Autoimmune reactivity in sheep induced by the visna retrovirus

Small ruminant lentiviruses: immunopathogenesis of visna-maedi and caprine arthritis and encephalitis virus

The small ruminant lentiviruses include the prototype for the genus, visna-maedi virus (VMV) as well as caprine arthritis encephalitis virus (CAEV). Infection of sheep or goats with these viruses causes slow, progressive, inflammatory pathology in many tissues, but the most common clinical signs result from pathology in the lung, mammary gland, central nervous system and joints. This review examines replication, immunity to and pathogenesis of these viruses and highlights major differences from and similarities to some of the other lentiviruses.

Retroviral sequences in rheumatoid arthritis synovium

There are several relationships between retroviruses and cellular transformation, as well as retroviruses being involved in the development of autoimmune diseases. Retroviruses have been discussed as etiologic agents modulating or triggering certain pathways in the pathogenesis of rheumatoid arthritis (RA). However, none of the currently known retroviruses has been identified as specific for RA. Due to the unique properties of retroviruses, distinct experimental approaches can be used to detect retroviral activity in cells and tissues. Current research in RA using state-of-the-art molecular biology techniques includes both the search for exogenous and endogenous retroviral gene sequences in synovium of patients with RA.

Antibody reactivity to the transmembrane protein of the caprine arthritis encephalitis virus correlates with severity of arthritis: no evidence for the involvement of epitope mimicry

Serum and synovial antibody reactivities of caprine arthritis encephalitis virus (CAEV) infected goats were assessed by Western blotting against purified CAEV antigen and the greatest intensity of reactivity in the serum of arthritic goats was to the gp45 transmembrane protein (TM). The extracytoplasmic domain of the TM gene was cloned into a pGEX vector and expressed in Escherichia coli as a glutathione S transferase fusion protein (GST-TM). This clone was found to be 90.5 and 89.2% homologous to published sequences of CAEV TM gene. Serum of 16 goats naturally infected with CAEV were examined by Western blotting for reactivity to the fusion protein. Antibody reactivity to the GST-TM correlated with clinically detectable arthritis (R = 0.642, P < or = 0.007). The hypothesis that the immune response to the envelope proteins of the CAEV contributes to the severity of arthritis in goats naturally infected with CAEV via epitope mimicry was tested. Antibodies from 5 CAEV infected goats were affinity purified against the GST-TM fusion protein and tested for cross-reactivity with a series of goat synovial extracts and proteogylcans. No serum antibody response or cross-reactivity of affinity purified antibodies could be detected. Peptides of the CAEV SU that were predicted to be linear epitopes and a similar heat shock protein 83 (HSP) peptide identified by database searching, were synthesized and tested for reactivity in CAEV goats using ELISA, in vitro lymphocyte proliferation and delayed type hypersensitivity (DTH) assays. Peripheral blood lymphocytes from 10 of 17 goats with long term natural CAEV infections proliferated in vitro in response to CAEV and in vivo 3 of 7 CAEV infected goats had a DTH reaction to CAEV antigen. However, none of the peptides elicited significant cell mediated immune responses from CAEV infected goats. No antibody reactivity to the SU peptides or HSP peptide was found. We observed that the antibody reactivity to the CAEV TM protein associated with severity of arthritis however epitope mimicry by the envelope proteins of CAEV is unlikely to be involved.

Immunoglobulin deposits in synovial membrane and cartilage and phenotype analysis of chondrocyte antigens in sheep infected with the visna retrovirus

Synovial membranes and cartilage slices from sheep infected with the maedi-visna retrovirus were examined for immunoglobulin deposits by immunohistology. Granular deposits of IgM and IgG were observed in the synovial membranes and upper layers of cartilage from about 40% of virus-infected sheep. These deposits were present in animals with subclinical joint disease, as well as those affected clinically. No significant deposits were found in the synovial membrane or cartilage from normal sheep. Infected animals tended to have reduced cartilage proteoglycan staining. Altered expression of MHC class II, CD1 and adhesion molecules by chondrocytes in cartilage from infected sheep with clinical or subclinical synovitis was observed suggesting that in vivo cell activation is an early event in cartilage degradation in these infections. Exogenously derived antiviral antibodies exhibited molecular mimicry towards chondrocyte antigens, but no in vivo evidence for cross-reactivity was observed. The results showed that IgM and IgG deposits, putatively containing either virus/antivirus immune complexes or autoantibodies were formed in the joints of sheep with clinical or subclinical synovitis. These immune deposits may initiate and perpetuate chronic inflammation with concomitant activation of chondrocytes leading to pannus formation and cartilage destruction.