DNA Vaccine Delivery Methods and Advancements

This assignment delves into various methods used for delivering DNA vaccines, highlighting the crucial role of efficient delivery systems. It explores the application of nanoparticles as carriers, discussing their benefits and limitations. Additionally, it examines the use of viral vectors like Vaccinia virus in vaccine delivery, analyzing their mechanisms of action, advantages in terms of immunogenicity, and potential challenges related to immune evasion and safety. The assignment emphasizes the significance of selecting appropriate delivery systems for optimizing DNA vaccine efficacy and overcoming hurdles in vaccine development.

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Production and Use of Vaccines
Name of the Student
Name of the University
Author note

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Table of Contents
Introduction......................................................................................................................................2
Discussion........................................................................................................................................2
Whole-Organism Vaccines..........................................................................................................3
Purified Macromolecule Vaccines...............................................................................................4
Bacterial Polysaccharide Capsules..........................................................................................5
Bacterial Exotoxin Vaccines....................................................................................................5
Synthetic Peptide Vaccines......................................................................................................5
Recombinant Vector Vaccines....................................................................................................5
DNA Vaccine...............................................................................................................................6
Multivalent subunit vaccine.........................................................................................................7
Conclusion.......................................................................................................................................8
References........................................................................................................................................9

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Introduction
The concept of vaccination was first introduced by Edward Jenner. Its contribution is
well known for the treatment of smallpox (Kupper 2012). Vaccine is capable of generating both
active and passive immunity. However, it is regarded as a potent medium to generate active
immunity. However, there still remains a crying need to the production of vaccines against
several deadly diseases, especially to those for AIDS (Picker, Hansen and Lifson 2012).
Moreover, increase in the incidence of multi drug resistant bacteria has further up regulated the
need for vaccine to combat infectious diseases caused by micro-organisms (Reardon 2014).
Recently trials have also been made for the generation of vaccine against cancer. The report here
sheds lights on different types of vaccines that are produced so far along with its advantages and
disadvantages.
Discussion
Vaccines confer immunity to the infectious micro-organisms and this is achieved via
active and passive immunization (Owen, Punt and Stranford 2013).
Types of
immunization
Active immunization Passive Immunization
Agents used for
Immunization
Immunization with microbial pathogen
or antigenic determinant of microbes
that elicit immune response but do not
cause infection
Antibodies derived from human or animals
or performed antibodies. Naturally passive
immunization occurs via transmission of
maternal antibodies through placenta and
milk
Common agent
used
Vaccines Agents Diseases
Attenuated organisms Horse antivenin Botulism
Inactivated organisms Horse antivenin Bite of black widow
spider
Cloned micro-organisms Hepatitis Pooled human
gamma globulin
Purified micro-organisms Measles Pooled human
gamma globulin
Recombinant proteins Rabies Pooled human
gamma globulin
Multivalent proteins Snake bite Horse antivenin
DNA and toxoid Tetanus Pooled human
gamma globulin and
horse antitoxin
Advantages and
Disadvantages
Active immunization is acquired
artificially via administration of
vaccines. Vaccines promotes the
proliferation of T-cells and B-cells and
Performed antibodies produced from another
species generate strong iso-typic response.
This response may generate IgE mediated
mast cell degranulation and systemic

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subsequent formation of memory cells anaphylaxis.
Diseases which
are cured
Hepatitis B vaccines, Diphtheria-
pertussis, tetanus, inactivated salk
vaccines, sabin vaccines, measles-
mumps-rubella, influenza, varicella
zoster, pneumococcal conjugate
vaccine
Diphtheria, Rabies, Hepatitis B
Table: Comparison between active and passive immunity
(Source: Owen, Punt and Stranford 2013)
Whole-Organism Vaccines
The whole organisms which are used as vaccines are bacteria or virus which are either
inactivated or live but in an attenuated stated (avirulent). Attenuated means, the virus or the
bacteria have already lost their ability to generate significant pathogenic response. However, they
have retained their capacity of transient growth within the body of the inoculated host (Todd et
al. 2013).
Figure: Classification of Whole Organism Vaccines
(Source: Owen, Punt and Stranford 2013)
Attenuation is achieved by growing the pathogenic microorganisms under abnormal
condition for a prolong time. For example Bacillus Calmatte-Guerin (BCG), was developed via
growing Mycobacterium bovis in medium containing bile. 13 years later strain adapted its growth
under the adverse condition leading to the generation of attenuated strain of M. bovis (Kawai et
al. 2013). Another example of attenuated vaccine is Sabin and Measles vaccines (attenuated
strains of virus) (Owen, Punt and Stranford 2013).

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Attenuated Vaccines
Advantages Disadvantages Latest Advancement
Prolong immune response
causing increased immunity
and generation of immune
response.
Possibility of reverting back
to the virulent form. This has
led to the generation of
inactivated polio vaccines,
Salk vaccine.
Heat inactivation causes the
degeneration of the antigenic
epitopes that is responsible to
the generation of immuno-
genecity
Attenuation is done irreversibly via the
application of genetic engineering
technique. This is done via gene
silencing. Removal or silencing of the
virulence causing genes.
Example: Herpes simplex virus vaccines
for pigs: virulent gene, thymidine kinase
(tk) is removed
Recently attenuated vaccines for
rotavirus (which causes diarrhoea) is
prepared via genetic engineering
They require only single dose
of immunization (Exception
is Sabin vaccine used for
polio virus which requires
three doses of immunization)
in comparison to the killed
vaccines which require
multiple booster doses
They generate cell-mediated
immune response in
comparison to killed vaccines
that is only capable of
generating humoral immune
response.
Table: Advantages and Disadvantages of Attenuated Vaccines
(Source: Owen, Punt and Stranford 2013)
Purified Macromolecule Vaccines
The risk of the killed whole organism vaccines and the attenuated vaccines lead to the
discovery of purified macromolecule vaccines (Nascimento and Leite 2012).

