86 research outputs found
A Mosquito Pick-and-Place System for PfSPZ-based Malaria Vaccine Production
The treatment of malaria is a global health challenge that stands to benefit
from the widespread introduction of a vaccine for the disease. A method has
been developed to create a live organism vaccine using the sporozoites (SPZ) of
the parasite Plasmodium falciparum (Pf), which are concentrated in the salivary
glands of infected mosquitoes. Current manual dissection methods to obtain
these PfSPZ are not optimally efficient for large-scale vaccine production. We
propose an improved dissection procedure and a mechanical fixture that
increases the rate of mosquito dissection and helps to deskill this stage of
the production process. We further demonstrate the automation of a key step in
this production process, the picking and placing of mosquitoes from a staging
apparatus into a dissection assembly. This unit test of a robotic mosquito
pick-and-place system is performed using a custom-designed micro-gripper
attached to a four degree of freedom (4-DOF) robot under the guidance of a
computer vision system. Mosquitoes are autonomously grasped and pulled to a
pair of notched dissection blades to remove the head of the mosquito, allowing
access to the salivary glands. Placement into these blades is adapted based on
output from computer vision to accommodate for the unique anatomy and
orientation of each grasped mosquito. In this pilot test of the system on 50
mosquitoes, we demonstrate a 100% grasping accuracy and a 90% accuracy in
placing the mosquito with its neck within the blade notches such that the head
can be removed. This is a promising result for this difficult and non-standard
pick-and-place task.Comment: 12 pages, 11 figures, Manuscript submitted for Special Issue of IEEE
CASE 2019 for IEEE T-AS
Chemically attenuated blood-stage Plasmodium yoelii parasites induce long-lived and strain-transcending protection
The development of a vaccine is essential for the elimination of malaria. However, despite many years of effort, a successful vaccinehas not been achieved. Most subunit vaccine candidates tested in clinical trials have provided limited efficacy, and thus attenuatedwhole-parasite vaccines are now receiving close scrutiny. Here, we test chemically attenuated Plasmodium yoelii 17Xand demonstrate significant protection following homologous and heterologous blood-stage challenge. Protection againstblood-stage infection persisted for at least 9 months. Activation of both CD4+ and CD8+ T cells was shown after vaccination;however, in vivo studies demonstrated a pivotal role for both CD4+ T cells and B cells since the absence of either cell type led toloss of vaccine-induced protection. In spite of significant activation of circulating CD8+ T cells, liver-stage immunity was notevident. Neither did vaccine-induced CD8+ T cells contribute to blood-stage protection; rather, these cells contributed to pathogenesis,since all vaccinated mice depleted of both CD4+ and CD8+ T cells survived a challenge infection. This study providescritical insight into whole-parasite vaccine-induced immunity and strong support for testing whole-parasite vaccines in humans
Chemically attenuated blood-stage Plasmodium yoelii parasites induce long-lived and strain-transcending protection
The development of a vaccine is essential for the elimination of malaria. However, despite many years of effort, a successful vaccine has not been achieved. Most subunit vaccine candidates tested in clinical trials have provided limited efficacy, and thus attenuated whole-parasite vaccines are now receiving close scrutiny. Here, we test chemically attenuated Plasmodium yoelii 17X and demonstrate significant protection following homologous and heterologous blood-stage challenge. Protection against blood-stage infection persisted for at least 9 months. Activation of both CD4+ and CD8+ T cells was shown after vaccination; however, in vivo studies demonstrated a pivotal role for both CD4+ T cells and B cells since the absence of either cell type led to loss of vaccine-induced protection. In spite of significant activation of circulating CD8+ T cells, liver-stage immunity was not evident. Neither did vaccine-induced CD8+ T cells contribute to blood-stage protection; rather, these cells contributed to pathogenesis, since all vaccinated mice depleted of both CD4+ and CD8+ T cells survived a challenge infection. This study provides critical insight into whole-parasite vaccine-induced immunity and strong support for testing whole-parasite vaccines in humans
Direct venous inoculation of Plasmodium falciparum sporozoites for controlled human malaria infection: a dose-finding trial in two centres
BACKGROUND: Controlled human malaria infection (CHMI)
accelerates development of anti-malarial interventions. So far,
CHMI is done by exposure of volunteers to bites of five
mosquitoes carrying Plasmodium falciparum sporozoites (PfSPZ), a
technique available in only a few centres worldwide.
