VACCIN , VACCINOLOGY, ANTIGEN, ANTIBODIES , IMMUNE SYSTEM , IMMUNOLOGY ,

1. ANTIGENS & CONCEPT
VACCINES
Dr. Shrutikirti
MBBS, M.D. Microbiology

2. Topics to be covered-
1. Antigens
2. Types of antigens
3. Vaccines
4. Concept of vaccines development
5. Types of vaccines
6. Recent advances

3. ANTIGENS
1. Substances that are capable of inducing specific immune response
2. They can be recognized by the surface antibody(B cells) or by the T cell receptors when
associated with MHC molecule.
3. They can bind specifically with the antibody or T-cell receptor

4. CLASSIFICATION
 EXOGENOUS ANTIGENS
1. Exogenous antigens are those antigens which enter into the host body from their
surroundings or external environments.
2. These are basically of pollutants, microorganisms, pollens, drugs.
 ENDOGENOUS ANTIGENS
They are again classified into –
1. Xeno-genic or Heterogenic antigens
2. Allogenic or Idiotypic antigens
3. Autologous antigen

5. Contd …..
XENOGENIC ANTIGENS-
Foreign items which are related with tissue transplantation and serology.
ALLOGENIC ANTIGENS-
Foreign items which enter when an individual receives a blood transfusion or undergoes
transplantation operation. AUTOLOGOUS ANTIGENS-
This group of antigens is very rare and unnatural.
In normal condition, self-components are non-immunogenic in nature, but in an abnormal
condition self-body components are started to be considered as non-self or antigenic
component

6. IMMUNOGENICITY AND ANTIGENICITY
Immunogenicity-
Ability to induce a humoral or cell mediated immune
response.
Antigenicity
Ability to combine specifically with the final products of
humoral or cell mediated immune response

7. FACTORS INFLUENCING IMMUNOGENICITY
• Contribution of the Immunogen
1. Foreignness
2. Molecular size
3. Chemical Composition
4. Physical Form
5. Degradability
• Contribution of the biological system
1. Genetic factors
2. Age
• Method of administration
1. Dose
2. Route
3. Adjuvant

8. CONTD …
1. Foreignness
• Only foreign molecules are immunogen
• The degree of immunogenicity depends on its Foreignness
2. Molecular Size
• Not absolute size above which a substance will be immunogenic
• larger the molecule the more immunogenic

9. CONTD…..
3. Degradability
• Easily phagocytosed = more immunogenic
• Some antigen required to be processed and presented to helper T cells by an antigen
presenting cell (APC)
4. Genetic factors
• Some substances are immunogenic in one individual but not in others.
• The species or individuals may lack or have altered genes that code for the receptors for
antigen on B cells and T cells
• They may not have the appropriate genes needed for the apc to present antigen to the helper
cell

10. Contd…..
5. Age
• Extreme of age have decreased immune response to immunogen
6. Chemical composition
• More complex substance = more immunogenic
• All four levels of protein can contribute to the antigenic determinant and hence affect the
immunogenicity.
7. Physical form
• In general particulate antigens are more immunogenic than soluble ones and denatured antigens
more immunogenic than the native form

11. Contd …
8. Dose
• There is a dose of antigen above or below which the immune response will not be optimal.
• An insufficient dose fails to activate enough lymphocytes
• An excessively high dose also can fail to induce response because it causes lymphocytes to enter a non responsive
state.
9. Route
• Intravenous : into a vein
• Intradermal : into the skin
• Subcutaneous : beneath the skin
• Intramuscular : into a muscle
• Intraperitoneal : into the peritoneal cavity
• Administration route determines which immune organs and cell populations will be involved in the response.
• Antigen administrated intravenously is carried first to the spleen, whereas antigen administrated subcutaneously moves
first to local lymph nodes.

12. Contd…..
10. Adjuvants
• Substances that are mixed with an antigen and injected with it, serve to enhance the immunogenicity of the
antigen.
• Boost the immune response when an antigen has low immunogenicity or when only small amounts of an antigen
are available, limiting the immunizing dosage.
• Aluminum potassium sulfate acts to increase antigen persistence
• Injection of this alum precipitate results in a slower release of antigen from the injection site, so that the effective
time of exposure to the antigen increases from a few days without adjuvant to several weeks with the adjuvant.
• The alum precipitate also increases the size of the antigen, thus increasing the likelihood of phagocytosis.

