Quantum dot/pMHC multimers vs. phycoerythrin/pMHC tetramers for identification of HLA-A*0201-restricted pHBV core antigen18–27-specific T cells

Detection of human leukocyte antigens-A2-restricted p-hepatitis B virus (HBV) core antigen‑specific cytotoxic T lymphocytes (CTLs) is important in the study of HBV immunopathogenesis and vaccine design. Currently, major histocompatibility complex (MHC) class I/peptide‑(p) MHCI tetramers are considered the optimal tools to detect antigen‑specific CTLs. However, the MHC‑tetramer technique also has certain drawbacks and is under continuous development. The quantum dot (QD) bioconjugates nanotechnology with its unique inorganic‑biological properties has been developing fast. However, QD/pMHC multimers have seldom been used for the identification of the C18‑27 epitope, which is important in HBV infection. QD/pMHC multimers were synthesized by metal‑affinity coordination and an avidin‑biotin system. In the present study they were characterized by transmission electron microscopy, dynamic light scattering and fluorescence spectrophotometry. C18‑27‑specific CTLs were obtained by ex vivo expansion of CD8+ T cells. Cultured CTLs were tested for the secretion level of interferon (IFN)‑γ by ELISA and for cytotoxicity by lactate dehydrogenase release assay. Then, the performance of phycoerythrin (PE)/pMHC tetramers and QD/pMHC multimers were compared by flow cytometry. The synthesized QD/pMHC multimers dispersed well and their emission spectrum exhibited only slight differences compared with original QDs. C18‑27‑specific CTLs not only secreted IFN‑γ but also effectively targeted T2 cells pulsed with peptide C18‑27. The frequencies of C18‑27‑specific CTLs determined by QD/pMHC multimers were higher compared with PE/pMHC tetramers. The present results suggested that QD/pMHC multimers may be able to characterize greater numbers of C18‑27‑specific CTLs with increased sensitivity compared to conventional strategies.