Biology subjects

Nambala, P.

Publications and source records attributed to Nambala, P..

4 recordsLinked to original sources

bioRxiv2024

GENETIC DIVERSITY OF T. B. RHODESIENSE SERUM RESISTANCE ASSOCIATED GENE IN MALAWIAN ISOLATES

BackgroundHuman African Trypanosomiasis (HAT) is a health burden in most remote areas of Sub-Saharan Africa. Only 2 species of the Trypanosome parasites, namely, T. b. rhodesiense and T. b. gambiense can establish infection in humans whereas other trypanosome parasites are lysed by human serum APOL-1 protein. The mechanism of T. b. gambiense resistance to APOL-1 activity is complex and involves several parasite factors. On the other hand, T. b. rhodesiense evades the lytic activity of APOL-1 by intracellular expression of a Serum Resistance Associated (SRA) gene that binds to APOL-1 when uptaken by the parasite thereby disabling APOL-1 from causing cellular membrane rupture. APOL-1 has 2 variants, namely, APOL-1 G1 and APOL-1 G2 with the later having mutations on the SRA binding sites which restores APOL-1 lytic activity in parasite lysis assays. This phenomenon remains elusive in clinical setting as limited data is available. In the present study we investigated the genetic diversity of T. b. rhodesiense SRA gene and APOL-1 genotypes in Malawian r-HAT clinical phenotypes. MethodsT. b. rhodesiense SRA gene from Malawi endemic HAT samples (n= 77) as well as from Zambia and Uganda (n= 13) was amplified by PCR and PCR products were commercially sequenced. APOL-1 variants were identified by restriction fragment length polymorphism (RFLP) after a PCR amplification (n= 61). Results and conclusionSequencing data revealed a heterozygosity of the SRA gene within Malawi T. b. rhodesiense isolates. Malawian SRA gene was genetically different from some isolates in Uganda and Zambia. Contrary to the current understanding that APOL-1 G2 variants are immune to T. b. rhodesiense infection, severe cases of r-HAT in G2 individuals were identified. This study has brought new insight in understanding the determinants of r-HAT severity.

genomics↗

bioRxiv2023

Transcriptome profiles of T.b. rhodesiense parasites in Malawi reveal focus specific gene expression Profiles associated with pathology

BackgroundSleeping sickness caused by T.b. rhodesiense is a fatal disease and endemic in Southern and Eastern Africa. There is an urgent need to develop novel diagnostic and control tools in order to achieve elimination of rhodesiense sleeping sickness which might be achieved through a better understanding of trypanosome gene expression and genetics using endemic isolates. Here, we describe transcriptome profiles and population structure of endemic T. b. rhodesiense isolates in human blood in Malawi. MethodologyBlood samples of r-HAT cases from Nkhotakota and Rumphi foci were collected in PaxGene tubes for RNA extraction before initiation of r-HAT treatment. 100 million reads were obtained per sample, reads were initially mapped to the human genome reference GRCh38 using HiSat2 and then the unmapped reads were mapped against Trypanosoma brucei reference transcriptome (TriTrypDB54_TbruceiTREU927) using HiSat2. Differential gene expression analysis was done using the DeSeq2 package in R. SNPs calling from reads that were mapped to the T. brucei genome was done using GATK in order to identify T.b. rhodesiense population structure. Results24 samples were collected from r-HAT cases of which 8 were from Rumphi and 16 from Nkhotakota foci. The isolates from Nkhotakota were enriched with transcripts for cell cycle arrest and stumpy form markers, whereas isolates in Rumphi focus were enriched with transcripts for folate biosynthesis and antigenic variation pathways. These parasite focus-specific transcriptome profiles are consistent with the more virulent disease observed in Rumphi and a more silent disease in Nkhotakota associated with the non-dividing stumpy form. Interestingly, the Malawi T.b. rhodesiense isolates expressed genes enriched for reduced cell proliferation compared to the Uganda T.b. rhodesiense isolates. PCA analysis using SNPs called from the RNAseq data showed that T. b. rhodesiense parasites from Nkhotakota are genetically distinct from those collected in Rumphi. ConclusionOur results have added new insights on how clinical phenotypes of r-HAT in Malawi might be associated with differences in gene expression profiles and population structure of T. b. rhodesiense from its two major endemic foci of Rumphi and Nkhotakota. Author SummaryA better understanding of T. b. rhodesiense gene expression profiles and population structure using endemic isolate may fast track the current search for novel diagnostic and control tools for rhodesiense sleeping sickness. Here, we analysed T. b. rhodesiense transcriptome profiles from endemic isolated from peripheral blood in Nkhotakota and Rumphi foci in Malawi. In Nkhotakota focus, T. b. rhodesiense transcripts were enriched for cell cycle arrest and stumpy marker whereas in Rumphi focus, the isolates were enriched for antigenic variation and folate biosynthesis biological pathways. Furthermore, we also found that T. b. rhodesiense population structure in Nkhotakota focus is different from Rumphi focus. The differences in trypanosome gene expression profiles and population structure are consistent with a less severe and acute sleeping sickness clinical profiles in Nkhotakota and Rumphi foci respectively.

genomics↗

bioRxiv2023

Transcriptome analysis of peripheral blood of Schistosoma mansoni infected children from the Albert Nile region in Uganda reveals genes implicated in fibrosis pathology.

