scholarly journals CD8+Cytotoxic-T-Lymphocyte Breadth Could Facilitate Early Immune Detection of Immunodeficiency Virus-Derived Epitopes with Limited Expression Levels

mSphere ◽  
2019 ◽  
Vol 4 (1) ◽  
Author(s):  
Tetsuo Tsukamoto ◽  
Hiroyuki Yamamoto ◽  
Tetsuro Matano
Keyword(s):  
T Lymphocyte ◽  
Cytotoxic T Lymphocyte ◽  
Physical Contact ◽  
Class I Mhc ◽  
Mhc I ◽  
Expression Levels ◽  
Immunodeficiency Virus ◽  
Infected Cells ◽  
Attenuated Viruses

ABSTRACTCytotoxic-T-lymphocyte (CTL) responses are important to control the replication of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV). Accumulating evidence suggests that the ability of a few immunodominant T-cell populations to detect and kill HIV/SIV-infected cells is important in individuals with a protective major histocompatibility complex class I (MHC-I) allele. On the other hand, immunization with live(-attenuated) viruses may be effective against superinfection of virulent viral strains regardless of the host’s MHC-I haplotypes, although the underlying mechanisms have not been fully documented. In this article, we propose a hypothesis that the early detection of infected cells in superinfected individuals may be partly facilitated by recognition of diverse CTL epitopes with limited expression levels. We further explain the hypothesis using simple mathematics that was written based on previousin vitroviral suppression assay results and by considering the physical contact of infected cells with CTLs.

scholarly journals Expression of Nef Downregulates CXCR4, the Major Coreceptor of Human Immunodeficiency Virus, from the Surfaces of Target Cells and Thereby Enhances Resistance to Superinfection

2006 ◽  
Vol 80 (22) ◽  
pp. 11141-11152 ◽  
Author(s):  
Stephanie Venzke ◽  
Nico Michel ◽  
Ina Allespach ◽  
Oliver T. Fackler ◽  
Oliver T. Keppler
Keyword(s):  
Human Immunodeficiency Virus ◽  
T Lymphocytes ◽  
Maximum Level ◽  
Target Cells ◽  
Class I Mhc ◽  
Mhc I ◽  
Immunodeficiency Virus ◽  
Infected Cells ◽  
Stromal Cell Derived Factor ◽  
Hiv 1

ABSTRACT Lentiviral Nef proteins are key factors for pathogenesis and are known to downregulate functionally important molecules, including CD4 and major histocompatibility complex class I (MHC-I), from the surfaces of infected cells. Recently, we demonstrated that Nef reduces cell surface levels of the human immunodeficiency virus type 1 (HIV-1) entry coreceptor CCR5 (N. Michel, I. Allespach, S. Venzke, O. T. Fackler, and O. T. Keppler, Curr. Biol. 15:714-723, 2005). Here, we report that Nef downregulates the second major HIV-1 coreceptor, CXCR4, from the surfaces of HIV-infected primary CD4 T lymphocytes with efficiencies comparable to those of the natural CXCR4 ligand, stromal cell-derived factor-1 alpha. Analysis of a panel of mutants of HIV-1SF2 Nef revealed that the viral protein utilized the same signature motifs for downmodulation of CXCR4 and MHC-I, including the proline-rich motif P73P76P79P82 and the acidic cluster motif E66E67E68E69. Expression of wild-type Nef, but not of specific Nef mutants, resulted in a perinuclear accumulation of the coreceptor. Remarkably, the carboxy terminus of CXCR4, which harbors the classical motifs critical for basal and ligand-induced receptor endocytosis, was dispensable for the Nef-mediated reduction of surface exposure. Functionally, the ability of Nef to simultaneously downmodulate CXCR4 and CD4 correlated with maximum-level protection of Nef-expressing target cells from fusion with cells exposing X4 HIV-1 envelopes. Furthermore, the Nef-mediated downregulation of CXCR4 alone on target T lymphocytes was sufficient to diminish cells' susceptibility to X4 HIV-1 virions at the entry step. The downregulation of chemokine coreceptors is a conserved activity of Nef to modulate infected cells, an important functional consequence of which is an enhanced resistance to HIV superinfection.

