Biology subjects

Velez, A.

Publications and source records attributed to Velez, A..

3 recordsLinked to original sources

bioRxiv2023

Elevated peripheral and nervous system inflammation is associated with decreased short-chain fatty acid levels in Zika-virus infected macaques

Zika virus (ZIKV) infection of central nervous system (CNS) tissue is associated with CNS inflammation, which contributes to ZIKV pathology. Similarly, ZIKV infection has been associated with increased vaginal and rectal mucosal inflammation. As mucosal dysfunction may contribute to elevated systemic inflammation, ZIKV-induced mucosal alterations could potentiate CNS disruptions, leading to ZIKV pathogenesis. However, the potential link between mucosal dysfunction, CNS inflammation and the underlying mechanisms causing these disruptions in ZIKV infection has not been well described. Here, we assessed plasma and CSF indicators of inflammation, including neopterin, tryptophan, kynurenine and serotonin by liquid chromatography tandem mass spectrometry. We observed significant increases in neopterin formation, tryptophan catabolism and serotonin levels in the plasma and CSF of ZIKV-infected pigtail macaques (PTM), rhesus macaques (RM) and in the plasma of ZIKV-infected humans. We next examined whether ZIKV infection resulted in microbial translocation across mucosal surfaces by evaluating plasma and cerebrospinal fluid (CSF) levels of soluble CD14 (sCD14) and lipopolysaccharide-binding protein (LBP) by enzyme-linked immunosorbent assay (ELISA). Increased sCD14 was observed in the CSF of PTM and rhesus macaque (RM), while increased LBP was observed in pigtail macaque (PTM) plasma. Finally, to examine whether ZIKV-induced microbial dysbiosis could underlie increased microbial translocation and inflammation, we characterized intestinal microbial communities by 16s rRNA gene sequencing and microbial functional changes by quantifying short-chain fatty acid (SCFA) concentrations by gas chromatography mass spectrometry. We observed that although ZIKV infection of PTM did not result in significant taxonomic shifts in microbial communities, there were significant reductions in SCFA levels. Loss of microbial function in ZIKV infection could cause decreased intestinal integrity, thereby contributing to elevated microbial translocation and systemic and CNS inflammation, providing a possible mechanism underlying ZIKV pathogenesis. Further, this may represent a mechanism underlying inflammation and pathogenesis in other diseases. Author SummaryZika virus (ZIKV) can be transmitted to humans via the bite of an infected mosquito or between humans during sexual intercourse, typically resulting in mild symptoms, which has been linked to elevated inflammation in the CNS and the development of more serious conditions, including severe neurological syndromes. Previous studies have observed that ZIKV infection is associated with increased mucosal dysfunction, including elevated inflammation in rectal and vaginal mucosal tissue. However, the mechanism of ZIKV-induced mucosal dysfunction may contribute to systemic and CNS inflammation has not been previously investigated. Here, we used the non-human primate (NHP) model and clinical specimens from ZIKV-infected humans to examine markers of systemic and CNS inflammation and microbial translocation. We observed elevated markers indicative of microbial translocation and inflammation in the CNS of ZIKV-infected macaques and humans. A potential association with mucosal dysfunction in ZIKV infection is shifts in microbial dysbiosis. We also observed that there were no significant overall taxonomic shifts in microbial communities, but a reduction of bacterial-derived short-chain fatty acid (SCFA) levels. Finally, we observed that the decrease in SCFA levels significantly negatively correlated with the elevated peripheral and CNS inflammatory markers, suggesting a link between ZIKV-driven disease pathology and microbial function. Taken together, our study provides new insight into a previously unconsidered mechanism underlying ZIKV pathogenesis.

microbiology↗

bioRxiv2022

Arginase 1 is a key driver of immune suppression in pancreatic cancer

An extensive fibroinflammatory stroma rich in macrophages is a hallmark of pancreatic cancer. In this disease, it is well appreciated that macrophages are immunosuppressive and contribute to the poor response to immunotherapy; however, the mechanisms of immune suppression are complex and not fully understood. Immunosuppressive macrophages are classically defined by expression of the enzyme Arginase 1 (Arg1), which we demonstrated is potently expressed in pancreatic tumor associated macrophages from both human patients and mouse models. While routinely used as a polarization marker, Arg1 also catabolizes arginine, an amino acid required for T cell activation and proliferation. To investigate this metabolic function, we used a genetic and a pharmacologic approach to target Arg1 in pancreatic cancer. Genetic inactivation of Arg1 in macrophages, using a dual recombinase genetically engineered mouse model of pancreatic cancer, delayed formation of invasive disease, while increasing CD8+ T cell infiltration. Treatment of established tumors with the arginase inhibitor CB-1158 exhibited further increased CD8+ T cell infiltration, beyond that seen with the macrophage-specific knockout, and sensitized the tumors to anti-PD1 immune checkpoint blockade. Thus, our data demonstrate that Arg1 is more than simply a marker of macrophage function. Rather, Arg1 is also a driver of immune suppression and represents a promising immunotherapeutic target for pancreatic cancer.

cancer biology↗

bioRxiv2021

Progressive sub-MIC Exposure of Klebsiella pneumoniae 43816 to Cephalothin Induces the Evolution of beta-lactam Resistance without Acquisition of beta-lactamase Genes

Bacterial exposure to antibiotic concentrations below the minimum inhibitory concentration (MIC) may result in a selection window allowing for the rapid evolution of resistance. These sub-MIC concentrations are commonly found in the greater environment. This study aimed to evaluate the adaptive genetic changes in Klebsiella pneumoniae 43816 after prolonged but increasing sub-MIC levels of the common antibiotic cephalothin over a fourteen-day period. Over the course of the experiment, antibiotic concentrations increased from 0.5 g/mL to 7.5 g/mL. At the end of this extended exposure, the final adapted bacterial culture exhibited clinical resistance to both cephalothin and tetracycline, altered cellular and colony morphology, and a highly mucoid phenotype. Cephalothin resistance exceeded 125 g/mL without the acquisition of beta-lactamase genes. Whole genome sequencing identified a series of genetic changes that could be mapped over the fourteen-day exposure period to the onset of antibiotic resistance. Specifically, mutations in the rpoB subunit of RNA Polymerase, the tetR/acrR regulator, and the wcaJ sugar transferase each fix at specific timepoints in the exposure regimen where the MIC susceptibility dramatically increases. These mutations indicate that alterations in the secretion of colanic acid and attachment of colonic acid to LPS, may contribute to the resistant phenotype. These data demonstrate that very low, sub-MIC concentrations of antibiotics can have dramatic impacts on the bacterial evolution of resistance. Additionally, this study demonstrates that beta-lactam resistance can be achieved through sequential accumulation of specific mutations without the acquisition of a beta-lactamase gene. ImportanceBacteria are constantly exposed to low levels of antibiotics in the environment. The impact of this low-level exposure on bacterial evolution is not well understood. In this work, we developed a model to expose Klebsiella pneumoniae to progressive, low doses of the antibiotic cephalothin. After a fourteen-day exposure regimen, our culture exhibited full clinical resistance to this antibiotic without the traditional acquisition of inactivating genes. This culture also exhibited resistance to tetracycline, had a highly mucoid appearance, and exhibited altered, elongated cellular morphology. Whole genome sequencing identified a collection of mutations to the bacterial genome that could be mapped to the emergence of the resistant phenotype. This study demonstrates that antibiotic resistance can be achieved in response to low level antibiotic exposure and without the traditional acquisition of resistance genes. Further, this study identifies new genes that may play a role in the evolution of antibiotic resistant bacteria.

microbiology↗