Polymorphism of the HLA system and weak antibody response to BNT162b2 mRNA vaccine

The polymorphism of the HLA system has been extensively studied in COVID-19 infection, however there are no data about the role of HLA on vaccine response. We report here the HLA-A, -B, -C, and DRB1 allelic frequencies of n = 111 individuals after BNT162b2 mRNA vaccine, selected on the basis of lower antibody levels (<5% percentile) after the second dose among a total of n = 2569 vaccinees, and compare them with the frequencies of a reference population. We found that differences in the frequencies of the alleles HLA-A*03:01, A*33:03, B*58:01 and at least one haplotype (HLA-A*24:02~C*07:01~B*18:01~DRB1*11:04) are associated with a weaker antibody response after vaccination, together with the age of vaccinees. Our results might suggest a role played by some HLA alleles or haplotypes in antibody production after the BNT162b2 mRNA vaccine, giving insights into the tracking of potentially susceptible individuals across populations. Further studies are needed to better define our exploratory findings and dissect the role of HLA polymorphism on response to anti-COVID-19 vaccines.

The number of HLA confirmatory tests during unrelated donor search as a driver for the evaluation of back-up haploidentical donor(s)

INTRODUCTION

the identification of a suitable donor in an appropriate timing represents a crucial step in the preparation of allogeneic stem cell transplantation (HSCT). At our Institution, for patients lacking an HLA-identical sibling, a haploidentical donor is considered in the absence of a 10/10-matched or a one-locus HLA-mismatched unrelated donor (UD), but the optimal timing of work-up of potential familiar haploidentical donor(s) by the Apheresis Team is actually unknown.

PATIENTS & METHODS

we analyzed here n = 167 UD searches launched at our Hospital between July 2013 and July 2018 and looked for any correlation between the number of HLA confirmatory tests received and the final type of donor selected for HSCT, in an attempt to identify those situations where prompt evaluation of haploidentical donor(s) is warranted.

RESULTS

a total of n = 117 transplants were performed and haploidentical HSCTs were n = 16 (14 %). In n = 93 cases (56 %) the number of HLA confirmatory tests received were two; they were one, zero and three for n = 52, n = 14 and n = 8 patients, respectively. Only 5 % of haploidentical donors were used when two confirmation test samples were received whereas this percentage rises to 17 % when only one sample reached the HLA lab. When no confirmation tests were available, haploidentical transplant occurred in 100 % of cases.

CONCLUSIONS

besides the situations with no HLA confirmation tests, the evaluation of any haploidentical donor(s) should be promptly started also when only one HLA confirmatory test is received, in order to optimise the potential work-up process and avoid delay in transplantation.

The Role of Quantitative Polymerase Chain Reaction in the Management of Follicular Lymphoma Patients

Aims and background

In order to increase the prognostic significance of polymerase chain reaction (PCR) data it has been suggested that quantitative PCR can be used to measure tumor burden. However, this option has not yet been definitely supported or refuted in patients with follicular lymphoma (FL). We decided to evaluate whether knowledge of the quantitative level of minimal residual disease and its variations can be of use in the management of FL patients.

Methods

We used qualitative and competitive PCR to study 11 patients with refractory or relapsed FL harboring the t(14;18) translocation who underwent autologous (nine patients) or allogeneic (two patients) stem cell transplantation (SCT). Competitive PCR was performed with a multiple competitor carrying specific sequences including Bcl2/lgH MBR and mcr, and the β-globin gene.

Results

After a median post-SCT follow-up of 44 months (range, 12-62), overall survival was 91% and disease-free survival 82%. The quantitative PCR data showed that: 1) effective chemotherapy before SCT substantially (1-2 log) reduced the tumor burden in the bone marrow (BM); 2) the increase in rearranged DNA detected in BM was associated with disease progression and relapse; 3) a PCR-negative autograft seemed to lead to lasting molecular remission even when it was performed in patients with a low level of BM infiltration before transplant; and 4) allo-SCT made and maintained the BM PCR negative even in the presence of a greater tumor burden before SCT. Six of the nine patients having CR after SCT (four auto and two allo) are in continuous molecular remission.

Conclusions

In FL patients qualitative and quantitative PCR may provide data that can be helpful for the prognostic evaluation of tumor progression and the early detection of impending relapse by highlighting biological features such as the quality of the infused material, the tumor burden at transplant, and the behavior of tumor cells after transplant.

