MicroRNAs in parasitic diseases: potential for diagnosis and targeting

MicroRNAs (miRNAs) are a recently discovered class of small non-coding RNAs that can down-regulate protein expression by specific mRNA recognition. Evidence is accumulating that the miRNAs are implicated in the course and outcome of infectious and non-infectious diseases. Both parasites specific miRNA sequences and the phenomenon of the alteration of host miRNA levels after parasite infection are known, although detailed information about the direct intervention of parasites in the alteration of host miRNA levels and how this is regulated by parasites at molecular level is still lacking. Circulating miRNAs can be detected in biological fluids as serum, saliva and others, exhibiting a good potential as non-invasive biomarkers. Their ability to function as master regulators of the gene expression and the possibility for a relative easy manipulation of the miRNA machinery and related events, coupled with their apparent lack of adverse events when administered, place miRNAs as promising targets for the treatment of diseases. Moreover, the dependence of parasites over the host cellular machinery to accomplish infection and complete their biological cycles, together with the potential manipulation of host's responses through parasite miRNAs, point out that the miRNA machinery is particularly interesting to seek for alternative therapeutic approaches against parasites. Additionally, the studies about parasitic manipulation of the host immune responses thought miRNAs could broaden our knowledge about basic aspects of the host-parasite relationships.