ALBERT

Description: Introduction: Allogeneic hematopoietic cell transplantation (allo-HCT) constitutes the only curative treatment for myelofibrosis (MF), but its associated toxicity remains high. Prognostic risk models are widely used in clinical practice to select those MF patients who are more likely to benefit from transplantation. Recently, a new prognostic model, the Myelofibrosis Transplant Scoring System (MTSS), has been developed to predict the outcome of MF patients undergoing allo-HCT (Gagelmann N et al, Blood 2019). We aimed to evaluate the performance of such model in an independent series of patients. Methods: This is a retrospective study that included all adult patients who underwent first allo-HCT for MF between January 2005 and May 2019 in 8 Spanish hospitals. Patients transplanted after leukemic transformation were excluded. Survival probability from the time of HCT was estimated by the method of Kaplan-Meier and compared by the log-rank test. Each parameter of the MTSS was tested for its potential association with survival in univariate analysis. Cumulative incidence functions were used to estimate incidence of Graft-versus-Host-Disease (GVHD), Relapse Incidence (RI), and Non-Relapse Mortality (NRM) within a competing risk setting. Statistical analyses were performed with SPSS 19 (SPSS Inc./IBM, Armonk, NY) and R. Results: Demographics and transplant characteristics of the overall series of 107 MF patients are shown in Table 1. After a median follow-up from allo-HCT of 5.3 years, 49 patients (46%) had died. The survival probability at 1, 3, and 5-years was 64.5%, 52%, and 50%, respectively. Transplantation outcome improved over the years. Thus, the survival probability at 3-years was 35% (95% CI: 12-58), 50% (95% CI: 33-67), and 65% (95% CI: 50-80) during the time periods 2005-2009 (n=17), 2010-2014 (n=34), and 2015-2019 (n=56), respectively (P=0.038). The cumulative incidence of grade II-IV acute GVHD at day 100 was 45%. The cumulative incidence of relapse at 1, 3, and 5-years was 16%, 19.5%, and 19.5%, respectively. NRM probability at 1, 3, and 5-years was 24%, 29%, and 31%, respectively. In univariate analysis, the only parameter included in the MTSS that was significantly associated with survival was the Karnofsky performance status 〈 90% (HR: 1.9, 95% CI: 1.1-3.4; P=0.031). Neither age 〉 57 years (P=0.68), platelets 25 x 109/L (P=0.38), ASXL1 mutations (P=0.34), non-CALR/MPL driver mutation (P=0.57) nor HLA-mismatched unrelated donor (P=0.22) correlated with survival. Among other classical risk factors for transplant outcome, only a comorbidity index 〉= 3 was significantly associated with shorter survival (HR: 2.1, 95% CI: 1.1-4; P=0.017). A total of 64 cases had all required clinical and molecular data to calculate the MTSS. Figure 1 shows the survival curves of the different risk groups as defined by the MTSS. As can be seen, the prognostic model was not able to discriminate four risk groups. We then pooled together patients assigned to the low (n=26) and intermediate risk (n=23) groups, and those within the high (n=9) and very high risk (n=6) groups. On this basis, two-categories could be identified: standard risk (n=49 [77% of patients]) and high risk (n=15 [23%]). The 3-year overall survival was 65% (95% CI: 51-79) in the standard risk and 17% (95% CI: 0-46) in the high risk categories (P=0.060)(Figure 2). Conclusions: the MTSS did not discriminate four different risk categories in our series. Both, the limited number of cases and the differences in patients and transplant characteristics in our series as compared to those of the original MTSS cohort might account for this finding. Nevertheless, the MTSS was able to identify a subset of patients with a very poor prognosis after transplantation. Such information could be useful to assist on transplant decision-making. Disclosures Sanchez-Guijo: Novartis: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Amgen: Honoraria; Roche: Honoraria. Hernandez Boluda:Incyte: Other: Travel expenses paid.

