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LTB consisted of five identical polypeptides and, as a pentameric form, has been demonstrated to bind to the GM1 ganglioside at cellular surface. The recombinant LTB has attracted much attention due to its non-toxicity and potential as a strong immunogenic antigen and immuno adjuvant for both system and mucosal immune responses. Actinobacillus pleuropneumoniae is the causal agent of swine pleuropneumoniae, a disease resulting in morbidity and mortality of pigs and accordingly economic losses within the swine industry. Toxins (APX) produced by A. pleuropneumoniae appear to be important virulence factors of swine pleuropneumoniae and are thought to be of particular importance in the induction of protective immunity. In order to use S.cerevisiae for effective delivery of APX to the gut-associated lymphoid tissue, a chimeric APX fused with LTB subunit (LTB::APX) was constructed and tested for the oligimerization, which enables the chimeric complex to bind the intestinal membrane GM1-ganglioside receptor. Westhern blot ananlysis and ELISA indicated that a chimeric fusion protein was produced in recombinant S. cerevisiae. However, assembly into the native pentameric structure did not occur probably due to the stearic hindrance caused by the increased size of LTB::APX fusion construct. Therefore, co-expression strategy using episomal and integrative vectors for LTB and LTB::APX, respectively, was adapted for the oligomerization of LTB and LTB::APX fusion construct. GM1-ELISA indicated that the LTB::APX fusion construct, along with the LTB, was oligomerized to make the functional pentameric form. APX-specific antibody was observed when the recombinant yeast expressing both LTB as well as LTB::APX was orally administered. Antibody titer of orally administered mouse was enhanced when using the recombinant yeast expressing the pentameric form instead of recombinant yeast expressing either LTB::APX fusion only or APX alone. Better protection against challenge of A. pleuropneumoniae was also observed in the case of recombinant yeast compared to others. This study clearly indicated that the coexpression strategy enable the LTB::APX fusion construct to participate the pentameric formation, which resulted in facilitating the uptake of the recombinant protein through the GM1-ganglioside. Through which, an improved induction of systemic immune responses was achieved, which resulted in better protective response against the A. pleuropneumoniae challenge.