Low IL-6, IL-10, and TNF- α and High IL-13 Cytokine Levels Are Associated with Severe Hepatic Fibrosis in Schistosoma mansoni Chronically Exposed Individuals

Abstract

Several studies have attributed the etiopathogenesis of chronic Schistosoma mansoni related hepatic fibrosis to unregulated immune responses against trapped parasite ova in the host. However, there is limited data on immune profiles associated with varying degrees of the disease in a population under chronic exposure to the parasite. We therefore investigated the role of selected T-helper (Th)1, Th2, and Th17 cytokines in relation to hepatic fibrosis severity among individuals resident in a hyper-Schistosoma mansoni endemic region of Western Zambia. Two hundred and forty-four S. mansoni infected individuals with and without fibrosis were analysed for cytokine profiles. Based on hepatic fibrosis stage as determined by ultrasound, participants were categorized into Group 0, Group I, Group II, and Group III. Cytokines were measured in S. mansoni egg stimulated whole blood culture supernatants using the BD Cytometric Bead Array kits. Compared to the nonfibrotic group, participants in the severe hepatic fibrotic group produced less interleukin- (IL-) 6, IL-10, and tumour necrosis factor-alpha (TNF-α). On the other hand, IL-13 was significantly elevated in this group compared to the nonfibrotic group (p < 0.001). Our results suggest that low IL-6, IL-10, and TNF-α and high IL-13 levels may influence S. mansoni disease progression.

Figure 1

Cytokine levels in relation to degree of fibrosis. Median differences between Group 0 (control) and each of the three groups were determined using Dunn's test for multiple comparisons. Group 0 (infected with no fibrosis), Group I (infected with mild fibrosis), Group II (infected with moderate fibrosis), and Group III (infected with severe fibrosis). The significant level was set at ≤ 0.05 for a two-sided test. ^∗p ≤ 0.05, ^∗∗p ≤ 0.01, ^∗∗∗p ≤ 0.001, and ^∗∗∗∗p ≤ 0.0001.

Figure 2

Cytokine Levels in female and male participants with or without fibrosis. Median values are shown by the horizontal line. The Mann–Whitney test was used to compare differences in median cytokine expression in individuals without fibrosis and those with fibrosis. ^∗p ≤ 0.05.