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At least 19 recordsLinked to original sources
PubMed1992

Requirement for macrophages in neuronal injury induced by HIV envelope protein gp120.

HIV-1-related neuronal injury may involve a complex web of viral proteins and cytokines, but neurons themselves are not infected. The HIV envelope protein gp120 has been shown to engender an early increase in neuronal free calcium followed by delayed excitotoxic-like damage, which is prevented by N-methyl-D-aspartate (NMDA) antagonists. In the present study, we found that the injurious effects of gp120 on retinal ganglion cell neurons require the presence of macrophages in mixed neuronal glial cultures of postnatal retina. Within 24 hours of incubation, 20 pM gp120 injured nearly 40% of retinal ganglion cells in cultures containing macrophages and other glial cells, whereas no deleterious effects of gp120 were noted on retinal ganglion cells in cultures depleted of macrophages. Thus, the toxic effect of gp120 on neurons appears to be an indirect one, mediated by activation of macrophages and perhaps other glial cells.

Animals↗
PubMed2001

Use of human CD4 transgenic mice for studying immunogenicity of HIV-1 envelope protein gp120.

HIV-1 envelope protein, gp120, is a major immunogenic protein of the AIDS virus. A specific feature of this protein is its interaction with the receptor protein, human CD4, an important component of the immune system. This interaction might affect the immunogenic properties of the gp 120 and modulate the immune response towards HIV. To test this hypothesis we used human CD4-transgenic mice for immunization with gp120. The dynamics of the immune response towards gp120, CD4 and other proteins was followed. The results show that the primary immune response to gp120 (two weeks) developed somewhat faster in CD4-transgenic mice versus non-transgenic mice. Both animals, however, ultimately mounted the same level of response over time. The primary immune response to gp120 when complexed with soluble CD4 before the immunization, developed similarly in both groups. The secondary immune response was earlier and markedly stronger in non-transgenic mice compared with the transgenic mice where a less efficient memory response to gp120 was observed. The ability of gp120 to directly interact with CD4+ helper lymphocytes appears to affect the humoral response towards this antigen. Moreover, these effects illustrate how viral modulation of these cells may in turn lead to potentially different states of immunological equilibrium.

AIDS Vaccines↗
PubMed2005

Surfactant protein D binds to human immunodeficiency virus (HIV) envelope protein gp120 and inhibits HIV replication.

The envelope protein (gp120) of human immunodeficiency virus (HIV) contains highly conserved mannosylated oligosaccharides. These glycoconjugates contribute to resistance to antibody neutralization, and binding to cell surface lectins on macrophages and dendritic cells. Mannose-binding lectin (MBL) binds to gp120 and plays a role in defence against the virus. In this study it is demonstrated that surfactant protein D (SP-D) binds to gp120 and inhibits HIV infectivity at significantly lower concentrations than MBL. The binding of SP-D was mediated by its calcium-dependent carbohydrate-binding activity and was dependent on glycosylation of gp120. Native dodecameric SP-D bound to HIV gp120 more strongly than native trimeric SP-D. Since one common polymorphic form of SP-D is predominantly expressed as trimers and associated with lower blood levels, these individuals may have less effective innate defence against HIV. A chimeric protein containing the N-terminal and collagen domains of SP-D linked to the neck and carbohydrate-recognition domains of MBL (called SP-D/MBL(neck+CRD)) had greater ability to bind to gp120 and inhibit virus replication than either SP-D or MBL. The enhanced binding of SP-D/MBL(neck+CRD) was dependent on assembly into higher molecular mass multimers (i.e. a trimeric form of the chimera did not bind to a greater extent than MBL). Hence, the enhanced binding of SP-D compared with MBL results from distinctive properties of its N-terminal and/or collagen domains. SP-D is present in lung and airway fluids, as well as in blood and various mucosal locations, and could, like MBL, play a role in restricting HIV transmission or replication in vivo.

HIV Envelope Protein gp120↗
PubMed1997

Mutant CD4 molecules with improved binding to HIV envelope protein gp120 selected by phage display.

Phage-display methodology has been used to select variant CD4 proteins exhibiting increased binding to the surface envelope glycoprotein, gp120, of Human Immunodeficiency Virus Type-1. To facilitate the selection, a library of mutant CD4 proteins was constructed by cloning a PCR-generated error prone population of the first two domains of CD4 into the phagemid expression vector pHEN1. Phage displaying CD4 in functional form were confirmed by Western blot with CD4-specific antibody and by phage ELISA on immobilized gp120. Biopanning of CD4 phage on immobilized gp120 followed by individual characterization identified five clones with increased binding to gp120. All of the selected variants had one or two amino acid substitutions within the V1 domain of CD4, notably at positions 15, 27, 30, 50, and 66 located in the strands surrounding the main binding loop. Variants which exhibited increased binding to recombinant gp120 in vitro were also shown to have an increased capacity for virus neutralization broadly in line with their in vitro binding activity.

