Assessment of Mendelian and risk-factor genes in Alzheimer disease: A prospective nationwide clinical utility study and recommendations for genetic screening

PURPOSE

To assess the likely pathogenic/pathogenic (LP/P) variants rates in Mendelian dementia genes and the moderate-to-strong risk factors rates in patients with Alzheimer disease (AD).

METHODS

We included 700 patients in a prospective study and performed exome sequencing. A panel of 28 Mendelian and 6 risk-factor genes was interpreted and returned to patients. We built a framework for risk variant interpretation and risk gradation and assessed the detection rates among early-onset AD (EOAD, age of onset (AOO) ≤65 years, n = 608) depending on AOO and pedigree structure and late-onset AD (66 < AOO < 75, n = 92).

RESULTS

Twenty-one patients carried a LP/P variant in a Mendelian gene (all with EOAD, 3.4%), 20 of 21 affected APP, PSEN1, or PSEN2. LP/P variant detection rates in EOAD ranged from 1.7% to 11.6% based on AOO and pedigree structure. Risk factors were found in 69.5% of the remaining 679 patients, including 83 (12.2%) being heterozygotes for rare risk variants, in decreasing order of frequency, in TREM2, ABCA7, ATP8B4, SORL1, and ABCA1, including 5 heterozygotes for multiple rare risk variants, suggesting non-monogenic inheritance, even in some autosomal-dominant-like pedigrees.

CONCLUSION

We suggest that genetic screening should be proposed to all EOAD patients and should no longer be prioritized based on pedigree structure.

Efficacy and safety of aerosolized intra-tracheal dornase alfa administration in patients with SARS-CoV-2-induced acute respiratory distress syndrome (ARDS): a structured summary of a study protocol for a randomised controlled trial

OBJECTIVES

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) may trigger severe pneumonia in coronavirus disease of 2019 (COVID-19) patients through release of damage-associated molecular patterns (DAMPs) and recruitment of neutrophils in the lungs. Activated neutrophils induce inflammation and severe alveolar injury by releasing neutrophil extracellular traps (NETs). The backbones of many DAMPs and NETs are made of extracellular, cell-free DNA decorated with highly toxic compounds such as elastase, myeloperoxidase and citrullinated histones. Dornase alfa is a FDA-approved recombinant human DNAse 1 for the treatment of cystic fibrosis, which cleaves extracellular DNA and may break up cell-free DNA, loosening sticky mucus in the distal airways and reducing NETs-induced toxicity on alveolar pneumocytes. The COVIDornase trial intends to define the impact of aerosolized intra-tracheal dornase alfa administration on the severity and progression of acute respiratory distress syndrome (ARDS) in COVID-19 patients. This drug might make lung mucus thinner and looser, promoting improved clearance of secretions and reduce extracellular double-stranded DNA-induced hyperinflammation in alveoli, preventing further damage to the lungs.

TRIAL DESIGN

COVIDornase is a prospective, randomized, controlled, 2-arm (1:1 ratio), multicentric, open-label clinical trial.

PARTICIPANTS

The study will recruit mechanically ventilated patients hospitalized in the intensive care unit (ICU) in the recruiting centres (at the time of writing: The Rothschild foundation hospital in Paris, the Strasbourg university hospitals, and Metz-Thionville hospital) who have been diagnosed with COVID-19 and meet ARDS criteria.

INCLUSION CRITERIA

- Adult patient (age ≥ 18 years old); - Hospitalized in ICU; - With severe COVID-19 pneumonia and ARDS according to Berlin criteria (PaO2/FiO2 < 300 and PEEP > 5 cmH2O); - Intubated for less than 8 days; - With an anticipated duration of mechanical ventilation > 48 hours; - Carrier of an arterial catheter; - For whom 4 PaO2/FiO2 values over the preceding 24 hours are available; NON-INCLUSION CRITERIA: - Known hypersensitivity to dornase alfa or any of its excipients; - Pregnant or breastfeeding status; - Patient under legal protection.

