A RABIES VACCINE FROM HAMSTER KIDNEY TISSUE CULTURES: PREPARATION AND EVALUATION IN ANIMALS1
PAUL FENJE
Abstract
A strain of fixed rabies virus adapted to hamster kidney tissue cells has produced culture fluids of high infectivity for rabbits and mice. These culture fluids were rendered non-infective by treatment with formaldehyde at a concentration of 8 mM. Rabbits immunized with this material produced antirabies antibody to a high titer and were subsequently proved to be resistant to intramuscular inoculation of rabies virus from the salivary glands of a naturally infected fox. Introduction The ideal method of preventing rabies both in man and animals is to induce active immunity by means of a living strain of virus which has become per- manently attenuated without loss of its immunogenic properties. For vet- erinary purposes, the chick-embryo-adapted Flury strain approximates to this ideal, and extensive experience under field conditions has shown it to be both effective and innocuous. For human prophylaxis, however, this type of vaccine has not advanced beyond the research stage. At present, therefore, we must still rely upon a vaccine which has been inactivated to the extent that it will pass the prescribed tests for absence of infectivity. Two rabies. vaccines which fall into this category are the duck embryo vaccine developed by Peck, Powell, and Culbertson (8) and the type exemplified by the Semple vaccine, which is a phenolized suspension of infected rabbit brain. It is not possible to come to any definite conclusion about the efficacy of the classical Pasteur treatment or of the Semple vaccine. On the evidence provided by laboratory tests employing immunization followed by challenge, there can be no doubt about the value of these vaccines; but experiments of this kind are artificial and do not reflect the conditions resulting from the bite of a rabid animal.
A serious disadvantage of most antirabies vaccines is the fact that they contain large amounts of host protein in proportion to their content of virus protein. In the case of the Semple vaccine, for example, the daily dose of the Connaught Medical Research Laboratories rabies vaccine is 2 ml of a 4% rabbit brain suspension. This represents 0.08 g of brain tissue. The amount of virus protein contained in this quantity of tissue cannot be determined exactly but it must be extremely small in view of the infectivity titers as determined by experiment. The usual infectivity figures for a fixed virus are 10" to 10" m.i.d. per gram of brain substance as determined by intracerebral inoculation of white mice. The antigenic stimulus provided by this quantity of virus must be very feeble in comparison with that provided by the associated 0.08 g of host protein. A similar objection, though less serious, can be made against vaccines prepared from avian embryo tissues. Glenny and his co-workers [end of text]
1 Manuscript received July 22, 1960. Contribution from the Connaught Medical Research Laboratories, University of Toronto, Toronto, Ontario.