Biology subjects

Hosch, S.

Publications and source records attributed to Hosch, S..

3 recordsLinked to original sources

bioRxiv2023

Comparison of different genotyping techniques to distinguish recrudescence from new infection in studies assessing the efficacy of antimalarial drugs against Plasmodium falciparum

Distinguishing recrudescence from new infections is crucial for the assessment of antimalarial drug efficacy against Plasmodium falciparum (P. falciparum). Different genotyping methods are used and may impede the comparison of drug efficacy estimates in space and time, particularly in patients from high transmission settings with polyclonal infections. We compared five different genotyping methods currently used to assess their sensitivity in detecting minority clones in polyclonal infections, their robustness, and the genetic diversity of the markers used. Our study utilized four well-characterized P. falciparum laboratory strains mixed in varying ratios, and 20 paired patient samples collected from a clinical trial. We found that high-resolution capillary electrophoresis (H-CE) using length-polymorphic markers, as well as targeted amplicon deep sequencing (TADS) using single nucleotide polymorphism (SNP)-rich markers, revealed the highest sensitivity in detecting minority clones, while also exhibiting robustness, and high genetic diversity in the used markers. Moreover, markers used by TADS gave more consistent results. We observed that microsatellites had a lower genetic diversity compared to markers such as msp1, msp2, glurp and SNP-rich markers, with some genotypes having allelic frequencies of > 30 %. The replacement of glurp by microsatellites did not result in a change in the genotyping outcome, probably due to the lower genetic diversity of microsatellites used in comparison to glurp. More studies with large sample sizes are necessary to identify the most suitable microsatellites that could replace glurp as per the latest recommendations from the World Health Organization (WHO) on genotyping to distinguish recrudescence from new infections in high transmission settings. Our study indicates that TADS should be considered the gold standard for genotyping to differentiate recrudescence from new infection and should be used to validate other techniques.

molecular biology↗

bioRxiv2021

The superior salinity tolerance of wheat cultivar Shanrong No. 3 cannot be attributed to elevated Ta-sro1 poly(ADP-ribose) polymerase activity

Saline soils limit the production of important staple crops such as wheat, particularly in arid and semiarid regions. Salt tolerance is a multi-gene trait and this complicates breeding of wheat varieties that deliver high yields under saline soil conditions. Notably, the elevated salinity tolerance of wheat cultivar Shanrong No. 3 (SR3) has been linked to a specific proteoform of the wheat SIMILAR TO RCD1 ONE (SRO1) protein that was created in an asymmetric genome hybridization with tall wheat grass. The two amino acid polymorphisms of the Ta-sro1 proteoform enhance the poly(ADP-ribose) polymerase (PARP) activity of the protein suggesting that altered poly-ADP-ribosylation of unknown substrate proteins or nucleic acids underlie the elevated salinity tolerance of cultivar SR3. To elucidate the molecular basis for the elevated PARP activity of the Ta-sro1 proteoform we solved a crystal structure of the catalytic PARP domain. Surprisingly, the structure revealed that the postulated binding site for the co-substrate NAD+ substantially differs from the structurally conserved NAD+ binding sites of canonical PARP enzymes. Consistently, we find that Ta-sro1 does not bind NAD+ and lacks ADP-ribosyltransferase activity. Therefore, although the structure revealed that one of the polymorphic amino acids is located close to the proposed active site, the elevated salinity tolerance of cultivar SR3 cannot be explained by altered ADP-ribosyltransferase activity of Ta-sro1.

plant biology↗

bioRxiv2021

Analysis of nucleic acids extracted from rapid diagnostic tests reveals a significant proportion of false positive test results associated with recent malaria treatment

Surveillance programs often use malaria rapid diagnostic tests (RDTs) to determine the proportion of the population carrying parasites in their peripheral blood to assess the malaria transmission intensity. Despite an increasing number of reports on false-negative and false-positive RDT results, there is a lack of systematic quality control activities for RDTs deployed in malaria surveillance programs. Our study provides a larger scale comparative evaluation of RDTs used in the 2018 Malaria Indicator Survey (MIS) conducted on Bioko Island, Equatorial Guinea. We conducted a molecular analysis by extraction of nucleic acids from 1,800 negative and 1,065 positive RDTs followed by qPCR analysis. These results were combined with a dataset collected in a comprehensive questionnaire from each MIS participant. Of the 2,865 RDTs that were collected in 2018 on Bioko Island and analysed in our study, 4.7% had a false-negative result. These false-negative RDT results were associated with low parasite density infections. In a substantial proportion of samples, we identified masked pfhrp2 and pfhrp3 gene deletions in which at least one P. falciparum strain carried a gene deletion. Among all positive RDTs analysed, 28.4% were tested negative by qPCR and therefore considered to be false-positive. Analysing the questionnaire data collected from the participants, this high proportion of false-positive RDT results could be explained by PfHRP2 antigen persistence after recent malaria treatment. We conclude that malaria surveillance depending solely on RDTs needs well-integrated quality control procedures assessing the extend and impact of reduced sensitivity and specificity of RDTs on malaria control programs.

microbiology↗