Multicenter phase 2 study of combination therapy with ruxolitinib and danazol in patients with myelofibrosis.

Myelofibrosis is a myeloproliferative neoplasm that is characterized by splenomegaly, profound symptom burden, and cytopenias. JAK inhibitor therapy offers improvements in splenomegaly, symptom burden, and potentially survival; however, cytopenias remain a significant challenge. Danazol has previously demonstrated improvements in myelofibrosis-associated anemia. We conducted a phase II clinical trial evaluating the efficacy and tolerability of combination therapy with ruxolitinib, an oral JAK inhibitor, and danazol. Fourteen intermediate or high-risk MF patients were enrolled at 2 institutions. Responses per IWG-MRT criteria were stable disease in 9 patients (64.2%) clinical improvement in 3 (21.4%) all of which were spleen responses, partial response in 1 (7.1%) and progressive disease in 1 (7.1%). Despite limited IWG-MRT response, stabilization of anemia and thrombocytopenia was demonstrated. In JAK inhibitor naïve patients, 4/5 (80%) had stable or increasing hemoglobin. Of the 9 patients on prior JAK inhibitor, 5 patients (55.5%) and 8 patients (88.9%) had stable or increasing hemoglobin or platelet levels, respectively. Adverse events possibly related included grade 3 or greater hematologic toxicity in ten patients (71.4%) and non-hematologic toxicity in two patients (14.3%). Although combination therapy did not lead to increased hematologic response per IWG-MRT criteria, hematologic stabilization was observed and may be clinically useful.

Epidemic Spread of Symbiotic and Non-Symbiotic Bradyrhizobium Genotypes Across California.

The patterns and drivers of bacterial strain dominance remain poorly understood in natural populations. Here, we cultured 1292 Bradyrhizobium isolates from symbiotic root nodules and the soil root interface of the host plant Acmispon strigosus across a >840-km transect in California. To investigate epidemiology and the potential role of accessory loci as epidemic drivers, isolates were genotyped at two chromosomal loci and were assayed for presence or absence of accessory "symbiosis island" loci that encode capacity to form nodules on hosts. We found that Bradyrhizobium populations were very diverse but dominated by few haplotypes-with a single "epidemic" haplotype constituting nearly 30 % of collected isolates and spreading nearly statewide. In many Bradyrhizobium lineages, we inferred presence and absence of the symbiosis island suggesting recurrent evolutionary gain and or loss of symbiotic capacity. We did not find statistical phylogenetic evidence that the symbiosis island acquisition promotes strain dominance and both symbiotic and non-symbiotic strains exhibited population dominance and spatial spread. Our dataset reveals that a strikingly few Bradyrhizobium genotypes can rapidly spread to dominate a landscape and suggests that these epidemics are not driven by the acquisition of accessory loci as occurs in key human pathogens.

Lotus hosts delimit the mutualism-parasitism continuum of Bradyrhizobium.

Symbioses are modelled as evolutionarily and ecologically variable with fitness outcomes for hosts shifting on a continuum from mutualism to parasitism. In a classic example, rhizobia fix atmospheric nitrogen for legume hosts in exchange for photosynthetic carbon. Rhizobial infection often enhances legume growth, but hosts also incur interaction costs because of root tissues and or metabolites needed to support symbionts in planta. Rhizobia exhibit genetic variation in symbiotic effectiveness, and ecological changes in light or mineral nitrogen availability can also alter the benefits of rhizobial infection for hosts. The net effects of symbiosis thus can range from mutualistic to parasitic in a context-dependent manner. We tested the extent of the mutualism-parasitism continuum in the legume-rhizobium symbiosis and the degree to which host investment can shape its limits. We infected Lotus strigosus with sympatric Bradyrhizobium genotypes that vary in symbiotic effectiveness. Inoculations occurred under different mineral nitrogen and light regimes spanning ecologically relevant ranges. Net growth benefits of Bradyrhizobium infection varied for Lotus and were reduced or eliminated dependent on Bradyrhizobium genotype, mineral nitrogen and light availability. But we did not detect parasitism. Lotus proportionally reduced investment in Bradyrhizobium as net benefit from infection decreased. Lotus control occurred primarily after infection, via fine-scale modulation of nodule growth, as opposed to control over initial nodulation. Our results show how divestment of symbiosis by Lotus can prevent shifts to parasitism.