A new sensitive serological assay for detection of lentivirus infections in small ruminants

Lentivirus infections in small ruminants represent an economic problem affe cting several European countries with important sheep-breeding industries. Programs for control and eradication of these infections are being initiate d and require reliable screening assays. This communication describes the c onstruction and evaluation of a new serological screening enzyme-linked imm nnosorbent assay (ELISA) for the detection of antibodies to maedi-visna vir us (MVV) in sheep and to caprine arthritis encephalitis virus (CAEV) in goa ts. The solid phase is sensitized with a combination of the major core prot ein p25 of MW produced in Escherichia coil and a peptide derived from the i mmunodominant region of the viral transmembrane protein gp46. The peptide c arries an N-terminal biotin residue and is complexed with streptavidin prio r to being coated. The new assay was evaluated with 2,336 sheep serum sampl es from different European countries with large differences in the levels o f prevalence of MW infections, and the results have been compared to those of the standard agar gel immunodiffusion test. Discrepant samples were anal yzed by Western blotting with viral lysate, and most sera could be classifi ed unambiguously. The estimated overall sensitivity of the new ELISA was 99 .4% (95% confidence interval [CI], 98.4 to 99.8%) and the specificity was 9 9.3% (95% CI, 98.7 to 99.6%). A limited set of goat sera (n = 212) was also analyzed, with similar results. These data indicate that the new assay is a reliable tool that can be used in control and eradication programs for sm all ruminant lentivirus infections.