This presentation talks about vaccines, currently being used in medicinal processes and therapeutics and their types. It elaborates the importance of the different types of vaccines along with their examples and their mechanism of action. The mode of production of all the types of vaccines is also discussed in the presentation including recent developments made for the production of mRNA vaccine against SARS-CoV-2

1. PRESENTATION
BY
TATHAGAT SAH
BTech. Biotechnology
URN – 1901181

2. VACCINES
Table of Contents
• Vaccine and Vaccination
• Immunization and Immunity
• Types of Vaccines
o Live-attenuated vaccines
o Inactivated vaccines
o Messenger RNA (mRNA) vaccines
o Subunit Vaccines – Toxoid, Polysaccharide and Recombinant
o Conjugate vaccines
o DNA vaccines
o Recombinant Vector vaccines

3. Vaccine and Vaccination
Vaccine is a biological product that stimulates a person’s immune
system to produce immunity to a specific disease, protecting the person
from that disease. Vaccines are usually administered through needle
injections, but can also be administered by mouth or sprayed into the
nose.
Vaccination refers to the act of introducing a vaccine into the body to
produce immunity to a specific disease.
Immunization and Immunity
Immunization is the process of being made immune or resistant to an
infectious disease, typically by the administration of a vaccine. It implies
that a person had an immune response.
Immunity refers to protection against a disease. There are two types of
immunity, passive and active. Immunity is indicated by the presence of
antibodies in the blood and can usually be determined with a laboratory
test.

4. Types of Vaccines
There are several different types of vaccines. Each type is designed to
teach the immune system how to fight off certain kinds of germs and
the serious diseases they cause.
When scientists create vaccines, they consider:
• How the immune system responds to the germ
• Who needs to be vaccinated against the germ
• The best technology or approach to create the vaccine
Based on a number of these factors, scientists decide which type of
vaccine they will make. There are several types of vaccines, including:
• Live-attenuated vaccines
• Inactivated vaccines
• Messenger RNA (mRNA) vaccines
• Subunit Vaccines – Toxoid, Polysaccharide and Recombinant
• Conjugate vaccines
• DNA vaccines
• Recombinant Vector vaccines

5. Live-Attenuated Vaccines
Live vaccines use a weakened (or attenuated) form of the germ that
causes a disease.
Attenuation can often be achieved by growing a pathogenic bacterium
or virus for prolonged periods under abnormal culture conditions. This
selects mutants that are better suited for growth in the abnormal
culture conditions than in the natural host.
For example, an attenuated strain of Mycobacterium bovis called
Bacillus Calmette-Guérin (BCG) was developed by growing M. bovis on a
medium containing increasing concentrations of bile.
Diseases against which LVA vaccines are used include:
• Measles, Mumps and Rubella (MMR Vaccine)
• Polio (Sabin vaccine)
• Rotavirus (Rotarix, Rota Teq, Rotavac, Rotavin-M1)
• Tuberculosis (BCG Vaccine)
• Varicella (Varivax, Varilrix)
• Yellow fever (YF-Vax, Stamaril)

6. Advantages of Live-Attenuated Vaccines
Because of their capacity for transient growth, such vaccines provide
prolonged immune system exposure to the individual epitopes on the
attenuated organisms and more closely mimic the growth patterns of
the “real” pathogen, resulting in increased immunogenicity and
efficient production of memory cells.
Thus, these vaccines often require only a single immunization. Just 1 or
2 doses of most live vaccines can induce a lifetime of protection against
an antigen and the disease it causes.
Disadvantages of Live-Attenuated Vaccines
The live forms may mutate and revert to virulent forms in vivo,
resulting in paralytic disease in the vaccinated individual and serving as
a source of pathogen transmission.
They need to be kept cool, so they don’t travel well. This means that
they can’t be used in countries with limited access to refrigerators.

7. Development of a poliovirus type 2 vaccine strain (nOPV2) that is genetically
more stable and less likely to regain virulence than the original Sabin2 strain.
Modifications were introduced at the 5′ un-translated region of the Sabin2
genome to stabilize attenuation determinants, 2C coding region to prevent
recombination, and 3D polymerase to limit viral adaptability.

