Impact of γ-chain cytokines on EBV-specific T cell cultures

Cytometric analysis of T cell phenotype using cytokine profiling for improved manufacturing of an EBV-specific T cell therapy

Adoptive immunotherapy using Epstein–Barr Virus (EBV)‐specific T cells is a potentially curative treatment for patients with EBV‐related malignancies where other clinical options have proved ineffective. We describe improved good manufacturing practice (GMP)‐compliant culture and analysis processes for conventional lymphoblastoid cell line (LCL)‐driven EBV‐specific T cell manufacture, and describe an improved phenotyping approach for analysing T cell products. We optimized the current LCL‐mediated clinical manufacture of EBV‐specific T cells to establish an improved process using xenoprotein‐free GMP‐compliant reagents throughout, and compared resulting products with our previous banked T cell clinical therapy. We assessed effects of changes to LCL:T cell ratio in T cell expansion, and developed a robust flow cytometric marker panel covering T cell memory, activation, differentiation and intracellular cytokine release to characterize T cells more effectively. These data were analysed using a t‐stochastic neighbour embedding (t‐SNE) algorithm. The optimized GMP‐compliant process resulted in reduced cell processing time and improved retention and expansion of central memory T cells. Multi‐parameter flow cytometry determined the optimal protocol for LCL stimulation and expansion of T cells and demonstrated that cytokine profiling using interleukin (IL)‐2, tumour necrosis factor (TNF)‐α and interferon (IFN)‐γ was able to determine the differentiation status of T cells throughout culture and in the final product. We show that fully GMP‐compliant closed‐process culture of LCL‐mediated EBV‐specific T cells is feasible, and profiling of T cells through cytokine expression gives improved characterization of start material, in‐process culture conditions and final product. Visualization of the complex multi‐parameter flow cytometric data can be simplified using t‐SNE analysis.

Early exposure to interleukin-21 limits rapidly generated anti-Epstein-Barr virus T-cell line differentiation

BACKGROUND AIMS

The adoptive transfer of ex vivo-expanded Epstein-Barr virus (EBV)-specific T-cell lines is an attractive strategy to treat EBV-related neoplasms. Current evidence suggests that for adoptive immunotherapy in general, clinical responses are superior if the transferred cells have not reached a late or terminal effector differentiation phenotype before infusion. The cytokine interleukin (IL)-21 has shown great promise at limiting late T-cell differentiation in vitro, but this remains to be demonstrated in anti-viral T-cell lines.

METHODS

We adapted a clinically validated protocol to rapidly generate EBV-specific T-cell lines in 12 to 14 days and tested whether the addition of IL-21 at the initiation of the culture would affect T-cell expansion and differentiation.

RESULTS

We generated clinical-scale EBV-restricted T-cell line expansion with balanced T-cell subset ratios. The addition of IL-21 at the beginning of the culture decreased both T-cell expansion and effector memory T-cell accumulation, with a relative increase in less-differentiated T cells. Within CD4 T-cell subsets, exogenous IL-21 was notably associated with the cell surface expression of CD27 and high KLF2 transcript levels, further arguing for a role of IL-21 in the control of late T-cell differentiation.

CONCLUSIONS

Our results show that IL-21 has profound effects on T-cell differentiation in a rapid T-cell line generation protocol and as such should be further explored as a novel approach to program anti-viral T cells with features associated with early differentiation and optimal therapeutic efficacy.

Infectious Mononucleosis

Infectious mononucleosis is a clinical entity characterized by sore throat, cervical lymph node enlargement, fatigue, and fever most often seen in adolescents and young adults and lasting several weeks. It can be caused by a number of pathogens, but this chapter only discusses infectious mononucleosis due to primary Epstein-Barr virus (EBV) infection. EBV is a γ-herpesvirus that infects at least 90% of the population worldwide. The virus is spread by intimate oral contact among teenagers and young adults. How preadolescents acquire the virus is not known. A typical clinical picture with a positive heterophile test is usually sufficient to make the diagnosis, but heterophile antibodies are not specific and do not develop in some patients. EBV-specific antibody profiles are the best choice for staging EBV infection. In addition to causing acute illness, there can also be long-term consequences as the result of acquisition of the virus. Several EBV-related illnesses occur including certain cancers and autoimmune diseases, as well as complications of primary immunodeficiency in persons with the certain genetic mutations. A major obstacle to understanding these sequelae has been the lack of an efficient animal model for EBV infection, although progress in primate and mouse models has recently been made. Key future challenges are to develop protective vaccines and effective treatment regimens.

Combination of Epstein-Barr virus nuclear antigen 1, 3 and lytic antigen BZLF1 peptide pools allows fast and efficient stimulation of Epstein-Barr virus-specific T cells for adoptive immunotherapy

BACKGROUND

Epstein-Barr virus (EBV) infection is a major cause of morbidity following hematopoietic stem cell transplantation. EBV-infected B cells may not respond to rituximab treatment and may lead to a life-threatening post-transplantation lymphoproliferative disorder. Adoptive cellular immunotherapy using EBV-lymphoblastoid cell lines (LCL) as stimulating antigen has proved effective in restoring specific immunity. However, EBV presents several immunodominant antigens, and developing a swift and effective clinical-grade immunotherapy relies on the definition of a Good Manufacturing Practices (GMP) universal stimulating antigen.

METHODS

Peripheral blood mononuclear cells (PBMCs) from six donors with a cellular immune response against EBV were immunoselected after stimulation with a new EBV antigen associated with an EBNA3 peptide pool.

RESULTS

After immunoselection, a mean of 0.53 ± 0.25 × 10⁶ cells was recovered consisting of a mean of 24.77 ± 18.01% CD4⁺-secreting interferon (IFN)-γ and 51.42 ± 26.92% CD8⁺-secreting IFN-γ. The T memory stem cell sub-population was identified. EBV-specific T cells were expanded in vitro, and their ability to secrete IFN-γ and to proliferate after re-stimulation with EBV antigen was confirmed. A specific lysis was observed against autologous target cells pulsed with EBV peptide pools (57.6 ± 11.5%) and against autologous EBV-LCL (18.3 ± 7.3%). A mean decrease of 94.7 ± 3.3% in alloreactivity against third-party donor mononuclear cells with EBV-specific T cells was observed compared with PBMCs before selection.

CONCLUSIONS

Our results show that a combination of peptide pools including EBNA3 is needed to generate EBV-specific T cells with good specific cytotoxicity and devoid of alloreactivity, but as yet GMP grade is not fully achieved.