Amino Acid Sequence↗
PubMed1998

Spatial structure model of the CD4 receptor-binding site of the HIV envelope protein gp120.

In this study we have undertaken attempt to predict 3D structure of the CD4 receptor-binding site of the HIV envelope protein gp120. The structure of this site has been constructed by the analysis of low-energy conformers of peptide T, an HIV reproduction inhibitor with amino acid sequence corresponding to the fragment Ala-Ser-Thr-Thr-Thr-Asn-Tyr-Thr of protein gp120, ensuring the interaction of virus with T4 lymphocytes. To do this, the following researches have been carried out: i) the spatial structure models of peptide T and similar fragment 4-11 of an analogues of vasoactive intestinal peptide have been modeled by the restrained molecular mechanics method developed earlier, ii) conformational parameters of these models have been compared to geometrical characteristics of homologous segments of unrelated proteins with known spatial structures. The following major conclusions have been made based on the comparative analysis: i) the conformation of C-terminal fragment Thr-Thr-Asn-Tyr-Thr of peptide T, responsible for the biological activity of the molecule, does not undergo the essential distortions while embedding into the peptide chains of unrelated proteins; ii) this conformation, that is realized in isolated molecule and includes two consecutive reverse turns of the polypeptide chain, adequately describes the main conformational features of an appropriate site of the HIV protein gp120; iii) the fragment Ala-Ser-Thr-Thr-Thr-Asn-Tyr-Thr of protein gp120 accepts one of six spatial forms which are characteristic for peptide T.

Binding Sites↗
PubMed1998

HIV envelope protein gp120 induces neuropeptide Y receptor-mediated proliferation of vascular smooth muscle cells: relevance to AIDS cardiovascular pathogenesis.

Hyperplasia of vascular smooth muscle cells (VSMCs) occurs during HIV infection, part of a spectrum of HIV-mediated cardiovascular and microvascular pathologies. These changes are not due to direct viral infection but may involve the receptor-mediated action of viral proteins, such as the envelope protein gp120. We sought to identify gp120 receptors which might mediate the vascular smooth muscle cell hyperplasia present in HIV infection. A homology between neuropeptide Y (NPY) and the previously identified receptor-active V2-region of gp120 defined by an octapeptide sequence (Peptide T) related to VIP was noted. Since NPY is mitogenic for VSMCs we therefore determined whether gp120 shares this activity. Rat aortic VSMCs were treated for 24 h with human (h)NPY and gp120 in the presence of 0.5% serum to measure [3H]thymidine incorporation, an index of cell proliferation. NPY increased [3H]thymidine incorporation by 80% after a 24-h treatment in a bimodal fashion, with peak effects at 10(-10) M and 10(-8) M. Gp120 was an even more potent mitogen for VSMCs with peak activity occurring at 10(-12) M. Peptide T was equipotent with gp120, and slightly less efficacious, suggesting that this domain may mediate gp120 effects on VSMCs. When combined, gp120 and NPY acted to antagonize one another, lowering DNA synthesis to basal levels. The profile of pharmacologic inhibition supports a role for NPY receptors since antagonists of Y1 and Y2 subtypes substantially or completely inhibited gp120-mediated VSMC proliferation. This is the first demonstration of the proliferative effects of HIV viral protein gp120 on VSMCs. The effect appears to be mediated via gp120 sequences related to VIP, peptide T, and NPY. These ligands may be competitive inhibitors of binding or gp120 processing. Novel treatments may emerge based upon VIP and NPY receptor antagonists if further work substantiates a role for gp120 in the vascular abnormalities of AIDS.

Amino Acid Sequence↗
PubMed1988

Inhibition of CD4+ T cell function by the HIV envelope protein, gp120.

The CD4 molecule is functionally involved in the class II MHC-restricted T cell response to Ag. CD4 is also the receptor for HIV-1, the major etiologic agent of AIDS. We have assessed whether the interaction of the HIV-1 envelope protein with the CD4 molecule might interfere with the normal function of CD4, thereby contributing to the immunosuppression observed after HIV infection. Using a murine T cell hybridoma which expresses the human CD4 protein and exhibits a CD4-dependent response to Ag, we demonstrate that the HIV envelope protein gp120 can specifically inhibit this response.

