Biology subjects

Urrea, V.

Publications and source records attributed to Urrea, V..

9 recordsLinked to original sources

bioRxiv2026

Humanized FLT3 mice display enhanced tissue engraftment and support HIV-1 persistence and rebound

Despite advances in antiretroviral therapy (ART), HIV-1 cure efforts remain hindered by viral reservoirs in long-lived myeloid cells and immune-privileged tissues that are less accessible and therefore unlikely to be assessed in human clinical trials. Consequently, there is a critical need for robust research platforms such as immune cell humanized mice to bridge preclinical and clinical HIV research. However, previously described humanized mouse models have demonstrated incomplete hematopoietic development, particularly showing low levels of NK or myeloid cells. Herein, we present the novel humanized FLT3 mouse model that develops NK cells, myeloid progenitors, monocytes, and both functional conventional (cDCs) and plasmacytoid dendritic cells (pDCs) to support HIV-1 infection. Human cord blood derived CD34+ hematopoietic stem cells (HSC) were engrafted in the FLT3 (Hu-FLT3) and NSG (Hu-NSG) mouse strains for comparison. Our data showed that while Hu-NSG and Hu-FLT3 mice have comparable human lymphocyte levels, the proportion of myeloid cells (including monocytes, pDCs and cDCs) in Hu-FLT3 mice (16.2 %) was three-fold higher than in Hu-NSG mice (5.6 %) and the proportion of NK cells was six-fold higher (12.8 % and 1.9 %, respectively). Both strains successfully supported HIV-1 infection, maintain viral replication for 17 weeks in untreated mice, and proviral DNA was detectable in peripheral blood, bone marrow and spleen. While ART effectively reduced viral load to undetectable levels in four weeks in both strains, we observed viral rebound after treatment discontinuation within 3 weeks, reaching the same levels of viral load pre-ART and mimicking what is observed in people living with HIV (PLWH).Human immune cells and HIV-1 RNA were higher in tissues of Hu-FLT3 mice compared to Hu-NSG mice, mirroring features reported in human tissue reservoirs. Our findings demonstrated that Hu-FLT3 mice support enhanced development of human innate immune cells in blood and tissues, which are associated with higher levels of HIV-1 replication compared to Hu-NSG mice. This study establishes a novel, robust and accessible in vivo platform to investigate potential HIV cure and persistence-targeting interventions with translational relevance to human therapeutic development thanks to the improved and more complete human immune repertoire in Hu-FLT3.

immunology↗

bioRxiv2026

MIF overexpression upon SARS-CoV-2 infection induces neural regeneration in human-derived brain organoids

While SARS-CoV-2 primarily targets the respiratory system, its neurological effects have become a significant clinical concern. Postmortem analyses reveal astrogliosis, neuronal death, and blood-brain barrier dysfunction, yet the interplay between neural injury and endogenous repair remains unclear. Here, we employed human embryonic stem cell-derived brain organoids to examine viral tropism, bystander effects, and regenerative responses following infection. Single-cell transcriptomics and histological assays showed that SARS-CoV-2 productively infects neurons, neural progenitors, astroglia, and choroid plexus cells, triggering widespread apoptosis and senescence in both infected and neighboring cells. Despite low infection rates, organoids activated robust regenerative programs, including axon guidance, Wnt pathway signaling in mature neurons, and radial glia proliferation. Importantly, macrophage migration inhibitory factor (MIF) emerged as a key mediator, being strongly upregulated in both infected and uninfected cells, particularly in the choroid plexus. Recombinant MIF promoted dendritic outgrowth and cortical progenitor activation in uninfected organoids. Computational analyses indicated that MIF stimulates neural regenerative via EGFR signaling and upregulates its own expression in non-infected cells. These findings identify MIF as a molecular link between SARS-CoV-2-induced neural damage and regenerative activation in cortical cells.

cell biology↗

bioRxiv2025

Pediatric Long COVID Is Characterized by Myeloid CCR6 Suppression and Immune Dysregulation

