A vaccine for tularaemia.

Francisella tularensis is an intracellular pathogen with a very low infectious dose for humans. Several forms of tularaemia occur, which range from a severely debilitating to a fatal disease. Diagnosis is difficult due to the generalised, nonspecific nature of symptoms and the difficulty in culturing the slow-growing and nutritionally fastidious pathogen. A live attenuated vaccine strain (LVS) has been used in humans as an investigational new drug and does appear to induce a protective response. However, the licensing of this vaccine has not yet been possible. For this reason, modern molecular biology approaches are being used in an attempt to devise replacement vaccines which may be more easily licensed. The approaches which are currently being considered include the production of subunit vaccines and the development of defined isogenic attenuated mutant strains of F. tularensis.