Antiserum against Escherichia coli J5: a re-evaluation of its in vitro and in vivo activity against heterologous gram-negative bacteria.

Antiserum against Escherichia coli J5, a "rough" mutant of E. coli 0111, has been reported to confer broad-spectrum protection against serologically unrelated gram-negative bacteria. In order to re-evaluate these findings, we examined the influence of rabbit antiserum against E. coli J5 on the phagocytosis of heterologous gram-negative bacteria by rabbit granulocytes in vitro and its ability to protect mice against gram-negative bacterial infection. In vitro, J5 antiserum enhanced the phagocytosis of E. coli 0111, E. coli 06 and Serratia marcescens 06/014:H2 when compared to normal rabbit serum. However, J5 antiserum did not enhance the phagocytosis of Klebsiella pneumoniae type 2 and Pseudomonas aeruginosa serotype 9. In vivo, the protective effect of J5 antiserum against lethal gram-negative infection was not superior to that of normal (pre-immune) serum with the exception of E. coli 0111 septicemia. In contrast, type-specific antiserum against each of the smooth gram-negative bacteria markedly enhanced phagocytosis in vitro and exerted significant protection in vivo. Thus, in this study antiserum against E. coli J5 proved to be of limited value for opsonization of gram-negative bacteria and protection against gram-negative bacterial infection.