Faculty Opinions recommendation of Co-expression of human calreticulin significantly improves the production of HIV gp140 and other viral glycoproteins in plants.

Plant molecular farming (PMF) is rapidly gaining traction as a viable alternative to the currently accepted paradigm of producing biologics. While the platform is potentially cheaper and more scalable than conventional manufacturing systems, expression yields and appropriate post-translational modifications along the plant secretory pathway remain a challenge for certain proteins. Viral fusion glycoproteins in particular are often expressed at low yields in plants and, in some cases, may not be appropriately processed. Recently, however, transiently or stably engineering the host plant has shown promise as a strategy for producing heterologous proteins with more complex maturation requirements. In this study we investigated the co-expression of a suite of human chaperones to improve the production of a human immunodeficiency virus (HIV) type 1 soluble gp140 vaccine candidate in Nicotiana benthamiana plants. The co-expression of calreticulin (CRT) resulted in a dramatic increase in Env expression and ameliorated the endoplasmic reticulum (ER) stress response - as evidenced by lower transcript abundance of representative stress-responsive genes. The co-expression of CRT similarly improved accumulation of glycoproteins from Epstein-Barr virus (EBV), Rift Valley fever virus (RVFV) and chikungunya virus (CHIKV), suggesting that the endogenous chaperone machinery may impose a bottleneck for their production. We subsequently successfully combined the co-expression of human CRT with the transient expression of human furin, to enable the production of an appropriately cleaved HIV gp140 antigen. These transient plant host engineering strategies are a promising approach for the production of high yields of appropriately processed and cleaved viral glycoproteins.© 2020 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd. PMID: 32096288 Funding information This work was supported by: National Institute for Health Research, Grant ID: 16/107/04 South African Medical Research Council, Wellcome Trust, United Kingdom Biotechnology and Biological Sciences Research Council, United Kingdom Grant ID: BBS/E/J/000PR9794 John Innes Foundation, Wellcome Trust Centre for Infectious Diseases Research in Africa, South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation, Harry Crossley Foundation, Biotechnology and Biological Sciences Research Council, United Kingdom Grant ID: BBS/E/J/00000166 More Less keyboard_arrow_down