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A new method of total RNA isolation by a single extraction with an acid guanidinium thiocyanate-phenol-chloroform mixture is described. The method provides a pure preparation of undegraded RNA in high yield and can be completed within 4 h. It is particularly useful for processing large numbers of samples and for isolation of RNA from minute quantities of cells or tissue samples.

BACKGROUNDThere is considerable variation in disease behavior among patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 . Genomewide association analysis may allow for the identification of potential genetic factors involved in the development of Covid-19. METHODSWe conducted a genomewide association study involving 1980 patients with Covid-19 and severe disease (defined as respiratory failure) at seven hospitals in the Italian and Spanish epicenters of the SARS-CoV-2 pandemic in Europe. After quality control and the exclusion of population outliers, 835 patients and 1255 control participants from Italy and 775 patients and 950 control participants from Spain were included in the final analysis. In total, we analyzed 8,582,968 single-nucleotide polymorphisms and conducted a meta-analysis of the two case-control panels. RESULTSWe detected cross-replicating associations with rs11385942 at locus 3p21.31 and with rs657152 at locus 9q34.2, which were significant at the genomewide level (P<5×10 −8 ) in the meta-analysis of the two case-control panels (odds ratio, 1.77; 95% confidence interval [CI], 1.48 to 2.11; P = 1.15×10 −10 ; and odds ratio, 1.32; 95% CI, 1.20 to 1.47; P = 4.95×10 −8 , respectively). At locus 3p21.31, the association signal spanned the genes SLC6A20, LZTFL1, CCR9, FYCO1, CXCR6 and XCR1. The association signal at locus 9q34.2 coincided with the ABO blood group locus; in this cohort, a blood-group-specific analysis showed a higher risk in blood group A than in other blood groups (odds ratio, 1.45; 95% CI, 1.20 to 1.75; P = 1.48×10 −4 ) and a protective effect in blood group O as compared with other blood groups (odds ratio, 0.65; 95% CI, 0.53 to 0.79; P = 1.06×10 −5 ). CONCLUSIONSWe identified a 3p21.31 gene cluster as a genetic susceptibility locus in patients with Covid-19 with respiratory failure and confirmed a potential involvement of the ABO blood-group system. (Funded by Stein Erik Hagen and others.

Since its introduction, the 'single-step' method has become widely used for isolating total RNA from biological samples of different sources. The principle at the basis of the method is that RNA is separated from DNA after extraction with an acidic solution containing guanidinium thiocyanate, sodium acetate, phenol and chloroform, followed by centrifugation. Under acidic conditions, total RNA remains in the upper aqueous phase, while most of DNA and proteins remain either in the interphase or in the lower organic phase. Total RNA is then recovered by precipitation with isopropanol and can be used for several applications. The original protocol, enabling the isolation of RNA from cells and tissues in less than 4 hours, greatly advanced the analysis of gene expression in plant and animal models as well as in pathological samples, as demonstrated by the overwhelming number of citations the paper gained over 20 years.

One hundred nine patients with hematologic malignancies, undergoing bone marrow transplants (BMT) from unrelated donors, were randomized in 2 consecutive trials to receive or not to receive antithymocyte globulin (ATG) in the conditioning regimen, as follows: (A) 54 patients (median age, 28 years; 39% with advanced disease) were randomized to no ATG (n ‫؍‬ 25) versus 7.5 mg/kg rabbit ATG (Thymoglobulin; Sangstat, Lyon, France) (n ‫؍‬ 29) ; (B) 55 patients (median age, 31 years, 71% with advanced disease) were randomized to no ATG (n ‫؍‬ 28) versus 15 mg/kg rabbit ATG (n ‫؍‬ 27). Grade III-IV graft-versus-host disease (GVHD) was diagnosed in 36% versus 41% (P ‫؍‬ .8) in the first and in 50% versus 11% (P ‫؍‬ .001) in the second trial. Transplant-related mortality (TRM), relapse, and actuarial 3-year survival rates were comparable in both trials. In fact, despite the reduction of GVHD in the second trial, a higher risk for lethal infections (30% vs 7%; P ‫؍‬ .02) was seen in the arm given 15 mg/kg ATG. Extensive chronic GVHD developed overall more frequently in patients given no ATG (62% vs 39%; P ‫؍‬ .04), as confirmed by multivariate analysis (P ‫؍‬ .03). Time to 50 ؋ 10 9 /L platelets was comparable in the first trial (21 vs 24 days; P ‫؍‬ .3) and delayed in the ATG arm in the second trial (23 vs 38 days; P ‫؍‬ .02). These trials suggest that (1) 15 mg/kg ATG before BMT significantly reduces the risk for grade III-IV acute GVHD, (2) this does not translate to a reduction in TRM because of the increased risk for infections, and (3) though survival is unchanged, extensive chronic GVHD is significantly reduced in patients receiving ATG. (Blood. 2001;98:2942-2947)

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This is an update of a randomized study on antithymocyte globulin (ATG; Thymoglobulin) before transplantation in patients undergoing unmanipulated marrow transplantation from unrelated donors. The median follow-up for surviving patients is 5.7 years. At last follow-up, chronic graft-versus-host disease (GVHD) was scored in 60% of non-ATG and in 37% of ATG patients (P=.05), and extensive chronic GVHD was present in 41% and 15%, respectively (P=.01). Chronic lung dysfunction was diagnosed in 51% versus 19% of patients (P=.005). Forced vital capacity decreased significantly with time in non-ATG patients (P=.005), but not in patients who received ATG (P=.30). The proportion of patients with Karnofsky scores of >or=90% at 4 years was 57% versus 89% in non-ATG versus ATG patients (P=.03). The actuarial 6-year survival for all patients randomized was 31% versus 44% (non-ATG versus ATG; P=.80). The cumulative incidence of transplant-related mortality was 51% versus 41% (P=.70) and of relapse was 32% versus 40% (P=.90). For patients who survived 1 year, transplant-related mortality was 25% versus 3% (P=.03), and actuarial survival was 58% versus 85% (P=.09). In conclusion, the addition of ATG to cyclosporine/methotrexate provides significant protection against extensive chronic GVHD and chronic lung dysfunction, reduces late transplant mortality, and improves quality of life in patients undergoing unrelated donor transplantation.

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