Analysis of ovine lentivirus infectivity and replication by using a focal immunoassay and an antigen-capture enzyme-linked immunosorbent assay

Abstract

A focal immunoassay and an antigen-capture enzyme-linked immunosorbent assay (antigen-capture ELISA) were developed to quantify infectious ovine lentivirus (OvLV) and OvLV capsid protein (CA) (p27), respectively. The in vitro kinetics of replication and cytopathogenicity of distinct biological clones of OvLV (rapid/high and slow/low phenotypic variants) were assessed. Both viruses were detected by focal immunoassay within 48 h postinfection, 2 days before syncytia were observed in goat synovial membrane cells infected with rapid/high OvLV and 4 days before they appeared in cultures infected with slow/low OvLV. CA was first detected by antigen-capture ELISA in supernatants of cells infected with rapid/high OvLV 4 days postinfection, and it reached a plateau by 10 days, 4 days after peak syncytium formation. In contrast, in cultures infected at the same multiplicity of infection with slow/low OvLV, CA was detected 8 days postinfection, and the titer gradually increased over the following 12 days while the number of syncytia gradually decreased. Peripheral blood mononuclear cells (PBMC) from seropositive sheep treated with phorbol 12-myristate 13-acetate (PMA) generally expressed CA earlier and at higher levels than PBMC treated with either phytohemagglutinin or concanavalin A. Serum CA levels above 3 ng/ml were found in 58% (18 of 31) of seropositive sheep. However, there was no correlation between PMA-induced CA expression and levels of antigenemia. Viral heterogeneity may account for variations both in CA expression in cultures of PBMC and in antigenemia, humoral immune response, and viral pathogenicity in infected animals.

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

“…Different ELISAs have been developed for detection of MVV infection. 11,12,21,30,34,36 ELISAs based on recombinant proteins and synthetic peptides have improved MVV diagnosis 1,15,17,18,22,24,31,39 and have been proposed for field diagnosis and control and eradication programs.…”

The Effects of Pharmacological and Lentivirus-Induced Immune Suppression on Orbivirus Pathogenesis: Assessment of Virus Burden in Blood Monocytes and Tissues by Reverse Transcription-In Situ PCR

“…Phenotypic differences in viral strains are common. Lentiviruses with "rapid-high" and "slowlow" growth potential have been described (37). After an initial burst of virus replication in monocytes, replication ensued in regional lymph nodes, followed by release and systemic spread of virus to resident mononuclear leukocytes in the lung, CNS, and lymphoid and hematogenous tissues and to vascular endothelium in a wide variety of tissues.…”

“…Animals with classical signs of lentivirus infection were shown to harbor OvLV by methods described previously, including virus isolation (8) and in situ hybridization (9,10). To assess the effects of lentivirus infection on BTV replication, monocytes were infected in vitro with OvLV strain 85/34 (37) and then later coinfected with BTV-3 or BTV-11. All animal inoculations and laboratory procedures utilizing foreign viruses were performed in a biocontainment level 3 facility.…”