding protein, acts after virion membrane fusion with human cells to increase HIV-1 infectivity. HIV-1 CA is similarly greeted by CypA soon after entry into rhesus macaque or African green monkey cells, where, paradoxically, the interaction decreases HIV-1 infectivity by facilitating TRIM5α-mediated restriction. These observations conjure a model in which CA recognition by the human TRIM5α orthologue is precluded by CypA. Consistent with the model, selection of a human cell line for decreased restriction of the TRIM5α-sensitive, N-tropic murine leukemia virus (N-MLV) rendered HIV-1 transduction of these cells independent of CypA. Additionally, HIV-1 virus-like particles (VLPs) saturate N-MLV restriction activity, particularly when the CA-CypA interaction is disrupted. Here the effects of CypA and TRIM5α on HIV-1 restriction were examined directly. RNA interference was used to show that endogenous human TRIM5α does indeed restrict HIV-1, but the magnitude of this antiviral activity was not altered by disruption of the CA-CypA interaction or by elimination of CypA protein. Conversely, the stimulatory effect of CypA on HIV-1 infectivity was completely independent of human TRIM5α. Together with previous reports, these data suggest that CypA protects HIV-1 from an unknown antiviral activity in human cells. Additionally, target cell permissivity increased after loading with heterologous VLPs, consistent with a common saturable target that is epistatic to both TRIM5α and the putative CypA-regulated restriction factor.
Inhibition of Human Immunodeficiency Virus Type 1 Replication with Artificial Transcription Factors Targeting the Highly Conserved Primer-Binding Site
Authors: Eberhardy Scott R. , Goncalves Joao , Coelho Sofia , Segal David J. , Berkhout Ben , Barbas Carlos F. 
Published: February 2006

ABSTRACT
The human immunodeficiency virus type 1 (HIV-1) primer-binding site (PBS) is a highly conserved region in the HIV genome and represents an attractive target for the development of new anti-HIV therapies. In this study, we designed four artificial zinc finger transcription factors to bind at or adjacent to the PBS and repress transcription from the HIV-1 long terminal repeat (LTR). These proteins bound to the LTR in vivo, as demonstrated by the chromatin immunoprecipitation assay. In transient reporter assays, three of the four proteins repressed transcription of a reporter driven by the HIV-1 LTR. Only one of these proteins, however, designated KRAB-PBS2, was able to prevent virus production when transduced into primary lymphocytes. We observed >90% inhibition of viral replication over the course of several weeks compared to untransduced cells, and no significant cytotoxicity was observed. Long-term exposure of HIV-1 to KRAB-PBS2 induced mutations in the HIV-1 PBS that reduced the effectiveness of the repressor, but these mutations also resulted in decreased rates of viral replication. These results show that KRAB-PBS2 has the potential to be used in antiviral therapy for AIDS patients and might complement other gene-based strategies.
Inhibition of Receptor Binding Stabilizes Newcastle Disease Virus HN and F Protein-Containing Complexes
Authors: McGinnes L. W. , Morrison T. G. 
Published: February 2006

ABSTRACT
Receptor binding of paramyxovirus attachment proteins and the interactions between attachment and fusion (F) proteins are thought to be central to activation of the F protein activity; however, mechanisms involved are unclear. To explore the relationships between Newcastle disease virus (NDV) HN and F protein interactions and HN protein attachment to sialic acid receptors, HN and F protein-containing complexes were detected and quantified by reciprocal coimmunoprecipitation from extracts of transfected avian cells. To inhibit HN protein receptor binding, cells transfected with HN and F protein cDNAs were incubated with neuraminidase from the start of transfection. Under these conditions, no fusion was observed, but amounts of HN and F protein complexes increased twofold over amounts detected in extracts of untreated cells. Stimulation of attachment by incubation of untransfected target cells with neuraminidase-treated HN and F protein-expressing cells resulted in a twofold decrease in amounts of HN and F protein complexes. In contrast, high levels of complexes containing HN protein and an uncleaved F protein (F-K115Q) were detected, and those levels were unaffected by neuraminidase treatment of cell monolayers or by incubation with target cells. These results suggest that HN and F proteins reside in a complex in the absence of receptor binding. Furthermore, the results show that not only receptor binding but also F protein cleavage are necessary for disassociation of the HN and F protein-containing complexes.
A Single Codon in the Nucleocapsid Protein C Terminus Contributes to In Vitro and In Vivo Fitness of Edmonston Measles Virus
Authors: Carsillo Thomas , Zhang Xinsheng , Vasconcelos Daphne , Niewiesk Stefan , Oglesbee Michael 
Published: February 2006