Description: Background: Polycythemia vera (PV) and essential thrombocythemia (ET) are myeloproliferative neoplasms that can progress to post-PV (PPV) myelofibrosis (MF) and post-ET (PET) MF, also known as secondary myelofibrosis (SMF). The 2009 International Working Group for Myelofibrosis Research and Treatment group (IWG-MRT) diagnostic criteria for SMF require the presence of grade 2 or 3 bone marrow fibrosis (BMF) according to the European classification. The prognostic value of BMF in primary MF has been recently explored. Aim of this study is to describe the relevance of BMF grading in terms of presentation and outcome in SMF. Methods: The MYSEC (Myelofibrosis Secondary to PV and ET Collaboration) project is an international retrospective collaboration that collected 805 SMF cases. BMF grade at time of SMF evolution was defined as grade 2 (BMF2) in case of a diffuse increase in reticulin with extensive intersections, occasional bundles of collagen and/or osteosclerosis, or as grade 3 (BMF3) if presenting with coarse bundles of collagen, often associated with osteosclerosis. Chi-square or Fisher exact test for categorical variables, Wilcoxon rank-sum test for continuous ones and multiple logistic regression analysis were applied in order to explore pattern of association between BMF grading and patients' characteristics. A Poisson regression model was applied to estimate incidence rate of events, together with 95% Confidence Interval (CI). Survival was estimated using the Kaplan-Meier method. Differences between BMF groups were compared by a Log-rank test. The MYSEC study was approved by the Review Board of each Institution and conducted in accordance with the Declaration of Helsinki. Results: Detailed information about BMF grade was available in 675 patients: BMF2 was reported in 443 (65.6%) and BMF3 in 232 (34.4%). We did not find any correlation between BMF grade and advanced age, marrow blasts percentage, spleen and liver size, presence of constitutional symptoms, abnormal karyotype at the time of SMF diagnosis. No imbalance was evident for gender and for time to progression from PV/ET to SMF. Looking at genotype, BMF grading was not differently distributed among the 3 phenotypic driver mutations as well as the "triple negative" cases. On the contrary, in univariate analysis we found a significant association between BMF3 and previous diagnosis of ET vs. PV, decreased hemoglobin levels, reduced platelet and leukocyte counts, higher percentage of circulating blast cells and higher LDH value (Table 1). In a multivariate analysis that took into consideration SMF subtypes, complete blood count and circulating blast cells in 437 SMF patients, PET-MF, lower hemoglobin levels and reduced platelet count maintained their association with BMF3 (Table 2). The cumulative incidence of thrombosis after SMF was 3.2% (CI 95%: 2.4-4.2) person-year of follow up (PYFU) in BMF2, equivalent to BMF3 (2.7% PYFU, CI 95%: 1.2-5.7) (P = 0.44). Besides, BMF grade did not impact on the cumulative incidence of post-SMF blast phase, which resulted 2.4% (CI 95%: 1.8-3.3) PYFU in case of BMF2 and 3% (CI 95%: 1.3-6.9) PYFU in the BMF3 cohort (P = 0.68). Overall, MYSEC-PM (MYSEC-Prognostic Model) risk categories were differently distributed between BMF grades: patients with BMF2 were more frequently included in lower risk groups, while those with BMF3 were enriched in the higher categories (Table 1). Finally, we found a significantly higher mortality in patients with BMF3 vs. BMF2, mainly due to SMF progression (Table 1). Figure 1 shows the Kaplan-Meier estimate of survival in the 2 populations, resulting significantly different. Nevertheless, when considering the MYSEC-PM score in a multivariate analysis, BMF grade lost its prognostic impact on survival. Conclusions: This study provides evidence that BMF grade does correlate with specific clinical phenotype in SMF. BMF3 was associated with a more "cytopenic" phenotype (lower hemoglobin levels and reduced platelet count) and clustered with higher MYSEC-PM scores. Survival is significantly reduced in patients with BMF3. In conclusion, irrespectively of the PV/ET duration, progressive anemia and thrombocytopenia imply more frequently BMF3, finally resulting in a worse survival. This highlights the need of performing bone marrow biopsy earlier in disease evolution. Disclosures Rumi: novartis: