Typhoid fever is a life-threatening disease, but little is known about the molecular bases for its unique clinical presentation. Typhoid toxin, a unique virulence factor of Salmonella Typhi (the cause of typhoid fever), recapitulates in an animal model many symptoms of typhoid fever. Typhoid toxin binding to its glycan receptor Neu5Ac is central, but, due to the ubiquity of Neu5Ac, how typhoid toxin causes specific symptoms remains elusive. Here we show that typhoid toxin displays in vivo tropism to cells expressing multiantennal glycoprotein receptors, particularly on endothelial cells of arterioles in the brain and immune cells, which is in line with typhoid symptoms. Neu5Ac displayed by multiantennal N-glycans, rather than a single Neu5Ac, appears to serve as the high-affinity receptor, as typhoid toxin possesses five identical binding pockets per toxin. Human counterparts also express the multiantennal Neu5Ac receptor. Here we also show that mice immunized with inactive typhoid toxins and challenged with wild-type typhoid toxin presented neither the characteristic in vivo tropism nor symptoms. These mice were protected against a lethal-dose toxin challenge, but Ty21a-vaccinated mice were not. Cumulatively, these results reveal remarkable features describing how a bacterial exotoxin induces virulence exclusively in specific cells at the organismal level.
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The authors thank J. E. Galán for his suggestion on the typhoid toxoid vaccination study, which was initiated while J.S. was at Yale, N. Nishimura for her comments on brain images, and X. Gao for plasmid pET21a-pltB-His6. This work was supported by a Cornell University Startup, PCCW Affinito-Stewart Award and the USDA/NIFA Hatch project 1010701 (to J.S.), the NIH, NCI, under contract no. HHSN261200800001E (to R.N.), the NIH, NIDCD intramural research programme (to J.Z.), and NIH R01 AI114730 to J.C.P. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Electronic supplementary material
Supplementary Figures 1–11, Supplementary Tables 1-4, Supplementary Methods, Supplementary References, Supplementary Data
Related to Fig. 3f and Supplementary Fig. 7. Lists of glycans and glycan microarray results. Data for individual glycans are reported as relative fluorescence intensities from four of six replicates (after removal of highest and lowest values)
Related to Fig. 1c. A representative video showing ataxia signs typically seen 4.5–5 days after WT toxin administration
Related to Fig. 1c. A representative video showing clonic seizure signs typically seen 5–6 days after WT toxin administration
Related to Fig. 1d. A representative balance beam test of C57BL/6 mice administered PBS. Balance beam tests were conducted 5 days after PBS buffer administration
Related to Fig. 1d. A representative result of balance beam tests of mice administered WT toxin. Balance beam tests were conducted 5 days after WT toxin administration
Related to Fig. 1d. Another representative result of balance beam tests of mice administered WT toxin. Balance beam tests were conducted 5 days after WT toxin administration
Related to Fig. 1d. A representative result of balance beam tests of mice administered a PltB catalytic mutant toxin. Balance beam tests were conducted 5 days after indicated toxin administration
Related to Fig. 1f. A representative result of balance beam tests of mice administered a PltA catalytic mutant toxin. Balance beam tests were conducted 5 days after indicated toxin administration
Related to Fig. 1f. A representative result of balance beam tests of mice administered a CdtB catalytic mutant toxin. Balance beam tests were conducted 5 days after indicated toxin administration
Related to Supplementary Fig. 2. A representative result of balance beam tests of mice infected with a lethal dose of S. Typhimurium. A group of C57BL/6 mice were infected orally with 107 S. Typhimurium SL1344. The balance beam test was conducted 5 days after infection
Related to Fig. 4i. A representative result of balance beam tests of mice immunized by typhoid toxoid and challenged by a lethal dose of typhoid toxin. A group of C57BL/6 mice were immunized by subcutaneous injections of typhoid toxoid via a standard prime-boost regimen. Two weeks after boost, the immunized mice were challenged with 2 μg WT typhoid toxin. Balance beam tests were conducted 5 days after the WT toxin challenge
About this article
Nature Microbiology (2018)
Molecular & Cellular Toxicology (2018)