Circulating T Cells Are Not Sufficient for Protective Immunity against Virulent Francisella tularensis.

Pulmonary infections elicit a combination of tissue-resident and circulating T cell responses. Understanding the contribution of these anatomically distinct cellular pools in protective immune responses is critical for vaccine development. Francisella tularensis is a highly virulent bacterium capable of causing lethal systemic disease following pulmonary infection for which there is no currently licensed vaccine. Although T cells are required for survival of F. tularensis infection, the relative contribution of tissue-resident and circulating T cells is not completely understood, hampering design of effective, long-lasting vaccines directed against this bacterium. We have previously shown that resident T cells were not sufficient to protect against F. tularensis, suggesting circulating cells may serve a critical role in host defense. To elucidate the role of circulating T cells, we used a model of vaccination and challenge of parabiotic mice. Intranasally infected naive mice conjoined to immune animals had increased numbers of circulating memory T cells and similar splenic bacterial burdens as vaccinated-vaccinated pairs. However, bacterial loads in the lungs of naive parabionts were significantly greater than those observed in vaccinated-vaccinated pairs, but despite early control of F. tularensis replication, all naive-vaccinated pairs succumbed to infection. Together, these data define the specific roles of circulating and resident T cells in defense against infection that is initiated in the pulmonary compartment but ultimately causes disseminated disease. These data also provide evidence for employing vaccination strategies that elicit both pools of T cells for immunity against F. tularensis and may be a common theme for other disseminating bacterial infections.

Contribution of Lipid Mediators in Divergent Outcomes following Acute Bacterial and Viral Lung Infections in the Obese Host.

Obesity is considered an important comorbidity for a range of noninfectious and infectious disease states including those that originate in the lung, yet the mechanisms that contribute to this susceptibility are not well defined. In this study, we used the diet-induced obesity (DIO) mouse model and two models of acute pulmonary infection, Francisella tularensis subspecies tularensis strain SchuS4 and SARS-CoV-2, to uncover the contribution of obesity in bacterial and viral disease. Whereas DIO mice were more resistant to infection with SchuS4, DIO animals were more susceptible to SARS-CoV-2 infection compared with regular weight mice. In both models, neither survival nor morbidity correlated with differences in pathogen load, overall cellularity, or influx of inflammatory cells in target organs of DIO and regular weight animals. Increased susceptibility was also not associated with exacerbated production of cytokines and chemokines in either model. Rather, we observed pathogen-specific dysregulation of the host lipidome that was associated with vulnerability to infection. Inhibition of specific pathways required for generation of lipid mediators reversed resistance to both bacterial and viral infection. Taken together, our data demonstrate disparity among obese individuals for control of lethal bacterial and viral infection and suggest that dysregulation of the host lipidome contributes to increased susceptibility to viral infection in the obese host.

Kidney transplantation in low- and middle-income countries: the Transplant Links experience.

Paediatric kidney failure is a global problem responsible for significant childhood morbidity and mortality. The gold-standard treatment is kidney transplantation. However, the availability of kidney transplantation remains limited in some low- and middle-income countries (LMICs). Transplant Links Community (TLC) is a UK-based charity that mentors units in LMICs wishing to start kidney transplantation; the ultimate goal is for these units to become self-sufficient. TLC provides this support through in-person training visits and skill transfer, plus direct mentorship from the UK that is maintained over many years. From such mentoring programmes, it is evident that there are numerous challenges in the initial establishment and long-term maintenance of kidney transplant services, with specific and unique barriers applying to setting up paediatric transplant programmes compared to their adult counterparts. This review summarises TLC's first-hand experience of developing paediatric kidney transplantation services in LMICs over the past 15 years, the challenges encountered, and the major ongoing barriers that must be addressed to facilitate further progress in delivering transplantation services to children globally.

Cutting Edge: Lung-Resident T Cells Elicited by SARS-CoV-2 Do Not Mediate Protection against Secondary Infection.

