Bioactive adrenomedullin and interleukin-6 in COVID-19: potential biomarkers of acute kidney injury and critical illness

BACKGROUND

The aim of this study was to investigate whether bioactive adrenomedullin (bio-ADM) and interleukin-6 (IL-6) are related to acute kidney injury (AKI) and severe illness in COVID-19 patients.

METHODS

153 patients with COVID-19 admitted to the emergency department (ED) were included. Blood samples were collected from each patient at admission. Bio-ADM and IL-6, as well as DPP3 and routinely measured markers were evaluated regarding the endpoints AKI (22/128 hospitalized patients) and a composite endpoint of admission to intensive care unit and/or in-hospital death (n = 26/153 patients).

RESULTS

Bio-ADM and IL-6 were significantly elevated in COVID-19 patients with AKI compared to COVID-19 patients without AKI (each p < 0.001). According to ROC analyses IL-6 and bio-ADM had the largest AUC (0.84 and 0.81) regarding the detection of AKI. Furthermore, bio-ADM and IL-6 were significantly elevated in COVID-19 patients reaching the composite endpoint (each p < 0.001). Regarding the composite endpoint ROC analysis showed an AUC of 0.89 for IL-6 and 0.83 for bio-ADM in COVID-19 patients. In the multivariable logistic model bio-ADM and IL-6 presented as independent significant predictors regarding both endpoints AKI and the composite endpoint in COVID-19 patients (as well as creatinine regarding the composite endpoint; each p < 0.05), opposite to leukocytes, C-reactive protein (CRP) and dipeptidyl peptidase 3 (DPP3; each p = n.s.).

CONCLUSION

Elevated levels of bio-ADM and IL-6 are associated with AKI and critical illness in patients with COVID-19. Therefore, both biomarkers may be potential tools in risk stratification in COVID-19 patients at presentation in the ED.

Dipeptidyl-peptidase 3 and IL-6: potential biomarkers for diagnostics in COVID-19 and association with pulmonary infiltrates

Coronavirus SARS-CoV-2 spread worldwide, causing a respiratory disease known as COVID-19. The aim of the present study was to examine whether Dipeptidyl-peptidase 3 (DPP3) and the inflammatory biomarkers IL-6, CRP, and leucocytes are associated with COVID-19 and able to predict the severity of pulmonary infiltrates in COVID-19 patients versus non-COVID-19 patients. 114 COVID-19 patients and 35 patients with respiratory infections other than SARS-CoV-2 were included in our prospective observational study. Blood samples were collected at presentation to the emergency department. 102 COVID-19 patients and 28 non-COVID-19 patients received CT imaging (19 outpatients did not receive CT imaging). If CT imaging was available, artificial intelligence software (CT Pneumonia Analysis) was used to quantify pulmonary infiltrates. According to the median of infiltrate (14.45%), patients who obtained quantitative CT analysis were divided into two groups (> median: 55 COVID-19 and nine non-COVID-19, ≤ median: 47 COVID-19 and 19 non-COVID-19). DPP3 was significantly elevated in COVID-19 patients (median 20.85 ng/ml, 95% CI 18.34-24.40 ng/ml), as opposed to those without SARS-CoV-2 (median 13.80 ng/ml, 95% CI 11.30-17.65 ng/ml; p < 0.001, AUC = 0.72), opposite to IL-6, CRP (each p = n.s.) and leucocytes (p < 0.05, but lower levels in COVID-19 patients). Regarding binary logistic regression analysis, higher DPP3 concentrations (OR = 1.12, p < 0.001) and lower leucocytes counts (OR = 0.76, p < 0.001) were identified as significant and independent predictors of SARS-CoV-2 infection, as opposed to IL-6 and CRP (each p = n.s.). IL-6 was significantly increased in patients with infiltrate above the median compared to infiltrate below the median both in COVID-19 (p < 0.001, AUC = 0.78) and in non-COVID-19 (p < 0.05, AUC = 0.81). CRP, DPP3, and leucocytes were increased in COVID-19 patients with infiltrate above median (each p < 0.05, AUC: CRP 0.82, DPP3 0.70, leucocytes 0.67) compared to infiltrate below median, opposite to non-COVID-19 (each p = n.s.). Regarding multiple linear regression analysis in COVID-19, CRP, IL-6, and leucocytes (each p < 0.05) were associated with the degree of pulmonary infiltrates, as opposed to DPP3 (p = n.s.). DPP3 showed the potential to be a COVID-19-specific biomarker. IL-6 might serve as a prognostic marker to assess the extent of pulmonary infiltrates in respiratory patients.

Intestinal IgA-positive plasma cells are highly sensitive indicators of alloreaction early after allogeneic transplantation and associate with both graft-versus-host disease and relapse-related mortality

