bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationships between CD4 Independence, Neutralization Sensitivity, and Exposure of a CD4-Induced Epitope in a Human Immunodeficiency Virus Type 1 Envelope Protein
Authors: Edwards Terri G. , Hoffman Trevor L. , Baribaud Frédéric , Wyss Stéphanie , LaBranche Celia C. , Romano Josephine , Adkinson Joshua , Sharron Matthew , Hoxie James A. , Doms Robert W. 
Published: July 2002

ABSTRACT
A CD4-independent version of the X4 human immunodeficiency virus type 1 (HIV-1) HXBc2 envelope (Env) protein, termed 8x, mediates infection of CD4-negative, CXCR4-positive cells, binds directly to CXCR4 in the absence of CD4 due to constitutive exposure of a conserved coreceptor binding site in the gp120 subunit, and is more sensitive to antibody-mediated neutralization. To study the relationships between CD4 independence, neutralization sensitivity, and exposure of CD4-induced epitopes associated with the coreceptor binding site, we generated a large panel of Env mutants and chimeras between 8x and its CD4-dependent parent, HXBc2. We found that a frameshift mutation just proximal to the gp41 cytoplasmic domain in 8x Env was necessary but not sufficient for CD4 independence and led to increased exposure of the coreceptor binding site. In the presence of this altered cytoplasmic domain, single amino acid changes in either the 8x V3 (V320I) or V4/C4 (N386K) regions imparted CD4 independence, with other changes playing a modulatory role. The N386K mutation resulted in loss of an N-linked glycosylation site, but additional mutagenesis showed that it was the presence of a lysine rather than loss of the glycosylation site that contributed to CD4 independence. However, loss of the glycosylation site alone was sufficient to render Env neutralization sensitive, providing additional evidence that carbohydrate structures shield important neutralization determinants. Exposure of the CD4-induced epitope recognized by monoclonal antibody 17b and which overlaps the coreceptor binding site was highly sensitive to an R298K mutation at the base of the V3 loop and was often but not always associated with CD4 independence. Finally, while not all neutralization-sensitive Envs were CD4 independent, all CD4-independent Envs exhibited enhanced sensitivity to neutralization by HIV-1-positive human sera, indicating that the humoral immune response can exert strong selective pressure against the CD4-independent phenotype in vivo. Whether this can be used to advantage in designing more effective immunogens remains to be seen.
Induction of Neutralizing Antibodies and Gag-Specific Cellular Immune Responses to an R5 Primary Isolate of Human Immunodeficiency Virus Type 1 in Rhesus Macaques
Authors: Montefiori David C. , Safrit Jeffrey T. , Lydy Shari L. , Barry Ashley P. , Bilska Miroslawa , Vo Ha T. T. , Klein Michel , Tartaglia James , Robinson Harriet L. , Rovinski Benjamin 
Published: July 2002

ABSTRACTThe ability to generate antibodies that cross-neutralize diverse primary isolates is an important goal for human immunodeficiency virus type 1 (HIV-1) vaccine development. Most of the candidate HIV-1 vaccines tested in humans and nonhuman primates have failed in this regard. Past efforts have focused almost entirely on the envelope glycoproteins of a small number of T-cell line-adapted strains of the virus as immunogens. Here we assessed the immunogenicity of noninfectious virus-like particles (VLP) consisting of Gag, Pro (protease), and Env from R5 primary isolate HIV-1Bx08. Immunogens were delivered to rhesus macaques in the form of either purified VLP, recombinant DNA and canarypox (ALVAC) vectors engineered to express VLP, or a combination of these products. Seroconversion to Gag and Pro was detected in all of the immunized animals. Antibodies that could neutralize HIV-1Bx08were detected in animals that received (i) coinoculations with DNABx08and VLPBx08, (ii) DNABx08followed by ALVACBx08boosting, and (iii) VLPBx08alone. The neutralizing antibodies were highly strain specific despite the fact that they did not appear to be directed to linear epitopes in the V3 loop. Virus-specific cellular immune responses also were generated, as judged by the presence of Gag-specific gamma interferon (IFN-γ)-producing cells. These cellular immune responses required the inclusion of DNABx08in the immunization modality, since few or no IFN-γ-producing cells were detected in animals that received either VLPBx08or ALVACBx08alone. The results demonstrate the feasibility of generating neutralizing antibodies and cellular immune responses that target an R5 primary HIV-1 isolate by vaccination in primates.
Nonenveloped Nucleocapsids of Hepatitis C Virus in the Serum of Infected Patients
Authors: Maillard P. , Krawczynski K. , Nitkiewicz J. , Bronnert C. , Sidorkiewicz M. , Gounon P. , Dubuisson J. , Faure G. , Crainic R. , Budkowska A. 
Published: July 2002

