scholarly journals Nef-Mediated Resistance of Human Immunodeficiency Virus Type 1 to Antiviral Cytotoxic T Lymphocytes

2002 ◽  
Vol 76 (4) ◽  
pp. 1626-1631 ◽  
Author(s):  
Otto O. Yang ◽  
Phuong Thi Nguyen ◽  
Spyros A. Kalams ◽  
Tanya Dorfman ◽  
Heinrich G. Göttlinger ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Major Histocompatibility Complex ◽  
Major Histocompatibility Complex Class ◽  
Cytotoxic T Lymphocytes ◽  
Complex Class ◽  
Accessory Gene ◽  
Histocompatibility Complex ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Although Nef has been proposed to effect the escape of human immunodeficiency virus type 1 (HIV-1) from cytotoxic T lymphocytes (CTL) through downmodulation of major histocompatibility complex class I molecules, little direct data have been presented previously to support this hypothesis. By comparing nef-competent and nef-deleted HIV-1 strains in an in vitro coculture system, we demonstrate that the presence of this viral accessory gene leads to impairment of the ability of HIV-1-specific CTL clones to suppress viral replication. Furthermore, inhibition by genetically modified CTL that do not require major histocompatibility complex class I-presented antigen (expressing the CD4 T-cell receptor [TCR] ζ-chain hybrid receptor) is similar for both nef-competent and -deleted strains, indicating that Nef does not impair the effector functions of CTL but acts at the level of TCR triggering. In contrast, we note that another accessory gene, vpr, does not induce resistance of HIV-1 to suppression by CTL clones. We conclude that Nef (and not Vpr) contributes to functional HIV-1 immune evasion and that this effect is mediated by diminished antigen presentation to CTL.

scholarly journals CD4 and Major Histocompatibility Complex Class I Downregulation by the Human Immunodeficiency Virus Type 1 Nef Protein in Pediatric AIDS Progression

2003 ◽  
Vol 77 (21) ◽  
pp. 11536-11545 ◽  
Author(s):  
Nicoletta Casartelli ◽  
Gigliola Di Matteo ◽  
Marina Potestà ◽  
Paolo Rossi ◽  
Margherita Doria
Keyword(s):  
Human Immunodeficiency Virus ◽  
Major Histocompatibility Complex ◽  
Cell Surface ◽  
Major Histocompatibility Complex Class ◽  
Complex Class ◽  
Mhc I ◽  
Histocompatibility Complex ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) nef gene is a crucial determinant in AIDS disease progression. Although several in vitro activities have been attributed to the Nef protein, identifying the one critical for in vivo pathogenicity remains elusive. In this study, we examined a large number of nef alleles derived at various time points from 13 perinatally infected children showing different progression rates: six nonprogressors (NPs), three slow progressors (SPs), and four rapid progressors (RPs). The patient-derived nef alleles were analyzed for their steady-state expression of a Nef protein, for their relative ability to downregulate cell surface expression of CD4 and major histocompatibility complex class I (MHC-I) and for their capacity to bind the clathrin adaptor AP-1 complex. We found that NP-derived nef alleles, compared to nef alleles isolated from SPs and RPs, had reduced CD4 and MHC-I downregulation activities. In contrast, SP- and RP-derived nef alleles did not differ and efficiently downregulated both CD4 and MHC-I. AP-1 binding was a conserved function of primary nef alleles not correlated with clinical progression. Defective Nef proteins from NPs, rather than sharing common specific changes in their sequences, accumulated various amino acid substitutions, mainly located outside the conserved domains previously associated with Nef biological properties. Our data indicate that Nef-mediated downregulation of cell surface CD4 and MHC-I significantly contributes to the expression of the pathogenic potential of HIV-1.

scholarly journals Human Immunodeficiency Virus Type 1 Nef Expression Prevents AP-2-Mediated Internalization of the Major Histocompatibility Complex Class II-Associated Invariant Chain

