1
|
Head-to-head comparison on the immunogenicity of two HIV/AIDS vaccine candidates based on the attenuated poxvirus strains MVA and NYVAC co-expressing in a single locus the HIV-1BX08 gp120 and HIV-1(IIIB) Gag-Pol-Nef proteins of clade B. Vaccine 2006; 25:2863-85. [PMID: 17113200 DOI: 10.1016/j.vaccine.2006.09.090] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2006] [Revised: 09/06/2006] [Accepted: 09/21/2006] [Indexed: 11/26/2022]
Abstract
In this investigation we have generated and defined the immunogenicity of two novel HIV/AIDS vaccine candidates based on the highly attenuated vaccinia virus strains, MVA and NYVAC, efficiently expressing in the same locus (TK) and under the same viral promoter the codon optimized HIV-1 genes encoding gp120 and Gag-Pol-Nef antigens of clade B (referred as MVA-B and NYVAC-B). In infected human HeLa cells, gp120 is released from cells and GPN is produced as a polyprotein; NYVAC-B induces severe apoptosis but not MVA-B. The two poxvirus vectors showed genetic stability of the inserts. In BALB/c and in transgenic HHD mice for human HLA-A2 class I, both vectors are efficient immunogens and induced broad cellular immune responses against peptides represented in the four HIV-1 antigens. Some differences were observed in the magnitude and breadth of the immune response in the mouse models. In DNA prime/poxvirus boost protocols, the strongest immune response, as measured by fresh IFN-gamma and IL-2 ELISPOT, was obtained in BALB/c mice boosted with NYVAC-B, while in HHD mice there were no differences between the poxvirus vectors. When the prime/boost was performed with homologous or with combination of poxvirus vectors, the protocols MVA-B/MVA-B and NYVAC-B/NYVAC-B, or the combination NYVAC-B/MVA-B gave the most consistent broader immune response in both mouse models, although the magnitude of the overall response was higher for the DNA-B/poxvirus-B regime. All of the immunization protocols induced some humoral response against the gp160 protein from HIV-1 clone LAV. Our findings indicate that MVA-B and NYVAC-B meet the criteria to be potentially useful vaccine candidates against HIV/AIDS.
Collapse
MESH Headings
- AIDS Vaccines/genetics
- AIDS Vaccines/immunology
- Animals
- Antigens, Viral/biosynthesis
- Antigens, Viral/genetics
- Antigens, Viral/immunology
- Apoptosis/immunology
- Base Sequence
- Chick Embryo
- Fusion Proteins, gag-pol/biosynthesis
- Fusion Proteins, gag-pol/genetics
- Fusion Proteins, gag-pol/immunology
- Gene Products, nef/biosynthesis
- Gene Products, nef/genetics
- Gene Products, nef/immunology
- Genomic Instability
- HIV Envelope Protein gp120/biosynthesis
- HIV Envelope Protein gp120/genetics
- HIV Envelope Protein gp120/immunology
- HLA-A2 Antigen/immunology
- HeLa Cells
- Humans
- Mice
- Mice, Inbred BALB C
- Mice, Transgenic
- Molecular Sequence Data
- Polymerase Chain Reaction/methods
- Poxviridae/genetics
- Poxviridae/immunology
- Vaccines, Attenuated/genetics
- Vaccines, Attenuated/immunology
- Viral Vaccines/genetics
- Viral Vaccines/immunology
Collapse
|
2
|
Production of recombinant HIV-1 Nef (negative factor) protein using Pichia pastoris and a low-temperature fed-batch strategy. Biotechnol Appl Biochem 2006; 44:151-8. [PMID: 16551271 DOI: 10.1042/ba20060001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In the present paper we describe the cloning and extracellular expression of the HIV-1 Nef (negative factor) protein utilizing the yeast Pichia pastoris, as well as the successful use of a low-temperature fed-batch strategy for decreasing end-product degradation by proteases. The nef gene in a pPICZalphaA vector was integrated into the genome of three different P. pastoris strains, namely X-33, GS115 and KM71H. On the basis of its efficient growth and production characteristics the wild-type strain (X-33) was found to be the best choice. The decreased end-product degradation at low temperatures was not due to lower amounts of proteases but due to their diminished activity. The yield of biomass from methanol was improved 1.44-fold utilizing the low-temperature strategy compared with the standard fermentation. Purification of histidine-tagged Nef was performed in one step using a Ni(2+)-nitrilotriacetate-Sepharose column. The purified product was characterized by SDS/PAGE, Western blotting, matrix-assisted laser-desorption ionization-time-of-flight MS, reversed-phase HPLC and N-terminal-sequence analysis.
Collapse
|
3
|
High and inducible expression of human immunodeficiency virus type 1 (HIV-1) Nef by adenovirus vector does not disturb potent antigen presentation by monocyte-derived dendritic cells. Microbes Infect 2006; 8:2522-30. [PMID: 16979362 DOI: 10.1016/j.micinf.2006.07.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Revised: 06/27/2006] [Accepted: 07/02/2006] [Indexed: 10/24/2022]
Abstract
Numerous studies indicated that Nef is a pleiotropic factor. Although it has been shown that Nef impairs the antigen-presenting activity of dendritic cells, more recent studies have shown no such impairment. This issue is critical for designing a vaccine expressing Nef. To refine our knowledge regarding the effect of Nef on dendritic cells, we developed constitutive and inducible adenovirus vector systems that express high levels of Nef in monocyte-derived dendritic cells (MDDCs). We showed here that Nef expression clearly downregulated CD4 expression of MDDCs but had little or no effect on other surface molecules, including MHC class I. Nef also did not affect the functional maturation of MDDCs. Use of the inducible Nef-expression system clearly revealed that adenovirus infection per se modulates cytokine secretion and the expression of apoptosis-related molecules in MDDCs, whereas Nef had no effect on these functions. Moreover, the antigen-presenting activity of MDDCs was not disturbed by the presence of Nef. On the contrary, we found that Nef-expressing MDDCs generated from HIV-1-infected individuals efficiently activated Nef-reactive T cells. Therefore, although adenovirus vector may modulate some aspects of MDDC function, Nef-expressing adenovirus would be served as one of HIV vaccine candidates.
Collapse
|
4
|
Abstract
Nef expression is not required for HIV-1 replication and is highly targeted by CD8+ CTL, raising the question of why Nef expression is not lost in order to evade immunity in vivo. We explore whether MHC class I (MHC-I) down-regulation to evade CTL in general is a selective pressure maintaining Nef. HIV-1 with functional Nef (wild type, WT) is compared to virus containing a Nef point mutation (M20A) that selectively ablates MHC-I down-regulation. WT-infected cells are relatively resistant to cytolysis and less suppressed for viral replication by Gag- and RT-specific CTL compared to M20A. These viruses grow similarly in vitro in the absence of CTL, but the presence of Gag- or RT-specific CTL strongly favors WT overgrowth of M20A. Finally, while in vitro selection by Nef-specific CTL readily drives disruption of the nef reading frame, the addition of Gag- or RT-specific CTL markedly limits such escape. These data indicate that MHC-I down-regulation is an important function favoring Nef maintenance due to a net selective advantage in the setting of the general CTL response.
Collapse
|
5
|
Codon-optimized reading frames facilitate high-level expression of the HIV-1 minor proteins. Mol Biotechnol 2005; 31:85-8. [PMID: 16118417 DOI: 10.1385/mb:31:1:085] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We have constructed reading frames for the HIV-1 YU-2 minor proteins Vpr, Vpu, Vif and Nef that are codon-optimized for high-level expression in mammalian cells. We show that, in the absence of the Rev/Rev-response element system, these codon-optimized reading frames result in greatly increased levels of expression of the corresponding proteins in cell culture systems when compared with the native reading frame. Northern blot analysis shows that the increase in expression found with the codon-optimized reading frames is largely owing to increased steady-state mRNA levels.
Collapse
MESH Headings
- Blotting, Northern
- Blotting, Western
- Codon
- Gene Expression
- Gene Expression Regulation, Viral
- Gene Products, nef/biosynthesis
- Gene Products, nef/genetics
- Gene Products, vif/biosynthesis
- Gene Products, vif/genetics
- Gene Products, vpr/biosynthesis
- Gene Products, vpr/genetics
- Genes, nef
- Genes, vif
- Genes, vpr
- Genes, vpu
- HIV-1/genetics
- HIV-1/metabolism
- Human Immunodeficiency Virus Proteins
- RNA, Messenger/biosynthesis
- Reading Frames
- Viral Regulatory and Accessory Proteins/biosynthesis
- Viral Regulatory and Accessory Proteins/genetics
- nef Gene Products, Human Immunodeficiency Virus
- vif Gene Products, Human Immunodeficiency Virus
- vpr Gene Products, Human Immunodeficiency Virus
Collapse
|
6
|
Nef expressed from human immunodeficiency virus type 1 extrachromosomal DNA downregulates CD4 on primary CD4+ T lymphocytes: implications for integrase inhibitors. J Gen Virol 2005; 86:765-771. [PMID: 15722538 DOI: 10.1099/vir.0.80570-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Recently developed integrase inhibitors targeting the HIV-1 integrase (IN) protein block integration of HIV DNA in the target cell, preventing subsequent virus replication. In the absence of integration, viral DNA is shunted towards the formation of extrachromosomal DNA (E-DNA). Although HIV-1 E-DNA does not support productive replication, it is transcriptionally active and produces viral proteins. However, the significance of E-DNA in virus replication and pathogenesis is poorly understood. In this study, the functional activity of the HIV-1 Nef protein expressed in the absence of viral integration was analysed. Using both a recombinant HIV-1 IN defective virus and a diketo acid IN inhibitor, evidence was provided showing that Nef expressed from E-DNA downregulates CD4 surface expression on primary CD4(+) T lymphocytes. These results suggest that proteins expressed in the absence of integration may have potential clinical consequences, an issue that should be further explored with the introduction of IN inhibitors.
