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Maedi-visna in sheep and caprine arthritis-encephalitis in goats are caused by two closely related and widespread lentiviruses. The infections are characterized by lifelong virus persistence and slow induction of antiviral antibodies. The diagnosis is based on the detection of antiviral antibodies. We have used the polymerase chain reaction (PCR) to amplify a part of the gag gene coding for the entire capsid protein and for parts of the matrix and nucleocapsid proteins. Sequencing of the PCR fragment of the Dutch maedi-visna virus strain ZZV 1050 revealed 85 and 92% homology to the DNA and deduced amino acid sequences, respectively, of the distantly related Icelandic visna virus strain 1514. The respective homologies with caprine arthritisencephalitis virus strain CO were 76 and 80%. The PCR fragment was cloned into pGEX-2T and expressed as a glutathione S-transferase fusion protein. The recombinant protein could be detected on immunoblots by using a monoclonal antibody and polyclonal antisera and was further purified by glutathione-based affinity chromatography. Enzyme-linked immunosorbent assay with purified recombinant fusion protein is shown to be a sensitive and specific diagnostic tool for the detection of lentiviral infection in goats and sheep.

Antigenic cross-reactivity of the human acquired immunodeficiency disease syndrome virus LAV/HTLV-III with the lentiviruses visna virus, caprine arthritis encephalitis virus (CAEV), and equine infectious anemia virus (EIAV) was determined with indirect enzyme-linked immunosorbent assays, immunoblot analysis, and virus-specific polyclonal antisera. Nonreciprocal cross-reactivity was seen between the gag gene products p24 of LAV/HTLV-III and p28 of EIAV. Reciprocal cross-reactivity was seen between the gag gene product p28 of visna virus and CAEV. No cross-reactivity was detected between visna virus (or CAEV) and EIAV (or LAV/HTLV-III). This suggests a closer relationship of LAV/ HTLV-ΠI with EIAV than with visna virus or CAEV.