Effects of gene replacement therapy with resamirigene bilparvovec (AT132) on skeletal muscle pathology in X-linked myotubular myopathy: results from a substudy of the ASPIRO open-label clinical trial

BACKGROUND

X-linked myotubular myopathy (XLMTM) is a rare, life-threatening congenital muscle disease caused by mutations in the MTM1 gene that result in profound muscle weakness, significant respiratory insufficiency, and high infant mortality. There is no approved disease-modifying therapy for XLMTM. Resamirigene bilparvovec (AT132; rAAV8-Des-hMTM1) is an investigational adeno-associated virus (AAV8)-mediated gene replacement therapy designed to deliver MTM1 to skeletal muscle cells and achieve long-term correction of XLMTM-related muscle pathology. The clinical trial ASPIRO (NCT03199469) investigating resamirigene bilparvovec in XLMTM is currently paused while the risk:benefit balance associated with this gene therapy is further investigated.

METHODS

Muscle biopsies were taken before treatment and 24 and 48 weeks after treatment from ten boys with XLMTM in a clinical trial of resamirigene bilparvovec (ASPIRO; NCT03199469). Comprehensive histopathological analysis was performed.

FINDINGS

Baseline biopsies uniformly showed findings characteristic of XLMTM, including small myofibres, increased internal or central nucleation, and central aggregates of organelles. Biopsies taken at 24 weeks post-treatment showed marked improvement of organelle localisation, without apparent increases in myofibre size in most participants. Biopsies taken at 48 weeks, however, did show statistically significant increases in myofibre size in all nine biopsies evaluated at this timepoint. Histopathological endpoints that did not demonstrate statistically significant changes with treatment included the degree of internal/central nucleation, numbers of triad structures, fibre type distributions, and numbers of satellite cells. Limited (predominantly mild) treatment-associated inflammatory changes were seen in biopsy specimens from five participants.

INTERPRETATION

Muscle biopsies from individuals with XLMTM treated with resamirigene bilparvovec display statistically significant improvement in organelle localisation and myofibre size during a period of substantial improvements in muscle strength and respiratory function. This study identifies valuable histological endpoints for tracking treatment-related gains with resamirigene bilparvovec, as well as endpoints that did not show strong correlation with clinical improvement in this human study.

FUNDING

Astellas Gene Therapies (formerly Audentes Therapeutics, Inc.).

A Rare Case of Acute Interstitial Pneumonia Diagnosed at Autopsy

Introduction/Objective

Acute interstitial pneumonia (AIP) is a rare disease clinically characterized by rapidly progressing respiratory failure in individuals with no history of respiratory illness or other inciting factors. While most often diagnosed in middle-aged adults, it may present in any age group. Initial presentation is described as influenza- like, and respiratory failure requiring ventilatory support often progresses within weeks to months. Prognosis is poor, with an estimated mortality rate approaching 80% without treatment.

Methods

We present the case of a 44-year-old male nonsmoker with no significant medical history, who presented in 2018 with 1.5 months of dyspnea and headache initially diagnosed as atypical pneumonia. Chest imaging revealed bilateral opacities; however, microbial workup revealed no evidence of infectious etiology. Autoimmune serology studies were likewise unrevealing. Despite aggressive supportive and medical management, he deteriorated to respiratory failure and succumbed.

Results

At autopsy, the lungs were symmetrically congested and edematous (combined weight 2,340 g) but free of evident consolidation or discrete lesions. Microscopic examination revealed diffuse alveolar damage with extensive hyaline membrane formation, interstitial edema, and fibroblastic proliferation. The vasculature was severely congested, and the alveoli contained hemorrhage and scattered macrophages. No fungal or mycobacterial elements were identified by staining. Based on the histologic features and clinical context, the diagnosis of AIP was made.

Conclusion

AIP is a rare, aggressive, and diagnostically challenging disease that includes a broad range of both clinical and histologic differentials. Timely recognition and intervention with aggressive respiratory support and high- dose glucocorticoids are the mainstays of clinical management. The diagnostic role of histology is significant, but hinges on early clinical consideration of AIP as disease progression may later preclude the biopsy procedure. We share this case to raise awareness of this rapidly progressive and diagnostically troubling interstitial lung disease while emphasizing the importance of clinicopathologic correlation.

