Myocardial tissue damage in rabbits injected with group A streptococci, types M1 and M22. Role of bacterial immunoglobulin G-binding surface proteins.

Acute rheumatic fever (ARF) and acute poststreptococcal glomerulonephritis (APSGN), two important sequelae of streptococcal throat or skin infections, according to current concepts may be elicited by autoimmune mechanisms due to molecular mimicry between group A streptococci (GAS) and human tissue. In the case of APSGN, however, our experimental data have indicated that GAS immunoglobulin-binding surface proteins (IgG BPs) might be of pathogenic significance by triggering anti-IgG production and immune complex formation leading to renal damage. Thus, rabbits injected with IgG-binding, as opposed to non-binding, GAS strains were found to develop renal deposition of IgG and complement factor C3 and inflammatory and degenerative glomerular changes resembling the picture seen in APSGN. In the present study, cardiac tissue material from rabbits injected with GAS was investigated. After 8 or more weeks of intravenous (i.v.) injections, minimal changes were seen in those animals receiving an IgG non-binding GAS strain, type T27, whereas those animals receiving either of two IgG-binding GAS strains, types M1 or M22, developed strong inflammatory and degenerative myocardial changes accompanied by deposition of IgG and C3. Furthermore, on injecting rabbits with defined mutants of a type M22 strain, the development of myocardial tissue damage proved to be dependent on the presence of streptococcal IgG-binding activity. Our results demonstrate that myocardial tissue changes may be induced in the rabbit by i.v. injection of whole heat-killed GAS of at least two M serotypes. Conceivably, induction of immune complexes by bacterial IgG BPs may lead to myocardial deposition of IgG, in turn triggering a series of events, involving the complement system and proinflammatory cytokines, with resulting tissue damage. Though many virulence factors may be involved in the development of ARF and APSGN, and a given GAS strain will never cause both, our results may suggest a new pathogenetic mechanism common to these two major non-suppurative complications.

Induction of myocarditis in rabbits injected with group A streptococci.

BACKGROUND & OBJECTIVES: We have earlier proposed that group A streptococcal (GAS) immunoglobulin binding surface proteins (IgGBPs) might trigger anti-IgG production and immune complex formation leading to glomerulonephritis. In the present study, cardiac tissue material from rabbits injected with heat-killed GAS was investigated. METHODS: Rabbits were injected intravenously with 10(9) colony forming units of streptococci three times weekly for 8 wk. Cardiac tissue samples were obtained at different times and deposition of IgG, C3, TNF-alpha and IL-6 was studied. RESULTS: After 8 or more weeks of intravenous (iv) injections, minimal changes were seen in animals receiving an IgG non-binding GAS strain, type T27, whereas in those animals receiving either of two IgG binding GAS strains, types M1 or M22, strong inflammatory and degenerative myocardial changes accompanied by deposition of IgG and C3 were noted. Furthermore, on injecting rabbits with defined mutants of a type M22 strain, the development of myocardial tissue damage proved to be dependent on the presence streptococcal IgGBPs. INTERPRETATION & CONCLUSION: The present data supported a role of streptococcal IgGBPs in the induction of myocardial tissue injury by GAS.

Triggering of renal tissue damage in the rabbit by IgG Fc-receptor-positive group A streptococci.

Our previous studies have shown that streptococcal IgG Fc receptors (FcR) act to elicit circulating anti-IgG as well as renal glomerular deposition of IgG in rabbits immunized with group A streptococci (GAS). In order to study if other FcR-positive bacteria might have similar effects, rabbits were immunized with either group G streptococci (GGS; strain G148) or Staphylococcus aureus (strain Cowan I) for two periods of 8 and 6 weeks, respectively. At the end of immunization, circulating anti-IgG was found in 6 of 20 (30%) and 4 of 19 (21%) animals receiving G148 and Cowan I, respectively, compared to all 28 receiving FcR-positive GAS strains of types M1, M4, M15 or M22 (p < 0.05 for both comparisons); furthermore, anti-IgG appeared earlier and at higher levels in the GAS groups. Weak glomerular IgG deposits occurred in 5 out of 10 (50%) and 2 out of 8 (25%) animals immunized with G148 and Cowan I, respectively. In contrast, all 11 rabbits examined, given GAS of types M1 or M15, displayed heavy deposits. None of four control animals immunized with either of two FcR-negative strains, GAS type T27 or group B streptococci (GBS) type Ia, exhibited any renal IgG deposits or circulating anti-IgG. Renal tissue materials from rabbits immunized with any of the four FcR-positive GAS strains showed strong inflammatory and degenerative glomerular changes, compatible with the picture seen in acute poststreptococcal glomerulonephritis (APSGN). Only transient renal changes were found in those rabbits immunized with G148 or Cowan I, or the controls injected with the FcR-negative strains, GAS type T27 or GBS. Thus, only the FcR-positive GAS strains showed capacity to induce high levels of anti-IgG, pronounced tissue deposition of IgG as well as irreversible glomerular changes. Our experimental data suggest that streptococcal IgG FcR activity might play an important role in triggering APSGN.

