Two hookworm vaccine candidates, Na-GST-1 and Na-APR-1, formulated with Glucopyranosyl Lipid A (GLA-AF) adjuvant, have been shown to be safe, well tolerated, and to induce antibody responses in a ...Phase 1 clinical trial (Clinicaltrials.gov NCT02126462) conducted in Gabon. Here, we characterized T cell responses in 24 Gabonese volunteers randomized to get vaccinated three times with Na-GST-1 and Na-APR-1 at doses of 30μg (n = 8) or 100μg (n = 10) and as control Hepatitis B (n = 6). Blood was collected pre- and post-vaccination on days 0, 28, and 180 as well as 2-weeks after each vaccine dose on days 14, 42, and 194 for PBMCs isolation. PBMCs were stimulated with recombinant Na-GST-1 or Na-APR-1, before (days 0, 28 and 180) and two weeks after (days 14, 42 and 194) each vaccination and used to characterize T cell responses by flow and mass cytometry. A significant increase in Na-GST-1 -specific CD4+ T cells producing IL-2 and TNF, correlated with specific IgG antibody levels, after the third vaccination (day 194) was observed. In contrast, no increase in Na-APR-1 specific T cell responses were induced by the vaccine. Mass cytometry revealed that, Na-GST-1 cytokine producing CD4+ T cells were CD161+ memory cells expressing CTLA-4 and CD40-L. Blocking CTLA-4 enhanced the cytokine response to Na-GST-1. In Gabonese volunteers, hookworm vaccine candidate, Na-GST-1, induces detectable CD4+ T cell responses that correlate with specific antibody levels. As these CD4+ T cells express CTLA-4, and blocking this inhibitory molecules resulted in enhanced cytokine production, the question arises whether this pathway can be targeted to enhance vaccine immunogenicity.
Abstract
Controlled human malaria infection (CHMI) using cryopreserved non-attenuated Plasmodium falciparum sporozoites (PfSPZ) offers a unique opportunity to investigate naturally acquired immunity ...(NAI). By analyzing blood samples from 5 malaria-naïve European and 20 African adults with lifelong exposure to malaria, before, 5, and 11 days after direct venous inoculation (DVI) with Sanaria
R
PfSPZ Challenge, we assessed the immunological patterns associated with control of microscopic and submicroscopic parasitemia. All (5/5) European individuals developed parasitemia as defined by thick blood smear (TBS), but 40% (8/20) of the African individuals controlled their parasitemia, and therefore remained thick blood smear-negative (TBS
−
Africans). In the TBS
−
Africans, we observed higher baseline frequencies of CD4
+
T cells producing interferon-gamma (IFNγ) that significantly decreased 5 days after PfSPZ DVI. The TBS
−
Africans, which represent individuals with either very strong and rapid blood-stage immunity or with immunity to liver stages, were stratified into subjects with sub-microscopic parasitemia (TBS
-
PCR
+
) or those with possibly sterilizing immunity (TBS
−
PCR
−
). Higher frequencies of IFNγ
+
TNF
+
CD8
+
γδ T cells at baseline, which later decreased within five days after PfSPZ DVI, were associated with those who remained TBS
−
PCR
−
. These findings suggest that naturally acquired immunity is characterized by different cell types that show varying strengths of malaria parasite control. While the high frequencies of antigen responsive IFNγ
+
CD4
+
T cells in peripheral blood keep the blood-stage parasites to a sub-microscopic level, it is the IFNγ
+
TNF
+
CD8
+
γδ T cells that are associated with either immunity to the liver-stage, or rapid elimination of blood-stage parasites.
Abstract Cellular metabolism is a key determinant of immune cell function. Here we found that CD14 + monocytes from Sub‐Saharan Africans produce higher levels of IL‐10 following TLR‐4 stimulation and ...are bioenergetically distinct from monocytes from Europeans. Through metabolomic profiling, we identified the higher IL‐10 production to be driven by increased baseline production of NADPH oxidase‐dependent reactive oxygen species, supported by enhanced pentose phosphate pathway activity. Together, these data indicate that NADPH oxidase‐derived ROS is a metabolic checkpoint in monocytes that governs their inflammatory profile and uncovers a metabolic basis for immunological differences across geographically distinct populations.
Hookworms cause substantial morbidity in children and women of reproductive age. The control strategy of mass drug administration is suboptimal, hence the need for a vaccine. Necator americanus ...aspartic protease-1 (Na-APR-1) and N americanus glutathione S-transferase-1 (Na-GST-1) are involved in the digestion and detoxification of haemoglobin in the hookworm digestive tract. In animal models, vaccination against these antigens resulted in protection from challenge infection. Both vaccine candidates were shown to be safe and well tolerated when administered separately to healthy adults. We assessed the safety and immunogenicity of co-administered Na-GST-1 and Na-APR-1 (M74) vaccines in healthy Gabonese adults.
This randomised, controlled, double-blind, phase 1, dose-escalation trial was done at the Centre de Recherches Médicales de Lambaréné, in a region of Gabon where N americanus and other helminths are prevalent. Healthy adults aged 18–50 years and living in Lambaréné or the surrounding areas were recruited to the study. Participants were enrolled consecutively into two dose cohorts (30 μg or 100 μg of the experimental vaccines) and randomly assigned in blocks (block size four) to receive three doses of either co-administered Na-GST-1 plus Na-APR-1 (M74; 30 μg or 100 μg of each), adjuvanted with Alhydrogel (aluminium hydroxide gel suspension) together with an aqueous formulation of glucopyranosyl lipid A, or hepatitis B vaccine plus saline (control group). Vaccines were administered intramuscularly on days 0, 28, and 180. The primary endpoint was safety, with immunogenicity a secondary endpoint. The intention-to-treat population was used for safety analyses, whereas for immunogenicity analyses, the per-protocol population was used (participants who received all scheduled vaccinations). Control vaccine recipients for both dose cohorts were combined for the analyses. The trial is registered with ClinicalTrials.gov, NCT02126462.
