Safety and immunogenicity of a recombinant hemagglutinin influenza-flagellin fusion vaccine (VAX125) in healthy young adults.

BACKGROUND: The need for worldwide seasonal and pandemic vaccine production has increased interest in the development of innovative technologies for influenza vaccine production. We evaluated a novel influenza vaccine consisting of the globular head of the HA1 domain of the A/Solomon Islands/3/2006 (H1N1) influenza virus (VAX125) genetically fused to the TLR5 ligand, flagellin, and produced in E. coli. METHODS: 128 healthy adult subjects 18-49 years old were enrolled in a clinical trial conducted in three stages at a single center. Stage 1 was an open-label, dose escalation study in which the VAX125 vaccine was administered intramuscularly (im) at doses of 0.1 µg, 0.3 µg, 1 µg, 2 µg, 3 µg, 5 µg and 8 µg to groups of 8 subjects each. Stage 2 was a double-blind, placebo-controlled study in which subjects were randomized to receive 1.0 µg and 2.0 µg VAX125 vaccine doses or placebo, with 16 subjects per group. Finally, an additional 24 subjects received a 0.5 µg dose of VAX125 in stage 3, which was a non-randomized, open label study. In all parts subjects were followed for adverse events and sera was tested by hemagglutination-inhibition (HAI) and microneutralization (MN) against egg-grown virus on days 0, 7, 14, and 28. Serum C-reactive protein (CRP), cytokine levels, and anti-flagellin antibody were also assessed. RESULTS: Vaccine was generally well tolerated and there were no serious adverse events. Pain at the injection site was the most common local adverse event, and was mild or moderate in intensity. Systemic symptoms after vaccination include fatigue and headache, and two subjects, who received either 3 or 8 µg, had moderately severe systemic symptoms accompanied by substantial increases in serum CRP. Serum antibody responses against SI were seen by HAI and MN in most study subjects, with the geometric mean titer of post vaccination antibody increasing in a dose-dependent fashion. Overall, four-fold or greater serum HAI responses were seen in 61 of 96 (64%) subjects who received doses of 0.5 µg or greater, including in 46 of 72 subjects who received doses from 0.5 µg to 2 µg. CONCLUSIONS: The globular head of the influenza HA expressed in a prokaryotic system was able to induce a functional antibody response against native virions. Vigorous responses were seen at relatively low doses of HA antigen suggesting that the addition of flagellin provided a substantial adjuvanting effect. The high levels of immune response at low doses of antigen and the relative ease of production associated with E. coli expression suggests that this approach may represent an effective strategy for enhancing the global influenza vaccine supply.

Immune responses of healthy subjects to a single dose of intramuscular inactivated influenza A/Vietnam/1203/2004 (H5N1) vaccine after priming with an antigenic variant.

BACKGROUND: We administered a single dose of influenza A/Vietnam/1203/2004 (H5N1, clade 1) vaccine to subjects who had received 2 doses of influenza A/Hong Kong/156/1997 (H5N1, clade 0) vaccine in 1998. METHODS: Thirty-seven subjects previously vaccinated with a baculovirus-expressed recombinant hemagglutinin A/Hong Kong/156/1997 vaccine in 1998 received a single intramuscular dose of 90 microg of inactivated subvirion A/Vietnam/1203/2004 vaccine in 2006. Serum antibody was measured before vaccination and 28 and 56 days after vaccination. Antibody responses were compared with those measured after one or two 90-microg doses in H5-naive subjects. RESULTS: On day 28 after a single dose, the geometric mean titer (GMT) of hemagglutination-inhibition antibody in primed subjects was 64.0 (95% confidence interval [CI], 37.8-108.5), with 68% responding (4-fold increase in antibody level to a titer of >or=1:40). In contrast, H5-naive subjects who received two 90-microg doses had a day 56 (28 days after the second dose) GMT of 27.7 (95% CI, 20.3-38.0), with only 43% responding. CONCLUSIONS: This study suggests that priming can result in immune responses to a single dose of an antigenically variant strain of H5N1 influenza virus and could be a useful strategy for pandemic control. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT00240903.

Intranasal administration of a proteosome-influenza vaccine is well-tolerated and induces serum and nasal secretion influenza antibodies in healthy human subjects.

Two randomized, blinded, active comparator-controlled trials of a prototype monovalent A/Beijing/262/95 (H1N1) - proteosome vaccine delivered by intranasal spray were performed in healthy adults. Overall, the intranasal proteosome-adjuvanted vaccine was well-tolerated with only mild stuffy nose and rhinorrhea seen more frequently in recipients of vaccine than in recipients of intranasal saline, and there were no serious adverse events. The intranasal proteosome-adjuvanted vaccine induced serum hemagglutination inhibiting (HAI) and nasal secretory IgA (sIgA) responses specific for the influenza antigen. Serum HAI responses were most influenced by the dosage level, whereas mucosal sIgA responses, although demonstrable with both single-dose and two-dose vaccine regimens, appeared to be greater in response to two-dose regimens (regardless of dose level). Further evaluation of mucosal influenza immunization using the proteosome adjuvant/delivery system is clearly warranted.

Clinical responses to undiluted and diluted smallpox vaccine.

BACKGROUND: To evaluate the potential to increase the supply of smallpox vaccine (vaccinia virus), we compared the response to vaccination with 10(8.1), 10(7.2), and 10(7.0) plaque-forming units (pfu) of vaccinia virus per milliliter. METHODS: In this randomized, single-blind, prospective study, 680 adults who had not been previously immunized were inoculated intradermally with undiluted vaccine (mean titer, 10(8.1) pfu per milliliter), a 1:5 dilution, or a 1:10 dilution of vaccinia virus with use of a bifurcated needle, and the site was covered with a semipermeable dressing. Subjects were monitored for vesicle formation (an indicator of the success of vaccination) and adverse events for 56 days after immunization. RESULTS: Success rates did not differ significantly among the groups and ranged from 97.1 to 99.1 percent after the first vaccination. Both the undiluted and diluted vaccines were reactogenic. In addition to the formation of pustules, common adverse events included the formation of satellite lesions, regional lymphadenopathy, fever, headache, nausea, muscle aches, fatigue, and chills consistent with the presence of an acute viral illness. Generalized and localized rashes, including two cases of erythema multiforme, were also observed. CONCLUSIONS: When given by a bifurcated needle, vaccinia virus vaccine can be diluted to a titer as low as 10(7.0) pfu per milliliter (approximately 10,000 pfu per dose) and induce local viral replication and vesicle formation in more than 97 percent of persons.