The respiratory syncytial virus nucleoprotein-RNA complex forms a left-handed helical nucleocapsid

Respiratory syncytial virus (RSV) is an important human pathogen. Its nucleocapsid (NC), which comprises the negative sense RNA viral genome coated by the viral nucleoprotein N, is a critical assembly that serves as template for both mRNA synthesis and genome replication. We have previously described the X-ray structure of an NC-like structure: a decameric ring formed of N-RNA that mimics one turn of the helical NC. In the absence of experimental data we had hypothesized that the NC helix would be right-handed, as the N–N contacts in the ring appeared to more easily adapt to that conformation. We now unambiguously show that the RSV NC is a left-handed helix. We further show that the contacts in the ring can be distorted to maintain key N–N-protein interactions in a left-handed helix, and discuss the implications of the resulting atomic model of the helical NC for viral replication and transcription.

A randomized, placebo-controlled, dose-ranging study of single-dose omalizumab in patients with H1-antihistamine-refractory chronic idiopathic urticaria

BACKGROUND

Proof-of-concept studies with omalizumab in patients with chronic idiopathic urticaria (CIU) have shown significant decreases in mean urticaria activity scores (UASs).

OBJECTIVE

We sought to evaluate the efficacy and safety of omalizumab in patients with CIU who remain symptomatic despite concomitant H(1)-antihistamine therapy.

METHODS

This phase II, prospective, double-blind, placebo-controlled, dose-ranging study investigated omalizumab in patients aged 12 to 75 years in the United States and 18 to 75 years in Germany with a UAS over 7 days (UAS7) of 12 or greater despite antihistamine therapy. Patients were randomized 1:1:1:1 to receive a single subcutaneous dose of 75, 300, or 600 mg of omalizumab or placebo added to a stable dose of H(1)-antihistamine. The primary efficacy outcome was change from baseline to week 4 in UAS7. Patients were followed for an additional 12 weeks to monitor safety.

RESULTS

Ninety patients from the United States or Germany were enrolled. Both the 300-mg omalizumab group (-19.9 vs -6.9, P < .001) and the 600-mg omalizumab group (-14.6 vs -6.9, P = .047) showed greater improvement versus the placebo group in UAS7. No meaningful difference was observed for the 75-mg omalizumab group. Similar results were seen for key secondary end points of weekly hive and itch scores. Onset of effect occurred after 1 to 2 weeks. Omalizumab was well tolerated, and the incidence of adverse events was similar across treatment groups.

CONCLUSION

This study demonstrated that a fixed dose of 300 or 600 mg of omalizumab provides rapid and effective treatment of CIU in patients who are symptomatic despite treatment with H(1)-antihistamines.

Vaginal delivery and serum markers of ischemia/reperfusion injury

OBJECTIVE

Vaginal deliveries have been associated with pelvic organ prolapse and incontinence. The objective was to show whether markers of ischemia/reperfusion injury are dependent upon the mode of delivery and length of labor.

METHOD

Complete venipuncture sets were obtained on 62 subjects. All samples collected were analyzed for serum creatine phosphokinase (CPK) and lactate dehydrogenase (LDH). Lipid peroxidation was analyzed, using thiobarbituric acid reactive substances (TBARS), on a subset of 37 patients.

RESULTS

There was a significant increase in CPK from admission to 1 h postpartum and postpartum day 1 in vaginal delivery versus cesarean delivery. Longer second stages were associated with significant increases in CPK. There were no significant changes in either LDH or TBARS from admission to any other time point regardless of mode of delivery.

CONCLUSION

Vaginal delivery and longer second stages were associated with a much greater increase in one of these injury markers.

Cytokine and adhesion molecule expression in SCID mice reconstituted with CD4+ T cells

The objectives of this study were to quantify colonic cytokine and endothelial cell adhesion molecule (ECAM) expression in the colons of severe combined immunodeficient (SCID) mice reconstituted with different subsets of CD4+ T lymphocytes. We found that animals injected with CD45RBhigh but not CD45RBlow T cells or phosphate-buffered saline (PBS) developed clinical evidence of colitis at 6-8 weeks following reconstitution, as assessed by loss of body weight, development of loose stools and/or diarrhea, and histopathology. Concurrent with the onset of distal bowel inflammation was enhanced expression of a variety of Th1 and macrophage-derived cytokines including interferon gamma, tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, IL-12, and IL-18 lymphotoxin-beta. In addition, message levels and vascular surface expression of ICAM-1, VCAM-1, and MAdCAM-1 were all significantly enhanced in the colitic SCID mice reconstituted with CD45RBhigh T cells compared with SCID mice reconstituted with PBS or CD45RBlow T cells that did not develop disease. Significant increases in some of these ECAMs were also noted in the cecum and stomach and to a lesser degree in the small bowel. Our data confirm that reconstitution of SCID mice with CD45RBhigh but not CD45RBlow T cells induces chronic colitis, and that the colonic inflammation is associated with enhanced expression of proinflammatory cytokines and different ECAMs in the colon. Furthermore, our studies demonstrate that reconstitution of SCID mice with CD45RBhigh T cells enhances ECAM expression in tissues distant from the site of active inflammation.

