The inhibitory capacities of the induced rat and rabbit antibodies following FV2 immunizations were very high. However, the different species-specific inhibitory FV2 antibodies do not necessarily target the same epitopes, but further analysis of the epitope targets of FV2 specific antibodies are needed to elucidate the mechanism of inhibition. For immunizations with single domains, the inhibition of IE binding to CSA varied between animal species. Only rats immunized with DBL4e induced IgG, which efficiently inhibited IE binding, whereas the rabbit sera specific against DBL4e were non-inhibitory. The inhibitory effect of the IgG was not an effect of antibody titer, since immunizations with DBL5e and DBL6e also induced high titers, but these were in general non-inhibitory. These findings are in contrast to what others have found [21, 28] . Differences in observations could be due to different domain boundaries or to the variance in posttranslational protein modifications introduced for example by the baculovirus transfected T. ni as opposed to the Pichia pastoris expression system, such as differences in glycosylation pattern.