Malaria is a major health problem and an effective vaccine is essential for the eradication of the disease. Despite extensive efforts, a malaria vaccine remains elusive due to the parasite's complex life cycle, diverse morphology, and immune system evasion mechanisms. Antibodies against C terminal domain of merozoite surface protein 1 (MSP1-19), a highly conserved protein and the main vaccine candidate for blood-stage malaria, can inhibit erythrocyte invasion by the parasite and alleviate the disease symptoms. However, MSP1-19 is poorly immunogenic and classic protein-in-adjuvant MSP1-19-based vaccine formulations failed to induce strong immune responses due to low immunogenicity and generation of ineffective antibodies. The aim of this study was to use hepatitis B virus core (HBc) particles to increase the immunogenicity of MSP1-19. HBc forms particles with protruding spikes and induces a strong and specific immune response against foreign epitopes inserted at the tips of the spikes. In addition, positioning of MSP1-19 on the particle can influence the accessibility of certain antibody binding sites, possibly altering elicited antibody fine specificity and vaccine efficiency. MSP1-19 domain was inserted into the middle of the HBc sequence so that it is displayed at the tips of the HBc particle. Two HBc-MSP1-19 constructs, having different insert flanking linkers, displayed soluble particle formation after bacterial expression and lysis optimization. The particles were purified and the suitability of these two constructs as malaria vaccine candidates was assessed. Firstly, binding of the conformational anti-MSP1-19 antibodies indicated that MSP1-19 domain in the chimeric proteins has the correct disulphide bond pattern which is crucial for the protective properties of an MSP1-19-based vaccine. Furthermore, electron microscopy imaging and determination of initial 3D structures confirmed that both HBc MSP1-19 constructs form particles resembling the wild-type HBc particles, meaning the insertion of MSP1-19 did not heavily distort the overall HBc particle structure. In addition, it was shown that MSP1-19 domains are displayed at the tips of the particle spikes. Particle formation and foreign epitope display are important for the epitope's immunogenicity improvement. The immunogenicity of the chimeric particles was then assessed in mice. Both constructs elicited similar high antibody titres without the use of additional adjuvants, but no difference was observed between the particulate constructs and a non-particulate control (an MSP1-19-based protein). Interestingly, although both HBc-MSP1-19 and non-particulate MSP1-19-elicited antibodies recognized native malarial parasite, only the particulate construct antibodies demonstrated a moderate parasite growth inhibition while the antibodies from the control group did not show parasite inhibition above the background levels. In conclusion, it was shown that MSP1-19 can be expressed in bacteria as a soluble correctly folded protein fused to HBc. More importantly, the fusion protein is capable of forming immunogenic particles which generate antibodies that recognize native MSP1 and inhibit parasite growth more effectively than the protein without the HBc. Therefore, this work lays grounds and supports further chimeric HBc-MSP1-19 research and development.

