Need And Importance Of Edible Vaccines Biology Essay

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One of the best and appropriate approaches to human health is the prevention of diseases. The use of vaccines activates as well as prepares the human body for protection through various methods so as to boost the system and be capable of fighting and avoiding pathogens that appear as a result of natural infection. Vaccine technology has recently developed and as a result has improved people's health to a large extent. Cynthia (1997, p. 499) shows that every year almost a million children born in the underdeveloped countries have found it difficult to access immunization services. This is because the traditional vaccines have become quite expensive and need special kinds of storage facilities. Their distribution channels are also weak and dispensing is not easy to monitor.

This study shows the types of edible vaccines used to prevent diseases, the problems that arise due to usage and the prospects that people pertain on the use of vaccines. One reason why the traditional vaccines are not so much accessible is that they are limited and therefore are not supplied in large quantities. Hein et al. (1996) describes that the edible vaccines have been known to be cheaper than the traditional ones and they are also quite easy to dispense. The storage does not also need a great deal of special conditions and this gives the reason why most people prefer using them. The vaccines are also readily acceptable by mostly the poor people in the developing countries. The method used in the production of edible vaccines includes the introduction of several types of genes of immunogenic proteins found in different pathogens which are then taken to plants and animals (Mason et al. 1998).

The altered organisms are then induced and used in the manufacturing of fixed proteins. The demand for transgenic crops has significantly grown both in the developed and developing countries. According to Landridge (2000, p. 70) this is because the future of edible vaccines mostly will vary according to how people will accept the introduction of genetically customized foods. In order to successfully accomplish the use of edible vaccines it will be important to know how well technical obstacles can be avoided. This will be through the avoidance of challenges that come with the legal issues and non-scientific problems. This study also will analyse the current position and the future of the new method which will be used to prevent diseases which will therefore bring a significant effect on the promotion of global health.

Vaccines are the measures used to introduce into healthy individuals that help in supporting and maintaining the immune system and also used to fight against agents that cause diseases in living organisms especially when they are found naturally. McGarvey et al. (1995) show that one example is the widespread utilisation of small pox vaccine that has enabled individuals all over the world to eradicate the deadly disease found mostly in early ages of development. There has also been a considerable programs meant for polio eradication which has resulted to increase usage in various countries and especially those which are highly populated for example the ongoing programs in India. There are various kinds of vaccines that are differentiated by either conventional which involves the introduction of killed vaccine but in inactivated forms of pathogens that are also formed through the use of a chemical or by either treating it physically for example the BCG vaccine, oral polio vaccine etc. (Singh 2004, p. 509-557).

These two and the rest have been found to be so easy to generate and the cost is low though they relapse easily to infective forms and therefore cause major disease if the conditions of storage and administration are not followed properly. The other type is the pure antigen vaccines that help in the development of polysaccharide which is also the protein purified through causative agents as toxoids of tetanus, diphtheria etc and the other one include recombinant vaccines which are produced through a combination of DNA technology. The vaccines used in this include the Subunit vaccines, DNA vaccines and Edible vaccines which can be got through identifying and separating the kind of genes. Training the immunogenic proteins of pathogenic organism and the cloning and how the gene is produced can be important to the host organism as it yields mass production of the concerned protein (Thanavala 1995).

Vaccines have also been known as biological preparation that tends to increase the level of immunity of a certain type of disease. Vaccines contains of agents acting in place of a microorganism that causes diseases in living things. The microorganism is made of weak forms of toxics. The type of agents used in the body identifies a foreign cell then destroys it if it is in the immune system. The purpose and goals of a vaccine include boost the immune response of a persons body and in the process produce memory cells which are important in case a pathogen attacks.

Vaccines can be in forms of prophylactic that is used to protect one from infection from natural infectious diseases. Vaccines are various types and are categorised according to their nature for example dead, inactive or others can be in form of purified products. The various types show various benefits for example in the reduction of illness as well as maintaining the immune system (Lal et al. 2007, p. 100).