Animals↗
PubMed1995

The HIV envelope protein gp120 is toxic to human brain-cell cultures through the induction of interleukin-6 and tumor necrosis factor-alpha.

OBJECTIVE: To investigate the induction of cytokines as a possible mechanism for the neurotoxicity of the HIV-1 envelope protein gp120. DESIGN: The gp120 protein was tested directly on primary human brain cultures to examine its ability to induce cytokines and its neurotoxicity on human neural cells because gp120 is known to be toxic to rodent ganglion cultures, and neural cells such as astrocytes and microglia produce cytokines when stimulated. METHODS: Primary cultures of human brain cell aggregates, astrocytes and macrophages were exposed to HIV-1 recombinant (r) gp120SF2. Induction of cytokines was assayed by enzyme-linked immunosorbent assay (ELISA) and reverse transcriptase polymerase chain reaction (RT-PCR); neurotoxicity of rgp120SF2 and interleukin (IL)-6 on human brain cultures was examined by electron microscopy. RESULTS: ELISA and RT-PCR studies revealed that rgp120SF2 induced IL-6 and tumor necrosis factor (TNF)-alpha in brain cultures; IL-6 could also be induced by TNF-alpha added to brain cultures. Both IL-6 and TNF-alpha were upregulated in astrocytes and macrophage cultures on rgp120SF2 treatment. Ultrastructural studies demonstrated that IL-6 treatment for 72 h induced large cytoplasmic vacuoles in neural cells with morphology consistent with neurons; rgp120SF2 treatment for 7 days resulted in chromatin condensation along the inner margins of nuclear envelopes of neural cells. CONCLUSIONS: Our results demonstrated that HIV-1 rgp120SF2 can upregulate at least two known neurotoxic cytokines, IL-6 and TNF-alpha, which may injure neural cells and contribute to the neuropathology observed in AIDS dementia patients.

Astrocytes↗
PubMed2001

The potent anti-HIV protein cyanovirin-N contains two novel carbohydrate binding sites that selectively bind to Man(8) D1D3 and Man(9) with nanomolar affinity: implications for binding to the HIV envelope protein gp120.

Cyanovirin-N (CVN) is a monomeric 11 kDa cyanobacterial protein that potently inactivates diverse strains of human immunodeficiency virus (HIV) at the level of cell fusion by virtue of high affinity interactions with the surface envelope glycoprotein gp120. Several lines of evidence have suggested that CVN-gp120 interactions are in part mediated by N-linked complex carbohydrates present on gp120, but experimental evidence has been lacking. To this end we screened a comprehensive panel of carbohydrates which represent structurally the N-linked carbohydrates found on gp120 for their ability to inhibit the fusion-blocking activity of CVN in a quantitative HIV-1 envelope-mediated cell fusion assay. Our results show that CVN specifically recognizes with nanomolar affinity Man(9)GlcNAc(2) and the D1D3 isomer of Man(8)GlcNAc(2). Nonlinear least squares best fitting of titration data generated using the cell fusion assay show that CVN binds to gp120 with an equilibrium association constant (K(a)) of 2.4 (+/- 0.1) x 10(7) M(-1) and an apparent stoichiometry of 2 equiv of CVN per gp120, Man(8)GlcNAc(2) D1D3 acts as a divalent ligand (2 CVN:1 Man(8)) with a K(a) of 5.4 (+/- 0.5) x 10(7) M(-1), and Man(9)GlcNAc(2) functions as a trivalent ligand (3 CVN:1 Man(9)) with a K(a) of 1.3 (+/- 0.3) x 10(8) M(-1). Isothermal titration calorimetry experiments of CVN binding to Man(9)GlcNAc(2) at micromolar concentrations confirmed the nanomolar affinity (K(a) = 1.5 (+/- 0.9) x 10(8) M(-1)), and the fitted data indicated a stoichiometry equal to approximately one (1 Man(9):1 CVN). The 1:1 stoichiometry at micromolar concentrations suggested that CVN has not only a high affinity binding site-relevant to the studies at nM concentrations-but a lower affinity site as well that facilitates cross-linking of CVN-oligomannose at micromolar concentrations or higher. The specificity of CVN for Man(8) D1D3 and Man(9) over the D1D2 isomer of Man(8) indicated that the minimum structure required for high affinity binding comprises Manalpha1 --> 2Manalpha. By following the (1)H-(15)N correlation spectrum of (15)N-labeled CVN upon titration with this disaccharide, we unambiguously demonstrate that CVN recognizes and binds to the disaccharide Manalpha1 --> 2Manalpha via two distinct binding sites of differing affinities located on opposite ends of the protein. The high affinity site has a K(a) of 7.2 (+/- 4) x 10(6) M(-1) and the low affinity site a K(a) of 6.8 (+/- 4) x 10(5) M(-1) as determined by isothermal titration calorimetry. Mapped surfaces of the carbohydrate binding sites are presented, and implications for binding to gp120 are discussed.

