The role of porcine teschovirus in causing diseases in endemically infected pigs.

Porcine teschoviruses (PTVs) belong to the genus Teschovirus within the family Picornaviridae. Hitherto, PTVs have had 13 serotypes associated with a variety of clinical diseases. The virulent PTV-1 strains were associated with highly fatal, nonsuppurative encephalomyelitis of pigs (Teschen disease) in the 1930-1950s. Today, less virulent Talfan strains of PTV-1 are more widespread, and PTVs have contaminated swine herds worldwide (endemic or enzootic) together with a variety of common swine pathogens (multi-infection status). The aim of this study was to investigate the extent to which PTVs play a role in causing diseases in the field, under the endemic and multi-infection situation, when most pigs in the herds are infected and immune. Based on the fecal-oral model of pathogenesis, a set of 15 organs were collected from 30 culled post-weanling piglets of 4-8 weeks old. For nested RT-PCR targeted on the 5'-NTR, the PTV detection rate was 96.7% (by heads), confirming the endemic status, and infection was most commonly detected in the intestines (averaged 61%) and lymphoid organs (averaged 59%), followed by visceral organs (averaged 37%) and the CNS (different parts varied from 17 to 47%). The correlation of PTVs detected by nested RT-PCR and a histological lesion were analyzed by Chi-square test showing that in the field situation only non-suppurative encephalitis in the caudal part of the brain (P=0.054) may be marginal significantly attributed to infection by PTVs. By genotyping based on partial VP1 sequences, 5 serotypes, namely PTV-1, -4, -6, -7, and -11, were identified, with some animals having two serotypes co-existed in different organs.

Effect of the VP3 gene of chicken anemia virus on canine mammary tumor cells.

OBJECTIVE: To investigate the antitumor effect of the chicken anemia virus (CAV) VP3 gene in canine mammary tumor (CMT) cells. SAMPLE POPULATIONS: Established primary canine cell lines that originated from epithelial cells of resected CMTs and nonneoplastic mammary gland epithelial (MGE) cells. PROCEDURES: Expression vectors and lentiviral vectors encoding the VP3 gene from a Taiwan-Ilan isolate of CAV were used to deliver the VP3 gene into CMT cells and nonneoplastic MGE cells. Ectopic gene expression and the pro-apoptotic effect of the VP3 gene on CMT and nonneoplastic MGE cells by either transfection or viral infection were evaluated via immunofluorescence microscopy, western blot analysis, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling analysis. RESULTS: Overexpression of the enhanced green fluorescent protein-VP3 fusion protein was detected predominantly in the nuclei of CMT cells. In contrast, the VP3 protein was localized to the cytoplasm of nonneoplastic MGE cells. Among the fusion protein-expressing CMT cells, most underwent characteristic changes of apoptosis, whereas apoptosis was not detected in fusion protein-expressing, nonneoplastic MGE cells. Induction of apoptosis by VP3 gene overexpression in CMT cells was associated with the caspase-9-, but not the caspase-8-, mediated apoptosis pathway. CONCLUSIONS AND CLINICAL RELEVANCE: These data indicate that the VP3 gene of the CAV induces apoptosis in malignant CMT cells, but not in nonneoplastic canine MGE cells. On the basis of such tumor cell-specific killing, the VP3 gene may be a promising agent for the treatment of malignant mammary gland tumors in dogs.

Immunopathological effects of porcine circovirus type 2 (PCV2) on swine alveolar macrophages by in vitro inoculation.

