Bacteremia

Example 7

Sepsis modeling was performed as described by Gorringe A. R., Reddin, K. M., Voet P. and Poolman J. T. (Methods Mol. Med. 66, 241 (Jan. 1, 2001)) and Johswich, K. O. et al. (Infect. Immun. 80, 2346 (Jul. 1, 2012)). Groups of 6 eight-week-old C57BL/6 mice (Charles River Laboratories) were inoculated via intraperitoneal injection with N. meningitidis strain B16B6, B16B6 Δtbpb, or B16B6 Δnmb0313 (N=2 independent experiments). To prepare inoculums, bacterial strains for infection were grown overnight on GC agar, resuspended and then grown for 4 h in 10 ml of Brain Heart Infusion (BHI) medium at 37° C. with shaking. Cultures were adjusted such that each final 500 μl inoculum contained 1×10⁶ colony forming units and 10 mg human holo-transferrin. Mice were monitored at least every 12 h starting 48 h before infection to 48 h after infection for changes in weight, clinical symptoms and bacteremia. Mice were scored on a scale of 0-2 based on the severity of the following clinical symptoms: grooming, posture, appearance of eyes and nose, breathing, dehydration, diarrhea, unprovoked behavior, and provoked behavior. Animals reaching endpoint criteria were humanely euthanized. Animal experiments were conducted in accordance with the Animal Ethics Review Committee of the University of Toronto.

FIG. 7 shows the results obtained. FIG. 7A shows a solid phase binding assay consisting of N.men cells fixed with paraformaldehyde (PFA) or lysed with SDS and were spotted onto nitrocellulose and probed with α-TbpB antibodies. ΔSLAM/tn5 refers to the original strain of SLAM deficient cells obtained through transposon insertion. ΔSLAM describes the knockout of SLAM in Neisseria meningitidis obtained by replacing the SLAM ORF with a kanamycin resistance cassette. FIG. 7B shows a Proteinase K digestion assay showing the degradation of TbpB, LbpB and fHbp only when Nm cells are SLAM deficient (ΔSLAM). Nm cells expressing individual SLPs alone and with SLAM were incubated with proteinase K and Western blots were used to detect levels of all three SLPs levels with and without protease digestion (−/+). Flow cytometry was used to confirm that ΔSLAM cells could not display TbpB (FIG. 7C) or fHbp (FIG. 7D) on the cell surface. Antibodies against TbpB and fHbp were used to bind surface exposed SLPs followed by incubation with a α-Rabbit antibody linked to phycoerythrin to provide fluorescence. The mean fluorescent intensity (MFI) of each sample was measured using the FL2 detector of a BD FACS Calibur. The signal obtained from wildtype cells was set to 100% for comparison with signals from knockout cells. Error bars represent the standard error of the mean (SEM) from three experiments. Shown in FIG. 7E are the results of mice infections with various strains. Mice were infected via intraperitoneal injection with 1×10⁶ CFU of wildtype N. meningitidis strain B16B6, B16B6 with a knockout of TbpB (ΔtbpB), or B16B6 with a knockout of nmb0313 Δslam and monitored for survival and disease symptoms every 12 h starting 48 hr pre-infection to 48 h post-infection and additionally monitored at 3 hr post-infection. Statistical differences in survival were assessed by a Mantel-Cox log rank test (GraphPad Prism 5) (*p<0.05, n.s. not significant). These results show a marked reduction in post-infection mortality in mice infected with the knockout of nmb0313 Δslam strain.