The Glycan Shield of HIV Is Predominantly Oligomannose Independently of Production System or Viral Clade

The N-linked oligomannose glycans of HIV gp120 are a target for both microbicide and vaccine design. The extent of cross-clade conservation of HIV oligomannose glycans is therefore a critical consideration for the development of HIV prophylaxes. We measured the oligomannose content of virion-associated gp120 from primary virus from PBMCs for a range of viral isolates and showed cross-clade elevation (62–79%) of these glycans relative to recombinant, monomeric gp120 (∼30%). We also confirmed that pseudoviral production systems can give rise to notably elevated gp120 oligomannose levels (∼98%), compared to gp120 derived from a single-plasmid viral system using the HIVLAI backbone (56%). This study highlights differences in glycosylation between virion-associated and recombinant gp120

Type I Interferons in NeuroHIV

Infection with Human Immunodeficiency Virus (HIV)-1 continues to cause HIV-associated neurocognitive disorders despite combined antiretroviral therapy. Interferons (IFNs) are important for any antiviral immune response, but the lasting production of IFNα causes exhaustive activation leading eventually to progression to AIDS. Expression of IFNα in the HIV-exposed central nervous system has been linked to cognitive impairment and inflammatory neuropathology. In contrast, IFNβ exerts anti-inflammatory effects, appears to control, at least temporarily, lentiviral infection in the brain and provides neuroprotection. The dichotomy of type I IFN effects on HIV-1 infection and the associated brain injury will be discussed in this review, because the underlying mechanisms require further investigation to allow harnessing these innate immune factors for therapeutic purposes

Transgenic mice expressing HIV-1 envelope protein gp120 in the brain as an animal model in neuroAIDS research

HIV-1 infection causes injury to the central nervous system (CNS) and is often associated with neurocognitive disorders. One model for brain damage seen in AIDS patients is the transgenic (tg) mouse expressing a soluble envelope protein gp120 of HIV-1 LAV in the brain in astrocytes under the control of the promoter of glial fibrillary acidic protein. These GFAP-gp120tg mice manifest several key neuropathological features observed in AIDS brains, such as decreased synaptic and dendritic density, increased numbers of activated microglia, and pronounced astrocytosis. Several recent studies show that brains of GFAP-gp120tg mice and neurocognitively impaired HIV patients share also a significant number of differentially regulated genes, activation of innate immunity and other cellular signaling pathways, disturbed neurogenesis, and learning deficits. These findings support the continued relevance of the GFAP-gp120tg mouse as a useful model to investigate neurodegenerative mechanisms and develop therapeutic strategies to mitigate the consequences associated with HIV infection of the CNS, neuroAIDS, and HAND

Combination of methamphetamine and HIV-1 gp120 causes distinct long-term alterations of behavior, gene expression, and injury in the central nervous system

Methamphetamine (METH) abuse is frequent in individuals infected with human immunodeficiency virus type-1 (HIV-1) and is suspected to aggravate HIV-associated neurocognitive disorders (HAND). METH is a psychostimulant that compromises several neurotransmitter systems and HIV proteins trigger neuronal injury but the combined effects of viral infection and METH abuse are incompletely understood. In this study we treated transgenic mice expressing the HIV envelope protein gp120 in the brain (HIV-1 gp120tg) at 3-4 months of age with an escalating-dose, multiple-binge METH regimen. The long-term effects were analyzed after 6-7 months of drug abstinence employing behavioral tests and analysis of neuropathology, electrophysiology and gene expression. Behavioral testing showed that both HIV-1 gp120tg and WT animals treated with METH displayed impaired learning and memory. Neuropathological analysis revealed that METH similar to HIV-1 gp120 caused a significant loss of neuronal dendrites and pre-synaptic terminals in hippocampus and cerebral cortex of WT animals. Electrophysiological studies in hippocampal slices showed that METH exposed HIV-1 gp120tg animals displayed reduced post-tetanic potentiation, whereas both gp120 expression and METH lead to reduced long-term potentiation. A quantitative reverse transcription-polymerase chain reaction array showed that gp120 expression, METH and their combination each caused a significant dysregulation of specific components of GABAergic and glutamatergic neurotransmission systems, providing a possible mechanism for synaptic dysfunction and behavioral impairment. In conclusion, both HIV-1 gp120 and METH caused lasting behavioral impairment in association with neuropathology and altered gene expression. However, combined METH exposure and HIV-1 gp120 expression resulted in the most pronounced, long lasting pre- and post-synaptic alterations coinciding with impaired learning and memory

Abundances of released N-linked glycans obtained from recombinant (monomeric), pseudoviral, and viral gp120^†.

<p>†Abundances obtained for desialylated N-linked glycans released from gp120 described in this study. Values were obtained from data presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023521#pone-0023521-g001" target="_blank">Figure 1</a> and Doores <i>et al.</i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023521#pone.0023521-Doores1" target="_blank">[11]</a>.</p><p>‡Values represent the increase in oligomannose population (Man_5-9GlNAc₂) for pseudoviral and viral gp120 compared to monomeric, recombinant gp120.</p

Comparison of recombinant, pseudoviral and viral gp120.

