Genetic variability of Plasmodium falciparum histidine-rich proteins 2 and 3 in Central America

Abstract

BackgroundMalaria is an important disease in many tropical countries. Rapid diagnostic tests (RDTs) are valuable tools for diagnosing malaria in remote areas. The majority of RDTs used for the diagnosis of Plasmodium falciparum are based on the detection of the specific histidine-rich proteins (PfHRP2 and PfHRP3). During the last decade, the threat posed by the lack of expression of these antigens and the variability of the proteins on the diagnosis of malaria has been widely discussed. The aim of this study was to evaluate the genetic diversity of pfhrp2 and pfhrp3 of P. falciparum isolates collected in three Central American countries.MethodsDNA samples were amplified and sequenced to assess the diversity of nucleotides and amino acids. A search for known epitopes within the amino acid sequence was carried out, and the sensitivity of the sequences was evaluated according to a predictive model. A phylogenetic analysis was carried out including homologous sequences from different regions of the world. Protein structures were predicted in silico.ResultsFive different patterns for PfHRP2 and one pattern for PfHRP3 were identified. Isolates from Central America show a high level of genetic diversity in pfhrp2; however, the amino acid sequences seem to contain enough motifs to be detected by the RDTs currently available.ConclusionIt is unlikely that the variability of the pfhrp2 and pfhrp3 genes has a significant impact on the ability of the RDTs to detect the PfHRP antigens in Central America.Electronic supplementary materialThe online version of this article (10.1186/s12936-019-2668-3) contains supplementary material, which is available to authorized users.

Plasmodium falciparum histidine-rich protein 2 (PfHRP2) diversity in Ghana

“…All other repeat types were found in over 90% of the isolates. These findings are consistent with previous reports from other countries [18,20,28,[30][31][32].…”

“…We did not detect the AYAHHAHHAAY motif in our isolates and HAHHAHHAADAHH occurred at a lower frequency. This is consistent with recent reports by Fontecha et al [28] and Willie et al [37] and corroborates with an earlier report by Lee et al that RDTs which employ the C2-3 and Genway mAbs are less sensitive [29].…”

“…However, some repeat organizations were shared between isolates. Most of our sequences started with type 1 and all terminated with type 12 as is consistent with previous studies [18][19][20]28]. Additionally, a semiconserved PfHRP2 repeat type motif (types 2, 3, 5, 7, 8, 2 and 7) and partial repeat motif (types 7, 8, 2 and 7) were found in about half and a quarter of our isolates, respectively.…”

“…Nucleotide sequences were translated in silico to corresponding amino acids using the correct open reading frame. Amino acid repeats were numerically coded based on previous reports [16,18,28]; the frequencies and percentages of each amino acid repeat were estimated. To compare amino acid sequences in this study with previously published data, we performed a protein-protein BLAST (BLASTP) analysis of our sequences with those in the GenBank database at the NCBI.…”

One-step PCR: A novel protocol for determination of pfhrp2 deletion status in Plasmodium falciparum

“…Reporting the presence or absence of just exon 1, or just exon 2 is commonplace, but this is not always informative enough [36,40]. While exon 1 includes the signal peptide and could indicate if protein is expressed [49], exon 2 contains the highly variable region with repeat types 2 and 7 that are targeted by RDT monoclonal antibodies. Reporting on presence of both exons can therefore indicate if HRP2 will be expressed and therefore if that particular strain would be expected to be detected by RDTs.…”