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Older kidney transplant recipients experience increased rates of infection and death, and less rejection, compared with younger patients. However, little is known about immune dysfunction in older compared with younger kidney transplant recipients and whether it is associated with infection. We evaluated T cell phenotypes including maturation, immune senescence, and exhaustion in a novel investigation into differences in older compared with younger patients receiving identical immune suppression regimens. We evaluated PBMC from 60 kidney transplant recipients (23 older and 37 matched younger patients) by multiparameter immune phenotyping. Older kidney transplant recipients demonstrated decreased frequency of naïve CD4+ and CD8+ T cells, and increased frequency of terminally differentiated, immune senescent, and NK T cells expressing KLRG1. There was a trend towards increased frequency of T cell immune senescence in patients experiencing infection in the first year after transplantation, which reached statistical significance in a multivariate analysis. This pilot study reveals immune dysfunction in older compared with younger transplant recipients, and suggests a likely mechanism for increased vulnerability to infection. The ability to assess T cell maturation and immune senescence in transplant recipients offers the potential for risk stratification and customization of immune suppression to prevent infection and rejection after transplantation.

Introduction: Belatacept has shown potential for prevention of rejection after kidney transplantation, given its demonstration of reduced nephrotoxicity in combination with absence of significant incidence of rejection. However, concerns have been raised regarding increased risk of viral infection., Methods: We set out to explore the impact of the switch to belatacept on alloimmune and antiviral immunity through the study of patients switched from calcineurin inhibitor (CNI) to belatacept within 3 months of kidney transplantation compared with a matched cohort of control patients on a CNI-based regimen., Results: After the switch to belatacept, immune phenotyping demonstrated a decrease in naive and an increase in terminally differentiated effector memory (TMRA) T cells, with no significant difference compared with control patients. Donor-specific immune response, measured by intracellular cytokine staining (ICS), did not change significantly either by single or double cytokine secretion, but it was associated with the appearance of donor-specific antibody (DSA) in the control but not the belatacept cohort ( P  = 0.039 for naive and P  = 0.002 for TMRA subtypes). Increased incidence of de novo DSA development was observed in the control group ( P  = 0.035). Virus-specific immune response, as measured by ICS in response to cytomegalovirus (CMV) or Epstein-Barr virus (EBV), was similar in both groups and stable over time., Conclusion: We found that belatacept use was associated with an absence of alloreactivity without impact on immune phenotype, while preserving the antiviral immune response, for patients switched from a CNI-based regimen. In parallel, the antiviral immune response against CMV and EBV was preserved after the belatacept switch (clinicaltrials.gov: NCT01953120)., (© 2022 Published by Elsevier Inc. on behalf of the International Society of Nephrology.)

Older kidney transplant recipients demonstrate increased rates of infection, and lower rates of rejection, compared with younger kidney transplant recipients. However, the mechanism behind this observation remains unknown. To develop a multifaceted view of age-associated immune dysfunction, we determined the function and phenotype of T cells predisposing to vulnerability to infection on a molecular level. Overlapping peptide pools representing the dominant CMV antigens were used to stimulate PBMC collected from 51 kidney transplant recipients, using cytokine secretion to determine specificity and intensity of response. Staphylococcal endotoxin B (SEB) was analyzed in parallel. To define immune cell subsets, we used single cell RNA sequencing (scRNAseq) to evaluate cellular surface markers and gene expression. We found increased frequency of SEB- and CMV-specific T cells was associated with freedom from infection, especially in older patients. Spatialized t-SNE analysis revealed decreased frequency of naïve T cells, increased frequency of TEMRA cells, and decreased frequency of IFNγ secreting T cells in patients with infection. Application of scRNAseq analysis revealed increased frequency of terminally differentiated T cells expressing NK-associated receptors and inhibitory markers. These findings offer unique insight into the mechanism behind vulnerability to infection in the kidney transplant recipient, revealing a specific T cell subtype of impaired antigen response and terminal effector phenotype as markers of T cell senescence., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Inc.)

CMV causes mostly asymptomatic but lifelong infection. Primary infection or reactivation in immunocompromised individuals can be life-threatening. CMV viremia often occurs in solid organ transplant recipients and associates with decreased graft survival and higher mortality. Furthering understanding of impaired immunity that allows CMV reactivation is critical to guiding antiviral therapy and examining the effect of CMV on solid organ transplant outcomes. This study characterized longitudinal immune responses to CMV in 31 kidney transplant recipients with CMV viremia and matched, nonviremic recipients. Recipients were sampled 3 and 12 months after transplant, with additional samples 1 week and 1 month after viremia. PBMCs were stained for NK and T cell markers. PBMC transcriptomes were characterized by RNA-Seq. Plasma proteins were quantified by Luminex. CD8+ T cell transcriptomes were characterized by single-cell RNA-Seq. Before viremia, patients had high levels of IL-15 with concurrent expansion of immature CD56bright NK cells. After viremia, mature CD56dim NK cells and CD28-CD8+ T cells upregulating inhibitory and NK-associated receptors were expanded. Memory NK cells and NK-like CD28-CD8+ T cells were associated with control of viremia. These findings suggest that signatures of innate activation may be prognostic for CMV reactivation after transplant, while CD8+ T cell functionality is critical for effective control of CMV.

