VACCINES AND OTHER BIOLOGICALS

Dr.D.RATHNAMMA
Professor and Head
Dept. of Veterinary Microbiology,
Veterinary College, KVAFSU, Hebbal, Bengaluru-560 024
• Vaccination is the most efficient and cost effective method
of controlling infectious diseases in human and animals.
• Small pox and Rinderpest eradicated from the globe, many
diseases have been controlled with use of effective vaccines.
• Vaccination/ immunization : two types: Active and Passive
• Passive immunization: Transfer of preformed antibodies to
susceptible animal, maternal antibodies to fetus /newborns,
provide immediate protection, short term immunity.
• Passive immunization is routinely administered to
individuals exposed to botulism, tetanus, diphtheria,
hepatitis, measles, and rabies.
• Passively administered antiserum is also used to provide
protection from poisonous snake and insect bites.
• Active immunization: involves administration of an
antigen to an animal, animal responds to the
antigen by producing immune response, no
immediate protection, but long lasting immunity is
produced.
• E.Jenner and L.Pasteur are recognized as the
pioneers of vaccination, or induction of active
immunity.
• Active immunization can be achieved by natural
infection with a microorganism, or it can be
acquired artificially by administration of a vaccine.
• In active immunization, the immune system plays
an active role; proliferation of antigen reactive T
and B cells results in the generation of immune
response and formation of memory cells.
 Vaccine
‘Vaccine’ – (Latin ) ‘vacca’ means ‘cow’
• Edward Jenner - 1798, smallpox vaccine using cow pox virus
• Louis Pasteur coined the term vaccine honoring Edward
Jenner; vaccines for fowl cholera, anthrax, and rabies.
• Vaccine : “A suspension of attenuated live or killed
microorganisms, or antigenic portions of them, introduced to a
potential host to induce immunity and prevent disease”.
Ideal vaccine should be;
• Affordable worldwide
• Heat stable
• Effective after a single dose
• Applicable to a number of diseases
• Administered by a mucosal route
• Suitable for administration early in life
Two types of vaccines:
I. Conventional vaccines:
• Live, attenuated vaccine
• Killed / Inactivated vaccines

II. Modern vaccines

• Subunit vaccines - only immunogenic protein /
polysaccharide from pathogen (Toxoid vaccines,
Conjugate vaccines).
• Recombinant organisms- genetically attenuated
• Recombinant vector vaccines
• DNA vaccines
Conventional vaccines:
1. Live, attenuated vaccines:
• High immunogenicity
• Modified live organisms infect host cells, processed
as endogenous antigen triggering CMI response
• More closely mimic an actual/natural infection.
• Elicits good, strong, long lasting immune
responses.
• Elicits both the arms of immune response (HI and
CMI)
• Generally life-long immunity is produced.
• 95% effective for many diseases.
• Attenuation : Process of reducing the virulence of
the organism.
• Attenuation can often be achieved by growing a
pathogenic bacterium or virus for a prolonged
periods under abnormal culture conditions.
• Eg: BCG vaccine : Mycobacterium bovis was
rendered avirulent by growing in bile saturated
growth medium for 13 years.
• Brucella abortus S-19 vaccine (calf hood vaccine)-
grown under nutrient deficient conditions.
• Virus attenuation - by culturing in cells to which they are
not adapted.
• Eg: PPR vaccine - passaged in vero cell culture systems,
unnatural host.
• Canine distemper virus- attacks lymphoid cells, virus is
cultured in canine kidney cells for vaccine purpose.
• Rinderpest vaccine- tissue culture adapted vaccine
• Flury strain of rabies virus –attenuated by prolonged passage
in chicken embryos.

