Abstract

To investigate the immunoprotective effects of the recombinant type A flagellin (FLA), the fla A gene of Legionella pneumophila serogroup 1 strain Paris was cloned into pET28a(+). Recombinant FLA (rFLA) was overexpressed in E. coli BL21 (DE3) and purified by Ni2+ exchange chromatography. Female BALB/c aged 6-8 weeks were immunized with 20 mu g of rFLA. Nonimmunized mice along with mice inoculated with a sublethal dose of live L. pneumophila intravenously were considered as negative and positive controls, respectively. A significant serum antibody response was observed in female BALB/c mice immunized with rFLA. Production of IFN-gamma and IL-12, and TNF-alpha in the serum and the splenocyte cultures, and antigen-specific splenocyte proliferation suggested a strong innate and adaptive cellmediated immunity response in rFLA-immunized mice. Intravenous lethal challenge with L. pneumophila serogroup 1 (strain Paris) showed that 60 of mice immunized with rFLA survived in a 10-day follow-up survey. These results show that rFLA from L. pneumophila can elicit strong innate and adaptive immune responses and suggest the possibility of a long-term immunity against lethal challenge with L. pneumophila. (C) 2017 S. Karger AG, Basel