Histamine Produced by Gram-Negative Bacteria Impairs Neutrophil's Antimicrobial Response by Engaging the Histamine 2 Receptor.

We found that histamine (10-9 M) did not have any effect on the in vitro capture of Escherichia coli by neutrophils but accelerated its intracellular killing. In contrast, histamine (10-6 M) delayed the capture of Escherichia coli by neutrophils and reduced the amounts of pHrodo zymosan particles inside acidic mature phagosomes. Histamine acted through the H4R and the H2R, which are coupled to the Src family tyrosine kinases or the cAMP/protein kinase A pathway, respectively. The protein kinase A inhibitor H-89 abrogated the delay in bacterial capture induced by histamine (10-6 M) and the Src family tyrosine kinase inhibitor PP2 blocked histamine (10-9 M) induced acceleration of bacterial intracellular killing and tyrosine phosphorylation of proteins. To investigate the role of histamine in pathogenicity, we designed an Acinetobacter baumannii strain deficient in histamine production (hdc::TOPO). Galleria mellonella larvae inoculated with the wild-type Acinetobacter baumannii ATCC 17978 strain (1.1 × 105 CFU) died rapidly (100% death within 40 h) but not when inoculated with the Acinetobacter baumannii hdc::TOPO mutant (10% mortality). The concentration of histamine rose in the larval haemolymph upon inoculation of the wild type but not the Acinetobacter baumannii hdc::TOPO mutant, such concentration of histamine blocks the ability of hemocytes from Galleria mellonella to capture Candida albicans in vitro. Thus, bacteria-producing histamine, by maintaining high levels of histamine, may impair neutrophil phagocytosis by hijacking the H2R.

Mini-XT, a miniaturized tagmentation-based protocol for efficient sequencing of SARS-CoV-2.

BACKGROUND: The COVID-19 pandemic has highlighted the importance of whole genome sequencing (WGS) of SARS-CoV-2 to inform public health policy. By enabling definition of lineages it facilitates tracking of the global spread of the virus. The evolution of new variants can be monitored and knowledge of specific mutations provides insights into the mechanisms through which the virus increases transmissibility or evades immunity. To date almost 1 million SARS-CoV-2 genomes have been sequenced by members of the COVID-19 Genomics UK (COG-UK) Consortium. To achieve similar feats in a more cost-effective and sustainable manner in future, improved high throughput virus sequencing protocols are required. We have therefore developed a miniaturized library preparation protocol with drastically reduced consumable use and costs. RESULTS: We present the 'Mini-XT' miniaturized tagmentation-based library preparation protocol available on protocols.io ( https://doi.org/10.17504/protocols.io.bvntn5en ). SARS-CoV-2 RNA was amplified using the ARTIC nCov-2019 multiplex RT-PCR protocol and purified using a conventional liquid handling system. Acoustic liquid transfer (Echo 525) was employed to reduce reaction volumes and the number of tips required for a Nextera XT library preparation. Sequencing was performed on an Illumina MiSeq. The final version of Mini-XT has been used to sequence 4384 SARS-CoV-2 samples from N. Ireland with a COG-UK QC pass rate of 97.4%. Sequencing quality was comparable and lineage calling consistent for replicate samples processed with full volume Nextera DNA Flex (333 samples) or using nanopore technology (20 samples). SNP calling between Mini-XT and these technologies was consistent and sequences from replicate samples paired together in maximum likelihood phylogenetic trees. CONCLUSIONS: The Mini-XT protocol maintains sequence quality while reducing library preparation reagent volumes eightfold and halving overall tip usage from sample to sequence to provide concomitant cost savings relative to standard protocols. This will enable more efficient high-throughput sequencing of SARS-CoV-2 isolates and future pathogen WGS.

Platform with biomimetic electrochemical sensors for adiponectin and leptin detection in human serum.

Two new biomimetic sensors for the detection of adiponectin (A) and leptin (L) through molecularly imprinted polymers (MIPs) onto gold working electrodes (GWEs) were fabricated. Based on electrochemical impedance spectroscopy (EIS) results and cyclic voltammetry (CV) characteristics recorded in the development stages of the fabricated sensors, the sensors were electrochemically optimized and used in an integrated microfluidic platform to detect adiponectin/leptin via conductance signals and non-imprinted electrodes were used as references. To overcome the limitation of the low response signals after template binding non-conductive polyphenol (PP) and poliscopoletin (PS) were used for templates formation. Under optimized experimental conditions the conductance and resistance signals were obtained in the linear range of 0-50 µg ml-1 for A and 1-32 ng∙ml-1 for L with low limits of detection (0.25 µg ml-1 for A and 0.110 ng ml-1 for L). The dedicated platform exhibited an excellent response with great selectivity and stability. Finally, the proposed biomimetic sensors were successfully applied to enable the determination of A and L in human patient's serum with very high accuracy when compared to enzyme-linked immunosorbent assay ELISA reference methods.