scholarly journals Major Histocompatibility Complex Class I Alleles Associated with Slow Simian Immunodeficiency Virus Disease Progression Bind Epitopes Recognized by Dominant Acute-Phase Cytotoxic-T-Lymphocyte Responses

2003 ◽  
Vol 77 (16) ◽  
pp. 9029-9040 ◽  
Author(s):  
David H. O'Connor ◽  
Bianca R. Mothe ◽  
Jason T. Weinfurter ◽  
Sarah Fuenger ◽  
William M. Rehrauer ◽  
...  
Keyword(s):  
Major Histocompatibility Complex ◽  
Disease Progression ◽  
Acute Phase ◽  
T Lymphocyte ◽  
Cytotoxic T Lymphocyte ◽  
Complex Class ◽  
Mhc I ◽  
Histocompatibility Complex ◽  
Immunodeficiency Virus ◽  
Ctl Responses

ABSTRACT Certain major histocompatibility complex class I (MHC-I) alleles are associated with delayed disease progression in individuals infected with human immunodeficiency virus (HIV) and in macaques infected with simian immunodeficiency virus (SIV). However, little is known about the influence of these MHC alleles on acute-phase cellular immune responses. Here we follow 51 animals infected with SIVmac239 and demonstrate a dramatic association between Mamu-A*01 and -B*17 expression and slowed disease progression. We show that the dominant acute-phase cytotoxic T lymphocyte (CTL) responses in animals expressing these alleles are largely directed against two epitopes restricted by Mamu-A*01 and one epitope restricted by Mamu-B*17. One Mamu-A*01-restricted response (Tat28-35SL8) and the Mamu-B*17-restricted response (Nef165-173IW9) typically select for viral escape variants in early SIVmac239 infection. Interestingly, animals expressing Mamu-A*1 and -B*17 have less variation in the Tat28-35SL8 epitope during chronic infection than animals that express only Mamu-A*01. Our results show that MHC-I alleles that are associated with slow progression to AIDS bind epitopes recognized by dominant CTL responses during acute infection and underscore the importance of understanding CTL responses during primary HIV infection.

scholarly journals Functional Characterization of the Human Immunodeficiency Virus Type 1 Nef Acidic Domain

2008 ◽  
Vol 82 (19) ◽  
pp. 9657-9667 ◽  
Author(s):  
Laura L. Baugh ◽  
J. Victor Garcia ◽  
John L. Foster
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Functional Characterization ◽  
Direct Interaction ◽  
Class I Mhc ◽  
Mhc I ◽  
Immunodeficiency Virus

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) accessory protein Nef downregulates major histocompatibility complex class I (MHC-I) from the cell surface. It has been proposed that the direct interaction of the acidic cluster (AC) of Nef, 62EEEE65, with the furin binding region (fbr) of PACS-1 is crucial for this Nef function. Contrary to this proposal, evidence is presented here that the four glutamates in Nef do not functionally engage the PACS-1 fbr. (i) The binding of Nef to the PACS-1 fbr in vitro is much weaker than the binding of the canonical furin AC to the PACS-1 fbr. (ii) The mutation of two of the four glutamates in Nef's AC to alanines does not alter Nef's ability to downregulate MHC-I, and triply mutated Nefs exhibit 50% activity. (iii) The introduction of lysine into the AC has little effect on Nef function. (iv) The mutation of all four glutamates to alanine does debilitate Nef MHC-I downregulation, but this quadruple mutation also impairs the ability of Nef to regulate p21-activated protein kinase and enhance viral particle infectivity. (v) The replacement of the Nef AC with the bona fide AC from furin results in the loss of the expected regulatory properties of the furin AC. (vi) The insertion of the conformation-disrupting amino acid proline into the Nef AC does not disrupt MHC-I downregulation. Our results are consistent with an alternative model in which 62EEEE65 plays a stabilizing role in the formation of a ternary complex between Nef, the MHC-I cytoplasmic domain, and AP-1.

