Immunologic basis for mouse protection provided by high-molecular-weight polysaccharide from immunotype 1 Pseudomonas aeruginosa.

Antibody responses were assayed in inbred strains of mice immunized with a high-molecular-weight polysaccharide (IT-1 PS) isolated from Fisher immunotype 1 Pseudomonas aeruginosa (P. aeruginosa 1). C3H/ANF mice generated the greatest antibody response after immunization with 1 microgram of antigen and could then survive challenge with 5 LD100 of P. aeruginosa 1 organisms. BALB/c mice produced lower levels of antibody and did so only after immunization with 50 micrograms of IT-1 PS. These mice could only withstand challenge with 1 LD100 of P. aeruginosa 1. The specificity of the antibody produced by these two strains differed. Antibody produced in C3H/ANF mice after primary immunization with either 1 microgram or 50 micrograms of IT-1 PS did not cross-react with other immunotypes of P. aeruginosa. Antibody produced in BALB/c mice after a primary immunization with 50 micrograms of IT-1 PS cross-reacted with polysaccharide isolated from Fisher immunotype 2 P. aeruginosa. These data indicate that, even within the same species, antibody responses to immunization with P. aeruginosa IT-1 PS may be qualitatively different. This kind of variation in immune response patterns will have to be considered in developing optimal regimens for immunization in human vaccine trials.