The biological mechanisms underlying long COVID in the pediatric population are poorly understood. Our study aimed to characterize the immune pathophysiology of long COVID in children and young people (CYP). We analyzed major immune cell compartments in PBMCs, as well as specific SARS-CoV-2 antibody response in CYP with (n=99) and without (n=18) long COVID at three months following acute infection. Our findings indicate that pediatric long COVID is associated with a dysregulated immune response characterized by altered innate immunity and overactivated T-, B- and NK-cell responses. Furthermore, CYP with long COVID had an impaired humoral response to SARS-CoV-2 marked by a dysregulated B-cell compartment and lower levels of anti-RBD IgG and IgA. This correlated with reduced neutralizing capacity against SARS-CoV-2. Random forest analysis identified CCR6 expression on myeloid cells as the most relevant biomarker that distinguishes long COVID from control individuals with 79% accuracy. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=154 SRC="FIGDIR/small/671713v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@1145480org.highwire.dtl.DTLVardef@1b7a635org.highwire.dtl.DTLVardef@fb13org.highwire.dtl.DTLVardef@63a49a_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2024

A human-ACE2 knock-in mouse model for SARS-CoV-2 infection recapitulates respiratory disorders but avoids neurological disease associated with the transgenic K18-hACE2 model.

Animal models have been instrumental in elucidating the pathogenesis of SARS-CoV-2 infection and testing COVID-19 vaccines and therapeutics. Wild-type (WT) mice are not susceptible to many SARS-CoV-2 variants, therefore transgenic K18-hACE2 mice have emerged as a standard model system. However, this model is characterized by severe disease, particularly associated with neuroinfection, which leads to early humane endpoint euthanasia. Here, we established a novel knock-in (KI) mouse model by inserting the original K18-hACE2 transgene into the collagen COL1A1 locus using a recombinase mediated cassette exchange (RMCE) system. Once the Col1a1-K18-hACE2 mouse colony was established, animals were challenged with a B.1 SARS-CoV-2 (D614G) isolate and were monitored for up to 14 days. Col1a1-K18-hACE2 mice exhibited an initial weight loss similar to the K18-hACE2 transgenic model but did not develop evident neurologic clinical signs. The majority of Col1a1-K18-hACE2 mice did not reach the preestablished humane endpoint, showing progressive weight gain after 9 days post-infection (dpi). Importantly, despite this apparent milder pathogenicity of the virus in this mouse model compared to the K18-hACE2 transgenic model, high levels of viral RNA were detected in lungs, oropharyngeal swab, and nasal turbinate. Remaining lesions and inflammation in lungs were still observed after 14 dpi. In contrast, although low level viral RNA could be detected in a minority of Col1a1-K18- hACE2 animals, no brain lesions were observed at any timepoint. Overall, Col1a1-K18- hACE2 mice constitute a new model for investigating SARS-CoV-2 pathogenesis and treatments, with potential implications for studying long-term COVID-19 sequelae. ImportanceK18-hACE2 mice express high levels of the human protein ACE2, the receptor for SARS- CoV-2, and can therefore be infected by this virus. These animals have been crucial to understand viral pathogenesis and to test COVID-19 vaccines and antiviral drugs. However, K18-hACE2 often die after infection with initial SARS-CoV-2 variants likely due to a massive brain infection that does not occur in humans. Here, we used a technology known as knock-in that allows for the targeted insertion of a gene into a mouse and we have generated a new hACE2-mouse. We have characterized this new animal model demonstrating that the virus replicates in the respiratory tract, damaging lung tissue and causing inflammation. In contrast to K18-hACE2 mice, only limited or no brain infection could be detected, and most animals recovered from infection with remaining lung lesions. This new model could be instrumental for the study of specific disease aspects such as post-COVID condition, sequelae, and susceptibility to reinfection.

microbiology↗

bioRxiv2023

VLP-mediated delivery of structure-selected neoantigens demonstrates immunogenicity and antitumoral activity in mice

