[Hog cholera diagnosis: an improved technique of seroneutralization based on use of a cytolytic virus strain in microplate (author's transl)].

An improved technique for the detection of hog cholera virus (HCV) neutralizing antibodies is described, in which running of the test is greatly facilitated by use of a cytolytic strain of HCV. This strain was isolated from persistently infected IB-RS 2, and was shown to induce a distinct cytopathic effect in several pig kidney cell lines (Laude, 1978). For the assay, serum samples at 1 : 10 are diluted serially twofold in disposable microplates, then 1 x 10(4) PFU of the virus-stock are added in each well. Trypsinized RP-TG cells are dispensed at 2 x 10(4)/well after 1 hour contact at 38 degrees C. After 4 days of incubation at 38 degrees C, plates are sequentially stained with neutral red and lugol, to make the undestroyed monolayers visualized. Neutralizing titre is expressed as the highest dilution of the serum affording a 75 percent protection of monolayer. This procedure has proved to be a labor saving technique yet being as reproducible and as sensitive as the immunofluorescence-tests. It combines the following advantages: 1) The immunofluorescence step is suppressed. 2) Results can be recorded without the aid of microscope. 3) The test is miniaturized. 4) Cultures of continuous cell lines are used. 5) The challenge virus is attenuated for the pig. Therefore this technique can be recommended for routine serological survey of the HCV-infection in pig-herds.