scholarly journals Loss of a Single N-Linked Glycan Allows CD4-Independent Human Immunodeficiency Virus Type 1 Infection by Altering the Position of the gp120 V1/V2 Variable Loops

2001 ◽  
Vol 75 (7) ◽  
pp. 3435-3443 ◽  
Author(s):  
Peter Kolchinsky ◽  
Enko Kiprilov ◽  
Peter Bartley ◽  
Roee Rubinstein ◽  
Joseph Sodroski
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Glycosylation Site ◽  
Ccr5 Chemokine Receptor ◽  
Gp120 Binding ◽  
Immunodeficiency Virus ◽  
Variable Loops ◽  
Hiv 1

ABSTRACT The gp120 envelope glycoprotein of primary human immunodeficiency virus type 1 (HIV-1) promotes virus entry by sequentially binding CD4 and the CCR5 chemokine receptor on the target cell. Previously, we adapted a primary HIV-1 isolate, ADA, to replicate in CD4-negative canine cells expressing human CCR5. The gp120 changes responsible for CD4-independent replication were limited to the V2 loop-V1/V2 stem. Here we show that elimination of a single glycosylation site at asparagine 197 in the V1/V2 stem is sufficient for CD4-independent gp120 binding to CCR5 and for HIV-1 entry into CD4-negative cells expressing CCR5. Deletion of the V1/V2 loops also allowed CD4-independent viral entry and gp120 binding to CCR5. The binding of the wild-type ADA gp120 to CCR5 was less dependent upon CD4 at 4°C than at 37°C. In the absence of the V1/V2 loops, neither removal of the N-linked carbohydrate at asparagine 197 nor lowering of the temperature increased the CD4-independent phenotypes. A CCR5-binding conformation of gp120, achieved by CD4 interaction or by modification of temperature, glycosylation, or variable loops, was preferentially recognized by the monoclonal antibody 48d. These results suggest that the CCR5-binding region of gp120 is occluded by the V1/V2 variable loops, the position of which can be modulated by temperature, CD4 binding, or an N-linked glycan in the V1/V2 stem.

scholarly journals A rat CD4 mutant containing the gp120-binding site mediates human immunodeficiency virus type 1 infection.

1993 ◽  
Vol 177 (4) ◽  
pp. 949-954 ◽  
Author(s):  
J H Simon ◽  
C Somoza ◽  
G A Schockmel ◽  
M Collin ◽  
S J Davis ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Syncytium Formation ◽  
Gp120 Binding ◽  
Ability To Act ◽  
Immunodeficiency Virus ◽  
Inhibitory Antibodies ◽  
Hiv 1

CD4 is the primary receptor for the human immunodeficiency virus type 1 (HIV-1). Early mutational studies implicated a number of residues of CD4, centered in the region 41-59, in binding to gp120. However, further mutational analyses, together with studies using inhibitory antibodies or CD4-derived peptides, have suggested that other regions of CD4 are also involved in binding or postbinding events during infection. To resolve these ambiguities, we used rat CD4 mutants in which particular regions were replaced with the corresponding sequence of human CD4. We have previously shown that some of these are able to bind HIV-1 gp120, and here we test their ability to act as functional receptors. We find that the presence of human CD4 residues 33-62 is enough to confer efficient receptor function to rat CD4, and we conclude that it is unlikely that regions of CD4 outside this sequence are involved in specific interactions with HIV-1 during either infection or syncytium formation.

scholarly journals Characterization of DC-SIGN/R Interaction with Human Immunodeficiency Virus Type 1 gp120 and ICAM Molecules Favors the Receptor's Role as an Antigen-Capturing Rather than an Adhesion Receptor

2005 ◽  
Vol 79 (8) ◽  
pp. 4589-4598 ◽  
Author(s):  
Greg A. Snyder ◽  
Jennifer Ford ◽  
Parizad Torabi-Parizi ◽  
James A. Arthos ◽  
Peter Schuck ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Cell Surface ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Trojan Horse ◽  
Gp120 Binding ◽  
Immunodeficiency Virus ◽  
Cell Surface Glycoproteins ◽  
Hiv 1