Collapse
|
7
|
Human immunodeficiency virus type 1 Nef protein mediates neural cell death: a neurotoxic role for IP-10. Virology 2005; 329:302-18. [PMID: 15518810 DOI: 10.1016/j.virol.2004.08.024] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2004] [Revised: 07/22/2004] [Accepted: 08/12/2004] [Indexed: 02/01/2023]
Abstract
HIV-1 Nef is expressed in astrocytes, but a contribution to neuropathogenesis and the development of HIV-associated dementia (HAD) remains uncertain. To determine the neuropathogenic actions of the HIV-1 Nef protein, the brain-derived (YU-2) and blood-derived (NL4-3) Nef proteins were expressed in neural cells using an alphavirus vector, which resulted in astrocyte death (P < 0.001). Supernatants from Nef-expressing astrocytes also caused neuronal death, suggesting the release of neurotoxic molecules by astrocytes. Analysis of pro-inflammatory gene induction in astrocytes expressing Nef revealed increased IP-10 mRNA expression (4000-fold) that was Nef sequence dependent. Recombinant IP-10 caused selective cell death in neurons (P < 0.001) but not astrocytes, and the cytotoxicity of supernatant from astrocytes expressing Nef YU-2 was blocked by an antibody directed against the chemokine receptor CXCR3 (P < 0.001). SCID/NOD mice implanted with a Nef YU-2-expressing vector displayed abnormal motor behavior (P < 0.05), neuroinflammation, and neuronal loss relative to controls. Analysis of mRNA levels in brains from patients with HAD also revealed increased expression of IP-10 (P < 0.05), which was confirmed by immunoreactivity detected principally in astrocytes. Phylogenetic and protein structure analyses of Nef sequences derived from HIV/AIDS patients with and without HAD suggested viral evolution toward a neurotropic Nef protein. These results indicate that HIV-1 Nef contributes to neuropathogenesis by directly causing astrocyte death together with indirect neuronal death through the cytotoxic actions of IP-10 on neurons. Furthermore, Nef molecular diversity was evident in brain tissue among patients with neurological disease and which may influence IP-10 production by astrocytes.
Collapse
MESH Headings
- AIDS Dementia Complex/metabolism
- AIDS Dementia Complex/physiopathology
- Animals
- Animals, Genetically Modified
- Astrocytes/metabolism
- Astrocytes/virology
- Cell Death
- Cells, Cultured
- Chemokine CCL2/biosynthesis
- Chemokine CCL2/genetics
- Chemokine CXCL10
- Chemokines, CXC/biosynthesis
- Chemokines, CXC/pharmacology
- Chemokines, CXC/physiology
- Gene Products, nef/biosynthesis
- Gene Products, nef/genetics
- Genetic Vectors
- HIV-1/genetics
- HIV-1/pathogenicity
- Humans
- Interleukin-1/biosynthesis
- Interleukin-1/genetics
- Interleukin-1beta
- Male
- Mice
- Mice, Inbred NOD
- Mice, SCID
- Molecular Sequence Data
- Neurons/drug effects
- Neurons/metabolism
- Neurons/pathology
- Neurotoxins/pharmacology
- Peptide Fragments/biosynthesis
- Peptide Fragments/genetics
- RNA, Messenger/analysis
- Recombinant Proteins/pharmacology
- nef Gene Products, Human Immunodeficiency Virus
Collapse
|
8
|
Cellular viral rebound after cessation of potent antiretroviral therapy predicted by levels of multiply spliced HIV-1 RNA encoding nef. J Infect Dis 2004; 190:1979-88. [PMID: 15529263 DOI: 10.1086/425983] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2004] [Accepted: 07/01/2004] [Indexed: 11/04/2022] Open
Abstract
To characterize newly arising replication of human immunodeficiency virus (HIV) type 1 in vivo at the cellular level, distinct viral RNA species in peripheral blood mononuclear cells (PBMCs) from HIV-1-infected patients were monitored during 2 weeks of structured treatment interruption (STI). HIV-1 RNA encoding tat/rev and PBMC-associated virions were almost completely depleted during antiretroviral therapy and emerged simultaneously after 2 weeks of STI, thus specifically reflecting productive viral infection at the cellular level. The magnitude of these correlates of reappearing cellular viral replication was predicted by during-therapy levels of nef transcripts in PBMCs. Significant rebound of plasma viremia, representing the progeny of a broader range of anatomical compartments, preceded and predicted productive infection in PBMCs. Thus, cellular viral rebound in PBMCs likely was primed before STI by the expression of nef in HIV-1-infected PBMCs that lacked virion production and was subsequently triggered by the plasma viremia that preceded the recurrence of productively infected PBMCs.
Collapse
MESH Headings
- Anti-HIV Agents/therapeutic use
- Cells, Cultured
- Drug Therapy, Combination
- Gene Products, nef/analysis
- Gene Products, nef/biosynthesis
- Gene Products, rev/metabolism
- Gene Products, tat/metabolism
- HIV Infections/blood
- HIV Infections/drug therapy
- HIV Infections/virology
- HIV-1/genetics
- HIV-1/isolation & purification
- Humans
- Leukocytes, Mononuclear/virology
- Neutrophils/virology
- RNA Splicing
- RNA, Viral/analysis
- RNA, Viral/biosynthesis
- Recurrence
- Virus Replication
- nef Gene Products, Human Immunodeficiency Virus
- rev Gene Products, Human Immunodeficiency Virus
- tat Gene Products, Human Immunodeficiency Virus
Collapse
|
9
|
Abstract
HIV Nef down-regulates CD4 from the cell surface in the absence of CD4 phosphorylation, whereas PMA down-regulates CD4 through a phosphorylation-dependent pathway. In this study we show that the down-regulation of CD4 in human Jurkat T cells expressing Nef was nearly complete (approximately 95%), whereas that induced by PMA was partial (approximately 40%). Unexpectedly, treating T cells expressing Nef with PMA restored the surface CD4 up to 35% of the steady state level. Both mutating the phosphorylation sites in the CD4 cytoplasmic tail (Ser408 and Ser415) and the use of a protein kinase C inhibitor, bisindolylmaleimide1, abolished the restoration of surface CD4, suggesting that the restoration required CD4 phosphorylation. CD4 and Nef could be cross-linked by a chemical cross-linker, 3,3-dithiobis[sulfosuccinimidyl-propionate], in control T cell membranes, but not in PMA-treated T cell membrane, suggesting that CD4 and Nef interacted with each other in T cells, and the phosphorylation disrupted the CD4-Nef interaction. We propose that this dissociation switches CD4 internalization from the Nef-mediated, nearly complete down-regulation to a phosphorylation-dependent, partial down-regulation, resulting in a net gain of CD4 on the T cell surface.
Collapse
|
10
|
Endogenously expressed HIV-1 nef down-regulates antigen-presenting molecules, not only class I MHC but also CD1a, in immature dendritic cells. Virology 2004; 326:79-89. [PMID: 15262497 DOI: 10.1016/j.virol.2004.06.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2004] [Accepted: 06/02/2004] [Indexed: 01/30/2023]
Abstract
The effects of Nef molecules on immature dendritic cells (iDCs) were analyzed using recombinant human immunodeficiency virus type 1 (HIV-1) with intact nef gene, pseudotyped with vesicular stomatitis virus glycoprotein, HIV/VSV-G/+Nef. When iDCs were infected with HIV/VSV-G/+Nef, the surface expression of CD1a, a molecule for presenting glycolipid/lipid antigens, was selectively down-regulated among CD1 molecules (CD1a, -b, -c, and -d) as well as class I MHC. Moreover, the CD1a molecules were also down-modulated and co-localized with DsRed2-tagged-Nef in CD1a-transfected cells. Their co-localization was dependent upon CD1a cytoplasmic tail and the CD1a was redistributed from cell surface to LAMP-1+ late endosomal/lysosomal compartment. These findings reveal that the HIV-1-Nef interferes with the intracellular trafficking of CD1a, and suggest the involvement of CD1a-restricted immune effectors in the protective immunity against HIV-1 infection, which implicates the feasibility of virus-derived glycolipid/lipid antigens together with epitope peptides for the vaccine development.
Collapse
|
11
|
Antibody-Dependent Cellular Cytotoxicity via Humoral Immune Epitope of Nef Protein Expressed on Cell Surface. THE JOURNAL OF IMMUNOLOGY 2004; 172:2401-6. [PMID: 14764710 DOI: 10.4049/jimmunol.172.4.2401] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Antibodies against various proteins of HIV type 1 (HIV-1) can be detected in HIV-1-infected individuals. We previously reported that the level of Ab response against one Nef epitope is correlated with HIV-1 disease progression. To elucidate the mechanism for this correlation, we examined Ab-dependent cellular cytotoxicity (ADCC) against target cells expressing Nef. We observed efficient cytotoxicity against Nef-expressing target cells in the presence of patient plasma and PBMCs. This ADCC activity was correlated with the dilution of plasma from HIV-1-infected patients. Addition of a specific synthetic peptide (peptide 31:FLKEKGGLE) corresponding to the Nef epitope reduced cell lysis to approximately 50%. These results suggest that PBMCs of HIV-1-infected patients may exert ADCC via anti-Nef Abs in the patients' own plasma and serve as a mechanism used by the immune system to regulate HIV-1 replication.
Collapse
|
12
|
Two-step purification of His-tagged Nef protein in native condition using heparin and immobilized metal ion affinity chromatographies. J Virol Methods 2003; 111:69-73. [PMID: 12821199 DOI: 10.1016/s0166-0934(03)00154-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The Nef protein encoded by human immunodeficiency virus type 1 (HIV-1) has been shown to be an important factor of progression of viral growth and pathogenesis in both in vitro and in vivo. The lack of a simple procedure to purify Nef in its native conformation has limited molecular studies on Nef function. A two-step procedure that includes heparin and immobilized metal ion affinity chromatographies (IMACs) was developed to purify His-tagged Nef (His(6)-Nef) expressed in bacteria in native condition. During the elaboration of this purification procedure, we identified two closely SDS-PAGE-migrating contaminating bacterial proteins, SlyD and GCHI, that co-eluted with His(6)-Nef in IMAC in denaturing condition and developed purification steps to eliminate these contaminants in native condition. Overall, this study describes a protocol that allows rapid purification of His(6)-Nef protein expressed in bacteria in native condition and that removes metal affinity resin-binding bacterial proteins that can contaminate recombinant His-tagged protein preparation.
