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The protozoan parasite Leishmania has evolved several strategies to undermine host defense mechanisms by inducing Th2-type adaptive immunity and suppressing effector functions of Th1 phenotype. In our earlier studies, using centrin gene-deleted Leishmania (LdCen-/-) parasites as an immunogen, we have shown induction of an effective Th1-type immunity and robust memory responses that mediate protection against virulent challenge. However, role of inhibitory signals in Leishmania vaccine induced immunity in general, and LdCen-/- in particular has not been studied. Herein, we report that immunization with LdCen-/- parasites produces more functional Th1-type CD4+ T cells via downregulation of CD200-CD200R immune inhibitory axis compared to wild-type infection. We found that expression of CD200 and CD200R was significantly reduced in LdCen-/- infection compared to wild-type infection. Diminished CD200-CD200R signaling in LdCen-/- infection enabled proliferation of CD4+ T cells and resulted in the induction of pro-inflammatory cytokines and suppression of anti-inflammatory response. The effects of diminished CD200-CD200R signaling by LdCen-/- were most evident in the suppression of IL-10-producing CD4+ T cells that helped enhance more Th1 cytokine producing and multi-functional T cells compared to wild-type infection. In vivo blocking of CD200 expression with anti-CD200 treatment in wild-type infected mice limited Th2 response as indicated by reduction of IL-10-producing Tr1 cells and reduced parasite burden. On the other hand, treatment with anti-CD200 improved the LdCen-/- vaccine-induced multifunctional response and reduction in splenic parasite load upon challenge. Taken together, these studies demonstrate the role of CD200-CD200R signals in the protection induced by LdCen-/- parasites. [ABSTRACT FROM AUTHOR]

Currently, there is no vaccine against visceral leishmaniasis (VL). Toward developing an effective vaccine, we have reported extensively on the immunogenicity of live attenuated LdCentrin-/- mutants in naive animal models. In VL endemic areas, asymptomatic carriers outnumber symptomatic cases of VL and are considered to be a reservoir of infection. Vaccination of asymptomatic cases represents a viable strategy to eliminate VL. Immunological correlates of protection thus derived might have limited applicability in conditions where the immunized host has prior exposure to virulent infection. To examine whether LdCen-/- parasites can induce protective immunity in experimental hosts that have lowlevel parasitemia from a previous exposure mimicking an asymptomatic condition, we infected C57Bl/6 mice with wildtype Leishmania donovani parasites expressing LLO epitope (LdWTLLO 10³, i.v.). After 3 weeks, the mice with low levels of parasitemia were immunized with LdCen-/- parasites expressing 2W epitope (LdCen-/-2W 3 × 106 i.v.) to characterize the immune responses in the same host. Antigen experienced CD+ T cells from the asymptomatic (LdWTLLO infected) LdCen-/-2W immunized, and other control groups were enriched using LLOand 2Wspecific tetramers, followed by Flow cytometric analysis. Our analysis showed that comparable CD+ T cell proliferation and CD+ memory T cell responses (TCM) represented by CD62Lhi, CCR7+, and IL7R+ T cell populations were induced with LdCen-/-2W in both asymptomatic and naive animals that received LdCen-/- immunization. Upon restimulation with peptide, TCM cells differentiated into effector T cells and there was no significant difference in the recall response in animals with asymptomatic infection. Following virulent challenge, comparable reduction in splenic parasite burden was observed in both asymptomatic and naive LdCen-/- immunized animals concomitant with the development of multifunctional CD+ and CD8+ T cells. Further, LdCen-/-2W immunization resulted in complete clearance of the preexisting asymptomatic infection (LdWTLLO). Our results demonstrate that LdCen-/-2W immunization could be efficacious for use in asymptomatic VL individuals. Further, immunization with LdCen-/- could help in reducing the parasite burden in the asymptomatic cases and aid in controlling the VL in endemic areas. [ABSTRACT FROM AUTHOR]

No licensed human vaccines are currently available against any parasitic disease including leishmaniasis. Several antileishmanial vaccine formulations have been tested in various animal models, including genetically modified live-attenuated parasite vaccines. Experimental infection studies have shown that Leishmania parasites utilize a broad range of strategies to undermine effector properties of host phagocytic cells, i.e., dendritic cells (DCs) and macrophages (MF). Furthermore, Leishmania parasites have evolved strategies to actively inhibit TH1 polarizing functions of DCs and to condition the infected MF toward anti-inflammatory/alternative/M2 phenotype. The altered phenotype of phagocytic cells is characterized by decreased production of antimicrobial reactive oxygen, nitrogen molecules, and pro-inflammatory cytokines, such as IFN-, IL-12, and TNF-a. These early events limit the activation of TH1-effector cells and set the stage for pathogenesis. Furthermore, this early control of innate immunity by the virulent parasites results in substantial alteration in the adaptive immunity characterized by reduced proliferation of CD4+ and CD8+ T cells and TH2-biased immunity that results in production of anti-inflammatory cytokines, such as TGF-β, and IL-10. More recent studies have also documented the induction of coinhibitory ligands, such as CTLA-4, PD-L1, CD200, and Tim-3, that induce exhaustion and/or non-proliferation in antigen-experienced T cells. Most of these studies focus on viral infections in chronic phase, thus limiting the direct application of these results to parasitic infections and much less to parasitic vaccines. However, these studies suggest that vaccine-induced protective immunity can be modulated using strategies that enhance the costimulation that might reduce the threshold necessary for T cell activation and conversely by strategies that reduce or block inhibitory molecules, such as PD-L1 and CD200. In this review, we will focus on the polarization of antigen-presenting cells and subsequent role of costimulatory and coinhibitory molecules in mediating vaccine-induced immunity using live-attenuated Leishmania parasites as specific examples. [ABSTRACT FROM AUTHOR]

The introduction of laparoscopic surgery, and more recently of robotics, has increased the number of living donor kidney transplants. This approach has already improved living donor acceptance rates. Even newer developments in the field have now been introduced with the purpose of further reducing postoperative pain and length of hospital stay, while offering better cosmetic results. In particular, single-incision surgery has gained popularity by improving the well-known benefits of minimally invasive surgery. In this case report, we present the first single-incision robotic-assisted living donor nephrectomy. [ABSTRACT FROM AUTHOR]