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Ann Clin Trials Vaccines Res. 2017 | Volume 1 Issue 2
Global Vaccines & Vaccination Summit & B2B
November 01-02, 2017 | Toronto, Canada
T
etanus toxoid is one of the most successful vaccines used
in immunization programme almost all over the world.
Neonatal tetanus can be prevented by immunizing women of
childbearing age with tetanus toxoid, either during pregnancy
or outside of pregnancy. Tetanus vaccine is used either in mono
or in combination with other antigens i.e. Diphtheria, Pertussis
(whole cell or acellular), Hepatitis B, Haemophilus influenzae
B, Inactivated polio vaccine etc. Tetanus toxoid is produced
batch-wise using complex media, often containing poorly
defined components. Therefore, batch related quality control
to guarantee safety and potency is a statutory requirement.
In the new concept, quality control is seen as an instrument
to monitor consistency of the critical steps in the production
process and testing of vaccines. Monitoring consistency places
emphasis on in-vitro methods, since in-vivo tests are less
appropriates (expensive, time consuming and inaccurate) for
this purpose. Immunochemical techniques may include the
use of polyclonal antibodies for direct ELISA or monoclonal
antibodies in capture ELISA and immunoblotting to indicate
local differences in antigenicity.
There is no uniformity in the potency test of tetanus toxoid.
Potency assays in animals may be seen as a way of estimating
relative antigen contents parallel to the in- vitro estimations;
e.g. by the flocculation tests or the Mancini test. In animal
tests, however, it is the ability to provoke production of
antibodies (immunogenicity) that is utilized and not just the
ability to react with antibodies (antigenicity). This distinction
might be carried even further. In challenge tests, the ability to
create protection against toxin challenge is the reaction used
(protective immunogenicity). In antibody production assays the
ability to provoke production of antibodies reacting in a certain
antibody detection system is used. In the past, the potency of
tetanus toxoid was being expressed in Lf - units. United States
Pharmacopoeia prescribed antibody induction method. British
Pharmacopoeia, other European countries and World Health
Organization recommended active challenge method for
assaying the potency of tetanus component. However, Indian
Pharmacopoeia prescribed both the methods viz. antibody
titration method and active challenge method.
For the potency estimation of tetanus toxoid component in
mono-valent or combination vaccines, the challenge test has
been in use for many years. Despite the use of large number
of animals (> 100 mice or guinea pigs) to test one batch of
tetanus toxoid, this test has not been shown to correlate
with immunogenicity in humans. However, toxin-neutralizing
antibodies induced by the vaccine are generally accepted
as correlates of protection. The three ‘R’s concept for the
replacement, reduction and refinement of the use of laboratory
animal testing is now widely accepted as not only need for
ethical but also for scientific reasons.
e:
rakesh.kumar@seruminstitute.comImmunological studies on Tetanus Toxoid
Rakesh Kumar
Serum Institute of India Limited, India