<p>MALDI-TOF MS analyses of released desialylated N-linked glycans ([M+Na]⁺ ions) from: (A) recombinant monomeric gp120_JRCSF expressed in HEK 293T cells; (B, C and D) respectively gp160_JRCSF, gp120_JRCSF and soluble, non-virion associated envelope gp120_JRCSF isolated from pseudoviral particle preparations generated by transfection of HEK 293T cells with the pSVIII-JRCSF and pSG3Δenv plasmids at a ratio of 1∶10; (E) gp120_JRCSF isolated from replication competent viral particles generated by transfection of HEK 293T cells with pLAI-JRCSF env molecular clone; (F, G and H) respectively gp120_92RW009, gp120_JRCSF and gp120_93IN905 isolated from virus obtained by infection of human PBMCs. Symbols used for the structural formulae in this and subsequent figures: <b>⋄</b>  =  Gal, ▪  =  GlcNAc, ○  =  Man,  =  Fuc <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023521#pone.0023521-Harvey1" target="_blank">[46]</a>. The linkage position is shown by the angle of the lines linking the sugar residues (vertical line  = 2-link, forward slash  = 3-link, horizontal line  = 4-link, back slash  = 6-link). Anomericity is indicated by full lines for β-bonds and broken lines for α-bonds <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023521#pone.0023521-Harvey1" target="_blank">[46]</a>. The oligomannose series are highlighted.</p

Multiple divergences of gp120 glycosylation from host cell glycosylation.

<p>Following removal of terminal α-linked glucose residues in the ER, folded glycoproteins contain exclusively oligomannose glycans. During transit through the ER, intermediate compartment (IC) and <i>cis</i>-Golgi apparatus, Manα1→2Man termini are removed by ER Mannosidase I and Golgi Mannosidases A–C to yield Man₅GlcNAc₂. However, the oligomannose cluster intrinsic to monomeric gp120 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023521#pone.0023521-Zhu1" target="_blank">[5]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023521#pone.0023521-Scanlan2" target="_blank">[14]</a> limits glycan processing on both monomeric and oligomeric gp120 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023521#pone.0023521-Doores1" target="_blank">[11]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023521#pone.0023521-Eggink1" target="_blank">[30]</a>. The steric consequences of trimerisation further limit Manα1→2Man trimming <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023521#pone.0023521-Eggink1" target="_blank">[30]</a> leading to an additional ‘trimer-associated’ population of Man_5–9GlcNAc₂. The exposed Man₅GlcNAc₂ glycans on gp120 that passage through the full extent of the Golgi apparatus and <i>trans</i> Golgi network (TGN) to the plasma membrane (PM) are processed by GnT I and subsequent enzymes to form complex-type glycans. However, envelope glycoprotein that does not follow this route to the PM is characterized by an elevated abundance of Man₅GlcNAc₂ (and closely resembles gp120 expressed in GnT I-deficient cells <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023521#pone.0023521-Doores1" target="_blank">[11]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023521#pone.0023521-Eggink1" target="_blank">[30]</a>), and reduced furin cleavage. Thus the intrinsic mannose patch, which includes the 2G12 epitope, persists from the earliest stages of glycan processing whilst other elements of the glycan shield exhibit variably processed glycans depending on oligomerization state and, at least in the case of pseudoviral gp160/gp120, cellular trafficking.</p

Combination of methamphetamine and HIV-1 gp120 causes distinct long-term alterations of behavior, gene expression, and injury in the central nervous system

Methamphetamine (METH) abuse is frequent in individuals infected with human immunodeficiency virus type-1 (HIV-1) and is suspected to aggravate HIV-associated neurocognitive disorders (HAND). METH is a psychostimulant that compromises several neurotransmitter systems and HIV proteins trigger neuronal injury but the combined effects of viral infection and METH abuse are incompletely understood. In this study we treated transgenic mice expressing the HIV envelope protein gp120 in the brain (HIV/gp120tg) at 3–4 months of age with an escalating-dose, multiple-binge METH regimen. The long-term effects were analyzed after 6–7 months of drug abstinence employing behavioral tests and analysis of neuropathology, electrophysiology and gene expression. Behavioral testing showed that both HIV/gp120tg and WT animals treated with METH displayed impaired learning and memory. Neuropathological analysis revealed that METH similar to HIV/gp120 caused a significant loss of neuronal dendrites and pre-synaptic terminals in hippocampus and cerebral cortex of WT animals. Electrophysiological studies in hippocampal slices showed that METH exposed HIV/gp120tg animals displayed reduced post-tetanic potentiation, whereas both gp120 expression and METH lead to reduced long-term potentiation. A quantitative reverse transcription-polymerase chain reaction array showed that gp120 expression, METH and their combination each caused a significant dysregulation of specific components of GABAergic and glutamatergic neurotransmission systems, providing a possible mechanism for synaptic dysfunction and behavioral impairment. In conclusion, both HIV-1/gp120 and METH caused lasting behavioral impairment in association with neuropathology and altered gene expression. However, combined METH exposure and HIV-1/gp120 expression resulted in the most pronounced, long lasting pre-and post-synaptic alterations coinciding with impaired learning and memory