Epstein-Barr Virus-Related Post-Transplantation Lymphoproliferative Disorders After Allogeneic Hematopoietic Stem Cell Transplantation

Development of pulmonary hypertension remains a major hurdle to corrective surgery in Down syndrome

Down syndrome is the most common chromosomal abnormality encountered in clinical practice with 50% of them having associated congenital heart disease (CHD). Shunt lesions account for around 75% of all CHDs in Down syndrome. Down syndrome patients, especially with large shunts are particularly predisposed to early development of severe pulmonary hypertension (PH) compared with shunt lesions in general population. This necessitates timely surgical correction which remains the only viable option to prevent long term morbidity and mortality. However, despite clear recommendations, there is wide gap between actual practice and fear of underlying PH which often leads to surgical refusals in Down syndrome even when the shunt is reversible. Another peculiarity is that Down syndrome patients can develop PH even after successful correction of shunt. It is not uncommon to come across Down syndrome patients with uncorrected shunts in adulthood with irreversible PH at which stage intracardiac repair is contraindicated and the only option available is a combined heart-lung transplant. However, despite the guidelines laid by authorities, the rates of cardiac transplant in adult Down syndrome remain dismal largely attributable to the high prevalence of intellectual disability in them. The index case presents a real-world scenario highlighting the impact of severe PH on treatment strategies and discrimination driven by the fear of worse outcomes in these patients.

Haploidentical hematopoietic cell transplant recipient presents with late-onset Epstein Barr virus-associated posttransplant lymphoproliferative disorder

Posttransplant lymphoproliferative disease (PTLD) is a potentially life-threatening complication of hematopoietic cell transplantation. With improvements in Epstein-Barr virus (EBV) monitoring and supportive care, PTLD incidence has decreased throughout the history of bone marrow transplantation. It is rare to develop PTLD after the first year following transplant, across all donor categories. In this case, we hope to elucidate details that may have predisposed to this unusual presentation. We present the case of a 55-year-old gentleman with acute myeloid leukemia who underwent a haploidentical transplant for consolidation and presented with fatigue, lethargy and presumed septic shock nearly 7 years after transplant.

Successful Treatment of Central Nervous System Involvement in Posttransplant EBV-related Lymphoproliferative Disease With Intrathecal Rituximab Therapy

The posttransplant lymphoproliferative disease is a severe cause of morbidity and mortality following allogeneic hematopoietic stem cell transplantation. Central Nervous System involvement in EBV-related PTLD is rare, and there is no standard treatment recommendation. We present our patient and discuss other previously reported cases of EBV-associated PTLD with CNS involvement.

Clinical application value of metagenomic second-generation sequencing technology in hematologic diseases with and without transplantation

Introduction

Hematological patients are at risk of infections. It is unknown whether the pathogenic microbial spectrum differs between HSCT and non-HSCT patients, and whether metagenomic next-generation sequencing (mNGS) of peripheral blood can be used as a substitute test specimen such as alveolar lavage.

Methods

A retrospective study was conducted to evaluate the clinical application value of mNGS in hematological patients with and without HSCT.

Results

Viruses were prevalent pathogens in both non-HSCT (44%) and HSCT (45%) patients, chiefly human cytomegalovirus and Epstein-Barr virus. In non-HSCT patients, Gram-negative bacilli accounted for 33% (predominantly Klebsiella pneumonia), and Gram-positive cocci accounted for 7% (predominantly Enterococcus faecium) of pathogens. However, in HSCT patients, Gram-negative bacilli accounted for 13% (predominantly Stenotrophomonas maltophilia), and Gram-positive cocci accounted for 24% (predominantly Streptococcus pneumonia) of pathogens. Mucor was the most common fungu s in two groups. The positive rate of pathogens by mNGS was 85.82%, higher than conventional detection (20.47%, P < 0.05). Mixed infection accounted for 67.00%, among which the mixed infection of bacteria and virus (25.99%) was the most common. 78 cases had pulmonary infection, the positive rate of traditional laboratory tests was 42.31% (33/78), and of mNGS in peripheral blood was 73.08% (57/78), showing a statistical difference (P = 0.000). The non-HSCT patients had a higher frequency of Klebsiella pneumonia (OR=0.777, 95% CI, 0.697-0.866, P = 0.01) and Torque teno virus (OR=0.883, 95% CI, 0.820-0.950, P = 0.031) infections than HSCT patients, while the rates of Streptococcus pneumonia (OR=12.828, 95% CI, 1.378-119.367, P = 0.016), Candida pseudosmooth (OR=1.100, 95% CI, 0.987-1.225, P = 0.016), human betaherpesvirus 6B (OR=6.345, 95% CI, 1.105-36.437, P = 0.039) and human polyomavirus 1 (OR=1.100, 95% CI, 0.987-1.225, P = 0.016) infections were lower. Leishmania could be detected by mNGS.

