Biology subjects

Silverman, J. B.

Publications and source records attributed to Silverman, J. B..

4 recordsLinked to original sources

bioRxiv2026

Title: Combinatorial bnAb and T Cell Immunization Enhances Post-Infection Control of SHIVSF162p3 Viremia in Rhesus Macaques

An ideal HIV-1 vaccine should provide broad protection against most HIV-1 variants, control early dissemination of infected cells after virus acquisition, and avoid the risk that vaccine-induced, HIV-specific CD4+ T cells serve as targets for viral transmission. In this study, we modeled this complex host-virus interaction in rhesus macaques challenged with a single high dose of SHIVSF162p3. Specifically, we evaluated the impact of T cell immunization with a human adenovirus-5-based candidate vaccine encoding an SIV Gag-Tat fusion (AdHu5SIVGag/Tat) alongside a partially protective, limiting dose of the broadly neutralizing antibody (bnAb) PGT121. Immunization with AdHu5SIVGag/Tat elicited Gag-specific CD4+ and CD8+ T cell responses in PBMC and mucosal tissue. T cell vaccination did not affect PGT121-mediated protection against SHIVSF162p3 acquisition. However, independently of vaccination, constitutively activated CD4+4{beta}7+Ki-67+ T cells in rectal tissue attenuated PGT121-mediated protection. Crucially, a unique pattern of post-infection control of SHIVSF162p3 viremia emerged in AdHu5SIVGag/Tat-immunized, PGT121-treated animals, characterized by an increased eclipse phase, lower peak viremia, and a late-phase decay in steady-state viremia. These results suggest potential synergy between bnAbs and AdHu5SIVGag/Tat-induced antiviral T cell responses, with significant implications for HIV-1 vaccine development and early interventions following infection.

immunology↗

bioRxiv2024

Intestinal tuft cells assemble a cytoskeletal superstructure composed of co-aligned actin bundles and microtubules

Background & AimsAll tissues consist of a distinct set of cell types, which collectively support organ function and homeostasis. Tuft cells are a rare epithelial cell type found in diverse epithelia, where they play important roles in sensing antigens and stimulating downstream immune responses. Exhibiting a unique polarized morphology, tuft cells are defined by an array of giant actin filament bundles that support [~]2 m of apical membrane protrusion and extend over 7 m towards the cells perinuclear region. Despite their established roles in maintaining intestinal epithelial homeostasis, tuft cells remain understudied due to their rarity (e.g. [~] 1% in the small intestinal epithelium). Details regarding the ultrastructural organization of the tuft cell cytoskeleton, the molecular components involved in building the array of giant actin bundles, and how these cytoskeletal structures support tuft cell biology remain unclear. MethodsTo begin to answer these questions, we used advanced light and electron microscopy to perform quantitative morphometry of the small intestinal tuft cell cytoskeleton. ResultsWe found that tuft cell core bundles consist of actin filaments that are crosslinked in a parallel "barbed-end out" configuration. These polarized structures are also supported by a unique group of tuft cell enriched actin-binding proteins that are differentially localized along the giant core bundles. Furthermore, we found that tuft cell actin bundles are co-aligned with a highly ordered network of microtubules. ConclusionsTuft cells assemble a cytoskeletal superstructure that is well positioned to serve as a track for subcellular transport along the apical-basolateral axis and in turn, support the dynamic sensing functions that are critical for intestinal epithelial homeostasis. SYNOPSISThis research leveraged advanced light and electron microscopy to perform quantitative morphometry of the intestinal tuft cell cytoskeleton. Three-dimensional reconstructions of segmented image data revealed a co-aligned actin-microtubule superstructure that may play a fundamental role in tuft cell function.

cell biology↗

bioRxiv2023

Adhesion-based capture stabilizes nascent microvilli at epithelial cell junctions

Differentiated transporting epithelial cells present an extensive apical array of microvilli - a "brush border" - where neighboring microvilli are linked together by intermicrovillar adhesion complexes (IMACs) composed of protocadherins CDHR2 and CDHR5. Although loss-of-function studies provide strong evidence that IMAC function is needed to build a mature brush border, how the IMAC contributes to the stabilization and accumulation of nascent microvilli remains unclear. We found that, early in differentiation, the apical surface exhibits a marginal accumulation of microvilli, characterized by higher packing density relative to medial regions of the surface. While medial microvilli are highly dynamic and sample multiple orientations over time, marginal protrusions exhibit constrained motion and maintain a vertical orientation. Unexpectedly, we found that marginal microvilli span the junctional space and contact protrusions on neighboring cells, mediated by complexes of CDHR2/CDHR5. FRAP analysis indicated that these transjunctional IMACs are highly stable relative to adhesion complexes between medial microvilli, which explains the restricted motion of protrusions in the marginal zone. Finally, long-term live imaging revealed that the accumulation of microvilli at cell margins consistently leads to accumulation in medial regions of the cell. Collectively, our findings suggest that nascent microvilli are stabilized by a capture mechanism that is localized to cell margins and enabled by the transjunctional formation of IMACs. These results inform our understanding of how apical specializations are assembled in diverse epithelial systems.

cell biology↗

bioRxiv2021

Polyclonal antibody responses to HIV Env immunogens resolved using cryoEM

In BriefHerein, we evaluated the immunogenicity of several BG505 SOSIP-based HIV Env immunogens in the rhesus macaque animal model using a combination of serology and biophysical approaches. We applied electron cryo-microscopy for high-resolution mapping of elicited polyclonal antibody responses, which provided detailed insights into the binding modes of the most common classes of antibodies elicited by BG505 SOSIP immunogens as well as the critical differences in immunogenicity that can occur as a consequence of engineered stabilizing mutations and partial glycan occupancy at different sites. SummaryEngineered ectodomain trimer immunogens based on BG505 envelope glycoprotein are widely utilized as components of HIV vaccine development platforms. In this study, we used rhesus macaques to evaluate the immunogenicity of several stabilized BG505 SOSIP constructs both as free trimers and presented on a nanoparticle. We applied a cryoEM-based method for high-resolution mapping of polyclonal antibody responses elicited in immunized animals (cryoEMPEM). Mutational analysis coupled with neutralization assays were used to probe the neutralization potential at each epitope. We demonstrate that cryoEMPEM data can be used for rapid, high-resolution analysis of polyclonal antibody responses without the need for monoclonal antibody isolation. This approach allowed to resolve structurally distinct classes of antibodies that bind overlapping sites. In addition to comprehensive mapping of commonly targeted neutralizing and non-neutralizing epitopes in BG505 SOSIP immunogens, our analysis revealed that epitopes comprising engineered stabilizing mutations and of partially occupied glycosylation sites can be immunogenic. Graphical abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

immunology↗