Increased enzyme-linked immunosorbent assay specificity with solubilized simian retrovirus 2-infected cell membranes

Simian type-D retrovirus (SRV) infection is a health problem in captive and wild-caught macaques; it interferes with acquired immune deficiency syndrome-related research. Because the enzyme-linked immunosorbent assay (ELISA) with gradient-purified SRV-2 virus yields a high percentage of false-positive results, the assay was modified with membrane antigens from SRV-2-infected and uninfected A549 cells. The SRV-2 membrane antigen contains the major proteins detected in positive sera by Western blotting: env proteins gp70 and gp20 and gag proteins p27, p14, p12, and p10. The original purified virus ELISA had a specificity of 74% compared with Western immunoblot. The modified ELISA using the difference in optical density between infected and control cell membrane antigens resulted in a specificity of 100% when the same samples were tested.