Human leukocyte antigen (HLA)-B has been recognized as a major determinant of discrepancies in disease outcomes, and recent evidence indicates a role in immune checkpoint blockade (ICB) efficacy. The B44 supertype, which features an electropositive binding pocket that preferentially displays peptides with negatively charged amino acid anchors, is associated with improved survival in ICB-treated melanoma. Yet this effect was not seen in ICB-treated non-small-cell lung cancer (NSCLC). Here we show that mutations leading to glutamic acid substitutions occur more often in melanoma than NSCLC based on mutational landscape. We additionally show stratifying B44 based on the presence of somatic mutations that lead to negatively charged glutamic acid anchors identifies patients with NSCLC with an ICB benefit similar to that seen in melanoma. We anticipate these findings could improve assessment of HLA-related outcomes and prediction of ICB benefit in those with B44, representing approximately half of the world's population., (© 2020. The Author(s), under exclusive licence to Springer Nature America, Inc.)

The extent to which immune cell phenotypes in the peripheral blood reflect within-tumor immune activity prior to and early in cancer therapy is unclear. To address this question, we studied the population dynamics of tumor and immune cells, and immune phenotypic changes, using clinical tumor and immune cell measurements and single-cell genomic analyses. These samples were serially obtained from a cohort of advanced gastrointestinal cancer patients enrolled in a trial with chemotherapy and immunotherapy. Using an ecological population model, fitted to clinical tumor burden and immune cell abundance data from each patient, we find evidence of a strong tumor-circulating immune cell interaction in responder patients but not in those patients that progress on treatment. Upon initiation of therapy, immune cell abundance increased rapidly in responsive patients, and once the peak level is reached tumor burden decreases, similar to models of predator-prey interactions; these dynamic patterns were absent in nonresponder patients. To interrogate phenotype dynamics of circulating immune cells, we performed single-cell RNA sequencing at serial time points during treatment. These data show that peripheral immune cell phenotypes were linked to the increased strength of patients' tumor-immune cell interaction, including increased cytotoxic differentiation and strong activation of interferon signaling in peripheral T cells in responder patients. Joint modeling of clinical and genomic data highlights the interactions between tumor and immune cell populations and reveals how variation in patient responsiveness can be explained by differences in peripheral immune cell signaling and differentiation soon after the initiation of immunotherapy., Competing Interests: Competing interest statement: S.S. reports clinical trial funding from Merck for this study, which did not support the research in this paper; clinical research funding from Novartis, GSK, Millennium, MedImmune, Johnson & Johnson, Gilead Sciences, Plexxikon, Onyx, Bayer, Blueprint Medicines, XuanZhu, Incyte, Toray Industries, Celgene, Hengrui Therapeutics, OncoMed, Tesaro, AADi, and Syndax outside the submitted work; equity from Salarius Pharmaceuticals, Iterion Therapeutics, Proterus Therapeutics, ConverGene, and Stingray Therapeutics outside the submitted work; and honoraria from Blend Therapeutics, Foundation Medicine, Guardant Health, Novartis, ARIAD, US Oncology, Exelixis, Genesis Biotechnology Group, LSK, Natera, Loxo Oncology, Hengrui Therapeutics, Tarveda Therapeutics, and Dracen Pharmaceuticals outside the submitted work. D.S. reports grants from Novartis, BMS, Bioverativ, and AstraZeneca outside the submitted work and personal fees from Salarius Pharmaceuticals, Iterion Therapeutics, GlycosBio, and BMS outside the submitted work.

Microbial metabolites are an emerging class of mediators influencing CD4 + T-cell function. To advance the understanding of direct causal microbial factors contributing to Crohn's disease, we screened 139 predicted Crohn's disease-associated microbial metabolites for their bioactivity on human CD4 + T-cell functions induced by disease-associated T helper 17 (Th17) polarizing conditions. We observed 15 metabolites with CD4 + T-cell bioactivity, 3 previously reported, and 12 unprecedented. A deeper investigation of the microbe-derived metabolite, ascorbate, revealed its selective inhibition on activated human CD4 + effector T cells, including IL-17A-, IL-4-, and IFNγ-producing cells. Mechanistic assessment suggested the apoptosis of activated human CD4 + T cells associated with selective inhibition of energy metabolism. These findings suggest a substantial rate of relevant T-cell bioactivity among Crohn's disease-associated microbial metabolites, and evidence for novel modes of bioactivity, including targeting of T-cell energy metabolism.