Between Oct 27, 2014, and Jan 31, 2015, 56 individuals were screened for eligibility, of whom 32 were enrolled and randomly assigned to one of the three study groups (12 each in the 30 μg and 100 μg experimental vaccine groups and eight in the control group). Both study vaccines were well tolerated in both dose groups. The most common adverse events were mild-to-moderate injection-site pain, headache, myalgia, and nausea. No severe or serious adverse events related to the vaccines were recorded. 52 unsolicited vaccine-related adverse events occurred during the study, but there was no difference in frequency between vaccine groups. IgG antibodies were induced to each of the vaccine antigens, with mean IgG levels increasing after each vaccination. Vaccination with 100 μg of each vaccine antigen consistently induced IgG seroconversion (IgG levels above the reactivity threshold). Peak IgG responses were observed 2 weeks after the third vaccine dose for both antigens, with all participants who received the 100 μg doses seroconverting at that timepoint. IgG levels steadily declined until the final study visit 6 months after the third vaccination, although they remained significantly higher than baseline in the 100 μg dose group.
Vaccination with recombinant Na-GST-1 and Na-APR-1 (M74) in healthy adults living in N americanus-endemic areas of Gabon was safe and induced IgG to each antigen. To our knowledge, this study is the first to report results of Na-APR-1 (M74) co-administered with Alhydrogel in participants from an N americanus-endemic area. Further clinical development of these vaccines should involve efficacy studies.
European Union Seventh Framework Programme.
Controlled human infections provide opportunities to study the interaction between the immune system and malaria parasites, which is essential for vaccine development. Here, we compared immune ...signatures of malaria-naive Europeans and of Africans with lifelong malaria exposure using mass cytometry, RNA sequencing and data integration, before and 5 and 11 days after venous inoculation with Plasmodium falciparum sporozoites. We observed differences in immune cell populations, antigen-specific responses and gene expression profiles between Europeans and Africans and among Africans with differing degrees of immunity. Before inoculation, an activated/differentiated state of both innate and adaptive cells, including elevated CD161
CD4
T cells and interferon-γ production, predicted Africans capable of controlling parasitemia. After inoculation, the rapidity of the transcriptional response and clusters of CD4
T cells, plasmacytoid dendritic cells and innate T cells were among the features distinguishing Africans capable of controlling parasitemia from susceptible individuals. These findings can guide the development of a vaccine effective in malaria-endemic regions.
The interaction of malaria parasites with their human host is extensively studied, yet only few studies reported how
infection affects urinary metabolite profiles and how this is associated with ...immunity. We present a longitudinal study of the urinary metabolic profiles of twenty healthy Africans with lifelong exposure to malaria and five malaria-naïve Europeans, who were all challenged with direct venous inoculation of live
sporozoïtes (PfSPZ) and followed up until they developed symptoms or became thick blood smear positive (TBS). Urine samples were collected before and at 2, 5, 9 and 11 days post challenge and were analysed. Upon infection, all Europeans became TBS positive, while Africans showed either a delay in time to parasitaemia or controlled infection. Our metabolic data showed that Europeans and Africans had distinct alterations in metabolite patterns, with changes mostly seen on days 5 and 9 post PfSPZ infection, and more prominently in Europeans. Within the African group, the levels of formate, urea, trimethylamine, threonine, choline, myo-inositol and acetate were significantly higher in TBS positive whereas the levels of pyruvate, 3-methylhistidine and dimethylglycine were significantly lower in individuals who remained TBS negative. Notably, before inoculation with PfSPZ, a group of metabolites including phenylacetylglutamine can potentially be used to predict parasitaemia control among Africans. Taken together, this study highlights the difference in urinary metabolic changes in response to malaria infection as a consequence of lifelong exposure to malaria and that change detectable before challenge might predict the control of parasitaemia in malaria-endemic areas.
Vaccination of malaria-naive volunteers with a high dose of Plasmodium falciparum sporozoites chemoattenuated by chloroquine (CQ) (PfSPZ-CVac CQ) has previously demonstrated full protection against ...controlled human malaria infection (CHMI). However, lower doses of PfSPZ-CVac CQ resulted in incomplete protection. This provides the opportunity to understand the immune mechanisms needed for better vaccine-induced protection by comparing individuals who were protected with those not protected. Using mass cytometry, we characterized immune cell composition and responses of malaria-naive European volunteers who received either lower doses of PfSPZ-CVac CQ, resulting in 50% protection irrespective of the dose, or a placebo vaccination, with everyone becoming infected following CHMI. Clusters of CD4+ and γδ T cells associated with protection were identified, consistent with their known role in malaria immunity. Additionally, EMRA CD8+ T cells and CD56+CD8+ T cell clusters were associated with protection. In a cohort from a malaria-endemic area in Gabon, these CD8+ T cell clusters were also associated with parasitemia control in individuals with lifelong exposure to malaria. Upon stimulation with P. falciparum-infected erythrocytes, CD4+, γδ, and EMRA CD8+ T cells produced IFN-γ and/or TNF, indicating their ability to mediate responses that eliminate malaria parasites.
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