Conclusion

mNGS of peripheral blood can be used as a substitute test method for hematological patients with pulmonary infection, the detection rate of mixed infections by mNGS was high, and mNGS has high clinical recognition rate and sensitivity in pathogen detection, and provides a basis for guiding the anti-infective treatment in hematological diseases with symptoms such as fever.

Epstein‒Barr virus-associated cellular immunotherapy

Epstein‒Barr virus (EBV) is a human herpes virus that is saliva-transmissible and universally asymptomatic. It has been confirmed that more than 90% of the population is latently infected with EBV for life. EBV can cause a variety of related cancers, such as nasopharyngeal carcinoma, diffuse large B-cell lymphoma, and Burkitt lymphoma. Currently, many clinical studies have demonstrated that EBV-specific cytotoxic T lymphocytes and other cell therapies can be safely and effectively transfused to prevent and treat some diseases caused by EBV. This review will mainly focus on discussing EBV-specific cytotoxic T lymphocytes and will touch on therapeutic EBV vaccines and chimeric antigen receptor T-cell therapy briefly.

Machine learning algorithm as a prognostic tool for Epstein-Barr virus reactivation after haploidentical hematopoietic stem cell transplantation

Epstein-Barr virus (EBV) reactivation is one of the most important infections after hematopoietic stem cell transplantation (HSCT) using haplo-identical related donors (HID). We aimed to establish a comprehensive model with machine learning, which could predict EBV reactivation after HID HSCT with anti-thymocyte globulin (ATG) for graft-versus-host disease (GVHD) prophylaxis. We enrolled 470 consecutive acute leukemia patients, 60% of them (n = 282) randomly selected as a training cohort, the remaining 40% (n = 188) as a validation cohort. The equation was as follows: Probability (EBV reactivation) =   1 1       +       e x p ( - Y ) , where Y = 0.0250 × (age) - 0.3614 × (gender) + 0.0668 × (underlying disease) - 0.6297 × (disease status before HSCT) - 0.0726 × (disease risk index) - 0.0118 × (hematopoietic cell transplantation-specific comorbidity index [HCT-CI] score) + 1.2037 × (human leukocyte antigen disparity) + 0.5347 × (EBV serostatus) + 0.1605 × (conditioning regimen) - 0.2270 × (donor/recipient gender matched) + 0.2304 × (donor/recipient relation) - 0.0170 × (mononuclear cell counts in graft) + 0.0395 × (CD34+ cell count in graft) - 2.4510. The threshold of probability was 0.4623, which separated patients into low- and high-risk groups. The 1-year cumulative incidence of EBV reactivation in the low- and high-risk groups was 11.0% versus 24.5% (P < .001), 10.7% versus 19.3% (P = .046), and 11.4% versus 31.6% (P = .001), respectively, in total, training and validation cohorts. The model could also predict relapse and survival after HID HSCT. We established a comprehensive model that could predict EBV reactivation in HID HSCT recipients using ATG for GVHD prophylaxis.