8. Inactivated Vaccines
Inactivated vaccines use the killed version of the germ that causes a
disease. The pathogen is generally treated with heat or chemicals to
achieve this.
Chemical inactivation with formaldehyde or various alkylating agents
has been successful. The Salk polio vaccine is produced by formaldehyde
inactivation of the poliovirus.
Inactivated vaccines are used to protect against:
• Cholera (Dukoral®, Shanchol™ and Euvichol®)
• Influenza
• Hepatitis A (Havrix, Vaqta)
• Plague
• Polio (Salk vaccine)
• Rabies (HDCV vaccine (Imovax, Sanofi Pasteur), PCECV vaccine
(RabAvert, Novartis))

9. Advantages of Inactivated Vaccines
• Stable
• Safer than live vaccines
• Refrigerated storage not required
Disadvantages of Inactivated Vaccines
• Killed vaccines often require repeated boosters to achieve a
protective immune status. Because they do not replicate in the host,
killed vaccines typically induce a predominantly humoral antibody
response and are less effective than attenuated vaccines in inducing
cell-mediated immunity or in eliciting a secretory IgA response.
• Even though the pathogens they contain are killed, inactivated
whole-organism vaccines still carry certain risks. A serious
complication with the first Salk vaccines arose when formaldehyde
failed to kill all the virus, leading to paralytic polio in a high
percentage of recipients.
• Risk is also encountered in the manufacture of the inactivated
vaccines. Large quantities of infectious agents must be handled safely

10. Messenger RNA (mRNA) Vaccines
mRNA vaccines make proteins in order to trigger an immune response
and this technology is used to make some of the COVID-19 vaccines.
COVID-19 mRNA vaccines give instructions for our cells to make a
harmless piece of what is called the “spike protein”. The spike protein is
found on the surface of the virus that causes COVID-19.
First, COVID-19 mRNA vaccines are given in the upper arm muscle. Once
the instructions (mRNA) are inside the immune cells, the cells use them
to make the protein piece. After the protein piece is made, the cell
breaks down the instructions and gets rid of them.
Next, the cell displays the protein piece on its surface. Our immune
systems recognize that the protein doesn’t belong there and begin
building an immune response and making antibodies, like what happens
in natural infection against COVID-19.
At the end of the process, our bodies have learned how to protect
against future infection.

13. Facts about COVID-19 mRNA Vaccines:
 They cannot give someone COVID-19
• mRNA vaccines do not use the live virus that causes COVID-19.
 They do not affect or interact with our DNA in any way.
• mRNA never enters the nucleus of the cell, which is where our
DNA is present.
• The cell breaks down and gets rid of the mRNA soon after it is
finished using the instructions.
Advantages of mRNA Vaccines
mRNA vaccines have several benefits compared to other types of
vaccines, including shorter manufacturing times and, because they do
not contain a live virus, no risk of causing disease in the person getting
vaccinated.

14. Subunit – Toxoid, Polysaccharide and Recombinant
Subunit vaccines use only specific, purified macromolecules derived
from the pathogen. The three most common applications of this
strategy are, inactivated exotoxins or toxoids, capsular polysaccharides
or surface glycoproteins, and key recombinant protein antigens.
Toxoid
Some bacterial pathogens, including those that cause diphtheria and
tetanus, produce exotoxins that account for all or most of the disease
symptoms resulting from infection.
Diphtheria and tetanus vaccines have been made by purifying the
bacterial exotoxin and then inactivating it with formaldehyde to form a
toxoid. Vaccination with the toxoid induces anti-toxoid antibodies, which
are capable of binding to the toxin and neutralizing its effects.
Conditions for the production of toxoid vaccines must be closely
controlled and balanced to avoid excessive modification of the
epitope structure while also accomplishing complete detoxification.

15. Polysaccharide
The virulence of some pathogenic bacteria depends primarily on the
anti-phagocytic properties of their hydrophilic polysaccharide capsule.
Coating the capsule with antibodies and/or complement greatly
increases the ability of macrophages and neutrophils to phagocytose
such pathogens. These findings provide the rationale for vaccines
consisting of purified capsular polysaccharides.
The vaccine for Streptococcus pneumoniae (the organism which causes
pneumococcal pneumonia) consists of 13 antigenically distinct capsular
polysaccharides (PCV13).
The vaccine for Neisseria meningitidis , a common cause of bacterial
meningitis, also consists of purified capsular polysaccharides.
Some viruses carry surface glycoproteins that have been tested for use
in antiviral vaccines, with little success. Glycoprotein-D from HSV-2 has
been shown to prevent genital herpes in clinical trials of some vaccines,
therefore this may be the approach for some antiviral vaccines as well.

