Edible vaccines against veterinary parasitic diseases--current status and future prospects

Molecular Farming for Immunization: Current Advances and Future Prospects in Plant-Produced Vaccines

Using plants as bioreactors, molecular farming has emerged as a versatile and sustainable platform for producing recombinant vaccines, therapeutic proteins, industrial enzymes, and nutraceuticals. This innovative approach leverages the unique advantages of plants, including scalability, cost-effectiveness, and reduced risk of contamination with human pathogens. Recent advancements in gene editing, transient expression systems, and nanoparticle-based delivery technologies have significantly enhanced the efficiency and versatility of plant-based systems. Particularly in vaccine development, molecular farming has demonstrated its potential with notable successes such as Medicago's Covifenz for COVID-19, illustrating the capacity of plant-based platforms to address global health emergencies rapidly. Furthermore, edible vaccines have opened new avenues in the delivery of vaccines, mainly in settings with low resources where the cold chain used for conventional logistics is a challenge. However, optimization of protein yield and stability, the complexity of purification processes, and regulatory hurdles are some of the challenges that still remain. This review discusses the current status of vaccine development using plant-based expression systems, operational mechanisms for plant expression platforms, major applications in the prevention of infectious diseases, and new developments, such as nanoparticle-mediated delivery and cancer vaccines. The discussion will also touch on ethical considerations, the regulatory framework, and future trends with respect to the transformative capacity of plant-derived vaccines in ensuring greater global accessibility and cost-effectiveness of the vaccination. This field holds great promise for the infectious disease area and, indeed, for applications in personalized medicine and biopharmaceuticals in the near future.

A preliminary study of the immunogenic response of plant-derived multi-epitopic peptide vaccine candidate of Mycoplasma gallisepticum in chickens

Mycoplasma gallisepticum (MG) is responsible for chronic respiratory disease in avian species, characterized by symptoms like respiratory rales and coughing. Existing vaccines for MG have limited efficacy and require multiple doses. Certain MG cytoadherence proteins (GapA, CrmA, PlpA, and Hlp3) play a crucial role in the pathogen's respiratory tract colonization and infection. Plant-based proteins and therapeutics have gained attention due to their safety and efficiency. In this study, we designed a 21.4-kDa multi-epitope peptide vaccine (MEPV) using immunogenic segments from cytoadherence proteins. The MEPV's effectiveness was verified through computational simulations. We then cloned the MEPV, introduced it into the plant expression vector pSiM24-eGFP, and expressed it in Nicotiana benthamiana leaves. The plant-produced MEPV proved to be immunogenic when administered intramuscularly to chickens. It significantly boosted the production of immunoglobulin Y (IgY)-neutralizing antibodies against cytoadherence protein epitopes in immunized chickens compared to that in the control group. This preliminary investigation demonstrates that the plant-derived MEPV is effective in triggering an immune response in chickens. To establish an efficient poultry health management system and ensure the sustainability of the poultry industry, further research is needed to develop avian vaccines using plant biotechnology.

Challenges and Prospective of Enhancing Hydatid Cyst Chemotherapy by Nanotechnology and the Future of Nanobiosensors for Diagnosis

Hydatid cysts have been widely recognized for decades as a common medical problem that affects millions of people. A revolution in medical treatment may be on the prospect of nanotechnology enhancing chemotherapy against hydatid cysts. An overview of nanotechnology's impact on chemotherapeutics is presented in the current review. It discusses some of the challenges as well as some of the opportunities. The application of nanotechnology to enhance chemotherapy against hydatid cysts is what this review will explore. Nanotechnology is a critical component of delivering therapeutic agents with greater precision and efficiency and targeting hydatid cysts with better efficacy, and minimizing interference with surrounding tissue. However, there are biodistribution challenges, toxicity, and resistance problems associated with nanotherapeutics. Additionally, nanobiosensors are being investigated to enable the early diagnosis of hydatid cysts. A nanobiosensor can detect hydatid cysts by catching them early, non-invasively, rapidly, and accurately. The sensitivity and specificity of diagnostic tests can be enhanced with nanobiosensors because they take advantage of the unique properties of nanomaterials. By providing more precise and customized treatment options for hydatid cysts, nanotechnology may improve therapeutic options and strategies for diagnosing the disease. In conclusion, treatment with nanotechnology to treat hydatid cysts is potentially effective but presents many obstacles. Furthermore, nanobiosensors are being integrated into diagnostic techniques, as well as helping to diagnose patients earlier and more accurately.

