Genetic variation of Plasmodium falciparum histidine-rich protein 2 and 3 in Assosa zone, Ethiopia: its impact on the performance of malaria rapid diagnostic tests

Background Rapid diagnostic tests (RDT) are commonly used for the diagnosis of malaria caused by Plasmodium falciparum. However, false negative results of RDT caused by genetic variation of P. falciparum histidine-rich protein 2 and 3 genes (pfhrp2/3) threaten existing malaria case management and control efforts. The main objective of this study was to investigate the genetic variations of the pfhrp2/3 genes. Methods A cross-sectional study was conducted from malaria symptomatic individuals in 2018 in Assosa zone, Ethiopia. Finger-prick blood samples were collected for RDT and microscopic examination of thick and thin blood films. Dried blood spots (DBS) were used for genomic parasite DNA extraction and molecular detection. Amplification of parasite DNA was made by quantitative PCR. DNA amplicons of pfhrp2/3 were purified and sequenced. Results The PfHRP2 amino acid repeat type isolates were less conserved compared to the PfHRP3 repeat type. Eleven and eight previously characterized PfHRP2 and PfHRP3 amino acid repeat types were identified, respectively. Type 1, 4 and 7 repeats were shared by PfHRP2 and PfHRP3 proteins. Type 2 repeats were found only in PfHRP2, while types 16 and 17 were found only in PfHRP3 with a high frequency in all isolates. 18 novel repeat types were found in PfHRP2 and 13 novel repeat types were found in PfHRP3 in single or multiple copies per isolate. The positivity rate for PfHRP2 RDT was high, 82.9% in PfHRP2 and 84.3% in PfHRP3 sequence isolates at parasitaemia levels > 250 parasites/µl. Using the Baker model, 100% of the isolates in group A (If product of types 2 × type 7 repeats ≥ 100) and 73.7% of the isolates in group B (If product of types 2 × type 7 repeats 50–99) were predicted to be detected by PfHRP2 RDT at parasitaemia level > 250 parasite/μl. Conclusion The findings of this study indicate the presence of different PfHRP2 and PfHRP3 amino acid repeat including novel repeats in P. falciparum from Ethiopia. These results indicate that there is a need to closely monitor the performance of PfHRP2 RDT associated with the genetic variation of the pfhrp2 and pfhrp3 gene in P. falciparum isolates at the country-wide level.

Genetic Variations of Plasmodium Falciparum Histidine-rich Protein 2 and 3 in Assosa Zone, Ethiopia: Its Impact on the Performance of Malaria Rapid Diagnostic Tests

Background: Rapid diagnostic tests (RDT) are commonly used for the diagnosis of Plasmodium falciparum malaria. However, false negative results of RDT caused by genetic variations of P. falciparum histidine-rich protein 2 and 3 genes (pfhrp2/3) threaten existing malaria case management and control efforts. The main objective of this study was to investigate the genetic variations of the pfhrp2/3 genes. Methods: A cross-sectional study was conducted from malaria symptomatic individuals in 2018 in Assosa zone, Ethiopia. Finger prick samples were collected for RDT and microscopic examination of thick and thin blood films. Dried blood spots (DBS) were used for genomic parasite DNA extraction and molecular detection. Amplification of parasite DNA was made by quantitative PCR. DNA amplicons of pfhrp2/3 were purified and sequenced. Results: The PfHRP2 repeat type isolates were less conserved compared to the PfHRP3 repeat type. A total of eleven and eight different PfHRP2 and PfHRP3 amino acid repeat types were identified, respectively. Type 1, 4 and 7 repeats were shared by PfHRP2 and PfHRP3 isolates. Type 2 repeats were found only in PfHRP2, while types 16 and 17 were found only in PfHRP3 with a high frequency in all isolates. 18 novel repeat types were found in PfHRP2 and 13 novel repeat types were found in PfHRP3 in single or multiple copies per isolate. The positivity rate for PfHRP2 RDT was high, 82.9% in PfHRP2 and 84.3 % in PfHRP3 sequence isolate at parasitemia levels >250 parasites/µl. Using the Baker model, 100 % of the isolates in group A and 73.7% of the isolates in group B were predicted to be detected by PfHRP2 RDT at parasitemia level> 250 parasite/μl. Conclusion: The findings of this study indicate the presence of different PfHRP2 and PfHRP3 amino acid repeat including novel repeats in P. falciparum from Ethiopia. These results indicate that there is a need to closely monitor the performance of PfHRP2 RDT associated with the genetic variation of the pfhrp2 and pfhrp3 gene in P. falciparum isolates at the country-wide level.