Types of vaccines

Attenuated

These are also known as live vaccines that consist of live microorganisms which are also live virus produced from a certain condition that is also known to disable some properties in the immune system. These may either be viruses in nature or bacteria which may also typically inflame long lasting immunological responses and therefore are mostly demanded by most individuals. Some of the diseases treated by this vaccine include yellow fever, measles and mumps. There are also other kinds of vaccines for example the ones used in the Mycobacterium tuberculosis vaccine which are produced through Calmette and Guérin and which are not made of contagious strain though they posses a strong customised damage referred to as Bacillus Calmette- Guerin (BCG) which is also helpful in the extraction of immunogenicity of the vaccine. The vaccine contains some living organisms and this makes it very unpredictable. It can also return to its pathogenic nature especially those that are too weak to be maintained in the system. To prevent this condition from happening, genetic engineers have introduced a method that will not allow the process of virulence.

Inactivated or Killed

These are inactivated organisms that make use of pathogens which can only be killed and after will not be in apposition of returning to the host. These kinds of pathogens can be inactivated through either keeping them near an open heat or by using certain kind of chemicals. The vaccine also assumes that the surface antigens are stable and safe thus cannot return to be some kind of disease causing nature. These kinds of vaccines are also important since their storage is cheap and therefore are preferred by most people in the developing countries since they do not need a refrigerator. They are also preferred by people who are always travelling for example the armed forces. The vaccine though has a weak immunity and for this reason the dosage is taken more than once. This makes it be known to have little effect on the immune system of a living organism. One example of this vaccine includes the flu shot, cholera vaccine and hepatitis A vaccine (Mason and Lam1992).

Subunit vaccines or purified antigen

These are the kinds of vaccines that are produced by the antigenic fragments and therefore they are capable of inducing the immune system. The vaccine has little side effects which if they are felt then the vaccine is said to be made from the entire organism. This type of vaccine can also be produced from the laboratory by the use of genetic methods of engineering. It can be used to prevent diseases such as pneumonia which is a disease caused by Streptococcus pneumonia and the other disease include meningitis. In the United States the vaccine has been legalized to be used against hepatitis B which is a virus infection. This vaccine is made by mixing some hepatitis B material with yeast where yeast releases an antigen and is later purified. This pure antigen is then mixed with an adjuvant which is responsible for stimulating the human immune system thus resulting to an effective effect (Beachy and Fitchen 1996, p. 45).

Toxoids

This is a kind of inactivated toxic which is a dangerous material that is generated from microorganisms. Most microorganisms are not harmful in nature but the toxics found within them are dangerous and thus causes various kinds of diseases. According to Arakawa et al. (1997, p. 403-407) one example of this is the bacteria toxic that causes tetanus on human body is naturally present and especially where there is presence of oxygen. This shows that it is harmless in nature but when the organism is placed in an environment without oxygen then it produces a toxic substance that causes tetanus. The substance produced is so powerful than the sodium cyanide. In order for this toxic to be released from the body, some materials such as formalin which is a mixture of sterile water and formaldehyde. This solution helps the production of toxoids which acts as protective medicine against diseases such as diphtheria and tetanus. However all the vaccines are not used for micro-organisms but can also be used to protect against snakebites for example Crotalus atrox.

Conjugate

These vaccines are applied for example in those kinds of bacteria that cause pneumococcal pneumonia or meningitis. The certain coat found in these kinds of organisms covers certain antigens which makes it difficult to be reached by the harmful substance that causes diseases. In this type of vaccine, toxins from other organisms are combined with the outer covering of the bacteria. This makes it easy for the immune system to be protected from the harmful substance causing diseases. These types of vaccines have now been used to protect infections from the bacterial causing agent which is Haemophilus influenza type b (Hib). This is found in meningitis which is an inflammation of the membranes covering the brain. These vaccines have been as important especially in the United States as it has reduced meningitis in young children (Charles and Richard 1998).

Recombinant Antigen

Due to the high rate of releasing subunit antigens from pathogens, the introduction of recombinant DNA methods is used to produce antigens as fast as they are wanted for use. One vaccine used is that of hepatitis B where the HBV soluble antigen is used. The method used in the introduction was very expensive and therefore needed much testing. However it was so importance as certain kinds of dangers were prevented such as infection of viruses caused by diseases such as foot and mouth. One advantage of this vaccine is that it is safe to use as the whole organisms are not employed (Haq et al. 1995, p. 715).