ABSTRACTOne of the characteristics of hepatitis C virus (HCV) is the high incidence of persistent infection. HCV core protein, in addition to forming the viral nucleocapsid, has multiple regulatory functions in host-cell transcription, apoptosis, cell transformation, and lipid metabolism and may play a role in suppressing host immune response. This protein is thought to be present in the bloodstream of the infected host as the nucleocapsid of infectious, enveloped virions. This study provides evidence that viral particles with the physicochemical, morphological, and antigenic properties of nonenveloped HCV nucleocapsids are present in the plasma of HCV-infected individuals. These particles have a buoyant density of 1.32 to 1.34 g/ml in CsCl, are heterogeneous in size (with predominance of particles 38 to 43 or 54 to 62 nm in diameter on electron microscopy), and express on their surface epitopes located in amino acids 24 to 68 of the core protein. Similar nucleocapsid-like particles are also produced in insect cells infected with recombinant baculovirus bearing cDNA for structural HCV proteins. HCV core particles isolated from plasma were used to generate anti-core monoclonal antibodies (MAbs). These MAbs stained HCV core in the cytoplasm of hepatocytes from experimentally infected chimpanzees in the acute phase of the infection. These chimpanzees had concomitantly HCV core antigen in serum. These findings suggest that overproduction of nonenveloped nucleocapsids and their release into the bloodstream are properties of HCV morphogenesis. The presence of circulating cores in serum and accumulation of the core protein in liver cells during the early phase of infection may contribute to the persistence of HCV and its many immunopathological effects in the infected host.
Antibody Protects Macaques against Vaginal Challenge with a Pathogenic R5 Simian/Human Immunodeficiency Virus at Serum Levels Giving Complete Neutralization In Vitro
Authors: Parren Paul W. H. I. , Marx Preston A. , Hessell Ann J. , Luckay Amara , Harouse Janet , Cheng-Mayer Cecilia , Moore John P. , Burton Dennis R. 
Published: July 2002

ABSTRACT

A major unknown in human immunodeficiency virus (HIV-1) vaccine design is the efficacy of antibodies in preventing mucosal transmission of R5 viruses. These viruses, which use CCR5 as a coreceptor, appear to have a selective advantage in transmission of HIV-1 in humans. Hence R5 viruses predominate during primary infection and persist throughout the course of disease in most infected people. Vaginal challenge of macaques with chimeric simian/human immunodeficiency viruses (SHIV) is perhaps one of the best available animal models for human HIV-1 infection. Passive transfer studies are widely used to establish the conditions for antibody protection against viral challenge. Here we show that passive intravenous transfer of the human neutralizing monoclonal antibody b12 provides dose-dependent protection to macaques vaginally challenged with the R5 virus SHIV
162P4
. Four of four monkeys given 25 mg of b12 per kg of body weight 6 h prior to challenge showed no evidence of viral infection (sterile protection). Two of four monkeys given 5 mg of b12/kg were similarly protected, whereas the other two showed significantly reduced and delayed plasma viremia compared to control animals. In contrast, all four monkeys treated with a dose of 1 mg/kg became infected with viremia levels close to those for control animals. Antibody b12 serum concentrations at the time of virus challenge corresponded to approximately 400 (25 mg/kg), 80 (5 mg/kg), and 16 (1 mg/kg) times the in vitro (90%) neutralization titers. Therefore, complete protection against mucosal challenge with an R5 SHIV required essentially complete neutralization of the infecting virus. This suggests that a vaccine based on antibody alone would need to sustain serum neutralizing antibody titers (90%) of the order of 1:400 to achieve sterile protection but that lower titers, around 1:100, could provide a significant benefit. The significance of such substerilizing neutralizing antibody titers in the context of a potent cellular immune response is an important area for further study.
The Pathogenicity of Human Immunodeficiency Virus (HIV) Type 1 Nef in CD4C/HIV Transgenic Mice Is Abolished by Mutation of Its SH3-Binding Domain, and Disease Development Is Delayed in the Absence of Hck
Authors: Hanna Zaher , Weng Xiaoduan , Kay Denis G. , Poudrier Johanne , Lowell Clifford , Jolicoeur Paul 
Published: July 2002

