Pre-Kidney Transplant Lower Extremity Impairment and Post-Kidney Transplant Mortality.

Prediction models for post-kidney transplantation mortality have had limited success (C-statistics ≤0.70). Adding objective measures of potentially modifiable factors may improve prediction and, consequently, kidney transplant (KT) survival through intervention. The Short Physical Performance Battery (SPPB) is an easily administered objective test of lower extremity function consisting of three parts (balance, walking speed, chair stands), each with scores of 0-4, for a composite score of 0-12, with higher scores indicating better function. SPPB performance and frailty (Fried frailty phenotype) were assessed at admission for KT in a prospective cohort of 719 KT recipients at Johns Hopkins Hospital (8/2009 to 6/2016) and University of Michigan (2/2013 to 12/2016). The independent associations between SPPB impairment (SPPB composite score ≤10) and composite score with post-KT mortality were tested using adjusted competing risks models treating graft failure as a competing risk. The 5-year posttransplantation mortality for impaired recipients was 20.6% compared to 4.5% for unimpaired recipients (p < 0.001). Impaired recipients had a 2.30-fold (adjusted hazard ratio [aHR] 2.30, 95% confidence interval [CI] 1.12-4.74, p = 0.02) increased risk of postkidney transplantation mortality compared to unimpaired recipients. Each one-point decrease in SPPB score was independently associated with a 1.19-fold (95% CI 1.09-1.30, p < 0.001) higher risk of post-KT mortality. SPPB-derived lower extremity function is a potentially highly useful and modifiable objective measure for pre-KT risk prediction.

CD4 T-cell hyporesponsiveness induced by schistosome larvae is not dependent upon eosinophils but may involve connective tissue mast cells.

In areas endemic for schistosomiasis, people can often be in contact with contaminated water resulting in repeated exposures to infective Schistosoma mansoni cercariae. Using a murine model, repeated infections result in IL-10-dependent CD4(+) T-cell hyporesponsiveness in the skin-draining lymph nodes (sdLN), which could be caused by an abundance of eosinophils and connective tissue mast cells at the skin infection site. Here, we show that whilst the absence of eosinophils did not have a significant effect on cytokine production, MHC-II(+) cells were more numerous in the dermal cell exudate population. Nevertheless, the absence of dermal eosinophils did not lead to an increase in the responsiveness of CD4(+) T cells in the sdLN, revealing that eosinophils in repeatedly exposed skin did not impact on the development of CD4(+) T-cell hyporesponsiveness. On the other hand, the absence of connective tissue mast cells led to a reduction in dermal IL-10 and to an increase in the number of MHC-II(+) cells infiltrating the skin. There was also a small but significant alleviation of hyporesponsiveness in the sdLN, suggesting that mast cells may have a role in regulating immune responses after repeated exposures of the skin to S. mansoni cercariae.

'Seeing is Believing'; the use of novel imaging approaches towards creating a greater understanding of parasite: host interactions.

This editorial highlights some of the key points made in the six invited reviews in this special issue of Parasite Immunology on the use of contemporary imaging technologies to investigate the parasite: host interface. Three of the reviews deal with the protozoa Trypanosoma, Leishmania, and Plasmodium, whilst the remainder focus on helminth parasites particularly Schistosoma. The reviews cover aspects related to how the development of transgenic parasites has vastly advanced our understanding of how parasites interact with host cells, particularly as a cause of pathology. Imaging technologies have also been exploited in revealing parasite localisation within host tissues and identifying novel therapeutic targets. Combined the reviews show how 'state of the art' imaging technologies have resulted in a seismic advance in our understanding of parasite biology and how this has the potential to develop new, and improved, strategies to combat disease caused by parasite infections.

Schistosome infection is associated with enhanced whole-blood IL-10 secretion in response to cercarial excretory/secretory products.

Infection of the human host by schistosome parasites follows exposure of skin to free-swimming cercariae and is aided by the release of excretory/secretory (E/S) material, which is rich in proteases and glycoconjugates. This material provides the initial stimulus to cells of the innate immune system. The study presented here is the first to examine human innate/early immune responsiveness to cercarial E/S in subjects from an area co-endemic for Schistosoma mansoni and S. haematobium. We report that in infected participants, stimulation of whole-blood cultures with cercarial E/S material (termed 0-3 hRP) caused the early (within 24 h) release of greater quantities of regulatory IL-10, compared with uninfected controls. Elevated levels of IL-10 but not pro-inflammatory TNFα or IL-8 were most evident in participants co-infected with S. mansoni and S. haematobium and were accompanied by a higher 0-3 h RP-specific IL-10: TNFα ratio. We also report that glycosylated components within 0-3 h RP appear to be important factors in the stimulation of IL-8, TNFα and IL-10 production by whole-blood cells.

