Au cours de ce travail de thèse intitulé " Identification chimique de métabolites secondaires de certains microorganismes, évaluation de leurs effets dans les domaines pharmaceutiques et agronomiques ", nous nous sommes intéressés à l'étude des effets des conditions de culture sur la production des composés organiques volatils microbiens à partir de deux souches bactériennes co-existantes dans le sol Français : Burkholderia sp. et Bacillus megaterium. A partir des différents extraits préparés, plus que cent composés ont été identifiés, comprenant les dicétopipérazines, les alcools, les composés soufrés, les esters et les acides carboxyliques, par le biais de plusieurs techniques chimiques, analytiques et spectroscopiques. Les résultats obtenus ont montré que les conditions de culture sont les pricipales responsables de la production des différentes familles chimiques des volatiles. Nous avons identifiés des composés qui sont rapportés pour la première fois à partir des bactéries tel que: la N-butylbenzènesulfonamide, triacontane, le proponaoate de 3- (3,5-di-tert-butyl-4-hydroxyphényl), (E) -5-chloro-3-(hydroxyimino) indoline-2-one et 1,3,5-triméthyl-2-octadecylcyclohexane. Sur le plan biologique, on a montré que les résultats obtenus sont fortement influencés par les conditions de culture utilisées pour cultiver les bactéries testées. En parallèle à cette investigation, nous avons montré que les extraits de Burkholderia sp. sont dotés d'un très important potentiel allélopathique. Enfin, une série des analogues de dicétopipérazines a été préparée et évaluée pour leurs activités anti-xanthine oxydase, anti a-amylase et anti 5-lipoxygénase ainsi que pour leurs activités cytotoxiques contre les lignées cellulaires suivantes ; OVCAR, MCF7 et HCT116. Un certain nombre de ces dérivés de dicétopiperazine ont montré des activités anti a-amylase et cytotoxique importantes. / In this thesis entitled " Chemical identification of secondary metabolites from microorganism, evaluation of their effects on pharmaceutical and agronomic fields ", we are interested in studying the effect of culture conditions on the production of microbial volatiles organic compounds by two bacteria that inhabit French soil which are: Burkholderia sp. and Bacillus megaterium. From different prepared extracts, more than one hundred compounds were identified, including diketopiperazine, alcohols, sulfur containing compounds, esters and carboxylic acids, by means of several chemical, analytical and spectroscopic techniques. Results showed that culture conditions of different bacteria are the mainly responsible of production of different blend of volatiles. Many identified compounds including N-butylbenzenesulfonamide, triacontane, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate, (E)-5-chloro-3-(hydroxyimino)indolin-2-one and 1,3,5-trimethyl-2-octadecylcyclohexane are reported for the first time from bacteria.Biologically, we have shown that obtained results are greatly influenced by the cultures conditions used in cultivation of tested bacteria. In addition to that, we have shown that Burkholderia sp. extracts possessed a very good allelopathic potential. Finally, a series new protested deketopiperazine derivatives have been prepared and evaluated in vitro against xanthine oxidase, a-amylase and 5-lipoxygenase enzymes, OVCAR, MCF7 and HCT116 cancer cell lines. Some of these molecules have been shown to be potent inhibitors of a-amylase and different cancer cell lines.

