Biology subjects

Ramos, S.

Publications and source records attributed to Ramos, S..

10 recordsLinked to original sources

bioRxiv2025

Biliverdin Reductase Catalytic Activity Is Essential for Malaria Resistance

Jaundice, a condition characterized by elevated levels of circulating bilirubin, is an adaptive response to malaria sustained through bilirubin production by biliverdin reductase A (BVRA). Beyond its enzymatic activity, BVRA acts as a protein kinase and as a transcription factor. To disentangle the contribution of BVRA catalytic activity over its non-canonical functions we generated BlvraG17A and BlvraE97A mice harboring G17A and E97A missense mutations in the BVRA NAD(P)H-binding domain and reductase motif, respectively. Both BlvraG17A and BlvraE97Amice presented a reduction in enzymatic activity and succumbed to malaria, otherwise non-lethal to wild-type (BlvraWT) mice. Quantification of circulating unconjugated bilirubin revealed a dose response effect whereby the mutant strains failed to reach a threshold of circulating bilirubin required to support its protective effect. These findings establish the antimalarial effect of the enzymatic activity of BVRA and define a concentration threshold of bilirubin required for malaria protection, informing therapeutic development and biomarker-guided malaria treatment strategies. Highlights- Establishment of catalytic deficient BVRA mouse mutants; - Anti-malarial effect of BVRA relies on its catalytic activity; - A minimal bilirubin threshold for parasite control; - A minimal bilirubin threshold for malaria resolution;

pathology↗

bioRxiv2025

A Metabolite-Based Resistance Mechanism Against Malaria

Whether jaundice, a common presentation of Plasmodium (P.) falciparum malaria (1-3) arising from the accumulation of circulating bilirubin, represents an adaptive or maladaptive response to Plasmodium spp. infection is not understood (1-3). We found that asymptomatic P. falciparum infection was associated with a >10-fold higher ratio of unconjugated bilirubin over parasite burden, compared to symptomatic malaria. Genetic suppression of bilirubin synthesis by biliverdin reductase A (BVRA) (4) increased parasite virulence and malaria mortality in mice. Accumulation of unconjugated bilirubin in plasma, via genetic inhibition of hepatic conjugation by UDP glucuronosyltransferase family 1 member A1 (UGT1A1) (5), was protective against malaria in mice. Unconjugated bilirubin inhibited P. falciparum proliferation in red blood cells (RBC) via a mechanism that suppressed mitochondrial pyrimidine synthesis. Moreover, unconjugated bilirubin inhibited hemozoin (Hz) crystallization and compromised the parasites food vacuole. In conclusion, jaundice represents a metabolic response to Plasmodium spp. infection that limits malaria severity.

immunology↗

bioRxiv2022

A Protective Inter-Organ Communication Response Against Life-Threatening Malarial Anemia

Anemia is a clinical hallmark and independent risk factor of malaria mortality, the disease caused by Plasmodium spp. infection. While malarial anemia arises from parasite-induced hemolysis, whether and how host metabolic adaptation to malaria regulates anemia severity is less understood. Here we demonstrate that reprogramming of organismal iron (Fe) metabolism by the kidneys is a central component of the host metabolic response regulating the pathogenesis of life-threatening malarial anemia. Renal proximal tubule epithelial cells (RPTEC) are the main cell compartment responsible for Fe storage and recycling during Plasmodium infection in mice. Transcriptional reprogramming of RPTEC couples immune resistance to Plasmodium infection to renal Fe export via the induction of the cellular Fe exporter SLC40A1/ferroportin 1. This integrated defense strategy is essential to deliver Fe to erythroblasts and support compensatory erythropoiesis to prevent the development of life-threatening anemia. Failure to mobilize Fe from RPTEC causes acute kidney injury (AKI) and is associated with life-threatening anemia in P. falciparum-infected individuals. These findings reveal an unexpected role of the kidneys in the control of organismal Fe metabolism and anemia severity during malaria.

