| Objective: Human respiratory syncytial virus (RSV) is the most important viral etiologic agent of pediatric respiratory disease worldwide. No effective vaccine is currently available for prophylaxis. The World Health Organization has affirmed RSV vaccines as one of the highest priority vaccine development projects. Among the encoded 11 viral proteins by RSV genome, fusion (F) glycoprotein is one of the neutralization antigens, which can induce protective immunity against RSV infection, and a good candidate antigen for the genetic engineering vaccine such as DNA vaccine, subunit vaccine. In order to investigate antibody responses generated by musocal DNA vaccines encoding the codon-optimized F protein of RSV delivered via attenuated Salmonella Typhimurium aroA strain SL7207 (SL7207). We vaccinate BALB/c mice with this vaccine intranasally (i.n.) or intragastrically (i.g.).Method: After the codon-optimized F gene was synthesized, we constructed eukaryotic expression plasmid pcDNA3.1/Fsyn and transformed it into SL7207 to get SL7207/pcDNA3.1/Fsyn. Then, SL7207/pcDNA3.1/Fsyn was evaluated for its immune efficacy as RSV vaccine in BALB/c mice i.n. and i.g. by indirect ELISA.Results: The plasmids extracted from SL7207/pcDNA3.1/Fsyn and SL7207/pcDNA3.1/Fwt were confirmed by restriction endonuclease assay and sequencing. Compared with intragastric immunization group, intranasal immunization group achieves higher level of RSV specific surum IgG and respiratory secretary IgA (SIgA) (P <0.05). Moreover, F protein expressed by Fsyn is of elevated immunogenicity, compared with wild type F (Fwt) (P <0.05).Conclusion: SL7207/pcDNA3.1/Fsyn have been constructed successfully. Intranasal immunization and codon optimization approaches can improve immune efficacy of RSV DNA vaccine delivered by SL7207. Therefore, we think this vaccine strategy has the combined merit of mucosal immunity and DNA vaccine, and is of great importance for vaccine against mucosally transmissible viruses such as RSV, rotavirus.
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