Role of the distal hydrogen-bonding network in regulating oxygen affinity in the truncated hemoglobin III from Campylobacter jejuni

Oxygen affinity in heme-containing proteins is determined by a number of factors, such as the nature and conformation of the distal residues that stabilize the heme bound-oxygen via hydrogen-bonding interactions. The truncated hemoglobin III from Campylobacter jejuni (Ctb) contains three potential hydrogen-bond donors in the distal site: TyrB10, TrpG8, and HisE7. Previous studies suggested that Ctb exhibits an extremely slow oxygen dissociation rate due to an interlaced hydrogen-bonding network involving the three distal residues. Here we have studied the structural and kinetic properties of the G8(WF) mutant of Ctb and employed state-of-the-art computer simulation methods to investigate the properties of the O(2) adduct of the G8(WF) mutant, with respect to those of the wild-type protein and the previously studied E7(HL) and/or B10(YF) mutants. Our data indicate that the unique oxygen binding properties of Ctb are determined by the interplay of hydrogen-bonding interactions between the heme-bound ligand and the surrounding TyrB10, TrpG8, and HisE7 residues.     

Recombinant adenovirus serotype 26 (Ad26) and Ad35 vaccine vectors bypass immunity to Ad5 and protect nonhuman primates against ebolavirus challenge

The use of adenoviruses (Ad) as vaccine vectors against a variety of pathogens has demonstrated their capacity to elicit strong antibody and cell-mediated immune responses. Adenovirus serotype C vectors, such as Ad serotype 5 (Ad5), expressing Ebolavirus (EBOV) glycoprotein (GP), protect completely after a single inoculation at a dose of 10(10) viral particles. However, the clinical application of a vaccine based on Ad5 vectors may be hampered, since impairment of Ad5 vaccine efficacy has been demonstrated for humans and nonhuman primates with high levels of preexisting immunity to the vector. Ad26 and Ad35 segregate genetically from Ad5 and exhibit lower seroprevalence in humans, making them attractive vaccine vector alternatives. In the series of studies presented, we show that Ad26 and Ad35 vectors generate robust antigen-specific cell-mediated and humoral immune responses against EBOV GP and that Ad5 immune status does not affect the generation of GP-specific immune responses by these vaccines. We demonstrate partial protection against EBOV by a single-shot Ad26 vaccine and complete protection when this vaccine is boosted by Ad35 1 month later. Increases in efficacy are paralleled by substantial increases in T- and B-cell responses to EBOV GP. These results suggest that Ad26 and Ad35 vectors warrant further development as candidate vaccines for EBOV.     

Nontypable Haemophilus influenzae displays a prevalent surface structure molecular pattern in clinical isolates

Non-typable Haemophilus influenzae (NTHi) is a gram negative pathogen that causes acute respiratory infections and is associated with the progression of chronic respiratory diseases. Previous studies have established the existence of a remarkable genetic variability among NTHi strains. In this study we show that, in spite of a high level of genetic heterogeneity, NTHi clinical isolates display a prevalent molecular feature, which could confer fitness during infectious processes. A total of 111 non-isogenic NTHi strains from an identical number of patients, isolated in two distinct geographical locations in the same period of time, were used to analyse nine genes encoding bacterial surface molecules, and revealed the existence of one highly prevalent molecular pattern (lgtF+, lic2A+, lic1D+, lic3A+, lic3B+, siaA-, lic2C+, ompP5+, oapA+) displayed by 94.6% of isolates. Such a genetic profile was associated with a higher bacterial resistance to serum mediated killing and enhanced adherence to human respiratory epithelial cells.     

Characterisation of genome-wide association epistasis signals for serum uric acid in human population isolates

Genome-wide association (GWA) studies have identified a number of loci underlying variation in human serum uric acid (SUA) levels with the SLC2A9 gene having the largest effect identified so far. Gene-gene interactions (epistasis) are largely unexplored in these GWA studies. We performed a full pair-wise genome scan in the Italian MICROS population (n = 1201) to characterise epistasis signals in SUA levels. In the resultant epistasis profile, no SNP pairs reached the Bonferroni adjusted threshold for the pair-wise genome-wide significance. However, SLC2A9 was found interacting with multiple loci across the genome, with NFIA - SLC2A9 and SLC2A9 - ESRRAP2 being significant based on a threshold derived for interactions between GWA significant SNPs and the genome and jointly explaining 8.0% of the phenotypic variance in SUA levels (3.4% by interaction components). Epistasis signal replication in a CROATIAN population (n = 1772) was limited at the SNP level but improved dramatically at the gene ontology level. In addition, gene ontology terms enriched by the epistasis signals in each population support links between SUA levels and neurological disorders. We conclude that GWA epistasis analysis is useful despite relatively low power in small isolated populations.     