Intestinal immunoglobulin A (IgA) is strongly involved in microbiota homeostasis. Since microbiota disruption is a major risk factor of acute graft-versus-host disease (GvHD), we addressed the kinetics of intestinal IgA-positive (IgA+) plasma cells by immunohistology in a series of 430 intestinal biopsies obtained at a median of 1,5 months after allogeneic stem cell transplantation (allo-SCT) from 115 patients (pts) at our center. IgA+ plasma cells were located in the subepithelial lamina propria and suppressed in the presence of histological aGvHD (GvHD Lerner stage 0: 131+/-8 IgA+ plasma cells/mm2; stage 1-2: 108+/-8 IgA+ plasma cells/mm2; stage 3-4: 89+/-16 IgA+ plasma cells/mm2; P=0.004). Overall, pts with IgA+ plasma cells below median had an increased treatment related mortality (P=0.04). Time courses suggested a gradual recovery of IgA+ plasma cells after day 100 in the absence but not in the presence of GvHD. Vice versa IgA+ plasma cells above median early after allo-SCT were predictive of relapse and relapse-related mortality (RRM): pts with low IgA+ cells had a 15% RRM at 2 and at 5 years, while pts with high IgA+ cells had a 31% RRM at 2 years and more than 46% at 5 years; multivariate analysis indicated high IgA+ plasma cells in biopsies (hazard ratio =2.7; 95% confidence interval: 1.04-7.00) as independent predictors of RRM, whereas Lerner stage and disease stage themselves did not affect RRM. In contrast, IgA serum levels at the time of biopsy were not predictive for RRM. In summary, our data indicate that IgA+ cells are highly sensitive indicators of alloreaction early after allo-SCT showing association with TRM but also allowing prediction of relapse independently from the presence of overt GvHD.

Urinary N-Terminal Pro-Brain Natriuretic Peptide Predicts Acute Kidney Injury and Severe Disease in COVID-19

INTRODUCTION

The ongoing COVID-19 pandemic is placing an extraordinary burden on our health care system with its limited resources. Accurate triage of patients is necessary to ensure medical care for those most severely affected. In this regard, biomarkers could contribute to risk evaluation. The aim of this prospective observational clinical study was to assess the relationship between urinary N-terminal pro-brain natriuretic peptide (NT-proBNP) and acute kidney injury (AKI) as well as severe disease in patients with COVID-19.

METHODS

125 patients treated with an acute respiratory infection in the emergency department of the University Hospital Regensburg were analyzed. These patients were divided into a COVID-19 cohort (n = 91) and a cohort with infections not caused by severe acute respiratory syndrome-coronavirus-2 (n = 34). NT-proBNP was determined from serum and fresh urine samples collected in the emergency department. Clinical endpoints were the development of AKI and a composite one consisting of AKI, intensive care unit admission, and in-hospital death.

RESULTS

11 (12.1%) COVID-19 patients developed AKI during hospitalization, whereas 15 (16.5%) reached the composite endpoint. Urinary NT-proBNP was significantly elevated in COVID-19 patients who suffered AKI or reached the composite endpoint (each p < 0.005). In a multivariate regression analysis adjusted for age, chronic kidney disease, chronic heart failure, and arterial hypertension, urinary NT-proBNP was identified as independent predictor of AKI (p = 0.017, OR = 3.91 [CI: 1.28-11.97] per standard deviation [SD]), as well as of the composite endpoint (p = 0.026, OR 2.66 [CI: 1.13-6.28] per SD).

CONCLUSION

Urinary NT-proBNP might help identify patients at risk for AKI and severe disease progression in COVID-19.

NAG: potential cardiorenal biomarker indicates progression of chronic kidney disease in implantable cardioverter defibrillator patients, contrary to KIM-1

Aim: NAG and KIM-1 as markers of tubular damage are suggested as potential biomarkers for the cardiorenal syndrome. Aim of the study was to assess the prognostic capability of NAG and KIM-1 regarding progression of chronic kidney disease (CKD) in patients with implantable cardioverter defibrillator (ICD). Materials & methods: We included 313 patients with an ICD and collected plasma and urine samples. Follow-up was performed after 51 months (interquartile range [IQR]: 25-55). Outcome of interest was continuous CKD progression defined as persistent decline in estimated glomerular filtration rate category accompanied by a ≥25% drop of baseline estimated glomerular filtration rate. Results: Average four (IQR: 2-6) follow-up values of serum creatinine per patient were obtained. During follow-up 29 patients (9%) developed a continuous CKD progression. NAG was shown as independent predictor for continuous CKD progression (p = 0.01), opposite to KIM-1 (p = n.s.). Conclusion: NAG was shown as predictor for a progressive and real deterioration of kidney function in patients with ICD.

N-acetyl-b-D-glucosaminidase: A potential cardiorenal biomarker with a relevant impact on ICD shock therapies and mortality

AIMS

Chronic heart failure may lead to chronic kidney disease. Previous studies suggest tubular markers N-acetyl-b-D-glucosaminidase (NAG) and Kidney-injury-molecule-1 (KIM-1) as potential markers for the cardiorenal syndrome (CRS). The prognostic value of NAG and KIM-1 regarding implantable cardioverter defibrillator (ICD) shock therapies is unknown.

METHODS

We included 314 patients with an ICD and collected plasma and urine samples. Urine-values of NAG and KIM-1 got related to urinary creatinine. Outcomes of interest were sustained adequate shock therapies and a combined endpoint of all-cause mortality, rehospitalisation due to congestive heart failure and adequate shock therapies. Follow up time was 32 months (IQR 6-35 months).

RESULTS

KIM-1 and NAG were positively correlated with NT-proBNP (KIM-1: r = .34, P < .001; NAG: r = .47, P < .001). NAG was significantly elevated in patients with primary prevention compared with secondary prevention ICD indication (P = .003). According to Kaplan Meier analysis, NAG as well as NT-proBNP were significant predictors for adequate ICD shock therapies and for the combined endpoint (each P < .001). Elevated KIM-1 showed no significant differences (each P = n.s.). In multivariate cox regression analysis, NAG as well as NT-proBNP were both independent predictors for adequate ICD shock therapies as well as the combined endpoint, beside ejection fraction <35% (each P < .05). Diabetes, primary prevention ICD indication, coronary artery disease, eGFR and age were no significant predictors for both endpoints (each P = n.s.).

