Investigation of the Genes Involved in Antigenic Switching at the vlsE Locus in Borrelia burgdorferi: An Essential Role for the RuvAB Branch Migrase

Persistent infection by pathogenic organisms requires effective strategies for the defense of these organisms against the host immune response. A common strategy employed by many pathogens to escape immune recognition and clearance is to continually vary surface epitopes through recombinational shuffling of genetic information. Borrelia burgdorferi, a causative agent of Lyme borreliosis, encodes a surface-bound lipoprotein, VlsE. This protein is encoded by the vlsE locus carried at the right end of the linear plasmid lp28-1. Adjacent to the expression locus are 15 silent cassettes carrying information that is moved into the vlsE locus through segmental gene conversion events. The protein players and molecular mechanism of recombinational switching at vlsE have not been characterized. In this study, we analyzed the effect of the independent disruption of 17 genes that encode factors involved in DNA recombination, repair or replication on recombinational switching at the vlsE locus during murine infection. In Neisseria gonorrhoeae, 10 such genes have been implicated in recombinational switching at the pilE locus. Eight of these genes, including recA, are either absent from B. burgdorferi, or do not show an obvious requirement for switching at vlsE. The only genes that are required in both organisms are ruvA and ruvB, which encode subunits of a Holliday junction branch migrase. Disruption of these genes results in a dramatic decrease in vlsE recombination with a phenotype similar to that observed for lp28-1 or vls-minus spirochetes: productive infection at week 1 with clearance by day 21. In SCID mice, the persistence defect observed with ruvA and ruvB mutants was fully rescued as previously observed for vlsE-deficient B. burgdorferi. We report the requirement of the RuvAB branch migrase in recombinational switching at vlsE, the first essential factor to be identified in this process. These findings are supported by the independent work of Lin et al. in the accompanying article, who also found a requirement for the RuvAB branch migrase. Our results also indicate that the mechanism of switching at vlsE in B. burgdorferi is distinct from switching at pilE in N. gonorrhoeae, which is the only other organism analyzed genetically in detail. Finally, our findings suggest a unique mechanism for switching at vlsE and a role for currently unidentified B. burgdorferi proteins in this process

Immunogenomic analyses associate immunological alterations with mismatch repair defects in prostate cancer.

Background Understanding the integrated immunogenomic landscape of advanced prostate cancer (APC) could impact stratified treatment selection.Methods Defective mismatch repair (dMMR) status was determined by either loss of mismatch repair protein expression on IHC or microsatellite instability (MSI) by PCR in 127 APC biopsies from 124 patients (Royal Marsden [RMH] cohort); MSI by targeted panel next-generation sequencing (MSINGS) was then evaluated in the same cohort and in 254 APC samples from the Stand Up To Cancer/Prostate Cancer Foundation (SU2C/PCF). Whole exome sequencing (WES) data from this latter cohort were analyzed for pathogenic MMR gene variants, mutational load, and mutational signatures. Transcriptomic data, available for 168 samples, was also performed.Results Overall, 8.1% of patients in the RMH cohort had some evidence of dMMR, which associated with decreased overall survival. Higher MSINGS scores associated with dMMR, and these APCs were enriched for higher T cell infiltration and PD-L1 protein expression. Exome MSINGS scores strongly correlated with targeted panel MSINGS scores (r = 0.73, P < 0.0001), and higher MSINGS scores associated with dMMR mutational signatures in APC exomes. dMMR mutational signatures also associated with MMR gene mutations and increased immune cell, immune checkpoint, and T cell-associated transcripts. APC with dMMR mutational signatures overexpressed a variety of immune transcripts, including CD200R1, BTLA, PD-L1, PD-L2, ADORA2A, PIK3CG, and TIGIT.Conclusion These data could impact immune target selection, combination therapeutic strategy selection, and selection of predictive biomarkers for immunotherapy in APC.Funding We acknowledge funding support from Movember, Prostate Cancer UK, The Prostate Cancer Foundation, SU2C, and Cancer Research UK

Rapid Effect Of Change In Cerebrospinal-fluid Sodium Concentration On Salt Appetite

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62648/1/280490a0.pd

Social capital, human capital and ethnic occupational niches: an analysis of ethnic and gender inequalities in the Spanish labour market

This article analyses the role of different types of social capital in the integration of immigrants into the labour market of Catalonia (Spain), according to the geographical distribution and ethnic characteristics of immigrants’ contacts. It aims to test the role of social networks, human capital and the ethno-stratification of the labour market in immigrants’ labour market performance; and to contribute to understanding the often overlooked but complex interactions between these factors and gender inequalities. Results show that transnational ties constitute a weak resource in obtaining job benefits, that labour-intensive ethnic occupational niches confine immigrants to low-skilled positions to a great extent and that, even controlling for human capital and industrial sectors, having supportive links with native-born Spaniards has a positive effect on migrants’ occupational status. Finally, gendered differences are also evident in respect of returns on social capital, indicating that the sexually segregated occupational structure of the Spanish labour market makes social capital a weaker resource for women immigrants

Nutrient dynamics in river bed sediments: effects of hydrological disturbances using experimental flow manipulations

International audiencePurpose River sediments play a crucial role in the storage and transformation of organic matter (OM). Nutrient dy- namics are controlled by the interaction of several key parameters, i.e. river discharge, channel geometry and ver- tical exchanges of water (upwelling vs. downwelling zones). The main aim of this study was to evaluate the effect of channel forms and discharge variation on nutrient spiralling in the hyporheic zone (HZ) of streams. Materials and methods Four experimental flow manipula- tions (EFM) were carried out at two reaches with different channel forms (straight vs. sinuous) in an oligotrophic sub- tropical river in Australia. Flow manipulation consisted of reducing the river width with a temporary dam, diverting and concentrating the main water flux on two different geomorphological units (riffle vs. gravel bar), in order to simulate flooding conditions. Hyporheic waters were ana- lysed for their physicochemical characteristics and nutrient (nitrates + nitrites 0 NOx and soluble reactive phosphorus [SRP]) and OM contents at two depths (10 and 50 cm) within the bed sediments, both upstream and downstream of the geomorphological units. Results and discussion The physicochemical parameters clearly demonstrated the existence of hyporheic flow paths, characterized by the alternation of downwelling and upwell- ing areas, with more consistent gradients in gravel bars than in riffles. The HZ acted as source for NOx and SRP, but this role varied between geomorphological units and reaches. The effect of EFM differed between sampling points, irre- spective of the type of geomorphological unit. In gravel bars, a flush out during high discharge was observed for NOx, SRP and particulate organic matter (POM) at the sinuous channel, whereas storage and removal were recorded at the straight channel for SRP and NOx, respec- tively. At the riffle of the sinuous channel, very fine POM accumulated, while removal was noticed for POM. In con- trast, at the riffle of the straight channel, SRP accumulated in the HZ and NOx was removed out of the HZ. Conclusions Nutrient dynamics in the HZ and the response to flow increases were not governed by the geomorphological unit type. Other parameters that determine water residence time in the sediments, such as local heterogeneity in sediment characteristics (grain size, porosity and hydraulic conductivi- ty), channel sinuosity, reach slope and the size and form of the gravel bar, may be more significant explanatory variables for understanding OM and nutrient dynamics in the HZ. This study emphasizes the need for caution in making generalisa- tions about the role of river sediment in nutrient storage and the impact of floods on nutrient dynamics