Recombinant truncated tilapia growth hormone enhances growth and innate immunity in tilapia fry (Oreochromis sp.)

Pichia pastoris cells transformed with a plasmid engineered for the expression of tilapia growth hormone as a secreted product produced a proteolytically cleaved form of the recombinant protein. The sequence of this truncated variant was obtained by mass spectrometry analysis. The cleavage site was determined to be between residues Tyr 158 and Tyr 159. The resulting truncated tilapia growth hormone was a single chain protein lacking 46 amino acids of the C-terminal portion. In this study, we showed that the truncated growth hormone produced in the P. pastoris culture supernatant has growth promoting effects and stimulates innate immune parameters (lysozyme and lectins) in tilapia larvae. These results suggest that the C-terminal portion of growth hormone is not required for its growth promoting activity and the innate immune functions studied herein in fish. In addition, we found that the culture supernatant containing truncated tilapia growth hormone has a stronger effect over growth and immune system than cells lysate containing intact tilapia growth hormone expressed in P. pastoris.