INVESTIGATIONAL VACCINE FOR ESCHERICHIA-COLI O157 - PHASE-I STUDY OF O157 O-SPECIFIC POLYSACCHARIDE PSEUDOMONAS-AERUGINOSA RECOMBINANT EXOPROTEIN-A CONJUGATES IN ADULTS

Escherichia coli 0157 causes severe enteritis and the extraintestinal complication hemolytic-uremic syndrome. Serum IgG against the surface polysaccharide antigen, the 0-specific polysaccharide of lipopolysacch aride (LPS), may confer protective immunity by lysing the inocula. In a phase 1 clinical study, three investigational vaccines were studied in 87 healthy adults. The vaccines were prepared by covalently binding E. coil 0157 0-specific polysaccharide with Pseudomonas aeruginosa re combinant exoprotein A. No significant reactions were reported. Most v olunteers (81%) responded with a >4-fold increase in IgG LPS antibodie s 1 week after vaccination; all volunteers responded with a >4-fold ri se at 4 weeks and this level was sustained for 26 weeks after injectio n. All three vaccines elicited high titers of serum bactericidal activ ity that roughly correlated with the serum IgG and IgM LPS antibody le vels. A phase 2 study in young children is planned.