Development and evaluation of ELISA procedures to detect antibodies against the major envelope protein (G(L)) of equine arteritis virus

Enzyme-linked immunosorbant assays (ELISAs) were developed for the detectio n of antibodies against the major envelope glycoprotein (G(L)) of equine ar teritis virus (EAV). A 6-Histidine tagged recombinant protein expressing th e complete G(L) ectodomain (G(L)-6His), a glutathione-S-transferase recombi nant protein expressing amino acids 55-98 of G(L) (G(L)-GST) and an ovalbum in-conjugated synthetic peptide representing amino acids 81-106 of G(L) (G( L)-OVA) were used as diagnostic antigens. An ELISA procedure was developed and optimised for each antigen. The G(L)-OVA and G(L)-6His assays showed th e greatest specificity while the G(L)-GST assay was slightly more sensitive that the G(L)-OVA and G(L)-6His assays; results based on the analysis of 5 0 virus neutralisation positive and 50 virus neutralisation negative sera. The G(L)-OVA ELISA was selected for further evaluation since it was simpler to use than ELISAs based on recombinant antigens and did not suffer from b ackground reactivity. The final sensitivity and specificity of the G(L)-OVA ELISA were 96.75 and 95.6%, respectively, results based on the analysis of 400 virus neutralisation positive and 400 virus neutralisation negative se ra. It also detected EAV antibody (100% efficiency) in seropositive sheddin g stallions and, in ponies infected experimentally with the UK93 isolate of EAV, the appearance of virus neutralising antibodies and G(L)-OVA ELISA-sp ecific immunoglobulins coincided. (C) 2000 Elsevier Science B.V. All rights reserved.