Decompression Sickness Treatment Using a Pressure Suit After Loss of Spacecraft Atmosphere.

BACKGROUND: Loss of spacecraft atmosphere (LOA) during Earth-Moon transit may require up to 144 h of pressure suit operations. This work investigates the feasibility of DCS treatment in this paradigm and discusses the operational and engineering implications.METHODS: Three scenarios of LOA-induced DCS were considered: a permanent LOA secondary to a 0.25-in (0.64 cm) hole (unrecoverable cabin leak), a transient LOA, and a permanent LOA with early suit over-pressurization (beyond suit specification). Each was simulated in the context of the current Orion spacecraft operational concept with regards to atmosphere and anticipated cabin depress profile. Probability of DCS symptom resolution (P(SR)) was estimated using the previously derived Hypobaric DCS Treatment Model, with ΔP calculated from a Three Region Well-Stirred Tissue (3RWT) bubble dynamics model. Analysis was conducted and analogies drawn from experiences with the development and testing of the Orion Crew Survival System (OCSS).RESULTS: Maintaining 8 psia at 100% Fio2 following LOA resulted in an eventual halt and regression of bubble growth with a P(SR) of 87% (at 8 h, time to symptom onset (Ts) = 105 min, with ambulation). If cabin atmosphere was not restored and psia dropped to 4.3, bubble growth returned, but again eventually slowed and regressed over time (P(SR) = 75% at 21 h). If the leak is repaired within the 8-h period, 8 psid (psia = 22.7) resulted in P(SR) of greater than 95%. Similarly, if the suit was over-pressurized (12 psid/psia) within 3 h after LOA, P(SR) exceeded 95%.DISCUSSION: A launch/entry pressure suit represents a contingency option for DCS management in the event of LOA.Greene MR, Jacobs SE. Decompression sickness treatment using a pressure suit after loss of spacecraft atmosphere. Aerosp Med Hum Perform. 2020; 91(7):571-577.

Hypothetical Case of Pancreatitis During a Long Duration Lunar Mission.

INTRODUCTION: This peer-reviewed hypothetical case was written to help the readership understand the challenges of dealing with quite common yet very debilitating diseases during space missions. This scenario is based on a real case of an astronaut who had previously flown in space and developed acute pancreatitis after being dehydrated from wilderness survival training. Many astronauts experience life threatening illness and injury before and after flight and, as space missions become longer and more remote, it is only a matter of time before these events occur during a mission. Future exploration space mission planners need to anticipate that these common catastrophic medical events will occur.CASE REPORT: You are a flight surgeon working on console at Mission Control during a long duration lunar mission. You have completed extensive space, military, and civilian aerospace medical training to address almost any anticipated medical event and can summon advice from medical experts located around the world. One crewmember is a 37-yr-old man who just completed an 8-h moonwalk and now describes a constant 7/10 dull epigastric pain with radiation around the left flank to his back. His pain is getting progressively worse and he is presently sitting with his trunk flexed and knees drawn up in extreme distress. Working with the flight director, you must decide in the next 12 h whether to recommend the multibillion-dollar mission be aborted and have the crew return to Earth immediately to save your patient.Hamilton DR, McBeth PB, Greene MR, Kirkpatrick AW, Ball CG. Hypothetical case of pancreatitis during a long duration lunar mission. Aerosp Med Hum Perform. 2019; 90(6):570-578.

Transduction of human CD34+ repopulating cells with a self-inactivating lentiviral vector for SCID-X1 produced at clinical scale by a stable cell line.

Self-inactivating (SIN)-lentiviral vectors have safety and efficacy features that are well suited for transduction of hematopoietic stem cells (HSCs), but generation of vector at clinical scale has been challenging. Approximately 280 liters of an X-Linked Severe Combined Immunodeficiency Disorder (SCID-X1) SIN-lentiviral vector in two productions from a stable cell line were concentrated to final titers of 4.5 and 7.2×10(8) tu/ml. These two clinical preparations and three additional development-scale preparations were evaluated in human CD34(+) hematopoietic cells in vitro using colony forming cell (CFU-C) assay and in vivo using the NOD/Lt-scid/IL2Rγ(null) (NSG) mouse xenotransplant model. A 40-hour transduction protocol using a single vector exposure conferred a mean NSG repopulating cell transduction of 0.23 vector genomes/human genome with a mean myeloid vector copy number of 3.2 vector genomes/human genome. No adverse effects on engraftment were observed from vector treatment. Direct comparison between our SIN-lentiviral vector using a 40-hour protocol and an MFGγ(c) γ-retroviral vector using a five-day protocol demonstrated equivalent NSG repopulating cell transduction efficiency. Clonality survey by linear amplification-mediated polymerase chain reaction (LAM-PCR) with Illumina sequencing revealed common clones in sorted myeloid and lymphoid populations from engrafted mice demonstrating multipotent cell transduction. These vector preparations will be used in two clinical trials for SCID-X1.

