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.