Type of Vaccines

Characteristics

Live attenuated

These simulate an infection without conferring the disease, mostly a single dose is more than enough.

Toxoid

Very efficient used against rattle snake bites.

Subunit

Potential toxins are avoided,

Combination

High efficiency

Inactivated whole organisms

These are very stable and safe ,do not require refrigeration a quality that makes it accessible to people in developing countries and to people who are highly mobile

Development of vaccines

The first vaccine to be developed was in 1796 which was meant to protect against small pox disease. According to Tacket et al. (2000, p. 302- 305) it was noticed that a virus was just a tiny RNA (Ribonucleic acid) or a DNA (deoxyribonucleic acid) which is present in all kinds of living organisms. A virus works by invading the cell. A vaccine is manufactured where small amount of a virus which is not contyaminated is used. This type of virus should be kept under certain conditions for example it should be frozen in nature and then stores in plastic cans. The amount should be about 5 cubic centimeters with million viruses which is necessary to yield almost hundred liters of the vaccine needed. The virus is then put into the cell factory that enables the virus to increase in nature. The pH of the mixture has to be stable where it is maintained by the sensors. The virus can then be extracted form the solution and placed into another type of medium where it is meant to grow. Yu and Langridge (2001) show once they grow to the expected number, the mixture is filtered where the virus passes through but the beads are not passed. The virus is then removed from the mixture and vaccines of different types are produced and combined for them to be packed together for sale.

Advantages and disadvantages of current administration and alternatives

There are various kinds of innovative vaccines that have been introduced and are in current use. Some of these include the Dendritic cell vaccines which is used to combine dendritic cells with antigens for them to be in a position of producing various kinds of antigens to the body's white blood cells. This then makes it possible to stimulate the immune system. The vaccines are important in treating brain tumors.

The other kind of vaccine in use include the recombinant vector which is produced by linking one micro-organism with DNA of another whereby the results include inducing immunity therefore capable of protecting living organisms against diseases that need major processes. DNA vaccination has also been introduced so much in use in recent years. The new vaccine DNA vaccination has been introduced which has been got from an infectious DNA agent. This kind of vaccine works by placing or by use of an expression meant to trigger the immune system in both human and animal cells.

There are other types of cells found in the immune system that work by protecting as the proteins present combine and affect these other kinds of proteins and cells. Since these kinds of cells take time to die, once the pathogen that helps to show these proteins determined later, and then the cells will be affected straight away by the immune system. DNA vaccines are important since they can be easily produced from the laboratory test and the storage is also easier. DNA vaccination for example has been experimental since 2006. The other types of vaccine that are to be introduced include the T-cell receptor peptide which will be of help to various kinds of diseases where models will be used for example valley fever, stomatitis and dermatitis (Yu and Langridge 2001).

To improve immunity of the cell, these kind peptides have been necessary as they adapt to cytokine production. The key bacterial virulence as a system can be neutralized through the process of identifying the proteins contained in that particular type of bacteria. The creation of vaccines can either be through inactivated or attenuated compounds which are present in various kinds of micro-organisms. Other kinds of vaccines such as the synthetic ones are collected from synthetic peptides which are either whole or main, and can also be collected from carbohydrates or other antigens.

Valence

Vaccines are said to be either monovalent or multivalent. Those referred to as monovalent vaccines are also considered to protect one against one single type of antigen microorganism. The multivalent vaccine can protect against two or more microorganisms. These types of vaccines are mostly used in cases where one needs to improve and have a strong immune system.

Developing immunity

The process of immunity is developed where the system works by identifying the agents used in the vaccines, removing dangers and responding to them ones they return. Once the stronger type of agent connects with the body, the body tends to identify the protein covering the virus. This makes it get ready to react by either neutralizing the agent used before it gets into the cells and it can also react through identifying the infected cells and destroying them earlier before they multiply as it will be very hard to deal with them (Das 2009, p. 113-127).

