[Evaluation of the Immunogenic effect of lipopolysaccharide [LPS] and protein fractions of Legionella pneumophila in challenging with lethal dose of this bacterium in mice]

Legionella pneumophila is the cause of legionellosis disease that can be fatal. Yet, no vaccine has been available for this infection. Also antigens of these bacteria can stimulate the immune system. The purpose of this study was to compare the immunogenic effect of lipopolysaccharide fraction with that of protein fraction of Legionella pneumophila in challenging with lethal dose of these bacteria in mice. After preparation of bacterial biomass, LPS and protein fractions were separated by hot phenol method and precipitated by enzyme digestion. LPS and protein fraction electrophoresis on poly acrylamide gel was performed. For preparation of vaccines from LPS and protein fractions, 10 micro g of each antigen was solved in 0.5 ml of normal saline and used for injection. Six groups of female BALB/c mice [each group consisted of 15 mice] were selected. Four groups of mice were vaccinated by intraperitoneal [i.p] injections at fortnightly intervals for three times. The two control groups of mice received normal saline injections. Two weeks after the last immunization, two groups of vaccinated mice and one control group were challenged with LD100 of the virulent strain of L. pneumophila. Also six weeks after the last immunization the other three groups [2 vaccinated and one control groups] were challenged. Result: The results of the first challenge showed the immunogenic efficiency gains of 86.66% and 73.33% for protein fraction and LPS respectively, and after six weeks of the last immunization the immunogenic efficiency gains were 60% for LPS and 86.66% for protein fractions. This study showed that the protein fraction and LPS of L.pneumophila have high immunogenic activity and can be proper candidates for vaccine studies

[Isolation of legionella pneumophila from environment and water system samples and evaluation of immuno-protective efficiency of its whole killed cell in mice model]

Legionella pneumophila is a cause of pneumonia in human beings. The purpose of this study was to separate L.pneumophila from stagnant and waste water, city squares, coolers and faucets and evaluation of the immunoprotective efficiency of its whole killed cells in mice model. Water samples were prepared, concentrated and then cultured on selective [GVPC] media. After identification of L.pneomophila the biomass of the organism was fixed with 0.5% formalin in sterile saline at 37§C for 24 hours in order to prepare whole killed cells. Four groups of female BALB/c mices [each group consisted of 15 mices] were selected. Two groups of mice were immunized by three intraperitoneal administrations of prepared antigen in a dose of 4x108 CFU from whole killed cells at two week intervals and control groups received only sterile saline injections. Two weeks after the last injection, one group of immunized mice and one of the control groups were challenged with the lethal dose of virulent strain of L.pneuophila and also the two other groups of mice were challenged six weeks after the last immunization. From 120 water samples 27 samples were contaminated with L.pneumophila. Challenge results showed that the immune efficiency of whole killed cell was 93.33% after two weeks of the last immunization, and 86.66% after six weeks of the last immunization. This study showed that, stagnant water had the highest rate of contamination with L.pneumophila and the whole killed cell of L.pneumophila is a proper candidate for L.pneumophila vaccine studies