Biology subjects

Kasturi, S. P.

Publications and source records attributed to Kasturi, S. P..

9 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↗

bioRxiv2026

Germinal centers can persist for up to one year with declining somatic hypermutation and ongoing plasma cell output

The total duration of primary germinal center (GC) responses, and how B cell evolution changes as these responses mature, remain poorly defined. Here, longitudinal sampling of rhesus macaques immunized with HIV Envelope protein revealed that a single slow-delivery prime sustained ongoing GCs for nearly a year without additional antigen. Somatic hypermutation (SHM) accumulated throughout these prolonged responses, but its rate declined substantially over time, independent of both priming strategy and boosting. Over the same period, subdominant non-base Env specificities became increasingly represented within the GC response. Delaying boosting until after primary GC contraction increased recruitment of recalled memory B cells into the GC response. Bone marrow plasma cells were generated throughout prolonged GC maturation, with the timing of their generation modulated by booster timing. Together, these findings reveal how GCs evolve across nearly a year and how this prolonged maturation shapes the memory and plasma cell compartments that underpin long-term humoral immunity.

immunology↗

bioRxiv2025

A unified network systems approach uncovers a core novel program underlying T follicular helper cell differentiation

T follicular helper (Tfh) cells are central to the adaptive immune response and exhibit remarkable functional diversity and plasticity. The complex nature of Tfh cell populations, inconsistent findings across experimental systems and potential differences across species have fueled ongoing debate regarding core regulatory pathways that govern Tfh differentiation. Many studies have experimentally investigated individual proteins and circuits involved in Tfh differentiation in limited contexts, each providing only a partial understanding of the process. To address this, we adopted a novel multi-scale network systems approach that incorporates both regulatory and protein-protein interactions. Our approach integrates diverse data types, captures regulation across multiple levels of immune system organization, and recapitulates known drivers. Further, we discover a core Tfh gene set that is conserved across tissue types and disease contexts, and is consistent across data modalities - bulk, single-cell and spatial. While components of this set have been individually reported, a novel aspect of our work lies in the discovery, characterization, and connectivity of this core signature using a single unbiased approach. Using this method, we also uncover a novel function of IL-12, a molecule with reported conflicting functions, in the regulation of Tfh differentiation. Notably, we find that, in both humans and mice, IL-12 is permissive for the differentiation of Tfh precursors, but blocks subsequent differentiation into GC Tfh cells. Overall, this work elucidates novel networks with unexplored roles in governing Tfh cell differentiation across species and tissues, paving the way for novel -therapeutic interventions.

immunology↗

bioRxiv2025

Fusion of Complement Fragment C3d Enhances Germinal Center Responses to HIV-1 Envelope Glycoproteins

Eliciting sustained germinal center (GC) responses is critical for the development of an effective HIV-1 vaccine, yet HIV-1 envelope glycoprotein (Env) immunogens often fail to elicit GC responses required for the maturation of cognate B cells that secrete broadly neutralizing antibodies (bNAbs). Effective antigen recognition is important for initial B cell priming, activation, and GC engagement. Since complement opsonization contributes to antigen recognition, we investigated whether C3d fusion could enhance the GC response of the stabilized HIV-1 Env immunogen based on a consensus sequence (ConM Env). Our results demonstrate that ConM Env-C3d induced potent HIV-specific B cell activation in vitro compared to ConM Env alone. We also observed that the C3d fusion enhanced antigen presentation by human tonsil-derived follicular dendritic cells (FDCs) to HIV-specific B cell lines. Moreover, mouse immunization studies combining ConM Env-C3d with the AddaS03 adjuvant revealed significantly enhanced early GC formation and prolonged antigen display and retention on FDCs for up to 56 days, highlighting improved antigen persistence within GCs. These immunological enhancements, including a more focused early antibody response, correlated with improved virus neutralization. Additionally, we observed sex-based differences in immune responses, with female mice showing stronger antibody responses and enhanced antigen retention compared to males. These findings suggest that C3d fusion can enhance GC engagement and improve the immunogenicity of HIV-1 vaccines.

immunology↗

bioRxiv2025

Vaccination with mRNA-encoded membrane-bound HIV Envelope trimer induces neutralizing antibodies in animal models

A protective vaccine against HIV will likely need to induce broadly neutralizing antibodies (bnAbs) that engage relatively conserved epitopes on the HIV envelope glycoprotein (Env) trimer. Nearly all vaccine strategies to induce bnAbs require the use of relatively complex immunization regimens involving a series of different immunogens, most of which are Env trimers. Producing protein-based clinical material to evaluate such relatively complex regimens in humans presents major challenges in cost and time. Furthermore, immunization with HIV trimers as soluble proteins induces strong non-neutralizing responses to the trimer base, which is normally occluded on the virion. These base responses could potentially detract from the induction of nAbs and the eventual induction of bnAbs. mRNA vaccine platforms offer potential advantages over protein delivery for HIV vaccine development, including increased production speed, reduced cost, and the ability to deliver membrane-bound trimers that might facilitate improved immuno-focusing to non-base epitopes. We report the design of mRNA-delivered soluble and membrane-bound forms of a stabilized native-like Env trimer (BG505 MD39.3), initial immunogenicity evaluation in rabbits that triggered clinical evaluation, and more comprehensive evaluation of B cell, T cell, and antibody responses in non-human primates. mRNA-encoded membrane-bound Env immunization elicited reduced off-target base-directed Env responses and stronger neutralizing antibody responses, compared with mRNA-encoded soluble Env. Overall, mRNA delivery of membrane-bound Env appears promising for enhancing B cell responses to subdominant epitopes and facilitating rapid translation to clinical testing, which should assist HIV vaccine development. One Sentence SummaryHIV envelope trimer mRNA enables membrane-bound expression and represents a functional immunogen in pre-clinical mammalian models.