Avirulent organisms are used as live vaccine

• Eg: Anthrax vaccine for animals- Live spore vaccine
Bacillus anthracis- Sterne strain , a non capsulated strain,
aivrulent
Advantages of Live Disadvantages of Live
vaccines vaccines
• Potential to revert to
• Single dose often virulence
sufficient to induce • Contraindicated in
long-lasting immunosuppressed
immunity patients
• Strong immune • Interference by viruses
response evoked or vaccines and passive
• Both humoral and antibody
CMI response • Poor stability – proper
• Local and systemic storage
immunity produced • Potential for
contamination
2. Killed/Inactivated vaccine:
• Inactivation - organisms are killed or inactivated by
physical or chemical agents without changing their
antigenicity.
• Most commonly used chemical is Formaldehyde, which
cross links proteins and nucleic acids.
• Most of Bacterial vaccines are Formaldehyde
inactivated vaccines.
• Eg: BQ vaccine, HS vaccine, ET vaccine
• Alkylating agents that cross link nucleic acid chains also
suitable for inactivation of organisms.
Eg: Ethylene oxide, ethyleneimine, acetyle
ethyleneimine, Beta propriolactone.
These are commonly used in veterinary vaccines.
Binary ethyleneimine is used for inactivation of FMDV
Beta propriolactone is used for rabies virus inactivation
Advantages of Live and Inactivated vaccines
Live vaccines Inactivated vaccines
Few doses are required Stable on storage

Adjuvants are not required Unlikely cause diseases through

residual virulence
Less chance of hypersensitivity Do not replicate in recipient

Induction of Interferon Unlikely to contain live

contaminating organisms
Relatively cheap Will not spread to other animals

Can be given by natural route Safe in immunodeficient patients

Stimulate both Humoral and CMI Easy to store

response
Long lasting immunity No risk of reversion
Modern vaccines / New generation vaccines:
1. Subunit vaccines - immunogenic purified
macromolecules from pathogens (Protein,
Polysaccharide )
Eg: Toxoid vaccine, Conjugate vaccine, Purified
polysaccharide capsule, recombinant antigens
2. Recombinant organisms - genetically attenuated
3. Recombinant vector vaccines
4. DNA vaccines
Toxoid vaccine:
• Inactivated bacterial exotoxins are referred as Toxoids
• Eg: Diphtheria and Tetanus vaccines have been made by
purifying the bacterial exotoxins 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 specific
toxin and neutralizing its effects.
Conjugate vaccine:
• Purified capsular polysaccharides conjugated with
protein carrier.
• Eg: Hib vaccine for Bacterial meningitis caused by
Haemophilus influenzae type b (Hib) - type ‘b’ capsular
polysaccharide covalently linked to a protein carrier,
tetanus toxoid - more immunogenic
• Purified polysaccharide bacterial capsules
Eg: Pneumococcal vaccine: Streptococcus
pneumoniae, which causes pneumonia in children,
consists of 23 antigenically different capsular
polysaccharides. The vaccine induces formation of
opsonizing antibodies.
Coating of the capsule with antibodies greatly
increases the ability of macrophages and neutrophils
to phagocytose pathogens.
• Vaccine for Neisseria meningitidis, a common cause
of bacterial meningitis, also consists of purified
capsular polysaccharides.
Subunit vaccine -
recombinant antigen
Proteins from the pathogens can be
produced by recombinant DNA
technology and used as subunit
vaccine.
Gene cloning can be used to produce
large quantities of purified antigen.
Eg: VP1 gene of FMD virus cloned in
plasmid, plasmid inserted into E.coli
and bacteria grown, the bacteria
synthesized large quantities of VP1
protein, harvested, purified and
incorporated into a vaccine.
First commercially available
recombinant subunit vaccine for
veterinary use is Feline leukemia
virus- major envelop protein of FeLV -
gp70.
Hepatitis B vaccine: first recombinant antigen (subunit
vaccine) vaccine approved for human use.
Developed by cloning the gene for the major surface
antigen of hepatitis B virus (HBsAg) and expressing it in
yeast cells.
Recombinant yeast cells are grown in large fermenters,
and HBsAg accumulates in the cells.
Yeast cells are harvested and disrupted by high pressure,
releasing the recombinant HBsAg, which is then purified
by conventional biochemical techniques and used as
subunit vaccine.
Genetically attenuated
organisms as vaccine
Eg: Pseudorabies in swine
• Thymidine kinase (TK) is
required by this herpes
virus to cause disease
• If TK gene is removed
from the virus, can infect
cells, but not replicate,
can not cause disease
• Block cell invasion by
virulent Psuedorabies
virus.
Recombinant vector vaccines
Genes that encode major antigens of especially virulent pathogens
can be introduced into attenuated viruses or bacteria.

