Detection of Avian Influenza Anti-H5 Maternally-derived Antibodies and Its Impact on Antibody-mediated Responses in Chickens after In Vivo Administration of Inactivated H5N9 Vaccine

In the current study, two experiments were performed to ascertain the existence of avian influenza H5 maternallyderived antibodies (MDA) in chickens and evaluate their effects on the humoral immune responses of chickens vaccinated with a commercial oil-emulsion inactivated avian influenza H5N9 vaccine.A total of 120 one-day-old ISA brown chicks were sourced from three different commercial hatcheries (n = 40 per hatchery) in Nigeria and used for this study.For the second experiment, ten chicks were randomly collected from each hatchery and grouped into A0, B0, and C0 at one day old, and one ml of blood was collected from five randomly selected chicks via the heart or brachial vein at 1, 7, 14, 21, 28, 35, and 42 days of age for the assessment of avian influenza H5 MDA.For the second experiment, 2 ml of blood was collected from the heart or brachial vein of 3 randomly selected chicks from each subgroup at 14, 21, 28, 35, and 42 days of age for evaluation of the interaction of MDA with anti-avian influenza vaccinal antibodies when different doses of the H5 antigen was administered via either IM or SC routes at 14 and 28 days of age.Sera were analyzed using ProFlok ® AIV ELISA kit.This study detected AIV H5 MDA in all chicks sampled, with total decay times of 22.3, 27.3, and 26 and mean half-life (t 1/2 ) of 2.5 ± 0.4, 3 ± 0.6, and 2.9 ± 0.4 days for chicks from hatcheries A, B, and C. The obtained results of the second experiment showed that at 21 days of age, the mean antibody titer levels of chicks from A1, B1, and C1 were respectively 57.7 ± 49.9, 260.7 ± 124.8, and 2205 ± 409.1 when the antigen was administered IM and the reported values for SC administration were respectively 53.3 ± 36, 646.3 ± 237.9 and 2,444.3± 1,110.6.This means that variable MDA titers interfered with the humoral immune responses of the chick's post-vaccination.Chicks may, therefore, be vaccinated against AIV H5 subtypes between day 14 and 21 of age, preferable via the SC route to avoid significant interference by AIV H5 MDA.