Biomedical subjects

Amanda M Walmsley

Publications and source records attributed to Amanda M Walmsley.

10 recordsLinked to original sources

PubMed2006

Plant-made subunit vaccine against pneumonic and bubonic plague is orally immunogenic in mice.

Yersinia pestis, the causative agent of plague, is an extremely virulent bacterium but there are no approved vaccines for protection against it. Our goal was to produce a vaccine that would address: ease of delivery, mucosal efficacy, safety, rapid scalability, and cost. We developed a novel production and delivery system for a plague vaccine of a Y. pestis F1-V antigen fusion protein expressed in tomato. Immunogenicity of the F1-V transgenic tomatoes was confirmed in mice that were primed subcutaneously with bacterially-produced F1-V and boosted orally with transgenic tomato fruit. Expression of the plague antigens in fruit allowed producing an oral vaccine candidate without protein purification and with minimal processing technology.

Administration, Oral↗

PubMed2006

Tomato (Lycopersicum esculentum).

Tomato (Lycopersicum esculentum) is an important fruit crop in the Americas, southern Europe, the Middle East, and India, with increasing production in China, Japan, and Southeast Asia. It is amenable to producing pharmaceuticals, particularly for oral delivery; for many of the same reasons, it is a popular vegetable. Its fruit does not contain toxic substances and is palatable uncooked; it is easily processed; the plants are able to be propagated by seed or clonally by tip or shoot cuttings; the plants have a high yield of fruit; there is reasonable biomass and protein content; and they are easily grown under containment. This chapter describes Agrobacterium-mediated transformation of the tomato nucleus using cotyledons as explants. We have used this protocol to generate transgenic lines from several tomato cultivars expressing various genes of interest and selectable markers. We also provide protocols for molecular characterization of transgenic lines and batch processing tomato fruit.

Agrobacterium tumefaciens↗

PubMed2005

Oral immunogenicity of a plant-made, subunit, tuberculosis vaccine.

Transgenic plants are a novel way to produce and deliver oral vaccines. Arabidopsis thaliana material shown previously to express the tuberculosis (TB) antigen ESAT-6 fused to the B subunit of Escherichia coli heat-labile enterotoxin (LTB) was fed to mice and the resulting immune response investigated. The plant-made LTB-ESAT-6 fusion protein induced antigen-specific responses from CD4+ cells and increased IFN-gamma production, indicating a Th1 response. In addition, a Th2 response was induced in the Peyer's patch. This is the first report of an orally delivered, subunit, tuberculosis vaccine priming an antigen-specific, Th1 response.

Administration, Oral↗

PubMed2005

Risk analysis for plant-made vaccines.

The production of vaccines in transgenic plants was first proposed in 1990 however no product has yet reached commercialization. There are several risks during the production and delivery stages of this technology, with potential impact on the environment and on human health. Risks to the environment include gene transfer and exposure to antigens or selectable marker proteins. Risks to human health include oral tolerance, allergenicity, inconsistent dosage, worker exposure and unintended exposure to antigens or selectable marker proteins in the food chain. These risks are controllable through appropriate regulatory measures at all stages of production and distribution of a potential plant-made vaccine. Successful use of this technology is highly dependant on stewardship and active risk management by the developers of this technology, and through quality standards for production, which will be set by regulatory agencies. Regulatory agencies can also negatively affect the future viability of this technology by requiring that all risks must be controlled, or by applying conventional regulations which are overly cumbersome for a plant production and oral delivery system. The value of new or replacement vaccines produced in plant cells and delivered orally must be considered alongside the probability and severity of potential risks in their production and use, and the cost of not deploying this technology--the risk of continuing with the status quo alternative.

Animals↗

PubMed2005

Expression systems and developments in plant-made vaccines.

Delivery of vaccines to mucosal surfaces can elicit humoral and cell-mediated responses of the mucosal and systemic immune systems, evoke less pain and discomfort than parenteral delivery, and eliminate needle-associated risks. Transgenic plants are an ideal means by which to produce oral vaccines, as the rigid walls of the plant cell protect antigenic proteins from the acidic environment of the stomach, enabling intact antigen to reach the gut associated lymphoid tissue. In the past few years, new techniques (such as chloroplast transformation and food processing) have improved antigen concentration in transgenic plants. In addition, adjuvants and targeting proteins have increased the immunogenicity of mucosally administered plant-made vaccines. These studies have moved plant-made vaccines closer to the development phase.

