PATHOGENESIS OF ALEUTIAN MINK DISEASE PARVOVIRUS INFECTIONS

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Persistent infection of mink with the Aleutian mink disease parvovirus (ADV) leads to disturbances of immune regulation, including hypergammaglobulinemia, plasmacytosis, immune complex disease, interstitial and glomerulonephritis. The major target cell population for viral replication and sequestration is macrophages. Infection is enhanced by anti-viral antibody, but is somehow restricted at the level of the individual cell. The purpose of this project is to elucidate the pathogenetic mechanisms by which viral infection causes this disorder. A summary of this year's studies includes: * Antibody response to ADV nonstructural proteins. ADV infected mink made antibody against amino acid sequences common to the viral nonstructural proteins, NS1, NS2 and NS3. Although antibody to the unique regions of NS1 was also present, no antibody against the unique regions of NS2 or NS3 was detected. * Subcellular localization of ADV proteins in permissive infection. In permissively infected CRFK cells prior to nucleolysis late in infection, ADV virion proteins (VP) formed shell-like intranuclear structures surrounding inclusions of viral DNA, NS1 and NS2. NS2 (ca. 50%) was also found in the cytoplasm, exhibiting some characteristics of a shuttling protein like HIV rev protein. * ADV restricted infection of monocyte cell line, K562. VP, NS1 and NS2 were found in nuclei of K562 cells after antibody dependent infection with ADV. Unlike permissive ADV infection of CRFK, NS2 was not noted in the cytoplasm of K562. ADV infection arrested the normal cell cycle of K562 in later stages, similar to cell cycle disruption seen in CRFK. Upregulation of interleukin 6 protein (IL-6) was not observed in ADV infected K562 cells. * ADV infection of mink peripheral blood mononuclear cells (PBMC). A system for studying ADV infection in mink PBMC was developed. Following ADV infection of purified PBMC from uninfected mink, virtually all monocytes exhibited specific cytoplasmic fluorescence. A low percentage went on to exhibit nuclear localization of antigen at later time points, indicating limited viral replication. * Comparison of polymerase chain reaction (PCR) with counterimmune electrophoresis (CEP) in diagnosis of ADV infections. CEP was found to be more sensitive than PCR for detecting ADV infections in a commercial mink ranch setting. * Cytokine response of ADV infected mink. Cytokine levels were assayed on lymphoid tissues from ADV infected mink using a non-radioactive RNAse protection assay (RPA). No consistent pattern was observed for IL-6, IL-10, IL-1, IL-12 p35, IL-12 p40 or TNF between infected and uninfected animals.