Influence of growth conditions on expression of immunoglobulin G binding in group A streptococci.

Many group A streptococci (GAS) bind the Fc part of IgG. In the present work, the possible influence of growth time and incubation atmosphere on the expression of the IgG binding activity by GAS of various serotypes was studied. Among 13 GAS reference strains, two categories were distinguished on aerobic incubation at 37 degrees C, one expressing similar IgG binding activity at 6 h and 18 h (types M1, M4, M13, M15), and a second one which showed higher binding at 6 h than at 18 h (M9, M14, M22, M25, M48, M49). Only one strain (M36) bound less IgG at 6 h than at 18 h. Seven of the strains (M5, M6, M22, M25, M36, M48, M49) showed higher binding of IgG when grown in a 5% CO2 atmosphere than in air, whereas one strain (M14) showed a reverse pattern and in the remaining five strains, no influence was found. Protease activity was detected in the growth supernatant of most of the strains. For five selected strains, the time of appearance of supernatant protease activity coincided with a decay of surface IgG binding activity. Purified streptococcal cysteine protease was found to reduce or abolish the binding of IgG by each of three studied strains (M1, M13 and M15) and of type M1 or M15 purified IgG binding material. When tested in the stationary phase, a majority of 62 clinical GAS isolates belonging to 6 different M types showed high protease activity but low binding of IgG. We conclude that streptococcal IgG binding is often better expressed on growth in 5% CO2 atmosphere than in air. Furthermore, due to its sensitivity to streptococcal protease, the IgG binding activity is mostly higher during the logarithmic than during the stationary phase of growth.

[New concepts of the mechanisms of immunopatholgies+ of Streptococcal etiology]. / Novye predstavleniia o mekhanizmakh immunopatologicheskikh sostoianii streptokokkovoi etiologii.

The paper summarizes the data on the role of immunoglobulin Fc-receptor proteins of group A streptococci as one of the leading agents of the pathogenicity that initiates severe poststreptococcal complications in the comprehensive immunological and morphological study of acute experimental glomerulonephritis. In addition to some pathogenic effects, evidence is presented for the capacity of IgG FcR-positive, rather than IgG FcR-negative, group A streptococci of inducing the synthesis of great quantities of anti-IgG which has been detected both in free circulation and as part of immune complexes. IgG FcR proteins induced the release of antiinflammatory cytokines (TNF-alpha in particular) and anti-IgG FcR proteins, concurrently with complement C, formed deposits in the structures of glomerules, resulting in destructive and degenerative changes. The morphological criteria for delayed hypersensitivity processes, which are typical of inflammatory reactions in immunopathologies are discussed in the paper. Immunomorphological and electron microscopic studies at early stages revealed signs of membrane-proliferative glomerulonephritis with a predominant response of podocytes and mesangial cells, which later progressed to developed fibrous, atrophic, glomerulonephritis. It should be stressed that IgG FcR proteins, such as A and G staphylococcal protein, group G streptococcal protein, unlike group A streptococcal protein with the similar function either failed to cause the described events or the latter occurred rarely or delayed. The findings provide evidence for the author's concept of the role of IgG Fc-receptors of group A streptococci in the development of complications of streptococcal etiology.

[Use of group A-specific polysaccharide antigen conjugated with protein carrier for detection of specific anti-polysaccharide antibodies]. / Ispo'lzovanie gruppospetsificheskogo A-polisakharidnogo antigena, ko''niugirovannogo s belkovym nositelem, dlia vyiavleniia spetsificheskikh antipolisakharidnykh antitel.

Group-A specific polysaccharide antigen has been obtained by extraction of streptococcal suspension using 4N NaNO2 and glacial acetic acid, conjugated with bovine serum albumin using CNBr. Testing of the preparation with a set of rabbit anti-sera by enzyme immunoassay (EIA) and passive hemagglutination reaction (PHR) revealed its antigenic specificity both in direct experiments and in N-acetyl-D-glucosamine absorption. Forty-seven sera of EIA-studied individuals and 35 sera of PHR-studied ones, all with group-specific polysaccharide antigen, were examined. Immune reactions showed the broad spectrum of antibody titres in the studied sera. Complete correlation of anti-polysaccharide antibodies detected by the two techniques was observed in the sera with high specific antibody titres. A possibility to use the obtained group-A specific polysaccharide antigen to detect anti-polysaccharide antibodies in the sera of streptococcal infection patients is discussed.