INTERVENTION AND COMPARATOR

Intervention 1, Study group Dornase alfa (Pulmozyme®, Roche, Switzerland) will be administered by aerosol, at a dose of 2500 IU twice daily, 12 hours apart, for 7 consecutive days, using a vibrating mesh nebulizer (Aerogen Solo®, Aerogen, Ireland). The remainder of the management will be performed in accordance with good clinical practice, including mechanical ventilation (protective ventilation, PEEP > 5 cmH2O, tracheal balloon pressure check every 4 hours or automatic device, 30° head of the bed elevation, tidal volume 6-8mL/kg, plateau pressure < 30 cmH2O), neuromuscular blockers if necessary, prone position if PaO2/FiO2 < 150, early enteral nutrition, glycemic control and a sedation protocol based on the RASS score. Intervention 2, Comparator Patients will receive usual care in accordance with good practice (as detailed above), without aerosols.

MAIN OUTCOMES

The primary outcome is the occurrence of at least one grade improvement between D0 (inclusion) and D7 in the ARDS scale severity (Berlin criteria). For instance from "severe" to "moderate" or from "moderate" to "mild".

RANDOMISATION

All consecutive patients meeting the inclusion criteria will be randomised 1:1 using an eCRF-based, computer-generated randomisation table, either to the dornase alfa arm or to the control arm. An interim analysis will be performed after inclusion of 20 patients. Inclusions may be stopped at the interim analysis per data safety and monitoring board (DSMB) advice, if statistical analyses conclude on the futility or efficacy of the intervention or by other DSMB decision.

BLINDING (MASKING)

The participants and caregivers will not be blinded to study group assignment. Those assessing the outcomes will be blinded to study group assignment.

NUMBERS TO BE RANDOMISED (SAMPLE SIZE)

Fifty patients will be randomized to each group, 100 patients in total.

TRIAL STATUS

Protocol version number 2, April 29th, 2020. Recruitment is ongoing. The trial started recruitment on the 21st April 2020. We estimate recruitment will finish August 21st 2020.

TRIAL REGISTRATION

The trial was registered in ClinicalTrials.gov on 21 April 2020, updated on 8 May 2020. Trial registration number is NCT04355364.

FULL PROTOCOL

The full protocol is attached as an additional file, accessible from the Trials website (Additional file 1). In the interest in expediting dissemination of this material, the familiar formatting has been eliminated. This Letter serves as a summary of the key elements of the full protocol.

Metastatic signet-ring cell carcinoma of unknown primary origin

About 3-5% of metastatic cancers originate from an unknown primary origin. Some have a signet-ring cell (SRC) component. We report the medical history of three patients with SRC carcinoma expressing both the oestrogen (ER) and progesterone receptors (PR). Although no primary breast cancer could be identified, we considered these three patients as having metastatic breast cancer. All of them were therefore treated with standard breast anti-hormonal therapies and all demonstrated benefit. The pitfalls of clinical presentation, diagnostic work-up, and treatment are discussed.

In vitro effect of cryptophycin 52 on microtubule assembly and tubulin: molecular modeling of the mechanism of action of a new antimitotic drug

Cryptophycin 52 (C52) is a new synthetic compound of the cryptophycin family of antitumor agents that is currently undergoing clinical evaluation for cancer chemotherapy. The cryptophycin class of compounds acts on microtubules. This report details the mechanism by which C52 substoichiometrically inhibits tubulin self-assembly into microtubules. The inhibition data were analyzed through a model described by Perez-Ramirez [Perez-Ramirez, B., Andreu, J. M., Gorbunoff, M. J., and Timasheff, S. N. (1996) Biochemistry 35, 3277-3285]. We thereby determined the values of the apparent binding constant of the tubulin-C52 complex to the end of a growing microtubule (K(i)) and the apparent binding constant of C52 to tubulin (K(b)). The binding of C52 depended on tubulin concentration, and binding induced changes in the sedimentation pattern of tubulin, which indicates that C52 induces the self-association of tubulin and tubulin aggregates other than microtubules. Using analytical ultracentrifugation and electron microscopy, we show that C52 induces tubulin to form ring-shaped oligomers (single rings). We also show that C52 inhibits the formation of double rings from either GTP- or GDP-tubulin. In addition, the advances made by electron crystallography in understanding the structure of the tubulin and the microtubule allowed us to visualize the putative binding site of C52 and to reconstruct C52-induced ring oligomers by molecular modeling.

