Development of a storable Leishmania tropica vaccine: field testing with frozen promastigotes

The development of a frozen vaccine against cutaneous leishmaniasis offers the possibility of controlling the quality, efficiency and sterility of the promastigotes used for inoculation. Thirty-nine soldiers in a settlement in a hyperendemic area were inoculated with a fresh isolate of Leishmania tropica that was stored at the temperature of liquid nitrogen. Thirty of the soldiers were injected by conventional syringe while the rest were inoculated by an intradermal jet injector. The infective material was transported either in ice or at liquid nitrogen temperature. All the subjects developed lesions at the site of inoculation, without unwarranted reactions. One month after inoculation 31 subjects were examined by a physician. All the reactions were positive--12 ulcers and 19 nodules. After four months, all 39 soldiers were examined: 25 (64%) had ulcers; eight (21%) had nodules; and six (15%) were without visible reaction. The different methods of transporting the vaccine, as well as the different responses of men and women, are discussed.