Evidence for histidine-rich protein 2 immune complex formation in symptomatic patients in Southern Zambia

Markwalter, Christine F.; Mudenda, Lwiindi; Leelawong, Mindy; Kimmel, Danielle W.; Nourani, Armin; Mbambara, Saidon; Thuma, Philip E.; Wright, David W.

doi:10.1186/s12936-018-2400-8

Cited by 14 publications

(9 citation statements)

References 42 publications

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“…This finding contrast with other studies in Rwanda [ 28 ] and Zanzibar [ 29 ]. The possible explanation for these differences might be due to variation in transmission intensity [ 28 , 30 ], host immunogenic response [ 31 , 32 ], drug used [ 33 ], geographical locations [ 8 , 34 ], sample size, and laboratory methods [ 35 – 37 ] used to analyse pfhrp 2/3 genes deletions.…”

Section: Discussionmentioning

confidence: 99%

Detection of high prevalence of Plasmodium falciparum histidine-rich protein 2/3 gene deletions in Assosa zone, Ethiopia: implication for malaria diagnosis

Alemayehu

Blackburn

López

et al. 2021

Malar J

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Background Rapid diagnostic tests (RDTs) targeting histidine rich protein 2(HRP2) are widely used for diagnosis of Plasmodium falciparum infections. Besides PfHRP2, the PfHRP3 antigen contributes to the detection of P. falciparum infections in PfHRP2 RDTs. However, the performance HRP2-based RDT is affected by pfhrp2/3 gene deletions resulting in false-negative test results. The objective of this study was to determine the presence and prevalence of pfhrp2/3 gene deletions including the respective flanking regions among symptomatic patients in Assosa zone, Northwest Ethiopia. Methods A health-facility based cross-sectional study was conducted in febrile patients seeking a malaria diagnosis in 2018. Blood samples were collected by finger-prick for microscopic examination of blood smears, malaria RDT, and molecular analysis using dried blood spots (DBS) prepared on Whatman filter paper. A total of 218 P. falciparum positive samples confirmed by quantitative PCR were included for molecular assay of pfhrp2/3 target gene. Results Of 218 P. falciparum positive samples, exon 2 deletions were observed in 17.9% of pfhrp2 gene and in 9.2% of pfhrp3 gene. A high proportion of deletions in short segments of pfhrp2 exon1-2 (50%) was also detected while the deletions of the pfhrp3 exon1-2 gene were 4.1%. The deletions were extended to the downstream and upstream of the flanking regions in pfhrp2/3 gene (above 30%). Of eighty-six PfHRP2 RDT negative samples, thirty-six lacked pfhrp2 exon 2. Five PfHRP2 RDT negative samples had double deletions in pfhrp2 exon 2 and pfhrp3 exon2. Of these double deletions, only two of the samples with a parasite density above 2000 parasite/µl were positive by the microscopy. Three samples with intact pfhrp3 exon2 in the pfhrp2 exon2 deleted parasite isolates were found to be positive by PfHRP2 RDT and microscopy with a parasite density above 10,000/µl. Conclusion This study confirms the presence of deletions of pfhrp2/3 gene including the flanking regions. Pfhrp2/3 gene deletions results in false-negative results undoubtedly affect the current malaria control and elimination effort in the country. However, further countrywide investigations are required to determine the magnitude of pfhrp2/3 gene deletions and its consequences on routine malaria diagnosis.

