T Cell Immunity to the Alkyl Hydroperoxide Reductase of Burkholderia pseudomallei: A Correlate of Disease Outcome in Acute Melioidosis.

There is an urgent need for a better understanding of adaptive immunity to Burkholderia pseudomallei, the causative agent of melioidosis that is frequently associated with sepsis or death in patients in Southeast Asia and Northern Australia. The imperative to identify vaccine targets is driven both by the public health agenda in these regions and biological threat concerns. In several intracellular bacterial pathogens, alkyl hydroperoxidase reductases are upregulated as part of the response to host oxidative stress, and they can stimulate strong adaptive immunity. We show that alkyl hydroperoxidase reductase (AhpC) of B. pseudomallei is strongly immunogenic for T cells of 'humanized' HLA transgenic mice and seropositive human donors. Some T cell epitopes, such as p6, are able to bind diverse HLA class II heterodimers and stimulate strong T cell immunity in mice and humans. Importantly, patients with acute melioidosis who survive infection show stronger T cell responses to AhpC relative to those who do not. Although the sequence of AhpC is virtually invariant among global B. pseudomallei clinical isolates, a Cambodian isolate varies only in C-terminal truncation of the p6 T cell epitope, raising the possibility of selection by host immunity. This variant peptide is virtually unable to stimulate T cell immunity. For an infection in which there has been debate about centrality of T cell immunity in defense, these observations support a role for T cell immunity to AhpC in disease protection

Lung defense through interleukin-8 carries a cost of chronic lung remodeling and impaired function

RATIONALE: IL-8 dependent inflammation is a hallmark of host lung innate immunity to bacterial pathogens, yet in many human lung diseases including COPD, bronchiectasis, and pulmonary fibrosis, there are progressive, irreversible pathologic, changes associated with elevated levels of IL-8 in the lung. OBJECTIVES: To better understand the duality of IL-8 dependent host immunity to bacterial infection and lung pathology, we targeted human IL-8 to express transgenically in murine bronchial epithelium, investigating the impact of over-expression on lung bacterial clearance, host immunity, lung pathology and function. MEASUREMENTS AND MAIN RESULTS: Persistent IL-8 expression in bronchial epithelium resulted in neutrophilia, neutrophil maturation, activation and chemtoaxis. There was enhanced protection from challenge with Pseudomonas aeruginosa and significant changes in baseline expression of innate and adaptive immunity transcripts for Ccl5, Tlr6, IL2 and Tlr1. There was increased expression of Tbet and Foxp3 in response to the Pseudomonas antigen, OprF, indicating a regulatory T cell phenotype. However, this enhanced bacterial immunity comes at the high price of progressive lung remodelling, with increased inflammation, mucus hyper-secretion, and fibrosis. There is increased expression of Ccl3 and reduced expressioh of Claudin 18 and F11r, with damage to epithelial organization leading to leaky tight junctions, all resulting in impaired lung function with reduced compliance, increased resistance and bronchial hyperreactivity measured by whole body plethysmography. CONCLUSIONS: IL-8 over-expression in the bronchial epithelium benefits lung immunity to bacterial infection, but specifically drives lung damage through persistent inflammation, lung remodelling and damaged tight junctions, leading to impaired lung function

Therapeutic vulnerability to PARP1,2 inhibition in RB1-mutant osteosarcoma

Loss-of-function mutations in the RB1 tumour suppressor are key drivers in cancer, including osteosarcoma. RB1 loss-of-function compromises genome-maintenance and hence could yield vulnerability to therapeutics targeting such processes. Here we demonstrate selective hypersensitivity to clinically-approved inhibitors of Poly-ADP-Polymerase1,2 inhibitors (PARPi) in RB1-defective cancer cells, including an extended panel of osteosarcoma-derived lines. PARPi treatment results in extensive cell death in RB1-defective backgrounds and prolongs survival of mice carrying human RB1-defective osteosarcoma grafts. PARPi sensitivity is not associated with canonical homologous recombination defect (HRd) signatures that predict PARPi sensitivity in cancers with BRCA1,2 loss, but is accompanied by rapid activation of DNA replication checkpoint signalling, and active DNA replication is a prerequisite for sensitivity. Importantly, sensitivity in backgrounds with natural or engineered RB1 loss surpasses that seen in BRCA-mutated backgrounds where PARPi have established clinical benefit. Our work provides evidence that PARPi sensitivity extends beyond cancers identifiable by HRd and advocates PARP1,2 inhibition as a personalised strategy for RB1-mutated osteosarcoma and other cancers.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Activated stromal cells transfer mitochondria to rescue acute lymphoblastic leukaemia cells from oxidative stress

We investigated and modelled the mesenchymal stromal cell (MSC) niche in adult acute lymphoblastic leukaemia (ALL). We used gene expression profiling, cytokine/chemokine quantification, flow cytometry and a variety of imaging techniques to show that MSC directly isolated from the primary bone marrow specimens of patients with ALL frequently adopted an activated, cancer-associated fibroblast phenotype. Normal, primary human MSC and the MSC cell line HS27a both became activated when exposed to the reactive oxygen species (ROS)-inducing chemotherapy agents cytarabine (AraC) and daunorubicin (DNR), a phenomenon blocked by the anti-oxidant N-acetyl cysteine. Chemotherapy-activated HS27a cells were functionally evaluated in a co-culture model with ALL targets. Activated MSC prevented therapy-induced apoptosis and death in ALL targets, via mitochondrial transfer through tunnelling nanotubes (TNT). Reduction of mitochondrial transfer by selective mitochondrial depletion or interference with TNT formation by microtubule inhibitors such as vincristine (VCR) - prevented the 'rescue' function of the activated MSC. Corticosteroids - also a mainstay of ALL therapy - prevented the activation of MSC. We also demonstrated that AraC (but not VCR) - induced activation of MSC, mitochondrial transfer and mitochondrial mass increase in a murine NSG model of disseminated SEM-derived ALL wherein CD19+ cells closely associated with nestin+ MSC after AraC but not the other conditions. Our data propose a readily clinically-exploitable mechanism for improving treatment ALL in which traditional, ROS-inducing chemotherapies are often ineffective at eradicating residual ALL, despite efficiently killing the bulk population