Evaluation of Plasmodium falciparum Histidine-Rich Protein 2 and 3 gene deletions in Kenya
Martha Nginya1,2, Brenda Makena 1,2, Marcel Nyambute1, Charles Okello1 Edwin Mwakio1, Gladys Chemwor1, Raphael Okoth1, Redemptah Yeda1, Agnes Cheruiyot1, Benjamin Opot1, Dennis Juma1, Victor Mobegi2, Hosea Akala1, Ben Andagalu1
1United States Army Medical Research Directorate-Kenya (USAMRD-K), Kenya Medical Research Institute (KEMRI); 2Centre for Biotechnology and Bioinformatics (CEBIB). The University of Nairobi, Nairobi, Kenya
The accuracy of Plasmodium falciparum Histidine-rich protein 2 (PfHRP2) based rapid diagnostic kits (RDTs) that accounts for 74% malaria tests globally is impaired by either deletion in HRP2 gene or cross-reaction with HRP3 antibodies. The WHO criteria that require greater than 95% accuracy as the threshold for selection of RDTs argue for active mapping of the distribution of PfHRP2 deletions. This is part of an on-going surveillance study with the aim of determining frequency and trends of PfHRP2 and PfHRP3 gene deletions in four malaria transmission regions of Kenya. The study will characterize 350 samples collected between 1998 and 2018 from Kisumu, Kisii, Kombewa, Kericho and Malindi regions in Kenya to assess the frequency of PfHRP2 and PfHRP3 gene deletion. Each sample will be diagnosed by microscopy, RDT and PCR. DNA will be extracted; PCR positive samples will be sequenced using Sanger sequencing platform, aligned to the 3D7 reference for detection of deletions. Additionally, the twelve neutral microsatellites markers will be amplified for characterizing parasites population structure using GeneAlex analysis program. Preliminary findings detection of 218 of the 357 enrolled so far are positive by microscopy and PCR. 31(14%) of these positive samples are negative by PfHRP2 based RDT. Molecular analysis is on-going for the positive samples and Enrolment of the 2018 samples is on course for analysis of trends. Findings will be essential to the World Health Organisation (WHO) in deciding the relevance of continued deployment of PfHRP2 based RDTs across Kenya. Additionally, temporal analyses and population structure determination will verify the role of evolution in the distribution of the PfHRP2 and PfHRP3 aberrant genotype.
Funding: Armed Forces Health Surveillance Branch (AFHSB) and Developing Excellence in Leadership and Genetics Training for Malaria Elimination in Sub-Africa (DELGEME)