16. Recombinant
Theoretically, the gene encoding any immunogenic protein can be
cloned and expressed in cultured cells using recombinant DNA
technology, and this technique has been applied widely in the design of
many types of subunit vaccines.
A number of genes encoding surface antigens from viral, bacterial, and
protozoan pathogens have been successfully cloned into cellular
expression systems for use in vaccine development.
The first such recombinant antigen vaccine approved for human use is
the hepatitis B vaccine, developed by cloning the gene for the major
hepatitis B surface antigen (HBsAg) and expressing it in yeast cells. The
recombinant yeast cells are grown in large fermenters, allowing HBsAg
to accumulate in the cells. The yeast cells are harvested and disrupted,
releasing the recombinant HBsAg, which is then purified by
conventional biochemical techniques.
Recombinant hepatitis B vaccine induces the production of protective
antibodies.

17. Therefore subunit vaccines are used to protect against:
• Hepatitis B
• Pertussis
• Diphtheria and Tetanus
Advantages and Disadvantages of Subunit Vaccines
Because these vaccines use only specific pieces of the germ, they give a
very strong immune response that’s targeted to key parts of the antigen.
They can also be used on almost everyone who needs them, including
people with weakened immune systems and long-term health problems.
One limitation of some subunit vaccines, especially polysaccharide
vaccines, is their inability to activate TH cells. Instead, they activate B
cells in a thymus- independent type 2 (TI-2) manner, resulting in IgM
production but little class switching, no affinity maturation, and little, if
any, development of memory cells. However, vaccines that conjugate a
polysaccharide antigen to a protein carrier can alleviate this problem by
inducing TH cell responses.

18. Conjugate or Multivalent Vaccines
These types of vaccines employ the fusing of a highly immunogenic
protein to a weak vaccine immunogen (a conjugate) or mixing in
extraneous proteins (multivalent) to enhance or supplement immunity
to the pathogen.
Although this type of vaccine can induce memory B cells, it cannot
induce memory T cells specific for the pathogen.
The vaccine against Haemophilus influenzae type b (Hib), a major cause
of bacterial meningitis and infection-induced deafness in children, is a
conjugate formulation consisting of type b capsular polysaccharide
covalently linked to a protein carrier, tetanus toxoid.
MCV4 vaccine is a multivalent vaccine consisting of individual capsular
Neisseria polysaccharide antigens joined to the highly immunogenic
diphtheria toxoid protein.

19. One common means of producing a multivalent vaccine that can deliver
many copies of the antigen into cells is to incorporate antigens into
protein micelles, lipid vesicles (liposomes), or immuno-stimulating
complexes.
Protein-containing liposomes are prepared by mixing the proteins with
a suspension of phospholipids under conditions that form lipid bilayer
vesicles; the proteins are incorporated into the bilayer with
the hydrophilic residues exposed.
Immuno-stimulating complexes (ISCOMs) are lipid carriers prepared by
mixing protein with detergent and a glycoside called Quil A, an adjuvant.
Membrane proteins from various pathogens, including influenza virus,
measles virus, hepatitis B virus, and HIV, have been incorporated into
micelles, liposomes, and ISCOMs and are being assessed as potential
vaccines.
In addition to their increased immunogenicity, liposomes and ISCOMs
appear to fuse with the plasma membrane to deliver the antigen intra-
cellularly, where it can be processed by the endogenous pathway,
leading to CTL responses.

20. (T)A conjugate vaccine is prepared by
conjugating the surface polysaccharide to a
protein molecule, making the vaccine more
immunogenic than either alone.
(R)ISCOMs and liposomes can deliver
agents inside cells, so they mimic
endogenous antigens. Subsequent
processing by the endogenous pathway and
presentation with class I MHC molecules
induces a cell-mediated response.