Interleukin-10 secretion from CD14+ peripheral blood mononuclear cells is downregulated in patients with acne vulgaris.

BACKGROUND: Acne is a common chronic inflammatory dermatosis of the pilosebaceous unit. It is characterized by seborrhoea, comedone formation and an inflammatory response consistent with defective cellular immunity to Propionibacterium acnes. OBJECTIVES: The objective of this study was to investigate the immune reactivity of patients with acne compared with healthy controls by examining the response of peripheral blood mononuclear cells (PBMCs) to stimulation with P. acnes. Particular focus was placed upon measuring the production of interleukin (IL)-10, which has an established immunoregulatory role. PATIENTS AND METHODS: Venous blood was collected from 47 patients with acne and 40 age- and sex-matched healthy controls with no prior history of acne. PBMCs were cultured and their cytokine response to P. acnes investigated. RESULTS: Proinflammatory IL-8 and tumour necrosis factor (TNF)-alpha secretion from PBMCs was higher in patients with acne when stimulated with P. acnes. In contrast, a statistically significant reduction in PBMC secretion of anti-inflammatory IL-10 in patients with acne was identified. The impaired production of IL-10 by PBMCs from patients with acne was confined to CD14+ cells presumed to be monocytes. The ability of CD14 cells from patients with acne to phagocytose P. acnes bacteria was also observed to be defective but the addition of exogenous IL-10 to PBMC cultures restored phagocytic activity. CONCLUSIONS: These data suggest that patients with acne have a proinflammatory cytokine milieu and crucially are unable to contain early inflammatory changes due to a specific defect in immunosurveillance, namely low monocyte IL-10 production. Our observations raise the possibility that acne therapeutics might profitably target IL-10 both as a regulator of proinflammatory cytokines and in augmenting the CD14+ cell phagocytic response.

Antibody responses induced by Trichobilharzia regenti antigens in murine and human hosts exhibiting cercarial dermatitis.

Cercariae of bird schistosomes (genus Trichobilharzia) are able to penetrate the skin of mammals (noncompatible hosts), including humans, and cause a Th2-associated inflammatory cutaneous reaction termed cercarial dermatitis. The present study measured the antibody reactivity and antigen specificity of sera obtained after experimental infection of mice and natural infection of humans. Sera from mice re-infected with T. regenti showed a bias towards the development of antigen-specific IgM and IgG1 antibodies and elevated levels of total serum IgE, indicative of a Th2 polarized immune response. We also demonstrate that cercariae are a source of antigens triggering IL-4 release from basophils collected from healthy human volunteers. Analysis of sera from patients with a history of cercarial dermatitis revealed elevated levels of cercarial-specific IgG, particularly for samples collected from adults (> 14 years old) compared with children (8-14 years old), although elevated levels of antigen-specific IgE were not detected. In terms of antigen recognition, IgG and IgE antibodies in the sera of both mice and humans preferentially bound an antigen of 34 kDa. The 34 kDa molecule was present in both homogenate of cercariae, as well as cercarial excretory/secretory products, and we speculate it may represent a major immunogen initiating the Th2-immune response associated with cercarial dermatitis.

Fractionation of schistosome antigens by high performance electrophoretic chromatography and their screening for the ability to induce Th1 lymphocyte activity.

The technique of high performance electrophoretic chromatography (HPEC) has been used to fractionate soluble antigens from adult Schistosoma mansoni worms on the basis of molecular weight (MW), prior to screening for their ability to stimulate T lymphocyte activity. Approximately 250 micrograms of protein were separated by continuous electrophoresis through an SDS polyacrylamide gel into 30-50 aqueous samples of minimal volume (80 microliters). Each consecutive sample contained a limited number of proteins of progressively greater MW, although the resolution of the fractionation was affected by a number of factors including acrylamide concentration, gel length, gel diameter and electrophoretic current. Following the extraction of SDS using Calbiosorb resin, the aqueous fractions were used directly to stimulate cultures of lymphocytes taken from the lymph nodes of infected or vaccinated mice. The most promising fractions were those containing proteins which induced the release of high levels of interferon-gamma relative to the extent of proliferation. This suggests that these proteins are good inducers of Th1 lymphocyte activity.

Immune responses to the radiation-attenuated schistosome vaccine: what can we learn from knock-out mice?