Anti-HIV Agents↗
PubMed1998

The HIV envelope protein gp120 in the nervous system: interactions with nitric oxide, interleukin-1beta and nerve growth factor signalling, with pathological implications in vivo and in vitro.

The neuronal loss often described at post-mortem in the brain neocortex of patients suffering from AIDS has been proposed to be responsible for the development of the AIDS dementia complex. Neuroinvasive strains of the HIV virus infect macrophages, microglial cells, and multinucleated giant cells, but not neurones. Processing of the virus by cells of the myelomonocytic lineage yields viral products known to initiate a complex network of events that may lead to the death of neurones and to the development of AIDS-associated neurological syndrome. The HIV-1 coat protein gp120, in particular, has been proposed as a likely etiologic agent of the described neuronal loss because it causes the death of neurones in culture. More recently, it has been shown that brain cortical cell death caused in rats by intracerebroventricular injection of gp120 occurs via apoptosis. This observation broadens our knowledge of the pathophysiology of the reported neuronal cell loss and opens a new avenue of experimental research for the development of novel therapeutic strategies for the treatment of patients suffering from AIDS-associated neurological syndrome.

AIDS Dementia Complex↗
PubMed1992

Learning impairment following intracerebral administration of the HIV envelope protein gp120 or a VIP antagonist.

The external envelope glycoprotein (gp120) of the human immunodeficiency virus (HIV) has been shown to be toxic to neurons in culture. To further investigate the neurological effects of gp120, the involvement of this protein with the acquisition of spatial discrimination was assessed. Both native and recombinant gp120 were administered into the cerebral ventricles of adult rats and performance was evaluated in the Morris swim maze. Gp120 treatment retarded acquisition after daily administration of 12 ng. The specificity of this impairment was demonstrated in that the performance of animals given the same amount of gp160 from recombinant baculovirus was not different from animals given saline. Vasoactive intestinal peptide (VIP) has been shown to block gp120-induced neurotoxicity in culture and a VIP receptor antagonist has displayed toxic properties to neurons in culture. We show here that this antagonist, which competitively inhibits VIP binding and blocks VIP-mediated functions in cell cultures from the CNS, also produced an impairment of performance. This retardation was attenuated by cotreatment with VIP, supporting the specificity of the observed impairment. Thus, gp120 and the VIP antagonist produced similar retardation of spatial discrimination, suggesting that both may impair memory for spatially related stimulus control.

Animals↗
PubMed2001

Amelioration of neurotoxic effects of HIV envelope protein gp120 by fibroblast growth factor: a strategy for neuroprotection.

Approximately two thirds of patients with human immunodeficiency virus encephalitis (HIVE) show cognitive impairment and neurodegeneration, while one third are cognitively unimpaired and their neuronal populations are preserved. Thus, it is possible that these individuals might have the capacity to produce neurotrophic factors capable of protecting neurons against the deleterious effects of HIV. In this context, the main objective of this study was to determine whether fibroblast growth factor 1 (FGF1) is protective against HIV. For this purpose levels of FGF1 immunoreactivity were determined in the frontal cortex of 35 AIDS cases subdivided into 4 groups according to the presence or absence of HIVE and neurodegeneration. In cases without both HIVE and neurodegeneration, mild to moderate levels of FGFI immunoreactivity were observed in pyramidal neurons, while in cases with HIVE but without neurodegeneration, levels were significiantly elevated. In contrast, individuals with both HIVE and neurodegeneration showed low levels of neuronal FGF1 immunoreactivity. Furthermore, studies in primary human neuronal cultures treated with the HIV envelope protein-gp120 in the presence or absence of FGF1 showed that FGF1 was protective against gpl20 neurotoxicity in a dose-dependent manner. Taken together, these results support the notion that upregulation of certain neurotrophic factors, such as FGF1, might protect the central nervous system from the neurotoxic effects of HIV.

AIDS Dementia Complex↗
PubMed1996

Conformational preferences of a chimeric peptide HIV-1 immunogen from the C4-V3 domains of gp120 envelope protein of HIV-1 CAN0A based on solution NMR: comparison to a related immunogenic peptide from HIV-1 RF.

