Dynamics of Plasmodium species and genotype diversity in adults with asymptomatic infection in Gabon

OBJECTIVES

We investigated the diversity and dynamics of Plasmodium infection in serially collected samples from asymptomatic participants of a clinical trial assessing the efficacy and safety of ivermectin in Gabon. We checked whether the baseline sample reflected the P. falciparum genotype and Plasmodium species diversity seen over 7 days of follow-up.

METHODS

Blood samples were collected at inclusion, every 8 hours until hour 72, daily until day 7, and on day 14. Plasmodium species was determined by qPCR and pfmsp1 length polymorphism was assessed for P. falciparum genotyping.

RESULTS

In 17/48 (35%) individuals, all pfmsp1 genotypes identified during the assessed period were detected at baseline; in 31/48 (65%), new genotypes were found during follow-up. Additional sampling at hour 24 allowed the identification of all genotypes seen over 7 days in 50% of the individuals. Ivermectin did not impact the genotype dynamics. Mixed Plasmodium spp. infections were detected in 28/49 (57%) individuals at baseline, and detection of non-falciparum infections during follow-up varied.

CONCLUSIONS

Our results reveal complex intra-host dynamics of P. falciparum genotypes and Plasmodium species and underscore the importance of serial sampling in clinical trials for antimalarial drugs with asymptomatically P. falciparum-infected individuals. This might allow a more accurate identification of genotypes in multiple infections, impacting the assessment of drug efficacy.

Whole genome analysis of two sympatric human Mansonella: Mansonella perstans and Mansonella sp "DEUX"

Introduction

Mansonella species are filarial parasites that infect humans worldwide. Although these infections are common, knowledge of the pathology and diversity of the causative species is limited. Furthermore, the lack of sequencing data for Mansonella species, shows that their research is neglected. Apart from Mansonella perstans, a potential new species called Mansonella sp "DEUX" has been identified in Gabon, which is prevalent at high frequencies. We aimed to further determine if Mansonella sp "DEUX" is a genotype of M. perstans, or if these are two sympatric species.

Methods

We screened individuals in the area of Fougamou, Gabon for Mansonella mono-infections and generated de novo assemblies from the respective samples. For evolutionary analysis, a phylogenetic tree was reconstructed, and the differences and divergence times are presented. In addition, mitogenomes were generated and phylogenies based on 12S rDNA and cox1 were created.

Results

We successfully generated whole genomes for M. perstans and Mansonella sp "DEUX". Phylogenetic analysis based on annotated protein sequences, support the hypothesis of two distinct species. The inferred evolutionary analysis suggested, that M. perstans and Mansonella sp "DEUX" separated around 778,000 years ago. Analysis based on mitochondrial marker genes support our hypothesis of two sympatric human Mansonella species.

Discussion

The results presented indicate that Mansonella sp "DEUX" is a new Mansonella species. These findings reflect the neglect of this research topic. And the availability of whole genome data will allow further investigations of these species.

Molecular Epidemiology of Mansonella Species in Gabon

Mansonella perstans, a filarial nematode, infects large populations in Africa and Latin America. Recently, a potential new species, Mansonella sp "DEUX," was reported. Carriage of endosymbiotic Wolbachia opens treatment options for Mansonella infections. Within a cross-sectional study, we assessed the prevalence of filarial infections in 834 Gabonese individuals and the presence of the endosymbiont Wolbachia. Almost half of the participants (400/834 [48%]) were infected with filarial nematodes, with Mansonella sp "DEUX" being the most frequent (295/400 [74%]), followed by Loa loa (273/400 [68%]) and Mansonella perstans (82/400 [21%]). Being adult/elderly, male, and living in rural areas was associated with a higher risk of infection. Wolbachia carriage was confirmed in M. perstans and Mansonella sp "DEUX." In silico analysis revealed that Mansonella sp "DEUX" is not detected with currently published M. perstans-specific assays. Mansonella infections are highly prevalent in Gabon and might have been underreported, likely also beyond Gabon.

Monitoring the threatened utility of malaria rapid diagnostic tests by novel high-throughput detection of Plasmodium falciparum hrp2 and hrp3 deletions: A cross-sectional, diagnostic accuracy study

Background

Plasmodium falciparum deficient for hrp2 and hrp3 genes are a threat to malaria management and elimination, since they escape widely used HRP2-based rapid diagnostic tests and treatment. Hrp2/hrp3 deletions are increasingly reported from all malaria endemic regions but are currently only identified by laborious methodologies.

Methods

We developed a novel hydrolysis probe-based, quantitative, real-time PCR (4plex qPCR) for detection and discrimination of P. falciparum infection (cytb) and hrp2 and hrp3 gene status, and to control assay validity (btub). A cross-sectional, diagnostic accuracy study was performed in Gabon for assay validation and deletion screening.

Findings

In parallel to identification of P. falciparum infection in samples down to 0.05 parasites/µl, the 4plex qPCR enabled specific and valid interrogation of the parasites´s hrp2 and hrp3 genes in one go - even in low parasitemic samples. The assay was precise and robust also when performed in a routine healthcare setting in Gabon. The risk of falsely identifying hrp2 or hrp3 deletion was reduced by 100-fold compared to conventional PCR. Evaluation against microscopy was performed on 200 blood samples collected in Gabon: sensitivity and specificity of 4plex qPCR (cytb) were 100% and 80%, respectively. Stringent testing revealed hrp2 deletion in 2 of 95 P. falciparum positive and validated samples.