ABSTRACT

The human immunodeficiency virus type 1 (HIV-1) Nef protein is an important determinant of AIDS pathogenesis. We have previously reported that HIV-1 Nef is responsible for the induction of a severe AIDS-like disease in CD4C/HIV transgenic (Tg) mice. To understand the molecular mechanisms of this Nef-induced disease, we generated Tg mice expressing a mutated Nef protein in which the SH3 ligand-binding domain (P
72
XXP
75
XXP
78
) was mutated to A
72
XXA
75
XXQ
78
. This mutation completely abolished the pathogenic potential of Nef, although a partial downregulation of the CD4 cell surface expression was still observed in these Tg mice. We also studied whether Hck, one of the effectors previously found to bind to this PXXP motif of Nef, was involved in disease development. Breeding of Tg mice expressing wild-type Nef on an
hck
−/−
(knockout) background did not abolish any of the pathological phenotypes. However, the latency of disease development was prolonged. These data indicate that an intact PXXP domain is essential for inducing an AIDS-like disease in CD4C/HIV Tg mice and suggest that interaction of a cellular effector(s) with this domain is required for the induction of this multiorgan disease. Our findings indicate that Hck is an important, but not an essential, effector of Nef and suggest that another factor(s), yet to be identified, may be more critical for disease development.
African Swine Fever Virus Protein p54 Interacts with the Microtubular Motor Complex through Direct Binding to Light-Chain Dynein
Authors: Alonso Covadonga , Miskin James , Hernáez Bruno , Fernandez-Zapatero Patricia , Soto Lourdes , Cantó Carmen , Rodrı́guez-Crespo Ignacio , Dixon Linda , Escribano José M. 
Published: July 2002

ABSTRACT
Dynein is a minus-end-directed microtubule-associated motor protein involved in cargo transport in the cytoplasm. African swine fever virus (ASFV), a large DNA virus, hijacks the microtubule motor complex cellular transport machinery during virus infection of the cell through direct binding of virus protein p54 to the light chain of cytoplasmic dynein (LC8). Interaction of p54 and LC8 occurs both in vitro and in cells, and the two proteins colocalize at the microtubular organizing center during viral infection. p50/dynamitin, a dominant-negative inhibitor of dynein-dynactin function, impeded ASFV infection, suggesting an essential role for dynein during virus infection. A 13-amino-acid domain of p54 was sufficient for binding to LC8, an SQT motif within this domain being critical for this binding. Direct binding of a viral structural protein to LC8, a small molecule of the dynein motor complex, could constitute a molecular mechanism for microtubule-mediated virus transport.
DC-SIGN Interactions with Human Immunodeficiency Virus: Virus Binding and Transfer Are Dissociable Functions
Authors: Pöhlmann Stefan , Leslie George J. , Edwards Terri G. , Macfarlan Todd , Reeves Jacqueline D. , Hiebenthal-Millow Kirsten , Kirchhoff Frank , Baribaud Frédéric , Doms Robert W. 
Published: July 2002

ABSTRACT
The C-type lectins DC-SIGN and DC-SIGNR capture and transfer human immunodeficiency virus (HIV) to susceptible cells, although the underlying mechanism is unclear. Here we show that DC-SIGN/DC-SIGNR-mediated HIV transmission involves dissociable binding and transfer steps, indicating that efficient virus transmission is not simply due to tethering of virus to the cell surface.
Requirement of Cysteines and Length of the Human Respiratory Syncytial Virus M2-1 Protein for Protein Function and Virus Viability
Authors: Tang Roderick S. , Nguyen Nick , Cheng Xing , Jin Hong 
Published: July 2002

ABSTRACT

The M2-1 protein of
human respiratory syncytial virus
(hRSV) promotes processive RNA synthesis and readthrough at RSV gene junctions. It contains four highly conserved cysteines, three of which are located in the Cys
3
-His
1
motif at the N terminus of M2-1. Each of the four cysteines, at positions 7, 15, 21, and 96, in the M2-1 protein of hRSV A2 strain was individually replaced by glycines. When tested in an RSV minigenome replicon system using β-galactosidase as a reporter gene, C7G, C15G, and C21G located in the Cys
3
-His
1
motif showed a significant reduction in processive RNA synthesis compared to wild-type (wt) M2-1. C96G, which lies outside the Cys
3
-His
1
motif, was fully functional in supporting processive RNA synthesis in vitro. Each of these cysteine substitutions was introduced into an infectious antigenomic cDNA clone derived from hRSV A2 strain. Except for C96G, which resulted in a viable virus, no viruses were recovered with mutations in the Cys
3
-His
1
motif. This indicates that the Cys
3
-His
1
motif is critical for M2-1 function and for RSV replication. The functional requirement of the C terminus of the M2-1 protein was examined by engineering premature stop codons that caused truncations of 17, 46, or 67 amino acids from the C terminus. A deletion of 46 or 67 amino acids abolished the synthesis of full-length β-galactosidase mRNA and did not result in the recovery of viable viruses. However, a deletion of 17 amino acids from the C terminus of M2-1 reduced processive RNA synthesis in vitro and was well tolerated by RSV. Relocation of the M2-1 termination codon upstream of the M2-2 initiation codons did not significantly affect the expression of the M2-2 protein. Both rA2-Tr17 and rA2-C96G did not replicate as efficiently as wt rA2 in HEp-2 cells and was restricted in replication in the respiratory tracts of cotton rats.
Stabilization but Not the Transcriptional Activity of Herpes Simplex Virus VP16-Induced Complexes Is Evolutionarily Conserved among HCF Family Members
Authors: Lee Soyoung , Herr Winship 
Published: July 2002

