Biology subjects

Beeson, J.

Publications and source records attributed to Beeson, J..

7 recordsLinked to original sources

bioRxiv2026

Dose-sparing self-amplifying RNA vaccine induces high functional antibodies to blood-stage Plasmodium falciparum malaria

IntroductionNext-generation malaria vaccines are urgently needed to provide greater efficacy and longevity. Antibodies targeting blood-stage merozoites can confer protection against clinical malaria through multiple Fc-mediated functions. In particular, merozoite surface protein 2 (PfMSP2), is a known target of protective antibodies that can clear merozoites via multiple antibody Fc-mediated functions, making is a highly promising vaccine candidate. MethodsWe developed PfMSP2 as a self-amplifying RNA (saRNA) vaccine, which was successfully validated for in vitro expression in mammalian cells. Subsequently, the PfMSP2-saRNA was formulated as lipid nanoparticles (LNP) and evaluated for immunogenicity in mice in a 3-dose regimen comparing 1 g and 10 g doses. We evaluated the induction of antibodies with functional activities relevant to protective immunity. ResultsOur PfMSP2-saRNA vaccine induced antigen-specific IgG responses that recognised the surface of whole merozoites. Both 1 g and 10 g dosing induced comparable antibodies to PfMSP2, and responses were predominantly murine cytophilic IgG subclasses. These vaccine-induced antibodies demonstrated potent Fc-mediated functions, including complement fixation and binding of human Fc{gamma}-receptor I (Fc{gamma}RI), after only two doses, which remained consistent after the third dose. ConclusionsPfMSP2 is highly immunogenic using the saRNA vaccine platform in a dose-sparing regimen, and induces antibodies with multiple Fc-mediated functions associated with protective immunity in humans. This saRNA platform is a promising strategy to develop highly efficacious vaccines requiring lower and fewer doses.

immunology↗

bioRxiv2026

Targeting a malaria merozoite surface protein with mRNA vaccine generates multifunctional antibodies

IntroductionMalaria is a leading health problem with high disease burden and mortality rates worldwide. Currently approved vaccines target the sporozoite form of Plasmodium falciparum that initially infects the liver, but only provide modest protection against malaria in young children. There is an urgent need to develop next-generation malaria vaccines that target multiple parasite developmental stages for greater efficacy. Antibodies to merozoites, which are involved in blood-stage replication, and are associated with clinical illness, have multiple functional activities and can protect against malaria. A promising merozoite vaccine candidate is Merozoite Surface Protein 2 (PfMSP2). Antibodies to PfMSP2 can promote multiple antibody Fc-mediated functional activities to clear merozoites. MethodsWe developed and evaluated monovalent and bivalent (3D7 and FC27 variants) PfMSP2-based mRNA vaccines. We designed and codon-optimised mRNA, which was validated for in vitro expression in mammalian cells, and subsequently formulated as lipid nanoparticles for vaccination of mice in a 3-dose regimen. Vaccination with recombinant PfMSP2 protein with adjuvant was performed for comparison. We evaluated the induction of antibodies and functional activities relevant to protective immunity. ResultsmRNA vaccines induced prominent IgG responses using monovalent (3D7 allele) and bivalent (3D7 and FC27 alleles) vaccines encoding near full-length PfMSP2, and antibodies recognised the surface of whole merozoites. Vaccine responses were equivalent to, or superior than, a recombinant protein-based PfMSP2 vaccine. The bivalent vaccine induced equivalent antibodies to the two PfMSP2 alleles. Vaccination induced cytophilic IgG subclasses with multiple functional activities, including complement fixation, binding of human Fc{gamma}-receptors I and IIa, and opsonic phagocytosis. ConclusionsPfMSP2 is highly immunogenic using the mRNA vaccine platform and induces antibodies with multiple functional activities associated with protective immunity in humans. Combining PfMSP2 with other merozoite and sporozoite antigens is a promising strategy to develop highly efficacious vaccines to achieve malaria control and elimination goals.

immunology↗

bioRxiv2025

An abundant merozoite surface protein of Plasmodium falciparum modulates susceptibility to inhibitory antibodies

Malaria merozoite surface proteins (MSPs), are thought to have important roles in red blood cell (RBC) invasion and their exposure on the parasite surface makes them attractive vaccine candidates. However, their role in invasion has not been directly demonstrated and their biological functions are unknown. One of the most abundant proteins is PfMSP2, which is likely an ancestral protein that has been maintained in the Plasmodium falciparum lineage and is a focus of vaccine development, whose function remains unknown. Using CRISPR-Cas9 gene-editing, we removed PfMSP2 from two different P. falciparum lines with no impact on parasite replication or phenotype in vitro, demonstrating that it is not essential for RBC invasion. However, loss of PfMSP2 led to increased inhibitory potency of antibodies targeting other merozoite proteins involved in invasion, particularly PfAMA1. In a solid-phase model, increasing concentrations of PfMSP2 protein reduced binding of different antibodies against PfAMA1 in a dose dependent manner. These data suggest that PfMSP2 can modulate the susceptibility of merozoites to protective inhibitory antibodies. The results of this study change our understanding of the potential functions of PfMSP2 and establishes a new concept in malaria where a surface protein can reduce the protective efficacy of antibodies targeting a different antigen. These findings have important implications for understanding malaria immunity and informing vaccine development.

microbiology↗

bioRxiv2024

IgM plays a prominent role in naturally acquired immunity against Plasmodium falciparum gametocytes