Clinical value of plasma and peripheral blood mononuclear cells Epstein–Barr Virus DNA dynamics on prognosis of allogeneic stem cell transplantation

The application of intracellular and extracellular Epstein–Barr virus (EBV) DNA in allogeneic hematopoietic stem cell transplantation (allo-HSCT) has been poorly characterized. We conducted a combined prospective-retrospective study of 300 patients who underwent allo-HSCT between 2016 to 2019 in our center and monitored for EBV DNA within the first year after HSCT. Combining the optimal cut-off value of EBV DNA load (7.3×10⁴ copies/10⁶ cells) in peripheral blood mononuclear cells (PBMCs) and qualitative detection in plasma (400 copies/mL) allowed for the better differentiation of EBV-related posttransplant lymphoproliferative disorders (EBV-PTLD), with increased sensitivity (100%) and specificity (86%), and provided the effective risk stratification of EBV DNA level according to their impact on transplant outcomes. By multivariate analysis, patients with intermediate-level of EBV DNA load (low EBV DNA load in PBMCs or high load in PBMCs but negative in plasma) was associated with superior overall survival (HR 1.92, 95% CI 1.03-3.57, p=0.039) and lower transplant-related mortality (HR 3.35, 95% CI 1.31-8.58, p=0.012) compared to those with high-level (high load in PBMCs and positive in plasma). Notably, high EBV-level group had poor reconstitution of CD4+ and CD8+T cells, and both low and high EBV-level groups showed abnormally increase in IL-10 level within one year. Additionally, patients with peak EBV DNA load in PBMCs during 3-12 months had a higher incidence of chronic graft versus host disease (GVHD) than those within 3 months post transplantation (17.4% vs 13.7%, p=0.029). Collectively, EBV DNA in PBMCs can synergistically predict the risk of EBV-PTLD and GVHD. The intermediate-level of EBV DNA presented in plasma and PBMCs might contribute to a better reconstitution of T cells associated with favorable prognosis of allo-HSCT.

Acute Neurological Involvement after Donor Lymphocyte Infusion for Post-Transplant Viral Infection: The Same Pattern of Novel Cancer Immunotherapy-Related CNS Toxicity?

Early post-transplant is the critical phase for the success of hematopoietic stem cell transplantation (HSCT). New viral infections and the reactivations associated with complete ablation of the recipient's T-cell immunity and inefficient reconstitution of the donor-derived system represent the main risks of HSCT. To date, the pharmacological treatments for post-HSCT viral infection-related complications have many limitations. Adoptive cell therapy (ACT) represents a new pharmacological strategy, allowing us to reconstitute the immune response to infectious agents in the post-HSC period. To demonstrate the potential advantage of this novel immunotherapy strategy, we report three cases of pediatric patients and the respective central nervous system complications after donor lymphocyte infusion.

Post-Transplantation Cyclophosphamide Is Associated with an Increase in Non-Cytomegalovirus Herpesvirus Infections in Patients with Acute Leukemia and Myelodysplastic Syndrome

The use of post-transplantation cyclophosphamide (PTCy) for graft-versus-host disease (GVHD) prophylaxis in recipients of haploidentical and fully matched transplantations is on the increase. Published studies have reported an increased incidence of cytomegalovirus (CMV) infection with the use of PTCy. Limited data exist on the incidence and outcomes of infection with non-CMV herpesviruses (NCHV) in this setting. The aim of this study was to evaluate the cumulative incidence of NCHV infections and the association of NCHV infections with transplantation-specific outcomes in recipients of haploidentical transplantation with PTCy (HaploCy), matched sibling donor transplantation with PTCy (SibCy), and matched sibling donor transplantation with calcineurin inhibitor-based prophylaxis (SibCNI). We hypothesized that, like CMV infection, HaploCy recipients of also will have a higher risk of NCHV infections. Using the Center for International Blood and Marrow Transplantation Research database, we analyzed 2765 patients (HaploCy, n = 757; SibCNI, n = 1605; SibCy, n = 403) who had undergone their first hematopoietic stem cell transplantation (HCT) between 2012 and 2017 for acute myelogenous leukemia, acute lymphoblastic leukemia, or myelodysplastic syndrome. The cumulative incidence of NCHV at 6 months post-NCT was 13.9% (99% confidence interval], 10.8% to 17.3%) in the HaploCy group, 10.7% (99% CI, 7.1% to 15%) in the SibCy group, and 5.7% (99% CI, 4.3% to 7.3%) in the Sib CNI group (P < .001). This was due primarily to a higher frequency of human herpesvirus 6 viremia reported in patients receiving PTCy. The incidence of Epstein-Barr viremia was low in all groups, and no cases of post-transplantation lymphoproliferative disorder were seen in either PTCy group. The incidence of NCHV organ disease was low in all 3 cohorts. The development of NCHV infection was associated with increased treatment-related mortality, particularly in the HaploCy group. There was no association with the development of GVHD, relapse, or disease-free survival. Patients in PTCy cohorts who did not develop NCHV infection had lower rates of cGVHD. This study demonstrates that the use of PTCy is associated with an increased risk of NCHV infection. The development of NCHV infection was associated with increased nonrelapse mortality, especially in the HaploCy group. Prospective trials should consider viral surveillance strategies in conjunction with assessment of immune reconstitution for a better understanding of the clinical relevance of viral reactivation in different HCT settings.