BackgroundNeoantigens are patient- and tumor-specific peptides that arise from somatic mutations. They stand as promising targets for personalized therapeutic cancer vaccines. The identification process for neoantigens has evolved with the use of next-generation sequencing technologies and bioinformatic tools in tumor genomics. However, in silico strategies for selecting immunogenic neoantigens still have very low accuracy rates, since they mainly focus on predicting peptide binding to Major Histocompatibility Complex (MHC) molecules, which is key but not the sole determinant for immunogenicity. MethodsWe developed a novel neoantigen selection pipeline based on existing software combined with a novel prediction method, the Neoantigen Optimization Algorithm (NOAH), which takes into account structural features of the peptide/MHC-I interaction in its prediction strategy. Moreover, to maximize neoantigens therapeutic potential, neoantigen-based vaccines should be manufactured in an optimal delivery platform that elicits robust de novo immune responses and bypasses central and peripheral tolerance. ResultsWe generated a highly immunogenic vaccine platform based on engineered HIV-1 Gag-based Virus-Like Particles (VLPs) expressing a high copy number of each in silico selected neoantigen. We tested different neoantigen-loaded VLPs (neoVLPs) in a B16-F10 melanoma mouse model to evaluate their capability to generate new immunogenic specificities. NeoVLPs were used in in vivo immunogenicity and tumor challenge experiments. ConclusionsNeoVLPs can promote the generation of de novo antitumor-specific immune responses, resulting in a delay in tumor growth. Vaccination with the neoVLP platform is a robust alternative to current therapeutic vaccine approaches and a promising candidate for future personalized immunotherapy. WHAT IS ALREADY KNOWN ON THIS TOPICIdentification of highly immunogenic neoantigens is still challenging, currently available pipelines base their prediction on MHC-I binding affinity. Moreover, neoantigen-based vaccine delivery needs to be improved to increase the potency of anti-tumor immune response. WHAT THIS STUDY ADDSNOAH is a novel pipeline for the identification and selection of neoantigens that combines binding affinity and structural features of the peptide/MHC-I interaction. Preclinical studies show highly immunogenic vaccine platform based on HIV-1 Gag based VLPs (neoVLPs) generates antitumor-specific immune responses, delaying tumor growth. HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICYThe combination of NOAH and neoVLP platform represents an alternative to current therapeutic vaccine approaches and a promising candidate for future personalized immunotherapy.

immunology↗

bioRxiv2023

Novel Spike-stabilized trimers with improved production protect K18-hACE2 mice and golden Syrian hamsters from the highly pathogenic SARS-CoV-2 Beta variant.

Most COVID-19 vaccines are based on the SARS-CoV-2 Spike glycoprotein (S) or their subunits. However, the S shows some structural instability that limits its immunogenicity and production, hampering the development of recombinant S-based vaccines. The introduction of the K986P and V987P (S-2P) mutations increases the production of the recombinant S trimer and, more importantly, its immunogenicity, suggesting that these two parameters are related. However, S-2P still shows some molecular instability and it is produced with low yield. Thus, S-2P production can be further optimized. Here we described a novel set of mutations identified by molecular modelling and located in the S2 region of the Spike that increase S-2P production up to five-fold. Besides their immunogenicity, the efficacy of two representative S-2P-based mutants, S-29 and S-21, protecting from a heterologous SARS-CoV-2 Beta variant challenge was assayed in K18-hACE2 mice (an animal model of severe SARS-CoV-2 disease) and golden Syrian hamsters (GSH) (a moderate disease model). S-21 induced higher level of WH1 and Delta variants neutralizing antibodies than S-2P in K18-hACE2 mice three days after challenge. Viral load in nasal turbinate and oropharyngeal samples were reduced in S-21 and S-29 vaccinated mice. Despite that, only the S-29 protein protected 100% of K18-hACE2 mice from severe disease. When GSH were analyzed, all immunized animals were protected from disease development irrespectively of the immunogen they received. Therefore, the higher yield of S-29, as well as its improved immunogenicity and efficacy protecting from the highly pathogenic SARS-CoV-2 Beta variant, pinpoint the S-29 spike mutant as an alternative to the S-2P protein for future SARS-CoV-2 vaccine development. Authors summaryThe rapid development of SARS-CoV-2 vaccines have been pivotal in the control of the COVID-19 pandemic worldwide. Most of these vaccines include the S glycoprotein as the main immunogen since this protein, and particularly its receptor binding domain (RBD), is the major target of neutralizing antibodies. SARS-CoV-2 have been evolving from the beginning of the pandemic and several variants with increased transmissibility, pathogenicity or resistance to infection- or vaccine-induced immunity have emerged. Different strategies have been adopted to improve vaccine protection including additional booster doses or the adaptation of the S immunogens to the novel SARS-CoV-2 variants. As a complementary strategy we have identified a combination of non-proline mutations that increase S production by 5-fold (S-29 protein). Despite the sequence of this novel S-29 immunogen is based on the ancestral SARS-CoV-2 WH1 variant, it effectively protects animal model from the highly pathogenic and neutralization resistant SARS-CoV-2 Beta variant. Thus, we describe a novel set of mutations that can increase the production and efficacy of S-based COVID-19 vaccines.

