IL-15 as an Immune Modulator in Schistosomiasis

Abstract Introduction Schistosomiasis affects approximately 200,000,000 people globally, with 93% of these cases in sub-Saharan Africa. Women who have been infected with Schistosoma haematobium have four times the risk of contracting HIV due to a change in their cervical mucosal immunity. The mechanism for this altered cervical mucosal immunity was not understood until a recent study published by Downs et al, which showed IL-15 levels were significantly lower in cervicovaginal lavage fluid samples of women with Schistosoma haematobium. Schistosoma mansoni, known to cause intestinal schistosomiasis, has also shown the potential to increase the risk of contracting HIV. The objective for this study is to see if IL-15 levels in peripheral blood are significantly different between patients positive for S mansoni and negative controls. Methods Enzyme-linked immunosorbent assays (BD Biosciences, San Jose, CA) for IL-15 were performed on plasma collected from 84 patients in villages in sub-Saharan Africa. These samples were collected at screening, 3-month follow-up, 6-month follow-up, and 9-month follow-up appointments. Results Of 249 plasma samples tested, 20 had detectable IL-15 levels ranging from 8.329 pg/mL to above the upper limit of detection of 500 pg/mL. While the patients that had detectable IL-15 in the peripheral blood were half S mansoni negative and half S mansoni positive, when an S mansoni–positive patient was positive for IL-15, it was across all timepoints. Conclusion The role of IL-15 as an immune modulator can explain the elevated levels in S mansoni–positive patients. All patients in the study were tested for significant comorbidities, with no correlation seen within the negative controls. Further testing is needed to investigate the role of IL-15 in the alteration of localized areas of infection with both Schistosoma mansoni and Schistosoma haematobium. More samples are currently being collected from the patient population in Tanzania, and future studies are planned.