Phenotypic diversity and selection maintain Leishmania amazonensis infectivity in BALB/c mouse model.

Benoît Espiau,Université De Bordeaux, France ,Aldina Barral,Labex Corail, Polynésie Française ,Virginia Vilhena,Faculdade Anhanguera De Brasília, Brasil ,Fundação Oswaldo Cruz, Brasil ,Instituto De Investigação Em Imunologia, Brasil ,Gilles Merlin,Armelle Cuvillier,B Cell Design, France

doi:10.1590/0074-02760160280

Abstract

Leishmania are protozoan parasites that show remarkable diversity, as revealed by the various clinical forms of leishmaniasis, which can range from mild skin lesions to severe metastatic cutaneous/mucosal lesions. The exact nature and extent of Leishmania phenotypic diversity in establishing infection is not fully understood. In order to try to understand some aspects of this diversity, we subcutaneously infected BALB/c mice with first and second generation subclones of a L. amazonensis strain isolated from a patient (BA125) and examined in vivo lesion growth rate and antimony susceptibility. In vivo fast-, medium- and slow-growing subclones were obtained; moreover, fast-growing subclones could generate slow-growing subclones and inversely, revealing the continuous generation of diversity after passage into mice. No antimony-resistant subclone appeared, probably a rare occurrence. By tagging subclone cells with a L. amazonensis genomic cosmid library, we found that only a very small number of founding cells could produce lesions. Leishmania clones transfected with in vivo selected individual cosmids were also diverse in terms of lesion growth rate, revealing the cosmid-independent intrinsic characteristics of each clone. Our results suggest that only a few of the infecting parasites are able to grow and produce lesions; later, within the cell mixture of each lesion, there coexist several parasite populations with different potentialities to grow lesions during the next infection round. This may reflect a sort of programmed heterogeneity of individual parasites, favoring the survival of some individuals in various environmental conditions.

Highlights

Leishmania are digenetic protozoan parasites of the Trypanosomatidae family that are responsible for severe diseases in tropical and subtropical countries
Our model consisted in an infectious strain of L. amazonensis isolated from a patient (BA125), the BALB/c mouse strain, and the footpad infection
The parental strain was transfected with a L. amazonensis cosmid genomic library, mice infected with the transfectants, and the cosmids recovered from the lesion cells

Summary

Introduction

Leishmania are digenetic protozoan parasites of the Trypanosomatidae family that are responsible for severe diseases in tropical and subtropical countries. With the aim to study Leishmania phenotypic diversity, we chose an in vivo infection animal model, simplified compared to natural infections, but with the advantages of some parameter constancy. Two criteria of clinically relevant potential diversity were examined, i.e., in vivo lesion growth rate and antimony susceptibility. L. amazonensis infectivity variability Benoît Espiau et al 45 from a parental lesion were subcloned and individual subclones used for new infections in mice treated or not with antimony; the cells of some of the obtained lesions were again subcloned as for the first sets. The parental strain was transfected with a L. amazonensis cosmid genomic library, mice infected with the transfectants, and the cosmids recovered from the lesion cells. Phenotype stability and cosmid occurrence in recovered lesion amastigotes were compared. We hypothesize that (i) among the cells used for infection, only a few are able to grow and produce lesions and (ii) different cells with different potentialities to grow lesions during the infection round coexist in the cell mixture of each lesion

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Conclusion