Abstract
In Leishmania, genetic exchange has been experimentally demonstrated to occur in the sand fly vector and in promastigote axenic cultures through a meiotic-like process. No evidence of genetic exchange in mammalian hosts have been reported so far, possibly due to the fact that the Leishmania species used in previous studies replicate within individual parasitophorous vacuoles. In the present work, we explored the possibility that residing in communal vacuoles may provide conditions favorable for genetic exchange for L. mexicana and L. amazonensis. Using promastigote lines of both species harboring integrated or episomal drug-resistance markers, we assessed whether genetic exchange can occur in axenic cultures, in infected macrophages as well as in infected mice. We obtained evidence of genetic exchange for L. amazonensis in both axenic promastigote cultures and infected macrophages. However, the resulting products of those putative genetic events were unstable as they did not sustain growth in subsequent sub-cultures, precluding further characterization.
Highlights
Protozoan parasites of the genus Leishmania are the causative agents of a spectrum of diseases known as leishmaniasis that range from self-healing cutaneous lesions to destructive mucocutaneous infections and visceral pathologies
To investigate the possibility that formation of hybrids and genetic exchange may occur among parasites of the L. mexicana complex, we used L. amazonensis LV79 and L. mexicana M379 expressing either episomal or integrated genes encoding resistance to Hygromycin B (HYG) or to G418 (NEO)
We generated one line of L. amazonensis and one line of L. mexicana in which the HYG resistance gene was integrated in one allele of the LPG2 gene (L. amazonensis LPG2/LPG2::DHYG and L. mexicana LPG2/LPG2::DHYG) (Figure 1A), one line of L. amazonensis in which a NEO-GFP construct was integrated into the ribosomal RNA locus (L. amazonensis +/SSU::NEO-GFP) (Figure 1A), one line of L. amazonensis and one line of L. mexicana with an episomal NEO-DsRed plasmid (L. amazonensis NEO-DsRede and L. mexicana NEO-DsRede), and one line of L. amazonensis with an episomal HYG-GFP plasmid (L. amazonensis HYG-GFPe)
Summary
Protozoan parasites of the genus Leishmania are the causative agents of a spectrum of diseases known as leishmaniasis that range from self-healing cutaneous lesions to destructive mucocutaneous infections and visceral pathologies. There is much evidence indicating that genetic exchange is part of the biology of Leishmania parasites, as Genetic Exchange in Leishmania amazonensis evidenced by the occurrence of hybrids in nature. These natural hybrids were described at the intraspecific level for L. tropica, L. donovani, L. infantum, and L. brasiliensis (Chargui et al, 2009; Rougeron et al, 2009; Gelanew et al, 2014; Rogers et al, 2014; Iantorno et al, 2017). Natural hybrids were reported for Leishmania species of the Leishmania subgenus such as L. major and L. arabica, L. major and L. infantum, as well as L. donovani and L. infantum (Evans et al, 1987; Kelly et al, 1991; Ravel et al, 2006; Volf et al, 2007; Odiwuor et al, 2011; Seblova et al, 2015; Cortes et al, 2019)
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