Collapse
|
13
|
Coxiella burnetii avoids macrophage phagocytosis by interfering with spatial distribution of complement receptor 3. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2003; 170:4217-25. [PMID: 12682255 DOI: 10.4049/jimmunol.170.8.4217] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Phagocytosis is a highly localized event requiring the formation of spatially and temporally restricted signals. Numerous microorganisms have taken advantage of this property to invade host cells. Coxiella burnetii, the agent of Q fever, is an obligate intracellular bacterium that has developed a survival strategy in macrophages based on subversion of receptor-mediated phagocytosis. The uptake of C. burnetii is mediated by alpha(v)beta(3) integrin and is restricted by impaired cross-talk of alpha(v)beta(3) integrin and complement receptor 3 (CR3) (CD11b/CD18). In this study, we showed that CR3 molecules remained outside the pseudopodal extensions induced by C. burnetii in THP-1 monocytes, although alpha(v)beta(3) integrin was present in the pseudopods. Chemoattractants such as RANTES restored CR3 localization to the front of pseudopodal extensions and increased C. burnetii phagocytosis, demonstrating that the localization of CR3 is critical for bacterial uptake. In addition, monocyte activation due to the expression of HIV-1 Nef protein also restored CR3-mediated phagocytosis of C. burnetii by allowing CR3 redistribution toward bacterial-induced pseudopods. The redistribution of CR3 and increased C. burnetii phagocytosis in THP-1 cells stimulated by RANTES or expressing Nef were associated with the inhibition of intracellular replication of C. burnetii. Hence, the localization of CR3 is critical for bacterial phagocytosis and also for the control of bacterial replication. This study describes a nonpreviously reported strategy of phagocytosis subversion by intracellular pathogens based on altered localization of monocyte receptors.
Collapse
|
14
|
Endogenously expressed nef uncouples cytokine and chemokine production from membrane phenotypic maturation in dendritic cells. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 169:4172-82. [PMID: 12370346 DOI: 10.4049/jimmunol.169.8.4172] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Immature dendritic cells (DCs), unlike mature DCs, require the viral determinant nef to drive immunodeficiency virus (SIV and HIV) replication in coculture with CD4(+) T cells. Since immature DCs may capture and get infected by virus during mucosal transmission, we hypothesized that Nef associated with the virus or produced during early replication might modulate DCs to augment virus dissemination. Adenovirus vectors expressing nef were used to introduce nef into DCs in the absence of other immunodeficiency virus determinants to examine Nef-induced changes that might activate immature DCs to acquire properties of mature DCs and drive virus replication. Nef expression by immature human and macaque DCs triggered IL-6, IL-12, TNF-alpha, CXCL8, CCL3, and CCL4 release, but without up-regulating costimulatory and other molecules characteristic of mature DCs. Coincident with this, nef-expressing immature DCs stimulated stronger autologous CD4(+) T cell responses. Both SIV and HIV nef-expressing DCs complemented defective SIVmac239 delta nef, driving replication in autologous immature DC-T cell cultures. In contrast, if DCs were activated after capturing delta nef, virus growth was not exacerbated. This highlights one way in which nef-defective virus-bearing immature DCs that mature while migrating to draining lymph nodes could induce stronger immune responses in the absence of overwhelming productive infection (unlike nef-containing wild-type virus). Therefore, Nef expressed in immature DCs signals a distinct activation program that promotes virus replication and T cell recruitment but without complete DC maturation, thereby lessening the likelihood that wild-type virus-infected immature DCs would activate virus-specific immunity, but facilitating virus dissemination.
Collapse
|
15
|
Abstract
Recent studies indicate that the time required for virus-infected cells to become vulnerable for the activity of CTL is of significance for the capacity of CTL to control ongoing viral reproduction. To investigate whether this applies to the effectiveness of HIV-1-specific CTL, we measured virus production in cultures containing CD4(+) T cells inoculated with HIV at low multiplicity of infection, and CTL directed against an early protein, Rev, or a late protein, RT. The Rev-specific CTL prevented at least 2 log(10) more HIV-1 production, in 10 days, than similar numbers of RT-specific CTL. To study how CTL effectiveness depends on variations in the potency of effector functions and kinetics of HIV protein expression, we developed a mathematical model describing CTL-target cell interactions during successive infection cycles. The results show that substantially higher CTL-mediated target cell elimination rates are required to achieve control as there is less time for CTL to act before infected cells release progeny virions. Furthermore, in vitro experiments with HIV recombinant viruses showed that the RT-specific CTL were at least as effective as the Rev-specific CTL, but only if the RT epitope was expressed as part of the early protein Nef. Together these results indicate that CTL control ongoing HIV reproduction more effectively if they are able to recognize infected cells earlier during individual viral replication cycles. This provides rationale for immunization strategies that aim at inducing, boosting or skewing CTL responses to early regulatory proteins in AIDS vaccine development.
Collapse
MESH Headings
- CD4-Positive T-Lymphocytes/immunology
- Cytotoxicity, Immunologic
- Epitopes/immunology
- Gene Expression Regulation, Viral
- Gene Products, nef/biosynthesis
- Gene Products, nef/immunology
- Gene Products, rev/biosynthesis
- Gene Products, rev/immunology
- HIV Antigens/biosynthesis
- HIV Antigens/immunology
- HIV Reverse Transcriptase/biosynthesis
- HIV Reverse Transcriptase/immunology
- HIV-1/immunology
- HIV-1/physiology
- Humans
- Kinetics
- Models, Immunological
- T-Lymphocyte Subsets/immunology
- T-Lymphocytes, Cytotoxic/immunology
- Virus Replication
- nef Gene Products, Human Immunodeficiency Virus
- rev Gene Products, Human Immunodeficiency Virus
Collapse
|
16
|
Abstract
The study of the immunologic response to whole human immunodeficiency virus type 1 (HIV-1) antigen is limited by the presence of highly immunogenic human leukocyte antigen (HLA) alloantigens on the envelope of wild type virus. This paper outlines the production of HIV-1 infectious virions free of HLA for use as whole viral antigens in immunoassays. An infectious molecular clone of HIV-1 was transfected into the K-562 cell line, which does not express HLA on the cell surface. After a 30-day selection period, to ensure stable transfection, cells and culture supernatants were analyzed for productive HIV-1 infection and virion infectivity. An enzyme-linked immunosorbent assay (ELISA) confirmed the presence of p24 in the culture supernatants. Molecular confirmation of HIV-1 transfection was achieved by gene amplification. Flow cytometric analysis was used to identify gp120 on the surface of the infected cells. Viral supernatants were tested for HIV infectivity in peripheral blood mononuclear cells (PBMCs). The usefulness of this viral preparation as whole virus antigens was validated using PBMCs from HIV-infected individuals. These results indicate the successful production of HIV-1 infectious virions, which do not have HLA molecules on their viral envelope, and demonstrate their utility for immunoassays.
Collapse
|
17
|
Abstract
DNA plasmid immunization has the important advantage over traditional vaccines of making it possible to combine selected genes into one vaccine. The efficacy of a combination of DNA plasmids encoding the nef, rev, and tat HIV-1 regulatory genes in inducing cellular immune responses was analyzed in asymptomatic HIV-1-infected patients. Patients initially selected for having low or no detectable immune responses to Nef, Rev, or Tat antigens developed MHC class I-restricted cytolytic activities as well as enhanced bystander effects. The induction of memory cells against target cells infected with the whole HIV-1 genome was analyzed by using a pseudovirus HIV-1/murine leukemia virus (MuLV), and target cells infected with vaccinia virus carrying the respective gene. The most remarkable change observed after immunization with the gene combination was an increase in cytotoxic T lymphocyte (CTL) precursors to target cells infected with the whole HIV-1 genome. Infection by the pseudotype HIV-1/MuLV virus should result in a multitude of HIV-1 peptides presented on the target cell surface, representative of the in vivo situation. An in vitro assessment of the expression of the single and combined gene products showed that this was consistent with the induction of CTL responses in vivo. No clinical advantage or adverse effects were noted. Therapeutic effects of such immunization may become measurable by structured therapy interruption.
Collapse
MESH Headings
- AIDS Vaccines/administration & dosage
- AIDS Vaccines/genetics
- AIDS Vaccines/immunology
- AIDS Vaccines/therapeutic use
- CD4 Lymphocyte Count
- CpG Islands/genetics
- Cytotoxicity, Immunologic
- Gene Expression
- Gene Products, nef/biosynthesis
- Gene Products, nef/genetics
- Gene Products, nef/immunology
- Gene Products, nef/therapeutic use
- Gene Products, rev/biosynthesis
- Gene Products, rev/genetics
- Gene Products, rev/immunology
- Gene Products, rev/therapeutic use
- Gene Products, tat/biosynthesis
- Gene Products, tat/genetics
- Gene Products, tat/immunology
- Gene Products, tat/therapeutic use
- Genes, Viral/genetics
- Genetic Vectors/administration & dosage
- Genetic Vectors/genetics
- HIV Antigens/biosynthesis
- HIV Antigens/genetics
- HIV Antigens/immunology
- HIV Infections/immunology
- HIV Infections/therapy
- HIV Infections/virology
- HIV-1/genetics
- HIV-1/immunology
- HeLa Cells
- Histocompatibility Antigens Class I/immunology
- Humans
- Leukemia Virus, Murine/genetics
- Lymphocyte Activation
- Plasmids/genetics
- T-Lymphocytes, Cytotoxic/cytology
- T-Lymphocytes, Cytotoxic/immunology
- Vaccination
- Vaccines, DNA/administration & dosage
- Vaccines, DNA/genetics
- Vaccines, DNA/immunology
- Vaccines, DNA/therapeutic use
- Vaccinia virus/genetics
- nef Gene Products, Human Immunodeficiency Virus
- rev Gene Products, Human Immunodeficiency Virus
- tat Gene Products, Human Immunodeficiency Virus
Collapse
|
18
|
Abstract
Lipid rafts, also known as detergent-resistant membranes (DRM), are microdomains in the plasma membrane enriched in sphingolipids and cholesterol (reviewed in [1, 2]). Human immunodeficiency virus 1 (HIV) buds via lipid rafts [3, 4]. However, the targeting of viral structural components to DRM and its consequences for viral replication are not understood. Moreover, the negative factor Nef from HIV increases viral infectivity (reviewed in [5, 6]). With no apparent differences in structural components and morphology between wild-type and DeltaNef virons, the latter viruses display less efficient reverse transcription in target cells. As Nef is expressed abundantly early in the viral replicative cycle [7], we hypothesized that Nef could affect viral morphogenesis and budding to render viruses more infectious. In this report, we demonstrated first that Nef increases viral budding from lipid rafts. Second, in the presence of Nef, viral envelopes contain more ganglioside (GM1), which is a major component of lipid rafts. This finding correlated directly with the increased infectivity of HIV. Finally, the depletion of exogenous and endogenous cholesterol biochemically and genetically, which disrupted lipid rafts, decreased viral infectivity only in the presence of Nef. Importantly, HIV lacking the nef gene remained unaffected by these manipulations. We conclude that lipids in virions are essential for viral infectivity. Thus, HIV becomes more infectious when it buds from lipid rafts, and Nef plays a major role in this process.
