Evaluation of Five Enzyme-Linked Immunosorbent Assays and an Agar Gel Immunodiffusion Test for Detection of Antibodies to Small Ruminant Lentiviruses

Abstract

ABSTRACT In the framework of the Dutch control program for small ruminant lentiviral (SRLV) infections, too many drawbacks were encountered with respect to serological testing. To improve the quality of testing, five enzyme-linked immunosorbent assays (ELISAs) and an agar gel immunodiffusion test (AGIDT) were evaluated. The focus was on the sensitivity, specificity, and variances of the commercially available tests. Clear differences were found among the tests in analytical and diagnostic sensitivity and overall diagnostic performance, whereas no significant differences in specificity were found. For serodiagnosis of sheep with clinical symptoms of maedi-visna virus (MVV) (histopathologically confirmed), one ELISA was significantly more sensitive than the other ELISAs and than the AGIDT, while for asymptomatic sheep originating from infected flocks, three ELISAs and the AGIDT demonstrated similar performance. The diagnostic performance appeared to be related to animal species and virus infection (MVV or caprine arthritis encephalitis virus [CAEV]) as well as the phase of infection/progression of disease. Receiver operating characteristic analysis, demonstrating the diagnostic potential of tests irrespective of defined cutoffs, again revealed clear differences between tests with respect to diagnostic performance for detection of antibodies against CAEV or MVV. An indirect ELISA, of which the solid phase is sensitized with a combination of the core protein p27 of MVV produced in Escherichia coli and a peptide derived from the transmembrane protein gp46, appeared to be the test of choice for serodiagnosis of SRLV infections in sheep and goats.