The attenuated organism serves as a vector, replicating within the

host and expressing the gene product of the pathogen.

A number of organisms have been used for vector vaccines,

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.
 Vaccinia virus, the attenuated vaccine used to eradicate smallpox,
has been widely employed as a vector vaccine.

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.
Recombinant vector
vaccine
Vaccinia virus : A good candidate
for a live recombinant viral
vector vaccine
Large stable genome express high
levels of new antigens.
The gene that encodes the desired
antigen from pathogen is inserted into
a plasmid vector adjacent to a vaccinia
promoter and flanked on either side
by the vaccinia thymidine kinase (TK)
gene.
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 (BUdr), which
kills TK + cells.
Eg: Vaccinia vectored
rabies vaccine
Gene for rabies virus
envelop G protein
inserted into Vaccinia
virus.
Used as oral bait vaccine
for wild carnivores
(Fox, Raccoons,
Coyotes) against rabies.

Fowlpox vectored NDV-

approved in USA;
H and F genes of NDV
inserted into fowlpox
virus, confer immunity
against both diseases
DNA vaccine
“Plasmid DNA encoding antigenic protein from a pathogen is
injected directly into the muscle of the recipient”.
• Muscle cells take up the DNA and the encoded protein
antigen is expressed, leading to both humoral antibody
response and CMI response.
• Injected DNA is taken up and expressed by the muscle cells
with much greater efficiency than in tissue culture.
• Easy to prepare, safe, stable, no need of cold chain.
• Administered intramuscularly
• DNA coding for the specific immunodominant epitopes are
used.
• Naked DNA/DNA coated gold nanoparticles are injected/
inoculated into body as DNA vaccine
 DNA vaccine induces both humoral and cellular immunity: antigenic
proteins are expressed and processed as endogenous and exogenous
antigens.
Commercially available DNA Vaccine for
Veterinary use
DNA vaccine for West Nile virus
Combined vaccines/ Multiple antigen vaccines
• Two (or more) different viruses are grown separately in same
cell lines, Separately attenuated and titrated then added in a
single base and given at ones to the animal
• Eg: PPR and sheep/goat pox
• PPRV grown in vero cell line attenuated by giving 70 passages ,
titrated to have 10 log 3 TCID 50 virus per dose (0.5 ml)
• Sheep/goat pox virus grown in vero cell line attenuated by
giving62 passages , titrated to have 10 log 3 TCID 50 virus per
dose (0.5 ml)
• Made into a single container of 1ml, lyophilized.
• Incoulated to animals by s/c, 1ml.
Advantages
• Avoids multiple visit to the animal
• Gives the same immunity as given separately
• Drastic reduction in cost of production
• Other examples
• Dogs: CD, Parvo, ICH , Parainfluenza, Rabies,
Leptospira bacterin
• Cattle: FMD and HS vaccine
• Cattle : BHV-1, BVD, Parainfluenza 3
Other Biologicals : Diagnostic antigens
• Brucella Diagnostic antigens: Agglutination test
1) RBPT(Rose Bengal Plate Test) antigen
2) Brucella abortus plain antigen for Standard tube
agglutination(STT)
3) ABR (Abortus Bang Ring ) antigen for Milk ring test
• Salmonella Pullorum coloured antigen – Whole
blood agglutination test for screening of poultry
flock for Salmonella
• Salmonella Gallinarum – Plain antigen - Serum
agglutination test for Fowl typhoid
• Bacterial strain used : Brucella abortus S-99
• Colored antigen: It contains 11% B.abortus cell suspension
diluted in formal saline. Cells are stained with crystal violet
or malachite green or Rose Bengal dye. Most commonly
used antigen is Rose Bengal plate antigen, the test is called
Rose Bengal plate test(RBPT) which is a rapid plate test.
• Plain antigen: It contains 1% B. abortus cell suspension
diluted in phenol saline for inactivation. This antigen is used
for standard tube agglutination test (STT).
• Abortus Bang Ring antigen: It contains 8% of cell suspension
stained with haematoxylin & tetrazolium, used for milk ring
test for herd diagnosis of Brucellosis in animals.
• Raw milk from animal has to be tested.
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