title: Immunologic features of porcine circovirus type 2 infection.
abstract: Clinical expression of porcine circovirus 2 (PCV-2) infection in swine may result in two distinct high mortality disease syndromes. In North America, postweaning multisystemic wasting syndrome (PMWS), while still sporadic in incidence, predominates. In Europe and elsewhere, both PMWS and a second syndrome, porcine dermatitis and nephropathy syndrome (PDNS), occur in endemic and epidemic forms. PMWS but not PDNS has been reproduced in piglets by inoculations with PCV-2 alone or in PCV-2-infected swine co-infected with porcine parvovirus (PPV) or porcine respiratory and reproductive syndrome (PRRS) virus and also if PCV-2-infected piglets are immunostimulated by injections with an immunogen emulsified in an oil-based macrophage-targeted adjuvant. Subclinical but active infection has been achieved by direct inoculation of piglets with cloned PCV-2 DNA and/or progeny virus derived from cloned DNA. Morphologic changes in lymphoid tissues and preliminary functional data suggest that immunosuppression may occur in PMWS-affected swine. This phenomenon appears to be mediated by generalized lymphoid depletion and replacement by infiltrating and proliferating histiocytes and macrophages. Accumulation of virus in both mononuclear phagocytes and follicular dendritic cells is characteristic of PCV-2 infection. Exogenous immunosuppression of PCV-2-infected gnotobiotic piglets with cyclosporine (Cys), but not corticosteroid (St), potentiates PCV-2 replication and promotes productive virus infection of hepatocytes in Cys-treated piglets, a tropism not previously apparent in experimentally induced PMWS in gnotobiotic swine. In the Cys-treated piglets, inflammatory lesions characteristic of PMWS are absent, even though tissues contain high titers of infectious virus, a finding which suggests that the granulomatous inflammatory lesions characteristic of PMWS are immune mediated.
authors.affiliation: Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio, USA. krakowka.1@osu.edu
authors.forename: Steven
authors.initials: S
authors.lastname: Krakowka
authors.forename: John A
authors.initials: JA
authors.lastname: Ellis
authors.forename: Francis
authors.initials: F
authors.lastname: McNeilly
authors.forename: Diedre
authors.initials: D
authors.lastname: Gilpin
authors.forename: Brian
authors.initials: B
authors.lastname: Meehan
authors.forename: Ken
authors.initials: K
authors.lastname: McCullough
authors.forename: Gordon
authors.initials: G
authors.lastname: Allan
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D018173:Circoviridae Infections / Q000276:immunology / Q000473:pathology / Q000662:veterinary* / Q000821:virology; D017925:Circovirus / Q000276:immunology*; D016867:Immunocompromised Host; D008221:Lymphoid Tissue / Q000473:pathology / Q000821:virology; D013552:Swine; D013553:Swine Diseases / Q000276:immunology* / Q000473:pathology / Q000821:virology; D019282:Wasting Syndrome / Q000276:immunology / Q000473:pathology / Q000662:veterinary* / Q000821:virology
chemical_list: D000914:Antibodies, Viral