Its two components are S1, which contains the receptor-binding domain (RBD) (7C9,15,18), and S2, which contains the fusion peptide (9a). to that caused by severe acute respiratory syndromecoronavirus (SARS-CoV) (2,20). As of 4 July 2014, there have been 827 confirmed cases of contamination with MERS-CoV, and 287 of the affected people died (www.who.org). Cases have been linked to many regions of Asia, Africa, Europe, and America. According to recent data, people with a moderate respiratory illness may be infected with MERS-CoV; in some cases, the infected people have no respiratory symptoms (5,20,21,23). Patients with a chronic disease or compromised immune system have a higher risk of becoming infected and/or developing complications (2,5,20,21,26). There have been small LXR-623 clusters of contamination in several countries, suggesting that person-to-person transmission is possible when close contact occurs (16,21). The rapid identification of effective therapeutics is usually a high priority, because there is currently no specific therapy or vaccine for MERS-CoV and the resulting disease is severe with a high case-fatality rate. MERS-CoV belongs to the genus species known to infect humans (22). CoVs are positive-strand RNA viruses (4). The virion comprises a nucleocapsid (N) core surrounded by an envelope made up of three membrane proteins: spike (S), membrane, and envelope. The S protein of MERS-CoV, a 1353-amino-acid type I membrane glycoprotein, is known to be responsible for receptor binding (9,15,19,22), membrane fusion (9a), and the induction of neutralising LXR-623 antibodies (7C9,18). Although the S protein of MERS-CoV shares little amino-acid identity with that of other CoVs (<30%) (22), it shares common structural features with the S proteins of other CoVs (11,15,22,23a). Its two components are S1, which contains the receptor-binding domain name (RBD) (7C9,15,18), and S2, which contains the fusion peptide (9a). Dipeptidyl peptidase 4 (also known as CD26) was identified as a functional receptor for MERS-CoV, and Hsh155 the structural basis of S/receptor engagement has been explored (15,19,20,21,23a). A recent report, indeed, showed the presence of S-specific neutralizing antibodies in MERS-CoV-infected patients (20,21,26). Therefore, the S protein is recognized as the primary target of neutralizing antibodies. Knowledge of the antigenic determinants that can elicit neutralizing antibodies could be beneficial for LXR-623 the development of a protective vaccine. In this study, we aimed at identifying neutralizing epitopes in the MERS-CoV S protein that may be used for the development of a vaccine or therapeutic brokers against MERS-CoV contamination. Although a properly folded RBD could be the most import target for neutralizing antibodies, as exhibited for SARS-CoV (6,10,13), the identification of other neutralizing epitopes in the S could assist in the development of a vaccine and therapeutics against MERS-CoV contamination. We LXR-623 synthesized peptides from different regions of the MERS-CoV S protein based on a bioinformatics analysis and used them to raise antibodies in rabbits. Recombinant RBD (rRBD) was used to raise LXR-623 polyclonal antibodies in mice. The antisera were then tested in terms of their ability to bind S protein derived from the transfection of the codon-optimized S gene and their capacity to neutralize MERS-CoV using an neutralizing assay based on lentiviral pseudotyped particles expressing full-length MERS-CoV S protein. We confirmed that this RBD could efficiently elicit neutralizing antibodies against MERS-CoV and is an essential target for vaccine development. A novel neutralizing epitope corresponding to amino-acid residues 736C761 of the S protein was also identified. Materials and Methods Cell lines and plasmids BHK-21, Huh-7, and 293FT were cultured in Dulbecco’s modified Eagle’s medium (Life Technologies).