Resistance-mediating polymorphisms of Plasmodium falciparum among isolates from children with severe malaria in kumasi, ghana

Transcriptomic analyses of differentially expressed human genes, micro RNAs and long-non-coding RNAs in severe, symptomatic and asymptomatic malaria infection

Malaria transmission and endemicity in Africa remains hugely disproportionate compared to the rest of the world. The complex life cycle of P. falciparum (Pf) between the vertebrate human host and the anopheline vector results in differential expression of genes within and between hosts. An in-depth understanding of Pf interaction with various human genes through regulatory elements will pave way for identification of newer tools in the arsenal for malaria control. Therefore, the regulatory elements (REs) involved in the over- or under-expression of various host immune genes hold the key to elucidating alternative control measures that can be applied for disease surveillance, prompt diagnosis and treatment. We carried out an RNAseq analysis to identify differentially expressed genes and network elucidation of non-coding RNAs and target genes associated with immune response in individuals with different clinical outcomes. Raw RNAseq datasets, retrieved for analyses include individuals with severe (Gambia-20), symptomatic (Burkina Faso-15), asymptomatic (Mali-16) malaria as well as uninfected controls (Tanzania-20; Mali-36). Of the total 107 datasets retrieved, we identified 5534 differentially expressed genes (DEGs) among disease and control groups. A peculiar pattern of DEGs was observed, with individuals presenting with severe/symptomatic malaria having the highest and most diverse upregulated genes, while a reverse phenomenon was recorded among asymptomatic and uninfected individuals. In addition, we identified 141 differentially expressed micro RNA (miRNA), of which 78 and 63 were upregulated and downregulated respectively. Interactome analysis revealed a moderate interaction between DEGs and miRNAs. Of all identified miRNA, five were unique (hsa-mir-32, hsa-mir-25, hsa-mir-221, hsa-mir-29 and hsa-mir-148) because of their connectivity to several genes, including hsa-mir-221 connected to 16 genes. Six-hundred and eight differentially expressed long non coding RNA (lncRNA) were also identified, including SLC7A11, LINC01524 among the upregulated ones. Our study provides important insight into host immune genes undergoing differential expression under different malaria conditions. It also identified unique miRNAs and lncRNAs that modify and/or regulate the expression of various immune genes. These regulatory elements we surmise, have the potential to serve a diagnostic purpose in discriminating between individuals with severe/symptomatic malaria and those with asymptomatic infection or uninfected, following further clinical validation from field isolates.

Use of proscribed chloroquine is associated with an increased risk of pfcrt T76 mutation in some parts of Ghana

Background

After years of disuse of chloroquine (CQ) as first-line anti-malarial drug in Ghana, reports from molecular studies conducted in parts of the country indicate varying prevalence of T76 mutation in the pfcrt gene. This situation has several health implications, one being that mutations that confer resistance to CQ have been reported to show substantial cross-resistance to other anti-malarial drugs. It is important to identify some of the factors contributing to the continuous presence of CQ resistance markers in the country. This study determined the prevalence of T76 mutation in pfcrt gene of Plasmodium falciparum isolates collected from selected areas of the Central region of Ghana and correlated with the level of CQ use in these areas.

Methods

Plasmodium falciparum DNA was extracted from collected blood-blot filter paper samples in the study sites. The prevalence of T76 point mutation in pfcrt gene was assessed using nested PCR followed by RFLP. CQ from pharmacy and chemical shops was obtained using mystery buying method. The extent of CQ use by the participants was determined by measuring the level of the drug in their urine samples using the Saker-Solomon method.

Results

Of the 214 P. falciparum isolates analysed, 71.9% were found to have T76 mutation of pfcrt gene. The study revealed that 14.49% of community pharmacies and chemical shops had stocks of CQ for sale while 16.9% of the participants had CQ in their urine samples. There is five times more risks of becoming infected with CQ resistant strain for staying in an area where CQ is stocked for sale [RR = 0.20, p < 0.0001] and thirteen times more risks of having CQ-resistant mutant from those who still use CQ than non-users [OR = 0.08, p < 0.0001].

Conclusion

This study has shown that high variation in the prevalence of T76 mutations of P. falciparum is linked with the level of CQ stocking and usage within study area.