E-Selectin expression in a murine model of chronic colitis

The objective of this study was to quantify E-selectin surface expression in the colon as well as other tissues in a CD4(+) T-cell model of chronic colitis in mice using the newly developed dual radiolabel monoclonal antibody technique. Male SCID mice were reconstituted with either 5 x 10(5) CD4(+) CD45RB(low) or CD45RB(high) T-cells isolated from normal CB-17 donor mouse spleens and subsequently monitored for clinical signs of colitis. We found that animals injected with CD45RB(high) but not CD45RB(low) T-cells nor PBS developed colitis at 6-8 weeks following reconstitution as assessed by loss of body weight, development of loose stools and/or diarrhea, and histopathology. Concurrent with the onset of distal bowel inflammation was enhanced expression of E-selectin compared to SCID mice injected with PBS or reconstituted with CD45RB(low) T-cells, both of which did not develop colitis. We also observed significant increases in E-selectin expression in cecum, small intestine, mesentery, and liver of colitic mice. Our data confirm that reconstitution of SCID mice with CD45RB(high) but not CD45RB(low) T-cells induces chronic colitis and demonstrate that this chronic colitis is associated with enhanced expression of an endothelial cell-specific adhesion molecule. Furthermore, our studies demonstrate that reconstitution of SCID mice with CD45RB(high) T-cells enhances E-selectin expression in a variety of tissues distant from the site of active inflammation.

Homozygous inactivation of the NF1 gene in bone marrow cells from children with neurofibromatosis type 1 and malignant myeloid disorders

BACKGROUND

The risk of malignant myeloid disorders in young children with neurofibromatosis type 1 is 200 to 500 times the normal risk. The gene for neurofibromatosis type 1 (NF1) encodes neurofibromin, a protein that negatively regulates signals transduced by Ras proteins. Genetic and biochemical data support the hypothesis that NF1 functions as a tumor-suppressor gene in immature myeloid cells, but inactivation of both NF1 alleles has not been demonstrated in leukemic cells from patients with neurofibromatosis type 1.

METHODS

Using an in vitro transcription and translation system, we screened bone marrow samples from 18 children with neurofibromatosis type 1 and myeloid disorders for NF1 mutations that cause a truncated protein. Mutations were confirmed by direct sequencing of genomic DNA from the patients, and from their affected parents, in cases of familial neurofibromatosis type 1.

RESULTS

Specimens from 9 of the 18 children contained abnormal peptide fragments, and truncating mutations of the NF1 gene were found in specimens from 8 of these children. The normal NF1 allele was absent in bone marrow samples from five of the eight children. We detected the same mutation in DNA from the affected parent of each child with familial neurofibromatosis type 1.

CONCLUSIONS

Both alleles of the NF1 gene are inactivated in leukemic cells in some patients with neurofibromatosis type 1. NF1 appears to function as a tumor-suppressor gene in immature myeloid cells.

Biochemical characterization of a novel KRAS insertion mutation from a human leukemia

A novel alteration in exon 1 of KRAS was detected by single strand conformational polymorphism analysis of DNA amplified from the bone marrow of a 4-year-old child with myeloid leukemia. Sequencing of this mutant allele revealed an insertion of three nucleotides between codons 10 and 11 resulting in an in-frame insertion of glycine. Expression of the mutant protein in NIH 3T3 cells caused cellular transformation, and expression in COS cells activated the Ras-mitogen-activated protein kinase signaling pathway. Surprisingly, Ras.GTP levels measured in COS cells established that this novel mutant accumulates to 90% in the GTP state, considerably higher than a residue 12 mutant. Biochemical analysis confirmed that the higher Ras.GTP levels correspond to a dramatic decrease in intrinsic GTP hydrolysis as well as resistance to GTPase-activating proteins. This mutation is the first dominant Ras mutation found in human cancer that does not involve residues 12, 13, or 61, and its biochemical properties should help elucidate the mechanism of oncogenic activation.

