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Plant-Made Vaccines in the Fight against Cancer
Anti-cancer vaccines are currently being developed through plant expression systems (Matic 60). It is important to note that plants possess various advantages that make them proper bioreactors for production of the subunit vaccines. This is because they are considered safe and can be utilized to produce the recombinant proteins at lower production cost. Nonetheless, different technical issues prevent anti-cancer vaccines being produced on a large scale level especially the plant based ones (Pujol 455). Several reviews have been done with regards to the design strategies so that the therapeutic and immunogenicity potency are enhanced when it comes to anti-cancer vaccines, procedures to enhance vaccine-expressing biomass in plants, and issues that are facing anti-cancer vaccines in terms of production in plants. In this paper, a literature review has been provided on the topic, Plant-Made Vaccines in the Fight against Cancer. The literature paper has been organized into numerous sub-sections that delve more on the various components of the topic. The last subsection of the paper provides for a conclusion and possible future directions.
Emerging Anticancer Biopharmaceuticals
Due to the advancements in the molecular immunology and biology, there have been successful developments in the recombinant subunit vaccines that effectively utilize the antigenic proteins and epitopes to curb against the infectious diseases (Vici 29). This differs from the process of making the conventional vaccines that originate from attenuated or killed pathogens. Moreover, the vaccines which express and process the recombinant proteins that are similar to the ones in naïve pathogenic organisms are normally produced in the insect, bacterial, yeast and mammalian cells (McKee et al 57).
It is important to note that in 1990 tobacco plants were used to develop the first plant vaccine in which their Streptococcus mutanssurface emitted protein AntigenA (Zhao 77). Ever since that time, there has been increase in the production of non-enteric and enteric pathogens, bacteria, antigenic proteins, and tumor-associated antigens from a broad variety of plants using the transient or stable expression systems. Antigenic proteins derived from plants have been used for vaccinations and they have the ability to prevent people from acquiring infectious diseases. Nonetheless, the concept of vaccines against cancer has probed potentially novel strategy towards the production of the tumor-associated antigens (TAAs) within plant systems (Pujol et al 456). Most anti-cancer vaccines that are expressed in plants were studied and approved for the clinical trials. However, the large-scale production of the anti-cancer vaccines within plants can be viable but only if there is proper understanding of the disadvantages and advantages of the systems.
Govea-Alonso et al (267) believe that the microenvironment is more recognized because it plays a key role when it comes to cancer as well as the biomaterials provided as the means to engineer the microenvironments in vivo and in vitro to manipulate and study cancer. In vitro, the cancer models that use 3D matrix recapitulate key elements of a tumor microenvironment and this this shows that there are new projections of cancer biology. Moreover, the cancer machines that are based on selected biomaterials have parallel permitted engineering of the therapeutic anticancer and durable prophylactic activity in the preclinical studies. Some of the vaccines have been clinically tested which has revealed that the influence of the biomaterials engineering with regards to cancer treatment will further enhance its significance in future.
The integration of the bioengineering in cancer therapy and research has not just improved the efficacy of the traditional cancer treatments like chemotherapy and surgery, but it has also opened up new modalities of the cancer therapy procedures. The therapeutic cancer vaccines are meant to generate the immune reactivity against the existing tumors within a host. This means that vaccination instigates the Antigen Presenting Cells (APC) like dendritic cells to produce the tumor specific CTLs (Yusibov 315). Activation of the APCs may be achieved through in vivo.
The biomaterial based vaccines have been projected to achieve accurate immune modulation because of their ability to control the delivery of antigens as well as adjuvants in time and space, regulate the immune cell trafficking with their chemical and physical characteristics, and mimic the stimulatory signals of the innate immunity (McKee et al 60). Additionally, the plant-generated vaccines differ from traditional bolus vaccination because their biomaterial based vaccine develops a physical environment within a body which activates, accumulates, and presents the stimulatory and antigen signals to the DCs in a span of two weeks.
