The Journal of Medical Microbiology, Vol 48, Issue 5 433-441, Copyright © 1999 by Society for General Microbiology
Cross-reactivity between six Enterobacteriaceae complete lipopolysaccharide core chemotypes
N. A. Nnalue, G. N. Khan and N. Mustafa
Department of Medical Microbiology, Faculty of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates.
To gain insight into the value of lipopolysaccharide (LPS) core
determinants for cross-protective immunisation the serological
relationships between six complete (LPS) core types from Enterobacteriaceae
were investigated. Hyperimmune sera were raised in mice by repeated
immunisation with heat-killed strains of Salmonella choleraesuis (Ra core
type) or Escherichia coli (core types R1, R2, R3, R4 and K12) and
characterised for reactivity with complete and incomplete core chemotypes
by ELISA and immunoblotting. Three sera (anti-Ra, anti-R2 and anti-R3)
reacted strongly with 3-5 different complete core types whereas the other
three (anti-R1, anti-R4 and anti-K12) reacted strongly only with their
homologous core types in these assays. Two approaches were used to examine
further the structural bases for cross-reactivity between these cores. By
the first approach the anti-complete-core sera were tested for
cross-reactivity with truncated forms of the Salmonella species core
(incomplete cores) derived from core-defective mutants. By the second
approach, antisera raised against some core-defective mutants were tested
for cross-reactivity with complete cores. The results of these
investigations revealed that several pair-wise combinations of core types
can be used as immunogens to elicit immune responses that recognise all six
core types and that the major determinants which mediate cross-reactivity
between complete cores are localised in the outer core region.
