Human Gene Expression in Uncomplicated Plasmodium falciparum Malaria

Abstract

To examine human gene expression during uncomplicated P. falciparum malaria, we obtained three samples (acute illness, treatment, and recovery) from 10 subjects and utilized each subject's recovery sample as their baseline. At the time of acute illness (day 1), subjects had upregulation of innate immune response, cytokine, and inflammation-related genes (IL-1β, IL-6, TNF, and IFN-γ), which was more frequent with parasitemias >100,000 per μL and body temperatures ≥ 39°C. Apoptosis-related genes (Fas, BAX, and TP53) were upregulated acutely and for several days thereafter (days 1-3). In contrast, the expression of immune-modulatory (transcription factor 7, HLV-DOA, and CD6) and apoptosis inhibitory (c-myc, caspase 8, and Fas Ligand G) genes was downregulated initially and returned to normal with clinical recovery (days 7-10). These results indicate that the innate immune response, cytokine, and apoptosis pathways are upregulated acutely in uncomplicated malaria with concomitant downregulation of immune-modulatory and apoptosis inhibitory genes.

Figure 1

Study design and flow chart for sample collection. The time line (upper left) provides the times when the 3 samples were collected. The insets provide sample results of the procedures used to test RNA quality: agarose gel electrophoresis performed on-site in Mali (left) and capillary electrophoresis using the Agilent Biolanalyzer 2100 in New Orleans (right). Flow chart for sample collection, quality control, and studies performed.

Figure 2

Heat map for changes in gene expression among subjects with uncomplicated malaria. Changes in gene expression with uncomplicated P. falciparum malaria revealed five major expression patterns: [A] genes upregulated at the time of acute illness, [AB] genes upregulated at the times of acute illness and treatment, [B] genes upregulated at the time of treatment, [BC] genes upregulated at the times of treatment and recovery, and [C] genes upregulated at the time of recovery. Based on Gene Ontology (GO) categories, profile A and AB genes were related to the immune response, AB genes to apoptosis, and C genes to immune-modulatory functions. In contrast, similar changes in gene expression were not observed in healthy control subjects without P. falciparum malaria (data not shown). Heat map for changes in gene expression among subjects with uncomplicated Plasmodium falciparum malaria.

Figure 3

Inflammatory and cytokine response pathways. GenMAPP illustration of genes upregulated with low parasitemias (a) and medium to high parasitemias (b). Several genes were upregulated more frequently with medium or high parasitemias (b) than low parasitemias (a). Among these were IL-1β, IL-6, IL-10, TNF, and INF-γ. Additionally, a number of genes, including IL-7, IL-15, and PGDFA (platelet-derived growth factor alpha polypeptide), were downregulated with low parasitemias and upregulated with medium to high parasitemias. TGF-β was downregulated more with medium to high than low parasitemias.

Figure 4

Apoptosis response pathway. Expression of most apoptosis-related genes correlated with the parasitemia. Note that the majority of these genes, including Fas (first apoptosis signal), FasL (Fas Ligand), and TP53 (tumor protein 53), were upregulated in subjects with medium to high parasitemias. In contrast, the BCL2 interacting protein (BNIP) family gene and the BCL2 and BCL2L1 apoptosis inhibitory genes were upregulated in subjects with low parasitemias and downregulated in subjects with medium to high parasitemias.