Individuals living in a malaria-endemic area of Cameroon do not have an acquired antibody response to Plasmodium falciparum histidine-rich protein 2

Malaria Journal

Research

Isabella A. Quakyi¹  Diane Wallace Taylor²  Naveen Bobbili²  Rose G. F. Leke³  Vedbar S. Khadka⁴ 

[1] Department of Biological, Environmental and Occupational Health Sciences, School of Public Health, College of Health Sciences, University of Ghana, P.O. Box LG 13, Legon, Accra, Ghana;Department of Tropical Medicine, Medical Microbiology and Pharmacology, John A. Burns School of Medicine, University of Hawaii at Manoa, 561 Ilalo Street, 96813, Honolulu, HI, USA;Faculty of Medicine and Biomedical Sciences, Biotechnology Center, University of Yaoundé I, Yaoundé, Cameroon;Office of Biostatistics & Quantitative Health Sciences, John A. Burns School of Medicine, University of Hawaii at Manoa, 561 Ilalo Street, 96813, Honolulu, HI, USA;

关键词: Plasmodium falciparum;    Malaria;    Diagnosis;    Rapid diagnostic tests;    Histidine-rich protein II;    HRP2;    HRP-II;    Antibodies;   

DOI  :  10.1186/s12936-017-1704-4

 received in 2016-11-29, accepted in 2017-01-19,  发布年份 2017

来源: Springer

【 摘 要 】

BackgroundDiagnosis of Plasmodium falciparum is often based on detection of histidine-rich protein 2 (HRP2) in blood. Most HRP2-based assays have high sensitivity and specificity; however, authors have suggested that antibodies (Ab) to HRP2 could reduce assay sensitivity. This study sought to characterize the antibody response to HRP2 with respect to prevalence, class, subclass, affinity, and age distribution in Cameroonian children and adults residing in an area with high P. falciparum transmission.MethodsPlasma samples from 181 Cameroonian children and adults who had been repeatedly exposed to P. falciparum and 112 samples from American adults who had never been exposed were tested for IgG Ab to HRP2. For comparison, Ab to the merozoite antigens MSP1, MSP2, MSP3 and the pregnancy-associated antigen VAR2CSA were measured using a multiplex bead-based assay. In addition, 81 plasma samples from slide-positive individuals were screened for IgM Ab to HRP2.ResultsAs expected, children and adults had IgG Ab to MSP1, MSP2 and MSP3, antibody levels increased with age, and only women of child-bearing age had Ab to VAR2CSA; however, no convincing evidence was found that these individuals had an acquired antibody response to HRP2. That is, using two sources of recombinant HRP2, identical results were obtained when plasma from 110 Cameroonian adults and 112 US adults were screened for IgG Ab. Further studies showed that antibody prevalence and levels did not increase with age in Cameroonians between ages 5 and >80 years. Although a few samples from slide-positive Cameroonians had IgM values slightly above the American cut-off, it was unclear if the individuals had a true IgM response to HRP2 or if the values were due to non-specific binding from elevated immunoglobulin levels associated with infection. Data from prediction models showed a paucity of Class II T cell epitopes in HRP2.ConclusionsThese data support the conclusion that most individuals in malaria-endemic areas do not produce an acquired humoral response to HRP2. The absence of Ab helps explain why HRP2-based assays are able to detect nanogram amounts of HRP2 and why HRP2 continues to circulate for a long time after parasite clearance.

【 授权许可】

CC BY   
© The Author(s) 2017