Retroviral and lentiviral vectors often use the envelope G protein from the vesicular stomatitis virus Indiana strain (VSVind.G). However, lentivector producer cell lines that stably express VSVind.G have not been reported, presumably because of its cytotoxicity, preventing simple scale-up of vector production. Interestingly, we showed that VSVind.G and other vesiculovirus G from the VSV New Jersey strain (VSVnj), Cocal virus (COCV), and Piry virus (PIRYV) could be constitutively expressed and supported lentivector production for up to 10 weeks. All G-enveloped particles were robust, allowing concentration and freeze-thawing. COCV.G and PIRYV.G were resistant to complement inactivation, and, using chimeras between VSVind.G and COCV.G, the determinant for complement inactivation of VSVind.G was mapped to amino acid residues 136–370. Clonal packaging cell lines using COCV.G could be generated; however, during attempts to establish LV producer cells, vector superinfection was observed following the introduction of a lentivector genome. This could be prevented by culturing the cells with the antiviral drug nevirapine. As an alternative countermeasure, we demonstrated that functional lentivectors could be reconstituted by admixing supernatant from stable cells producing unenveloped virus with supernatant containing envelopes harvested from cells stably expressing VSVind.G, COCV.G, or PIRYV.G.

Quantifying circulating nucleic acids is an important new approach to cancer diagnosis/monitoring. We compared the suitability of serum versus plasma for measuring miRNAs using qRT-PCR and assessed how preanalytic variables that can affect circulating tumor DNA (ctDNA) quantification in plasma also influence miRNA levels. Across 62 blood-derived specimens, plasma samples in EDTA, Streck-DNA, and Streck-RNA tubes showed significantly higher values for multiple housekeeping miRNAs, compared with serum samples. For the EDTA-plasma tubes, this difference was only seen when including the high-speed centrifugation protocol used to optimize ctDNA extraction. In plasma samples derived from blood stored at room temperature for up to 14 days (conditions that typically apply to samples processed for biobanking), levels of endogenous housekeeping miRNAs gradually increased, in parallel with the hemolysis marker hsa-miR-451a, consistent with release from blood cells/platelets. It was necessary to normalize levels of the housekeeping miRNAs to those of hsa-miR-451a, to obtain the stable values needed for referencing test miRNA levels. Our data indicate that plasma samples prepared for ctDNA extraction are suboptimal for miRNA quantification and require the incorporation of multiple data normalization steps. For prospective studies designed to measure both miRNAs and ctDNA, the most suitable approach would be to obtain both serum (for miRNAs) and plasma (for ctDNA). If only plasma can be collected, we recommend an initial low-speed centrifugation step, followed by aliquoting the supernatant into parallel samples, one for direct miRNA quantification, and the other for a further high-speed centrifugation step to optimize ctDNA retrieval. These recommendations will help "future-proof" clinical studies in which quantification of circulating miRNAs is a component. .

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Rapamycin (RAPA) induces unresponsiveness toward heart allografts by at least two mechanisms: selective production of noncytotoxic IgG2c-blocking Ab and preferential activation of Th2 cells. RAPA (0.8 mg/kg/day) delivered via a 14-day osmotic pump to Wistar Furth (WF; RT-1u) recipients prolongs Buffalo (BUF; RT-1b) heart allograft survival from a mean survival time (MST) of 6.5 +/- 0.5 days to 75.0 +/- 18.9 days (n = 18; p < 0.001), with 6 of 18 grafts beating for more than 100 days. Recipient sera or their IgG but not IgM fraction, obtained after postgrafting day 40, passively transfer the unresponsive state to sublethally irradiated secondary recipients in a dose-dependent and immunologically-specific fashion. Sera obtained after untreated WF hosts rejected BUF hearts contained IgG moieties of all subclasses that bound to class I MHC BUF epitopes. In contrast, the unresponsive sera contained predominantly non-C'-fixing IgG2c and only marginal amounts of activated (C') fixing IgG1, IgG2a, and IgG2b Ab. The transcription of IL-2, IL-4, and IL-10 mRNAs was assessed using a PCR method. There were similar increases in the levels of IL-2, IL-4, and IL-10 mRNA in heart allografts from both untreated and RAPA-treated recipients on day 5 postgrafting. In contrast, on days 60 and 300 postgrafting heart allografts from RAPA-treated unresponsive recipients showed increased levels of IL-10 and IL-4 but not of IL-2 mRNA, suggesting preferential activation of Th2 cells. Thus, RAPA treatment selectively inhibits the synthesis of C'-binding of IgG subclasses, spares the non C-binding blocking IgG2c Ab, and preferentially activates Th2 cells.

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