CONCLUSION

Similar to NT-proBNP, NAG showed promising value for overall prognostication in ICD patients. Especially, NAG seems to incorporate an additional prognostic value regarding occurrence of ICD shock therapies.

Atomic model of human cystic fibrosis transmembrane conductance regulator: membrane-spanning domains and coupling interfaces

We describe herein an atomic model of the outward-facing three-dimensional structure of the membrane-spanning domains (MSDs) and nucleotide-binding domains (NBDs) of human cystic fibrosis transmembrane conductance regulator (CFTR), based on the experimental structure of the bacterial transporter Sav1866. This model, which is in agreement with previous experimental data, highlights the role of some residues located in the transmembrane passages and directly involved in substrate translocation and of some residues within the intracellular loops (ICL1-ICL4) making MSD/NBD contacts. In particular, our model reveals that D173 ICL1 and N965 ICL3 likely interact with the bound nucleotide and that an intricate H-bond network (involving especially the ICL4 R1070 and the main chain of NBD1 F508) may stabilize the interface between MSD2 and the NBD1F508 region. These observations allow new insights into the ATP-binding sites asymmetry and into the molecular consequences of the F508 deletion, which is the most common cystic fibrosis mutation.

Archaeosomes based on synthetic tetraether-like lipids as novel versatile gene delivery systems

Novel cationic liposomes, termed "archaeosomes", based on mixtures of neutral/cationic bilayer-forming lipids and archaeobacterial synthetic tetraether-type bipolar lipids show efficient in vitro gene transfection properties and represent a new approach for modulating the lipidic membrane fluidity of the complexes they form with DNA.

Nucleotide binding domains of human CFTR: a structural classification of critical residues and disease-causing mutations

Defective function of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) causes CF, the most frequent lethal inherited disease among the Caucasian population. The structure of this chloride ion channel includes two nucleotide-binding domains (NBDs), whose ATPase activity controls channel gating. Recently, the experimental structures of mouse and human CFTR NBD1 and our model of the human CFTR NBD1/NBD2 heterodimer have provided new insights into specific structural features of the CFTR NBD dimer. In the present work, we provide a structural classification of CF-causing mutations which may complement the existing functional classification. Our analysis also identified amino acid residues which may play a critical role in interdomain interaction and are located at the NBD1-NBD2 interface or on the surface of the dimer. In particular, a cluster of aromatic amino acids, which includes F508 and straddles the two NBDs, might be directly involved in the interaction of the NBD1/NBD2 heterodimer with the channel-forming membrane-spanning domains.

The Design of Cationic Lipids for Gene Delivery

Synthetic gene delivery vectors are gaining increasing importance in gene therapy as an alternative to recombinant viruses. Among the various types of non-viral vectors, cationic lipids are especially attractive as they can be prepared with relative ease and extensively characterised. Further, each of their constituent parts can be modified, thereby facilitating the elucidation of structure-activity relationships. In this forward-looking review, cationic lipid-mediated gene delivery will mainly be discussed in terms of the structure of the three basic constituent parts of any cationic lipid: the polar headgroup, hydrophobic moiety and linker. Particular emphasis will be placed on recent advances in the field as well as on our own original contributions. In addition to reviewing critical physicochemical features (such as headgroup hydration) of monovalent lipids, the use of headgroups with known nucleic-acid binding modes, such as linear and branched polyamines, aminoglycosides and guanidinium functions, will be comprehensively assessed. A particularly exciting innovation in linker design is the incorporation of environment-sensitive groups, the intracellular hydrolysis of which may lead to more controlled DNA delivery. Examples of pH-, redox- and enzyme-sensitive functional groups integrated into the linker are highlighted and the benefits of such degradable vectors can be evaluated in terms of transfection efficiency and cationic lipid-associated cytotoxicity. Finally, possible correlations between the length and type of hydrophobic moiety and transfection efficiency will be discussed. In conclusion it may be foreseen that in order to be successful, the future of cationic lipid-based gene delivery will probably require the development of sophisticated virus-like systems, which can be viewed as "programmed supramolecular systems" incorporating the various functions required to perform in a chronological order the different steps involved in gene transfection.

Nucleotide-binding domains of human cystic fibrosis transmembrane conductance regulator: detailed sequence analysis and three-dimensional modeling of the heterodimer

The cystic fibrosis transmembrane conductance regulator (CFTR) protein is encoded by the gene that is defective in cystic fibrosis, the most common lethal inherited disease among the Caucasian population. CFTR belongs to the ABC transporter superfamily, whose members form macromolecular architectures composed of two membrane-spanning domains and two nucleotide-binding domains (NBDs). The experimental structures of NBDs from several ABC transporters have recently been solved, opening new avenues for understanding the structure/function relationships and the consequences of some disease-causing mutations of CFTR. Based on a detailed sequence/structure analysis, we propose here a three-dimensional model of the human CFTR NBD heterodimer. This model, which is in agreement with recent experimental data, highlights the specific features of the CFTR asymmetric active sites located at the interface between the two NBDs. Moreover, additional CFTR-specific features can be identified at the subunit interface, which may play critical roles in active site interdependence and are uncommon in other NBD dimers.

