A New Sensitive Serological Assay for Detection of Lentivirus Infections in Small Ruminants

Abstract

Lentivirus infections in small ruminants represent an economic problem affecting several European countries with important sheep-breeding industries. Programs for control and eradication of these infections are being initiated and require reliable screening assays. This communication describes the construction and evaluation of a new serological screening enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to maedi-visna virus (MVV) in sheep and to caprine arthritis encephalitis virus (CAEV) in goats. The solid phase is sensitized with a combination of the major core protein p25 of MVV produced in Escherichia coli and a peptide derived from the immunodominant region of the viral transmembrane protein gp46. The peptide carries an N-terminal biotin residue and is complexed with streptavidin prior to being coated. The new assay was evaluated with 2,336 sheep serum samples from different European countries with large differences in the levels of prevalence of MVV infections, and the results have been compared to those of the standard agar gel immunodiffusion test. Discrepant samples were analyzed by Western blotting with viral lysate, and most sera could be classified unambiguously. The estimated overall sensitivity of the new ELISA was 99.4% (95% confidence interval [CI], 98.4 to 99.8%) and the specificity was 99.3% (95% CI, 98.7 to 99.6%). A limited set of goat sera (n = 212) was also analyzed, with similar results. These data indicate that the new assay is a reliable tool that can be used in control and eradication programs for small ruminant lentivirus infections.

Early Detection of Maedi-Visna (Ovine Progressive Pneumonia) Virus Seroconversion in Field Sheep Samples

“…When comparing the performance of ELISA and AGID, a similarly high specificity was observed, although ELISA had a 21.5% higher sensitivity (97.8 vs. 76.3%; Tables 4, 5) and a 10.7% higher overall efficacy. Analogous figures on ELISA sensitivity and specificity have been obtained in previous studies involving various breeds, 31 and encouraging results have been published using other ELISAs. 11,15,22,30,34,36 The low sensitivity of AGID (Table 5) may explain why, in the comparison between ELISA and AGID, the ELISA had an apparently low specificity (84.2%) and why, in relation to the reference result, the specificity of both tests (ELISA and AGID) was virtually the same (98.2% vs. 98.3%, respectively).…”

“…Absorbance of the test solution was read at dual wavelengths of 450 and 595 nm with an ELISA reader within 15 min. The cutoff value was calculated as previously indicated for this ELISA, 31 i.e., by dividing the mean of the absorbance of the positive control wells by 4 and adding to that value the mean of the absorbance of the negative control wells. The optical density (OD) ratio was defined as the result obtained after dividing the mean absorbance of duplicates by the cutoff value.…”

Granulocyte macrophage colony stimulating factor is elevated in alveolar macrophages from sheep naturally infected with maedi-visna virus and stimulates maedi-visna virus replication in macrophagesin vitro

“…Previous examination of the source flock revealed no evidence of interrecurrent respiratory disease that was not associated with MVV infection [19]. Sheep from flocks not infected with MVV were purchased locally and examined by the agar gel immunodiffusion test (AGID) [20] and ELISA [21]. Uninfected and infected animals were housed separately but otherwise managed under similar conditions.…”

Comparison of immunoassay and real-time PCR methods for the detection of Jembrana disease virus infection in Bali cattle

“…An immunodominant epitope was identified in the N-terminal portion of BIV TM (Chen et al, 1994) and a TM peptide ELISA was developed from peptide mapping this region (Scobie et al, 1999). The combination of recombinant CA and TM peptides has now been applied to diagnostic ELISAs for JDV and SRLV (Barboni et al, 2001;Saman et al, 1999). Unlike other lentiviral assays where serological diagnosis usually occurs well before the clinical stage of the disease due to the chronic nature of these infections, reliable detection of seroconversion to JDV using immunoassays cannot be achieved until 5-15 weeks after the onset of clinical disease (Desport et al, 2009).…”