Immunity to pulmonary infection typically requires elicitation of lung-resident T cells that subsequently confer protection against secondary infection. The presence of tissue-resident T cells in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) convalescent patients is unknown. Using a sublethal mouse model of coronavirus disease 2019, we determined if SARS-CoV-2 infection potentiated Ag-specific pulmonary resident CD4+ and CD8+ T cell responses and if these cells mediated protection against secondary infection. S protein-specific T cells were present in resident and circulating populations. However, M and N protein-specific T cells were detected only in the resident T cell pool. Using an adoptive transfer strategy, we found that T cells from SARS-CoV-2 immune animals did not protect naive mice. These data indicate that resident T cells are elicited by SARS-CoV-2 infection but are not sufficient for protective immunity.

Cutting Edge: Severe SARS-CoV-2 Infection in Humans Is Defined by a Shift in the Serum Lipidome, Resulting in Dysregulation of Eicosanoid Immune Mediators.

The COVID-19 pandemic has affected more than 20 million people worldwide, with mortality exceeding 800,000 patients. Risk factors associated with severe disease and mortality include advanced age, hypertension, diabetes, and obesity. Each of these risk factors pathologically disrupts the lipidome, including immunomodulatory eicosanoid and docosanoid lipid mediators (LMs). We hypothesized that dysregulation of LMs may be a defining feature of the severity of COVID-19. By examining LMs and polyunsaturated fatty acid precursor lipids in serum from hospitalized COVID-19 patients, we demonstrate that moderate and severe disease are separated by specific differences in abundance of immune-regulatory and proinflammatory LMs. This difference in LM balance corresponded with decreased LM products of ALOX12 and COX2 and an increase LMs products of ALOX5 and cytochrome p450. Given the important immune-regulatory role of LMs, these data provide mechanistic insight into an immuno-lipidomic imbalance in severe COVID-19.

Itaconate indirectly influences expansion of effector T cells following vaccination with Francisella tularensis live vaccine strain.

The metabolite itaconate plays a critical role in modulating inflammatory responses among macrophages infected with intracellular pathogens. However, the ability of itaconate to influence developing T cells responses is poorly understood. To determine if itaconate contributes to the quality of T cell mediated immunity against intracellular infection, we used Francisella tularensis as a model of vaccine induced immunity. Following vaccination with F. tularensis live vaccine strain, itaconate deficient mice (ACOD KO) had a prolonged primary infection but were more resistant to secondary infection with virulent F. tularensis relative to wild type controls. Improved resistance to secondary challenge was associated with both increased numbers and effector function of CD4+ and CD8+ T cells in ACOD KO mice. However, additional data suggest that improved T cell responses was not T cell intrinsic. These data underscore the consequences of metabolic perturbations within antigen presenting cells on the development of vaccine-elicited immune responses.

Risk models for recurrence and survival after kidney cancer: a systematic review.

OBJECTIVE: To systematically identify and compare the performance of prognostic models providing estimates of survival or recurrence of localized renal cell cancer (RCC) in patients treated with surgery with curative intent. MATERIALS AND METHODS: We performed a systematic review (PROSPERO CRD42019162349). We searched Medline, EMBASE and the Cochrane Library from 1 January 2000 to 12 December 2019 to identify studies reporting the performance of one or more prognostic model(s) that predict recurrence-free survival (RFS), cancer-specific survival (CSS) or overall survival (OS) in patients who have undergone surgical resection for localized RCC. For each outcome we summarized the discrimination of each model using the C-statistic and performed multivariate random-effects meta-analysis of the logit transformed C-statistic to rank the models. RESULTS: Of a total of 13 549 articles, 57 included data on the performance of 22 models in external populations. C-statistics ranged from 0.59 to 0.90. Several risk models were assessed in two or more external populations and had similarly high discriminative performance. For RFS, these were the Sorbellini, Karakiewicz, Leibovich and Kattan models, with the UCLA Integrated Staging System model also having similar performance in European/US populations. All had C-statistics ≥0.75 in at least half of the validations. For CSS, they the models with the highest discriminative performance in two or more external validation studies were the Zisman, Stage, Size, Grade and Necrosis (SSIGN), Karakiewicz, Leibovich and Sorbellini models (C-statistic ≥0.80 in at least half of the validations), and for OS they were the Leibovich, Karakiewicz, Sorbellini and SSIGN models. For all outcomes, the models based on clinical features at presentation alone (Cindolo and Yaycioglu) had consistently lower discrimination. Estimates of model calibration were only infrequently included but most underestimated survival. CONCLUSION: Several models had good discriminative ability, with there being no single 'best' model. The choice from these models for each setting should be informed by both the comparative performance and availability of factors included in the models. All would need recalibration if used to provide absolute survival estimates.

