12.2 Overview of Crop Biotechnology in 2019

Green biotechnology has increased about 112 folds from 1996, with an accumulated biotech area of 2.7 billion hectares and economic gains of US$255 billion.

Top Crops and Countries for Commercial GM Crop Production

Figure 12.7: Top Crops and Countries for Commercial GM Crop Production

72 countries have began adopting biotechnology, and biotech crops offer a wider variety of options. Such crops also increase productivity, reduce agrichemical usage, and also contributes to biodiversity and safer environments.

12.2.1 What about in the One Health context?

Some benefits of GM crops include:

  1. More resistant to disease and environmental stresses
  2. More tolerant of insects
  3. Less soil erosion and less usage of pesticides

In addition to the above, GM crops also bring a number of health benefits:

  1. Golden rice addresses vitamin A deficiencies
  2. Soybean oil high in Oleic acid is also healthier
  3. More medicine can be produced via plants’ secondary metabolism
  4. Edible vaccines can be made against human and animal diseases

Furthermore, GM crops can also serve as biofuels (e.g., corn husks), a source of renewable materials, remediation.

12.2.2 Case study 1: plant-derived GCD for Gaucher’s disease

Cell Stain of a Patient with Gaucher's Disease

Figure 12.8: Cell Stain of a Patient with Gaucher’s Disease

Gaucher’s disease is caused by a mutation to the genes that encode for glucocerebrosidase (i.e., GCD), leading to liver swelling, anemia, decreased platelet count in the blood, and bone degeneration. The disease is autosomal recessive with a high occurence in the Ashkenazi Jewish population (8.9% as opposed to the 1% in the American public).

Tertiary Structure of GCD With Secondary Structures Present

Figure 12.9: Tertiary Structure of GCD With Secondary Structures Present

GCD contains about 497 amino acids and 5 glycosylation sites. The enzyme must be glycosylated at its oligosaccharide chains and do so at a high mannose concentration for proper activity.

Replacement therapy for patients with Gaucher’s disease involve using recombinant GCD (i.e., rGCD) that have been produced in Chinese hamster ovary cells (i.e., CHO cells) - a process that requires in-vitro glycan modification to expose terminal mannose residues.

The above costs about USD 300000 per year for the rest of the person’s life.

12.2.2.1 Technicalities of prGCD

prGCD (i.e., a recombinant human GCD made in a carrot cell suspension culture) was found to have terminal mannose residues and was - within the cell - directed to storage vacuoles by C-terminal sorting.

Data on prGCD in a Carrot Cell Culture

Figure 12.10: Data on prGCD in a Carrot Cell Culture

Because of this, prGCD was the first approved plant protein drug in many countries including the US, Israel, Brazil, and several other countries.

Uptake Rate of prGCD versus Normal, Human GCD

Figure 12.11: Uptake Rate of prGCD versus Normal, Human GCD

Like seen in the above line graph, prGCD performs the same action as normal human GCD, albeit it has a faster rate of uptake.

12.2.2.2 Plant-based oral vaccines

Zoonotic diseases are a major burden to the livestock industry and human health.

While immunization is the best option available, it can also be very difficult or expensive and in some cases, unfeasible for humans.

Process of Creating Vaccines Based on Plants

Figure 12.12: Process of Creating Vaccines Based on Plants

Hence, plant-based oral vaccines can be attractive because it is low cost, stable, and scalable.

12.2.3 Case study 2: plant-based vaccines for cholera and malaria

Both cholera and malaria are infectious diseases. However, vaccines against cholera are expensive and only offer short-term protection for children and for adults, is not fully protective.

Malaria is a global health problem that affects more than 100 countries, resulting in about a million deaths per year. However, there is no licensed vaccine against malaria yet.

12.2.3.1 Technical summaries of vaccines

Cholera toxin-B (i.e., CTB) is fused to the malaria vaccine antigens AMA1 and MSP1.

According to experimental data, CTB-AMA1 and CTB-MSP1 accumulated up to 13.2% / 10.1% in soluble proteins in tobacco and 7.3% / 6.1% in lettuce. Purified tobacco leaves or transplastomic tobacco leaves were used to immunize mice subcutaneously or orally.

Data on Antibody Quantities in Mice

Figure 12.13: Data on Antibody Quantities in Mice

A significant number of antibodies were then observed to have stopped the proliferation of malarial parasites and cross react with native proteins.

Dual immunity was observed in the mice for more than 300 days.