Division Transmissible gastro-enteritis (TGE)X1

All sera are heat-inactivated at 56 °C for 30 minutes before use.

The constant virus-varying serum neutralisation test on microtitre plates employs A72 (dog tumour) cells or other sensitive cell systems. TGE virus is used at 100 TCID50 per 0,025 ml; inactivated undiluted serum samples are mixed with an equal volume (0,025 ml) of virus suspension. The virus/serum mixtures are incubated for 30 to 60 minutes at 37 °C in the microtitre plates before the appropriate cells are added. Cells are used at a concentration which forms a complete monolayer after 24 hours. Each cell receives 0,1 ml of cell suspension.

(i) virus infectivity assay, (ii) serum toxicity controls, (iii) uninoculated cell culture controls, (iv) reference antisera.

The results of the neutralisation test and the titre of the virus used in the test are recorded after three to five days incubation at 37 °C. Serum titres less than 1/2 (final dilution) are considered negative. If undiluted serum samples are toxic to the tissue cultures, these sera may be diluted 1/2 before being used in the test. This is equivalent to 1/4 final dilution of serum. Serum titres of less than 1/4 (final dilution) are considered negative in these cases.