Transmission-blocking vaccines have the potential to be key contributors to malaria elimination. Such vaccines elicit antibodies that inhibit parasites during their development in Anopheles ...mosquitoes, thus breaking the cycle of transmission. To date, characterization of humoral responses to Plasmodium falciparum transmission-blocking vaccine candidate Pfs25 has largely been conducted in pre-clinical models. Here, we present molecular analyses of human antibody responses generated in a clinical trial evaluating Pfs25 vaccination. From a collection of monoclonal antibodies with transmission-blocking activity, we identify the most potent transmission-blocking antibody yet described against Pfs25; 2544. The interactions of 2544 and three other antibodies with Pfs25 are analyzed by crystallography to understand structural requirements for elicitation of human transmission-blocking responses. Our analyses provide insights into Pfs25 immunogenicity and epitope potency, and detail an affinity maturation pathway for a potent transmission-blocking antibody in humans. Our findings can be employed to guide the design of improved malaria transmission-blocking vaccines.
The Plasmodium falciparum Pfs25 protein (Pfs25) is a leading malaria transmission-blocking vaccine antigen. Pfs25 vaccination is intended to elicit antibodies that inhibit parasite development when ...ingested by Anopheles mosquitoes during blood meals. The Pfs25 three-dimensional structure has remained elusive, hampering a molecular understanding of its function and limiting immunogen design. We report six crystal structures of Pfs25 in complex with antibodies elicited by immunization via Pfs25 virus-like particles in human immunoglobulin loci transgenic mice. Our structural findings reveal the fine specificities associated with two distinct immunogenic sites on Pfs25. Importantly, one of these sites broadly overlaps with the epitope of the well-known 4B7 mouse antibody, which can be targeted simultaneously by antibodies that target a non-overlapping site to additively increase parasite inhibition. Our molecular characterization of inhibitory antibodies informs on the natural disposition of Pfs25 on the surface of ookinetes and provides the structural blueprints to design next-generation immunogens.
The United States holds a commanding 22% of the market share of international students, more than double that of the second leading country (United Kingdom). The number of international students ...studying at U.S. institutions has had a steady incline for decades and these students now make up approximately 5% of all higher education students in the U.S. Even still, there have been previous examinations of international students’ perceptions of online learning readiness. As online and blended learning elements are an integral part of nearly every degree program, and, indeed, nearly every course, it is imperative that we gain a better understanding of what international students perceive to be important, how confident they view themselves on those same items, if there is a difference between what they perceive as important and their confidence, and the effect of demographic factors on these perceptions. This study examines these questions through the Student Readiness for Online Learning instrument developed by Martin et al. (2020) across four subscales: online student attributes, time management, technological competency, and communication competency. Data were gathered from currently enrolled residential international students at U.S. institutions. There were 117 valid respondents. Descriptive statistics, repeated measures ANOVAs, and correlation matrices were used to address the research questions. Data analysis revealed that the average student viewed all four subscales as being between somewhat to very important and themselves as being somewhat to very confident. Demographic variables did not interact with the dependent variables, though there were correlations for GDP per capita ppp and internet users % per capita. This study shed much needed light on the perceptions of international students online learning readiness. Results indicate the need for further study as well as the development of more comprehensive assessments.
Malaria is an ongoing global health crisis with cases and resistance to treatments on the rise. Only one malaria vaccine is currently recommended for use in endemic regions in Africa by the WHO, ...which has middling efficacy that drops to approximately 35% protection against clinical disease after a year. Novel approaches are urgently needed. Transmission-blocking vaccines aim to inhibit the malaria parasite, Plasmodium falciparum, while in the mosquito vector, so the parasite is not viable to transmit to the human host. However, both biological and biophysical understanding is lacking for most target antigens within the field. This thesis establishes the groundwork for the molecular understanding of antibody recognition of leading transmission-blocking antigens Pfs25 and Pfs48/45 by solving multiple crystal structures of Fabs bound in complex to the antigens. Herein is described the first atomic resolution structure of Pfs25, as well as the molecular characterizations of both murine and human monoclonal antibody epitopes of high and low potency, providing a comprehensive map of the immunogenicity and potency of Pfs25. This thesis also leverages molecular blueprints of Pfs48/45 to stabilize its structure using integrative structural biology approaches leading to increases in recombinant expression (~30x), thermostability (>25°C improvement in melting temperature from wild-type), and potency (1-2 log) of the antibody response elicited through immunization. Overall, this work provides foundational molecular understandings and improvements to two of the most high- priority transmission-blocking vaccine targets against malaria.
