Requirements for syncytium formation mediated by the fusion glycoprotein of human parainfluenza virus type 3.
|Title:||Requirements for syncytium formation mediated by the fusion glycoprotein of human parainfluenza virus type 3.|
|Authors:||Ebata, Sharon Nori.|
|Abstract:||Recombinant vaccinia viruses VF and VHN were shown to express glycoproteins with molecular weights similar to authentic HPIV3 F and HN proteins that were transported to the cell surface and recognized by monoclonal antibodies specific for HPIV3 F and HN. The HN glycoprotein in VHN-infected cells exhibited both hemagglutinin and neuraminidase activities. Both cleaved and uncleaved forms of the F glycoprotein were immunizers from VF-infected cell lysates. Fusogenic activity of the F protein was demonstrated only upon coinfection of HeLa T4$\sp+$ cells with VF + VHN and resulted in syncytium formation and hemolysis. Recombinant adenoviruses AdF and AdHN, expressed the HPIV3 F and HN proteins on the surface of infected HeLa T4$\sp+$ cells, respectively. AdHN-infected cells produced HN protein that was glycosylated and exhibited both hemagglutinin and neuraminidase activities. AdF infection led to the synthesis of glycosylated F$\sb0$ that was proteolytically cleaved. As was observed for vaccinia virus recombinants, syncytium formation was only observed upon coinfection of HeLa T4$\sp+$ cells with AdF + AdHN The F and HN proteins expressed by recombinant adenoviruses were recognized by monoclonal antibodies specific for the HPIV3 F or HN protein and were immunogenic in mice. Sera from AdF-or AdHN-inoculated mice immunoprecipitated appropriate glycoproteins from lysates of HPIV3-infected cells and neutralized HPIV3. Amino acid substitutions were introduced into three regions of the HPIV3 F protein to identify sequences involved in fusogenic activity. Substitution of uncharged amino acids for positively charged residues within the cytoplasmic tail, or introduction of a charged residue within the transmembrane domain, did not appear to affect fusogenic activity. Several different mutations designed to disrupt the leucine zipper or the heptad repeat motifs resulted in mutant F proteins that not only exhibited decreased fusogenic activity but concomitantly lost the ability to react with monoclonal antibody c128, which recognized an epitope in antigenic site B of the HPIV3 F glycoprotein. An association between the heptad repeat and leucine zipper domains, therefore, appears to be required for the HPIV3 F glycoprotein to adopt a conformation that is recognized by antibody c128 and that appears to be important for fusogenic activity.|
|Collection||Thèses, 1910 - 2010 // Theses, 1910 - 2010|