pathology↗

bioRxiv2021

Neutralizing antibody-independent immunity to SARS-CoV-2 in hamsters and hACE-2 transgenic mice immunized with a RBD/Nucleocapsid fusion protein

The nucleocapsid (N) and the receptor binding domain (RBD) of the Spike (S) proteins elicit robust antibody and T cell responses either in vaccinated or COVID-19 convalescent individuals. We generated a chimeric protein that comprises the sequences of RBD from S and N antigens (SpiN). SpiN was highly immunogenic and elicited a strong IFN{gamma} response from T cells and high levels of antibodies to the inactivated virus, but no neutralizing antibodies. Importantly, hamsters and the human Angiotensin Convertase Enzyme-2-transgenic mice immunized with SpiN were highly resistant to challenge with the wild type SARS-CoV-2, as indicated by viral load, clinical outcome, lung inflammation and lethality. Thus, the N protein should be considered to induce T-cell-based immunity to improve SARS-CoV-2 vaccines, and eventually to circumvent the immune scape by variants.

immunology↗

bioRxiv2021

A HYPOMETABOLIC DEFENSE STRATEGY AGAINST PLASMODIUM INFECTION

Hypoglycemia is a clinical hallmark of severe malaria, the often-lethal presentation of Plasmodium falciparum infection of humans. Here we report that mice reduce blood glucose levels in response to Plasmodium infection via a coordinated response whereby labile heme, an alarmin produced via hemolysis, induces anorexia and represses hepatic glucose production (HGP). While protective against unfettered immune-mediated inflammation, organ damage and anemia, when sustained over time heme-driven repression of HGP can progress towards hypoglycemia, compromising host energy expenditure and thermoregulation. This hypometabolic state arrests the development of asexual stages of Plasmodium spp., which undergo pyknosis and develop mitochondrial dysfunction. In response, Plasmodium activates a transcriptional program reducing its virulence and inducing sexual differentiation towards the production of transmissible gametocytes. We infer that malaria-associated hypoglycemia represents a trade-off of an evolutionarily conserved defense strategy restricting Plasmodium spp. from accessing host-derived glucose and balancing parasite virulence and transmission.

immunology↗

bioRxiv2021

RIPK1 activates distinct gasdermins in macrophages and neutrophils upon pathogen blockade of innate immune signalling

Injection of effector proteins to block host innate immune signalling is a common strategy used by many pathogenic organisms to establish an infection. Pathogenic Yersinia species for example inject the acetyltransferase YopJ into target cells to inhibit NF-{kappa}B and MAPK signalling. To counteract this, detection of YopJ activity in myeloid cells promotes the assembly of a RIPK1-caspase-8 death-inducing platform that confers antibacterial defence. While recent studies revealed that caspase-8 cleaves the pore-forming protein, gasdermin D (GSDMD) to trigger pyroptosis in macrophages, whether RIPK1 activates additional substrates downstream of caspase-8 to promote host defence is unclear. Here, we report that the related gasdermin family member gasdermin E (GSDME) is activated upon detection of YopJ activity in a RIPK1 kinase-dependent manner. Specifically, GSDME promotes neutrophil pyroptosis and IL-1{beta} release, which is critical for anti-Yersinia defence. During in vivo infection, IL-1{beta} neutralisation increases bacterial burden in wild type but not Gsdme-deficient mice. Thus, our study establishes GSDME as an important mediator that counteracts pathogen blockade of innate immune signalling.

immunology↗

bioRxiv2020

Intradermal-delivered DNA vaccine provides anamnestic protection in a rhesus macaque SARS-CoV-2 challenge model

Coronavirus disease 2019 (COVID-19), caused by the SARS-CoV-2 virus, has had a dramatic global impact on public health, social, and economic infrastructures. Here, we assess immunogenicity and anamnestic protective efficacy in rhesus macaques of the intradermal (ID)-delivered SARS-CoV-2 spike DNA vaccine, INO-4800. INO-4800 is an ID-delivered DNA vaccine currently being evaluated in clinical trials. Vaccination with INO-4800 induced T cell responses and neutralizing antibody responses against both the D614 and G614 SARS-CoV-2 spike proteins. Several months after vaccination, animals were challenged with SARS-CoV-2 resulting in rapid recall of anti-SARS-CoV-2 spike protein T and B cell responses. These responses were associated with lower viral loads in the lung and with faster nasal clearance of virus. These studies support the immune impact of INO-4800 for inducing both humoral and cellular arms of the adaptive immune system which are likely important for providing durable protection against COVID-19 disease.