Miu Fei Fei. / On t.p. "42" are subscripts following the word "MSP-1" in the title. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 117-125). / Abstracts in English and Chinese. / ACKNOWLEGEMENTS --- p.i / ABSTRACT --- p.ii / TABLE OF CONTENTS --- p.v / LIST OF FIGURE --- p.vii / LIST OF ABBREVIATIONS --- p.ix / CHAPTERS: / Chapter 1. --- BACKGROUND OF MALARIA / Chapter 1.1 --- Epidemilogy --- p.2 / Chapter 1.2 --- Mode of Infection --- p.4 / Chapter 1.3 --- Conventional Control & Vaccination --- p.9 / Chapter 1.4 --- Vaccine Candidate PfMSV-142 --- p.16 / Chapter 1.5 --- Cloning and Expression of pfMSP-142 --- p.26 / Chapter 1.6 --- Aims of Study --- p.32 / Chapter 2. --- Materials and Methods / Chapter 2.1 --- Materials --- p.32 / Chapter 2.2 --- Methods --- p.38 / Chapter 3. --- Construction of recombinants N-PfMSP-142 and C- PfMSP-142 / Chapter 3.1 --- Construction of C-PfMSP-l42 --- p.51 / Chapter 3.2 --- Construction ofN-PfMSP-l42 --- p.56 / Chapter 4. --- Purification with IMAC / Chapter 4.1 --- Immobilized Metal Affinity Chromatography (IMAC) --- p.58 / Chapter 4.2 --- Purification ofN-PfMSP-l42 --- p.61 / Chapter 4.3 --- Purification profile of N-PfMSP-142 --- p.68 / Chapter 4.4 --- Purification of C-PfMSP-l42 --- p.70 / Chapter 4.5 --- Purification profile of C-PfMSP-142 --- p.73 / Chapter 4.6 --- Expression pattern of recombinants PfMSP-142 --- p.76 / Chapter 5. --- Purification combined with other chromatography method / Chapter 5.1 --- Affinity chromatography --- p.78 / Chapter 5.2 --- Gel filtration chromatography --- p.80 / Chapter 5.3 --- Ion exchange chromatography --- p.83 / Chapter 5.4 --- Conclusion --- p.93 / Chapter 6. --- Characteristic of IMAC products --- p.94 / Chapter 7. --- Characteristic of N-hisPfMSP-l42 & C-hisPfMSP-l --- p.42 / Chapter 7.1 --- Immunogenitcity of N-PfMSP-l42 and C-PfMSP-142 --- p.100 / Chapter 7.2 --- Competitive ELISA --- p.105 / Chapter 8. --- Discussion --- p.107 / REFERENCE --- p.117

Leung Wai-hang. / "November 2002." / On t.p. "33" and "42" are subscripts following the word "MSP-1" in the title. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (p. 162-171). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

In the second part of the project, the immunology of PfMSP-133 was studied. During the invasion of merozoites, PfMSP--142 is processed into two fragments with molecular weight of 33kDa and 19kDa. The 19kDa fragment (PfMSP-119) originating from the carboxyl--terminal of PfMSP--142 is relatively more immuno-dominant in different malarial species such as P. falciparum, P. vivax and P. yoelii. In the past, only limited researches about PfMSP-1 33 were performed. Apart from its difficulty in expression, PfMSP-1 33 was also believed to be incapable of inducing protection. / Nevertheless, following the breakthrough of expressing recombinant PfMSP-1 33 in our laboratory, we have demonstrated in this study that recombinant MSP-133 can elicit antibodies with a titer up to a million. Also, we observed that MSP-133 can help MSP-119 to induce protective immunity and such effect is independent from the covalent linkage between these two proteins. Most importantly, our results show that recombinant PfMSP-133 can elicit the production of antibodies that can potentiate the inhibitory effect of anti-MSP-142 serum at high serum dilution. Results of this study give new insights in malarial vaccine development in terms of optimizing the use of adjuvant and immunization regimens. / The 42kDa carboxyl terminal fragment of Plasmodium falciparum Merozoite Surface Protein-1 (PfMSP--142) is one of the most promising candidate antigens in the development of malarial vaccine. In vivo experiments in the 1990's showed that Aotus monkeys immunized with PfMSP--142 were protected from malarial