scholarly journals Concanamycin A counteracts HIV-1 Nef to enhance immune clearance of infected primary cells by cytotoxic T lymphocytes

2020 ◽  
Vol 117 (38) ◽  
pp. 23835-23846
Author(s):  
Mark M. Painter ◽  
Gretchen E. Zimmerman ◽  
Madeline S. Merlino ◽  
Andrew W. Robertson ◽  
Valeri H. Terry ◽  
...  
Keyword(s):  
T Lymphocytes ◽  
Cytotoxic T Lymphocytes ◽  
Primary Cells ◽  
Down Regulation ◽  
Class I Mhc ◽  
Mhc I ◽  
Concanamycin A ◽  
Immune Mediated ◽  
Immunodeficiency Virus ◽  
Infected Cells

Nef is an HIV-encoded accessory protein that enhances pathogenicity by down-regulating major histocompatibility class I (MHC-I) expression to evade killing by cytotoxic T lymphocytes (CTLs). A potent Nef inhibitor that restores MHC-I is needed to promote immune-mediated clearance of HIV-infected cells. We discovered that the plecomacrolide family of natural products restored MHC-I to the surface of Nef-expressing primary cells with variable potency. Concanamycin A (CMA) counteracted Nef at subnanomolar concentrations that did not interfere with lysosomal acidification or degradation and were nontoxic in primary cell cultures. CMA specifically reversed Nef-mediated down-regulation of MHC-I, but not CD4, and cells treated with CMA showed reduced formation of the Nef:MHC-I:AP-1 complex required for MHC-I down-regulation. CMA restored expression of diverse allotypes of MHC-I in Nef-expressing cells and inhibited Nef alleles from divergent clades of HIV and simian immunodeficiency virus, including from primary patient isolates. Lastly, we found that restoration of MHC-I in HIV-infected cells was accompanied by enhanced CTL-mediated clearance of infected cells comparable to genetic deletion of Nef. Thus, we propose CMA as a lead compound for therapeutic inhibition of Nef to enhance immune-mediated clearance of HIV-infected cells.

scholarly journals MHC class I antigen cross-presentation mediated by PapMV nanoparticles in human antigen-presenting cells is dependent on autophagy

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0261987
Author(s):  
David Possamaï ◽  
Laïla-Aïcha Hanafi ◽  
Angélique Bellemare-Pelletier ◽  
Katia Hamelin ◽  
Paméla Thébault ◽  
...  
Keyword(s):  
Antigen Presentation ◽  
T Lymphocyte ◽  
Cytotoxic T Lymphocyte ◽  
Antigen Presenting Cells ◽  
Class I ◽  
Class I Mhc ◽  
Mhc I ◽  
Cross Presentation ◽  
Antigen Presenting ◽  
Papmv Nanoparticles

Nanoparticles made of the coat protein of papaya mosaic virus (PapMV) and a single-strand RNA were previously shown to be an efficient antigen presentation system for the trigger of cellular immunity. Engineering of PapMV nano with a cytotoxic T lymphocyte epitope was previously shown activating specific T lymphocytes through a proteasome-independent major histocompatibility complex class I (MHC-I) cross-presentation. In this study, we provide new insights into the mechanism of the MHC-I cross-presentation mediated by PapMV nanoparticles. We demonstrate that PapMV nanoparticles do not require the transporter associated with antigen presentation (TAP), but rather depend on lysosome acidification and cathepsin S protease activity for presentation of the T cell epitope. We have also linked the induction of autophagy with this vacuolar MHC-I cross-presentation process. Interestingly, autophagy is induced in antigen-presenting cells after PapMV nanoparticles exposure and inhibition of autophagy reduce MHC-I cross-presentation. This study demonstrates that autophagy is associated with TAP- and proteasome-independent MHC-I cross-presentation. A deeper understanding of the autophagy-dependent MHC-I cross-presentation will be useful in designing vaccination platforms that aim to trigger an efficient cytotoxic T lymphocyte response.

scholarly journals Nef-Mediated Disruption of HLA-A2 Transport to the Cell Surface in T Cells