immunology↗

bioRxiv2020

SARS-CoV-2 assays to detect functional antibody responses that block ACE2 recognition in vaccinated animals and infected patients

SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) has caused a global pandemic of COVID-19 resulting in cases of mild to severe respiratory distress and significant mortality. The global outbreak of this novel coronavirus has now infected >8 million people worldwide with >2 million cases in the US (June 17th, 2020). There is an urgent need for vaccines and therapeutics to combat the spread of this coronavirus. Similarly, the development of diagnostic and research tools to determine infection and vaccine efficacy are critically needed. Molecular assays have been developed to determine viral genetic material present in patients. Serological assays have been developed to determine humoral responses to the spike protein or receptor binding domain (RBD). Detection of functional antibodies can be accomplished through neutralization of live SARS-CoV2 virus, but requires significant expertise, an infectible stable cell line, a specialized BioSafety Level 3 (BSL-3) facility. As large numbers of people return from quarantine, it is critical to have rapid diagnostics that can be widely adopted and employed to assess functional antibody levels in the returning workforce. This type of surrogate neutralization diagnostic can also be used to assess humoral immune responses induced in patients from the large number of vaccine and immunotherapy trials currently on-going. Here we describe a rapid serological diagnostic assay for determining antibody receptor blocking and demonstrate the broad utility of the assay by measuring the antibody functionality of sera from small animals and non-human primates immunized with an experimental SARS-CoV-2 vaccine and using sera from infected patients.

immunology↗

bioRxiv2020

Establishment of a pig influenza challenge model for evaluation of monoclonal antibody delivery platforms

Monoclonal antibodies are a possible adjunct to vaccination and drugs in treatment of influenza virus infection. However questions remain whether small animal models accurately predict efficacy in humans. We have established the pig, a large natural host animal for influenza, with many physiological similarities to humans, as a robust model for testing monoclonal antibodies. We show that a strongly neutralizing monoclonal antibody (2-12C) against the hemagglutinin head administered prophylactically at 15 mg/kg reduced viral load and lung pathology after pandemic H1N1 influenza challenge. A lower dose of 1 mg/kg of 2-12C or a DNA plasmid encoded version of 2-12C, reduced pathology and viral load in the lungs, but not viral shedding in nasal swabs. We propose that the pig influenza model will be useful for testing candidate monoclonal antibodies and emerging delivery platforms prior to human trials.

immunology↗

bioRxiv2019

Different roles of eye absent in the basal ovarian follicle and germarium of developing cockroach ovaries

Eyes absent (Eya), is a protein structurally conserved from hydrozoans to humans, for which two basic roles have been reported: it can act as a transcription cofactor and as a protein tyrosine phosphatase. Eya was discovered in the fly Drosophila melanogaster in relation to its function in eye development, and the same function was later reported in other insects. Eya is also involved in insect oogenesis, although studies in this sense are limited to D. melanogaster, which has meroistic ovaries, and where eya mutations abolish gonad formation. In the present work we studied the function of eya in the panoistic ovary of the cockroach Blattella germanica. We show that eya is essential for correct development of panoistic ovaries. In B. germanica, eya acts at different level and in a distinct way in the germarium and the vitellarium. In the germarium, eya contributes to maintain the correct number of somatic and germinal cells by regulating the expression of steroidogenic genes in the ovary. In the vitellarium, eya facilitates follicle cells proliferation and contributes to regulate the cell program, in the context of basal ovarian follicle maturation. Thus, eya-depleted females of B. germanica arrest the growth and maturation of basal ovarian follicles and become sterile.

developmental biology↗