ABSTRACT
The major inducible 70-kDa heat shock protein (hsp72) increases measles virus (MV) transcription and genome replication. This stimulatory effect is attributed to hsp72 interaction with two highly conserved hydrophobic domains in the nucleocapsid protein (N) C terminus of Edmonston MV. These domains are known as Box-2 and Box-3. A single amino acid substitution in Box-3 of Edmonston MV (i.e., N522D) disrupts hsp72 binding. The prevalence of the N522D substitution in contemporary wild-type MV isolates suggests that this sequence has been positively selected. The present work determined if the N522D substitution enhances viral fitness and the degree to which any fitness advantage is influenced by hsp72 levels. Both parent Edmonston MV (Ed N) and an N522D substitution mutant (Ed N-522D) exhibited similar growth on Vero and murine neuroblastoma cells and in cotton rat lung, although Ed N-522D virus exhibited an attenuated in vitro response to hsp72 overexpression. In contrast, mixed infections showed a significantly reduced in vitro and in vivo fitness of Ed N-522D virus. Results support the involvement of additional selectional pressures that maintain the circulation of virus containing N-522D despite the cost to viral fitness.
A Hydrophobic Binding Surface on the Human Immunodeficiency Virus Type 1 Nef Core Is Critical for Association with p21-Activated Kinase 2
Authors: Agopian Kristin , Wei Bangdong L. , Garcia J. Victor , Gabuzda Dana 
Published: February 2006

ABSTRACT

The interaction of human immunodeficiency virus type 1 (HIV-1) Nef with p21-activated kinase 2 (Pak2) has been proposed to play an important role in T-cell activation and disease progression during viral infection. However, the mechanism by which Nef activates Pak2 is poorly understood. Mutations in most Nef motifs previously reported to be required for Pak2 activation (G
2
, PxxP
72
, and RR
105
) also affect other Nef functions, such as CD4 or major histocompatibility complex class I (MHC-I) downregulation. To better understand Nef interactions with Pak2, we performed mutational analysis of three primary HIV-1 Nef clones that exhibited similar capacities for downregulation of CD4 and MHC-I but variable abilities to associate with activated Pak2. Our results demonstrate that Nef amino acids at positions 85, 89, 187, 188, and 191 (L, H, S, R, and F in the clade B consensus, respectively) are critical for Pak2 association. Mutation of these Nef residues dramatically altered association with Pak2 without affecting Nef expression levels or CD4 and MHC-I downregulation. Furthermore, compensation occurred at positions 89 and 191 when both amino acids were substituted. Since residues 85, 89, 187, 188, and 191 cluster on the surface of the Nef core domain in a region distinct from the dimerization and SH3-binding domains, we propose that these Nef residues form part of a unique binding surface specifically involved in association with Pak2. This binding surface includes exposed and recessed hydrophobic residues and may participate in an as-yet-unidentified protein-protein interaction to facilitate Pak2 activation.
Analysis of the pH Requirement for Membrane Fusion of Different Isolates of the Paramyxovirus Parainfluenza Virus 5
Authors: Bissonnette Mei Lin Z. , Connolly Sarah A. , Young Daniel F. , Randall Richard E. , Paterson Reay G. , Lamb Robert A. 
Published: February 2006

