Abstract
BackgroundLive anticoccidial vaccines have been a tremendous success for disease prevention. The establishment of the reverse genetic manipulation platform has enabled the development of Eimeria parasites, the live anticoccidial vaccine strains, as vaccine vectors. In our previous study, recombinant E. tenella expressing a single immunodominant antigen of E. maxima (Et-EmIMP1) was able to protect chickens against challenge infection with E. maxima. This promising result encouraged us to further explore strategies to improve the protection efficacy of recombinant Eimeria and develop it as a vaccine vector.ResultsWe constructed a novel recombinant Eimeria line expressing apical membrane antigen 1 of E. maxima (Et-EmAMA1) and then immunized chickens with Et-EmAMA1 and/or Et-EmIMP1. We found that the E. maxima soluble antigen-specific cell-mediated immunity was much stronger in the birds that were co-immunized with Et-EmAMA1 and Et-EmIMP1 than in those that were immunized with Et-EmAMA1 or Et-EmIMP1 alone. The oocyst production after E. maxima infection was significantly reduced in the recombinant Eimeria-immunized birds compared with the wild-type-immunized and naïve birds. The oocyst production in the birds co-immunized with Et-EmAMA1 and Et-EmIMP1 was consistently the lowest among the treatment groups after E. maxima infection.ConclusionsThese results demonstrated that Eimeria is an effective vaccine vector that can carry and deliver heterologous Eimeria antigens to the host immune system and trigger specific immune responses. Our results also suggested that increasing the number of recombinant Eimeria lines is an effective approach to enhance protective immunity against infections with heterologous pathogens.
Highlights
Live anticoccidial vaccines have been a tremendous success for disease prevention
The transfection plasmid, pSDEP2AAMA1S (Fig. 1a) was constructed based on the previously constructed pSDEP2AIMP1S plasmid [12]. This new plasmid contains a single expression cassette in which the selected marker gene and EmAMA1 gene tagged with the flag epitope were linked by a P2A sequence, which mediates the cleavage of the dual flanking proteins [24]
Et‐EmAMA1 elicited E. maxima antigen specific cellular immunity In our previous study, we demonstrated that exogenous antigen, i.e. EmIMP1, expressed by Eimeria efficiently elicited EmIMP1 and E. maxima antigen-specific immune responses [12]
Summary
Live anticoccidial vaccines have been a tremendous success for disease prevention. The establishment of the reverse genetic manipulation platform has enabled the development of Eimeria parasites, the live anticoccidial vaccine strains, as vaccine vectors. Recombinant E. tenella expressing a single immunodominant antigen of E. maxima (Et-EmIMP1) was able to protect chickens against challenge infection with E. maxima This promising result encouraged us to further explore strategies to improve the protection efficacy of recombinant Eimeria and develop it as a vaccine vector. Eimeria vectors carrying immunoprotective or immunodominant antigen(s) of heterologous Eimeria species to elicit cross-protective immunities against the parental and heterologous Eimeria species is a novel strategy to develop next-generation coccidiosis vaccines. Using this strategy, one or several Eimeria species of the vaccine formulation can be removed, which can reduce the adverse pathological reaction caused by vaccination. The cost will be reduced and the safety will be improved for the novel coccidiosis vaccines [12, 16]
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