2008 ◽  
Vol 82 (17) ◽  
pp. 8373-8382 ◽  
Author(s):  
Hélène Toussaint ◽  
François-Xavier Gobert ◽  
Michael Schindler ◽  
Carina Banning ◽  
Patrycja Kozik ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Major Histocompatibility Complex ◽  
Major Histocompatibility Complex Class ◽  
Human Immunodeficiency Virus Type ◽  
Complex Class ◽  
Histocompatibility Complex ◽  
Chain Complexes ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT The lentiviral Nef protein has been studied extensively for its ability to induce the downregulation of several immunoreceptors on the surfaces of infected cells. However, Nef expression is unique in inducing highly effective upregulation of the major histocompatibility complex class II-associated chaperone invariant (Ii) chain complexes in different cell types. Under normal conditions, endocytosis of the Ii chain and other molecules, like the transferrin receptor and CD4, is rapid and AP-2 dependent. Human immunodeficiency virus type 1 (HIV-1) Nef expression strongly reduces the internalization of the Ii chain, enhances that of CD4, and does not modify transferrin uptake. The mutation of AP-2 binding motifs LL164 and DD174 in Nef leads to the inhibition of Ii chain upregulation. In AP-2-depleted cells, surface levels of the Ii chain are high and remain unmodified by Nef expression, further indicating that Nef regulates Ii chain internalization via the AP-2 pathway. Immunoprecipitation experiments revealed that the Ii chain can interact with Nef in a dileucine-dependent manner. Importantly, we have shown that Nef-induced CD4 downregulation and Ii chain upregulation are genetically distinguishable. We have identified natural nef alleles that have lost one of the two functions but not the other one. Moreover, we have characterized Nef mutant forms possessing a similar phenotype in the context of HIV-1 infection. Therefore, the Nef-induced accumulation of Ii chain complexes at the cell surface probably results from a complex mechanism leading to the impairment of AP-2-mediated endocytosis rather than from direct competition between Nef and the Ii chain for binding AP-2.

scholarly journals Direct Binding of Human Immunodeficiency Virus Type 1 Nef to the Major Histocompatibility Complex Class I (MHC-I) Cytoplasmic Tail Disrupts MHC-I Trafficking

2002 ◽  
Vol 76 (23) ◽  
pp. 12173-12184 ◽  
Author(s):  
Maya Williams ◽  
Jeremiah F. Roeth ◽  
Matthew R. Kasper ◽  
Rebekah I. Fleis ◽  
Chris G. Przybycin ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Major Histocompatibility Complex ◽  
Major Histocompatibility Complex Class ◽  
Human Immunodeficiency Virus Type ◽  
Cytoplasmic Tail ◽  
Complex Class ◽  
Mhc I ◽  
Histocompatibility Complex ◽  
Immunodeficiency Virus

ABSTRACT Nef, an essential pathogenic determinant for human immunodeficiency virus type 1, has multiple functions that include disruption of major histocompatibility complex class I molecules (MHC-I) and CD4 and CD28 cell surface expression. The effects of Nef on MHC-I have been shown to protect infected cells from cytotoxic T-lymphocyte recognition by downmodulation of a subset of MHC-I (HLA-A and -B). The remaining HLA-C and -E molecules prevent recognition by natural killer (NK) cells, which would otherwise lyse cells expressing small amounts of MHC-I. Specific amino acid residues in the MHC-I cytoplasmic tail confer sensitivity to Nef, but their function is unknown. Here we show that purified Nef binds directly to the HLA-A2 cytoplasmic tail in vitro and that Nef forms complexes with MHC-I that can be isolated from human cells. The interaction between Nef and MHC-I appears to be weak, indicating that it may be transient or stabilized by other factors. Supporting the fact that these molecules interact in vivo, we found that Nef colocalizes with HLA-A2 molecules in a perinuclear distribution inside cells. In addition, we demonstrated that Nef fails to bind the HLA-E tail and also fails to bind HLA-A2 tails with deletions of amino acids necessary for MHC-I downmodulation. These data provide an explanation for differential downmodulation of MHC-I allotypes by Nef. In addition, they provide the first direct evidence indicating that Nef functions as an adaptor molecule able to link MHC-I to cellular trafficking proteins.