The Plant Viruses and Molecular Farming: How Beneficial They Might Be for Human and Animal Health?

Plant viruses have traditionally been studied as pathogens in the context of understanding the molecular and cellular mechanisms of a particular disease affecting crops. In recent years, viruses have emerged as a new alternative for producing biological nanomaterials and chimeric vaccines. Plant viruses were also used to generate highly efficient expression vectors, revolutionizing plant molecular farming (PMF). Several biological products, including recombinant vaccines, monoclonal antibodies, diagnostic reagents, and other pharmaceutical products produced in plants, have passed their clinical trials and are in their market implementation stage. PMF offers opportunities for fast, adaptive, and low-cost technology to meet ever-growing and critical global health needs. In this review, we summarized the advancements in the virus-like particles-based (VLPs-based) nanotechnologies and the role they played in the production of advanced vaccines, drugs, diagnostic bio-nanomaterials, and other bioactive cargos. We also highlighted various applications and advantages plant-produced vaccines have and their relevance for treating human and animal illnesses. Furthermore, we summarized the plant-based biologics that have passed through clinical trials, the unique challenges they faced, and the challenges they will face to qualify, become available, and succeed on the market.

Rapid and Highly Efficient Genetic Transformation and Application of Interleukin-17B Expressed in Duckweed as Mucosal Vaccine Adjuvant

Molecular farming utilizes plants as a platform for producing recombinant biopharmaceuticals. Duckweed, the smallest and fastest growing aquatic plant, is a promising candidate for molecular farming. However, the efficiency of current transformation methods is generally not high in duckweed. Here, we developed a fast and efficient transformation procedure in Lemna minor ZH0403, requiring 7-8 weeks from screening calluses to transgenic plants with a stable transformation efficiency of 88% at the DNA level and 86% at the protein level. We then used this transformation system to produce chicken interleukin-17B (chIL-17B). The plant-produced chIL-17B activated the NF-κB pathway, JAK-STAT pathway, and their downstream cytokines in DF-1 cells. Furthermore, we administrated chIL-17B transgenic duckweed orally as an immunoadjuvant with mucosal vaccine against infectious bronchitis virus (IBV) in chickens. Both IBV-specific antibody titer and the concentration of secretory immunoglobulin A (sIgA) were significantly higher in the group fed with chIL-17B transgenic plant. This indicates that the duckweed-produced chIL-17B enhanced the humoral and mucosal immune responses. Moreover, chickens fed with chIL-17B transgenic plant demonstrated the lowest viral loads in different tissues among all groups. Our work suggests that cytokines are a promising adjuvant for mucosal vaccination through the oral route. Our work also demonstrates the potential of duckweed in molecular farming.

Current state-of-the-art in the use of plants for the production of recombinant vaccines against infectious bursal disease virus

Infectious bursal disease is a widely spread threatening contagious viral infection of chickens that induces major damages to the Bursa of Fabricius and leads to severe immunosuppression in young birds causing significant economic losses for poultry farming. The etiological agent is the infectious bursal disease virus (IBDV), a non-enveloped virus belonging the family of Birnaviridae. At present, the treatment against the spread of this virus is represented by vaccination schedules mainly based on inactivated or live-attenuated viruses. However, these conventional vaccines present several drawbacks such as insufficient protection against very virulent strains and the impossibility to differentiate vaccinated animals from infected ones. To overcome these limitations, in the last years, several studies have explored the potentiality of recombinant subunit vaccines to provide an effective protection against IBDV infection. In this review, we will give an overview of these novel types of vaccines with special emphasis on current state-of-the-art in the use of plants as "biofactories" (plant molecular farming). In fact, plants have been thoroughly and successfully characterized as heterologous expression systems for the production of recombinant proteins for different applications showing several advantages compared with traditional expression systems (Escherichia coli, yeasts and insect cells) such as absence of animal pathogens in the production process, improved product quality and safety, reduction of manufacturing costs, and simplified scale-up.

