Biology subjects

Amann, M.

Publications and source records attributed to Amann, M..

6 recordsLinked to original sources

bioRxiv2026

Stabilizing Plasmodium falciparum Proteins for Small Molecule Drug Discovery

Early-stage drug discovery relies on the availability of stable protein for reliable biophysical characterization of ligand binding. However, many Plasmodium falciparum proteins are challenging to produce in heterologous systems, which limits their experimental utility. To address this, we tested whether ProteinMPNN-guided sequence design could generate stabilized surrogate constructs that retain wild-type-like structure and binding thermodynamics. Designs were generated with constraints to maintain conserved and binding-site residues for three therapeutically relevant targets: PfBDP1-BRD, PfBDP4-BRD, and PfK13-KREP. The resulting constructs showed markedly increased thermal stability. Using PfBDP1-BRD as a benchmark, isothermal titration calorimetry confirmed that the stabilized variants retained wild-type-like binding thermodynamics with a known ligand. Extending this approach to other targets, a PfK13-KREP construct led to an apo structure with a binding pocket closely matching the wild type, and a stabilized PfBDP4-BRD surrogate - a previously unstable target - enabled the identification of PfBDP4-BRD binders and a 1.25 [A] co-crystal structure with a newly found inhibitor. Our findings demonstrate that computationally stabilized surrogates are practical and effective tools for robust biophysics and structure-enabled drug discovery against otherwise challenging malaria proteins.

biochemistry↗

bioRxiv2025

Chronic Antigen Stimulation in Solid Tumors Induces T Cell Exhaustion and Limits Efficacy of T Cell Bispecific Therapies

T cell bispecific antibodies (TCBs) have demonstrated promising results in patients with solid tumors. However, the underlying immunological and molecular mechanisms influencing these clinical outcomes require in depth evaluation. T cell exhaustion, a state induced by prolonged antigen exposure, is known to undermine T cell-based immunotherapies, though its specific impact on TCB efficacy remains unclear. In this study, we assessed the effectiveness of TCBs on tumor-specific T cells, focusing on their functional status. Utilizing a fully immunocompetent mouse model with a solid tumor expressing an immunogenic antigen, we showed that tumor-specific T cells acquire an exhausted phenotype and fail to expand under TCB treatment. By employing both mouse and human tumor-specific T cells in vitro, our study established that chronically stimulated tumor-specific T cells show impaired response to TCB treatment. The comparison of TCB efficacy in T cell-inflamed tumors with immunogenic antigens versus non-inflamed tumors with low antigen presence in mice revealed TCB success in solid tumors is more reliant on T cell functional fitness than on their abundance before treatment. The data also indicate that solid tumors with elevated levels of both, intratumoral regulatory T cells, and T cells expressing co-inhibitory receptors, show diminished responses to TCB therapy, aligning with similar observations described in hematological cancers. These findings highlight the critical role of T cell exhaustion due to chronic antigen exposure and illustrate that exhausted tumor-specific T cells are likely not the driver population redirected by TCBs for tumor elimination. Our research highlights the importance of maintaining T cell fitness and preventing T cell exhaustion to improve TCB therapy outcomes. This may help better identify patient populations with solid tumors that could benefit from TCB treatments most in clinical settings.

cancer biology↗

bioRxiv2025

A novel inhibitor against the bromodomain PfBDP1 of the malaria pathogen Plasmodium falciparum

The rise of drug resistances in malaria necessitates the exploration of novel therapeutic strategies. Targeting epigenetic pathways could open new, promising treatment avenues. In this study, we focus on PfBDP1, an essential bromodomain protein in P. falciparum. Utilizing the pan-selective bromodomain inhibitor MPM6, we identified a potent initial hit and subsequently developed it into a nanomolar binder. Through a combination of virtual docking, isothermal titration calorimetry, and X-ray crystallography, we elucidated the molecular interactions of the new inhibitors with PfBD1. Our findings include the first cocrystallized structures of PfBD1 and PvBD1 with these inhibitors, providing insights into their binding mechanisms. Further validation using conditional knockdown of PfBDP1 in P. falciparum demonstrated parasite sensitivity to the inhibitor, underscoring its potential as a targeted therapeutic approach against malaria.

biochemistry↗

bioRxiv2024

IL15/IL15Rα complex induces an anti-tumor immune response following radiation therapy only in the absence of Tregs and fails to induce expansion of progenitor TCF1+ CD8 T cells

