AIMS: This study aimed to examine changes in the repertoire of functional T-cells specific for six leukemia-associated antigens (LAA), including WT1, PRAME, MUC1, CCNA1, NPM1, and NPM1c, during immune reconstitution following allogeneic transplantation of hematopoietic stem cells (HSCT) in patients with acute myeloid leukemia. PATIENTS & METHODS: LAA-specific T cell response was measured by ELISPOT- IFNγ and intracellular cytokine staining in 47 patients before starting conditioning therapy (baseline) and 7 months after HSCT. RESULTS: The positive cumulative LAA-specific T cell response before HSCT was associated with a decreased risk of relapse after HSCT. The prevalent genetic aberration - an internal tandem duplication of Fms 3 - related receptor tyrosine kinase, which has been previously implicated in immune escape mechanisms, is presented here for the first time as a factor associated with the absence of an adaptive T cell response against multiple LAAs. T-cell specific responses against wild-type and mutated NPM1 antigens were less frequent in the study cohort and did not correlate with mutations in the NPM1 gene. CONCLUSIONS: Our results showed that the T-cell response to LAA can be reconstituted after HSCT. Measurement of functional pre-transplant T-cell responses against multiple LAAs could help to find patients with an increased risk of relapse.

• Keywords
• ELISPOT-interferon gamma, Flt3-ITD, Leukemia associated antigen, T cell response, acute myeloid leukemia, hematopoietic stem cell transplantation, relapse,
• MeSH
• Leukemia, Myeloid, Acute * therapy   genetics   immunology   MeSH
• Antigens, Neoplasm immunology   MeSH
• Adult MeSH
• Transplantation, Homologous MeSH
• Nuclear Proteins genetics   MeSH
• Middle Aged MeSH
• Humans MeSH
• Adolescent MeSH
• Young Adult MeSH
• Mutation MeSH
• Nucleophosmin MeSH
• Recurrence MeSH
• Aged MeSH
• T-Lymphocytes * immunology   MeSH
• Hematopoietic Stem Cell Transplantation * MeSH
• fms-Like Tyrosine Kinase 3 * genetics   MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Adolescent MeSH
• Young Adult MeSH
• Male MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Antigens, Neoplasm MeSH
• FLT3 protein, human MeSH Browser
• Nuclear Proteins MeSH
• NPM1 protein, human MeSH Browser
• Nucleophosmin MeSH
• fms-Like Tyrosine Kinase 3 * MeSH

BACKGROUND: Allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients are at high risk of complications associated with COVID-19 infection due to dysfunction of their immune system. Vaccination can protect from the adverse consequences of COVID-19. However, studies on the efficacy of COVID-19 vaccines in HSCT recipients with insufficient post-HSCT immune reconstitution are still scarce. In our study, we determined how immunosuppressive medication and the reconstitution of the cellular immune system influenced T cell responses specific for the surface glycoprotein of SARS-CoV-2 virus (S antigen) after two doses of mRNA vaccine against COVID-19 in patients with myeloid malignancies treated with HSCT. METHODS: Vaccination outcomes were followed in 18 (allo-HSCT) recipients and 8 healthy volunteers. The IgG antibodies against SARS-CoV-2 spike (S) and nucleocapsid (NCP) protein were determined in ELISA and S-specific T cells were detected using a sensitive ELISPOT-IFNγ based on in vitro expansion and restimulation of T cells in pre- and post-vaccination blood samples. Multiparametric flow cytometry analysis of peripheral blood leukocyte differentiation markers was employed for determination of reconstitution of the main subpopulations of T cells and NK cells at month 6 after HSCT. RESULTS: S- specific IgG antibody response detected in 72% of the patients was lower than in healthy vaccinees (100%). Vaccine-induced T-cell responses to S1 or S2 antigen were significantly reduced in HSCT recipients, which were treated with corticosteroids in dose 5 mg of prednisone- equivalents or higher during the vaccination period or in preceeding 100 days in comparison with recipients un-affected with corticosteroids. A significant positive correlation was found between the level of anti-SARS-Cov-2 spike protein IgG antibodies and the number of functional S antigen-specific T cells. Further analysis also showed that the specific response to vaccination was significantly influenced by the interval between administration of vaccine and transplantation. Vaccination outcomes were not related to age, sex, type of mRNA vaccine used, basic diagnosis, HLA match between HSC donor and recipient, and blood counts of lymphocytes, neutrophils, and monocytes at the time of vaccination. Multiparametric flow cytometry analysis of peripheral blood leukocyte differentiation markers showed that good humoral and cellular S-specific immune responses induced by vaccination were associated with well-reconstituted CD4+ T cells, mainly CD4+ effector memory subpopulation at six months after HSCT. CONCLUSIONS: The results showed that both humoral and cellular adaptive immune responses of HSCT recipients to the SARS-CoV-2 vaccine were significantly suppressed by corticosteroid therapy. Specific response to the vaccine was significantly affected by the length of the interval between HSCT and vaccination. Vaccination as early as 5 months after HSCT can lead to a good response. Immune response to the vaccine is not related to age, gender, HLA match between HSC donor and recipient, or type of myeloid malignancy. Vaccine efficacy was dependent on well-reconstituted CD4+ T cells, at six months after HSCT.

• Keywords
• Allogeneic hematopoietic stem cell transplantation, Antibodies, COVID-19, Immune reconstitution, SARS-Cov-2, T cells, Vaccination,
• MeSH
• COVID-19 * prevention & control   MeSH
• Immunity MeSH
• Immunoglobulin G MeSH
• Immunosuppression Therapy MeSH
• Humans MeSH
• mRNA Vaccines MeSH
• Neoplasms * MeSH
• SARS-CoV-2 MeSH
• Hematopoietic Stem Cell Transplantation * adverse effects   MeSH
• COVID-19 Vaccines MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Immunoglobulin G MeSH
• mRNA Vaccines MeSH
• COVID-19 Vaccines MeSH

Nucleophosmin (NPM1, B23) is a multifunctional phosphoprotein expressed in all tissues. The protein is mainly localized in nucleoli. In hematological malignancies, NPM1 belongs to commonly altered genes. Its mutation, always heterozygous, leads to the re-localization of the NPM1 protein from the nucleolus to the cytoplasm (NPM1c+). NPM1c+ is found in 30% of acute myeloid leukemia (AML). Our study showed that an AML patient, whose leukemia cells carried the NPM1c+ mutation and who was the recipient of allogeneic HSCT from a haploidentical donor, raised a robust allorestricted CD8+ T cell response directed against the NPM1wt protein. Favourably, the response against NPM1wt was not accompanied by side effects such as GvHD. Moreover, the induction of a high NPM1wt-specific response coincided with the decrease in NPM1c+ transcripts detected, implying a beneficial graft versus leukemia effect. On the basis of these results, we suppose that TCRs from allorestricted NPM1wt-specific T cells are worth studying in other recipients of grafts from haploidentical donors as a possible tool for TCR gene therapy.

• Keywords
• T cell response, acute myeloid leukemia, hematopoietic stem cell transplantation, mutation, nucleophosmin 1,
• MeSH
• Leukemia, Myeloid, Acute * genetics   metabolism   therapy   MeSH
• CD8-Positive T-Lymphocytes metabolism   pathology   MeSH
• Hematopoietic Stem Cells metabolism   pathology   MeSH
• Nuclear Proteins genetics   metabolism   MeSH
• Humans MeSH
• Nucleophosmin * MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Nuclear Proteins MeSH
• Nucleophosmin * MeSH