ABSTRACT

Paramyxoviruses enter cells by fusing their envelopes with the plasma membrane, a process that occurs at neutral pH. Recently, it has been found that there is an exception to this dogma in that a porcine isolate of the paramyxovirus parainfluenza virus 5 (PIV5), known as SER, requires a low-pH step for fusion (S. Seth, A. Vincent, and R. W. Compans, J. Virol.
77:
6520-6527, 2003). As a low-pH activation mechanism for fusion would greatly facilitate biophysical studies of paramyxovirus-mediated membrane fusion, we have reexamined the triggering of the PIV5 SER fusion protein. Using multiple assays, we could not find a requirement for low-pH triggering of PIV5 SER fusion. The challenge of discovering how the paramyxovirus receptor binding protein (HN, H, or G) activates the metastable fusion protein to cause membrane fusion at neutral pH remains.
Reovirus Delays Diabetes Onset but Does Not Prevent Insulitis in Nonobese Diabetic Mice
Authors: Wetzel J. Denise , Barton Erik S. , Chappell James D. , Baer Geoffrey S. , Mochow-Grundy Michelle , Rodgers Steven E. , Shyr Yu , Powers Alvin C. , Thomas James W. , Dermody Terence S. 
Published: February 2006

ABSTRACT
Mice infected with reovirus develop abnormalities in glucose homeostasis. Reovirus strain type 3 Abney (T3A) was capable of systemic infection of nonobese diabetic (NOD) mice, an experimental model of autoimmune diabetes. Reovirus antigen was detected in pancreatic islets of T3A-infected mice, and primary cultures of pancreatic islets from NOD mice supported T3A growth. Significantly fewer T3A-infected animals compared to uninfected controls developed diabetes. However, despite the alteration in diabetes penetrance, insulitis was evident in T3A-infected mice. These results suggest that viral infection of NOD mice alters autoimmune responses to β-cell antigens and thereby delays development of diabetes.
Sequential CD134-CXCR4 Interactions in Feline Immunodeficiency Virus (FIV): Soluble CD134 Activates FIV Env for CXCR4-Dependent Entry and Reveals a Cryptic Neutralization Epitope
Authors: de Parseval Aymeric , Grant Chris K. , Sastry K. Jagannadha , Elder John H. 
Published: February 2006

ABSTRACT
Recombinant soluble CD134 (sCD134) facilitated feline immunodeficiency virus (FIV) entry into CXCR4-positive, cell surface CD134-negative target cells. sCD134-activated entry was dose dependent and CXCR4 dependent. We used the sCD134 activation system to explore the neutralization by four anti-V3 monoclonal antibodies (MAbs). V3 MAbs weakly neutralized FIV infection using target cells expressing both CD134 and CXCR4 but potently inhibited sCD134-activated entry into target cells expressing CXCR4 alone. These findings provide direct evidence for a sequential interaction of FIV Env with CD134 and CXCR4 and reveal the presence of a cryptic epitope in V3 that is masked in the mature envelope oligomers.
In Vitro Characterization of a Koala Retrovirus
Authors: Oliveira Nidia M. , Farrell Karen B. , Eiden Maribeth V. 
Published: February 2006

ABSTRACT
Recently, a new endogenous koala gammaretrovirus, designated KoRV, was isolated from koalas. The KoRV genome shares 78% nucleotide identity with another gammaretrovirus, gibbon ape leukemia virus (GALV). KoRV is endogenous in koalas, while GALV is exogenous, suggesting that KoRV predates GALV and that gibbons and koalas acquired the virus at different times from a common source. We have determined that subtle adaptive differences between the KoRV and GALV envelope genes account for differences in their receptor utilization properties. KoRV represents a unique example of a gammaretrovirus whose envelope has evolved to allow for its expanded host range and zoonotic potential.
Differential Requirement for Conserved Tryptophans in Human Immunodeficiency Virus Type 1 Vif for the Selective Suppression of APOBEC3G and APOBEC3F
Authors: Tian Chunjuan , Yu Xianghui , Zhang Wei , Wang Tao , Xu Rongzhen , Yu Xiao-Fang 
Published: February 2006

