Effects of hydrostatic pressure on the Leptospira interrogans: high immunogenicity of the pressure-inactivated serovar hardjo

The Hardjoprajitno strain of Leptospira interrogans serovar hardjo was subj ected to different hydrostatic pressures. Complete inactivation occurred wh en the leptospires were treated with 2 kbar for 60 min. Electron microscopy showed dislocation of the outer membrane, partial loss of the helical shap e and extrusion of the axial filament from the cytoplasmic cylinder of the pressurized leptospires. When the pressure-treated leptospires were inocula ted into rabbits they were highly immunogenic, The sera of these animals pr esented a titer of 2048 in the microscopic serum agglutination reaction. Fl uorescence measurements indicated that the action of pressure on the leptos pires might have resulted from perturbation on membrane protein components, permitting the binding of the fluorescent probe bis (8-anilinonaphthalene- 1-sulfonate) (Bis-ANS). This is the first report of the use of hydrostatic pressure to inactivate pathogenic bacteria with the potential to lead to a vaccine. (C) 2001 Elsevier Science Ltd. All rights reserved.