EXPRESSION OF ALEUTIAN MINK DISEASE PARVOVIRUS CAPSID PROTEINS IN A BACULOVIRUS EXPRESSION SYSTEM FOR POTENTIAL DIAGNOSTIC USE

A 2.3-kb cDNA clone encoding Aleutian mink disease parvovirus (ADV) st ructural proteins VP1 and VP2 was inserted into the polyhedron gene of Autographa californica nuclear polyhedrosis virus (AcNPV) and express ed by the recombinant virus, AcADV-1, in Spodoptera frugiperda-9 cells . Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and wester n immunoblot analysis (WIA) indicated that synthesis of both VP1 and V P2 was being directed by AcADV-1. Fluorescence microscopic examination of AcADV-1-infected S. frugiperda-9 cells indicated that the recombin ant protein was present within the nucleus of the cells, and electron microscopic examination of these cells revealed the presence of small particles 23-25 nm in diameter. Structures resembling empty ADV capsid s could be purified on CsCl density gradients, thus indicating that th e ADV proteins were self-assembling. The antigenicity of recombinant V P1 and VP2 was evaluated by WIA. Sera collected from 16 mink prior to infection with ADV did not react with VP1 and VP2. Ten sera collected from mink with counter current immunoelectrophoresis (CIE) titers grea ter than 4 (log2) reacted with VP1 and VP2 in WIA. Two of 6 sera with CIE titers of 4 and 1 of 14 sera with CIE titers < 4 reacted with the recombinant proteins. These results suggest that baculovirus recombina nt ADV capsid proteins may be useful as diagnostic antigens.