If the live attenuated types of vaccine mixed in one form, there is a big possibility of them interfering. This happens in case one vaccine component is extra healthy as compared to the other type of vaccine. This occurs where the growth of one is the immune reaction of the other component. Other kinds of vaccines have been known to add to the eradication of certain kinds of diseases such as smallpox which has been known as the most contagious especially in humans.

Other types of diseases include polio, measles, chickenpox, and typhoid which have significantly reduced since they were known to exist. If most people agree with the process of vaccination, the outbreak of these diseases will no longer be in existence. The above type of outcome can be known as group immunity. One of the disease which has been known to spread especially in human beings include polio and for this reason more campaigns have been introduced in order to eradicate the disease. Thanavala (1995, p. 95) describe that some of the countries that have embraced these programs include Afghanistan, Nigeria and Pakistan. However there have been several challenges which include accessing all those children in need especially in the developing countries. The other challenge faced includes cultural misunderstandings.

Schedule

To provide children with the best immunity, it is necessary to give them the immunity at the scheduled time that is recommended for them. These vaccines are particularly meant to boost the child's immune system whereby they are supposed to be immunized at maybe 8 months or after one year. In United States for example it is advisable for all children to be vaccinated against various kinds of diseases at their tender age which include; hepatitis A and B, polio, mumps, measles, rubella, diphtheria, tetanus, HiB, chickenpox, influenza etc. (Verch et al. 1998).

It has also been recommended for children to be injected around 12 vaccines before they get to two years. This recommendation has brought about too many problems for example for them to be agreed upon. To avoid many people from declining, the US has introduced several methods of advising individuals on the need to take up vaccination and currently many types of injections have been offered such as Pneumococcal conjugate vaccine and MMRV vaccine. These two helps to give protection against many childhood diseases (Tacket et al. 1998).

Apart from these types of recommendations given towards infants, there are other kinds of vaccines that have to be submitted at a later date or should be repeated throughout an individual's life. Some of these vaccines include measles, tetanus, influenza, and pneumonia. Other are given to special kinds of people for example the pregnant women who have to be screened to avoid rubella. Human papillomavirus vaccine is now being used in the U.S. and UK by children from 11-25 years. The old tend to focus more on pneumonia and influenza which have been known to cause more deaths. In 2006 there was a certain kind of vaccine that was introduced against shingles which led to chickenpox virus that is known to affects the elderly.

Effectiveness

The use of vaccines has not always been a guarantee that one is completely protected form the disease. This is because at times the vaccine may fail to respond to the system. The cause of this condition may be brought about by weak immunity system caused by diabetes, HIV infection and age. The above illness may make ones immune system to depreciate as it lacks the B cell that is important in the production of antibodies to an antigen. Though the body maybe in a position of producing the needed antibodies, the immune system may not have the minimum immunity needed for it to be protected against the disease.

To boost immunity it will be necessary to make use of adjuvant and especially the aluminium one which contain squalene. Gomez et al. (1998, p. 352-358) show for the elderly probably 50 years and above it is necessary to make use of many doses of this vaccine. A vaccine can be effective in various kinds of ways depending on the above factors such as; the kind of disease that an individual is suffering from this is because various vaccines perform well when used to prevent a different kind of disease. The other factor that matters include the strength of the disease as vaccines is manufactured with varying strains. Effectiveness of the vaccines is achieved if one adheres to the scheduled time that the vaccine was to be administered. Effectiveness will also depend on the type of body cells the individual has for example there are those that respond very quickly and others it may take a lot of time to respond. Other factors that affect effectiveness of the vaccine include age, ethnicity and the genes.

There are other types of factors that have to be considered to facilitate vaccination program effectiveness. This is that the program should be monitored carefully and the effect of the campaign should be anticipated. The other factor includes having enough information about the kind of disease to be vaccinated and the new type of vaccine finally it is necessary to sustain a higher rate of immunization. Studies show that the number of deaths had reduced in 1958 where a new type of vaccination was introduced to protect people against measles. Previously the deaths had been more than 500 but then were reduced to 150 every year (Verch et al. 1997).

