Safety and efficacy of Sofosbuvir and Velpatasvir in children with active hepatitis C virus infection undergoing haploidentical transplantation.

Direct Acting Antivirals (DAA) have changed the landscape of hepatitis C virus (HCV) infection with high cure rates across genotypes. However, the use of these agents in the setting of allogeneic hematopoietic cell transplantation (HCT) has been limited. In this context, we report the outcome of five children (5-12 years) with relapsed and refractory leukemia and active HCV infection (genotype 1b), who underwent urgent haploidentical HCT and were treated with Sofosbuvir and Velpatasvir (Sof-Vel) from initiation of treatment to 24 weeks post-HCT. All achieved complete virologic response (VR) at a median of 2 weeks, with normalization of liver enzymes. There were no adverse events related to the use of Sof-Vel, with no major fluctuations in cyclosporine levels. Two of the patients developed chronic GVHD and one relapsed. Sof-Vel was continued in one of them along with sirolimus without affecting drug levels. With a median follow-up of 15 months, four patients are disease free with sustained VR. Our study shows that combination of Sof-Vel might be effective in inducing rapid complete and sustained VR during HCT without any major untoward drug interaction.

CTLA4Ig in an Extended Schedule along with Sirolimus Improves Outcome with a Distinct Pattern of Immune Reconstitution Following Post-Transplantation Cyclophosphamide-Based Haploidentical Transplantation for Hemoglobinopathies.

The major hindrances to the success of a haploidentical hematopoietic cell transplantation for hemoglobinopathies are graft failure, early post-transplant hemophagocytic syndrome (PTHPS), and graft-versus-host disease (GVHD). Following the successful incorporation of CTLA4Ig (abatacept) in post-transplantation cyclophosphamide-based haploidentical transplantation, we piloted this approach in 10 patients (aged 3 to 19 years), with thalassemia major (TM, n=5) and sickle cell disease (n = 5). Pretransplant immunosuppressive therapy (pTIST) was administered for 10 weeks. Conditioning was myeloablative. CTLA4Ig was administered every 2 weeks during pTIST and on days -1, +5, +20, and +35 and every 4 weeks thereafter for 6 months, along with sirolimus. A short course of low-dose dexamethasone was given from day +6 for 14 days. Nine patients engrafted at a median of 15 days, with 1 patient with TM dying of sepsis on day +19. None of the patients developed acute or chronic GVHD. All 9 patients are alive and disease free at a median follow-up of 28 months. Only 4 patients had cytomegalovirus reactivation. The pattern of immune reconstitution showed a prompt and sustained recovery of T cell subsets with memory phenotype, along with early and sustained increase of Tregs and NKG2C+ natural killer (NK) cells. This novel approach, targeting CD80 and CD86 on monocytes/macrophages, promoted engraftment and limited early-onset PTHPS and graft failure. The lack of GVHD and serious infections with this approach reflects an early recovery of Tregs, memory T cells, and persistence of NKG2C+ NK cells.

Impact of extended infusional mesna prophylaxis on the incidence of BK viruria and hemorrhagic cystitis following post-transplantation cyclophosphamide and CTLA4Ig-based haploidentical transplantation.

Hemorrhagic cystitis (HC) has been reported with increased frequency following post-transplantation cyclophosphamide (PTCy)-based haploidentical hematopoietic cell transplantation (HCT) along with a strong association with BK viruria. We prospectively evaluated the incidence of BK viruria and HC in 115 patients (median age 20 years, 2-65) undergoing PTCy-based haploidentical HCT with (n = 71) or without (n = 44) CTLA4Ig. HC prophylaxis consisted of a continuous infusion of mesna 30 min prior and 48 h post-PTCy. The overall incidence of BK viruria was 65.7%. None with BK viruria < 104 copies/ml developed clinical symptoms (n = 65). The incidence of BK viruria ≥ 104 copies/ml was 7.1% (n = 8) and 75% developed HC. The incidence of HC was 5.4% at a median of 30 days. Both BK viruria ≥ 104 copies/ml and HC were strongly associated with acute GVHD (p < 0.001). A higher NRM was observed in those with BK viruria ≥ 104 copies/ml, related to GVHD and its complications (41.7% vs 12.6%, p = 0.04). The incidences of acute GVHD, vis-à-vis, overall BK viruria, BK viruria ≥ 104 copies/ml, and HC, tended to be lower in patients receiving CTLA4Ig. Thus, extended infusional mesna, coupled with significant reduction in alloreactivity along with possible preservation of antiviral immunity associated with the use of CTLA4Ig, was probably responsible for a much lower incidence of BK viruria and resultant HC than reported previously following PTCy-based haploidentical HCT.

