Vaccination with Enzymatically Cleaved GPI-Anchored Proteins from Schistosoma mansoni Induces Protection against Challenge Infection

Hindawi Publishing Corporation Clinical and Developmental Immunology Volume 2012, Article ID 962538, 11 pages doi:10.1155/2012/962538 Research Article Vaccination with Enzymatically Cleaved GPI-Anchored Proteins from Schistosoma mansoni Induces Protection against Challenge Infection Vicente P. Martins,1, 2, 3 Carina S. Pinheiro,1, 2 Barbara C. P. Figueiredo,1, 2 Natan R. G. Assis,1, 2 Suellen B. Morais,1, 2 Marcelo V. Caliari,4 Vasco Azevedo,3 William Castro-Borges,5 R. Alan Wilson,6 and Sergio C. Oliveira1, 2 1 Departamento de Bioquı́mica, Imunologia do Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil 2 Instituto Nacional de Ciência e Tecnologia em Doenças Tropicais (INCT-DT), CNPq MCT, 40110-160 Salvador, BA, Brazil 3 Departamento de Biologia Geral do Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil 4 Departamento de Patologia Geral do Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil 5 Departamento de Ciências Biológicas, Universidade Federal de Ouro Preto, 35400-000 Ouro Preto, MG, Brazil 6 Centre for Immunology & Infection, Department of Biology, University of York, Heslington, York YO10 5DD, UK Correspondence should be addressed to Sergio C. Oliveira, Received 11 April 2012; Accepted 21 June 2012 Academic Editor: Anderson Sá-Nunes Copyright © 2012 Vicente P. Martins et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The flatworm Schistosoma mansoni is a blood fluke parasite that causes schistosomiasis, a debilitating disease that occurs throughout the developing world. Current schistosomiasis control strategies are mainly based on chemotherapy, but many researchers believe that the best long-term strategy to control schistosomiasis is through immunization with an antischistosomiasis vaccine combined with drug treatment. In the search for potential vaccine candidates, numerous tegument antigens have been assessed. As the major interface between parasite and mammalian host, the tegument plays crucial roles in the establishment and further course of schistosomiasis. Herein, we evaluated the potential of a GPI fraction, containing representative molecules located on the outer surface of adult worms, as vaccine candidate. Immunization of mice with GPI-anchored proteins induced a mixed Th1/Th2 type of immune response with production of IFN-γ and TNF-α, and low levels of IL-5 into the supernatant of splenocyte cultures. The protection engendered by this vaccination protocol was confirmed by 42% reduction in worm burden, 45% reduction in eggs per gram of hepatic tissue, 29% reduction in the number of granulomas per area, and 53% reduction in the granuloma fibrosis. Taken together, the data herein support the potential of surface-exposed GPI-anchored antigens from the S. mansoni tegument as vaccine candidate. 1. Introduction Schistosomiasis mainly occurs in developing countries and it is the most important human helminth infection in terms of global mortality. This parasitic disease affects more than 200 million people worldwide causing more than 250,000 deaths per year [1]. Furthermore, schistosomiasis causes up to 4.5 million DALY (disability adjusted life year) losses annually [2]. Current schistosomiasis control strategies are mainly based on chemotherapy but, in spite of decades of mass treatment, the number of infected people remains constant [3]. Extensive endemic areas and constant reinfection of individuals together with poor sanitary conditions in developing countries make drug treatment alone inefficient 2 [4]. Many consider that the best long-term strategy to control schistosomiasis is through immunization with an antischistosomiasis vaccine combined with drug treatment [5]. A vaccine that induces even a partial reduction in worm burdens could considerably reduce pathology and limit parasite transmission [6]. Currently, the most promising schistosome vaccine candidates are located in the tegument of the worms [7], such as TSP-2 [8] and Sm29 [9]. The tegument is a dynamic host-interactive surface involved in nutrition, immune evasion/modulation, excretion, osmoregulation, sensory reception, and signal transduction [10, 11]. The outer surface of this major parasite/host interactive surface is rich in GPI-anchored proteins [12], as well as other antigens such as aquaporin, phosphohydrolases, annexin-2, and Sm200 [13]. Sm200 and Sm29 are among the most abundant GPIanchored proteins in the S. mansoni tegument surface [12, 13]. Even with unknown function, these two proteins are intriguing because their high levels of expression in the schistosomulum and adult stages imply that they are certainly playing important roles in the parasite host interaction. The glycosylphosphatidylinositol (GPI) anchor is a posttranslational modification that anchors the carboxi-terminus of modified proteins in the outer leaflet of the cell membrane [14–17]. GPI-anchored proteins comprise molecules with a variety of functions and structures playing central roles in biological systems, such as signal transduction, immune responses, and the pathophysiology of some pathogenic diseases [18]. Given that the S. mansoni outer surface is loaded with GPI-anchored proteins, it is reasonable to assume that these molecules are involved in host/parasite interactions, placing them as potential targets for immune and chemotherapeutic treatment of schistosomiasis. The use of preparations containing tegument proteins as antigens to immunize and protect mice was earlier shown to be feasible [19]. Herein, we evaluated the potential of GPIanchored proteins of S. mansoni to elicit an immunological response able to protect mice against cercarial challenge and reduce the pathology associated with schistosomiasis. 2. Materials and Methods 2.1. Ethics Statement. Animal experiments were conducted in accordance with the Brazilian Federal Law number 11.794 which regulates the scientific use of animals and IACUC guidelines. All protocols were approved by the Committee of Ethics for Animal Experimentation (CETEA) at UFMG under permit 179/2010. 2.2. Mice and Parasites. Female C57BL/6 or Swiss mice aged 6–8 weeks were purchased from the Federal University of Minas Gerais (UFMG) animal facility. Cercariae of S. mansoni (LE strain) was maintained routinely on Biomphalaria glabrata snails at CPqRR (Centro de Pesquisa René-RachouFiocruz) and prepared by exposing infected snails to light for 1 h to induce shedding. Cercarial numbers and viability were determined using a light microscope prior to infection. Clinical and Developmental Immunology 2.3. Phosphatidylinositol-Phospholipase C (PiPLC) Treatment of Live Parasites. GPI-anchored proteins were recovered f (...truncated)