Cross-protective immunity to Gram-negative bacilli: studies with core glycolipid of Salmonella minnesota and antigens of Streptococcus pneumoniae.

Two immunoprophylactic approaches to the control of infections caused by gramnegative bacilli were evaluated by study of experimental infections in animals. The core glycolipid antigen derived from the Re mutant of Salmonella minnesota R595 is shared by virtually all enteric bacteria, and immunization with this endotoxin protects against the hemodynamic sequelae of bacterial infection and pyrexia without enhancing intravascular clearance of bacteria. The degree of protection afforded by active and passive immunization with core glycolipid was significantly less than that conferred by type-specific immunization. Escherichia coli and Klebsiella pneumoniae share capsular antigens with some strains of Streptococcus pneumoniae; by the mechanism of enhanced opsonization, antibodies to S. pneumoniae may cross-protect against infection with E. coli or K. pneumoniae.