Prevalence of HRP2/3 Gene Deletion in Plasmodium falciparum Parasites in Abuja, Nigeria

Abstract

Purpose: Histidine Rich Protein 2 (HRP2) rapid diagnostic tests (RDTs) have been widely used for malaria diagnosis in Nigeria, the single most heavily malaria-burdened country in the world. Some countries have reported HRP2 gene deletion as a contributor to false negative HRP2 RDT results, however there is a dearth of research on HRP2 gene deletions in Nigeria. This study estimated the prevalence of Plasmodium falciparum (HRP2/ HRP3) gene deletions among symptomatic P. falciparum patients with false-negative HRP2 RDT results in Abuja, Nigeria. Methods & Materials: This was a cross-sectional study, in which malaria microscopy and RDT were carried out on 370 patients with clinical symptoms of malaria. Performance of HRP2 RDT was compared to microscopy. Samples that gave false negative results to the RDT were analysed using 18SrRNA PCR to confirm the presence of P. falciparum. All samples positive to 18SrRNA PCR were subjected to HRP2 and 3 genotyping, merozoite surface protein 1 and 2 (msp1 and msp2) gene amplification using high resolution melt analysis and PgMET qPCR assay. True HRP2/HRP3 gene deletion was confirmed if samples negative to HRP2 genotyping were positive to msp 1 and 2 genes, and qPCR gave parasitaemia of ≥ 200 p/µl, which is the limit of detection of HRP2 RDTs. Genetic variation was explored in 20 samples without HRP2/3 gene deletion by sequencing the HRP2 Exon 2 gene. Results: Seventy-five RDTs gave false negatives results, 66/75 were confirmed to be P. falciparum using the 18SrRNA PCR. The HRP 2 and 3 gene deletion was confirmed in 5.3 % (4/75) and 1.33 % (1/75) samples, respectively. There was 1.33 % (1/75) double deletion of HRP2 and 3 in one sample. Therefore, the prevalence of HRP2 and 3 gene deletion among the 75 false negative RDT results was 7.96 % (6/75). Genomic sequencing showed no gene variations. Conclusion: The HRP2/3 gene deletion was present in 7.96 % of P. falciparum samples that gave false negative results. There is need to carry out a large-scale study to determine the true prevalence and diagnostic significance of these deletions.