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Biomedical subjects

R W Morgan

Publications and source records attributed to R W Morgan.

114 records · Page 7Linked to original sources
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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.

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Inhibition of Marek's disease virus DNA transfection by a sequence containing an alphaherpesvirus origin of replication and flanking transcriptional regulatory elements.

A co-transfection method was used to identify regions of the Marek's disease virus (MDV) genome that inhibit plaque formation when introduced along with total DNA from MDV-infected chicken embryo fibroblasts into secondary chicken embryo fibroblasts. Co-transfections involving MDV plasmids containing the BamHI-D or BamHI-H regions of the genome inhibited plaque formation more than 10-fold. The inhibitory region was localized to a 222-base-pair region that contains a sequence homologous to the consensus origin of replication of alphaherpesviruses. The region also contains several potential transcriptional regulatory elements, including two CCAAT boxes, one Sp1 binding site, and an octamer element. The sequence of this region has been reported previously. Transfection inhibition was also observed for the BamHI-I2 region, although the effect was weaker.

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Transfection of chicken embryo fibroblasts with Marek's disease virus DNA.

Total DNA from Marek's disease virus (MDV)-infected chicken embryo fibroblasts was transfected into freshly plated secondary chicken embryo fibroblasts using calcium phosphate-mediated transfection. Transfection frequencies were dose-dependent and non-linear. The maximum transfection frequencies of nine MDV DNA preparations using 8-25 micrograms total DNA ranged from 45 to 898 plaques per calcium phosphate/DNA precipitate. Approximately 100-200 plaques per 60-mm tissue-culture dish using 1-5 micrograms total DNA from MDV-infected chicken embryo fibroblasts were typically obtained. Transfection was most efficient when the pH of the HEPES buffer was 7.0, no additional carrier DNA was added to the precipitates, and the cultures were exposed for 3 minutes to 15% buffered glycerol 4 hours after the addition of the calcium phosphate/DNA precipitates.

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Epidemiology↗
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Efficacy in chickens of a herpesvirus of turkeys recombinant vaccine containing the fusion gene of Newcastle disease virus: onset of protection and effect of maternal antibodies.

The onset of protection against Newcastle disease and the effect of maternal antibodies to Newcastle disease virus (NDV) and Marek's disease virus (MDV) on vaccine efficacy were determined following vaccination of chickens with a recombinant herpesvirus of turkeys (HVT) vaccine expressing the fusion (F) glycoprotein gene of NDV. Onset of protection following intra-abdominal administration of the recombinant HVT/F vaccine at 1 day of age and subsequent ocular challenge with the neurotropic velogenic Texas GB strain of NDV was determined to occur between days 14 and 21 post-vaccination (PV). Vaccination with the Hitchner B1 strain of NDV resulted in protection by day 6 PV, and vaccination with an inactivated NDV oil-emulsion vaccine induced protection by day 14 PV. One-day-old broiler-type chickens with maternal antibodies to both NDV and MDV and 1-day-old specific-pathogen-free (SPF) white leghorn chickens lacking maternal antibodies were vaccinated with the recombinant HVT/F vaccine or with control vaccines, challenged intra-abdominally with the very virulent RB1B strain of MDV on day 8 PV, and challenged with the Texas GB strain of NDV on day 29 PV. The HVT/F and NDV strain Hitchner B1 vaccines provided 73% and 80% protection, respectively, against NDV in broilers, whereas both vaccines resulted in 100% protection in SPF leghorns.

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