[Micro-epidemiology and micro-plaque titration of infectious bovine rhinotracheitis virus on primary calf kidney cells by means of immunofluorescence].

Immunofluorescence was used to study the virus of infectious bovine rhinotracheitis and the course of infection in cell cultures of calf kidney. An indirect relationship was found to exist between the magnitude of inoculation and the onset of specific fluorescence. Fluorescent plaques are formed as a result of inoculate dilution. The plaques will grow along with incubation time. Release of virus into the culturing medium will first lead to the formation of secondary plaques, then followed by generalised infection of the cell culture. The time at which the infection will begin to be disseminated was found to depend on both multiplicity of the infection and quality of the cell culture. Therefore, no limitation is possible of the time during which only primary infectious foci are recordable. Antibody present in the culturing medium prevent propagation of the infection, but this does not inhibit the course of primary infection nor intercellular virus transmission. The conditions are defined for the microplaque fluorescence method and its use on quantitative virus assay. While reproducible results are offered by that method, its sensitivity is below that of the tubule method, when it comes to identifying the infection due to the cytopathic effect. The microplaque fluorescence method was used to study the conditions for absorption of virus of infectious bovine rhinotracheitis by calf-kidney cell cultures. Absorption was tested under temperatures of 20 degrees C, 37 degrees C, and 40 degrees C and found to be accelerated by higher temperatures. Yet, the total quantity of virus absorbed in 120 minutes was found to be almost the same in all three temperatures. The degree of virus absorption was found to depend on the kind of medium, with the rate of absorption having been strongly increased by adding to the medium serum of different animal species. About 70 per cent of the virus present in the inoculate were absorbed by the calf-kidney cell cultures under defined experimental conditions.