Glycosidase active site mutations in human alpha-L-iduronidase

Mucopolysaccharidosis type I (MPS I; McKusick 25280) results from a deficiency in alpha-L-iduronidase activity. Using a bioinformatics approach, we have previously predicted the putative acid/base catalyst and nucleophile residues in the active site of this human lysosomal glycosidase to be Glu182 and Glu299, respectively. To obtain experimental evidence supporting these predictions, wild-type alpha-L-iduronidase and site-directed mutants E182A and E299A were individually expressed in Chinese hamster ovary-K1 cell lines. We have compared the synthesis, processing, and catalytic properties of the two mutant proteins with wild-type human alpha-L-iduronidase. Both E182A and E299A transfected cells produced catalytically inactive human alpha-L-iduronidase protein at levels comparable to the wild-type control. The E182A protein was synthesized, processed, targeted to the lysosome, and secreted in a similar fashion to wild-type alpha-L-iduronidase. The E299A mutant protein was also synthesized and secreted similarly to the wild-type enzyme, but there were alterations in its rate of traffic and proteolytic processing. These data indicate that the enzymatic inactivity of the E182A and E299A mutants is not due to problems of synthesis/folding, but to the removal of key catalytic residues. In addition, we have identified a MPS I patient with an E182K mutant allele. The E182K mutant protein was expressed in CHO-K1 cells and also found to be enzymatically inactive. Together, these results support the predicted role of E182 and E299 in the catalytic mechanism of alpha-L-iduronidase and we propose that the mutation of either of these residues would contribute to a very severe clinical phenotype in a MPS I patient.

Sterically stabilized BGTC-based lipoplexes: structural features and gene transfection into the mouse airways in vivo

BACKGROUND

Colloidal stability of lipid/DNA aggregates is a major requirement for cationic lipid-mediated transfection which is particularly difficult to fulfil at the high DNA concentrations used for in vivo gene delivery. Thus, we have investigated the potential of poly(ethyleneglycol) (PEG) conjugates for steric stabilization of lipoplexes formed by bis(guanidinium)-tren-cholesterol/dioleoyl phosphatidylethanolamine (BGTC/DOPE) liposomes, a class of cationic liposomes we have developed over the past few years.

METHODS AND RESULTS

We demonstrate that adequate lipophilic PEG derivatives can stabilize BGTC/DOPE lipoplexes formed at high DNA concentration. We also report the results of cryotransmission electron microscopy studies indicating that PEG-stabilized lipoplexes form DNA-coated structures which assemble into clusters exhibiting various complex morphologies. Finally, we report data from in vivo transfection experiments suggesting that PEG-mediated colloidal stabilization of concentrated lipoplex solutions may allow enhanced transfection of the mouse airways via intranasal administration.

CONCLUSION

Our results represent an important step towards the design of multimodular BGTC-based systems for improved in vivo gene transfection.

Efficient gene transfection by bisguanylated diacetylene lipid formulations

We have previously shown that cationic cholesterol derivatives bearing guanidinium groups were efficient vectors for gene transfer. To further evaluate the potentiality of this novel class of cationic lipids, we undertook to study the transfection efficiency of guanidinium-based lipids with other hydrophobic moieties. Specifically, we synthesized a reagent where two guanidinium groups are linked to a diacetylene lipid which may provide the lipoplexes with favorable structural features. We report here that the cationic lipid bisguanidinium-diacetylene (BGDA) is highly efficient for in vitro gene transfection when formulated with dioleoylphosphatidyl ethanolamine (DOPE). We also show that liposomes composed of BGDA, DOPE, and a neutral diacetylene colipid, hydroxyethylenediacetylene (HEDA), are efficient for transfection. Thus, diacetylene-based lipids provide a novel scaffold for gene transfection and will be particularly useful for gaining new insights into the structure-activity relationships of the lipid/DNA complexes as they offer a means to study the effects of polymerizable domains.

Human glucocerebrosidase: heterologous expression of active site mutants in murine null cells

Using bioinformatics methods, we have previously identified Glu235 and Glu340 as the putative acid/base catalyst and nucleophile, respectively, in the active site of human glucocerebrosidase. Thus, we undertook site-directed mutagenesis studies to obtain experimental evidence supporting these predictions. Recombinant retroviruses were used to express wild-type and E235A and E340A mutant proteins in glucocerebrosidase-deficient murine cells. In contrast to wild-type enzyme, the mutants were found to be catalytically inactive. We also report the results of various studies (Western blotting, glycosylation analysis, subcellular fractionation, and confocal microscopy) indicating that the wild-type and mutant enzymes are identically processed and sorted to the lysosomes. Thus, enzymatic inactivity of the mutant proteins is not the result of incorrect folding/processing. These findings indicate that Glu235 plays a key role in the catalytic machinery of human glucocerebrosidase and may indeed be the acid/base catalyst. As concerns Glu340, the results both support our computer-based predictions and confirm, at the biological level, previous identification of Glu340 as the nucleophile by use of active site labeling techniques. Finally, our findings may help to better understand the molecular basis of Gaucher disease, the human lysosomal disease resulting from deficiency in glucocerebrosidase.

