Figure 3.

Immunogenic comparison of in-ovo and post-hatch vaccination with NDV vaccine strains. Commercial chickens were in-ovo or post-hatch vaccinated with the indicated NDV vaccine strains and challenged with virulent NDV strain HB0901 at 28 dph. (A) The NDV-specific hemagglutinin-inhibition antibody titers of immunized birds before challenge. (B) Survival percentages of birds after challenge with virulent NDV. Statistical significances in survival between different groups were analyzed by Log Rank test. (C, D) Percentages of CD3⁺ CD8⁺ and CD3⁺ CD4⁺ subsets of the splenic lymphocytes collected from vaccinated birds at the indicated dph. Statistical significance in the percentages of splenic lymphocyte was determined by 2-tailed t-test (ns, P > 0.05; *, P < 0.05; **, P < 0.01).