Genetic Diversity and Allelic Frequency of Glutamate-Rich Protein (GLURP) in Plasmodium falciparum Isolates from Sub-Saharan Africa

Genetic diversity of glutamate-rich protein (GLURP) in Plasmodium falciparum isolates from school-age children in Kinshasa, DRC

Malaria infections in school-age children further make it difficult to control the disease's spread. Moreover, the genetic diversity of glutamate-rich protein, potentially a candidate for vaccine development, has not yet been investigated in the Democratic Republic of Congo. Therefore, we aimed to assess the genetic diversity of the immunodominant C-terminal repetitive region (R2) of Plasmodium falciparum glutamate-rich protein gene (pfglurp) among school-age children living in Kinshasa, DRC. We conducted nested PCR targeting R2 of pfglurp and the amplicon were directly sequenced. We summarized the prevalence of mutations of bases and amino acids and indicated the amino acid repeat sequence in the R2 region by the unit code. We then statistically analyzed whether there was a relationship between the number of mutations in the pfglurp gene and attributes. In 221 samples, haplotype 1 was the most common (n = 137, 61.99%), with the same sequence as the 3D7 strain. Regarding the number of base mutations, it was higher in urban areas than rural areas (p = 0.0363). When genetic neutrality was tested using data from 171 samples of the single strain, Tajima's D was -1.857 (p = 0.0059). In addition, FST as the genetic distance between all attributes was very small and no significant difference was observed. This study clarified the genetic mutation status and relevant patient attributes among School-age children in the DRC. We found that urban areas are more likely to harbour pfglurp mutations. Future research needs to clarify the reason and mechanism involved.

Genetic diversity of Plasmodium falciparum among asymptomatic pregnant women on intermittent preventive treatment with sulfadoxine-pyrimethamine in Nigeria

This study investigated the genetic diversity of Plasmodium falciparum among asymptomatic pregnant women on intermittent preventive treatment with sulfadoxine-pyrimethamine (IPTp-Sp) in Osogbo, southwest Nigeria. Blood sample was obtained from consenting pregnant women attending antenatal clinics. Microscopy and Polymerase chain reaction (PCR) were employed to diagnose and analyse genetic diversity. Of the 301 samples, 53 (18%) and 83 (28%) were positive for P. falciparum by microscopy and PCR, respectively. Using the merozoite surface protein (msp)-1, msp-2, and glutamate-rich protein (glurp) genes of P. falciparum as polymorphic markers, the msp-1 gene showed nine alleles with R033 (66.7%) being predominant, followed by K1 (45.5%) and MAD20 (33.3%). The msp-2 gene had 16 alleles (eight each for FC27 and 3D7). The 3D7 alleles (82.1%) was significantly more than FC27 alleles (48.2%) (p = 0.0093). Nine alleles were detected with glurp gene, presenting with the highest monoclonal and the lowest polyclonal infection. The multiplicity of infection (MOI) of 1.5, 1.8, and 1.2 were obtained for msp-1, msp-2 and glurp genes. In light of the high P. falciparum genetic diversity among pregnant women on IPT-Sp in this study, additional strategies for preventing and controlling malaria in pregnancy might be required.

Genetic diversity of Plasmodium falciparum isolates in Nigeria. A review

Background

The complexity of infection in malaria-endemic areas is exacerbated by the presence of genetically diverse Plasmodium falciparum strains. There is a risk that more virulent or drug-resistant versions of the disease may arise. Therefore, we reviewed most reported molecular markers that have been detailed to date in Nigeria.

Main body of the abstract

In this review, we have summarized the genetic diversity of P. falciparum in Nigeria using the two well-reported genes (msp1 and msp2) as genetic diversity biomarkers. The review includes the findings obtained from research conducted in all major geopolitical regions of the country. We found that MSP-2 infection complexity is generally moderate to high in the North-central region. However, in the South-West, there were several regions where the multiplicity of infection (MOI) was either low or extremely high.