ABSTRACT

The human herpes simplex virus (HSV) protein VP16 induces formation of a transcriptional regulatory complex with two cellular factors—the POU homeodomain transcription factor Oct-1 and the cell proliferation factor HCF-1—to activate viral immediate-early-gene transcription. Although the cellular role of Oct-1 in transcription is relatively well understood, the cellular role of HCF-1 in cell proliferation is enigmatic. HCF-1 and the related protein HCF-2 form an HCF protein family in humans that is related to a
Caenorhabditis elegans
homolog called CeHCF. In this study, we show that all three proteins can promote VP16-induced-complex formation, indicating that VP16 targets a highly conserved function of HCF proteins. The resulting VP16-induced complexes, however, display different transcriptional activities. In contrast to HCF-1 and CeHCF, HCF-2 fails to support VP16 activation of transcription effectively. These results suggest that, along with HCF-1, HCF-2 could have a role, albeit probably a different role, in HSV infection. CeHCF can mimic HCF-1 for both association with viral and cellular proteins and transcriptional activation, suggesting that the function(s) of HCF-1 targeted by VP16 has been highly conserved throughout metazoan evolution.
Identification of Novel HLA-A2-Restricted Human Immunodeficiency Virus Type 1-Specific Cytotoxic T-Lymphocyte Epitopes Predicted by the HLA-A2 Supertype Peptide-Binding Motif
Authors: Altfeld Marcus A. , Livingston Brian , Reshamwala Neha , Nguyen Phuong T. , Addo Marylyn M. , Shea Amy , Newman Mark , Fikes John , Sidney John , Wentworth Peggy , Chesnut Robert , Eldridge Robert L. , Rosenberg Eric S. , Robbins Gregory K. , Brander Christian , Sax Paul E. , Boswell Steve , Flynn Theresa , Buchbinder Susan , Goulder Philip J. R. , Walker Bruce D. , Sette Alessandro , Kalams Spyros A. 
Published: July 2002

ABSTRACTVirus-specific cytotoxic T-lymphocyte (CTL) responses are critical in the control of human immunodeficiency virus type 1 (HIV-1) infection and will play an important part in therapeutic and prophylactic HIV-1 vaccines. The identification of virus-specific epitopes that are efficiently recognized by CTL is the first step in the development of future vaccines. Here we describe the immunological characterization of a number of novel HIV-1-specific, HLA-A2-restricted CTL epitopes that share a high degree of conservation within HIV-1 and a strong binding to different alleles of the HLA-A2 superfamily. These novel epitopes include the first reported CTL epitope in the Vpr protein. Two of the novel epitopes were immunodominant among the HLA-A2-restricted CTL responses of individuals with acute and chronic HIV-1 infection. The novel CTL epitopes identified here should be included in future vaccines designed to induce HIV-1-specific CTL responses restricted by the HLA-A2 superfamily and will be important to assess in immunogenicity studies in infected persons and in uninfected recipients of candidate HIV-1 vaccines.
Rapid Definition of Five Novel HLA-A∗3002-Restricted Human Immunodeficiency Virus-Specific Cytotoxic T-Lymphocyte Epitopes by Elispot and Intracellular Cytokine Staining Assays
Authors: Goulder Philip J. R. , Addo , Marylyn M. , Altfeld Marcus A. , Rosenberg Eric S. , Tang Yanhua , Govender Ugene , Mngqundaniso Nolwandle , Annamalai Ken , Vogel Thorsten U. , Hammond Mike , Bunce Michael , Coovadia Hoosen M. , Walker Bruce D. 
Published: July 2002

