Studies of the ecology and pathogenicity of Newcastle disease virus.

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The purpose of the present study is to evaluate the ecology and pathogenicity of Newcastle disease virus (NDV). The hemagglutinin-neuraminidase (HN) and fusion (F) proteins of NDV were known to play key roles in the course of NDV infection. We examined biological and immunological properties of the expressed HN or F protein after inserting these genes into vaccinia virus (VN), fowlpox virus (FPV) or baculovius (BV). The following results were obtained.1) The role of immune responses to HN protein in protection against NDV infection was investigated using a recombinant vaccinia virus (rVV-HN) expressing the HN protein. Chickens inoculated with Eve rVV-HN(8x10^<>6 PFU) were completely protected from lethal infection with virulent NDV. Chickens inoculated with inactivated RVV-HN were not protected. Specific antibodies against the HN protein of NDV were detected in stra from survivors but not from dying birds.2) We constructed a recombinant FPV (rFPV-HN) expressing the HN protein under con … More trol of VV promoter p7.5 within thymidine kinase gene of FPV. The RFPV-HN reacted with ante-HN monoclonal antibody with virus neutralizing activity. The expressed HN protein had the same mobility on SDS-PAGE as the authentic HN glycoprotein.3) Spodoptera frugiperda (Sf) cells which infected with a recombinant BV (rBV-HN) containing a cDNA which encodes HN of NDV were expressed the antigen on their surface. The expressed HN protein had the same mobility on SDS-PAGE as the authentic HN glycoprotein, and tunicamycin treatment reduced the apparent mol. wt. of the expressed protein to the mol. wt. of unglycosylated HN protein which is calculated from the nucleotide sequence.4) Four recombinant BV carrying F protein genes of virulent and avirulent strains of NDV with two different forms, intact and truncate form which lacks a C-terminal membrane anchor domain, were constructed the expressed proteins were analyzed. Only intact form of the F protein of virulent strain was proteolytically cleaved into F_1 and F_2 subunits which were bound intermolecularly by disulfide bound. Less