Leishmania (L.) amazonensis: Fusion between parasitophorous vacuoles in infected bone-marrow derived mouse macrophages

[Leishmania (L.)] amazonensis amastigotes reside in macrophages within spacious parasitophorous vacuoles (PVs) which may contain numerous parasites. After sporadic fusion events were detected by time-lapse cinemicrography, PV fusion was examined in two different models. in single infections, it was inferred from the reduction in PV numbers per cell. in a reinfection model, macrophages infected with unlabeled amastigotes were reinfected with GFP-transfected- or carboxyfluorescein diacetate succinimidyl ester-labeled parasites, and fusion was detected by the colocalization of labeled and unlabeled amastigotes in the same PVs. the main findings were: (1) as expected, fusion frequency increased with the multiplicity of infection; (2) most fusion events took place in the first 24 h of infection or reinfection, prior to the multiplication of incoming parasites; (3) resident and incoming parasites multiplied at similar rates in fused PVs. the model should be useful in studies of parasite and host cell factors and mechanisms involved in PV fusogenicity. (C) 2007 Elsevier Inc. All rights reserved.Universidade Federal de São Paulo, Dept Microbiol Immunol & Parasitol, BR-04023062 São Paulo, BrazilINSERM, Serv Microcinematog, F-78110 Le Vesinet, FranceUniversidade Federal de São Paulo, Dept Microbiol Immunol & Parasitol, BR-04023062 São Paulo, BrazilWeb of Scienc