Biology subjects

Rao, S. P. S.

Publications and source records attributed to Rao, S. P. S..

6 recordsLinked to original sources

bioRxiv2025

Screening of a chemogenetic library unveils dual-stage antimalarials with low cytotoxicity

The global effort to eradicate malaria requires the development of drugs with novel mechanisms of action and differentiated pharmacological profiles. Both liver and blood phases of Plasmodium infection are essential for disease progression and transmission, making them primary targets for therapeutic intervention. In this study, we established a dual-luciferase reporter assay to simultaneously assess Plasmodium berghei liver-stage development and host cell viability. Screening a library of bioactive small molecules with annotated human targets revealed several inhibitors with potent liver-stage activity and minimal cytotoxicity. Further profiling against P. falciparum asexual blood stages identified compounds with dual-stage activity, underscoring their potential utility for development as either prophylactic or therapeutic agents. Knowledge of their human targets will facilitate investigation into host- or parasite- directed antimalarial mechanisms, thereby accelerating both biological insight and rational drug development. Our findings constitute a valuable resource for research on malaria biology and the discovery of next-generation antimalarials.

microbiology↗

bioRxiv2025

Statins do not reduce the parasite burden during experimental Trypanosoma cruzi infection

Cardiomyopathy is the most common pathology associated with Trypanosoma cruzi infection. Reports that statins have both cardioprotective and trypanocidal activity have generated interest in their potential as a therapeutic treatment. Using a highly-sensitive bioluminescent mouse model, we show that 5 days treatment with statins has no significant impact on parasite load. The free systemic concentrations fail to reach the level required for potency. Hence, clinical trials to investigate trypanocidal activity of statins lack experimental justification.

microbiology↗

bioRxiv2024

Tissue damage during acute Trypanosoma cruzi infection is associated with reduced reparative regulatory T cell response and can be attenuated by early interleukin-33 administration.

Tissue-repair regulatory T cells (trTregs) constitute a specialized regulatory subset renowned for orchestrating tissue homeostasis and repair. While extensively investigated in sterile injury models, their role in infection-induced tissue damage and the regulation of protective antimicrobial immunity remains largely unexplored. This investigation examines trTregs dynamics during acute Trypanosoma cruzi infection, a unique scenario combining extensive tissue damage with robust antiparasitic CD8+ immunity. Contrary to conventional models of sterile injury, our findings reveal a pronounced reduction of trTregs in secondary lymphoid organs and tissues during acute T. cruzi infection. This unexpected decline correlates with systemic as well local tissue damage, as evidenced by histological alterations and downregulation of repair-associated genes in skeletal muscle. Remarkably, a parallel decrease in systemic levels of IL-33, a crucial factor for trTregs survival and expansion, was detected. We found that early treatment with systemic recombinant IL-33 during infection induces a notable surge in trTregs, accompanied by an expansion of type 2 innate lymphoid cells and parasite-specific CD8+ cells. This intervention results in a mitigated tissue damage profile and reduced parasite burden in infected mice. These findings shed light on trTregs biology during infection-induced injury and demonstrate the feasibility of enhancing a specialized Tregs response without impairing the magnitude of effector immune mechanisms, ultimately benefiting the host. Furthermore, this study settles groundwork of relevance for potential therapeutic strategies in Chagas disease and other infections. AUTHOR SUMMARYChagas disease, caused by the protozoan Trypanosoma cruzi, induces severe organ damage caused by the interplay between the parasite and the immune response. In our investigation, we delved into the role of tissue-repair regulatory T cells (trTregs) during the acute phase of T. cruzi infection in mice. Surprisingly, we observed a reduction in trTregs during the peak of tissue damage, contrary to their usual accumulation after injury in other contexts. This decline aligned with decreased levels of interleukin-33, a critical factor for trTregs survival. Administering interleukin-33 at early infection times not only boosted trTregs but also expanded other reparative and antiparasitic immune cells. Consequently, these treated mice exhibited reduced damage and lower parasite levels in tissues. Our findings offer insights into trTregs behavior during infection-induced injury, suggesting a promising avenue for therapeutic interventions in Chagas disease and related conditions. This study lays the groundwork for potential strategies that balance the immune response, supporting tissue repair without compromising the ability to control the infection, which could have broader implications for infectious diseases and tissue damage-related pathologies.

