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Patients with chronic lymphocytic leukemia (CLL) may be more susceptible to Coronavirus disease 2019 (COVID-19) due to age, disease, and treatment-related immunosuppression. We aimed to assess risk factors of outcome and elucidate the impact of CLL-directed treatments on the course of COVID-19. We conducted a retrospective, international study, collectively including 941 patients with CLL and confirmed COVID-19. Data from the beginning of the pandemic until March 16, 2021, were collected from 91 centers. The risk factors of case fatality rate (CFR), disease severity, and overall survival (OS) were investigated. OS analysis was restricted to patients with severe COVID-19 (definition: hospitalization with need of oxygen or admission into an intensive care unit). CFR in patients with severe COVID-19 was 38.4%. OS was inferior for patients in all treatment categories compared to untreated (p

Progressió clínica; Evasió immune Progresión clínica; Evasión inmune Clinical progression; Immune evasion Background Mechanisms driving the progression of chronic lymphocytic leukemia (CLL) from its early stages are not fully understood. The acquisition of molecular changes at the time of progression has been observed in a small fraction of patients, suggesting that CLL progression is not mainly driven by dynamic clonal evolution. In order to shed light on mechanisms that lead to CLL progression, we investigated longitudinal changes in both the genetic and immunological scenarios. Methods We performed genetic and immunological longitudinal analysis using paired primary samples from untreated CLL patients that underwent clinical progression (sampling at diagnosis and progression) and from patients with stable disease (sampling at diagnosis and at long-term asymptomatic follow-up). Results Molecular analysis showed limited and non-recurrent molecular changes at progression, indicating that clonal evolution is not the main driver of clinical progression. Our analysis of the immune kinetics found an increasingly dysfunctional CD8+ T cell compartment in progressing patients that was not observed in those patients that remained asymptomatic. Specifically, terminally exhausted effector CD8+ T cells (T-betdim/−EomeshiPD1hi) accumulated, while the the co-expression of inhibitory receptors (PD1, CD244 and CD160) increased, along with an altered gene expression profile in T cells only in those patients that progressed. In addition, malignant cells from patients at clinical progression showed enhanced capacity to induce exhaustion-related markers in CD8+ T cells ex vivo mainly through a mechanism dependent on soluble factors including IL-10. Conclusions Altogether, we demonstrate that the interaction with the immune microenvironment plays a key role in clinical progression in CLL, thereby providing a rationale for the use of early immunotherapeutic intervention. This work was supported by the Instituto de Salud Carlos III, Fondo de Investigaciones Sanitarias (PI17/00950, M.C., PI18/01392, P.A. and PI17/00943, F.B.) and co-financed by the European Regional Development Fund (ERDF) and Fundación Asociación Española Contra el Cáncer (M.C. and P.A.), Gilead Fellowships (GLD16/00144, GLD18/00047, F.B.) and Fundació la Marató de TV3 (201905–30-31 F.B). S.B. is the recipient of a postdoctoral fellowship from Fundación Alfonso Martin Escudero. R.V-M. is supported by a Torres Quevedo fellowship from the Spanish Ministry of Science and Innovation (PTQ-16-08623). A.E-C. is funded by ISCIII/MINECO (PT17/0009/0019) which is co-funded by FEDER. M.C. holds a contract from Ministerio de Ciencia, Innovación y Universidades (RYC-2012-2018).

