Composite transport wing technology development: Design development tests and advanced structural concepts

Numerous design concepts, materials, and manufacturing methods were investigated for the covers and spars of a transport box wing. Cover panels and spar segments were fabricated and tested to verify the structural integrity of design concepts and fabrication techniques. Compression tests on stiffened panels demonstrated the ability of graphite/epoxy wing upper cover designs to achieve a 35 percent weight savings compared to the aluminum baseline. The impact damage tolerance of the designs and materials used for these panels limits the allowable compression strain and therefore the maximum achievable weight savings. Bending and shear tests on various spar designs verified an average weight savings of 37 percent compared to the aluminum baseline. Impact damage to spar webs did not significantly degrade structural performance. Predictions of spar web shear instability correlated well with measured performance. The structural integrity of spars manufactured by filament winding equalled or exceeded those fabricated by hand lay-up. The information obtained will be applied to the design, fabrication, and test of a full-scale section of a wing box. When completed, the tests on the technology integration box beam will demonstrate the structural integrity of an advanced composite wing design which is 25 percent lighter than the metal baseline

Type Six Secretion System of <i>Bordetella bronchiseptica</i> and Adaptive Immune Components Limit Intracellular Survival During Infection

<div><p>The Type Six Secretion System (T6SS) is required for <i>Bordetella bronchiseptica</i> cytotoxicity, cytokine modulation, infection, and persistence. However, one-third of recently sequenced <i>Bordetella bronchiseptica</i> strains of the predominantly human-associated Complex IV have lost their T6SS through gene deletion or degradation. Since most human <i>B</i>. <i>bronchiseptica</i> infections occur in immunocompromised patients, we determine here whether loss of Type Six Secretion is beneficial to <i>B</i>. <i>bronchiseptica</i> during infection of immunocompromised mice. Infection of mice lacking adaptive immunity (Rag1^-/- mice) with a T6SS-deficient mutant results in a hypervirulent phenotype that is characterized by high numbers of intracellular bacteria in systemic organs. In contrast, wild-type <i>B</i>. <i>bronchiseptica</i> kill their eukaryotic cellular hosts via a T6SS-dependent mechanism that prevents survival in systemic organs. High numbers of intracellular bacteria recovered from immunodeficient mice but only low numbers from wild-type mice demonstrates that <i>B</i>. <i>bronchiseptica</i> survival in an intracellular niche is limited by B and T cell responses. Understanding the nature of intracellular survival during infection, and its effects on the generation and function of the host immune response, are important to contain and control the spread of <i>Bordetella</i>-caused disease.</p></div

Clinical <i>B</i>. <i>bronchiseptica</i> strains that have lost their T6SS locus are aggregated in Complex IV.

<p>Genomes of 58 <i>B</i>. <i>bronchiseptica</i> clinical isolates were compared to prototypical RB50 genome. Presence of T6SS loci, as well as presence of pseudogenes in T6SS loci, was determined for all clinical isolates. Clinical strains containing an intact T6SS (blue), strains lacking a T6SS locus (red), and strains containing a pseudogene in the T6SS locus (pink) were divided based on whether they come from Complex I (A) or Complex IV (B).</p

Loss of <i>clpV</i> is required for systemic recovery.

<p>Groups of Rag1^-/- mice were either infected singly with RB50 (blue circles, n = 3) or RB50Δ<i>clpV</i> (red circles, n = 4) or co-infected with RB50 and RB50Δ<i>clpV</i> (red squares and blue squares, n = 4), and (A) respiratory tract bacterial numbers or (B) systemic organ bacterial numbers were enumerated on day 21 post-inoculation. This experiment was performed twice with similar results and a representative dataset is shown. ND signifies not detected. Grey line indicates the limit of detection.</p

<i>clpV</i> lowers inflammation and pathology <i>in vivo</i>.

<p>(A) Groups of four Rag1^-/- mice were inoculated with 5x10⁵ CFU of RB50 (blue) or RB50Δ<i>clpV</i> (red) and a histopathological analysis was conducted on the lung and liver of infected mice on day 21 p.i. for scoring of inflammation. (B) Representative H&E lung and liver sections from Rag1^-/- mice on day 21 p.i. after inoculation with 5x10⁵ CFU of RB50 (blue) or RB50Δ<i>clpV</i> (red) with average pathology scores in parentheses. (C) Groups of Rag1^-/- mice were inoculated with 5x10⁵ CFU RB50 (blue) and RB50Δ<i>clpV</i> (red) and elicited IL-1β levels were determined from the lung and spleen on day 21 p.i. This experiment was performed twice with similar results and a representative dataset is shown. ND signifies not detected. * denotes p value <0.05.</p

The T6SS modulates virulence and bacterial dissemination.

<p>(A) Groups of Rag1^-/- mice (n = 8) were inoculated with 5x10⁵ CFU of RB50 (blue) or RB50Δ<i>clpV</i> (red) and were monitored for survival. (B) Groups of Rag1^-/- mice (n = 4 per group) were inoculated with 5x10⁵ CFU of RB50 (blue) versus RB50Δ<i>clpV</i> (red) and dissected on day 21 p.i. for bacterial enumeration in respiratory tract and systemic organs. The experiment was performed three times with similar results and a representative data set is shown. (C) Rag^-/- mice were inoculated with 5x10⁵ CFU RB50 (blue) versus RB50Δ<i>clpV</i> (red) and bacteria were enumerated from the spleen, liver, and kidney on days 3, 7, 21, and 35. With the exception of RB50Δ<i>clpV</i> on day 21 (n = 1), three mice were sacrificed per group per timepoint. * denotes p value <0.05. Grey dotted line indicates the limit of detection.</p

Deletion of <i>clpV</i> increases intracellular survival <i>in vitro</i>.

<p>(A) RAW264.7 macrophages were infected with RB50 (blue, n = 4) or RB50Δ<i>clpV</i> (red, n = 4) at an MOI of 100 and bacterial invasion and intracellular survival was determined at 1, 24, and 48 hour after addition of gentamicin. The experiment was conducted five times with similar results and a representative dataset is shown. (B) The cytotoxicity of RAW264.7 macrophages infected with RB50 (blue) or RB50Δ<i>clpV</i> (red) at an MOI of 100 was determined 1 hour and 24 hours after gentamicin application. The average percent cytotoxicity of four wells in three different experiments was measured by (LDH release from a well / LDH release from positive control well) x 100 ±SE is shown. * denotes p value <0.05. Grey line indicates limit of detection.</p