immunology↗

bioRxiv2021

De-novo generation of novel phenotypically active molecules for Chagas disease from biological signatures using AI-driven generative chemistry

Designing novel molecules with targeted biological activities and optimized physicochemical properties is a challenging endeavor in drug discovery. Recent developments in artificial intelligence have enhanced the early steps of de novo drug design and compound optimization. Herein, we present a generative adversarial network trained to design new chemical matter that satisfies a given biological signature. Our model, called pqsar2cpd, is based on the activity of compounds across multiple assays obtained via pQSAR (profile-quantitative structure-activity relationships). We applied pqsar2cpd to Chagas disease and designed a novel molecule that was experimentally confirmed to inhibit growth of parasites in vitro at low micromolar concentrations. Altogether, this approach bridges chemistry and biology into one single framework for the design of novel molecules with promising biological activity.

pharmacology and toxicology↗

bioRxiv2020

A Cyclic Phosphoramidate Prodrug of 2-deoxy-2-fluoro-2-C-methylguanosine for the Treatment of Dengue Infection

Monophosphate prodrug analogs of 2-deoxy-2-fluoro-2-C-methylguanosine have been reported as potent inhibitors of hepatitis C virus (HCV) RNA-dependent RNA polymerase. These prodrugs also display potent anti-dengue activities in cellular assays although their prodrug moieties were designed to produce high levels of triphosphate in the liver. Since peripheral blood mononuclear cells (PBMCs) are one of the major targets of dengue virus, different prodrug moieties were designed to effectively deliver 2-deoxy-2-fluoro-2-C-methylguanosine monophosphate prodrugs and their corresponding triphosphates into PBMCs after oral administration. We identified a cyclic phosphoramidate prodrug 17 demonstrating a well-balanced anti-dengue cellular activity and in vitro stability profiles. In dogs, oral administration of 17 resulted in high PBMC triphosphate level, exceeding TP50 (the intracellular triphosphate concentration at which 50% of virus replication is inhibited) at 10 mg/kg. Compound 17 demonstrated 1.6- and 2.2 log viremia reduction in the dengue mouse model at 100 and 300 mg/kg twice daily, respectively. At 100 mg/kg twice daily, the terminal triphosphate concentration in PBMCs reached above TP50, defining for the first time the minimum efficacious dose for a nucleos(t)ide prodrug. In the two-week dog toxicity studies at 30 to 300 mg/kg/day, no observed adverse effect level (NOAEL) could not be achieved due to pulmonary inflammation and hemorrhage. The preclinical safety results suspended further development of 17. Nevertheless, present work has proven the concept that an efficacious monophosphate nucleoside prodrug could be developed for the potential treatment of dengue infection.

microbiology↗

bioRxiv2019

Targeting the trypanosome kinetochore with CLK1 protein kinase inhibitors

The kinetochore is a macromolecular structure that assembles on the centromeres of chromosomes and provides the major attachment point for spindle microtubules during mitosis. In Trypanosoma brucei the proteins that make up the kinetochore are highly divergent, with the inner kinetochore comprising at least 20 distinct and essential proteins (KKT1-20) that include four protein kinases, CLK1 (KKT10), CLK2 (KKT19), KKT2 and KKT3. We performed a phenotypic screen of T. brucei bloodstream forms with a Novartis kinase-focused inhibitor library, which identified a number of selective inhibitors with potent pan-kinetoplastid activity. Deconvolution of an amidobenzimidazole series using a selection of 37 T. brucei mutants that over-express known essential protein kinases identified CLK1 as the primary target. Biochemical studies show that the irreversible competitive inhibition of CLK1 is dependent on a Michael acceptor forming an irreversible bond with C215 in the ATP binding pocket, a residue that is not present in human CLK1, thereby providing selectivity. Chemical inhibition of CLK1 impairs inner kinetochore recruitment and compromises cell cycle progression, leading to cell death. We show that KKT2 is a substrate for CLK1 and identify phosphorylation of S508 to be essential for KKT2 function and for kinetochore assembly. We propose that CLK1 is part of a novel signalling cascade that controls kinetochore function via phosphorylation of the inner kinetochore protein kinase KKT2. This work highlights a novel drug target for trypanosomatid parasitic protozoa and a new chemical tool for investigating the function of their divergent kinetochores.

microbiology↗