scholarly journals Human Immunodeficiency Virus Type 1 Nef Domains Required for Disruption of Major Histocompatibility Complex Class I Trafficking Are Also Necessary for Coprecipitation of Nef with HLA-A2

2005 ◽  
Vol 79 (1) ◽  
pp. 632-636 ◽  
Author(s):  
Maya Williams ◽  
Jeremiah F. Roeth ◽  
Matthew R. Kasper ◽  
Tracey M. Filzen ◽  
Kathleen L. Collins
Keyword(s):  
Human Immunodeficiency Virus ◽  
Major Histocompatibility Complex ◽  
Major Histocompatibility Complex Class ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Complex Class ◽  
Mhc I ◽  
Histocompatibility Complex ◽  
Immunodeficiency Virus

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) Nef is a critical protein that is necessary for HIV pathogenesis. Its roles include the disruption of major histocompatibility complex class I (MHC-I) and CD4 trafficking to promote immune evasion and viral spread. Mutational analyses have revealed that separate domains of Nef are required to affect these two molecules. To further elucidate how Nef disrupts MHC-I trafficking in T cells, we examined the role of protein domains that are required for this function (N-terminal alpha helix, polyproline, acidic, and oligomerization domains). We found that each of these regions was required for Nef to disrupt the transport of HLA-A2 to the cell surface and for Nef to coprecipitate with HLA-A2.

scholarly journals Human Immunodeficiency Virus Type 1 Vpu Protein Interacts with CD74 and Modulates Major Histocompatibility Complex Class II Presentation

2007 ◽  
Vol 82 (2) ◽  
pp. 893-902 ◽  
Author(s):  
Amjad Hussain ◽  
Clement Wesley ◽  
Mohammad Khalid ◽  
Ashutosh Chaudhry ◽  
Shahid Jameel
Keyword(s):  
Human Immunodeficiency Virus ◽  
Major Histocompatibility Complex ◽  
Complex Class ◽  
Yeast Two Hybrid ◽  
Mhc Ii ◽  
Histocompatibility Complex ◽  
Immunodeficiency Virus ◽  
Two Hybrid ◽  
Hiv 1

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) Vpu accessory protein is a transmembrane protein that down regulates CD4 expression and promotes the release of new virions. We screened a human leukocyte-specific yeast two-hybrid expression library to discover novel Vpu-interacting cellular proteins. The major histocompatibility complex class II (MHC II) invariant chain, also called Ii or CD74, was found to be one such protein. We show direct binding of Vpu and CD74 by using a yeast two-hybrid assay and coimmunoprecipitation from HIV-1-infected cells. The cytoplasmic region of Vpu was found to interact with the 30-amino-acid cytoplasmic tail of CD74. Human monocytic U937 cells infected with wild-type or Vpu-defective HIV-1 and transfected cells showed that Vpu down modulated the surface expression of mature MHC II molecules. The reduction in cell surface mature MHC II molecules correlated with decreased antigen presentation to T cells in culture. Thus, the Vpu protein also contributes to viral persistence by attenuating immune responses during HIV infection. This report further exemplifies the rich diversity and redundancy shown by HIV in immune evasion.

scholarly journals The Pro78 residue regulates the capacity of the human immunodeficiency virus type 1 Nef protein to inhibit recycling of major histocompatibility complex class I molecules in an SH3-independent manner