Glimpses at the recognition of peptide/MHC complexes by T-cell antigen receptors

More than a decade after the first description of the primary structure of a T-cell antigen receptor (TCR), the recent determination of the crystal structure of several unliganded TCR ectodomains and of two TCRs complexed to peptide-MHC ligand provides a structural basis for understanding the initial event that triggers T-cell activation. This review focuses on the topology of the variable (V) domains found in TCRs and immunoglobulins and attempts to delineate the structural features that may render the TCR complementarity-determining regions particularly suited to dock on the peptide/MHC surface. Finally, the available TCR structures provide an opportunity to re-evaluate the molecular basis for intrathymic positive selection as well as the mechanisms that make a given TCR neither infinitely specific, nor so flexible that it engages productively any MHC-binding peptides.

A novel method for the production of antibodies against ACTH: their characterization and use in epitope mapping

Our earlier attempts at immunization with human adrenocorticotropin hormone (ACTH) were unsuccessful and we therefore developed a new strategy including the chemical modification of the hormone by succinic anhydride in order to increase its immunogenicity. This process allowed us to obtain antisera with titers of up to 1/1000 and yielded 39 anti-succinylated ACTH (sACTH)-secreting hybridomas. Subsequently, the epitopes of sACTH were mapped by testing monoclonal antibodies two by two for simultaneous binding to sACTH and for their capacity to recognize its succinylated fragments 1-13, 1-17 and 1-24. The results, obtained with the use of radioactive tracers, were confirmed by and complemented with experiments conducted with biosensor technology. Seven groups of antibodies were defined on the basis of their pattern of reactivity and it was shown that four monoclonal antibodies could bind simultaneously to sACTH. Their dissociation constants (Kd) for sACTH were calculated and ranged from 10(-8) M to 10(-11) M. In order to obtain a fast and sensitive immunoassay for the hormone, we developed a protocol for the chemical modification of ACTH in serum and the most efficient monoclonal antibodies were selected on the basis of the epitope map and of their dissociation constants.

cDNA cloning and sequencing reveal the major horse allergen Equ c1 to be a glycoprotein member of the lipocalin superfamily

The gene encoding the major horse allergen, designated Equus caballus allergen 1 (Equ c1), was cloned from total cDNA of sublingual salivary glands by reverse transcription-polymerase chain reaction using synthetic degenerate oligonucleotides deduced from N-terminal and internal peptide sequences of the glycosylated hair dandruff protein. A recombinant form of the protein, with a polyhistidine tail, was expressed in Escherichia coli and purified by immobilized metal affinity chromatography. The recombinant protein is able to induce a passive cutaneous anaphylaxis reaction in rat, and it behaves similarly to the native Equ c1 in several immunological tests with allergic patients' IgE antibodies, mouse monoclonal antibodies, or rabbit polyclonal IgG antibodies. Amino acid sequence identity of 49-51% with rodent urinary proteins from mice and rats suggests that Equ c1 is a new member of the lipocalin superfamily of hydrophobic ligand-binding proteins that includes several other major allergens. An RNA blot analysis demonstrates the expression of mRNA Equ c1 in liver and in sublingual and submaxillary salivary glands.

Cross-antigenicity of horse serum albumin with dog and cat albumins: study of three short peptides with significant inhibitory activity towards specific human IgE and IgG antibodies

Horse serum albumin is present in the near vicinity of the animal, while dog and cat serum albumins are very common allergens present in house dust. Human patients clinically defined as allergic to horse could react with horse serum albumin by means of IgE or IgG antibodies. Studies regarding the specificities of these antibodies by inhibition enzyme-linked immunosorbent assay (ELISA) and depletion experiments have demonstrated that they are directed against dog serum albumin and cross-react not only with horse serum albumin but with other serum albumins from different origins. To investigate these observations further, we isolated and characterized three tryptic peptides (P1, P2 and P3) from horse serum albumin. The peptide P1 contains loops 1 and 2 of the first domain, P2 is derived from loop 4 of the second domain, and P3 contains the disulphide loop 9 of the third domain. These were able to inhibit the binding of the patients' IgE and IgG antibodies to horse albumin as well as to dog and cat serum albumins. This indicates that these peptides are involved in the observed cross-reactions. They also shared common epitopes, as revealed by human IgE antibodies. After reduction and alkylation, they totally lost their inhibitory capacity, suggesting that the intra-chain disulphide bridges, essential for the preservation of the loop structure, probably maintain their allergenic/antigenic reactivity.

Thymus and immunity--I. Early thymus research

This paper is a review of early results in thymus research that found their full significance after several decades, when the strategic role of the organ in immunology was recognized.