ABSTRACT
Diagnosis of bovine viral diarrhea (BVD) relies on the detection of antibodies against its viral causing agent, bovine viral diarrhea virus (BVDV). Here, we designed a novel competitive ELISA (cELISA) using the most immunogenic part of BVDV nonstructural protein 3 (NS3), as a single ELISA recombinant antigen, along with a monoclonal antibody to detect antibodies against BVDV in sera of infected animals. Hence, 197 serum samples were tested by this cELISA and the results were compared to the results obtained from virus neutralization test (VNT) as the gold standard method for diagnosis of BVD. McNemar's test indicated that there was no significant difference between the results of this newly designed cELISA and VNT. Meanwhile, kappa coefficients showed that there was a high correlation between these two assays. The relative sensitivity and specificity of cELISA with respect to VNT were 93.90% and 100%, respectively, suggesting that this newly designed cELISA could be a useful diagnostic tool for detection of BVDV infection. Moreover, as NS3 is highly conserved among Pestiviruses and the developed ELISA is a competitive one, it could potentially be applied to detect BVDV infection in other domestic and wildlife species.
ABSTRACT
BACKGROUND: Bovine viral diarrhea (BVD) is an economically important disease of cattle distributed worldwide. Diagnosis of BVD relies on laboratory-based detection of its viral causing agent or virus specific antibodies and the most common laboratory method for this purpose is Enzyme-Linked Immunosorbent Assay (ELISA). OBJECTIVES: The current study was aimed to develop a simple indirect ELISA to detect antibodies against Bovine Viral Diarrhea Virus (BVDV) in the sera of infected cattle. MATERIALS AND METHODS: A new simple indirect ELISA method was developed to detect BVDV infection by prokaryotically (Escherichia coli, BL21 strain) expressed recombinant whole nonstructural protein 3 (NS3) of BVDV (NADL strain). Four hundred bovine serum samples were evaluated by the newly developed NS3-ELISA and virus neutralization test (VNT) as the gold standard method to diagnose BVD. Among these samples, 289 sera had been previously tested by a commercial ELISA kit. RESULTS: Statistical analyses showed a very high correlation between the results of the developed NS3-ELISA and VNT (kappa coefficient = 0.935, P < 0.001), with the relative sensitivity and specificity of 94% and 98.8%, respectively. There was also a high correlation between the results of NS3-ELISA and the commercial ELISA kit (kappa coefficient = 0.802, P < 0.001) with the relative sensitivity and specificity of 90.72% and 91.15%, respectively. CONCLUSIONS: The newly developed simple indirect ELISA showed high sensitivity and specificity with respect to VNT. Developing such a simple, sensitive, and specific ELISA which is much less expensive than the available commercial ELISA kits can improve the detection of BVDV infections, help to eliminate the disease from herds, and decrease economic losses caused by this disease.