Mosquito-mediated CHMI is logistically complex, exact PfSPZ
dosage is impossible and live mosquito-based interventions are
not suitable for further clinical development. METHODS: An
open-labelled, randomized, dose-finding study in 18-45 year old,
healthy, malaria-naive volunteers was performed to assess if
intravenous (IV) injection of 50 to 3,200 aseptic, purified,
cryopreserved PfSPZ is safe and achieves infection kinetics
comparable to published data of mosquito-mediated CHMI. An
independent study site verified the fully infectious dose using
direct venous inoculation of PfSPZ. Parasite kinetics were
assessed by thick blood smear microscopy and quantitative real
time PCR. RESULTS: IV inoculation with 50, 200, 800, or 3,200
PfSPZ led to parasitaemia in 1/3, 1/3, 7/9, and 9/9 volunteers,
respectively. The geometric mean pre-patent period (GMPPP) was
11.2 days (range 10.5-12.5) in the 3,200 PfSPZ IV group.
Subsequently, six volunteers received 3,200 PfSPZ by direct
venous inoculation at an independent investigational site. All
six developed parasitaemia (GMPPP: 11.4 days, range: 10.4-12.3).
Inoculation of PfSPZ was safe. Infection rate and pre-patent
period depended on dose, and injection of 3,200 PfSPZ led to a
GMPPP similar to CHMI with five PfSPZ-infected mosquitoes. The
infectious dose of PfSPZ predicted dosage of
radiation-attenuated PfSPZ required for successful vaccination.
CONCLUSIONS: IV inoculation of PfSPZ is safe, well tolerated and
highly reproducible. It shall further accelerate development of
anti-malarial interventions through standardization and
facilitation of CHMI. Beyond this, rational dose selection for
whole PfSPZ-based immunization and complex study designs are now
possible. TRIAL REGISTRATION: ClinicalTrials.gov NCT01624961 and
NCT01771848
Advancing global health through development and clinical trials partnerships: a randomized, placebo-controlled, double-blind assessment of safety, tolerability, and Immunogenicity of Plasmodium falciparum sporozoites vaccine for malaria in healthy Equatoguinean men
Equatorial Guinea (EG) has implemented a successful malaria control program on Bioko Island. A highly effective vaccine would be an ideal complement to this effort and could lead to halting transmission and eliminating malaria. Sanaria® PfSPZ Vaccine (Plasmodium falciparum sporozoite Vaccine) is being developed for this purpose. To begin the process of establishing the efficacy of and implementing a PfSPZ Vaccine mass vaccination program in EG, we decided to conduct a series of clinical trials of PfSPZ Vaccine on Bioko Island. Because no clinical trial had ever been conducted in EG, we first successfully established the ethical, regulatory, quality, and clinical foundation for conducting trials. We now report the safety, tolerability, and immunogenicity results of the first clinical trial in the history of the country. Thirty adult males were randomized in the ratio 2:1 to receive three doses of 2.7 × 105 PfSPZ of PfSPZ Vaccine (N = 20) or normal saline placebo (N = 10) by direct venous inoculation at 8-week intervals. The vaccine was safe and well tolerated. Seventy percent, 65%, and 45% of vaccinees developed antibodies to Plasmodium falciparum (Pf) circumsporozoite protein (PfCSP) by enzyme-linked immunosorbent assay, PfSPZ by automated immunofluorescence assay, and PfSPZ by inhibition of sporozoite invasion assay, respectively. Antibody responses were significantly lower than responses in U.S. adults who received the same dosage regimen, but not significantly different than responses in young adult Malians. Based on these results, a clinical trial enrolling 135 subjects aged 6 months to 65 years has been initiated in EG; it includes PfSPZ Vaccine and first assessment in Africa of PfSPZ-CVac. ClinicalTrials.gov identifier: NCT02418962
Spark plasma sintering of Ti-diamond composites
Laser melting of Ti-diamond powders have been found to enhance the mechanical properties of technologically important material like titanium matrix composite (TMC). However, there is a tendency for the diamond to graphitise during the laser melting process. In order to overcome this fallacy, an alternate processing route, namely, spark plasma sintering (SPS) was adopted for fabricating the TMC's. A wide range of powder compositions varying from 5 to 50 wt percentage of diamond (0.25 mu m) was added to titanium and the as-sintered compacts were investigated by X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscope (SEM), and Energy Dispersive Spectroscopy (EDAX). In-situ phase changes were observed with increase in diamond content in the composition. Addition of diamond upto 15% led to formation of a mixed Ti and TiC phase in the matrix. Interestingly there was no trace of metallic titanium with 20% diamond in the composition and a TiC-only phase was observed, corroborated by an abrupt increase in hardness to 1076 Hv. At even higher diamond percentages there was trace of unreacted carbon along with TiC. This work indicates, for the first time, the use of SPS as an alternate route for fabricating in-situ TMCs with enhanced mechanical properties
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