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BACKGROUND: Neoantigens are promising immunogens for cancer vaccines and are often delivered as adjuvanted peptide vaccines. Adenoviral (Ad) vectors have been shown to induce strong CD8+ T cell responses as vaccines against SARS-CoV-2, Ebola, and Zika, but their utility as neoantigen delivery vectors remains largely unexplored. In this study, we examine how an Ad-vectored neoantigen vaccine would impact tumor immunity compared with a peptide neoantigen vaccine.

METHODS: We generated Ad serotype 26 (Ad26) vaccine candidates encoding B16-F10-ovalbumin (OVA) and MC38-specific neoantigens. Ad26 vaccines were compared with adjuvanted peptide delivery as prophylactic vaccines in B16-F10-OVA and MC38 challenge models. Immune responses induced by the best Ad26 vaccine (Ad26.VP22.7Epi) were compared with peptide vaccination systemically and within the tumor. Following vaccination with Ad26.VP22.7Epi, peptide, or sham, tumor-infiltrating CD45+ cells were analyzed using single-cell RNA sequencing (scRNA-seq) and T cell receptor sequencing (TCR-seq) to identify vaccine-induced differences in the tumor microenvironment.

RESULTS: Single-shot Ad26 vaccines induced greater neoantigen-specific interferon-γ CD8+ T cell immune responses than two-shot adjuvanted peptide vaccines in mice, and Ad26.VP22.7Epi also provided superior protective efficacy compared with the peptide vaccine following tumor challenge. Ad26.VP22.7Epi induced a robust immunodominant CD8+ T cell response against the Adpgk neoantigen, while the peptide vaccine-induced lower responses against both Adpgk and Reps1 neoantigens. scRNA-seq analysis of CD45+ tumor-infiltrating cells demonstrated that both Ad26.VP22.7Epi and peptide vaccine-induced similar numbers of infiltrating CD8+ T cells. However, Ad26.VP22.7Epi induced CD8+ T cells showed more upregulation of T cell maturation, activation, and Th1 pathways compared with peptide vaccine induced CD8+ T cells, suggesting improved functional T cell quality. TCR-seq of these tumor-infiltrating lymphocytes also demonstrated that Ad26.VP22.7Epi generated larger T cell hyperexpanded clones compared with the peptide vaccine.

CONCLUSIONS: These results suggest that the Ad26.VP22.7Epi vaccine led to improved tumor control compared with the peptide vaccine due to increased T cell hyperexpansion and functional activation. Our data suggest that future cancer vaccine development strategies should focus on inducing functional hyperexpanded CD8+ T cell responses and not only maximizing tumor infiltrating CD8+ T cell numbers.

As the first responder to immunological challenges, the innate immune system shapes and regulates the ensuing adaptive immune response. Many clinical studies evaluating the role of innate immunity in initiating vaccine-elicited adaptive immune responses have largely been confined to blood due to inherent difficulty in acquiring tissue samples. However, the absence of vaccine-site and draining lymph node information limits understanding of early events induced by vaccination that could potentially shape vaccine-elicited immunity. We therefore utilized a mouse model to investigate the spatiotemporal evolution of the immune response within the first 24 hours following intramuscular adenovirus serotype 26 (Ad26) vector vaccination in tissues. We show that the Ad26 vaccine-elicited innate immune response commences by one hour and rapidly evolves in tissues and blood within the first 24 hours as reflected by the detection of cytokines, chemokines, cellular responses, and transcriptomic pathways. Furthermore, serum levels of IL-6, MIG, MIP-1α, and MIP-1β at 6 hours post-vaccination correlated with the frequency of vaccine-elicited memory CD8+ T cell responses evaluated at 60 days post-vaccination in blood and tissues. Taken together, our data suggests that the immune response to Ad26 vector vaccination commences quickly in tissues by one hour and that events by as early as 6 hours post-vaccination can shape vaccine-elicited CD8+ T cell responses at later memory time points.

Zika virus (ZIKV) is a mosquito-borne flavivirus that caused a global pandemic in 2016-2017 with continued ongoing transmission at low levels in several countries. In the absence of an approved ZIKV vaccine, neutralizing monoclonal antibodies (mAbs) provide an option for the prevention and treatment of ZIKV infection. Previous studies identified a potent neutralizing human mAb ZIKV-117 that reduced fetal infection and death in mice following ZIKV challenge. In this study, we report exquisite potency of ZIKV-117-LALA-YTE, which has been engineered to reduce Fc receptor binding and to extend half-life, in a titration study in rhesus macaques to protect against ZIKV challenge. We show complete protection at a dose of 0.016 mg/kg ZIKV-117-LALA-YTE, which resulted in median serum concentrations of 0.13 µg/mL. The high potency of this mAb supports its potential clinical development as a novel biotherapeutic intervention for ZIKV.IMPORTANCEIn this study, we report the potency of the Zika virus (ZIKV)-specific neutralizing antibody ZIKV-117-LALA-YTE against ZIKV challenge in a titration study rhesus macaques. This high potency supports the further development of this monoclonal antibody for ZIKV.