The most recent scenario in which the plant-derived vaccines have been used is in personalized medicine; for instance, the procedure has been used in the treatment of Non-Hodgkins Disease (NHL) which is the cancer that affects B-Lymphocytes by over proliferating them. Every NHL patient has a unique idiotype on their over-proliferating cells and the fact that the plants have the ability to produce the vaccine antigens rapidly and cheaply makes them the most ideal candidates when it comes to combating cancers like these (Pujol 457). Through the plant production platform, there have been high levels of the idiotype that may be emitted and reintroduced as the vaccine to the NHL patients; this will enable them to stop or prevent the disease before it spreads. This was not applicable when only conventional vaccination strategies were used.
A transient expression system was used to produce colorectal cancer antigen using tobacco mosaic plant viral vector (Yusibovet al 317). This stimulated the humoral immune response within the mice that were test subjects; nevertheless, the sera produced by the mice failed to show adequate antibody-dependent cytotoxicity and the Complement Depend Cytotoxicity (CDC) in comparison with response to the mammalian derived ones. It is important to note that the plant-derived vaccines prevent the deterioration in the function and viability of transplanted cells within ACT by developing optimal cytokine presentation within a cellular microenvironment.
The biomaterials derived cancer vaccines are supposed to synergize and complement with a checkpoint blockade as well as ACT therapies that are rapidly moving towards the front of the cancer treatment (Zhao 79). A combination like this may address two main factors for successful immunotherapy that include inhibition of the tumor-induced immunosuppression and generation of the robust tumor CTLs. In fact, the personalized cancer vaccines have been essential because of the heterogeneity of the tumors in patients specifically from an immunotherapy standpoint (Govea-Alonso et al 268). The incorporation of the patient specific neoantigens are identified by the genetic profiling which may improve efficacy of the cancer vaccines that are biomaterials based.
Matic (34) suggest that clinical adaptation of the immunotherapies may force a pharmaceutical industry to instill more emphasis on the materials in engineering and science as compared to the past. This could include new approaches needed for the manufacturing of similar kinds of therapies as compared to the smaller biologics and molecule drugs as well as altered approval and regulatory pathways concerning resultant combinations of the drugs and materials.
Applications of Plant-Made Biopharmaceutical as Anticancer Therapeutics
There are several challenges as well as deficiencies when it comes to chemotherapeutic drugs specifically drug resistances which appear in the cancer chemotherapy (Rosales-Mendoza et al 126). Even though chemotherapeutic drugs are effective, there are severe side effects that limit their use. Patients need to be more attentive to the cancer drugs that come from natural sources so that they can increase anti-cancer agents that are present within the drugs. From a historical point of view, the plant-derived drugs provide active ingredients from therapeutic agents especially during tumor therapy (Zhao 80). The natural products have an important role in discovering new drug compounds and it is essential when it comes to providing a unique role and novel structure within the anti-tumor compounds.
The natural products that are got from the herbs, fruits, and vegetables have proven to be effective with regards to combating cancer. These compounds have been properly characterized as having the broad variety of the antitumor properties (Pujol 456). For instance, the induction of the autophagy and apoptosis in addition to the inhibition of cell proliferation. These active ingredients such as flavonoids, alkaloids, polysaccharide and terpenoids are derived from the natural products possess potent biological properties like anti-inflammatory, analgesia, anti-tumor, anti-viral, and immunomodulation (Matic 100).
Production of Plant-Made Monoclonal antibodies that Fight Cancer
It has been discovered that plants produce the monoclonal antibodies which are used in cancer immunotherapy (Rosales-MendozaCarlos and Beatriz 126). The monoclonal antibodies trigger the localized immune response that can be used against the tumors through activation of the natural killer cells, macrophages, as well as the complement system that may result in the complement-dependent and antibody-dependent cytotoxicity. Nonetheless, the monoclonal antibody therapy could be hard to implement because of accessibility concerning scalability and cost (Pujol 458). In addition, they have the potential for the contamination of systems of mammalian expression with the human pathogens (McKee Anne‐Sophie and Graham 60).This means that there is a need for the post-translational modification which inhibits use of bacterial expression systems for production of the monoclonal antibodies for cancer therapeutic uses. Generation of the monoclonal antibodies within plants for vaccination of cancer was first discovered during the development of plant-derived pharmaceutical (Matic 90).
