Evaluation of the protective immunity of the Legionella pneumophila recombinant protein FlaA/MompS/PilE in an A/J mouse model

To investigate the protect effects of the recombinant protein FlaA/MompS/PilE against Legionella pneumophila (L. pneumophila), the coding sequences of the three proteins were optimized by DNA Star software firstly, cloned, expressed by Escherichia coli BL21, and purified. To give an enhanced the immunological response, the proteins were linked together with (Linker) or without a linker insert (NLinker) and were purified from E. coli BL21. The A/J mouse model was used to determine the level of the induction of protective immunity from the purified proteins. Our results showed that the IgG titer, which was measured by ELISA, was increased after the administration of the five proteins. Compared to the administration of the individual proteins, the chimeric Linker and NLinker proteins displayed lasting immunity to a lethal dose of L. pneumophila challenge. The Linker protein protected the A/J mouse against a higher dose of L. pneumonia compared to the other proteins used in this study, as it contained a more effective immunogen. The work presented here demonstrates that the bioinformatics software, DNA Star, is a valid tool to analyse the epitopes of proteins and was useful in the optimization of proteins that could induce the protective immune response to L. pneumophila. The cross-immunity of recombinant proteins, such as the Linker and the NLinker chimera, have higher generates a greater immune than the single proteins.