The goal of an effective schistosomiasis vaccine has proved elusive but the protective immunity induced in mice by radiation-attenuated cercaria larvae provides an appropriate model from which such a vaccine might be developed. Using gene-disrupted mice, we have analysed the process of immune priming by attenuated larvae of Schistosoma mansoni and the nature of the pulmonary effector response directed against a challenge infection. Vaccination stimulates expansion of IFNgamma-producing T-helper cells in the skin-draining lymph nodes. IL-12 is crucial in determining the Thl direction of this initial response but the cells of origin and the parasite components which stimulate its production are unknown. In the effector response, focal aggregates comprising mainly mononuclear cells accumulate around challenge larvae in the lungs, a process orchestrated by IFNgamma. This cytokine up-regulates nitric oxide synthase activity but we were unable to implicate nitric oxide as a cytotoxic agent causing challenge parasite elimination. An alternative action for IFNgamma may be to up-regulate adhesion molecule expression, increasing the cohesiveness of effector foci the better to block parasite migration, but the adhesive interactions so far examined do not appear relevant. In contrast, TNF induction is essential to protection, and we are currently testing the hypothesis that it determines the speed of the effector response following arrival of challenge larvae in the lungs.

Interleukin-12 and protective immunity to schistosomes.

The attenuated vaccine against Schistosoma mansoni induces Th1-mediated protective immunity and we have sought to identify a role for IL-12 in this model. Elevated levels of IL-12 (p40 mRNA) were detected in the lymph nodes (LN) and the lungs of vaccinated mice, whilst treatment of vaccinated mice with anti-IL-12 antibodies decreased the ratio of IFN gamma:IL-4 secreted by in vitro-cultured LN cells. However, there was only marginal abrogation of the level of resistance in these mice. Soluble antigens from the lung-stage of the parasite (SLAP) appeared to be efficient stimulators of IFN gamma and IL-12 secretion. These antigens when used to immunise mice in conjunction with IL-12 as an adjuvant, elicited a polarised Th1 response with abundant IFN gamma secretion but no IL-4. This immunisation regime also induced significant protection against reinfection, whereas inoculation of mice with SLAP alone did not. The induction of a dominant Th1 response using SLAP + IL-12 probably operates via IFN gamma production by natural killer (NK) cells stimulated by IL-12, since in vivo ablation of NK cells using anti-NK1.1 antibody reduced CD4(+)-dependent IFN gamma production from cultured LN cells by over 97%. Nevertheless, in mice with a genetic disruption of the IFN gamma receptor, administration of SLAP + IL-12 induced levels of IFN gamma equal to those in wild-type mice, thus showing that in this model IL-12 can directly prime T cells independent of IFN gamma. Clearly, IL-12 has a critical role in protective immunity to schistosomes and it may aid the development of an effective vaccine against this disease.

Can a brain drain be good for growth in the source economy?

"This paper analyzes the interaction between income distribution, human capital accumulation and migration. It shows that when migration is not a certainty, a brain drain may increase average productivity and equality in the source economy even though average productivity is a positive function of past average levels of human capital in an economy. It is also shown how the temporary possibility of emigration may permanently increase the average level of productivity of an economy."

Comparison of cysteine peptidase activities in Trichobilharzia regenti and Schistosoma mansoni cercariae.

Cercariae of the bird schistosome Trichobilharzia regenti and of the human schistosome Schistosoma mansoni employ proteases to invade the skin of their definitive hosts. To investigate whether a similar proteolytic mechanism is used by both species, cercarial extracts of T. regenti and S. mansoni were biochemically characterized, with the primary focus on cysteine peptidases. A similar pattern of cysteine peptidase activities was detected by zymography of cercarial extracts and their chromatographic fractions from T. regenti and S. mansoni. The greatest peptidase activity was recorded in both species against the fluorogenic peptide substrate Z-Phe-Arg-AMC, commonly used to detect cathepsins B and L, and was markedly inhibited (> 96%) by Z-Phe-Ala-CHN2 at pH 4.5. Cysteine peptidases of 33 kDa and 33-34 kDa were identified in extracts of T. regenti and S. mansoni cercariae employing a biotinylated Clan CA cysteine peptidase-specific inhibitor (DCG-04). Finally, cercarial extracts from both T. regenti and S. mansoni were able to degrade native substrates present in skin (collagen II and IV, keratin) at physiological pH suggesting that cysteine peptidases are important in the pentration of host skin.

Immunity induced by the radiation-attenuated schistosome vaccine.

