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SUMMARYMycobacterium-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 Mw+ChAdOx1 group, only 2 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 TLR2-MYD88 pathway and concomitant attenuation of downstream inflammatory pathways. This might have resulted in robust protection during the pandemic with the delta variant.

Allogenic hematopoietic cell transplant (HCT) is the best curative approach patients with severe aplastic anemia (SAA). Outcome of HCT from haploidentical family donor (HFD) has improved, making it a feasible option for patients lacking HLA-identical donor. However, data on HFD-HCT for younger patients with SAA is sparse. In multicentre retrospective study, we report outcome of 79 patients undergoing HFD-HCT for SAA. All were heavily pre-transfused, median time to HCT12 months and 67% had failed previous therapies. Conditioning was based on Flu-Cy-ATG/TBI with or without thiotepa/melphalan (TT/Mel). Post-transplantation cyclophosphamide (PTCy) and CNI/Sirolimus were employed as GvHD prophylaxis with or without abatacept. Primary graft failure (PGF) was 16.43%, less in those conditioned with TT/Mel. Incidence of acute and chronic GVHD were 26.4% and 18.9%. 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/EFS were better in TT/Mel group and with abatacept as GVHD prophylaxis. On multivariate analysis, use of Abatacept was found to favourably 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, where optimisation of conditioning and GVHD prophylaxis might improve outcomes further.

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., In a cohort of patients with severe COVID‐19 lung disease who continued to have severe illness even after clearance of virus, lack of recovery of NKG2C+ adaptive NK cells correlated with cytomegalovirus viral load and increased mortality.