Collapse
|
19
|
Continuous-exchange cell-free protein-synthesizing system: synthesis of HIV-1 antigen Nef. Biochem Biophys Res Commun 2001; 280:914-7. [PMID: 11162611 DOI: 10.1006/bbrc.2000.4188] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
HIV-1 antigen Nef, Green Fluorescent Protein (GFP), and the fusion protein GFP-Nef ("Green Fluorescent Nef") were synthesized in bacterial cell-free system with continuous supply of substrates and continuous removal of low-molecular-weight products through a dialysis membrane during incubation, the so-called continuous-exchange cell-free (CECF) system. The identity of synthesized proteins was confirmed by electrophoretic mobility, Western blotting, and GFP fluorescence. The system produced several nanomoles (hundreds of microg) of each protein per ml of the reaction mixture. Construction of GFP-fused proteins is considered as a general strategy for visualization and monitoring of cell-free production of the proteins that have no easily testable functions.
Collapse
|
20
|
Resistance to apoptosis in HIV-infected CD4+ T lymphocytes is mediated by macrophages: role for Nef and immune activation in viral persistence. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 165:6437-46. [PMID: 11086083 DOI: 10.4049/jimmunol.165.11.6437] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Apoptosis or programmed cell death may play a critical role in AIDS pathogenesis through depletion of both CD4(+) and CD8(+) T lymphocytes. Using a reporter virus, a recombinant HIV infectious clone expressing the green fluorescent protein (GFP), apoptosis was measured in productively infected CD4(+) T lymphocytes, in the presence and absence of autologous macrophages. The presence of macrophages in the culture increased the frequency of nonapoptotic GFP-positive productively infected CD4(+) T lymphocytes. The appearance of nonapoptotic productively infected CD4(+) T lymphocytes in the culture required intercellular contacts between macrophages and PBLs and the expression of the HIV Nef protein. The presence of macrophages did not reduce apoptosis when CD4(+) T lymphocytes were infected with a GFP-tagged virus deleted for the nef gene. TNF-alpha (TNF) expressed on the surface of macrophages prevented apoptosis in nef-expressing, productively infected CD4(+) T lymphocytes. Similarly, following TNF stimulation, apoptosis was diminished in Jurkat T cells transfected with a nef-expressing plasmid. TNF stimulation of nef-expressing Jurkat T cells resulted in NF-kappaB hyperactivation, which has been shown to deliver anti-apoptotic signals. Our results indicate that intercellular contacts with macrophages increase the rate of productively infected nonapoptotic CD4(+) T lymphocytes. The survival of productively infected CD4(+) T lymphocytes requires Nef expression as well as activation by TNF expressed on the surface of macrophages and might participate in the formation and maintenance of viral reservoirs in HIV-infected persons.
Collapse
|
21
|
Abstract
IL-10 plays a pivotal role in the pathogenesis of several diseases and is elevated in sera of HIV-infected patients. Recently, we demonstrated that HIV Nef induces IL-10 mRNA expression as well as IL-10 production using PBMCs, H9 or U937 cells. This induction of IL-10 is inhibited by a calmodulin antagonist, W-7. In the present study, T or B lymphocytes or monocytes were isolated from PBMCs of healthy HIV-negative donors. Production of IL-10 and mRNA gene expression were analyzed on each isolated cell population after treatment with Nef or SEA for 3-24 h. The results show that Nef induces IL-10 production as well as mRNA expression significantly using monocytes but not with T or B lymphocytes. By contrast, SEA induced IL-10 production as well as mRNA expression using T lymphocytes but not with monocytes or B lymphocytes.
Collapse
|
22
|
Abstract
Many different HIV-1 vaccine strategies have been developed, but as yet none has been completely successful. Promising results from combined DNA prime/protein boost vaccines have been reported. Specific immune responses generated by DNA vaccines can be modulated by the co-delivery of genes coding for cytokines. In this study, we have used the intradermal route by needle injection of a plasmid coding for the HIV-1 Nef accessory protein. We show that DNA prime/protein boost vaccine combinations increase the humoral and cellular immune responses against HIV-1 Nef and that the co-injection of DNA encoding Interleukin-18 (IL-18) modulates the specific immune response towards a Th1 type.
Collapse
MESH Headings
- AIDS Vaccines/administration & dosage
- AIDS Vaccines/immunology
- Animals
- Antibody Formation/drug effects
- DNA, Viral/administration & dosage
- DNA, Viral/immunology
- Female
- Gene Products, nef/administration & dosage
- Gene Products, nef/biosynthesis
- Gene Products, nef/genetics
- Gene Products, nef/immunology
- HIV-1/genetics
- HIV-1/immunology
- Immunity, Cellular/drug effects
- Immunization, Secondary
- Interleukin-18/genetics
- Interleukin-18/immunology
- Mice
- Mice, Inbred BALB C
- Plasmids/genetics
- Recombinant Proteins/administration & dosage
- Recombinant Proteins/immunology
- Vaccines, DNA/administration & dosage
- Vaccines, DNA/immunology
- Viral Proteins/administration & dosage
- Viral Proteins/immunology
- nef Gene Products, Human Immunodeficiency Virus
Collapse
|
23
|
Analysis of the SH3-binding region of HIV-1 nef: partial functional defects introduced by mutations in the polyproline helix and the hydrophobic pocket. Virology 1999; 262:55-63. [PMID: 10489340 DOI: 10.1006/viro.1999.9897] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An SH3-binding domain within the Nef protein of primate lentiviruses has been reported to be important to viral replication and infectivity and dispensable for CD4 downregulation, but its precise role remains unclear. This study investigates the effects of mutations in both the polyproline helix and in the hydrophobic pocket that constitute the SH3-binding domain of Nef. The data demonstrate that the well-studied mutation of the central prolines is only partially disruptive to viral infectivity and replication. The central prolines also make a subtle contribution to the efficiency of CD4 downregulation, detectable only using low levels of Nef expression. Mutation of a conserved arginine in the polyproline helix abrogated more completely Nef-mediated enhancement of viral infectivity; this mutation also adversely affected CD4 downregulation at low levels of Nef expression. Only the R77A mutation substantially impaired downregulation of class I MHC. However, mutation of the central prolines and of R77 yielded proteins that were expressed less efficiently than wild-type Nef. The R77A mutant was expressed most poorly, compatible with its defective phenotypes in all assays. Mutations of the hydrophobic pocket were minimally detrimental to both the virologic and the receptor modulatory functions of Nef. Taken together, this analysis suggests that mutations in the SH3-binding domain do not abrogate fully any Nef-associated phenotype in the absence of detrimental effects on protein expression. We suggest that mutations in this domain can introduce incomplete effects caused by subtle impairments to protein expression; these effects may appear selective under certain experimental conditions due to different sensitivities of the assays to the level of Nef expression.
Collapse
|
24
|
Expression of a novel Nef epitope on the surface of HIV type 1-infected cells. AIDS Res Hum Retroviruses 1999; 15:1001-9. [PMID: 10445812 DOI: 10.1089/088922299310511] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We compared antibody responses to various structural and accessory gene products of HIV-1 between long-term nonprogressors and patients who have progressed to AIDS. On the basis of our results, we performed epitope mapping of the Nef protein and identified a novel epitope. This novel epitope of the Nef protein was found to be exposed on the surface of HIV-1-infected cells. The antibody response against it correlated with CD4+ cell counts among HIV-1-infected patients (r = 0.457, p < 0.001). Although further research is necessary, we suspect that antibody response against the epitope may be protective against disease progression.
Collapse
|
25
|
HIV-1 nef expression inhibits the activity of a Ca2+-dependent K+ channel involved in the control of the resting potential in CEM lymphocytes. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 1999; 162:5359-66. [PMID: 10228012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
The HIV-1 Nef protein plays an important role in the development of the pathology associated with AIDS. Despite various studies that have dealt with different aspects of Nef function, the complete mechanism by which it alters the physiology of infected cells remains to be established. Nef can associate with cell membranes, therefore supporting the hypothesis that it might interact with membrane proteins as ionic channels and modify their electrical properties. By using the patch-clamp technique, we found that Nef expression determines a 25-mV depolarization of lymphoblastoid CEM cells. Both charybdotoxin (CTX) and the membrane-permeable Ca2+ chelator BAPTA/AM depolarized the membrane of native cells without modifying that of Nef-transfected cells. These data suggested that the resting potential in native CEM cells is settled by a CTX- and Ca2+-sensitive K+ channel (KCa,CTX), whose activity is absent in Nef-expressing cells. This was confirmed by direct measurements of whole-cell KCa,CTX currents. Single-channel recordings on excised patches showed that a KCa,CTX channel of 35 pS with a half-activation near 400 nM Ca2+ was present in both native and Nef-transfected cells. The measurements of free intracellular Ca2+ were not different in the two cell lines, but Nef-transfected cells displayed an increased Ca2+ content in ionomycin-sensitive stores. Taken together, these results indicate that Nef expression alters the resting membrane potential of the T lymphocyte cell line by inhibiting a KCa,CTX channel, possibly by intervening in the regulation of intracellular Ca2+ homeostasis.
