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.

中文翻译：

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人钙网蛋白的共表达显着提高了植物中 HIV gp140 和其他病毒糖蛋白的产量。

植物分子农业（PMF）作为当前公认的生物制剂生产模式的可行替代方案正在迅速获得关注。虽然该平台可能比传统制造系统更便宜且更具可扩展性，但植物分泌途径中的表达产量和适当的翻译后修饰仍然是某些蛋白质的挑战。尤其是病毒融合糖蛋白在植物中的表达产量通常较低，并且在某些情况下可能无法进行适当的加工。然而，最近，瞬时或稳定地改造宿主植物已显示出作为生产具有更复杂成熟要求的异源蛋白质的策略的前景。在这项研究中，我们研究了一套人类伴侣的共表达，以提高烟草植物中人类免疫缺陷病毒 (HIV) 1 型可溶性 gp140 候选疫苗的生产。钙网蛋白 (CRT) 的共表达导致 Env 表达显着增加，并改善内质网 (ER) 应激反应——代表性应激反应基因的转录本丰度较低就证明了这一点。CRT 的共表达同样改善了 Epstein-Barr 病毒 (EBV)、裂谷热病毒 (RVFV) 和基孔肯雅病毒 (CHIKV) 糖蛋白的积累，表明内源性伴侣机制可能对其生产造成瓶颈。随后，我们成功地将人 CRT 的共表达与人弗林蛋白酶的瞬时表达结合起来，从而能够产生适当切割的 HIV gp140 抗原。这些瞬时植物宿主工程策略是一种有前途的方法，可以高产地生产经过适当加工和切割的病毒糖蛋白。