Differentiation of classical swine fever virus infection from CP7_E2alf marker vaccination by a multiplex microsphere immunoassay.
Classical swine fever (CSF) is a highly contagious viral disease of pigs that has a tremendous socioeconomic impact. Vaccines are available for disease control. However, most industrialized countries are implementing stamping-out strategies to eliminate the disease and avoid trade restrictions. These restrictions can be avoided through the use of marker vaccines such as CP7_E2alf. Marker vaccines have to be accompanied by reliable and robust discriminatory assays. In this context, a multiplex microsphere immunoassay for serological differentiation of infected from vaccinated animals (DIVA) was developed to distinguish CSF virus (CSFV)-infected animals from CP7_E2alf-vaccinated animals. To this end, three viral proteins, namely, CSFV E2, CSFV E(rns), and bovine viral diarrhea virus (BVDV) E2, were produced in insect cells using a baculovirus expression system; they were used as antigens in a microsphere immunoassay, which was further evaluated by testing a large panel of pig sera and compared to a well-characterized commercial CSFV E2 antibody enzyme-linked immunosorbent assays (ELISAs) and a test version of an improved CSFV E(rns) antibody ELISA. Under a cutoff median fluorescence intensity value of 5,522, the multiplex microsphere immunoassay had a sensitivity of 98.5% and a specificity of 98.9% for the detection of antibodies against CSFV E2. The microsphere immunoassay and the CSFV E(rns) ELISA gave the same results for 155 out of 187 samples (82.8%) for the presence of CSFV E(rns) antibodies. This novel multiplex immunoassay is a valuable tool for measuring and differentiating immune responses to vaccination and/or infection in animals.
Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
Hongyan
H
Xia
Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
Rajiv
R
Harimoorthy
Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
Balaje
B
Vijayaraghavan
Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.
Sandra
S
Blome
Department of Virology, Immunobiology and Parasitology, National Veterinary Institute (SVA), Uppsala, Sweden.
Frederik
F
Widén
Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.
Martin
M
Beer
Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden Department of Virology, Immunobiology and Parasitology, National Veterinary Institute (SVA), Uppsala, Sweden.
Sándor
S
Belák
Department of Virology, Immunobiology and Parasitology, National Veterinary Institute (SVA), Uppsala, Sweden lihong.liu@sva.se.
Lihong
L
Liu
D000818:Animals; D000956:Antigens, Viral; D006691:Classical Swine Fever / Q000276:immunology*; D006692:Classical Swine Fever Virus / Q000276:immunology*; D003937:Diagnosis, Differential; D007118:Immunoassay / Q000379:methods*; D008863:Microspheres; D012680:Sensitivity and Specificity; D013552:Swine; D022581:Vaccines, Marker / Q000008:administration & dosage / Q000276:immunology; D014765:Viral Vaccines / Q000008:administration & dosage / Q000276:immunology*
D000956:Antigens, Viral; D022581:Vaccines, Marker; D014765:Viral Vaccines