As a paradigm for the development of a vaccine against human schistosomiasis, the radiation-attenuated (RA) vaccine has enabled the dissection of different immune responses as putative effector mechanisms. This review considers advances made in the past, and updates our knowledge with reference to recent studies that have provided new information relevant particularly to the early innate events after vaccination, and to the nature of the protective effector mechanism. Priming of a protective response by RA larvae is a highly co-ordinated series of events starting in the skin, draining lymph nodes and lungs, leading to the development of various effector responses, ranging from Th1-associated cell-mediated activity, to anti-parasitic antibodies, all of which contribute to the elimination of challenge larvae to varying extents. In this respect, the RA vaccine elicits a multifaceted immune response, from which we can derive valuable insights relevant to the future design of novel delivery systems and adjuvants for recombinant and subunit vaccines.

Modulation of the host's immune response by schistosome larvae.

Schistosomes appear to have evolved several strategies to down-regulate the host's immune response in order to promote their own survival. For the host, down-regulation is also beneficial as it can limit the extent of pathology. It is widely accepted that schistosomes modulate the immune response during the chronic phase of infection after egg deposition has started. However, there is increasing evidence that modulation of the immune response can occur much earlier at the time infective cercariae penetrate the host skin. In this review, we explore the various lines of evidence that excretory/secretory (ES) molecules from cercariae down-regulate the host's immune response. We highlight the immunological factors that are produced and may be involved in regulating the immune system (e.g. IL-10, and eicosanoids), as well as speculating on possible mechanisms of immune modulation (e.g. mast-cell activation, T-cell apoptosis, and/or the skewed activation of antigen-presenting cells [APCs]). Finally, we draw attention to several molecules of schistosome origin that have the potential to stimulate the regulatory response (e.g. glycans) and link these to potential host receptors (e.g. TLRs and C-type lectins).

Interleukin-12 and the host response to parasitic helminths; the paradoxical effect on protective immunity and immunopathology.

In general, helminth infections are associated with the development of dominant Th2-mediated immune responses which may be host protective but can also be the cause of immunopathology. Interleukin 12 (IL-12) is known to be a potent inhibitor of Th2 immune responses and as such it might be expected to have an important modulatory role in helminth-induced immune responses. In this review, we discuss the effect of IL-12 on susceptibility to infection, protective immunity and immunopathology, in the context of exposure to a range of helminths including intestinal nematodes, filariae and schistosomes. It is apparent that the effects of IL-12 are complex and can be beneficial as well as detrimental for the host. The precise role of IL-12 depends upon a number of factors including the type of helminth and the specific tissue involved in the inflammatory response.

Schistosoma mansoni: the effect of regional lymphadenectomy on the level of protection induced in mice by radiation-attenuated cercariae.

The lymph nodes which drain the sites of percutaneous vaccination with optimally irradiated cercariae of Schistosoma mansoni were surgically excised in studies to determine their role in the induction of protective immunity. Lymphadenectomy of the axillary and inguinal nodes which drain the abdominal exposure site, or of the cervical node which drains the aural site of exposure, five days prior to vaccination reduced the levels of resistance by two-thirds. Excision of these nodes on Days 5, 10, 15, or 20 postvaccination also significantly reduced the levels of immunity induced, though ablation was less effective at later times. Removal of lymph nodes not draining the site of vaccination had no effect on the induction of resistance. We interpret the results as indicating that successful vaccination of mice against S. mansoni requires the presentation of antigen to lymphocytes in local lymph nodes draining the vaccination site, rather than distant lymphoid organs such as the spleen.

Fate of attenuated schistosomula administered to mice by different routes, relative to the immunity induced against Schistosoma mansoni.

Newly transformed schistosomula and day 8 lung parasites, derived from optimally irradiated cercariae, were used to immunize groups of C57Bl/6 mice via 4 different injection routes. Schistosomula administered intradermally induced high levels of protection, comparable with that achieved by percutaneous vaccination. Intermediate levels were elicited by delivery of parasites via intraperitoneal or intratracheal routes. In contrast, intravenous injection of schistosomula to the lungs resulted in little or no resistance. Attenuated day 8 schistosomula administered intradermally were at least as immunogenic as irradiated cercariae. The fate of radio-isotope labelled attenuated lung schistosomula, injected via the various routes, was examined by compressed organ autoradiography. After intradermal vaccination, a proportion of parasites migrated from the site of injection to the draining lymph node and lungs. Conversely, schistosomula administered via the other 3 routes persisted to varying degrees at the injection site, but little onward migration was observed. We suggest that successful vaccination requires that some attenuated parasites migrate to, and sequester in, lymph nodes draining the vaccination site; persistence at the site of administration alone is not an adequate stimulus.