Honoraria, Research Funding. Rambaldi:Omeros: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau, travel support; Celgene: Membership on an entity's Board of Directors or advisory committees, Other: travel support, Speakers Bureau; Amgen: Membership on an entity's Board of Directors or advisory committees, Other: travel support, Research Funding, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Other: travel support, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees, Other: travel support, Speakers Bureau; Italfarmaco: Membership on an entity's Board of Directors or advisory committees, Other: travel support, Research Funding, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Other: travel support, Research Funding, Speakers Bureau. Komrokji:Incyte: Consultancy; pfizer: Consultancy; JAZZ: Speakers Bureau; celgene: Consultancy; JAZZ: Consultancy; Novartis: Speakers Bureau; Agios: Consultancy; DSI: Consultancy. Gotlib:Deceiphera: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Seattle Genetics: Research Funding; Promedior: Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Research Funding; Blueprint Medicines: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Allakos: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Kiladjian:Novartis: Honoraria, Research Funding; AOP Orphan: Honoraria, Research Funding; Celgene: Consultancy. Cervantes:Novartis: Honoraria, Speakers Bureau; Celgene: Consultancy, Speakers Bureau. Palandri:Novartis: Consultancy, Honoraria. Silver:PharmEssentia: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Benevolo:Novartis Pharmaceuticals: Consultancy. Albano:Incyte: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Iurlo:Novartis: Other: Speaker Honoraria; Incyte: Other: Speaker Honoraria; Pfizer: Other: Speaker Honoraria. Vannucchi:Incyte: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees; Italfarmaco: Membership on an entity's Board of Directors or advisory committees; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Passamonti:Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Consultancy, Speakers Bureau; Celgene Corporation: Consultancy, Speakers Bureau; Janssen: Consultancy, Speakers Bureau.

Description: Background Persons with multiple sclerosis (MS) are sometimes treated with high-dose immune suppressive or cytotoxic drugs and an autotransplant. Use of autotransplants may be substantially more common as many cases are not reported. Therapy-related mortality (TRM) has decreased to 70%, extended Disability Status Scale (EDSS ≤8 in the 2 w pretransplant), CNS magnetic resonance image (MRI) ≤3 mo pretransplant, no prior bone marrow toxic drugs, normal heart, liver, lung and kidney function, ≥6 mo since exposure to immune suppressive drugs. Results 495 females and 244 males were included; median age was 47 years. 310 patients presented with relapsing remitting MS (RRMS), 273 with secondary progressive (SPMS) and 156 with primary progressive (PPMS). All procedures were started on an outpatient basis and only 31 persons needed to be admitted to the hospital during the procedure. In order to obtain at least 1x106/Kg viable CD34 cells, one to three apheresis were performed (median 1). Total number of viable CD34+ cells infused ranged between 1 and 37.83 x106 / Kg (median 5.62). Patients recovered above 0.5 x109/L absolute granulocytes on day 8 (median, range 2-13), whereas platelet recovery above 20 x109/L on day 4 (median, range 0-10). Seven individuals required red blood cells and eight needed platelet transfusions. There was one transplant related death and the 30-month overall survival of the patients is 99.9%. Patients with RRMS or PPMS had a significant drop in the EDSS before and 15-mo after the transplant, whereas patients with SPMS remained stable (A). The response rate (either drop or stabilization of the EDSS score) at 12 months was 78% for RRMS, 81% for PPMS and 73% for SPMS (B), whereas the relapse-free survival was 84% for all patients (92% for PPMS, 83% for RRMS and 81% for SPMS). Conclusions Changes in the EDSS score consonant with neurological improvement were observed in persons with all types of MS after HSCT employing the "Mexican method". Figure 1 Disclosures Gomez-Almaguer: Amgen: Consultancy, Speakers Bureau; Janssen: Consultancy, Speakers Bureau; Teva: Consultancy, Speakers Bureau; Takeda: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau.