Prophylactic oseltamivir during major seasonal influenza H1N1 outbreak might reduce both H1N1 and associated pulmonary aspergillosis in children undergoing haploidentical transplantation.

Following a major seasonal outbreak of H1N1 influenza in 2018 September, prophylactic oseltamivir for six months was initiated in children undergoing haploidentical HCT with regular monitoring for influenza and other respiratory virus infections. Influenza was not detected in 22 children undergoing prophylaxis, compared to 8 H1N1 infections in 21 adults without prophylaxis (P = .01). Four children on prophylaxis were detected to have other respiratory viruses, compared to 8 in those without prophylaxis. Invasive pulmonary aspergillosis (IPA) was observed only in association with H1N1 (4/8 with H1N1 vs 0/35 without H1N1, P = .001) and was thus lower in the prophylaxis group (P = .04). The overall incidence of episodes of respiratory illness and hospital stay were also lower in those on prophylaxis (P = .001). There were no untoward side effects associated with prophylactic oseltamivir. Prophylactic oseltamivir was safe and effective in prevention of H1N1 infection and subsequent IPA in children at-risk, early after haploidentical HCT.

CTLA4Ig Primed Donor Lymphocyte Infusion: A Novel Approach to Immunotherapy after Haploidentical Transplantation for Advanced Leukemia.

CTLA4Ig attenuates T cell activation by co-stimulation blockade, but natural killer (NK) cells are not only resistant to CTLA4Ig, they also may demonstrate better antileukemia effect in the presence of CTLA4Ig. To explore this phenomenon we used sequential CTLA4Ig primed donor lymphocyte infusion (DLI) after post-transplant cyclophosphamide-based haploidentical transplantation. Thirty patients (CTLA4Ig-DLI group) with advanced leukemia received CTLA4Ig on day -1 and subsequently on days +7, +21, and +35, followed 12hours later by DLI of 1 to 10 × 106 CD3+ T cells/kg containing .1 to 3.27 × 106/kg CD56+ NK cells, with low dose cyclosporine for 60days. The incidences of acute graft-versus-host disease (GVHD), chronic GVHD and nonrelapse mortality (NRM) were 6.7%, 21%, and 4.5 %, respectively, with disease progression of 23.3% and overall survival of 79% at 18 months. Patients without disease progression had a significant early surge in CD56dimCD16+NK cells with lower NKG2A expression. CTLA4Ig primed DLI was associated with an upregulation of CD86 in mature NK cells that was not witnessed with CTLA4Ig administration alone. Thus, CTLA4Ig primed DLI resulted in early proliferation of mature NK cells with cytotoxic potential enabling early institution of adoptive immunotherapy to mitigate the risk of relapse in advanced leukemia with reduced GVHD and NRM.

Impact of Preemptive Granulocyte Infusions During Febrile Neutropenia in Patients Colonized with Carbapenem-Resistant Gram-Negative Bacteria Undergoing Haploidentical Transplantation.

We prospectively studied the impact of preemptive granulocyte infusions (pGIs) in 69 patients colonized with carbapenem-resistant gram-negative bacteria (CRGNB) undergoing haploidentical hematopoietic cell transplantation (HCT) compared with a previous cohort of 33 patients who received only antimicrobials directed toward CRGNB at the onset of neutropenic fever (non-pGI group). All patients developed neutropenic fever at a median of day +8 (range, -4 to +12) after transplantation. Engraftment kinetics were similar for both groups. The median number of GIs was 2 (range, 1 to 7), and the median dose of granulocytes infused was 5 × 1010 granulocytes per infusion (range, 1 to 30). The overall incidence of CRGNB bloodstream infections (BSIs) was 21.2% in non-pGI group (7/33) and 17.5% (12/69) in the pGI group (P = .8). However, the CRGNB-related mortality among those with BSI was 100% (7/7) in the non-pGI group versus 16.6% (2/12) in the pGI group (P = .001). The day 100 (4.4% versus 24.4%, P = .002) and 2-year nonrelapse mortality (7.5% versus 35.6%, P = .0001) were significantly reduced in the pGI group. The overall survival at 2 years was 75.6% in the pGI group versus 21.2% in the non-pGI group (P = .0001). Colonization and subsequent BSI with CRGNB are associated with a high incidence of mortality in patients undergoing HCT. pGI reduced early mortality associated with CRGNB in colonized patients undergoing post-transplant cyclophosphamide-based haploidentical HCT.