A critical problem to overcome on HIV vaccine design is the variability among HIV strains. One strategy to solve this problem is the construction of multicomponent immunogens reflective of common HIV motifs. Currently, it is not known if these motifs should be based primarily on amino acid sequence or higher-order structure of the viral proteins of a combination of the two. In this paper, we report NMR-derived solution conformations for a sympathetic peptide taken from the C4 and V3 domains of HIV-1 CAN0A gp120 envelope protein. This peptide, designated T1-SP10CAN0(A), is compared to a recently reported C4-V3 peptide. T1-SP10RF(A) from the HIV-1 RF strain [de Lorimier et al. (1994) Biochemistry 33, 2055-2062], in terms of conformational features and immune responses in mice [Haynes et al. (1995) AIDS Res. Hum. Retroviruses 11, 211-221]. The T1 segment of 16 amino acids from the gp120 C4 domain is identical in both peptides and exhibits nascent helical character. The SP10 region, taken from the gp120 V3 loop, differs from that of T1-SP10RF(A) in both sequence and conformations. A reverse turn is observed at the conserved GPGX sequence. The rest of the Sp10 domain is extended with the exception of the last three residues which show evidence for a helical arrangement. Modeling of the turn region of the T1-SP10CAN0(A) peptide shows exposure of a continuous apolar stretch of side chains similar to that reported in the crystal structure of a V3 peptide from HIV-1 MN complexed with a monoclonal antibody [Rini et al. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 6325-6329]. this hydrophobic patch is interrupted by a charged Lys residue in the T1-SP10RF(A) peptide. This observation suggests that the HIV-1 CAN0A and HIV-1 RF C4-V3 peptides can induce widely different anti-HIV antibodies. consistent with immunogenic results.

Amino Acid Sequence↗
PubMed1992

7-Chlorokynurenate Ameliorates Neuronal Injury Mediated by HIV Envelope Protein gp120 in Rodent Retinal Cultures.

Prior studies with in vitro model systems have suggested that at least part of the neurological manifestations of AIDS may stem from neuronal injury involving the HIV-1 coat protein gp120. This form of neuronal damage is most probably mediated indirectly by a complex set of cellular interactions among macrophages, astrocytes, and neurons, resulting in a final common pathway of overstimulation of N-methyl-d-aspartate (NMDA) receptors. We studied the neuroprotective effect from gp120-induced neuronal injury of an antagonist of the glycine site of the NMDA receptor, 7-chlorokynurenate. In identified rat retinal ganglion cells in culture, we found that 50 microM 7-chlorokynurenate significantly abrogated the injury engendered by 20 pM gp120. Addition of 300 microM exogenous glycine prevented this protective effect of 50 microM 7-chlorokynurenate. These data suggest that glycine site antagonists of the NMDA receptor may have therapeutic potential for ameliorating neuronal damage associated with gp120.

Journal Article↗
PubMed1999

HIV-1 gp120 envelope protein modulates proliferation of human glomerular epithelial cells.

Glomerular epithelial cells (GEC) have been demonstrated to undergo morphological alterations in human immunodeficiency virus (HIV)-associated focal glomerulosclerosis. In the present study, we evaluated the effect of HIV-1 gp120 envelope protein on the growth of cultured human (H) GEC. gp120 protein enhanced (P < 0.001) the proliferation of HGEC at lower concentrations. The mitogenic effect of gp120 protein on HGEC was further confirmed by enhanced accumulation of proliferating nuclear cell antigen (PCNA) by gp120 protein-treated cells, as compared with control cells. On the contrary, gp120 protein at higher concentrations suppressed (P < 0. 001) the growth of HGEC. To evaluate the mechanism of gp120 protein-induced HGEC growth suppression, we examined the effect of gp120 protein on HGEC apoptosis. gp120 protein at higher concentrations promoted the apoptosis of HGEC. At higher concentrations, gp120 protein also enhanced DNA fragmentation of HGEC. Anti-gp120 antibody attenuated the proliferative as well as the apoptotic effects of gp120 protein on HGEC. Because protein kinase C as well as tyrosine kinase inhibitors partially inhibited gp120-induced proliferation, gp120 appears to be activating both the protein kinase C and tyrosine kinase pathways. In addition, gp120 protein at lower concentrations enhanced mRNA expression of c-fos and at higher concentrations promoted mRNA expression of c-jun. We conclude that gp120 has a bimodal effect on proliferation of HGEC. This effect may be mediated through the activation of early growth genes.

Apoptosis↗