PURPOSE Among Bruton's tyrosine kinase inhibitors, acalabrutinib has greater selectivity than ibrutinib, which we hypothesized would improve continuous therapy tolerability. We conducted an open-label, randomized, noninferiority, phase III trial comparing acalabrutinib and ibrutinib in patients with chronic lymphocytic leukemia (CLL). METHODS Patients with previously treated CLL with centrally confirmed del(17)(p13.1) or del(11)(q22.3) were randomly assigned to oral acalabrutinib 100 mg twice daily or ibrutinib 420 mg once daily until progression or unacceptable toxicity. The primary end point was independent review committee–assessed noninferiority of progression-free survival (PFS). RESULTS Overall, 533 patients (acalabrutinib, n = 268; ibrutinib, n = 265) were randomly assigned. At the data cutoff, 124 (46.3%) acalabrutinib patients and 109 (41.1%) ibrutinib patients remained on treatment. After a median follow-up of 40.9 months, acalabrutinib was determined to be noninferior to ibrutinib with a median PFS of 38.4 months in both arms (95% CI acalabrutinib, 33.0 to 38.6 and ibrutinib, 33.0 to 41.6; hazard ratio: 1.00; 95% CI, 0.79 to 1.27). All-grade atrial fibrillation/atrial flutter incidence was significantly lower with acalabrutinib versus ibrutinib (9.4% v 16.0%; P = .02); among other selected secondary end points, grade 3 or higher infections (30.8% v 30.0%) and Richter transformations (3.8% v 4.9%) were comparable between groups and median overall survival was not reached in either arm (hazard ratio, 0.82; 95% CI, 0.59 to 1.15), with 63 (23.5%) deaths with acalabrutinib and 73 (27.5%) with ibrutinib. Treatment discontinuations because of adverse events occurred in 14.7% of acalabrutinib-treated patients and 21.3% of ibrutinib-treated patients. CONCLUSION In this first direct comparison of less versus more selective Bruton's tyrosine kinase inhibitors in CLL, acalabrutinib demonstrated noninferior PFS with fewer cardiovascular adverse events.

Chronic lymphocytic leukemia (CLL) is a disease of the elderly, characterized by immunodeficiency. Hence, patients with CLL might be considered more susceptible to severe complications from COVID-19. We undertook this retrospective international multicenter study to characterize the course of COVID-19 in patients with CLL and identify potential predictors of outcome. Of 190 patients with CLL and confirmed COVID-19 diagnosed between 28/03/2020 and 22/05/2020, 151 (79%) presented with severe COVID-19 (need of oxygen and/or intensive care admission). Severe COVID-19 was associated with more advanced age (≥65 years) (odds ratio 3.72 [95% CI 1.79–7.71]). Only 60 patients (39.7%) with severe COVID-19 were receiving or had recent (≤12 months) treatment for CLL at the time of COVID-19 versus 30/39 (76.9%) patients with mild disease. Hospitalization rate for severe COVID-19 was lower (p < 0.05) for patients on ibrutinib versus those on other regimens or off treatment. Of 151 patients with severe disease, 55 (36.4%) succumbed versus only 1/38 (2.6%) with mild disease; age and comorbidities did not impact on mortality. In CLL, (1) COVID-19 severity increases with age; (2) antileukemic treatment (particularly BTK inhibitors) appears to exert a protective effect; (3) age and comorbidities did not impact on mortality, alluding to a relevant role of CLL and immunodeficiency.

5 p.-2 fig., In chronic lymphocytic leukemia (CLL), α4β1 integrin (the main α4 heterodimer in CLL) and vascular endothelial growth factor (VEGF) share several pathological properties, including involvement in cell migration and survival.Accordingly, elevated expression of α4 integrin (≥30% cells) constitutes an adverse prognostic marker and VEGF serum levels increase with CLL progression and could also have prognostic value. CLL cells express VEGF receptor 1 (VEGFR1), VEGFR2, and VEGFR3 receptors.VEGFR2 is the main signaling receptor in response to VEGF165 and its elevated expression correlates with CLL aggressivenes. Previous studies in endothelial cells have demonstrated interactions and functional cross talk between integrins (αvβ3, α9β1, α3β1, α5β1) and the VEGF/VEGFR2 system, including integrin-mediated adhesion to VEGF and VEGF-induced integrin activation.Moreover, shedding of syndecan-1 in endothelial cells induced coupling of α4β1 integrin and VEGFR2, VEGFR2 activation, and angiogenesis. It is not known whether α4β1 interacts with VEGF/VEGFR2 or/and contributes to VEGF functions in CLL and we have addressed this in the present study., This work was supported by grants SAF2015-69180R from the Ministry of Economy and Competitivity (Spain) and S2010/BMD-2314 from the Comunidad de Madrid/European Union (A.G.-P.).

