SPECIFICITY AND FUNCTIONAL-ACTIVITY OF ANTI-BURKHOLDERIA PSEUDOMALLEIPOLYSACCHARIDE ANTIBODIES

The lipopolysaccharide (LPS) of Burkholderia pseudomallei, the causati ve agent of melioidosis, consists of two O-antigenic polysaccharides d esignated O-PS I and O-PS II. In this study, the O-PS specificity and functional activity of a protective polyclonal antiserum and an immuno globulin M (IgM) monoclonal antibody were determined, The polyclonal a ntiserum recognized both Q-PS I and O-PS II, while the monoclonal anti body was O-PS II specific, Both mediated phagocytic killing of B, pseu domallei by polymorphonuclear leukocytes, Patients acutely infected wi th B. pseudomallei also produced antibodies to the two O-PSs, but thes e antibodies were not produced by asymptomatic individuals from an are a of endemicity who were seropositive by an indirect hemagglutination test using sonicated heat-killed whole organisms as antigen, IgM antib odies were detected only in patients,vith localized infection, Ige ant ibodies were detected in all acutely infected patients, but there was no significant difference in antibody levels among patients with local ized infection, patients who survived septicemic illness, and patients who died from septicemic illness, Further analysis of the Ige respons e revealed production of IgG1 and IgG2 antibodies by all patient group s, while an IgG3 response was seen only in survivors of septicemic inf ection. IgG4 was not detectable even when a fivefold-lower serum dilut ion was used, Patient sera also mediated phagocytic killing by polymor phonuclear leukocytes, and the killing effect was enhanced by compleme nt. These results suggest that antibodies to the LPS O-polysaccharides of B, pseudomallei are protective by promoting phagocytic killing. Th e antibodies develop during human infection and may facilitate clearan ce of the organisms, as seen in a diabetic rat model of B, pseudomalle i infection.