Co-encapsulation of synthetic lipidated TLR4 and TLR7/8 agonists in the liposomal bilayer results in a rapid, synergistic enhancement of vaccine-mediated humoral immunity

To increase vaccine immunogenicity, modern vaccines incorporate adjuvants, which serve to enhance immune cross-protection, improve humoral and cell-mediated immunity, and promote antigen dose sparing. Pattern recognition receptors (PRRs), including the Toll-like receptor (TLR) family are promising targets for development of agonist formulations for use as vaccine adjuvants. Combinations of co-delivered TLR4 and TLR7/8 ligands have been demonstrated to have synergistic effects on innate and adaptive immune response. Here, we create liposomes that stably co-encapsulate CRX-601, a synthetic TLR4 agonist, and UM-3004, a lipidated TLR7/8 agonist, within the liposomal bilayer in order to achieve co-delivery, allow tunable physical properties, and induce in vitro and in vivo immune synergy. Co-encapsulation demonstrates a synergistic increase in IL-12p70 cytokine output in vitro from treated human peripheral blood mononuclear cells (hPBMCs). Further, co-encapsulated formulations give significant improvement of early IgG2a antibody titers in BALB/c mice following primary vaccination when compared to single agonist or dual agonists delivered in separate liposomes. This work demonstrates that co-encapsulation of TLR4 and lipidated TLR7/8 agonists within the liposomal bilayer leads to innate and adaptive immune synergy which biases a Th1 immune response. Thus, liposomal co-encapsulation may be a useful and flexible tool for vaccine adjuvant formulation containing multiple TLR agonists.

A review of Eimeria antigen identification for the development of novel anticoccidial vaccines

Coccidiosis is a major poultry disease which compromises animal welfare and costs the global chicken industry a huge economic loss. As a result, research entailing coccidial control measures is crucial. Coccidiosis is caused by Eimeria parasites that are highly immunogenic. Consequently, a low dosage of the Eimeria parasite supplied by a vaccine will enable the host organism to develop an innate immune response towards the pathogen. The production of traditional live anticoccidial vaccines is limited by their low reproductive index and high production costs, among other factors. Recombinant vaccines overcome these limitations by eliciting undesired contaminants and prevent the reversal of toxoids back to their original toxigenic form. Recombinant vaccines are produced using defined Eimeria antigens and harmless adjuvants. Thus, studies regarding the identification of potent novel Eimeria antigens which stimulate both cell-mediated and humoral immune responses in chickens are essential. Although the prevalence and risk posed by Eimeria have been well established, there is a dearth of information on genetic and antigenic diversity within the field. Therefore, this paper discusses the potential and efficiency of recombinant vaccines as an anticoccidial control measure. Novel protective Eimeria antigens and their antigenic diversity for the production of cheap, easily accessible recombinant vaccines are also reviewed.

A Preliminary Study of a Lettuce-Based Edible Vaccine Expressing the Cysteine Proteinase of Fasciola hepatica for Fasciolosis Control in Livestock

Oral vaccination with edible vaccines is one of the most promising approaches in modern vaccinology. Edible vaccines are an alternative to conventional vaccines, which are typically delivered by injection. Here, freeze-dried transgenic lettuce expressing the cysteine proteinase of the trematode Fasciola hepatica (CPFhW) was used to orally vaccinate cattle and sheep against fasciolosis, which is the most important trematode disease due to the parasite's global distribution, wide spectrum of host species and significant economic losses of farmers. In the study, goals such as reducing the intensity of infection, liver damage and F. hepatica fecundity were achieved. Moreover, we demonstrated that the host sex influenced the outcome of infection following vaccination, with female calves and male lambs showing better protection than their counterparts. Since differences occurred following vaccination and infection, different immunization strategies should be considered for different sexes and host species when developing new control methods. The results of the present study highlight the potential of oral vaccination with plant-made and plant-delivered vaccines for F. hepatica infection control.

Current Research of Trichinellosis in China

Trichinellosis, caused by Trichinella, is an emerging or re-emerging zoonotic parasitic disease, which is distributed worldwide with major socio-economic importance in some developing countries. In particular, it has been calculated that more than 40 million people are at risk of Trichinella infection in China. This review summarizes the current information on the epidemiology, laboratory diagnosis and vaccines of trichinellosis in China. Moreover, study of the treatment potential of using Trichinella for immune-related diseases and cancer, as well as the transcription and post-transcription modification of Trichinella were also collected, providing viewpoints for future investigations. Current advances in research will help us to develop new strategies for the prevention and control of trichinellosis and may potentially yield biological agents for treating other diseases.

