Innovative Multistage ML-QSAR Models for Malaria: From Data to Discovery.

Malaria presents a significant challenge to global public health, with around 247 million cases estimated to occur annually worldwide. The growing resistance of Plasmodium parasites to existing therapies underscores the urgent need for new and innovative antimalarial drugs. This study leveraged artificial intelligence (AI) to tackle this complex challenge. We developed multistage Machine Learning Quantitative Structure-Activity Relationship (ML-QSAR) models to effectively analyze large datasets and predict the efficacy of chemical compounds against multiple life cycle stages of Plasmodium parasites. We then selected 16 compounds for experimental evaluation, six of which showed at least dual-stage inhibitory activity and one inhibited all life cycle stages tested. Moreover, explainable AI (XAI) analysis provided insights into critical molecular features influencing model predictions, thereby enhancing our understanding of compound interactions. This study not only empowers the development of advanced predictive AI models but also accelerates the identification and optimization of potential antiplasmodial compounds.

São Paulo School of Advanced Sciences on Vaccines: an overview

Two years ago, we held an exciting event entitled the São Paulo School of Advanced Sciences on Vaccines (SPSASV). Sixty-eight Ph.D. students, postdoctoral fellows and independent researchers from 37 different countries met at the Mendes Plaza Hotel located in the city of Santos, SP - Brazil to discuss the challenges and the new frontiers of vaccinology. The SPSASV provided a critical and comprehensive view of vaccine research from basics to the current state-of-the-art techniques performed worldwide. For 10 days, we discussed all the aspects of vaccine development in 36 lectures, 53 oral presentations and 2 poster sessions. At the end of the course, participants were further encouraged to present a model of a grant proposal related to vaccine development against individual pathogens. Among the targeted pathogens were viruses (Chikungunya, HIV, RSV, and Influenza), bacteria (Mycobacterium tuberculosis and Streptococcus pyogenes), parasites (Plasmodium falciparum or Plasmodium vivax), and the worm Strongyloides stercoralis. This report highlights some of the knowledge shared at the SPSASV.(AU)

Adjuvant requirement for successful immunization with recombinant derivatives of Plasmodium vivax merozoite surface protein-1 delivered via the intranasal route

Recently, we generated two bacterial recombinant proteins expressing 89 amino acids of the C-terminal domain of the Plasmodium vivax merozoite surface protein-1 and the hexa-histidine tag (His6MSP1(19)). One of these recombinant proteins contained also the amino acid sequence of the universal pan allelic T-cell epitope (His6MSP1(19)-PADRE). In the present study, we evaluated the immunogenic properties of these antigens when administered via the intra-nasal route in the presence of distinct adjuvant formulations. We found that C57BL/6 mice immunized with either recombinant proteins in the presence of the adjuvants cholera toxin (CT) or the Escherichia coli heat labile toxin (LT) developed high and long lasting titers of specific serum antibodies. The induced immune responses reached maximum levels after three immunizing doses with a prevailing IgG1 subclass response. In contrast, mice immunized by intranasal route with His6MSP1(19)-PADRE in the presence of the synthetic oligonucleotides adjuvant CpG ODN 1826 developed lower antibody titers but when combined to CT, CpG addition resulted in enhanced IgG responses characterized by lower IgG1 levels. Considering the limitations of antigens formulations that can be used in humans, mucosal adjuvants can be a reliable alternative for the development of new strategies of immunization using recombinant proteins of P. vivax.

Immunogenic properties of a recombinant fusion protein containing theC-terminal 19 kDa of Plasmodium falciparum merozoite surface protein-1 and the innate immunity agonist FliC flagellin of Salmonella Typhimurium

In a recent study, we demonstrated the immunogenic properties of a new malaria vaccine polypeptidebased on a 19 kDa C-terminal fragment of the merozoite surface protein-1 (MSP119) from Plasmodiumvivax and an innate immunity agonist, the Salmonella enterica serovar Typhimurium flagellin (FliC).Herein, we tested whether the same strategy, based on the MSP119 component of the deadly malariaparasite Plasmodium falciparum, could also generate a fusion polypeptide with enhanced immunogenicity.The His6FliC-MSP119 fusion protein was expressed from a recombinant Escherichia coli and showedpreserved in vitro TLR5-binding activity. In contrast to animals injected with His6MSP119, mice subcutaneouslyimmunised with the recombinant His6FliC-MSP119 developed strong MSP119-specific systemicantibody responses with a prevailing IgG1 subclass. Incorporation of other adjuvants, such as CpG ODN1826, complete and incomplete Freund’s adjuvants or Quil-A, improved the IgG responses after the second,but not the third, immunising dose. It also resulted in a more balanced IgG subclass response, asevaluated by the IgG1/IgG2c ratio, and higher cell-mediated immune response, as determined by thedetection of antigen-specific interferon- secretion by immune spleen cells. MSP119-specific antibodiesrecognised not only the recombinant protein, but also the native protein expressed on the surface of P.falciparum parasites. Finally, sera from rabbits immunised with the fusion protein alone inhibited the invitro growth of three different P. falciparum strains. In summary, these results extend our previous observationsand further demonstrate that fusion of the innate immunity agonist FliC to Plasmodium antigensis a promising alternative to improve their immunogenicity

CD8+ T cell adjuvant effects of Salmonella FliCd flagellin in live vaccine vectors or as purified protein

Salmonella flagellin, the flagellum structural subunit, has received particular interest as a vaccineadjuvant conferring enhanced immunogenity to soluble proteins or peptides, both for activation of antibody and cellular immune responses. In the present study, we evaluated the Salmonella enterica FliCd flagellin as a T cell vaccine adjuvant using as model the 9-mer (SYVPSAEQI) synthetic H2d-restricted CD8+ T cell-specific epitope (CS280–288) derived from the Plasmodium yoelii circumsporozoite (CS) protein. The FliCd adjuvant effects were determined under two different conditions: (i) as recombinant flagella,expressed by orally delivered live S. Dublin vaccine strains expressing the target CS280–288 peptide fused at the central hypervariable domain, and (ii) as purified protein in acellular vaccines in which flagellin was administered to mice either as a recombinant protein fused or admixed with the target CS280–288 peptide. The results showed that CS280–288-specific cytotoxic CD8+ T cells were primed when BALB/c mice were orally inoculated with the expressing the CS280–288 epitope S. Dublin vaccine strain. In contrast, mice immunized with purified FliCd admixed with the CS280–288 peptide and, to a lesser extent,fused with the target peptide developed specific cytotoxic CD8+ T cell responses without the need of a heterologous booster immunization. The CD8+ T cell adjuvant effects of flagellin, either fused or not with the target peptide, correlated with the in vivo activation of CD11c+ dendritic cells. Taken together,the present results demonstrate that Salmonella flagellins are flexible adjuvant and induce adaptativeimmune responses when administered by different routes or vaccine formulations.