Conclusion

Understanding how Nigeria's malaria situation fits into various reports on P. falciparum genetic variation can improve treatment and immunization options. This review will be helpful for future treatment strategies that would be tailored to the specific needs of Nigeria's malaria-endemic populations.

SNP Diversity in CD14 Gene Promoter Suggests Adaptation Footprints in Trypanosome Tolerant N'Dama (Bos taurus) but not in Susceptible White Fulani (Bos indicus) Cattle

Immune response to infections has been shown to be mediated by genetic diversity in pattern recognition receptors, leading to disease tolerance or susceptibility. We elucidated naturally occurring variations within the bovine CD14 gene promoter in trypanosome-tolerant (N'Dama) and susceptible (White Fulani) cattle, with genomic and computational approaches. Blood samples were collected from White Fulani and N'Dama cattle, genomic DNA extracted and the entire promoter region of the CD14 gene amplified by PCR. We sequenced this region and performed in silico computation to identify SNP variants, transcription factor binding sites, as well as micro RNAs in the region. CD14 promoter sequences were compared with the reference bovine genome from the Ensembl database to identify various SNPs. Furthermore, we validated three selected N'Dama specific SNPs using custom Taqman SNP genotyping assay for genetic diversity. In all, we identified a total of 54 and 41 SNPs at the CD14 promoter for N'Dama and White Fulani respectively, including 13 unique SNPs present in N'Dama only. The significantly higher SNP density at the CD14 gene promoter region in N'Dama may be responsible for disease tolerance, possibly an evolutionary adaptation. Our genotype analysis of the three loci selected for validation show that mutant alleles (A/A, C/C, and A/A) were adaptation profiles within disease tolerant N'Dama. A similar observation was made for our haplotype analysis revealing that haplotypes H1 (ACA) and H2 (ACG) were significant combinations within the population. The SNP effect prediction revealed 101 and 89 new transcription factor binding sites in N'Dama and White Fulani, respectively. We conclude that disease tolerant N'Dama possessing higher SNP density at the CD14 gene promoter and the preponderance of mutant alleles potentially confirms the significance of this promoter in immune response, which is lacking in susceptible White Fulani. We, therefore, recommend further in vitro and in vivo study of this observation in infected animals, as the next step for understanding genetic diversity relating to varying disease phenotypes in both breeds.

Genetic Diversity of the Plasmodium falciparum Glutamate-Rich Protein R2 Region Before and Twelve Years after Introduction of Artemisinin Combination Therapies among Febrile Children in Nigeria

The genetic diversity of glutamate-rich protein (GLURP) R2 region in Plasmodium falciparum isolates collected before and 12 years after the introduction of artemisinin combination treatment of malaria in Osogbo, Osun State, Nigeria, was compared in this study. Blood samples were collected on filter paper in 2004 and 2015 from febrile children from ages 1-12 years. The R2 region of the GLURP gene was genotyped using nested polymerase chain reaction and by nucleotide sequencing. In all, 12 GLURP alleles were observed in a total of 199 samples collected in the two study years. The multiplicity of infection (MOI) marginally increased over the two study years; however, the differences were statistically insignificant (2004 samples MOI = 1.23 versus 2015 samples MOI = 1.47). Some alleles were stable in their prevalence, whereas two GLURP alleles, VIII and XI, showed considerable variability between both years. This variability was replicated when GLURP sequences from other regions were compared with ours. The expected heterozygosity (He) values (He = 0.87) were identical for the two groups. High variability in the rearrangement of the amino acid repeat units in the R2 region were observed, with the amino acid repeat sequence DKNEKGQHEIVEVEEILPE more prevalent in both years, compared with the two other repeat sequences observed in the study. The parasite population characterized in this study displayed extensive genetic diversity. The detailed genetic profile of the GLURP R2 region has the potential to help guide further epidemiological studies aimed toward the rational design of novel chemotherapies that are antagonistic toward malaria.