Rotavirus infection following post-transplantation cyclophosphamide based haploidentical hematopoietic cell transplantation in children is associated with hemophagocytic syndrome and high mortality.

We evaluated the incidences and consequences of rotavirus induced diarrhea in a cohort of 115 patients undergoing T-cell replete haploidentical transplantation. Four out of 115 patients developed rotavirus-induced diarrhea between 47 and 147 days. The incidence of rotavirus infection was 9.7% in children compared to none in adults (P = .01). This was 25.3% in those with GVHD compared to 1.2% in those without GVHD (P = .001). Rotavirus infection was followed by post-transplantation hemophagocytic syndrome (PTHPS) at a median of 4 days (range, 3-10 days) in all four patients. Three patients succumbed to the complications related to PTHPS. Only one patient, who is long-term survivor, was able to eliminate this virus after 2 weeks. Children undergoing T-replete haploidentical hematopoietic cell transplantation who develop GVHD are at a higher risk of community-acquired rotavirus infection which was strongly associated with PTHPS with poor outcome.

Higher CD45RA+ Regulatory T Cells in the Graft Improves Outcome in Younger Patients Undergoing T Cell-Replete Haploidentical Transplantation: Where Donor Age Matters.

To understand the phenomenon of early alloreactivity (EA) in younger children undergoing post-transplantation cyclophosphamide (PTCy)-based haploidentical transplantation, we studied the graft composition and the immune reconstitution in 32 consecutive patients (aged 2 to 25 years) undergoing PTCy and T cell costimulation blockade based peripheral blood stem cell transplantation with emphasis on CD45RA+ subset of regulatory T cells (Tregs). All but 1 engrafted, and 14 patients experienced EA (acute graft-versus-host disease grades II to IV, n = 8; and post-transplantation hemophagocytic syndrome, n = 6) with a cumulative incidence of 43.7%; 42% developed mild chronic graft-versus-host disease. The overall survival was 70.2% with a nonrelapse mortality of 16.8% at a median of 19 months. Age < 10 years, donor age > 45 years, and poor recovery of Tregs correlated with EA. Not Tregs but higher CD45RA+ Tregs in the graft was associated with less EA (11.7% versus 32.5%, P = .0001). Higher donor age correlated with a lower CD45RA+ Tregs in the graft (P = .01). However, only higher CD45RA+ Treg percentage in the graft favorably impacted EA as well as nonrelapse mortality and overall survival. Our study demonstrates a critical role for CD45RA+ Tregs in determining EA and outcome after PTCy-based haploidentical peripheral blood stem cell transplantation, and the age-related physiologic decline in this population might be responsible for adverse impact of donor age.

Impact of Single-Dose Plerixafor as an Adjunct to Granulocyte Colony-Stimulating Factor-Based Peripheral Blood Stem Cell Mobilization on the Graft Composition and Outcome for T Cell-Replete Haploidentical Peripheral Blood Stem Cell Transplantation with Post-Transplantation Cyclophosphamide: A Comparative Study.

We conducted a prospective study on T and natural killer (NK) cell subset composition of graft and transplant outcomes in T cell-replete haploidentical transplantation with a single dose of subcutaneous plerixafor (Px) added to granulocyte colony-stimulating factor (G-CSF)-based mobilization in allogeneic donors to collect 10 × 106/kg CD34+ hematopoietic stem cells (HSCs) at single apheresis. Twnety-six donors received G-CSF + Px and 25 G-CSF alone for mobilization. Despite significantly lower peripheral blood (PB) CD34+ HSCs on day 4 in the G-CSF + Px group (33 [range, 6-47] cells/µL versus 81 [range, 50-168] cells/µL in the G-CSF group; P = .0001), PB CD34+ HSC count (median 136 versus 139 cells/µL) on day 5 as well as that in the graft (2.7 versus 2.3 × 106/mL, P = .1) were comparable between the 2 groups. The total nucleated cell count was higher (3.4 versus 3.1 × 108/mL, P = .05), but CD4+ T cells (2.3 versus 2.7 × 107/mL, P = .09) were lower in the G-CSF group with mobilization of regulatory T cells being similar. NK cells were skewed toward the CD56+/16- subset in both groups, varying significantly from the steady-state NK subset ratio in PB. The time to engraftment, incidences of acute and chronic graft-versus-host disease, nonrelapse mortality, and overall survival were also similar. Addition of single-dose Px to G-CSF mobilization improves CD34 recovery and does not significantly alter the T and NK cell composition of the graft, including regulatory T cells, with no adverse impact on transplant outcomes.

