First-in-class Microbial Ecosystem Therapeutic 4 (MET4) in combination with immune checkpoint inhibitors in patients with advanced solid tumors (MET4-IO trial)

BACKGROUND

The intestinal microbiome has been associated with response to immune checkpoint inhibitors (ICIs) in humans and causally implicated in ICI responsiveness in animal models. Two recent human trials demonstrated that fecal microbiota transplant (FMT) from ICI responders can rescue ICI responses in refractory melanoma, but FMT has specific limitations to scaled use.

PATIENTS AND METHODS

We conducted an early-phase clinical trial of a cultivated, orally delivered 30-species microbial consortium (Microbial Ecosystem Therapeutic 4, MET4) designed for co-administration with ICIs as an alternative to FMT and assessed safety, tolerability and ecological responses in patients with advanced solid tumors.

RESULTS

The trial achieved its primary safety and tolerability outcomes. There were no statistically significant differences in the primary ecological outcomes; however, differences in MET4 species relative abundance were evident after randomization that varied by patient and species. Increases in the relative abundance of several MET4 taxa, including Enterococcus and Bifidobacterium, taxa previously associated with ICI responsiveness, were observed and MET4 engraftment was associated with decreases in plasma and stool primary bile acids.

CONCLUSIONS

This trial is the first report of the use of a microbial consortium as an alternative to FMT in advanced cancer patients receiving ICI and the results justify the further development of microbial consortia as a therapeutic co-intervention for ICI treatment in cancer.

The impact of cervical cytobrush sampling on cervico-vaginal immune parameters and microbiota relevant to HIV susceptibility

The immunology and microbiota of the female genital tract (FGT) are key determinants of HIV susceptibility. Cervical cytobrush sampling is a relatively non-invasive method permitting the longitudinal assessment of endocervical immune cells, but effects on FGT immunology are unknown. Blood, cervico-vaginal secretions and cervical cytobrushes were collected from sexually transmitted infection (STI)-free women at baseline and after either 6 hours or 48 hours. Endocervical immune cell subsets were assessed by flow cytometry, and pro-inflammatory cytokines by multiplex ELISA. The density of Lactobacillus species and key bacterial vaginosis-associated bacterial taxa were determined by qPCR. Paired changes were assessed before and after cytobrush sampling. After 6 hours there were significant increases in CD4 + T cell, antigen presenting cell (APC) and neutrophil numbers; APC elevations persisted at 48 hours, while neutrophil and CD4 + T cell numbers returned to baseline. In addition, pro-inflammatory cytokine levels were increased at 6 hours and returned to baseline by 48 hours. No significant changes were observed in the absolute abundance of Lactobacillus species or BV-associated bacteria at either time point. Overall, cytobrush sampling altered genital immune parameters at 6 hours, but only APC number increases persisted at 48 hours. This should be considered in longitudinal analyses of FGT immunology.

Immune biomarkers of response to immune-checkpoint inhibitors in head and neck squamous cell carcinoma

Anti-programmed cell death protein 1 (PD-1) agents have become the standard of care for platinum-refractory recurrent/metastatic head and neck squamous cell carcinoma (HNSCC) and are currently being evaluated in various disease settings. However, despite the gain in overall survival seen in some of the clinical trials, the majority of patients display primary resistance and do not benefit from these agents. Taking into consideration the potentially severe immune-related toxicities and their high cost, the search for predictive biomarkers of response is crucial. Besides Programmed death ligand-1 (PD-L1) expression, other biomarkers such as immune infiltration, tumor mutational burden or immune-gene expression profiling have been explored, but none of them has been validated in this disease. Among these, the microbiota has recently garnered tremendous interest since it has proven to influence the efficacy of PD-1 blockade in some tumor types. With the accumulating evidence on the effect of the microbiota in HNSCC tumorigenesis and progression, the study of its potential role as a predictive immune biomarker is warranted. This review examines the available evidence on emerging immune predictive biomarkers of response to anti-PD-1/PD-L1 therapy in HNSCC, introducing the microbiota and its potential use as a predictive immune biomarker in this disease.

Decision-support models for empiric antibiotic selection in Gram-negative bloodstream infections

OBJECTIVES

Early empiric antibiotic therapy in patients can improve clinical outcomes in Gram-negative bacteraemia. However, the widespread prevalence of antibiotic-resistant pathogens compromises our ability to provide adequate therapy while minimizing use of broad antibiotics. We sought to determine whether readily available electronic medical record data could be used to develop predictive models for decision support in Gram-negative bacteraemia.

METHODS

We performed a multi-centre cohort study, in Canada and the USA, of hospitalized patients with Gram-negative bloodstream infection from April 2010 to March 2015. We analysed multivariable models for prediction of antibiotic susceptibility at two empiric windows: Gram-stain-guided and pathogen-guided treatment. Decision-support models for empiric antibiotic selection were developed based on three clinical decision thresholds of acceptable adequate coverage (80%, 90% and 95%).

