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Sequence variations in HCV core-derived epitopes alter binding of KIR2DL3 to HLA-C?03:04 and modulate NK cell function.

ABSTRACT: Both natural killer (NK) cells and human leukocyte antigen (HLA)/killer cell immunoglobulin like receptor (KIR) interactions have been shown to play an important role in the control, clearance and progression of hepatitis C virus (HCV) disease. Here we aimed at elucidating the effects of viral peptides derived from HCV on HLA stabilization, changes in KIR binding and primary NK cell function.Transporter for antigen presentation-deficient 722.221 cells stably transfected with HLA-C?03:04 were used to screen 200 overlapping peptides, covering the non-structural protein 3 (NS3) and core protein of HCV genotype 1, for their ability to bind and stabilize HLA-C?03:04. Binding of KIR2DL3 to the HLA-peptide complex was assessed using a KIR2DL3-IgG fusion construct. Primary NK cells were isolated from healthy donors to investigate the effects of identified peptides on KIR2DL3(+) NK cell function.Thirty-one peptides able to stabilize HLA-C?03:04 were identified. One 9mer peptide, YIPLVGAPL, resulted in significantly higher KIR2DL3 binding to HLA-C?03:04(+) 722.221 cells and suppression of primary KIR2DL3(+) NK cell function. Interestingly this sequence exhibited a high frequency of mutations in different HCV genotypes. These genotype-specific peptides showed lower HLA-C?03:04 stabilization, decreased binding of the inhibitory KIR2DL3 and lower inhibition of NK cell function.Taken together we show that a viral peptide derived from the core protein of HCV genotype 1 binding to HLA-C?03:04 results in a sequence-dependent engagement of the inhibitory NK cell receptor KIR2DL3, while the large majority of the remaining 30 HLA-C?03:04 binding HCV core peptides did not. These data show that sequence variations within HCV can modulate NK cell function, providing potential pathways for viral escape.We identified a HCV peptide that dampens NK cell responses, and thereby possibly prevents killing of infected cells through this part of the innate immune system. This is facilitated via presentation of the viral peptide on HLA?03:04 to the inhibitory KIR receptor KIR2DL3 on NK cells. Naturally occurring sequence mutations in the peptide alter these interactions making the inhibition less efficient.

SUBMITTER: Lunemann S

PROVIDER: S-EPMC4955726 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Sequence variations in HCV core-derived epitopes alter binding of KIR2DL3 to HLA-C∗03:04 and modulate NK cell function.

Lunemann Sebastian S Martrus Gloria G Hölzemer Angelique A Chapel Anais A Ziegler Maja M Körner Christian C Garcia Beltran Wilfredo W Carrington Mary M Wedemeyer Heiner H Altfeld Marcus M

Journal of hepatology 20160404 2

<h4>Background & aims</h4>Both natural killer (NK) cells and human leukocyte antigen (HLA)/killer cell immunoglobulin like receptor (KIR) interactions have been shown to play an important role in the control, clearance and progression of hepatitis C virus (HCV) disease. Here we aimed at elucidating the effects of viral peptides derived from HCV on HLA stabilization, changes in KIR binding and primary NK cell function.<h4>Methods</h4>Transporter for antigen presentation-deficient 722.221 cells st ...[more]

PMID: 27057987

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Project description:BackgroundViruses can evade immune surveillance, but the underlying mechanisms are insufficiently understood. Here, we sought to understand the mechanisms by which natural killer (NK) cells recognize HIV-1-infected cells and how this virus can evade NK-cell-mediated immune pressure.Methods and findingsTwo sequence mutations in p24 Gag associated with the presence of specific KIR/HLA combined genotypes were identified in HIV-1 clade C viruses from a large cohort of infected, untreated individuals in South Africa (n = 392), suggesting viral escape from KIR+ NK cells through sequence variations within HLA class I-presented epitopes. One sequence polymorphism at position 303 of p24 Gag (TGag303V), selected for in infected individuals with both KIR2DL3 and HLA-C*03:04, enabled significantly better binding of the inhibitory KIR2DL3 receptor to HLA-C*03:04-expressing cells presenting this variant epitope compared to the wild-type epitope (wild-type mean 18.01 ± 10.45 standard deviation [SD] and variant mean 44.67 ± 14.42 SD, p = 0.002). Furthermore, activation of primary KIR2DL3+ NK cells from healthy donors in response to HLA-C*03:04+ target cells presenting the variant epitope was significantly reduced in comparison to cells presenting the wild-type sequence (wild-type mean 0.78 ± 0.07 standard error of the mean [SEM] and variant mean 0.63 ± 0.07 SEM, p = 0.012). Structural modeling and surface plasmon resonance of KIR/peptide/HLA interactions in the context of the different viral sequence variants studied supported these results. Future studies will be needed to assess processing and antigen presentation of the investigated HIV-1 epitope in natural infection, and the consequences for viral control.ConclusionsThese data provide novel insights into how viruses can evade NK cell immunity through the selection of mutations in HLA-presented epitopes that enhance binding to inhibitory NK cell receptors. Better understanding of the mechanisms by which HIV-1 evades NK-cell-mediated immune pressure and the functional validation of a structural modeling approach will facilitate the development of novel targeted immune interventions to harness the antiviral activities of NK cells.

Project description:ObjectiveViral infections influence intracellular peptide repertoires available for presentation by HLA-I. Alterations in HLA-I/peptide complexes can modulate binding of killer immunoglobuline-like receptors (KIRs) and thereby the function of natural killer (NK) cells. Although multiple studies have provided evidence that HLA-I/KIR interactions play a role in HIV-1 disease progression, the consequence of HIV-1 infection for HLA-I/KIR interactions remain largely unknown.DesignWe determined changes in HLA-I presented peptides resulting from HIV-1-infection of primary human CD4 T cells and assessed the impact of changes in peptide repertoires on HLA-I/KIR interactions.MethodsLiquid chromatography-coupled tandem mass spectrometry to identify HLA-I presented peptides, cell-based in-vitro assays to evaluate functional consequences of alterations in immunopeptidome and atomistic molecular dynamics simulations to confirm experimental data.ResultsA total of 583 peptides exclusively presented on HIV-1-infected cells were identified, of which only 0.2% represented HIV-1 derived peptides. Focusing on HLA-C*03 : 04/KIR2DL3 interactions, we observed that HLA-C*03 : 04-presented peptides derived from noninfected CD4 T cells mediated stronger binding of inhibitory KIR2DL3 than peptides derived from HIV-1-infected cells. Furthermore, the most abundant peptide presented by HLA-C*03 : 04 on noninfected CD4 T cells (VIYPARISL) mediated the strongest KIR2DL3-binding, while the most abundant peptide presented on HIV-1-infected cells (YAIQATETL) did not mediate KIR2DL3-binding. Molecular dynamics simulations of HLA-C*03 : 04/KIR2DL3 interactions in the context of these two peptides revealed that VIYPARISL significantly enhanced the HLA-C*03 : 04/peptide contact area to KIR2DL3 compared with YAIQATETL.ConclusionThese data demonstrate that HIV-1 infection-induced changes in HLA-I-presented peptides can reduce engagement of inhibitory KIRs, providing a mechanism for enhanced activation of NK cells by virus-infected cells.

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Sequence variations in HCV core-derived epitopes alter binding of KIR2DL3 to HLA-C?03:04 and modulate NK cell function.

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Sequence variations in HCV core-derived epitopes alter binding of KIR2DL3 to HLA-C∗03:04 and modulate NK cell function.

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