Anti-Thymocyte Globulin Prophylaxis in Patients With Hematological Malignancies Undergoing Allogeneic Hematopoietic Stem Cell Transplantation: An Updated Meta-Analysis

Background

Anti-thymocyte globulin (ATG) prophylaxis reduces graft-versus-host disease (GVHD) incidence. This meta-analysis aimed to explore the long-term efficacy of ATG and the influencing factors in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT).

Methods

PubMed, Embase, and Cochrane databases were searched for the relevant studies published up to August 2020. Data from randomized controlled trials (RCTs) on ATG prophylaxis for GVHD prevention in allo-HSCT patients were extracted.

Results

A total of eight relevant RCTs (1,348 patients) were included. ATG significantly reduced the incidence of grade III–IV aGVHD (P = 0.001) and cGVHD (P < 0.001). ATG significantly improved the GVHD relapse-free survival (GRFS) (P < 0.001). The immunosuppressive regimen (number and dose of immunosuppressants) was significantly reduced when using ATG (P = 0.005). Epstein-Barr virus (EBV) reactivation was high in patients receiving ATG (P = 0.003). No significant differences were detected in relapses, overall survival (OS), relapse-free survival (RFS), and non-relapse mortality (NRM) between the ATG and no ATG groups. Subgroup analyses revealed that the donor type and ATG formulation might be the possible sources of heterogeneity among the included studies. Meta-regression analysis showed that the cumulative dose of ATG did not affect GVHD, OS, relapse, RFS, and NRM.

Conclusion

Although ATG had no significant effect on relapse, RFS, and NRM, it significantly reduced the occurrence and severity of GVHD, improved the GRFS, and reduced the number and dose of immunosuppressants in patients undergoing allo-HSCT.

An outlook on antigen-specific adoptive immunotherapy for viral infections with a focus on COVID-19

Although not a standard-of-care yet, adoptive immunotherapeutic approaches have gradually earned a place within the list of antiviral therapies for some of fatal and hard-to-treat viral diseases. To maintain robust antiviral immunity and to effectively target the viral particles and virally-infected cells, immune cells capable of recognizing the viral antigens are required. While conventional vaccination can induce these cells in vivo; another option is to prime and generate antigen-specific immune cells ex vivo. This approach has been successfully trialed for virulent opportunistic viral infections after bone marrow transplantation. Amid the crisis of SARS-CoV2 pandemic, which has been followed by the success of certain early-authorized vaccines; some institutions and companies have explored the effects of viral-specific adoptive cell transfers (ACTs) in trials, as alternative treatments. Aimed at outlining a perspective on antigen-specific adoptive immunotherapy for viral infections, this review article specifically provides an appraisal of ACT-based studies/trials on SARS-CoV2 infection.

