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Title: Oral and nasal infectivity and immunogenicity of Plasmodium berghei and yoelii sporozoites and longevity of Plasmodium falciparum trophozoites and schizonts
Author: Alshahrani, Mohammed A. S.
ISNI:       0000 0004 6498 7465
Awarding Body: Prifysgol Bangor University
Current Institution: Bangor University
Date of Award: 2017
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Malaria is one of the most problematic diseases that human being has ever confronted. The quest for an effective, robust vaccine has been going on for more than a century. The whole Plasmodium sporozoites vaccine strategy has proven to be the best approach for eliciting up to 70% protection and for up to 6 months after the last immunization. Most of the robust vaccines that we have nowadays against several microbiological organisms are given by either oral or nasal routes. Infectivity and immunogenicity of Plasmodium berghei ANKA and P. yoelii Nigeriensis sporozoites have never been tested against BALB/c or C57BL/6 mice after being inoculated via oral and nasal routes. Results of this study show that inoculation of sporozoites of the species P. berghei or P. yoelii into BALB/c or C57BL/6 mice are infective and immunogenic. Furthermore, there was a cross-reactivity between the two parasite species when tested against several synthetic peptides. These findings shed light on the importancy of the oral and nasal canal as routes for experimentations of the immunization regime. The large subunit vaccines development concentrated on the erythrocytic stage of malaria parasites has generated disappointing results, Therefore, there is currently a renewed focus on the whole Plasmodium blood stage parasite. In the current study, we aim to assess whether it is possible to obtain a living, whole entity of the blood stage that can be kept alive under minimal conditions and ideally without cryopreservation which could be used in developing countries a live, whole organism blood stage vaccine. we examined the viability as well as the invasiveness potency of Plasmodium falciparum parasites after being isolated from RBCs and incubated at 37˚C and RT. We showed here that the Plasmodium parasites were able to retain their invasiveness for 16 days despite being incubated at far lower temperature (at RT) than the optimal temperature. Also we showed that the Plasmodium falciparum at late trophozoites and early schizonts were capable to remain viable for 10 months (nearly 300 days) outside the RBCs at RT. The diversity of malaria disease in animals is larger ecologically and systematically than we commonly expected. The Plasmodium genus is a member within the order Haemosporidia, is consider one of the largest genus in this order, and currently encompass more than 250 Plasmodium species. Most of these species have only been defined morphologically. Most animals show simultaneous infections with more than one species of Plasmodium and most species descriptions originated from such multiple infections, which prevents the molecular characterization of most Plasmodium species as sequence data cannot be assigned to particular morphospecies. We have successfully developed genus- and species-specific FISH probes based on the small and large ribosomal subunit for Plasmodium falciparum as a proof of concept for the interrogation of animal morphospecies of Plasmodium parasites. This will open up the future for molecular screening of animal malaria, not only in blood samples but also in fecal samples, and might lead to a better understanding of the epidemiology and ecology of malaria parasites in many animal species in temperate and in tropical regions.
Supervisor: Braig, Henk Sponsor: Najran University
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available