Neutralization is an antigen–antibody reaction in which the
biological effects of viruses and toxins are neutralized by homologous
antibodies known as neutralizing antibodies. These tests are broadly of two
types: (a) virus neutralization tests
and (b) toxin neutralization tests.
Neutralization of viruses by their specific antibodies are called
virus neutralization tests. Inoculation of viruses in cell cul-tures, eggs, and
animals results in the replication and growth of viruses. When virus-specific
neutralizing antibodies are injected into these systems, replication and growth
of viruses is inhibited. This forms the basis of virus neutralization test.
Viral hemagglutination inhibition test is an example of virusneutralization
test frequently used in the diagnosis of viral infections, such as influenza,
mumps, and measles. If patient’s serum contains antibodies against certain
viruses that have the property of agglutinating the red blood cells, these
antibodies react with the viruses and inhibit the agglutination of the red
Toxin neutralization tests are based on the principle that
bio-logical action of toxin is neutralized on reacting with specific
neutralizing antibodies called antitoxins. Examples of neutral-ization tests
In vivo—(a) Schick test to demonstrate immunity againstdiphtheria and (b) Clostridium
welchii toxin neutralization test in guinea pig or mice.
In vitro—(a) antistreptolysin O test and (b)
Nagler reactionused for rapid detection of C.