immunology↗

bioRxiv2023

A Novel Monoclonal Antibody Targeting a Large Surface of the Receptor Binding Motif Shows Pan-neutralizing SARS-CoV-2 Activity Including BQ.1.1 Variant

In the present study we report the functional and structural characterization of 17T2, a new highly potent pan-neutralizing SARS-CoV-2 human monoclonal antibody (mAb) isolated from a convalescent COVID-19 individual infected during the first wave of the COVID-19 pandemic. 17T2 is a class 1 VH1-58/{kappa}3-20 antibody, derived from a receptor binding domain (RBD)-specific IgA memory B cell and developed as a human recombinant IgG1. Functional characterization revealed that 17T2 mAb has a high and exceptionally broad neutralizing activity against all SARS-CoV-2 spike variants tested, including BQ.1.1. Moreover, 17T2 mAb has in vivo prophylactic activity against Omicron BA.1.1 infection in K18-hACE2 transgenic mice. 3D reconstruction from cryogenic-electron microscopy (cryo-EM) showed that 17T2 binds the Omicron BA.1 spike protein with the RBD domains in "up" position and recognizes an epitope overlapping with the receptor binding motif, as it is the case for other structurally similar neutralizing mAbs, including S2E12. Yet, unlike S2E12, 17T2 retained its high neutralizing activity against all Omicron sublineages tested, probably due to a larger contact area with the RBD, which could confer a higher resilience to spike mutations. These results highlight the impact of small structural antibody changes on neutralizing performance and identify 17T2 mAb as a potential candidate for future therapeutic and prophylactic interventions.

immunology↗

bioRxiv2021

Previous SARS-CoV-2 infection increases B.1.1.7 cross-neutralization by vaccinated individuals.

To assess the potential impact of predominant circulating SARS-CoV-2 variants on neutralizing activity of infected and/or vaccinated individuals, we analyzed neutralization of pseudoviruses expressing the spike of the original Wuhan strain, the D614G and B.1.1.7 variants. Our data show that parameters of natural infection (time from infection and infecting variant) determined cross-neutralization. Importantly, upon vaccination, previously infected individuals developed equivalent B.1.1.7 and Wuhan neutralizing responses. In contrast, uninfected vaccinees showed reduced neutralization against B.1.1.7. FundingThis study was funded by Grifols, the Departament de Salut of the Generalitat de Catalunya, the Spanish Health Institute Carlos III, CERCA Programme/Generalitat de Catalunya, and the crowdfunding initiatives #joemcorono, BonPreu/Esclat and Correos.

immunology↗

bioRxiv2020

Stable neutralizing antibody levels six months after mild and severe COVID-19 episode

Understanding mid-term kinetics of immunity to SARS-CoV-2 is the cornerstone for public health control of the pandemic and vaccine development. However, current evidence is rather based on limited measurements, thus losing sight of the temporal pattern of these changes1-6. In this longitudinal analysis, conducted on a prospective cohort of COVID-19 patients followed up to 242 days, we found that individuals with mild or asymptomatic infection experienced an insignificant decay in neutralizing activity that persisted six months after symptom onset or diagnosis. Hospitalized individuals showed higher neutralizing titers, which decreased following a two-phase pattern, with an initial rapid decline that significantly slowed after day 80. Despite this initial decay, neutralizing activity at six months remained higher among hospitalized individuals. The slow decline in neutralizing activity at mid-term contrasted with the steep slope of antibody titers change, reinforcing the hypothesis that the quality of immune response evolves over the post-convalescent stage4,5.

immunology↗