Temporal Requirement for Pulmonary Resident and Circulating T Cells during Virulent Francisella tularensis Infection.

The lung is a complex organ with anatomically distinct pools of T cells that play specific roles in combating infection. Our knowledge regarding the generation and/or maintenance of immunity by parenchymal or circulating T cells has been gathered from either persistent (>60 d) or rapidly cleared (<10 d) infections. However, the roles of these distinct T cell pools in infections that are cleared over the course of several weeks are not understood. Clearance of the highly virulent intracellular bacterium Francisella tularensis subspecies tularensis (Ftt) following pulmonary infection of immune animals is a protracted T cell-dependent process requiring ∼30-40 d and serves as a model for infections that are not acutely controlled. Using this model, we found that intranasal vaccination increased the number of tissue-resident CD4+ effector T cells, and subsequent challenge of immune mice with Ftt led to a significant expansion of polyfunctional parenchymal CD4+ effector T cells compared with the circulating pool. Despite the dominant in vivo response by parenchymal CD4+ T cells after vaccination and challenge, circulating CD4+ T cells were superior at controlling intracellular Ftt replication in vitro. Further examination in vivo revealed temporal requirements for resident and circulating T cells during Ftt infection. These requirements were in direct contrast to other pulmonary infections that are cleared rapidly in immune animals. The data in this study provide important insights into the role of specific T cell populations that will be essential for the design of novel effective vaccines against tularemia and potentially other agents of pulmonary infection.

Inclusion of Epitopes That Expand High-Avidity CD4+ T Cells Transforms Subprotective Vaccines to Efficacious Immunogens against Virulent Francisella tularensis.

T cells are the immunological cornerstone in host defense against infections by intracellular bacterial pathogens, such as virulent Francisella tularensis spp. tularensis (Ftt). The general paucity of novel vaccines for Ftt during the past 60 y can, in part, be attributed to the poor understanding of immune parameters required to survive infection. Thus, we developed a strategy utilizing classical immunological tools to elucidate requirements for effective adaptive immune responses directed against Ftt. Following generation of various Francisella strains expressing well-characterized lymphocytic choriomeningitis virus epitopes, we found that survival correlated with persistence of Ag-specific CD4(+) T cells. Function of these cells was confirmed in their ability to more effectively control Ftt replication in vitro. The importance of understanding the Ag-specific response was underscored by our observation that inclusion of an epitope that elicits high-avidity CD4(+) T cells converted a poorly protective vaccine to one that engenders 100% protection. Taken together, these data suggest that improved efficacy of current tularemia vaccine platforms will require targeting appropriate Ag-specific CD4(+) T cell responses and that elucidation of Francisella epitopes that elicit high-avidity CD4(+) T cell responses, specifically in humans, will be required for successful vaccine development.

Distinct innate responses are induced by attenuated Salmonella enterica serovar Typhimurium mutants.

Upon bacterial infection the host cells generate a wide variety of cytokines. Genetic attenuation of bacterial physiological pathogens can be accomplished not only by disruption of normal bacterial processes, but also by the loss of the ability to redirect the host immune system. We examined nine attenuated Salmonella Typhimurium mutants for their ability to replicate as well as the cytokines produced after infection of Bone Marrow Derived Macrophages (BMDM). Infection of BMDM with attenuated Salmonella mutants led to host cytokine patterns distinct from those that followed WT infection. Surprisingly, each bacterial mutant had a unique cytokine signature. Because some of the mutants induced an IL-10 response not seen in WT, we examined the role of IL-10 on Salmonella replication. Surprisingly, addition of IL-10 before or concurrent with infection restricted growth of WT Salmonella in BMDM. Bacterial attenuation is not a single process and results in attenuated host responses, which result in unique patterns for each attenuated mutants.