On the other hand, vaccination of cancer has been initiated through nanoparticle technology; synthetic nanoparticles may elicit localized immune response that will prevent development of cancer cells (Yusibov Stephen and Natasha 315). Because plant viruses have the ability to self-assemble developing into organized structures, they can still be utilized as nanoparticles that are nontoxic, biodegradable and stable. Furthermore, the plant viruses are essential because they cannot cause diseases in humans; this is why they are used for therapy and imaging (Vici 35).Virus particles from rod-shaped plants like potex-viruses may become functionalized through the modification so that they can target cancer cells delivery.
Zhao (80) believes that CPMV, an icosahedral plant virus, may be modifies so that it can encompass cargo molecules like drugs in their internal cavity. This means that plant viruses could be utilized for immunotherapy and diagnosis of cancer. The plant viruses have a unique immunostimulatory characteristic that can be used for the tumor medical imaging. Similarly, the plant virus nanoparticles are used to hinder progression of different kinds of cancer which further supports their ability to contribute to the medical practice (Vici 32).
Cervical Cancer Prevention
Plant molecular pharming is a biotechnology that is well established and it entails production of the protein biopharmaceuticals like hormones, enzymes, vaccine antigens and antibodies in the plant systems (Rosales-Mendozaet al 130). Nevertheless, the proteins produced by plants represent the essential fraction of the pharmaceuticals in clinical and preclinical trial status. However, the plant platforms offer some drawbacks like time consumption during the generation of stable transgenic lines, impact of diseases and pests even if the plants are placed in controlled conditions, and the growth within conditions that are non-sterile (Vici 29).
The therapeutic HPV vaccines and the candidate prophylactic are produced from plants and have been effectively tested on animals. Plant-derived vaccines that lacked adjuvants had the ability to elicit protective Th1 cell response among the mice (Govea-Alonso et al 270). The same adjudicating activity presented itself in the other tobacco plant derived protein of HPV 16 E7: the preparation of this antigen induced particular CD8+T stimulation which elicited the therapeutic influence on the experimental tumors. This means that E7 can be produced with a higher immunological activity within the microalgae which will open up ways of producing antigens affordably while retaining the adulating activity of the plant derived antigens (Govea-Alonso et al 270).
Currently, there are two vaccines which comprise of Gardasil, VLPs, and Cervariz; they guard against the limited HPV genotypes as well as high costs of production that limit their accessibility (applies to developing countries) (Rosales-MendozaCarlos and Beatriz 128). There is a growing scalability as well as facile production of the plants especially since they are used as the production platforms for the human biologics; this has resulted in concerted efforts to concentrate on the plant-derived vaccines that particularly target cervical cancer and HPV.
The expression vectors from the plant virus have been used to produce the HPV vaccines. For instance, Govea-Alonso Edward and Sergio (270) have pointed out optimized methods that express the VLPs based on HPV 16 L 1 protein while utilizing a TMV-deconstructed vector expression system from the tobacco plants. A single construct seemed to be expressed effectively while producing VLPs and it contained an open reading L1 frame that is fused to the chloroplast transit. Govea-Alonso Edward and Sergio (270) predict that the chloroplast targeted the transient expression process which can feasibly generate the vaccine for cervical cancer on the basis of HPV16 which may be both efficacious and inexpensive.
Additionally, the utilization of L1 and L2 structural proteins to develop VLP based vaccines has led to plant-based immunotherapies that are used for HPV infected patients (Vici 32). In such cases, this strategy can induce the HPV immune response on the E6 and E7 co-proteins. Rosales-MendozaCarlos and Beatriz (130) pointed out that the use of potexvirus (PVX) to produce HPV E7 can effectively prevent tumor growth among mice. Similarly, the researchers fused the E7 modified version to the plant protein (lichenase) so that it can act as the adjuvant as well as enhance an immune response. Furthermore, the fusion construct originated from the launch vector in TMV; this was proven to stop tumor growth. A vaccine successfully cured established tumors within orthotopic and non-orthotopicmose subjects which validates feasibility of the plant-derived immunotherapy for the patients who are HPV infected (Matic 87).

