Standardization of a protein-G ELISA (ELISA-G) for diagnosis of Small Ruminants Lentiviruses (SRLV) in goats

Abstract

The world animal health organization recommends both the agar-gel immunodiffusion technique (AGID) and the ELISA for the serodiagnosis of small ruminant lentivirus (SRLV) infections. The ELISA has a higher sensitivity but is prone to false-positive results. Aiming to reduce this drawback, the standardization of a novel g-protein ELISA (G- ELISA) was performed, using conjugated protein G in place of the regular second antibody, which has a very high avidity to both sheep and goat antibodies. Sera were taken as reactive or not if similar results were obtained in AGID (CAEV antigen – AGID, Biovetech, Recife, Brazil) and western blot. The positive/negative ratio of standard sera were significantly higher in G-ELISA (10.9) than in standard ELISA (4.8) (P < 0,05). In a second set of serum samples, however, the p/n ratio was similar between both tests (4.68 vs. 3.33). These results point toward a higher discriminative value for G-ELISA, and supports a broader evaluation with both goat and sheep sera, taken from different endemic areas in Brazil, in order to enable its future use in SRLV control programs.