Plasmodium falciparum Histidine-Rich Protein 2 Gene Variation in a Malaria-Endemic Area of Papua New Guinea.

Histidine-rich protein 2 of Plasmodium falciparum (PfHRP2) forms the basis of many current malaria rapid diagnostic tests (RDTs). It is concerning that there are parasites that lack part or all of the pfhrp2 gene, and thus do not express the PfHRP2 protein; such parasites are not identifiable by PfHRP2-detecting RDTs. Very limited information is available regarding pfhrp2 genetic variation in Papua New Guinea (PNG). In the present study, this gene variation was evaluated using 169 samples previously collected from the Wosera area in East Sepik Province of PNG. Molecular diagnosis of these samples showed that 81% were infected, and P. falciparum was present in 91% of those infected samples. One hundred and twenty samples were amplified for pfhrp2 exon-2, from which 12 randomly selected amplicons were sequenced, yielding 18 sequences, all of which were unique. Baker repeat type 2 × type 7 numbers ranged from 0 to 108. Epitope mapping analysis revealed that three major epitopes, DAHHAHHA, AHHAADAHHA, and AHHAADAHH, were present in high prevalence and frequencies. These major epitopes have been shown to be recognized by the monoclonal antibodies 3A4 and PTL-3 (DAHHAHHA), C1-13 (AHHAADAHHA), and S2-5 and C2-3 (AHHAADAHH). This study provides further information on the high genetic variation of pfhrp2 and its unclear relationship with prediction of RDT detection sensitivity, and identifies major epitopes in this gene from PNG. These results could be relevant and useful to understand the genetic diversity of this gene and the performance of current and future RDTs in this malarious region of the world.

Insights into the Performance of SD Bioline Malaria Ag P.f/Pan Rapid Diagnostic Test and Plasmodium falciparum Histidine-Rich Protein 2 Gene Variation in Madagascar.

Plasmodium falciparum histidine-rich protein 2 (PfHRP2) forms the basis of many current malaria rapid diagnostic tests (RDTs). However, the parasites lacking part or all of the pfhrp2 gene do not express the PfHRP2 protein and are, therefore, not identifiable by PfHRP2-detecting RDTs. We evaluated the performance of the SD Bioline Malaria Ag P.f/Pan RDT together with pfhrp2 variation in Madagascar. Genomic DNA isolated from 260 patient blood samples were polymerase chain reaction (PCR)-amplified for the parasite 18S rRNA and pfhrp2 genes. Post-PCR ligation detection reaction-fluorescent microsphere assay (LDR-FMA) was performed for the identification of parasite species. Plasmodium falciparum histidine-rich protein 2 amplicons were sequenced. Polymerase chain reaction diagnosis of patient samples showed that 29% (75/260) were infected and P. falciparum was present in 95% (71/75) of these PCR-positive samples. Comparing RDT and P. falciparum detection by LDR-FMA, eight samples were RDT negative but P. falciparum positive (false negatives), all of which were pfhrp2 positive. The sensitivity and specificity of the RDT were 87% and 90%, respectively. Seventy-three samples were amplified for pfhrp2, from which nine randomly selected amplicons were sequenced, yielding 13 sequences. Amplification of pfhrp2, combined with RDT analysis and P. falciparum detection by LDR-FMA, showed that there was no indication of pfhrp2 deletion. Sequence analysis of pfhrp2 showed that the correlation between pfhrp2 sequence structure and RDT detection rates was unclear. Although the observed absence of pfhrp2 deletion from the samples screened here is encouraging, continued monitoring of the efficacy of the SD Bioline Malaria Ag P.f/Pan RDT for malaria diagnosis in Madagascar is warranted.

Vitamin A status of pre-school-age children aged 6 to 59 months in the National Capital District, Papua New Guinea.

Assessing the vitamin A status among pre-school-age children is essential for evaluating the magnitude and public health status of vitamin A deficiency in a population. This cross-sectional study assessed the vitamin A status of children aged 6 to 59 months resident in the National Capital District (NCD), Papua New Guinea. Children attending the Children's Outpatient Clinic at Port Moresby General Hospital participated in this study. Informed consent was obtained from parents before using blood samples from their children. Assay of plasma retinol was carried out using the 'Clin-Rep' complete kit for assay of vitamins A and E in plasma by high performance liquid chromatography (HPLC). A commercial enzyme immunoassay kit was used to assay C-reactive protein (CRP) in plasma. Of the 132 children in the study 108 (82%) had received vitamin A capsules. The median plasma retinol concentration of the 132 children was 0.98 micromol/l and the interquartile range 0.65-1.38 micromol/l. Of the 132 children, 35 (27%) had a plasma retinol concentration below 0.70 micromol/l. 75 children (57%) had normal plasma CRP levels and in 57 (43%) the CRP levels were elevated. The median plasma retinol concentration of the children with normal plasma CRP was 1.19 micromol/l and the interquartile range 0.93-1.50 micromol/l. The prevalence of vitamin A deficiency (VAD) in the children with normal plasma CRP was 11%, indicating a moderate public health problem. 74 (56%) males and 58 (44%) females were included in the study. The prevalence of VAD in the male and female children with normal plasma CRP was 14% and 8%, respectively, indicating a moderate public health problem among the male children and a mild public health problem among the female children. The prevalence of subclinical (mild to moderate) and marginal VAD among the children with and without elevated CRP strongly suggests the need for continuous monitoring of the vitamin A status of the vulnerable groups in NCD.