Biology subjects

Silva, L. S.

Publications and source records attributed to Silva, L. S..

3 recordsLinked to original sources

bioRxiv2025

Cyclodextrin-Based Delivery of the Annexin A1 Mimetic Peptide Ac2-26 Enhances Anti-Inflammatory Effects and PreventsDengue-Induced Lethality in Combination with AntiviralTherapy

Severe dengue is characterized by systemic inflammation, cytokine storm, vascular leakage, and hemorrhagic manifestations, largely driven by the host immune response to dengue virus (DENV) infection. Despite its burden, no licensed antivirals or host-directed therapies are currently available. Our group has previously identified Annexin A1 (AnxA1) as an endogenous regulator of inflammation in dengue. Treatment with the AnxA1 peptidomimetic, Ac2-26, improved clinical outcomes in murine models of severe dengue by promoting resolution of inflammation without affecting viral control. To explore new delivery strategies, we developed a novel formulation of Ac2-26 complexed with hydroxypropyl-{beta}-cyclodextrin (CDX-Ac2-26). In DENV-2-infected A129 mice, both intraperitoneal and oral CDX-Ac2-26 improved clinical scores and reversed thrombocytopenia. Notably, CDX-Ac2-26 reduced mast cell degranulation, MCPT-1 plasma levels, and CCL2 expression in spleen, with no effect on viral titers, indicating a host-targeted mechanism and overcoming the anti-inflammatory effects of the free peptide. Intraperitoneal administration achieved the same efficacy as oral dosing with only one-third of the dose. Importantly, the combination of CDX-Ac2-26 with the antiviral nucleotide analog sofosbuvir fully prevented disease and mortality in infected mice, highlighting a combinatorial effect between host-directed and antiviral therapies. These findings underscore the therapeutic potential of anti-inflammatory/pro-resolving strategies in severe dengue and support the development of CDX-Ac2-26 as a novel adjunctive treatment. Combining anti-inflammatory and antiviral approaches may enhance efficacy and reduce treatment-associated toxicity, offering a promising path for clinical translation. What is already known on this topic?O_LIPlasma levels of Annexin A1 are inversely correlated with the severity of clinical outcomes in dengue virus infection. C_LIO_LIThe Annexin A1 peptidomimetic Ac2-26 exhibits anti-inflammatory and pro-resolving effects against severe dengue in a murine model. C_LI What does this study add?O_LIThe Ac2-26-cyclodextrin complex enhances the anti-inflammatory effects of the peptide against dengue virus infection, allowing for lower dosing and oral administration. C_LIO_LIThe administration of the CDX-Ac2-26 with a nucleoside analog antiviral exhibits a combinatorial effectt, providing complete protection against the lethal outcome of severe dengue. C_LI What is the clinical significance?O_LICurrent dengue treatment relies on symptomatic management, as no directed anti-inflammatory agents or antivirals are currently available. We have identified a novel host-targeted strategy to resolve the disease. C_LIO_LIOur findings strongly support CDX-Ac2-26 as a promising adjunctive treatment strategy in combination with antiviral therapy for severe dengue, highlighting the potential of combinatorial approaches. C_LI

immunology↗

bioRxiv2025

Knocking out histidine ammonia-lyase by using CRISPR-Cas9 abolishes histidine role in the bioenergetics and the life cycle of Trypanosoma cruzi.

Trypanosoma cruzi, the causing agent of Chagas disease, is the only known trypanosomatid pathogenic to humans having a complete histidine to glutamate pathway, which involves a series of four enzymatic reactions that convert histidine into downstream metabolites, including urocanate, 4-imidazolone-5-propionate, N-formimino-L-glutamate and L-glutamate. Recent studies have highlighted the importance of this pathway in ATP production, redox balance, and the maintenance of cellular homeostasis in T. cruzi. In this work, we focus on the first step of the histidine degradation pathway, which is performed by the enzyme histidine ammonia lyase. Here we determined the kinetic and biochemical parameters of the T. cruzi histidine ammonia-lyase. By generating null mutants of this enzyme using CRISPR-Cas9 we observed that disruption of the first step of the histidine degradation pathway completely abolishes the capability of this parasite to metabolise histidine, compromising the use of this amino acid as an energy and carbon source. Additionally, we showed that the knockout of the histidine ammonia lyase affects metacyclogenesis when histidine is the only metabolizable source and diminishes trypomastigote infection in vitro.

biochemistry↗

bioRxiv2023

The Escherichia coli TolC efflux pump protein is immunogenic and elicits protective antibodies

Antimicrobial resistance is an increasing worldwide public health burden that threatens to make the existent antimicrobials obsolete. Among the mechanisms of antimicrobial resistance is the overexpression of efflux pumps, such as the AcrA-AcrB-TolC which extrude diverse compounds, reducing the intracellular concentration of antimicrobials. TolC is the outer membrane protein of this pump and has recently gained attention as a therapeutic target. However, little is known about the immune response generated against the TolC protein. Here we evaluated the cellular and humoral immune response against the TolC from Escherichia coli. An in silico epitope prediction of the E. coli TolC showed several residues could bind to human antibodies, and we showed that human plasma presented anti-TolC IgG and IgA antibodies. Gram-negative infected patients presented a slight increase in anti-TolC IgM amounts, compared to controls. Recombinant E. coli TolC protein stimulated macrophages in vitro to produce nitric oxide, as well as IL-6 and TNF-, assessed by Griess assay and ELISA, respectively. Immunization of mice with TolC intraperitoneally and an in vitro re-stimulation of lymph node cells led to increased percentage of T cell proliferation and IFN{gamma} production, evaluated by flow cytometry and ELISA, respectively. We observed that TolC mouse immunization stimulated anti-TolC IgM and IgG production, with a higher level of IgG1 and IgG2, amongst the IgG subclasses. Finally, TolC IgG from mouse immune serum could bind to live E. coli, increase bacterial uptake by macrophages in vitro. TolC immunized mice had a survival rate increased in 60% post infection with E. coli. Our results showed that TolC is immunogenic, activating macrophages, T and B cells, leading to the production of protective antibodies against E. coli.

immunology↗