En raison de la nature symbiotique des micro-organismes endophytes, cette étude visait à étudier l'activité antibactérienne, antifongique et cytotoxique chez les métabolites secondaires des extraits endophytes foliaires de plantes de l'Amazonie brésilienne et du Cerrado. Dans ce travail de thèse 147 micro-organismes cultivables ont été isolés (130 champignons, 3 bactéries e 14 champignons non-identifiés ou inconnus) à partir de 28 plantes (4 espèces collectées au Brésil et 24 en Guyane Française). Tous les micro-organismes furent identifiés par analyse moléculaire des régions spécifiques de l'ADNr en utilisant des techniques de séquençage génomique. Des champignons endophytes de l’ordre des Xylariales furent ceux de plus importante fréquence d’isolation dans cette étude, représentés par 25 isolats. Des extraits bruts à l’AcOEt furent produits à partir de cultures de chaque micro-organisme isolé. Une proportion relative signifiante (23,1%) des extraits démontra une activité sur Candida albicans ATCC 10213, pendant que 4% furent actifs sur Staphylococcus aureus ATCC 29213. Le potentiel cytotoxique des extraits fut évalué pour des lignées cellulaires humaines KB (carcinome cervical utérin), MDA-MB-435 (mélanome), et MRC-5 (fibroblastes de poumon normal), résultant en proportion signifiante avec activité d’inhibition de la prolifération cellulaire (24,4%, 23,1% e 16,3%, respectivement).Dix-huit métabolites secondaires furent isolés et identifiés à partir du fractionnement des extraits bruts de huit endophytes. Dix-sept de ces substances furent déjà décrites précédemment dans la littérature: l’acide piliformique (24) et la griséofulvine (25) isolés à partir de Xylaria cubensis SNB-GCI02; La phomopirone (26), la pyrenocine (27), l’alterpérilenol (28) et la novae-zelandine (29), isolés de Lewia infectoria SNB-GTC2402; 5-métilmelleina (31) et la dihidrosporothrioride (32) isolées à partir de Xylaria sp. SNB-GTC2501; La mycoleptodiscine (34) et la mycoleptodiscine B (35) isolées à partir de Mycoleptodiscus sp. SNB-GTC2304; le mycoepoxidiène (36) et la altiloxina A (37) isolés à partir de Diaporthe pseudomangiferae SNB-GSS10; L’acremonisol (40), le semicochliodinol (41) et le cochliodinol (42) isolés à partir de Chaetomium globosum SNB-GTC2114; la colletofragarone A2 (43) isolée à partir de Colletotrichum sp. SNB-GTC0201; la flavoglaucine (44) isolée à partir de Eurotium rubrum BBS01. Parmi ces substances, la flavoglaucine (44) isolée à partir de E. rubrum BBS01 démontra une activité comparable au contrôle fluconazol en C. albicans (CIM de 4 µg.mL-1). La substance (44) présenta IC50 >10 µM sur cellules normales MRC-5, ce qui en fait un candidat pour des études ultérieures. Dans ce travail, fut identifié pour la première fois l’activité de la colletofragarone A2 (43) isolée à partir de Colletotrichum sp. SNB-GTC0201. La substance inédite nommée pyrrocidine C (30) fut isolée à partir de L. infectoria SNB-GTC2402 et identifiée par des analyses spectroscopiques (Casella et al., 2013). La pyrrocidine C (30) fut active en S. aureus ATCC 10213 (CIM de 2 µg.mL-1) et ne fut pas considérées cytotoxique pour les cellules normales MRC-5 (IC50 >10 µM), démontrant une sélectivité dans l’action antimicrobienne. Ces résultats démontrent la grande diversité des endophytes fongiques chez les plantes de l'Amazonie brésilienne et du Cerrado et la grande chimiodiversité associée aux métabolites secondaires de ces micro-organismes. Des champignons endophytes tropicaux, comme ceux présentés dans cette étude, peuvent apparaître comme une nouvelle source de substances antimicrobiennes et cytotoxiques. / Because of the symbiotic nature of endophytes, this survey aims to investigate the probality of discovering antibacterial, antifungal and cytotoxic activities in secondary metabolites of leaf endophytes isolated from plants of Amazon and Cerrado biomes. In this study, 147 cultivable microorganisms were isolated (130 fungi, 3 bacteria and 14 unidentified or unknown microbes) from 28 plant species (4 species collected in Brazil and 24 in French Guyana). All endophytes were identified by molecular analyses of specific rDNA regions, with genomic sequencing techniques. Fungal endophytes belonging to Xylariales order were the most frequently isolated in this study, represented by 25 isolates. Crude AcOEt extracts were produced from cultures of each isolated endophyte. A significant relative proportion (23,1%) of extracts showed activity in Candida albicans ATCC 10213, while 4% were active in Staphylococcus aureus ATCC 29213. The cytotoxic potencial of the extracts was evaluated for human cell lines KB (uterin cervical carcinome), MDA-MB-435 (melanoma) and MRC-5 (normal lung fibroblasts), and a significant proportion of them showed cellular proliferation inhibition (24,4%, 23,1% e 16,3%, respectively).Eighteen secondary metabolites were isolated by the fractionation of eight endophytic extracts. Seventeen of these substances had already been previously described in the literature: piliformic acid (24) and griseofulvin (25) isolated from Xylaria cubensis SNB-GCI02; phomopiron A (26), pyrenocin A (27), alterperilenol (28) and novae-zelandin A (29) isolated from Lewia infectoria SNB-GTC2402; 5-metilmellein (31) and dihidrosporothriorid (32) isolated from Xylaria sp. SNB-GTC2501; mycoleptodiscin A (34) and mycoleptodiscin B (35) isolated from Mycoleptodiscus sp. SNB-GTC2304; mycoepoxidien (36) and altiloxin A (37) isolated from Diaporthe pseudomangiferae SNB-GSS10; acremonisol A (40), semicochliodinol A (41) and cochliodinol (42) isolated from Chaetomium globosum SNB-GTC2114; colletofragaron A2 (43) isolated from Colletotrichum sp. SNB-GTC0201; flavoglaucin (44) isolated from Eurotium rubrum BBS01. Among these substances, flavoglaucin (44), isolated from E. rubrum BBS01, showed comparable antifungal activity with the positive control fluconazol in C. albicans (MIC of 4 µg.mL-1). Flavoglaucin (44) also showed IC50 >10 µM in normal MRC-5 cells, becoming a good candidate for further studies. In this work, the cytotoxic activity of colletofragaron A2 (43), isolated from Colletotrichum sp. SNB-GTC0201 was described for the first time. The unpublished substance named pyrrocidin C (30) isolated from L. infectoria SNB-GTC2402 was identified by spectroscopic analyses (Casella et al., 2013). The pyrrocidin C (30) was active in S. aureus ATCC 10213 (MIC of 2 µg.mL-1), and was not considered cytotoxic for normal MRC-5 cells (IC50 >10 µM), showing selectivity in antimicrobial activity. These results demonstrate the great endophytic fungal diversity in plants of Amazon and Cerrado biomes, along with the chemodiversity associated to the secondary metabolites of these endophytes. Tropical fungal endophytes, like those seen in this work, may emerge as a new source of antimicrobial and cytotoxic substances. / Devido à natureza simbiótica dos micro-organismos endofíticos, este estudo teve como objetivo investigar a atividade antibacteriana, antifúngica e citotóxica em metabólitos secundários de extratos de fungos endofíticos foliares de plantas do bioma Amazônia e Cerrado. Neste trabalho de tese foram isolados 147 micro-organismos cultiváveis (130 fungos, 3 bactérias e 14 fungos não-identificados ou desconhecidos) a partir de 28 plantas (4 espécies coletadas no Brasil e 24 na Guiana Francesa). Todos os micro-organismos foram identificados por análise molecular de regiões específicas de DNAr, com uso de técnicas de sequenciamento genômico. Fungos endofíticos da ordem Xylariales foram os de maior frequência de isolamento neste estudo, representados por 25 isolados. Extratos brutos em AcOEt foram produzidos a partir de culturas de cada micro-organismo isolado. Uma proporção relativa significante (23,1%) dos extratos demonstrou atividade em Candida albicans ATCC 10213, enquanto 4% foram ativos em Staphylococcus aureus ATCC 29213. O potencial citotóxico dos extratos foi avaliado para as linhagens celulares humanas KB (carcinoma cervical uterino), MDA-MB-435 (melanoma), e MRC-5 (fibroblastos de pulmão normal), resultando em proporção significante com atividade de inibição da proliferação celular (24,4%, 23,1% e 16,3%, respectivamente). Dezoito metabólitos secundários foram isolados a partir do fracionamento de oito extratos brutos endofíticos. Dezessete destas substâncias já tinham sido descritas anteriormente na literatura: ácido pilifórmico (24) e griseofulvina (25) isoladas de Xylaria cubensis SNB-GCI02; phomopirona A (26), pyrenocina A (27), alterperilenol (28) e novae-zelandina A (29) isoladas de Lewia infectoria SNB-GTC2402; 5-metilmelleina (31) e Dihidrosporothriolida (32) isoladas de Xylaria sp. SNB-GTC2501; mycoleptodiscina A (34) e mycoleptodiscina B (35) isoladas de Mycoleptodiscus sp. SNB-GTC2304; mycoepoxidieno (36) e altiloxina A (37) isoladas de Diaporthe pseudomangiferae SNB-GSS10; acremonisol A (40), semicochliodinol A (41) e cochliodinol (42) isoladas de Chaetomium globosum SNB-GTC2114; colletofragarona A2 (43) isolada de Colletotrichum sp. SNB-GTC0201; flavoglaucina (44) isolada de Eurotium rubrum BBS01. Dentre estas substâncias, a flavoglaucina (44) isolada de E. rubrum BBS01, demonstrou atividade comparável ao controle fluconazol em C. albicans (CIM de 4 µg.mL-1). Esta substância (44) apresentou IC50 >10 µM em células normais MRC-5, tornando-se candidata para estudos posteriores. Neste trabalho foi identificado pela primeira vez a atividade citotóxica da colletofragarona A2 (43), isolada de Colletotrichum sp. SNB-GTC0201. A substância inédita nomeada pyrrocidina C (30) foi isolada a partir de L. infectoria SNB-GTC2402 e identificada através de análises espectroscópicas (Casella et al., 2013). A pyrrocidina C (30) foi ativa em S. aureus ATCC 10213 (CIM de 2 µg.mL-1), e não foi considerada citotóxica para as células normais MRC-5 (IC50 >10 µM), demonstrando seletividade na ação antimicrobiana. Estes resultados demonstram a grande diversidade fúngica endofítica em plantas do bioma Amazônia e Cerrado, e a quimiodiversidade associada aos metabólitos secundários destes micro-organismos. Fungos endofíticos tropicais, como os vistos neste trabalho, podem emergir como uma nova fonte de substâncias antimicrobianas e citotóxicas.