ABSTRACT
APOBEC3G (A3G) and related cytidine deaminases, such as APOBEC3F (A3F), are potent inhibitors of retroviruses. Formation of infectious human immunodeficiency virus type 1 (HIV-1) requires suppression of multiple cytidine deaminases by Vif. Whether HIV-1 Vif recognizes various APOBEC3 proteins through a common mechanism is unclear. The domains in Vif that mediate APOBEC3 recognitions are also poorly defined. The N-terminal region of HIV-1 Vif is unusually rich in Trp residues, which are highly conserved. In the present study, we examined the role of these Trp residues in the suppression of APOBEC3 proteins by HIV-1 Vif. We found that most of the highly conserved Trp residues were required for efficient suppression of both A3G and A3F, but some of these residues were selectively required for the suppression of A3F but not A3G. Mutant Vif molecules in which Ala was substituted for Trp79 and, to a lesser extent, for Trp11 remained competent for A3G interaction and its suppression; however, they were defective for A3F interaction and therefore could not efficiently suppress the antiviral activity of A3F. Interestingly, while the HIV-1 Vif-mediated degradation of A3G was not affected by the different C-terminal tag peptides, that of A3F was significantly influenced by its C-terminal tags. These data indicate that the mechanisms by which HIV-1 Vif recognizes its target molecules, A3G and A3F, are not identical. The fact that several highly conserved residues in Vif are required for the suppression of A3F but not that of A3G suggests a critical role for A3F in the restriction of HIV-1 in vivo.
Molecular characterisation of pancreatic ductal adenocarcinoma in patients under 40
Authors: Bergmann F , Aulmann S , Wente M N , Penzel R , Esposito I , Kleeff J , Friess H , Schirmacher P 
Published: February 2006

Background:Pancreatic ductal adenocarcinoma (PDAC) rarely affects people under 40.Objectives:To determine whether the clinical, pathomorphological and genetic features of PDAC occurring in young patients (⩽40 years) differ from those in elderly patients.Methods:Clinical and pathomorphological data were obtained from seven patients presenting with PDAC, with age ranging from 35 to 40 years of age (mean 38 years). All tumours were characterised by using immunohistochemistry and molecular genetics.Results:All seven patients were women and lacked an association to cancer-predisposing genetic syndromes. Four patients were smokers and one had non-hereditary chronic pancreatitis. Pathomorphologically, tumours in three patients displayed moderate differentiation and four showed poor differentiation including one adenosquamous carcinoma. All tumours showed overexpression of transforming growth factor β1 and loss or significant reduction of Smad4. Accumulation of p53 and overexpression of epidermal growth factor receptor (EGFR) were seen in five and four patients, respectively. No expression of p16, oestrogen hormone receptor or progesterone receptor was found. Mismatch repair gene products (MutL homologue 1 (MLH1), MSH2 and MSH6) were expressed in all tumours. Mutational analyses showed K-rasmutations in only three of the seven tumours.Conclusion:A large clinical, pathomorphological and genetic overlap of PDAC in young patients aged under 40 is seen with that in elderly patients. The existence of yet undefined initiating events of pancreatic carcinogenesis is suggested by the low rate of K-rasmutations, in at least a subgroup of young patients.
Expression and heterodimer-binding activity of Ku70 and Ku80 in human non-melanoma skin cancer
Authors: Parrella P , Mazzarelli P , Signori E , Perrone G , Marangi G F , Rabitti C , Delfino M , Prencipe M , Gallo A P , Rinaldi M , Fabbrocini G , Delfino S , Persichetti P , Fazio V M 
Published: February 2006

