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Order Articulavirales
Published in Paul Pumpens, Peter Pushko, Philippe Le Mercier, Virus-Like Particles, 2022
Paul Pumpens, Peter Pushko, Philippe Le Mercier
The baculovirus-driven M1-based influenza VLPs were used as a core to generate a malaria vaccine candidate (Lee SH et al. 2020). The VLPs carried the merozoite surface protein 9 (MSP-9), one of the antigens located within the merozoite surface and parasitophorous vacuole of the infected erythrocytes, from Plasmodium berghei. The VLP administration in a mouse model resulted in a significantly prolonged survival time of infected animals.
Edible Vaccine
Published in Hafiz Ansar Rasul Suleria, Megh R. Goyal, Masood Sadiq Butt, Phytochemicals from Medicinal Plants, 2019
Vivek K. Chaturvedi, Sushil K. Dubey, N. Tabassum, M.P. Singh
Malaria is caused by protozoan parasite of genus Plasmodium. The antigens, which are being researched for the improvement of EVs for jungle fever (malaria) are merozoite surface protein MsP4 and MsP5 from Plasmodium falciparum and MsP4/MsP5 from Plasmodium yoelii6,51 Oral administration of recombinant MsP4, MsP5, and MsP4/5 coregulated with cholera poison B (CTB) as mucosal adjuvant demonstrated compelling counteracting agent reaction against blood arrange parasite mice.62
Immunology of malaria
Published in David A Warrell, Herbert M Gilles, Essential Malariology, 2017
At first glance, it looks as though the malaria parasite ought to be well protected once it leaves the liver and enters the erythrocytic cycle, because it spends most of its time inside the host erythrocyte. Only at schizont rupture is the parasite directly exposed to the host immune system, when, for a few seconds, daughter merozoites have to attach to and enter new red cells. Much attention has therefore been given to the merozoite as a potential target of host immune responses. Antibody-mediated protective responses directed against the surface of the merozoite could act either by blocking key steps in the invasion process or by rendering the merozoite susceptible to secondary effects such as phagocytosis or complement-mediated damage. Alternatively, an antibody-mediated response could be directed at non-surface molecules released transiently as part of the invasion process. In fact, there is experimental evidence for all these possibilities and, as with the sporozoite, the difficulty is in determining which, if any, are important. Two components of the merozoite surface coat seem to be particularly important. Vaccination with various parts of both merozoite surface protein 1 (MSP-1) and MSP-2 leads to protection in a number of animal models of malaria (Miller et al., 1998). Interestingly, both proteins exist in two major allelic forms, though with many minor variations in sequence within these forms, and this could clearly fit with the idea that immunity is directed to a limited number of major strains. Although evidence is still limited, several field studies have suggested that antibody responses to parts of these molecules may play a role in protecting against clinical disease. Several parasite proteins produced in internal organelles of the merozoite, and playing a role in red cell invasion, are capable of inducing protective immune responses and are being considered for inclusion in potential vaccines.
Correlates of malaria vaccine efficacy
Published in Expert Review of Vaccines, 2021
Danielle I. Stanisic, Matthew B. B. McCall
Opsonized merozoites can be phagocytosed by neutrophils which triggers the production of soluble mediators such as reactive oxygen species (ROS), which are toxic for blood-stage parasites, in a process termed ADRB. This was associated with protection from clinical malaria in a cohort study of NAI [56] and with IgG targeting different merozoite antigens (e.g. merozoite surface protein 5 (MSP5) [75] and the 19kDa C-terminal region of merozoite surface protein 1 (MSP1-19) [76]) in naturally exposed individuals. Antibodies induced by MSP1 vaccination also simulate ADRB [77], although its association with protection has not been assessed in vaccine studies. Together these data suggest it may also be useful as a correlate of protective immunity for blood-stage vaccine candidates. These neutrophil respiratory bursts can be quantified via chemiluminescence-dependent detection of ROS in an ADRB assay combining neutrophils from healthy donors with pre-incubated merozoites and serum [56]. Recent optimization and standardization of this assay should facilitate wider application into clinical studies [78].
Dynamics of Plasmodium falciparum genetic diversity among asymptomatic and symptomatic children in three epidemiological areas in Cote d’Ivoire
Published in Pathogens and Global Health, 2019
Akpa Paterne Gnagne, Abibatou Konate, Akoua Valérie Bedia-Tanoh, Mireille Amiah-Droh, Hervé Ignace Eby Menan, Assanvo Simon-Pierre N’Guetta, William Yavo
The elimination of the malaria vector by insecticides, the use of antimalarial drugs for both curative and prophylactic treatment, the improvement of the living environment and the development of antimalarial vaccines are strategies used to control this endemic disease. To be successful, malaria elimination will require knowledge of parasite genome variation in different geographical locations and a better understanding of the factors that determine gene flow between locations. Plasmodium falciparum merozoite surface protein-1 (Pfmsp1) and Plasmodium falciparum merozoite surface protein-2 (Pfmsp2) which are asexual blood stage antigens are considered as prime candidates for the development of a malaria vaccine and are also suitable markers for the identification of genetically distinct Plasmodium falciparum parasite populations [3]. However, since the publication of the complete genome of the 3D7 reference clone of P. falciparum [4] and the sequencing of other plasmodial isolates, there have been some insights into the genetic variations responsible for phenotypes such as parasite chemo-resistance and virulence [5]. But, in these studies, parasites have been often collected from symptomatic cases. One of the difficulties of this elimination lies in the fact that most strategies concern symptomatic carriers of Plasmodium. Thus, little work on genetic polymorphism and resistance markers of P. falciparum has been done on asymptomatic infections.
Malaria vaccines in the eradication era: current status and future perspectives
Published in Expert Review of Vaccines, 2019
K. L. Wilson, K. L. Flanagan, M. D. Prakash, M. Plebanski
The viral vectored prime-boost immunisation regimen has also been employed for other blood-stage antigens, notably merozoite surface protein 1 (MSP1). A phase 1 trial in healthy adults demonstrated strong induction of both cellular and humoral immunity, although IgG antibody titres were not high enough to provide growth inhibitory activity against parasites in vitro [88]. In a CHMI model using the same viral vector regimen with both MSP1 and AMA1 co-administered together, strong T cell responses were induced [89]. However, the co-administered antigens possibly displayed immune interference, shown by reduced T cell responses when the vaccines were co-administered compared to when given alone (MSP1 was immunodominant) and none of the groups reached significant efficacy [89]. Another vaccine based on the 42-kDa C-terminal fragment of MSP1 [MSP1(42)] showed only 5.2% efficacy in a phase IIb trial in Kenya [90]. By contrast, the Combination B vaccine comprising MSP1, MSP2 and ring-infected erythrocyte surface antigen (RESA) in an oil-based adjuvant (Montanide ISA 720) showed a 62% reduction in parasite density in children in a Phase I-2b trial in 120 5–9 year old children in Papua New Guinea (PNG) [91]. The impact on circulating MSP2 genotypes in this study suggests that MSP2 contributed to the efficacy of Combination B.