19 p.-9 fig.-1 tab., CLL remains an incurable disease in spite of the many new compounds being tested. Arsenic trioxide (ATO) induces apoptosis in all CLL cell types and could constitute an efficient therapy. To further explore this, we have studied the gene expression profile induced by ATO in CLL cells. ATO modulated many genes, largely involved in oxidative stress, being HMOX1 the most upregulated gene, also induced at the protein level. ATO also increased MMP-9, as we previously observed, both at the mRNA and protein level. Using specific inhibitors, qPCR analyses, and gene silencing approaches we demonstrate that upregulation of MMP-9 by ATO involved activation of the p38 MAPK/AP-1 signaling pathway. Moreover, gene silencing HMOX1 or inhibiting HMOX1 activity enhanced p38 MAPK phosphorylation and c-jun expression/activation, resulting in transcriptional upregulation of MMP-9. Overexpression of HMOX1 or enhancement of its activity, had the opposite effect. Cell viability analyses upon modulation of HMOX1 expression or activity demonstrated that HMOX1 had a proapoptotic role and enhanced the cytotoxic effect of ATO in CLL cells. We have therefore identified a new mechanism in which HMOX1 plays a central role in the response of CLL cells to ATO and in the regulation of the anti-apoptotic protein MMP-9. Thus, HMOX1 arises as a new therapeutic target in CLL and the combination of HMOX1 modulators with ATO may constitute an efficient therapeutic strategy in CLL., This work was supported by grants SAF2012-31613 and SAF2015-69180R (AGP) and RTICC (Red Temática de Investigación Cooperativa en Cáncer) RD12/0036/0061 (AGP), from the Ministry of Economy and Competitiveness (MINECO), Spain; S2010/BMD-2314-Neoplasbim (AGP) from the Comunidad de Madrid/European Union; and a grant from the Fundación para la Investigación Biomédica Hospital Universitario Puerta de Hierro, Madrid (JAGM).

CLL remains an incurable disease in spite of the many new compounds being studied. Arsenic trioxide (ATO) induces apoptosis in all CLL cell types and could constitute an efficient therapy. To further explore this, we have studied the influence of stromal cells, key components of the CLL microenvironment, on the response of CLL cells to ATO. Bone marrow stromal cells induced CLL cell resistance to 2 μM ATO and led to activation of Lyn, ERK, PI3K and PKC, as well as NF-κB and STAT3. Mcl-1, Bcl-xL, and Bfl-1 were also upregulated after the co-culture. Inhibition experiments indicated that PI3K and PKC were involved in the resistance to ATO induced by stroma. Moreover, idelalisib and sotrastaurin, specific inhibitors for PI3Kδ and PKCβ, respectively, inhibited Akt phosphorylation, NF-κB/STAT3 activation and Mcl-1 upregulation, and rendered cells sensitive to ATO. Mcl-1 was central to the mechanism of resistance to ATO, since: 1) Mcl-1 levels correlated with the CLL cell response to ATO, and 2) blocking Mcl-1 expression or function with specific siRNAs or inhibitors overcame the protecting effect of stroma. We have therefore identified the mechanism involved in the CLL cell resistance to ATO induced by bone marrow stroma and show that idelalisib or sotrastaurin block this mechanism and restore sensibility to ATO. Combination of ATO with these inhibitors may thus constitute an efficient treatment for CLL.

