The oncosphere-killing assay was used to test for the production of anti-EG95 effector antibodies; a correlate of protective immunity. The oncosphere-killing assay is dependent on complement-fixing antibody, and all IgG antibodies are capable of binding complement. Heath et al. (23) have shown that in sheep, both IgG2 and IgG1 anti-EG95 antibodies are equally effective in this assay. The oncosphere-killing assay showed that biologically relevant effector antibodies were elicited by VV399. These molecules were fully effective at a serum dilution of 1 : 4 (50 μL of diluted serum and 50 oncospheres in

the culture). It is tempting to speculate that these mice would have been refractory to an oral challenge with E. granulosus click here eggs, as described by Dempster et al. (24). Consistent with the mouse experiments, there was evidence of a priming response in sheep from an infection with VV399. Sheep primed with VV399 and boosted with EG95 protein produced an antibody response that correlated with antibody levels that could potentially afford 90% protection against an oral challenge of 2000 freshly collected E. granulosus eggs. Heath et al. (16) have established that serology can be used to validate batches of

the EG95-based vaccine by immunizing AZD6244 manufacturer sheep and then determining the ELISA absorbance 2 weeks after the second immunization. Their study concluded that the correlation between ELISA absorbance and degree of protection against a challenge infection with E. granulosus eggs explained 50% of the variation in results and was sufficiently strong to allow serology to be used as validation for new batches of recombinant vaccine and thus STK38 obviate any need to perform challenge experiments and necropsy at 12 months (minimum) post-infection. In support of these findings, we observed that

anti-EG95 antibody levels determined by ELISA correlated significantly with effector antibody levels determined in the oncosphere-killing assay. We have used recombinant VACV as a model system to gain some insight into whether a viral vector expressing EG95 can elicit protective immunity against E. granulosus. Our results demonstrate that both a priming and secondary response can be induced against this organism and are consistent with studies in possums immunized by oronasal inoculation with VV399 (15). In addition, a priming response has also been shown where EG95 is delivered using recombinant parapoxvirus (orf virus) and infection of sheep by scarification (25). Some VACV recombinants have been shown to effectively immunize against other viruses (19) and also against the protozoan disease Leishmania (26) after only a single vaccination dose. The immunological basis for this appears to lie in the complex nature of the immune response against viruses that involve IFN producing cells, cytotoxic T cells and neutralizing antibody. The protective response against E.