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Girgis, S. T.

Publications and source records attributed to Girgis, S. T..

2 recordsLinked to original sources

De novo assembly of complete Plasmodium falciparum isolate genomes using PacBio HiFi sequencing technology

Plasmodium falciparum possesses a highly structured genome with extensive sequence diversity concentrated in Variant Surface Antigen (VSA) families. These genes--var, rif, and stevor--play key roles in immune evasion and pathogenesis and are difficult to assemble using short-read sequencing technologies. Here, we applied PacBio HiFi long-read sequencing to generate high-quality de novo genome assemblies from 43 P. falciparum parasite cultures originating from community cases in The Gambia. Parasites were culture-adapted, cloned by limiting dilution where possible, and sequenced using high molecular weight DNA extracts. Assemblies from single-genotype lineages were constructed using hifiasm, producing complete chromosomal-length scaffolds with high base accuracy without requiring short-read polishing. We recovered full repertoires of var, rif, and stevor genes and classified them into known subgroups. Together, our results demonstrate that PacBio HiFi sequencing enables accurate assembly of complex P. falciparum genomes from natural infections. This work provides a valuable genomic resource for future studies of parasite evolution, transmission dynamics, and antigenic diversity, and suggests that VSA repertoires can serve as reliable proxies of genetic relatedness across infections.

genomics↗

Nanopore sequencing for real-time genomic surveillance of Plasmodium falciparum

Malaria is a global public health priority causing over 600,000 deaths annually, mostly young children living in Sub-Saharan Africa. Molecular surveillance can provide key information for malaria control, such as the prevalence and distribution of antimalarial drug resistance. However, genome sequencing capacity in endemic countries can be limited. Here, we have implemented an end-to-end workflow for P. falciparum genomic surveillance in Ghana using Oxford Nanopore Technologies, targeting antimalarial resistance markers and the leading vaccine antigen circumsporozoite protein (csp). The workflow was rapid, robust, accurate, affordable and straightforward to implement, and could be deployed using readily collected dried blood spot samples. We found that P. falciparum parasites in Ghana had become largely susceptible to chloroquine, with persistent sulfadoxine-pyrimethamine (SP) resistance, and no evidence of artemisinin resistance. Multiple Single Nucleotide Polymorphism (SNP) differences from the vaccine csp sequence were identified, though their significance is uncertain. This study demonstrates the potential utility and feasibility of malaria genomic surveillance in endemic settings using Nanopore sequencing.

genomics↗