Risk factors evaluation of post-transplant lymphoproliferative disorders after allogeneic haematopoietic stem cell transplantation with comparison between paediatric and adult

To describe the clincopathological features and evaluate risk factors of post-transplant lymphoproliferative disorder (PTLD) after allogeneic haematopoietic stem cell transplants (allo-HSCT), with comparison between paediatric and adult .Clinicopathological features of 81 cases of PTLD after allo-HSCT were analysed by histopatholgy, immunohistochemistry and in situ hybridisatioin.The cases included 58 males and 23 females with a median age of 26.7 years (range 6-55 years) and the PTLDs developed 1-60 months post-transplant (mean 5.9 months). The histological types indicated 10 cases of non-destructive PTLD, including 4 of plasmacytic hyperplasia, 5 of infectious mononucleosis and 1 of florid follicular hyperplasia. Fifty-six cases were polymorphic PTLD, and 15 were monomorphic PTLD, including thirteen of diffuse large B cell lymphoma, 1 of extranodal nasal type natural killer (NK)/T cell lymphoma and 1 of plasmablastic lymphoma. Foci and sheets of necrosis were observed in 31 cases. The infected ratio of Epstein-Barr virus (EBV) was 91.4%. Some cases were treated by reduction of immunosuppression, antiviral therapy, donor lymphocyte infusion or anti-CD20 monoclonal rituximab. Thirty-three cases died. Compared with that of adult, overall survival of paediatric recipient may be better.The first half year after allo-HSCT is very important for the development of PTLD. Type of PTLD, EBV infection and graft-versus-host disease are risk factors. The prognosis of PTLD is poor, and PTLD after allo-HSCT exhibits some features different from that after solid organ transplantation and some differences existing between adult and paediatric recipients.

Epstein-Barr virus-positive lymphoproliferative disorder manifesting as pulmonary disease in a patient with acute myeloid leukemia: a case report

Background

 Patients with lymphoproliferative disorders following hematopoietic stem cell transplant (HSCT) most commonly present with fever and lymphadenopathy within the first 5 months of transplant. Pulmonary post-transplant lymphoproliferative disorder (PTLD) is a particularly aggressive and rapidly progressive disease, with high morbidity and mortality. There are a very limited number of reported pulmonary PTLD cases following HSCT in patients with acute myeloid leukemia (AML). Early diagnosis and detection of pulmonary PTLD is critical given its high lethality. However, variable clinical presentations and nonspecific radiographic findings make pulmonary PTLD difficult to distinguish from other more common causes of pulmonary disease in AML patients.

Case presentation

Here, we describe a 68-year-old Caucasian man who presented for salvage induction therapy following relapse of his AML after a haploidentical allogeneic HSCT 10 months earlier. He developed recurrent fevers, dry cough, and hypoxemia, with chest computed tomography (CT) showing bibasilar consolidations and increased nodularity without increased lymphadenopathy. His symptoms initially improved with antibiotic and antifungal therapy, but his follow-up chest CT showed progression of disease despite symptomatic improvement. Epstein–Barr virus (EBV) was detected in his blood by polymerase chain reaction (PCR), and a lung biopsy revealed monomorphic PTLD with B cells positive for EBV. Unfortunately, the patient’s condition rapidly deteriorated, and he passed away prior to treatment initiation.

Conclusions

 To our knowledge, this is the first reported case of an AML patient developing pulmonary PTLD relatively late in his post-transplant course in the setting of relapsed disease and salvage therapy. Pulmonary PTLD, a rare but highly lethal disorder, can imitate the symptoms and radiographic findings of pneumonia, a common diagnosis in immunocompromised AML patients. This case illustrates the importance of considering pulmonary PTLD in the differential diagnosis for pulmonary disease in AML patients with a history of HSCT, especially in the setting of progressive radiographic findings despite broad antibacterial and antifungal therapy. Further, our case demonstrates the importance of biopsy and uninterrupted EBV DNA monitoring in the definitive diagnosis of PTLD, given nonspecific symptomatology and radiographic findings.