Field evaluation of poultry red mite (Dermanyssus gallinae) native and recombinant prototype vaccines

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Field trial testing of a native and recombinant poultry red mite vaccines.

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Vaccination with a soluble mite extract (SME) resulted in a 78% reduction in mite numbers.

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Poor antibody persistence may relate to lack of effect of a recombinant cocktail vaccine.

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A semi-protective naturally acquired immunity may develop.

Vaccination is a desirable emerging strategy to combat poultry red mite (PRM), Dermanyssus gallinae. We performed trials, in laying hens in a commercial-style cage facility, to test the vaccine efficacy of a native preparation of soluble mite extract (SME) and of a recombinant antigen cocktail vaccine containing bacterially-expressed versions of the immunogenic SME proteins Deg-SRP-1, Deg-VIT-1 and Deg-PUF-1. Hens (n = 384 per group) were injected with either vaccine or adjuvant only (control group) at 12 and 17 weeks of age and then challenged with PRM 10 days later. PRM counts were monitored and, at the termination of the challenge period (17 weeks post challenge), average PRM counts in cages containing birds vaccinated with SME were reduced by 78% (p < 0.001), compared with those in the adjuvant-only control group. When the trial was repeated using the recombinant antigen cocktail vaccine, no statistically significant differences in mean PRM numbers were observed in cages containing vaccinated or adjuvant-only immunised birds. The roles of antigen-specific antibody levels and duration in providing vaccine-induced and exposure-related protective immunity are discussed.

Disease Prevention: An Opportunity to Expand Edible Plant-Based Vaccines?

The lethality of infectious diseases has decreased due to the implementation of crucial sanitary procedures such as vaccination. However, the resurgence of pathogenic diseases in different parts of the world has revealed the importance of identifying novel, rapid, and concrete solutions for control and prevention. Edible vaccines pose an interesting alternative that could overcome some of the constraints of traditional vaccines. The term “edible vaccine” refers to the use of edible parts of a plant that has been genetically modified to produce specific components of a particular pathogen to generate protection against a disease. The aim of this review is to present and critically examine “edible vaccines” as an option for global immunization against pathogenic diseases and their outbreaks and to discuss the necessary steps for their production and control and the list of plants that may already be used as edible vaccines. Additionally, this review discusses the required standards and ethical regulations as well as the advantages and disadvantages associated with this powerful biotechnology tool.

Immune response of rats vaccinated orally with various plant-expressed recombinant cysteine proteinase constructs when challenged with Fasciola hepatica metacercariae

Background

Cysteine proteinases of Fasciola hepatica are important candidates for vaccine antigens because of their role in fluke biology and host-parasite relationships. In our previous experiments, we found that a recombinant cysteine proteinase cloned from adult F. hepatica (CPFhW) can protect rats against liver fluke infections when it is administered intramuscularly or intranasally in the form of cDNA. We also observed considerable protection upon challenge following mucosal vaccination with inclusion bodies containing recombinant CPFhW produced in Escherichia coli.

In this study, we explore oral vaccination, which may be the desired method of delivery and is potentially capable of preventing infections at the site of helminth entry. To provide antigen encapsulation and to protect the vaccine antigen from degradation in the intestinal tract, transgenic plant-based systems are used.

Methodology

In the present study, we aimed to evaluate the protective ability of mucosal vaccinations of 12-week-old rats with CPFhW produced in a transgenic-plant-based system. To avoid inducing tolerance and to maximise the immune response induced by oral immunisation, we used the hepatitis B virus (HBV) core protein (HBcAg) as a carrier. Animals were immunised with two doses of the antigen and challenged with 25 or 30 metacercariae of F. hepatica.

Conclusions

We obtained substantial protection after oral administration of the plant-produced hybrids of CPFhW and HBcAg. The highest level of protection (65.4%) was observed in animals immunised with transgenic plants expressing the mature CPFhW enzyme flanked by Gly-rich linkers and inserted into c/e1 epitope of truncated HBcAg. The immunised rats showed clear IgG1 and IgM responses to CPFhW for 4 consecutive weeks after the challenge.

