Novelty in Biomedicine NBM 16 Novelty in Biomedicine 2017, 1, 16-23 Original Article Expression of Leishmania major LmSTI1 in Yeast Pichia Pastoris Mehdi Shokri 1,4 , Soheila Ajdary* 1 , Mina Ebrahimi-Rad 2 , Arash Memarnejadian 3 , Mohamad-Hossein Alimohamadian 1 , Fatemeh Motevali 3 , Farzin Roohvand 4* 1 Immunology Department, Pasteur Institute of Iran, Tehran, Iran 2 Biochemistry Department, Pasteur Institute of Iran, Tehran, Iran 3 Hepatitis and AIDS Department, Pasteur Institute of Iran, Tehran, Iran 4 Virology Department, Pasteur Institute of Iran, Tehran, Iran Received: 27 Feburary, 2016; Accepted: 19 June, 2016 Abstract Background: Leishmania major LmSTI1 is a conserved protein among different species of leishmania, and expressed in both amastigote and promastigote forms of L. major life cycle. It has previously been expressed in bacterial systems. Materials and Methods: To express LmSTI1 in the methylotrophic yeast Pichia pastoris (P. pastoris), the shuttle vector pPICZA containing gene lmsti1 was constructed under the control of the AOX1 promoter. The recombinant vector was electro-transformed into P. pastoris, and induced by 0.5% methanol in the buffered medium. The expression of the LmSTI1 protein was visualized in the total soluble protein of P. pastoris by 12% SDS-PAGE, and further confirmed by Western blotting with L.major-infected mouse sera and HRP- conjugated goat anti-mouse IgG as the first and secondary antibodies, respectively. Results: The expression level was 0.2% of total soluble proteins. Conclusion: It might be possible to use this formulation as a whole yeast candidate vaccine against cutaneous leishmanization. Keywords: Pichia pastoris, LmSTI1, Leishmania major * Equally as corresponding authors: Soheila Ajdari, Immunology Department, Pasteur Institute of Iran, Tehran, Iran. Email: sohary@yahoo.com Farzin Roohvand, Virology Department, Pasteur Institute of Iran, Tehran, Iran. Email: farzin.roohvand@gmail.com Please cite this article as: Shokri M, Ajdary S, Ebrahimi-Rad M, Memarnejadian A, Alimohamadian M H, Motevali F, Roohvand F. Expression of leishmania major LmSTI1 in yeast Pichia pastoris. 2017;5(1):16-23. Introduction Leishmaniasis is an endemic disease, ranging from localized cutaneous to visceral forms. Cutaneous leishmaniasis is caused by different leishmania parasites including leishmania major (L.major) , L. tropica, L. aethiopica, L. mexicana, L. guyanensis, L. peruviana, and L. braziliensi 1,2 . According to WHO estimation, the annual incidence of leishmaniasis in new cases is about 2 million people worldwide, most of which (1.5 million) suffer from cutaneous leishmaniasis (http://www.who.org). Leishmaniasis is primarily mediated by T lymphocytes. To neutralize intracellular parasitic infections such as leishmania, cellular immunity was demonstrated to play a critical role in inducing protective immunity 3 . In mouse models of leishmania infection, the Th1 response phenotype is observed in protected animals such as C57BL/6 mice by increasing IFN-gamma and TNF-alpha while the Th2 response phenotype producing IL-4 and IL-5 is associated with susceptibility or disease progression 4-6 . In the