Leishmania mexicana recombinant filamentous acid phosphatase as carrier for Toxoplasma gondii surface antigen 1 expression in Leishmania tarentolae.

Leishmania tarentolae has been used to produce recombinant intracellular and secreted proteins for their easy handling and posttranslational modifications. Filamentous acid phosphatase is a multimeric protein complex composed of many subunits assembled in a linear highly glycosylated filament, which is secreted in vast amounts into the culture supernatant via the flagellar pocket of Leishmania mexicana promastigotes. This suggested that the protein could be used as a carrier for the Surface Antigen1 protein of a Toxoplasma gondii (SAG1) for easy purification to generate a protein with multiple SAG1 subunits suitable for immunisation. SAG1 has an immunodominant structure that is involved in binding to host cells. Previous studies used this surface protein for vaccination for its immunological importance for triggering a type 1 immune response in the host. This study aims to determine the production of recombinant filamentous protein carried subunits of the surface protein of Toxoplasma gondii for vaccination purposes. Leishmania codon-optimised SAG1 was cloned as a fusion construct into pLEXSY-ble2.1 plasmid and introduced into Leishmania tarentolae to generate recombinant cell lines expressing a filamentous fusion protein called SAP2SAG1. PCR confirmed the correct integration into the small ribosomal subunit RNA gene locus of Leishmania tarentolae. Immunofluorescences and Immunoblot analyses were used to detect the fusion protein in the sediment of culture supernatants of recombinant L. tarentolae promastigotes after purification by ultracentrifugation. The yield of purified protein was low that suggested further investigations of other methods for scaling large production of secreted protein.