Bronchodilator Response in Post-COVID-19 Patients Undergoing Pulmonary Rehabilitation.

INTRODUCTION: SARS-CoV-2 infections can result in a broad spectrum of symptoms from mild to life-threatening. Long-term consequences on lung function are not well understood yet. METHODS: In our study, we have examined 134 post-COVID patients (aged 54.83 ± 14.4 years) with dyspnea on exertion as a leading symptom 6 weeks to 24 months after a SARS-CoV-2 infection for bronchodilator responsiveness during their stay in our pulmonary rehabilitation clinic. RESULTS: Prior to bronchial dilation, 6 out of 134 patients (4.47%) presented an FEV1/FVC ratio below lower limit of normal (Z-score = -1.645) indicative of an obstructive airway disease. Following inhalation of a ß2-adrenergic agonist we measured a mean FEV1 increase of 181.5 mL in our cohort, which was significantly elevated compared to a historical control group (ΔFEV1 = 118 mL). 28.7% of the patients showed an increase greater than 200 mL and 12% displayed a significant bronchodilation response (>200 mL ΔFEV1 and >12% FEV1 increase). Interestingly, no significant difference in bronchial dilation effect was observed when comparing patients hospitalized and those non-hospitalized during the course of their SARS-CoV-2 infection. CONCLUSION: Our data provide evidence for increased prevalence of obstructive ventilatory defects and increased bronchodilator responsiveness in patients with persisting symptoms after COVID-19. Depending on the extent of this complication, post-COVID patients may benefit from an adapted ß2-inhalation therapy including subsequent reevaluation.

In vivo adenine base editing reverts C282Y and improves iron metabolism in hemochromatosis mice.

Hemochromatosis is one of the most common inherited metabolic diseases among white populations and predominantly originates from a homozygous C282Y mutation in the HFE gene. The G > A transition at position c.845 of the gene causes misfolding of the HFE protein, ultimately resulting in its absence at the cell membrane. Consequently, the lack of interaction with the transferrin receptors 1 and 2 leads to systemic iron overload. We screened potential gRNAs in a highly precise cell culture assay and applied an AAV8 split-vector expressing the adenine base editor ABE7.10 and our candidate gRNA in 129-Hfetm.1.1Nca mice. Here we show that a single injection of our therapeutic vector leads to a gene correction rate of >10% and improved iron metabolism in the liver. Our study presents a proof-of-concept for a targeted gene correction therapy for one of the most frequent hereditary diseases affecting humans.

Correction: Pathological mechanism and antisense oligonucleotide-mediated rescue of a non-coding variant suppressing factor 9 RNA biogenesis leading to hemophilia B.

[This corrects the article DOI: 10.1371/journal.pgen.1008690.].

Identification of the Cleavage Domain within Glycoprotein G of Herpes Simplex Virus Type 2.

Glycoprotein G (gG) from herpes simplex virus type 1 and 2 (HSV-1 and HSV-2, respectively) functions as a viral chemokine binding protein (vCKBP). Soluble recombinant forms of gG of HSV-1 and HSV-2 (SgG1 and SgG2, respectively) enhance chemokine-mediated leukocyte migration, in contrast to most known vCKBPs, including those from animal alpha-herpesviruses. Furthermore, both proteins bind to nerve growth factor (NGF), but only SgG2 enhances NGF-dependent neurite outgrowth. The basis and implications of this functional difference between the two proteins are still unknown. While gG1 and gG2 are positional homologues in the genome, they share very limited sequence homology. In fact, US4, the open reading frame encoding gG is the most divergent genetic locus between these viruses. Full-length gG1 and gG2 are type I transmembrane proteins located on the plasma membrane of infected cells and at the viral envelope. However, gG2 is larger than gG1 and is cleaved during protein maturation, secreting the N-terminal domain to the supernatant of infected cells, whereas gG1 is not. The enzyme involved in gG2 cleavage and the functional relevance of gG2 cleavage and secretion are unknown. We aim to identify the gG2 sequence required for cleavage to determine its functional role in future experiments. Our results prove the existence of at least two cleavage motifs in gG2 within the amino acid region 314-343. Transfer of this sequence to a fusion protein results in cleavage. Finally, we show that propeptide convertases like furin are responsible for gG2 cleavage.