Extensive diversity in the allelic frequency of Plasmodium falciparum merozoite surface proteins and glutamate-rich protein in rural and urban settings of southwestern Nigeria

Background

Nigeria carries a high burden of malaria which makes continuous surveillance for current information on genetic diversity imperative. In this study, the merozoite surface proteins (msp-1, msp-2) and glutamate-rich protein (glurp) of Plasmodium falciparum collected from two communities representing rural and urban settings in Ibadan, southwestern Nigeria were analysed.

Methods

A total of 511 febrile children, aged 3–59 months, whose parents/guardians provided informed consent, were recruited into the study. Capillary blood was obtained for malaria rapid diagnostic test, thick blood smears for parasite count and blood spots on filter paper for molecular analysis.

Results

Three-hundred and nine samples were successfully genotyped for msp-1, msp-2 and glurp genes. The allelic distribution of the three genes was not significantly different in the rural and urban communities. R033 and 3D7 were the most prevalent alleles in both rural and urban communities for msp-1 and msp-2, respectively. Eleven of glurp RII region genotypes, coded I–XII, with sizes ranging from 500 to 1100 base pairs were detected in the rural setting. Genotype XI (1000–1050 bp) had the highest prevalence of 41.5 and 38.5% in rural and urban settings, respectively. Overall, 82.1 and 70.0% of samples had multiclonal infection with msp-1 gene resulting in a mean multiplicity of infection (MOI) of 2.8 and 2.6 for rural and urban samples, respectively. Msp-1 and msp-2 genes displayed higher levels of diversity and higher MOI rates than the glurp gene.

Conclusion

Significant genetic diversity was observed between rural and urban parasite populations in Ibadan, southwestern Nigeria. The results of this study show that malaria transmission intensity in these regions is still high. No significant difference was observed between rural and urban settings, except for a completely different msp-1 allele, compared to previous reports, thereby confirming the changing face of malaria transmission in these communities. This study provides important baseline information required for monitoring the impact of malaria elimination efforts in this region and data points useful in revising current protocols.

Climate Change Contribution to the Emergence or Re-Emergence of Parasitic Diseases

The connection between our environment and parasitic diseases may not always be straightforward, but it exists nonetheless. This article highlights how climate as a component of our environment, or more specifically climate change, has the capability to drive parasitic disease incidence and prevalence worldwide. There are both direct and indirect implications of climate change on the scope and distribution of parasitic organisms and their associated vectors and host species. We aim to encompass a large body of literature to demonstrate how a changing climate will perpetuate, or perhaps exacerbate, public health issues and economic stagnation due to parasitic diseases. The diseases examined include those caused by ingested protozoa and soil helminths, malaria, lymphatic filariasis, Chagas disease, human African trypanosomiasis, leishmaniasis, babesiosis, schistosomiasis, and echinococcus, as well as parasites affecting livestock. It is our goal to impress on the scientific community the magnitude a changing climate can have on public health in relation to parasitic disease burden. Once impending climate changes are now upon us, and as we see these events unfold, it is critical to create management plans that will protect the health and quality of life of the people living in the communities that will be significantly affected.

Genetic Diversity of CD14 Promoter Gene Polymorphism (rs2569190) is Associated With Regulation of Malaria Parasitemia and Susceptibility to Plasmodium falciparum Infection

