Figure 8.

The protective efficacy of rNDV expressing codon optimized S protein of IBV against IBV challenge in immunized SPF chicks at 1-day-old age, by the intraocular (IO) challenge route. (A) Respiratory clinical signs of IBV following challenge with virulent IBV strain Mass-41. Three weeks after immunization, chickens were challenged with 10⁴ EID₅₀ of a virulent IBV strain Mass-41 by the intraocular route. The severity scores of IBV clinical signs, described in the legend of Fig. 1, were recorded twice a day for each chicken for 10 days after challenge. The severity score represents as average score of clinical signs measured for each chicken over 10 days. (B) Each tracheal fluid was tested for IBV specific lesions on chicken embryo by inoculation (0.2 ml) of five 10-day-old embryonated SPF chicken egg. IN = intranasal