The distribution of KIR-HLA functional blocks is different from north to south of Italy

The killer cell immunoglobulin-like receptor (KIR)-human leukocyte antigen (HLA) interaction represents an example of genetic epistasis, where the concomitant presence of specific genes or alleles encoding receptor-ligand units is necessary for the activity of natural killer (NK) cells. Although KIR and HLA genes segregate independently, they co-evolved under environmental pressures to maintain particular KIR-HLA functional blocks for species survival. We investigated, in 270 Italian healthy individuals, the distribution of KIR and HLA polymorphisms in three climatic areas (from cold north to warm south), to verify their possible geographical stratification. We analyzed the presence of 13 KIR genes and genotyped KIR ligands belonging to HLA class I: HLA-C, HLA-B and HLA-A. We did not observe any genetic stratification for KIR genes and HLA-C ligands in Italy. By contrast, in a north-to-south direction, we found a decreasing trend for the HLA-A3 and HLA-A11 ligands (P = 0.012) and an increasing trend for the HLA-B ligands carrying the Bw4 epitope (P = 0.0003) and the Bw4 Ile80 epitope (P = 0.0005). The HLA-A and HLA-B KIR ligands were in negative linkage disequilibrium (correlation coefficient -0.1211), possibly as a consequence of their similar function in inhibiting NK cells. The distribution of the KIR-HLA functional blocks was different along Italy, as we observed a north-to-south ascending trend for KIR3DL1, when coupled with HLA-B Bw4 ligands (P = 0.0067) and with HLA-B Bw4 Ile80 (P = 0.0027), and a descending trend for KIR3DL2 when coupled with HLA-A3 and HLA-A11 ligands (P = 0.0044). Overall, people from South Italy preferentially use the KIR3DL1-HLA-B Bw4 functional unit, while those from the North Italy equally use both the KIR3DL2-HLA-A3/A11 and the KIR3DL1-HLA-B Bw4 functional units to fight infections. Thus, only KIR3DL receptors, which exert the unique role of microbial sensors through the specific D0 domain, and their cognate HLA-A and HLA-B ligands are selectively pressured in Italy according to geographical north-to-south distribution.

Chronic myelogenous leukemia with acquired c-kit activating mutation and transient bone marrow mastocytosis

Mutations of the c-kit gene have been reported in myeloproliferative disorders. We describe here a case of Ph+ (b2a2) chronic myelogenous leukemia that, during the course of disease, showed an unusual bone marrow mast-cell infiltration. A mutational screening for the c-kit gene, performed on DNA routinely cryopreserved during the follow-up, evidenced the D816Y-activating mutation as an additional genetic abnormality. Treatment with imatinib mesylate resulted in a substantial decrease of the BCR-ABL/ABL ratio and in the absence of c-kit mutation. It is likely that the superimposed c-kit mutation, in this case, may account for the transient bone marrow mastocytosis.

The expression of the non-receptor tyrosine kinases Arg and c-abl is differently modulated in B lymphoid cells at different stages of differentiation

The products of the human ARG gene and the human ABL gene characterize the Abelson family of non-receptor tyrosine protein kinases. Both genes are ubiquitously expressed. The interactions of these two similar protein kinases are still not well known, although it has been suggested that they could cooperate, with redundant actions, to provide intracellular signals in the cells. Lymphopenia occurs in mice with homozygous disruption of c-abl, indicating that in certain tissues Arg is unable to substitute c-abl functions. In B and T lymphoid cell lines at different stages of differentiation, we studied, by a reverse transcriptase-competitive polymerase chain reaction and Western blotting, Arg and c-abl in order to evaluate whether the expression pattern of the two genes could give insight as to why they do not exhibit overlapping roles in lymphocytes and whether the product levels of the two genes are related to lymphoid differentiation. The data showed that their expression is differently modified in lymphoid B cell lines. The highest Arg transcript and protein levels are in the mature B cells.

The possible influences of B2A2 and B3A2 BCR/ABL protein structure on thrombopoiesis in chronic myeloid leukaemia

The Philadelphia chromosome, t(9;22)(q34;q11) gives rise more frequently, in chronic myeloid leukaemia (CML), to two BCR/ABL chimeric transcripts differing only by the absence of 75 nucleotides and defined as b2a2 and b3a2 types, encoding two 210-kDa tyrosine kinase proteins differing only by the absence of 25 amino acids coded by the b3 exon. In the present study the two transcripts, detected by RT-PCR in 88 consecutive unselected CML patients, were correlated with haematological findings at diagnosis and with the megakaryocyte size and frequency by morphometric evaluation of 45 bone marrow biopsies. The secondary structure prediction and hydrophobicity of the b2a2 and b3a2 type BCR/ABL protein were also obtained. The prediction results for the b3 exon amino acids using GOR IV and NnPredict methods showed a short beta strand corresponding to the hydrophobic portion of the peptide. Significantly higher values were found in the platelet count of patients carrying b3a2 transcripts. The megakaryocyte size and frequency in bone marrow biopsies did not show significant differences between the two groups of patients. Stratifying the patients on the basis of white blood cell (WBC) count below or above 100x10(9)/l we still had, in both groups, a significant difference in the platelet count between the b2a2 and b3a2 patients. The possible relationships between the structure of b2a2 and b3a2 types of BCR/ABL fused protein and thrombopoiesis are discussed.