ANTISERUM AGAINST ESCHERICHIA-COLI J5 CONTAINS ANTIBODIES REACTIVE WITH OUTER-MEMBRANE PROTEINS OF HETEROLOGOUS GRAM-NEGATIVE BACTERIA

The binding of Ige in antiserum to Escherichia coli J5 to the surface of Enterobacteriaceae and to cell wall fragments released from serum-e xposed bacteria was studied in a search for potentially protective epi topes other than lipopolysaccharide (LPS). IgG titers to multiple hete rologous gramnegative smooth bacteria increased following incubation o f the bacteria in serum and decreased following absorption with serum- exposed heterologous bacteria. IgG eluted from absorbing bacteria boun d to at least three conserved bacterial outer membrane proteins (OMPs) , but not LPS, as assessed by immunoblotting. The same OMPs were prese nt in LPS-containing macromolecular cell wall fragments released by in cubation of heterologous gram-negative bacteria in human serum. Part o f the protection offered by J5 antiserum could be from binding of IgG to conserved OMPs at the bacterial surface or to OMPs in cell-wall fra gments released from dying bacteria.