Controversy

The introduction of vaccination has been important to many people's lives however several critics have been received for example following the side effects of vaccination. Other kinds of disputes include reduced morality, the society's ethics, lack of effectiveness and some vaccines are also not safe to use. There are other religious that are against the exercise of immunization and therefore the members fail to attend the campaigns. Others governments oppose the use of vaccination to their citizens basing on giving their citizens liberty to choose.

Economics of development

The process of vaccination brought a major challenge to the economy this is because most kinds of diseases which are so prevalent in the developing countries such as tuberculosis and HIV need to be vaccinated. Verch et al. (1998) show for this reasons these countries have to plan properly for the immunization programs since other pharmaceutical businesses and biotechnology firms are not in the position of providing vaccinations to all these diseases this is because there is little or no revenue to sustain the country. This also happens in more wealthy countries where the revenue returns are minimal or if they are faced with many risks. Currently vaccines have been government's initiatives where the government has to fund hospitals thus people get to be immunized.

This is because vaccines reduces more cost on treating the disease and thus boosts citizens' health. Currently immunization programs have been on the rise especially those that are given to infants. This exercise has been due to governments policies introduced and their need to support the move and it is not all about offering economic incentives. To motivate the programs researchers and policy makers have introduced another method of dealing with the situation where they propose for few prices and tax which will be helpful to businesses wanting to offer vaccines to people especially the HIV vaccine which will also ensure that everyone get access to the treatment (Fumio 2006).

Patents have been filed showing the introduction of these vaccines which has also been a hindrance to the introduction of new vaccines. This is also due to the poor security given to the product and the need for secrecy. The production of vaccines involves various kinds of processes. This is where the mammalian cells that become somehow necessary as compared to their options such as the chicken cells that are few in production and are easily contaminated. The introduced technology shows that the detoxified vaccine grows due to the toxoids contained in the bacteria. Vaccines such as combination are meant to reduce some antigens thus reducing interference brought about by the use of pathogens.

Excipients

The production of vaccines contains several kinds of properties which include; Aluminum salts or gels that are used as an adjuvant which are then mixed to increase the potential of the vaccine in use. By use of these the vaccine will only be taken once and not regularly. Other properties used in making vaccines include antibiotics which are helpful in preventing multiplication of bacteria as the vaccine is being made and stored. Egg proteins are also necessary in the production of the vaccine especially those used to protect against influenza as they contain chicken eggs (Pizza et al. 2001, p. 35).

Bacteria products are inactivated using formaldehyde which is a property used in toxoids. It is also used in destroying viruses and bacteria that may cause some interference. To stabilize the vaccine incase it is exposed to direct heat, humidity or acidity it is necessary to make use of monosodiumglumate and finally the thimerosal is used in preserving the vaccine. This is because it contains some mercury that is mixed in the mixture to avoid multiplications of bacteria.

Role of preservatives

Storage of vaccines has always been a major challenge to most manufacturers and producers. They therefore need to be preserved in the right manner in order to protect them from adverse effects. One example of a problem experienced due to lack of preservatives include diphtheria vaccine that killed about 12 adults and 22 children this was in 1928. Some preservatives available today include thiomersal which protects vaccines against bacteria. Preservatives are also important as they increase stability, safety and ability to act effectively. In terms of delivering vaccines it is important to provide certain systems to be used in the delivery method. Some methods that are currently been used include liposomes (Gomez et al. 1998, p. 355).

There has also been an improvement in technology that is used in the delivery methods for example the polio vaccine does not need much training as it had earlier been tested and this resulted to increased use of this vaccine. Oral vaccines have been preferred as it is impossible for them to be contaminated easily and since they are solid in nature they are stable and would not freeze easily. They however need to be kept under certain conditions from the time of manufacture to the time they are administered to the patient.

The development of vaccines has had some evolution since the time they started been used for immunization. They have mostly been used by children currently the adults have been targeted also. There has been a vaccine that have more than one constituent and which are mostly used around the world. New methods of administering the vaccines have also been introduced for example instead of injection the vaccine can be taken through oral means. The vaccines have also been developed in order to stimulate the adaptive reactions of the cells and other ideas proposed include introducing vaccines to protect against chronic diseases.

