Moreover, Photorhabdus asymbiotica which can infect either insects or humans, possesses a plasmid related to pMT-1 found in Y. pestis. Besides their animal hosts, Y. enterocolitica as well as Y. pseudotuberculosis are commonly found in water, soil and vegetables. Several studies have shown that Y. pestis can also be found in soil. Moreover, several experiments have highlighted the survival of Y. enterocolitica, Y. pseudotuberculosis and Y. pestis in free living soil amoeba. Since pathogenic Yersiniae are able to persist in soil and are phylogenetically very close to the bacterial symbionts of EPNs, we wondered whether Yersiniae would be able to intrude the symbiotic relationship associating EPNs and their natural symbiont. In order to test this hypothesis, we used an experimental model consisting of insect larvae of the species Galleria mellonella used as prey for an African species of entomopathogenic Steinernema hosting its natural Xenorhabdus symbiont as well as a Y. pseudotuberculosis field isolate naturally resistant to the anti-microbial compounds produced by Xenorhabdus.We show that Y. pseudotuberculosis can be successfully transmitted by the EPN carrier XL880 inside an insect larva in which it persists and multiplies. Moreover, EPNs emerging from the insect cadaver after 10 to 15 days where found to host large numbers of Y. pseudotuberculosis cells in their gastro-intestinal tract. These EPNs were in turn able to transmit Y. pseudotuberculosis to a new insect larva and so on for at least 7 successive infectious cycles. If they turn out to have an ecological significance, these findings may reveal an unexpected biotic reservoir for the long-term persistence and dissemination of pathogenic Yersiniae in the environment. Corneal transplantation has been performed successfully for over 100 years, and it is the most common form of solid tissue transplantation in humans. In the USA alone, approximately 26,000 corneal transplants are performed every year. Unlike other solid organ transplantation, human leukocyte antigen typing and systemic immunosuppressive drugs are not used, yet 90% of those considered normal-risk transplants such as first-time grafts in avascular graft beds and non-inflamed graft beds can survive 5 years after surgery. However, this number decreases with time, to 43% corneal graft survival at 15 years for low-risk corneal dystrophies and 77% for keratoconus. These numbers become progressively important with the increasing age of the population worldwide. Moreover, preoperative conditions known to abrogate immune privilege and that BAY-60-7550 PDE inhibitor characterize high-risk grafts, such as vascularization of the graft-recipient bed, rejection of a previous graft, inflammation at the time of transplant, or atopy, increase the problem of survival of the corneal graft transplant. In these high-risk recipients, graft survival is even poorer: for herpetic eye, 72% survival is achieved at 5 years, and 49% at 15 years; for corneal ulcers, 48% survival at 5 years is reported and decreases to 21% at 15 years. The acceptance of corneal allografts compared with other categories of allografts is known as immune privilege. Immune privilege is actively sustained by the expression of soluble and cell membrane molecules that can block the induction of immune response, deviate immune responses down a tolerogenic pathway, or inhibit the expression of effector T cells and complement activation. However, some conditions dismantle the immune privilege of the corneal allograft and promote rejection, which remains the leading cause of corneal allograft failure. Nevertheless, a high proportion of the human corneal allografts that undergo rejection are not perceived to be a high rejection risk pre-transplant.