<i>In vitro</i> Infection of Murine Macrophage by <i>Leishmania brasiliensis</i>. Mechanism of Penetration

Abstract

The in vitro infection of peritoneal murine macrophages by a cultured pathogenic strain of Leishmania brasiliensis was studied. By phase contrast and light microscopy it could be observed that L. brasiliensis is rapidly endocytosed by the macrophages and localized in the cytoplasm in a vacuole inside which it multiplies. By phase contrast and electron microscopy it was observed that L. brasiliensis enters the macrophage by the anterior end through which it first attaches to the cell membrane. This penetration involves invagination of the cell membrane around the entering flagellum and parasite body. A mechanism of entry involving an active participation of the parasite membrane through receptor sites and membrane activity by the microfilament system is presented.

The Attachment and Entry of Leishmania (Leishmania) Major into Macrophages: Observation by Scanning Electron Microscope

“…Rittig et al reported that L.(L.) mexicana, L.(L.) tropica, L.(L.) major, L.(L.) aethiopica and L.(Viannia) braziliensis attached to the host cell by either the tip or the base of the flagellum, whereas L.(L.) donovani attached to the cell by either the flagellar tip or the aflagellar pole (posterior pole) (8). Many other researchers have reported the same findings (7, 10–16). However, our findings obtained by SEM observations revealed that the attachment of L.(L) major to J774‐1A macrophage occurred not only by the flagellar tip, flagellar base, and/or aflagellar tip (posterior pole), but also on the body of the parasite.…”

In vitro parasite-monocyte interactions in human leishmaniasis. Evidence for an active role of the parasite in attachment.

“…An understanding of these mechanisms might be exploited in designing novel chemotherapeutic strategies. Electron microscopic investigations of host cell-parasite interactions in vitro have suggested that Toxoplasma gondii, Trypanosoma cruzi, and Leishmania species enter mononuclear phagocytes by endocytosis (1)(2)(3). Furthermore, cytochalasin (antiphagocytic agents) prevented parasite interiorization into host cells in vitro (2,4,5).…”

“…Prior in vitro studies of these interactions (e.g., 3, 5, 7) examined attachment and entry of the motile flagellated extracellular forms of the parasite (promastigotes) that exist only briefly in the host before they transform into the aflagellate obligate intracellular forms, the amastigotes. Once infection is established, only amastigotes persist.…”

Flow cytometric analysis of the effects exerted by monoclonal antibodies on binding and uptake of Leishmania mexicana subsp. mexicana promastigotes by murine peritoneal macrophages

“…Since promastigotes are susceptible to lysis by components of the extracellular fluid (25,29), prompt attachment to and uptake by the macrophage is required for the successful maintenance Qf infection. Leishmania-macrophage membrane interactions have been examined extensively by using phagocytes from humans or rodents in combination with amastigotes or promastigotes of various Leishmania species (5,7,10,11,24,30,33,34). While these studies have established that optimum conditions for an in vitro demonstration of leishmania-macrophage binding may vary depending on the assay system and the particular species of parasite and host involved, several characteristics are common to all models.…”