Oral administration of the probiotic bacterium strain L-55 modulates the immunological parameters of the laying hen inoculated with a Newcastle disease virus-based live attenuated vaccine.

Probiotic supplements containing living bacteria have attracted interest as a potential source of health benefits for humans and livestock. The aim of this study was to determine whether administration of strain L-55 (LaL-55) enhances the immune response among chicks exposed to a Newcastle disease virus (NDV)-based live attenuated vaccine. Oral administration of LaL-55 augmented the elevation in the total numbers of leukocytes and lymphocytes following inoculation with the NDV-based live attenuated vaccine. Monocyte counts increased after LaL-55 administration independent of inoculation with the NDV vaccine. Among chicks that were administered LaL-55, there was a dose-dependent increase in the NK cell activity measured by a Cr release assay at 2 weeks after the secondary NDV vaccine inoculation. Two weeks after the secondary inoculation with the NDV vaccine, interferon (IFN)-γ-mRNA expression was significantly elevated in mononuclear splenocytes from chicks that were administered LaL-55. Meanwhile, LaL-55 administration did not change the mRNA levels of IFN-α, IFN-β, and interleukin-1β. These results may suggest that coadministration of LaL-55 with an NDV vaccine augments the immune response against the virus. Therefore, LaL-55 may help protect against viral diseases in poultry.