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D C Merz

Publications and source records attributed to D C Merz.

27 records · Page 2Linked to original sources
PubMed1981

Functions of surface glycoproteins of myxoviruses and paramyxoviruses and their inhibition.

Two glycoproteins, HN and F, are present on the surface of paramyxoviruses. HN has receptor-binding amd neuraminidase activities. F is involved in viral penetration, cell fusion and haemolysis and is activated by proteolytic cleavage by a host enzyme into two disulphide-bonded subunits (f1 and F2). The ability of the virus to initiate infection and undergo multiple cycle replication depends on the presence of an activating protease in the host; thus cleavage of F is a major determinant of pathogenesis. The new N-terminus generated on F1 by cleavage is involved in biological activity, and the amino acid sequence of this region of F1 by cleavage is involved in biological activity, and the amino acid sequence of this region of F1 is hydrophobic and highly conserved among para-myxoviruses. In an attempt to design specific inhibitors, oligopeptides and analogous to this region were synthesized and found to be highly active, specific inhibitors of viral penetration, cell fusion and haemolysis. Inhibition is amino-acid-sequence-specific and affected by peptide length, steric configuration and addition of groups to the n-terminal and C-terminal amino acids. Replication of influenza virus was also specifically inhibited by oligopeptides resembling the N-terminus of the HA2 polypeptide. Like that of F1 protein the N-terminus of HA2 is generated by a proteolytic cleavage that activates infectivity. These results have provided information on the action of proteins in viral penetration and membrane fusion and they suggest a possible new approach to chemical inhibition of viral replication. Studies with specific antibodies to each of the paramyxovirus glycoproteins have shown that antibodies to the F protein are essential for effective prevention of the spread of infection. Antibodies to the HN protein, although capable of neutralizing released virus, do not prevent spread to adjacent cells through membrane fusion mediated by the F protein. These findings have implications for the design of effective vaccines against paramyxoviruses and also provided additional insight into the mechanisms involved in the atypical and severe infections observed in individuals who received inactivated paramyxovirus vaccines and were later infected.

Amino Acid Sequence↗
PubMed1981

The functions and inhibition of the membrane glycoproteins of paramyxoviruses and myxoviruses and the role of the measles virus M protein in subacute sclerosing panencephalitis.

The F glycoprotein of paramyxoviruses is responsible for cell fusion and hemolysis and for virus penetration via fusion of viral and cell membranes. These functions are activated by specific proteolytic cleavage of an inactive precursor (F0) into two disulfide-linked polypeptides (F1 and F2). The susceptibility of the F0 protein to cleavage by a host protease is a major determinant of virus host range and virulence. Synthetic oligopeptides that mimic the N-terminal region of the F1 polypeptide are specific inhibitors of paramyxoviruses, and oligopeptides that mimic the N-terminus of the HA2 polypeptide of influenza virus, also generated by cleavage, specifically inhibit that virus. Antibodies to F protein prevent the spread of paramyxovirus infection via membrane fusion, but antibodies to HN protein do not, although they neutralize released virus. These results and previous findings that formalin-treated virus does not induce antibodies to F protein provide an explanation for atypical measles. The HN protein has both receptor-binding and neuraminidase activities, and Cl- inhibition of neuraminidase may modulate these antagonistic activities. Studies in patients with subacute sclerosing panencephalitis (SSPE) suggest that there is a host restriction of synthesis of the M protein of measles virus in brain cells which is involved in the abortive, persistent infection that causes SSPE.

Antibodies, Viral↗
PubMed1980

Importance of antibodies to the fusion glycoprotein of paramyxoviruses in the prevention of spread of infection.

The effects of monospecific antibodies to the viral glycoprotein with hemagglutinating and neuraminidase activity (HN) and the viral glycoprotein with membrane-fusing activity (F) of the paramyxovirus simian virus 5 (SV5) on the spread of infection in two cell types have been investigated. In CV-1 cells, infection can spread by either released progeny virus adsorbing to and infecting other cells, or by fusion of an infected cell with an adjacent cell as a result of the cell-fusing activity of the F glycoprotein. In these cells, antibodies specific for the HN glycoprotein prevented the dissemination of infection by released infectious virus, but spread by cell fusion was not inhibited. Antibodies to the F glycoprotein completely prevented the spread of infection in these cells. In Madin-Darby bovine kidney cells, which are relatively resistant to SV5-induced fusion, antibodies to either the HN or F glycoproteins were capable of preventing the dissemination of infection. These results indicate that effective immunological prevention of the spread of paramyxovirus infection requires the presence of antibodies that inactivate the F glycoprotein. This requirement for anti-F antibodies has obvious implications for the design of effective paramyxovirus vaccines and provides an explanation for previous failures of formalin-inactivated paramyxovirus vaccines as well as additional insight into the possible immunopathological mechanisms involved in the atypical and severe infections that have occurred in individuals who received inactivated paramyxovirus vaccines and were subsequently infected by the virus.

Animals↗
PubMed1975

Analysis of polypeptide disposition in human erythrocyte membranes employing membrane inversion.

High resolution segregation of erythrocyte membrane polypeptides achieved by isoelectric focusing in 8 M urea was employed in conjunction with surface-restricted radioiodination to analyze the disposition of polypeptides within the human erythrocyte membrane. Several membrane polypeptides showed significant uptake of radioiodine, with the principal labeled component migrating between pH values of 3.0 and 3.5. Two approaches were taken in examining membrane polypeptide disposition on both faces of the erythrocyte membrane. Saturation labeling of the outer face of the membrane with one iodine isotope followed by cell lysis and reiodination with a second iodine isotope did not prove feasible and another procedure based on surface iodination with 125-I, formation of sealed inside-out vesicles and re-iodination with 131-I was adopted. Studies of sialic acid release from the membrane surface and trypsin cleavage of radioiodinated peptides indicated that selectively labeled, sealed inside-out vesicles had been formed. The ratio of 125-I to 131-I in membrane polypeptides separated by isoelectric focusing confirmed the existence of externally disposed, internally disposed and spanning proteins.

Cell Membrane↗
PubMed1974

A functional examination of hapten-binding derivatives from a murine myeloma protein with immunoglobulin features.

Various enzymatic derivatives of the murine myeloma protein IgA(MOPC-315) were subjected to hapten-binding quantitation and circular dichroic analysis in an attempt to ascertain the structural localization and functional definition of the immunoglobulin active site. The extrinsic Cotton effects observed with near saturation of the active site of the derivatives using epsilon-Dnp-L-lysine were qualitatively and quantitatively identical when normalized with respect to their macromolecular content of Dnp-binding sites; ellipticity maxima of 378 and 438 nm and an ellipticity minimum of 325 nm were recorded. Fluorescence quenching data confirmed the molecular nature of the derivation products of IgA(MOPC-315) but also introduced disparity with respect to binding kinetics, i.e., K values of 2.31 x 10(6), 6.62 x 10(6), and 2.06 x 10(7) M(-1) were determined for IgA(MOPC-315), Fab'(MOPC-315), and Fv(MOPC-315), respectively. We speculate that the results can be explained by possible modulating effects on haptenbinding contributed by novel conformations introduced through proteolysis.

Animals↗