Effect of cysteine peptidase inhibitor of Eudiplozoon nipponicum (Monogenea) on cytokine expression of macrophages in vitro.

The gills of the common carp, whose mucosal surface belongs to the key defence mechanisms of piscine immunity, can be infested with both the larval and adult stage of Eudiplozoon nipponicum (Monogenea). Although on their own, monogeneans do not considerably compromise their hosts' health status, fish with epithelial barriers damaged in parasite feeding and attachment sites are at an increased risk of bacterial challenge with possible harmful consequences. Several studies suggest that helminth parasites of teleost fish evade and manipulate host immune system via their excretory-secretory products, but our knowledge of these processes in the monogeneans is limited. Cysteine peptidase inhibitors (CPI), which are found in the secretions of numerous parasites, often induce immunosuppression by subverting Th1 mechanisms and drawing the immune system towards a Th2/Treg response. We employed the qPCR to test the effect of recently characterised CPI of E. nipponicum (rEnStef) on the mRNA expression of pro-inflammatory cytokine TNF-α and anti-inflammatory cytokine IL-10 produced by porcine macrophages in vitro. After an initial preincubation with rEnStef, we stimulated the macrophages using LPS. By inducing a Th1 pro-inflammatory response, we imitated the immune reaction during a bacterial challenge in tissue damaged by the feeding and attachment of E. nipponicum. We observed a significant dose-dependent downregulation of the expression of TNF-α and IL-10 cytokines. The observed suppression of TNF-alpha expression by rEnStef could result in decreased pathogen control, which might in turn lead to increased rates of secondary bacterial infections in fish infected by E. nipponicum.

Concurrent infection of monocyte-derived macrophages with porcine reproductive and respiratory syndrome virus and Haemophilus parasuis: A role of IFNα in pathogenesis of co-infections.

Porcine reproductive and respiratory syndrome virus (PRRSV) predisposes pigs to secondary bacterial infection caused by Haemophilus parasuis. The aim of the present study was to analyse the immune response of monocyte-derived macrophages (MDMs), serving as a model of macrophages accumulating at the site of inflammation. The second part of the study was focused on the role of IFNα in the production of inflammatory cytokines in co-infected MDMs. Concurrent infection with PRRSV and H. parasuis decreased gene expression of pro-inflammatory cytokines (IL-1ß, IL-8) in MDMs in comparison with MDMs infected with PRRSV or H. parasuis alone. Our data showed that MDMs express IFNα after PRRSV infection. Thereafter, we exposed cells to the experimental addition of IFNα and a subsequent infection with H. parasuis, and detected a decreased expression/production of pro-inflammatory cytokines. Thus, we assume that IFNα, produced after PRRSV infection, could affect the immune response of monocyte-derived macrophages. Down-regulation of pro-inflammatory cytokine expression in inflammatory macrophages may allow the development of secondary bacterial infections in pigs.

Concurrent infection with porcine reproductive and respiratory syndrome virus and Haemophilus parasuis in two types of porcine macrophages: apoptosis, production of ROS and formation of multinucleated giant cells.

Porcine reproductive and respiratory syndrome (PRRS) is one of the most significant and economically important infectious diseases affecting swine worldwide and can predispose pigs to secondary bacterial infections caused by, e.g. Haemophilus parasuis. The aim of the presented study was to compare susceptibility of two different types of macrophages which could be in contact with both pathogens during infection with PRRS virus (PRRSV) and in co-infection with H. parasuis. Alveolar macrophages (PAMs) as resident cells provide one of the first lines of defence against microbes invading lung tissue. On the other hand, monocyte derived macrophages (MDMs) represent inflammatory cells accumulating at the site of inflammation. While PAMs were relatively resistant to cytopathogenic effect caused by PRRSV, MDMs were much more sensitive to PRRSV infection. MDMs infected with PRRSV increased expression of pro-apoptotic Bad, Bax and p53 mRNA. Increased mortality of MDMs may be also related to a higher intensity of ROS production after infection with PRRSV. In addition, MDMs (but not PAMs) infected with H. parasuis alone formed multinucleated giant cells (MGC); these cells were not observed in MDMs infected with both pathogens. Higher sensitivity of MDMs to PRRSV infection, which is associated with limited MDMs survival and restriction of MGC formation, could contribute to the development of multifactorial respiratory disease of swine.