bluuebunny/crossref_metadata_2025_split huggingface dataset:
Establishment of New Transmissible and Drug-Sensitive Human Immunodeficiency Virus Type 1 Wild Types due to Transmission of Nucleoside Analogue-Resistant Virus
Authors: de Ronde Anthony , van Dooren Maaike , van der Hoek Lia , Bouwhuis Denise , de Rooij Esther , van Gemen Bob , de Boer Rob , Goudsmit Jaap 
Published: July 2002

ABSTRACT
Sequence analysis of human immunodeficiency virus type 1 (HIV-1) from 74 persons with acute infections identified eight strains with mutations in the reverse transcriptase (RT) gene at positions 41, 67, 68, 70, 215, and 219 associated with resistance to the nucleoside analogue zidovudine (AZT). Follow-up of the fate of these resistant HIV-1 strains in four newly infected individuals revealed that they were readily replaced by sensitive strains. The RT of the resistant viruses changed at amino acid 215 from tyrosine (Y) to aspartic acid (D) or serine (S), with asparagine (N) as a transient intermediate, indicating the establishment of new wild types. When we introduced these mutations and the original threonine (T)-containing wild type into infectious molecular clones and assessed their competitive advantage in vitro, the order of fitness was in accord with the in vivo observations: 215Y < 215D = 215S = 215T. As detected by real-time nucleic acid sequence-based amplification with two molecular beacons, the addition of AZT or stavudine (d4T) to the viral cultures favored the 215Y mutant in a dose-dependent manner. Our results illustrate that infection with nucleoside analogue-resistant HIV leads in newly infected individuals to mutants that are sensitive to nucleoside analogues, but only a single mutation removed from drug-resistant HIV. Such mutants were shown to be transmissible, stable, and prone to rapid selection for resistance to AZT or d4T as soon as antiretroviral therapy was administered. Monitoring of patients for the presence of new HIV-1 wild types with D, S, or N residues at position 215 may be warranted in order to estimate the threat to long-term efficacy of regimens including nucleoside analogues.
Analysis of the Noncoding Regions of Measles Virus Strains in the Edmonston Vaccine Lineage
Authors: Parks Christopher L. , Lerch Robert A. , Walpita Pramila , Wang Hai-Ping , Sidhu Mohinder S. , Udem Stephen A. 
Published: July 2002

ABSTRACT

The noncoding sequence of five Edmonston vaccine viruses (AIK-C, Moraten, Rubeovax, Schwarz, and Zagreb) and those of a low-passage Edmonston wild-type (wt) measles virus have been determined and compared. Twenty-one nucleotide positions were identified at which Edmonston wt and one or more vaccine strains differed. The location of some of these nucleotide substitutions suggests that they may influence the efficiency of mRNA synthesis, processing, and translation, as well as genome replication and encapsidation. Five nucleotide substitutions were conserved in all of the vaccine strains. Two of these were in the genomic 3′-terminal transcriptional control region and could affect RNA synthesis or encapsidation. Three were found within the 5′-untranslated region of the F mRNA, potentially altering translation control sequences. The remaining vaccine virus base changes were found in one to four vaccine strains. Their genomic localization suggests that some may modify
cis
-acting regulatory domains, including the Kozak consensus element of the P and M genes, the F gene-end signal, and the F mRNA 5′-untranslated sequence.
Infection of Lymphoid Cells by Integration-Defective Human Immunodeficiency Virus Type 1 Increases De Novo Methylation
Authors: Fang Jing-Yuan , Mikovits Judy A. , Bagni Rachel , Petrow-Sadowski Cari L. , Ruscetti Francis W. 
Published: July 2002

ABSTRACT

DNA methylation, by regulating the transcription of genes, is a major modifier of the eukaryotic genome. DNA methyltransferases (DNMTs) are responsible for both maintenance and de novo methylation. We have reported that human immunodeficiency virus type 1 (HIV-1) infection increases DNMT1 expression and de novo methylation of genes such as the gamma interferon gene in CD4
+
cells. Here, we examined the mechanism(s) by which HIV-1 infection increases the cellular capacity to methylate genes. While the RNAs and proteins of all three DNMTs (1, 3a, and 3b) were detected in Hut 78 lymphoid cells, only the expression of DNMT1 was significantly increased 3 to 5 days postinfection. This increase was observed with either wild-type HIV-1 or an integrase (IN) mutant, which renders HIV replication defective, due to the inability of the provirus to integrate into the host genome. Unintegrated viral DNA is a common feature of many retroviral infections and is thought to play a role in pathogenesis. These results indicate another mechanism by which unintegrated viral DNA affects the host. In addition to the increase in overall genomic methylation, hypermethylation and reduced expression of the
p16