Plant-derived Vaccines That Prevent Solid Tumors
Plant-made vaccines are considered potentially effective against cancer related solid tumors. For instance, MagnICONexpression system for plants was constructed so that it can display epitope which is responsible for the elicitation of a stronger immune response against cancer of the breast (Pujol 456). The Her2-targeting immunization needs conjugation to the foreign immunogenic carrier so that it can become more effective. This vaccine was tested on mice and had positive results. On the other hand, Pujol (458) suggested that PVX nanoparticles should transport the monoclonal Herceptin antibodies as the targeted therapy for patients with breast cancer. The PVX based nanofilaments have the ability to catalyze the apoptosis within cell lines in breast cancer.
One of the plant-based vaccines that was initiated targets human epithelial mucin (MUC1) that is considered to be a glycosylated transmembrane protein that is expressed on the secretory epithelial gland and duct cells (Pujol 458). Vici (35) implies that the MUC1 is aberrantly glycosylated and overexpressed in most human epithelial tumors; however, it is relevant for immunotherapies.
Matic (76) showed that the immunogenic epitope originates from human epithelial mucin (MUC1) when combined with enterotoxin B as the adjuvant. MUC1 is the transmembrane protein which aberrantly glycosylated and overexpressed most of the breast cancers in humans. MagnICON system applied to production antibodies and platform against MUC1 can be functional and trigger antibodies from the mammalian cell culture (Vici 34).
Prostate cancer affects men and is linked with disable prostate epithelial cells that undergo apoptosis (Zhao 80). Par-4 protein may lead to tumor regression among animal models through the promotion of apoptosis of the cancer cells. According to Govea-Alonso Edward and Sergio (278), Par-4 is usually down regulated and suffers deleterious mutations among patients with cancer. Par-4 SAC domain is highly conserved among rats, mice and humans which represents a domain responsible for triggering apoptosis and can be utilized for the regimens of anticancer to catalyze tumor suppression (Rosales-MendozaCarlos and Beatriz, 142).Furthermore, SAC of the Par 4can be fused with fluorescent protein as well as expressed by transgenic tobacco plants. Plant made SAC emits anticancer effects through cell proliferation; the progression of tumor was investigated in rats and this revealed that the SAC from plants have cytotoxic influence on the cancer cell lines and limit tumor progression among animal model.
It is important to note that the antigenic proteins derived from plants have been used for vaccinations and they have the ability to prevent people from acquiring infectious diseases. Nonetheless, the concept of vaccines against cancer has probed potentially novel strategy towards the production of the tumor-associated antigens (TAAs) within plant systems (Pujol et al 456). Most anti-cancer vaccines that are expressed in plants were studied and approved for the clinical trials. However, the large-scale production of the anti-cancer vaccines within plants can be viable but only if there is proper understanding of the disadvantages and advantages of the systems.
The cancer immunotherapies have active and passive approaches. Passive approaches are monoclonal antibodies that are effectivebut need occasional dosing because they are short-term responses (Matic 76). Contrastingly, active immunotherapies catalyze the adaptive immune responses by using the antigenic formulation. The approach comprises of the T cell transfer where isolated autologous T cells get expanded and reinfused to the patient (Rosales-MendozaCarlos and Beatriz, 144). The other advanced approach fights against cancer while relying on an ex vivo in which dendritic cells (DCs) work with TAAs. Nonetheless, the approaches are complicates and costly while in situ immunization formulations contain TAAs with more convenient approach that will induce specific and strong anticancer immunization response.
