Infectivity of Leishmania infantum treated with amphotericin B plus Phlebotomus salivary gland in BALB/c mice

Amphotericin B (AMB) has been widely used in visceral leishmaniasis treatment in Europe, namely in Leishmania/HIV co-infections and paediatric cases. However, only few studies on resistance to AMB are available so far. The purpose of this work is to anticipate the possibility of emerging AMB-resistant isolates in nature. BALB/c mice were intradermally (ID) inoculated with L. infantum wild-type strain and AMB in vitro treated parasites in presence or absence of Phlebotomus perniciosus salivary gland. The course of infection was followed-up during 12 weeks. Parasite load and cytokine expression were determined. Specific humoral and cellular responses were also evaluated. Our results confirm that ID inoculation of L. infantum in mice causes visceral infection and all infected mice developed a mixed immune response i.e. pro and anti -inflamatory responses. No significant difference in the parasite load was observed among infected groups, showing that treatment of parasites with AMB and the presence of saliva did not affect their infectivity on the vertebrate host. However, the presence of AMB treated parasites in the skin of infected mice allow to suggest that AMB resistant strains could arise and be transmitted in nature as a result of the use of AMB on human and canine leishmaniasis therapy.