FIG. 4.
Western blot demonstrating the reactivity of sera from vaccinated (+) and unvaccinated (−) birds against four O. rhinotracheale serotype A and G in vitro-expressed antigens with molecular masses ranging from 40 to 65 kDa. Note that the reactivity of the 40-kDa protein of O. rhinotracheale serotype G is very weak (indicated with an arrow).