TAAs have to be taken by inducing the adaptive immune responses through antigen presenting cells which results in induction of the cellular T cell populations (Govea-Alonso Edward and Sergio 270). TAA based formulation has to attain therapeutic response without forming autoimmune pathology. The plant made vaccines may be developed as parenteral vaccines but the plant material produces inexpensive or oral formulations. Even though cancers influencing gastrointestinal tract could be assumed to be primary targets for the oral immunization when it comes to plant-made vaccines, evidence shows that the oral plant derives vaccines may induce the protective responses against the systematic pathologies and pathogens influencing distant organs.
Conclusions and Future Directions
Plants normally express antibodies that need to be purified so that they can establish the use of protein G- or A- based affinity of chromatography (Vici 35). The purification of plant tissues has to be homogenized in order to disrupt cell walls that release noxious chemicals, cell debris as well as contaminants that could be removed through a purification process. This purification procedure is challenging because of the large scale factor in which affinity matrix column cannot avoid the clogging problems within a column; this is caused by a plant cell wall that is left over during the removal and homogenization process (Yusibov Stephen and Natasha 315).
Plant-made vaccines target malignancies and this can be proven through evidence that the plant cell can synthesize antigens which are functional within cancer immunotherapies (Matic 67). Various advancements have been made in the application and development of the technology by addressing the unresolved issues. The targeted malignancy are explored separately and most of the vaccines are parenterally administered. Vaccine formulation and the mode of delivery are important because they influence accessibility and safety of vaccination and patient comfort. The fight against cancer has shown that the parenteral formulations can be a main approach when it comes to therapy that shows a need for purification. It is important to note that purification enhances the cost of vaccine production, cheap raw plant material, higher quality of obtained proteins and lack of the mammalian pathogens which still represent attractive benefits over the other technologies.
Based on clinical and preclinical evidence, the plant-made vaccines give new technology to prevent cancer with sole attributes. This is envisaged that the significant advances address regulatory and technical challenges that are linked with development of similar vaccines can be attained in future. It is important to note that plants possess various advantages that make them proper bioreactors for production of the subunit vaccines. This is because they are considered safe and can be utilized to produce the recombinant proteins at lower production cost. Nonetheless, different technical issues prevent anti-cancer vaccines being produced on a large scale level especially the plant based ones (Pujol 455).

Works Cited
Govea-Alonso, Dania, Edward Rybicki, and Sergio Rosales-Mendoza. “Plant-based vaccines as a global vaccination approach: current perspectives.” Genetically Engineered Plants as a Source of Vaccines Against Wide Spread Diseases. Springer New York, 2014. 265-280.
Matic, Slavica. “The rat ErbB2 tyrosine kinase receptor produced in plants is immunogenic in mice and confers protective immunity against ErbB2 mammary cancer.” Plant Biotechnol J 14.1 (2015): 153-9.
McKee, Sara, Anne‐Sophie Bergot, and GrahamLeggatt. “Recent progress in vaccination against human papillomavirus‐mediated cervical cancer.” Reviews in medical virology 25.S1 (2015): 54-71.
Pujol, Merardo. “Fighting cancer with plant-expressed pharmaceuticals.” Trends in biotechnology 25.10 (2007): 455-459.
Rosales-Mendoza, Sergio, Carlos Angulo, and Beatriz Meza. “Food-grade organisms as vaccine biofactories and oral delivery vehicles.” Trends in biotechnology 34.2 (2016): 124-136.
Vici, Patrizia. “Immunologic treatments for precancerous lesions and uterine cervical cancer.” Journal of Experimental & Clinical Cancer Research 33.1 (2014): 29.
Yusibov, Vidadi, Stephen J. Streatfield, and Natasha Kushnir. “Clinical development of plant-produced recombinant pharmaceuticals: vaccines, antibodies and beyond.” Human vaccines 7.3 (2011): 313-321.
Zhao, Jian. “Nutraceuticals, nutritional therapy, phytonutrients, and phytotherapy for improvement of human health: a perspective on plant biotechnology application.” Recent patents on biotechnology 1.1 (2007): 75-97.