Functions exerted by the virulence-associated type-three secretion systems duringSalmonella entericaserovar Enteritidis invasion into and survival within chicken oviduct epithelial cells and macrophages

Abstract

Salmonella enterica serovar Enteritidis (SE) infection of chickens is a major contributing factor to non-typhoidal salmonellosis. The roles of the type-three secretion systems (T3SS-1 and T3SS-2) in the pathogenesis of SE infection of chickens are poorly understood. In this study, the functions of T3SS-1 and T3SS-2 during SE infection of primary chicken oviduct epithelial cells (COEC) and macrophages were characterized. The T3SS-1 and T3SS-2 mutants (sipB and ssaV), impaired in translocation and secretion, respectively, were significantly less invasive than their wild-type parent strain. The genes encoding effector proteins of T3SS-1 (SipA, SopB, and SopE2) and T3SS-2 (PipB) contributed equally to the entry of SE into COEC. The sipA mutant had reduced survival and the pipB mutant had enhanced replication in COEC. Mutations in the T3SS-2 genes ssaV and pipB reduced the survival of SE in chicken peripheral blood leukocyte-derived macrophages (PBLM), but not in the established chicken macrophage cell line HD11. A mutation in the ssaV gene also abolished SE-induced PBLM death between 1 h post-inoculation and 4 h post-inoculation. This study has shown that both T3SS-1 and T3SS-2 are required by SE to invade COEC; that SipA and PipB are necessary for the survival of SE in COEC and chicken PBLM, respectively; and that T3SS-2 triggers PBLM death during the early stages of SE infection, and this process does not depend on PipB.

Cell invasion of poultry-associated Salmonella enterica serovar Enteritidis isolates is associated with pathogenicity, motility and proteins secreted by the type III secretion system

“…Previous studies have also revealed that genes encoded by SPI-1 TTSS are involved in intestinal invasion whereas genes encoded on SPI-2 are required for systemic infection and survival within macrophages (Desin et al, 2009;Dieye et al, 2009;Jones et al, 2007;Li et al, 2009;Rychlík et al, 2009;Wisner et al, 2010). Mutations in the genes encoding secretory effector proteins or genes that regulate their expression lead to virulence attenuation in S. Enteritidis (Amy et al, 2004;Fardini et al, 2007;Parker & GuardPetter, 2001).…”

Impact ofSalmonella entericaType III Secretion System Effectors on the Eukaryotic Host Cell

“…PipB associates with host membranes and is enriched in detergent-resistant microdomains, also known as lipid rafts [188]. Interestingly, PipB is implicated in intestinal tract colonization of chicks by S. enterica serovar Typhimurium [189] and contributes to invasion and survival of S. enterica serovar Enteritidis in chicken oviduct epithelial cells [190]. In addition, PipB plays a role in repressing avian β-defensins genes [191] and in stimulating inducible nitric oxide synthase in these cells [192].…”

Salmonella enterica Serovar Enteritidis Antimicrobial Peptide Resistance Genes Aid in Defense against Chicken Innate Immunity, Fecal Shedding, and Egg Deposition

“…Primary chicken oviduct epithelium cells (COEC) were prepared as described previously (10). Briefly, oviduct tissue (isthmus region) from 20-to 23-week-old Hy-line W36 chickens was obtained from a local poultry producer.…”

“…To survive inside macrophages, Salmonella has to defend itself against many host killing factors: low Mg 2ϩ and Ca 2ϩ , acidic pH, and reactive oxygen species (7). To survive in this environment, Salmonella utilizes the components of T3SS-1 and T3SS-2 and the PhoP/PhoQ regulon (10)(11)(12)(13). S. Enteritidis has been shown to colonize the ovary and the reproductive tract within laying hens, with a higher recovery from the ovary than from any other reproductive tissue (14,15).…”

“…In the intestine, Salmonella evades innate immune responses, such as bile salts and avian ␤-defensins, to interact with the epithelium (7,8). Salmonella pathogenicity island 1 (SPI-1)-and SPI-2-encoded type-three secretion system 1 (T3SS-1) and T3SS-2 are used to invade tissue and to establish and maintain Salmonella-containing vacuoles in macrophages, respectively (9,10).…”