Abundance of IFN-α and IFN-γ gene transcripts and absence of IL-2 transcripts in the blood of chickens vaccinated with live or inactivated NDV.

As immune responses to live and inactivated vaccines might differ, temporal responses of broiler chickens to vaccination were examined on the basis of the abundance in the circulating blood of gene transcripts of IFN-α, IFN-γ and IL-2, critical cytokines for immune responses. Blood samples were collected 6, 12 and 24 hours, and 7 and 14 days following vaccination with either live or inactivated Newcastle disease virus, La Sota strain, at 14 days of age, and the abundance of transcripts for each cytokine was assayed by real-time RT-PCR. Physiological saline and vaccine emulsion without viral antigen were administered to control groups for live and inactivated vaccine groups, respectively. The abundance of IFN-γ transcripts was elevated during the early times following vaccination and had reached baseline by the seventh day but the abundance of IFN-α transcripts remained elevated. Transcripts for neither IFN gene were detected in the control birds. The abundance of transcripts for each IFN was not different between the two vaccinated groups at any time. Transcripts for IL-2 were detected only in spleens from chicken embryos that had been inoculated with the live virus. The results show that cells stimulated to produce IFN-α and IFN-γ enter the circulating blood but those stimulated to produce IL-2 do not, or in very low number, and the IFN responses to both vaccines are the same.

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