Detection of Circulating Parasite-Derived MicroRNAs in Filarial Infections

Abstract

Filarial nematodes cause chronic and profoundly debilitating diseases in both humans and animals. Applications of novel technology are providing unprecedented opportunities to improve diagnosis and our understanding of the molecular basis for host-parasite interactions. As a first step, we investigated the presence of circulating miRNAs released by filarial nematodes into the host bloodstream. miRNA deep-sequencing combined with bioinformatics revealed over 200 mature miRNA sequences of potential nematode origin in Dirofilaria immitis-infected dog plasma in two independent analyses, and 21 in Onchocerca volvulus-infected human serum. Total RNA obtained from D. immitis-infected dog plasma was subjected to stem-loop RT-qPCR assays targeting two detected miRNA candidates, miR-71 and miR-34. Additionally, Brugia pahangi-infected dog samples were included in the analysis, as these miRNAs were previously detected in extracts prepared from this species. The presence of miR-71 and miR-34 discriminated infected samples (both species) from uninfected samples, in which no specific miRNA amplification occurred. However, absolute miRNA copy numbers were not significantly correlated with microfilaraemia for either parasite. This may be due to the imprecision of mf counts to estimate infection intensity or to miRNA contributions from the unknown number of adult worms present. Nonetheless, parasite-derived circulating miRNAs are found in plasma or serum even for those species that do not live in the bloodstream.

Chagas Disease Diagnostic Applications

“…Theoretically, these strategies would have the additional advantage to discriminate between active from past infections and/or to assist in monitoring disease progression, as validated in other human diseases (Karsdal et al, 2010; Leeansyah et al, 2013; Tritten et al, 2014). In this context, it is important to keep in mind i) the extent of variability due to host genetic background on setting these putative biochemical markers and ii) that T. cruzi -derived molecules, and particularly during the chronic phase of Chagas disease, are present in biological fluids at extremely low concentrations, and likely aggregated in membrane-coated vesicles (Bayer-Santos et al, 2013; Fernandez-Calero et al, 2015; Lantos et al, 2016; Trocoli Torrecilhas et al, 2009).…”

Metabolite profiling of infection-associated metabolic markers of onchocerciasis

“…Recent modeling studies indicate the usefulness of Ov16 seropositivity in conjunction with skin snip results for MDA and surveillance programs for onchocerciasis [13]. A search for better biomarkers resulted in the identification of parasite-derived microRNAs [14, 15] or seropositivity with novel stage-specific proteins [16] though robust assays to detect these in low quantity in human specimens have not been developed. Moreover, whether any of these biomarkers provide the necessary sensitivity, specificity and dynamic range for use in endemic areas remains to be seen.…”

Expanding the MDx toolbox for filarial diagnosis and surveillance

“…Circulating miRNAs released by the intestinal nematode Heligmosomoides polygyrus [83] and filarial parasite Litomosoides sigmodontis [83] were found in sera from infected mice. More recently, circulating miRNAs have been described from other filarial parasites including O. volvulus, Dirofilaria immitis, Brugia pahangi, L. loa, and O. ochengi [81,84]. These studies set the stage for a future in RNA-based detection for filarial diagnostics.…”