Identification of early interactions between Francisella and the host.

The adaptive immune response to Francisella tularensis is dependent on the route of inoculation. Intradermal inoculation with the F. tularensis live vaccine strain (LVS) results in a robust Th1 response in the lungs, whereas intranasal inoculation produces fewer Th1 cells and instead many Th17 cells. Interestingly, bacterial loads in the lungs are similar early after inoculation by these two routes. We hypothesize that the adaptive immune response is influenced by local events in the lungs, such as the type of cells that are first infected with Francisella. Using fluorescence-activated cell sorting, we identified alveolar macrophages as the first cell type infected in the lungs of mice intranasally inoculated with F. novicida U112, LVS, or F. tularensis Schu S4. Following bacterial dissemination from the skin to the lung, interstitial macrophages or neutrophils are infected. Overall, we identified the early interactions between Francisella and the host following two different routes of inoculation.

Plasmodium falciparum GBP2 Is a Telomere-Associated Protein That Binds to G-Quadruplex DNA and RNA.

In the early-diverging protozoan parasite Plasmodium, few telomere-binding proteins have been identified and several are unique. Plasmodium telomeres, like those of most eukaryotes, contain guanine-rich repeats that can form G-quadruplex structures. In model systems, quadruplex-binding drugs can disrupt telomere maintenance and some quadruplex-binding drugs are potent anti-plasmodial agents. Therefore, telomere-interacting and quadruplex-interacting proteins may offer new targets for anti-malarial therapy. Here, we report that P. falciparum GBP2 is such a protein. It was identified via 'Proteomics of Isolated Chromatin fragments', applied here for the first time in Plasmodium. In vitro, PfGBP2 binds specifically to G-rich telomere repeats in quadruplex form and it can also bind to G-rich RNA. In vivo, PfGBP2 partially colocalises with the known telomeric protein HP1 but is also found in the cytoplasm, probably due to its affinity for RNA. Consistently, its interactome includes numerous RNA-associated proteins. PfGBP2 is evidently a multifunctional DNA/RNA-binding factor in Plasmodium.

Impairing RAGE signaling promotes survival and limits disease pathogenesis following SARS-CoV-2 infection in mice.

Cellular and molecular mechanisms driving morbidity following SARS-CoV-2 infection have not been well defined. The receptor for advanced glycation end products (RAGE) is a central mediator of tissue injury and contributes to SARS-CoV-2 disease pathogenesis. In this study, we temporally delineated key cell and molecular events leading to lung injury in mice following SARS-CoV-2 infection and assessed efficacy of therapeutically targeting RAGE to improve survival. Early following infection, SARS-CoV-2 replicated to high titers within the lungs and evaded triggering inflammation and cell death. However, a significant necrotic cell death event in CD45- populations, corresponding with peak viral loads, was observed on day 2 after infection. Metabolic reprogramming and inflammation were initiated following this cell death event and corresponded with increased lung interstitial pneumonia, perivascular inflammation, and endothelial hyperplasia together with decreased oxygen saturation. Therapeutic treatment with the RAGE antagonist FPS-ZM1 improved survival in infected mice and limited inflammation and associated perivascular pathology. Together, these results provide critical characterization of disease pathogenesis in the mouse model and implicate a role for RAGE signaling as a therapeutic target to improve outcomes following SARS-CoV-2 infection.

Risk prediction models for symptomatic patients with bladder and kidney cancer: a systematic review.