Structural features of normal and mutant human lysosomal glycoside hydrolases deduced from bioinformatics analysis

Lysosomal storage diseases are due to inherited deficiencies in various enzymes involved in basic metabolic processes. As with other genetic diseases, accurate structure data for these enzymatic proteins should help in better understanding the molecular effects of mutations identified in patients with the corresponding lysosomal diseases; however, no such three-dimensional (3D) structure data are available for many lysosomal enzymes. Thus, we herein intend to illustrate for an audience of molecular geneticists how structure information can nonetheless be obtained via a bioinformatics approach in the case of five human lysosomal glycoside hydrolases. Indeed, using the two-dimensional hydrophobic cluster analysis method to decipher the sequence information available in data banks for the large group of glycoside hydrolases (clan GH-A) to which these human lysosomal enzymes belong, we could deduce structure predictions for their catalytic domains and propose explanations for the molecular effects of mutations described in patients. In addition, in the case of human beta-glucuronidase for which experimental 3D data have been reported, we also show here that bioinformatics methods relying on the available 3D structure information can be used to obtain further insights into the effects of various mutations described in patients with Sly disease. In a broader perspective, our work stresses that, in the context of a rapid increase in protein sequence information through genome sequencing, bioinformatics approaches might be highly useful for generating structure-function predictions based on sequence-structure interrelationships.

Structural characteristics of supramolecular assemblies formed by guanidinium-cholesterol reagents for gene transfection

We have recently discovered that cationic cholesterol derivatives characterized by guanidinium polar headgroups are very efficient for gene transfection in vitro and in vivo. In spite of being based on some rationale at the molecular level, the development of these new synthetic vectors was nevertheless empirical. Indeed, the factors and processes underlying cationic lipid-mediated gene transfer are still poorly understood. Thus, to get a better insight into the mechanisms involved, we have examined the supramolecular structure of lipid/DNA aggregates obtained when using reagent bis(guanidinium)-tren-cholesterol (BGTC), either alone or as a liposomal formulation with the neutral phospholipid dioleoyl phosphatidylethanolamine (DOPE). We here report the results of cryotransmission electron microscopy studies and small-angle x-ray scattering experiments, indicating the presence of multilamellar domains with a regular spacing of 70 A and 68 A in BGTC/DOPE-DNA and BGTC-DNA aggregates, respectively. In addition, DNA lipoplexes with similar lamellar patterns were detected inside transfected HeLa cells by conventional transmission electron microscopy. These results suggest that DNA condensation by multivalent guanidinium-cholesterol cationic lipids involves the formation of highly ordered multilamellar domains, the DNA molecules being intercalated between the lipid bilayers. These results also invite further investigation of the intracellular fate of the internalized lipid/DNA structures during their trafficking toward the cell nucleus. The identification of the basic features of active complexes should indeed help in the design of improved guanidinium-based vectors.

Phylogenetic analysis of cystic fibrosis transmembrane conductance regulator gene in mammalian species argues for the development of a rabbit model for cystic fibrosis

The species-specific pattern of cystic fibrosis transmembrane conductance regulator (CFTR) expression was investigated in order to identify species closely related to man which can be used as potential cystic fibrosis (CF) animal models. To this purpose, the nucleotide sequences of the CFTR promoter region of eight mammalian species representing four different orders (Primates, Artiodactyla, Lagomorpha and Rodentia) were analyzed. Distance matrices and unrooted trees of the CFTR promoter region sequences yielded two deeply separated groups, one including man (Homo sapiens), nonhuman primates (Hylobates lar, Macaca fascicularis, Saimiri sciureus), cow (Bos taurus), and rabbit (Oryctolagus cuniculus) and the other including the rodents (Rattus norvegicus, Mus musculus). Divergences between rodent and nonrodent groups have been observed in putative cis transcriptional regulatory elements and can be involved in the differences of pattern of expression between these two groups. Comparison of the available CFTR cDNA sequences enabled us to root the tree with a noneutherian outgroup and to perform a phylogenetic analysis. This analysis did not detect any base composition bias and supported polyphyletic Glires. Although a long-branch attraction artifact cannot be completely excluded, these findings converge toward the recent statement (Graur, Duret, and Gouy 1996) that Lagomorpha is more closely related to Primates than to Rodentia. In addition, the phenylalanine residue in exon 10 involved in the most common CF mutation in man is conserved in rabbit. These phylogenetic analyses as well as anatomical and developmental data suggest that, once rabbit embryonic stem cells become available, the rabbit will provide a suitable tool for both gene transfer and pharmacological investigations and could lead to a better CF model than the current murine models.

Gene transfer by guanidinium-cholesterol cationic lipids into airway epithelial cells in vitro and in vivo

Synthetic vectors represent an attractive alternative approach to viral vectors for gene transfer, in particular into airway epithelial cells for lung-directed gene therapy for cystic fibrosis. Having recently found that guanidinium-cholesterol cationic lipids are efficient reagents for gene transfer into mammalian cell lines in vitro, we have investigated their use for gene delivery into primary airway epithelial cells in vitro and in vivo. The results obtained indicate that the lipid bis(guanidinium)-tren-cholesterol (BGTC) can be used to transfer a reporter gene into primary human airway epithelial cells in culture. Furthermore, liposomes composed of BGTC and dioleoyl phosphatidylethanolamine (DOPE) are efficient for gene delivery to the mouse airway epithelium in vivo. Transfected cells were detected both in the surface epithelium and in submucosal glands. In addition, the transfection efficiency of BGTC/DOPE liposomes in vivo was quantitatively assessed by using the luciferase reporter gene system.

