264
ABSTRACT
[Vol. XVIII, Part IV,
There is a relationship between the antigenic value of the tissues and their actual virus content
but it is probable that they owe their antigenic properties to the manner in which the virus is attached
to certain component cells. It is not necessary that an animal inoculated with rinderpest virus should
show a reaction so that the tissues are suitable for vaccine production. The antigenic value of those
tissues is as good as in animal reacting fully. The deterioration of rinderpest vaccine is shown both
by its failure to produce immunity and the irregular reaction in vaccinated animals. A low
storage temperature is fundamentally necessary in the conservation of the full antigenic potency of
emulsion vaccines. A toluine vaccine gives better results than a formalinized vaccine. It possesses
stronger immunizing value, especially marked when freshly prepared, and antigenic qualities are
better maintained in storage. Dried formalinized vaccine is better than liquid and retains its full
potency better. It is somewhat inferior as a vaccine compared with toluine vaccine but it has the
advantage of a small bulk and this balances, in practice in the field, its somewhat poorer antigenic
value. It does not appear that the immunity following two vaccinations is any better than a single
vaccination but the advantage of the former method is definitely apparent in the building of a stronger
immunity in the week's following vaccination. The administration of the large quantity of vaccine
notably prolongs the duration of immunity but after a period of eight months the benefit of massive
inoculation is not so obvious. Comparing the results of vaccination with formalinized, toluine, and
flourine vaccines inclines one to the belief that a relationship exists between the reaction at the site
of inoculation and the duration of immunity conferred by the inoculation . The fact that a vaccinated
animal can withstand a moderate test dose of virus does not infer that it can tolerate without
severe reaction a larger test dose. An animal which has failed to react to several small test doses
of virus will certainly react strongly to a large dose of the same virus. The quality of the vaccine,
the dose given, the time elapsing after vaccination, the size of the test dose are, however, factors
that operate in immunity. In animals vaccinated and tested by standard methods, 10-20 per cent
of them remain or later become susceptible to infection with rinderpest virus. The antigenic value
of a virulent pulp vaccines is generally feeble. The intravenous inoculation of a vaccine has no
prophylactic value ; given in the incubation phase or in the preliminary febrile phase the vaccine
will not avert the normal development of the disease. Consequent to vaccination with massive
doses of formalinized vaccine the serum of some young cattle acquires a strongly prophylactic value.
Young calves, the offspring of highly immunized cows, may be successfully immunized by means of
a virulent spleen and other tissue extracts ; there is no incompatibility between the immunity of
maternal origin which lasts until weaning and that resulting from a later vaccination.
The addition of aluminium hydroxide to formalinized suspensions is an improvement. Vaccine
adsorbed on aluminum gel gives a solid immunity with a tenth of the dose of the ordinary forma-
linized vaccine used immediately on preparation and it also retains its antigenic value longer. Thus,
the ratio of activity at the first test is 1/10, 1/15, 1/20 and on retest two to three months later 1/20,
1/30, 1/40, proviced that both vaccines under test have been subject to optimum storage temperatures.
Absorbed vaccine possesses when just prepared and even on storage a uniformity of antigenic value
that the other vaccine never possesses, even when freshly prepared. Tissue vaccines treated with
aluminum gel are comparable in their antigenic power with ordinary tissue suspension vaccines, but
their effect is slightly more durable. The increase of antigenic potency of the vaccine is directly
related to the quantity of adjuvant incorporated in the vaccine ; 60 parts of pulp mixed with 100
parts of gel equivalent to 5.5 gm. aluminum hydroxide is the most satisfactory working ratio and
fulfils all practical needs. The gel seems to exercise a double roll ; it stimulates the development
of immunity (action on the tissues) and protects the formalinized pulp against deterioration (action
on the vaccine).
Between the years 1940-45, 55,000,000 c.c. gel rinderpest vaccine have been used in Indo-China
and at least 2,000,000 cattle have been vaccinated. Wherever it has been properly used, the ad-
sorbed vaccine has given the results expected of it. Of the practical results following the use of
this vaccine, mention must be made of the saving of young cattle used for the provision of vaccine
material, a ratio of almost 1/3 compared with the preparation of other tissue vaccines. [J. F. S.].