ABSTRACT The dendritic cell (DC)-specific intercellular adhesion molecule 3 (ICAM-3)-grabbing nonintegrin binding receptor (DC-SIGN) was shown to bind human immunodeficiency virus type 1 (HIV-1) viral envelope protein gp120 and proposed to function as a Trojan horse to enhance trans-virus infection to host T cells. To better understand the mechanism by which DC-SIGN and DC-SIGNR selectively bind HIV-1 gp120, we constructed a series of deletion mutations in the repeat regions of both receptors. Different truncated receptors exist in different oligomeric forms. The carbohydrate binding domain without any repeats was monomeric, whereas the full extracellular receptors existed as tetramers. All reconstituted receptors retained their ability to bind gp120. The dissociation constant, however, differed drastically from micromolar values for the monomeric receptors to nanomolar values for the tetrameric receptors, suggesting that the repeat region of these receptors contributes to the avidity of gp120 binding. Such oligomerization may provide a mechanism for the receptor to selectively recognize pathogens containing multiple high-mannose-concentration carbohydrates. In contrast, the receptors bound to ICAMs with submicromolar affinities that are similar to those of two nonspecific cell surface glycoproteins, FcγRIIb and FcγRIII, and the oligomerization of DC-SIGNR resulted in no increase in binding affinity to ICAM-3. These findings suggest that DC-SIGN may not discriminate other cell surface glycoproteins from ICAM-3 binding. The pH dependence in DC-SIGN binding to gp120 showed that the receptor retained high-affinity gp120 binding at neutral pH but lost gp120 binding at pH 5, suggesting a release mechanism of HIV in the acidic endosomal compartment by DC-SIGN. Our work contradicts the function of DC-SIGN as a Trojan horse to facilitate HIV-1 infection; rather, it supports the function of DC-SIGN/R (a designation referring to both DC-SIGN and DC-SIGNR) as an antigen-capturing receptor.

scholarly journals Human Immunodeficiency Virus Type 1 Coreceptor Switching: V1/V2 Gain-of-Fitness Mutations Compensate for V3 Loss-of-Fitness Mutations

2006 ◽  
Vol 80 (2) ◽  
pp. 750-758 ◽  
Author(s):  
C. Pastore ◽  
R. Nedellec ◽  
A. Ramos ◽  
S. Pontow ◽  
L. Ratner ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Target Cells ◽  
Immunodeficiency Virus ◽  
Variable Loops ◽  
The Right ◽  
Virus Survival ◽  
Hiv 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) entry into target cells is mediated by the virus envelope binding to CD4 and the conformationally altered envelope subsequently binding to one of two chemokine receptors. HIV-1 envelope glycoprotein (gp120) has five variable loops, of which three (V1/V2 and V3) influence the binding of either CCR5 or CXCR4, the two primary coreceptors for virus entry. Minimal sequence changes in V3 are sufficient for changing coreceptor use from CCR5 to CXCR4 in some HIV-1 isolates, but more commonly additional mutations in V1/V2 are observed during coreceptor switching. We have modeled coreceptor switching by introducing most possible combinations of mutations in the variable loops that distinguish a previously identified group of CCR5- and CXCR4-using viruses. We found that V3 mutations entail high risk, ranging from major loss of entry fitness to lethality. Mutations in or near V1/V2 were able to compensate for the deleterious V3 mutations and may need to precede V3 mutations to permit virus survival. V1/V2 mutations in the absence of V3 mutations often increased the capacity of virus to utilize CCR5 but were unable to confer CXCR4 use. V3 mutations were thus necessary but not sufficient for coreceptor switching, and V1/V2 mutations were necessary for virus survival. HIV-1 envelope sequence evolution from CCR5 to CXCR4 use is constrained by relatively frequent lethal mutations, deep fitness valleys, and requirements to make the right amino acid substitution in the right place at the right time.

scholarly journals CCR5 use by human immunodeficiency virus type 1 is associated closely with the gp120 V3 loop N-linked glycosylation site

2006 ◽  
Vol 87 (3) ◽  
pp. 607-612 ◽  
Author(s):  
Peter Clevestig ◽  
Lotta Pramanik ◽  
Thomas Leitner ◽  
Anneka Ehrnst
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Prediction Models ◽  
Close Association ◽  
Glycosylation Site ◽  
V3 Loop ◽  
Immunodeficiency Virus ◽  
Hiv 1

Human immunodeficiency virus type 1 (HIV-1) enters cells through the chemokine receptors CCR5 (R5 virus) and/or CXCR4 (X4 virus). Loss of N-linked glycans and increased net charge of the third variable loop (V3) of the gp120 envelope glycoprotein have been observed to be important steps towards CXCR4 use. All reported sequences using CCR5 or CXCR4 exclusively, or using both, were gathered from the Los Alamos HIV Database and analysed with regard to the V3 N-linked glycosylation motifs (sequons) and charge. The V3 loop glycan had a sensitivity of 0·98 and a 0·92 positive predictive value in the context of CCR5 use. The difference from X4 was remarkable (P<10−12). Especially, the sequon motif NNT within the V3 loop was conserved in 99·2 % of the major clades. The results suggest a close association between the V3 loop glycan and CCR5 use and may provide new insight into HIV-1 tropism and help to improve phenotype-prediction models.

scholarly journals Adaptation of a CCR5-Using, Primary Human Immunodeficiency Virus Type 1 Isolate for CD4-Independent Replication