Background:Experimental data suggest that exposure to ultraviolet radiation may indirectly induce DNA double-strand breaks.Aim:To investigate the contribution of the non-homologous end-joining repair pathway in basal and squamous cell carcinomas.Methods:Levels of Ku70 and Ku80 proteins were determined by immunohistochemical analysis and Ku70–Ku80 heterodimer-binding activity by electrophoretic mobility shift assay. Matched pathological normal margins and skin from healthy people were used as controls.Results:A significant increase in Ku70 and Ku80 protein levels was found for both tumour types as compared with normal skin (p<0.001). Squamous cell carcinoma showed increased immunostaining as compared with basal cell tumours (p<0.02). A direct correlation was found between Ku70 and Ku80 protein levels and expression of the proliferation markers Ki-67/MIB-1 (p<0.02 and p<0.002, respectively) in basal cell carcinoma. DNA binding activity was increased in basal cell carcinoma samples as compared with matched skin histopathologically negative for cancer (p<0.006). In squamous cell carcinomas, however, the difference was significant only with normal skin (p<0.02) and not with matched pathologically normal margins.Conclusions:Overall, an up regulation of the Ku70 and Ku80 protein levels seems to correlate only with tumour proliferation rate. As non-homologous end joining is an error-prone mechanism, its up regulation may ultimately increase genomic instability, contributing to tumour progression.
Associations of perceived work strain with nicotine dependence in a community sample
Authors: John U , Riedel J , Rumpf H-J , Hapke U , Meyer C 
Published: February 2006

Background:Little is known about work strain and smoking, and even less about work strain and nicotine dependence.Aim:To investigate the relations of perceived work strain with nicotine dependence among an adult general population sample.Method:Cross sectional survey with a probability sample of residents of a northern German area with 4075 participants, aged 18–64 years (participation rate 70.2%). The current study is based on 2549 participants who were working 15 or more hours per week. Face to face at-home computer aided interviews (World Health Organization Composite International Diagnostic Interview) were carried out. Work strain, defined as high work demand and low work control, was assessed with a questionnaire. Nicotine dependence was diagnosed according to the Diagnostic and Statistical Manual (DSM-IV) of the American Psychiatric Association. In addition, the Fagerström Test for Nicotine Dependence (FTND) was used.Results:Subjects with work strain had an odds ratio of 1.6 (95% CI 1.2 to 2.3) for nicotine dependence compared to those who had no work strain. In a general linear model, higher work strain was associated with a stronger relation between work demand and work control and the FTND. The findings were adjusted for alcohol use disorders, occupational status, age, and sex.Conclusion:Perceived work strain is related to nicotine dependence in this general adult population.
Associations between temporary employment and occupational injury: what are the mechanisms?
Authors: Benavides F G , Benach J , Muntaner C , Delclos G L , Catot N , Amable M 
Published: February 2006

Objective:To determine whether observed higher risks of occupational injury among temporary workers are due to exposure to hazardous working conditions and/or to lack of job experience level.Methods:Data systematically recorded for 2000 and 2001 by the Spanish Ministry of Labour and Social Affairs on fatal and non-fatal traumatic occupational injuries were examined by type of employment and type of accident, while adjusting for gender, age, occupation, and length of employment in the company. In the study period there were 1500 fatal and 1 806 532 non-fatal traumatic occupational injuries that occurred at the workplace. Incidence rates and rate ratios (RR) were estimated using Poisson regression models.Results:Temporary workers showed a rate ratio of 2.94 for non-fatal occupational injuries (95% CI 2.40 to 3.61) and 2.54 for fatal occupational injuries (95% CI 1.88 to 3.42). When these associations were adjusted by gender, age, occupation, and especially length of employment, they loose statistic significance: 1.05 (95% CI 0.97 to 1.12) for non-fatal and 1.07 (95% CI 0.91 to 1.26) for fatal.Conclusions:Lower job experience and knowledge of workplace hazards, measured by length of employment, is a possible mechanism to explain the consistent association between temporary workers and occupational injury. The role of working conditions associated with temporary jobs should be assessed more specifically.