212 research outputs found
Mutations in the cytoplasmic tail of murine leukemia virus envelope protein suppress fusion inhibition by R peptide
No full textThis article cites 51 articles, 31 of which can be accessed fre
Analysis of the pH requirement for membrane fusion of different isolates of the paramyxovirus parainfluenza virus 5.
No full textParamyxoviruses enter cells by fusing their envelopes with the plasma membrane, a process that occurs at neutral pH. Recently, it has been found that there is an exception to this dogma in that a porcine isolate of the paramyxovirus parainfluenza virus 5 (PIV5), known as SER, requires a low-pH step for fusion (S. Seth, A. Vincent, and R. W. Compans, J. Virol. 77: 6520-6527, 2003). As a low-pH activation mechanism for fusion would greatly facilitate biophysical studies of paramyxovirus-mediated membrane fusion, we have reexamined the triggering of the PIV5 SER fusion protein. Using multiple assays, we could not find a requirement for low-pH triggering of PIV5 SER fusion. The challenge of discovering how the paramyxovirus receptor binding protein (HN, H, or G) activates the metastable fusion protein to cause membrane fusion at neutral pH remains.</p
Coreceptor-Dependent Inhibition of the Cell Fusion Activity of Simian Immunodeficiency Virus Env Proteins
No full textABSTRACT
The cytoplasmic tail (R peptide) sequence is able to regulate the fusion activity of the murine leukemia virus (MuLV) envelope (Env) protein. We have previously shown that this sequence exerts a profound inhibitory effect on the fusion activity of simian immunodeficiency virus (SIV)-MuLV chimeric Env proteins which contain the extracellular and transmembrane domains of the SIV Env protein. Recent studies have shown that SIV can utilize several alternative cellular coreceptors for its fusion and entry into the cell. We have investigated the fusion activity of SIV and SIV-MuLV chimeric Env proteins using cells that express different coreceptors. HeLa cells were transfected with plasmid constructs that carry the SIV or SIV-MuLV chimeric Env protein genes and were overlaid with either CEMx174 cells or Ghost Gpr15 cells, which express the Gpr15 coreceptor for SIV, or Ghost CCR5 cells, which express CCR5, an alternate coreceptor for SIV. The R-peptide sequence in the SIV-MuLV chimeric proteins was found to inhibit the fusion with CEMx174 cells or Ghost Gpr15 cells. However, a significant level of fusion was still observed when HeLa cells expressing the chimeric Env proteins were cocultivated with Ghost CCR5 cells. These results show that the R-peptide sequence exerts differential effects on the fusion activity of SIV Env proteins using target cells that express alternative coreceptors.</jats:p
Oligomerization, Secretion, and Biological Function of an Anchor-Free Parainfluenza Virus Type 2 (PI2) Fusion Protein
No full textAbstractA number of studies indicate that the transmembrane domain, the cytoplasmic domain, or both regions of viral surface glycoproteins are involved in quaternary structure formation. In this report, the transmembrane domain and cytoplasmic tail coding sequence of the fusion (F) glycoprotein gene from parainfluenza type 2 virus was truncated by PCR and the resulting gene (PI2F′) was expressed in HeLa-T4 cells by using the vaccinia virus-T7 transient expression system. Pulse–chase experiments indicated that the anchor-free PI2F′ was expressed and processed into F1 and F2 subunits. Both the processed and the unprocessed anchor-free PI2F′ proteins were found to be efficiently secreted into the culture medium. Examination of the oligomeric form of the anchor-free PI2F′ by chemical cross-linking demonstrated that it assembles posttranslationally into dimers and trimers with a pattern similar to that of the wild-type PI2F protein. In an effort to better understand the biological properties of the truncated form of PI2F′, we anchored PI2F′ by a glycosyl-phosphatidylinositol (GPI) linkage. The GPI-anchored PI2F′ protein, when coexpressed with PI2HN, did not induce cell fusion seen as syncytium formation, but was found to initiate lipid mixing (hemifusion) as observed by transfer of R-18 rhodamine from red blood cells to the GPI-PI2F′/PI2HN cotransfected cells. The results therefore indicate that the extracellular domain of the PI2 fusion protein contains not only the structural information sufficient to direct assembly into higher oligomers, but also is competent to initiate membrane fusion, suggesting that the anchor-free PI2F′ may be useful for further structural studies
Thermostabilization of influenza vaccine in microneedle patches
No full textVaccine delivery to the skin via microneedles confers several advantages over the traditional hypodermic needle and syringe. This work focuses on developing microneedles as a thermostable delivery method for the influenza vaccine that can be completely removed from the cold-chain, thus minimizing cost and wastage during storage and transportation. Microneedle formulations were screened for their effect on influenza vaccine activity during drying. A number of excipients, particularly the combination of arginine and heptagluconate, successfully stabilized influenza vaccine during storage in the dried state and in microneedle patches at ambient or elevated temperatures for up to eighteen months. Influenza vaccine microneedle patches were shown to be resistant against several stresses and remained immunogenic in a mouse model after long-term storage. The primary mechanism of influenza vaccine activity loss during drying was aggregation, which can be mitigated by stabilizing excipients.Ph.D
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