Abstract
Evidence is accumulating that miRNAs are critically implicated in the outcome of diseases, but little information is available for infectious diseases. This study investigates the hepatic miRNA signature in female C57BL/6 mice infected with self-healing Plasmodium chabaudi malaria. Primary infections result in approximately 50% peak parasitemia on day 8 p.i., approximately 80% survival, and development of protective immunity. The latter is evidenced as 100% survival and 1.5% peak parasitemia upon homolog re-infections of those mice which are still alive on day 56 after primary infection. Such immune mice exhibit increased levels of IgG2a and IgG2b isotypes and still contain P. chabaudi-infected erythrocytes in their livers as revealed by light microscopy and PCR analysis. Primary infections, but not secondary infections, induce an upregulation of hepatic mRNAs encoding IL-1 beta, TNF alpha, IFN gamma, NF-kappa B, and iNOS, and a downregulation of mRNAs for CYP7A1 and SULT2A2, respectively. Using miRXplore microarrays containing 634 mouse miRNAs in combination with quantitative RT-PCR, the liver is found to respond to primary infections with an upregulation of the three miRNA species miR-26b, MCMV-miR-M23-1-5p, and miR-1274a, and a downregulation of the 16 miRNA species miR-101b, let-7a, let-7g, miR-193a-3p, miR-192, miR-142-5p, miR-465d, miR-677, miR-98, miR-694, miR-374(*), miR-450b-5p, miR-464, miR-377, miR-20a(*), and miR-466d-3p, respectively. Surprisingly, about the same pattern of miRNA expression is revealed in immune mice, and this pattern is even sustained upon homolog re-infections of immune mice. These data suggest that development of protective immunity against malarial blood stages of P. chabaudi is associated with a reprogramming of the expression of distinct miRNA species in the female mouse liver.