Studies on pathogenic, immunogenic, and protective efficiency of fox rabies virus before and after adaptation to cell culture: application to vaccination against rabies.

Rabies virus from the submandibular salivary gland of a naturally infected fox was adapted to growth in BHK-21 cells. The pathogenicity of the original isolate and the cell culture adapted virus were compared by the intramuscular and oral routes in mice and foxes. Animals surviving exposure were tested for serum rabies antibodies (immunogenic efficiency) and for their ability to survive a second challenge with rabies virus (protective efficiency).

[Modelling of spatial evolution and dynamics of a population of healthy then rabies infected foxes].

The authors describe the main feature of a computer model which helps to simulate the evolution of a rabies epi-enzootic in foxes. They show first the goals and interests of the study, then the originality of used methodology. Their results deal successively with dynamic evolution of a healthy population of foxes, then with this same population infected with rabies and, at last, spatial and temporal evolution of the enzootics.

[Radio-tracking of rabid foxes].

Three wild foxes were trapped, inoculated with rabid fox salivary glands virus and radio-tracked straightaway for about three weeks until the death of the animal. Comparison of movements between incubation and clinical period indicate principally no obvious alteration of the activity area; an important increase in movement, especially during the day-time and lastly some variable changes in the activity pattern according to the individual. A common characteristic was a long period of immobility, before death, near the border of the usual activity area.

[Antigenic variants of rabies virus in France. Monoclonal antibodies].

One hundred and sixteen rabies field isolates from France were studied with monoclonal antibodies for analysis of their nucleocapside antigenic characteristics (by direct or indirect immunofluorescence) or glycoprotein determinants (by neutralization in mice). These studies verified that nucleocapside antigens had only two variants, apparently uncorrelated to animal species or geographic areas. Glycoprotein antigens had also variants which could explain partial defection in cross protection observed in mice having received rabies vaccine prepared from heterologous strains.

Assessment of fox control in areas of wildlife rabies.

This paper describes a technique for the analysis of the interaction between rabies control measures and the annual turnover of a fox population. The basic conditions are deduced from data on the turnover of a steady fox population, which have been found to be representative for large parts of central Europe. These conditions, together with field data on the critical density for rabies transmission and the recovery of reduced fox populations, provide a model for the prediction and evaluation of various measures of rabies control.

A model in mice for the study of the early death phenomenon after vaccination and challenge with rabies virus.

The reactions of mice were studied for a period of 10 days after their vaccination with an inactivated rabies vaccine. The kinetics of their resistance to an intracerebral challenge and neutralizing antibody activity of their serum were determined daily. Protection began on the fourth day after vaccination and was approximately correlated with virus-neutralizing antibody titres from the sixth to the tenth day.

[Kinetics of the reactions to experimental infection in mice after or without vaccination against rabies: study of etio-pathogenesis (author's transl)].

When challenged by intramuscular route with the rabies strain CVS, mice treated with cyclophosphamide and then vaccinated died during the four days following vaccination in larger numbers and earlier than controls which had been treated but not vaccinated. This phenomenon can be transferred, via splenocytes of mice treated with cyclophosphamide and then vaccinated, into syngenic mice infected 24 h earlier by a large amount of virus (10.000 LD50 by intracerebral route).

Kinetics of different specific immunological parameters after rabies vaccination in mice.

A significant protection to an intracerebral challenge of 70 mean lethal doses of a standard live rabies virus strain was obtained in BCG-pretreated mice or in normal mice which had been immunized with a single subcutaneous injection of a beta-propiolactone-inactivated rabies vaccine. Concomitantly, levels of delayed-type hypersensitivity (measured in vivo by the footpad test) and serum-neutralizing activity were evaluated at various times after immunization. All immune criteria were significantly augmented in the BCG-pretreated, rabies-immune mice as compared to normal, rabies-immune mice.

[The influence of thymus on mouse resistance against rabies before and after vaccination (author's transl)].

Thymus participation was investigated in a comparative study of natural resistance to rabies in Nude mice and normal litter mates. Such participation does not seem to happen during Challenge Virus Strain infection but might change the host cell-virus metabolism during street rabies infection by inhibition of Negri bodies genesis. However, this participation seems indispensable (except in few cases) to allow resistance after vaccination.

[Potency testing of inactivated rabies vaccines. Problems posed by the use of the Habel test].

Rabies vaccines containing inactivated virus are often tested for potency by the Habel test. Even though many people use the Habel test, a humpbacked curve of mortality is always observed for the vaccinated mice, with a linear regression for the control animals. This unexpected survival of vaccinated mice given the greatest doses of virus is an artefact since the phenomenon is not observed after a non intracerebral challenge.

[Mathematical model of the propagation of a vulpine rabies epizootic (author's transl)].

A mathematical model of propagation of a vulpine rabies epizootic has been worked out in order to build a prediction tool and to fix a suitable prophylaxis. The main ecological hypotheses and their mathematical expression are presented. This consists of a system of two integro-differential equations which have been discretizited to approximate their solution numerically.