2. INTRODUCTION:
Definition.
Ideal properties of the vaccine.
Types of vaccines.
A) Conventional vaccines.
1) killed vaccines.
2) live-attenuated vaccines.
3) sub unit vaccines.
4) recombinant vaccines.
B) Modern vaccines.
1) peptide based vaccines.
2) nucleic acid based vaccines.
3. PEPTIDE BASED VACCINES:
Peptide vaccine consists of those peptides from the microbial
antigen that stimulates protective immunity.
The protective immune response to a pathogenic micro organism
or parasite usually involves the induction of both humoral and
cell mediated response.
In many cases, the peptides used for producing synthetic
vaccines were selected only on their likelihood of forming
surface epitope.
After the identification of a protective epitope, it is possible to
incorporate the corresponding peptide sequence into a carrier
protein.
The term epitope refers to a stretch of 6-8 amino acids on antigen
that specifically binds to antibody or to receptors on immune T-
cells.
4. PEPTIDE VACCINE DELIVERY METHODS:
Emulsion:
All emulsion based particulate carriers for vaccine are based
on a common mechanism of action of formation a depot at the
injection site that is capable of attracting the immune cells.
The stability of emulsion as delivery system is directly
proportional to vaccine safety and efficacy.
o Liposome:
Most popular and extensively used as vehicles for vaccine.
Composition of liposomes can be tailored for
biocompatibility and adoptability in order to deliver their
contents to antigen presenting cells.
Where cross presentation is facilitated promoting cellular
response.
5. Virosomes – are composed of assembled viral membrane proteins
which render then enhanced binding to APCs and promote cytosolic
delivery.
ISCOMS – immunostimulatory complexes are particulate antigen
delivery system composed of antigen, cholesterol, phospholipids and
saponin.
Polymeric particles – natural, synthetic, Biodegradable.
Other Particulate Systems - Other particulate systems used to deliver
vaccine antigens include carbon nanotubes, silicon dioxide
nanoparticles, dendrimers, ferritin nanoparticles, peptide nanocarriers,
gold nanoparticles, liposome- poly cation -DNA (LPD) complex,
oligosaccharide ester derivatives (OEDs) micro particles and
combination systems, e.g., liposomes and w/o emulsion.
6. Advantages:
* If the peptide that induces protective immunity is identified it can be
synthesized easily on a large scale.
* It is safe and can be administered to immunodeficient and pregnant
individuals.
Disadvantages:
* Poor antigenicity, Peptide fragments don’t stimulate the immune
system as well as a whole organism vaccine.
* Not applicable to all viruses Ex: polio virus which has 2 antigens.
Challenges:
1)stability of recombinant peptides (recombinant peptides may be
readily digested by enzymes in body),
2)peptide antigenicity (peptide antigenicity may result in immune
responses) and
3)production scales (different production scales may require a
completely different technology for synthesis and purification).
7. NUCLEIC ACID BASED VACCINES:
Nucleic acid vaccines are based on DNA or RNA encoding
the antigen of interest.
In their simplest form, they can consist of highly purified
nucleic acid formulate in a buffer.
Most often, however, specialized delivery systems are
utilized to increase vaccine potency.
8. DNA VACCINES:
* In this DNA sequence is used.
* The introduced DNA is taken up by cells and it is translated
to form antigenic protein.
As this protein is foreign to cell so immune
response against this protein.
* The concept of nucleic acid vaccine evolved from initial
studies in experimental animals in which the inoculation with
naked plasmid DNA resulted in a protective immune
response.
* After inoculation into a muscle, the efficiency of cellular
uptake of the naked DNA is degraded before it reaches the
nucleus for transcription.
11. DNA VACCINE DELIVERY SYSTEM:
Delivery of DNA vaccine using electroporation:
Principle is to temporarily permeabilise cell membranes to allow
for increased uptake of large molecules such as plasmid DNA.
Because electroporation permeabilizes membranes it can work in a
wide variety of tissues including skin and muscle.
Surface modified biodegradable microspheres for DNA vaccine
deliver:
For sustained delivery, DNA can be encapsulated in biodegradable
microspheres, which are capable of releasing DNA molecules for a
period of up to several months in order to help to direct the
microsphere to desired cell types, cell type
specific targeting ligands can be fixed to the microsphere surface.
12. Gene gun:
DNA coated on the surface of gold pellets which are air-
propelled into the epidermis, mainly non applicable to
cancer.
Needle-Free injection:
Is accomplished by forcing liquid medications at high
speed through a micro-orifice. E.g.: Bioject, vita jet3 etc.
13. ADVANTAGES
* Elicit both humoral and cell mediated immunity.
* Long term immunity.
* Heat stability
* Ease of large scale production.
* Can be made in a short time span and very cheap to make.
DISADVANTAGES
* Formation of anti nucleic acid antibody possible.
* Extended immune stimulation leads to chronic
inflammation.
* No DNA vaccine has been licensed for use in humans yet.
14. RNA VACCINES:
An RNA is injected in the body. This RNA encodes the information to
produce the antigen, which is a protein from a pathogen, that will
stimulate the immune system.
Typically mRNA vaccines are synthetically produced by an enzymatic
process, and offer the advantage of tight control over the immunogenic
profile, pharmacokinetics and dosing.
However, RNA vaccines have several attributes that provide potential
advantages over DNA vaccines
1. There is a finite chance that plasmid DNA vaccines can integrate
into the genome of the immunized host. Use of RNA would eliminates
this.
2. Plasmid DNA vaccines must be delivered into and transcribed
within the nucleus in order to transfect a cell i.e they must transfers
two membrane barriers (plasma and nuclear membrane).since RNA
vaccines are translated directly in the cytoplasm.
15. ADVANTAGES:
* Active in non dividing cells.
* No need for promoter.
* Lyophilized vaccines retain full biological activity.
* Needs to cross only one membrane to be active in the
cytoplasm.
DISADVANTAGES:
* Cost effective.
16. REFERENCES
https://www.slideshare.net/tayedesta7/dna-vaccine-final-ppt
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4514143/
http://www.uniroma2.it/didattica/BAC-
TEK/deposito/Rna_vaccines.pdf
https://www.genengnews.com/gen-exclusives/rna-based-
therapeutics-and-vaccines/77900520
Pharmaceutical Biotechnology : An Introduction for Pharmacists
and Pharmaceutical Scientists by Crommelin, D. J. A.; Sindelar,
Robert D.
https://www.researchgate.net/publication/6997375_Design_of_P
eptide-Based_Vaccines_for_Cancer