CD56-enriched donor cell infusion after post-transplantation cyclophosphamide for haploidentical transplantation of advanced myeloid malignancies is associated with prompt reconstitution of mature natural killer cells and regulatory T cells with reduced incidence of acute graft versus host disease: A pilot study.

We conducted a pilot study on the feasibility of CD56-enriched donor cell infusion after post-transplantation cyclophosphamide (PTCy) for 10 patients with advanced myeloid malignancies undergoing haploidentical peripheral blood stem cell transplantation with cyclosporine alone as graft-versus-host disease (GVHD) prophylaxis and compared the outcome and immune reconstitution with a control group of 20 patients undergoing the same without CD56-enriched donor cell infusion. An early and rapid surge of mature NK cells as well as CD4+ T cells and regulatory T cells (Tregs) was noted compared with the control group. KIR of donor phenotype reconstituted as early as day 30 with expression of CD56dimCD16+NKG2A-KIR+ phenotype. None experienced viral or fungal infections, and non-relapse mortality was 10% only. The incidence of grade 2-4 acute GVHD was 50% in the control group with none in the CD56 group (P = 0.01). Only two had de novo chronic GVHD in each group. Relapse occurred in five patients in CD56 group with a median follow-up of 12 months, similar to the control group. Our preliminary data show that CD56+ donor cell infusion after PTCy and short-course cyclosporine is feasible with prompt engraftment, rapid reconstitution of CD4+T cells, Tregs and NK cells and reduced incidence of acute GVHD.

Haploidentical Peripheral Blood Stem Cell Transplantation with Post-Transplantation Cyclophosphamide in Children with Advanced Acute Leukemia with Fludarabine-, Busulfan-, and Melphalan-Based Conditioning.

Post-transplantation cyclophosphamide (PTCY) therapy has made haploidentical transplantation a global reality in adults, but the literature is largely silent on the feasibility of this approach in children. We conducted a prospective study of 20 patients (median age, 12 years; range, 2-20 years) with advanced acute leukemia to evaluate the feasibility of PTCY-based haploidentical peripheral blood stem cell (PBSC) transplantation in children. The conditioning regimen comprised fludarabine, i.v. busulfan, and melphalan (Flu-Bu-Mel). PTCY on days +3 and +4 was followed by mycophenolate mofetil for 14-21 days and cyclosporine for 60 days. Thirteen patients (65%) had refractory or relapsed myelogenous leukemia, and the remainder had high-risk lymphoblastic leukemia. Prompt engraftment was noted at a median of 14 days, with full donor chimerism by day +28. The cumulative incidence of acute and chronic graft-versus-host disease was 35% and 5%, respectively. Nonrelapse mortality at 1 year was 20%. The incidence of disease progression was 25.7%. The actuarial overall survival at 2 years was 64.3% (95% confidence interval, 53.4%-75.2%). Our data suggest that Flu-Bu-Mel-based conditioning followed by PTCY-based haploidentical PBSC transplantation with reduced duration of immunosuppression is feasible in pediatric patients with advanced leukemia.

Improved Outcome of Refractory/Relapsed Acute Myeloid Leukemia after Post-Transplantation Cyclophosphamide-Based Haploidentical Transplantation with Myeloablative Conditioning and Early Prophylactic Granulocyte Colony-Stimulating Factor-Mobilized Donor Lymphocyte Infusions.

