Abstract
Human cytomegalovirus (CMV) infection is widespread among adults (60–90%) and is usually undetected in healthy individuals without symptoms but can cause severe diseases in immunocompromised hosts. T-cell receptor (TCR)-like antibodies (Abs), which recognize complex antigens (peptide–MHC complex, pMHC) composed of MHC molecules with embedded short peptides derived from intracellular proteins, including pathogenic viral proteins, can serve as diagnostic and/or therapeutic agents. In this study, we aimed to engineer a TCR-like Ab specific for pMHC comprising a CMV pp65 protein-derived peptide (495NLVPMVATV503; hereafter, CMVpp65495-503) in complex with MHC-I molecule human leukocyte antigen (HLA)-A*02:01 (CMVpp65495-503/HLA-A*02:01) to increase affinity by sequential mutagenesis of complementarity-determining regions using yeast surface display technology. Compared with the parental Ab, the final generated Ab (C1-17) showed ~67-fold enhanced binding affinity (KD ≈ 5.2 nM) for the soluble pMHC, thereby detecting the cell surface-displayed CMVpp65495-503/HLA-A*02:01 complex with high sensitivity and exquisite specificity. Thus, the new high-affinity TCR-like Ab may be used for the detection and treatment of CMV infection.
Highlights
Human cytomegalovirus (CMV), a β-herpes virus with a double-stranded DNA, infects a wide variety of cells and establishes latency in the host [1]
H9 reformatted into the bivalent immunoglobulin G (IgG) form showed binding specificity to soluble peptide–MHC complex (pMHC) comprising the CMVpp65495-503 /human leukocyte antigen (HLA)-A*02:01 complex with relatively weak binding affinity (KD ≈ 300 nM) [13]
CMVpp65495-503 /HLA-A*02:01 complex, generated by external peptide pulsing of cells expressing HLA-A*02:01 at various levels (Figure 1A)
Summary
Human cytomegalovirus (CMV), a β-herpes virus with a double-stranded DNA, infects a wide variety of cells and establishes latency in the host [1]. Major histocompatibility complex class I (MHC-I) molecules, known as human leukocyte antigen I (HLA-I), are cell-surface antigen-presenting proteins displaying peptide fragments (8–10 amino acid residues in length) derived from intracellular cytoplasmic proteins, including self, viral, and tumor antigens, for recognition by CD8+ T cells [4]. Among the pp65-derived CTL epitope peptides, the 9-mer peptide 495 NLVPMVATV503 (residues 495–503; hereafter referred to as CMVpp65495-503 peptide) is the most immunogenic T cell epitope predominantly displayed on HLA-A*02:01, the most common MHC-I allele in the population [6,7,8]. Detection and targeting of the highly prevalent CMVpp65495-503 /HLA-A*02:01 complex on the surface of CMV-infected cells are crucial for the development of detection and/or therapeutic modalities [9,10]
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