الفهرس Only 14 pages are availabe for public view
 |  | from | 223 |  |  |
| | | from | 223 | | |
Abstract
In the present study, DNA plasmid constructed to encode HA1 fragment of HA gene of selected Egyptian H5N1 virus from 2012 circulating viruses which was isolated from breaks in commercial chickens. In a challenge trial, SPF chicks received one and two doses of the H5-DNA plasmid were used to prime the inactivated H5N2 vaccine and the immune response, protection, and virus shedding were determined compared to the groups of SPF chicks received either DNA plasmid or inactivated H5N2 vaccine alone. Positive and negative control groups were also included. Purified Egyptian H5N1 challenge virus A/chicken/Egypt/128s/2012(H5N1) HPAI clade 2.2.1/C was used in the trial. Results showed that SPF chickens received H5-DNA vaccine in one or two doses were not able to overcome the challenge virus with 0% and 10% protection; respectively. Results of qRTPCR for virus confirmation revealed virus shedding of 2.2 x 104 at 3 days post challenge in 1 survived bird of the group received 2 doses of plasmids with 10 days interval. Whereas, the SPF chicks received one or two doses of H5-DNA plasmid prime to vaccination with H5N2 vaccine showed 80% protection after challenge with virus shedding of 1.2 x 104 and 1.6 x104 at 3 days post challenge; respectively. Both groups did not shed the virus from the survived birds at 5 and 7 days post challenge. In the H5N2 vaccinated birds, the protection was 70% with high virus shedding 1.8x 104 in the survived birds at 3 days post challenge. All chicks in the positive control group died. HI titers in the birds in the trial were sufficient to protect the survived chicks. The study reports the efficacy of H5-DNA plasmid to reduce the shedding of the challenge HPAI H5N1 virus when applied in prime-boost program at one day old in combination with the inactivated AI vaccine at 10 days old