We carried out post-transplantation cyclophosphamide (PTCy)-based haploidentical peripheral blood stem cell transplantation in 51 patients with refractory/relapsed acute myeloid leukemia not in remission. The first 10 patients received nonmyeloablative conditioning followed by planned granulocyte colony-stimulating factor (G-CSF)-mobilized donor lymphocyte infusions (DLIs) on days 35, 60, and 90. No patient developed graft-versus-host disease (GVHD), but 90% had disease progression between 3 and 6 months. A subsequent 41 patients received myeloablative conditioning (MAC); the first 20 patients did not receive DLIs (MAC group) and the next 21 patients received G-CSF-mobilized DLIs (G-DLI) on days 21, 35, and 60 (MAC-DLI group). The incidence of disease progression and progression-free survival at 18 months were 66% and 25% in the MAC group compared with 21.4% and 61.9% in the MAC-DLI group (P = .01). Chronic GVHD but not acute GVHD was increased in the MAC-DLI group (41.2% versus 11%, P = .05). Natural killer cell alloreactive donor was associated with lower incidence of disease progression in the MAC but not in MAC-DLI group. The only factor favorably influencing disease progression and progression-free survival was administration of G-DLI after myeloablative conditioning. Our study shows that early administration of G-DLI is feasible after PTCy-based haploidentical hematopoietic stem cell transplantation for refractory/relapsed acute myeloid leukemia and might be associated with improved survival after MAC.

Haploidentical transplantation in children with unmanipulated peripheral blood stem cell graft: The need to look beyond post-transplantation cyclophosphamide in younger children.

Haploidentical transplantation with PTCY following marrow or PBSC graft has been associated with low incidence of GVHD in adults with similar data lacking in children. We report on the outcome of 25 patients <20 yr of age (median age 12 yr), undergoing a haploidentical PBSC transplantation for both malignant and non-malignant disorders. Engraftment was prompt and sustained. Cumulative incidences of acute GVHD and chronic GVHD were 40.3% and 16.7%, respectively. On subgroup analysis, it was evident that acute GVHD developed in 80% of patients <10 yr compared to only 13.3% in those between 10 and 20 yr [log-rank p = 0.001], despite similar graft composition with significantly higher NRM (60% vs. 0%; p = 0.001). The FFS was 63.5%; (79% in >10 yr and 40% in <10 yr, p = 0.01). Our data suggest that PTCY-based haploidentical PBSC transplantation is feasible in older children, but results in early and severe alloreactivity in younger children. These findings, despite being counterintuitive, could be explained by the variable metabolism of CY and oral mycophenolate in younger children indicating that PTCY-based approach as used in adults might not be adequate for younger children.

Long-Term Follow-Up of Abatacept, Post-Transplantation Cyclophosphamide, and Sirolimus-Based Haploidentical Transplantation in Younger Patients with Nonmalignant Diseases.

Haploidentical (haplo) hematopoietic cell transplantation (HCT) for nonmalignant disease (NMD) carries inherent challenges of both alloreactivity and graft failure. Building on promising results from pilot studies in which abatacept was combined with post-transplantation cyclophosphamide (PTCy) and sirolimus (AbaCyS) in younger NMD patients undergoing haplo-HCT, we present the long-term outcomes of this protocol. On the back of uniform disease-specific conditioning regimens containing antithymocyte globulin 4.5 mg/kg from day -9 to day -7, GVHD prophylaxis with AbaCyS consisted of abatacept administered on days 0, +5, +20, +35, and monthly until 180 days with PTCy and sirolimus. The patients were followed up with longitudinal assessment of immune reconstitution, growth, and reproductive development and quality of life (QoL) analyses. Among 40 patients (aplastic anemia, n = 24; hemoglobinopathies, n = 14; and primary immunodeficiencies, n = 2) with a median age of 10 years (range, 2 to 25 years), 95% achieved sustained engraftment. Post-transplantation hemophagocytic syndrome was detected in 3 patients, leading to graft failure in 2 cases. The incidence of acute graft-versus-host disease (GVHD) was 2.6%, and that of chronic GVHD (cGVHD) was 14.3%. Cytomegalovirus, adenovirus, and Epstein-Barr virus infections were observed in 45%, 5%, and 0% respectively. Rates of nonrelapse mortality, overall survival, event-free survival, and GVHD-free, event-free survival were 5%, 95%, 90%, and 82%, respectively, at a median follow-up of 4.6 years. Absence of cGVHD correlated with younger patient age and early sustained recovery of regulatory T cells and mature natural killer cells, which in turn was associated with improved QoL and lack of late infections. The AbaCyS protocol was associated with excellent long-term survival, with attenuation of both early and late alloreactivity in >80% of younger patients undergoing haplo-HCT for NMD. This study sheds light on predispositions to cGVHD and its impact on QoL, warranting further optimization of this approach.

