Bound antibody was detected with streptavidinHRP (Pierce) diluted 1:10 000 in PBS (30 min, RT) and the ELISA was developed by incubation with a TMB peroxidase substrate (BD Pharmingen). Introduction == Schistosomes are parasitic helminths that are able to ensconce themselves in the human host for decades [1]. They were discovered in the mid-19th century [2], but must have infected their human hosts during thousands of years, as calcified eggs had already been BINA discovered in mummies [3]. Their persistent existence over thousands of years might be one of the reasons why, during co-evolution with their human host, schistosomes developed into well-adapted parasites capable of escaping the host immune response and establishing themselves in such an unfriendly environment BINA as the human venous system. Today, an estimated number of 200 million people are infected withSchistosomaspp., withS. mansoni,S. haematobiumandS. japonicumthe most important species [4]. Despite many decades of research, praziquantel is the only chemotherapeutic drug available for treatment of schistosomiasis effective against all five schistosome species infecting humans [5]. Concern about the emergence of developing praziquantel resistance [6], the biphasic sensitivity of the parasite to the drug [7], with juvenile worm stages being insensitive to drug treatment [8], and the lack of protection against reinfection [9], are among the major disadvantages of a chemotherapeutic treatment of the infection. Consequently, the development of a schistosomiasis vaccine is highly desirable, although more than 10 years ago it was already stated to be a difficult but achievable goal [10]. This prediction proves true, in so far as no vaccine candidate is currently in the late stages of clinical development [11]. However, since 2009 theS. mansonigenome sequence has been fully available [12]. This remarkable achievement, together with a substantial amount of high-quality data generated by the various other -omics disciplines, pave the way for vaccine research against this and other schistosome species [[13,14]]. Some of the most interesting vaccine candidates are transmembrane proteins localized on theS. mansonitegument, as they are seen immediately by the host immune system [15]. Proteins highly expressed in the early intramammalian stages ofS. mansoni, such as schistosomula, are also considered to be favourable vaccine targets [16]. Schistosomes have to defend themselves against the host immune system BINA at various stages in their life cycle [[1719]]. The initial phase of invasion is characterized by evading innate immunity at the time of skin penetration and migration to small vessels. During this phase Rabbit Polyclonal to SFRS11 the host complement may attack the cercariae [20]. However, schistosomes express several complement regulators/inhibitors on their surface, which apparently block host complement [21]. We have recently described a new putative complement regulator inS. mansoni, termed SmTOR for tetraspanning orphan receptor [22]. This receptor is characterized by a 111 amino acid extracellular domain 1 (SmTORed1) containing the C-terminal H17 motif shown to bind C2 and interfere with its cleavage by C1s, thereby limiting the extent of the complement C3 convertase formation [23]. Its highest expression in cercariae and surface localization inS. mansoniearly intramammalian stages would not only suggest a role for the receptor as a complement regulator at an early time-point of infection, but also make it an interesting vaccine target. In this work, we wanted to define whether recombinant SmTORed1 induces immune responses in mice and confers protection against infection. An additional question was whether or not humans infected withS. mansonidevelop specific antibodies. == Materials and methods == == Animals == Female C57BL/6 and female BALB/c mice (n= 80, age: 4 weeks, weight: 14 g) used for the first round of immunization were purchased from Harlan Laboratories (Horst, the Netherlands). Female BALB/c mice (n= 30, age: 4 weeks, weight: 14 g) used for the immunization challenge experiment were purchased from Charles River Laboratories (Sulzfeld, Germany). Animals were kept in groups of five (preliminary experiment) or 10 (immunization infection) in environmentally controlled conditions (temperature: 25C; humidity: 50%; 12-h light/dark cycle) BINA and acclimatized for 1 week. They had free access to water and rodent diet. All experiments were approved by the ethical committees of the Swiss authorities at the Federal Veterinary Department (Bern, Switzerland) and the cantonal veterinary office Basel-Stadt (Switzerland) (permission number: 2346). They were conducted according to local guidelines (Verordnung Veterinramt Basel-Stadt) and the Swiss animal protection law (TschG) at the Department of.