Monoclonal antibodies to HLA-E bind epitopes carried by unfolded β2m-free heavy chains

Elisa Tremante, Elisa Lo Monaco, Tiziano Ingegnere, Camilla Sampaoli, Rocco Fraioli, Patrizio Giacomini

Research output: Contribution to journalArticlepeer-review

Abstract

Since HLA-E heavy chains accumulate free of their light β2-microglobulin (β2m) subunit, raising mAbs to folded HLA-E heterodimers has been difficult, and mAb characterization has been controversial. Herein, mAb W6/32 and 5 HLA-E-restricted mAbs (MEM-E/02, MEM-E/07, MEM-E/08, DT9, and 3D12) were tested on denatured, acid-treated, and natively folded (both β2m-associated and β2m-free) HLA-E molecules. Four distinct conformations were detected, including unusual, partially folded (and yet β2m-free) heavy chains reactive with mAb DT9. In contrast with previous studies, epitope mapping and substitution scan on thousands of overlapping peptides printed on microchips revealed that mAbs MEM-E/02, MEM-E/07, and MEM-E/08 bind three distinct α1 and α2 domain epitopes. All three epitopes are linear since they span just 4-6 residues and are "hidden" in folded HLA-E heterodimers. They contain at least one HLA-E-specific residue that cannot be replaced by single substitutions with polymorphic HLA-A, HLA-B, HLA-C, HLA-F, and HLA-G residues. Finally, also the MEM-E/02 and 3D12 epitopes are spatially distinct. In summary, HLA-E-specific residues are dominantly immunogenic, but only when heavy chains are locally unfolded. Consequently, the available mAbs fail to selectively bind conformed HLA-E heterodimers, and HLA-E expression may have been inaccurately assessed in some previous oncology, reproductive immunology, virology, and transplantation studies.

Original languageEnglish
Pages (from-to)2356-2364
Number of pages9
JournalEuropean Journal of Immunology
Volume45
Issue number8
DOIs
Publication statusPublished - Aug 1 2015

Keywords

  • -B
  • -C
  • Conformation
  • HLA-A
  • HLA-E
  • MAbs
  • β<inf>2</inf>-microglobulin (β<inf>2</inf>m)

ASJC Scopus subject areas

  • Immunology
  • Immunology and Allergy
  • Medicine(all)

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