AN ELISA BASED ON WHOLE VIRUS FOR THE DETECTION OF ANTIBODIES TO SMALL-RUMINANT LENTIVIRUSES

A new ELISA kit was developed, based on highly purified whole-virus an tigen derived from the Swiss maedi-visna virus strain OLV. The sensiti vity, specificity and accuracy of this assay were compared with that o f an established ELISA based on recombinant GAG (group-specific antige ns)-GST (glutathione S-transferase) fusion protein expressed in E. col i (GAG-GST ELISA). The whole-virus ELISA exhibits at least comparable specificity (99.3 %) but higher sensitivity (98.6 versus 86.3 %) and a greement with the 'true' status beyond chance in the detection of anti viral antibodies in serum from goats. Antibodies in milk samples are d etected with higher specificity (98.9 versus 97.8 %) but lower sensiti vity (91.4 versus 98.2 %) than in GAG-GST ELISA. The specificity of th e new ELISA in the detection of antibodies in serum might be superior, since a set of 40 samples falsely rated positive in GAG-GST ELISA in routine diagnostic work was negative in the new ELISA. In both assays, milk samples can be tested instead of serum, although with slightly r educed sensitivity in the new ELISA. The major advantage of the new te st kit is the low number of equivocal samples needing confirmation in a supplementary test. Results obtained with sheep sera indicate that t he new ELISA kit is also suitable for the detection of antibodies to m aedi-visna virus.