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An Introduction to Parasitism
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
A young mother sits in her home near lake victoria in rural africa. on her lap lies a listless infant dying of malaria, an infection caused by the mosquito-transmitted parasite plasmodium falciparum. She may live too far from a clinic or simply lack the resources to purchase the medicine that could save her child’s life. This is an all-too-common scene, with a death of a child in Africa from malaria occurring on average about every 2 minutes. We have made considerable strides in controlling malaria, even in deploying a new anti-malaria vaccine. But, as discussed in several places throughout the book, our progress is fragile, and the emergence of drug resistance by malaria parasites or insecticide resistance by the mosquito vectors pose ever-present threats. Exotic malaria vectors are being introduced into new locations. Malaria proves to be a most formidable adversary! In addition, other parasites thrive in the same region: over 90% of the children may be afflicted with schistosomiasis transmitted in the nearby lake or carry heavy burdens of intestinal worms. Add to this the uncertainties posed in the future with respect to a rapidly increasing population or global warming (Box 1.1), and we can begin to appreciate that parasites still exert a powerful grip on the welfare not only of humans but also of domestic and wild animals and plant species vital to our well-being and survival.
Malaria Vaccines: Prospects and Problems
Published in Max J. Miller, E. J. Love, Parasitic Diseases: Treatment and Control, 2020
After extensive evaluation of toxicity and immunogenicity in laboratory animals, careful clinical testing of prototype vaccines will have to be carried out in human volunteers in both nonendemic and endemic areas. Vaccines will have to be shown to be nontoxic, immunogenic, and protective in healthy nonimmune adults from nonmalarious countries before any testing is carried out in endemic countries. The response to a vaccine can be expected to differ between people who have never been exposed to malaria and those who have already been infected; in addition, genetic and other factors may also cause differences in the response to a vaccine in populations in endemic and nonendemic areas. The same rigorous, step-wise clinical testing will therefore be required in different population groups in endemic areas, first in adults and later in special high-risk groups, particularly infants and pregnant women. Only after this full clinical evaluation can malaria vaccines be licensed for general use.18
Malaria vaccines
Published in David A Warrell, Herbert M Gilles, Essential Malariology, 2017
Stephen L Hoffman, Judith E Epstein
The importance and difficulty of this task must not be underestimated. In 1962, malaria was an important enough problem for the USA, along with many other countries, to release stamps commemorating attempts to eradicate malaria (Figure 13.7). That was at about the same time that President Kennedy vowed to put a man on the moon. The first man walked on the moon in 1969, but we are still far from eradicating malaria. We believe that the development of malaria vaccines will be crucial to realizing the dream of malaria eradication.
In vitro antiplasmodial activity, hemocompatibility and temporal stability of Azadirachta indica silver nanoparticles
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2022
Joseph Hawadak, Loick Pradel Kojom Foko, Veena Pande, Vineeta Singh
Malaria is an endemic disease of the intertropical regions caused by a protozoan belonging to the genus Plasmodium and transmitted to human through infected female Anopheles mosquito. According to World Health Organization (WHO), 241 million malaria cases were recorded worldwide in 2020, with 82.2% of cases in the sub-Saharan African (sSA) region [1]. The fight against this disease includes prophylaxis, regular screening and early treatment mainly in children under five years of age and pregnant women, the main vulnerable targets. The coverage use of insecticide-treated mosquito nets ∼65% in sSA is constantly increasing with a satisfactory impact [1]. Artemisinin-based combination therapies (ACT) recommended by WHO remain the most effective antimalarial till date even though resistance has been reported from some South Asian and African regions [2,3]. No effective vaccine for malaria is available currently, though clinical trial results of RTS, S/AS01 vaccine are promising and new generation malaria vaccines (e.g.: R21/Matrix-M) are already in clinical phases [4]. In sSA countries, the low standards of living and the lack of good quality anti-malarial drugs would be the limiting factors for malaria elimination programs [1–3,5].
The challenges of a circumsporozoite protein-based malaria vaccine
Published in Expert Review of Vaccines, 2021
Deepyan Chatterjee, Ian Andrew Cockburn
While RTS,S represents a strong proof of principle that PfCSP-based subunit vaccines can work, it is also clear that significant improvements durability and protective capacity will be required for a truly effective malaria vaccine. To this end the goal has been set – in the malaria vaccines roadmap – for a vaccine that gives 75% efficacy for 5 years [90]. Approaches to improve PfCSP vaccination must thus be based on improving the durability of the immune response, for example, through better adjuvants, or improving the quality of the antibody response. To this end structure-based vaccine design examining how potent protective mAbs interact with target epitopes on the surface of pathogens has been applied to understanding action of CSP binding antibodies [91,92]. Additionally, there has been a renewed focus on understanding the B cell response to PfCSP that underlies the antibody response including understanding how this response is regulated after both PfCSP and RAS vaccination [93].
Biological strategies and political hurdles in developing malaria vaccines
Published in Expert Review of Vaccines, 2021
Michael F. Good, Danielle I. Stanisic
A further unique issue for malaria vaccine development applies to immunity to the sexual-stages of the parasite. This immunity, referred to as ‘transmission-blocking’ immunity, aims to kill the gametes or zygotes in the mosquito mid-gut via antibodies taken up by the feeding mosquito. Thus, unlike sporozoite/liver-stage and blood-stage vaccines, a sexual-stage vaccine will not directly protect the vaccinated individual from contracting malaria but will prevent the vaccinee from passing the malaria parasite to another person. All malaria vaccines have the ability to have an impact on the transmission of the parasite. By reducing the parasite burden in the blood or limiting infection duration, a blood-stage vaccine will lead to fewer gametocytes and reduced transmission and a sporozoite vaccine with 100% efficacy will completely prevent transmission. However, vaccines that intentionally target the sexual-stage of the parasite and aim to prevent development of the malaria parasite in the mosquito midgut are also being developed [14]. Structure-based vaccine design may facilitate the induction of an enhanced and more focused antibody response against sexual-stage antigens associated with potent inhibitory activity in the mosquito [15].