Phase II safety and immunogenicity study of type F botulinum toxoid in adult volunteers.

An aluminum hydroxide (alum)-adsorbed, purified, botulinum F toxoid (Bot F) vaccine was manufactured to be administered as a stand-alone monovalent vaccine or to be added to the current botulinum pentavalent toxoid vaccine to make a hexavalent vaccine. We conducted a phase II trial of the Bot F vaccine over 3 years in 144 healthy adult volunteers to identify one of three vaccination schedules that was safe and maximally immunogenic for adult volunteers. We vaccinated 116 volunteers 1-3 times with Bot vaccine, and 28 volunteers 1-3 times with a licensed, alum-adsorbed hepatitis B vaccine (Engerix-B) as a reaction control group. After 1 year, 42 Bot volunteers with low, mouse anti-toxin titers (<0.10 IU/ml) received a booster injection and were followed for an additional year. The Bot vaccine inoculated three times over 28-42 days was generally well tolerated and safe, whether injected by the subcutaneous (s.c.) or intramuscular (i.m.) route, although it caused significantly more local reactions than did the HBV vaccine. Two vaccination schedules of three primary injections over 42 days (days 0, 14 and 42 or days 0, 21 and 42) provided significantly better protective immunity (anti-toxin levels >0.02 IU/ml) than did vaccinations given over 28 days (days 0, 7 and 28). Vaccine reactogenicity and immunogenicity were similar over 42 days whether administered subcutaneously or intramuscularly. However, even the most immunogenic schedule left 7-16% of volunteers unprotected at day 56 and 33-42% of vaccinees unprotected at 1 year. The booster dose administered at 1 year induced high levels of protective serum anti-toxin in all persons assayed which persisted for at least one additional year. A more potent vaccine formulation will be required to protect more individuals after primary immunization.

Phase I trial of 16 formulations of a tetravalent live-attenuated dengue vaccine.

Laboratory-attenuated strains of each of the four dengue serotypes previously tested as monovalent vaccines in volunteers were combined and tested for immunogenicity, safety, and reactogenicity in 16 dosage combinations. Tetravalent vaccines made using combinations of high (10(5-6) plaque-forming units [PFU]/dose) or low (10(3.5-4.5) PFU/dose) dosage formulations of each of the four viruses were inoculated in 64 flavivirus non-immune adult volunteers to determine which, if any, formulation raised neutralizing antibodies in at least 75% of volunteers to at least three of four dengue serotypes following one or two inoculations. Such formulations, if safe and sufficiently non-reactogenic, would be considered for an expanded Phase II trial in the future. Formulations 1-15 were each inoculated into three or four volunteers (total = 54) on days 0 and 28. Formulation 16 was tested in 10 volunteers, five volunteers inoculated on days 0 and 30, one volunteer on days 0 and 120, and four volunteers on days 0, 30, and 120. Blood was drawn for serologic assays immediately before and one month after each vaccination, and for viremia assay on day 10 after each vaccination. The 16 formulations were safe, but variably reactogenic after the first vaccination, and nearly non-reactogenic after the second and third vaccinations. Reactogenicity was positively correlated with immunogenicity. Similar proportions of volunteers seroconverted to dengue-1 (69%), dengue-2 (78%), and dengue-3 (69%), but significantly fewer volunteers seroconverted to dengue-4 (38%). The geometric mean 50% plaque reduction neutralization test titers in persons who seroconverted were significantly higher to dengue-1 (1:94) than to dengue-2 (1:15), dengue-3 (1:10), and dengue-4 (1:2). Seven formulations met the serologic criteria required for an expanded trial, and three of these were sufficiently attenuated clinically to justify further testing.

Immediate-type hypersensitivity and other clinical reactions in volunteers immunized with a synthetic multi-antigen peptide vaccine (PfCS-MAP1NYU) against Plasmodium falciparum sporozoites.

We tested the clinical reactions to a synthetic, Plasmodium falciparum, circumsporozoite multiple antigen peptide (MAP) vaccine in 39 volunteers immunized two to three times over 2-8 months using a dose escalation design. Immediate pain at the injection site was associated with the adjuvant QS-21 (P<0.001), and delayed local inflammatory reactions were associated with high-titered circulating IgG anti-MAP antibody (P=0.03). Because two volunteers developed acute, systemic urticaria after the third immunization associated with development of serum IgE MAP antibody, we employed immediate-type hypersensitivity skin tests (ITH-STs) using intradermal injections of diluted MAP vaccine to identify persons sensitized to the vaccine. ITH-STs were negative in seven volunteers tested 27 days after the first vaccination, but six of these individuals developed positive wheal and flare reactions when tested 14 or 83 days after the second vaccination; IgE MAP antibody was detected in only one of them. Another cohort of 16 volunteers, including the 2 allergic individuals, were ITH-ST negative when first tested late after their second or third vaccination at 6-7 months. Five of five non-immunized persons were also ITH-ST negative. ITH-STs may help identify individuals sensitized to malaria peptides and at potential risk of developing systemic allergic reactions after re-vaccination.

Delayed-type hypersensitivity in volunteers immunized with a synthetic multi-antigen peptide vaccine (PfCS-MAP1NYU) against Plasmodium falciparum sporozoites.

During the testing of the safety and immunogenicity of an adjuvanted, synthetic Plasmodium falciparum CS multiple antigen peptide (MAP) vaccine, we investigated the potential for using cutaneous delayed-type hypersensitivity (DTH) reactions as a correlate of immune response. We evaluated 27 of our volunteers for DTH reactions to intradermal inoculation (0.02 ml) of several concentrations of the MAP vaccine and adjuvant control solutions. Induration was measured 2 days after skin tests were applied. Nine of 14 vaccinees (64%) with serum, high-titered anti-MAP antibody developed positive DTH (>or=5mm induration), that first appeared by 29 days after immunization and persisted for at least 3-6 months after 1-2 more immunizations. In contrast, DTH responses were negative in eight of eight vaccinees with no or low antibody titers, and in five of five non-immunized volunteers. Biopsies of positive DTH skin test sites were histologically compatible with a DTH reaction. We conclude that the presence of T cell functional activity reflected by a positive DTH skin test response to the MAP antigen serves as another marker for vaccine immunogenicity.