Preclinical and Clinical Demonstration of Immunogenicity by mRNA Vaccines against H10N8 and H7N9 Influenza Viruses

Abstract

Recently, the World Health Organization confirmed 120 new human cases of avian H7N9 influenza in China resulting in 37 deaths, highlighting the concern for a potential pandemic and the need for an effective, safe, and high-speed vaccine production platform. Production speed and scale of mRNA-based vaccines make them ideally suited to impede potential pandemic threats. Here we show that lipid nanoparticle (LNP)-formulated, modified mRNA vaccines, encoding hemagglutinin (HA) proteins of H10N8 (A/Jiangxi-Donghu/346/2013) or H7N9 (A/Anhui/1/2013), generated rapid and robust immune responses in mice, ferrets, and nonhuman primates, as measured by hemagglutination inhibition (HAI) and microneutralization (MN) assays. A single dose of H7N9 mRNA protected mice from a lethal challenge and reduced lung viral titers in ferrets. Interim results from a first-in-human, escalating-dose, phase 1 H10N8 study show very high seroconversion rates, demonstrating robust prophylactic immunity in humans. Adverse events (AEs) were mild or moderate with only a few severe and no serious events. These data show that LNP-formulated, modified mRNA vaccines can induce protective immunogenicity with acceptable tolerability profiles.

Keywords: H10N8; H7N9; immunogenicity; influenza; mRNA; mRNA vaccines; pandemic; vaccines.

Figure 1

Mice Immunized with H10 or H7 mRNA Generate Robust and Stable Antibody Responses Consistent with a TH1 Profile BALB/c mice were vaccinated ID with a single 10-μg dose of formulated H10 or H7 mRNA. (A) H10 and H7 indicate mean HAI titers (limit of detection is 1:10). Dotted line indicates the correlate of protection in humans (1:40). (B and C) IgG1 and IgG2a titers were measured for both H10 (B) and H7 (C) via ELISA (n = 5/group). ^ap = 0.0070, ^bp = 0.0017, and ^cp = 0.0185 versus IgG2a at the same time point. (D) BALB/c mice were immunized ID with a single 10-μg dose of formulated H10 mRNA. A subset of these mice received a 10-μg boost on day 21. Serum was collected at the indicated time points, and neutralizing antibody titers were determined by HAI (n = 15/group). Placebo controls were also included. ^dp < 0.05 single dose versus boosting dose at the same time point. Error bars indicate standard mean error.

Figure 2

A Single Injection of an H7 mRNA Vaccine Achieves Rapid and Sustained Protection in Mice BALB/c mice were vaccinated ID with 10, 2, or 0.4 μg formulated H7 mRNA. Placebo and 10 μg formulated H7 mRNA with a reduced 5′ cap structure (−15 Da cap) were included as negative controls. On day 7, 21, or 84 post-immunization, mice were challenged via intranasal (IN) instillation with a target dose of 2.5 × 10⁵ TCID₅₀ of influenza A/Anhui/1/2013 (H7N9). Serum was collected prior to challenge (days 6, 20, and 83). (A–C) Survival curves of mice challenged on day 7 (A), day 21 (B), or day 84 (C) post-immunization at the indicated doses. p < 0.0001 10-, 2-, and 0.4-μg dose groups versus placebo or −15 Da cap at days 7, 21, and 84 post-immunization. (D–F) Weight curves of mice challenged on day 7 (D), day 21 (E), or day 84 (F) post-immunization at the indicated doses (n = 15/group). Error bars indicate standard mean error.

Figure 3

A Single Dose of H10 mRNA in Ferrets Generates Robust HAI Titers, Which Are Significant and Comparable at All Time Points Ferrets were vaccinated ID with 50 or 100 μg formulated H10 mRNA. p < 0.0001, days 21, 35, and 49 versus day 0 with single doses of 50 or 100 μg; p < 0.0001 100-μg single dose, day 7 versus day 0. A subset of immunized ferrets received a boost on day 21 and an additional subset received a second boost on day 35. HAI titers were measured on days 0, 7, 21, 35, and 49 (n = 8/group). p < 0.0001 50 or 100 μg boosting dose(s), days 35 and 49 versus day 0.

Figure 4

Vaccination with Either H10 or H7 mRNA Generates Strong HAI Titers in Nonhuman Primates following ID and IM Immunizations (A and B) Male or female cynomolgus monkeys (cynos) were immunized on day 1 with 0.2 or 0.4 mg formulated H7 mRNA, both IM and ID, and received a boosting immunization on day 22. Serum was collected on days 1, 8, 15, 22, 29, 36, and 43 to determine HAI titers. (C) Male and female cynos were immunized with 0.4 mg formulated H10 mRNA via an IM or ID route and received a boosting immunization on day 22. Serum was collected on days 1, 8, 15, 22, 29, 36, and 43 to determine HAI titers (n = 1/group).

Figure 5

H10 mRNA Immunogenicity in Humans (A and B) A greater percentage of subjects who received active vaccine had an HAI ≥ 40 (A) and MN ≥ 20 (B) compared to placebo. (C and D) HAI (C) and MN (D) titers of individual subjects were substantially more pronounced in those who received active vaccine compared to placebo. Error bars indicate SEM (100 μg IM, n = 23; placebo, n = 8).