Description: Abstract 1768 B-cell chronic lymphocytic leukemia (CLL) is characterized by deregulated expression of microRNAs (miRNAs). These post-transcriptional regulators of gene expression play a crucial role in controlling multiple cellular processes. By microarray analysis and quantitative RT-PCR we observed significantly lower levels of miR-126, miR-130a, miR-143, miR-181a and miR-326 in primary CLL cells compared to normal B cells. Transfection of synthetic miR-130a or miR-143 induced a significant reduction in cell viability of both primary CLL cells and the CLL cell line MEC-1. As autophagy is connected to cancer cell survival and resistance to apoptosis, we investigated the effect of these two miRNAs on autophagy by following the specific autophagosome marker LC3 (microtubule-associated protein 1 light chain 3). Therefore, we generated MEC-1 cells stably expressing GFP-tagged LC3 and analyzed autophagosome formation by using an imaging flow cytometer quantifying GFP-positive dots. These experiments revealed that autophagy is induced in these cells upon starvation, and that introduction of miR-130a, but not miR-143, resulted in a reduction of autophagosome formation (see Figure). These findings were verified by LC3 Western blot analysis, and extended to primary CLL cells, showing for the first time that autophagy is an active process in these cells and that miR-130a inhibits autophagy in primary CLL cells as well. To further elucidate the molecular mechanism of miR-130a-mediated CLL cell survival and autophagy, we aimed at identifying putative target genes of this miRNA and identified ATG2B, an autophagy-related gene, as well as DICER1 and AGO4, two components of the miRNA processing machinery, as direct target genes of miR-130a in CLL cells. The relevance and role of these three novel target genes in miR-130a-regulated cell death/cell survival programs is under current investigation. Figure: Analysis of autophagy using MEC-1 cell line stably expressing GFP-tagged LC3 protein. Green dots representing autophagosomes were quantified in MEC-1/GFP-LC3 cells under starvation by imaging flow cytometry (Image Stream, Amnis). Transfection with synthetic miR-130a reduced the autophagic flux in these cells compared to scrambled negative control miRNA (NC). Figure:. Analysis of autophagy using MEC-1 cell line stably expressing GFP-tagged LC3 protein. Green dots representing autophagosomes were quantified in MEC-1/GFP-LC3 cells under starvation by imaging flow cytometry (Image Stream, Amnis). Transfection with synthetic miR-130a reduced the autophagic flux in these cells compared to scrambled negative control miRNA (NC). Disclosures: No relevant conflicts of interest to declare.

Description: Background: After long-term treatment with tyrosine kinase inhibitors (TKIs), an important proportion of patients with chronic myeloid leukemia (CML) achieve and maintain a deep molecular response (DMR) that allows them to stop treatment indefinitely. However, approximately 50% of these patients on treatment-free remission (TFR) experience relapse by undetermined reasons. It has been described that TKIs may induce a potent antileukemic response that conditions the outcome of the discontinuation. Our objective was to analyze different immune parameters that could be used as biomarkers of safer treatment discontinuation. Objectives: To determine the modulation of immune biomarkers that could be related to current treatment with TKIs on patients with CML ("On TKI") or to successful TFR in patients that maintain DMR after treatment withdrawal ("Off TKI") or to relapse after TFR on patients that lost DMR. Materials & methods: We analyzed by flow cytometry the peripheral blood mononuclear cells (PBMCs) from 45 patients with CML "On TKI" for at least 9 months (imatinib (11), nilotinib (9), dasatinib (20) or bosutinib (5)), 17 patients "Off TKI" for at least 7 months who kept DMR at the moment of sampling (last TKI before TFR: imatinib (7), nilotinib (6), dasatinib(4)), 7 patients "Off TKI" for at least 1 year and 4 months who relapsed during TFR (samples from 3 patients were taken previous to TKI reintroduction (on relapse); samples from 4 patients were taken after they restarted treatment with TKIs ("On TKI" relapse), 4 patients with recent diagnosis of CML still untreated, and 20 healthy donors as basal control. Results: 1) Patients characteristics are shown in table 1. 2) Treatment with TKIs induced an increase of 8.6±1.2% ((p4%; CD86+