Malaria transmission-blocking vaccines (TBVs) aim to elicit human antibodies that inhibit sporogonic development of Plasmodium falciparum in mosquitoes, thereby preventing onward transmission. ...Pfs48/45 is a leading clinical TBV candidate antigen and is recognized by the most potent transmission-blocking monoclonal antibody (mAb) yet described; still, clinical development of Pfs48/45 antigens has been hindered, largely by its poor biochemical characteristics. Here, we used structure-based computational approaches to design Pfs48/45 antigens stabilized in the conformation recognized by the most potently inhibitory mAb, achieving >25°C higher thermostability compared with the wild-type protein. Antibodies elicited in mice immunized with these engineered antigens displayed on liposome-based or protein nanoparticle-based vaccine platforms exhibited 1-2 orders of magnitude superior transmission-reducing activity, compared with immunogens bearing the wild-type antigen, driven by improved antibody quality. Our data provide the founding principles for using molecular stabilization solely from antibody structure-function information to drive improved immune responses against a parasitic vaccine target.
Malaria transmission-blocking vaccines (TBVs) aim to induce antibodies that interrupt malaria parasite development in the mosquito, thereby blocking onward transmission, and provide a much-needed ...tool for malaria control and elimination. The parasite surface protein Pfs48/45 is a leading TBV candidate. Here, we isolated and characterized a panel of 81 human Pfs48/45-specific monoclonal antibodies (mAbs) from donors naturally exposed to Plasmodium parasites. Genetically diverse mAbs against each of the three domains (D1–D3) of Pfs48/45 were identified. The most potent mAbs targeted D1 and D3 and achieved >80% transmission-reducing activity in standard membrane-feeding assays, at 10 and 2 μg/mL, respectively. Co-crystal structures of D3 in complex with four different mAbs delineated two conserved protective epitopes. Altogether, these Pfs48/45-specific human mAbs provide important insight into protective and non-protective epitopes that can further our understanding of transmission and inform the design of refined malaria transmission-blocking vaccine candidates.
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•Isolated 81 unique mAbs directed to Pfs48/45 elicited in naturally exposed individuals•The most potent mAbs target domains 1 and 3 of Pfs48/45•Antibodies against domain 2 have low or no transmission-reducing activity•Potent antibodies against domain 3 target two conserved epitopes
The malaria parasite surface protein Pfs48/45 is a leading transmission-blocking vaccine candidate, but little is known about the specificity of naturally acquired antibodies against this target. Fabra-García et al. isolate and characterize a panel of 81 human monoclonal antibodies from naturally exposed individuals and demonstrate that the most potent antibodies target domains 1 and 3 of Pfs48/45.
My thesis, titled "From Mount Fuji to Mint Juleps: The Collected Works of Joseph Cortezi" is a collection of my original poetry presented as the works of a fictional author of my creation. Through ...the use of a character, I delve into a variety of themes ranging from birth to old-age, from childhood memories to sexuality. Utilizing a character whose life has already ended, I was able to present the gambit of human experiences. Cortezi, as I have envisioned him, is a Southern-American, bisexual, globally-minded, poet and photographer. In my work, I take advantage of several poetic forms including tanka, lyric, black-out, prose, visual (vispo), oulipo, acrostic, ekphrastic, found, cento, and free verse. Considering the profound changes that occur in poetry during Cortezi's lifetime (1930s to near-present), the use of these forms was necessary. My title, coming from two of the enclosed poems, represents the wide range of themes explored.
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