Need and importance of Edible Vaccines:

New strategies for supplying vaccines have recently been developed by The World Health Organization (WHO). This is after an estimate that more than 10 million children below five years die in developing countries due to the spread of infectious diseases that could have otherwise been prevented through administration of vaccines. Charles J. Arntzen witnessed a meeting in New York where it was found out that certain plants could be used for the production of immunogenic proteins. He used this idea of using the known plants for creation of immunogenic proteins whereby they will be easily available to everyone and will be at lowered costs thus the poor and those in the developing countries will be in a position of using them.

This method improved accessibility of vaccines that were too difficult to be bought by the poor in the society. The system was also meant to improve agricultural procedures where farmers will be needed to plat more of the plant. Vaccines that need to be injected on humans need one to be more careful and therefore it is necessary to give the right treatment. Diseases such as hepatitis B, C and HIV are easily spread through the use of same needles for injections. Other care needed include the storage of the vaccine where some of them need to be kept in a refrigerator which is a major challenge to people living in rural and remote areas (Arakawa et al. 1998, p. 292).

It is therefore necessary to use a cost effective type of vaccine that will need few procedures and will be easy to store and safe. These types of plants are kept in way that they are able to generate the expected type of vaccine that will protect individuals and people against harmful pathogens. Edible vaccines are produced through the combination of certain kinds of inventions found in plant science as this are important in the creation of medical products that are effective to use and cheap. The products form edible vaccines are also preferred since it is easy to administer them to patients and more so to children. The vaccines also do not need one to be a professional as the procedure is simple (Charles and Richard 1998).

Since the introduction of these kinds of vaccines, large scale businesses have been formulated which have effective services that enable the vaccine to be available at any time and whose distribution makes it easy for all to access. The vaccine is offered to children when it is not pure and this lowers the cost of producing the product. The plant used in extraction of the vaccine can also be grown at home thus citizens will not have to spend more on capital intensive methods of manufacturing. Edible vaccines have both genetic and thermal stability that enables the vaccine to stabilize even when not kept on a refrigerator when storing or transporting it to the needy.

The advantages of these edible vaccines include the fact that they are very effective once they are consumed in the body especially if consumed through food. The other reason is that the adjuvant does not have to be present to enhance effectiveness. As compared to other injections, the feasibility of edible vaccines is properly administered. They can also be easily separated from other materials found in plants and then later can be purified to obtain a better solution. The edible vaccines can effectively protect one from pathogens found in animal cells as it is convenience to use, easy to store and also can be transported easily to rural parts.

The temperature contained in the cultivation of the plant can be stabilized thus the vaccines are not damaged. The breeding is easy and bring about multiplication of the needed materials. The vaccine can also be produced at a lower cost unlike the other types of vaccines which are so costly. The administration of the vaccine does not necessarily need trained personnel as there are no procedures to be followed. Verch (1997, pp. 69-75) show there is also no need for sterile injections as many types of vaccines are taken through food. A community that has adhered to this method of manufacturing edible vaccine is able to increase in its economic conditions as they do not spend more of their revenue purchasing other vaccines or depending on foreign aid. The disadvantages of the edible vaccine are very few and they include that the dosage is not advisable to be administered to infants as their immunity is very low and the other reason is that the dosage of the vaccine does not offer the right schedule of using it.

Strategy for production of Edible Vaccines:

The process of producing edible vaccines involves the selection of various kinds of genes which are found in plants and animals. The plants are formed in a way that they produce the proteins needed in the manufacture of vaccines. The protein used in this process includes the transformation that is found in plants and the one found in animals in known as transgenic. The edible vaccine can be compared to those of subunit since they contain an antigenic protein substance. These kinds of vaccines are preferred since they do not cause any kind of infection on the user thus are very safe to use especially to patients whose immune system is weak. The vaccine is administered by giving human food made from the plant where an active antigen that is consumed through the mouth is present and it acts in a way that the pathogen causing diseases is identified and destroyed (Fumio 2006).

Comparing the edible vaccine method of administration with the conventional one, it is very cheap to use edible vaccines. This is because the substance known as immunoglobulin has been of major significance as it is made from tobacco plants. The method of immunization is very passive just like how the antibodies are made in the mother's milk that helps children to be protected against harmful pathogens. Some of the edible vaccines that are known to have been successful in the preventing diseases includes; Escherichia coli, Norwalk virus etc.

