No description available.

No description available.

No description available.

Malaria vaccine research has been battling with persistent challenges, including polymorphisms of vaccine antigens, difficulties with production processes, and limited immune protection against the disease. Intrinsically unstructured proteins (IUPs) are a fairly newly classified group of proteins that have no stable 3D structure and are generally heat-resistant. They usually contain low complexity regions and repetitive sequences, both of which are distinct characteristics of the malaria proteome. Surprisingly, some of the vaccine candidates that have been extensively studied were later reported to have unstructured regions, some of which serve as targets of protective immunity. In keeping with their interesting immunological profiles and their unique properties, which are exceptionally beneficial for vaccine production, malarial IUP antigens may be good vaccine candidates. This PhD project has the following aims:- 1) to develop a synthetic unstructured protein antigen based on the Block 2 region of MSP-1, named the MSP-1 hybrid 2) to characterize a novel vaccine antigen derived from the MSP-3.3 protein, namely an IUP region of PF10_0347 gene product, for its potential as a vaccine candidate 3) to develop a second-generation vaccine by combining the MSP-1 hybrid, with two allelic variants of MSP-2, to overcome antigenic polymorphism and strain-specific immune responses 4) to validate protocols for IUP identification from proteins extracted from the malaria parasite. This study showed that 1) MSP-1 hybrid production was scalable, yielding high protein yields with comparable immunological properties to small-scale production. MSP-1 hybrid was shown to be compatible with different adjuvants, and elicited specific antibodies covering the whole range of Block 2 allelic diversities. 2) A novel antigen, MSP-3.3C, an IUP based on the 3’ region of the PF10_0347 gene, was cloned, expressed and purified. Anti-MSP3.3C antibodies showed very strong parasite growth inhibitory effects in vitro. 3) The MSP-multihybrid antigen was expressed using simple techniques, but only at low levels. It contains epitopes from all three parasite antigen components, and is recognized by specific naturally acquired antibodies. 4) an unconventional 2D gel technique was tested as a method of malaria parasite IUP identification. Plans for further validation of this technique were discussed.

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

As the number of drug-resistant malaria parasites continues to grow, pressure is increasing to find an effective, cross-protective, multi-valent malaria vaccine (32). Expression library immunisation is an un-biased screening technique that leads to the identification of novel, protective antigens that can be administered as components of a multivalent DNA vaccine (9, 50, 75, 86, 92). Here, a P. c. adami DS expression library has been evaluated as a malaria vaccine in mice, and several subpools of cross-protective plasmids have been identified. Upon vaccination with these plasmid subpools, mice demonstrate significantly lower mean cumulative parasitemia values than control vaccinated mice, when challenged with avirulent heterologous P. c. adami DK parasites. These cross-protective responses correlate with the induction of opsonizing antibodies against infected red blood cells and the production of IFN-gamma by T-cells. The determination of P. c. adami antigens capable of inducing strain-transcending immunity implies the identification of orthologues in the P. falciparum genome that may be applied as components of a human malaria vaccine.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2001. / Includes bibliographical references (leaves 65-75). Also available on microfiche.

No description available.

No description available.

Transmission-blocking vaccines (TBVs) target Plasmodium parasite sexual stages, aiming to block further development of the parasite within the mosquito host. Plasmodium falciparum zygote/ookinete surface protein Pfs25 is one of the leading TBV candidate antigens and antibodies against Pfs25 have been shown to exhibit complete transmission-blocking activity in pre-clinical studies. Phase 1 human clinical trials have revealed that Pfs25 was a poor immunogen in humans in the formulations tested and high titers of anti-Pfs25 antibodies are required to achieve good transmission-blocking activity in the ex vivo standard membrane feeding assay which measures the functional activity of the antibodies induced. Work in this thesis describes the production of recombinant monomeric Pfs25 protein, Pfs25 based particulate vaccines (Pfs25-IMX313 nanoparticle, Pfs25-HBsAg VLP and Pfs25-Qβ VLP) and a Pfs25-Pfs28 multivalent protein vaccine in the Pichia pastoris protein expression system. These proteins were tested in mice using protein-in-adjuvant formulations and their immunogenicity was assessed. Pfs25-IMX313 nanoparticle induced significantly higher anti-Pfs25 antibodies than monomeric Pfs25 and the antibodies had higher avidity and transmission-blocking activity. All of the candidate vaccines generated, except for Pfs25-HBsAg VLP, were immunogenic. The Pfs25-IMX313 nanoparticle induced the highest antibody response in mice followed by the Pfs25-Pfs28 multivalent protein and Pfs25-Qβ VLP.