The development of transmission-blocking vaccines against Plasmodium falciparum malaria could facilitate malaria elimination. However, limitations in the knowledge of the human immune responses against P. falciparum transmission stages, known as gametocytes, represent a critical roadblock to vaccine development. We evaluated human antibodies acquired through natural malaria exposure to whole gametocytes and recombinant antigens expressed by transmission stages, including the major transmission-blocking vaccine candidates Pfs230 and Pfs48/45 and other transmission stages, Pf38, Pf12 and Pf41. Among individuals residing in Kenya and Papua New Guinea, we found substantial antibody responses to whole gametocytes and to all recombinant transmission stage antigens with high levels of IgG, IgG subclasses and IgM. Complement fixation by antibodies to gametocytes is key for effective transmission-blocking activity. We found that purified IgM was substantially more potent than IgG at mediating complement fixation and activation. Higher antibody levels were generally observed in individuals positive for P. falciparum infection, including gametocyte positive individuals, and these antibodies generally increased with age. Our findings reveal that IgM is a prominent feature of antibody responses to gametocytes and that antibodies target multiple antigens. The further demonstration that IgM has high functional activity against gametocytes suggests IgM plays an important role in immunity to transmission stages. Our data provide new insights to inform the development of potent transmission-blocking vaccines.

immunology↗

bioRxiv2021

Age dependent changes in circulating Tfh cells influence the development of functional antibodies to malaria in children.

T-follicular helper (Tfh) cells are key drivers of antibodies that protect from malaria. However, little is known regarding the host and parasite factors that influence Tfh and functional antibody development. Here, we use samples from a large cross-sectional study of children residing in an area of high malaria transmission in Uganda to characterize Tfh cells and functional antibodies to multiple parasites stages. We identify a dramatic re-distribution of the Tfh cell compartment with age that is independent of malaria exposure, with Th2-Tfh cells predominating in early childhood, while Th1-Tfh cell gradually increase to adult levels over the first decade of life. Functional antibody acquisition is age-dependent and hierarchical acquired based on parasite stage, with merozoite responses followed by sporozoite and gametocyte antibodies. Antibodies were boosted in children with current infection, and were higher in females. The children with the very highest antibody levels had increased Tfh cell activation and proliferation, consistent with a key role of Tfh cells in antibody development. Together, these data reveal a complex relationship between the circulating Tfh compartment, antibody development and protection from malaria.

immunology↗

bioRxiv2020

Novel virus-like particle vaccine encoding the circumsporozoite protein of Plasmodium falciparum is immunogenic and induces functional antibody responses

RTS,S is the leading malaria vaccine in development, but has demonstrated only moderate protective efficacy in clinical trials. RTS,S is a virus-like particle (VLP) that uses the human hepatitis B virus as scaffold to display the malaria sporozoite antigen, circumsporozoite protein (CSP). Particle formation requires fourfold excess scaffold antigen, and as a result, CSP represents only a small portion of the final vaccine construct. Alternative VLP or nanoparticle platforms that reduce the amount of scaffold antigen and increase the amount of the target CSP antigen present in particles may enhance vaccine immunogenicity and efficacy. Here, we describe the production and characterization of a novel VLP that uses the small surface antigen (dS) of duck hepatitis B virus to display CSP. The CSP-dS fusion protein successfully formed VLPs without the need for excess scaffold antigen, and thus CSP represented a larger portion of the vaccine construct. Importantly, this is the first report of a dS-based vaccine that formed particles without excess scaffold protein. CSP-dS formed large particles approximately 31-74 nm in size and were confirmed to display CSP on the surface. The CSP-dS VLP was highly immunogenic in mice and induced antibodies to multiple regions of CSP, even when administered at a lower vaccine dosage. Vaccine-induced antibodies demonstrated functional activity, including the ability to interact with complement and Fc{gamma}-receptors, both previously identified as important in malaria immunity. Our novel platform to produce VLPs without excess scaffold protein has wide implications for the future development of innovative vaccines for malaria and other infectious diseases.

immunology↗

bioRxiv2020

Impact of a rapid decline in malaria transmission on antimalarial IgG subclasses and avidity

Understanding how immunity to malaria is affected by declining transmission is important to aid vaccine design and understand disease resurgence. Both IgG subclasses and avidity of antigen-specific responses are important components of an effective immune response.Using a multiplex bead array assay, we measured the total IgG, IgG subclasses, and avidity profiles of responses to 18 P. falciparum blood stage antigens in samples from 160 Ugandans collected at 2 time points during high malaria transmission and 2 time points following a dramatic reduction in transmission.Results demonstrated that, for the antigens tested, (i) the rate of decay of total IgG following infection declined with age and was driven consistently by the decrease in IgG3 and occasionally the decrease in IgG1; (ii) the proportion of IgG3 relative to IgG1 in the absence of infection increased with age; (iii) the increase in avidity index (the strength of association between the antibody and antigen) following infection was largely due to a rapid loss of non-avid compared to avid total IgG; and (iv) both avid and non-avid total IgG in the absence of infection increased with age.Further studies are required to understand the functional differences between IgG1 and IgG3 in order to determine their contribution to the longevity of protective immunity to malaria. Measuring changes in antibody avidity may be a better approach of detecting affinity maturation compared to avidity index due to the differential expansion and contraction of high and low avidity total IgG.Competing Interest StatementThe authors have declared no competing interest.View Full Text

immunology↗