Collapse
|
26
|
Cutting edge: induction of enhanced CTL-dependent protective immunity in vivo by N-end rule targeting of a model tumor antigen. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 1999; 162:639-42. [PMID: 9916680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
There is much interest in vaccines that will enhance the induction of CTL. One mechanism to enhance Ag-specific CTL responses involves targeting Ag to undergo rapid cytoplasmic degradation by the N-end rule pathway. We have analyzed the ability of N-end rule targeting to confer protection in an immunization-challenge setting. Using the HIV-1 nef protein as a model tumor Ag, we found that in mice immunized with a vaccinia vector expressing a form of nef that is targeted for rapid cytoplasmic degradation, there was enhanced induction of nef-specific CTL and protection from a lethal challenge with the syngeneic CT26 tumor cells that had been transfected with nef. Protection from tumor challenge correlated with the magnitude of the CTL response. Thus, the targeting of tumor or viral Ags for rapid cytoplasmic degradation by the N-end rule pathway may represent a strategy for the induction of protective Ag-specific CTL responses in vivo.
Collapse
MESH Headings
- Adenocarcinoma/immunology
- Adenocarcinoma/prevention & control
- Animals
- Antigens, Neoplasm/genetics
- Antigens, Neoplasm/immunology
- Antigens, Neoplasm/metabolism
- Cytotoxicity, Immunologic
- Dose-Response Relationship, Immunologic
- Gene Products, nef/biosynthesis
- Gene Products, nef/genetics
- Gene Products, nef/immunology
- HIV-1/genetics
- HIV-1/immunology
- Immunity, Innate
- Lymphocyte Activation
- Mice
- Mice, Inbred BALB C
- Models, Immunological
- Neoplasm Transplantation
- Recombinant Fusion Proteins/immunology
- T-Lymphocytes, Cytotoxic/immunology
- Ubiquitins/genetics
- Ubiquitins/immunology
- Viral Vaccines/genetics
- Viral Vaccines/immunology
- nef Gene Products, Human Immunodeficiency Virus
Collapse
|
27
|
Diminished production of human immunodeficiency virus type 1 in astrocytes results from inefficient translation of gag, env, and nef mRNAs despite efficient expression of Tat and Rev. J Virol 1999; 73:352-61. [PMID: 9847339 PMCID: PMC103840 DOI: 10.1128/jvi.73.1.352-361.1999] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Astrocytes infected with human immunodeficiency virus type 1 (HIV-1) produce only minimal quantities of virus. The molecular events that limit acute-phase HIV-1 infection of astrocytes were examined after inducing acute-phase replication by transfection with the pNL4-3 proviral plasmid. The levels of HIV-1 mRNA were similarly high in both astrocytes and HeLa cells, but astrocytes produced approximately 50-fold less supernatant p24 than HeLa cells. We found that diminished HIV-1 production in astrocytes resulted from inefficient translation of gag, env, and nef mRNAs that were efficiently transported to the cytoplasm. Tat- or Rev-dependent reporter constructs showed no defect in Tat or Rev function in astrocytes compared with HeLa cells. HIV-1 mRNAs were correctly spliced, but only Rev and Tat proteins were efficiently translated from their native mRNAs. Pulse-chase labelling and immunoblot experiments revealed no defect in protein processing, but levels of Gag, Env, or Nef protein expressed were dramatically reduced in astrocytes compared to HeLa cells. These results demonstrate that inefficient translation of HIV-1 structural proteins underlies the restricted infection of astrocytes. The efficient expression of functional Tat and Rev by astrocytes may contribute to HIV-1 neuropathogenesis.
Collapse
MESH Headings
- 5' Untranslated Regions
- Astrocytes/virology
- Gene Products, env/biosynthesis
- Gene Products, gag/biosynthesis
- Gene Products, nef/biosynthesis
- Gene Products, rev/biosynthesis
- Gene Products, tat/biosynthesis
- HIV Core Protein p24/biosynthesis
- HIV-1/physiology
- Humans
- Protein Biosynthesis
- RNA, Messenger/analysis
- Tumor Cells, Cultured
- nef Gene Products, Human Immunodeficiency Virus
- rev Gene Products, Human Immunodeficiency Virus
- tat Gene Products, Human Immunodeficiency Virus
Collapse
|
28
|
Abstract
Simian immunodeficiency virus strain PBj14, SIVsmmPBj14, is unique among primate lentiviruses in its ability to trigger the proliferation of resting simian lymphocytes and to cause the rapid death of experimentally inoculated pigtailed macaques. Severe enteropathy, immune activation, and extensive apoptosis, particularly within gut-associated lymphoid tissue, characterize the acute disease syndrome associated with SIVsmmPBj14 infection. In the present study, we examined whether the ability of this virus to cause widespread apoptosis might be linked to the up-regulation of Fas ligand (CD95L) expression in virally infected cells. In vitro studies revealed that expression of the viral Nef protein, in the absence of any other viral gene product, was sufficient to up-regulate the transcriptional activity of the CD95L promoter and to cause cell surface expression of Fas ligand. This up-regulation was NFAT dependent (inhibited by cyclosporin A) and did not occur in cells that expressed a mutated derivative of the viral Nef protein, lacking a previously defined immunoreceptor tyrosine-based activation motif. These findings were corroborated by analysis of tissue sections from virally infected macaques. Immunohistochemical staining revealed that Fas ligand expression was efficiently up-regulated in the GALT of animals that had been experimentally infected with wild-type SIVsmmPBj14 but not in animals that were infected with a nonacutely pathogenic viral mutant lacking the Nef ITAM. Taken together, these results suggest that the ability of SIVsmmPBj14 to cause acutely lethal disease and to up-regulate FasL expression may be linked. Additional studies will be required to determine whether the induction of FasL expression is in itself important for acute disease pathogenesis.
Collapse
|
29
|
The HIV-1 nef protein inhibits extracellular signal-regulated kinase-dependent DNA synthesis in a human astrocytic cell line. J Neurochem 1998; 70:778-85. [PMID: 9453574 DOI: 10.1046/j.1471-4159.1998.70020778.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The role of nonproductive infection of astrocytes by human immunodeficiency virus type 1 (HIV-1), characterized by the overexpression of nef, in brain disease progression is largely unknown. We investigated the consequences of stable expression of nef from the HIV-1 strain LAI in the human astrocytic cell line U373. DNA synthesis induced by endothelin-1 (ET-1) was largely decreased by nef. Stable expression of nef did not affect the ET-1-induced tyrosine phosphorylation of focal adhesion kinase, an adhesion-dependent pathway known to participate in DNA synthesis in astrocytes. Conversely, the activation of extracellular signal-regulated kinase (ERK) by ET-1 was largely inhibited in cells stably or transiently expressing nef. A similar inhibitory action of nef on ERK activation was observed after direct stimulation of G proteins. Furthermore, the inhibitory action of nef did not require protein kinase C (PKC) and affected mainly the PKC-independent pathway of ERK activation. Following chemokine receptor CXCR4-mediated infection of U373 cells stably expressing CXCR4 with the T-tropic HIV-1 strain m7-NDK, ET-1-induced activation of ERK was also inhibited. Altogether, these results indicate that intracellular signaling pathways associated with the growth factor activity of ET-1 are impaired in nef-expressing and HIV-1-infected astrocytes, suggesting that infection of astrocytes may play a significant role in the neuropathogenesis of HIV-1 encephalopathy.
Collapse
|
30
|
Clustered localization of oligomeric Nef protein of human immunodeficiency virus type 1 on the cell surface. FEBS Lett 1996; 395:257-61. [PMID: 8898107 DOI: 10.1016/0014-5793(96)01048-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We studied human immunodeficiency virus type 1 (HIV-1) Nef protein biochemically and histologically. HIV-1 Nef, derived from baculosystem and from cells infected with HIV-1, formed homomeric monomers, dimers, trimers, and further polymers. These oligomers were non-covalently associated. In cells infected with HIV-1, Nef molecules were clustered at the cell surface as well as cytoplasm. Our previous results have indicated that the Nef on the surface of cells infected with HIV-1 is cytotoxic against uninfected CD4+ T cells. Thus, it is very likely that the HIV-1-mediated cytotoxic reaction is due, at least in part, to the clustered localization of oligomeric Nef on the cell surface.
Collapse
|
31
|
Abstract
Previously we reported that Nef protein from human immunodeficiency virus (HIV) induces proliferation of human peripheral blood mononuclear cells (PBMC). Herein, we show that HIV replicates in cells activated by Nef. PBMC proliferated in response to Nef and were capable of producing significant amounts of infectious virus upon infection. Polyclonal antibodies to Nef synthetic peptides blocked proliferation and neutralized infection. Characteristic of superantigens, T-cell proliferation in response to Nef required antigen-presenting cells and showed CD4 Vb preferences as previously shown. These findings suggest that Nef is a virally encoded T-cell superantigen and, as such, may be vital in the establishment of HIV infection in a new host and in subsequent disease pathogenesis.
Collapse
|
32
|
Abstract
Studies on Nef, a regulatory protein encoded by human immunodeficiency virus (HIV), suggest it plays an important role in HIV pathogenesis. Previously, we reported that Nef binds to class II MHC antigens and induces proliferation of human peripheral blood mononuclear cells (PBMC). Herein, we further characterize PBMC responses to Nef. Polyclonal antisera generated against Nef synthetic peptides blocked proliferation. Responses were T cell-specific and required antigen-presenting cells (APC). T cells responded in the presence of paraformaldehyde-inactivated APC, suggesting that Nef is presented in an unprocessed form. Nef-stimulated cells produced IL 2 and IFN gamma, products of T helper-1 cells. Thus, Nef has superantigen properties in that it binds to MHC class II antigens, does not need processing to be presented by APC, and activates T cells, causing proliferation and production of the T helper 1 cytokines, IL 2 and IFN gamma. The identification of an HIV protein that activates T cells is of considerable interest, given that HIV replicates in T cell blasts but not in quiescent cells.