Active-site motifs of lysosomal acid hydrolases: invariant features of clan GH-A glycosyl hydrolases deduced from hydrophobic cluster analysis

The clan GH-A is a group of more than 200 proteins representing nine established families of glycosyl hydrolases that act on a large variety of substrates. This clan includes five enzymes implicated in lysosomal storage diseases: beta-glucuronidase (Sly disease), beta-glucocerebrosidase (Gaucher disease), beta-galactosidase (Landing disease and Morquito type B disease), beta-mannosidase (mannosidosis) and alpha-L-iduronidase (Hurler-Scheie disease). Examination of known 3D structures from some families of the clan allowed us to deduce structural and functional features shared by these proteins. We then used the hydrophobic cluster analysis method to study the protein sequences of the entire clan. Our results reveal that, despite low levels of sequence identity, all the proteins of the clan (including the aforementioned lysosomal enzymes) likely share a similar catalytic domain consisting of an (alpha/beta)8 barrel with conserved functional amino acids located at the C-terminal ends of six of the eight strands constituting the beta-barrel. Interestingly, several mutations reported to be responsible for lysosomal storage diseases are located within these conserved regions of the lysosomal enzyme catalytic domains.

[Transgenic human thymopoiesis from retrovirally transduced umbilical cord blood hematopoietic stem cells: experimental studies in the SCID-hu mouse]

The gene encoding the CD2 mouse cell surface antigen was retrovirally transduced into cord blood CD34+ cells. On infection by culture at the contact of retrovirus-packaging cells, the mCD2 marker was expressed by 30-40% CD34+ cells, that included the most primitive stem cell-enriched Thy-1+ and CD38- subsets. Accordingly, sorted cord blood CD34+Thy-1+ cells could be directly infected in the same conditions. mCD2- transgenic cord blood CD34+ cells were then used to reconstitute human fetal thymus implanted in SCID mice. Five to 8 weeks later, the mCD2 antigen was detected on approximately 10% of the human thymocytes repopulating the thymus grafts and the transgene genome was detected in graft cell DNA by Southern blot. These results demonstrate efficient gene transfer into primitive cord blood hematopoietic cells endowed with lymphoid potential and suggest gene therapy schemes in neonates suffering inherited or acquired-such as HIV infection-disorders of the T-cell lineage.

Guanidinium-cholesterol cationic lipids: efficient vectors for the transfection of eukaryotic cells

Two cationic lipids, bis-guanidinium-spermidine-cholesterol (BGSC) and bis-guanidinium-trencholesterol (BGTC)-cholesterol derivatives bearing two guanidinium groups-have been synthesized and tested as artificial vectors for gene transfer. They combine the membrane compatible features of the cholesterol subunit and the favorable structural and high pKa features of the guanidinium functions for binding DNA via its phosphate groups. Reagent BGTC is very efficient for transfection into a variety of mammalian cell lines when used as a micellar solution. In addition, both BGTC and BGSC present also a high transfection activity when formulated as liposomes with the neutral phospholipid dioleoylphosphatidyl ethanolamine. These results reveal the usefulness of cholesterol derivatives bearing guanidinium groups for gene transfer.

A cell surface marker gene transferred with a retroviral vector into CD34+ cord blood cells is expressed by their T-cell progeny in the SCID-hu thymus

Gene transduction into immature hematopoietic cells collected at birth from the umbilical cord could be useful for the treatment of genetic or acquired disorders of the hematopoietic system diagnosed during pregnancy. The SCID-hu mouse is a convenient model to investigate T-cell lineage gene therapy, since it allows replication of human intrathymic T-cell development. CD34+ cells isolated from cord blood were cocultured with CRIP MFG-murine CD2 (mCD2) cells that produce recombinant retroviruses encoding the mCD2 antigen, a cell surface marker easily detectable by flow cytometry. After 3 and 4 days in coculture, a mean of 19% and 39% human hematopoietic cells, respectively, expressed the mCD2 antigen. CD34+ cells cocultured for 4 days were used to reconstitute human fetal thymus implanted in SCID mice. Five to 10 weeks later, the mCD2 antigen was detected on approximately 10% of human thymocytes repopulating the thymic grafts in four of nine SCID mouse chimeras. Vector genomes were detected in graft cell DNA by Southern blot. Analysis of vector integration indicated that positive cells were of polyclonal origin in three animals and predominantly monoclonal in the other one. Our data show that foreign genes can be transduced into CD34+ cord blood cells endowed with T-cell differentiation potential, and suggest strategies for T-cell lineage gene therapy in the neonate.

Increased levels of spliced RNA account for augmented expression from the MFG retroviral vector in hematopoietic cells

A persistent obstacle in the use of vector systems for gene therapy has been the inability to attain high-level expression of the target gene in primary cells in vivo. The MFG retroviral vector was designed to yield improved expression over the widely used N2 or LN vectors; however, the molecular basis for this effect has not been examined. Using the human glucocerebrosidase (GC) enzyme as a reporter, we compared expression from the MFG and N2 vector backbones in transduced murine hematopoietic cells after syngeneic bone marrow transplantation. Reporter enzyme activities in primary spleen colonies of transplanted mice were seven-fold higher per vector copy in cells transduced with the (MFG-based) MGC vector than in cells bearing the (N2-based) G2 vector. In spleen colonies harboring the MGC vector, the ratio of spliced to unspliced vector RNA was increased four-fold relative to the G2 vector transcripts in Northern blot analyses. Further analyses indicated that MGC-transduced cells contained five-fold higher levels of spliced RNA per vector copy. Since translation of spliced RNA species (in which the complex secondary structure of the packaging signal has been excised) is likely to proceed with enhanced efficiency, the augmented levels of spliced RNA produced by MFG may represent the key element of increased protein expression from this vector. These findings suggest that the MFG retroviral vector may provide higher level expression of target genes used in human gene therapy.