Interpretation

The novel 4plex qPCR is sensitive, accurate and allows resource-efficient rapid screening. Monitoring and mapping of hrp2/hrp3 deletions is required to identify areas where control strategies may need to be adapted to ensure appropriate patient care and ultimately achieve malaria elimination.

Funding

BMBF (03VP00402).

Cellular Vesicles: New Insights in Engineering Methods, Interaction with Cells and Potential for Brain Targeting

Cellular vesicles (CVs) have been proposed as alternatives to exosomes for targeted drug delivery. CVs, prepared from human embryonic kidney 293 cells (HEK-293), C57BL/6 mouse B16F10 skin melanoma cells (B16F10), and immortalized human cerebral microvascular endothelial cells (hCMEC/D3) by liposome technology methods, were characterized for morphology, cytotoxicity, and cell uptake properties. CV brain-targeting potential was evaluated in vitro on the hCMEC/D3 blood-brain barrier (BBB) model, and in vivo/ex vivo. CV sizes were between 135 and 285 nm, and the ζ-potential was negative. The dehydration-rehydration method conferred highest calcein loading and latency to CVs compared with other methods. The increased calcein leakage from CVs when compared with liposomes indicated their poor integrity, which was increased by pegylation. The in vivo results confirmed lower liver uptake by PEG-CVs (compared with nonpegylated) proving that the calcein integrity test is useful for prediction of CV biodistribution, as used for liposomes. The cell uptake of homologous origin CVs was not always higher compared with that of non-homologous. Nevertheless, CVs from hCMEC/D3 demonstrated the highest BBB permeability (in vitro) compared with OX-26 targeted liposomes, and brain localization (in vivo). CVs from hCMEC/D3 cells grown in different media demonstrated decreased interaction with brain cells and brain localization. Significant differences in proteome of the two latter CV types were identified by proteomics, suggesting a potential methodology for identification of organotropism-determining CV components.

[The dural arteriovenous fistula - an unimposing morphological correlate with imposing consequences]

Dural arteriovenous fistulas (DAVFs) are abnormal arteriovenous shunts located within the dura mater representing approximately 10 - 15 % of all arteriovenous shunts in the central nervous system. The aetiology of spontaneous DAVFs remains to be elucidated. The symptoms associated with DAVFs can be highly variable and dependent upon the direction of the blood flow, the amount of arteriovenous shunting and the specific location of the fistula. Considering the diversity of clinical presentation in the setting of unremarkable imaging results, diagnosing a DAVF can be difficult. To avoid permanent neurological deficits due to DAVFs, it is important to consider the possibility of a DAVF whenever one encounters unclear neurological symptoms and to initiate appropriate diagnostic procedures including intraarterial DSA and MRI/MRA. The current DAVF classification accounts for the disparity of clinical symptoms, therapeutic/interventional implications as well as vital complications depending on each particular fistula subtype. While type I DAVFs drain anterogradely into a cerebral sinus and mainly cause functional deficits, the risk for severe intracerebral bleeding increases when DAVFs drain retrogradely (type II), or into cortical (types III and IV), perimedullar or radiculo-medullar veins (type V), respectively. In particular in the case of type IIb to V DAVFs, the appropriate treatment option is a complete fistula occlusion by transvenous embolization, transarterial glue or particulate embolization or surgery. In the following we systematically explain the differential anatomy underlying DAVFs and discuss possible symptoms and necessary diagnostic and therapeutic means. In that, we are seeking to increase attention for this rare, but clinically relevant neurological disease.

Automatic sleep-wake scoring in the rat on microcomputer APPLE II

An automatic scoring system in real time of sleep-wake behavior in the rat was elaborated on microcomputer APPLE II. Four electrophysiological recording channels were used to distinguish seven behavioral states. Because the rat shows behavioral stages which are short-lasting, the analysis is performed second by second. It is based on the detection of the signal energy in specific frequency bands. The percentage of time passed in each stage is computed every 15 min, 1 h, 6 h and 24 h, the analysis extending during several days without interruption. The data are also printed out in a listing in real time and histograms in batch mode. Because of the interindividual differences, a calibration is needed. It is performed with a program in batch mode which allows an adjustment of parameters of determination from given specific digitized sequence in each rat. The accuracy of the automatic method was tested by the C contingency test, the theoretical maximal level being at 0.93: the intra- and inter-researchers contingency was 0.89, that between researchers and the computer was 0.85.

Electroencephalographic recordings during parachute jump sessions

Electroencephalographic (EEG) recordings of experienced parachutists were done by means of telemetry before, during, and after jumps of up to 3500m. During free-fall and after stabilization, alpha rhythm was recorded from several alpha reactive subjects when they closed their eyes. No pathological EEG recordings were obtained during the different phases of the jump.

[Radiotelemetric study of heart rate and electroencephalogram during parachute jumping (author's transl)]

Twelve subjects, experienced parachutists, have been recorded by telemetry before, during and after free-fall parachute jumps. The heart rate showed a statistically significant tachycardia during the different events of the jump (exit, free-fall, opening, open parachute and landing) compared to the baseline before boarding the aircraft. This tachycardia indicates a stress reaction confirmed by a significant increase of adrenalin and noradrenalin in urine. The electroencephalographic invesitgation does not show any adnormalities. Alpha rhythms have been recorded from alpha reactive subjects during free-fall stabilization.