ABSTRACTHuman immunodeficiency virus (HIV)-specific cytotoxic T lymphocytes (CTL) play a major role in control of viral replication. To understand the contribution of this antiviral response, an initial step is to fully define the specific epitopes targeted by CTL. These studies focused on CTL responses restricted by HLA-A∗3002, one of the HLA-A molecules most prominent in African populations. To avoid the time-consuming effort and expense involved in culturing CTL prior to defining epitopes and restricting alleles, we developed a method combining Elispot assays with intracellular gamma interferon staining of peripheral blood mononuclear cells to first map the optimal epitopes targeted and then define the HLA restriction of novel epitopes. In two A∗3002-positive subjects whose CTL responses were characterized in detail, the strongest response in both cases was to an epitope in p17 Gag, RSLYNTVATLY (residues 76 to 86). Using this method, CTL epitopes for which there were no motif predictions were optimized and the HLA restriction was established within 48 to 72 h of receipt of blood. This simple and convenient approach should prove useful especially in the characterization of CTL responses specific to HIV and other viruses, particularly in localities where performing cytotoxicity assays would be problematic.
Fluorescent Tagging of Herpes Simplex Virus Tegument Protein VP13/14 in Virus Infection
Authors: Donnelly Michelle , Elliott Gillian 
Published: July 2002

ABSTRACT
The cellular site of herpesvirus tegument assembly has yet to be defined. We have previously used a recombinant herpes simplex virus type 1 expressing a green fluorescent protein (GFP)-tagged tegument protein, namely VP22, to show that VP22 is localized exclusively to the cytoplasm during infection. Here we have constructed a similar virus expressing another fluorescent tegument protein, YFP-VP13/14, and have visualized the intracellular localization of this second tegument protein in live infected cells. In contrast to VP22, VP13/14 is targeted predominantly to the nuclei of infected cells at both early and late times in infection. More specifically, YFP-13/14 localizes initially to the nuclear replication compartments and then progresses into intense punctate domains that appear at around 12 h postinfection. At even later times this intranuclear punctate fluorescence is gradually replaced by perinuclear micropunctate and membranous fluorescence. While the vast majority of YFP-13/14 seems to be targeted to the nucleus, a minor subpopulation also appears in a vesicular pattern in the cytoplasm that closely resembles the pattern previously observed for GFP-22. Moreover, at late times weak fluorescence appears at the cell periphery and in extracellular virus particles, confirming that YFP-13/14 is assembled into virions. This predominantly nuclear targeting of YFP-13/14 together with the cytoplasmic targeting of VP22 may imply that there are multiple sites of tegument protein incorporation along the virus maturation pathway. Thus, our YFP-13/14-expressing virus has revealed the complexity of the intracellular targeting of VP13/14 and provides a novel insight into the mechanism of tegument, and hence virus, assembly.
Expression of Human MxA Protein in Mosquito Cells Interferes with LaCrosse Virus Replication
Authors: Miura Tanya A. , Carlson Jonathan O. , Beaty Barry J. , Bowen Richard A. , Olson Ken E. 
Published: July 2002

ABSTRACT

Human MxA protein inhibits LaCrosse virus (LAC virus; family
Bunyaviridae
) replication in vertebrate cells and
MxA
-transgenic mice. LAC virus is transmitted to humans by
Aedes triseriatus
mosquitoes. In this report, we have shown that transfected mosquito cells expressing the human
MxA
cDNA are resistant to LAC virus but permissive for Sindbis virus (family
Togaviridae
) infection.
Evaluation of Accumulation of Hepatitis C Virus Mutations in a Chronically Infected Chimpanzee: Comparison of the Core, E1, HVR1, and NS5b Regions
Authors: Lu Ling , Nakano Tatsunori , Orito Etsuro , Mizokami Masashi , Robertson Betty H. 
Published: July 2002

ABSTRACT

Four hepatitis C virus genome regions (the core, E1, HVR1, and NS5b) were amplified and sequenced from yearly samples obtained from a chronically infected chimpanzee over a 12-year span. Nucleotide substitutions were found to accumulate in the core, E1, and HVR1 regions during the course of chronic infection; substitutions within the NS5b region were not detected for the first 8 years and were found to be minimal during the last 4 years. The rate of accumulation of mutations in the core and E1 regions, based on a direct comparison between the first 1979 sequence and the last 1990 sequence, was 1.120 × 10
−3
, while phylogenetic ancestral comparison using the 12 yearly sequences showed a rate of 0.816 × 10
−3
bases per site per year. Temporal evaluation of the sequences revealed that there appeared to be periods in which substitutions accumulated and became fixed, followed by periods with relative stasis or random substitutions that did not persist. Synonymous and nonsynonymous substitutions within the core, E1, and HVR1 regions were also analyzed. In the core and E1 regions, synonymous substitutions predominated and gradually increased over time. However, within the HVR1 region, nonsynonymous substitutions predominated but gradually decreased over time.