Leishmania Life Cycle into another macrophage ( amastigote ) - - PDF document

sandfly ingests macrophages (amastigote) to the gut amastigotes released from the macrophage differentiates to promastigote sandfly dividing form attaches to the intestine wall metacyclic promastigote blockage of the pharynx infective to the vert. host Sandfly bite “throat clearing” no salivary infection promastigote into macrophage amastigote still in the macrophage dividing form release from macrophage (amastigote) into another macrophage (amastigote) differentiates to amastigote in the macrophage macrophage filled with amastigotes in the bloodstream

Leishmania Life Cycle

Agglutination – a decreased number of free promastigotes compared to the control Peanut (PNA) and ricin (RCA) are two-D-galactose-binding lectins Left panels : percent agglutination using PNA and RCA agglutinin log-phase promastigotes – solid line stationary promastigotes – dashed line 100% agglutination with PNA and RCA in log-phase cells 50% agglutination using stationary cells Right panel : Percent infectivity (macrophage survival) at various growth time points Solid bars - % of promastigotes surviving thru change to amastigotes Open bars - % unagglutinated (infective) promastigotes of total recovered Conclusions: Only stationary phase promastigotes (metacyclic) are able to survive in the macrophage (~50%). Virtually all surviving cells are stationary phase, PNA non-binding (non-agglutinated.) Non-agglutination is the result of a change in surface binding sites. Changes in the cell surface (lengthening of the coat) are part of the metacyclic pre-adaption.

Lectins (Ricin, peanut agglutinin, PpGalectin ) : Bind to D-Galactose

ProcyclicPromastigote LPG (fly midgut) Metacyclic Promastigote LPG (fly midgut) Hence, the metacyclic promastigote LPG does not bind the PpGalectin in the midgut and out it goes

LPG: Lipophosphoglycan Pro Meta

L.donovani

• L. Major
• GPI anchored

phospholipid chain polymer with branching sugar moeities

• Major surface

molecule of the parasite

• Different LPGs in

Metacyclic vs Procyclic promastigotes

• This change

corresponds to different infectivities in different life stages!

• Procyclic

Promastigotes(Insect midgut) =Not infective to Mammals

• Metacyclic

Promastigotes (Insect Salivary gland = Infective to mammals

LPGs in the insect