2003 ◽  
Vol 77 (5) ◽  
pp. 3041-3049 ◽  
Author(s):  
Matthew R. Kasper ◽  
Kathleen L. Collins
Keyword(s):  
T Cells ◽  
Cell Surface ◽  
Hela Cells ◽  
Kinase Inhibitor ◽  
Phosphatidylinositol 3 Kinase ◽  
Class I Mhc ◽  
Mhc I ◽  
Immunodeficiency Virus ◽  
Infected Cells ◽  
Steady State Levels

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) Nef is a key pathogenic factor necessary for the development of AIDS. One important function of Nef is to reduce cell surface levels of major histocompatibility complex class I (MHC-I) molecules, thereby protecting HIV-infected cells from recognition by cytotoxic T lymphocytes. The mechanism of MHC-I downmodulation by Nef has not been clearly elucidated, and its reported effect on MHC-I steady-state levels ranges widely, from 2-fold in HeLa cells to 200-fold in HIV-infected primary T cells. Here, we directly compared downmodulation of HLA-A2 in HIV-infected HeLa cells to that in T cells. We found that similar amounts of Nef protein resulted in a much more dramatic downmodulation of HLA-A2 in T cells than in HeLa cells. A comparison of Nef's effects on HLA-A2 endocytosis, recycling, and transport rates indicated that the most prominent effect of Nef on HLA-A2 in T cells was to inhibit transport to the cell surface. The phosphatidylinositol 3-kinase inhibitor, LY294002, previously reported to inhibit Nef-mediated MHC-I downmodulation in astrocytic cells, did not directly affect Nef's ability to block transport of MHC-I to the cell surface in T cells.

scholarly journals Cross-Reactivity against Multiple HIV-1 Epitopes Is Characteristic of HIV-1-Specific Cytotoxic T Lymphocyte Clones

2018 ◽  
Vol 92 (16) ◽  
Author(s):  
Arumugam Balamurugan ◽  
Hwee L. Ng ◽  
Otto O. Yang
Keyword(s):  
T Lymphocyte ◽  
Cytotoxic T Lymphocyte ◽  
Cross Reactivity ◽  
Type I ◽  
Mhc I ◽  
Infected Cells ◽  
High Concentrations ◽  
High Level ◽  
Hiv 1 ◽  
Ctl Responses

ABSTRACT Although a high level of promiscuity for heterologous epitopes is believed to exist for cellular immunity, limited data explore this issue for human immunodeficiency virus type 1 (HIV-1)-specific CD8+ T lymphocyte (CTL) responses. Here, we found an unexpected degree of heterologous cross-reactivity against HIV-1 epitopes, in addition to the targeted index epitope. Most CTL clones screened cross-reacted against other known HIV-1 epitopes of the same major histocompatibility complex type I (MHC-I) restriction, up to 40% of tested nonindex epitopes in some cases. The observed cross-reactivity was universally lower avidity than recognition of the index epitope when examined for several A*02- and B*57-restricted CTL clones, demonstrating that the high concentrations of exogenous epitope typically used for screening of CTL responses are prone to detect such cross-reactivity spuriously. In agreement with this, we found that these cross-reactive responses do not appear to mediate CTL activity against HIV-1-infected cells. Overall, our data indicate that low-level cross-reactivity is remarkably common for HIV-1-specific CTLs. The role of this phenomenon is unclear, but low-avidity interactions have been shown to foster homeostatic proliferation of memory T cells. IMPORTANCE This study raises two issues related to HIV-1-specific CTL responses. These are key immune responses that retard disease progression in infected persons that are highly relevant to immunotherapies and vaccines for HIV-1. First, we make the novel observation that these responses are promiscuous and that CTLs targeting one epitope may cross-recognize other, completely distinct epitopes in the virus. While these are low-avidity interactions that do not appear to contribute directly to the antiviral activity of CTLs, this raises interesting biologic implications regarding the purpose of the phenomenon, such as providing a stimulus for these responses to persist long term. Second, the data raise a technical caveat to detection of CTL responses against particular epitopes, suggesting that some methodologies may unintentionally detect cross-reactivity and overestimate responses against an epitope.

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