Porcine circovirus type 2 (PCV2) is the primary causative agent of postweaning multisystemic wasting syndrome (PMWS), a multifactorial disease, in pigs. Monocyte/macrophage lineage cells, including alveolar macrophages (AMs), are the major target cells for PCV2. Swine AMs are essential for the pulmonary defense system against various pathogens. Concurrent infection of lung with opportunistic pathogens in pigs suffered from PMWS is speculated as a feature of immunosuppression. The present study was conducted to characterize the effects of PCV2 inoculation on swine AMs in the in vitro system. The parameters selected for evaluation included PCV2 antigen- and nucleic acid-containing rate, viability, TUNEL-positive rate, phagocytosis, microbicidal capability, and capacity for production of reactive oxygen species (superoxide anion, O2-, and hydrogen peroxide, H2O2), cytokines, and chemokines. High intracytoplasmic PCV2 antigen- and nucleic acid-containing rate, absence of intranuclear signals for PCV2 antigen and nucleic acid, and lack of noticeable cell death were seen in PCV2-inoculated AMs. The PCV2-inoculated AMs displayed a transient as well as persistent reduction in the up-take and destruction of Candida albicans, respectively, accompanied by decrease in the production of O2- and H2O2. In PCV2-inoculated AMs, the levels of tumor necrosis-alpha (TNF-alpha) and interleukin-8 (IL-8) were significantly increased; the mRNA expression levels of alveolar macrophage-derived neutrophil chemotactic factors-II (AMCF-II), granulocyte colony-stimulating factor (G-CSF), monocyte chemotactic protein-1 (MCP-1), and IL-8 were strongly up-regulated. The reduced phagocytosis and microbicidal capability in conjunction with decreased production of reactive oxygen species in PCV2-inoculated AMs suggest that PCV2-containing AMs may favor the survival and spread of PCV2. It is speculated that the functional alterations observed in PCV2-containing AMs may be potentially harmful to the lung tissue and local pulmonary defense system, especially in those PCV2-infected pigs conditioned by various PMWS development-dependent co-factors.

Reduction of porcine reproductive and respiratory syndrome virus (PRRSV) infection in swine alveolar macrophages by porcine circovirus 2 (PCV2)-induced interferon-alpha.

Two common viral pathogens of swine, namely, porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV), were investigated in regard to their effects on monolayer cultures of swine alveolar macrophages (AMs). The purpose was to identify selected cellular changes and responses potentially associated with the clinical reactions of pigs infected with either or both of these viruses. Measurements included the (1) absolute and relative numbers of infected, viable, and apoptotic cells; (2) distribution of viral antigens; (3) levels of interferon-alpha (IFN-alpha) and tumor necrosis factor-alpha (TNF-alpha) produced and their association with the extent of virus-induced cytopathology. Four groups of AMs were studied, including mock-infected, PCV2 alone-infected (PCV2-A), PRRSV alone-infected (PRRSV-A), and PCV2 and PRRSV dually infected (PCV2/PRRSV) groups. The AMs of PCV2-A group had high antigen-containing rate without cell death. There was a marked increase in cell death and apoptosis in PRRSV-A group. However, a lower PRRSV-induced infectious rate, cell death, and apoptosis were seen in PCV2/PRRSV group. High levels of IFN-alpha production were detected in PCV2-infected groups, but not in mock-infected and PRRSV-A groups. The PRRSV-induced cytopathic effect (CPE) on MARC-145 cells or swine AMs was markedly reduced by pre-incubation of the cells with UV-treated or non-UV-treated supernatants of PCV2-infected AMs. In addition, the reduction in CPE was abolished when the supernatants of PCV2-infected AMs were pre-treated with a mouse anti-recombinant porcine IFN-alpha antibody. The results suggest that swine AMs were an important reservoir of PCV2; PCV2 infection reduced PRRSV infection and PRRSV-associated CPE in PCV2/PRRSV AMs; the reduction of PRRSV infection in AMs was mediated by IFN-alpha generated by PCV2 infection. The reduced PRRSV-associated CPE in AMs and increased pro-inflammatory cytokine production may lead to a more severe pneumonic lesion in those dually infected pigs.

High incidence of polyarteritis nodosa in the brains of culled sows.

A total of 307 brains of purebred sows obtained from an abattoir were retrospectively examined. These sows were culled with reasons of reproductive failure, urogenital infections, or locomotor problems. The most common macroscopic lesions were cavitations or lacunae in the basal nuclei (9.1%, 28/307) and coarse and thickened leptomeninges with marked vessels (3.9%, 12/307). The most frequent microscopic lesion was polyarteritis nodosa (21.2%, 65/307), which was found in all 40 brains with the above-mentioned gross lesions and in all 25 brains with microscopic cerebral infarcts or cavitations. The affected arteries of polyarteritis nodosa were distributed primarily in the cerebral leptomeninges, basal nuclei, and internal and external capsules. Histopathologically, a characteristic change of the affected arteries was transmural fibrinoid necrosis with severe infiltration of mixed inflammatory cells; narrowing or occlusion of the lumen. The inflammatory cells were chiefly composed of lymphocytes, macrophages, and plasma cells, with a few eosinophils and occasional multinucleated giant cells. Polyarteritis nodosa was found at a high percentage in the brains from culled sows. It may result in cerebral ischemia, infarcts, and hemorrhage, and possibly play a role in the necessity for culling due to locomotor problems.