challenge. Later on, other experiments also demonstrated the possibility of using recombinant PfMSP-142 as candidate antigen for malarial vaccine. Previously, recombinant PfMSP-142 (Bvp42) was expressed with the baculovirus expression system and characterized in our laboratory. / The aim of the first part of this project is to improve the production of Bvp42. Experimental results have shown that the expression level of Bvp42 was increased under a BMN compatible baculovirus expression vector---pVL1393. Besides, a codon optimized MSP-142 nucleotide is constructed for the construction of a baculovirus carrying codon optimized MSP-142 gene and aimed for higher expression level. Unfortunately, no Bvp42 expression is observed in the transfection samples and the reason of this observation is unclear. Meanwhile, the purification of Bvp42 was also improved. Pretreatment of the hemolymph with Q--sepharose before affinity chromatography could enhance the purity of the final product. / Yuen, Sai-hang Don. / "July 2007." / Adviser: Walter K. K. Ho. / Source: Dissertation Abstracts International, Volume: 69-01, Section: B, page: 0220. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 183-195). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Tam, Hou Si. / 33 in title is subscript. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 174-187). / Abstracts in English and Chinese. / THESIS COMMITTEE --- p.i / ACKNOWLEDGEMENTS --- p.ii / ABSTRACT --- p.iii / 摘要 --- p.v / TABLE OF CONTENTS --- p.vii / LIST OF FIGURES --- p.xii / LIST OF TABLES --- p.xvii / LIST OF ABBREVIATIONS --- p.xviii / CHAPTER / Chapter 1. --- INTRODUCTION / Chapter 1.1 --- Malaria --- p.1 / Chapter 1.2 --- Malaria is a public health problem --- p.1 / Chapter 1.3 --- Malarial parasite --- p.3 / Chapter 1.4 --- Life cycle of P. falciparum --- p.3 / Chapter 1.4.1 --- The pre-erythrocytic stage --- p.3 / Chapter 1.4.2 --- The asexual erythrocytic stage --- p.3 / Chapter 1.4.3 --- The sexual transmission stage --- p.6 / Chapter 1.5 --- Chemoprophylaxis and chemotherapy of malaria --- p.7 / Chapter 1.6 --- Drug resistance of malaria parasite --- p.7 / Chapter 1.7 --- The progress for malaria vaccine --- p.10 / Chapter 1.8 --- Vaccine candidates for asexual erythrocytic stage --- p.11 / Chapter 1.9 --- Merozoite Surface Protein-1 (MSP-1) --- p.13 / Chapter 1.9.1 --- Structure of MSP-1 --- p.13 / Chapter 1.9.2 --- The processing of MSP-1 --- p.17 / Chapter 1.9.3 --- MSP-1 as a blood-stage vaccine --- p.19 / Chapter 1.9.4 --- The vaccine potency of MSP-133 --- p.23 / Chapter 1.10 --- Merits of E. coli expression system --- p.25 / Chapter 1.11 --- Aim of study --- p.26 / Chapter 2. --- MATERIALS AND METHODS / Chapter 2.1 --- Materials --- p.30 / Chapter 2.2 --- Methods --- p.39 / Chapter 3. --- EXPRESSION AND PURIFICATION OF RECOMBINANT MSP-l33kv+19 PROTEIN / Chapter 3.1 --- Introduction --- p.63 / Chapter 3.2 --- Results / Chapter 3.2.1 --- Construction of pET32a/MSP-l33kv+19 expression vector --- p.64 / Chapter 3.2.2 --- SDS-PAGE analysis of the expressed protein --- p.74 / Chapter 3.2.3 --- Western blot analysis of the expressed protein --- p.78 / Chapter 3.2.4 --- Modification of the expression conditions --- p.78 / Chapter 3.2.5 --- Protein purification by IMAC --- p.82 / Chapter 3.2.6 --- Cleavage of fusion partner from the rMSP-133kv+19 protein --- p.82 / Chapter 3.2.7 --- Verification of non-fused recombinant MSPl33kv+19 protein by N-terminal amino acid sequencing --- p.86 / Chapter 3.2.8 --- Separation of target protein from the fusion mixture by IMAC --- p.86 / Chapter 3.2.9 --- Separation of digestion product by Size Exclusion Chromatography --- p.89 / Chapter 3.2.10 --- Conformational test of the purified protein --- p.89 / Chapter 3.2.11 --- Separation of target protein