Figure 3. Long-term in vitro maintenance of L. infantum promastigotes results in loss of virulence in vivo.

Balb/c mice were infected with stationary phase promastigotes submitted to 4, 21 or 31 successive in vitro passages. After 6 weeks post-infection, the parasite load was determined in liver (A) and spleen (B) by limiting dilution. The mean and standard deviation are shown. *P<0,05; **P<0,01; ***P<0,001.