CD14 is a multifunctional receptor expressed on many cell types and has been shown to mediate immune response resulting in the activation of an inflammatory cascade, with polymorphism of its promoter (rs2569190) found to be associated with susceptibility to several diseases. In malaria infection, the CD14 gene demonstrated a pathogenic profile in regulating experimental cerebral malaria, with reports of elevated levels of soluble CD14 in serum of patients but no definitive conclusion. We present a detailed analysis of genetic diversity of CD14 promoter gene (snp −159 C/T; rs2519190) polymorphism between a malaria-infected group and uninfected controls and its association with clinical parameters of disease. Genomic DNA samples obtained from 106 Plasmodium falciparum malaria–infected patients and 277 uninfected controls were elucidated with a polymerase chain reaction-restriction fragment length polymorphism (RFLP) assay. Our results show a significant diversity (P = 3.32E−06) in the genotypic frequency (3.8% versus 22.4%) of the rs2569190 mutant variant between the malaria-infected group and controls, respectively. The mutant allele had the lowest frequency among the malaria-infected group demonstrating its necessity for infection. Mean parasitemia (parasites/μL of blood) was significantly regulated based on CD14 polymorphic profile (19 855 versus 37 041 versus 49 396 for homozygote mutants, heterozygotes, and homozygote wild type, respectively). Interestingly, we found no association between CD14 genetic variants with fever, age of patients, or anemia. How this affects disease severity between subregional and continental groups deserves further clarification, including extending these studies in a larger group and among severe and asymptomatic patients with malaria.

Critical Evaluation of Molecular Monitoring in Malaria Drug Efficacy Trials and Pitfalls of Length-Polymorphic Markers

Estimation of drug efficacy in antimalarial drug trials requires parasite genotyping to distinguish new infections from treatment failures. When using length-polymorphic molecular markers, preferential amplification of short fragments can compromise detection of coinfections, potentially leading to misclassification of treatment outcome. We quantified minority clone detectability and competition among msp1, msp2, and glurp amplicons using mixtures of Plasmodium falciparum strains and investigated the impact of template competition on genotyping outcomes in 44 paired field samples. Substantial amplification bias was detected for all three markers, with shorter fragments outperforming larger fragments. The strongest template competition was observed for the marker glurp Detection of glurp fragments in multiclonal infections was severely compromised. Eight of 44 sample pairs were identified as new infections by all three markers. Ten pairs were defined as new infections based on one marker alone, seven of which were defined by the questionable marker glurp The impact of size-dependent template competition on genotyping outcomes therefore calls for necessary amendments to the current WHO recommendations for PCR correction of malaria drug trial endpoints. Accuracy of genotyping outcomes could be improved by separate amplification reactions per allelic family and basing results on markers msp1 and msp2 first, with glurp only used to resolve discordant results.

Plasmodium falciparum genotype and gametocyte prevalence in children with uncomplicated malaria in coastal Ghana

BACKGROUND

Plasmodium falciparum gametocytes are vital to sustaining malaria transmission. Parasite densities, multiplicity of infection as well as asexual genotype are features that have been found to influence gametocyte production. Measurements of the prevalence of Plasmodium sp. gametocytes may serve as a tool to monitor the success of malaria eradication efforts.

METHODS

Whole blood was collected from 112 children aged between 6 months and 13 years with uncomplicated P. falciparum malaria attending three health facilities in southern Ghana from June to August, 2014 before (day 0) and 4 days after completion of anti-malaria drug treatment (day 7). Malaria parasites were observed by microscopy and polymerase chain reaction (PCR); submicroscopic gametocyte carriage was measured by a Pfs25 (PF3D7_1031000) mRNA real time reverse transcriptase polymerase chain reaction (RT-PCR). Parasite genotyping was performed on gDNA extracted from dried filter paper blood blots by amplification of the polymorphic regions of msp1 (PF3D7_0930300) and msp2 (PF3D7_0206800) using PCR.

RESULTS

Microscopy estimated 3.1% (3/96) of the total population to carry gametocytes on day 0, which decreased to 2.1% (2/96) on day 7. In contrast, reverse transcriptase-real time PCR (RT-PCR) analysis of a subset of 35 samples estimated submicroscopic gametocyte carriage to be as high as 77% (27/35) using primers specific for Pfs25 (CT < 35) on day 0 and by day 7 this only declined to 60% (21/35). Genotyping the msp2 gene identified higher levels of MOI than the msp1 gene.

CONCLUSIONS

Although below detection by microscopy, gametocyte prevalence at submicroscopic levels are high in this region and emphasize the need for more effective elimination approaches like the development of transmission-blocking vaccines and safer gametocytocidal drugs.