The key role of peptidoglycan in the opsonization of Staphylococcus aureus.

Abstract

A B S T R A C T In an effort to determine the staphylococcal cell surface component(s) of importance in opsoniization, cell walls (peptidoglycan and teichoic acid) and peptidoglycan were isolated from Staphylococcus aureus strain H grown in [3H]glycine-containing broth. After incubation of the cell walls and peptidoglycan with various opsonic sources, uptake by human pol'ymorphonuclear leukocytes wvas measured. The opsonic requirements for phagocvtosis of cell walls and peptidoglycan were found to be similar to those of intact bacteria. Removal of teichoic acid from the cell wall did not affect opsonization. Likewise, a teichoic acid-deficient mutant strain of S. aureus H was opsonized in a manner similar to that of the parent strain. Immunoglobulin G functionied as the major heat-stable opsonic factor and both the classical and alternative pathways participated in opsonization. Kinetic studies revealed that opsonization of peptidoglycan, as well as C3-C9 consumption by peptidoglycan, proceeded at a slower rate via the alternative pathway (C2-deficient serum) than when the classical pathway was present (normal serum). The ability of peptidoglycan to activate C3-C9 was significantly reduced when normal and C2-deficient sera were preabsorbed with peptidoglycan at 2°C suggesting that antibodies to peptidoglycan may be involved in activation of'both the classical aind alternative complemenit pathways. Thus, peptidoglvcan appears to be the kev cell wall comiipoineint iinvolved in staphylococcal opsonlizationi, aind it is suggested that host response to peptidlogl-can, a major cell wall component of most gramn-positive bacteria, max be related to the develop-

The structure of the cell wall of Staphylococcus aureus studied with neutron scattering and magnetic birefringence

“…The plots of ZcQZ@ against p gave a straight line within a range 0.6 < QRt < 1. 2 (example in fig.1). Fig.2 shows that the plot of ([Z(Q)Q2]0/c)l/2 against D20 content is linear in accordance with the Guinier approximation for monodispersed sheets.…”

“…We have therefore taken the average subunit composition of the peptidoglycan and teichoic acid from [13] which is very similar to that given in [2], the slight differences have negligible effect on the fol-…”

“…If Ax is positive the particle symmetry axis moves nearer to the field direction and at full alignment parallel to the field @ = 1. Whereas if Ax is negative the particles rotate to bring their symmetry axis in a plane perpendicular to the field and with all the particles so oriented @ = -0.5 (thus Counter ions may make up as much as 8.5% of the dry weight of the cell wall [2]. To investigate how these would influence the results the calculations were redone assuming 6% by wt of sodium counter ions in the complex in addition to the 1% included above with the teichoic acid.…”

“…The wall is porous to cellular products, nutrients, and ions and is involved in such phenomena as opsonization, phage binding and pathogenicity [ 1,2]. The staphylococcal wall is typical of Gram-positive bacteria and has three main constituents: peptidoglycan, ribitol teichoic acid and protein [3].…”

“…It is a negatively charged polymer which can bind Mg2+ necessary for various bacterial enzyme systems [6], acts as an antigen [7] and is involved in phage attachment [l]. The proteins in the staphylococcal wall make up to 10% by wt of the whole wall and are probably covalently bonded to the peptidoglycan matrix but can be removed by proteolytic enzymes without damaging wall integrity [2].…”