The Spread of a Pathogenic and an Apathogenic Strain of Newcastle Disease Virus in the Chick Embryo as Depending on the Protease Sensitivity of the Virus Glycoproteins

Abstract

SUMMARYThe pathogenic strain Italien and the apathogenic strain Ulster of Newcastle disease virus have been compared with respect to organ tropism and spread of infection in I I-day-old chick embryos. After infection of the endodermal layer of the chorioallantoic membrane by intra-allantoic inoculation with strain Italien, high virus titres are found in all extra-embryonic membranes and fluids and in the embryo itself. Infection results in early death of the embryo. In contrast, after infection with strain Ulster by the same route of inoculation, high virus titres are found only in the allantoic sac and embryos are not killed. Inoculation with strain Italien on to the ectodermal layer through an artificial air sac results in rapid spread of infection in the chorioallantoic membrane and the embryo dies before the virus invades other tissues including the embryo. Under the same conditions of infection, strain Ulster neither spreads within chorioallantoic membrane nor does it kill the embryo. Virus spread in each germinal layer of the chorioallantoic membrane was analysed by immune fluorescence. These studies showed that endoderm as well as mesoderm and ectoderm allowed the spread of strain ltalien, whereas only the endoderm is permissive for strain Ulster. These differences in host range are based upon differential activation of the virus glycoproteins by proteolytic cleavage. The glycoproteins of strain ltalien are cleaved in each germinal layer, whereas those of strain Ulster are cleaved only in endoderm. These studies demonstrate that, in the system analysed here, spread of infection and organ tropism are important factors for pathogenicity and both of these factors are determined by the susceptibility of the virus glycoproteins to proteolytic cleavage.

Intracellular processing of the human respiratory syncytial virus fusion glycoprotein: amino acid substitutions affecting folding, transport and cleavage

“…However, F313 did not form stable oligomeric structures, its oligosaccharide chains were not modified to complex forms and are not cleaved to form F1 and F2. Our interest in investigating the phenotypic and genetic differences between the cleaved and uncleaved F proteins was based on studies on other paramyxoviruses, which have demonstrated that cleavage of the F protein is essential for fusion (Scheid & Choppin, 1977), an important determinant of virus pathogenicity (Nagai et at., 1976(Nagai et at., , 1979. Nucleotide sequence analysis and expression of chimeric F proteins created by restriction fragment exchange revealed that two amino acid differences in the F1 domain (Val to Ala at residue 301 ; Val to Met at residue 447) were responsible for the lack of F protein cleavage.…”

“…In addition, the length and composition of amino acids at the cleavage activation site, a stretch of hydrophilic residues that precede the N-terminal hydrophobic residues of the FI subunit, are important factors that influence the ability of paramyxovirus F proteins to be cleaved (Glickman et al, 1987;Paterson et aL, 1989;Toyoda et al, 1987). A strict correlation has been demonstrated between the ability of F proteins of 0001-0700 © 1992 SGM different strains of Newcastle disease virus to be cleaved and the extent of virus pathogenicity (Nagai et al, 1976(Nagai et al, , 1979.…”

Single Amino Acid Substitution of Sendai Virus at the Cleavage Site of the Fusion Protein Confers Trypsin Resistance

“…Since the cleavage of the F glycoprotein occurs post-translationally and is accomplished by some protease(s) in the chorioallantoic fluid of embryonated chicken eggs (Muramatsu & Homma, 1980), in tissue culture cells (Shibuta et al, 1971 ;Silver et al, 1978) or in mouse lung (Tashiro & Homma, 1983 a), we and other authors have suggested that the presence of the activating enzyme(s) for Sendai virus will determine its host range and organ tropism (Homma, 1972b;Ishida & Homma, 1978;Silver et al, 1978). A similar proposal has been made concerning the virulence of Newcastle disease virus (Garten et al, 1980;Nagai et al, 1979).…”

Biosynthesis of Mumps Virus F Glycoprotein: Non-fusing Strains Efficiently Cleave the F Glycoprotein Precursor

“…Past studies of paramyxoviruses have shown that proteolytic cleavage of the F 0 precursor confers infectivity, haemolytic and cell-fusing activities on virions which correlate with virulence (Scheid & Choppin, 1974Nagai et al, 1976Nagai et al, , 1979Nagai & Klenk, 1977;Fujinami & Oldstone, 1981). Our results show that the mumps F0 precursor is completely cleaved in infected cells, resulting in its absence in purified infectious virions of both non-fusing and fusing strains (Fig.…”

“…This conclusion is based on several elegant studies using precisely defined F protein mutants of Sendai virus (Scheid & Choppin, 1976) and naturally occurring strains of Newcastle disease virus (NDV) (Nagai et al, 1976(Nagai et al, , 1979Madansky &Bratt, 1981). These studies have shown that persistence of the inactive F 0 form, either due to an inability of the host cell to cleave F 0 or to an insensitivity of the F 0 precursor to proteolytic activation, results in a limited, non-cytopathic infection.…”