Abstract
Neurocysticercosis (NCC), a major cause of neurological morbidity worldwide, is caused by the larvae of Taenia solium. Cestodes secrete molecules that block the Th1 response of their hosts and induce a Th2 response permissive to their establishment. Mature microRNAs (miRs) are small noncoding RNAs that regulate gene expression and participate in immunological processes. To determine the participation of Taenia miRs in the immune response against cysticercosis, we constructed small RNA (sRNA) libraries from larvae of Taenia solium and Taenia crassiceps. A total of 12074504 and 11779456 sequencing reads for T. solium and T. crassiceps, respectively, were mapped to the genomes of T. solium and other helminths. Both larvae shared similar miRNome, and miR-10-5p was the most abundant in both species, followed by let-7-5p in T. solium and miR-4989-3p in T. crassiceps, whereas among the genus-specific miRs, miR-001-3p was the most abundant in both, followed by miR-002-3p in T. solium and miR-003a-3p in T. crassiceps. The sequences of these miRs were identical in both. Structure and target prediction analyses revealed that these pre-miRs formed a hairpin and had more than one target involved in immunoregulation. Culture of macrophages, RT-PCR and ELISA assays showed that cells internalized miR-10-5p and let-7-5p into the cytoplasm and the miRs strongly decreased interleukin 16 (Il6) expression, tumor necrosis factor (TNF) and IL-12 secretion, and moderately decreased nitric oxide synthase inducible (Nos2) and Il1b expression (pro-inflammatory cytokines) in M(IFN-γ) macrophages and expression of Tgf1b, and the secretion of IL-10 (anti-inflammatory cytokines) in M(IL-4) macrophages. These findings could help us understand the role of miRs in the host–Taenia relationship.
Highlights
Neurocysticercosis (NCC) in humans is caused by larvae of Taenia solium
Total RNA extracted from T. solium and T. crassiceps larvae presented the characteristic pattern of the RNAs from cestodes (Figure 1A, lane 1), showing the majority of mRNAs between 0.5 and ∼7000 nt, a single ribosomal RNA band of ∼2438 nts, and an small RNA (sRNA) fraction of ∼200 nts
The mappable reads from T. solium (58.2%) and T. crassiceps (50.7%), correspond to know and predicted miRs, 12.8 and 10.2%, respectively were mapped to mRNAs, and 14.2 and 11.4%, respectively, were mapped to small nucleolar RNA (snoRNA), small interfering RNA (siRNA), tRNAs, and ribosomal RNA (rRNA) fragments
Summary
Neurocysticercosis (NCC) in humans is caused by larvae of Taenia solium. It is the leading cause of seizures and epilepsy and is considered a serious health problem worldwide [1]. In human NCC, the intensity of symptoms depends primarily on the inflammatory response, which is associated with the Th1 response with high levels of TNF, IFN-γ, IL-17, and IL-23 and coincides with degeneration of the larvae [2,3], whereas the Th2 response (anti- inflammatory response) is associated with asymptomatic NCC with high level of IL-10, IL- 4, IL5, and IL-13 and viable larvae [3,4]. In animal NCC, swine and murine granulomas and their inflammatory responses are similar than in humans [5,6,7,8]. The exact role of classically and alternatively activated macrophages/microglia and their secreted molecules in NCC patients remains to be elucidated.
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