Plant candidates for production of Edible vaccines:

In choosing the best plant to use in the production of edible vaccine, it is important to check on the availability of procedures to be followed in the manufacturing of the genetic vaccine. Most of these products used in the manufacture of edible vaccines include the tobacco which has been known as the best plant to use in the processes. Other plants used in the processes of the vaccines include fruit trees since it is easy to use the fruits as they can either be taken as raw or through cooking them. The raw fruits are helpful as the antigens are not to be activated in the process of cooking. Fruits such as bananas are also used in the manufacture of these vaccines and thus protect one against the antigens.

The table 1 below shows that despite the successful effort of generating certain proteins in transgenic plants, the antigen found in plants has been used in earlier for example CT-B which is found in potato, LT-B contained in tobacco and potato, rabies virus-G protein in tomato, HBsAg in tobacco and potato and finally is the Norwalk virus in tobacco and potato.

Table 1: Transgenic plants producing antigens (Lal et al.1997).

S. No.

Plant

Antigen

1.

Tobacco

Hepatitis B surface antigen

2.

Potato

E. coli heat labile enterotoxin B subunit

3.

Tomato

Rabies virus glycoprotein

4.

Tobacco

Novark virus capsid protein

5.

Potato, Tobacco

Cholera Toxin B subunit

6.

Tobacco

Influenza antigen

7.

Spinach

Rabies antigen

8.

Tobacco

HIV antigen

9.

Tobacco

Colon cancer antigen

10.

Arabidopsis

Glycoprotein of swine transmissible gastroenteritis virus

Second generation of Edible Vaccines:

The foreign genes found in plant cells and the parts that can be eaten has made it easier to be given an opportunity of increasing the production of vaccines and the introduction of other kinds of plants that are needed in expressing the antigen proteins. To produce a multi-component vaccine, one needs to combine both plant and animal proteins since each one of it contains varying antigens. The subunit vaccine known as Vibro cholera toxic (VC-B) is combined with other copies thus being in a position of forming a doughnut shape. This strategy makes it easy for various types of antigen to be formed in the immune system such as the edible vaccine that protects humans against rotavirus and cholera.

The approach used in this is accepted socially and in most cultures. Programs have also been introduced such as the global alliance for vaccines and immunization (GAVI) which enables the manufacturers to be in a position of combining these kinds of vaccines. The vaccines are capable of bringing out a systemic reaction once they have been used. Those taken through food are able to get to the intestines where they are absorbed in the proteins (Cynthia, W 1997, p. 499).

Limitations in administration of Edible Vaccines:

Optimization of dose of vaccine: For immunization to be said that it has been successful the antigen present has to be administered in and the dosage should be given according to age, psychological state of the user, level of immunity etc. Higher amounts of dosage may be tolerated by the body but other times it may occur that the dosage of not sufficient thus does not perform the work it was meant to. Dosage got from the edible vaccine vary according to the type of plant used for example fruit trees, the plant itself, the size and the amount of protein contained in the plant. One problem is that children at the age of five may not be capable of eating the plant unless the vaccine is in powder form. Thus these kinds of difficulties and others such as lack of dosage uniformity and purity lead to major challenges (Verch et al. 1997).

Protein content of transgenic organisms: Immunogenic protein is not highly concentrated in the transgenic organisms and this thus lowers the immunogenicity. This reason makes it possible for the edible vaccines to be given in big amounts. Increasing copies of foreign genes results to harming the organism contained in the transgenic. To attain higher levels of the transgenes, the constituents are combined together with the components of the regulatory thus making it possible to express the transgene in certain organs.

Immunogenicity: The edible vaccines have been viewed by many as if they contain lower levels of immunity. For the vaccines to be capable of achieving immunogenicity it is necessary to include adjuvants, use if the body has a higher immunity system for example if there are presence of M cells that are contained in the lining of the intestines which are later transferred to the immune cells (Modelska et al. 1997).