Conserved catalytic machinery and the prediction of a common fold for several families of glycosyl hydrolases

The regions surrounding the catalytic amino acids previously identified in a few "retaining" O-glycosyl hydrolases (EC 3.2.1) have been analyzed by hydrophobic cluster analysis and have been used to define sequence motifs. These motifs have been found in more than 150 glycosyl hydrolase sequences representing at least eight established protein families that act on a large variety of substrates. This allows the localization and the precise role of the catalytic residues (nucleophile and acid catalyst) to be predicted for each of these enzymes, including several lysosomal glycosidases. An identical arrangement of the catalytic nucleophile was also found for S-glycosyl hydrolases (myrosinases; EC 3.2.3.1) for which the acid catalyst is lacking. A (beta/alpha)8 barrel structure has been reported for two of the eight families of proteins that have been grouped. It is suggested that the six other families also share this fold at their catalytic domain. These enzymes illustrate how evolutionary events led to a wide diversification of substrate specificity with a similar disposition of identical catalytic residues onto the same ancestral (beta/alpha)8 barrel structure.

Efficient retroviral-mediated gene transfer into primary culture of murine and human hepatocytes: expression of the LDL receptor

The ex vivo approach to hepatic gene therapy involves several steps, which include the isolation and culture of hepatocytes, followed by their transduction with a retrovirus. Subsequently, autologous hepatocytes are transplanted. The number of hepatocytes that can be transduced by retroviruses bearing the therapeutic gene is one of the limiting steps that can impair the success of this strategy. We presently describe an experimental approach that leads to improved transduction efficiency in mouse and human hepatocytes in vitro. By using a recombinant retrovirus bearing the Escherichia coli beta-galactosidase gene, we show that addition of growth factors to the cells, namely human hepatocyte growth factor (HGF), allows marked increase in the transduction efficiency in mouse (up to 80%) and human (40%) hepatocytes. Familial hypercholesterolemia (FH) is due to mutation in the low-density lipoprotein (LDL) receptor gene and results in a deficiency in LDL receptors. Transduction of the human LDL receptor cDNA under the transcriptional control of the L-type pyruvate kinase promoter-activator into mouse hepatocytes led to an elevated tissue-specific expression of the human protein. These results suggest that the ex vivo approach remains a promising alternative for hepatic gene therapy.

[General principles of the production and use of retroviral vectors]

This paper describes the various strategies for somatic gene therapy. There are two main scenarios: the ex vivo approach and the in vivo approach. As recombinant retroviruses were used in the first clinical trials of gene therapy, their main characteristics (structure, efficient production of helper-free viral stocks by using packaging cells, transduction procedures) are discussed as well as the related safety issues. Finally, retroviral vectors can also be used as a new tool to investigate various clinical situations as they allow to mark cells by stably integrating in the cellular genome.

Use of prostaglandin E1 for prevention of liver veno-occlusive disease in leukaemic patients treated by allogeneic bone marrow transplantation

Prostaglandin E1 (PGE1) was used to prevent veno-occlusive disease (VOD) of the liver after allogeneic bone marrow transplantation (BMT) for leukaemia. It was given in continuous i.v. infusion from day--8 to day 30 after BMT at a dose of 0.3 micrograms/kg/h. The patients were studied according to the risk factors for VOD: diagnosis, intensification of the conditioning and previous liver abnormalities. The diagnosis of VOD was made on at least two of the following factors: weight gain, hepatomegaly, jaundice, ascitis, pain of the right upper quadrant, increased platelet consumption. 109 patients were studied, 50 were treated by PGE1 and 59 did not receive it. The actuarial incidence of VOD was 12.2% in the PGE1 group and 25.5% in the non PGE1 group (P = 0.05). In acute leukaemia, the incidence was 39.1% in the non-treated group and 12.8% in the PGE1 treated group (P = 0.02). Patients with previous hepatitis had an incidence of 62.5% in the non treated group and 15.5% in the treated group (P = 0.05). A positive cytomegalovirus (CMV) serology seemed to increase the risk of VOD: the incidence of VOD was 31.4% in non-treated patients and 22% in PGE1 treated patients. The multivariate analysis of the risk factors for VOD shows that unfavourable factors were: recipient positive CMV serology (P = 0.06), hepatic disease prior to transplant (P = 0.02) and the absence of PGE1 treatment (P = 0.02). This study suggests that prophylactic PGE1 treatment may decrease the incidence of VOD in patients treated for leukaemia by allogeneic bone marrow transplantation.

Long-term study of chimaerism in bone marrow transplantation recipients for severe aplastic anaemia

We used minisatellite probes to analyse by DNA fingerprints the long-term engraftment (median 4.3 years, range 1-2) of 21 bone marrow transplantation recipients for severe aplastic anaemia. Patients received their graft from histocompatible siblings. They were conditioned with cyclophosphamide (150 mg/kg) and a 6GY thoracoabdominal irradiation and did not have ex-vivo T cell depletion of marrow donor. DNA was extracted peripheral mononuclear cells and analysed by Southern blotting with 32P-labelled single-stranded RNA probes. Seven out of 21 donor-recipient pairs were sex-mismatched and additionally studied with a probe detecting a male specific repeated sequence on the Y chromosome. Red cell surface phenotype was also used as marker of engraftment in most cases. Long-term engraftment appeared complete for all patients studied with respect to the three methods.

