Respiratory syncytial virus (RSV) is a ubiquitous human pathogen and the leading cause of lower respiratory tract infections in infants. Infection of cells and subsequent formation of syncytia occur through membrane fusion mediated by the RSV fusion protein (RSV-F). A novel in vitro assay of recombinant RSV-F function has been devised and used to characterize a number of escape mutants for three known inhibitors of RSV-F that have been isolated. Homology modeling of the RSV-F structure has been carried out on the basis of a chimera derived from the crystal structures of the RSV-F core and a fragment from the orthologous fusion protein from Newcastle disease virus (NDV). The structure correlates well with the appearance of RSV-F in electron micrographs, and the residues identified as contributing to specific binding sites for several monoclonal antibodies are arranged in appropriate solvent-accessible clusters. The positions of the characterized resistance mutants in the model structure identify two promising regions for the design of fusion inhibitors.

SummaryDendritic cells isolated from thymus and tonsil were tested for susceptibility to HIV-1 strains that are tropic for macrophages or for T cell lines. DCs were purified by cell sorting and before infection expressed high levels of CD4 and HLA-DR and lacked markers for T, B, NK cells, or macrophages. Viral entry and reverse transcription was found after pulsing with strains of HIV-1 that could infect macrophages. During the first 36 h the PCR signals for gag sequences increased in DCs and macrophages. In contrast litde if any viral DNA was found after pulsing macrophages or DCs with HIV-1 that was able to infect T cell lines. DCs pulsed with HIV-1 were able to transmit infection to responding T cells during an allogeneic or superantigen response.Selection for virus able to infect lymphoid DCs and other DCs expressing CD4 and its transfer to T cells during subsequent immune responses may provide a mechanism for the observed predominance ofmacrophage-tropic HIV-1 after in vivo transmission.

We review recent work on the extent of HIV-1 infection of dendritic cells (DCs) and the consequences of exposure to virus. The reported levels of infection of DCs from blood have varied from "explosive" to "undetectable." The only study that used sorted DCs demonstrated little if any infectability, which may not be surprising given the very low levels of CD4 on the populations that were studied. HIV-1-pulsed, highly purified DCs function as potent antigen-presenting cells during the mixed leukocyte reaction and responses to superantigens. At the same time that the HIV-1-pulsed DCs stimulate CD4+ T cells in DC-T clusters, the virus is transferred to the responding lymphocytes and a vigorous productive infection of the T cells takes place. This pool of transferable HIV-1 is short lived in cultured human blood DCs and likely reflects the capacity of these cells to internalize and recycle vesicles in the endocytic pathway, as revealed with experiments using 0.1-micron fluorescent latex beads. Current efforts are directed to analyzing the interaction of HIV-1 with several populations of DCs that express higher levels of CD4. These include DCs studied in fresh, uncultured blood, as well as skin, thymus, and tonsil DCs. In each case, entry and reverse transcription of HIV-1 are seen, but again, coculture with T cells is required for a productive infection to take place. We conclude that DCs could play a critical role in the pathogenesis of HIV-1 infection, but that the interaction with CD4+ T cells is a critical variable in analyzing the extent of productive infection and its consequences.

Both macrophages and glomerular mesangial cells have the potential to synthesize interleukin 1 (IL-1), however, their respective contributions to IL-1 production in anti-GBM glomerulonephritis (GN) are unknown. To address this problem, IL-1 production by glomeruli from rabbits with macrophage-associated anti-GBM GN (passive autologous anti-GBM GN [PAGBMGN]) and macrophage independent (heterologous phase) anti-GBM GN was studied. Macrophage-infiltrated nephritic glomeruli produced IL-1 bioactivity which was inhibitable by an anti-IL-1 antibody, and had a molecular weight consistent with rabbit IL-1. Glomerular IL-1 production in PAGBMGN was markedly augmented (1.43 +/- 0.79 U/10(3) glomeruli [gloms]/24 hr) compared to normal glomeruli (0.13 +/- 0.06 U/10(3) gloms/24 hr, P less than 0.05) or glomeruli from rabbits with macrophage independent GN (0.11 +/- 0.07 U/10(3) gloms/24 hr, P less than 0.05). IL-1 production by glomeruli from leukocyte depleted rabbits with PAGBMGN (0.16 +/- 0.07 U/10(3) gloms/24 hr) was not significantly elevated compared to normal glomeruli. Glomerular macrophages from rabbits with PAGBMGN produced more IL-1 (3.62 +/- 1.63 U/10(3) cells/24 hr) than blood monocytes (0.51 +/- 0.30 U/10(3) cells/24 hr) or alveolar macrophages (0.24 +/- 0.12 U/10(3) cells/24 hr) from the same animals. These results show that in experimental anti-GBM GN where injury is macrophage dependent, IL-1 production is also macrophage dependent and infiltrating glomerular macrophages are the major source of IL-1. Further, as glomerular IL-1 production was not significantly augmented in GN in the absence of macrophages, glomerular deposition of immunoglobulin and complement alone do not stimulate significant IL-1 production by intrinsic glomerular cells in experimental anti-GBM GN.

BLZ-100 (tozuleristide) is an intraoperative fluorescent imaging agent that selectively detects malignant tissue and can be used in real time to guide tumor resection. The purpose of this study was to assess the safety, tolerability, and pharmacokinetics of BLZ-100 and to explore the pharmacodynamics of fluorescence imaging of skin tumors. In this first-in-human study, BLZ-100 was administered intravenously to 21 adult patients 2 days before excising known or suspected skin cancers. Doses were 1, 3, 6, 12, and 18 mg, with 3–6 patients/cohort. Fluorescence imaging was conducted before and up to 48 h after dosing. BLZ-100 was well tolerated. There were no serious adverse events, deaths, or discontinuations due to adverse events, and no maximum tolerated dose (MTD) was identified. Headache (n = 2) and nausea (n = 2) were the only BLZ-100 treatment-related adverse events reported for >1 patient. Median time to maximal serum concentration was <0.5 h. Exposure based on maximal serum concentrations increased in a greater than dose-proportional manner. For intermediate dose-levels (3–12 mg), 4 of 5 basal cell carcinomas and 4 of 4 melanomas were considered positive for BLZ-100 fluorescence. BLZ-100 was well tolerated at all dose levels tested and these results support further clinical testing of this imaging agent in surgical oncology settings. Clinicaltrials.gov: NCT02097875.