Treatment of Schistosoma mansoni with miltefosine in vitro enhances serological recognition of defined worm surface antigens.
PLoS Negl Trop Dis 2017;
11:e0005853. [PMID:
28841653 PMCID:
PMC5589257 DOI:
10.1371/journal.pntd.0005853]
[Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 09/07/2017] [Accepted: 08/04/2017] [Indexed: 11/19/2022] Open
Abstract
Background
Miltefosine, an anti-cancer drug that has been successfully repositioned for treatment of Leishmania infections, has recently also shown promising effects against Schistosoma spp targeting all life cycle stages of the parasite. The current study examined the effect of treating Schistosoma mansoni adult worms with miltefosine on exposure of worm surface antigens in vitro.
Methodology/Principal findings
In an indirect immunofluorescence assay, rabbit anti-S.mansoni adult worm homogenate and anti-S. mansoni infection antisera gave strong immunofluorescence of the S. mansoni adult worm surface after treatment with miltefosine, the latter antiserum having previously been shown to synergistically enhance the schistosomicidal activity of praziquantel. Rabbit antibodies that recognised surface antigens exposed on miltefosine-treated worms were recovered by elution off the worm surface in low pH buffer and were used in a western immunoblotting assay to identify antigenic targets in a homogenate extract of adult worms (SmWH). Four proteins reacting with the antibodies in immunoblots were purified and proteomic analysis (MS/MS) combined with specific immunoblotting indicated they were the S. mansoni proteins: fructose-1,6 bisphosphate aldolase (SmFBPA), Sm22.6, alkaline phosphatase and malate dehydrogenase. These antibodies were also found to bind to the surface of 3-hour schistosomula and induce immune agglutination of the parasites, suggesting they may have a role in immune protection.
Conclusion/Significance
This study reveals a novel mode of action of miltefosine as an anti-schistosome agent. The immune-dependent hypothesis we investigated has previously been lent credence with praziquantel (PZQ), whereby treatment unmasks parasite surface antigens not normally exposed to the host during infection. Antigens involved in this molecular mechanism could have potential as intervention targets and antibodies against these antigens may act to increase the drug’s anti-parasite efficacy and be involved in the development of resistance to re-infection.
Schistosomiasis (Bilharzia) is a serious public health problem caused by a parasite of genus Schistosoma. There is an increasing concern about development of parasite resistance to the only drug available for treatment, praziquantel (PZQ). Miltefosine, a repurposed anti-cancer drug for treatment of Leishmania infection, was shown to have activity against Schistosoma in animal models at all the parasite’s life cycle stages. In this work, we examined the potential that miltefosine could act to expose parasite surface antigens that are normally hidden during natural infection as a way to avoid lethal effects of host immunity. We used two immunobinding techniques, immunofluorescence and western immunoblotting, and a protein identification technique, namely mass spectrometry, to identify proteins exposed on the worm surface following incubation with miltefosine. Four S. mansoni proteins were shown to be exposed by miltefosine treatment: fructose-bisphosphate aldolase (SmFBPA), Sm22.6, alkaline phosphatase and malate dehydrogenase. Antibodies specific for these antigens recognised and bound to the surface of early-stage schistosome larvae and antibodies specific for SmFBPA induced clumping of the larvae, suggesting a potential role in early parasite killing and protection against infection. These antibodies may be utilised to increase miltefosine’s anti-parasite efficacy and may be involved in resistance to re-infection.
Collapse