EBV-PTLD in a patient after haploidentical stem-cell transplantation with post-transplant cyclophosphamide

Here, we describe the case of a male patient with Epstein-Barr virus post-transplantation lymphoproliferative disorder (EBV-PTLD), which developed 18 months after a haploidentical hematopoietic stem cell transplantation (haplo-HSCT) and the administration of post-transplant cyclophosphamide (PTCy). Of note, no anti-thymoglobulin was used in the entire clinical course. Prior to the onset of EBV-PTLD, the patient had pulmonary chronic graft-versus-host disease and was treated with prednisolone and tacrolimus. After stopping immunosuppressive therapy, he was diagnosed with EBV-positive infectious mononucleosis PTLD, and EBV-associated hemophagocytic syndrome; therefore, dexamethasone and rituximab monotherapies were administered. After four courses of rituximab, EBV-DNA was no longer detected in the peripheral blood, and the patient's laboratory data improved. Overall, this study highlights the need to predict the risk factors associated with the development of EBV-PTLD in transplanted patients after haplo-HSCT with PTCy.

Clinical features and treatment strategies for post-transplant and iatrogenic immunodeficiency-associated lymphoproliferative disorders

A specific category termed immunodeficiency-associated lymphoproliferative disorders (LPD) exists in the 2016 revised WHO classification concerning lymphoid neoplasms. This category is defined by etiology and includes LPD developing in association with organ transplantation or immunosuppressive/immunomodulatory agents including methotrexate. The functional mechanism is chiefly explained by the autonomous proliferation of Epstein-Barr virus (EBV)-infected lymphocytes induced by host-immune suppression. This category ranges from reactive lymphocyte hyperplasia to monomorphic lymphoma. Its clinical behavior varies depending on host immunity and pathological features; pathological confirmation by biopsy is thus important for deciding treatment strategies. Owing to the spontaneous regression observed in some patients, uniform chemotherapy is not recommended. The main initial treatment options include the reduction in immunosuppressive drugs, immunotherapy with the anti-CD20 antibody rituximab, chemotherapy, or a combination of these. Other novel treatments such as adoptive immunotherapy with EBV-specific cytotoxic T cells, could be an alternative for relapsed/refractory diseases in clinical trials.

Central Nervous System Involvement in Epstein-Barr Virus-Related Post-Transplant Lymphoproliferative Disorders after Allogeneic Hematopoietic Stem Cell Transplantation

Central nervous system (CNS) involvement in Epstein-Barr virus-related post-transplant lymphoproliferative disorders (EBV-PTLDs) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is poorly defined. We analyzed the incidence, clinical and pathological characteristics, and impact on outcomes of EBV-PTLDs with CNS involvement (CNS-PTLDs) in 1009 consecutive adult patients undergoing allo-HSCT at a single-center institution. Four hundred eighty-two patients received matched sibling donor (MSD) transplants, 388 umbilical cord blood transplants (UCBTs), 56 matched unrelated donor (MUD) transplants, and 83 haploidentical transplants. We detected 25 cases of biopsy-proven EBV-PTLDs. Of these, nine patients (36%) had CNS-PTLDs: six after UCBT (67%), one after MSD transplantation (11%), one after MUD transplantation (11%), and one after haploidentical transplantation (11%). The 5-year cumulative incidence risk of CNS-PTLDs was 0.9%. Median time from transplant to CNS-PTLDs was 187 days, and all patients had neurological symptoms at diagnosis. Six out of the nine cases (67%) occurred with systemic involvement, and three cases (33%) had isolated CNS involvement. The most frequent histological subtype was monomorphic EBV-PTLD, and laboratory characteristics were similar to EBV-PTLDs without CNS involvement. We observed statistical differences in the rate of positive EBV DNA detection in plasma between isolated CNS-PTLDs (detection in one out of three, 33%) and the rest of the EBV-PTLDs (100%) (P = .01). Treatment strategies included chemotherapy, radiotherapy, and T cell therapy. However, seven out of nine patients died due to progression of the CNS-PTLDs at a median time of 17 days (range, 8 to 163) from diagnosis. The 5-years overall survival in patients who developed CNS-PTLDs was 22% (95% confidence interval [CI], 7% to 75%) and 5-year treatment-related mortality was 78% (95% CI, 51% to 100%), with no statistically significant differences between CNS-PTLDs and the rest of the EBV-PTLDs. In conclusion, despite advances in EBV monitoring and treatment strategies, CNS-PTLDs remain an uncommon but serious complication after allo-HSCT, with very poor prognosis.