Impact of Conditioning Regimen and Graft-versus-Host Disease Prophylaxis on The Outcome of Haploidentical Peripheral Blood Stem Cell Transplantation for High-Risk Severe Aplastic Anemia in Children and Young Adults: A Report from the Pediatric Severe Aplastic Anemia Consortium of India.

Allogenic hematopoietic cell transplantation (HCT) is the best curative approach for patients with severe aplastic anemia (SAA). The outcomes of HCT from haploidentical family donors (HFDs) have improved, making it a feasible option for patients lacking an HLA-identical donor. However, data on HFD-HCT for younger patients with SAA is sparse. In this multicenter retrospective study, we evaluated the outcomes of 79 patients undergoing HFD-HCT for SAA. All the patients were heavily pretransfused, the median time to HCT was >12 months, and 67% had failed previous therapies. Conditioning was based on fludarabine (Flu)-cyclophosphamide (Cy)-antithymocyte globulin (ATG)/total body irradiation (TBI) with or without thiotepa/melphalan (TT/Mel). Post-transplantation Cy (PTCy) and calcineurin inhibitors (CNIs)/sirolimus were used as graft-versus-host disease (GVHD) prophylaxis with or without abatacept. The rate of primary graft failure (PGF) was 16.43% overall, lower in patients conditioned with TT/Mel. The incidences of acute and chronic GVHD were 26.4% and 18.9%, respectively. At a median follow-up of 48 months, the overall survival (OS) and event-free survival (EFS) were 61.6% and 58.1%, respectively. Both OS and EFS were better in the TT/Mel recipients and with abatacept as GVHD prophylaxis. On multivariate analysis, the use of abatacept was found to favorably impact the outcome variables, including GVHD and EFS. Our study suggests that PTCy-based HFD-HCT is a reasonable option for young patients with high-risk SAA, in whom optimization of conditioning and GVHD prophylaxis might further improve outcomes.

Augmenting Vaccine Efficacy against Delta Variant with 'Mycobacterium-w'-Mediated Modulation of NK-ADCC and TLR-MYD88 Pathways.

Mycobacterium-w (Mw) was shown to boost adaptive natural killer (ANK) cells and protect against COVID-19 during the first wave of the pandemic. As a follow-up of the trial, 50 healthcare workers (HCW) who had received Mw in September 2020 and subsequently received at least one dose of ChAdOx1 nCoV-19 vaccine (Mw + ChAdOx1 group) were monitored for symptomatic COVID-19 during a major outbreak with the delta variant of SARS-CoV-2 (April-June 2021), along with 201 HCW receiving both doses of the vaccine without Mw (ChAdOx1 group). Despite 48% having received just a single dose of the vaccine in the Mw + ChAdOx1 group, only two had mild COVID-19, compared to 36 infections in the ChAdOx1 group (HR-0.46, p = 0.009). Transcriptomic studies revealed an enhanced adaptive NK cell-dependent ADCC in the Mw + ChAdOx1 group, along with downregulation of the TLR2-MYD88 pathway and concomitant attenuation of downstream inflammatory pathways. This might have resulted in robust protection during the pandemic with the delta variant.

Impact of adaptive natural killer cells, KLRC2 genotype and cytomegalovirus reactivation on late mortality in patients with severe COVID-19 lung disease.

OBJECTIVE: SARS-CoV-2 infection results in severe lung disease in up to 50% of hospitalised patients. The aetiopathogenesis in a subset of such patients, who continue to have progressive pulmonary disease following virus clearance, remains unexplored. METHODS: We investigated the role of NKG2C+/NKG2A- adaptive natural killer (ANK) cells, KLRC2 genotype and cytomegalovirus (CMV) reactivation in 22 such patients. RESULTS: The median duration of virus positivity was 23 days, and the median duration of hospitalisation was 48 days. The overall survival at 60 days in this group was 50%. Older age and comorbidities impacted survival negatively. CMV viraemia was documented in 11 patients, with a survival of 25% vs 80% in those without viraemia with viral load correlating with mortality. Both NK and T cells were markedly depressed in all patients at day 15. However, only persistently low ANK cells at 30 days along with an inversely high NKG2C-/NKG2A+ inhibitory NK cells significantly correlated with high CMV viraemia and mortality, irrespective of KLRC2 genotype. However, day 30 ANK cells were significantly lower in the KLRC2 deletion group. The release of IFN-γ and perforin was severely compromised in all patients at day +15, with significant improvement in the survivors at day +30, but not in those with adverse outcome. CONCLUSION: Patients with progressive lung disease even after negative SARS-CoV-2 status, with persistently reduced and functionally compromised ANK cells, are more likely to have CMV reactivation and an adverse outcome, independent of KLRC2 genotype.