Infection with Fasciola hepatica, a liver fluke, is one of the most significant veterinary problems due to the worldwide distribution of this parasite, a wide spectrum of host organisms and the resulting economic loss. Human fasciolosis caused by F. hepatica is recognised by the World Health Organization as an important emerging but neglected tropical disease. Development of an effective vaccine against this disease is becoming a priority, especially as the appearance of drug-resistant strains undermine the currently employed drug-based treatments. The two primary issues when developing a vaccine are the selection of an appropriate vaccine antigen and the route of antigen administration. In our studies, we use one of the F. hepatica cysteine proteinases, which are promising antigens for vaccine construction. We evaluate the immunogenicity and protective ability of various modifications of this cysteine proteinase produced in plants. We show that substantial protection can be obtained when plant-expressed hybrid proteins are administered orally.

Molecular Breeding to Create Optimized Crops: From Genetic Manipulation to Potential Applications in Plant Factories

Crop cultivation in controlled environment plant factories offers great potential to stabilize the yield and quality of agricultural products. However, many crops are currently unsuited to these environments, particularly closed cultivation systems, due to space limitations, low light intensity, high implementation costs, and high energy requirements. A major barrier to closed system cultivation is the high running cost, which necessitates the use of high-margin crops for economic viability. High-value crops include those with enhanced nutritional value or containing additional functional components for pharmaceutical production or with the aim of providing health benefits. In addition, it is important to develop cultivars equipped with growth parameters that are suitable for closed cultivation. Small plant size is of particular importance due to the limited cultivation space. Other advantageous traits are short production cycle, the ability to grow under low light, and high nutriculture availability. Cost-effectiveness is improved from the use of cultivars that are specifically optimized for closed system cultivation. This review describes the features of closed cultivation systems and the potential application of molecular breeding to create crops that are optimized for cost-effectiveness and productivity in closed cultivation systems.

Challenges in Veterinary Vaccine Development and Immunization

In approaching the development of a veterinary vaccine, researchers must choose from a bewildering array of options that can be combined to enhance benefit. The choice and combination of options is not just driven by efficacy, but also consideration of the cost, practicality, and challenges faced in licensing the product. In this review we set out the different choices faced by veterinary vaccine developers, highlight some issues, and propose some pressing needs to be addressed.

Bringing plant-based veterinary vaccines to market: Managing regulatory and commercial hurdles

The production of recombinant vaccines in plants may help to reduce the burden of veterinary diseases, which cause major economic losses and in some cases can affect human health. While there is abundant research in this area, a knowledge gap exists between the ability to create and evaluate plant-based products in the laboratory, and the ability to take these products on a path to commercialization. The current report, arising from a workshop sponsored by an Organisation for Economic Co-operation and Development (OECD) Co-operative Research Programme, addresses this gap by providing guidance in planning for the commercialization of plant-made vaccines for animal use. It includes relevant information on developing business plans, assessing market opportunities, manufacturing scale-up, financing, protecting and using intellectual property, and regulatory approval with a focus on Canadian regulations.

Role of parasitic vaccines in integrated control of parasitic diseases in livestock

Parasitic infections adversely affect animal’s health and threaten profitable animal production, thus affecting the economy of our country. These infections also play a major role in the spread of zoonotic diseases. Parasitic infections cause severe morbidity and mortality in animals especially those affecting the gastrointestinal system and thus affect the economy of livestock owner by decreasing the ability of the farmer to produce economically useful animal products. Due to all these reasons proper control of parasitic infection is critically important for sustained animal production. The most common and regularly used method to control parasitic infection is chemotherapy, which is very effective but has several disadvantages like drug resistance and drug residues. Integrated approaches to control parasitic infections should be formulated including grazing management, biological control, genetic resistance of hosts, and parasitic vaccines. India ranks first in cattle and buffalo population, but the majority of livestock owners have fewer herds, so other measures like grazing management, biological control, genetic resistance of hosts are not much practical to use. The most sustainable and economical approach to control parasitic infection in our country is to vaccinate animals, although vaccines increase the initial cost, but the immunity offered by the vaccine are long lived. Thus, vaccination of animals for various clinical, chronic, subclinical parasitic infections will be a cheaper and effective alternative to control parasitic infection for long time and improve animal production.

