Project description:Microarray studies using synchronized Plasmodium falciparum parasites have revealed a ‘continuous cascade’ of gene expression. Reports vary regarding the stability in these transcriptional patterns in the presence of external stressors. Using Plasmodium yoelii 17X parasites replicating in vivo, we have examined differential gene expression in parasites isolated from individual mice, from independent infections, during ascending and peak parasitemia and in the presence and absence of host antibody responses. Across experimental conditions, transcription was surprisingly stable. Differential gene expression was greatest when comparing differences due to parasite load and/or host cell availability; however, even these changes were modest. Of genes that were differentially expressed, many are of unknown function. There was little to no differential expression of members of the yir and pyst-a multigene families, although a relatively large number of these were expressed during blood-stage infection regardless of experimental condition. Taken together, these results indicate that 1) P. yoelii gene expression remains stable in the presence of a changing host environment and 2) concurrent expression of a large number of the yir and pyst-a genes may function to divert host immune responses away from invariant protective antigens. 1. P. yoelii 17X gene expression profiles were determined in blood-stage parasites isolated from infected Balb/c mice (male, 8-12 weeks old) as follows: a. Mouse 1 (M1), Mouse 2 (M2), Mouse 3 (M3), Donor (D) mouse – three mice simultaneously infected with P. yoelii 17X iRBCs from a single donor mouse. Parasite RNA was isolated early during infection when parasitemia was ascending as follows: M1 - day 11 at 13.0% parasitemia; M2 - day 10 at 11.1% parasitemia; M3 - day 10 at 18.6% parasitemia; D – day 11 at 18.7% parasitemia. b. Infection #1 (I1), infection #2 (I2), infection #3 (I3), infection #4 (I4) – four groups of mice infected on four separate occasions using P. yoelii 17X iRBCs obtained from four separate donor mice. In each case, P. yoelii 17X RNA was isolated from iRBCs obtained on days 10-11 of infection when parasitemia was ascending and was ~15%. c. Day 10 (D10), Day 14 (D14) – P. yoelii 17X RNA isolated from iRBCs during infection #2 on day 10 (14% parasitemia, 14.4% reticulocytes) and on day 14 of infection #2 (43.5% parasitemia, 57.9% reticulocytes). d. WT and JHD - P. yoelii 17X RNA isolated from iRBCs during infection #4 from immunologically intact, wild-type Balb/c mice and B cell deficient, JHD mice on a Balb/c background (ascending infection, 15% parasitemia). e. QA and RMP - P. yoelii 17X RNA isolated from iRBCs during infection #1 from mice previously immunized with a preparation of membrane proteins isolated from P. yoelii 17X infected reticulocytes (PyRMP) (day 12, 13.3% parasitemia and Quil A immunized (QA) control mice (day 10, 15.6% parasitemia) 2. On each array, gene expression in P. yoelii 17X blood-stage parasites was evaluated relative to a standard comparator of purified P. yoelii 17XL total RNA (pooled RNA from 45 mice, mean parasitemia ~35%). Each sample was analyzed on three replicate arrays, one of which was a standard dye-flip. One exception was the infection #3 sample which was analyzed on only on two arrays. On each array, oligonucleotides were spotted in duplicate. 3. Through the use of the standard reference RNA, the following 15 pairwise comparisons across samples were made: (M1 vs M2); (M2 vs M3); (M1 vs M3); (D vs M1); (D vs M2); (D vs M3); (I1 vs I2); (I1 vs I3); (I1 vs I4); (I2 vs I3); (I2 vs I4); (I3 vs I4); (D10 vs D14); (WT vs JHD); (QA vs RMP)
Project description:Plasmodium yoelii is a rodent parasite commonly used as a model to study liver-stage development in host system during malaria infection. Mass spectrometry-based proteomics approaches helps in understanding the proteomic profiling of parasite and provided opportunities to explore the mechanisms controlling parasite functions. It will further help in identifying new targets for therapeutic interventions, identification of Plasmodium associated virulence in the host. It will also help in the extensive refinement of parasite genome, and understanding of Post-translational modifications (PTM) in Plasmodium yoelii biology. In the present study, we performed a proteomic shotgun analysis of the Plasmodium yoelii 17XNL strain.
Project description:Exosomes are a subclass of nanometer-sized vesicles formed by the endocytic pathway which contain genetic and protein material and reflect the contents of their cells of origin. In Plasmodium infections, vesicles derived from the parasite or parasite-infected cells have been shown to induce the expression of pro-inflammatory elements, which have been correlated with manifestations of clinic disease. Thus, these vesicles are of great interest as therapeutic targets, or as vehicles for immunomodulatory control. Herein, the identification and characterization of proteins within naturally occurring exosomes from a rodent Plasmodium yoelii infection is described. Our results establish that exosomes derived from an infection with P. yoelii contain proteins of interest as vaccine candidates (e.g. p235 rhoptry protein, multiple members of the yir multi-gene protein family, and the ribosomal protein S12), uncharacterized proteins which may be good targets of T cell immunoreactivity, and proteins involved in metabolic processes, homeostasis and immunity. These findings add to the growing interest on parasite exosomes and provide a different way to understand the interactions between host and parasite and identify novel proteins potentially targeted by protective immune responses. Together with evidence that exosomes can interact with the host immune system and generate an immune response, these data provide a solid foundation for future studies aimed at novel vaccination strategies in the context of parasitic diseases, where the classical approaches that have thus far failed.
Project description:To study the function of gene SAP1. We knocked out SAP1 gene in P. yoelii, and compared the global gene expression profiles of the P. yoelii SAP1 knockout parasites isolated from mosquito salivary gland to that of wild type P. yoelii parasites.