Changes in CD4 ⁺ , CD8 ⁺ , CD4 ⁺ CD8 ⁺ , and Immunoglobulin M-Positive Peripheral Blood Mononuclear Cells of Postweaning Multisystemic Wasting Syndrome-Affected Pigs and Age-Matched Uninfected Wasted and Healthy Pigs Correlate with Lesions and Porcine Circovirus Type 2 Load in Lymphoid Tissues

Abstract

Forty-one 8-to 12-week-old wasted pigs were selected from several conventional farms with histories of postweaning multisystemic wasting syndrome (PMWS) and classified into two groups according to their porcine circovirus type 2 (PCV2) infection status, as determined by in situ hybridization (ISH). Twenty-four pigs tested positive for PCV2 (PCV2-positive group), while 17 pigs tested negative for PCV2 (PCV2-negative group). In addition, eight uninfected healthy pigs from an experimental farm were used as controls. Heparinized blood samples were taken to obtain peripheral blood mononuclear cells. The CD4, and immunoglobulin M-positive (IgM ؉ ) cell subsets were analyzed by flow cytometry with appropriate monoclonal antibodies. Histopathological studies were done to evaluate the apparent degrees of lymphocyte depletion in different lymphoid organs (superficial inguinal and mesenteric lymph nodes, Peyer's patches, tonsils, and spleen) and to determine the viral load of the PCV2 genome by using an ISH technique. Animals of the PCV2-positive group showed a significant downshift of the CD8 ؉ and DP cell subsets compared to the other groups (P < 0.05). Moreover, in PCV2-positive pigs, the amount of PCV2 genome in lymphoid tissues was related to the degree of cell depletion in those tissues (P < 0.05) as well as to the relative decrease in IgM ؉ and CD8 ؉ cells in peripheral blood. These data support the notion that PCV2-positive pigs might have an impaired immune response.

Identification and Functional Analysis of the Novel ORF4 Protein Encoded by Porcine Circovirus Type 2

“…Our results suggest that the ORF4-deficient PCV2 is involved in virulence and replication in vivo. We also found that the relative proportions of CD4 ϩ , CD8 ϩ , and CD4 ϩ CD8 ϩ T cells were downregulated in PCV2⌬-and wPCV2-infected mice, similar to previous findings for PCV2-infected pigs (52). Furthermore, compared to wPCV2-infected mice, the mutant virus exhibited a greater decrease of CD4 ϩ and CD8 ϩ T cells in infected mice (Fig.…”

Dendritic Cells Harbor Infectious Porcine CircovirusType 2 in the Absence of Apparent Cell Modulation or Replication of theVirus

“…PCV2 can induced a lymphopenia, involving an early loss of B lymphocytes, concomitant with depletion of helper (both naive and memory/ activated), cytotoxic, and ␥␦ T cells, as well as natural killer cells (37). Despite these observations, virus antigen has not been clearly demonstrated in lymphocytes (11,42,45,47). It has been reported that virus impairment of DC function can have consequences on T-lymphocyte survival and anergy (23).…”

Circovirose suína

“…Em condições experimentais, o período de incubação pode chegar a 2-4 semanas (Allan et al 1999a, Balash et al 1999, Harms et al 2001, período no qual o acúmulo de vírus necessário para iniciar a doença é alcançado. Quanto maior a quantidade de antígeno vírico detectada, maior a depleção linfóide , Darwich et al 2002, Chianini et al 2003, Darwich et al 2003.…”