Abstract: Disclosed is a transformed microalga including a nucleic acid sequence operatively linked to a promoter, wherein the nucleic acid sequence encodes an amino acid sequence including (i) an heterologous signal peptide; and (ii) a therapeutic antibody, a functional fragment or a derivative thereof, the transformed microalga expressing the therapeutic antibody, functional fragment or derivative thereof secreted in the extracellular media and the microalga being selected among green algae except Volvocales, and among red algae, chromalveolates, and euglenids. Preferably, therapeutic antibody, functional fragment or derivative thereof has an increased antibody-dependant cell-mediated cytotoxicity (ADCC) and a low fucose content.

Abstract: The present invention concerns a transformed microalga producing a protein harboring a “high mannose” pattern of glycosylation in the plastid of the transformed microalga, wherein 1) the transformed microalga has a Chloroplast Endoplasmic Reticulum (CER); 2) the microalga has been transformed with a nucleic acid sequence operatively linked to a promoter, the nucleic acid sequence encoding an amino acid sequence including (i) an amino-terminal bipartite topogenic signal (BTS) sequence composed of at least a signal peptide followed by a transit peptide; and (ii) The sequence of the protein, 3) the xylosyltransferases and fucosyltransferases of the microalga have not been inactivated; 4) the N-acetylglycosyltransferase I of the microalga has not been inactivated, preferably the N-acetylglycosyltranferases II, III, IV, V and VI, mannosidase II and glycosyltransferases of the microalga have not been inactivated.

Abstract: A transformed diatom includes a nucleic acid sequence operatively linked to a promoter, wherein the nucleic acid sequence encodes an amino acid sequence including (i) an heterologous signal peptide and (ii) a polypeptide, the heterologous signal peptide leading to the secretion of the polypeptide in the extracellular medium of the transformed diatom; a method for producing a polypeptide which is secreted in the extracellular medium, the method including the steps of (i) culturing a transformed diatom, (ii) harvesting the extracellular medium of the culture and (iii) purifying the secreted polypeptide in the extracellular medium; and use of the transformed diatom for the secretion of a polypeptide in the extracellular medium.