Torque Teno Virus Viral Load as a Marker of Immune Function in Allogeneic Haematopoietic Stem Cell Transplantation Recipients

Torque teno virus (TTV) has been proposed as a surrogate biomarker of T-cell function in allogeneic–haematopoietic–stem-cell transplantation (allo-HSCT). Conflicting data exists regarding the value of TTV to assess the degree of immunosuppression. The aim of the present study was to investigate the correlation between TTV viral load and immune function. Using samples from a prospective cohort composed of healthy-volunteers (HV) and allo-HSCT recipients at 6 months post-transplantation, we assessed the correlation between TTV viraemia and immune cell counts or T-cell proliferation capacity post-phytohaemagglutinin stimulation. TTV viraemia was detected in 68% of HV (n = 80) and 100% of allo-HSCT recipients (n = 41; p < 0.001); it was significantly higher in allo-HSCT recipients (3.9 vs. 2.1 Log copies/mL, p < 0.001). There was no correlation between T-cell function and CD3⁺T-cell count (rho: 0.002) suggesting that T-cell count can normalise without full functional recovery. Furthermore, no significant correlation was observed between TTV viraemia and absolute total/subset lymphocyte counts (rho: <0.13). The highest correlation was observed between TTV viral load and T-cell proliferation capacity (rho: −0.39). We therefore report an inverse correlation between T-cell function and TTV viraemia that is independent of T-cell count. Monitoring of TTV viraemia could be a fast suitable option to objectively assess the competence of immune function in at-risk populations.

Induction of E. coli-derived endonuclease MazF suppresses HIV-1 production and causes apoptosis in latently infected cells

The current antiretroviral therapy cannot cure the patients infected with human immunodeficiency virus type 1 (HIV-1) due to the existence of latently infected cells capable of virus production from harboring proviral DNA. MazF is an ACA nucleotide sequence-specific endoribonuclease derived from Escherichia coli. The conditional expression of MazF by binding of HIV-1 Tat to the promoter region of a MazF-expression vector has previously been shown to selectively inhibit HIV-1 replication in acutely infected cells. The expression of MazF significantly suppressed tumor necrosis factor (TNF)-α-induced HIV-1 production and viral RNA expression in the HIV-1 latently infected cell line OM-10.1 transduced with the MazF-expression vector (OM-10.1/MFR). Moreover, the viability of OM-10.1/MFR cells decreased with increasing concentrations of TNF-α, whereas such decrease was not observed for HL-60 cells transduced with the MazF-expression vector (HL-60/MFR), the uninfected parental cell line of OM-10.1. TNF-α increased the expression of cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase in OM-10.1/MFR cells, indicating that the cell death was caused by the induction of apoptosis. TNF-α-induced expression of MazF mRNA was detected in OM-10.1/MFR but not HL-60/MFR cells, suggesting that TNF-α-induced apoptosis of latently infected cells was due to the expression of MazF. Thus, the anti-HIV-1 gene therapy using the MazF-expression vector may have potential for the cure of HIV-1 infection in combination with suitable latency reversing agents through reducing the size of latently infected cells without viral reactivation.

