Long-term <i>in vitro</i> maintenance of <i>L. infantum</i> promastigotes results in loss of virulence <i>in vivo</i>.

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