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Figure: Classification of Purified Macromolecule Vaccines
(Source: Owen, Punt and Stranford 2013)
Bacterial Polysaccharide Capsules
Polysaccharide capsules for bacteria are selected as a target for vaccine production
because virulence of several bacteria depends on the antiphagocytic properties of these
polysaccharide capsules which are hydrophilic in nature. The logic is, coating of these capsular
polysaccharide with antibody uplift the ability of neutrophils and macrophages to phagocyte the
pathogens. However, polysaccharide vaccines only activate TH cells. It also activates B-cell in an
thymus independent type 2 manner (TI-2). TI-2 causes only IgM maturation but no affinity
maturation and class switching and thus little or no development of memory cells (Lockyer et al.
2015; Vinuesa and Chang 2013). Advanced are being made via conjugation of polysaccharide
capsules with a protein in order to generated memory response.
Bacterial Exotoxin Vaccines
Diphtheria and tetanus vaccines are produced via purifying bacterial exotoxin and then
the inactivation is done via formaldehyde and then the compound is known as toxoid. These
toxoid produced anti-toxin antibodies are thus capable of neutralizing the harmful bacterial
toxins. Genetic engineering techniques are used to clone genes of these toxins in order to
produce toxoid in substantial amount (Tanom et al. 2013).
Synthetic Peptide Vaccines
Synthetic peptides are used also used as vaccines. However, peptides due to their small
structure are not as immunogenic as proteins and hence lag behind in generating humoral and
cell mediated immunity. Synthetic peptides are now administered with adjuvants and conjugates
in order to generate protective immunity. At present peptide vaccines are in a trial for the
generation effective vaccination remedy against cancer (Vacchelli et al. 2012).
Recombinant Vector Vaccines
Vaccina is large complex virus with 200 genes (Smith et al. 2013). It is used as an
attenuated vaccine to treat smallpox. At present it is genetically engineered to propagate dozen of
foreign genes without tampering its ability to infect host cells and simultaneous replication. This
genetically engineered vaccina virus is infected in the host body via scratching of skin that
causes localised infection (Wyatt, Earl and Moss 2015).

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Figure: Production of Vaccina vector vaccine
(Source: Owen, Punt and Stranford 2013)
Other virus which are used as vectors for the recombinant vaccine production include
canarypox virus. It is usually engineered to carry bacteria that cause cholera and typhoid (Teigler
et al., 2014).
DNA Vaccine
DNA vaccine is the most recent advancement in the field of vaccine. It is generally
produced via plasmid DNA that is being genetically engineered containing antigenic proteins.
Plasmid DNA is directly injected into the muscle cells. The cells take up the DNA leading to the
generation of both humoral and cell-mediated immune response. Muscle is used as the target of
injection because muscle cells have greater power to express the injected DNA. DNA injected
either gets integrated into the chromosome (passed on to generation) or remains within the cell as
an episomal form (Williams 2013). The main advantage of DNA vaccine is gets expressed into
the host in its natural from with no denaturation. Thus the immune response generated is exactly
like that of the antigen that injects the cell. DNA vaccine generates both cell mediated and
humoral immunity. Moreover, the DNA vaccine does not require refrigeration and thus do not
require storage, reducing the cost of maintenance (Tretyakova et al. 2013). Moreover, gene gun
method promotes rapid administration of the DNA vaccine (Xu et al. 2012; Shah et al. 2014).

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Figure: DNA vaccine generating both humoral and cell mediated immune response
(Source: Owen, Punt and Stranford 2013)
Multivalent subunit vaccine
Multivalent subunit vaccine is an advanced mode of the synthetic peptide vaccine that
contains multiple copies of the given peptide. It is generally injected intra-cellularly in order to
generate cytotoxic T-cells (Azmi et al. 2014). Protein micelles, liposomes and
immunostimulating complexes (ISCOMs) are used to deliver multivalent subunit vaccine (Cruz-
Bustos et al. 2012).
Figure: Delivery of Multivalent subunit vaccine via ISCOMS

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(Source: Owen, Punt and Stranford 2013)
Figure: Comparative study between different vaccines
(Source: Owen, Punt and Stranford 2013)
Conclusion
Thus from the above discussion it can be concluded that vaccines are an effective agent
for controlling infectious disease. Vaccine help in the generation of both humoral and cell
mediated immune response that helps to combat recurrent infection via generating memory cells.
However, there lies certain disadvantage of using vaccine like the live attenuated vaccines can
reverse back to its virulent form, resulting in an epidemic. Recent researchers are most
concentrated in the development of DNA vaccines, synthetic peptide vaccines and multivalent
subunit vaccines via the application of genetic engineering techniques. Though DNA vaccines
are cost-effective in terms of storage, there lies huge expenditure of cost in generation of these.
Moreover, further research are required in this field in order to generate vaccines against the
most fatal disease that are prevalent in mankind like cancer and HIV AIDS (Human
Immunodeficiency Virus-Acquired Immuno Deficiency Syndrome).

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References
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González, F. and Osuna, A., 2012. Functionalization of immunostimulating complexes
(ISCOMs) with lipid vinyl sulfones and their application in immunological techniques and
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