A new Pseudomonas vaccine: preliminary trial on human volunteers

Fifteen healthy volunteers were given three weekly subcutaneous injections of a new polyvalent Pseudomonas aeruginosa vaccine (PEV-01). Four doses - 1-0 RHD (manufacturer's recommended human dose), 0-75 RHD, 0-5 RHD and 0-1 RHD - were used in separate groups of volunteers. Blood samples taken before each of the injections and one taken 7 days after the last injection were examined for immune response to the vaccine and for possible adverse clinical, biochemical and haematological effects. Raised titres of antibody in serum of volunteers given 0-5-1-0 RHD vaccine were shown, often by the seventh day, in passive haemagglutination tests against all of the 16 serotypes of Ps. aeruginosa represented in the vaccine; serum from volunteers who received 0-1 RHD usually showed a reduced antibody titre. Tests of mouse protection by serum against intraperitoneal challenge with Ps. aeruginosa P14 showed increased titres of mouse protective antibody in the blood of volunteers given 1-0, 0-75 or 0-5 RHD of vaccine but a reduced mouse-protective titre in two out of three sera from volunteers given 0-1 RHD vaccine. There was a suggestion of enhanced phagocytic ingestion and intracellular killing of two strains of Ps. aeruginosa by the blood of vaccinated volunteers, and more definite enhancement of ingestion of inert latex particles, which were less well ingested than were the bacterial cells by phagocytes from unvaccinated volunteers. Apart from slight or moderate local reactions and a transient rise of temperature in some volunteers, there were no clinical, biochemical or haematological abnormalities in the vaccinated volunteers.