MicroRNAs: Biological Regulators in Pathogen–Host Interactions

Abstract

An inflammatory response is essential for combating invading pathogens. Several effector components, as well as immune cell populations, are involved in mounting an immune response, thereby destroying pathogenic organisms such as bacteria, fungi, viruses, and parasites. In the past decade, microRNAs (miRNAs), a group of noncoding small RNAs, have emerged as functionally significant regulatory molecules with the significant capability of fine-tuning biological processes. The important role of miRNAs in inflammation and immune responses is highlighted by studies in which the regulation of miRNAs in the host was shown to be related to infectious diseases and associated with the eradication or susceptibility of the infection. Here, we review the biological aspects of microRNAs, focusing on their roles as regulators of gene expression during pathogen–host interactions and their implications in the immune response against Leishmania, Trypanosoma, Toxoplasma, and Plasmodium infectious diseases.

Trypanosoma cruzi and Toxoplasma gondii Induce a Differential MicroRNA Profile in Human Placental Explants

“…In addition, certain parasites including T. cruzi and T. gondii can alter host miRNA expression to favor both parasite clearance and infection (18,19). Moreover, different strains of T. gondii can induce specific miRNAs in mice that have been proposed as biomarkers for early infection (19,36). Mature miRNAs regulate the expression of over 30% of fundamental genes; these are involved in key biological processes including development, cellular proliferation and differentiation, apoptosis, metabolism, and immune response (18,19,37); all of these determine infection success or failure.…”

“…Moreover, different strains of T. gondii can induce specific miRNAs in mice that have been proposed as biomarkers for early infection (19,36). Mature miRNAs regulate the expression of over 30% of fundamental genes; these are involved in key biological processes including development, cellular proliferation and differentiation, apoptosis, metabolism, and immune response (18,19,37); all of these determine infection success or failure. Moreover, epigenetic and genetic defects in miRNAs and their processing machinery are a common hallmark of infection and diseases that include pregnancy-specific pathologies such as preeclampsia (17,38).…”

“…T. gondii also reprograms host cells, primarily targeting cell-specific transcription factors that regulate host defenses (i.e., NF-κB, interferon regulatory factor, and JAK/STAT) by regulating their intrinsic activities and expression levels ( 35 ). In addition, certain parasites including T. cruzi and T. gondii can alter host miRNA expression to favor both parasite clearance and infection ( 18 , 19 ). Moreover, different strains of T. gondii can induce specific miRNAs in mice that have been proposed as biomarkers for early infection ( 19 , 36 ).…”

“…In addition, certain parasites including T. cruzi and T. gondii can alter host miRNA expression to favor both parasite clearance and infection ( 18 , 19 ). Moreover, different strains of T. gondii can induce specific miRNAs in mice that have been proposed as biomarkers for early infection ( 19 , 36 ).…”

“…In this context, both parasites display sophisticated strategies to avoid host defenses and virulence factors that increase the chance of establishing infection and long-term persistence. One of these strategies is the ability to modulate host cell gene expression ( 14 – 16 ) through small non-coding RNAs such as microRNAs (miRNAs) that repress mRNAs in a sequence-specific manner by either an mRNA degradation process or through mRNA translation inhibition ( 17 – 19 ). MiRNAs play a key role in fine tuning gene expression in multiple physiological and pathological conditions including T. cruzi ( 20 ) or T. gondii ( 21 ) infection.…”