immunology↗

bioRxiv2024

Diverse priming outcomes under conditions of very rare precursor B cells

Rare B cells can have special pathogen-recognition features giving them the potential to make outsized contributions to protective immunity. However, rare naive B cells infrequently participate in immune responses. We investigated how germline-targeting vaccine antigen delivery and adjuvant selection affect priming of exceptionally rare BG18-like HIV broadly neutralizing antibody-precursor B cells (~1 in 50 million) in non-human primates. Only escalating dose (ED) priming immunization using the saponin adjuvant SMNP elicited detectable BG18-like cells in germinal centers (GCs). All groups had strong GC responses, but only ED+SMNP and bolus+SMNP induced BG18-like memory B cells in >50% of animals. One group had vaccine-specific GC responses equivalent to ED+SMNP, but BG18-like memory B cells were rarely detected. Following homologous boosting, BG18-like memory B cells were more frequent in a bolus priming group, but had lower somatic hypermutation and affinities. This outcome was inversely associated with post-prime antibody titers, suggesting antibody feedback can significantly influence rare precursor B cell responses.

immunology↗

bioRxiv2024

Dose-dependent regulation of immune memory responses against HIV by saponin monophosphoryl lipid A nanoparticle adjuvant

The induction of durable protective immune responses is the main goal of prophylactic vaccines, and adjuvants play an important role as drivers of such responses. Despite advances in vaccine strategies, a safe and effective HIV vaccine remains a significant challenge. The use of an appropriate adjuvant is crucial to the success of HIV vaccines. Here we assessed the saponin/MPLA nanoparticle (SMNP) adjuvant with an HIV envelope (Env) trimer, evaluating the safety and impact of multiple variables including adjuvant dose (16-fold dose range), immunization route, and adjuvant composition on the establishment of Env-specific memory T and B cell responses (TMem and BMem) and long-lived plasma cells in non-human primates. Robust BMem were detected in all groups, but a 6-fold increase was observed in the highest SMNP dose group vs. the lowest dose group. Similarly, stronger vaccine responses were induced in the highest SMNP dose for CD40L+OX40+ CD4 TMem (11-fold), IFN{gamma}+ CD4 TMem (15-fold), IL21+ CD4 TMem (9-fold), circulating TFH (3.6-fold), bone marrow plasma cells (7-fold), and binding IgG (1.3-fold). Substantial tier-2 neutralizing antibodies were only observed in the higher SMNP dose groups. These investigations highlight the dose-dependent potency of SMNP in non-human primates, which are relevant for human use and next-generation vaccines.

immunology↗

bioRxiv2022

Modulation of type I interferon responses potently inhibits SARS-CoV-2 replication and inflammation in rhesus macaques

Type-I interferons (IFN-I) are critical mediators of innate control of viral infections, but also drive recruitment of inflammatory cells to sites of infection, a key feature of severe COVID-19. Here, and for the first time, IFN-I signaling was modulated in rhesus macaques (RMs) prior to and during acute SARS-CoV-2 infection using a mutated IFN2 (IFN-modulator; IFNmod), which has previously been shown to reduce the binding and signaling of endogenous IFN-I. In SARS-CoV-2-infected RMs, IFNmod reduced both antiviral and inflammatory ISGs. Notably, IFNmod treatment resulted in a potent reduction in (i) SARS-CoV-2 viral load in Bronchoalveolar lavage (BAL), upper airways, lung, and hilar lymph nodes; (ii) inflammatory cytokines, chemokines, and CD163+MRC1-inflammatory macrophages in BAL; and (iii) expression of Siglec-1, which enhances SARS-CoV-2 infection and predicts disease severity, on circulating monocytes. In the lung, IFNmod also reduced pathogenesis and attenuated pathways of inflammasome activation and stress response during acute SARS-CoV-2 infection. This study, using an intervention targeting both IFN- and IFN-{beta} pathways, shows that excessive inflammation driven by type 1 IFN critically contributes to SARS-CoV-2 pathogenesis in RMs, and demonstrates the potential of IFNmod to limit viral replication, SARS-CoV-2 induced inflammation, and COVID-19 severity.

immunology↗

bioRxiv2020

Baricitinib treatment resolves lower airway inflammation and neutrophil recruitment in SARS-CoV-2-infected rhesus macaques

Effective therapeutics aimed at mitigating COVID-19 symptoms are urgently needed. SARS-CoV-2 induced hypercytokinemia and systemic inflammation are associated with disease severity. Baricitinib, a clinically approved JAK1/2 inhibitor with potent anti-inflammatory properties is currently being investigated in COVID-19 human clinical trials. Recent reports suggest that baricitinib may also have antiviral activity in limiting viral endocytosis. Here, we investigated the immunologic and virologic efficacy of baricitinib in a rhesus macaque model of SARS-CoV-2 infection. Viral shedding measured from nasal and throat swabs, bronchoalveolar lavages and tissues was not reduced with baricitinib. Type I IFN antiviral responses and SARS-CoV-2 specific T cell responses remained similar between the two groups. Importantly, however, animals treated with baricitinib showed reduced immune activation, decreased infiltration of neutrophils into the lung, reduced NETosis activity, and more limited lung pathology. Moreover, baricitinib treated animals had a rapid and remarkably potent suppression of alveolar macrophage derived production of cytokines and chemokines responsible for inflammation and neutrophil recruitment. These data support a beneficial role for, and elucidate the immunological mechanisms underlying, the use of baricitinib as a frontline treatment for severe inflammation induced by SARS-CoV-2 infection.

immunology↗