BACKGROUND: Timely diagnosis of bladder and kidney cancer is key to improving clinical outcomes. Given the challenges of early diagnosis, models incorporating clinical symptoms and signs may be helpful to primary care clinicians when triaging at-risk patients. AIM: To identify and compare published models that use clinical signs and symptoms to predict the risk of undiagnosed prevalent bladder or kidney cancer. DESIGN AND SETTING: Systematic review. METHOD: A search identified primary research reporting or validating models predicting the risk of bladder or kidney cancer in MEDLINE and EMBASE. After screening identified studies for inclusion, data were extracted onto a standardised form. The risk models were classified using TRIPOD guidelines and evaluated using the PROBAST assessment tool. RESULTS: The search identified 20 661 articles. Twenty studies (29 models) were identified through screening. All the models included haematuria (visible, non-visible, or unspecified), and seven included additional signs and symptoms (such as abdominal pain). The models combined clinical features with other factors (including demographic factors and urinary biomarkers) to predict the risk of undiagnosed prevalent cancer. Several models (n = 13) with good discrimination (area under the receiver operating curve >0.8) were identified; however, only eight had been externally validated. All of the studies had either high or unclear risk of bias. CONCLUSION: Models were identified that could be used in primary care to guide referrals, with potential to identify lower-risk patients with visible haematuria and to stratify individuals who present with non-visible haematuria. However, before application in general practice, external validations in appropriate populations are required.

Age-related differences in immune dynamics during SARS-CoV-2 infection in rhesus macaques.

Advanced age is a key predictor of severe COVID-19. To gain insight into this relationship, we used the rhesus macaque model of SARS-CoV-2 infection. Eight older and eight younger macaques were inoculated with SARS-CoV-2. Animals were evaluated using viral RNA quantification, clinical observations, thoracic radiographs, single-cell transcriptomics, multiparameter flow cytometry, multiplex immunohistochemistry, cytokine detection, and lipidomics analysis at predefined time points in various tissues. Differences in clinical signs, pulmonary infiltrates, and virus replication were limited. Transcriptional signatures of inflammation-associated genes in bronchoalveolar lavage fluid at 3 dpi revealed efficient mounting of innate immune defenses in both cohorts. However, age-specific divergence of immune responses emerged during the post-acute phase. Older animals exhibited sustained local inflammatory innate responses, whereas local effector T-cell responses were induced earlier in the younger animals. Circulating lipid mediator and cytokine levels highlighted increased repair-associated signals in the younger animals, and persistent pro-inflammatory responses in the older animals. In summary, despite similar disease outcomes, multi-omics profiling suggests that age may delay or impair antiviral cellular immune responses and delay efficient return to immune homeostasis.

In patients with multi-vessel coronary artery diseases, does hybrid revascularization provide similar outcomes to conventional coronary artery bypass grafting?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was: In [patients with multivessel coronary artery diseases (CAD)] is [hybrid revascularization (HCR)] equal to [coronary artery bypass grafting (CABG)] in regard to [mortality, myocardial infarction, stroke and target vessel revascularization (TVR)]? Three-hundred and fifty-five papers were found using the reported search, of which 8 represented the best evidence to answer the question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. The studies included 4 observational studies, 3 randomized controlled trials (RCTs) and 1 meta-analysis. The meta-analysis consisted of predominantly observational data with 1 randomized controlled trial and suggested non-significant differences in all major clinical outcomes. The observational studies generally cited benefit towards hybrid revascularization on the basis of equivalent major clinical outcomes rates compared to coronary artery bypass grafting, yet favourable in-hospital outcomes. One randomized controlled trial provided robust evidence of equivalent 5-year outcomes; however, the others were insufficiently powered for an effective comparison. There is a paucity of robustly designed studies to answer our clinical question effectively, given hybrid procedures are not routine in clinical practice. On the basis of mostly observational and small randomized cohorts with relatively short follow-up intervals, we conclude that current evidence suggests similar mid-term rates of major clinical outcomes after hybrid revascularization and coronary artery bypass grafting. However, without longer-term follow-up, the comparison of the two techniques, particularly relating to repeat revascularization, is still very much uncertain.

Validation and Application of a Benchtop Cell Sorter in a Biosafety Level 3 Containment Setting.