Human immunodeficiency virus type 1 (HIV-1)-specific broadly neutralizing monoclonal antibodies (bNAbs) have to date shown transient viral suppression when administered as monotherapy or as a cocktail of two antibodies1-4. A combination of three bNAbs provides improved neutralization coverage of global viruses, which may more potently suppress viral escape and rebound5-7. Here we performed an open-label, two-part study evaluating a single intravenous dose of HIV-1 bNAbs, PGT121, PGDM1400 and VRC07-523LS, in six adults without HIV in part 1 and a multicenter trial of up to six monthly infusions of these three bNAbs in 12 people living with HIV with an antiretroviral therapy (ART) interruption in part 2. The primary endpoints were safety, tolerability and pharmacokinetics, and the secondary endpoints in part 2 were antiviral activity following ART discontinuation, changes in CD4+ T cell counts and development of HIV-1 sequence mutations associated with bNAb resistance. The trial met its prespecified endpoints. The bNAb treatment was generally safe and well tolerated. In part 2, 83% of participants (10 of 12) maintained virologic suppression for the duration of antibody therapy for at least 28 weeks, and 42% of participants (5 of 12) showed virologic suppression for at least 38-44 weeks, despite the decline of serum bNAb concentrations to low or undetectable levels. In exploratory analyses, early viral rebound in two individuals correlated with baseline resistance to PGT121 and PGDM1400, whereas long-term virologic control in five individuals correlated with reduced immune activation, T cell exhaustion and proinflammatory signaling following bNAb therapy. Our data show the potential of a triple bNAb cocktail to suppress HIV-1 in the absence of ART. ClinicalTrials.gov registration: NCT03721510 .

A limitation of current SARS-CoV-2 vaccines is that they provide minimal protection against infection with current Omicron subvariants1,2, although they still provide protection against severe disease. Enhanced mucosal immunity may be required to block infection and onward transmission. Intranasal administration of current vaccines has proven inconsistent3-7, suggesting that alternative immunization strategies may be required. Here we show that intratracheal boosting with a bivalent Ad26-based SARS-CoV-2 vaccine results in substantial induction of mucosal humoral and cellular immunity and near-complete protection against SARS-CoV-2 BQ.1.1 challenge. A total of 40 previously immunized rhesus macaques were boosted with a bivalent Ad26 vaccine by the intramuscular, intranasal and intratracheal routes, or with a bivalent mRNA vaccine by the intranasal route. Ad26 boosting by the intratracheal route led to a substantial expansion of mucosal neutralizing antibodies, IgG and IgA binding antibodies, and CD8+ and CD4+ T cell responses, which exceeded those induced by Ad26 boosting by the intramuscular and intranasal routes. Intratracheal Ad26 boosting also led to robust upregulation of cytokine, natural killer, and T and B cell pathways in the lungs. After challenge with a high dose of SARS-CoV-2 BQ.1.1, intratracheal Ad26 boosting provided near-complete protection, whereas the other boosting strategies proved less effective. Protective efficacy correlated best with mucosal humoral and cellular immune responses. These data demonstrate that these immunization strategies induce robust mucosal immunity, suggesting the feasibility of developing vaccines that block respiratory viral infections.

A limitation of current SARS-CoV-2 vaccines is that they provide minimal protection against infection with current Omicron subvariants1,2, although they still provide protection against severe disease. Enhanced mucosal immunity may be required to block infection and onward transmission. Intranasal administration of current vaccines has proven inconsistent3-7, suggesting that alternative immunization strategies may be required. Here we show that intratracheal boosting with a bivalent Ad26-based SARS-CoV-2 vaccine results in substantial induction of mucosal humoral and cellular immunity and near-complete protection against SARS-CoV-2 BQ.1.1 challenge. A total of 40 previously immunized rhesus macaques were boosted with a bivalent Ad26 vaccine by the intramuscular, intranasal and intratracheal routes, or with a bivalent mRNA vaccine by the intranasal route. Ad26 boosting by the intratracheal route led to a substantial expansion of mucosal neutralizing antibodies, IgG and IgA binding antibodies, and CD8+ and CD4+ T cell responses, which exceeded those induced by Ad26 boosting by the intramuscular and intranasal routes. Intratracheal Ad26 boosting also led to robust upregulation of cytokine, natural killer, and T and B cell pathways in the lungs. After challenge with a high dose of SARS-CoV-2 BQ.1.1, intratracheal Ad26 boosting provided near-complete protection, whereas the other boosting strategies proved less effective. Protective efficacy correlated best with mucosal humoral and cellular immune responses. These data demonstrate that these immunization strategies induce robust mucosal immunity, suggesting the feasibility of developing vaccines that block respiratory viral infections.