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In vitro assays play an important role in the discovery and development of new antileishmanial drugs. The classic macrophage-amastigote models using murine peritoneal macrophages or human-monocyte derived macrophages as host cells are useful for drug screening. A major limitation of these models is the dependence on microscopic counting, a time-consuming and subjective method of analysis. The present study describes a detailed protocol for applying quantitative real-time PCR (qPCR) as an accurate and sensitive tool to assess parasite load in an amastigote-macrophage model. This assay can be performed in a standardized medium-to-high throughput procedure, replacing traditional readout of number of amastigote per macrophages by DNA load measurement., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Phlebotomine sand flies are the only proven biological vectors of Leishmania parasites. However, Rhipicephalus sanguineus ticks have long been suspected to transmit Leishmania infantum in studies carried out in laboratory and natural conditions. In the present study, 5 microl of L. infantum promastigotes (1x10(6) cells per ml) was injected into the hemocel through the coxa I of four engorged females (F1, F2, F3 and F4). Control ticks (F5 and F6) were injected with sterile phosphate-buffered saline (PBS) using the same procedure. Then, these females, their eggs, and the originated larvae were tested by real time polymerase chain reaction (real-time PCR) for the presence of L. infantum kinetoplast DNA (kDNA). Females and eggs were tested after the end of the oviposition period (about 5 weeks post-inoculation) whereas larvae were tested about 4 months after the inoculation of females. All artificially infected females were positive for L. infantum kDNA. In addition, two pools of eggs (one from F2 and other from F4) and four pools of larvae (one from each F1 and F4 and two from F2) were positive for L. infantum kDNA. These results showed, for the first time, the transovarial passage of L. infantum kDNA in R. sanguineus ticks, thus suggesting that the transovarial transmission of L. infantum protozoa in ticks is worth to be investigated., (Copyright (c) 2010 Elsevier Inc. All rights reserved.)