Over 290 million people are infected by schistosomes worldwide. Schistosomiasis control efforts focus on mass drug treatment with praziquantel (PZQ), a drug that kills the adult worm of all Schistosoma species. Nonetheless, re-infections have continued to be detected in endemic areas with individuals living in the same area presenting with varying infection intensities. Our objective was to characterize the transcriptome profiles in peripheral blood of children between 10 - 15 years with varying intensities of Schistosoma mansoni infection living along the Albert Nile in Uganda. RNA extracted from peripheral blood collected from 44 S. mansoni infected (34 high and 10 low by circulating anodic antigen [CAA] level) and 20 uninfected children was sequenced using Illumina NovaSeq S4 and the reads aligned to the GRCh38 human genome. Differential gene expression analysis was done using DESeq2 and enriched pathways in differentially expressed genes (DEGs) were identified using REACTOME. Principal component analysis revealed clustering of gene expression by gender when S. mansoni infected children were compared with uninfected children. In addition, we identified 14 DEGs between S. mansoni infected and uninfected individuals, 56 DEGs between children with high infection intensity and uninfected individuals, 33 DEGs between those with high infection intensity and low infection intensity and no DEGs between those with low infection and uninfected individuals. We also observed upregulation and downregulation of some DEGs that are associated with fibrosis and its regulation. These data suggest expression of fibrosis associated genes as well as genes that regulate fibrosis in S. mansoni infection. The relatively few significant DEGS observed in children with schistosomiasis suggests that chronic S. mansoni infection is a stealth infection that does not stimulate a strong immune response. Author SummarySchistosomiasis is a neglected tropical disease transmitted via an intermediate snail host through contact with contaminated fresh water. Even with routine Mass Drug Administration for treatment of the infection, re-infections are still common and variations in infection intensity and pathology are still observed in individuals in the same location. These may be due to differences in individuals response to S. mansoni infection. In this study, we used RNAseq to identify differentially expressed genes associated with S. mansoni infection in children between 10-15 years. We conducted comparisons between phenotypes including infection intensities measured by circulating anodic antigen, wasting by body mass index and stunting by height-for-age z score. Our data showed very low numbers of significant differentially expressed genes in all comparisons. Some of the few differentially expressed genes that were observed were associated with fibrosis which is the cause of pathology in humans and has been observed in late stages of S. mansoni infection in murine studies.

genomics↗

bioRxiv2022

Distinct Differences in Gene Expression Profiles in Early and Late Stage Rhodesiense HAT Individuals in Malawi

T. b. rhodesiense is the causative agent of rhodesian Human African trypanosomiasis (r-HAT) in Malawi. Clinical presentation of r-HAT in Malawi varies between the different foci and differs from East African HAT clinical phenotypes. The purpose of this study was to gain more insights into the transcriptomic profiles of patients with early stage 1 and late stage 2 HAT disease in Malawi. Whole blood from individuals infected with T. b. rhodesiense was used for RNA-Seq. Control samples were from healthy trypanosome negative individuals matched on sex, age range, and disease focus. Illumina sequence FASTQ reads were aligned to the GRCh38 release 84 human genome sequence using HiSat2 and differential analysis was done in R using the DESeq2 package. XGR, ExpressAnalyst and InnateDB algorithms were used for functional annotation and gene enrichment analysis of significant differentially expressed genes. RNA-seq was done on 25 healthy controls and 23 r-HAT case samples of which 3 case samples were excluded for downstream analysis as outliers. 4519 genes were significantly differentially expressed (p adjusted <0.05) in individuals with early stage 1 r-HAT disease (n = 12) and 1824 genes in individuals with late stage 2 r-HAT disease (n = 8). Enrichment of innate immune response genes through neutrophil activation was identified in individuals with both early and late stages of the disease. Additionally, lipid metabolism genes were enriched in late stage 2 disease. We further identified uniquely upregulated genes (log2 Fold Change 1.4 - 2.0) in stage 1 (ZNF354C) and stage 2 (TCN1 and MAGI3) blood. Our data brings new insight into the human transcriptome landscape during T. b. rhodesiense infection. We have further identified key biological pathways and transcripts during stage 1 and stage 2 r-HAT. Lastly, we have identified potential diagnostic biomarkers that may be used for staging of r-HAT disease.

genetics↗