Alpha-interferon in hairy cell leukaemia: direct effects on hairy cells or indirect cytotoxicity?

This report presents the results of a clinical trial on 53 patients with hairy cell leukaemia using low-dose alpha-interferon as therapy. Improvement of cytopenia and/or bone marrow hairy cell infiltration occurred in all but one patient. Often, blood and bone marrow improvements were dissociated and, after 7 or 13 months of therapy, complete remission was only observed in about 40% of patients. Recurrence of the disease was observed in some cases after cessation of therapy. A summary of the following results is presented: alpha-interferon receptor analysis, oncogene expression, study of the sensitivity of hairy cells to natural killer cells, and the effects of interferon on T-cell receptor gene rearrangement and on the function of T-cell clones. Results are also presented which show that myelofibrosis may be due to a release of platelet derived growth factor. The immunological findings and oncogene expression in 2 patients with a variant form of hairy cell leukaemia for which resistance to therapy was observed are also described. All the results show that interferon acts on hairy cells and are consistent with a direct effect by interferon in the treatment of hairy cell leukaemia.

Modulation of c-fos and c-myc mRNA levels in normal human lymphocytes by calcium ionophore A23187 and phorbol ester

A transient expression of the proto-oncogenes c-fos and c-myc is rapidly induced by growth factors or mitogens in different cell types including lectin-stimulated lymphocytes. To elucidate the early events of lymphocyte activation, we determined (by Northern blot analysis) the steady-state levels of c-fos and c-myc mRNA in normal human peripheral blood lymphocytes (PBL) stimulated with the Ca2+ ionophore A23187 and/or 12-O-tetradecanoylphorbol-13-acetate (TPA), whose biological activities are well defined. We report that ionophore A23187 (0.5 microM) or, to a significantly lesser extent, TPA (0.5 ng/ml), neither of which is mitogenic alone at these concentrations, nevertheless can induce a transient accumulation of the proto-oncogene transcripts. These results indicate that a significant accumulation of c-fos and c-myc mRNA can occur without subsequent lymphocyte proliferation. The combination of these two mitogens increases the induced levels of both types of c-onc mRNAs. The level of mRNA accumulation correlates with the degree of proliferation induced by mitogenic combinations of ionophore A23187 and TPA, as measured by [3H]thymidine incorporation. Thus, these compounds act synergistically both with respect to c-fos and c-myc mRNA accumulation and to mitogenicity in human PBL. We also studied the level of c-fos transcripts following stimulation of the T lymphocyte T3/Ti receptor complex, using monoclonal anti-T3 antibodies. We observed that mitogenic doses of anti-T3 also induce an accumulation of c-fos mRNA, whose induction also is synergized by TPA. These results suggest that transient accumulation of c-fos; as well as c-myc, mRNA is a normal event of the immune response. They confirm that Ca2+ ionophore combined with TPA can mimic some molecular features of the early steps of normal human PBL activation.

c-myc and c-fos expression during interferon-alpha therapy for hairy cell leukemia

Low-dose interferon-alpha (IFN-alpha) therapy is consistently effective in the treatment of hairy cell leukemia (HCL). In two cases of resistance to IFN-alpha administration, we diagnosed variant HCL, a form of HCL with intermediate features between typical HCL and B cell prolymphocytic leukemia. We tried to distinguish variant and typical hairy cells (HCs) by Northern blot analysis of the oncogenes expressed in vivo. We report that variant HCs contain c-myc transcripts in contrast to typical HCs, whereas c-fos transcripts are detected in both cell types. We also report that the mRNA levels of c-myc are not modified in variant HCs by IFN-alpha treatment, whereas the level of c-fos mRNA is modulated in both types of HCs. Our findings suggest that the failure to modulate c-myc expression in vivo might indicate the limits of low-dose IFN-alpha therapy.

Bone marrow transplantation for chronic granulocytic leukemia

Thirty-seven patients with chronic granulocytic leukemia have been treated with supralethal chemoradiotherapy followed by transplantation of bone marrow from HLA-identical donors. All patients showed engraftment, and the Philadelphia chromosome (PH1) disappeared in each case. Four patients had syngeneic grafts before blast crisis and are still alive; 2 are in remission not maintained by therapy, and 2 others are receiving chemotherapy after having relapsed in the chronic phase. Thirty-three patients had allogeneic grafts; only 2 received the grafts during blast crisis, and neither is a long-term survivor. Of the 13 patients who had grafts in the accelerated phase, 6 died of complications related to the transplantation, and 1 died after a myeloblastic relapse. Thus 6 patients are in unmaintained remission with a median follow-up of 13 months. Eighteen patients received grafts in the chronic phase. All 10 survivors are in unmaintained remission with a median follow-up of 14 months; in this group, no patient has relapsed. The granulocytic hyperplasia of the chronic phase can be more effectively ablated than established blastic leukemia. The mortality rate of transplant-related complications must be weighted against the typical rate of progression of chronic granulocytic leukemia. Although a longer follow-up period is needed for full evaluation, bone marrow transplantation may now be offered to patients in the chronic phase in an attempt to achieve long-term survival or cure of more than one-half of these patients.