Polymorphism in Human Cytomegalovirus UL40 Impacts on Recognition of Human Leukocyte Antigen-E (HLA-E) by Natural Killer Cells

Abstract

Natural killer (NK) cell recognition of the nonclassical human leukocyte antigen (HLA) molecule HLA-E is dependent on the presentation of a nonamer peptide derived from the leader sequence of other HLA molecules to CD94-NKG2 receptors. However, human cytomegalovirus can manipulate this central innate interaction through the provision of a "mimic" of the HLA-encoded peptide derived from the immunomodulatory glycoprotein UL40. Here, we analyzed UL40 sequences isolated from 32 hematopoietic stem cell transplantation recipients experiencing cytomegalovirus reactivation. The UL40 protein showed a "polymorphic hot spot" within the region that encodes the HLA leader sequence mimic. Although all sequences that were identical to those encoded within HLA-I genes permitted the interaction between HLA-E and CD94-NKG2 receptors, other UL40 polymorphisms reduced the affinity of the interaction between HLA-E and CD94-NKG2 receptors. Furthermore, functional studies using NK cell clones expressing either the inhibitory receptor CD94-NKG2A or the activating receptor CD94-NKG2C identified UL40-encoded peptides that were capable of inhibiting target cell lysis via interaction with CD94-NKG2A, yet had little capacity to activate NK cells through CD94-NKG2C. The data suggest that UL40 polymorphisms may aid evasion of NK cell immunosurveillance by modulating the affinity of the interaction with CD94-NKG2 receptors.

Human CD8 T lymphocytes recognize Mycobacterium tuberculosis antigens presented by HLA‐E during active tuberculosis and express type 2 cytokines

“…Tetramer staining was carried out as described in detail previously [31,37,54]. PBMCs (10 6 /mL) were incubated in U-bottom 96-well plates, washed twice in PBS containing 1% FCS (Sigma), and stained for 30 min at 4°C with PE-labeled tetramers (5 μL each) prepared as previously described [31,37,54]; they were washed and subsequently stained with FITC-labeled anti-CD8 mAb (RPA-TB, BD Biosciences) and analyzed by flow cytometry on a FACSCanto.…”

Cytomegalovirus-Infected Primary Endothelial Cells Trigger NKG2C⁺ Natural Killer Cells

“…To test the hypothesis that the maintenance of HLA-E expression on infected EC could be due to the loading of the UL40 peptide on HLA-E molecule, we sequenced the UL40 gene from VHL/E-infected cells. Indeed, an amino acid sequence alignment of VHL/E UL40 peptide (VMAPRTLLL) with previously published ones [27] highlighted a full homology between the VHL/E and Towne strains (table 1). It has been published that the UL40 peptide from the Towne strain leads to HLA-E expression and its functional engagement with CD94/ NKG2A and CD94/NKG2C receptors [27].…”

“…Indeed, an amino acid sequence alignment of VHL/E UL40 peptide (VMAPRTLLL) with previously published ones [27] highlighted a full homology between the VHL/E and Towne strains (table 1). It has been published that the UL40 peptide from the Towne strain leads to HLA-E expression and its functional engagement with CD94/ NKG2A and CD94/NKG2C receptors [27]. Thus, in accordance with these published results, we suggest that the UL40 signal peptide from VHL/E is processed and loaded specifically in the groove of HLA-E, maintaining its membrane expression.…”

“…Primers to amplify the UL40 gene were designed using the sequences for human herpesvirus 5 strain AD169 and wild-type strain Merlin as previously described [27] and were 5′-GGCTCTGTCTCGTCGTCATT-3′ (forward) and 5′-CGACACCGATCGATTTTCTT-3′ (reverse) (Geneworks, Hindmarsh, S.A., Australia). UL40 cDNA sequencing was performed as previously described for HLA-E genotyping.…”

NK cell interplay with cytomegaloviruses

“…The benefits of inhibitory NKG2A engagement may in important settings outweigh the hazards of activating NKG2C engagement [30] (Figure 1i). Interestingly, some clinical HCMV isolates display polymorphisms in peptide-mimetic region of UL40 that abrogate recognition by activating NKG2C but preserve inhibition through NKG2A [31]. Recent data suggest that HCMV can drive stable expansion of NK cells only through engagement of activating KIR receptors in patients receiving blood from NKG2C-donors [32 ].…”