INK4A

gene, one of the most commonly altered genes in human cancer, were seen in cells infected with both wild-type and IN-defective HIV-1. Thus, infection of lymphoid cells with integration-defective HIV-1 can increase the methylation of CpG islands in the promoters of genes such as the
p16

INK4A

gene, silencing their expression.
Overexpression of the Adenovirus Type 12 (Ad12) pTP or E1A Gene Facilitates Ad12 DNA Replication in Nonpermissive BHK21 Hamster Cells
Authors: Hösel Marianna , Webb Dennis , Schröer Jörg , Schmitz Birgit , Doerfler Walter 
Published: July 2002

ABSTRACT

In the adenovirus type 12 (Ad12) hamster cell system, abortive virus infection is one of the factors associated with the highly efficient oncogenesis in newborn Syrian hamsters. We have shown earlier that the replication and efficient late transcription of the Ad12 genome are blocked in Syrian hamster cells. Some of the early Ad12 functions are transcribed in these cells, although at a minimal rate. In the present study, we demonstrate that low expression levels of the E1A and precursor to terminal protein (pTP) genes of Ad12 seem to be responsible for the lack of Ad12 DNA replication in hamster cells. The Ad12 genes for the E1A functions or for pTP were tethered to the strong early promoter of the human cytomegalovirus and transfected into BHK21 cells. Subsequently, these cells were infected with Ad12 virions. In Ad12-infected BHK21 cells, which overexpressed pTP or E1A, full-length Ad12 DNA was de novo synthesized, as documented by metabolic labeling with [
3
H]thymidine and by zone velocity sedimentation in alkaline sucrose gradients followed by gel electrophoresis of the
3
H-labeled DNA and Southern blot hybridization to
32
P-labeled Ad12 DNA. Transfection of the cloned E1A region of Ad2 yielded similar results. The newly synthesized Ad12 DNA was covalently linked to pTP. The Ad12 DNA binding protein (DBP) and DNA polymerase (
pol
) genes were transcribed at levels similar to those in merely Ad12-infected cells. In pTP or E1A gene-transfected and Ad12-infected BHK21 cells, marginal levels of late Ad12 mRNA were detectable. Late Ad12 proteins were, however, not synthesized. Apparently, Ad12 DNA replication in hamster cells is rendered impossible due to insufficient threshold levels of the viral E1A and/or pTP.
mRNA Decay during Herpesvirus Infections: Interaction between a Putative Viral Nuclease and a Cellular Translation Factor
Authors: Feng Pinghui , Everly David N. , Read G. Sullivan 
Published: July 2002

ABSTRACT

During lytic infections, the virion host shutoff (Vhs) protein (UL41) of herpes simplex virus destabilizes both host and viral mRNAs. By accelerating mRNA decay, it helps determine the levels and kinetics of viral and cellular gene expression. In vivo, Vhs shows a strong preference for mRNAs, as opposed to non-mRNAs, and degrades the 5′ end of mRNAs prior to the 3′ end. In contrast, partially purified Vhs is not restricted to mRNAs and causes cleavage of target RNAs at various sites throughout the molecule. To explain this discrepancy, we searched for cellular proteins that interact with Vhs using the
Saccharomyces cerevisiae
two-hybrid system. Vhs was found to interact with the human translation initiation factor, eIF4H. This interaction was verified by glutathione
S
-transferase pull-down experiments and by coimmunoprecipitation of Vhs and epitope-tagged eIF4H from extracts of mammalian cells. The interaction was abolished by several point mutations in Vhs that abrogate its ability to degrade mRNAs in vivo. The results suggest that Vhs is a viral mRNA degradation factor that is targeted to mRNAs, and to regions of translation initiation, through an interaction with eIF4H.
Role of Stem B, Loop B, and Nucleotides next to the Primer Binding Site and the Kissing-Loop Domain in Human Immunodeficiency Virus Type 1 Replication and Genomic-RNA Dimerization
Authors: Shen Ni , Jetté Louis , Wainberg Mark A. , Laughrea Michael 
Published: July 2002

