Extracellular vesicles (EVs), including exosomes and shed vesicles, have been implicated in intercellular communication; however, their biomarker potential is less clear. Therefore, EVs derived from MCF7 and MCF10A cells were analyzed to identify unique microRNA (miR) profiles that distinguish their origin. One characteristic common to the miR profiles of MCF7 EVs and their parent cells is the high abundance of miR-21, let-7a, miR-100, and miR-125b, and low levels of miR-205. A second characteristic is the high abundance of “microRNA-like” transfer RNA (tRNA) fragments, which is unique to the MCF7 EVs, and is not found in comparing the cellular profiles. In addition, correlations were examined in the MCF7 cellular expression levels of these five miRs and two tRNA-derived miRNAs, miR-720 and miR-1274b, and compared to the correlations in MCF7 EV levels. Interestingly, correlations in the cellular expression of miR-125b, miR-100, and let-7a are mirrored in the EVs. In contrast, correlations in tRNA-derived miRNA levels are found only in the EVs. The findings suggest that EV miR clusters can be defined based on functional miR interactions related to correlated cellular expression levels or physical miR interactions – e.g., aggregation due to comparable binding affinities to common targets. Implications: These results point to using high levels of tRNA-derived small RNA fragments in combination with known miR signatures of tumors to distinguish tumor-derived EVs in circulation from EVs derived from other cell sources. Such biomarkers would be unique to the EVs where high abundances of tRNA fragments are amplified with respect to their cellular levels.

Anti-dengue T-cell responses have been implicated in both protection and immunopathology. However, most of the T-cell studies for dengue include few epitopes, with limited knowledge of their inter-serotype variation and the breadth of their human leukocyte antigen (HLA) affinity. In order to expand our knowledge of HLA-restricted dengue epitopes, we screened T-cell responses against 477 overlapping peptides derived from structural and non-structural proteins of the dengue virus serotype 3 (DENV3) by use of HLA class I and II transgenic mice (TgM): A2, A24, B7, DR2, DR3 and DR4. TgM were inoculated with peptides pools and the T-cell immunogenic peptides were identified by ELISPOT. Nine HLA class I and 97 HLA class II novel DENV3 epitopes were identified based on immunogenicity in TgM and their HLA affinity was further confirmed by binding assays analysis. A subset of these epitopes activated memory T-cells from DENV3 immune volunteers and was also capable of priming naïve T-cells, ex vivo, from dengue IgG negative individuals. Analysis of inter- and intra-serotype variation of such an epitope (A02-restricted) allowed us to identify altered peptide ligands not only in DENV3 but also in other DENV serotypes. These studies also characterized the HLA promiscuity of 23 HLA class II epitopes bearing highly conserved sequences, six of which could bind to more than 10 different HLA molecules representing a large percentage of the global population. These epitope data are invaluable to investigate the role of T-cells in dengue immunity/pathogenesis and vaccine design.

Acellular hemoglobin (Hb)-based O2 carriers (HBOCs) are being investigated as red blood cell (RBC) substitutes for use in transfusion medicine. However, commercial acellular HBOCs elicit both vasoconstriction and systemic hypertension which hampers their clinical use. In this study, it is hypothesized that encapsulation of Hb inside the aqueous core of liposomes should regulate the rates of NO dioxygenation and O2 release, which should in turn regulate its vasoactivity. To test this hypothesis, poly(ethylene glycol) (PEG) conjugated liposome-encapsulated Hb (PEG-LEHs) dispersions were prepared using human and bovine Hb. In this study, the rate constants for O2 dissociation, CO association, and NO dioxygenation were measured for free Hb and PEG-LEH dispersions using stopped-flow UV-visible spectroscopy, while vasoactivity was assessed in rat aortic ring strips using both endogenous and exogenous sources of NO. It was observed that PEG-LEH dispersions had lower O2 release and NO dioxygenation rate constants compared with acellular Hbs. However, no difference was observed in the CO association rate constants between free Hb and PEG-LEH dispersions. Furthermore, it was observed that Hb encapsulation inside vesicles prevented Hb dependent inhibition of NO-mediated vasodilation. In addition, the magnitude of the vasoconstrictive effects of Hb and PEG-LEH dispersions correlated with their respective rates of NO dioxygenation and O2 release. Overall, this study emphasizes the pivotal role Hb encapsulation plays in regulating gaseous ligand binding/release kinetics and the vasoactivity of Hb.

Background: Recent discoveries have established that cancer tumors exhibit distinct microRNA (miR) expression profiles compared to normal tissues. Detection of miRs in the peripheral blood of cancer patients is possible due to their high stability. This stability is attributed to encapsulation of the miRs inside microvesicles (MVs) where they are protected from endogenous RNase activity in circulation. The tumor cell-secreted MVs of primary interest are circulating exosomes, a subpopulation of MVs distinguished by their relatively small size: 40 to 100 nm in diameter. The isolation of circulating tumor-derived exosomes from the other cell-secreted MVs in peripheral blood is the critical barrier to successful development of a robust assay for cancer-specific miR signatures. We describe the development of such an assay to: (1) capture/isolate circulating exosomes based on characteristic surface markers that correlate with different cell types, and (2) characterize exosome-specific miR signatures based on these surface markers. Materials and Methods: We apply sequential ultracentrifugation to isolate cell-secreted MVs, followed by asymmetric flow field-flow fractionation to selectively separate exosomes based on their intrinsically small size and characteristic surface markers. Isolated exosomes are then screened for surface markers by selectively capturing them on microarrays printed with antibodies against a library of known cell-surface markers for breast cancer. For the assessment of exosome-specific miR signatures, we have devised an antibody microarray assay that also enables the in situ characterization of miR profiles of the captured exosomes locally by qRT-PCR analysis confined to subarrays of printed spots in 50-µl microwells of a custom-designed, multi-well microarray. Assay development has been carried out using two human cancer cell lines (MCF 7 and MDA MB 231) and a non-malignant cell line (MCF 10a) representing pre-malignant cells and cancer of the breast at different epithelial and mesenchymal states. Results: We have used light scattering and cryo-transmission electron microscopy to characterize the size, size distribution, and morphology of exosomes as a sub-population of the secreted MVs from each of the three cell lines. We have also screened for surface markers by selective capturing the exosome sub-populations derived from these cell lines on antibody microarrays, and correlated these surface markers with the miR content of MVs using qRT-PCR analysis. Discussion: Our results demonstrate that correlating the miR signatures of circulating exosomes with characteristic surface markers on these exosomes leads to robust distinctions between the three cell lines that could not be achieved using either analysis or characterization alone. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-09-04.

<p>Supplemental Tables S1-2, Figures S1-2. Table S1. NanoString nCounterTM assay measurements of miRNA copy numbers/cell detected in MCF7 and MCF10A cells at 72 hrs of serum deprivation and in EVs derived from MCF7 and MCF10A cells over 72 hrs of serum deprivation. Table S2. qRT-PCR assay measurements of miRNA copy numbers/cell detected in MCF7 and MCF10A cells at 72 hrs of serum deprivation and in EVs secreted from MCF7 and MCF10A cells over 72 hrs of serum deprivation. Figure S1. Total cellular RNA concentration (top panel) and changes in miR-21 expression levels (middle panel) and changes in miR-1274a and miR-1274b expression levels (bottom panel) for MCF10A cells (open symbols) and MCF7 cells (filled symbols) as a function of time in response to serum deprivation at 0 hrs. Figure S2. Sequence alignments for miRNA pairs depicting positions that share identical nucleotides.</p>