Chronic lymphocytic leukemia (CLL) is the most common adult leukemia in the Western world. Pathogenic mechanisms involve multiple external events (such as microenvironmental and antigenic stimuli) and internal events (genetic and epigenetic alterations) that are associated with the transformation, progression and evolution of CLL. CLL is characterized by an accumulation of mature B cells in peripheral blood, bone marrow and lymphoid tissues. Extracellular stimuli play an important role in the development and maintenance of neoplastic cells. B-CLL cells proliferate and activate pathogenic signaling pathways in anatomical structures known as proliferation centers, which are usually more conspicuous in involved lymph nodes.1 Its clinical course is quite heterogeneous, whereby some patients progress rapidly and have short survival, whereas others have a more stable clinical course that may not need treatment for years. This work was supported by grants from the Ministerio de Economía y Competitividad (MINECO) (SAF2013-47416-R) Instituto de Salud Carlos III (ISCIII)- FEDER – MINECO- AES (CP11/00018, PI10/00621, RD012/0036/0060), and Asociación Española contra el Cancer (AECC). MS-B is supported by a Miguel Servet contract from ISCIII-FEDER (CP11/00018). Salary support to SG is provided by CP11/00018, from ISCIII-FEDER. JG-R is supported by a predoctoral grant from the Fundación Investigación Puerta de Hierro. Sí

16 p.-1 tab.-11 fig., Background: Matrix metalloproteinase-9 (MMP-9) contributes to chronic lymphocytic leukemia (CLL) pathology by regulating cell migration and preventing spontaneous apoptosis. It is not known if MMP-9 is involved in CLL cell response to chemotherapy and we address this in the present study, using arsenic trioxide (ATO) and fludarabine as examples of cytotoxic drugs. Methods: We used primary cells from the peripheral blood of CLL patients and MEC-1 cells stably transfected with an empty vector or a vector containing MMP-9. The effect of ATO and fludarabine was determined by flow cytometry and by the MTT assay. Expression of mRNA was measured by RT-PCR and qPCR. Secreted and cell-bound MMP-9 was analyzed by gelatin zymography and flow cytometry, respectively. Protein expression was analyzed by Western blotting and immunoprecipitation. Statistical analyses were performed using the two-tailed Student’s t-test. Results: In response to ATO or fludarabine, CLL cells transcriptionally upregulated MMP-9, preceding the onset of apoptosis. Upregulated MMP-9 primarily localized to the membrane of early apoptotic cells and blocking apoptosis with Z-VAD prevented MMP-9 upregulation, thus linking MMP-9 to the apoptotic process. Culturing CLL cells on MMP-9 or stromal cells induced drug resistance, which was overcome by anti-MMP-9 antibodies. Accordingly, MMP-9-MEC-1 transfectants showed higher viability upon drug treatment than Mock-MEC-1 cells, and this effect was blocked by silencing MMP-9 with specific siRNAs. Following drug exposure, expression of anti-apoptotic proteins (Mcl-1, Bcl-xL, Bcl-2) and the Mcl-1/Bim, Mcl-1/Noxa, Bcl-2/Bax ratios were higher in MMP-9-cells than in Mock-cells. Similar results were obtained upon culturing primary CLL cells on MMP-9. Conclusions: Our study describes for the first time that MMP-9 induces drug resistance by modulating proteins of the Bcl-2 family and upregulating the corresponding anti-apoptotic/pro-apoptotic ratios. This is a novel role for MMP-9 contributing to CLL progression. Targeting MMP-9 in combined therapies may thus improve CLL response to treatment., This work was supported by grants SAF2012-31613 (AGP) and RTICC (Red Temática de Investigación Cooperativa en Cáncer) RD12/0036/0061 (AGP), from the Ministry of Economy and Competitiveness (MINECO), Spain; S2010/BMD-2314-Neoplasbim (AGP) from the Comunidad de Madrid/European Union; and by a grant from the Fundaci?n Puerta de Hierro, Madrid (JAGM). IAJ and EB were were supported by the Junta de Ampliación de Estudios program, CSIC/EU, Spain.

