The presence of serum bactericidal antibodies is a proven correlate of protection against systemic infection with the important human pathogen Neisseria meningitidis. We have identified three serogroup C N. meningitidis (MenC) isolates recovered from patients with invasive meningococcal disease that resist killing by bactericidal antibodies induced by the MenC conjugate vaccine. None of the patients had received the vaccine, which has been successfully introduced in countries in North America and Europe. The increased resistance was not caused by changes either in lipopolysaccharide sialylation or acetylation of the α2-9–linked polysialic acid capsule. Instead, the resistance of the isolates resulted from the presence of an insertion sequence, IS1301, in the intergenic region (IGR) between the sia and ctr operons, which are necessary for capsule biosynthesis and export, respectively. The insertion sequence led to an increase in the transcript levels of surrounding genes and the amount of capsule expressed by the strains. The increased amount of capsule was associated with down-regulation of the alternative pathway of complement activation, providing a generic mechanism by which the bacterium protects itself against bactericidal antibodies. The strains with IS1301 in the IGR avoided complement-mediated lysis in the presence of bactericidal antibodies directed at the outer membrane protein, PorA, or raised against whole cells.

Tissue engineering-based approaches have the potential to improve stem cell engraftment by increasing cell delivery to the myocardium. Our objective was to develop and characterize a naturally-derived, autologous, biodegradable hydrogel in order to improve acute stem cell retention in the myocardium. HA-blood hydrogels(HA-Bl) were synthesized by mixing in a 1:1(v/v) ratio, lysed whole blood and hyaluronic acid(HA), whose carboxyl groups were functionalized with N-hydroxysuccinimide(NHS) to yield HA succinimidyl succinate(HA-NHS). We performed physical characterization and measured survival/proliferation of cardiosphere-derived cells(CDCs) encapsulated in the hydrogels. Hydrogels were injected intramyocardially or applied epicardially in rats. NHS-activated carboxyl groups in HA react with primary amines present in blood and myocardium to form amide bonds, resulting in a 3D hydrogel bound to tissue. HA-Bl hydrogels had a gelation time of 58±12s, swelling ratio of 10±0.5, compressive and elastic modulus of 14±3 and 1.75±0.6 kPa respectively. These hydrogels were not degraded at 4wks by hydrolysis alone. CDC encapsulation promoted their survival and proliferation. Intra-myocardial injection of CDCs encapsulated in these hydrogels greatly increased acute myocardial retention(p=0.001). Epicardial application of HA-blood hydrogels improved left ventricular ejection fraction following myocardial infarction (P=0.01). HA-blood hydrogels are highly adhesive, biodegradable, promote CDC survival and increase cardiac function following epicardial application after myocardial infarction.

Rationale Molecular imaging is useful for longitudinal assessment of engraftment. However, it is not known which factors, other than cell number can influence the molecular imaging signal obtained from reporter genes. Objective The effects of cell dissociation/suspension on cellular bioenergetics and the signal obtained by firefly luciferase(fluc) and human Na-I symporter(hNIS) labeling of cardiosphere-derived cells (CDCs) was investigated. Methods and Results 18FDG uptake, ATP levels, 99mTc-pertechnetate uptake and bioluminescence were measured in vitro, in adherent and suspended CDCs. In vivo dual isotope SPECT-CT imaging or bioluminescence imaging (BLI) were performed 1hr and 24hrs following CDC transplantation. SPECT quantification was performed using a phantom for signal calibration. Cell loss between 1hr & 24hrs post-transplantation was quantified by qPCR and ex vivo luciferase assay. Cell dissociation followed by suspension for 1hr resulted in decreased glucose uptake, cellular ATP, 99mTc uptake and BLI signal by 82%, 43%, 42%, and 44% respectively, when compared to adherent cells, in vitro. In vivo 99mTc uptake was significantly lower at 1hr, when compared to 24hrs following cell transplantation in the non-infarct (p<0.001, n=3) and infarct (p<0.001, n =4) model, despite significant cell loss during this period. The in vivo BLI signal was significantly higher at 1hr than at 24hrs (p<0.01), with the BLI signal being higher when CDCs were suspended in glucose-containing medium compared to saline(PBS). Conclusion Adhesion is an important determinant of cellular bioenergetics, 99mTc-pertechnetate uptake and BLI signal. BLI and NIS imaging may be useful for in vivo optimization of bioenergetics in transplanted cells.

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BackgroundLate gadolinium enhancement (LGE-) cardiovascular magnetic resonance (CMR) is well-validated for cardiac mass (CMASS) tissue characterization to differentiate neoplasm (CNEO) from thrombus (CTHR): Prognostic implications of CMASS subtypes among systemic cancer patients are unknown.MethodsCMASS + patients and controls (CMASS -) matched for cancer diagnosis and stage underwent a standardized CMR protocol, including LGE-CMR (IR-GRE) for tissue characterization and balanced steady state free precession cine-CMR (SSFP) for cardiac structure/function. CMASS subtypes (CNEO, CTHR) were respectively defined by presence or absence of enhancement on LGE-CMR; lesions were quantified for tissue properties (contrast-to-noise ratio (CNR); signal-to-noise ratio (SNR) and size. Clinical follow-up was performed to evaluate prognosis in relation to CMASS etiology.ResultsThe study population comprised 126 patients with systemic neoplasms referred for CMR, of whom 50% (n = 63) had CMASS + (CNEO = 32%, CTHR = 18%). Cancer etiology differed between CNEO (sarcoma = 20%, lung = 18%) and CTHR (lymphoma = 30%, GI = 26%); cardiac function (left ventricular ejection fraction: 63 ± 9 vs. 62 ± 10%; p = 0.51∣ right ventricular ejection fraction: 53 ± 9 vs. 54 ± 8%; p = 0.47) and geometric indices were similar (all p = NS). LGE-CMR tissue properties assessed by CNR (13.1 ± 13.0 vs. 1.6 ± 1.0; p < 0.001) and SNR (29.7 ± 20.4 vs. 15.0 ± 11.4, p = 0.003) were higher for CNEO, consistent with visually-assigned diagnostic categories. CTHR were more likely to localize to the right atrium (78% vs. 25%, p < 0.001); nearly all (17/18) were associated with central catheters. Lesion size (17.3 ± 23.8 vs. 2.0 ± 1.5 cm2; p < 0.001) was greater with CNEO vs. CTHR, as was systemic disease burden (cancer-involved organs: 3.6 ± 2.0 vs. 2.3 ± 2.1; p = 0.02). Mortality during a median follow-up of 2.5 years was markedly higher among patients with CNEO compared to those with CTHR (HR = 3.13 [CI 1.54–6.39], p = 0.002); prognosis was similar when patients were stratified by lesion size assessed via area (HR = 0.99 per cm2 [CI 0.98–1.01], p = 0.40) or maximal diameter (HR = 0.98 per cm [CI 0.91–1.06], p = 0.61). CTHR conferred similar mortality risk compared to cancer-matched controls without cardiac involvement (p = 0.64) whereas mortality associated with CNEO was slightly higher albeit non-significant (p = 0.12).ConclusionsAmong a broad cancer cohort with cardiac masses, CNEO defined by LGE-CMR tissue characterization conferred markedly poorer prognosis than CTHR, whereas anatomic assessment via cine-CMR did not stratify mortality risk. Both CNEO and CTHR are associated with similar prognosis compared to CMASS - controls matched for cancer type and disease extent.