A self-inactivating lentiviral vector for SCID-X1 gene therapy that does not activate LMO2 expression in human T cells.

To develop safer and more effective vectors for gene therapy of X-linked severe combined immunodeficiency (SCID-X1), we have evaluated new self-inactivating lentiviral vectors based on the HIV virus. The CL20i4-hgamma(c)-Revgen vector contains the entire human common gamma chain (gamma(c)) genomic sequence driven by the gamma(c) promoter. The CL20i4-EF1alpha-hgamma(c)OPT vector uses a promoter fragment from the eukaryotic elongation factor alpha (EF1alpha) gene to express a codon-optimized human gamma(c) cDNA. Both vectors contain a 400-bp insulator fragment from the chicken beta-globin locus within the self-inactivating long-terminal repeat. Transduction of bone marrow cells using either of these vectors restored T, B, and natural killer lymphocyte development and function in a mouse SCID-X1 transplantation model. Transduction of human CD34(+) bone marrow cells from SCID-X1 patients with either vector restored T-cell development in an in vitro assay. In safety studies using a Jurkat LMO2 activation assay, only the CL20i4-EF1alpha-hgamma(c)OPT vector lacked the ability to transactivate LMO2 protein expression, whereas the CL20i4-hgamma(c)-Revgen vector significantly activated LMO2 protein expression. In addition, the CL20i4-EF1alpha-hgamma(c)OPT vector has not caused any tumors in transplanted mice. We conclude that the CL20i4-EF1alpha-hgamma(c)OPT vector may be suitable for testing in a clinical trial based on these preclinical demonstrations of efficacy and safety.

Neither DNA hypomethylation nor changes in the kinetics of erythroid differentiation explain 5-azacytidine's ability to induce human fetal hemoglobin.

5-azacytidine (5-Aza) is a potent inducer of fetal hemoglobin (HbF) in people with beta-thalassemia and sickle cell disease. Two models have been proposed to explain this activity. The first is based on the drug's ability to inhibit global DNA methylation, including the fetal globin genes, resulting in their activation. The second is based on 5-Aza's cytotoxicity and observations that HbF production is enhanced during marrow recovery. We tested these models using human primary cells in an in vitro erythroid differentiation system. We found that doses of 5-Aza that produce near maximal induction of gamma-globin mRNA and HbF do not alter cell growth, differentiation kinetics, or cell cycle, but do cause a localized demethylation of the gamma promoter. However, when we reduced gamma promoter methylation to levels equivalent to those seen with 5-Aza or to the lower levels seen in primary fetal erythroid cells using DNMT1 siRNA and shRNA, we observed no induction of gamma-globin mRNA or HbF. These results suggest that 5-Aza induction of HbF is not the result of global DNA demethylation or of changes in differentiation kinetics, but involves an alternative, previously unrecognized mechanism. Other results suggest that posttranscriptional regulation plays an important role in the 5-Aza response.

Defensive applications of gene transfer technology in the face of bioterrorism: DNA-based vaccines and immune targeting.

Gene transfer involves the introduction of an engineered gene into a person's cells with the expectation that the protein expressed from the gene will produce a therapeutic benefit. Strategies based on this principle have led to the approval of > 600 clinical trials and enrollment of approximately 3500 subjects worldwide in attempts to treat diseases ranging from cancer to AIDS to cystic fibrosis. While gene therapy has met with limited success and still has many hurdles to overcome before it sees wide application, it may be useful as a defensive strategy against bioterrorism agents including infectious microbes and toxins. Although many defensive strategies are possible, immunological strategies are currently the most developed and are being actively applied to the development of strategies against several of the most virulent potential bio-weapons. While most of these strategies are not yet ready for human application, DNA-based vaccines appear to be among the most promising in the fight against bioterrorism.