Type-specific opsonophagocytosis of group A Streptococcus by use of a rapid chemiluminescence assay

M type 1 and 3 group A streptococci stimulate tissue factor-mediated procoagulant activity in human monocytes and endothelial cells

Streptococcal toxic shock syndrome (StrepTSS) is an invasive infection characterized by marked coagulopathy, multiple organ failure, and rapid tissue destruction and is strongly associated with M type 1 and 3 group A streptococci (GAS). Initiation of the coagulation cascade with formation of microvascular thrombi contributes to multiple organ failure in human cases of gram-negative bacteremia; however, little is known regarding the mechanism of coagulopathy in StrepTSS. Thus, we investigated the abilities of several strains of M type 1 and 3 GAS isolated from human cases of StrepTSS to stimulate production of tissue factor (TF), the principal initiator of coagulation in vivo. Washed, killed M type 1 and 3 GAS, but not M type 6 GAS, elicited high-level TF-mediated procoagulant activity from both isolated human monocytes and cultured human umbilical vein endothelial cells. M type 1 GAS consistently elicited higher levels of TF from monocytes than did M type 3 GAS. GAS-induced TF synthesis in monocytes did not correlate with production of tumor necrosis factor alpha or interleukin-8. Conversely, M type 3 GAS were consistently more potent than M type 1 GAS in stimulating endothelial cell TF synthesis. These results demonstrate that (i) M type 1 and 3 strains of GAS are potent inducers of TF synthesis, (ii) GAS-induced TF synthesis is not simply an epiphenomenon of cytokine generation, and (iii) induction of TF in endothelial cells and monocytes may be M type specific. In total, these findings suggest that a novel interaction between GAS and host cells contributes to the observed coagulopathy in StrepTSS.

Opsonization of T1M1 group A Streptococcus: dynamics of antibody production and strain specificity

A chemiluminescence method was used to study opsonization of group A Streptococcus (GAS) of serotype T1M1 in serum samples ("sera") obtained from Swedish patients with invasive and noninvasive GAS infection and from healthy blood donors. Acute-phase serum samples ("acute sera") generally demonstrated low ability to opsonize the patient's own GAS isolate, regardless of clinical manifestation. Only approximately 15% of serum samples obtained from healthy blood donors demonstrated high opsonic activity against a standard T1M1 strain. Opsonization of 62 T1M1 isolates (obtained during 1980-1998) by a single immune serum sample showed considerable variation; this indicates that high opsonic immunity may develop only against the infecting isolate or identical clones. T1M1 GAS isolated from 1987 through 1990 were better opsonized by the immune serum sample than were isolates obtained before 1987 or after 1990, a finding that suggests a temporal change of the surface properties that affect opsonization.