ABSTRACT
Stem-loop B is a 12-nucleotide [nt]-long completely conserved sequence postulated to form a 4-bp stem and a 4-nt internal loop under the kissing-loop hairpin (klh) (nt 248 to 270) of human immunodeficiency virus type 1 (HIV-1) genomic RNA. We investigated its role in viral replication, genomic RNA dimerization, and dimerization of partial HIV-1 RNA transcripts. The putative CUCG246-CGAG277 duplex was replaced by nine alternative complementary sequences, five likely to base pair only in short RNAs and four likely to base pair in long (∼500-nt) RNAs, as assessed by the algorithm mfold. Among the five former sequences, none preserved genome dimerization and all reduced viral replication by 98 to 99.9%. Among the four latter sequences, three (MB6, -9, and -10) preserved genome dimerization, one (MB7) did not significantly inhibit it, and two (MB9 and -10) preserved viral replication. We conclude that duplex formation by stem B nucleotides is necessary for viral infectivity and complete genome dimerization. Deleting the 5′ or 3′ side of loop B or of stem B had little impact on dimerization of partial RNA transcript and no impact on klh folding (and, for loop B mutations, on stem B folding), but each deletion inhibited genome dimerization almost as much as klh destruction. This suggests that loop B is required for complete genome dimerization and that loop B and stem B stimulate dimerization only in very long RNAs and/or in the presence of unidentified viral and cellular factors. Finally, we asked if nine deletions or nucleotide substitutions within nt 200 to 242 and/or nt 282 to 335 could influence genome dimerization. These mutations had intermediate inhibitory impacts consistent with their predicted influence on stem B, loop B, and klh formation. Two exceptions were Δ200–226 and Δ236–242 genomic RNAs, which dimerized relatively poorly despite having neutral or positive influences on stem B, loop B, and klh folding.
Overexpression of Cytochromecby a Recombinant Rabies Virus Attenuates Pathogenicity and Enhances Antiviral Immunity
Authors: Pulmanausahakul Rojjanaporn , Faber Milosz , Morimoto Kinjiro , Spitsin Sergei , Weihe Eberhard , Hooper D. Craig , Schnell Matthias J. , Dietzschold Bernhard 
Published: July 2002

ABSTRACTThe pathogenicity of individual rabies virus strains appears to correlate inversely with the extent of apoptotic cell death they induce and with the expression of rabies virus glycoprotein, a major inducer of an antiviral immune response. To determine whether the induction of apoptosis by rabies virus contributes to a decreased pathogenicity by stimulating antiviral immunity, we have analyzed these parameters in tissue cultures and in mice infected with a recombinant rabies virus construct that expresses the proapoptotic protein cytochromec. The extent of apoptosis was strongly increased in primary neuron cultures infected with the recombinant virus carrying the active cytochromecgene [SPBN-Cytoc(+)], compared with cells infected with the recombinant virus containing the inactive cytochromecgene [SPBN-Cytoc(−)]. Mortality in mice infected intranasally with SPBN-Cytoc(+) was substantially lower than in SPBN-Cytoc(−)-infected mice. Furthermore, virus-neutralizing antibody (VNA) titers were significantly higher in mice immunized with SPBN-Cytoc(+) at the same dose. The VNA titers induced by these recombinant viruses paralleled their protective activities against a lethal rabies virus challenge infection, with SPBN-Cytoc(+) revealing an effective dose 20 times lower than that of SPBN-Cytoc(−). The strong increase in immunogenicity, coupled with the marked reduction in pathogenicity, identifies the SPBN-Cytoc(+) construct as a candidate for a live rabies virus vaccine.
Functional Correlates of Insertion Mutations in the Protease Gene of Human Immunodeficiency Virus Type 1 Isolates from Patients
Authors: Kim Eun-Young , Winters Mark A. , Kagan Ron M. , Merigan Thomas C. 
Published: July 2002

