Dual transcriptome analysis reveals differential gene expression modulation influenced by Leishmania arginase and host genetic background

The outcome of Leishmania infection is strongly influenced by the host’s genetic background. BALB/c mice are susceptible to Leishmania infection, while C57BL/6 mice show discrete resistance. Central to the fate of the infection is the availability of l-arginine and the related metabolic processes in the host and parasite. Depending on l-arginine availability, nitric oxide synthase 2 (NOS2) of the host cell produces nitric oxide (NO) controlling the parasite growth. On the other hand, Leishmania can also use host l-arginine for the production of polyamines through its own arginase activity, thus favouring parasite replication. Considering RNA-seq data, we analysed the dual modulation of host and parasite gene expression of BALB/c or C57BL/6 mouse bone marrow-derived macrophages (BMDMs) after 4 h of infection with Leishmania amazonensis wild-type (La-WT) or L. amazonensis arginase knockout (La-arg(-)). We identified 12 641 host transcripts and 8282 parasite transcripts by alignment analysis with the respective Mus musculus and L. mexicana genomes. The comparison of BALB/c_La-arg(-) versus BALB/c_La-WT revealed 233 modulated transcripts, with most related to the immune response and some related to the amino acid transporters and l-arginine metabolism. In contrast, the comparison of C57BL/6_La-arg(-) vs. C57BL/6_La-WT revealed only 30 modulated transcripts, including some related to the immune response but none related to amino acid transport or l-arginine metabolism. The transcriptome profiles of the intracellular amastigote revealed 94 modulated transcripts in the comparison of La-arg(-)_BALB/c vs. La-WT_BALB/c and 45 modulated transcripts in the comparison of La-arg(-)_C57BL/6 vs. La-WT_C57BL/6. Taken together, our data present new insights into the impact of parasite arginase activity on the orchestration of the host gene expression modulation, including in the immune response and amino acid transport and metabolism, mainly in susceptible BALB/c-infected macrophages. Moreover, we show how parasite arginase activity affects parasite gene expression modulation, including amino acid uptake and amastin expression.