Circulating antibodies against Plasmodium falciparum histidine-rich proteins 2 interfere with antigen detection by rapid diagnostic tests

Abstract

BackgroundRapid diagnostic tests (RDTs) for detection of Plasmodium falciparum infection that target P. falciparum histidine-rich protein 2 (PfHRP2), a protein that circulates in the blood of patients infected with this species of malaria, are widely used to guide case management. Understanding determinants of PfHRP2 availability in circulation is therefore essential to understanding the performance of PfHRP2-detecting RDTs.MethodsThe possibility that pre-formed host anti-PfHRP2 antibodies may block target antigen detection, thereby causing false negative test results was investigated in this study.ResultsAnti-PfHRP2 antibodies were detected in 19/75 (25%) of plasma samples collected from patients with acute malaria from Cambodia, Nigeria and the Philippines, as well as in 3/28 (10.7%) asymptomatic Solomon Islands residents. Pre-incubation of plasma samples from subjects with high-titre anti-PfHRP2 antibodies with soluble PfHRP2 blocked the detection of the target antigen on two of the three brands of RDTs tested, leading to false negative results. Pre-incubation of the plasma with intact parasitized erythrocytes resulted in a reduction of band intensity at the highest parasite density, and a reduction of lower detection threshold by ten-fold on all three brands of RDTs tested.ConclusionsThese observations indicate possible reduced sensitivity for diagnosis of P. falciparum malaria using PfHRP2-detecting RDTs among people with high levels of specific antibodies and low density infection, as well as possible interference with tests configured to detect soluble PfHRP2 in saliva or urine samples. Further investigations are required to assess the impact of pre-formed anti-PfHRP2 antibodies on RDT performance in different transmission settings.Electronic supplementary materialThe online version of this article (doi:10.1186/1475-2875-13-480) contains supplementary material, which is available to authorized users.

Development of an Immunosensor for PfHRP 2 as a Biomarker for Malaria Detection

“…The sensitivity and reproducibility of the sensors in this assay are shown to be adequate for the detection of the malaria biomarker, since a blood level of ~ 9.45 ng∙mL −1 has been reported to be Plasmodium sp. specific and malaria positive [ 38 , 39 , 40 ].…”

Malaria surveys using rapid diagnostic tests and validation of results using post hoc quantification of Plasmodium falciparum histidine-rich protein 2

“…Third, characteristics of the host and parasite population could affect the RDT performance. Heterogeneity in HRP2 size (and epitope number) has been widely hypothesized to play a role in reliability of RDT tests [ 15 – 17 ], but the variables of Pfhrp2 transcription levels [ 18 ] and host antibodies [ 19 ] may also affect field test results. Additionally, direct comparison of the RDT LODs estimated here among populations in separate surveys is limited due to inherent differences in filter paper, collection and storage procedures.…”

Plasmodium falciparum histidine rich protein-2 diversity and the implications for PfHRP 2: based malaria rapid diagnostic tests in Ghana

“…The accuracy of malaria RDT results can be affected by test antibody stability, product design and quality as well as the transport and storage conditions of the kits and sample parasite density [ 10 ]. Accurate diagnosis of malaria by PfHRP-2 RDT kits can be affected by the pfhrp 2 and or pfhrp 3 genotype of the parasite [ 5 , 10 , 11 ], the amount of PfHRP-2 antigen produced by the parasite [ 12 , 13 ] as well as the longevity of PfHRP-2 antigen after parasite clearance. One major obstacle in the diagnosis of malaria by RDT, without additional confirmation of parasitaemia is false positive test results, which leads to the unnecessary administration of anti-malarial drugs when no malaria parasites are actually present in the patient.…”