Rosetting in Plasmodium vivax: A Cytoadhesion Phenotype Associated with Anaemia

Background

Plasmodium vivax can potentially lead to life-threatening episodes but the mechanisms underlying severe disease remain poorly defined. Cytoadhesion of infected erythrocytes may contribute to P. vivax sequestration and organ injury although its physiological impact is still unknown. Here, we aimed to describe clinically-relevant cytoadhesive phenotypes of P. vivax isolates.

Methodology/Principal findings

Rosetting and adhesion to CSA, CD36, ICAM1, placental and brain cryosections were determined in P. vivax peripheral isolates from 12 pregnant women, 24 non-pregnant women and 23 men from Manaus (Brazil). P. falciparum co-infection was excluded by PCR and P. vivax isolates were genotyped by assessing the size polymorphism of microsatellites ms2, ms20 and msp1F3 through capillary electrophoresis of PCR products. P. vivax monoinfection was confirmed by PCR in 59 isolates, with 50 (85%) of them being single-clone infections. One P. vivax haplotype was more frequently found among pregnant women (33%) than in non-pregnant women (0%) and men (4%; p = 0.010). Rosetting was observed in 64% of the isolates, adhesion to CSA in 15%, to ICAM1 in 12% and to placental cryosections in 9%, being similar among pregnant and non-pregnant groups. Intensity of rosetting was higher among anaemic individuals compared to non-anaemic (p = 0.010) and decreased with increasing haematocrit (p = 0.033) and haemoglobin levels (p = 0.015).

Conclusions/Significance

P. vivax peripheral isolates from pregnant women do not exhibit a prominent adhesion to CSA, although other parasite phenotypes still unknown may increase the propagation of certain P. vivax clones observed among pregnant hosts. Rosetting is a frequent cytoadhesive phenotype in P. vivax infections that may contribute to the development of anaemia.     

Lack of Prophylactic Efficacy of Oral Maraviroc in Macaques despite High Drug Concentrations in Rectal Tissues

Maraviroc (MVC) is a potent CCR5 coreceptor antagonist that is in clinical testing for daily oral pre-exposure prophylaxis (PrEP) for HIV prevention. We used a macaque model consisting of weekly SHIV_162p3 exposures to evaluate the efficacy of oral MVC in preventing rectal SHIV transmission. MVC dosing was informed by the pharmacokinetic profile seen in blood and rectal tissues and consisted of a human-equivalent dose given 24 h before virus exposure, followed by a booster postexposure dose. In rectal secretions, MVC peaked at 24 h (10,242 ng/ml) with concentrations at 48 h that were about 40 times those required to block SHIV infection of peripheral blood mononuclear cells (PBMCs) in vitro. Median MVC concentrations in rectal tissues at 24 h (1,404 ng/g) were 30 and 10 times those achieved in vaginal or lymphoid tissues, respectively. MVC significantly reduced macrophage inflammatory protein 1β-induced CCR5 internalization in rectal mononuclear cells, an indication of efficient binding to CCR5 in rectal lymphocytes. The half-life of CCR5-bound MVC in PBMCs was 2.6 days. Despite this favorable profile, 5/6 treated macaques were infected during five rectal SHIV exposures as were 3/4 controls. MVC treatment was associated with a significant increase in the percentage of CD3⁺/CCR5⁺ cells in blood. We show that high and durable MVC concentrations in rectal tissues are not sufficient to prevent SHIV infection in macaques. The increases in CD3⁺/CCR5⁺ cells seen during MVC treatment point to unique immunological effects of CCR5 inhibition by MVC. The implications of these immunological effects on PrEP with MVC require further evaluation.     

Evaluación del efecto del sentido de coherencia en la carga percibida y en la adherencia a un programa psicoeducativo para cuidadores informales de personas dependientes

Introduction

The care of dependent persons is arduous, and requires time, energy, and physical effort on the part of caregivers. Personal characteristics, such as the sense of coherence (SOC), can influence the perceived burden and care giving.