Porcine Alveolar Macrophage Cells Research Articles

Antiviral Activity of Tilmicosin for Type 1 and Type 2 Porcine Reproductive And Respiratory Syndrome Virus In Cultured Porcine Alveolar Macrophages

Tilmicosin was investigated in a stable porcine alveolar macrophage cell line for its antiviral activity against types 1 and 2 porcine reproductive and respiratory syndrome virus (PRRSV). Tilmicosin exhibited strong antiviral effects on both genotypes of PRRSV replication in cultured porcine alveolar macrophages. The antiviral activity was more potent for type 1 PRRSV as indicated by reduction in infectious virus yield of nearly 43-fold for type 1 as compared to 14-fold for type 2. Real-time RT-PCR for detection of viral nucleocapsid gene confirmed the reduction of infectious virus titer in the presence of tilmicosin. Lysosomotropic and ion-channel blocking agents efficiently inhibited PRRSV replication, suggesting that the antiviral mechanism of tilmicosin is likely associated with the alteration of endosomal pH and possibly the ion-channel activity on the viral membrane. This study indicates that tilmicosin may have potential as an early treatment or preventative measure against PRRSV infections, especially for areas where the type 1 genotype is prevalent.

Porcine reproductive and respiratory syndrome virus attachment is mediated by the N-terminal domain of the sialoadhesin receptor

Sialoadhesin (Sn) is an important receptor for viral attachment and internalization of porcine reproductive and respiratory syndrome virus (PRRSV) to porcine alveolar macrophages (PAM). To investigate whether the N-terminal domain of Sn is sufficient and/or necessary for PRRSV attachment, we constructed a series of truncated fragments of porcine Sn and expressed these in the non-permissive PK15 cell line. The first 150 amino acids comprising the entire first domain of the Sn N-terminal region was necessary for PRRSV binding to cells, and the N-terminal domain alone was sufficient for virus attachment. The attachment of PRRSV to PAM cells was inhibited by polyclonal anti-serum against the N-terminal region of porcine Sn in a dose-dependent manner. The present study demonstrates that the first domain at the N-terminus of Sn mediates PRRSV attachment to PAM cells and contributes to better understanding the interaction between PRRSV and its host cells.

Generation of a porcine alveolar macrophage cell line for the growth of porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome virus (PRRSV) has a marked tropism for cells of the monocyte–macrophage lineage and accordingly, replicates in fully differentiated alveolar macrophages in the natural host. Despite the identification of several putative receptors for PRRSV on porcine alveolar macrophages (PAM), only CD163 was found to be able to make non-permissive cells susceptible to PRRSV, indicating a requirement for CD163 in productive infection. Interestingly, the preliminary experiments revealed that the immortalized PAM cell line, which was previously shown to fail to support PRRSV replication, does not express detectable levels of CD163. These data suggest that there may be a correlation between the CD163 undetectable expression level and PRRSV non-susceptibility in the continuous PAM cell line. In this study, therefore, it was attempted to stably transfect non-permissive PAM cells with CD163 cDNA to generate cell lines constitutively expressing CD163 and to evaluate their permissivity to PRRSV. The newly established PAM cell lines were demonstrated to express robust levels of CD163 and to be fully permissive for both type 1 and 2 PRRSV strains. This PRRSV-permissive PAM cell line will be a valuable tool not only to facilitate virus propagation but also to advance in vitro studies on virus pathogenesis.