Antibodies neutralize viruses in three different ways. In contrast to what is commonly perceived, very sensitive and specific tests demonstrating antigens and antibodies can be elaborated on basis of the regular reaction lines demonstrated. The action of the non-neutralizing antibodies is of the greatest importance in combatting and preventing infections.
This analytical
review aims to clarify the complex lines of antigen-antibody interactions in vitro, to achieve a better
understanding of the impact of various antibodies and the reaction lines on the
basis of which sensitive and standardized tests for demonstrating antigen and
antibody can be elaborated. A variety of aspects of the antigen-antibody
binding reactions are evaluated, including 1) the reactions in a conventional
neutralization test, 2) the first-order antigen-antibody reaction demonstrated,
3) the formula for the regular reaction without aggregations presenting the log
antibody/log virus equivalence factor of neutralization, 4) the lines of two
different aggregation reactions inactivating viruses, 5) irreversibility of
antigen-antibody bindings, 6) lines for elaborating gold and reference standard
assays and highly sensitive routine tests, 7) a “persistent fraction of virus”,
and 8) the “Percentage Law”. A series of important conclusions are presented.
Antibodies are bound
firmly and irreversibly to their antigenic determinants on a virus. The binding
reaction does not lead to an equilibrium state as commonly perceived. The
sensitivity of antigen-antibody tests may consequently be both variable and
adjustable to high levels. Antibodies neutralize viruses in three clearly
distinct ways. Neutralization of virus by antibody in a virus-antibody mixture
without presence of the complement component C1q proceeds as two separate
reactions, i.e., 1) a first-order
reaction caused by particularly neutralizing antibodies being bound
monovalently to their antigenic neutralization determinant and 2) an early “over-neutralization” reaction that can
be attributed to the formation of virus aggregates created by the di- and
polyvalent antibodies which to a wide extent are non-neutralizing. This
aggregation is caused by the various antibodies, in a synergistic action. It is
highly dependent on a sufficient antibody concentration and is prompt and short
lasting. In the serial dilutions of a conventional neutralization test, an
early aggregation is readily diluted away with increasing reaction periods. In
contrast, the first-order neutralization reaction is slowly progressing but enduring. The test sensitivity, cf. Definitions will be directly
proportional to the reaction time but temperature-dependent. The third
neutralization reaction is dependent on the presence of a complement. The
hexa-valent C1q component will enhance the neutralizing effect of antibodies by
aggregating virions that have been bound to a non-neutralizing antibody. Such
an antibody is sensitized for binding to the C1q component by being bound to
its antigenic determinant on the virion. In a complement-enriched neutralization
test, two different reaction rates will be observed. Practically instantly, C1q
will react with all pre-formed virus-antibody complexes and, because of the
multi-valency of that molecule, include them in aggregates but thereafter, with
increasing reaction time, the reaction will be of first-order following the
continuous first-order binding of non-neutralizing- antibodies to their
antigenic determinants. In a herpesviruses complement-enriched neutralization
test, the reaction with non-neutralizing IgG antibodies increased titers
recorded for neutralizing IgG antibodies in a conventional neutralization test
by a factor of approx. 8, but for IgM antibodies the neutralizing effect by
complement was enormous. A significant neutralizing effect could be
demonstrated in blood as early as 4 days after experimental nasal infection and
after 8 to 15 days, the neutralizing effect was demonstrated in serum diluted
1:10.000 or more. The huge neutralizing potential of the non-neutralizing
antibodies in a joint action with complement indicates a fundamental role of
these antibodies in combatting infections. The so-called Percentage Law. according to which the rate of virus neutralization
will be independent of the virus concentration was found invalid. The formula
for the regular lines of antigen-antibody interactions in vitro not comprising
aggregation has been presented earlier. Highly sensitive antigen-antibody
tests, elaborated on basis of the reaction lines documented, have been in use
for a long time in the veterinary medical field.
Author
(s) Details
Viggo
Bitsch
The State Veterinary Serum Laboratory, Copenhagen and The
Department of Cattle Diseases, The Danish Dairy Board, Aarhus, Denmark.
Please see the book here:- https://doi.org/10.9734/bpi/crpbs/v8/3721
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