Objective To clone and construct a recombinant expression plasmid for rhoptry protein 18of Toxoplasma gondii in Escherichia coli Methods PCR primers were designed based on the rhoptry protein 18sequence of T.gondii in GenBank.Fragments were amplified using apolymerase chain reaction and then cloned into the vector pET-28a.The recombinant plasmid was transformed into BL21-competent cells of E.coli and induced using IPTG.The expression of the recombinant plasmid was analyzed using SDS-PAGE and Western blottin...