BackgroundThis work seeks to understand whether IL15-incorporating treatments improve response to radiotherapy and uncover mechanistic rationale for overcoming resistance to IL15 agonism using novel therapeutic combinations. Experimental DesignOrthotopic tumor models of PDAC were used to determine response to treatment. IL15-/- and Rag1-/- mouse models were employed to determine dependence on IL15 and CTLs, respectively. Flow cytometry was used to assess immune cell frequency and activation state. Phospho-proteomic analyses were used to characterize intracellular signaling pathways. ResultsWe show that the combination of radiation therapy (RT) and an IL15/IL15Ra fusion complex (denoted IL15c) fails to confer anti-tumor efficacy; however, a CD8-driven anti-tumor immune response is elicited with the concurrent administration of an aCD25 Treg-depleting antibody. Using IL15-/- and Rag1-/- mice, we demonstrate that response to RT + IL15c + aCD25 is dependent on both IL15 and CTLs. Furthermore, despite an equivalent survival benefit following treatment with RT + IL15c + aCD25 and combination RT + PD1-IL2v, a novel immunocytokine with PD-1 and IL2R{beta}{gamma} binding domains, CTL immunophenotyping and phospho-proteomic analysis of intracellular metabolites showed significant upregulation of activation and functionality in CD8 T cells treated with RT + PD1-IL2v. Finally, we show the immunostimulatory response to RT + PD1-IL2v is significantly diminished with a concurrent lack of TCF+ CD8 T cell generation in the absence of functional IL15 signaling. ConclusionsOur results are illustrative of a mechanism wherein unimpeded effector T cell activation through IL2R{beta} signaling and Treg inhibition are necessary in mediating an anti-tumor immune response.

cancer biology↗

bioRxiv2024

Divergent response to radio-immunotherapy is defined by intrinsic features of the tumor microenvironment

BackgroundTreatment with immunotherapy can elicit varying responses across cancer types, and the mechanistic underpinnings that contribute to response vs. progression remain poorly understood. However, to date there are few preclinical models that accurately represent these disparate disease scenarios. MethodsUsing combinatorial radio-immunotherapy consisting of PD-1 blockade, IL2R{beta}{gamma} biased signaling, and OX40 agonism we were able to generate preclinical tumor models with conflicting responses, where head and neck squamous cell carcinoma (HNSCC) models responds and pancreatic ductal adenocarcinoma (PDAC) progresses. ResultsBy modeling these disparate states, we find that regulatory T cells (Tregs) are expanded in PDAC tumors undergoing treatment, constraining tumor reactive CD8 T cell activity. Consequently, the depletion of Tregs restores the therapeutic efficacy of our treatment and abrogates the disparity between models. Moreover, we show that through heterotopic implantations that the site of tumor development defines the response to therapy, as implantation of HNSCC tumors into the pancreas resulted in comparable levels of tumor progression. ConclusionsThis work highlights complexity of combining immunotherapies within the tumor microenvironment and further defines the immune and non-immune components of the tumor microenvironment as an intrinsic feature of immune suppression. What is already known on this topicO_LIIn Head and neck squamous cell carcinomas (HNSCC) and pancreatic ductal adenocarcinoma (PDAC), targeting PD-1 and IL2R{beta}{gamma} simultaneously (PD1-IL2v) has been shown to be effective when combined with radiation therapy (RT), yet complete response is still limited. The T cell co-stimulatory receptor OX40 (TNFRSF4) has pleiotropic effects, promoting T cell survival, expansion, and memory differentiation in conventional effector T cells, while subsequently limiting regulatory T cell (Treg) suppression by constraining induction and expression of Foxp3. Expression of OX40 is highly upregulated after treatment with PD1-IL2v, and we postulated that combining OX40 agonism with PD1-IL2v and RT would provide additional benefit. C_LI What this study addsO_LIUsing orthotopic models of HNSCC and PDAC, we found that the addition of OX40 agonism unexpectedly drives tumor progression in PDAC, but not HNSCC. Intriguingly, this effect dependent on the tumor microenvironment as the effect is reversed by swapping the location of tumor implantation. This progression was also abrogated by the depletion of regulatory T cells (Tregs), a known mediator of resistance in these models. C_LI How this study might affect research, practice or policyO_LIOur data demonstrate that unexpected and deleterious effects can stem from combining multiple immunotherapies. These findings hold particular translational relevance as the use of combination immunotherapies is increasingly common on trial. C_LI

immunology↗

bioRxiv2023

Exposure to Pseudomonas spp. increases Anopheles gambiae insecticide resistance in a population-dependent manner

The microbiota of mosquitoes influences many aspects of their biology, including developmental processes, mating and sexual reproduction, immune functions, and refractoriness to pathogens. Here, we considered their role in resistance against insecticides. In particular, we assessed how larval infection of a permethrin-resistant and a sensitive colony of Anopheles gambiae by four strains belonging to three different Pseudomonas species affects several life history traits and the impact of the insecticide on adult mortality. Our data showed that all four Pseudomonas strains persisted in adults until death. The bacteria increased the likelihood that mosquitoes survived 24 hours after exposure to permethrin by up to two-fold. The impact of the bacteria depended on the bacterial strains and the mosquito colony: in the resistant colony, all bacteria increased survival by about 2-fold, while in the sensitive colony, only two of the four strains increased survival. The benefit concerning insecticide resistance came with little to no impact on the other traits (i.e., larval mortality, developmental time and adult longevity). Altogether, our results highlight the importance of considering environmental microbial exposure and mosquito microbial communities in epidemiological and vector-control studies, while also suggesting a possible role for Pseudomonas spp. as a symbiont in A. gambiae.

evolutionary biology↗