Killing of Brucella abortus by bovine serum

Abstract

Studies of the serum bactericidal system in bovine brucellosis were undertaken to investigate the role of the humoral immune response in protection of cattle against the facultative intracellular parasite Brucella abortus. Fresh sera from normal control cattle, infected cattle, and cattle immunized with B. abortus cell envelopes were collected before treatment and during the course of immunization or infection. Normal fresh bovine serum or fresh agammaglobulinemic serum from colostrum-deprived calves was effective in killing smooth virulent B. abortus 2308, but rough strains RB51 (a rough mutant of strain 2308) and 45/20 were much more senitive to serum. The difference in susceptibility to serum was shown to be correlated with differences in lipopolysaccharide chemotype, with the more resistant strain 2308 having 0 polysaccharide and the more susceptible strains 45/20 and RB51 lacking 0 side chains. By treatment of fresh serum with MgCl2 and EGTA [ethylene glycol-bis(IO-aminoethyl ether)-N,N,N',N'-tetraacetic acid] killing was shown to occur via the classical pathway of complement activation. When antibody to B. abortus was present, killing of strain RB51 increased but killing of smooth strain 2308 decreased. The earliest antibody response in serum from infected animals did not interfere with killing. When affinity-purified bovine immunoglobulins specific for B. abortus smooth lipopolysaccharide were added to fresh normal bovine serum, immunoglobulin Gl (IgGl) and IgG2 isotypes blocked killing but IgM and IgA isotypes did not. Thus, it appears that serum from previously unexposed animals or animals early during infection can kill smooth B. abortus, an appropriate defense mechanism before the organism becomes intracellular. At later stages of infection, blocking antibodies predominate.

Transposon-Derived Brucella abortus Rough Mutants Are Attenuated and Exhibit Reduced Intracellular Survival

“…Brucellae are sensitive to complement-mediated lysis via the classical pathway (12). Using B. abortus 45/20 and RB51, Corbeil et al concluded that increased sensitivity to the killing activity of complement was attributable to the lack of O antigen (12). Sensitivity to complement was used as a predictor of sensitivity to extracellular killing within the host (Fig.…”

“…Bactericidal assays. Brucella strains were tested for sensitivity to bovine serum by a procedure based on that described by Corbeil et al (12). Sera were collected from the blood of five naive Angus bovine calves and pooled for storage at Ϫ80°C.…”

Penetration and intracellular growth of Brucella abortus in nonphagocytic cells in vitro

“…In preliminary experiments, we did not find any effect of 10% FCS on the viability of different strains of B. abortus. The brucellicidal effect of bovine serum is complement dependent (5). Because the FCS used in this study was frozen and thawed at least twice before addition to the minimal essential medium (MEM), its complement activity was probably minimal.…”

Identification and comparison of macrophage-induced proteins and proteins induced under various stress conditions in Brucella abortus

“…Brucella abortus is a facultative intracellular pathogen that survives ingestion by macrophages and neutrophils (21,30). The ability to survive inside macrophages allows B. abortus to interfere with the function of macrophages and also provides the bacteria with protection from the immune system and the factors in blood which are capable of killing B. abortus (12). After uptake of B. abortus by macrophages, bacteria are found in a membrane-bound vacuole referred to as a phagosome.…”