11 p.-6 fig.-2 tab., (pro)MMP-9 binds to CLL cells through the PEX9 domain and contributes to CLL progression. To biochemically characterize this interaction and identify potential therapeutic targets, we prepared GST-PEX9 forms containing structural blades B1B2 or B3B4. We recently described a sequence in blade B4 (P3 sequence) that bound α4β1 integrin and partially impaired cell adhesion and migration. We have now studied the possible contribution of the B1B2 region to cell interaction with PEX9. CLL cells bound to GST-B1B2 and CD44 was the primary receptor. GST-B1B2 inhibited CLL cell migration as effectively as GST-B3B4. Overlapping synthetic peptides spanning the B1B2 region identified the sequence FDAIAEIGNQLYLFKDGKYW, present in B1 and contained in peptide P6, as the most effective site. P6 inhibited cell adhesion to PEX9 in a dose-dependent manner and with an IC50 value of 90 μM. P6 also inhibited cell adhesion to hyaluronan but had no effect on adhesion to VCAM-1 (α4β1 integrin ligand), confirming its specific interaction with CD44. Spatial localization analyses mapped P6 to the central cavity of PEX9, in close proximity to the previously identified P3 sequence. Both P6 and P3 equally impaired cell adhesion to (pro)MMP-9. Moreover, P6 synergistically cooperated with P3, resulting in complete inhibition of CLL cell binding to PEX9, chemotaxis, and transendothelial migration. Thus, P6 is a novel sequence in PEX9 involved in cell-PEX9/(pro)MMP-9 binding by interacting with CD44. Targeting both sites, P6 and P3, should efficiently prevent (pro)MMP-9 binding to CLL cells and its pathological consequences., This work was supported by Grant SAF2012-31613 and by the Red Temática de Investigación Cooperativa en Cáncer (RD12/0036/0061) (to A. G. P.) from the Ministry of Economy and Competitivity (Madrid, Spain); S2010/BMD-2314 (to A. G. P.) from the Comunidad de Madrid/European Union; and by a grant from the Fundación Puerta de Hierro (Madrid, Spain) (to J. A. G.-M.).

Lymphoma patients with persistent disease undergoing autologous transplantation have a very poor prognosis in the rituximab era. The addition of radioimmunotherapy to the conditioning regimen may improve the outcome for these patients. In a prospective, phase 2 study, we evaluated the safety and efficacy of the addition of 90Y-ibritumomab tiuxetan to the conditioning chemotherapy in patients with refractory diffuse large B-cell lymphoma. Thirty patients with induction failure (primary refractory; n=18) or refractory to salvage immunochemotherapy at relapse (n=12) were included in the study. The median age of the patients was 53 years (range, 25–67). All patients were given 90Y-ibritumomab tiuxetan at a fixed dose of 0.4 mCi/kg (maximum dose 32 mCi) 14 days prior to the preparative chemotherapy regimen. Histological examination showed that 22 patients had de novo diffuse large B-cell lymphoma and eight had transformed diffuse large B-cell lymphoma. All patients had persistent disease at the time of transplantation, with 25 patients considered to be chemorefractory. The median time to neutrophil recovery (>500 white blood cells/μL) was 11 days (range, 9–21), while the median time to platelet recovery (>20,000 platelets/μL) was 13 days (range, 11–35). The overall response rate at day +100 was 70% (95% CI, 53.6–86.4) with 60% (95% CI, 42.5–77.5) of patients obtaining a complete response. After a median follow-up of 31 months for alive patients (range, 16–54), the estimated 3-year overall and progression-free survival rates are 63% (95% CI, 48–82) and 61% (95% CI, 45–80), respectively. We conclude that autologous transplantation with conditioning including 90Y-ibritumomab tiuxetan is safe and results in a very high response rate with promising survival in this group of patients with refractory diffuse large B-cell lymphoma with a very poor prognosis. Study registered at European Union Drug Regulating Authorities Clinical Trials (EudraCT) N. 2007-003198-22.