Background Previously, we identified a major myeloid-derived proinflammatory subpopulation of human blood dendritic cells which we termed slanDCs (e.g. Schäkel et al. (2006) Immunity 24, 767–777). The slan epitope is an O-linked sugar modification (6-sulfo LacNAc, slan) of P-selectin glycoprotein ligand-1 (PSGL-1). As slanDCs can induce neoantigen-specific CD4+ T cells and tumor-reactive CD8+ cytotoxic T cells, they appear as promising targets for an in vivo delivery of antigens for vaccination. However, tools for delivery of antigens to slanDCs were not available until now. Moreover, it is unknown whether or not antigens delivered via the slan epitope can be taken up, properly processed and presented by slanDCs to T cells. Methodology/Principal Findings Single chain fragment variables were prepared from presently available decavalent monoclonal anti-slan IgM antibodies but failed to bind to slanDCs. Therefore, a novel multivalent anti-slanDC scaffold was developed which consists of two components: (i) a single chain bispecific recombinant diabody (scBsDb) that is directed on the one hand to the slan epitope and on the other hand to a novel peptide epitope tag, and (ii) modular (antigen-containing) linker peptides that are flanked at both their termini with at least one peptide epitope tag. Delivery of a Tetanus Toxin-derived antigen to slanDCs via such a scBsDb/antigen scaffold allowed us to recall autologous Tetanus-specific memory T cells. Conclusions/Significance In summary our data show that (i) the slan epitope can be used for delivery of antigens to this class of human-specific DCs, and (ii) antigens bound to the slan epitope can be taken up by slanDCs, processed and presented to T cells. Consequently, our novel modular scaffold system may be useful for the development of human vaccines.

Neuroblastoma is a childhood cancer of the peripheral sympathetic nervous system, emerging from cells of the neural crest. In Sweden, neuroblastoma accounts for 20 cases out of all, 300-350, pediatric cancer cases each year (Barncancerfonden 2019, Turup on behalf of Cancer Centrum 2019). This cancer often appears in the sympathetic ganglia and/or the adrenal gland and has a high rate of metastasis that often results in morbidity (Matthay et al. 2016). Recent findings implicating a mutation in the Rho/Rac signaling pathway, a pathway involved in neural crest differentiation and migration, were found in every fourth neuroblastoma patient (Dyberg et al. 2017) These mutations tend to shift Rho to a more active state which is believed to lead to more downstream Rho-associated Kinase (ROCK) activation. While inhibition of ROCK has been seen to promote MYCN protein degradation, induce neuroblastoma cell differentiation and repress neuroblastoma growth in vitro and in vivo (Dyberg et al. 2017). Rho/ROCK signaling pathway effects on cytoskeletal arrangement and cell shape have also been suggested to be involved in tumor promoted changes of the TME (Johan and Samuel, 2018). In this master’s thesis project, we explore the effects of the Rho/ROCK pathway on the tumor microenvironment (TME) and immune response (IR) in neuroblastoma. More specifically we are focusing on populations of T cells, macrophages and fibroblasts in tumors, and looking into tumor vascular structure (such as blood vessel) and extracellular matrix (ECM) formation after ROCK inhibitor treatment within neuroblastoma tumors from transgenic mice model TH-MYCN and multi-cellular tumor spheroids (MCTS), a three-dimensional (3D) in vitro model simulating TME in neuroblastoma cell lines. Through our studies we hope to find insights into the Rho/ROCK signaling pathway and involvement of the tumor microenvironment in cancer therapy, while elucidating potential new drugs and drug targets for improving outcomes in neuroblastoma treatment.