Description: INTRODUCTION Anemia is the most frequent cytopenia in lower-risk MDS. Erythropoietic-stimulating agents (ESAs) are commonly used in these patients. The use of ÒclassicalÓ parameters (EPO and ferritin levels) and the revised IPSS (IPSS-R) has been proposed1 (SantiniÕs score) to predict response to ESAs and overall survival (OS) among patients with lower risk MDS by IPSS and a favorable Nordic group score2. OBJECTIVES The main objective of the study was to evaluate overall response rate (ORR) to ESAs and OS according to the proposed SantiniÕs score in an independent and large cohort of anemic lower risk MDS patients receiving treatment with ESAs. METHODS Data from 530 anemic patients with low/int1 risk IPSS de novo MDS (according to FAB and WHO criteria) and sufficient follow-up data available were recorded in Spresas3 (SPanish Registry of Erythropoietic Stimulating Agents Study from GESMD). Two hundred and twenty six patients (42.6% of the patients) were selected according to specific criteria regarding the published SantiniÕs score1: Hb level 350 ng/mL(=1) and IPSS-R very low=0, low=1, intermediate=2 and high=3) yielded a score ranging from 0 to 5. ESAs response rate and overall survival were analysed according to these score. Response to treatment was evaluated according to IWG 2006 response criteria and a multivariate logistic regression analysis was used to identify independent predictors of erythroid response (ER). OS were defined as the time between diagnosis and the corresponding event or last follow up (Feb 2015) and were analyzed using univariable and multivariable Cox proportional hazards regression methods. RESULTS Median age was 77 years (interquartile range [IQR] 25%-75%: 71-83 y), median Hb level at start of treatment was 10 g/dL (IQR25-75: 9-10), median EPO level was 90 (IQR25-75: 27,25-108) and median ferritin level was 338,5 (IQR25-75: 146,5-568,75). Among 139 patients with this data available, 85 patients (61,1%) were RBC transfusion dependent before ESAs treatment. Median time from diagnosis to ESAs treatment was 82 (IQR25-75: 27-353) days. According to the IPSS, 68.6% (N=155) and 31.4% (N=71) were in low and Int-1 risk groups, respectively. Regarding IPSS-R, 23% (N=52), 66.8% (N=151), 9.7% (N=22) and 0.4% (N=1) were in very low, low, intermediate and high risk, respectively. ORR to ESA treatment was 71.2% (N=161), with a median duration of response of 2.06 years. Prognosis factors of ER showed a trend toward to a higher ER among patients in the lower IPSS-R (P〉0.05), low IPSS (p=0.039) and lower EPO levels (p

Description: Abstract 4452 Background: Molecular Monitoring of BCR-ABL through standardized qPCR according to the international scale (IS) has been recently included in the follow-up of CML patients treated with tyrosine kinase inhibitors (TKIs) at the IMSS. The Molecular Biology Laboratory of the “Hospital of Specialties” at the “National Medical Center Siglo XXI”, have recently achieved full standardization of the qPCR technique to the international scale (using a conversion factor provided by Adelaide lab). The use of the IS in the molecular monitoring expressed as Bcr-Abl/Abl ratio in percentage is very important, since this is the best way to adopt appropriate strategies with TKI therapy. Objective: To report the evaluation of molecular status of 485 patients with CML attended at the Instituto Mexicano del Seguro Social using the IS in a reference standardized Mexican laboratory. Material and Methods: From August 2011 to May 2012, peripheral blood samples of 485 patients with CML, were sent to our laboratory. We extracted RNA as previously described. A minimum of 5 ml of whole blood was required in order to maximize optimal results. Then we put these results in our database and classified patient samples in five groups according the percentage of Bcr-Abl/Abl in the international scale: The first group were patients with 〉10% of Bcr-Abl; the second group were patients with 〉1–10% of Bcr-Abl; the third group were patients with 〉0.1–1%; the fourth group were patients with ≤0.1% and the fifth group were patients with undetectable Bcr-Abl transcripts. Results: We found the following distribution: Group I (〉 10% Bcr-Abl): 91 patients (18.76%); Group II (〉1–10% Bcr-Abl): 65 patients (13.4%); Group III (〉0.1–1% Bcr-Abl) 83 patients (17.11%); Group IV (≤0.1% Bcr-Abl) 122 patients (25.15%); and Group V: undetectable Bcr-Abl: 124 patients (25.56%). Conclusion: Fifty percent of CML patients treated with nilotinib, imatinib or dasatinib, have reached a deep molecular response, that is, Major Molecular response (MMR) or better. Another 17% has reached a molecular response (〉0.1–1%) that is equivalent to Complete Cytogenetic response (CCyR). This information is very useful for clinicians and should be interpreted individually according the lenght of treatment with TKIs, following current CML guidelines and recommendations. Until now, molecular monitoring using the IS was only possible through sending samples to US laboratories. It is important that Mexican clinicians at our institution have now the opportunity to rely on a Mexican validated and standardized laboratory. The results of the molecular response in this cohort of CML patients can be compared to the data of another countries using the IS. Classifying patients according to their molecular status could help to optimized therapies at our institution. Disclosures: Nacho-Vargas: Novartis Oncology: Employment.

