Biology subjects

Sala, K. A.

Publications and source records attributed to Sala, K. A..

5 recordsLinked to original sources

bioRxiv2026

Comparing the transmission blocking efficacy of Primaquine and Tafenoquine with in vivo pre-clinical models

The 8-aminoquinoline family are a well-established class of antimalarial drugs containing two clinically relevant analogues, primaquine and tafenoquine. These compounds have two therapeutically significant activities across the plasmodial lifecycle; elimination of Plasmodium vivax hypnozoites as part of a radical cure (relapse prevention), and as prophylactic transmission blocking compounds. Primaquine is currently recommended as a single low (0.25 mg/kg) dose administered with artemisinin-based combination therapy to reduce malarial transmission in areas at high risk of artemisinin partial resistance. Tafenoquine was approved in 2018 for radical cure when co-administered with chloroquine however, its transmission blocking efficacy in humans has not yet been fully evaluated, and direct head-to-head comparisons of transmission-blocking efficacy of primaquine and tafenoquine have not been performed. Given that primaquine and tafenoquine are presumed to have similar mechanisms of action, tafenoquine may have potential use as a transmission blocking intervention. Furthermore, tafenoquine has a substantially longer half-life than primaquine, which could provide a pharmacokinetic advantage if such efficacy is confirmed. However, assessment of 8-aminoquinoline efficacy against the sexual stages of Plasmodium is complicated by the requirement for metabolic activation to generate parasite-reactive species, limiting the utility of in vitro assays. Here, we directly compare the transmission blocking effects of primaquine and tafenoquine using two in vivo preclinical models. We titrate the transmission blocking efficacy of each compound, and evaluate the pharmacokinetics of each compound over time, linking drug exposure to efficacy. The evidence presented here suggests that beyond 24 hours, a single dose of tafenoquine is likely to have more clinically desirable pharmacokinetics, resulting in higher transmission blocking efficacy than primaquine. These findings are observed across multiple models, both in the absence or presence of a partner schizonticide and thus demonstrate a potential advantage of the utilisation of tafenoquine when compared to primaquine.

microbiology↗

bioRxiv2024

Targeted CRISPR Screens Reveal Genes Essential for Cryptosporidium Survival in the Host Intestine

The Cryptosporidium parasite is one of the leading causes of diarrheal morbidity and mortality in children, and adolescent infections are associated with chronic malnutrition. There are no vaccines available for protection and only one drug approved for treatment that has limited eKicacy. A major barrier to developing new therapeutics is a lack of foundational knowledge of Cryptosporidium biology, including which parasite genes are essential for survival and virulence. Here, we iteratively improve the tools for genetically manipulating Cryptosporidium and develop a targeted CRISPR-based screening method to rapidly assess how the loss of individual parasite genes influence survival in vivo. Using this method we examine the parasites pyrimidine salvage pathway and a set of leading Cryptosporidium vaccine candidates. From this latter group we determined the parasite gene known as Cp23 to be essential for survival, which was confirmed through inducible knockout in vitro and in vivo. Parasites deficient in Cp23 were able to replicate within and emerge from infected epithelial cells, yet unable to initiate gliding motility which is essential for the reinfection of neighbouring cells. The targeted screening method presented here is highly versatile and will enable researchers to more rapidly expand the knowledge base for Cryptosporidium infection biology, paving the way for new therapeutics.

microbiology↗

bioRxiv2021

Structural basis of malaria transmission blockade by a monoclonal antibody to gamete fusogen HAP2

HAP2 is a transmembrane gamete fusogen found in multiple eukaryotic kingdoms and is structurally homologous to viral class II fusogens. Studies in Plasmodium have suggested that HAP2 is an attractive target for vaccines that block transmission of malaria. HAP2 has three extracellular domains, arranged in the order D2, D1, and D3. Here, we report monoclonal antibodies against the D3 fragment of Plasmodium berghei HAP2 and crystal structures of D3 in complex with Fab fragments of two of these antibodies, one of which blocks fertilization of Plasmodium berghei in vitro and transmission of malaria in mosquitos. We also show how this Fab binds the complete HAP2 ectodomain with electron microscopy. The two antibodies cross-react with HAP2 among multiple plasmodial species. Our characterization of the Plasmodium D3 structure, HAP2 ectodomain architecture, and mechanism of inhibition provide insights for the development of a vaccine to block malaria transmission.

immunology↗

bioRxiv2020

Dissection-independent production of a protective whole-sporozoite malaria vaccine

Complete protection against human malaria challenge has been achieved using infected mosquitoes as the delivery route for immunization with Plasmodium parasites. Strategies seeking to replicate this efficacy with either a manufactured whole-parasite or subunit vaccine, however, have shown only limited success. A major roadblock to whole parasite vaccine progress and understanding of the human infective sporozoite form in general, is reliance on manual dissection for parasite isolation from infected mosquitoes. We report here the development of a four-step process based on whole mosquito homogenization, slurry and density-gradient filtration, combined with free-flow electrophoresis that is able to rapidly produce a pure, aseptic sporozoite inoculum from hundreds of mosquitoes. Murine P. berghei or human-infective P. falciparum sporozoites produced in this way are 2-3-fold more infective with in vitro hepatocytes and can confer sterile protection when immunized intravenously with subsequent challenge using a mouse malaria model. Critically, we can also demonstrate for the first time 60-70% protection when the same parasites are administered via intramuscular (i.m.) route. In developing a process amenable to industrialisation and demonstrating efficacy by i.m. route these data represent a major advancement in capacity to produce a whole parasite malaria vaccine at scale. One-Sentence SummaryA four-step process for isolating pure infective malaria parasite sporozoites at scale from homogenized whole mosquitoes, independent of manual dissection, is able to produce a whole parasite vaccine inoculum that confers sterilizing protection.

microbiology↗

bioRxiv2018

Male-Specific Protein Disulphide Isomerase Function is Essential for Plasmodium Fertilization and Transmission

Inhibiting transmission of Plasmodium is an essential strategy in malaria eradication, and the biological process of gamete fusion during fertilization is a proven target for this approach. The lack of knowledge of the mechanisms underlying fertilization have been a hindrance in the development of transmission-blocking interventions. Here we describe a protein disulphide isomerase essential for malarial transmission (PDI-Trans/PBANKA_0820300) to the mosquito. We show that PDI-Trans activity is male-specific, surface expressed, essential for fertilization/transmission, and exhibits disulphide isomerase activity which is up-regulated post-gamete activation. We demonstrate that PDI-Trans is a viable anti-malarial drug and vaccine target blocking malarial transmission with the use of the PDI inhibitor bacitracin (98.21%/92.48% reduction in intensity/prevalence), and anti-PDI-Trans peptide antibodies (66.22%/33.16% reduction in intensity/prevalence). To our knowledge, these results provide the first primary evidence that protein disulphide isomerase function is essential for malarial transmission, and emphasize the potential of anti-PDI agents to act as anti-malarials, facilitating the future development of novel transmission-blocking compounds or vaccines.

microbiology↗