Translational profiling of macrophages infected with Leishmania donovani identifies mTOR- and eIF4A-sensitive immune-related transcripts

The protozoan parasite Leishmania donovani ( L. donovani ) causes visceral leishmaniasis, a chronic infection which is fatal when untreated. While previous studies showed that L. donovani reprograms transcription to subvert host cell functions, it remains unclear whether the parasite also alters host mRNA translation to establish a successful infection. To assess this, we compared transcriptome-wide translation in primary mouse macrophages infected with L. donovani promastigotes or amastigotes using polysome-profiling. This identified ample selective changes in translation (3,127 transcripts) which were predicted to target central cellular functions by inducing synthesis of proteins related to chromatin remodeling and RNA metabolism while inhibiting those related to intracellular trafficking and antigen presentation. Parallel quantification of protein and mRNA levels for a set of transcripts whose translation was activated upon L. donovani infection ( Papbpc1, Eif2ak2, and Tgfb ) confirmed, as indicated by polysome-profiling, increased protein levels despite largely unaltered mRNA levels. Mechanistic in silico analyses suggested activated translation depending on the kinase mTOR (e.g. Pabpc1 ) and the RNA helicase eIF4A (e.g. Tgfb ) during infection. Accordingly, treatment with mTOR inhibitors torin-1 or rapamycin reversed L. donovani -induced PABPC1 without affecting corresponding transcript levels. Similarly, the production of TGF-β decreased in presence of the eIF4A inhibitor silvestrol despite unaltered Tgfb mRNA levels. Consistent with parasite modulation of host eIF4A-sensitive translation to promote infection, silvestrol suppressed L. donovani replication within macrophages. In contrast, parasite survival was favored under mTOR inhibition. In summary, infection-associated changes in translation of mTOR- and eIF4A-sensitive mRNAs contribute to modulate mRNA metabolism and immune responses in L. donovani -infected macrophages. Although the net outcome of such translation programs favours parasite propagation, individual translation programs appear to have opposing roles during L. donovani infection, thereby suggesting their selective targeting as key for therapeutic effects. .