Pathological mechanism and antisense oligonucleotide-mediated rescue of a non-coding variant suppressing factor 9 RNA biogenesis leading to hemophilia B.

Loss-of-function mutations in the human coagulation factor 9 (F9) gene lead to hemophilia B. Here, we dissected the consequences and the pathomechanism of a non-coding mutation (c.2545A>G) in the F9 3' untranslated region. Using wild type and mutant factor IX (FIX) minigenes we revealed that the mutation leads to reduced F9 mRNA and FIX protein levels and to lower coagulation activity of cell culture supernatants. The phenotype could not be compensated by increased transcription. The pathomechanism comprises the de novo creation of a binding site for the spliceosomal component U1snRNP, which is able to suppress the nearby F9 poly(A) site. This second, splicing-independent function of U1snRNP was discovered previously and blockade of U1snRNP restored mutant F9 mRNA expression. In addition, we explored the vice versa approach and masked the mutation by antisense oligonucleotides resulting in significantly increased F9 mRNA expression and coagulation activity. This treatment may transform the moderate/severe hemophilia B into a mild or subclinical form in the patients. This antisense based strategy is applicable to other mutations in untranslated regions creating deleterious binding sites for cellular proteins.

Ex Vivo/In vivo Gene Editing in Hepatocytes Using "All-in-One" CRISPR-Adeno-Associated Virus Vectors with a Self-Linearizing Repair Template.

Adeno-associated virus (AAV)-based vectors are considered efficient and safe gene delivery systems in gene therapy. We combined two guide RNA genes, Cas9, and a self-linearizing repair template in one vector (AIO-SL) to correct fumarylacetoacetate hydrolase (FAH) deficiency in mice. The vector genome of 5.73 kb was packaged into VP2-depleted AAV particles (AAV2/8ΔVP2), which, however, did not improve cargo capacity. Reprogrammed hepatocytes were treated with AIO-SL.AAV2ΔVP2 and subsequently transplanted, resulting in large clusters of FAH-positive hepatocytes. Direct injection of AIO-SL.AAV8ΔVP2 likewise led to FAH expression and long-term survival. The AIO-SL vector achieved an ∼6-fold higher degree of template integration than vectors without template self-linearization. Subsequent analysis revealed that AAV8 particles, in contrast to AAV2, incorporate oversized genomes distinctly greater than 5.2 kb. Finally, our AAV8-based vector represents a promising tool for gene editing strategies to correct monogenic liver diseases requiring (large) fragment removal and/or simultaneous sequence replacement.

Homozygous frame shift variant in ATP7B exon 1 leads to bypass of nonsense-mediated mRNA decay and to a protein capable of copper export.

Wilson disease (WD) is an autosomal recessive disease of copper excess due to pathogenic variants in the ATP7B gene coding for a copper-transporting ATPase. We present a 5-year-old girl with the homozygous frame shift variant NM_000053.3: c.19_20del in exon 1 of ATP7B (consecutive exon numbering with c.1 as first nucleotide of exon 1), detected by whole-exome sequencing as a secondary finding. The variant leads to a premature termination codon in exon 2. The girl exhibited no WD symptoms and no abnormalities in liver biopsy. ATP7B liver mRNA expression was comparable to healthy controls suggesting that nonsense-mediated mRNA decay (NMD) could be bypassed by the mechanism of translation reinitiation. To verify this hypothesis, a CMV-driven ATP7B minigene (pcDNA3) was equipped with the authentic ATP7B 5' untranslated region  and a truncated intron 2. We introduced c.19_20del by site-directed mutagenesis and overexpressed the constructs in HEK293T cells. We analyzed ATP7B expression by qRT-PCR, northern and western blot, and examined protein function by copper export capacity assays. Northern blot, qRT-PCR, and western blot revealed that c.19_20del ATP7B mRNA and protein is expressed in size and amount comparable to wild-type. Copper export capacity was also comparable to wild-type. Our results indicate that c.19_20del in ATP7B is able to bypass NMD by translation reinitiation, demonstrating that the classification of truncating variants as pathogenic without additional investigations should be done carefully.

