“…The stability of the parasite must be assured in any vaccine development strategy. Changes of the characteristics of the parasites in culture have been re-examined elegantly for many Leishmania species in recent years (Giannini, 1974;Keithly & Bienen, 1981;Sacks & Perkins, 1984;Franke, McGreevy, Katz & Sacks, 1985;Wozencraft & Blackwell, 1987;Melo, Williams, Magalhaes-Rocha, Baba, Mayrink, Michalick, Da Costa, Diaz & Magalhaes, 1987;Turco, Hull, Orlandi, Sheperd, Homans, Dweck & Rademacher, 1987;Howard, Sayers & Miles, 1987;Celeste & Guimaraes, 1988), and inhibition of one species by another in a mixed culture has also been seen (Pacheco, Grimaldi & Morel, 1987).…”