Role engineered adjuvant for edible vaccine

Antigenic variability: It has always been so difficult to introduce edible vaccines that can be used against diseases brought about by anti genetically groups of pathogens in addition to other types of pathogens brought by various kinds of organisms. Other may be compound in nature but containing varying life cycles of parasites such as those used in breeding malaria or transforming organisms causing HIV virus.

Thermal Stability: The protein contained in foods is hardly affected by heat. Cooking of these foods however tampers with the protein contents thus destroying them and so will not be effective in achieving immunity as it affects the nature of the protein. It is therefore necessary to observe much care while introducing immunogenic proteins in edible foods. Studies have shown that the stability of heat in the immunogenic proteins in addition to the losses caused due to cooking these foods. It has also been discovered that transgenic potatoes boiled for 3 minutes will loose about 50% of the immunogenic protein (Daniell et al. 2001, pp. 219-226).

Lack of Awareness and Funds: Most people in business especially in small companies have tried to research on the marketing procedures to be used in selling edible vaccines to the developing countries. According to Tacket and Mason (1999) other people operating large companies have wanted to introduce edible vaccines to be used by farm animals and not by human beings. Private and government funding agencies have not been supporting the move to research on edible vaccines and for this reason other international agencies stopped supporting them once there was a global alarm alongside the use of genetically customised vaccines.

Regulatory Issues: The government has found it difficult on which category to place the edible vaccines. This is because the vaccine has to be food, drug or an agricultural product. The government is also not decided whether it will be necessary to license the antigen or produced fruit or the transgenic seeds. The plants used in the production should be customized and be kept in green houses thus separate with other plants as this ensures that such plants will not be available to the outside world. Transgenes are capable of being transferred through pollen grains, sucking insects, soil microbes where the plant wounds or tend to break roots thus causing pollution of the surface and the ground. The proteins contained in humans are usually restricted to be tested in clinics particularly by certain ethics.

Future of Edible Vaccines: edible vaccines are to last in future but certain conditions have to be observed. One is the socio-cultural factor where the vaccines are should be acceptable by all as a modified plants. Mishra et al. (2008, p. 285) describe that the transgenic should also be kept stable as it will enable the increase of productivity. The transgenic plants should also be separated from other plants to avoid exposing them to the outside environment and the other reason includes avoiding potential side effects of the vaccine especially where the proteins mat lead to allergens. These kinds of vaccines have been very important to many individuals as they provide better health care for the entire society since the 20th century. According to Arntzen (1998, p. 20) innovation of technology have also increased the production of many edible vaccines for example the oral DNA vaccines, intranasal drugs and the plant vaccines that are consumed in the body through food. This introduction has been useful as it has led to a bright future of safe products and more effective.

The reasons why most pharmaceutical companies have not greatly developed on the use of the edible vaccines include the fact that there are doubts brought about by the potential for the returns on investments. This means that these businesses think that they would not achieve more profits if they sell or supply edible vaccines since most people will buy the cheaper drugs which will serve the same function. The other reason is because there are several uncertainties which may arise in the process of regulating the sale of edible vaccines.

This is because the government may fail to regulate a business to sell these products as the other types of vaccines bring the country more revenue through taxes. Kirti (2010, p. 30) show the human clinical trial data may also be very limited thus it will not be capable of establishing the right dosage to be used by various kinds of people for example the right dosage for children and one that will not affect their development. The timing of the delivery may also not be known to the pharmacists and this makes is the reason why the edible vaccines are not sold by pharmacists. The evaluation of adverse immunological effects may also be difficult to study.

Conclusion

The edible vaccines are therefore very safe to use and the most effective method used in immunization of the diseases that are easily spread. These types of vaccines are preferred than the traditional vaccines in terms of production, distribution and delivery to the needy people in the society. However, there are several aspects that have to be considered before using the vaccines for instance technical difficulties which cause a major challenge on the implementation of the vaccine. A cost effective method has also been introduced which will help to eradicate certain kinds of diseases such as AIDS, malaria, other types of disorders that are spread globally. It is the hope of those producing the edible vaccine that they shall one day be the day to day protection against the deadly diseases and that the vaccines shall be accepted globally.

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