Vaccination against Schistosomiasis: The case for Lung-stage Antigens.

The development of an effective vaccine against human schistosomiasis remains a highly desirable yet elusive goal. In this article, Adrian Mountford and Richard Harrop focus attention on an approach that aims to identify proteins from Schistosoma mansoni that are capable of stimulating protective Th1 cell-mediated immune responses. They propose that the most likely source of such antigens is the lung-stage schistosomulum.

Phenotypic analysis of the cellular responses in regional lymphoid organs of mice vaccinated against Schistosoma mansoni.

The cellular responses in regional lymphoid organs of C57B1/6 mice were examined, following protective immunization with 20 krad.-irradiated cercariae of S. mansoni. Marked changes in total cell number were observed, with peak increases of 13.5-fold in the skin-draining (axillary) lymph nodes and 6.9-fold in the lung-draining (mediastinal) lymph nodes. In contrast, cellular responses were small in the spleen and undetectable in the brachial lymph nodes. The temporal pattern of responses was coincident with the kinetics of parasite migration, events in the mediastinal lymph node being apparent only after day 7. Phenotypic analysis of the cellular changes revealed an increase both in T lymphocytes and, to a greater extent, in B lymphocytes. The changes in Thy1+ cells comprised an increase in both L3T4+ and Lyt2+ populations. A comparison of mice exposed to non-immunizing parasites (normal or 80 krad.-irradiated cercariae) with protected animals, revealed smaller and more transient cellular changes in the axillary lymph nodes of the former. We suggest that the successful immunization of mice with attenuated parasites depends upon the prolonged priming of lymphocytes within the lymph nodes draining the skin-exposure site and that the persistence of 20 krad.-irradiated parasites within these nodes provides the requisite stimulus.

The profile of IgG1 and IgG2a antibody responses in mice exposed to Schistosoma mansoni.

The segregation of IgG2a and IgG1 immunoglobulin isotypes as markers for Th1 and Th2 lymphocytes respectively, was investigated in mice exposed to normal or optimally-irradiated S. mansoni cercariae. Using a panel of ELISAs, soluble antigens from lung-stage schistosomula, adult worms, or eggs, were probed with serum samples collected at biweekly intervals. Infected mice developed increased IgG1 responsiveness to all three antigens, especially between weeks five and seven, whereas IgG2a responses were lower, particularly to egg antigens. This confirms that Th2 responses are dominant after the onset of patency in infected mice. In comparison, vaccinated mice developed lower levels of IgG1, and higher levels of IgG2a to larval and worm antigens. Thus, they had balanced expression of IgG1 and IgG2a, despite having a dominant Th1 lymphocyte population. An elevated IgG1 response to egg antigens in vaccinated mice challenged with normal parasites, occurred two weeks later than in normal mice. Mice exposed to male-only cercariae developed IgG1 and IgG2a antibodies to larval and worm antigens. However, they also had elevated IgG1 to egg antigens from week five, despite a total absence of eggs. Therefore, adult worm antigens may cross react with the egg and stimulate the switch to Th2 dominated responsiveness.

Antigen localization and the induction of resistance in mice vaccinated with irradiated cercariae of Schistosoma mansoni.

The fate of 75Se-labelled parasites and their released pre-synthesized macromolecules has been followed in three murine infection models. Parasite numbers in specific tissues were determined by autoradiography, and released material was estimated by gamma-counting of tissues, with adjustment for the presence of parasite-associated radiolabel. Marked differences were found between the three models. The pattern of migration of normal schistosomula was similar to that previously reported. In addition we have described the transit of parasites through the lymph nodes draining the infection site. Significant quantities of released material were detected in the skin, draining lymph nodes, bloodstream and liver. The circulating material was of parasite origin, macromolecular, and hence potentially antigenic. In comparison to the normal infection, radiation-attenuated parasites (inducing a high level of resistance to challenge) persisted in the skin, draining lymph nodes and lungs, releasing a proportionally greater amount of material in the nodes. In mice exposed to attenuated parasites and treated with the compound RO11-3128 at 24 h (inducing a low level of resistance) there was an early death and rapid clearance of the parasites whilst still in the skin. This situation resulted in the highest levels of released material in the skin, bloodstream and liver, but negligible levels in the draining lymph nodes. We suggest that the persistence of radiation-attenuated parasites in the skin and draining lymph nodes, together with the prolonged release of antigen in the latter site, compared to the normal situation, are major factors in the induction of resistance.