Safety and immunogenicity of a plant-produced recombinant monomer hemagglutinin-based influenza vaccine derived from influenza A (H1N1)pdm09 virus: a Phase 1 dose-escalation study in healthy adults.

BACKGROUND: Novel influenza viruses continue to pose a potential pandemic threat worldwide. In recent years, plants have been used to produce recombinant proteins, including subunit vaccines. A subunit influenza vaccine, HAC1, based on recombinant hemagglutinin from the 2009 pandemic A/California/04/2009 (H1N1) strain of influenza virus, has been manufactured using a plant virus-based transient expression technology in Nicotiana benthamiana plants and demonstrated to be immunogenic and safe in pre-clinical studies (Shoji et al., 2011). METHODS: A first-in-human, Phase 1, single-center, randomized, placebo-controlled, single-blind, dose escalation study was conducted to investigate safety, reactogenicity and immunogenicity of an HAC1 formulation at three escalating dose levels (15 µg, 45 µg and 90 µg) with and without Alhydrogel(®), in healthy adults 18-50 years of age (inclusive). Eighty participants were randomized into six study vaccine groups, a saline placebo group and an approved monovalent H1N1 vaccine group. Recipients received two doses of vaccine or placebo (except for the monovalent H1N1 vaccine cohort, which received a single dose of vaccine, later followed by a dose of placebo). RESULTS: The experimental vaccine was safe and well tolerated, and comparable to placebo and the approved monovalent H1N1 vaccine. Pain and tenderness at the injection site were the only local solicited reactions reported following vaccinations. Nearly all adverse events were mild to moderate in severity. The HAC1 vaccine was also immunogenic, with the highest seroconversion rates, based on serum hemagglutination-inhibition and virus microneutralization antibody titers, in the 90 µg non-adjuvanted HAC1 vaccine group after the second vaccine dose (78% and 100%, respectively). CONCLUSIONS: This is the first study demonstrating the safety and immunogenicity of a plant-produced subunit H1N1 influenza vaccine in healthy adults. The results support further clinical investigation of the HAC1 vaccine as well as demonstrate the feasibility of the plant-based technology for vaccine antigen production.

Recombinant Liver Stage Antigen-1 (LSA-1) formulated with AS01 or AS02 is safe, elicits high titer antibody and induces IFN-gamma/IL-2 CD4+ T cells but does not protect against experimental Plasmodium falciparum infection.

Plasmodium falciparum Liver Stage Antigen 1 (LSA-1) is a pre-erythrocytic stage antigen. Our LSA-1 vaccine candidate is a recombinant protein with full-length C- and N-terminal flanking domains and two of the 17 amino acid repeats from the central repeat region termed "LSA-NRC." We describe the first Phase I/II study of this recombinant LSA-NRC protein formulated with either the AS01 or AS02 adjuvant system. We conducted an open-label Phase I/II study. Thirty-six healthy malaria-naïve adults received one of four formulations by intra-deltoid injection on a 0 and 1 month schedule; low dose (LD) LSA-NRC/AS01:10microg LSA-NRC/0.5ml AS01 (n=5), high dose (HD) LSA-NRC/AS01: 50microg LSA-NRC/0.5ml AS01 (n=13); LD LSA-NRC/AS02: 10microg LSA-NRC/0.5ml AS02 (n=5) and HD LSA-NRC/AS02: 50microg LSA-NRC/0.5ml AS02 (n=13). Two weeks post-second immunization, the high dose vaccinees and 6 non-immunized infectivity controls underwent experimental malaria sporozoite challenge. The vaccines showed a reassuring safety profile but were moderately reactogenic. There were no serious adverse events. All subjects seroconverted after the first immunization. Following the second immunization, LSA-1-specific CD4+ T cells producing two cytokines (IL-2 and IFN-gamma) were found by intra-cellular staining in all subjects in the LD LSA-NRC/AS01B group and in 3 of 5 subjects in the LD LSA-NRC/AS02 group. In contrast, the HD LSA-NRC/AS01 and HD LSA-NRC/AS02 group subjects had fewer LSA-1-specific CD4+ T cells, and minimal to no IFN-gamma responses. There was no increase in LSA-1-specific CD8+ T cells found in any group. Per protocol, 22 high dose vaccinees, but no low dose vaccinees, underwent P. falciparum homologous malaria challenge (3D7 clone). All vaccinees became parasitemic and there was no delay in their pre-patent period versus controls (p=0.95). LSA-NRC/AS01 and LSA-NRC/AS02 elicited antigen-specific antibody and CD4+ T cell responses, but elicited no protective immunity. Although the optimal antigen dose of LSA-NRC may not have been selected for the challenge portion of the protocol, further vaccine development based upon LSA-1 should not be excluded and should include alternative vaccine platforms able to elicit additional effector mechanisms such as CD8+ T cells.