Interfering of maternal derived antibodies with the protection of local inactivated reassortant H5N1 Avian influenza vaccines with antigenic content of 300 HA units in commercial broiler chickens
Interfering of maternal derived antibodies with the protection of local inactivated reassortant H5N1 Avian influenza vaccines with antigenic content of 300 HA units in commercial broiler chickens
Maha M. Khedr1, Reem A. Suliman1, Marwa F. Mohamed1, Mounir D. El Safty1, Hussein A.
Hussein2
ABSTRACT
Background: Influenza virus is an Orthomyxovirus that known as one of the causes of significant
numbers of natural infections and disease, mainly infecting the upper respiratory tract, in humans,
domestic pigs, horses, and numerous bird species. Maternal derived antibodies could interfere with the
efficacy of vaccination against avian influenza in early age in chicks.
Methods: Eight groups of one-day old commercial broiler chicks were kept in isolators along the whole
period of the study. Groups 1, 2 and 3 were vaccinated with the prepared vaccine; group 4, 5 and 6 were
vaccinated with one of the imported reassortant H5N1 containing 300 HAU at 1, 5 and 10 days of age;
respectively. Groups 7 and 8 were positive and negative groups for the challenge trial. Blood samples
were collected weekly for 4 weeks of age and tested by HI test. Post challenge, tracheal and cloacal swabs
were collected at 3, 5, 7, and 10 days and tested by both real time RT-PCR (rRT-PCR) and virus titration
in SPF eggs.
Results: HI test revealed no significant difference between groups in the first 3 weeks post vaccination
and group 2 showed lower significant statistical difference. Results of the challenge trial revealed 0, 14,
80 % and 0, 14 and 86 % of protection in groups 1,2,3 and groups 4, 5, and 6; respectively. RT-PCR and
virus isolation revealed that all chicken groups vaccinated at 1 and 5 days of age demonstrated 100%
shedding at 3, 5, 7 and 10 days post challenge. However, groups 3 and 6 which were vaccinated at 10
days of age revealed difference in shedding pattern where group 3 (vaccinated with local prepared
vaccine) showed 100 shedding by rRT-PCR and 100%, 60% and 60 % of the chickens in tracheal swabs
and 100%, 80% and 60%in cloacal swabs when tested by virus isolation in eggs at 3, 5 and 7 days post
challenge; respectively. Swabs of 10 days post challenge of group 3 were positive by rRT-PCR and
negative by virus isolation. On the other hand, group 6 (vaccinated with imported vaccine) demonstrated
shedding % at 3 and 5 days post challenge by both rt-RT-PCR and virus isolation were positive in 60%
and 20% for tracheal and 80% and 20% for cloacal swabs ; respectively. At 7 and 10 days shedding of all
chickens in group 6 were negative by both rRT-PCR and virus isolation.
Conclusion: Indeed, there is evidence of interfering of maternal antibodies to vaccination at 1, and 5 days.
Also, the 300 HAU of antigen in the prepared avian influenza H5N1 vaccine are not enough in reducing
of virus shedding post challenge.
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July 2018
Vol. 4, Pages 1-71
