Stabilisation of Salmonella vaccine vectors by the induction of trehalose biosynthesis

The growth of an aroA mutant of Salmonella typhimurium (SL3261) in minimal medium containing 0.5 M NaCl resulted in the intracellular accumulation of 2.2 mu mol trehalose/mg total protein. The vacuum drying of these bacteria in the presence of trehalose allowed the recovery of 35% of the viable cell s that were present before drying. In contrast, bacteria cultured in contro l medium accumulated 0.4 mu mol trehalose/mg total protein and only 5% of t he viable cells were recovered after vacuum drying with trehalose. Similar results were obtained when S. typhimurium SL3261, expressing the vaccine an tigen (F1-antigen) of Yersinia pestis, was cultured in minimal medium with or without 0.5 M NaCl and dried in the presence of trehalose. Although thes e results indicate the potential for trehalose stabilisation of vaccine str ains of S. typhimiurium, growth in minimal medium containing 0.5 M NaCl res ulted in the loss of invasion competence of the bacteria. (C) 2000 Elsevier Science Ltd. All rights reserved.