PLAPROVA

Plant Production of Vaccines

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 Obiettivo del progetto (Objective)

'Advances in the technologies for expressing proteins and extracting them from plants have allowed several plant-made products to be assessed for safety and efficacy. The results have been favourable and have culminated in the demonstration that plant-produced vaccine can protect target animals against challenge. However, most of these successes have concerned the production of antigens which had previously been produced using established methods such as mammalian cell culture. For plants to fulfil their potential as a means of producing vaccines, it is now imperative that methods are developed for the rapid production and characterisation of a large number of vaccine candidates. This project will exploit recent developments in transient expression technologies to screen a range of vaccine candidates in plants. These methods can produce milligram quantities of candidate proteins in a matter of days using only small amounts (tens of grams) of plant tissue. The project will concentrate on screening vaccine candidate proteins which are capable of forming virus-like particles (VLPs), as such particulate structures are known to be potent stimulators of the immune system. Furthermore, they can be used as carriers of additional immunogenic sequences for the developments of novel vaccines. The project will focus on diseases which are particularly relevant to both the EU and Russia, including Avian Influenza virus (AIV), Blue Tongue Virus (BTV) Porcine Respiratory and Reproductive Syndrome Virus (PRRSV). The ability to screen many candidate VLPs will result in the development of novel vaccines against these and other important pathogens. At the same time as the screening is carried out, methods will be developed to allow the rapid translation of the information gained through the transient studies into larger scale production systems for the most promising candidates. This will enable low cost vaccines to be developed for use for livestock and, ultimately, humans.'

Introduzione (Teaser)

Producing pharmaceuticals in plants is potentially efficient compared to conventional production methods. Ease of plant engineering and lower production costs could guarantee success for plant-generated vaccines against animal and human diseases.

Descrizione progetto (Article)

Plants are increasingly being investigated as alternative production systems for recombinant proteins. Technological advances allow either transient expression methods or the establishment of permanent plant lines that produce stable target proteins.

The EU-funded http://www.plaprova.eu/ (PLAPROVA) (Plant production of vaccines) project has exploited plant expression systems to screen a range of vaccine candidates. Project partners focused on the development of virus-like particles (VLPs) against important diseases of livestock such as avian influenza virus and bluetongue. VLPs stimulate the immune system and can therefore be used as vaccines.

Researchers used plant viruses such as the cowpea mosaic virus (CPMV) and the tobacco mosaic virus (TMV) for delivery and transient expression of vaccine antigens in plants. Refinement of the CPMV system enabled the simultaneous expression of multiple polypeptides within one plant cell.

Scientists expressed VLPs consisting of a single polypeptide and also more complex, multi-chain VLPs in plants. .At least four proteins could be co-expressed in a controlled manner using bluetongue virus (BTV) capsids in tests. These successfully assembled into complex VLPs demonstrating their functional capacity.

Purified, assembled VLPs were administered to experimental animals to determine their antigenic and immunogenic properties. Complex VLPs from BTV protected sheep against viral challenge. Similarly, a plant-expressed foot and mouth disease virus polyepitope was successfully used to vaccinate guinea pigs.

An important achievement of the project was the expression of candidate prophylactic vaccines against human papillomavirus and bovine papilloma virus. Using a novel membrane protein (M2e) as an immunogen, TMV particles protected mice against Asian influenza virus.

Scientists also managed to tackle the prior toxicity of porcine respiratory and reproductive syndrome virus proteins expressed in plants. To achieve this, they engineered proteins with reduced toxicity and genetic instability while retaining their immunological properties.

The PLAPROVA initiative has demonstrated that it is possible to produce high levels of proteins in plants for subsequent use as vaccines. Low production costs will endow important economic benefits to both the pharmaceutical and agricultural industries.