Pestivirus is a common contaminant in maedi-visna and caprine arthritis-encephalitis virus stocks.

Eight different laboratory stocks of maedi-visna or caprine arthritis-encephalitis virus were examined for the presence of pestiviruses by a fixed-cell immunoperoxidase assay with polyclonal and monoclonal antibodies. All of the viral stocks examined were found to contain noncytopathic pestivirus contaminants. The panel of monoclonal antibodies could not type the isolates as being more related to bovine virus diarrhea virus or border disease virus. However, the results did indicate that all isolates were not the same, except for two from the same laboratory where the source of pestivirus contamination may have been common.

Evaluation of an enzyme-linked immunosorbent assay for the detection of antibodies to caprine arthritis-encephalitis virus in goat serum.

An indirect enzyme-linked immunosorbent assay (ELISA), was evaluated for its ability to detect serum antibodies against caprine arthritis-encephalitis virus (CAEV). The ELISA was compared to three other serological immunoassays, agar gel immunodiffusion test (AGIDT), immunoblot assay (IBA), and a fixed-cell immunoperoxidase assay (FCIPA). A total of 511 samples, from 40 farms representing a variety of goat breeds and ages were tested. An estimate of the ELISA sensitivity and specificity was made, relative to combined test results of the three other CAEV serological assays. The degree of agreement of test results among these four assays was evaluated. The number of positives detected by the ELISA, AGIDT, IBA and IPA tests was 193, 154, 204 and 163, respectively. Of the 511 sera tested, 172 were positive to any two or all three of these tests, and were defined as reference positive. A total of 237 samples were negative to all three reference tests, and were defined as reference negative. Relative to these references, the ELISA had a point estimate of 98.3% sensitivity and 97.9% specificity. There was good agreement between the ELISA and the other three assays with a kappa statistic of agreement greater than 0.7 for all three comparisons. The ELISA is therefore considered a suitable assay, with high sensitivity and specificity, for detection of antibodies to CAEV in serum.

An enzyme-linked immunosorbent assay for detection of antibodies to maedi-visna virus in sheep. I. A simple technique for production of antigen using sodium dodecyl sulfate treatment.

We report the efficacy of an anionic detergent, sodium dodecyl sulfate (SDS) for preparing maedi-visna antigens for an indirect enzyme-linked immunosorbent assay (i-ELISA). Ovine maedi-visna virus (MVV) pelleted by differential centrifugation followed by liquid chromatography was treated with SDS or one of three lipid solvents: ethyl ether, chloroform or fluorocarbon. The SDS-treated antigen resulted in higher optical density values with positive serum and better discrimination between positive and negative serum samples from specific-pathogen-free (SPF) sheep experimentally inoculated with the virus. Optimal results were obtained when MVV was treated with concentrations of 0.25% and 0.125% of SDS. A viral antigen prepared by centrifugation and treatment of a viral pellet with SDS was also suitable for the i-ELISA. This latter technique may facilitate the production of MVV antigens for use in the i-ELISA.

An enzyme-linked immunosorbent assay for detection of antibodies to maedi-visna virus in sheep. II. Comparison to conventional agar gel immunodiffusion test.

A study was conducted to compare the indirect enzyme-linked immunosorbent-assay (i-ELISA) test using antigen prepared by a simple technique using sodium dodecyl sulfate (SDS) treatment to the conventional agar gel immunodiffusion test (AGID). Ten specific-pathogen-free (SPF) sheep were inoculated with maedi-visna virus (MVV) and serum antibody titers compared over a period of 14 weeks. All the sheep seroconverted by the i-ELISA compared to 90% by the AGID. The i-ELISA detected antibody at a mean of 2.6 weeks prior to the AGID. In both tests, fluctuations were observed in the serum antibody response of two sheep. The i-ELISA had a specificity of at least 98.8% and an increased relative sensitivity of 15.5% compared to the AGID, based on the analysis of sera from experimental sheep with MVV free status and sera from sheep from various sources. Of the sera from a seronegative flock which had been monitored with the AGID after a "test and remove" eradication program, 10.2% were positive by the i-ELISA. It was concluded that the AGID test may not be adequate to monitor samples for an eradication scheme.