Brucella spp. are facultative intracellular bacteria that cause brucellosis in humans and other animals. Brucella spp. are taken up by macrophages, and the outcome of the macrophage-Brucella interaction is a basis for establishment of a chronic Brucella infection. Microarrays were used to analyze the transcriptional response of the murine macrophage-like J774.A1 cell line to infection with virulent Brucella melitensis strain 16M. It was found that most significant changes in macrophage gene transcription happened early following infection, and global macrophage gene expression profiles returned to normal between 24 and 48 h postinfection. These findings support the observation that macrophages kill the majority of Brucella cells at the early infection stage, but the surviving Brucella cells are able to avoid macrophage brucellacidal activity inside replicative phagosomes at the later infection stage. At 4 h postinfection, macrophage genes involved in cell growth, metabolism, and responses to endogenous stimuli were down-regulated, while the inflammatory response (e.g., tumor necrosis factor alpha and Toll-like receptor 2), the complement system, the responses to external stimuli, and other immune responses were up-regulated. It is likely that the most active brucellacidal activity happened between 0 and 4 h postinfection. Mitochondrion-associated gene expression, which is involved in protein synthesis and transport, electron transfer, and small-molecule transfer, and many other mitochondrial functions were significantly down-regulated at 4 h postinfection. Although there were both proand antiapoptosis effects, B. melitensis 16M appears to inhibit apoptosis of macrophages by blocking release of cytochrome c and production of reactive oxygen species in the mitochondria, thus preventing activation of caspase cascades.Brucellosis in humans and other animal species is caused by facultative intracellular bacteria belonging to the genus Brucella. Unlike many pathogenic bacteria, the brucellae lack classical virulence factors, such as invasive proteases, exotoxins, endotoxic lipopolysaccharide (LPS), capsules, fimbriae, pili, virulence plasmids, and lysogenic phages (29,48). Brucella virulence relies on the ability of the organism to survive and replicate within vacuolar phagocytic compartments of macrophages (37). The host macrophage-Brucella interaction is critical for establishment of chronic Brucella infections. For example, both the type IV secretion system encoded by the virB operon (7) and the two-component regulatory system encoded by the bvrRS operon (44) are necessary for successful replication of Brucella inside macrophages. Smooth Brucella strains with intact LPS O side chains are virulent and invade macrophages through lipid rafts (56). Immediately after entry into macrophages, Brucella strains reside in an acidified compartment that fuses with components of the early endosomal pathway (56). The majority of Brucella strains are killed at the early infection stage (14, 56). However, a subpopulation of virule...

Abstract. Porcine circovirus type 2 (PCV2) is associated with reproductive failure in female pigs. However, the association of PCV2-positive semen in the pathogenesis has not been elucidated. The objectives of this study were to determine whether semen spiked with PCV2 causes infection in PCV2-naïve, mature female pigs and whether delivery of PCV2 via artificial insemination causes reproductive failure or fetal infection. Nine sows were randomly allocated into 3 groups of 3 sows each and artificially inseminated with PCV2 DNA-negative semen (group 1), PCV2 DNA-negative semen spiked with PCV2a (group 2), or PCV2b (group 3). All sows in groups 2 and 3 developed PCV2 viremia 7 to 14 days after insemination. None of the group 2 sows became pregnant, whereas all group 3 sows (3/3) farrowed at the expected date. At parturition, presuckle serum samples were collected, and live-born piglets, stillborn fetuses, and mummified fetuses were necropsied. All live-born piglets (n 5 8) in group 3 were PCV2 viremic at birth. Stillborn fetuses (n 5 2) had gross lesions of congestive heart failure. Mummified fetuses (n 5 25) varied in crown-rump length from 7 to 27 cm, indicating fetal death between 42 and 105 days of gestation. PCV2 antigen was detected in the myocardium by immunohistochemistry of 7/8 (88%) live-born piglets, 2/2 (100%) of the stillborn fetuses, and 25/25 (100%) of the mummified fetuses. In addition, 4/25 mummified fetuses had PCV2 antigen associated with smooth muscle cells and fibroblasts. The results of this study indicate that intrauterine administration of PCV2 causes reproductive failure in naïve sows.

Porcine circovirus type 2 (PCV2) is divided into two genetic clusters designated PCV2a and PCV2b. The objectives of this study were to determine whether isolates from different clusters vary in virulence and to determine whether infection with PCV2a isolates induces protective immunity against subsequent infection with a recent PCV2b isolate. One-hundred and thirteen conventional specific-pathogen-free (SPF) pigs were assigned randomly to treatment groups and rooms: pigs inoculated with PCV2a cluster isolates (ISU-40895 or ISU-4838), pigs inoculated with PCV2b cluster isolates (NC-16845 or Can-17639) and uninoculated pigs. Necropsies were performed at 16 or 51 days post-inoculation (p.i.). There were no significant differences in PCV2-associated lymphoid lesions between PCV2a and PCV2b clusters; however, within the same cluster, significant differences were found between isolates: ISU-4838-and Can-17639-inoculated pigs had significantly (P,0.05) less severe lesions compared with ISU-40895-and NC-16845-inoculated pigs. To evaluate cross-protection, six pigs within each group were challenged at 35 days p.i. with an isolate from the heterologous cluster and were necropsied 51 days p.i. The severity of PCV2-associated lesions was reduced in pigs with prior exposure to an isolate from the heterologous cluster in comparison with singly inoculated pigs. Results indicate that the virulence of PCV2a and PCV2b isolates is not different in the conventional SPF pig model; however, the virulence of isolates within the same cluster differs. Increased virulence as reported to be associated with PCV2b isolates in the field was not observed under the conditions of this study. Moreover, cross-protection between PCV2a and PCV2b exists. INTRODUCTIONPorcine circovirus (PCV) is a small, circular, nonenveloped, single-stranded DNA virus (Tischer et al., 1982) that belongs to the genus Circovirus of the family Circoviridae (Todd et al., 2005). To date, two types of PCV have been recognized (Allan et al., 1998;Hamel et al., 1998;Morozov et al., 1998) in pigs: the non-pathogenic PCV type 1 (PCV1) and the pathogenic PCV type 2 (PCV2), which is the aetiological agent of porcine circovirusassociated disease (PCVAD). Previously, phylogenetic analyses have shown that PCV2 isolates can be further divided into two main clusters (Larochelle et al., 2002;Mankertz et al., 2000;Olvera et al., 2007) now commonly referred to as PCV2a and PCV2b (Gagnon et al., 2007).Systemic PCV2 infection, which is also known as postweaning multisystemic wasting syndrome (PMWS), is characterized clinically by wasting or decreased weight gain, enlarged lymph nodes and dyspnoea (Harding & Clark, 1997;Opriessnig et al., 2007). The hallmark microscopic lesions of systemic PCV2 infection are lymphoid depletion and granulomatous lymphadenitis associated with the presence of PCV2 antigen or nucleic acids (Sorden, 2000). Systemic PCV2 infection or PMWS was initially observed in a Canadian high-health-statusThe GenBank/EMBL/DDBJ accession numbers for the complete genomic sequ...