Surfactant protein A protects growing cells and reduces TNF-alpha activity from LPS-stimulated macrophages

In addition to its effect on surfactant lipids, surfactant protein (SP)-A promotes host defense. To define further the role of SP-A in regulating immune cell function, we evaluated the effect of SP-A on lipopolysaccharide (LPS)-activated alveolar macrophages in two settings. First, cocultured LPS-activated macrophages significantly inhibited lung fibroblast growth, but SP-A (added daily) attenuated this effect. Both LPS and SP-A acted via macrophages rather than directly on the fibroblasts, at least partially by affecting tumor necrosis factor (TNF)-alpha activity. TNF-alpha reproduced the growth suppression, anti-TNF-alpha antibodies attenuated the effect LPS-activated macrophages, and SP-A reduced TNF-alpha activity in conditioned medium. Second, SP-A reduced TNF-alpha activity in medium from isolated LPS-stimulated macrophages. The effects of SP-A were noted with or without serum, were dose-dependent and reversible, and were seen with two different serotypes of smooth LPS. Equimolar concentrations of immunoglobulin G and C1q had no effect. Thus SP-A both enhances host defense and modulates immune functions of alveolar macrophages.

Transcutaneous oxygen (tcPO2) measurements as an aid to fluid therapy in necrotizing enterocolitis

Impaired peripheral perfusion is a major problem in necrotizing enterocolitis with delayed recognition and definite documentation being primary factors. While blood pressure and other clinical measurements may improperly estimate the severity of the problem, changes in transcutaneous oxygen measurements and their relationship to arterial oxygen (the tcPO2/PaO2 ratio) potentially afford a sensitive measurement of peripheral perfusion. Experience in our unit confirms a close relationship between tcPO2/ and PaO2 being 0.97 +/- 0.04 (SE). Ten infants with birth weights of 640 to 1380 g, who subsequently developed necrotizing enterocolitis, had strikingly lower ratios initially (0.00, 0.00, 0.00, 0.17, 0.21, 0.43, 0.44, 0.48, and 0.56). Use of the tcPO2/PaO2 ratio to monitor fluid therapy was related to outcome, suggesting that this ratio is important in managing necrotizing enterocolitis.

Proteus mirabilis brain abscess in a neonate

Occasionally a brain abscess has been observed in a neonate. This report presents a unique case of a septic infant who developed a proteus mirabilis brain abscess shortly after birth, which persisted undetected until 21/2 months of age.

Hormonal regulation of cultured rabbit endometrial cells

A technique for culturing primary explants of rabbit endometrial cells in chemically defined medium has been developed. Diethylstilbestrol and natural estrogens were found to increase the rate of DNA initiation while progesterone had the opposite effect. Ultrastructural studies revealed that with estrogens, the cultures had the appearance of rapidly dividing cells having large euchromatic nuclei and prominent nucleoli, with aboundant free ribosomes in the cytoplasm. On the other hand, progesterone induced the formation of large multinucleated cells and also converted the cells to a more secretory type. When the cultures appear secretory, a protein called blastokinin (uteroglobin) is believed secreted. We have found that cultured cells synthesize blastokinin and progesterone is necessary for its continuous synthesis. The cultures were found to have receptors for the ovarian hormones and these receptors exhibited saturation kinetics. The dissociation constants for the receptors were also determined. A hypothetical model for the hormonal regulation of cell proliferation and differentiation is proposed.

Apparent Incipient speciation in the midge Chironomus oppositus Walker (Diptera: Chironomidae)

Field collections of Chironomus oppositus from certain localities in Tasmania, in particular from Bellerive, consistently show distributions of inversions different to those found in the normal form, which is referred to as form A and occurs in mainland Australia and most other Tasmanian populations. These collections showed: (1) a marked deficiency of almost all inversion heterozygotes; (2) significant groups of associated sequences which can be used to define two additional forms, referred to as form B and form C. Since forms B and C have so far only been found together, it would appear that this represents an unusual situation in insect speciation. This karyotypic divergence must be maintained by some restriction on interbreeding, both between these two groups and also between them and form A, with which they appear to coexist in some localities.

Regulation of the cell cycle by diethylstilbestrol and progesterone in cultured endometrial cells

Cultures of primary explanted rabbit endometrium epithelial cells were found to be a mixture of dividing or cycling (20%) and non-dividing or GO (80%) cells. The addition of diethylstilbestrol had the effect of switching most of the GO cells into the cell cycle and to shorten the length of the cell cycle through a shortening of G1 and S. Progesterone had the opposite effects.