Plastids: The Green Frontiers for Vaccine Production

Abstract

Infectious diseases pose an increasing risk to health, especially in developing countries. Vaccines are available to either cure or prevent many of these diseases. However, there are certain limitations related to these vaccines, mainly the costs, which make these vaccines mostly unaffordable for people in resource poor countries. These costs are mainly related to production and purification of the products manufactured from fermenter-based systems. Plastid biotechnology has become an attractive platform to produce biopharmaceuticals in large amounts and cost-effectively. This is mainly due to high copy number of plastids DNA in mature chloroplasts, a characteristic particularly important for vaccine production in large amounts. An additional advantage lies in the maternal inheritance of plastids in most plant species, which addresses the regulatory concerns related to transgenic plants. These and many other aspects of plastids will be discussed in the present review, especially those that particularly make these green biofactories an attractive platform for vaccine production. A summary of recent vaccine antigens against different human diseases expressed in plastids will also be presented.

Keywords: biopharmaceuticals; cost-effective vaccines; developing countries; infectious diseases; molecular farming; plant-based vaccines; plastids.

Figure 1

Diagrammatic presentation of constituents of expression cassette along with their respective expression levels for vaccine antigens. Combinations of similar insertion sites, promoters, regulatory elements and terminators are shown in one color. SM, selection marker; RE, regulatory elements; UTR, untranslated region; psbA, psbA gene; TpsbA, Terminator of psbA gene; rrn16, rrn 16 gene; T7g10, leader sequence of gene 10 of the lambda phage T7; rbcL, rbcL gene; TrbcL, Terminator of rbcL gene; TrrnB, Escherichia coli rrnB terminator; TSP, total soluble protein; TLP, total leaf protein.