Electron microscopy also showed that in the case of the wild-type S. Enteritidis uptake, the Salmonella-containing vacuoles (SCV) developed towards the spacious ones while in the case of all the rfa mutants, the vacuole closely fitted the S. Enteritidis cell inside and signs of bacterial cell disintegration could be observed inside the vacuole (Fig. 2). In this study, we have characterized the interactions between attenuated S. Enteritidis mutants and porcine WBC in vitro. Such knowledge might be useful for the prediction of the properties of attenuated click here S. enterica mutants used as vaccines against salmonellosis itself or as vectors for targeting particular cell types including cancer cells. Three different
types of association profiles have been found among the tested attenuated mutants. First, the phoP and aroA mutants did not differ from the wild-type S. Enteritidis in any of the assays. Second, the check details fliC and ΔSPI1-5 mutants, exhibited only minor differences when compared with the wild-type strain – likely due to the defect in chemotaxis in the fliC mutant (Khoramian-Falsafi et al., 1990; Jones et al., 1992) and the defect in cell invasion in the ΔSPI1-5 mutant (Kaniga et al., 1995). The last group comprising of rfaC,
rfaG and rfaL mutants was characterized by a highly increased association with the host immune cells. The differences from the interaction with the wild-type strain could also be seen in the development of SCV, which, unlike the spacious one seen after the wild-type strain infection (Alpuche-Aranda et al., 1994; Boyen et al., 2006), fitted closely to the surface of the rfaC mutant (Fig. 2). Our results show that type III secretion systems encoded by SPI-1, SPI-2 or flagellar operons have only a minor influence on the initial interactions of S. Enteritidis with porcine leukocytes. Instead, this interaction was dependent on the oligosaccharides Celecoxib exposed at the surface of S. Enteritidis. Interestingly, even within the rfa mutants, there were certain differences. In the absence of serum, the rfaL mutant expressing
lipopolysaccharide without the O-antigen exhibited an increased affinity for T-lymphocytes while the rfaC and rfaG mutants expressing lipopolysaccharide without the outer and the inner oligosaccharide core, respectively, associated more than the rfaL mutant with B-lymphocytes. All of these results might be used in rational vaccine design. However, if critically evaluated, live Salmonella vaccines for animal use are administered orally and therefore will be exposed to blood leukocytes only very rarely. On the other hand, attenuated S. enterica strains that were tested for tumor therapy in mice and humans were administered intravenously (Toso et al., 2002; Zhao et al., 2005; Leschner et al., 2009; Vendrell et al., 2011), i.e. they were immediately subjected to interactions with the blood leukocytes and via the circulation also to other cell types.