64 research outputs found
Membrane-Associated Heparan Sulfate Proteoglycan Is a Receptor for Adeno-Associated Virus Type 2 Virions
The human parvovirus adeno-associated virus (AAV) infects a broad range of cell types, including human, nonhuman primate, canine, murine, and avian. Although little is known about the initial events of virus infection, AAV is currently being developed as a vector for human gene therapy. Using defined mutant CHO cell lines and standard biochemical assays, we demonstrate that heparan sulfate proteoglycans mediate both AAV attachment to and infection of target cells. Competition experiments using heparin, a soluble receptor analog, demonstrated dose-dependent inhibition of AAV attachment and infection. Enzymatic removal of heparan but not chondroitin sulfate moieties from the cell surface greatly reduced AAV attachment and infectivity. Finally, mutant cell lines that do not produce heparan sulfate proteoglycans were significantly impaired for both AAV binding and infection. This is the first report that proteoglycan has a role in cellular attachment of a parvovirus. Together, these results demonstrate that membrane-associated heparan sulfate proteoglycan serves as the viral receptor for AAV type 2, and provide an explanation for the broad host range of AAV. Identification of heparan sulfate proteoglycan as a viral receptor should facilitate development of new reagents for virus purification and provide critical information on the use of AAV as a gene therapy vector
Gain-flattened erbium-doped fiber amplifier with flexible selective band for optical networks
Erbium-doped fiber amplifier with flat gain over 30 nm bandwidth is demonstrated using flexible selective band methods. The band optical amplifier was designed to cater 44 wavelength division multiplexing channels which were separated into bands of 4 nm. Without using any gain flattening filter, the gain of optical amplifier was maintained at 19 dB with a maximum gain variation of less than 1.6 dB even though the input signal power was varied from -19 to -6 dBm. The amplifier was able to maintain 1 dB gain flatness with 83% chance for any selective bands of 4 nm within the wavelength range from 1530 to 1565 nm. This feature is very attractive to support band optical networks
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The effect of extratropical cyclones on satellite-retrieved aerosol properties over ocean
Extratropical cyclones may have a signicant effect on
column aerosol properties over ocean. European Centre
for Medium Range Weather Forecasts (ECMWF) derived
storm-centric composites of MODerate resolution Imaging
Spectroradiometer (MODIS) and Advanced Along-Track
Scanning Radiometer (AATSR) aerosol optical depth and
aerosol size parameters are produced for the North Atlantic
and the South Atlantic oceans. It is found that retrieved
aerosol optical depth and aerosol size both increase near
the center of the composite extratropical cyclones. Using
composites of ECMWF ERA-Interim reanalysis data, it is
demonstrated that wind speed is a considerably more likely
explanatory variable than relative humidity for the aerosol
observations. A comparison of composites for both MODIS
and AATSR, which uses a wind speed dependent sea-surface
brightness model in the aerosol retrieval, suggests that although
surface brightness eects may contribute towards
some of the observations, wind speed dependent emission
of sea salt also appears to make a signicant contribution to
the observed aerosol properties
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