High incidence but low mortality of EBV-reactivation and PTLD after alloHCT using ATG and PTCy for GVHD prophylaxis

We explore risk factors and impacts of post-transplant EBV-Reactivation (EBV-R) and PTLD in 270 patients that underwent RIC alloHCT using ATG-PTCy and cyclosporine for GVHD prophylaxis. Twenty-five (12%) patients had probable (n = 7) or proven (n = 18) PTLD. Patients were managed with reduction of immunosuppression and 22 with weekly rituximab (375 mg/m² IV). ORR was 84%; 8 (32%) recipients died, and one-year OS and NRM of patients with PTLD was 59.7% and 37%, respectively. One hundred seventy-two (63.7%) recipients had EBV-R. One-year OS and RFS of patients with EBV-R were 68.2% and 60.6%, and of EBV-Negative patients were 62.1% and 50.1%, respectively. High incidence but low mortality of EBV-R and PTLD was documented. EBV-R induced a protective effect on RFS in multivariable analysis (HR 0.91, p = .011). Therefore, EBV-R may have a protective effect on RFS in this setting. Further research is necessary to evaluate the interplay of EBV-R, immune reconstitution, and post-transplant outcomes.

Key Aspects of the Immunobiology of Haploidentical Hematopoietic Cell Transplantation

Hematopoietic stem cell transplantation from a haploidentical donor is increasingly used and has become a standard donor option for patients lacking an appropriately matched sibling or unrelated donor. Historically, prohibitive immunological barriers resulting from the high degree of HLA-mismatch included graft-vs.-host disease (GVHD) and graft failure. These were overcome with increasingly sophisticated strategies to manipulate the sensitive balance between donor and recipient immune cells. Three different approaches are currently in clinical use: (a) ex vivo T-cell depletion resulting in grafts with defined immune cell content (b) extensive immunosuppression with a T-cell replete graft consisting of G-CSF primed bone marrow and PBSC (GIAC) (c) T-cell replete grafts with post-transplant cyclophosphamide (PTCy). Intriguing studies have recently elucidated the immunologic mechanisms by which PTCy prevents GVHD. Each approach uniquely affects post-transplant immune reconstitution which is critical for the control of post-transplant infections and relapse. NK-cells play a key role in haplo-HCT since they do not mediate GVHD but can successfully mediate a graft-vs.-leukemia effect. This effect is in part regulated by KIR receptors that inhibit NK cell cytotoxic function when binding to the appropriate HLA-class I ligands. In the context of an HLA-class I mismatch in haplo-HCT, lack of inhibition can contribute to NK-cell alloreactivity leading to enhanced anti-leukemic effect. Emerging work reveals immune evasion phenomena such as copy-neutral loss of heterozygosity of the incompatible HLA alleles as one of the major mechanisms of relapse. Relapse and infectious complications remain the leading causes impacting overall survival and are central to scientific advances seeking to improve haplo-HCT. Given that haploidentical donors can typically be readily approached to collect additional stem- or immune cells for the recipient, haplo-HCT represents a unique platform for cell- and immune-based therapies aimed at further reducing relapse and infections. The rapid advancements in our understanding of the immunobiology of haplo-HCT are therefore poised to lead to iterative innovations resulting in further improvement of outcomes with this compelling transplant modality.

Low dose Rituximab for pre-emptive treatment of Epstein Barr virus reactivation after allogenic hematopoietic stem cell transplantation

INTRODUCTION

The most used preemptive therapy for Epstein Barr virus reactivation post allogeneic hematopoietic stem cell (HSCT) transplant is Rituximab, 375 mg/m2, once weekly until EBV viremia negativity. There is no data suggesting such a high dose.

OBJECTIVE

We hypothesized that a lower dose of Rituximab would be as efficient with less toxicity.

PATIENTS

In a retrospective, monocentric study, we analyzed 16 consecutive patients treated preemptively with low dose Rituximab for EBV reactivation post HSCT. Patients were treated with low Rituximab dose of 100 mg/m² weekly. Success was defined by a decrease of EBV viremia of 1 log¹⁰ and below 1000 UI/ml, and the absence of post-transplant lymphoproliferative disorder (PTLD).

RESULTS

Success rate was 93.4% (15/16). One (1/16, 6%) PTLD was diagnosed after preemptive therapy, despite a negative viremia.

CONCLUSION

A low dose of Rituximab of 100 mg/m² per injection for pre-emptive therapy of EBV reactivation post HSCT is safe and effective for preventing PTLD. Prospective, randomized, multicentric trials with larger number of patient are needed to determine the best rituximab dose.