from contaminants by Anion-Exchange Chromatography --- p.92 / Chapter 3.2.12 --- Separation of target protein from contaminants by Immuno-Affinity Chromatography --- p.95 / Chapter 3.3 --- Conclusion --- p.95 / Chapter 4. --- IMMUNOLOGICAL CHARACTERIZATION OF BACTERIAL EXPRESSED rMSP-l33kv+19 / Chapter 4.1 --- Introduction --- p.97 / Chapter 4.2 --- Results / Chapter 4.2.1 --- Immunogenicity of recombinant NfMSP-133kV+19 protein --- p.98 / Chapter 4.2.2 --- Specificity of anti-NfMSP-133kv+19 sera to MSP-l33kv. MSP-l33 and MSP-l19 --- p.98 / Chapter 4.2.3 --- Cross reactivity of anti-MSP-133kv+19 and anti-BVp42 serum --- p.103 / Chapter 4.2.4 --- Competitive ELISA --- p.103 / Chapter 4.2.5 --- Test for the presence of inhibitory B-cell epitopes on rMSP-l33kv+19 --- p.111 / Chapter 4.2.6 --- In vitro parasitic growth inhibition assay --- p.113 / Chapter 4.3 --- Conclusion --- p.115 / Chapter 5. --- EXPRESSION AND PURIFICATION OF RECOMBINANT MSP-l33kc+19 PROTEIN / Chapter 5.1 --- Introduction --- p.116 / Chapter 5.2 --- Results / Chapter 5.2.1 --- Construction of pET32a/MSP-133kv+19 expression vector --- p.117 / Chapter 5.2.2 --- Expression of recombinant MSP-133kc+19 protien (rMSP-133kc+19) --- p.124 / Chapter 5.2.3 --- Purification of rMSP-l33kc+19 by IMAC --- p.127 / Chapter 5.2.4 --- Cleavage of fusion partner from target protein --- p.127 / Chapter 5.2.5 --- Construction of pRSETA/MSP-l3X33kc+19 expression vector --- p.135 / Chapter 5.2.6 --- SDS-PAGE analysis of the protein expression --- p.146 / Chapter 5.3 --- Conclusion --- p.153 / Chapter 6. --- DISCUSSION / Chapter 6.1 --- Expression of rMSP-l33kv+19 --- p.154 / Chapter 6.2 --- Purification of rMSP-l3.3kv+19 --- p.156 / Chapter 6.3 --- Conformational test of rMSP-133kv+19 --- p.157 / Chapter 6.4 --- Biological and immunological activity of NfMSP-133kv+19 --- p.158 / Chapter 6.5 --- Expression of rMSP-133kc+19 --- p.166 / Chapter 6.6 --- Future prospects --- p.167 / REFERENCES --- p.174 / APPENDICES / Chapter 1. --- HiTrap NHS-activated HP for ligand coupling procedure --- p.188 / Chapter 2. --- Reuse of Ni+-NTA Resin procedure --- p.190 / Chapter 3. --- Sequence alignment of MSP-133 (MAD20 & Welcome/Kl alleles) --- p.191 / Chapter 4. --- Nucleotide sequence and amino acid sequence of P. falciparum MSP-l33kv+19 --- p.192 / Chapter 5. --- Nucleotide sequence and amino acid sequence of P. falciparum MSP-l33kc+19 --- p.193 / Chapter 6. --- "Nucleotide sequence and amino acid sequence of P. falciparum MSP-142 (3D7 isolate, MAD20 allele)" --- p.194 / Chapter 7. --- Amino acid sequence of Plasmodium falciparum MSP-l42 --- p.195

Here we report the identification of 15 potential MSP-like proteins from the P. falciparum 3D7 genome using a bioinformatics-based approach. One candidate, renamed URF1, was further characterized by cloning into the Gateway system. We were able to demonstrate expression of URF1 during the blood stage, especially the trophozoite, early and late schizont phases, by immunofluorescence on infected RBC using antisera raised in mice with an URF1 DNA vaccine. URF1 expression in the merozoite stage could not be confirmed in this study. Future co-localization and immunosorbent electron microscopy (EM) experiments would help us determine the exact localization of URF1 on the parasite before officially categorizing URF1 as a merozoite surface protein. As a whole, this research project demonstrates the success of using bioinformatics in identifying potential new MSP-like proteins found in the malaria genome. Further characterization and sequence analysis of the other 15 candidates may reveal other novel antigens expressed during the erythrocytic stage, especially in the merozoite stage. Such antigens may prove to be good vaccine candidates.

No description available.

