A randomized, double-blind, placebo-controlled, dose-escalating phase I trial to evaluate safety and immunogenicity of a plant-produced, bivalent, recombinant norovirus-like particle vaccine

Abstract

Noroviruses (NoV) are the leading cause of epidemic acute gastroenteritis in humans worldwide and a safe and effective vaccine is needed. Here, a phase I, double-blind, placebo-controlled clinical trial was performed in 60 healthy adults, 18 to 40 years old. Safety (primary objective) and immunogenicity (secondary and exploratory objectives) of a bivalent (GI.4 and GII.4), plant-produced, virus-like particle (VLP), NoV vaccine candidate formulation were investigated at two dose levels (50 µg + 50 µg and 150 µg + 150 µg) without adjuvant. Overall, 13 subjects (65.0%) in the 50 µg group, 16 subjects (80.0%) in the 150 µg group, and 14 subjects (70.0%) in the placebo group reported at least 1 solicited local or general symptom during the 7-day post-vaccination periods following each dose. Severe solicited adverse events (AEs) were rare (2 events in the 50 µg group). A total of 8 subjects (40.0%) in each group reported at least one unsolicited AE during the 28-day post-vaccination periods. Immunogenicity was assessed on days 1, 8, 29, 57, 183 and 365. All subjects were pre-exposed to norovirus as indicated by baseline levels of the different immunological parameters examined. Vaccine-specific humoral and cellular immune responses increased after the first dose but did not rise further after the second vaccination. Increased GI.4- and GII.4-specific IgG titers persisted until day 365. The vaccine elicited cross-reactive IgG antibodies against non-vaccine NoV VLPs, which was more pronounced for NoV strains of the same genotype as the GII.4 vaccine strain than for non-vaccine genotypes. Significant blocking anti-GI.4 and anti-GII.4 VLP titers were triggered in both dose groups. Lymphoproliferation assays revealed strong cell-mediated immune responses that persisted until day 365. In conclusion, both dose levels were safe and well-tolerated, and no higher incidence of AEs was observed in the higher dose group. The data show that a single dose of the vaccine formulated at 50 µg of each VLP is sufficient to reach a peak immune response after 8 to 28 days. The results of this Phase I study warrant further evaluation of the non-adjuvanted vaccine candidate.

Clinical trial registration: https://ichgcp.net/clinical-trials-registry/NCT05508178, identifier (NCT05508178).

Keywords: adults; clinical trial; immunogenicity; norovirus; plant-produced; safety; vaccine; virus-like particle.

Conflict of interest statement

Author GL-R was retained as a consultant by Icon Genetics GmbH (Halle, Germany) to assist in the design and management of the trial, analysis of results and development of the manuscript. AD, FJ, FT, VK, HA, and KH are employees of Icon Genetics GmbH (Halle, Germany), a wholly owned subsidiary of DENKA Company, Ltd (Tokyo, Japan). The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declare that this trial has received funding from DENKA Company, Ltd (Tokyo, Japan), through its wholly owned subsidiary company, Icon Genetics GmbH (Halle, Germany). The funder was involved in the study design, analysis and interpretation of data, the writing of this article, and the decision to submit it for publication.

Copyright © 2022 Leroux-Roels, Maes, Joye, Jacobs, Jarczowski, Diessner, Janssens, Waerlop, Tamminen, Heinimäki, Blazevic, Leroux-Roels, Klimyuk, Adachi, Hiruta and Thieme.

Figures

Figure 1

Electron micrographs of the highly purified, plant-produced, norovirus-like particles and vaccine formulations. VLPs formed by (A) GI.4 Chiba 407 (1987) capsid protein VP1 (batch IN003); (B) GII.4 Aomori 2 (2006) capsid protein VP1 (batch IN002); and formulated vaccine (1:1 mixture of both) at (C) 50 µg + 50 µg (batch IN004) and (D) 150 µg + 150 µg (batch IN005). Clinical batches were examined by transmission electron microscopy following negative staining with uranyless. The black bar corresponds to 250 nm. VLP, virus-like particle.

Figure 2

Subject disposition.

Figure 3

Solicited local and general adverse events during the 7-day post-vaccination period. Percentages of participants (with exact 95% confidence intervals) reporting solicited local adverse events (pain, redness and swelling) and general adverse events (arthralgia, fatigue, gastrointestinal symptoms, headache, myalgia, shivering and fever) possibly related to the vaccination during the 7-day post-vaccination period after each dose and overall per subject. Gastrointestinal symptoms defined as nausea, vomiting, diarrhea and/or abdominal pain. Fever defined as temperature ≥38.0°C. Error bars for zero values are omitted for the sake of clarity.

Figure 4

Humoral anti-GI.4 and anti-GII.4 VLP IgG responses. Humoral anti-GI.4 and anti-GII.4 VLP IgG responses by scheduled time for each treatment. OD values were processed using a 4-parameter logistic fitting algorithm to the standard curve, allowing the determination of antibody concentration in the samples, expressed as EU/mL. Anti-GI.4 (A) and anti-GII.4 (B). VLP IgG responses for rNV-2v 50 µg (grey), 150 µg (black) and placebo (white) are shown as boxplots. The horizontal line represents the median, the bottom and top of the box represent 25th and 75th percentiles of the values, respectively, and the upper and lower error bar represent 5th and 95th percentile of the values, respectively. Diamond indicates mean value. Dots represent outliers. IgG, immunoglobulin G, VLP, virus-like particle.

Figure 5

Humoral, cross-reactive anti-GI.3, anti-GII.4 and anti-GII.17 VLP IgG responses. Humoral, cross-reactive IgG responses against non-vaccine strain VLP scheduled time for each treatment. The cross-reactive IgG titer is defined as the reciprocal of the highest serum dilution that gives a positive result. Anti-GI.3 (2002) (A), anti-GII.4 (1999) (B), anti-GII.17 Kawasaki 308 (2015) (C) and anti-GII.4 Sydney (2012) (D) VLP IgG responses for rNV-2v 50 µg (grey), 150 µg (black) and placebo (white) are shown as boxplots. The horizontal line represents the median, the bottom and top of the box represent 25th and 75th percentiles of the values, respectively, and the upper and lower error bar represent 5th and 95th percentile of the values, respectively. IgG, immunoglobulin G, VLP virus-like particle.

Figure 6

Serum antibodies blocking GI.4 and GII.4 VLP binding to histo-blood group antigen. Blocking of binding of GI.4 VLP (A) and GII.4 VLP (B) to Pig Gastric Mucin by antibodies elicited by rNV-2v 50µg (gray), 150 µg (black) and placebo (white) expressed as half maximal inhibitory concentration (IC50) which represents the effective concentration (titer) of the serum where the blocking of the VLP binding is reduced by half of the maximal VLP blocking. The horizontal line represents the median, the bottom and top of the box represent 25th and 75th percentiles of the values, respectively, and the upper and lower error bar represent 5th and 95th percentile of the values, respectively. PGM, Pig Gastric Mucin, VLP, virus-like particle.

Figure 7

Cellular immune response. Cellular immune response measured as GI.4 and GII.4 VLP-specific lymphoproliferative responses by scheduled time for each study group. GI.4 (A) and GII.4 (B) VLP-specific responses for rNV-2v 50µg (grey), 150 µg (black) and placebo (white) are expressed as stimulation indices and shown as boxplots. The horizontal line represents the median, the bottom and top of the box represent 25th and 75th percentiles of the values, respectively, and the upper and lower error bar represent 5th and 95th percentile of the values, respectively. VLP, virus-like particle.