Introduction: Fluorescent-activated cell sorting (FACS) is often the most appropriate technique to obtain pure populations of a cell type of interest for downstream analysis. However, aerosol droplets can be generated during the sort, which poses a biosafety risk when working with samples containing risk group 3 pathogens such as Francisella tularensis, Mycobacterium tuberculosis, Yersinia pestis, and severe acute respiratory syndrome coronavirus 2. For many researchers, placing the equipment required for FACS at biosafety level 3 (BSL-3) is often not possible due to expense, space, or expertise available. Methods: We performed aerosol testing as part of the biosafety evaluation of the MACSQuant Tyto, a completely closed, cartridge-based cell sorter. We also established quality control procedures to routinely evaluate instrument performance. Results: The MACSQuant Tyto does not produce aerosols as part of the sort procedure. Discussion: These data serve as guidance for other facilities with containment laboratories wishing to use the MACSQuant Tyto for cell sorting. Potential users should consult with their Institutional Biosafety Committees to perform in-house risk assessments of this equipment. Conclusion: The MACSQuant Tyto can safely be used on the benchtop to sort samples at BSL-3.

Pulmonary infection induces persistent, pathogen-specific lipidomic changes influencing trained immunity.

Resolution of infection results in development of trained innate immunity which is typically beneficial for defense against unrelated secondary infection. Epigenetic changes including modification of histones via binding of various polar metabolites underlie the establishment of trained innate immunity. Therefore, host metabolism and this response are intimately linked. However, little is known regarding the influence of lipids on the development and function of trained immunity. Utilizing two models of pulmonary bacterial infection combined with multi-omic approaches, we identified persistent, pathogen-specific changes to the lung lipidome that correlated with differences in the trained immune response against a third unrelated pathogen. Further, we establish the specific cellular populations in the lung that contribute to this altered lipidome. Together these results expand our understanding of the pulmonary trained innate immune response and the contributions of host lipids in informing that response.

Twelve tips for UK medical students undertaking laboratory-based intercalated research projects.

This article was migrated. The article was marked as recommended. Laboratory-based intercalated research projects are a popular undertaking for medical students in the UK. Such projects can provide students with a wealth of valuable experiences and the chance to develop new skills that will be highly beneficial to their future careers. Laboratory-based intercalated research projects however represent a very different challenge to other aspects of medical education, with distinct expectations and requirements of students in order for success to be achieved. In this article, the author compiled twelve tips based on current literature and their experiences carrying out a laboratory-based intercalated research project as a UK medical student. These tips will help ensure UK medical students are well prepared before commencing their intercalated research project, in order to maximise the benefits of the opportunities presented to them. Although focused on a UK perspective, many of the tips will similarly be applicable to medical students in other countries conducting laboratory-based projects, albeit in slightly different contexts.

Validation and Application of a Bench Top Cell Sorter in a BSL-3 Containment Setting.

Rigorous assessment of the cellular and molecular changes during infection typically requires isolation of specific immune cell subsets for downstream application. While there are numerous options for enrichment/isolation of cells from tissues, fluorescent activated cell sorting (FACS) is accepted as a method that results in superior purification of a wide variety of cell types. Flow cytometry requires extensive fluidics and aerosol droplets can be generated during collection of target cells. Pathogens such as Francisella tularensis, Mycobacterium tuberculosis, Yersinia pestis, and SARS-CoV-2 require manipulation at biosafety level-3 (BSL-3). Due to the concern of potential aerosolization of these pathogens, use of flow cytometric-based cell sorting in these laboratory settings requires placement of the equipment in dedicated biosafety cabinets within the BSL-3. For many researchers, this is often not possible due to expense, space, or expertise available. Here we describe the safety validation and utility of a completely closed cell sorter that results in gentle, rapid, high purity, and safe sorting of cells on the benchtop at BSL-3. We also provide data demonstrating the need for cell sorting versus bead purification and the applicability of this technology for BSL-3 and potentially BSL-4 related infectious disease projects. Adoption of this technology will significantly expand our ability to uncover important features of the most dangerous infectious diseases leading to faster development of novel vaccines and therapeutics.