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Section: Discussionmentioning

confidence: 99%

Detection of high prevalence of Plasmodium falciparum histidine-rich protein 2/3 gene deletions in Assosa zone, Ethiopia: implication for malaria diagnosis

Alemayehu

Blackburn

López

et al. 2021

Malar J

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“…The influence of preceding infections on cRDT sensitivity could be mediated by differential clearance rates of HRP2 by age, specifically here if HRP2 is cleared more rapidly in adults; this idea is supported by models indicating that HRP2 persistence after treatment is more prolonged in children than in adults, 33 but it is unclear if this observation is the result of higher starting densities in children. Alternatively, HRP2 may be rendered less detectable in adults by anti-HRP2 IgG, which can be present in measurable quantities in clinical samples 34 but are of uncertain diagnostic impact. 35 Because the PCR-estimated parasite prevalence was similar in adults to other age-groups and because these represent a large proportion of prevalent, likely transmissible infections, the low sensitivity in adults further renders cRDTs unsuitable as a tool by which to identify and treat infections, and thereby efficiently reduce transmission.…”

Section: Discussionmentioning

confidence: 99%

Direct Estimation of Sensitivity of Plasmodium falciparum Rapid Diagnostic Test for Active Case Detection in a High-Transmission Community Setting

Taylor

Sumner

Freedman

et al. 2019

The American Journal of Tropical Medicine and Hygiene

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Community-based active case detection of malaria parasites with conventional rapid diagnostic tests (cRDTs) is a strategy used most commonly in low-transmission settings. We estimated the sensitivity of this approach in a hightransmission setting in Western Kenya. We tested 3,547 members of 912 households identified in 2013-2014 by index children with (case) and without (control) cRDT-positive malaria. All were tested for Plasmodium falciparum with both a cRDT targeting histidine-rich protein 2 and with an ultrasensitive real-time polymerase chain reaction (PCR). We computed cRDT sensitivity against PCR as the referent, compared prevalence between participant types, and estimated cRDT detectability as a function of PCR-estimated parasite density. Parasite prevalence was 22.9% by cRDTs and 61.5% by PCR. Compared with children aged < 5 years or adults aged > 15 years, geometric mean parasite densities (95% CI) were highest in schoolage children aged 5-15 years (8.4 p/uL; 6.6-10.6). The overall sensitivity of cRDT was 36%; among asymptomatic household members, cRDT sensitivity was 25.5% and lowest in adults aged > 15 years (15.8%). When modeled as a function of parasite density, relative to school-age children, the probability of cRDT positivity was reduced in both children aged < 5 years (odds ratio [OR] 0.48; 95% CI: 0.34-0.69) and in adults aged > 15 years (OR: 0.35; 95% CI: 0.27-0.47). An HRP2-detecting cRDT had poor sensitivity for active P. falciparum case detection in asymptomatic community members, and sensitivity was lowest in highly prevalent low-density infections and in adults. Future studies can model the incremental effects of high-sensitivity rapid diagnostic tests and the impacts on transmission.

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“…On the other hand, type 2 repeat was absent in all isolates of PfHRP3 sequence in Ethiopia as well as other parts of Africa [29][30][31], but type 2 repeat has been reported in PfHRP3 in few isolates from Kenya [30] and India [32]. This variation observed in PfHRP2 and PfHRP3 repeat types might be due to differences in geographical and transmission settings [8,38,39], frequency of exposure of drug and level of immunity of study participants [40,41], clinical versus asymptomatic study participants, and methods used for molecular analysis. Interestingly, of all the novels repeat types identi ed in this study, 15 in PfHRP2 and 12 in PfHRP3 had not been reported elsewhere.…”

Section: Discussionmentioning

confidence: 99%

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

Alemayehu

Messele

López

et al. 2021

Preprint

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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.

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Evidence for histidine-rich protein 2 immune complex formation in symptomatic patients in Southern Zambia

Cited by 14 publications

References 42 publications

Detection of high prevalence of Plasmodium falciparum histidine-rich protein 2/3 gene deletions in Assosa zone, Ethiopia: implication for malaria diagnosis

Detection of high prevalence of Plasmodium falciparum histidine-rich protein 2/3 gene deletions in Assosa zone, Ethiopia: implication for malaria diagnosis

Direct Estimation of Sensitivity of Plasmodium falciparum Rapid Diagnostic Test for Active Case Detection in a High-Transmission Community Setting

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

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