Protection of chickens from Newcastle and Marek's diseases with a recombinant herpesvirus of turkeys vaccine expressing the Newcastle disease virus fusion protein.

Recombinant strains of herpesvirus of turkeys (HVT) were constructed that contain either the fusion protein gene or the hemagglutinin-neuraminidase gene of Newcastle disease virus (NDV) inserted into a nonessential gene of HVT. Expression of the NDV antigens was regulated from a strong promoter element derived from the Rous sarcoma virus long terminal repeat. Recombinant HVT strains were stable and fully infectious in cell culture and in chickens. Chickens receiving a single intra-abdominal inoculation at 1 day of age with recombinant HVT expressing the NDV fusion protein had an immunological response and were protected (> 90%) against lethal intramuscular challenge at 28 days of age with the neurotropic velogenic NDV strain Texas GB. Recombinant HVT expressing the NDV hemagglutinin-neuraminidase provided partial protection (47%) against the same challenge. Chickens vaccinated with recombinant HVT vaccines had low levels of protection against NDV replication in the trachea when challenged ocularly. Recombinant HVT vaccines and the parent HVT strain provided similar levels of protection to chickens challenged with the very virulent RB1B strain of Marek's disease virus, indicating that insertion of foreign sequences into the HVT genome did not compromise the ability of HVT to protect against Marek's disease.

Demonstration of the genetic stability of a Mycoplasma gallisepticum strain following in vivo passage.

A Mycoplasma gallisepticum strain designated 6/85 (MGI) exhibiting reduced virulence for both chickens and turkeys was sequentially passaged 10 times in each species. DNA extracted from organisms before passage and those isolated after the third, sixth, and 10th passages was studied by restriction endonuclease DNA analysis using BamHI, BglII, EcoRI, HindIII, and PstI endonucleases. The virulent-type strain designated S6 was used as a comparison. Comparison of DNA fragment patterns of MGI and S6 strains showed distinct differences, although some similarities were evident. Passage of the strain in vivo did not affect DNA fragment patterns of the MGI strain. Electrophoretic protein patterns produced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed very similar band patterns in both the MGI and S6 strains. The most notable differences were seen in bands located in the molecular-mass regions of approximately 46.5, 50-54, 58-64, and 105-140 kilodaltons. Alteration of band pattern profiles following in vivo passage of the MGI strain was apparent in a single band at approximately 86 kilodaltons that appeared to stain more intensely following passage.

Pseudorabies virus glycoprotein gI: in vitro and in vivo analysis of immunorelevant epitopes.

Overlapping fragments of the gene encoding glycoprotein gI of pseudorabies virus (PRV; herpesvirus suis 1) were expressed in bacteria. Using the fusion proteins and a panel of monoclonal antibodies (MAbs) against gI as well as swine sera we found that the N-terminal part of gI (residues 33 to approximately 100) contains a highly antigenic and immunogenic domain. Transfer of antibodies binding to this region as well as vaccination with fusion proteins containing the N terminus of gI are able to confer protection to mice against a lethal challenge of virus. The results show that gI, which is non-essential for virus replication in tissue culture, can induce neutralizing and protective antibodies. The potential suitability of fusion proteins encompassing N-terminal parts of gI as diagnostic tools is demonstrated.