Extraction and downstream processing of plant-derived recombinant proteins

Plants offer the tantalizing prospect of low-cost automated manufacturing processes for biopharmaceutical proteins, but several challenges must be addressed before such goals are realized and the most significant hurdles are found during downstream processing (DSP). In contrast to the standardized microbial and mammalian cell platforms embraced by the biopharmaceutical industry, there are many different plant-based expression systems vying for attention, and those with the greatest potential to provide inexpensive biopharmaceuticals are also the ones with the most significant drawbacks in terms of DSP. This is because the most scalable plant systems are based on the expression of intracellular proteins in whole plants. The plant tissue must therefore be disrupted to extract the product, challenging the initial DSP steps with an unusually high load of both particulate and soluble contaminants. DSP platform technologies can accelerate and simplify process development, including centrifugation, filtration, flocculation, and integrated methods that combine solid-liquid separation, purification and concentration, such as aqueous two-phase separation systems. Protein tags can also facilitate these DSP steps, but they are difficult to transfer to a commercial environment and more generic, flexible and scalable strategies to separate target and host cell proteins are preferable, such as membrane technologies and heat/pH precipitation. In this context, clarified plant extracts behave similarly to the feed stream from microbes or mammalian cells and the corresponding purification methods can be applied, as long as they are adapted for plant-specific soluble contaminants such as the superabundant protein RuBisCO. Plant-derived pharmaceutical proteins cannot yet compete directly with established platforms but they are beginning to penetrate niche markets that allow the beneficial properties of plants to be exploited, such as the ability to produce 'biobetters' with tailored glycans, the ability to scale up production rapidly for emergency responses and the ability to produce commodity recombinant proteins on an agricultural scale.

Plant-based solutions for veterinary immunotherapeutics and prophylactics

An alarming increase in emergence of antibiotic resistance among pathogens worldwide has become a serious threat to our ability to treat infectious diseases according to the World Health Organization. Extensive use of antibiotics by livestock producers promotes the spread of new resistant strains, some of zoonotic concern, which increases food-borne illness in humans and causes significant economic burden on healthcare systems. Furthermore, consumer preferences for meat/poultry/fish produced without the use of antibiotics shape today's market demand. So, it is viewed as inevitable by the One Health Initiative that humans need to reduce the use of antibiotics and turn to alternative, improved means to control disease: vaccination and prophylactics. Besides the intense research focused on novel therapeutic molecules, both these strategies rely heavily on the availability of cost-effective, efficient and scalable production platforms which will allow large-volume manufacturing for vaccines, antibodies and other biopharmaceuticals. Within this context, plant-based platforms for production of recombinant therapeutic proteins offer significant advantages over conventional expression systems, including lack of animal pathogens, low production costs, fast turnaround and response times and rapid, nearly-unlimited scalability. Also, because dried leaves and seeds can be stored at room temperature for lengthy periods without loss of recombinant proteins, plant expression systems have the potential to offer lucrative benefits from the development of edible vaccines and prophylactics, as these would not require "cold chain" storage and transportation, and could be administered in mass volumes with minimal processing. Several biotechnology companies currently have developed and adopted plant-based platforms for commercial production of recombinant protein therapeutics. In this manuscript, we outline the challenges in the process of livestock immunization as well as the current plant biotechnology developments aimed to address these challenges.

Transgenic plants: a 5-year update on oral antipathogen vaccine development

The progressive interest in transgenic plants as advantageous platforms for the production and oral delivery of vaccines has led to extensive research and improvements in this technology over recent years. In this paper, the authors examine the most significant advances in this area, including novel approaches for higher yields and better containment, and the continued evaluation of new vaccine prototypes against several infectious diseases. The use of plants to deliver vaccine candidates against viruses, bacteria, and eukaryotic parasites within the last 5 years is discussed, focusing on innovative expression strategies and the immunogenic potential of new vaccines. A brief section on the state of the art in mucosal immunity is also included.

Coccidiosis: recent advancements in the immunobiology of Eimeria species, preventive measures, and the importance of vaccination as a control tool against these Apicomplexan parasites

Coccidiosis, caused by parasites of the genus Eimeria, is probably the most expensive parasitic disease of poultry. Species of Eimeria are ubiquitous where poultry are raised and are known to cause drastic reductions in performance and induce mortality, thereby affecting the overall health status of poultry. Chemotherapy has been the predominant form of disease control for many years, even though vaccination is steadily gaining importance as a feasible control method. The objective of this review is to highlight recent advancements in understanding the role of host immunity against coccidiosis. In addition, pros and cons associated with chemotherapy and the role of vaccination as an increasingly popular disease control method are discussed. Finally, the role played by recombinant vaccines as a potential vaccination tool is highlighted. With interest growing rapidly in understanding host–parasite biology, recent developments in designing recombinant vaccines and potential epitopes that have shown promise are mentioned.