The prognosis for fit patients with mantle cell lymphoma has improved with intensive strategies. Currently, the role of maintenance/consolidation approaches is being tested as relapses continue to appear. In this trial we evaluated the feasibility, safety and efficacy of rituximab-hyperCVAD alternating with rituximab-methotrexate-cytarabine followed by consolidation with 90Y-ibritumomab tiuxetan. Patients received six cycles followed by a single dose of 90Y-ibritumomab tiuxetan. Thirty patients were enrolled; their median age was 59 years. Twenty-four patients finished the induction treatment, 23 achieved complete remission (77%, 95% confidence interval 60–93) and one patient had progressive disease (3%). Eighteen patients (60%), all in complete remission, received consolidation therapy. In the intent-to-treat population, failure-free, progression-free and overall survival rates at 4 years were 40% (95% confidence interval 20.4–59.6), 52% (95% confidence interval 32.4–71.6) and 81% (95% confidence interval 67.28–94.72), respectively. For patients who received consolidation, failure-free and overall survival rates were 55% (95% confidence interval 31.48–78.52) and 87% (95% confidence interval 70–100), respectively. Hematologic toxicity was significant during induction and responsible for one death (3.3%). After consolidation, grade 3–4 neutropenia and thrombocytopenia were observed in 72% and 83% of patients, with a median duration of 5 and 12 weeks, respectively. Six (20%) patients died, three due to secondary malignancies (myelodysplastic syndrome and bladder and rectum carcinomas). In conclusion, in our experience, rituximab-hyperCVAD alternated with rituximab-methotrexate-cytarabine and followed by consolidation with 90Y-ibritumomab tiuxetan was efficacious although less feasible than expected. The unacceptable toxicity observed, especially secondary malignancies, advise against the use of this strategy. Trial registration: clinical.gov identifier: NCT2005-004400-37

Chronic lymphocytic leukemia (CLL) is a heterogeneous disease without a well-defined genetic alteration responsible for the onset of the disease. Several lines of evidence coincide in identifying stimulatory and growth signals delivered by B-cell receptor (BCR), and co-receptors together with NFkB pathway, as being the driving force in B-cell survival in CLL. However, the molecular mechanism responsible for this activation has not been identified. Based on the hypothesis that BCR activation may depend on somatic mutations of the BCR and related pathways we have performed a complete mutational screening of 301 selected genes associated with BCR signaling and related pathways using massive parallel sequencing technology in 10 CLL cases. Four mutated genes in coding regions (KRAS, SMARCA2, NFKBIE and PRKD3) have been confirmed by capillary sequencing. In conclusion, this study identifies new genes mutated in CLL, all of them in cases with progressive disease, and demonstrates that next-generation sequencing technologies applied to selected genes or pathways of interest are powerful tools for identifying novel mutational changes.

The recent introduction on the market of instruments for real-time PCR has prompted the development of quantitative assays for the most common fusion transcripts detectable in hematologic malignancies. However, because the ABI PRISM apparatus (ABI; Applied Biosystems) was the first available instrument for real-time PCR, most of the methods developed for the ABI PRISM use TaqMan probe chemistry (1)(2)(3). With the introduction of other real-time PCR instruments, such as the LightCycler (LC; Roche), other methods have been described (4)(5)(6)(7). The instruments differ in several respects, including the light sources and the approach to acquisition of fluorescence data. Few reports have compared the results obtained with different types of real-time PCR instruments (8). To the best of our knowledge, no such multicenter studies with common calibrators and common methods have been reported. In the present study we analyzed the results obtained with two of the more widely used instruments for real time PCR, i.e., the ABI and LC, for amplifying two rearrangements frequently detectable in human leukemia, the BCR-ABL and PML-RARa fusion genes. For BCR-ABL several quantitative methods have been established for both instruments (3)(4)(5)(6)(7), whereas for PML-RARa most of the quantitative methods have been developed for the ABI PRISM (1). The quantification of BCR-ABL transcripts is clinically relevant for monitoring patients with chronic myeloid leukemia undergoing allogeneic hematopoietic stem cell transplantation (4)(9) or treatment with interferon-a or imatinib mesylate (9)(10)(11). For example, low numbers of BCR-ABL transcripts after 2 weeks of imatinib treatment predict a good response to imatinib after 4 weeks (9). With respect to PML-RARa , recent reports have shown that …

