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Human cytomegalovirus (HCMV) frequently reactivates after hematopoietic stem cell transplantation (HSCT). Antiviral medication is not universally effective and has side effects that prohibit prophylaxis and limit pre-emptive use. Adoptive transfer of HCMV-specific T lymphocytes can protect patients at risk of HCMV disease, but such T cells are difficult to obtain if the HSC donor is HCMV-negative. Transferring the T cell receptor (TCR) genes of HCMV-specific T cell clones to donor T cells will convey HCMV specificity to those cells. But if αβ T cells are engineered to co-express a second αβ TCR, mixed αβ TCR heterodimers of unknown and potentially hazardous specificity may form. This problem can be solved by expressing αβ TCRs in γδ T cells from the donor. HCMV-specific CD8+ T cells limit HCMV infection, but presentation of their antigenic peptides is effectively impaired by HCMV’s immunoevasins, especially in case of human leukocyte antigen (HLA)-A and -B allotypes. In contrast, CD8+ T cells restricted by HLA-C*07:02 resist the immunoevasins. In this study, the genes of eight HLA-C*07:02-restricted TCRs specific for immediate-early protein 1 (IE-1) or UL28 protein were derived from CD8+ T cell clones and retrovirally transferred into T cells from HCMV-negative donors. While all of those TCRs mediated strong recognition of an HCMV strain that is devoid of the four immunoevasins, their response to target cells infected with wild-type HCMV strains was weaker. Transduction experiments with different variations of the TCRs pointed to the existence of additional T cell-endogenous factors that contribute to recognition of infected cells. HCMV-specific CD4+ T cells are known to play a critical role in controlling HCMV and maintaining immunity. Nonetheless, possibilities of their transgenic generation have not been explored. In this study, HCMV-specific TCRs from CD4+ T cell clones were expressed in T cells from HCMV-negative donors. A panel of ten HCMV-specific, HLA class II-restricted TCRs was established that target seven distinct epitopes of phosphoprotein 65 (pp65) and IE-1 presented by a wide range of HLA class II allotypes. These TCR genes were retrovirally transferred into αβ T cells and γδ T cells from HCMV-negative donors. The resulting T cells specifically recognised HLA-matched, HCMV-infected dendritic cells. TCR-transduced αβ and γδ T cells were similarly effective, but backgrounds due to alloreactivity were even lower in γδ T cells than in αβ T cells. Experiments with inactivated virus showed that pp65-specific, HLA class II-restricted TCRs conveyed similar sensitivity towards HCMV-infected target cells and target cells that had acquired viral proteins through ingestion of extracellular material. In contrast, IE-1-specific, HLA class II-restricted TCRs mediated selective recognition of bona fide infected target cells. These results identify γδ T cells that transgenically express HLA class II-restricted TCRs as particularly promising immunotherapeutic agents against HCMV infection. |