2006 ◽  
Vol 87 (8) ◽  
pp. 2291-2296 ◽  
Author(s):  
Nicoletta Casartelli ◽  
Giorgia Giolo ◽  
Francesca Neri ◽  
Claudia Haller ◽  
Marina Potestà ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Major Histocompatibility Complex ◽  
Cell Surface ◽  
Major Histocompatibility Complex Class ◽  
Human Immunodeficiency Virus Type ◽  
Complex Class ◽  
Mhc I ◽  
Histocompatibility Complex ◽  
Immunodeficiency Virus

The Nef protein is a crucial pathogenicity factor of human immunodeficiency virus type 1 (HIV-1) that contains a proline-rich motif consisting of four conserved prolines: Pro69 (P69), P72, P75 and P78. P72 and P75 were shown to bind Src homology domains 3 (SH3) and have been implicated in many biological functions of Nef, including downmodulation of cell-surface major histocompatibility complex class I (MHC-I). P78 is involved together with P69 in positioning of the Nef–SH3 complex and it has been shown to be essential for Nef activity of MHC-I downmodulation. It is shown here that alteration of P78 affects recycling of MHC-I molecules to the cell surface, but does not interfere with SH3 binding. In addition, it is demonstrated that P72 and P75, and thus the SH3-binding capacity, are fully dispensable for Nef activity on MHC-I.

scholarly journals Characterization of a Major Histocompatibility Complex Class II X-Box-Binding Protein Enhancing Tat-Induced Transcription Directed by the Human Immunodeficiency Virus Type 1 Long Terminal Repeat

2000 ◽  
Vol 74 (19) ◽  
pp. 8989-9001 ◽  
Author(s):  
Carlo Mischiati ◽  
Giordana Feriotto ◽  
Monica Borgatti ◽  
Patrizio Giacomini ◽  
Roberto Gambari
Keyword(s):  
Human Immunodeficiency Virus ◽  
Transcription Factors ◽  
Major Histocompatibility Complex ◽  
Class Ii ◽  
The Other ◽  
Nuclear Proteins ◽  
Histocompatibility Complex ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT The X-box element present within the promoter region of genes belonging to the major histocompatibility complex (MHC) plays a pivotal role in the expression of class II molecules, since it contains the binding sites for several well-characterized transcription factors. We have analyzed a randomly selected compilation of viral genomes for the presence of elements homologous to the X box of the HLA-DRA gene. We found that human immunodeficiency virus type 1 (HIV-1) shows the highest frequency of X-like box elements per 1,000 bases of genome. Within the HIV-1 genome, we found an X-like motif in the TAR region of the HIV-1 long terminal repeat (LTR), a regulative region playing a pivotal role in Tat-induced HIV-1 transcription. The use of a decoy approach for nuclear proteins binding to this element, namely, XMAS (X-like motif activator sequence), performed by transfection of multiple copies of this sequence into cells carrying an integrated LTR-chloramphenicol acetyltransferase construct, suggests that this element binds to nuclear proteins that enhance Tat-induced transcription. In this report we have characterized two proteins, one binding to the XMAS motif and the other to the flanking regions of XMAS. Mobility shift assays performed on crude nuclear extracts or enriched fractions suggest that similar proteins bind to XMAS from HIV-1 and the X box of the HLA-DRA gene. Furthermore, a UV cross-linking assay suggests that one protein of 47 kDa, termed FAX (factor associated with XMAS)-1, binds to the XMAS of HIV-1. The other protein of 56 kDa was termed FAX-2. In a decoy ex vivo experiment, it was found that sequences recognizing both proteins are required to inhibit Tat-induced HIV-1 LTR-driven transcription. Taken together, the data reported in this paper suggest that XMAS and nearby sequences modulate Tat-induced HIV-1 transcription by binding to the X-box-binding proteins FAX-1 and FAX-2. The sequence homology between XMAS and X box is reflected in binding of a common protein, FAX-1, and similar functional roles in gene expression. To our knowledge, this is the first report showing that transcription factors binding to the X box of the MHC class II genes enhance the transcription of HIV-1.

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