Administration, Oral↗

PubMed2004

Application of Quillaja saponaria extracts as oral adjuvants for plant-made vaccines.

Extracts from the Quillaja saponaria tree are known to provide immune potentiating responses and, hence, can be useful as adjuvants. Partial purification from the crude (food-grade) extract results in Quil A, which is contained in several veterinary vaccines. Further purification can provide concentrated saponin fractions such as QS-21, which is currently under investigation as a potential adjuvant for use in humans. Purified saponins have proven safe and effective when injected and have significantly enhanced the efficacy of some oral vaccines under clinical investigation. Toxicity of the food-grade extract from Quillaja saponaria has limited its use as a parenteral adjuvant; however, this toxicity seems to be abated when delivered orally. It is commonly used within the food and beverage industries and has no documented toxicity in humans at the present levels of consumption. Use of transgenic plants has been proposed as an alternative system for oral vaccine production and administration, and it is likely that an oral adjuvant will be required in most cases. Food-grade saponins have significant advantages for use with plant-made vaccines and are likely to provide a broad adjuvant effect due to the multiple saponin components. A review of the origin, production, biological activity, toxicity and use in the food industry is provided for Quillaja saponaria extract. Previous evaluation of this adjuvant in preclinical studies with plant made vaccines is discussed and a proposed level of experimental use in humans is provided.

Adjuvants, Immunologic↗

PubMed2003

Passive immunization of mice pups through oral immunization of dams with a plant-derived vaccine.

Passive immunization plays an important role in protecting young mammals against pathogens before the maturation of their own immune systems. Although many reports have shown active immunization of animals and human through the use of plant-derived vaccines, only one report has given evidence of passive immunization of offspring through oral immunization of parents using plant-derived vaccines. In this case, a challenge alone provided the evidence of passive immunization and the mechanism through which this occurred was not investigated. This report describes the first step in elucidating the mechanism of passive immunization of offspring through actively immunizing the female parent through an orally delivered, plant-derived vaccine. The authors found passive immunization of offspring was caused by transfer of antigen-specific IgG through either transplacental transfer or ingesting colostrum. Future studies will investigate the roles of transplacental antibody transfer and ingesting colostrum in passive immunization and the possible involvement of IgA in this immunization route.

Administration, Oral↗

PubMed2003

Vaccine antigen production in transgenic plants: strategies, gene constructs and perspectives.

Stable integration of a gene into the plant nuclear or chloroplast genome can transform higher plants (e.g. tobacco, potato, tomato, banana) into bioreactors for the production of subunit vaccines for oral or parental administration. This can also be achieved by using recombinant plant viruses as transient expression vectors in infected plants. The use of plant-derived vaccines may overcome some of the major problems encountered with traditional vaccination against infectious diseases, autoimmune diseases and tumours. They also offer a convenient tool against the threat of bio-terrorism. State of the art, experimental strategies, safety and perspectives are discussed in this article.

Administration, Oral↗

PubMed2003

Targeting of plant-derived vaccine antigens to immunoresponsive mucosal sites.

Most pathogenic microorganisms enter their host via the mucosal surfaces lining the digestive, respiratory and urino-reproductive tracts of the body. The most efficient means of protecting these surfaces is through mucosal immunization. Transgenic plants are safe and inexpensive vehicles to produce and mucosally deliver protective antigens. However, the application of this technology is limited by the poor response of the immune system to non-particulate, subunit vaccines. Co-delivery of therapeutic proteins with targeting proteins, such as the B subunit of the Escherichia coli heat labile enterotoxin (LTB), could increase the effectiveness of such antigens.

Antigens↗

PubMed2003

Plant cell factories and mucosal vaccines.

Many advances continue to be made in the field of plant-derived vaccines. Plants have been shown capable of expressing a multicomponent vaccine that when orally delivered induces a T-helper cell subset 1 response and enables passive immunization. Furthermore, a plant-derived vaccine has been shown to protect against challenge in the target host. Increased antigen expression levels (up to 4.1% total soluble protein) have been obtained through transformation of the chloroplast genome. In view of these findings, plant-derived vaccines have been proved as valuable commodities to the world's health system; however, before their application, studies need to focus on optimization of immunization strategies and to investigate antigen stability.

Administration, Oral↗