Early blood stream infection after BMT is associated with cytokine dysregulation and poor overall survival

The key complications of allogeneic bone marrow transplant (BMT) remain graft-versus-host disease (GVHD) and opportunistic infection. We have analyzed the blood stream infections (BSI) occurring between day -7 and day 100 in a cohort of 184 adult patients undergoing allogeneic BMT in our center. 167 of the 184 patients (91%) had blood cultures collected, and 69 (38%) patients had a confirmed BSI. Enterobacteriaceae, Pseudomonas aeruginosa, Enterococcus spp. and viridans Streptococcus spp. were the most commonly isolated organisms. Gender, conditioning (myeloablative vs. reduced intensity) and donor type (sibling vs. unrelated) did not differ significantly between those with and without confirmed BSI. Elevated temperature (>38°C) at the time of culture collection was associated with an almost 2-fold increased likelihood of returning a positive blood culture. The absence of a BSI was associated with a significant improvement in overall survival at 2 years, due to a significant reduction in non-relapse mortality predominantly unrelated to the primary BSI. The presence of a BSI prior to engraftment was associated with the dysregulation of IL-6 and IL-8. Our findings suggest that BSI early after BMT defines a group of high-risk patients with enhanced cytokine dysregulation and poor transplant outcome

Bone marrow transplantation generates T cell–dependent control of myeloma in mice

Transplantation with autologous hematopoietic progenitors remains an important consolidation treatment for patients with multiple myeloma (MM) and is thought to prolong the disease plateau phase by providing intensive cytoreduction. However, transplantation induces inflammation in the context of profound lymphodepletion that may cause hitherto unexpected immunological effects. We developed preclinical models of bone marrow transplantation (BMT) for MM using Vk*MYC myeloma-bearing recipient mice and donor mice that were myeloma naive or myeloma experienced to simulate autologous transplantation. Surprisingly, we demonstrated broad induction of T cell-dependent myeloma control, most efficiently from memory T cells within myeloma-experienced grafts, but also through priming of naive T cells after BMT. CD8+ T cells from mice with controlled myeloma had a distinct T cell receptor (TCR) repertoire and higher clonotype overlap relative to myeloma-free BMT recipients. Furthermore, T cell-dependent myeloma control could be adoptively transferred to secondary recipients and was myeloma cell clone specific. Interestingly, donor-derived IL-17A acted directly on myeloma cells expressing the IL-17 receptor to induce a transcriptional landscape that promoted tumor growth and immune escape. Conversely, donor IFN-γ secretion and signaling were critical to protective immunity and were profoundly augmented by CD137 agonists. These data provide new insights into the mechanisms of action of transplantation in myeloma and provide rational approaches to improving clinical outcomes

Imaging the immunological synapse between dendritic cells and T cells

Immunological synapse formation between antigen-specific T cells and antigen presenting cells (APC) involves reorganization of the cellular cytoskeleton (polymerization of filamentous actin) and recruitment of adhesion molecules (e.g. LFA-1, ICAM-1). This engagement is critical for the generation of specific immune responses. Until recently, quantitative, high-throughput measurements of these interactions have not been possible. Instead, previous assessment was reliant on qualitative microscopy of live cells, where typically the APC is adhered to a surface and the suspended T cell is required to migrate to facilitate synapse formation. While this methodology can demonstrate the capacity for synapse formation, it cannot accommodate quantification of large numbers of interacting cell pairs, nor does it allow for statistically robust comparison between test conditions

Low rates of antibiotic resistance and infectious mortality in a cohort of high-risk hematology patients: A single center, retrospective analysis of blood stream infection.

Febrile neutropenia (FN) is a medical emergency and can represent a life-threatening complication for hematology patients treated with intensive chemotherapy regimens. In clinical practice, the diagnostic yield of blood cultures and other investigations which aim to identify a causative organism or site of infection is low. We have retrospectively examined all blood cultures collected in a "real world" cohort of patients receiving chemotherapy for acute leukemia and patients with aggressive lymphoma treated with Hyper-CVAD/MTX-cytarabine, at a single tertiary center over a five-year period. In this cohort, the 30-day mortality following confirmed blood stream infection (BSI) was 5.9%, which is lower than most reports in the recent literature. We compared the blood culture results of inpatients undergoing induction chemotherapy and outpatients presenting with fevers and found a significantly higher rate of proven BSI in the outpatient group. In all settings, gram-negative organisms were most common. The rate of resistance to first-line empiric antibiotics among pathogenic isolates was 11.6% in the whole cohort, independent of blood culture circumstances. There was a trend to higher resistance rates among inpatients undergoing induction chemotherapy compared to patients presenting to the emergency department (17.4% vs 7.5%) but this did not reach statistical significance. We also report low rates of ciprofloxacin resistance (5% of isolates), in a center where universal fluoroquinolone prophylaxis is not employed. Our low resistance and mortality rates support our current therapeutic strategies, however presence of resistant organisms across the spectrum of indications for BC collection highlights the importance of surveilling local patterns, escalating antimicrobial therapy in the deteriorating patient, and considering advanced techniques for the rapid identification of resistance in this patient population

Development of a Multiplexed Microsphere PCR for Culture-Free Detection and Gram-Typing of Bacteria in Human Blood Samples

Bloodstream infection is a significant clinical problem, particularly in vulnerable patient groups such as those undergoing chemotherapy and bone marrow transplantation. Clinical diagnostics for suspected bloodstream infection remain centered around blood culture (highly variable timing, in the order of hours to days to become positive), and empiric use of broad-spectrum antibiotics is therefore employed for patients presenting with febrile neutropenia. Gram-typing provides the first opportunity to target therapy (e.g., combinations containing vancomycin or teicoplanin for Gram-positives; piperacillin-tazobactam or a carbapenem for Gram-negatives); however, current approaches require blood culture. In this study, we describe a multiplexed microsphere-PCR assay with flow cytometry readout, which can distinguish Gram-positive from Gram-negative bacterial DNA in a 3.5 h time period. The combination of a simple assay design (amplicon-dependent release of Gram-type specific Cy3-labeled oligonucleotides) and the Luminex-based readout (for quantifying each specific Cy3-labeled sequence) opens opportunities for further multiplexing. We demonstrate the feasibility of detecting common Gram-positive and Gram-negative organisms after spiking whole bacteria into healthy human blood prior to DNA extraction. Further development of DNA extraction methods is required to reach detection limits comparable to blood culture