THE USE OF SUCROSE-ACETONE-EXTRACTED RIFT-VALLEY FEVER VIRUS-ANTIGEN DERIVED FROM CELL-CULTURE IN AN INDIRECT ENZYME-LINKED-IMMUNOSORBENT-ASSAY AND HEMAGGLUTINATION-INHIBITION TEST

A sucrose-acetone-extracted, Madin-Darby-bovine-kidney (MDBK)-derived Rift Valley fever virus (RVFV) antigen was tested both in an indirect ELISA and a haemagglutination-inhibition test for its ability to detec t serum antibodies to RVFV. Optimal conditions for antigen concentrati on, serum and conjugate dilutions for the ELISA were established by ch eckerboard titration. The specificity and sensitivity of ELISA were de termined by the use of paired pre- and post-vaccination sheep-serum sa mples. Compared with the virus neutralization test, the overall ELISA specificity and sensitivity were 97,4 and 97,3%, respectively. There w as a 100% correlation between the results obtained in haemagglutinatio n-inhibition tests with a RVFV sucrose-acetone-extracted antigen deriv ed from hamster liver, and from MDBK cells. A total of 10 582 field-se rum samples (84 cattle, 3 659 sheep, 6 839 goats) collected in 1994-19 95 from animals of unknown vaccination status in different regions of South Af rica were tested with ELISA for antibodies against RVFV. Ther e were no seropositive cattle, 0,16% seropositive sheep and 0,12% sero positive goats. This study demonstrates the potential diagnostic appli cation of cell-culture-derived, sucrose-acetone-extracted RVFV antigen in an indirect ELISA and HI test.