Plasmodium-encoded murine IL-6 impairs liver stage infection and elicits long-lasting sterilizing immunity

IntroductionPlasmodium sporozoites (SPZ) inoculated by Anopheles mosquitoes into the skin of the mammalian host migrate to the liver before infecting hepatocytes. Previous work demonstrated that early production of IL-6 in the liver is detrimental for the parasite growth, contributing to the acquisition of a long-lasting immune protection after immunization with live attenuated parasites.MethodsConsidering that IL-6 as a critical pro-inflammatory signal, we explored a novel approach whereby the parasite itself encodes for the murine IL-6 gene. We generated transgenic P. berghei parasites that express murine IL-6 during liver stage development.Results and DiscussionThough IL-6 transgenic SPZ developed into exo-erythrocytic forms in hepatocytes in vitro and in vivo, these parasites were not capable of inducing a blood stage infection in mice. Furthermore, immunization of mice with transgenic IL-6-expressing P. berghei SPZ elicited a long-lasting CD8+ T cell-mediated protective immunity against a subsequent infectious SPZ challenge. Collectively, this study demonstrates that parasite-encoded IL-6 attenuates parasite virulence with abortive liver stage of Plasmodium infection, forming the basis of a novel suicide vaccine strategy to elicit protective antimalarial immunity

Emergence of IFN-alpha TRAIL-expressing killer pDCs (IKpDCs) as a consequence of a crosstalk with NK cells. Influence of HIV-1 infection and implication of HMGB1

International audienceEmergence of IFN-alpha TRAIL-expressing killer pDCs (IKpDCs) as a consequence of a crosstalk with NK cells. Influence of HIV-1 infection and implication of HMGB

Role of host cell traversal by the malaria sporozoite during liver infection

International audienceMalaria infection starts when the sporozoite stage of the Plasmodium parasite is injected into the skin by a mosquito. Sporozoites are known to traverse host cells before finally invading a hepatocyte and multiplying into erythrocyte-infecting forms, but how sporozoites reach hepatocytes in the liver and the role of host cell traversal (CT) remain unclear. We report the first quantitative imaging study of sporozoite liver infection in rodents. We show that sporozoites can cross the liver sinusoidal barrier by multiple mechanisms, targeting Kupffer cells (KC) or endothelial cells and associated or not with the parasite CT activity. We also show that the primary role of CT is to inhibit sporozoite clearance by KC during locomotion inside the sinusoid lumen, before crossing the barrier. By being involved in multiple steps of the sporozoite journey from the skin to the final hepatocyte, the parasite proteins mediating host CT emerge as ideal antibody targets for vaccination against the parasite

Tools to Decipher Vector-Borne Pathogen and Host Interactions in the Skin (chapitre 12)

International audience© 2018 Elsevier Inc. All rights reserved. Several pathogens transmitted by hematophagous vectors are inoculated in the host skin during an infective bite. Viruses, bacteria, and parasites stay at the inoculation site from minutes to days until disseminating throughout the host. Notably, early excision of the bite site profoundly inhibits host infection, indicating that most, if not all, pathogens are deposited together with saliva in the extravascular regions of the host skin. This delayed migration is a hallmark of this initial, and little explored, skin phase of infection, which is further characterized by the dynamic interaction of vector saliva components, the vector-borne pathogens, and resident and immune host cells. Here, we emphasize the commonality of this skin phase in the life history of pathogens transmitted by hematophagous vectors and present some tools to decipher host-pathogen interactions in this cutaneous environment. In the first part of the chapter, we focus on the effectiveness of in vivo imaging to characterize and functionally analyze this skin phase using a rodent malaria model. In the second part, we exploit the utilization of skin explants and primary cell culture to further investigate the cellular and molecular mechanisms of infection and persistence of various vector-borne pathogens in the human skin. Finally, we discuss the possibility of combining these two approaches aiming at the direct and unprecedented observation of the in vivo behavior of vector-borne pathogens in the human skin explants engrafted in humanized mice

Yeast lysates carrying the nucleoprotein from measles virus vaccine as a novel subunit vaccine platform to deliver Plasmodium circumsporozoite antigen

International audienceBackground: Yeast cells represent an established bioreactor to produce recombinant proteins for subunit vaccine development. In addition, delivery of vaccine antigens directly within heat-inactivated yeast cells is attractive due to the adjuvancy provided by the yeast cell. In this study, Pichia pastoris yeast lysates carrying the nucleoprotein (N) from the measles vaccine virus were evaluated as a novel subunit vaccine platform to deliver the circumsporozoite surface antigen (CS) of Plasmodium. When expressed in Pichia pastoris yeast, the N protein auto-assembles into highly multimeric ribonucleoparticles (RNPs). The CS antigen from Plasmodium berghei (PbCS) was expressed in Pichia pastoris yeast in fusion with N, generating recombinant PbCS-carrying RNPs in the cytoplasm of yeast cells.Results: When evaluated in mice after 3-5 weekly subcutaneous injections, yeast lysates containing N-PbCS RNPs elicited strong anti-PbCS humoral responses, which were PbCS-dose dependent and reached a plateau by the pre-challenge time point. Protective efficacy of yeast lysates was dose-dependent, although anti-PbCS antibody titers were not predictive of protection. Multimerization of PbCS on RNPs was essential for providing benefit against infection, as immunization with monomeric PbCS delivered in yeast lysates was not protective. Three weekly injections with N-PbCS yeast lysates in combination with alum adjuvant produced sterile protection in two out of six mice, and significantly reduced parasitaemia in the other individuals from the same group. This parasitaemia decrease was of the same extent as in mice immunized with non-adjuvanted N-PbCS yeast lysates, providing evidence that the yeast lysate formulation did not require accessory adjuvants for eliciting efficient parasitaemia reduction.Conclusions: This study demonstrates that yeast lysates are an attractive auto-adjuvant and efficient platform for delivering multimeric PbCS on measles N-based RNPs. By combining yeast lysates that carry RNPs with a large panel of Plasmodium antigens, this technology could be applied to developing a multivalent vaccine against malaria

Longitudinal proliferation mapping in vivo reveals NADPH oxidase-mediated dampening of Staphylococcus aureus growth rates within neutrophils

AbstractUpon the onset of inflammatory responses, bacterial pathogens are confronted with altered tissue microenvironments which can critically impact on their metabolic activity and growth. Changes in these parameters have however remained difficult to analyze over time, which would be critical to dissect the interplay between the host immune response and pathogen physiology. Here, we established an in vivo biosensor for measuring the growth rates of Staphylococcus aureus (S. aureus) on a single cell-level over days in an ongoing cutaneous infection. Using intravital 2-photon imaging and quantitative fluorescence microscopy, we show that upon neutrophil recruitment to the infection site and bacterial uptake, non-lethal dampening of S. aureus proliferation occurred. This inhibition was supported by NADPH oxidase activity. Therefore, reactive oxygen production contributes to pathogen containment within neutrophils not only by killing S. aureus, but also by restricting the growth rate of the bacterium.</jats:p