Collapse
|
33
|
Attenuated SIV imparts immunity to challenge with pathogenic spleen-derived SIV but cannot prevent repair of the nef deletion. Immunol Lett 1996; 51:129-35. [PMID: 8811357 DOI: 10.1016/0165-2478(96)02567-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
To date, some success has been achieved with several experimental vaccines against AIDS in the available animal models. In the simian immunodeficiency virus (SIV) macaque model protection against superinfection was obtained by preinfection with a virus attenuated by a deletion in nef. To investigate the efficacy of SIVmac32H(pC8), a nef deletion mutant of SIVmac251, as a live-attenuated vaccine, rhesus monkeys were infected intravenously (i.v.) with this virus. All monkeys became productively infected by the pC8 virus. The animals had low cell-associated viral loads but developed a strong cellular and humoral antiviral immune response. Two out of eight preinfected monkeys developed signs of immunodeficiency and were excluded from the challenge. Sequence analysis of reisolates from one of them revealed a complete repair of the nef deletion. The remaining six monkeys, two preinfected for 42 weeks and four for 22 weeks, were challenged i.v. with a pathogenic SIV derived ex vivo from the spleen of a SIV infected macaque. Four of the monkeys challenged resisted the second infection whereas in two monkeys preinfected for 22 weeks full length nef was detectable. All monkeys maintained a virus-specific CD4-cell proliferative response after challenge. Thus, even after short preinfection periods with an attenuated SIV sterilising immunity against a challenge with a pathogenic SIV can be obtained. However, such a vaccine is unsafe since the attenuated virus frequently reverts to a more virulent form.
Collapse
|
34
|
Regulation of HIV-1 infection in astrocytes: expression of Nef, TNF-alpha and IL-6 is enhanced in coculture of astrocytes with macrophages. J Neurovirol 1996; 2:158-66. [PMID: 8799208 DOI: 10.3109/13550289609146878] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
'Restricted' human immunodeficiency virus type (HIV-1) infection of astrocytes is recognized in vivo in some pediatric and adult AIDS brains and in vitro in a small proportion of transfected primary fetal astrocytes. We investigated the extent of HIV-1JR-FL expression in fetal astrocytes and macrophages cultivated alone or together. Peak HIV-1 p24 antigen titres in supernatant fluids of macrophage cultures were increased with monocyte/macrophages from certain donors and were higher when macrophages were cocultivated with astrocytes. Structural HIV-1 gene (gp 41 and pol) products (protein and mRNA) were observed only in macrophages. Ten days after HIV-1JR-FL infection, astrocytes in a monoculture were stained negative or only weakly positive (1-2+) for Nef, whereas in a coculture up to 100% of astrocytes displayed Nef staining (up to 4+) in the cytoplasm. The streptavidine-biotine-peroxidase technique with certain monoclonal antibodies to Nef (Ovod et al, 1992) was specific for infected astrocytes. The intensity of Nef staining was higher in astrocytes cultivated with monocyte/macrophages from certain donors. In the coculture, tumor necrosis factor-alpha (TNF-alpha) was expressed in the astrocyte cytoplasm earlier after coinfection with HIV-1 and cytomegalovirus (CMV) compared to infection with HIV-1 alone. Interleukin-6 (IL-6) was secreted spontaneously and transiently in uninfected cocultures, but in a prolonged fashion following HIV-1 and HIV-1/CMV infections. The interactions between HIV-1- and CMV-infected macrophages and astrocytes lead to upregulation of TNF-alpha and IL-6 and enhancement of productive HIV-1 infection of macrophages and of 'restricted' HIV-1 infection of astrocytes with implications for the pathogenesis of AIDS dementia.
Collapse
|
35
|
Construction of human immunodeficiency virus 1/simian immunodeficiency virus strain mac chimeric viruses having vpr and/or nef of different parental origins and their in vitro and in vivo replication. J Gen Virol 1995; 76 ( Pt 9):2181-91. [PMID: 7561755 DOI: 10.1099/0022-1317-76-9-2181] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We constructed a series of human immunodeficiency virus 1 (HIV-1)/simian immunodeficiency virus strain mac (SIVmac) chimeric viruses having vpr and/or nef genes of either HIV-1 or SIVmac based on a chimeric virus with LTRs, gag, pol, vif and vpx derived from SIVmac and tar, rev, vpu and env from HIV-1. All of the chimeric viruses replicated in human and macaque peripheral blood mononuclear cells (PBMCs) and in several CD4+ human cell lines, though their growth potentials were slightly different depending on whether vpr and nef were from HIV-1 or SIVmac, or were defective. The presence of nef accelerated replication in all the cells used and the replication of each chimera appeared to reflect that of the parental virus from which nef was derived. The presence of vpr had no clear effect in human and monkey PBMCs, but the replication of each chimera was influenced by the origin of vpr in H9 and A3.01 cells. NM-3rN, which carries HIV-1 vpr and SIVmac nef, was inoculated intravenously into three rhesus monkeys, three cynomolgus monkeys and two pig-tailed monkeys. From 2 to 14 weeks after inoculation, viruses were consistently re-isolated from all the monkeys and virus loads were as high as that of SIVmac reported previously. The results indicate that infection with NM-3rN is more efficient than any of our previous chimeric viruses and suggest that NM-3rN, having HIV-1 Env, will be a useful challenge virus for evaluating AIDS vaccines based on HIV-1 Env in macaque monkeys instead of chimpanzees.
Collapse
|
36
|
In vitro binding and phosphorylation of human immunodeficiency virus type 1 Nef protein by serine/threonine protein kinase. J Gen Virol 1995; 76 ( Pt 6):1337-44. [PMID: 7540194 DOI: 10.1099/0022-1317-76-6-1337] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Although the human immunodeficiency virus type 1 (HIV-1) nef gene still has no precisely defined function, in vivo studies have demonstrated that Nef is an important pathogenic determinant of HIV. In order to identify cellular proteins capable of binding to Nef, the HIV-1LAI nef gene product was expressed in the bacterial vector pGEX-2T as a glutathione S-transferase (GST)-Nef fusion protein. Deletion mutants corresponding to 86 and 35 N-terminal residues of the Nef protein were prepared. The GST-Nef constructs were used to identify cellular kinases capable of interacting with Nef. After incubation with a Jurkat cell lysate, the GST-Nef constructs immobilized on glutathione-agarose beads bound to cellular kinase(s) and were phosphorylated at three sites in vitro: one on threonine at position 15, one on serine between residues 1 and 35, and one on threonine between residues 36 and 86. The Nef-phosphorylating activity was inhibited by protein kinase C (PKC)-selective inhibitors. Cell fractionation showed that this Nef-binding kinase was mainly in the membrane-associated fraction. These results suggest that kinase(s) of the PKC family are specifically bound to and phosphorylate Nef in vitro. The interaction of Nef with cellular kinases and its phosphorylation may be important in mediating the effects of Nef in HIV-1 pathogenesis.
Collapse
|
37
|
Recombinant BCG strains expressing the SIVmac251nef gene induce proliferative and CTL responses against nef synthetic peptides in mice. Vaccine 1995; 13:471-8. [PMID: 7543715 DOI: 10.1016/0264-410x(94)00001-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
CTL responses are known to be important for the control of HIV and SIV infections. Such responses are targeted against various components of these viruses including regulatory proteins like Nef. The SIVmac251nef gene was cloned in Mycobacterium bovis BCG under the control of P(AN), a promoter from Mycobacterium paratuberculosis. Nef was expressed as a fused polypeptide with ORF2, an open reading frame adjacent to P(AN). Mice inoculated with rBCG(SIVmac251nef) exhibited proliferative and CD8+ cytotoxic T-cell (CTL) responses against several Nef synthetic peptides. A mapping of the epitopes recognized by CTLs revealed that the central region of Nef is mainly involved in responses. This region had already been demonstrated to induce CTLs in experimentally SIV-infected macaques as well as in HIV-infected individuals. These results demonstrate the feasibility of constructing BCG vaccine strains expressing nef for eliciting cytotoxic responses.
Collapse
MESH Headings
- Animals
- Base Sequence
- CD8-Positive T-Lymphocytes/drug effects
- CD8-Positive T-Lymphocytes/immunology
- Cloning, Molecular
- Epitopes/immunology
- Female
- Gene Expression
- Gene Products, nef/biosynthesis
- Gene Products, nef/genetics
- Gene Products, nef/pharmacology
- Genes, Viral
- Genes, nef
- Immunity, Cellular/drug effects
- Immunity, Cellular/immunology
- Lymphocyte Activation/drug effects
- Mice
- Mice, Inbred BALB C
- Molecular Sequence Data
- Mycobacterium bovis/genetics
- Mycobacterium bovis/metabolism
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Recombinant Proteins/pharmacology
- Simian Immunodeficiency Virus/genetics
- T-Lymphocytes, Cytotoxic/drug effects
- T-Lymphocytes, Cytotoxic/immunology
- Viral Proteins/biosynthesis
- Viral Proteins/genetics
- Viral Proteins/pharmacology
Collapse
|
38
|
Oligomerization of the HIV type 2 Nef protein: mutational analysis of the heptad leucine repeat motif and cysteine residues. AIDS Res Hum Retroviruses 1995; 11:65-79. [PMID: 7734198 DOI: 10.1089/aid.1995.11.65] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The human immunodeficiency virus type 2 (HIV-2) Nef protein expressed in Escherichia coli forms highly stable homooligomeric complexes in vitro. Similarly, the native protein synthesized in the persistently infected H9 T cell line also forms stable homooligomers in vivo. To determine whether homooligomer formation is mediated by the leucine zipper-type sequence located in the middle region of the protein, site-directed mutagenesis was used to introduce double and triple point mutations at heptad leucine positions L1, L2, and L4 within the HIV-2NIHZ Nef protein sequence. Here, we show that substitution of a serine residue for the L1 (residue 108) and L2 (residue 115) heptad leucines, and a glutamine residue for the L4 (residue 129) heptad leucine, did not prevent Nef homooligomer formation in vitro. However, a more drastic substitution of alpha-helix-breaking proline residue for the L2 and L4 heptad leucines significantly abrogated ability of the protein to form stable homooligomers. In addition, because significantly higher levels of the Nef oligomers were consistently observed under the nonreducing SDS-PAGE condition, site-specific mutagenesis was also used to examine the role of cysteine residues in generating disulfide-linked Nef dimers in vitro. Here, we also show that single cysteine-to-glycine substitutions at positions 28, 32, or 55 drastically reduced covalent Nef dimer formation and thermal stability of the Nef protein in vitro. Therefore, these results demonstrate that the leucine zipper-type motif in the HIV-2 Nef protein mediates stable homooligomer formation in vitro, and also establish a role for covalent disulfide bonds in the formation of linked Nef dimers and thermal stability of the monomer Nef in vitro.