MSc (Chemistry) / Department of Chemistry / Rauvolfia caffra Sond, a species of evergreen trees and shrubs in the dogbane family, (Apocynaceae), is used as a medicinal plant among traditional communities in many countries for the treatment of malaria, diabetes, coughs, gastrointestinal disturbances, skin infections, impotence, insomnia, diarrhoea, dysentery, scabies, worm infections, and both parasitic and microbial infections. Phytochemical studies have revealed that indole alkaloids are the major constituents of the stem bark. However, there are limited studies linking the compounds with the ethnomedicinal uses. The aim of this study is to isolate and characterize bioactive compounds from Rauvolfia caffra Sond. The highest phenolic content found in a fraction was 16.06±0.125 mg GAE/g, while the highest flavonoid content measured was 9.453±0.081 mg QE/g. In the DPPH free radical scavenging activity and reducing power tests, a lowest IC50 value of 0.022±0.003 μg/mL and IC0.5 value 0.518±0.044 μg/mL, respectively, was found. Six compounds were isolated from the stem bark, including lupeol, a pentacyclic tri-terpenoid isolated for the first time from the genus Rauvolfia; raucaffricine, a rare glycoalkaloid of the monoterpenoid indole class; N-methylsarpagine, an indole alkaloid isolated for the time from R. caffra and spegatrine, an indole alkaloid isolated for the first time from R. caffra, respectively. Concerning antimicrobial activity, the highest activity of a fraction was against B. cereus with MIC values as low as 12.5 mg/mL. One fraction at the tested concentration (250 μg/mL) decreased the viability of Plasmodium falciparum (4.149±6.979 %) with an IC50 value of 6.533 μg/mL. The crude extract and some fractions affected the viability of the Trypanosomes at the tested concentration (250 μg/mL), giving -0.133 ± 0.206 %, 11.334 ± 2.692 %, 1.026 ± 0.143 % and 20.769 ± 9.054 % with IC50 values of 18.50 μg/mL, 14.15 μg/mL, 15.58 μg/mL and 34.71 μg/mL, respectively. Furthermore, the fractions did not show significant cytotoxic effects at a concentration of 50 μg/mL. / NRF

This study aims at the development of materials for biodegradable fiducial markers for X-ray based medical imaging and their anchorage in soft tissue. Towards this goal a degradable polymer matrix of poly(L-lactide-co-ε-caprolactone) (P[LAcoCL]) was combined with barium sulfate (BaSO₄) and hydroxyapatite (HAp) as radio-opaque fillers. Low pressure plasma treatment was applied to the composite materials to improve cell adhesion and subsequent tissue integration. In particular, the effects of oxygen and ammonia plasmas were evaluated and compared using X-ray photoelectron spectroscopy, atomic force microscopy and dynamic water contact angle measurements as well as in vitro studies using the murine fibroblast cell line L929. To exclude the cytotoxic effects of degradation products of P[LAcoCL] and released BaSO₄ or HAp cytotoxicity assays with the degradation products of the composite materials were conducted. The results obtained by this broad range of analytical techniques suggest the application of composites of P[LAcoCL] with BaSO₄ and HAp as promising material systems for innovative fiducial markers for soft tissue in X-ray based medical imaging.

Of the eleven species of bacteria that comprise the genus Yersinia of the family Enterobacteriaceae, three species are pathogenic for humans. Yersinia pseudotuberculosis and Yersinia enterocolitica usually cause a mild, self-limiting mesenteric lymphadenitis or ileitis. Yersinia pestis causes a highly invasive often fatal disease known as plague. All three elaborate a type three secretion system that is essential for virulence and encoded on closely related plasmids. In Y. pestis, all the effectors, structural components and chaperones are encoded on the 70kb plasmid, pCD1. Of these, LcrV from Y. enterocolitica has been implicated in playing an immunosuppressive role through its interaction with host Toll-like receptor 2 (TLR2) and induction of IL-10. Through expression and purification of recombinant LcrV from Escherichia coliwe show that only high molecular weight species of rLcrV are able to stimulate TLR2. In a highly sensitive subcutaneous mouse infection model we demonstrate no difference in the time to death between TLR2-sufficient or deficient mice. Analysis of cytokine levels between these two genotypes also shows no significant difference between splenic IL-10 and IL-6 or levels of bacteria. We conclusively show that this interaction, if it does occur, plays no significant role in vivo. In a separate set of experiments, we also determined that the expression of F1, a peptide shown to be responsible for 37°C-dependent inhibition of invasion by Y. pestis in vitro, was significantly decreased under high oxygen conditions. This led us to re-examine the invasion phenotype both in vitro and in vivo. These results give new insights into virulence gene expression in Y. pestis by environmental cues other than temperature.

