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

Abstract

A B S T R A C T Leishmania are obligate intracellular parasites of mononuclear phagocytes in the mammalian host. To more clearly define features of the early events in host-parasite interaction, human monocytes were co-cultured with Leishmania tropica amastigotes in vitro. Infection of monocytes was time dependent and inhibited at 4°C and in the presence of cytochalasin B. Pretreatment of amastigotes with cytochalasins prevented their attachment to normal monocytes. Untreated amastigotes attached normally but could not enter cytochalasin-pretreated monocytes. This suggests that amastigotes actively participate in attachment but require host cell participation for interiorization.

Phagocytosis of leprosy bacilli is mediated by complement receptors CR1 and CR3 on human monocytes and complement component C3 in serum.

“…These include serum-derived molecules such as complement component C3 (1, 2, 6, 9-12) and fibronectin (13,14), and glycosylated parasite surface molecules (15)(16)(17)(18).…”

Role of fibronectin in Pneumocystis carinii attachment to cultured lung cells.

“…These include staphylococci (1 1, 12), streptococci (13,14), Treponema pallidum (15), Trypanosoma cruzi (16), Leishmania spp. (17), and Candida albicans (18). Staphylococci and streptococci bind to Fn at separate sites on the amino terminus of the molecule (19,20).…”

A biological role for haemagglutination activity ofLeishmaniapromastigotes and amastigotes

“…the major surface antigen lipophosphoglycan (LPG) (Kel- Leishmania, amastigotes, phagocytes, attachment, activité « lectinlike », Leptomonas. leher et al, 1992 ;Mosser & Handman, 1992) and the metalloproteinase gp63 of the parasite (Russel & Wilhelm, 1986) ; fibronectin, mannose, CR3, CR1, and advanced glycosylation endproducts receptors of macrophages (Wyler et al, 1985 ;Blackwell, 1985 ;Dasilva et al, 1989 ;Wilson & Pearson, 1986 ;Mosser et al, 1987). Considerably less is known about the amastigote-phagocyte interaction.…”

“…Considerably less is known about the amastigote-phagocyte interaction. LPG, CR3, fibronectin and heparin-binding activity have been proposed as mediating amastigote adhesion (Kelleher et al, 1995 ;Guy & Belosevic, 1993;Wyler et al, 1985;Love et al, 1993). Among the multiple, redundant mechanisms of Leishmania adhesion to macrophages, carbohydrates and lectin-like receptors are involved (Chang, 1981;Bray, 1983 ;Hernándes et al, 1986).…”