A MSP-1 de Plasmodium vivax (PvMSP-1), o principal alvo para o desenvolvimento de uma vacina contra a malária, é constituída por seis domínios altamente polimórficos flanqueados por seqüências conservadas. Apesar de evidências de que a divergência na seqüência da PvMSP-1 é está sendo mantida por mais de cinco milhões de anos por seleção balanceada exercida pela imunidade adquirida pelo hospedeiro, a especificidade dos anticorpos adquiridos naturalmente contra a PvMSP-1 ainda é pouco estudada. Este trabalho mostra que 15 proteínas recombinantes que correspondem às variantes da PvMSP-1 comumente encontradas em parasitos locais foram pouco reconhecidas por 376 indivíduos não-infectados com idade entre 5 e 90 anos expostos à malária na Amazônia rural; menos de 30% dos indivíduos tiveram anticorpos IgG detectáveis contra no mínimo uma variante dos blocos 2, 6 e 10 que foram expressas, embora 54,3% reconheceram o domínio conservado C-terminal PvMSP-119. Apesar da proporção de respondedores às variantes da PvMSP-1 ter aumentado substancialmente durante infecções agudas subseqüentes por P. vivax, os anticorpos não foram necessariamente específicos para as variantes da PvMSP-1 encontradas nos parasitos infectantes. São discutidos a contribuição relativa do polimorfismo antigênico, a fraca imunogenicidade e o pecado antigênico original (a tendência de a exposição a uma nova variante antigênica induzir resposta de anticorpos com especificidade pré-existente) para os padrões observados de reconhecimento por anticorpos da PvMSP-1. É sugerido que a resposta de anticorpos ao repertório de domínios variáveis da PvMSP-1 em indivíduos continuamente expostos é induzida somente após algumas infecções repetidas e requerem re-estímulo freqüente, com claras implicações para o desenvolvimento de subunidades de vacinas baseadas na PvMSP-1. / The merozoite surface protein 1 of Plasmodium vivax (PvMSP-1), a major target for malaria vaccine development, contains six highly polymorphic domains interspersed with conserved sequences. Although there is evidence that the sequence divergence in PvMSP-1 has been maintained over five million years by balanced selection exerted by host?s acquired immunity, the variant-specificity of naturally acquired antibodies to PvMSP-1 remains little investigated. Here we show that 15 recombinant proteins corresponding to PvMSP-1 variants commonly found in local parasites were poorly recognized by 376 noninfected subjects aged 5-90 years exposed to malaria in rural Amazonia; less than onethird of them had detectable IgG antibodies to at least one variant of blocks 2, 6 and 10 that were expressed, although 54.3% recognized the invariant C-terminal domain PvMSP-119. Although the proportion of responders to PvMSP-1 variants increased substantially during subsequent acute P. vivax infections, the specificity of IgG antibodies did not necessarily match the PvMSP-1 variant(s) found in infecting parasites. We discuss the relative contribution of antigenic polymorphism, poor immunogenicity, and original antigenic sin (the skew in the specificity of antibodies elicited by exposure to new antigenic variants due to preexisting variant-specific responses) to the observed patterns of antibody recognition of PvMSP-1. We suggest that antibody responses to the repertoire of variable domains of PvMSP-1 to which subjects are continuously exposed are only elicited after several repeated infections and may require frequent boosting, with clear implications for the development of PvMSP-1-based subunit vaccines.