Homologous recombination mediates stable Fah gene integration and phenotypic correction in tyrosinaemia mouse-model.

AIM: To stably correct tyrosinaemia in proliferating livers of fumarylacetoacetate-hydrolase knockout (Fah-/-) mice by homologous-recombination-mediated targeted addition of the Fah gene. METHODS: C57BL/6 Fah∆exon5 mice served as an animal model for human tyrosinaemia type 1 in our study. The vector was created by amplifying human Fah cDNA including the TTR promoter from a lentivirus plasmid as described. The Fah expression cassette was flanked by homologous arms (620 bp and 749 bp long) of the Rosa26 gene locus. Mice were injected with 2.1 × 108 VP of this vector (rAAV8-ROSA26.HAL-TTR.Fah-ROSA26.HAR) via the tail vein. Mice in the control group were injected with 2.1 × 108 VP of a similar vector but missing the homologous arms (rAAV8-TTR.Fah). Primary hepatocytes from Fah-/- recipient mice, treated with our vectors, were isolated and 1 × 106 hepatocytes were transplanted into secondary Fah-/- recipient mice by injection into the spleen. Upon either vector application or hepatocyte transplantation NTBC treatment was stopped in recipient mice. RESULTS: Here, we report successful HR-mediated genome editing by integration of a Fah gene expression cassette into the "safe harbour locus" Rosa26 by recombinant AAV8. Both groups of mice showed long-term survival, weight gain and FAH positive clusters as determined by immunohistochemistry analysis of liver sections in the absence of NTBC treatment. In the group of C57BL/6 Fah∆exon5 mice, which have been transplanted with hepatocytes from a mouse injected with rAAV8-ROSA26.HAL-TTR.Fah-ROSA26.HAR 156 d before, 6 out of 6 mice showed long-term survival, weight gain and FAH positive clusters without need for NTBC treatment. In contrast only 1 out 5 mice, who received hepatocytes from rAAV8-TTR.Fah treated mice, survived and showed few and smaller FAH positive clusters. These results demonstrate that homologous recombination-mediated Fah gene transfer corrects the phenotype in a mouse model of human tyrosinaemia type 1 (Fah-/- mice) and is long lasting in a proliferating state of the liver as shown by withdrawal of NTBC treatment and serial transplantation of isolated hepatocytes from primary Fah-/- recipient mice into secondary Fah-/- recipient mice. This long term therapeutic efficacy is clearly superior to our control mice treated with episomal rAAV8 gene therapy approach. CONCLUSION: HR-mediated rAAV8 gene therapy provides targeted transgene integration and phenotypic correction in Fah-/- mice with superior long-term efficacy compared to episomal rAAV8 therapy in proliferating livers.

The combined repetitive oligopeptides of clostridium difficile toxin A counteract premature cleavage of the glucosyl-transferase domain by stabilizing protein conformation.

Toxin A (TcdA) and B (TcdB) from Clostridium difficile enter host cells by receptor-mediated endocytosis. A prerequisite for proper toxin action is the intracellular release of the glucosyltransferase domain by an inherent cysteine protease, which is allosterically activated by inositol hexaphosphate (IP6). We found that in in vitro assays, the C-terminally-truncated TcdA1-1065 was more efficient at IP6-induced cleavage compared with full-length TcdA. We hypothesized that the C-terminally-located combined repetitive oligopeptides (CROPs) interact with the N-terminal part of the toxin, thereby preventing autoproteolysis. Glutathione-S-transferase (GST) pull-down assays and microscale thermophoresis confirmed binding between the CROPs and the glucosyltransferase (TcdA1-542) or intermediate (TcdA1102-1847) domain of TcdA, respectively. This interaction between the N- and C-terminus was not found for TcdB. Functional assays revealed that TcdB was more susceptible to inactivation by extracellular IP6-induced cleavage. In vitro autoprocessing and inactivation of TcdA, however, significantly increased, either by acidification of the surrounding milieu or following exchange of its CROP domain by the homologous CROP domain of TcdB. Thus, TcdA CROPs contribute to the stabilization and protection of toxin conformation in addition to function as the main receptor binding domain.