No abstract

We have developed an ELISA for IgM and IgG antibodies to the core glycolipid (CGL) of the Re mutant Salmonella minnesota R 595, and to lipid A. Anti-CGL antibodies have been detected in sera from 37% of healthy blood donors, whereas anti-lipid A activities were found in 13% of individuals only. The anti-CGL and anti-lipid A activities were examined in patients in a surgical intensive care unit, selected on the basis of a definite risk of infectious complications due to Gram-negative bacteria. Of the patients who developed such infections, the rate of favourable outcome was significantly higher in patients with either stable positive or increasing anti-CGL activities than in patients found to be negative. Our results provide clear evidence that anti-CGL antibodies contribute to host defence against various Gram-negative bacteria.

Mice were passively immunized with sera from blood donors active for rough lipopolysaccharides (LPS), the J5 (Rc chemotype) mutant of Escherichia coli O111:B4, and the Re595 (Re chemotype) mutant of Salmonella minnesota. All protected the mice against lethal challenge with smooth E. coli WF96 LPS, E. coli and Salmonella rough mutant LPS, or free lipid A. Epitopes recognized by monoclonal antibodies (MAbs) reacting with the LPS of S. minnesota Re595 or lipid A were localized in the 2-keto-3-deoxy-D-manno-octulosonic acid (KDO) region and on lipid A. Core-reactive MAbs reacted with their homologous Re LPS and with free lipid A. One, GL11, cross-reacted with the KDO alone. MAbs GL6, GL11, L.4, L.6, and L.8 protected the actinomycin D-sensitized mice against the lethal effects of LPS from E. coli WF96, Salmonella enteritidis, E. coli J5, S. minnesota Re595, and free lipid A. The GL11 antibody was also protective when injected after LPS challenge. These results indicate that antibodies directed against the core glycolipid of S. minnesota Re595 LPS may be useful as an additive form of therapy that may enable decreased mortality during gram-negative bacterial sepsis.

Direct enzyme-linked immunosorbent assay methods offer several advantages in assessing past or recent exposure to cytomegalovirus (CMV) infection, but there persist many pitfalls in the use of these methods for determining specific immunoglobulin M (IgM). The efficiency of absorption of sera by IgG-coated latex beads, aggregated human IgG, or Staphylococcus aureus, i.e., for removing nonspecific CMV IgM activities, was evaluated in comparison with the effect of an anti-human IgG hyperimmune serum. Large routine series comprising serum samples from patients of various clinical groups and healthy individuals were examined. The CMV IgM-positive samples were at first treated with latex or aggregated IgG, but these absorptions left too many CMV IgM-positive individuals. S. aureus increased the nonspecific activity of some sera and, in other cases, removed or impaired specific IgM activities. The anti-IgG treatment caused the disappearance of nonspecific CMV IgM activities that had resisted the other treatments, whereas specific activities remained intact. Utilizing this method, only 1.03% of the routine series patients remained CMV IgM positive by the enzyme-linked immunosorbent assay, a figure in good agreement with a mean probability of CMV antibody acquisition of 0.33% for the population living in Belgium. On the other hand, in a series of patients who were investigated for serological response to several viruses, eight individuals displayed multiple IgM activities after anti-IgG treatment. In these cases, most IgM activities were found in patients who had IgG toward the related antigen for a long time before transient IgM was detected. This result implies that to assess a diagnosis of primary infection, it is necessary to examine serial specimens for IgG acquisition accompanying specific IgM.