Dados do Trabalho

Título

The frequent presence of deletions in the pfhrp2 and pfhrp3 genes in Plasmodium falciparum and high estimates of accuracy of RDTs: Implications for molecular surveillance and harmonization of protocols

Introdução

Malaria is an infectious disease caused by the parasite of the genus Plasmodium. Despite efforts to control the disease, 142,202 cases were recorded in 2023 in the country. Among the diagnostic techniques are routine microscopy, rapid diagnostic tests (RDTs) for detection of antigens from the pfhrp2/3 genes and Polymerase Chain Reaction (PCR). Disagreements between the results of RDTs and other techniques indicate a potential association with genetic variations in pfhrp genes of Plasmodium falciparum, which can affect the diagnosis, control and monitoring of malaria. Despite the WHO recommendation to monitor deletions in the pfhrp2/3 genes, this data is scarce in Brazil.  

Objetivo (s)

To analyze the genetic variations in P. falciparum and their respective impacts on the diagnosis of malaria through RDTs based on the detection of the HRP2 antigen.

Material e Métodos

The 51 participants positive for P. falciparum by qPCR included in this study were treated at the Centro de Pesquisa em Medicina Tropical de Rondônia (CEPEM-RO), during the period from July to September 2022. This study is approved by the CEP-CEPEM/CONEP system. The performance of three RDTs (RDT 1- SD BIOLINE Malaria Ag P.f, RDT 2- SD Bioline Malaria Ag Pf/Pv and RDT 3- SD BIOLINE Malaria Ag P.f/P.f/P.v), all of them approved by ANVISA, were analyzed separately by thick-film microscopy and qPCR (reference technique in this study). To analyze the implications of deletion in exon 2 of the pfhrp2 and pfhrp3 genes, fragments of ~700 base pairs were obtained by conventional PCR and the amplicons were subjected to Sanger Sequencing.  

Resultados e Conclusão

The positive diagnosis for P. falciparum by microscopy was observed for 37% of the participants (19/51), while for RDT 1 this estimate was noted for 94% (48/51), RDT 2 for 96% (49/51) and RDT 3 for 92% (47/51) of the positive cases. The presence of deletions observed in this study highlights the genetic variability of Plasmodium falciparum in the Rondônia population through the high frequency of deletion in pfhrp3 (94%; 48/51) and an important frequency for pfhrp2 (6%; 3/51). These frequencies are still different from previous estimates in the literature, ranging from 10% to 82% for pfhrp2 and 41% to 96% for pfhrp3. Additionally, the presence of numerous substitutions and/or deletion/insertion of amino acids not yet described in Brazil, with potential clinical implications in diagnosis and treatment, underscores the importance of epidemiological and molecular surveillance in Amazon region.

Palavras Chave

malária; Plasmodium falciparum; RDTs; Genetic variability; Surveillance.