Combating Human Viral Diseases: Will Plant-Based Vaccines Be the Answer?

Abstract

Molecular pharming or the technology of application of plants and plant cell culture to manufacture high-value recombinant proteins has progressed a long way over the last three decades. Whether generated in transgenic plants by stable expression or in plant virus-based transient expression systems, biopharmaceuticals have been produced to combat several human viral diseases that have impacted the world in pandemic proportions. Plants have been variously employed in expressing a host of viral antigens as well as monoclonal antibodies. Many of these biopharmaceuticals have shown great promise in animal models and several of them have performed successfully in clinical trials. The current review elaborates the strategies and successes achieved in generating plant-derived vaccines to target several virus-induced health concerns including highly communicable infectious viral diseases. Importantly, plant-made biopharmaceuticals against hepatitis B virus (HBV), hepatitis C virus (HCV), the cancer-causing virus human papillomavirus (HPV), human immunodeficiency virus (HIV), influenza virus, zika virus, and the emerging respiratory virus, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) have been discussed. The use of plant virus-derived nanoparticles (VNPs) and virus-like particles (VLPs) in generating plant-based vaccines are extensively addressed. The review closes with a critical look at the caveats of plant-based molecular pharming and future prospects towards further advancements in this technology. The use of biopharmed viral vaccines in human medicine and as part of emergency response vaccines and therapeutics in humans looks promising for the near future.

Challenges and Prospects of Plant-Derived Oral Vaccines against Hepatitis B and C Viruses

“…While the proof of concept that an immune response induced by oral vaccines has all the required properties to neutralize viral infections is well documented, making this immunity efficient is still problematic. Public concerns regarding the use of genetically modified plants and environmental risk assessments should also be considered for the economical evaluation of these vaccines' production on a large scale [111].…”

Recombinant vaccines in 2022: a perspective from the cell factory

“…Even though plants can be stably modified, most approaches focus on transient expression, frequently using Agrobacterium tumefaciens or to a lesser extent other viruses such as Tobacco mosaic virus (TMV), a process that is less time-consuming and renders higher and more consistent yields [ 213 ]. Lately, chloroplast transformation has emerged as an alternative since it allows proteins to fold and accumulate in the subcellular compartment, even though this strategy still faces drawbacks regarding low efficiency and impaired glycosylation [ 217 ].…”

“…The plant-produced VLPs were successful in preclinical trials and were able to induce both humoral and cellular immune responses in phases I and II trial in humans, presenting a satisfactory safety profile and modest results in phase III trials [210][211][212]. In the last years, several plant-based vaccine strategies are being assessed in clinical trials, developed against hepatitis B, cholera, Ebola, influenza, and other infectious diseases [213]. More recently, the COVID-19 pandemics pushed plant-made vaccines to the spotlight, with 3 phase 3 trials taking place targeting SARS-CoV-2 and presenting encouraging results [214].…”

Microalgae as an Efficient Vehicle for the Production and Targeted Delivery of Therapeutic Glycoproteins against SARS-CoV-2 Variants

“…The vaccine was claimed to be able to trigger significant immune responses with a single dose and was also stable at room temperature [94]. These plant-based vaccines showed high immunogenicity and were well-tolerated in phase I, II, and III clinical trials [95,96]. However, other reports have revealed that the plant-produced vaccine contained plant-specific N-glycan epitopes that could cause immunogenic or allergic reactions in humans [97,98].…”