Matrix metalloproteinase-9 (MMP-9) is the major MMP produced by B-CLL cells and contributes to their tissue infiltration by degrading extracellular and membrane-anchored substrates. Here we describe a different function for MMP-9 in B-CLL, which involves the hemopexin domain rather than its catalytic function. Binding of soluble or immobilized (pro)MMP-9, a catalytically inactive proMMP-9 mutant, or the MMP-9 hemopexin domain to its docking receptors α4β1 integrin and CD44v, induces an intracellular signaling pathway that prevents B-CLL apoptosis. This pathway is induced in all B-CLL cases, is active in B-CLL lymphoid tissues, and consists of Lyn activation, STAT3 phosphorylation, and Mcl-1 upregulation. Our results establish that MMP/receptor binding induces intracellular survival signals and highlight the role of (pro)MMP-9 in B-CLL pathogenesis, This work was supported by grants PI060400, SAF2009-07035, and RTICC RD06/0020/0011 (to A.G.P.), by grants PI061637 and RTICC RD06/0020/0080 (to M.J.T.) from the Ministerio de Ciencia e Innovacio´ n, and by the Fundacio´ n de Investigacio´nMe´ dica Mutua Madrilen ˜ a (to A.G.P.). Research on the human proMMP-9 mutants was supported by the Geconcerteerde OnderzoeksActies (GOA 2007-2011) and the Fund for Scientific Research-Flanders (FWO-Vlaanderen). Research on the murine proMMP-9-PEX domain was supported by grants Ro 957/6-1 and Ro 957/7-1 from the Deutsche Forschungsgemeinschaft. J.R.M. was supported by the Fundacio´ n Ramo´ n Areces. P.E.V.D.S. is a postdoctoral fellow of the FWOVlaanderen.

We have co-infused mobilized purified hematopoietic stem cells (HSC) from a third party donor to shorten neutropenia in single unit cord blood transplantation (CBT). We describe post-engraftment infectious complications in 33 consecutive adults with high-risk hematologic malignancies. Median age was 30 (range 16–59), 22 were male. Patients were conditioned with TBI or busulfan, fludarabine, cyclophosphamide and ATG. GVHD prophylaxis included CyA and steroids. Non-bacterial prophylaxis included fluconazol, acyclovir, trimethoprim-sulfamethoxazole and azithromycin or Fansidar (toxopositive cases). Median total infused CB cell dose was 2.26 x 107/kg (1.31–3.7). Pre-CBT toxoplasma serology was positive in 12, negative in 13 (4 received HSC from a seropositive donor) and unknown in 8 cases. Pre-CBT CMV serology was positive in 30 cases. Pre-CBT, 7 patients were HBsAb(+), HBsAg(−) and 1 HBsAg(+) HBsAb(−). ANC>500/uL was achieved by 32/33, median time 10 days (9–36). Full CB chimerism was achieved in 32/33 cases. Most clinically significant infections occurred after ANC recovery (no major neutropenic infections).There were 34 episodes of CMV reactivation (3 patients developed CMV peumonitis and died Short and long term results in adult CBT are improving. However we and others are reporting high incidence of post-engraftment unusual infections which seem related to delayed recovery of cell-mediated immunity. CMV, for which early diagnostic techniques and antiviral agents are available, heads the list. Our toxoplasma cases have prompted us to use prophylaxis in seropositive patients. HBV reactivation among HBsAb(+) HBsAg(−) patients raises the issue of prophylaxis during CBT versus close serological monitoring and pre-emptive therapy. Leishmaniasis is endemic among our city’s dogs, so we actively search for it in FUO (BM examination and culture). Polyomavirus can be found in the urine of up to 50% of BM recipients, viruria preceding symptoms. The value of prospective monitoring and the role of antivirals are unknown. Other unusual infections (as tripanosomiasis in our country) require high index of awareness and consideration in FUO protocols (BM, PB smears). Adult CB recipients are at very high risk of fastidious non-bacterial infections requiring wide pre-BMT screening, close analytical and clinical monitoring, prophylactic/preemptive strategies or early aggressive therapy and innovative immunotherapeutic approaches.