ORCID Profile
0000-0003-2301-2664
Current Organisation
University of Oxford
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Publisher: American Society of Hematology
Date: 22-01-2015
DOI: 10.1182/BLOOD-2014-07-589150
Abstract: CMV serostatus significantly influences chimerism levels after T-cell–depleted allogeneic transplantation. CMV-specific T cells are exclusively of recipient origin after R+/D− T-cell–depleted transplants and appear to provide protective immunity.
Publisher: Oxford University Press (OUP)
Date: 2011
DOI: 10.1093/CID/CIQ042
Abstract: Adoptive transfer of virus-specific T cells may accelerate reconstitution of antigen-specific immunity and limit the morbidity and mortality of viral infections following allogeneic hematopoietic stem cell transplantation. The logistics of producing virus-specific T cells has, however, limited the application of cellular therapies, particularly following the introduction of more-recent regulatory stipulations. We investigated the ability of cytomegalovirus-specific T cells, directly isolated from donor leucapheresates on the basis of interferon γ secretion, to restore antiviral immunity in a group of 25 patients following related-donor transplantation in a single-arm phase I-II study. Selected cells were administered early following transplantation, either after the detection of cytomegalovirus DNA by polymerase chain reaction-based surveillance or prophylactically between day 40 and day 50. Cell selection was successful in all cases, yielding a product biased towards CD4(+) over CD8(+) T cells. The target cell dose of 1 × 10(4) CD3(+) T cells/kg of recipient weight contained a median of 2840 cytomegalovirus-specific CD4(+) cells/kg and 630 cytomegalovirus-specific CD8(+) cells/kg, with a median purity of 43.9% interferon γ-secreting cells. Expansions of both CD4(+) and CD8(+) cytomegalovirus-specific T cells were observed in vivo within days of adoptive transfer. These cells were predominantly terminally differentiated effector-memory cells and showed the same T cell receptor variable β chain (TCRBV) -restriction as the infused cells. They offered protection from reinfection in the majority of patients. These data indicate that application of cytomegalovirus-specific T cells generated by direct selection using γ-capture is both feasible and effective in a clinical environment. These simple in vitro methodologies should allow more widespread application of virus-specific T cell immunotherapies.
Publisher: The American Association of Immunologists
Date: 15-04-2011
Abstract: Cutaneous vaccination with lentiviral vectors generates systemic CD8 T cell responses that have the potential to eradicate tumors for cancer immunotherapy. However, although s.c. immunization with & million lentiviral particles clearly primes cytotoxic T cells, vaccination with much higher doses has routinely been used to define the mechanisms of T cell activation by lentiviral vectors. In particular, experiments to test presentation of lentiviral Ags by dendritic cells (DC) require injection of high viral titers, which may result in aberrant transduction of different DC populations. We exploited inducible murine models of DC depletion to investigate which DC prime the lentiviral response after s.c. immunization with low doses of lentiviral particles. In this article, we demonstrate that conventional DC are required to present Ag to CD8 T cells in draining lymph nodes. Langerhans cells are not required to activate the effector response, and neither Langerhans cells nor plasmacytoid DC are sufficient to prime Ag-specific T cells. Immunization drives the generation of endogenous long-lived memory T cells that can be reactivated to kill Ag-specific targets in the absence of inflammatory challenge. Furthermore, lentiviral vaccination activates expansion of endogenous CD4 Th cells, which are required for the generation of effector CD8 T cells that produce IFN-γ and kill Ag-specific targets. Collectively, we demonstrate that after cutaneous immunization with lentiviral particles, CD4-licensed lymph node conventional DC present Ag to CD8 T cells, resulting in the generation of protective endogenous antitumor immunity that may be effective for cancer immunotherapy.
Publisher: American Society of Hematology
Date: 30-06-2011
DOI: 10.1182/BLOOD-2011-01-329185
Abstract: Langerhans cells (LCs) are a distinct population of dendritic cells that form a contiguous network in the epidermis of the skin. Although LCs possess many of the properties of highly proficient dendritic cells, recent studies have indicated that they are not necessary to initiate cutaneous immunity. In this study, we used a tractable model of cutaneous GVHD, induced by topical application of a Toll-like receptor agonist, to explore the role of LCs in the development of tissue injury. By adapting this model to permit inducible and selective depletion of host LCs, we found that GVHD was significantly reduced when LCs were absent. However, LCs were not required either for CD8 T-cell activation within the draining lymph node or subsequent homing of effector cells to the epidermis. Instead, we found that LCs were necessary for inducing transcription of IFN-γ and other key effector molecules by donor CD8 cells in the epidermis, indicating that they license CD8 cells to induce epithelial injury. These data demonstrate a novel regulatory role for epidermal LCs during the effector phase of an inflammatory immune response in the skin.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Ronjon Chakraverty.