Description: In humans, whether B cells with the IgM+IgD+CD27+ phenotype represent an independent lineage involved in T-independent responses, similar to mouse marginal zone B cells, or whether they are part of the germinal center-derived memory B-cell pool generated during responses to T-dependent antigens, is still a debated issue. To address this question, we performed high-throughput Ig sequencing of B-cell subsets from paired blood and spleen samples and analyzed the clonal relationships between them. We isolated and analyzed 3 different B cell subsets based on CD27 and IgD staining from both blood and spleen: IgD+CD27+ (MZ) - amplified with Cmu primers IgD-CD27+ (switched and IgM-only) with Cmu, Cgamma and Calpha primers IgD-CD27- (CD27- memory or double-negative DN) with the same three primers We obtained 95729 unique sequences that clustered in 49199 different clones: 1125 clones were shared between blood and spleen of the same B-cell subset, and 1681 clones were shared between different subsets, allowing us to trace their relationships. We analyzed these clones that share sequences from different subsets/tissues for their mutation frequency distribution, CDR3-length, and VH/JH family usage, and compared these different characteristics with the bulk of sequences from their respective subset of origin. The analysis of clones shared between blood and spleen for switched IgG/IgA and for MZ subsets suggests different recirculation dynamics. For switched cells, the blood appears to be a mixture of splenic and other lymphoid tissues B cells. For MZ B cells in contrast, the blood appear to be only composed of a subgroup of the splenic repertoire, in agreement with the observation that marginal zone B cells recirculate and are mainly generated in the spleen. Clonal relationships between the IgM clones (originating from the MZ, IgM-only and double negative compartments) show that the clones involved display the characteristics of IgM-only B cells whatever their subset of origin, even in the case of the paired MZ/double-negative sequences that were not supposed to include IgM-only sequences. We therefore conclude that the clones shared between the various IgM subsets do not represent b between them, but rather correspond to a heterogeneous phenotype of the IgM-only population that concerns both IgD and CD27 expression, leading to a partial overlap with the MZ and double-negative gates. Clones shared between the MZ and the switched IgG and IgA compartment also show, for their IgM part, the mutation and repertoire characteristics of IgM-only cells and not of MZ B cells, reinforcing the conclusion that IgM-only are true memory B cells, and constitute the only subset showing clonal relationships with switched memory B cells. In summary, we report that MZ B cells have different recirculation characteristics and do not show real clonal relationships with IgM-only and switched memory B cells, in agreement with the notion that they represent a distinct differentiation pathway. In contrast, the only precursor-product relationship between IgM memory and switched B cells appear to concern a B cell subset that has been described as "IgM-only", but appears to have a more heterogeneous expression of IgD than previously reported and therefore contribute to 3-15% of the MZ compartment. Searching for markers that would permit to discriminate between marginal zone and germinal center-derived IgM memory B cells is obviously required to further delineate their respective function. Disclosures No relevant conflicts of interest to declare.

Description: To investigate the role of viral expression in individuals infected with human T-cell lymphotropic virus type 1 (HTLV-1), a real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) of HTLV-1 tax messenger RNA (mRNA) using ABI Prism 7700 Sequence Detection System was developed. Using this system, the HTLV-1tax mRNA load was compared with HTLV-1 proviral DNA load, HTLV-1 Tax protein expression, HTLV-1 Tax-specific CD8+T-cell frequency, and disease severity of HTLV-1–associated myelopathy/tropical spastic paraparesis (HAM/TSP). This approach was a sensitive and specific technique for the precise quantification of HTLV-1 tax mRNA. The total amount of HTLV-1 taxmRNA and mRNA expression level in HTLV-1–infected cells (mRNA/DNA ratio) were higher in HAM/TSP patients than in asymptomatic HTLV-1 carriers. The HTLV-1 tax mRNA load correlated with the HTLV-1 proviral DNA load ex vivo, the Tax protein expression in vitro, and the Tax-specific CD8+ T-cell frequency ex vivo. The HTLV-1 tax mRNA load also correlated with disease severity in HAM/TSP patients. These data suggest that increased HTLV-1 expression plays an important role in the pathogenesis of HAM/TSP, and the HTLV-1 tax mRNA level could be a useful predictor of disease progression in patients with HAM/TSP.