21. DNA Vaccines
These utilize plasmid DNA encoding antigenic proteins that are injected
directly into the muscle of the recipient. This strategy relies on the host
cells to take up the DNA and produce the immunogenic protein in vivo,
thus directing the antigen through endogenous MHC class I presentation
pathways, helping to activate better CTL responses.
The DNA appears either to integrate into the chromosomal DNA or to be
maintained for long periods in an episomal form, and is often taken up
by dendritic cells or muscle cells in the injection area.
DNA vaccines are able to induce protective immunity against a number
of pathogens, including influenza and rabies viruses.
The addition of a follow-up booster shot with protein antigen (called a
DNA prime and protein boost strategy), or inclusion of supplementary
DNA sequences in the vector, may enhance the immune response. One
sequence that has been added to some vaccines is the common CpG
DNA motif found in some pathogens.

22. Comparative
Analysis of
Vector DNA and
mRNA vaccines.
• It can be seen that
the process of
transcription occurs
when vector DNA
vaccine is
administered, which
produces mRNA
which is then
translated into viral
spike proteins.
• In mRNA vaccines,
the host cell directly
translates the
mRNA strand into
spike proteins.

23. Advantages of DNA Vaccines
DNA vaccines offer some potential advantages over many of the existing
vaccine approaches:
• Since the encoded protein is expressed in the host in its natural
form—there is no denaturation or modification—the immune
response is directed to the antigen exactly as it is expressed by the
pathogen, inducing both humoral and cell-mediated immunity.
• DNA vaccines also induce prolonged expression of the antigen,
enhancing the induction of immunological memory.
• No refrigeration of the plasmid DNA is required, eliminating long
term storage challenges.
• In addition, the same plasmid vector can be custom tailored to insert
DNA encoding a variety of proteins, which allows the simultaneous
manufacture of a variety of DNA vaccines for different pathogens,
saving time and money.

24. Recombinant Vector Vaccines
Individual genes that encode key antigens of especially virulent
pathogens can be introduced into attenuated viruses or bacteria. The
attenuated organism serves as a vector, replicating within the
vaccinated host and expressing the gene product of the pathogen.
However, since most of the genome of the pathogen is missing,
reversion potential is virtually eliminated. Recombinant vector vaccines
have been prepared utilizing existing licensed live, attenuated vaccines
and adding to them genes encoding antigens present on newly
emerging pathogens.
Yellow fever vaccine – engineered to express antigens of WNV.
A number of organisms have been used as the vector in RVV
preparations, including vaccinia virus, the canarypox virus, attenuated
poliovirus, adenoviruses, attenuated strains of Salmonella , the BCG
strain of Mycobacterium bovis, and certain strains of Streptococcus that
normally exist in the oral cavity.

25. Production of vaccine using a recombinant
vaccinia vector. (T) The gene that encodes the
desired antigen (orange) is inserted into a plasmid
vector adjacent to a vaccinia promoter (pink) and
flanked on either side by the vaccinia thymidine
kinase (TK) gene (green).
(R)When tissue culture cells are incubated
simultaneously with vaccinia virus and the
recombinant plasmid, the antigen gene and
promoter are inserted into the vaccinia virus
genome by homologous recombination at the site of
the nonessential TK gene, resulting in a TK-
recombinant virus. Cells containing the recombinant
vaccinia virus are selected by addition of
bromodeoxyuridine (BrdU), which kills TK+ cells.

26. Examples and Advantages of RVV
Vaccinia virus, the attenuated vaccine used to eradicate smallpox, has
been widely employed as a vector for the design of new vaccines. This
large, complex virus, with a genome of about 200 genes, can be
engineered to carry several dozen foreign genes without impairing its
capacity to infect host cells and replicate. The genetically engineered
vaccinia expresses high levels of the inserted gene product, which can
then serve as a potent immunogen in an inoculated host.
A relative of vaccinia, the canarypox virus, can also be engineered to
carry multiple genes. Unlike vaccinia, it does not appear to be virulent,
even in individuals with severe immune suppression.
Another possible vector is an attenuated strain of Salmonella
typhimurium, which has been engineered with genes from the
bacterium that causes cholera (Vibrio cholerae).
Recombinant vectors maintain the advantages of live attenuated
vaccines while avoiding the risk of reverting to pathogenic forms.

27. SUMMARY

28. END
OF
PRESENTATION!