IFNAR1-Signalling Obstructs ICOS-mediated Humoral Immunity during Non-lethal Blood-Stage Plasmodium Infection

Funding: This work was funded by a Career Development Fellowship (1028634) and a project grant (GRNT1028641) awarded to AHa by the Australian National Health & Medical Research Council (NHMRC). IS was supported by The University of Queensland Centennial and IPRS Scholarships. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Type I Interferons Induce T Regulatory 1 Responses and Restrict Humoral Immunity during Experimental Malaria

We thank Christopher Hunter and Bob Axtell for critical feedback, and the Flow Cytometry Laboratory at OUHSC for technical assistance.Author Summary Humoral immunity is essential for host resistance to pathogens that trigger highly inflammatory immune responses, including Plasmodium parasites, the causative agents of malaria. Long-lived, secreted antibody responses depend on a specialized subset of CD4 T cells called T follicular helper (Tfh) cells. However, anti-Plasmodium humoral immunity is often short-lived, non-sterilizing, and immunity rapidly wanes, leaving individuals susceptible to repeated bouts of malaria. Here we explored the relationship between inflammatory type I interferons, the regulation of pathogen-specific CD4 T cell responses, and humoral immunity using models of experimental malaria and systemic virus infection. We identified that type I interferons promote the formation and accumulation of pathogen-specific CD4 T regulatory 1 cells that co-express interferon-gamma and interleukin-10. Moreover, we show that the combined activity of interferon-gamma and interleukin-10 limits the magnitude of infection-induced Tfh responses, the secretion of parasite-specific secreted antibody, and parasite control. Our study provides new insight into the regulation of T regulatory 1 responses and humoral immunity during inflammatory immune reactions against systemic infections.Yeshttp://www.plospathogens.org/static/editorial#pee

Profile of adverse events in patients receiving treatment for malaria in urban Ghana: a cohort-event monitoring study

BACKGROUND:Antimalarial treatment strategies have changed much in the last 15 years, resulting in an increased variety of medicines available. Active pharmacovigilance methods are important for continued safety surveillance of these medicines, particularly in environments in which there is variability in treatments prescribed and limited confirmatory diagnostic capacity as well as limited ability of spontaneous reporting pharmacovigilance systems to generate much needed safety information quickly and efficiently.OBJECTIVE:Our objective was to use the cohort-event monitoring (CEM) technique to gather drug utilization and adverse event data for patients prescribed antimalarial medicines in an outpatient setting.METHODS:The characteristics of a large urban African cohort of outpatients (n = 2,831) receiving antimalarial medications are described. The cohort was actively surveyed over the subsequent week to record adverse events, using follow-up phone calls, paper reports, and/or voluntary return clinic visits. Adverse events reported in the cohort were analysed overall and by clinically relevant age and medication groupings.RESULTS:At least one event was reported in 29.4 % of patients. Adverse events were more likely to be reported in subjects older than 12 years of age, and by patients prescribed an artesunate-amodiaquine combination. A range of adverse events were reported, the most frequent higher level terms being asthenic conditions (10.1 % of total cohort), neurological signs and symptoms (4.5 %), headaches (3.1 %), appetite disorders (2.1 %), and disturbances in consciousness (1.6 %). There were three reports of possible extrapyramidal events (two cases of tremor "hand and back shaking all over" and one case of tongue protrusion), which may appear to be related to combinations including amodiaquine and an artemisinin.CONCLUSION:The CEM methodology is a useful tool for monitoring the safety of widely available and utilized medicines, particularly in an urban environment where spontaneous reporting yields poor results and where the availability of various regimens and high levels of medicine usage can give valuable 'real-life' safety data. The types and frequencies of events reported reflected the types of events expected in patients prescribed antimalarials and nearly all events reported are listed in the summary of product characteristics of the medicines involved

Malaria-induced interferon-γ drives the expansion of Tbethi atypical memory B cells

Many chronic infections, including malaria and HIV, are associated with a large expansion of CD21-CD27- 'atypical' memory B cells (MBCs) that exhibit reduced B cell receptor (BCR) signaling and effector functions. Little is known about the conditions or transcriptional regulators driving atypical MBC differentiation. Here we show that atypical MBCs in malaria-exposed individuals highly express the transcription factor T-bet, and that T-bet expression correlates inversely with BCR signaling and skews toward IgG3 class switching. Moreover, a longitudinal analysis of a subset of children suggested a correlation between the incidence of febrile malaria and the expansion of T-bethi B cells. The Th1-cytokine containing supernatants of malaria-stimulated PBMCs plus BCR cross linking induced T-bet expression in naïve B cells that was abrogated by neutralizing IFN-γ or blocking the IFN-γ receptor on B cells. Accordingly, recombinant IFN-γ plus BCR cross-linking drove T-bet expression in peripheral and tonsillar B cells. Consistent with this, Th1-polarized Tfh (Tfh-1) cells more efficiently induced T-bet expression in naïve B cells. These data provide new insight into the mechanisms underlying atypical MBC differentiation

Inducing Humoral and Cellular Responses to Multiple Sporozoite and Liver-Stage Malaria Antigens Using Exogenous Plasmid DNA

A vaccine candidate that elicits humoral and cellular responses to multiple sporozoite and liver-stage antigens may be able to confer protection against Plasmodium falciparum malaria; however, a technology for formulating and delivering such a vaccine has remained elusive. Here, we report the preclinical assessment of an optimizedDNAvaccine approach that targets four P. falciparum antigens: circumsporozoite protein (CSP), liver stage antigen 1 (LSA1), thrombospondin-related anonymous protein (TRAP), and cell-traversal protein for ookinetes and sporozoites (CelTOS). Synthetic DNA sequences were designed for each antigen with modifications to improve expression and were delivered using in vivo electroporation (EP). Immunogenicity was evaluated in mice and nonhuman primates (NHPs) and assessed by enzyme-linked immunosorbent assay (ELISA), gamma interferon (IFN-) enzyme-linked immunosorbent spot (ELISpot) assay, and flow cytometry. In mice, DNA with EP delivery induced antigen-specific IFN- production, as measured by ELISpot assay and IgG seroconversion against all antigens. Sustained production of IFN-, interleukin-2, and tumor necrosis factor alpha was elicited in both the CD4+ and CD8+ T cell compartments. Furthermore, hepatic CD8+ lymphocytes produced LSA1-specific IFN-. The immune responses conferred to mice by this approach translated to the NHP model, which showed cellular responses by ELISpot assay and intracellular cytokine staining. Notably, antigen-specific CD8+ granzyme B+ T cells were observed in NHPs. Collectively, the data demonstrate that delivery of gene sequences by DNA/EP encoding malaria parasite antigens is immunogenic in animal models and can harness both the humoral and cellular arms of the immune system