Impact of an Immune Modulator Mycobacterium-w on Adaptive Natural Killer Cells and Protection Against COVID-19.

The kinetics of NKG2C+ adaptive natural killer (ANK) cells and NKG2A+inhibitory NK (iNK) cells with respect to the incidence of SARS-CoV-2 infection were studied for 6 months in a cohort of healthcare workers following the administration of the heat-killed Mycobacterium w (Mw group) in comparison to a control group. In both groups, corona virus disease 2019 (COVID-19) correlated with lower NKG2C+ANK cells at baseline. There was a significant upregulation of NKG2C expression and IFN-γ release in the Mw group (p=0.0009), particularly in those with a lower baseline NKG2C expression, along with the downregulation of iNK cells (p<0.0001). This translated to a significant reduction in the incidence and severity of COVID-19 in the Mw group (incidence risk ratio-0.15, p=0.0004). RNA-seq analysis at 6 months showed an upregulation of the ANK pathway genes and an enhanced ANK-mediated antibody-dependent cellular cytotoxicity (ADCC) signature. Thus, Mw was observed to have a salutary impact on the ANK cell profile and a long-term upregulation of ANK-ADCC pathways, which could have provided protection against COVID-19 in a non-immune high-risk population.

Early and Sustained Expansion of Adaptive Natural Killer Cells Following Haploidentical Transplantation and CTLA4Ig-Primed Donor Lymphocyte Infusions Dissociate Graft-versus-Leukemia and Graft-versus-Host Effects.

BACKGROUND: Adaptive or memory natural killer (NK) cells with epigenetic imprints similar to memory T cells have been shown to develop in response to cytomegalovirus (CMV) infection with upregulation of activating receptor NKG2C. These cells have been shown to possess strong anti-tumour efficacy both in-vitro as well as in-vivo. OBJECTIVES: To determine if reconstitution of adaptive NK cells (CD56dimNKG2C+NKG2A-) in patients with advanced leukemia undergoing haploidentical HCT had any impact on disease progression (DP). STUDY DESIGN: The study cohort comprised of 60 patients with advanced acute leukemia, aged 2-65 years, receiving myeloablative PTCy based haploidentical transplantation from CMV seropositive donors, followed by CTLA4Ig-primed donor lymphocyte infusions (DLI). They were evaluated for the kinetics of reconstitution of adaptive NK cells, both phenotypic and functional, at days +30,+60, +90 and at regular intervals, to 3 years of follow-up, in relation to DP. Reconstitution of adaptive NK cells was compared with a retrospective cohort of patients in the same protocol receiving DLI without CTLA4Ig. RESULTS: Non-relapse mortality, acute and chronic GVHD were 5.1%, 10.3% and 14.5%. DP was 17.5% at a median follow-up of 28 months. Adaptive NK cells were significantly higher in patients without DP at days+30, +60 and +90 (p = 0.0001), irrespective of CMV reactivation and remained elevated until 36 months post-HCT. These cells maintained their functional competence as measured by robust interferon-gamma production with higher expressions of KIR, NKG2D and CD57, without any increase in PD1 expression. Grafts from donors with higher adaptive NK cells were associated with a lower risk of DP (p = 0.0001). In multivariate analysis, adaptive NK cell recovery at day +90 had the most favorable impact on DP (HR-0.7). Tregs reconstituted briskly along with the adaptive NK cells and were sustained as well, without compromising the GVL effect. Comparison with a retrospective cohort receiving the same protocol with DLI without CTLA4Ig, showed a superior reconstitution of adaptive NK cells in those receiving CTLA4Ig-DLI (p < 0.0001). CONCLUSION: Our study suggests that myeloablative transplantation from CMV seropositive haploidentical donors augmented with CTLA4Ig-primed DLI might favor early and sustained expansion of functionally competent adaptive NK cells irrespective of CMV reactivation, with a favorable outcome.