1999 ◽  
Vol 73 (10) ◽  
pp. 8120-8126 ◽  
Author(s):  
Peter Kolchinsky ◽  
Tajib Mirzabekov ◽  
Michael Farzan ◽  
Enko Kiprilov ◽  
Mark Cayabyab ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Chemokine Receptors ◽  
Ccr5 Chemokine Receptor ◽  
Major Function ◽  
Immunodeficiency Virus ◽  
Independent Replication ◽  
Hiv 1

ABSTRACT The gp120 envelope glycoprotein of the human immunodeficiency virus type 1 (HIV-1) promotes virus entry by sequentially binding CD4 and chemokine receptors on the target cell. Primary, clinical HIV-1 isolates require interaction with CD4 to allow gp120 to bind the CCR5 chemokine receptor efficiently. We adapted a primary HIV-1 isolate, ADA, to replicate in CD4-negative canine cells expressing human CCR5. The gp120 changes responsible for the adaptation were limited to alteration of glycosylation addition sites in the V2 loop–V1-V2 stem. The gp120 glycoproteins of the adapted viruses bound CCR5 directly, without prior interaction with CD4. Thus, a major function of CD4 binding in the entry of primary HIV-1 isolates can be bypassed by changes in the gp120 V1-V2 elements, which allow the envelope glycoproteins to assume a conformation competent for CCR5 binding.

scholarly journals Alanine Substitutions of Polar and Nonpolar Residues in the Amino-Terminal Domain of CCR5 Differently Impair Entry of Macrophage- and Dualtropic Isolates of Human Immunodeficiency Virus Type 1

1998 ◽  
Vol 72 (4) ◽  
pp. 3464-3468 ◽  
Author(s):  
Gwénaël E. E. Rabut ◽  
Jason A. Konner ◽  
Francis Kajumo ◽  
John P. Moore ◽  
Tatjana Dragic
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Amino Terminal ◽  
Terminal Domain ◽  
Gp120 Binding ◽  
Immunodeficiency Virus ◽  
Amino Terminal Domain ◽  
Hiv 1

ABSTRACT Multiple extracellular domains of the CC-chemokine receptor CCR5 are important for its function as a human immunodeficiency virus type 1 (HIV-1) coreceptor. We have recently demonstrated by alanine scanning mutagenesis that the negatively charged residues in the CCR5 amino-terminal domain are essential for gp120 binding and coreceptor function. We have now extended our analysis of this domain to include most polar and nonpolar amino acids. Replacement of alanine with all four tyrosine residues and with serine-17 and cysteine-20 decrease or abolish gp120 binding and CCR5 coreceptor activity. Tyrosine-15 is essential for viral entry irrespective of the test isolate. Substitutions at some of the other positions impair the entry of dualtropic HIV-1 isolates more than that of macrophagetropic ones.

scholarly journals Species-Specific Tropism Determinants in the Human Immunodeficiency Virus Type 1 Capsid

2004 ◽  
Vol 78 (11) ◽  
pp. 6005-6012 ◽  
Author(s):  
Theodora Hatziioannou ◽  
Simone Cowan ◽  
Uta K. von Schwedler ◽  
Wesley I. Sundquist ◽  
Paul D. Bieniasz
Keyword(s):  
Human Immunodeficiency Virus ◽  
Binding Site ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Restriction Factors ◽  
Immunodeficiency Virus ◽  
Variable Loops ◽  
Hiv 1 ◽  
Cypa Binding

ABSTRACT Retroviral tropism is determined in part by cellular restriction factors that block infection by targeting the incoming viral capsid. Indeed, human immunodeficiency virus type 1 (HIV-1) infection of many nonhuman primate cells is inhibited by one such factor, termed Lv1. In contrast, a restriction factor in humans, termed Ref1, does not inhibit HIV-1 infection unless nonnatural mutations are introduced into the HIV-1 capsid protein (CA). Here, we examined the infectivity of a panel of mutant HIV-1 strains carrying substitutions in the N-terminal CA domain in cells that exhibit restriction attributable to Lv1 or Ref1. Manipulation of HIV-1 CA could alter HIV-1 tropism, and several mutations were identified that increased or decreased HIV-1 infectivity in a target-cell-specific manner. Many residues that affected HIV-1 tropism were located in the three variable loops that lie on the outer surface of the modeled HIV-1 conical capsid. Some tropism determinants, including the CypA binding site, coincided with residues whose mutation conferred on HIV-1 CA the ability to saturate Ref1 in human cells. Notably, a mutation that reverses the infectivity defect in human cells induced by CypA binding site mutation inhibits recognition by Ref1. Overall, these findings demonstrate that exposed variable loops in CA and a partial CypA “coat” can modulate restriction and HIV-1 tropism and suggest a model in which the exposed surface of the incoming retroviral capsid is the target for inhibition by host cell-specific restriction factors.

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