The SARS-CoV-2 index-virus nanoparticle protein vaccine (NVX-CoV2373) induces humoral and cell-mediated immune responses that protect against severe COVID-19, including from SARS-CoV-2 variants. Limited information exists on NVX-CoV2373-induced cell-mediated immune responses to ancestral SARS-CoV-2 and the Omicron variant following a homologous booster (third dose), and on T-cell responses following a booster dose compared to a single dose.
T-cell responses were investigated in participants from a randomised, placebo-controlled, phase 2A/2B trial of NVX-CoV2373 in South Africa, who had a blinded crossover at 6 months post-enrolment. Peripheral blood mononuclear cells were available for 34 participants, 7 days post-vaccination with one NVX-CoV2373 dose (n = 17) or a homologous booster (n = 17). T-cell responses to the full-length spike (FLS) glycoprotein of ancestral Wuhan-Hu-1 SARS-CoV-2 and mutated spike protein regions found in Omicron (BA.4/BA.5) were characterised by intracellular cytokine staining.
Here we show that FLS-specific T-cell responses are similar between single-dose and booster-dose recipients (CD4+: p = 0.871; CD8+: p = 0.491) and are predominantly monofunctional (IFN-γ or TNF-α). A third NVX-CoV2373 dose increases the FLS-specific polyfunctional cytokine production profile of CD4+ T cells compared with after a single dose (p = 0.045), whereas CD8+ T cells remain unaffected (p = 0.462). Only CD4+ T cells exhibit reduced reactivity to Omicron compared with ancestral SARS-CoV-2 in single-dose (p = 0.010) and in booster-dose recipients (p = 0.028).
NVX-CoV2373-induced T-cell responses to ancestral SARS-CoV-2 are comparable following vaccination with a single dose compared with a third dose administered 6 months after the second dose. Our findings suggest that an NVX-CoV2373 booster dose does not enhance T-cell immunity. Furthermore, NVX-CoV2373 vaccination induces greater T-cell response magnitudes to ancestral SARS-CoV-2, from which the vaccine is derived, compared with the Omicron variant.
© 2025. The Author(s).

Human immunodeficiency virus (HIV) persistence during antiretroviral therapy (ART) is associated with heightened plasma interleukin-10 (IL-10) levels and PD-1 expression. We hypothesized that IL-10 and PD-1 blockade would lead to control of viral rebound following analytical treatment interruption (ATI). Twenty-eight ART-treated, simian immunodeficiency virus (SIV)mac239-infected rhesus macaques (RMs) were treated with anti-IL-10, anti-IL-10 plus anti-PD-1 (combo) or vehicle. ART was interrupted 12 weeks after introduction of immunotherapy. Durable control of viral rebound was observed in nine out of ten combo-treated RMs for >24 weeks post-ATI. Induction of inflammatory cytokines, proliferation of effector CD8+ T cells in lymph nodes and reduced expression of BCL-2 in CD4+ T cells pre-ATI predicted control of viral rebound. Twenty-four weeks post-ATI, lower viral load was associated with higher frequencies of memory T cells expressing TCF-1 and of SIV-specific CD4+ and CD8+ T cells in blood and lymph nodes of combo-treated RMs. These results map a path to achieve long-lasting control of HIV and/or SIV following discontinuation of ART.
© 2024. The Author(s).

Fibrolamellar carcinoma (FLC) is a liver tumor with a high mortality burden and few treatment options. A promising therapeutic vulnerability in FLC is its driver mutation, a conserved DNAJB1-PRKACA gene fusion that could be an ideal target neoantigen for immunotherapy. In this study, we aim to define endogenous CD8 T cell responses to this fusion in FLC patients and evaluate fusion-specific T cell receptors (TCRs) for use in cellular immunotherapies. We observe that fusion-specific CD8 T cells are rare and that FLC patient TCR repertoires lack large clusters of related TCR sequences characteristic of potent antigen-specific responses, potentially explaining why endogenous immune responses are insufficient to clear FLC tumors. Nevertheless, we define two functional fusion-specific TCRs, one of which has strong anti-tumor activity in vivo. Together, our results provide insights into the fragmented nature of neoantigen-specific repertoires in humans and indicate routes for clinical development of successful immunotherapies for FLC.
Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.

SARS-CoV-2 infection in children typically results in asymptomatic or mild disease. There is a paucity of studies on SARS-CoV-2 antiviral immunity in African children. We investigated SARS-CoV-2-specific T cell responses in 71 unvaccinated asymptomatic South African children who were seropositive or seronegative for SARS-CoV-2. SARS-CoV-2-specific CD4+ T cell responses were detectable in 83% of seropositive and 60% of seronegative children. Although the magnitude of the CD4+ T cell response did not differ significantly between the two groups, their functional profiles were distinct, with SARS-CoV-2 seropositive children exhibiting a higher proportion of polyfunctional T cells compared to their seronegative counterparts. The frequency of SARS-CoV-2-specific CD4+ T cells in seronegative children was associated with the endemic human coronavirus (HCoV) HKU1 IgG response. Overall, the presence of SARS-CoV-2-responding T cells in seronegative children may result from cross-reactivity to endemic coronaviruses and could contribute to the relative protection from disease observed in SARS-CoV-2-infected children.
© 2023 The Authors.

T cell receptor (TCR) repertoire diversity enables the orchestration of antigen-specific immune responses against the vast space of possible pathogens. Identifying TCR/antigen binding pairs from the large TCR repertoire and antigen space is crucial for biomedical research. Here, we introduce copepodTCR , an open-access tool for the design and interpretation of high-throughput experimental assays to determine TCR specificity. copepodTCR implements a combinatorial peptide pooling scheme for efficient experimental testing of T cell responses against large overlapping peptide libraries, useful for “deorphaning” TCRs of unknown specificity. The scheme detects experimental errors and, coupled with a hierarchical Bayesian model for unbiased results interpretation, identifies the response-eliciting peptide for a TCR of interest out of hundreds of peptides tested using a simple experimental set-up. We experimentally validated our approach on a library of 253 overlapping peptides covering the SARS-CoV-2 spike protein. We provide experimental guides for efficient design of larger screens covering thousands of peptides which will be crucial for the identification of antigen-specific T cells and their targets from limited clinical material.