RESULTS

A total of 1832 patients with Gram-negative bacteraemia were evaluated. Multivariable models showed good discrimination across countries and at both Gram-stain-guided (12 models, areas under the curve (AUCs) 0.68-0.89, optimism-corrected AUCs 0.63-0.85) and pathogen-guided (12 models, AUCs 0.75-0.98, optimism-corrected AUCs 0.64-0.95) windows. Compared to antibiogram-guided therapy, decision-support models of antibiotic selection incorporating individual patient characteristics and prior culture results have the potential to increase use of narrower-spectrum antibiotics (in up to 78% of patients) while reducing inadequate therapy.

CONCLUSIONS

Multivariable models using readily available epidemiologic factors can be used to predict antimicrobial susceptibility in infecting pathogens with reasonable discriminatory ability. Implementation of sequential predictive models for real-time individualized empiric antibiotic decision-making has the potential to both optimize adequate coverage for patients while minimizing overuse of broad-spectrum antibiotics, and therefore requires further prospective evaluation.

SUMMARY

Readily available epidemiologic risk factors can be used to predict susceptibility of Gram-negative organisms among patients with bacteraemia, using automated decision-making models.

Utility of prior cultures in predicting antibiotic resistance of bloodstream infections due to Gram-negative pathogens: a multicentre observational cohort study

OBJECTIVES

Appropriate empiric antibiotic therapy in patients with bloodstream infections due to Gram-negative pathogens can improve outcomes. We evaluated the utility of prior microbiologic results for guiding empiric treatment in Gram-negative bloodstream infections.

METHODS

We conducted a multicentre observational cohort study in two large health systems in Canada and the United States, including 1832 hospitalized patients with Gram-negative bloodstream infection (community, hospital and intensive care unit acquired) from April 2010 to March 2015.

RESULTS

Among 1832 patients with Gram-negative bloodstream infection, 28% (n = 504) of patients had a documented prior Gram-negative organism from a nonscreening culture within the previous 12 months. A most recent prior Gram-negative organism resistant to a given antibiotic was strongly predictive of the current organism's resistance to the same antibiotic. The overall specificity was 0.92 (95% confidence interval (CI) 0.91-0.93), and positive predictive value was 0.66 (95% CI 0.61-0.70) for predicting antibiotic resistance. Specificities and positive predictive values ranged from 0.77 to 0.98 and 0.43 to 0.78, respectively, across different antibiotics, organisms and patient subgroups. Increasing time between cultures was associated with a decrease in positive predictive value but not specificity. An heuristic based on a prior resistant Gram-negative pathogen could have been applied to one in four patients and in these patients would have changed therapy in one in five.

CONCLUSIONS

In patients with a bloodstream infection with a Gram-negative organism, identification of a most recent prior Gram-negative organism resistant to a drug of interest (within the last 12 months) is highly specific for resistance and should preclude use of that antibiotic.

Loss of p75 neurotrophin receptor expression accompanies malignant progression to human and murine retinoblastoma

We studied the expression of pro-apoptotic neurotrophin receptor p75 (p75(NTR)) in human and murine retinoblastoma, compared to normal retina, and examined changes in p75(NTR) expression with the onset of apoptosis in the course of murine retinoblastoma progression, using immunohistochemistry and quantitative real-time RT-PCR. The murine retinoblastoma is induced by retinal specific expression of SV40 T-antigen (TAg), which blocks the function of the retinoblastoma protein (pRB) and related proteins, and is a well-studied model that closely simulates human retinoblastoma. The majority of human retinoblastoma either lacked or expressed decreased levels of p75(NTR) mRNA, compared to human retina. Moreover, p75(NTR) protein was not detected in any tumor studied, unlike normal retina. Like human retinoblastoma, advanced murine retinoblastoma did not express p75(NTR). However, before tumors emerged, small clusters of TAg-positive cells coexpressed p75(NTR) and activated caspase-3, a marker of apoptosis. Furthermore, in three rare human eyes containing retinoblastoma adjacent to regions resembling the benign retinal tumor retinoma, both normal retina and retinoma-like tissue expressed p75(NTR) protein, while the retinoblastoma did not. We suggest that p75(NTR) loss accompanies progression from retinoma to retinoblastoma.

Paraplegic ambulation: a systems point of view

Neurophysiological systems preserved distal to a complete spinal lesion, and relevant to walking, are reviewed in the manner of an engineering control systems analysis. On that basis, an outline is given of theoretical concepts, current developments and future possibilities for neuromuscular electrical stimulation to provide paraplegic ambulation.