Authors
S Roy1; 1 Indian Association for the Cultivation of Sciences, IndiaDiscussion
Leishmania donovani<,/i> (LD) causes visceral leishmaniasis (VL) and replicates within the parasitophorous vacuoles of macrophages (MΦ). Antimony (Sb) compounds have historically been used for the treatment of VL; however, the emergence of Sb-resistant LDs (SbRLD) has resulted in the discontinuation of antimonials for decades in the Indian subcontinent. Despite this, recent field isolates continue to demonstrate resistance, exhibiting remarkable fitness. Our findings indicate that SbRLD-infected MΦ (SbRLD-MΦ) displayed an enhanced autophagic flux, co-localisation with MDC-positive vesicles, conversion from LC3BI to LC3BII, enhanced beclin-1 expression, and homing into double-membrane enfolded vesicles. In contrast, Sb-sensitive LD (SbSLD)-infected MΦ (SbSLD-MΦ) do not exhibit most of these effects. The dynamic changes observed in SbRLD-MΦ were in agreement with autophagy. The Vsp-34-Beclin-1-Bcl-2 trinary was found to swerve into two binaries: Beclin-1-Bcl-2 and Beclin-1-Vps34, at different stages of autophagy. We demonstrated that both the binaries remain associated for about 8h in SbRLD-MΦ, an event not observed in SbSLD-MΦ. Furthermore, we showed that the transcription and post-transcription of Beclin-1 were regulated by Nrf2 and miR-30a, respectively. Unlike SbSLD-MΦ, SbRLD-MΦ facilitated the maturation of pre-miRNA30a to miRNA30a. Knockdown of Nrf2 resulted in the cessation of autophagy in the cell line and also in the animal model, and infection by SbRLD showed reduced organ parasites. The halting of autophagy was accompanied by Ca²⁺-dependent caspase-8-mediated cleavage of beclin-1, accompanied by a molecular switch from autophagy to apoptosis with a higher SbRLD egress compared to SbSLD. Our results illustrate that SbRLD exploits autophagy, contributing to an aggressive infection in mammalian hosts.