Collapse
|
39
|
Superinfection of a defective human immunodeficiency virus type 1 provirus-carrying T cell clone with vif or vpu mutants gives cytopathic virus particles by homologous recombination. AIDS Res Hum Retroviruses 1995; 11:45-53. [PMID: 7734196 DOI: 10.1089/aid.1995.11.45] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The partially CD4-expressing T cell clone, Vpr-1, which carries a latent vpr-defective HIV-1 genome and expresses HIV-1 Nef protein only, was permissive to superinfection by HIV-1. Superinfection of Vpr-1 with vif- or vpu-defective mutants, which were noncytopathic, reactivated the vpr-defective virus and led to homologous recombination and cytopathogenesis. The data provide an experimental model for homologous recombination being an important mechanism whereby HIV-1 acquires genetic heterogeneity, and when occurring among defective virus in vivo bestows novel biological activities and virulence.
Collapse
MESH Headings
- CD4-Positive T-Lymphocytes/metabolism
- CD4-Positive T-Lymphocytes/virology
- Clone Cells
- Gene Expression Regulation, Viral
- Gene Products, nef/biosynthesis
- Gene Products, nef/genetics
- Gene Products, vif/biosynthesis
- Gene Products, vif/genetics
- Gene Products, vpr/biosynthesis
- Gene Products, vpr/genetics
- Genome, Viral
- HIV Infections/genetics
- HIV-1/genetics
- HIV-1/pathogenicity
- Humans
- Mutation
- Recombination, Genetic
- Superinfection/genetics
- nef Gene Products, Human Immunodeficiency Virus
- vif Gene Products, Human Immunodeficiency Virus
- vpr Gene Products, Human Immunodeficiency Virus
Collapse
|
40
|
Physical interaction of the HIV-1 Nef protein with beta-COP, a component of non-clathrin-coated vesicles essential for membrane traffic. J Biol Chem 1994; 269:30073-6. [PMID: 7982906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Nef is a 27-kDa myristylated protein conserved in most human immunodeficiency virus (HIV)-1, HIV-2, and simian immunodeficiency virus isolates. Simian immunodeficiency virus Nef is required in macaques for both high viral load and full pathological effects. Nef down-regulates the cell surface expression of CD4 by a post-translational mechanism that is not yet fully elucidated. We have used the yeast two-hybrid system to identify cellular proteins that interact with Nef. A cDNA was isolated which encodes a COOH-terminal fragment of human beta-COP, a major coat component of non-clathrin-coated vesicles. Nef and beta-COP interacted in vitro and were found to be physically associated in HIV-1-infected cells by co-immunoprecipitation. These observations suggest that beta-COP might be one of the cellular mediators of Nef function in HIV-1-infected cells.
Collapse
|
41
|
Abstract
We have studied two isoforms of Nef, Nef-27 and Nef-25, which were produced in E. coli. Nef-25 lacked the first 18 N-terminal residues of Nef-27 and both were nonmyristylated. Nef-27 fuses small unilamellar dipalmitoyl phosphatidylcholine vesicles (SUVs), as indicated by enhanced light scattering of SUVs and lipid mixing using concentration-dependent fluorescence dequenching. Nef-27 also causes the appearance of a shifted isotropic peak in the 31P NMR spectra of these vesicles, suggesting that protein interactions induce nonlamellar lipid structures. Recombinant Nef-25, which lacks only the 18 N-terminal residues of Nef-27, does not fuse vesicles and has little effect on the 31P NMR spectra. On the other hand, synthetic peptides consisting of 18 or 21 of the N-terminal residues of Nef-27 are strongly membrane perturbing, causing vesicle fusion and inducing isotropic peaks in the 31P NMR spectrum. Endogenous fluorescence spectra of the N-terminal peptide (21 residues) with SUVs show that the N-terminal sequence of Nef may achieve these perturbing effects by inserting its hydrophobic side into the lipid bilayer. Theoretical calculations using hydrophobic moment plot analysis indicate that short-length stretches (i.e., six amino acid residues) of the N-terminal sequence may insert into the lipid bilayer as multimeric alpha helices or beta sheets. The above-described membrane activities of Nef-27, which principally reside in its N-terminal domain, may play critical role(s) in certain functional properties of the full-length protein. For example, the fusogenic activity of the N-terminal sequence may be involved in the extracellular release of Nef-27, much of which appears to be associated with small membrane vesicles. The fusion activity may also be relevant to the ability of Nef-27 to downregulate CD4 and IL-2 receptors when this protein is electroporated into cultured lymphocytes, an activity not possessed by Nef-25.
Collapse
MESH Headings
- 1,2-Dipalmitoylphosphatidylcholine
- Amino Acid Sequence
- Antigens, Bacterial/chemistry
- Gene Products, nef/biosynthesis
- Gene Products, nef/chemistry
- Gene Products, nef/metabolism
- HIV-1/metabolism
- Light
- Liposomes
- Magnetic Resonance Spectroscopy
- Membrane Fusion
- Molecular Sequence Data
- Peptide Fragments/chemical synthesis
- Peptide Fragments/chemistry
- Protein Structure, Secondary
- Recombinant Proteins/biosynthesis
- Recombinant Proteins/metabolism
- Scattering, Radiation
- Sequence Homology, Amino Acid
- Spectrometry, Fluorescence
- nef Gene Products, Human Immunodeficiency Virus
Collapse
|
42
|
Expression kinetics and subcellular localization of HIV-1 regulatory proteins Nef, Tat and Rev in acutely and chronically infected lymphoid cell lines. Arch Virol 1994; 139:365-78. [PMID: 7832642 DOI: 10.1007/bf01310798] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Information concerning the expression kinetics and subcellular localization of HIV regulatory proteins is of importance in understanding the viral pathogenesis and may be relevant for drug and vaccine development, as well. We have used combined immunocytochemistry and in situ hybridization to study firstly, the order of expression of regulatory HIV-1 proteins Nef, Rev and Tat in relation to non-spliced and spliced mRNA expression and secondly, the subcellular localization of these proteins in acutely and chronically infected human T-cell lines. We used monoclonal antibodies against HIV-1 Nef, Tat, Rev and gp160, and RNA probes reacting either with all mRNAs (nef) or only with the full-length mRNA (gag-pol). In acutely infected MT-4 and H9 cells, four distinct phases of infection could be defined. In the first phase lasting from 0 to 6 h post-infection, only incoming virus could be demonstrated by gp160 immunocytochemistry. During the second, regulatory phase (6-9 h), abundant cytoplasmic expression of Nef, Rev and Tat proteins and a positive in situ RNA hybridization with the nef probe was seen, while the in situ hybridization with full-length mRNA probe and immunohistochemistry for gp160 were still negative. The productive phase (12-48 h) was characterized by abundant expression of full-length mRNA and gp160, and by the nuclear localization of Nef and Tat proteins. In contrast, an antibody that recognized the RRE binding region of the Rev protein localized Rev in the cytoplasm both during the regulatory and productive phase. During the fourth, cytopathic phase, the expression of mRNA or viral proteins decreased and the regulatory proteins studied were again mainly localized in the cytoplasm. Based on the results, we speculate that HIV Nef may function as a nuclear factor, and that Tat is possibly bound by cellular proteins before its transport to the nucleus.
Collapse
MESH Headings
- Cell Death
- Cell Line
- Cell Nucleus/chemistry
- Cytopathogenic Effect, Viral
- Cytoplasm/chemistry
- Gene Expression
- Gene Products, nef/analysis
- Gene Products, nef/biosynthesis
- Gene Products, nef/genetics
- Gene Products, rev/analysis
- Gene Products, rev/biosynthesis
- Gene Products, rev/genetics
- Gene Products, tat/analysis
- Gene Products, tat/biosynthesis
- Gene Products, tat/genetics
- HIV-1/genetics
- HIV-1/metabolism
- HIV-1/physiology
- Humans
- In Situ Hybridization
- Kinetics
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Viral/genetics
- RNA, Viral/metabolism
- T-Lymphocytes/metabolism
- T-Lymphocytes/virology
- nef Gene Products, Human Immunodeficiency Virus
- rev Gene Products, Human Immunodeficiency Virus
- tat Gene Products, Human Immunodeficiency Virus
Collapse
|
43
|
Restricted expression of HIV1 in human astrocytes: molecular basis for viral persistence in the CNS. RESEARCH IN VIROLOGY 1994; 145:147-53. [PMID: 7800939 DOI: 10.1016/s0923-2516(07)80016-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Besides macrophages and microglial cells, cells of astroglial origin are thought to be targets of HIV1 in the brain. HIV1 infection of astroglial cells results in restricted production of the virus. To analyse the molecular basis of this restricted infection phenotype, we established a chronically HIV1-infected low-producer astrocytoma cell line. These cells show only low levels of mRNA encoding structural proteins, due to a cell-determined blockage in the Rev/RRE regulatory axis. The low-producer state could not be overcome by treatment with known stimulators of virus expression such as phorbol ester, (12-O-tetradecanoylphorbol-13-acetate), tumour necrosis factor alpha or sodium butyrate. This indicates that the molecular mechanisms involved in restricting virus production in astroglial cells differ from those in latently infected T cells and monocytes.