13. EPITOPES
• It is the part of an antigen that is recognized by the immune system specifically by antibodies, B cells
or T cells.
• They are also known as epitopes or antigenic determinants. B and T cell recognize different epitopes
on the same antigenic molecule.
• In the case of protein antigens, an epitope may involve elements of the primary, secondary, tertiary
and even quaternary structure of the protein.
• In the case of polysaccharide antigens, excessive side chain branching via glycosidic bonds affects
the overall three dimensional conformation of individual epitope

14. Contd….
• T and B cell exhibit fundamental difference in antigen recognition.
• B cells bind antigen that is free in solution, the epitopes they recognize tend to be highly accessible
sites on the exposed surface of the immunogen.
• T cells only recognize processed peptides associated with mhc molecule on the surface of antigen
presenting cell and altered self cells

15. MITOGENS
• Agents capable of inducing cell division in a high percentage of T or B cells.
• Activate many clones of T or B cells irrespective of their antigen specificity
• Also known as polyclonal activators.
• Most common are sugar binding proteins called lecithins which bind specifically to different glycoproteins on the surface
of various cells including lymphocytes which leads to agglutination, or clustering of the cells which may trigger cellular
activation and proliferation. Contd..
• Some mitogens preferentially activate B cells, some preferentially activate T cells and some activate both populations.

16. Contd…
• Three common lectins with mitogenic activity are
1. concanavalin a,
2. phytohemagglutinin(pha),
3. pokeweed mitogen (pmw).
• The lipopolysaccharide component of the gram negative bacterial cell wall functions as a B cell mitogen.
• The mitogenic activity of LPS is due to its lipid moiety, which is thought to interact with the plasma membrane, resulting in a cellular
activation signal superantigens
They are the most potent t-cell mitogens known.

17. Superantigens
• Superantigens bind to residues in the V (variable) domain of the T-cell receptor and to residues in
class ii MHC molecule outside of the antigen-binding cleft.
• In this way a superantigen can cross-link a T cell to a class II MHC molecule even when the TCR
does not recognize the bound antigenic peptide, leading to activation of the T cell.
• Thus a superantigen can activate all T cells expressing the V domain to which that superantigen
binds.
• Common superantigens include –
1. Staphylococcal enterotoxins(SES)
2. Toxic shock syndrome toxin(tss1)

18. Concept of vaccine
• Vaccines are biological products that prevent and control the occurrence of infectious diseases,
epidemic.
• Vaccine is designed to direct against:
1. bacteria
2. viruses
3. fungi
4. parasitic diseases
5. non-infectious diseases
6. cancer cells
7. autoimmune disease
8. neurodegenerative disease vaccines

19. Vaccine development stages
• pre-clinical development is research carried out in lab assays and on animals.
1. Discovery of relevant antigens
2. evaluation of vaccine efficacy
3. in vivo assays and in vitro assays
4. vaccine concept design
5. manufacture of the vaccine to good manufacturing practice standards
• Clinical development is when the vaccine is first tested in humans.
1. Phase I clinical trials - small-scale trials, safety immune response
2. phase II clinical trials - larger-scale trials, efficacy of the vaccine,safetydose ranging side-effects immune
response
3. phase III clinical trials -large-scale trials, vaccine efficacy under natural disease conditions • license-
submission preparation
4. phase Ⅳ clinical trials - iv-post-marketing surveillance

20. Process of vaccine manufacturing-
• good manufacturing practices (GMP)
• ensure that products are safe for use in humans
• ensure that the identity, strength, quality and purity of products consistently meet
regulatory specifications.
• Quality control measures
• Propagation- amplify the living organism used in the vaccine
• isolate the antigen- separate of the living organism from the propagation step
• purification- purify the antigen to produce a high purity/quality product.
• Formulation- add other components like adjuvants, preservatives, stabilizers,
inactivators
• packaging- aseptic packaging in vials or syringes

21. Methods in manufacturing of vaccines
1. Viral vaccines
viruses are grown on primary cells such as cells from chicken embryos or using fertilised
eggs (e.g. Influenza vaccine) or cell lines that reproduce repeatedly (e.G. Hepatitis A)
2. Bacterial vaccines
Bacteria are grown in bioreactors which are devices that use a particular growth medium
that optimizes the production of the antigens
3. Recombinant vaccine
Recombinant proteins derived from the pathogen can be generated either in yeast,
bacteria or cell cultures

22. Types of vaccines
1. Live attenuated vaccine
2. Inactivated vaccine
3. Subunit vaccine
4. Toxoid vaccine
5. Recombinant vaccine
6. M RNA vaccine
7. DNA vaccine
8. Recombinant vector vaccine

24. Thank you