Improved BM212 MmpL3 Inhibitor Analogue Shows Efficacy in Acute Murine Model of Tuberculosis Infection

1,5-Diphenyl pyrroles were previously identified as a class of compounds endowed with high in vitro efficacy against M. tuberculosis. To improve the physical chemical properties and drug-like parameters of this class of compounds, a medicinal chemistry effort was undertaken. By selecting the optimal substitution patterns for the phenyl rings at N1 and C5 and by replacing the thiomorpholine moiety with a morpholine one, a new series of compounds was produced. The replacement of the sulfur with oxygen gave compounds with lower lipophilicity and improved in vitro microsomal stability. Moreover, since the parent compound of this family has been shown to target MmpL3, mycobacterial mutants resistant to two compounds have been isolated and characterized by sequencing the mmpL3 gene; all the mutants showed point mutations in this gene. The best compound identified to date was progressed to dose-response studies in an acute murine TB infection model. The resulting ED₉₉ of 49 mg/Kg is within the range of commonly employed tuberculosis drugs, demonstrating the potential of this chemical series. The in vitro and in vivo target validation evidence presented here adds further weight to MmpL3 as a druggable target of interest for anti-tubercular drug discovery.     

Tolerance to Copper and to Salinity in Daphnia longispina: Implications within a Climate Change Scenario

Considering IPPC climate change scenarios, it is pertinent to predict situations where coastal ecosystems already impacted with chemical contamination became exposed to an additional stressor under a future scenario of seawater intrusion. Accordingly, the present study aimed at evaluating if a negative association between tolerance to a metal and to saltwater exists among genotypes of a freshwater organism. For this, five clonal lineages of the cladoceran Daphnia longispina O.F. Müller, exhibiting a differential tolerance to lethal levels of copper, were selected. Each clonal lineage was exposed to lethal and sublethal concentrations of sodium chloride (assumed as a protective surrogate to evaluate the toxicity of increased salinity to freshwater organisms). Mortality, time to release the first brood and total number of neonates per female were monitored and the somatic growth rate and intrinsic rate of natural increase were computed for each clonal lineage. Data here obtained were compared with their lethal responses to copper and significant negative correlations were found. These results suggest that genetically eroded populations of D. longispina, due to copper or salinity, may be particularly susceptible to a later exposure to the other contaminant supporting the multiple stressors differential tolerance.     

Inhibition of Dual/Mixed Tropic HIV-1 Isolates by CCR5-Inhibitors in Primary Lymphocytes and Macrophages

Background

Dual/mixed-tropic HIV-1 strains are predominant in a significant proportion of patients, though little information is available regarding their replication-capacity and susceptibility against CCR5-antagonists in-vitro. The aim of the study was to analyze the replication-capacity and susceptibility to maraviroc of HIV-1 clinical isolates with different tropism characteristics in primary monocyte-derived-macrophages (MDM), peripheral-blood-mononuclear-cells (PBMC), and CD4⁺T-lymphocytes.

Methods

Twenty-three HIV-1 isolates were phenotipically and genotipically characterized as R5, X4 or dual (discriminated as R5⁺/X4, R5/X4, R5/X4⁺). Phenotypic-tropism was evaluated by multiple-cycles-assay on U87MG-CD4⁺-CCR5⁺−/CXCR4⁺-expressing cells. Genotypic-tropism prediction was obtained using Geno2Pheno-algorithm (false-positive-rate [FPR] = 10%). Replication-capacity and susceptibility to maraviroc were investigated in human-primary MDM, PBMC and CD4⁺T-cells. AMD3100 was used as CXCR4-inhibitor. Infectivity of R5/Dual/X4-viruses in presence/absence of maraviroc was assessed also by total HIV-DNA, quantified by real-time polymerase-chain-reaction.

Results

Among 23 HIV-1 clinical isolates, phenotypic-tropism-assay distinguished 4, 17 and 2 viruses with R5-tropic, dual/mixed-, and X4-tropic characteristics, respectively. Overall, viruses defined as R5⁺/X4-tropic were found with the highest prevalence (10/23, 43.5%). The majority of isolates efficiently replicated in both PBMC and CD4⁺T-cells, regardless of their tropism, while MDM mainly sustained replication of R5- or R5⁺/X4-tropic isolates; strong correlation between viral-replication and genotypic-FPR-values was observed in MDM (rho = 0.710;p-value = 1.4e-4). In all primary cells, maraviroc inhibited viral-replication of isolates not only with pure R5- but also with dual/mixed tropism (mainly R5⁺/X4 and, to a lesser extent R5/X4 and R5/X4⁺). Finally, no main differences by comparing the total HIV-DNA with the p24-production in presence/absence of maraviroc were found.

Conclusions

Maraviroc is effective in-vitro against viruses with dual-characteristics in both MDM and lymphocytes, despite the potential X4-mediated escape. This suggests that the concept of HIV-entry through one of the two coreceptors “separately” may require revision, and that the use of CCR5-antagonists in patients with dual/mixed-tropic viruses may be a therapeutic-option that deserves further investigations in different clinical settings.     

