Expression of Histophilus somni IbpA DR2 protective antigen in the diatom Thalassiosira pseudonana

• Published in: Applied microbiology and biotechnology 2017-07, Vol.101 (13), p.5313-5324
• Main Authors: Davis, Aubrey, Crum, Lauren T., Corbeil, Lynette B., Hildebrand, Mark
• Format: Article
• Language: English
• Subjects: adjuvants; Algae; Animals; Antibodies, Bacterial; Antigens; Antigens, Bacterial - biosynthesis; Antigens, Bacterial - genetics; Antigens, Bacterial - immunology; Aquatic microorganisms; Bacillariophyceae; Bacterial Vaccines - genetics; Bacterial Vaccines - immunology; Biomedical and Life Sciences; Biotechnologically Relevant Enzymes and Proteins; Biotechnology; bovine respiratory disease; Carbon dioxide; Carbon Dioxide - metabolism; Carbon Dioxide - pharmacology; Cattle; Cattle Diseases - microbiology; Cattle Diseases - prevention & control; Cell culture; Cell division; Cell walls; Cultivation; Diatoms; Diatoms - drug effects; Diatoms - genetics; Diatoms - growth & development; Diatoms - metabolism; Flux; Gene expression; genes; Genetic aspects; Haemophilus somni; Identification and classification; Immune response; Immune system; Immunization; Life Sciences; Light; Mice; microalgae; Microbial Genetics and Genomics; Microbiology; Pasteurella; Pasteurellaceae - genetics; Pasteurellaceae Infections - immunology; Pasteurellaceae Infections - prevention & control; Pasteurellaceae Infections - veterinary; Plankton; Protective antigen; Protein expression; Protein purification; protein synthesis; Proteins; recombinant proteins; Recombinant Proteins - administration & dosage; Recombinant Proteins - biosynthesis; Recombinant Proteins - immunology; Recombinant Proteins - isolation & purification; Respiratory diseases; Respiratory Tract Infections - immunology; Respiratory Tract Infections - microbiology; Respiratory Tract Infections - prevention & control; Respiratory Tract Infections - veterinary; Silicon; Silicon - pharmacology; Sodium dodecyl sulfate; Supplements; Thalassiosira; Transcription; transcription (genetics); Transcription Factors - genetics; Transcription Factors - metabolism; vaccines; Vaccines, Synthetic - administration & dosage; Vaccines, Synthetic - genetics; Vaccines, Synthetic - immunology; Walls
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-017-8267-8

Increasing demand for the low-cost production of valuable proteins has stimulated development of novel expression systems. Many challenges faced by existing technology may be overcome by using unicellular microalgae as an expression platform due to their ability to be cultivated rapidly, inexpensively, and in large scale. Diatoms are a particularly productive type of unicellular algae showing promise as production organisms. Here, we report the development of an expression system in the diatom Thalassiosira pseudonana by expressing the protective IbpA DR2 antigen from Histophilus somni for the production of a vaccine against bovine respiratory disease. The utilization of diatoms with their typically silicified cell walls permitted development of silicon-responsive transcription elements to induce protein expression. Specifically, we demonstrate that transcription elements from the silicon transporter gene SIT1 are sufficient to drive high levels of IbpA DR2 expression during silicon limitation and growth arrest. These culture conditions eliminate the flux of cellular resources into cell division processes, yet do not limit protein expression. In addition to improving protein expression levels by molecular manipulations, yield was dramatically increased through cultivation enhancement including elevated light and CO 2 supplementation. We substantially increased recombinant protein production over starting levels to 1.2% of the total sodium dodecyl sulfate-extractable protein in T. pseudonana , which was sufficient to conduct preliminary immunization trials in mice. Mice exposed to 5 μg of diatom-expressed DR2 in whole or sonicated cells (without protein purification) exhibited a modest immune response without the addition of adjuvant.