A gold nanoparticle/peptide vaccine designed to induce SARS-CoV-2-specific CD8 T cells: a double-blind, randomized, phase 1 study in Switzerland

Abstract

Background: New vaccines with broader protection against SARS-CoV-2 are needed to reduce the risk of immune escape and provide broad and long-lasting cellular immunity. The objectives of the naNO-COVID trial were to evaluate the safety and immunogenicity of a CD8 + T cell, gold nanoparticle-based, peptide COVID-19 vaccine.

Methods: A randomized, double-blind, vehicle-controlled, phase 1 trial in healthy adults to receive PepGNP-Covid19 or Vehicle-GNP, followed over 180 days, using a dose-escalation strategy.

Results: Twenty participants received PepGNP-Covid19 (low dose [LD] or high dose [HD], n = 10 each) and six Vehicle-GNP (LD or HD, n = 3 each). Vaccinations were safe. No serious adverse events were reported. Most of the adverse events were mild, two adverse events of special interest related to the product (fever and fatigue). Reactogenicity was similar overall between vaccine, comparator, and doses. Virus-specific humoral responses in LD PepGNP-Covid19 and Vehicle-GNP groups coincided with SARS-CoV-2 infections. PepGNP-Covid19 vaccination induced the modulation of Covid19-specific CD137 + CD69 + CD8 + , and an increase at day 35 particularly in central and effector memory T cells in LD group, and in late effector memory cells in HD group.

Conclusions: The favourable safety profile and cellular responses observed support further development of PepGNP-Covid19.

Trial registration: ClinicalTrials.gov, NCT05113862, approved 09.11.2021.

Keywords: COVID-19; Cellular; Immunity; Nanoparticle; SARS-CoV-2; Vaccine.

Fig. 1

Graphical abstract. Overview of the naNO-COVID trial

Fig. 2

naNO-COVID trial profile and COVID-19 epidemiological context. a Participants were enrolled according to a dose-escalation protocol and randomly assigned within each dose group to receive two doses of PepGNP-Covid19 (gold nanoparticles and SARS-CoV-2 peptides) or Vehicle-GNP (gold nanoparticles only). Two participants did not receive the second vaccination: one HD PepGNP-Covid19-recipient due to an allergic reaction (rash, pruritus and CRP elevation) after the first injection and one LD PepGNP-Covid19-recipient due to confirmed COVID-19 preceding the second vaccination. All participants completed 180 days of follow-up. GNP = gold nanoparticle. b Time of events: time of first COVID-19 vaccination (if any) in blue; time of first COVID-19 (if any) in orange, orange asterisks refer to 3 probable COVID-19 infections (cases of flu-like symptoms followed by a raise in anti-N IgG); time of first and second PepGNP-Covid19 injections in yellow; the green line represents the number of weekly COVID-19 cases in Switzerland

Fig. 3

Local and systemic solicited reactogenicity* and delayed erythema and swelling. n = 3 in the LD and HD vehicle-GNP groups. n = 10 in the LD and HD PepGNP-Covid19 groups, except for the second vaccination in which n = 9. *Solicited local and systemic reactogenicity: signs/symptoms occurring within 7 and 14 days post-vaccination, respectively. GNP = gold nanoparticles; LD = low-dose; HD = high-dose

Fig. 4

Anti-SARS-CoV-2 serology. Kinetics of anti-S (top panels) and anti-N (bottom panels) IgG levels are shown in Vehicle-GNP (n = 6), LD-PepGNP-Covid19 (n = 10) and HD-PepGNP-Covid19 (n = 10) groups. Intra-group comparisons using Friedman tests, p values < 0.05 are indicated below each panel. Inter-group comparison using Kruskal–Wallis tests at each time-point; *, p < 0.05; **, p < 0.01. Anti-N IgG titres above 6 AU (green line) are positive. Symbols: grey, COVID-19; pink, flu-like symptoms; yellow, Spike SARS-CoV-2 vaccination. N, nucleoprotein

Fig. 5

PepGNP-Covid19-elicited specific CD8 T cells. a AIM + CD8 responses. Kinetics of CD8 responses were evaluated in groups Vehicle-GNP (n = 6), LD-PepGNP-Covid19 (n = 10) and HD-PepGNP-Covid19 (n = 10). Results are expressed as percentage of Covid-specific CD8 + over total CD8 + , stimulated minus control (Vehicle-GNP or unstimulated), specific CD8 + defined as co-expressing CD137 and CD69 (top) or CD107a and CD25 (bottom) upon stimulation with PepGNP-Covid19 (left) or Covid19 peptides (right). b Dextramer CD8 responses were evaluated using eight Covid19 dextramers (C-dextr) in groups Vehicle-GNP (n = 5), LD-PepGNP-Covid19 (n = 10) and HD-PepGNP-Covid19 (n = 10) at D0, D35 and D180. Results are expressed as number of C-dextr + CD8 + T cells over 10⁵ total CD8 + T cells, as the sum of C-dextr + responses for each volunteer and number of responders (left), and as change from baseline as the ratio of post-/ pre-vaccination response (right). Responses to one to four C-dextr per volunteer were assessed. Green lines indicate cut-offs used to define responder: 112.2 C-dextr + CD8 + / 10.⁵ CD8 + T cells and a post/pre ratio of 1.2. a and b) intra-group comparison with D0 using Friedman tests; inter group comparisons using Kruskal–Wallis tests. Bars indicate medians and 95% CI, boxes indicate IQR. p values < 0.05 are indicated. Symbols: grey, reported COVID-19; pink, probable COVID-19

Fig. 6

PepGNP-Covid19-specific CD8 + memory subsets. Covid19-specific responses were assessed in volunteers from group Vehicle-GNP (n = 5), LD-PepGNP-Covid19 (n = 10) and HD-PepGNP-Covid19 (n = 10), from D0 to D180, by measuring the frequency of specific AIM + CD8 + (PepGNP-Covid19-CD137 + CD69 + CD8 + , left panels) or using HLA class I compatible Covid19 dextramers from a list of eight peptide/flurochrome combinations (Covid19-dextr + CD8, right panels). Results are expressed as percentage of AIM + CD8 + and number of C-dextramer + CD8 + T cells + over 10.⁵ total CD8 + T cells for each memory subset for each volunteer. CD8 + T cells subsets were defined as naïve (CD45RA + CCR7 + CD95-), stem cell memory (Tscm, CD45RA + CCR7 + CD95 +), central memory (Tcm, CD45RA-CCR7 +), effector memory (Tem, CD45RA-CCR7-) and differentiated effector memory (TemRA, CD45RA + CCR7-). Responses to one to four C-dextramers minus negative control were summed per volunteer. Intra-group comparison with D0 used Friedman tests. Inter-group comparison used Kruskal–Wallis tests. p values < 0.05 are indicated. Bars indicate medians and 95% CI. Tscm not done for AIM. Symbols: grey, reported COVID-19; pink, probable COVID-19