Moriya C, Horiba S, Inoue M, Iida A, Hara H, Shu T, Hasegawa M, Matano T. this way, the antigen is usually actively expressed around the surfaces of vaccine particles in its prefusion conformation, and as recently reported for other vectored vaccines, the occurrence of silencing mutations of the transgene in the vaccine genome can be prevented. In addition, its active gene expression contributes to further stimulation of the immune response. In order to understand the best route of immunization, we compared vaccine efficacies after intranasal (i.n.) or intramuscular (i.m.) immunization of BALB/c mice. Via both routes, substantial RSV-specific immune responses were induced, consisting of serum IgG and neutralizing antibodies, as well as cytotoxic T cells. Moreover, i.n. immunization was also able to stimulate specific mucosal IgA in the upper and lower respiratory tract. In computer virus challenge experiments, animals were guarded against RSV contamination after both i.n. and i.m. immunization without inducing vaccine-enhanced disease. Above all, the replication-deficient SeV appeared to be safe and well tolerated. IMPORTANCE Respiratory syncytial computer virus (RSV) is a major cause of respiratory diseases in young children and elderly people worldwide. There is a great demand for a licensed vaccine. Promising existing vaccine methods based on live-attenuated vaccines or viral vectors have suffered from unforeseen drawbacks related to immunogenicity and attenuation. We provide a novel RSV vaccine concept based on a genome replication-deficient Sendai vector that has many favorable vaccine characteristics. The specific vaccine design guarantees genetic stability of the transgene; furthermore, it supports a favorable presentation of the antigen, activating the adaptive response, features that other vectored vaccine methods have often experienced difficulties with. Wide immunological and pathological analyses in mice confirmed the validity and efficacy of this approach after both parenteral and mucosal administration. Above all, this concept is suitable for initiating clinical studies, and it could also be applied to other infectious diseases. were immunogenic for RSV, unlike vector particles that express antigens only after infecting cells; (ii) by inserting the RSV F protein as an essential structural component, mutations that silence its gene expression Rabbit polyclonal to USP37 are not expected to occur; (iii) the RSV F antigen is present on vector particles in its native prefusion conformation and on the surfaces of infected target cells, contributing to efficient neutralizing responses (26,C29). In the present study, we characterized the vaccine candidate phenotype and genotype and assessed its immunological efficacy in mice. In RSV challenge studies, we analyzed the capacity of this novel vaccine to protect animals against RSV infection and evaluated its potential to induce a pathological form of enhanced disease. Immunological responses and efficacies were compared after vaccine administration via systemic and mucosal routes. To our knowledge, this is the only replication-deficient single-stranded RNA viral vector concept currently being used for developing vaccines. RESULTS Design and generation of a chimeric RSV vaccine construct. We generated a virus-vectored RSV vaccine candidate based on a fully genome replication-deficient Sendai CL2A-SN-38 vector backbone (19, 20; W. J. Neubert, S. Bossow, and S. Schlecht, August 2006, International patent application PCT/EP2006/001251). As an antigenic component, we included the RSV F gene, approved as the most efficient RSV antigen in most subunit vaccine candidates to date. We used a Sendai virus as a viral vector to exclude preexisting anti-vector immunity. Further, we generated a chimeric vector construct containing the RSV F gene instead of the Sendai virus F CL2A-SN-38 gene (SeV76). In particular, we exchanged the ectodomain of the SeV F protein with the counterpart from RSV (Fig. 1A). In this way, we created a viral vector that contained two surface proteins, F and HN, from two different paramyxoviruses. As previously shown, CL2A-SN-38 this combination can yield viable and reproductive virus in cell culture (30), where both surface proteins contribute essentially CL2A-SN-38 to virus replication and spread. With this approach, our aim was to address the following issues as important features to enhance vaccine efficacy: (i) prevention of silencing mutations in the antigen by incorporating it as an essential structural protein without which no viable virus can be grown, (ii) reduction of antivector.