ABSTRACT
Co-infection with Plasmodium and chikungunya virus (CHIKV) has been reported in humans, but the impact of co-infection on pathogenesis remains unclear. Here, we show that prior exposure to Plasmodium suppresses CHIKV-associated pathologies in mice. Mechanistically, Plasmodium infection induces IFNγ, which reduces viraemia of a subsequent CHIKV infection and suppresses tissue viral load and joint inflammation. Conversely, concomitant infection with both pathogens limits the peak of joint inflammation with no effect on CHIKV viraemia. Reduced peak joint inflammation is regulated by elevated apoptosis of CD4+ T-cells in the lymph nodes and disrupted CXCR3-mediated CD4+ T-cell migration that abolishes their infiltration into the joints. Virus clearance from tissues is delayed in both infection scenarios, and is associated with a disruption of B cell affinity-maturation in the spleen that reduces CHIKV-neutralizing antibody production.
Subject(s)
Chikungunya Fever/immunology , Chikungunya virus/immunology , Coinfection/immunology , Malaria/immunology , Plasmodium/immunology , Animals , Apoptosis/immunology , Arthritis/genetics , Arthritis/immunology , Arthritis/metabolism , CD4-Positive T-Lymphocytes/immunology , CD4-Positive T-Lymphocytes/metabolism , Chikungunya Fever/virology , Chikungunya virus/physiology , Coinfection/parasitology , Coinfection/virology , Female , Humans , Interferon-gamma/genetics , Interferon-gamma/immunology , Interferon-gamma/metabolism , Malaria/metabolism , Malaria/parasitology , Male , Mice, Inbred C57BL , Mice, Knockout , Plasmodium/physiology , Viral Load/immunology , Viremia/immunology , Viremia/virologyABSTRACT
Ex vivo assay systems provide a powerful approach to studying human malaria parasite biology and to testing antimalarials. For rodent malaria parasites, short-term in vitro culture and ex vivo antimalarial susceptibility assays are relatively cumbersome, relying on in vivo passage for synchronization, since ring-stage parasites are an essential starting material. Here, we describe a new approach based on the enrichment of ring-stage Plasmodium berghei, P. yoelii, and P. vinckei vinckei using a single-step Percoll gradient. Importantly, we demonstrate that the enriched ring-stage parasites develop synchronously regardless of the parasite strain or species used. Using a flow cytometry assay with Hoechst and ethidium or MitoTracker dye, we show that parasite development is easily and rapidly monitored. Finally, we demonstrate that this approach can be used to screen antimalarial drugs.
Subject(s)
Antimalarials/pharmacology , Drug Evaluation, Preclinical/methods , Malaria/parasitology , Plasmodium/drug effects , Plasmodium/physiology , Animals , Disease Models, Animal , Female , Flow Cytometry/methods , Malaria/drug therapy , Male , Mice, Inbred C57BL , Microbial Sensitivity Tests , Plasmodium/pathogenicity , Plasmodium berghei/drug effects , Plasmodium berghei/pathogenicity , Plasmodium berghei/physiologyABSTRACT
Microscopic examination of Giemsa-stained thin blood smears remains the gold standard method used to quantify and stage malaria parasites. However, this technique is tedious, and requires trained microscopists. We have developed a fast and simple flow cytometry method to quantify and stage, various malaria parasites in red blood cells in whole blood or in vitro cultured Plasmodium falciparum. The parasites were stained with dihydroethidium and Hoechst 33342 or SYBR Green I and leukocytes were identified with an antibody against CD45. Depending on the DNA stains used, samples were analyzed using different models of flow cytometers. This protocol, which does not require any washing steps, allows infected red blood cells to be distinguished from leukocytes, as well as allowing non-infected reticulocytes and normocytes to be identified. It also allows assessing the proportion of parasites at different developmental stages. Lastly, we demonstrate how this technique can be applied to antimalarial drug testing.