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Sendai virus (SeV) is an enveloped virus with a nonsegmented negative strand RNA genome. The recovery of infectious virus from cDNA and generation of recombinant SeV carrying a foreign gene at the promoter proximal position has been demonstrated. In this study, we constructed a series of recombinant SeVs carrying a reporter human secreted alkaline phosphatase (SEAP) gene at each viral gene junction or the 5' distal end in order to measure the expression level of the foreign gene. We demonstrated that there was a gradient in the reporter gene expression level that depended on location, due to the polarity of transcription. In contrast, the growth and final titers of these recombinant viruses showed an opposite gradient to the foreign gene expression level. This suggests the potential for matching therapeutic gene expression level to individual therapy programs by changing the position of the foreign gene when SeVs are used as vectors for human gene therapy.

The primary structure of the F protein of a host range mutant of the Ulster strain of Newcastle Disease virus (NDV) has been determined by nucleotide sequence analysis and compared to that of the wild type and other NDV strains. The cleavage site of the mutant had the sequence Gly-Lys-Gln-Arg-Arg as compared to two isolated basic amino acids [Gly-Lys(Arg)-Gln-Gly-Arg] with the apathogenic strains and two pairs of basic amino acids [Arg-Arg-Gln-Lys(Arg)-Arg] with the pathogenic strains. The data indicate that the cleavability of the F protein of NDV increases with the number of arginine and lysine residues at the cleavage site and that the susceptibility of the pathogenic strains to ubiquitous host proteases depends on both pairs of basic amino acids.

We have prepared and characterized monoclonal antibodies against the three internal structural proteins, M, P and NP, of Newcastle disease virus. At least two non-overlapping antigenic sites were delineated on the M protein, four on the P, and two on the NP by competitive binding assay. One of the two non-overlapping antigenic sites on the M protein was found to be a cluster of at least three distinct epitopes. Enhancement of antibody binding by the binding of a second antibody was observed with the M protein. The reactivity of these monoclonal antibodies with heterologous strains was studied by enzyme-linked immunosorbent assay. The results indicated that there are both highly conserved antigenic sites and those subject to remarkable change on both M and P proteins. On the other hand, NP appeared to be antigenically more stable.