Collapse
|
44
|
HIV-1 Nef inhibits a common activation pathway in NIH-3T3 cells. J Biol Chem 1994; 269:6656-60. [PMID: 8120020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) Nef is a myristylated 27-kDa, cytoplasmic protein. It is attributed to have suppressive effects on LTR-based expression and T cell activation. Additionally, SIV nef has been shown to possess an essential in vivo function in the development of immunodeficiency. To define the biochemical activity of HIV-1 Nef in a signal transduction pathway, we have transduced murine NIH-3T3 cells with a retroviral nef expression system. In nef-expressing cells, but not in controls, the proliferative response to bombesin and platelet-derived growth factor (PDGF) was eliminated. Analysis of an early signal pathway metabolite, inositol 1,4,5-trisphosphate, following bombesin and PDGF treatment to quiscent cells, revealed that both control and nef-transformed cells displayed similar kinetics of signal formation. Normally, inositol 1,4,5-trisphosphate mediates increase in the cytosolic free Ca2+ ([Ca2+]i). Upon stimulation with bombesin or PDGF, control cells displayed a 2-4-fold increase of [Ca2+]i over the basal level, while the [Ca2+]i response in nef-expressing NIH-3T3 cells was lacking or highly diminished. However, the release of [Ca2+]i from the intracellular store of the nef-expressing cells by an endomembrane Ca2+ ATPase inhibitor, thapsigargin, revealed that these cells contained normal Ca2+ stores. These results suggest a specific, definable biochemical activity for the HIV-1 Nef protein in the context of a well characterized cellular activation pathway. Our results thus define, for the first time, a unique function of Nef that is not limited to an alteration of T cell function or of expression of a T cell surface antigen.
Collapse
|
45
|
Large-scale production and characterization of recombinant human immunodeficiency virus type 1 Nef. J Gen Virol 1994; 75 ( Pt 3):651-5. [PMID: 8126463 DOI: 10.1099/0022-1317-75-3-651] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Sequences encoding the 27K and 25K nef gene products (Nef 27 and Nef 25) were amplified by PCR from a human immunodeficiency virus type 1 infectious clone and subcloned directly into Escherichia coli, yeast and baculovirus expression vectors. The yeast- and baculovirus-derived Nef had native N termini but the expression levels were low. The expression levels of the E. coli-derived glutathione S-transferase-Nef fusion proteins were very high and a major portion was soluble. Large-scale production of E. coli-derived Nef 27 and Nef 25 was carried out by growing recombinant cells in a fermenter under fed-batch conditions followed by affinity purification on glutathione-Sepharose before and after thrombin cleavage. Large quantities of highly purified recombinant Nef proteins have been produced for functional and structural studies. Under non-reducing conditions both Nef 27 and Nef 25 existed as a mixture of monomers, dimers and small amounts of higher oligomers, but when reduced were monomeric. The highly purified Nef proteins had no G protein activities, however Nef 27 was biologically active. When electroporated into uninfected CD4+ T lymphocytes both E. coli-derived Nef 27 and yeast-derived myristylated Nef 27 down-regulated the surface expression of CD4, demonstrating that this method can be used to assess the biological activity of purified recombinant Nef.
Collapse
|
46
|
Highly localized tracks of human immunodeficiency virus type 1 Nef in the nucleus of cells of a human CD4+ T-cell line. Proc Natl Acad Sci U S A 1993; 90:11895-9. [PMID: 8265644 PMCID: PMC48091 DOI: 10.1073/pnas.90.24.11895] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
A human T-cell line constitutively expressing the nef gene from the human immunodeficiency virus type 1 SF2 isolate was used to examine the distribution of the Nef protein in the nucleus. High-resolution immunogold labeling/electron microscopic studies with polyclonal anti-Nef antibodies on nef+ and nef- cells revealed that a small fraction of Nef is in the nucleus and it is localized in specific curvilinear tracks that extend between the nuclear envelope and the nucleoplasm. An examination of the sequence of the SF2 nef gene revealed a putative nuclear targeting sequence that was previously found in several other eukaryotic nucleoplasmic proteins. The nuclear localization of Nef suggests a potential nuclear function for this protein. The presence of Nef in distinct nuclear tracks suggests that Nef is transported along a specific pathway that extends from the nuclear envelope into the nucleoplasm. A previous study [Meier, U. T. & Blobel, G. (1992) Cell 70, 127-138] has shown that the nucleolar protein of rat liver cells (Nopp140) shuttles from the nucleolus to the nuclear envelope on distinct tracks. The present study has suggested that the transport of a nucleoplasmic protein may also occur on distinct nuclear pathways.
Collapse
|
47
|
Abstract
The pathophysiological consequence of HIV-1 nef gene expression was investigated in transgenic mice carrying a cDNA for Nef linked to either the HIV-1 LTR or the MMTV LTR. In HIV/Nef transgenic mouse lines, nef expression was detected exclusively in the skin and a significant fraction of HIV/Nef transgenic animals (30-75%, depending on the line) spontaneously developed discrete proliferative skin lesions resembling papillomas that were often accompanied by a progressive ulceration of the epidermal cell layer. Nef protein was detected in the basal cell layer of the epidermis and was elevated in the proliferating epidermis. Epidermal cell proliferation could be induced by UV-C irradiation of HIV/Nef transgenic animals but not control mice. An increase in nef expression in the skin accompanied this proliferation. MMTV/Nef mouse lines expressed Nef RNA and protein in organs typically permissive for MMTV LTR-directed transcription but with no obvious pathological consequence.
Collapse
|
48
|
Abstract
The negative factor, Nef, of HIV-1 was found to associate to an extent of 16-42% with the detergent insoluble cytoskeletal fraction of T lymphocytes. Furthermore, Escherichia coli expressed Nef protein was found to bind during in vitro reactions with the cytoskeletal matrix to an extent of 30-50%. Cytoskeletal association of Nef was significantly enhanced by myristoylation. The specificity of the myristoylation-enhanced binding was demonstrated by the lack of an effect of myristoylation on binding of the HIV-1 Gag protein to the cytoskeleton. Cytoskeletal binding was saturable, and inhibited by high concentrations of sodium chloride, or with SDS or urea. Binding of Nef to the cytoskeletal matrix may be important in mediating its effects on HIV-1 replication.
Collapse
|
49
|
Abstract
The nef genes of the human immunodeficiency viruses type 1 and 2 (HIV-1 and HIV-2) and the related simian immunodeficiency viruses (SIVs) encode a protein (Nef) whose role in virus replication and cytopathicity remains uncertain. As an attempt to elucidate the function of nef, we characterized the nucleotide and corresponding protein sequences of naturally occurring nef genes obtained from several HIV-1-infected individuals. A consensus Nef sequence was derived and used to identify several features that were highly conserved among the Nef sequences. These features included a nearly invariant myristylation signal, regions of sequence polymorphism and variable duplication, a region with an acidic charge, a (Pxx)4 repeat sequence, and a potential protein kinase C phosphorylation site. Clustering of premature stop codons at position 124 was noted in 6 of the 54 Nef sequences. Further analysis revealed four stretches of residues that were highly conserved not only among the patient-derived HIV-1 Nef sequences, but also among the Nef sequences of HIV-2 and the SIVs, suggesting that Nef proteins expressed by these retroviruses are functionally equivalent. The "Nef-defining" sequences were used to evaluate the sequence alignments of known proteins reported to share sequence similarity with Nef sequences and to conduct additional computer-based searches for similar protein sequences. A gene encoding the consensus Nef sequence was also generated. This gene encodes a full-length Nef protein that should be a valuable tool in further studies of Nef function.
Collapse
MESH Headings
- Acquired Immunodeficiency Syndrome/blood
- Acquired Immunodeficiency Syndrome/microbiology
- Amino Acid Sequence
- Base Sequence
- Cloning, Molecular
- DNA, Viral/blood
- DNA, Viral/genetics
- DNA, Viral/isolation & purification
- Databases, Factual
- Gene Products, nef/analysis
- Gene Products, nef/biosynthesis
- Gene Products, nef/genetics
- Genes, nef
- Genetic Vectors
- HIV-1/genetics
- HIV-1/isolation & purification
- HIV-1/metabolism
- HeLa Cells
- Humans
- Immunoblotting
- Molecular Sequence Data
- Moloney murine leukemia virus/genetics
- Oligodeoxyribonucleotides
- Polymerase Chain Reaction/methods
- Proviruses/genetics
- Proviruses/isolation & purification
- Proviruses/metabolism
- Sequence Homology, Amino Acid
- Transduction, Genetic
- Transfection
- nef Gene Products, Human Immunodeficiency Virus
Collapse
|
50
|
Nef from primary isolates of human immunodeficiency virus type 1 suppresses surface CD4 expression in human and mouse T cells. J Virol 1993; 67:4923-31. [PMID: 8331733 PMCID: PMC237880 DOI: 10.1128/jvi.67.8.4923-4931.1993] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) nef gene was originally described as a negative regulator of transcription from the viral long terminal repeat promoter. This observation has been disputed, and the function of Nef remains unclear. In vivo experiments have indicated that an intact nef gene is required for disease progression in macaques infected with simian immunodeficiency virus, suggesting a role for Nef in the pathogenesis of AIDS. We and others have previously shown that expression of Nef in cells bearing surface CD4 results in a sustained decrease in surface CD4 expression. This was demonstrated for Nef from two laboratory strains of HIV-1, Bru and SF2. Because both of these isolates were passaged in vitro prior to molecular cloning and in vitro passage can result in mutations which might alter nef gene function, we have analyzed two primary isolates of Nef for their ability to suppress cell surface CD4 expression. The nef genes of HIV-1 isolates from two patients with fewer than 200 CD4+ T cells per mm3 of blood were introduced into human and mouse T-cell lines by retrovirus-mediated gene transfer. Expression of Nef from both isolates correlated with a decrease in surface expression of both human and mouse CD4. To determine whether the ability to suppress surface CD4 expression is a general function of Nef, we also tested an artificially generated consensus nef gene derived from analysis of 54 patient isolates of HIV-1. Expression of the consensus Nef protein also correlated with decreased cell surface CD4 expression in both mouse and human T-cell lines. These results suggest that the ability to suppress cell surface CD4 expression is an intrinsic feature of HIV-1 Nef.
Collapse
|