Biology subjects

Galula, J. U.

Publications and source records attributed to Galula, J. U..

4 recordsLinked to original sources

bioRxiv2025

Structural Insights into Immature Dengue Virus-Like Particles Revealed by Cryo-EM and Molecular Dynamics Simulations

The lack of efficacious vaccines against dengue (DENV) infections imposes an enormous burden on global health and the economy. Virus-like particles (VLPs), such as mature DENV VLPs (mDVLPs), have been shown to induce broadly neutralizing antibodies, making them promising next-generation vaccine candidates. However, the limited structural details have restricted efforts to engineer VLPs to attain the desired biophysical and immunological properties. In the current work, we present the cryo-electron microscopy (cryo-EM) structure of immature dengue serotype 2 VLP (imD2VLPs), revealing an architecture composed of a glycoprotein layer with prominent spikes in a T=1 arrangement. These spikes, composed of envelope (E) and precursor membrane (prM) protein heterodimers capped by pr domains, closely resemble immature flavivirus particles. Complementing the static structural details, we performed multiscale molecular dynamics (MD) simulations to elucidate the functional dynamics of imD2VLPs in the context of different lipid envelope compositions. Additionally, MD simulations uncovered the transition pathway between our previously solved mature VLP structure and immature VLP from this work. Here we show that VLP maturation involves a simple sliding-rotating motion without any clashes between E proteins. Our results also indicated that lipid composition plays a critical role in VLP stability, with phospholipid-dominant environments providing greater stability than diacylglycerol-rich vesicles. In addition, we demonstrated enhanced production efficiency of VLPs by generating a stable mammalian cell line using CHO-K1 cells. These findings enabled us not only to predict and manipulate the immunogenic properties of dengue VLPs but also underscored the potential of VLPs as a simplified and manageable model for investigating the structural basis of the dengue virus more effectively.

bioinformatics↗

bioRxiv2018

Cross-reactivity reduced dengue virus serotype 2 vaccine does not confer cross-protection against other serotypes of dengue viruses

The four serotypes of dengue virus (DENV) cause the most important rapidly emerging arthropod-borne disease globally. The humoral immune response to DENV infection is predominantly directed against the immunodominant cross-reactive weakly neutralizing epitopes located in the highly conserved fusion peptide of ectodomain II of envelope (E) protein (EDIIFP). Antibodies recognizing EDIIFP have been shown to associate with immune enhancement in an ex vivo animal model. In this study, we explored how prime-boost strategies influence the immunogenicity of a cross-reactivity reduced (CRR) DENV-2 vaccine with substitutions in EDIIFP residues (DENV-2 RD) and found that mice in various DENV-2 RD prime-boost immunizations had significantly reduced levels of EDIIFP antibodies. In addition, heterologous DENV-2 RD DNA-VLP prime-boost immunization induced higher and broader levels of total IgG and neutralizing antibodies (NtAbs) although IgG titers to DENV-2 and 3 were statistically significant. Consistently, mice from DENV-2 RD DNA-VLP prime-boost immunization were fully protected from homologous DENV-2 lethal challenge and partially protected (60% survival rate) from heterologous lethal DENV-3 challenge. Our results conclude that the CRR DENV-2 RD vaccine requires a multivalent format to effectively elicit a balanced and protective immunity across all four DENV serotypes.\n\nImportanceThe low vaccine efficacy of the live-attenuated chimeric yellow fever virus-DENV tetravalent dengue vaccine (CYD-TDV) is unexpected and there is an urgent need to develop a next generation of dengue vaccine. Antibodies against the fusion peptide in envelope protein (E) ectodomain II (EDIIFP) can potentially induce a severe disease via antibody-dependent enhancement (ADE) of infection. This study evaluated different formats of an EDIIFP-modified DENV-2 vaccine (DENV-2 RD) in its capability of inducing a reduced EDIIFP antibodies, and sculpting the immune response towards an increased DENV complex-reactive neutralizing antibodies (CR NtAb). The results from this study confirmed the poor correlate of neutralizing assay with protection as suggested by the results of CYD-TDV clinical trials. There is a urgent need to develop a biological correlate with protection while evaluating the efficacy of the next generation dengue vaccine.

immunology↗

bioRxiv2018

An epitope-resurfaced virus-like particle can induce broad neutralizing antibody against four serotypes of dengue virus

Dengue fever is caused by four different serotypes of dengue virus (DENV) which is the leading cause of worldwide arboviral diseases in humans. Virus-like particles (VLPs) containing flavivirus prM/E proteins have been demonstrated to be a potential vaccine candidate; however, the structure of dengue VLP is poorly understood. Herein we show for the first time that mD2VLP particles possess a T=1 icosahedral symmetry with a groove located within the E-protein dimers near the 2-fold vertices that exposed highly overlapping, cryptic neutralizing epitopes through cryo-electron microscopy reconstruction. Mice vaccinated with highly matured virus-like particles derived from DENV serotype 2 (mD2VLP) can generate higher cross reactive (CR) neutralization antibodies (NtAbs) and were protected against all 4 serotypes of DENV through clonal expansion supported by hybridoma and B-cell repertoire analysis. Our results revealed that a \"epitope-resurfaced\" mature-form dengue VLP has the potential to induce quaternary structure-recognizing broad CR NtAbs.

microbiology↗

bioRxiv2018

A dengue monovalent vaccine with novel structure provides cross-protection against four serotypes of dengue virus

Dengue fever is caused by four different serotypes of dengue virus (DENV) which is the leading cause of worldwide arboviral diseases in humans. The vaccine candidates under development require a tetravalent immunogen to induce a balanced immunity against all four serotypes of dengue virus. Herein we show that mice vaccinated with highly matured virus-like particles derived from DENV serotype 2 (mD2VLP) can generate higher and broader neutralization antibodies (NtAbs) against all 4 serotypes of DENV through clonal expansion supported by hybridoma and B-cell repertoire analysis. The cryo-electron microscopy reconstruction showed that mD2VLP particles possess a T=1 icosahedral symmetry with a groove located within the E-protein dimers near the 2-fold vertices that exposed highly overlapping, cryptic neutralizing epitopes. Most importantly, maternally transferred antibodies derived from mD2VLP-vaccinated female mice protected suckling mice from lethal challenge by all four serotypes of DENV. Our results support the fact that a universal dengue vaccine that protects against all four serotypes of dengue viruses can be achieved by using an immunogen such as mD2VLP.

microbiology↗