Abstract
Salmonella enterica serovar Gallinarum is a host-restricted bacterial pathogen that causes a serious systemic disease exclusively in birds of all ages. Salmonella enterica serovar Typhimurium is a host-generalist serovar. Dendritic cells (DCs) are key antigen-presenting cells that play an important part in Salmonella host-restriction. We evaluated the differential response of chicken blood monocyte-derived dendritic cells (chMoDCs) exposed to S. Gallinarum or S. Typhimurium. S. Typhimurium was found to be more invasive while S. Gallinarum was more cytotoxic at the early phase of infection and later showed higher resistance against chMoDCs killing. S. Typhimurium promoted relatively higher upregulation of costimulatory and other immune function genes on chMoDCs in comparison to S. Gallinarum during early phase of infection (6 h) as analyzed by real-time PCR. Both Salmonella serovars strongly upregulated the proinflammatory transcripts, however, quantum was relatively narrower with S. Gallinarum. S. Typhimurium-infected chMoDCs promoted relatively higher proliferation of naïve T-cells in comparison to S. Gallinarum as assessed by mixed lymphocyte reaction. Our findings indicated that host restriction of S. Gallinarum to chicken is linked with its profound ability to interfere the DCs function. Present findings provide a valuable roadmap for future work aimed at improved vaccine strategies against this pathogen.
Highlights
Salmonellae are facultative intracellular, anaerobic, rod-shaped, Gram-negative bacteria
Cultured cells were characterized as chicken blood monocytederived dendritic cells (chMoDCs) based on their morphologic changes on alternate days and mRNA expression of CD14 and CD83
Expression of CD14 mRNA on immature and LPStreated mature chMoDCs was compared with that obtained against unstimulated PBMCs
Summary
Salmonellae are facultative intracellular, anaerobic, rod-shaped, Gram-negative bacteria They are of length 2–5 microns and width 0.5–1.5 microns. Several microbial pathogens have evolved molecular mechanisms aimed at interfering with phagocytic cell (dendritic cells (DCs), macrophages) functions to allow survival within the h ost[6]. This is considered to be a hallmark of host-restriction for certain Salmonella serovars[7]. Studies have shown that host-restricted Salmonella serovars can interfere with the capacity of DCs to “prime” adaptive immunity against bacteria. Host-generalist Salmonella serovars could be unable to interfere with DC function, result in activation of the adaptive immune response and bacterial clearance[11,12]. Gallinarum may be related to its ability to interfere with DC function and, weak induction of the adaptive immune response
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