Noninvasive immunologic analysis of peripheral blood holds promise for explaining the mechanism of development of adverse clinical outcomes, and may also become a method for patient risk stratification before or after mechanical circulatory support device (MCSD) implantation. Dysregulation of the innate immune system is associated with increased patient age but has yet to be evaluated in the older patient with advanced heart failure undergoing MCSD surgery. Patients pre- and post-MCSD implantation had peripheral blood mononuclear cells (PBMC) and serum isolated. Multiparameter flow cytometry was used to analyze markers of innate cell function, including monocyte subtypes. Multiplex cytokine analysis was performed. MELD-XI and SOFA scores were utilized as surrogate markers of outcomes. Increased levels of pro-inflammatory cytokines including IL-15, TNF-α, and IL-10 were associated with increased MELD-XI and SOFA scores. IL-8, TNF- α, and IL-10 were associated with risk of death after MCSD implantation, even with correction for patient age. Increased frequency of 'classical' monocytes (CD14 + CD16-) were associated with increased MELD-XI and SOFA scores. This suggests that inflammation and innate immune system activation contribute to progression to multiorgan system failure and death after MCSD surgery. Development of noninvasive monitoring of peripheral blood holds promise for biomarker development for candidate selection and patient risk stratification., (Copyright © 2018. Published by Elsevier Inc.)

Background: The number of elderly patients with end-stage kidney disease requiring kidney transplantation continues to grow. Evaluation of healthy older adults has revealed proinflammatory changes in the immune system, which are posited to contribute to age-associated illnesses via "inflamm-aging." Immunologic dysfunction is also associated with impaired control of infections. Whether these immunologic changes are found in older kidney transplant recipients is not currently known, but may have important implications for risk for adverse clinical outcomes., Methods: Three months after transplant, innate immune phenotype was evaluated by flow cytometry from 60 kidney transplant recipients (22 older [≥60 years] and 38 younger [<60 years old]). Multiplex cytokine testing was used to evaluate plasma cytokine levels. Younger patients were matched to older patients based on transplant type and induction immune suppression., Results: Older kidney transplant recipients demonstrated decreased frequency of intermediate monocytes (CD14++CD16+) compared with younger patients (1.2% vs 3.3%, P = 0.007), and a trend toward increased frequency of proinflammatory classical monocytes (CD14++CD16-) (94.5% vs 92.1%) ( P = 0.065). Increased levels of interferon-gamma (IFN-γ) were seen in older patients., Conclusions: In this pilot study of kidney transplant recipients, we identified differences in the innate immune system in older as compared with younger patients, including increased levels of IFN-γ. This suggests that age-associated nonspecific inflammation persists despite immune suppression. The ability to apply noninvasive testing to transplant recipients will provide tools for patient risk stratification and individualization of immune suppression regimens to improve outcomes after transplantation., Competing Interests: The authors declare no conflicts of interest.

Determination of the mechanism of action of FK506 and cyclosporin A has yielded new molecular targets involved in signal transduction during T cell activation. A common target of FK506 and cyclosporin A is inhibition of activation of the NFAT transcription factor, for which a specific binding region is present in the promoter of the IL-2 gene. A reporter gene assay has been used to screen for agents that interfere with this early step in T cell activation. Simple aromatic compounds that block NFAT-dependent transcription and show in vitro immunosuppressive activity were isolated from the broth and mycelia of two Streptomyces sp. fermentations. The compounds were active at concentrations that were not directly cytotoxic.

The dorrigocins are new secondary metabolites produced by submerged fermentation of a streptomycete which was isolated from a soil sample collected in Australia. The dorrigocins show moderate antifungal activity and reverse the morphology of ras-transformed NIH/3T3 cells from a transformed phenotype to a normal one. The producing culture was identified as Streptomyces platensis subsp. rosaceus strain AB1981F-75.

Coumamidines are water-soluble basic antibiotics related to the glycocinnamoylspermidines. They are produced by a soil isolate designated Saccharopolyspora sp. AB 1167L-65. The coumamidines have broad spectrum activity and were selected in a screen for substances which inhibit Pseudomonas aeruginosa.

A complex of 18-membered macrolide antibiotics has been discovered in the fermentation broth of strain AB718C-41. The producing culture, isolated from a soil sample collected in Hamden, Connecticut, was identified as a strain of Dactylosporangium aurantiacum and was designated D. aurantiacum subsp. hamdenesis subsp. nov. The antibiotic complex was produced in a New Brunswick 150-liter fermentor using a medium consisting of glucose, soybean oil, soybean flour, beef extract and inorganic salts. Several of the antibiotics were active against sensitive and multiple antibiotic-resistant strains of pathogenic Gram-positive bacteria.