ABSTRACT
Twenty-four of over 24,000 patients genotyped over the past 3 years were found to have human immunodeficiency virus (HIV) isolates that possess an insert in the protease gene. In this report, we evaluated the spectrum of protease gene insertion mutations in patient isolates and analyzed the effect of these various insertion mutations on viral phenotypes. The inserts were composed of 1, 2, 5, or 6 amino acids that mapped at or between codons 35 and 38, 17 and 18, 21 and 25, or 95 and 96. Reduced susceptibility to protease inhibitors was found in isolates which possess previously reported drug resistance mutations. Fitness assays, including replication and competition experiments, showed that most of the isolates with inserts grew somewhat better than their counterparts with a deletion of the insert. These experiments demonstrate that, rarely, insertion mutations can develop in the HIV type 1 protease gene, are no more resistant than any other sequences which have similar associated resistance mutations, and can provide a borderline advantage in replication.
Identification of Protein Kinases Dysregulated in CD4+T Cells in Pathogenic versus Apathogenic Simian Immunodeficiency Virus Infection
Authors: Bostik Pavel , Wu Peggy , Dodd Geraldine L. , Villinger Francois , Mayne Ann E. , Bostik Vanda , Grimm Bennett D. , Robinson Dan , Kung Hsing-Jien , Ansari Aftab A. 
Published: July 2002

ABSTRACTHuman immunodeficiency virus infection in humans and simian immunodeficiency virus (SIV) infection in rhesus macaques (RM) leads to a generalized loss of immune responses involving perturbations in T-cell receptor (TCR) signaling. In contrast, naturally SIV-infected sooty mangabeys (SM) remain asymptomatic and retain immune responses despite relatively high viral loads. However, SIV infection in both RM and SM led to similar decreases in TCR-induced Lck phosphorylation. In this study, a protein tyrosine kinase (PTK) differential display method was utilized to characterize the effects of in vivo SIV infection on key signaling molecules of the CD4+T-cell signaling pathways. The CD4+T cells from SIV-infected RM, but not SIV-infected SM, showed chronic downregulation of baseline expression of MLK3, PRK, and GSK3, and symptomatically SIV-infected RM showed similar downregulation of MKK3. In vitro TCR stimulation with or without CD28 costimulation of CD4+T cells did not lead to the enhancement of gene transcription of these PTKs. While the CD4+T cells from SIV-infected RM showed a significant increase of the baseline and anti-TCR-mediated ROR2 transcription, SIV infection in SM led to substantially decreased anti-TCR-stimulated ROR2 transcription. TCR stimulation of CD4+T cells from SIV-infected RM (but not SIV-infected SM) led to the repression of CaMKKβ and the induction of gene transcription of MLK2. Studies of the function of these molecules in T-cell signaling may lead to the identification of potential targets for specific intervention, leading to the restoration of T-cell responses.
Individual and Bivalent Vaccines Based on Alphavirus Replicons Protect Guinea Pigs against Infection with Lassa and Ebola Viruses
Authors: Pushko Peter , Geisbert Joan , Parker Michael , Jahrling Peter , Smith Jonathan 
Published: July 2002

ABSTRACT
Lassa and Ebola viruses cause acute, often fatal, hemorrhagic fever diseases, for which no effective vaccines are currently available. Although lethal human disease outbreaks have been confined so far to sub-Saharan Africa, they also pose significant epidemiological concern worldwide as demonstrated by several instances of accidental importation of the viruses into North America and Europe. In the present study, we developed experimental individual vaccines for Lassa virus and bivalent vaccines for Lassa and Ebola viruses that are based on an RNA replicon vector derived from an attenuated strain of Venezuelan equine encephalitis virus. The Lassa and Ebola virus genes were expressed from recombinant replicon RNAs that also encoded the replicase function and were capable of efficient intracellular self-amplification. For vaccinations, the recombinant replicons were incorporated into virus-like replicon particles. Guinea pigs vaccinated with particles expressing Lassa virus nucleoprotein or glycoprotein genes were protected from lethal challenge with Lassa virus. Vaccination with particles expressing Ebola virus glycoprotein gene also protected the animals from lethal challenge with Ebola virus. In order to evaluate a single vaccine protecting against both Lassa and Ebola viruses, we developed dual-expression particles that expressed glycoprotein genes of both Ebola and Lassa viruses. Vaccination of guinea pigs with either dual-expression particles or with a mixture of particles expressing Ebola and Lassa virus glycoprotein genes protected the animals against challenges with Ebola and Lassa viruses. The results showed that immune responses can be induced against multiple vaccine antigens coexpressed from an alphavirus replicon and suggested the possibility of engineering multivalent vaccines based upon alphavirus vectors for arenaviruses, filoviruses, and possibly other emerging pathogens.
Molecular Genetic Analysis of Revertants from a Poliovirus Mutant That Is Specifically Adapted to the Mouse Spinal Cord
Authors: Jia Qingmei , Hogle James M. , Hashikawa Tsutomu , Nomoto Akio 
Published: July 2002