A MSP-1 de Plasmodium vivax (PvMSP-1), o principal alvo para o desenvolvimento de uma vacina contra a malária, é constituída por seis domínios altamente polimórficos flanqueados por seqüências conservadas. Apesar de evidências de que a divergência na seqüência da PvMSP-1 é está sendo mantida por mais de cinco milhões de anos por seleção balanceada exercida pela imunidade adquirida pelo hospedeiro, a especificidade dos anticorpos adquiridos naturalmente contra a PvMSP-1 ainda é pouco estudada. Este trabalho mostra que 15 proteínas recombinantes que correspondem às variantes da PvMSP-1 comumente encontradas em parasitos locais foram pouco reconhecidas por 376 indivíduos não-infectados com idade entre 5 e 90 anos expostos à malária na Amazônia rural; menos de 30% dos indivíduos tiveram anticorpos IgG detectáveis contra no mínimo uma variante dos blocos 2, 6 e 10 que foram expressas, embora 54,3% reconheceram o domínio conservado C-terminal PvMSP-119. Apesar da proporção de respondedores às variantes da PvMSP-1 ter aumentado substancialmente durante infecções agudas subseqüentes por P. vivax, os anticorpos não foram necessariamente específicos para as variantes da PvMSP-1 encontradas nos parasitos infectantes. São discutidos a contribuição relativa do polimorfismo antigênico, a fraca imunogenicidade e o pecado antigênico original (a tendência de a exposição a uma nova variante antigênica induzir resposta de anticorpos com especificidade pré-existente) para os padrões observados de reconhecimento por anticorpos da PvMSP-1. É sugerido que a resposta de anticorpos ao repertório de domínios variáveis da PvMSP-1 em indivíduos continuamente expostos é induzida somente após algumas infecções repetidas e requerem re-estímulo freqüente, com claras implicações para o desenvolvimento de subunidades de vacinas baseadas na PvMSP-1. / The merozoite surface protein 1 of Plasmodium vivax (PvMSP-1), a major target for malaria vaccine development, contains six highly polymorphic domains interspersed with conserved sequences. Although there is evidence that the sequence divergence in PvMSP-1 has been maintained over five million years by balanced selection exerted by host?s acquired immunity, the variant-specificity of naturally acquired antibodies to PvMSP-1 remains little investigated. Here we show that 15 recombinant proteins corresponding to PvMSP-1 variants commonly found in local parasites were poorly recognized by 376 noninfected subjects aged 5-90 years exposed to malaria in rural Amazonia; less than onethird of them had detectable IgG antibodies to at least one variant of blocks 2, 6 and 10 that were expressed, although 54.3% recognized the invariant C-terminal domain PvMSP-119. Although the proportion of responders to PvMSP-1 variants increased substantially during subsequent acute P. vivax infections, the specificity of IgG antibodies did not necessarily match the PvMSP-1 variant(s) found in infecting parasites. We discuss the relative contribution of antigenic polymorphism, poor immunogenicity, and original antigenic sin (the skew in the specificity of antibodies elicited by exposure to new antigenic variants due to preexisting variant-specific responses) to the observed patterns of antibody recognition of PvMSP-1. We suggest that antibody responses to the repertoire of variable domains of PvMSP-1 to which subjects are continuously exposed are only elicited after several repeated infections and may require frequent boosting, with clear implications for the development of PvMSP-1-based subunit vaccines.

Malaria, caused by the Plasmodium parasite and transmitted by mosquitoes, kills almost half a million people each year. Drug resistance in both the parasite and its vector make preventative measures increasingly important, and a fully protective vaccine is absolutely necessary to eradicate the disease. However, genetic diversity of the parasite makes vaccine development difficult. One of the best vaccine candidates is MSP2, a surface protein present during the blood stage of P. falciparum infection. Antibodies, which are important for natural immunity, have been shown to bind MSP2 and prevent parasite infection of blood cells. The purpose of this study was to analyze MSP2 sequence diversity in a cohort of patients infected while traveling or living in sub-Saharan Africa, and to investigate patient antibody responses to MSP2 variants infecting other individuals. Parasite isolates from our cohort were made up of 47% 3D7 alleles and 53% FC27 alleles. Protein sequences showed similar levels of conservation within allelic families, and blocks of conserved amino acids between different variants suggest there may be epitopes that can induce antibody production targeting multiple variants. Antibody reactivity tests suggest the variable region of MSP2 is important for antibody binding to variants of the same allelic type, while the conserved region is important for reactivity to different allelic types. This thesis gives evidence to the importance of including epitopes from conserved and variable regions of both MSP2 allelic families in order to induce strain-transcending immunity against P. falciparum malaria. / A genomic surveillance platform for indel-rich genes from Plasmodium spp. using long-read amplicon sequencing