GFOGER Peptide Modifies the Protein Content of Extracellular Vesicles and Inhibits Vascular Calcification

ObjectiveVascular calcification (VC) is an active process during which vascular smooth muscle cells (VSMCs) undergo an osteogenic switch and release extracellular vesicles (EVs). In turn, the EVs serve as calcification foci via interaction with type 1 collagen (COL1). We recently showed that a specific, six-amino-acid repeat (GFOGER) in the sequence of COL1 was involved in the latter’s interaction with integrins expressed on EVs. Our main objective was to test the GFOGER ability to inhibit VC.ApproachWe synthesized the GFOGER peptide and tested its ability to inhibit the inorganic phosphate (Pi)-induced calcification of VSMCs and aortic rings. Using mass spectrometry, we studied GFOGER’s effect on the protein composition of EVs released from Pi-treated VSMCs.ResultsCalcification of mouse VSMCs (MOVAS-1 cells), primary human VSMCs, and rat aortic rings was lower in the presence of GFOGER than with Pi alone (with relative decreases of 66, 58, and 91%, respectively; p < 0.001 for all) (no effect was observed with the scramble peptide GOERFG). A comparative proteomic analysis of EVs released from MOVAS-1 cells in the presence or absence of Pi highlighted significant differences in EVs’ protein content. Interestingly, the expression of some of the EVs’ proteins involved in the calcification process (such as osteogenic markers, TANK-binding kinase 1, and casein kinase II) was diminished in the presence of GFOGER peptide (data are available via ProteomeXchange with identifier PXD018169∗). The decrease of osteogenic marker expression observed in the presence of GFOGER was confirmed by q-RT-PCR analysis.ConclusionGFOGER peptide reduces vascular calcification by modifying the protein content of the subsequently released EVs, in particular by decreasing osteogenicswitching in VSMCs.

Plasmodium falciparum histidine-rich protein 2 (PfHRP2) diversity in Ghana

Background: In the absence of microscopy, Plasmodium falciparum histidine-rich proteins 2 (PfHRP2)-based rapid diagnostic tests (RDTs) are recommended for the diagnosis of falciparum malaria, particularly in endemic regions. However, genetic variability of the PfHRP2 gene threatens the usefulness of the test. This study aimed to investigate the diversity of PfHRP2 in malaria cases among children in Ghana.Methods: A cross-sectional study was conducted at the Adidome Government Hospital in the Volta Region of Ghana. A total of 50 children with mean age of 6.6±3.5 years and diagnosed of falciparum malaria were included. Blood samples were collected for complete blood count, malaria parasite identification and counting. DNA samples were amplified and sequenced. Nucleotide sequences were translated in silico to corresponding amino acids and the deduced amino acids sequences were analyzed for diversity.Results: The number of repeats and number of each repeat within PfHRP2 varied between isolates. Twelve rare PfHRP2 repeat types, two of which are previously unreported, were identified in this study. Our HRP2 sequence shared high similarity with isolates from Kenya. Using Baker’s regression model, Group B was the highest occurring type (58.0%). Screening of all sequences for epitopes recognized by PfHRP2-specific monoclonal antibodies (mAbs), we found the predominant motif to be AHHAADAHH, which is recognized by the C1-13 mAbs.Conclusion: This study reports diversity of P. falciparum histidine-rich proteins 2 in samples from Ghanaian children with symptomatic malaria. We highlight the existence of extra amino acid repeat types which adds to the PfHRP2 antigenic variability. The findings of this study will contribute to the understanding of the performance of PfHRP2-based RDTs in the Ghanaian setting.