Subsequent hematoxylin-eosin (H&E) stains of each ear were randomized and blinded, then scored by one of us (A.N.W., a Board-certified pathologist) for the extent of inflammation using a scale from 0 (no inflammation, PBS control) to 4+ (greatest inflammatory
response observed). Examples of PBS control (A, inflammatory score = 0) and 86-028NP infected (B, inflammatory score = 4+) H&E-stained chinchilla middle ears are shown in Figure 7. Consistent with the numbers of viable bacteria recovered, the middle ear sections from animals click here infected with the mutant strains exhibited less inflammation on average than the wild type parent strain (Table 1). This suggests that the vap mutants were killed and cleared earlier in the infection process, supporting both the role of these TA operons in the pathogenesis
of otitis media and the importance of these modules as new therapeutic targets. Figure 7 Chinchilla middle ear sections from control and infected animals. Representative H&E stained sections from A) PBS control (inflammatory score = 0) selleck screening library and B) 86-028NP-infected (inflammatory score = 4+) animals. Scale bars are 10 μm. Table 1 Inflammatory response scores of chinchilla middle ear sections Strain Inflammatory scorea 1+ 2+ 3+ 4+ 86-028NP 1 2 4 1 ΔvapBC-1 1 6 1 0 ΔvapXD 2 4 2 0 ΔvapBC-1 ΔvapXD 4 4 0 0 a8 middle ears were scored for each challenge strain. VapD displays ribonuclease activity We have previously shown that VapC-1 is a ribonuclease . Since the ΔvapXD mutant was also attenuated for survival in vitro and in vivo, we assayed eltoprazine the purified VapD toxin for RNase activity, and found that it was a potent ribonuclease (Figure 8). These data are consistent with a recent publication that demonstrated the ribonuclease activity of a VapD homologue from Helicobacter pylori. Figure 8 shows a RNase activity assay conducted over time using the RNaseAlert (Integrated DNA Technologies, Coralville,
IA) substrate with increasing amounts of VapD protein. The single-stranded RNA substrate has a quencher on one end and a fluorophore (FAM) on the other, and fluoresces brightly when cleaved. We included protein elution buffer, purified Cat (chloramphenicol acetyltransferase), and antitoxin VapX PLX3397 proteins as negative controls, which were overexpressed and purified in the identical fashion as VapD. The VapD protein displayed concentration-dependent RNase activity over time in this assay. Figure 8 RNase activity assays with purified VapD, Cat, and VapX. Ribonuclease activity over time of the protein elution buffer control (blue), 0.2 μg (red), 0.4 μg (green), and 0.6 μg (purple) of purified VapD, 0.6 μg of chloramphenicol acetyltransferase (Cat, turquoise), or 0.