Algae-based oral recombinant vaccines

Recombinant subunit vaccines are some of the safest and most effective vaccines available, but their high cost and the requirement of advanced medical infrastructure for administration make them impractical for many developing world diseases. Plant-based vaccines have shifted that paradigm by paving the way for recombinant vaccine production at agricultural scale using an edible host. However, enthusiasm for “molecular pharming” in food crops has waned in the last decade due to difficulty in developing transgenic crop plants and concerns of contaminating the food supply. Microalgae could be poised to become the next candidate in recombinant subunit vaccine production, as they present several advantages over terrestrial crop plant-based platforms including scalable and contained growth, rapid transformation, easily obtained stable cell lines, and consistent transgene expression levels. Algae have been shown to accumulate and properly fold several vaccine antigens, and efforts are underway to create recombinant algal fusion proteins that can enhance antigenicity for effective orally delivered vaccines. These approaches have the potential to revolutionize the way subunit vaccines are made and delivered – from costly parenteral administration of purified protein, to an inexpensive oral algae tablet with effective mucosal and systemic immune reactivity.

Display of Eimeria tenella EtMic2 protein on the surface of Saccharomyces cerevisiae as a potential oral vaccine against chicken coccidiosis

S. cerevisiae is generally regarded as safe and benign organism and its surface display system may be used as a unique eukaryotic expression system that is suitable for expressing eukaryotic antigen. In addition to the convenience of vaccine delivery, the yeast cell wall has been shown to enhance the innate immunity when immunized with the yeast live oral vaccine. In the present study, we expressed the chicken coccidian E. tenella EtMic2, a microneme protein, on the surface of the S. cerevisiae and evaluated it as a potential oral vaccine for chicken against E. tenella challenge. The protective efficacy against a homologous challenge was evaluated by body weight gains, lesion scores and fecal oocyst shedding. The results showed that the live oral vaccine can improve weight gains, reduced cecal pathology and lower oocyst fecal shedding compared with non immunized controls. In addition, the yeast oral vaccine could stimulate humoral as well as cell mediate immune responses. These results suggested that EtMic2 displayed on the cell surface of S. cerevisiae could be used as potential live vaccine against chicken coccidiosis.

The potential of Physcomitrella patens as a platform for the production of plant-based vaccines

The moss Physcomitrella patens has a number of advantages for the production of biopharmaceuticals, including: i) availability of standardized conditions for cultivation in bioreactors; ii) not being part of the food chain; iii) high biosafety; iv) availability of highly efficient transformation methods; v) a haploid, fully sequenced genome providing genetic stability and uniform expression; vi) efficient gene targeting at the nuclear level allows for the generation of mutants with specific post-translational modifications (e.g., glycosylation patterns); and vii) oral formulations are a viable approach as no toxic effects are attributed to ingestion of this moss. In the light of this panorama, this opinion paper analyzes the possibilities of using P. patens for the production of oral vaccines and presents some specific cases where its use may represent significant progress in the field of plant-based vaccine development. The advantages represented by putative adjuvant effects of endogenous secondary metabolites and producing specific glycosylation patterns are highlighted.

Plant molecular pharming for the treatment of chronic and infectious diseases

Plant molecular pharming has emerged as a niche technology for the manufacture of pharmaceutical products indicated for chronic and infectious diseases, particularly for products that do not fit into the current industry-favored model of fermenter-based production campaigns. In this review, we explore the areas where molecular pharming can make the greatest impact, including the production of pharmaceuticals that have novel glycan structures or that cannot be produced efficiently in microbes or mammalian cells because they are insoluble or toxic. We also explore the market dynamics that encourage the use of molecular pharming, particularly for pharmaceuticals that are required in small amounts (such as personalized medicines) or large amounts (on a multi-ton scale, such as blood products and microbicides) and those that are needed in response to emergency situations (pandemics and bioterrorism). The impact of molecular pharming will increase as the platforms become standardized and optimized through adoption of good manufacturing practice (GMP) standards for clinical development, offering a new opportunity to produce inexpensive medicines in regional markets that are typically excluded under current business models.