No description available.

La chimiothérapie cytotoxique reste une option de traitement de première intention pour la majorité des cancers. Un effet secondaire majeur dans les schémas chimio-thérapeutiques est la neutropénie. La thérapie prophylactique avec le facteur de stimulation des colonies de granulocytes (G-CSF), une cytokine endogène responsable de la régulation de la production de neutrophiles, est administrée en concomitance. Le moment et la dose exacts pour administrer la chimiothérapie et le G-CSF représentent des éléments cruciaux pour obtenir les résultats souhaités du traitement. En nous appuyant sur des travaux antérieurs qui optimisaient les schémas thérapeutiques du G-CSF, nous sommes basés sur une approche de pharmacologie quantitative des systèmes (QSP) pour étudier la fréquence et l’intensité de la dose dans le but de maximiser les effets anti-tumoraux de la chimiothérapie tout en minimisant la neutropénie. Dans ce travail, nous avons effectué une optimisation sur une large gamme de longueurs de cycle et de valeurs des doses de chimiothérapie afin d’identifier les meilleurs schémas en combinaison avec le G-CSF. Nos résultats suggèrent que la doxorubicine 45mg/BSA tous les 14 jours a un impact positif sur le contrôle de la croissance tumorale, et qu’il est préfèrable de retarder l’administration du G-CSF au septième jour après la chimiothérapie et de donner moins de doses pour minimiser le risque de neutropénie et le fardeau de ce médicament. Cette étude suggère des pistes possibles pour des schémas optimaux de chimiothérapie, avec le soutien prophylactique du G-CSF spécifiquement dans le contexte du cancer du sein triple négatif. / Cytotoxic chemotherapy continues to be a first-line treatment option for the majority of cancers. A major side effect in chemotherapy regimens is neutropenia. Prophylactic therapy with granulocyte colony stimulating factor (G-CSF), an endogenous cytokine responsible for regulating neutrophil production, is administered concomitantly; the exact timing of the combination chemotherapy and G-CSF is crucial for achieving treatment results. Leveraging on previous work that optimized treatment regimens based on G-CSF timing, we developed a quantitative systems pharmacology (QSP) framework to study dose frequency and intensity of chemotherapy in order to maximize anti-tumor effects while minimizing neutropenia. In this work, we performed an optimization across a wide range of cycle lengths and dose sizes to identify the best cytotoxic chemotherapy regimens with G-CSF support. Our results suggest that doxorubicin 45mg/BSA every 14 days, has a positive impact on tumour growth control, and that to minimize the risk of neutropenia and the burden to patients it is best to delay the administration of G-CSF to day seven after chemotherapy and give fewer doses . This study suggests possible avenues for optimal chemotherapy regimens with prophylactic support of G-CSF in the context of Triple Negative Breast Cancer.

<p>Interleukin-15 (IL-15) is a cytokine that promotes maintenance and activation of cytotoxic immune cells. Therapeutic IL-15 stimulates these cells to fight cancer and chronic infections, such as Human Immunodeficiency Virus (HIV). Animal models of HIV have demonstrated that IL-15 agonists can suppress the virus, but this was transient and was not observed in all cohorts. We developed a mechanistic mathematical model of IL-15 therapy of HIV to explain these differences in efficacy and to explore solutions. First, the model was applied to evaluate mitigating factors, including immune regulation, viral escape, and drug tolerance, using Akaike Information Criterion.  We found that immune regulatory mechanisms could explain the viral rebound observed with continued IL-15 therapy. Next, the model was expanded to allow it to simultaneously explain both the transient viral suppression noted above and the lack of viral suppression observed in another animal cohort.  In this cohort, the model suggested that higher pre-treatment viral load came with higher activation of immune cells and a balancing regulatory inhibition of cytotoxicity. Finally, we conducted stability analysis at a range of IL-15 therapeutic strengths. While there was an ideal IL-15 strength, monotherapy could not maintain viral levels below what would clinically be considered to be safely controlled. Stable viral control in the model required the combination of IL-15 with blockade of key regulatory pathways. Immune therapy of complex diseases will likely require combinations of medicines that boost the immune response at multiple key points. Mathematical models like this can expedite development of these treatments.</p>