No abstract

A better understanding of the reconstitution of the B-cell compartment during and after treatment in B-cell precursor acute lymphoblastic leukaemia (BCP-ALL) will help to assess the immunological status and needs of post-treatment BCP-ALL patients. Using 8-colour flow cytometry and proliferation-assays, we studied the composition and proliferation of both the B-cell precursor (BCP) population in the bone marrow (BM) and mature B-cell population in peripheral blood (PB) during and after BCP-ALL therapy. We found a normal BCP differentiation pattern and a delayed formation of classical CD38 -naive mature B-cells, natural effector B-cells and memory B-cells in patients after chemotherapy. This B-cell differentiation/maturation pattern was strikingly similar to that during initial B-cell development in healthy infants. Tissue-resident plasma cells appeared to be partly protected from chemotherapy. Also, we found that the fast recovery of naive mature B-cell numbers after chemotherapy was the result of increased de novo BCP generation, rather than enhanced B-cell proliferation in BM or PB. These results indicate that post-treatment BCP-ALL patients will eventually re-establish a B-cell compartment with a composition and B-cell receptor repertoire similar to that in healthy children. Additionally, the formation of a new memory B-cell compartment suggests that revaccination might be beneficial after BCP-ALL therapy.

Immunotherapies targeting truly tumor-specific targets focus on the expansion and activation of T cells against neoantigens or oncogenic viruses. One target is the human papilloma virus type 16 (HPV16), responsible for several anogenital cancers and oropharyngeal carcinomas. Spontaneous and vaccine-induced HPV-specific T cells have been associated with better clinical outcome. However, the epitopes and restriction elements to which these T cells respond remained elusive. To identify CD8+ T cell epitopes in cultures of tumor infiltrating lymphocytes, we here used multimers and/or a functional screening platform exploiting single HLA class I allele-engineered antigen presenting cells. This resulted in the detection of 20 CD8+ T cell responses to 11 different endogenously processed HLA-peptide combinations within 12 HPV16-induced tumors. Specific HLA-peptide combinations dominated the response in patients expressing these HLA alleles. T cell receptors (TCRs) reactive to seven different HLA class I-restricted peptides could be isolated and analysis revealed tumor reactivity for five of the six TCRs analyzed. The tumor reactive TCRs to these dominant HLA class I peptide combinations can potentially be used to engineer tumor-specific T cells for adoptive cell transfer approaches to treat HPV16-induced cancers.