Opposite Roles of NMDA Receptors in Relapsing and Primary Progressive Multiple Sclerosis

Synaptic transmission and plasticity mediated by NMDA receptors (NMDARs) could modulate the severity of multiple sclerosis (MS). Here the role of NMDARs in MS was first explored in 691 subjects carrying specific allelic variants of the NR1 subunit gene or of the NR2B subunit gene of this glutamate receptor. The analysis was replicated for significant SNPs in an independent sample of 1548 MS subjects. The C allele of rs4880213 was found to be associated with reduced NMDAR-mediated cortical excitability, and with increased probability of having more disability than the CT/TT MS subjects. MS severity was higher in the CC group among relapsing-remitting MS (RR-MS) patients, while primary progressive MS (PP-MS) subjects homozygous for the T allele had more pronounced clinical worsening. Mean time to first relapse, but not to an active MRI scan, was lower in the CC group of RR-MS patients, and the number of subjects with two or more clinical relapses in the first two years of the disease was higher in CC compared to CT/TT group. Furthermore, the percentage of relapses associated with residual disability was lower in subjects carrying the T allele. Lesion load at the MRI was conversely unaffected by the C or T allele of this SNP in RR-MS patients. Axonal and neuronal degeneration at the optical coherence tomography was more severe in the TT group of PP-MS patients, while reduced retinal nerve fiber thickness had less consequences on visual acuity in RR-MS patients bearing the T allele. Finally, the T allele was associated with preserved cognitive abilities at the Rao’s brief repeatable neuropsychological battery in RR-MS. Signaling through glutamate NMDARs enhances both compensatory synaptic plasticity and excitotoxic neurodegeneration, impacting in opposite ways on RR-MS and PP-MS pathophysiological mechanisms.     

Improvement in cyst recovery and molecular detection of Giardia duodenalis from stool samples

Molecular Biology Reports - Molecular detection of Giardia duodenalis by polymerase chain reaction (PCR) is difficult in faecal samples due to inhibitors that contaminate DNA preparations, or due...     

F508del disturbs the dynamics of the nucleotide binding domains of CFTR before and after ATP hydrolysis

The cystic fibrosis transmembrane conductance regulator (CFTR) channel is an ion channel responsible for chloride transport in epithelia and it belongs to the class of ABC transporters. The deletion of phenylalanine 508 (F508del) in CFTR is the most common mutation responsible for cystic fibrosis. Little is known about the effect of the mutation in the isolated nucleotide binding domains (NBDs), on dimer dynamics, ATP hydrolysis and even on nucleotide binding. Using molecular dynamics simulations of the human CFTR NBD dimer, we showed that F508del increases, in the prehydrolysis state, the inter-motif distance in both ATP binding sites (ABP) when ATP is bound. Additionally, a decrease in the number of catalytically competent conformations was observed in the presence of F508del. We used the subtraction technique to study the first 300 ps after ATP hydrolysis in the catalytic competent site and found that the F508del dimer evidences lower conformational changes than the wild type. Using longer simulation times, the magnitude of the conformational changes in both forms increases. Nonetheless, the F508del dimer shows lower C-α RMS values in comparison to the wild-type, on the F508del loop, on the residues surrounding the catalytic site and the portion of NBD2 adjacent to ABP1. These results provide evidence that F508del interferes with the NBD dynamics before and after ATP hydrolysis. These findings shed a new light on the effect of F508del on NBD dynamics and reveal a novel mechanism for the influence of F508del on CFTR.     

Feeding behavior of Brevicoryne brassicae in resistant and susceptible collard greens genotypes: interactions among morphological and chemical factors

The cabbage aphid, Brevicoryne brassicae (L.) (Hemiptera: Aphididae), is distributed throughout the tropical and subtropical areas of the world. The main crops attacked by B. brassicae are cabbage, collard greens, broccoli, Brussels sprouts, and cauliflower. To survive the attack of pest insects, plants have evolved various resistance mechanisms that may affect pest feeding behavior. The use of electronic monitoring through EPG (electrical penetration graph) can help characterize and distinguish the resistance mechanisms involved. This study evaluated the feeding behavior of B. brassicae in eight genotypes of collard greens, Brassica oleraceae L. var. acephala (Brassicaceae), exhibiting antixenosis and/or antibiosis resistance to this insect. Possible correlations were established between the glucosinolate levels, the hardness, and the epicuticular wax on the leaves vs. aphid feeding behavior. On the genotypes 22V, 5E, and 27VA, for which many ‘potential drop’ waves were performed, aphid development was slower, indicating antixenosis as resistance type. Aphids on the genotypes 22V and 24X required more time until accessing the phloem, also suggesting antixenosis as resistance category. Genotypes 22V and PE had hard leaves, which also points at antixenosis. Genotypes 20T and HS had higher total wax and wax mg⁻¹. Feeding parameters on ARI and 24X were similar to those observed on HS; antibiosis is likely to be the predominant resistance category of this germplasm. Because HS was considered as a susceptible standard genotype in this study, a higher gluconapin amount indicates that this compound does not influence cabbage aphid feeding behavior. The present study confirms that analysis of the physical and chemical aspects of collard greens genotypes by the EPG technique can provide a useful approach for the study of plant resistance to cabbage aphids.