ABSTRACT
SA virus, a mutant of the Mahoney strain of type 1 poliovirus (PV1/Mahoney), replicates specifically in the spinal cords of mice and causes paralysis, although the PV1/Mahoney strain does not show any mouse neurovirulence (Q. Jia, S. Ohka, K. Iwasaki, K. Tohyama, and A. Nomoto, J. Virol. 73:6041–6047, 1999). The key mutation site for the mouse neurovirulence of SA was mapped to nucleotide (nt) 928 of the genome (A to G), resulting in the amino acid substitution of Met for Ile at residue 62 within the capsid protein VP4 (VP4062). A small-plaque phenotype of SA appears to be indicative of its mouse-neurovirulent phenotype. To identify additional amino acid residues involved in the host range determination of PV, a total of 14 large-plaque (LP) variants were isolated from a single point mutant, Mah/I4062M, that showed the SA phenotype. All the LP variants no longer showed any mouse neurovirulence when delivered via an intraspinal inoculation route. Of these, 11 isolates had a back mutation at nt 928 (G to A) that restored the nucleotide of the PV1/Mahoney type. The reversions of the remaining three isolates (LP8, LP9, and LP14) were mediated by a second site mutation. Molecular genetic analysis involving recombinants between Mah/I4062M and the LP variants revealed that the mere substitution of an amino acid residue at position 107 in VP1 (Val to Leu) (LP9), position 33 in VP2 (Val to Ile) (LP14), or position 231 in VP3 (Ile to Thr) (LP8) was sufficient to restore the PV1/Mahoney phenotype. These amino acid residues are located either on the surface or inside of the virus particle. Our results indicate that the mouse neurovirulence of PV is determined by the virion surface structure, which is formed by all four capsid proteins.
Vaccination with Attenuated Simian Immunodeficiency Virus by DNA Inoculation
Authors: Kent Stephen J. , Dale C. Jane , Preiss Scott , Mills John , Campagna Daniella , Purcell Damian F. J. 
Published: July 2002

ABSTRACT

Delivering attenuated lentivirus vaccines as proviral DNA would be simple and inexpensive. Inoculation of macaques with wild-type simian immunodeficiency virus strain mac239 (SIV
mac239
) DNA or SIV
mac239
DNA containing a single deletion in the 3′
nef
-long terminal repeat overlap region (
nef
/LTR) led to sustained SIV infections and AIDS. Injection of SIV
mac239
DNA containing identical deletions in both the 5′ LTR and 3′
nef
/LTR resulted in attenuated SIV infections and substantial protection against subsequent mucosal SIV
mac251
challenge.
Hepatitis C Virus Core and Envelope Proteins Do Not Suppress the Host's Ability To Clear a Hepatic Viral Infection
Authors: Sun Jiaren , Bodola Francis , Fan Xuegong , Irshad Habib , Soong Lynn , Lemon Stanley M. , Chan Teh-Sheng 
Published: July 2002

ABSTRACTSeveral hepatitis C virus (HCV) proteins have been shown in vitro to interact with host cellular components that are involved in immune regulation. However, there is a paucity of data supporting the relevance of these observations to the in vivo situation. To test the hypothesis that such an interaction suppresses immune responses, we studied a line of transgenic C57BL/6 mice that express the HCV core and envelope proteins in the liver. The potential effects of these proteins on the hepatic immune response were evaluated by challenging these mice with a hepatotropic adenovirus. Both transgenic and nontransgenic mice developed similar courses of infection and cleared the virus from the liver by 28 days postinfection. Both groups of mice mounted similar immunoglobulin G (IgG), IgG2a, interleukin-2, and tumor necrosis factor alpha responses against the virus. Additionally, BALB/c mice were able to clear infection with recombinant adenovirus that does or does not express the HCV core and envelope 1 proteins in the same manner. These data suggest that HCV core and envelope proteins do not inhibit the hepatic antiviral mechanisms in these murine experimental systems and thus favor a model in which HCV circumvents host responses through a mechanism that does not involve general suppression of intrahepatic immune responses.